1
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Aplin C, Cerione RA. Probing the mechanism by which the retinal G protein transducin activates its biological effector PDE6. J Biol Chem 2024; 300:105608. [PMID: 38159849 PMCID: PMC10838916 DOI: 10.1016/j.jbc.2023.105608] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2023] [Revised: 11/23/2023] [Accepted: 12/14/2023] [Indexed: 01/03/2024] Open
Abstract
Phototransduction in retinal rods occurs when the G protein-coupled photoreceptor rhodopsin triggers the activation of phosphodiesterase 6 (PDE6) by GTP-bound alpha subunits of the G protein transducin (GαT). Recently, we presented a cryo-EM structure for a complex between two GTP-bound recombinant GαT subunits and native PDE6, that included a bivalent antibody bound to the C-terminal ends of GαT and the inhibitor vardenafil occupying the active sites on the PDEα and PDEβ subunits. We proposed GαT-activated PDE6 by inducing a striking reorientation of the PDEγ subunits away from the catalytic sites. However, questions remained including whether in the absence of the antibody GαT binds to PDE6 in a similar manner as observed when the antibody is present, does GαT activate PDE6 by enabling the substrate cGMP to access the catalytic sites, and how does the lipid membrane enhance PDE6 activation? Here, we demonstrate that 2:1 GαT-PDE6 complexes form with either recombinant or retinal GαT in the absence of the GαT antibody. We show that GαT binding is not necessary for cGMP nor competitive inhibitors to access the active sites; instead, occupancy of the substrate binding sites enables GαT to bind and reposition the PDE6γ subunits to promote catalytic activity. Moreover, we demonstrate by reconstituting GαT-stimulated PDE6 activity in lipid bilayer nanodiscs that the membrane-induced enhancement results from an increase in the apparent binding affinity of GαT for PDE6. These findings provide new insights into how the retinal G protein stimulates rapid catalytic turnover by PDE6 required for dim light vision.
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Affiliation(s)
- Cody Aplin
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York, USA
| | - Richard A Cerione
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York, USA; Department of Molecular Medicine, Cornell University, Ithaca, New York, USA.
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2
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Singh S, Srivastava D, Boyd K, Artemyev NO. Reconstitution of the phosphodiesterase 6 maturation process important for photoreceptor cell function. J Biol Chem 2024; 300:105576. [PMID: 38110033 PMCID: PMC10819763 DOI: 10.1016/j.jbc.2023.105576] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2023] [Revised: 12/01/2023] [Accepted: 12/10/2023] [Indexed: 12/20/2023] Open
Abstract
The sixth family phosphodiesterases (PDE6) are principal effector enzymes of the phototransduction cascade in rods and cones. Maturation of nascent PDE6 protein into a functional enzyme relies on a coordinated action of ubiquitous chaperone HSP90, its specialized cochaperone aryl hydrocarbon receptor-interacting protein-like 1 (AIPL1), and the regulatory Pγ-subunit of PDE6. Deficits in PDE6 maturation and function underlie severe visual disorders and blindness. Here, to elucidate the roles of HSP90, AIPL1, and Pγ in the maturation process, we developed the heterologous expression system of human cone PDE6C in insect cells allowing characterization of the purified enzyme. We demonstrate that in the absence of Pγ, HSP90, and AIPL1 convert the inactive and aggregating PDE6C species into dimeric PDE6C that is predominantly misassembled. Nonetheless, a small fraction of PDE6C is properly assembled and fully functional. From the analysis of mutant mice that lack both rod Pγ and PDE6C, we conclude that, in contrast to the cone enzyme, no maturation of rod PDE6AB occurs in the absence of Pγ. Co-expression of PDE6C with AIPL1 and Pγ in insect cells leads to a fully mature enzyme that is equivalent to retinal PDE6. Lastly, using immature PDE6C and purified chaperone components, we reconstituted the process of the client maturation in vitro. Based on this analysis we propose a scheme for the PDE6 maturation process.
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Affiliation(s)
- Sneha Singh
- Department of Molecular Physiology and Biophysics, The University of Iowa Carver College of Medicine, Iowa City, Iowa, USA
| | - Dhiraj Srivastava
- Department of Molecular Physiology and Biophysics, The University of Iowa Carver College of Medicine, Iowa City, Iowa, USA
| | - Kimberly Boyd
- Department of Molecular Physiology and Biophysics, The University of Iowa Carver College of Medicine, Iowa City, Iowa, USA
| | - Nikolai O Artemyev
- Department of Molecular Physiology and Biophysics, The University of Iowa Carver College of Medicine, Iowa City, Iowa, USA; Department of Ophthalmology and Visual Sciences, The University of Iowa Carver College of Medicine, Iowa City, Iowa, USA.
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3
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Moakedi F, Aljammal R, Poria D, Saravanan T, Rhodes SB, Reid C, Guan T, Kefalov VJ, Ramamurthy V. Prenylation is essential for the enrichment of cone phosphodiesterase-6 (PDE6) in outer segments and efficient cone phototransduction. Hum Mol Genet 2023; 32:2735-2750. [PMID: 37384398 PMCID: PMC10460490 DOI: 10.1093/hmg/ddad108] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2023] [Revised: 06/20/2023] [Accepted: 06/23/2023] [Indexed: 07/01/2023] Open
Abstract
Phosphodiesterase-6 (PDE6) is the key phototransduction effector enzyme residing in the outer segment (OS) of photoreceptors. Cone PDE6 is a tetrameric protein consisting of two inhibitory subunits (γ') and two catalytic subunits (α'). The catalytic subunit of cone PDE6 contains a C-terminus prenylation motif. Deletion of PDE6α' C-terminal prenylation motif is linked to achromatopsia (ACHM), a type of color blindness in humans. However, mechanisms behind the disease and roles for lipidation of cone PDE6 in vision are unknown. In this study, we generated two knock-in mouse models expressing mutant variants of cone PDE6α' lacking the prenylation motif (PDE6α'∆C). We find that the C-terminal prenylation motif is the primary determinant for the association of cone PDE6 protein with membranes. Cones from PDE6α'∆C homozygous mice are less sensitive to light, and their response to light is delayed, whereas cone function in heterozygous PDE6α'∆C/+ mice is unaffected. Surprisingly, the expression level and assembly of cone PDE6 protein were unaltered in the absence of prenylation. Unprenylated assembled cone PDE6 in PDE6α'∆C homozygous animals is mislocalized and enriched in the cone inner segment and synaptic terminal. Interestingly, the disk density and the overall length of cone OS in PDE6α'∆C homozygous mutants are altered, highlighting a novel structural role for PDE6 in maintaining cone OS length and morphology. The survival of cones in the ACHM model generated in this study bodes well for gene therapy as a treatment option for restoring vision in patients with similar mutations in the PDE6C gene.
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Affiliation(s)
- Faezeh Moakedi
- Department of Biochemistry and Molecular Medicine, School of Medicine, West Virginia University, Morgantown, WV 26506, USA
- Department of Ophthalmology and Visual Sciences, School of Medicine, West Virginia University, Morgantown, WV 26506, USA
| | - Rawaa Aljammal
- Department of Biochemistry and Molecular Medicine, School of Medicine, West Virginia University, Morgantown, WV 26506, USA
- Department of Ophthalmology and Visual Sciences, School of Medicine, West Virginia University, Morgantown, WV 26506, USA
| | - Deepak Poria
- Department of Ophthalmology, Gavin Herbert Eye Institute, University of California, Irvine, CA 92697, USA
| | - Thamaraiselvi Saravanan
- Department of Biochemistry and Molecular Medicine, School of Medicine, West Virginia University, Morgantown, WV 26506, USA
- Department of Ophthalmology and Visual Sciences, School of Medicine, West Virginia University, Morgantown, WV 26506, USA
| | - Scott B Rhodes
- Department of Biochemistry and Molecular Medicine, School of Medicine, West Virginia University, Morgantown, WV 26506, USA
- Department of Ophthalmology and Visual Sciences, School of Medicine, West Virginia University, Morgantown, WV 26506, USA
| | - Chyanne Reid
- Department of Biochemistry and Molecular Medicine, School of Medicine, West Virginia University, Morgantown, WV 26506, USA
- Department of Ophthalmology and Visual Sciences, School of Medicine, West Virginia University, Morgantown, WV 26506, USA
| | - Tongju Guan
- Department of Biochemistry and Molecular Medicine, School of Medicine, West Virginia University, Morgantown, WV 26506, USA
- Department of Ophthalmology and Visual Sciences, School of Medicine, West Virginia University, Morgantown, WV 26506, USA
| | - Vladimir J Kefalov
- Department of Ophthalmology, Gavin Herbert Eye Institute, University of California, Irvine, CA 92697, USA
| | - Visvanathan Ramamurthy
- Department of Biochemistry and Molecular Medicine, School of Medicine, West Virginia University, Morgantown, WV 26506, USA
- Department of Ophthalmology and Visual Sciences, School of Medicine, West Virginia University, Morgantown, WV 26506, USA
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4
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Munezero D, Aliff H, Salido E, Saravanan T, Sanzhaeva U, Guan T, Ramamurthy V. HSP90α is needed for the survival of rod photoreceptors and regulates the expression of rod PDE6 subunits. J Biol Chem 2023; 299:104809. [PMID: 37172722 PMCID: PMC10250166 DOI: 10.1016/j.jbc.2023.104809] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2023] [Revised: 04/19/2023] [Accepted: 04/20/2023] [Indexed: 05/15/2023] Open
Abstract
Heat shock protein 90 (HSP90) is an abundant molecular chaperone that regulates the stability of a small set of proteins essential in various cellular pathways. Cytosolic HSP90 has two closely related paralogs: HSP90α and HSP90β. Due to the structural and sequence similarities of cytosolic HSP90 paralogs, identifying the unique functions and substrates in the cell remains challenging. In this article, we assessed the role of HSP90α in the retina using a novel HSP90α murine knockout model. Our findings show that HSP90α is essential for rod photoreceptor function but was dispensable in cone photoreceptors. In the absence of HSP90α, photoreceptors developed normally. We observed rod dysfunction in HSP90α knockout at 2 months with the accumulation of vacuolar structures, apoptotic nuclei, and abnormalities in the outer segments. The decline in rod function was accompanied by progressive degeneration of rod photoreceptors that was complete at 6 months. The deterioration in cone function and health was a "bystander effect" that followed the degeneration of rods. Tandem mass tag proteomics showed that HSP90α regulates the expression levels of <1% of the retinal proteome. More importantly, HSP90α was vital in maintaining rod PDE6 and AIPL1 cochaperone levels in rod photoreceptor cells. Interestingly, cone PDE6 levels were unaffected. The robust expression of HSP90β paralog in cones likely compensates for the loss of HSP90α. Overall, our study demonstrated the critical need for HSP90α chaperone in the maintenance of rod photoreceptors and showed potential substrates regulated by HSP90α in the retina.
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Affiliation(s)
- Daniella Munezero
- Department of Pharmaceutical and Pharmacological Sciences, West Virginia University, Morgantown, West Virginia, USA; Ophthalmology and Visual Sciences, West Virginia University, Morgantown, West Virginia, USA
| | - Hunter Aliff
- Ophthalmology and Visual Sciences, West Virginia University, Morgantown, West Virginia, USA; Biochemistry and Molecular Medicine, West Virginia University, Morgantown, West Virginia, USA
| | - Ezequiel Salido
- Ophthalmology and Visual Sciences, West Virginia University, Morgantown, West Virginia, USA; Biochemistry and Molecular Medicine, West Virginia University, Morgantown, West Virginia, USA
| | - Thamaraiselvi Saravanan
- Ophthalmology and Visual Sciences, West Virginia University, Morgantown, West Virginia, USA; Biochemistry and Molecular Medicine, West Virginia University, Morgantown, West Virginia, USA
| | - Urikhan Sanzhaeva
- Ophthalmology and Visual Sciences, West Virginia University, Morgantown, West Virginia, USA; Biochemistry and Molecular Medicine, West Virginia University, Morgantown, West Virginia, USA
| | - Tongju Guan
- Ophthalmology and Visual Sciences, West Virginia University, Morgantown, West Virginia, USA; Biochemistry and Molecular Medicine, West Virginia University, Morgantown, West Virginia, USA
| | - Visvanathan Ramamurthy
- Department of Pharmaceutical and Pharmacological Sciences, West Virginia University, Morgantown, West Virginia, USA; Ophthalmology and Visual Sciences, West Virginia University, Morgantown, West Virginia, USA; Biochemistry and Molecular Medicine, West Virginia University, Morgantown, West Virginia, USA.
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5
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Faber S, Letteboer SJF, Junger K, Butcher R, Tammana TVS, van Beersum SEC, Ueffing M, Collin RWJ, Liu Q, Boldt K, Roepman R. PDE6D Mediates Trafficking of Prenylated Proteins NIM1K and UBL3 to Primary Cilia. Cells 2023; 12:cells12020312. [PMID: 36672247 PMCID: PMC9857354 DOI: 10.3390/cells12020312] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2022] [Revised: 01/02/2023] [Accepted: 01/09/2023] [Indexed: 01/18/2023] Open
Abstract
Mutations in PDE6D impair the function of its cognate protein, phosphodiesterase 6D (PDE6D), in prenylated protein trafficking towards the ciliary membrane, causing the human ciliopathy Joubert Syndrome (JBTS22) and retinal degeneration in mice. In this study, we purified the prenylated cargo of PDE6D by affinity proteomics to gain insight into PDE6D-associated disease mechanisms. By this approach, we have identified a specific set of PDE6D-interacting proteins that are involved in photoreceptor integrity, GTPase activity, nuclear import, or ubiquitination. Among these interacting proteins, we identified novel ciliary cargo proteins of PDE6D, including FAM219A, serine/threonine-protein kinase NIM1 (NIM1K), and ubiquitin-like protein 3 (UBL3). We show that NIM1K and UBL3 localize inside the cilium in a prenylation-dependent manner. Furthermore, UBL3 also localizes in vesicle-like structures around the base of the cilium. Through affinity proteomics of UBL3, we confirmed its strong interaction with PDE6D and its association with proteins that regulate small extracellular vesicles (sEVs) and ciliogenesis. Moreover, we show that UBL3 localizes in specific photoreceptor cilium compartments in a prenylation-dependent manner. Therefore, we propose that UBL3 may play a role in the sorting of proteins towards the photoreceptor outer segment, further explaining the development of PDE6D-associated retinal degeneration.
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Affiliation(s)
- Siebren Faber
- Department of Human Genetics, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, 6525 GA Nijmegen, The Netherlands
| | - Stef J. F. Letteboer
- Department of Human Genetics, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, 6525 GA Nijmegen, The Netherlands
| | - Katrin Junger
- Division of Experimental Ophthalmology and Medical Proteome Center, Center of Ophthalmology, University of Tübingen, 72076 Tübingen, Germany
| | - Rossano Butcher
- Department of Ophthalmology, Ocular Genomics Institute, Massachusetts Eye and Ear, Harvard Medical School, Boston, MA 02115, USA
| | - Trinadh V. Satish Tammana
- Department of Human Genetics, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, 6525 GA Nijmegen, The Netherlands
| | - Sylvia E. C. van Beersum
- Department of Human Genetics, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, 6525 GA Nijmegen, The Netherlands
| | - Marius Ueffing
- Division of Experimental Ophthalmology and Medical Proteome Center, Center of Ophthalmology, University of Tübingen, 72076 Tübingen, Germany
| | - Rob W. J. Collin
- Department of Human Genetics, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, 6525 GA Nijmegen, The Netherlands
| | - Qin Liu
- Department of Ophthalmology, Ocular Genomics Institute, Massachusetts Eye and Ear, Harvard Medical School, Boston, MA 02115, USA
| | - Karsten Boldt
- Division of Experimental Ophthalmology and Medical Proteome Center, Center of Ophthalmology, University of Tübingen, 72076 Tübingen, Germany
| | - Ronald Roepman
- Department of Human Genetics, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, 6525 GA Nijmegen, The Netherlands
- Correspondence:
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6
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Yadav RP, Boyd K, Artemyev NO. Molecular insights into the maturation of phosphodiesterase 6 by the specialized chaperone complex of HSP90 with AIPL1. J Biol Chem 2022; 298:101620. [PMID: 35065964 PMCID: PMC8857470 DOI: 10.1016/j.jbc.2022.101620] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2021] [Revised: 01/10/2022] [Accepted: 01/11/2022] [Indexed: 12/18/2022] Open
Abstract
Phosphodiesterase 6 (PDE6) is a key effector enzyme in vertebrate phototransduction, and its maturation and function are known to critically depend on a specialized chaperone, aryl hydrocarbon receptor-interacting protein-like 1 (AIPL1). Defects in PDE6 and AIPL1 underlie several severe retinal diseases, including retinitis pigmentosa and Leber congenital amaurosis. Here, we characterize the complex of AIPL1 with HSP90 and demonstrate its essential role in promoting the functional conformation of nascent PDE6. Our analysis suggests that AIPL1 preferentially binds to HSP90 in the closed state with a stoichiometry of 1:2, with the tetratricopeptide repeat domain and the tetratricopeptide repeat helix 7 extension of AIPL1 being the main contributors to the AIPL1/HSP90 interface. We demonstrate that mutations of these determinants markedly diminished both the affinity of AIPL1 for HSP90 and the ability of AIPL1 to cochaperone the maturation of PDE6 in a heterologous expression system. In addition, the FK506-binding protein (FKBP) domain of AIPL1 encloses a unique prenyl-binding site that anchors AIPL1 to posttranslational lipid modifications of PDE6. A mouse model with rod PDE6 lacking farnesylation of its PDE6A subunit revealed normal expression, trafficking, and signaling of the enzyme. Furthermore, AIPL1 was unexpectedly capable of inducing the maturation of unprenylated cone PDE6C, whereas mutant AIPL1 deficient in prenyl binding competently cochaperoned prenylated PDE6C. Thus, we conclude neither sequestration of the prenyl modifications is required for PDE6 maturation to proceed, nor is the FKBP-lipid interaction involved in the conformational switch of the enzyme into the functional state.
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Affiliation(s)
- Ravi P Yadav
- Department of Molecular Physiology and Biophysics, The University of Iowa Carver College of Medicine, Iowa City, Iowa, USA
| | - Kimberly Boyd
- Department of Molecular Physiology and Biophysics, The University of Iowa Carver College of Medicine, Iowa City, Iowa, USA
| | - Nikolai O Artemyev
- Department of Molecular Physiology and Biophysics, The University of Iowa Carver College of Medicine, Iowa City, Iowa, USA; Department of Ophthalmology and Visual Sciences, The University of Iowa Carver College of Medicine, Iowa City, Iowa, USA.
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7
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Kajtna J, Tsang SH, Koch SF. Late-stage rescue of visually guided behavior in the context of a significantly remodeled retinitis pigmentosa mouse model. Cell Mol Life Sci 2022; 79:148. [PMID: 35195763 PMCID: PMC8866266 DOI: 10.1007/s00018-022-04161-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2021] [Revised: 01/13/2022] [Accepted: 01/19/2022] [Indexed: 11/25/2022]
Abstract
Patients with progressive neurodegenerative disorder retinitis pigmentosa (RP) are diagnosed in the midst of ongoing retinal degeneration and remodeling. Here, we used a Pde6b-deficient RP gene therapy mouse model to test whether treatment at late disease stages can halt photoreceptor degeneration and degradative remodeling, while sustaining constructive remodeling and restoring function. We demonstrated that when fewer than 13% of rods remain, our genetic rescue halts photoreceptor degeneration, electroretinography (ERG) functional decline and inner retinal remodeling. In addition, in a water maze test, the performance of mice treated at 16 weeks of age or earlier was indistinguishable from wild type. In contrast, no efficacy was apparent in mice treated at 24 weeks of age, suggesting the photoreceptors had reached a point of no return. Further, remodeling in the retinal pigment epithelium (RPE) and retinal vasculature was not halted at 16 or 24 weeks of age, although there appeared to be some slowing of blood vessel degradation. These data suggest a novel working model in which restoration of clinically significant visual function requires only modest threshold numbers of resilient photoreceptors, halting of destructive remodeling and sustained constructive remodeling. These novel findings define the potential and limitations of RP treatment and suggest possible nonphotoreceptor targets for gene therapy optimization.
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Affiliation(s)
- Jacqueline Kajtna
- Department of Pharmacy, Center for Drug Research, Ludwig-Maximilians-Universität München, Munich, Germany
- Physiological Genomics, BioMedical Center, Ludwig-Maximilians-Universität München, Planegg/Martinsried, Germany
| | - Stephen H Tsang
- Jonas Children's Vision Care, Columbia Stem Cell Initiative, Departments of Ophthalmology, Pathology and Cell Biology, Institute of Human Nutrition, Vagelos College of Physicians and Surgeons, Columbia University, New York, NY, 10032, USA
- Edward S. Harkness Eye Institute, New York-Presbyterian Hospital, New York, NY, 10032, USA
| | - Susanne F Koch
- Department of Pharmacy, Center for Drug Research, Ludwig-Maximilians-Universität München, Munich, Germany.
- Physiological Genomics, BioMedical Center, Ludwig-Maximilians-Universität München, Planegg/Martinsried, Germany.
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8
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Zhang L, Chen C, Fu J, Lilley B, Berlinicke C, Hansen B, Ding D, Wang G, Wang T, Shou D, Ye Y, Mulligan T, Emmerich K, Saxena MT, Hall KR, Sharrock AV, Brandon C, Park H, Kam TI, Dawson VL, Dawson TM, Shim JS, Hanes J, Ji H, Liu JO, Qian J, Ackerley DF, Rohrer B, Zack DJ, Mumm JS. Large-scale phenotypic drug screen identifies neuroprotectants in zebrafish and mouse models of retinitis pigmentosa. eLife 2021; 10:e57245. [PMID: 34184634 PMCID: PMC8425951 DOI: 10.7554/elife.57245] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2020] [Accepted: 06/28/2021] [Indexed: 11/25/2022] Open
Abstract
Retinitis pigmentosa (RP) and associated inherited retinal diseases (IRDs) are caused by rod photoreceptor degeneration, necessitating therapeutics promoting rod photoreceptor survival. To address this, we tested compounds for neuroprotective effects in multiple zebrafish and mouse RP models, reasoning drugs effective across species and/or independent of disease mutation may translate better clinically. We first performed a large-scale phenotypic drug screen for compounds promoting rod cell survival in a larval zebrafish model of inducible RP. We tested 2934 compounds, mostly human-approved drugs, across six concentrations, resulting in 113 compounds being identified as hits. Secondary tests of 42 high-priority hits confirmed eleven lead candidates. Leads were then evaluated in a series of mouse RP models in an effort to identify compounds effective across species and RP models, that is, potential pan-disease therapeutics. Nine of 11 leads exhibited neuroprotective effects in mouse primary photoreceptor cultures, and three promoted photoreceptor survival in mouse rd1 retinal explants. Both shared and complementary mechanisms of action were implicated across leads. Shared target tests implicated parp1-dependent cell death in our zebrafish RP model. Complementation tests revealed enhanced and additive/synergistic neuroprotective effects of paired drug combinations in mouse photoreceptor cultures and zebrafish, respectively. These results highlight the value of cross-species/multi-model phenotypic drug discovery and suggest combinatorial drug therapies may provide enhanced therapeutic benefits for RP patients.
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Affiliation(s)
- Liyun Zhang
- Department of Ophthalmology, Wilmer Eye Institute, Johns Hopkins UniversityBaltimoreUnited States
| | - Conan Chen
- Department of Ophthalmology, Wilmer Eye Institute, Johns Hopkins UniversityBaltimoreUnited States
| | - Jie Fu
- The Center for Nanomedicine, Wilmer Eye Institute, Johns Hopkins UniversityBaltimoreUnited States
| | - Brendan Lilley
- Department of Ophthalmology, Wilmer Eye Institute, Johns Hopkins UniversityBaltimoreUnited States
| | - Cynthia Berlinicke
- Department of Ophthalmology, Wilmer Eye Institute, Johns Hopkins UniversityBaltimoreUnited States
| | - Baranda Hansen
- Department of Ophthalmology, Wilmer Eye Institute, Johns Hopkins UniversityBaltimoreUnited States
| | - Ding Ding
- Department of Biostatistics, Johns Hopkins UniversityBaltimoreUnited States
| | - Guohua Wang
- Department of Ophthalmology, Wilmer Eye Institute, Johns Hopkins UniversityBaltimoreUnited States
| | - Tao Wang
- The Center for Nanomedicine, Wilmer Eye Institute, Johns Hopkins UniversityBaltimoreUnited States
- School of Chemistry, Xuzhou College of Industrial TechnologyXuzhouChina
- College of Light Industry and Food Engineering, Nanjing Forestry UniversityNanjingChina
| | - Daniel Shou
- The Center for Nanomedicine, Wilmer Eye Institute, Johns Hopkins UniversityBaltimoreUnited States
| | - Ying Ye
- The Center for Nanomedicine, Wilmer Eye Institute, Johns Hopkins UniversityBaltimoreUnited States
| | - Timothy Mulligan
- Department of Ophthalmology, Wilmer Eye Institute, Johns Hopkins UniversityBaltimoreUnited States
| | - Kevin Emmerich
- Department of Ophthalmology, Wilmer Eye Institute, Johns Hopkins UniversityBaltimoreUnited States
- Department of Genetic Medicine, Johns Hopkins UniversityBaltimoreUnited States
| | - Meera T Saxena
- Department of Ophthalmology, Wilmer Eye Institute, Johns Hopkins UniversityBaltimoreUnited States
| | - Kelsi R Hall
- School of Biological Sciences, Victoria University of WellingtonWellingtonNew Zealand
| | - Abigail V Sharrock
- Department of Biostatistics, Johns Hopkins UniversityBaltimoreUnited States
- School of Biological Sciences, Victoria University of WellingtonWellingtonNew Zealand
| | - Carlene Brandon
- Department of Ophthalmology, Medical University of South CarolinaCharlestonUnited States
| | - Hyejin Park
- Department of Neurology, Johns Hopkins UniversityBaltimoreUnited States
| | - Tae-In Kam
- Department of Neurology, Johns Hopkins UniversityBaltimoreUnited States
- Institute for Cell Engineering, Johns Hopkins UniversityBaltimoreUnited States
| | - Valina L Dawson
- Department of Neurology, Johns Hopkins UniversityBaltimoreUnited States
- Institute for Cell Engineering, Johns Hopkins UniversityBaltimoreUnited States
- Department of Pharmacology and Molecular Sciences, Johns Hopkins UniversityBaltimoreUnited States
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins UniversityBaltimoreUnited States
| | - Ted M Dawson
- Department of Neurology, Johns Hopkins UniversityBaltimoreUnited States
- Institute for Cell Engineering, Johns Hopkins UniversityBaltimoreUnited States
- Department of Pharmacology and Molecular Sciences, Johns Hopkins UniversityBaltimoreUnited States
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins UniversityBaltimoreUnited States
| | - Joong Sup Shim
- Faculty of Health Sciences, University of Macau, TaipaMacauChina
| | - Justin Hanes
- Department of Ophthalmology, Wilmer Eye Institute, Johns Hopkins UniversityBaltimoreUnited States
- The Center for Nanomedicine, Wilmer Eye Institute, Johns Hopkins UniversityBaltimoreUnited States
| | - Hongkai Ji
- Department of Biostatistics, Johns Hopkins UniversityBaltimoreUnited States
| | - Jun O Liu
- Department of Pharmacology and Molecular Sciences, Johns Hopkins UniversityBaltimoreUnited States
- Department of Oncology, Johns Hopkins UniversityBaltimoreUnited States
| | - Jiang Qian
- Department of Ophthalmology, Wilmer Eye Institute, Johns Hopkins UniversityBaltimoreUnited States
| | - David F Ackerley
- School of Biological Sciences, Victoria University of WellingtonWellingtonNew Zealand
| | - Baerbel Rohrer
- Department of Ophthalmology, Medical University of South CarolinaCharlestonUnited States
| | - Donald J Zack
- Department of Ophthalmology, Wilmer Eye Institute, Johns Hopkins UniversityBaltimoreUnited States
- The Center for Nanomedicine, Wilmer Eye Institute, Johns Hopkins UniversityBaltimoreUnited States
- Department of Genetic Medicine, Johns Hopkins UniversityBaltimoreUnited States
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins UniversityBaltimoreUnited States
- Department of Molecular Biology and Genetics, Johns Hopkins UniversityBaltimoreUnited States
| | - Jeff S Mumm
- Department of Ophthalmology, Wilmer Eye Institute, Johns Hopkins UniversityBaltimoreUnited States
- The Center for Nanomedicine, Wilmer Eye Institute, Johns Hopkins UniversityBaltimoreUnited States
- Department of Genetic Medicine, Johns Hopkins UniversityBaltimoreUnited States
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins UniversityBaltimoreUnited States
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Wang J, Xiao H, Barwick S, Liu Y, Smith SB. Optimal timing for activation of sigma 1 receptor in the Pde6b rd10/J (rd10) mouse model of retinitis pigmentosa. Exp Eye Res 2021; 202:108397. [PMID: 33310057 PMCID: PMC7808329 DOI: 10.1016/j.exer.2020.108397] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2020] [Revised: 11/24/2020] [Accepted: 12/07/2020] [Indexed: 11/18/2022]
Abstract
Sigma 1 Receptor (Sig1R), a pluripotent modulator of cell survival, is a promising target for treatment of retinal degenerative diseases. Previously, we reported that administration of the high-affinity, high-specificity Sig1R ligand (+)-pentazocine, ((+)-PTZ) beginning at post-natal day 14 (P14) and continuing every other day improves visual acuity and delays loss of photoreceptor cells (PRCs) in the Pde6βrd10/J (rd10) mouse model of retinitis pigmentosa. Whether administration of (+)-PTZ, at time points concomitant with (P18) or following (P21, P24) onset of PRC death, would prove neuroprotective was investigated in this study. Rd10 mice were administered (+)-PTZ intraperitoneally [0.5 mg/kg], starting at either P14, P18, P21 or P24. Injections continued every other day through P42. Visual acuity was assessed using the optokinetic tracking response (OKR). Rd10 mice treated with (+)-PTZ beginning at P14 retained visual acuity for the duration of the study (~0.33 c/d at P21, ~0.38 c/d at P28, ~0.32 c/d at P35, ~0.32 c/d at P42), whereas mice injected beginning at P18, P21, P24 showed a decline in acuity when tested at P35 and P42. Their acuity was only slightly better than rd10-non-treated mice. Electrophysiologic function was assessed using scotopic and photopic electroretinography (ERG) to assess rod and cone function, respectively. Photopic a- and b-wave amplitudes were significantly greater in rd10 mice treated with (+)-PTZ beginning at P14 compared with non-treated mice and those in the later-onset (+)-PTZ injection groups. Retinal architecture was visualized in living mice using spectral domain-optical coherence tomography (SD-OCT) allowing measurement of the total retinal thickness, the inner retina and the outer retina (the area most affected in rd10 mice). The outer retina measured ~35 μm in rd10 mice treated with (+)-PTZ beginning at P14, which was significantly greater than mice in the later-onset (+)-PTZ injection groups (~25 μm) and non-treated rd10 mice (~25 μm). Following the visual function studies performed in the living mice, eyes were harvested at P42 for histologic analysis. While the inner retina was largely intact in all (+)-PTZ-injection groups, there was a marked reduction in the outer retina of non-treated rd10 mice (e.g. in the outer nuclear layer there were ~10 PRCs/100 μm retinal length). The rd10 mice treated with (+)-PTZ beginning at P14 had ~20 PRCs/100 μm retinal length, whereas the mice in groups beginning P18, P21 and P24 had ~16 PRCs/100 μm retinal length. In conclusion, the data indicate that delaying (+)-PTZ injection past the onset of PRC death in rd10 mice - even by a few days - can negatively impact the long-term preservation of retinal function. Our findings suggest that optimizing the administration of Sig1R ligands is critical for retinal neuroprotection.
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Affiliation(s)
- Jing Wang
- Department of Cellular Biology and Anatomy, Medical College of Georgia at Augusta University, Augusta, GA, United States; James and Jean Culver Vision Discovery Institute, Augusta University, Augusta, GA, United States
| | - Haiyan Xiao
- Department of Cellular Biology and Anatomy, Medical College of Georgia at Augusta University, Augusta, GA, United States; James and Jean Culver Vision Discovery Institute, Augusta University, Augusta, GA, United States
| | - Shannon Barwick
- Department of Cellular Biology and Anatomy, Medical College of Georgia at Augusta University, Augusta, GA, United States; James and Jean Culver Vision Discovery Institute, Augusta University, Augusta, GA, United States
| | - Yutao Liu
- Department of Cellular Biology and Anatomy, Medical College of Georgia at Augusta University, Augusta, GA, United States; James and Jean Culver Vision Discovery Institute, Augusta University, Augusta, GA, United States
| | - Sylvia B Smith
- Department of Cellular Biology and Anatomy, Medical College of Georgia at Augusta University, Augusta, GA, United States; James and Jean Culver Vision Discovery Institute, Augusta University, Augusta, GA, United States; Department of Ophthalmology, Medical College of Georgia at Augusta University, Augusta, GA, United States.
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10
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Gupta R, Liu Y, Wang H, Nordyke CT, Puterbaugh RZ, Cui W, Varga K, Chu F, Ke H, Vashisth H, Cote RH. Structural Analysis of the Regulatory GAF Domains of cGMP Phosphodiesterase Elucidates the Allosteric Communication Pathway. J Mol Biol 2020; 432:5765-5783. [PMID: 32898583 PMCID: PMC7572642 DOI: 10.1016/j.jmb.2020.08.026] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Revised: 08/28/2020] [Accepted: 08/31/2020] [Indexed: 12/26/2022]
Abstract
Regulation of photoreceptor phosphodiesterase (PDE6) activity is responsible for the speed, sensitivity, and recovery of the photoresponse during visual signaling in vertebrate photoreceptor cells. It is hypothesized that physiological differences in the light responsiveness of rods and cones may result in part from differences in the structure and regulation of the distinct isoforms of rod and cone PDE6. Although rod and cone PDE6 catalytic subunits share a similar domain organization consisting of tandem GAF domains (GAFa and GAFb) and a catalytic domain, cone PDE6 is a homodimer whereas rod PDE6 consists of two homologous catalytic subunits. Here we provide the x-ray crystal structure of cone GAFab regulatory domain solved at 3.3 Å resolution, in conjunction with chemical cross-linking and mass spectrometric analysis of conformational changes to GAFab induced upon binding of cGMP and the PDE6 inhibitory γ-subunit (Pγ). Ligand-induced changes in cross-linked residues implicate multiple conformational changes in the GAFa and GAFb domains in forming an allosteric communication network. Molecular dynamics simulations of cone GAFab revealed differences in conformational dynamics of the two subunits forming the homodimer and allosteric perturbations on cGMP binding. Cross-linking of Pγ to GAFab in conjunction with solution NMR spectroscopy of isotopically labeled Pγ identified the central polycationic region of Pγ interacting with the GAFb domain. These results provide a mechanistic basis for developing allosteric activators of PDE6 with therapeutic implications for halting the progression of several retinal degenerative diseases.
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Affiliation(s)
- Richa Gupta
- Department of Molecular, Cellular and Biomedical Sciences, University of New Hampshire, 46 College Rd., Durham, NH 03824, USA
| | - Yong Liu
- Department of Chemical Engineering, University of New Hampshire, 33 Academic Way, Durham, NH 03824, USA
| | - Huanchen Wang
- Signal Transduction Laboratory, NIEHS/NIH, 111 T.W. Alexander Drive, Research Triangle Park, NC 27709, USA
| | - Christopher T Nordyke
- Department of Molecular, Cellular and Biomedical Sciences, University of New Hampshire, 46 College Rd., Durham, NH 03824, USA
| | - Ryan Z Puterbaugh
- Department of Molecular, Cellular and Biomedical Sciences, University of New Hampshire, 46 College Rd., Durham, NH 03824, USA
| | - Wenjun Cui
- Department of Biochemistry and Biophysics and Lineberger Comprehensive Cancer Center, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Krisztina Varga
- Department of Molecular, Cellular and Biomedical Sciences, University of New Hampshire, 46 College Rd., Durham, NH 03824, USA
| | - Feixia Chu
- Department of Molecular, Cellular and Biomedical Sciences, University of New Hampshire, 46 College Rd., Durham, NH 03824, USA
| | - Hengming Ke
- Department of Biochemistry and Biophysics and Lineberger Comprehensive Cancer Center, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Harish Vashisth
- Department of Chemical Engineering, University of New Hampshire, 33 Academic Way, Durham, NH 03824, USA
| | - Rick H Cote
- Department of Molecular, Cellular and Biomedical Sciences, University of New Hampshire, 46 College Rd., Durham, NH 03824, USA.
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11
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Georgiou M, Robson AG, Singh N, Pontikos N, Kane T, Hirji N, Ripamonti C, Rotsos T, Dubra A, Kalitzeos A, Webster AR, Carroll J, Michaelides M. Deep Phenotyping of PDE6C-Associated Achromatopsia. Invest Ophthalmol Vis Sci 2019; 60:5112-5123. [PMID: 31826238 PMCID: PMC6905659 DOI: 10.1167/iovs.19-27761] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2019] [Accepted: 10/23/2019] [Indexed: 11/29/2022] Open
Abstract
Purpose To perform deep phenotyping of subjects with PDE6C achromatopsia and examine disease natural history. Methods Eight subjects with disease-causing variants in PDE6C were assessed in detail, including clinical phenotype, best-corrected visual acuity, fundus autofluorescence, and optical coherence tomography. Six subjects also had confocal and nonconfocal adaptive optics scanning light ophthalmoscopy, axial length, international standard pattern and full-field electroretinography (ERG), short-wavelength flash (S-cone) ERGs, and color vision testing. Results All subjects presented with early-onset nystagmus, decreased best-corrected visual acuity, light sensitivity, and severe color vision loss, and five of them had high myopia. We identified three novel disease-causing variants and provide phenotype data associated with nine variants for the first time. No subjects had foveal hypoplasia or residual ellipsoid zone (EZ) at the foveal center; one had an absent EZ, three had a hyporeflective zone, and four had outer retinal atrophy. The mean width of the central EZ lesion on optical coherence tomography at baseline was 1923 μm. The mean annual increase in EZ lesion size was 48.3 μm. Fundus autofluorescence revealed a central hypoautofluorescence with a surrounding ring of increased signal (n = 5). The mean hypoautofluorescent area at baseline was 3.33 mm2 and increased in size by a mean of 0.13 mm2/year. Nonconfocal adaptive optics scanning light ophthalmoscopy revealed residual foveal cones in only one of two cases. Full-field ERGs were consistent with severe generalized cone system dysfunction but with relative preservation of S-cone sensitivity. Conclusions PDE6C retinopathy is a severe cone dysfunction syndrome often presenting as typical achromatopsia but without foveal hypoplasia. Myopia and slowly progressive maculopathy are common features. There are few (if any) residual foveal cones for intervention in older adults.
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Affiliation(s)
- Michalis Georgiou
- UCL Institute of Ophthalmology, University College London, London, United Kingdom
- Moorfields Eye Hospital NHS Foundation Trust, City Road, London, United Kingdom
| | - Anthony G. Robson
- UCL Institute of Ophthalmology, University College London, London, United Kingdom
- Moorfields Eye Hospital NHS Foundation Trust, City Road, London, United Kingdom
| | - Navjit Singh
- UCL Institute of Ophthalmology, University College London, London, United Kingdom
- Moorfields Eye Hospital NHS Foundation Trust, City Road, London, United Kingdom
| | - Nikolas Pontikos
- UCL Institute of Ophthalmology, University College London, London, United Kingdom
- Moorfields Eye Hospital NHS Foundation Trust, City Road, London, United Kingdom
| | - Thomas Kane
- UCL Institute of Ophthalmology, University College London, London, United Kingdom
- Moorfields Eye Hospital NHS Foundation Trust, City Road, London, United Kingdom
| | - Nashila Hirji
- UCL Institute of Ophthalmology, University College London, London, United Kingdom
- Moorfields Eye Hospital NHS Foundation Trust, City Road, London, United Kingdom
| | | | - Tryfon Rotsos
- First Division of Ophthalmology, National and Kapodistrian University of Athens, General Hospital of Athens, Athens, Greece
| | - Alfredo Dubra
- Department of Ophthalmology, Stanford University, Palo Alto, California, United States
| | - Angelos Kalitzeos
- UCL Institute of Ophthalmology, University College London, London, United Kingdom
- Moorfields Eye Hospital NHS Foundation Trust, City Road, London, United Kingdom
| | - Andrew R. Webster
- UCL Institute of Ophthalmology, University College London, London, United Kingdom
- Moorfields Eye Hospital NHS Foundation Trust, City Road, London, United Kingdom
| | - Joseph Carroll
- Department of Ophthalmology & Visual Sciences, Medical College of Wisconsin, Milwaukee, Wisconsin, United States
| | - Michel Michaelides
- UCL Institute of Ophthalmology, University College London, London, United Kingdom
- Moorfields Eye Hospital NHS Foundation Trust, City Road, London, United Kingdom
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12
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Domingo-Prim J, Abad-Morales V, Riera M, Navarro R, Corcostegui B, Pomares E. Generation of an induced pluripotent stem cell line (FRIMOi007-A) derived from an incomplete achromatopsia patient carrying a novel homozygous mutation in PDE6C gene. Stem Cell Res 2019; 40:101569. [PMID: 31520890 DOI: 10.1016/j.scr.2019.101569] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/21/2019] [Revised: 08/19/2019] [Accepted: 09/03/2019] [Indexed: 11/17/2022] Open
Abstract
Incomplete achromatopsia (ACHM) is a disorder in which there is function defect of cone photoreceptors in the retina and individuals with such disease retain residual color vision. Here, we have generated an induced pluripotent stem cell (iPSC) line carrying a homozygous mutation in the PDE6C gene, already related with this vision disorder. Skin fibroblasts from a patient with incomplete ACHM were reprogrammed to iPSCs by the non-integrative Sendai-virus method. Finally, the iPSC line has been characterized expressing the pluripotency markers and being capable to differentiate to endoderm, mesoderm and ectoderm in vitro.
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Affiliation(s)
- Judit Domingo-Prim
- Fundació de Recerca de l'Institut de Microcirurgia Ocular, Barcelona, Spain; Departament de Genètica, Institut de Microcirurgia Ocular (IMO), Barcelona, Spain
| | - Víctor Abad-Morales
- Fundació de Recerca de l'Institut de Microcirurgia Ocular, Barcelona, Spain; Departament de Genètica, Institut de Microcirurgia Ocular (IMO), Barcelona, Spain
| | - Marina Riera
- Fundació de Recerca de l'Institut de Microcirurgia Ocular, Barcelona, Spain; Departament de Genètica, Institut de Microcirurgia Ocular (IMO), Barcelona, Spain
| | - Rafael Navarro
- Fundació de Recerca de l'Institut de Microcirurgia Ocular, Barcelona, Spain; Departament de Retina, Institut de Microcirurgia Ocular (IMO), Barcelona, Spain
| | - Borja Corcostegui
- Fundació de Recerca de l'Institut de Microcirurgia Ocular, Barcelona, Spain; Departament de Retina, Institut de Microcirurgia Ocular (IMO), Barcelona, Spain
| | - Esther Pomares
- Fundació de Recerca de l'Institut de Microcirurgia Ocular, Barcelona, Spain; Departament de Genètica, Institut de Microcirurgia Ocular (IMO), Barcelona, Spain.
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13
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Plotnikov D, Shah RL, Rodrigues JN, Cumberland PM, Rahi JS, Hysi PG, Atan D, Williams C, Guggenheim JA. A commonly occurring genetic variant within the NPLOC4-TSPAN10-PDE6G gene cluster is associated with the risk of strabismus. Hum Genet 2019; 138:723-737. [PMID: 31073882 PMCID: PMC6611893 DOI: 10.1007/s00439-019-02022-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2018] [Accepted: 04/20/2019] [Indexed: 12/31/2022]
Abstract
Strabismus refers to an abnormal alignment of the eyes leading to the loss of central binocular vision. Concomitant strabismus occurs when the angle of deviation is constant in all positions of gaze and often manifests in early childhood when it is considered to be a neurodevelopmental disorder of the visual system. As such, it is inherited as a complex genetic trait, affecting 2-4% of the population. A genome-wide association study (GWAS) for self-reported strabismus (1345 cases and 65,349 controls from UK Biobank) revealed a single genome-wide significant locus on chromosome 17q25. Approximately 20 variants across the NPLOC4-TSPAN10-PDE6G gene cluster and in almost perfect linkage disequilibrium (LD) were most strongly associated (lead variant: rs75078292, OR = 1.26, p = 2.24E-08). A recessive model provided a better fit to the data than an additive model. Association with strabismus was independent of refractive error, and the degree of association with strabismus was minimally attenuated after adjustment for amblyopia. The association with strabismus was replicated in an independent cohort of clinician-diagnosed children aged 7 years old (116 cases and 5084 controls; OR = 1.85, p = 0.009). The associated variants included 2 strong candidate causal variants predicted to have functional effects: rs6420484, which substitutes tyrosine for a conserved cysteine (C177Y) in the TSPAN10 gene, and a 4-bp deletion variant, rs397693108, predicted to cause a frameshift in TSPAN10. The population-attributable risk for the locus was approximately 8.4%, indicating an important role in conferring susceptibility to strabismus.
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Affiliation(s)
- Denis Plotnikov
- School of Optometry and Vision Sciences, Cardiff University, Cardiff, CF24 4HQ, UK
| | - Rupal L Shah
- School of Optometry and Vision Sciences, Cardiff University, Cardiff, CF24 4HQ, UK
| | - Jamille N Rodrigues
- Population Health Sciences, Bristol Medical School, University of Bristol, 1-5 Whiteladies Road, Bristol, BS8 1NU, UK
| | - Phillippa M Cumberland
- Life Course Epidemiology and Biostatistics Section, Institute of Child Health, University College London, London, WC1N 1EH, UK
- Ulverscroft Vision Research Group, University College London Institute of Child Health, London, WC1N 1EH, UK
| | - Jugnoo S Rahi
- Life Course Epidemiology and Biostatistics Section, Institute of Child Health, University College London, London, WC1N 1EH, UK
- Ulverscroft Vision Research Group, University College London Institute of Child Health, London, WC1N 1EH, UK
- University College London Great Ormond Street Institute of Child Health, London, WC1N 3JH, UK
- National Institute for Health Research Biomedical Research Centre at Moorfields Eye Hospital NHS Foundation Trust and University College London Institute of Ophthalmology, London, WC1E 6BT, UK
| | - Pirro G Hysi
- Department of Twin Research and Genetic Epidemiology, King's College London, St Thomas' Hospital, London, SE1 7EH, UK
| | - Denize Atan
- Population Health Sciences, Bristol Medical School, University of Bristol, 1-5 Whiteladies Road, Bristol, BS8 1NU, UK
| | - Cathy Williams
- Population Health Sciences, Bristol Medical School, University of Bristol, 1-5 Whiteladies Road, Bristol, BS8 1NU, UK.
| | - Jeremy A Guggenheim
- School of Optometry and Vision Sciences, Cardiff University, Cardiff, CF24 4HQ, UK.
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14
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Du J, An J, Linton JD, Wang Y, Hurley JB. How Excessive cGMP Impacts Metabolic Proteins in Retinas at the Onset of Degeneration. Adv Exp Med Biol 2019; 1074:289-295. [PMID: 29721955 DOI: 10.1007/978-3-319-75402-4_35] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Aryl-hydrocarbon receptor interacting protein-like 1 (AIPL1) is essential to stabilize cGMP phosphodiesterase 6 (PDE6) in rod photoreceptors. Mutation of AIPL1 leads to loss of PDE6, accumulation of intracellular cGMP, and rapid degeneration of rods. To understand the metabolic basis for the photoreceptor degeneration caused by excessive cGMP, we performed proteomics and phosphoproteomics analyses on retinas from AIPL1-/- mice at the onset of rod cell death. AIPL1-/- retinas have about 18 times less than normal PDE6a and no detectable PDE6b. We identified twelve other proteins and thirty-nine phosphorylated proteins related to cell metabolism that are significantly altered preceding the massive degeneration of rods. They include transporters, kinases, phosphatases, transferases, and proteins involved in mitochondrial bioenergetics and metabolism of glucose, lipids, amino acids, nucleotides, and RNA. In AIPLI-/- retinas mTOR and proteins involved in mitochondrial energy production and lipid synthesis are more dephosphorylated, but glycolysis proteins and proteins involved in leucine catabolism are more phosphorylated than in normal retinas. Our findings indicate that elevating cGMP rewires cellular metabolism prior to photoreceptor degeneration and that targeting metabolism may be a productive strategy to prevent or slow retinal degeneration.
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Affiliation(s)
- Jianhai Du
- Departments of Ophthalmology, and Biochemistry, West Virginia University, Morgantown, WV, USA
- Department of Ophthalmology, University of Washington, Seattle, WA, USA
| | - Jie An
- Department of Medicine, University of Washington, Seattle, WA, USA
| | - Jonathan D Linton
- Department of Ophthalmology, University of Washington, Seattle, WA, USA
| | - Yekai Wang
- Departments of Ophthalmology, and Biochemistry, West Virginia University, Morgantown, WV, USA
| | - James B Hurley
- Department of Ophthalmology, University of Washington, Seattle, WA, USA.
- Department of Biochemistry, University of Washington, Seattle, WA, USA.
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15
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Pattis JG, Kamal S, Li B, May ER. Catalytic Domains of Phosphodiesterase 5, 6, and 5/6 Chimera Display Differential Dynamics and Ligand Dissociation Energy Barriers. J Phys Chem B 2019; 123:825-835. [PMID: 30616346 PMCID: PMC6502234 DOI: 10.1021/acs.jpcb.8b11370] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The enzyme phosphodiesterase 6 (PDE6) is a critical component of the visual signaling pathway and functions to convert cGMP to GMP. The ability of PDE6 to affect cellular cGMP levels leads to deactivation of cGMP-gated ion channels in both rod and cone cells. PDE6 has been difficult to structurally characterize experimentally, though the structures of the closely related PDE5 and a PDE5/6 chimera have been determined by X-ray crystallography. In this work, we employ a computational approach to study the dynamics of the catalytic domains of PDE6, PDE5, and the PDE5/6 chimera. Through equilibrium molecular dynamics (MD) simulations, we identify a region of PDE6 (α12) to be correlated to distal regions of the enzyme (H- and M-loops), which surround the catalytic center. These correlations are not observed for PDE5, and we speculate that these unique motions in PDE6 may relate to the high catalytic efficiency of PDE6 and the requirement for an endogenous inhibitory subunit (Pγ). We further investigate the ligand binding pathways and energetics by enhanced sampling simulations (metadynamics) using the inhibitor sildenafil and GMP. The energetics and pathways of ligand binding are consistent with the high efficiency of PDE6 and further implicate the α12 region as an important regulatory element for PDE6 functional dynamics.
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Affiliation(s)
| | | | - Boyang Li
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, CT 06269
| | - Eric R. May
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, CT 06269
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16
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Ying G, Boldt K, Ueffing M, Gerstner CD, Frederick JM, Baehr W. The small GTPase RAB28 is required for phagocytosis of cone outer segments by the murine retinal pigmented epithelium. J Biol Chem 2018; 293:17546-17558. [PMID: 30228185 PMCID: PMC6231133 DOI: 10.1074/jbc.ra118.005484] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2018] [Revised: 09/12/2018] [Indexed: 12/19/2022] Open
Abstract
RAB28, a member of the RAS oncogene family, is a ubiquitous, farnesylated, small GTPase of unknown function present in photoreceptors and the retinal pigmented epithelium (RPE). Nonsense mutations of the human RAB28 gene cause recessive cone-rod dystrophy 18 (CRD18), characterized by macular hyperpigmentation, progressive loss of visual acuity, RPE atrophy, and severely attenuated cone and rod electroretinography (ERG) responses. In an attempt to elucidate the disease-causing mechanism, we generated Rab28-/- mice by deleting exon 3 and truncating RAB28 after exon 2. We found that Rab28-/- mice recapitulate features of the human dystrophy (i.e. they exhibited reduced cone and rod ERG responses and progressive retina degeneration). Cones of Rab28-/- mice extended their outer segments (OSs) to the RPE apical processes and formed enlarged, balloon-like distal tips before undergoing degeneration. The visual pigment content of WT and Rab28-/- cones was comparable before the onset of degeneration. Cone phagosomes were almost absent in Rab28-/- mice, whereas rod phagosomes displayed normal levels. A protein-protein interaction screen identified several RAB28-interacting proteins, including the prenyl-binding protein phosphodiesterase 6 δ-subunit (PDE6D) and voltage-gated potassium channel subfamily J member 13 (KCNJ13) present in the RPE apical processes. Of note, the loss of PDE6D prevented delivery of RAB28 to OSs. Taken together, these findings reveal that RAB28 is required for shedding and phagocytosis of cone OS discs.
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Affiliation(s)
- Guoxin Ying
- From the Department of Ophthalmology and Visual Sciences, University of Utah Health Science Center, Salt Lake City, Utah 84132,
| | - Karsten Boldt
- the Institute for Ophthalmic Research, Centre for Ophthalmology, University of Tübingen, Elfriede-Aulhorn-Strasse 7, D-72076 Tübingen, Germany, and
| | - Marius Ueffing
- the Institute for Ophthalmic Research, Centre for Ophthalmology, University of Tübingen, Elfriede-Aulhorn-Strasse 7, D-72076 Tübingen, Germany, and
| | - Cecilia D Gerstner
- From the Department of Ophthalmology and Visual Sciences, University of Utah Health Science Center, Salt Lake City, Utah 84132
| | - Jeanne M Frederick
- From the Department of Ophthalmology and Visual Sciences, University of Utah Health Science Center, Salt Lake City, Utah 84132
| | - Wolfgang Baehr
- From the Department of Ophthalmology and Visual Sciences, University of Utah Health Science Center, Salt Lake City, Utah 84132,
- the Departments of Neurobiology and Anatomy and
- Biology, University of Utah, Salt Lake City, Utah 84112
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17
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Cruz-Nova P, Schnoor M, Correa-Basurto J, Bello M, Briseño-Diaz P, Rojo-Domínguez A, Ortiz-Mendoza CM, Guerrero-Aguirre J, García-Vázquez FJ, Hernández-Rivas R, Thompson-Bonilla MDR, Vargas M. The small organic molecule C19 binds and strengthens the KRAS4b-PDEδ complex and inhibits growth of colorectal cancer cells in vitro and in vivo. BMC Cancer 2018; 18:1056. [PMID: 30382908 PMCID: PMC6211466 DOI: 10.1186/s12885-018-4968-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2018] [Accepted: 10/17/2018] [Indexed: 11/26/2022] Open
Abstract
BACKGROUND Colorectal cancer is the third most common cancer worldwide; and in 40% of all cases, KRAS4b-activating mutations occur. KRAS4b is transported by phosphodiesterase-6δ (PDEδ) to the plasma membrane, where it gets activated. PDEδ downregulation prevents redistribution and activation of KRAS4b. Thus, targeting the KRAS4b-PDEδ complex is a treatment strategy for colorectal cancer. METHODS Using docking and molecular dynamics simulations coupled to molecular mechanics, the generalized born model and solvent accessibility (MMGBSA) approach to explore protein-ligand stability, we found that the compound ((2S)-N-(2,5-diclorofenil)-2-[(3,4-dimetoxifenil)metilamino]-propanamida), termed C19, bound and stabilized the KRAS4b-PDEδ complex. We investigated whether C19 decreases the viability and proliferation of colorectal cancer cells, in addition to knowing the type of cell death that it causes and if C19 decreases the activation of KRAS4b and their effectors. RESULTS C19 showed high cytotoxicity in the colorectal cancer cell lines HCT116 and LoVo, with a stronger effect in KRAS-dependent LoVo cells. Importantly, C19 significantly decreased tumor size in a xenograft mouse model and showed lower side effects than 5-fluorouracil that is currently used as colorectal cancer treatment. CONCLUSIONS Mechanistically, the cytotoxic effect was due to increased apoptosis of tumor cells and decreased phosphorylation of Erk and Akt. Therefore, our results suggest that C19 may serve as a promising new treatment for colorectal cancer.
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Affiliation(s)
- Pedro Cruz-Nova
- Departamento de Biomedicina Molecular, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional (CINVESTAV-IPN), Av. I.P.N, 2508, México City, Mexico
| | - Michael Schnoor
- Departamento de Biomedicina Molecular, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional (CINVESTAV-IPN), Av. I.P.N, 2508, México City, Mexico
| | - José Correa-Basurto
- Laboratorio de Modelado Molecular y diseño de fármacos de la Escuela Superior de Medicina, Instituto Politécnico Nacional, México City, Mexico
| | - Martiniano Bello
- Laboratorio de Modelado Molecular y diseño de fármacos de la Escuela Superior de Medicina, Instituto Politécnico Nacional, México City, Mexico
| | - Paola Briseño-Diaz
- Departamento de Biomedicina Molecular, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional (CINVESTAV-IPN), Av. I.P.N, 2508, México City, Mexico
| | - Arturo Rojo-Domínguez
- Departamento de Ciencias Naturales, Universidad Autónoma Metropolitana Unidad Cuajimalpa, México City, Mexico
| | - Carlos M Ortiz-Mendoza
- Investigación Biomédica y Traslacional, Laboratorio de Medicina Genómica, Hospital 1° de Octubre, ISSSTE, México City, Mexico
| | - Jorge Guerrero-Aguirre
- Investigación Biomédica y Traslacional, Laboratorio de Medicina Genómica, Hospital 1° de Octubre, ISSSTE, México City, Mexico
| | | | - Rosaura Hernández-Rivas
- Departamento de Biomedicina Molecular, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional (CINVESTAV-IPN), Av. I.P.N, 2508, México City, Mexico
| | | | - Miguel Vargas
- Departamento de Biomedicina Molecular, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional (CINVESTAV-IPN), Av. I.P.N, 2508, México City, Mexico.
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18
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Qureshi BM, Behrmann E, Schöneberg J, Loerke J, Bürger J, Mielke T, Giesebrecht J, Noé F, Lamb TD, Hofmann KP, Spahn CMT, Heck M. It takes two transducins to activate the cGMP-phosphodiesterase 6 in retinal rods. Open Biol 2018; 8:180075. [PMID: 30068566 PMCID: PMC6119865 DOI: 10.1098/rsob.180075] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2018] [Accepted: 07/06/2018] [Indexed: 12/21/2022] Open
Abstract
Among cyclic nucleotide phosphodiesterases (PDEs), PDE6 is unique in serving as an effector enzyme in G protein-coupled signal transduction. In retinal rods and cones, PDE6 is membrane-bound and activated to hydrolyse its substrate, cGMP, by binding of two active G protein α-subunits (Gα*). To investigate the activation mechanism of mammalian rod PDE6, we have collected functional and structural data, and analysed them by reaction-diffusion simulations. Gα* titration of membrane-bound PDE6 reveals a strong functional asymmetry of the enzyme with respect to the affinity of Gα* for its two binding sites on membrane-bound PDE6 and the enzymatic activity of the intermediary 1 : 1 Gα* · PDE6 complex. Employing cGMP and its 8-bromo analogue as substrates, we find that Gα* · PDE6 forms with high affinity but has virtually no cGMP hydrolytic activity. To fully activate PDE6, it takes a second copy of Gα* which binds with lower affinity, forming Gα* · PDE6 · Gα*. Reaction-diffusion simulations show that the functional asymmetry of membrane-bound PDE6 constitutes a coincidence switch and explains the lack of G protein-related noise in visual signal transduction. The high local concentration of Gα* generated by a light-activated rhodopsin molecule efficiently activates PDE6, whereas the low density of spontaneously activated Gα* fails to activate the effector enzyme.
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Affiliation(s)
- Bilal M Qureshi
- Institut für Medizinische Physik und Biophysik, Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany
| | - Elmar Behrmann
- Institut für Medizinische Physik und Biophysik, Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany
| | - Johannes Schöneberg
- Department of Mathematics, Computer Science and Bioinformatics, Freie Universität Berlin, Berlin, Germany
| | - Justus Loerke
- Institut für Medizinische Physik und Biophysik, Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany
| | - Jörg Bürger
- Institut für Medizinische Physik und Biophysik, Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany
| | - Thorsten Mielke
- Institut für Medizinische Physik und Biophysik, Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany
- Microscopy and Cryo Electron Microscopy Group, Max-Planck Institut für Molekulare Genetik, Berlin, Germany
| | - Jan Giesebrecht
- Institut für Medizinische Physik und Biophysik, Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany
| | - Frank Noé
- Department of Mathematics, Computer Science and Bioinformatics, Freie Universität Berlin, Berlin, Germany
| | - Trevor D Lamb
- Eccles Institute of Neuroscience, John Curtin School of Medical Research, Australian National University, Canberra, Australian Capital Territory 2600, Australia
| | - Klaus Peter Hofmann
- Institut für Medizinische Physik und Biophysik, Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany
- Zentrum für Biophysik und Bioinformatik, Humboldt-Universität zu Berlin, Berlin, Germany
| | - Christian M T Spahn
- Institut für Medizinische Physik und Biophysik, Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany
| | - Martin Heck
- Institut für Medizinische Physik und Biophysik, Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany
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19
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Hossain RA, Dunham NR, Enke RA, Berndsen CE. In silico modeling of epigenetic-induced changes in photoreceptor cis-regulatory elements. Mol Vis 2018; 24:218-230. [PMID: 29563767 PMCID: PMC5851326] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2017] [Accepted: 03/12/2018] [Indexed: 10/30/2022] Open
Abstract
Purpose DNA methylation is a well-characterized epigenetic repressor of mRNA transcription in many plant and vertebrate systems. However, the mechanism of this repression is not fully understood. The process of transcription is controlled by proteins that regulate recruitment and activity of RNA polymerase by binding to specific cis-regulatory sequences. Cone-rod homeobox (CRX) is a well-characterized mammalian transcription factor that controls photoreceptor cell-specific gene expression. Although much is known about the functions and DNA binding specificity of CRX, little is known about how DNA methylation modulates CRX binding affinity to genomic cis-regulatory elements. Methods We used bisulfite pyrosequencing of human ocular tissues to measure DNA methylation levels of the regulatory regions of RHO, PDE6B, PAX6, and LINE1 retrotransposon repeats. To describe the molecular mechanism of repression, we used molecular modeling to illustrate the effect of DNA methylation on human RHO regulatory sequences. Results In this study, we demonstrate an inverse correlation between DNA methylation in regulatory regions adjacent to the human RHO and PDE6B genes and their subsequent transcription in human ocular tissues. Docking of CRX to the DNA models shows that CRX interacts with the grooves of these sequences, suggesting changes in groove structure could regulate binding. Molecular dynamics simulations of the RHO promoter and enhancer regions show changes in the flexibility and groove width upon epigenetic modification. Models also demonstrate changes in the local dynamics of CRX binding sites within RHO regulatory sequences which may account for the repression of CRX-dependent transcription. Conclusions Collectively, these data demonstrate epigenetic regulation of CRX binding sites in human retinal tissue and provide insight into the mechanism of this mode of epigenetic regulation to be tested in future experiments.
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Affiliation(s)
- Reafa A. Hossain
- Department of Biology, James Madison University, Harrisonburg, VA
| | | | - Raymond A. Enke
- Department of Biology, James Madison University, Harrisonburg, VA
- Center for Genome and Metagenome Studies, James Madison University, Harrisonburg, VA
| | - Christopher E. Berndsen
- Department of Chemistry and Biochemistry, James Madison University, Harrisonburg, VA
- Center for Genome and Metagenome Studies, James Madison University, Harrisonburg, VA
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20
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Gopalakrishna KN, Boyd K, Artemyev NO. Mechanisms of mutant PDE6 proteins underlying retinal diseases. Cell Signal 2017; 37:74-80. [PMID: 28583373 DOI: 10.1016/j.cellsig.2017.06.002] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2017] [Revised: 05/30/2017] [Accepted: 06/01/2017] [Indexed: 12/15/2022]
Abstract
Mutations in PDE6 genes encoding the effector enzymes in rods and cones underlie severe retinal diseases including retinitis pigmentosa (RP), autosomal dominant congenital stationary night blindness (adCSNB), and achromatopsia (ACHM). Here we examined a spectrum of pathogenic missense mutations in PDE6 using the system based on co-expression of cone PDE6C with its specialized chaperone AIPL1 and the regulatory Pγ subunit as a potent co-chaperone. We uncovered two mechanisms of PDE6C mutations underlying ACHM: (a) folding defects leading to expression of catalytically inactive proteins and (b) markedly diminished ability of Pγ to co-chaperone mutant PDE6C proteins thereby dramatically reducing the levels of functional enzyme. The mechanism of the Rambusch adCSNB associated with the H258N substitution in PDE6B was probed through the analysis of the model mutant PDE6C-H262N. We identified two interrelated deficits of PDE6C-H262N: disruption of the inhibitory interaction of Pγ with mutant PDE6C that markedly reduced the ability of Pγ to augment the enzyme folding. Thus, we conclude that the Rambusch adCSNB is triggered by low levels of the constitutively active PDE6. Finally, we examined PDE6C-L858V, which models PDE6B-L854V, an RP-linked mutation that alters the protein isoprenyl modification. This analysis suggests that the type of prenyl modifications does not impact the folding of PDE6, but it modulates the enzyme affinity for its trafficking partner PDE6D. Hence, the pathogenicity of PDE6B-L854V likely arises from its trafficking deficiency. Taken together, our results demonstrate the effectiveness of the PDE6C expression system to evaluate pathogenicity and elucidate the mechanisms of PDE6 mutations in retinal diseases.
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MESH Headings
- Adaptor Proteins, Signal Transducing/genetics
- Adaptor Proteins, Signal Transducing/metabolism
- Animals
- Carrier Proteins/genetics
- Carrier Proteins/metabolism
- Color Vision Defects/genetics
- Color Vision Defects/metabolism
- Cyclic Nucleotide Phosphodiesterases, Type 6/analysis
- Cyclic Nucleotide Phosphodiesterases, Type 6/genetics
- Cyclic Nucleotide Phosphodiesterases, Type 6/metabolism
- Eye Diseases, Hereditary/genetics
- Eye Diseases, Hereditary/metabolism
- Eye Proteins/analysis
- Eye Proteins/genetics
- Eye Proteins/metabolism
- Gene Expression
- Genetic Diseases, X-Linked/genetics
- Genetic Diseases, X-Linked/metabolism
- HEK293 Cells
- Humans
- Mice
- Models, Molecular
- Mutation, Missense
- Myopia/genetics
- Myopia/metabolism
- Night Blindness/genetics
- Night Blindness/metabolism
- Protein Folding
- Protein Prenylation
- Retinal Diseases/genetics
- Retinal Diseases/metabolism
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Affiliation(s)
- Kota N Gopalakrishna
- Department of Molecular Physiology and Biophysics, The University of Iowa Carver College of Medicine, Iowa City, IA 52242, United States
| | - Kimberly Boyd
- Department of Molecular Physiology and Biophysics, The University of Iowa Carver College of Medicine, Iowa City, IA 52242, United States
| | - Nikolai O Artemyev
- Department of Molecular Physiology and Biophysics, The University of Iowa Carver College of Medicine, Iowa City, IA 52242, United States; Department of Ophthalmology and Visual Sciences, The University of Iowa Carver College of Medicine, Iowa City, IA 52242, United States.
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21
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Yu L, Yadav RP, Artemyev NO. NMR resonance assignments of the FKBP domain of human aryl hydrocarbon receptor-interacting protein-like 1 (AIPL1) in complex with a farnesyl ligand. Biomol NMR Assign 2017; 11:111-115. [PMID: 28236226 PMCID: PMC5385707 DOI: 10.1007/s12104-017-9730-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/21/2016] [Accepted: 02/17/2017] [Indexed: 06/06/2023]
Abstract
Aryl hydrocarbon receptor-interacting protein-like 1 (AIPL1) is a specialized chaperone of phosphodiesterase 6, a key effector enzyme in the phototransduction cascade. The FKBP domain of AIPL1 is known to bind the farnesyl moiety of PDE6. Mutations in AIPL1, including many missense mutations in the FKBP domain, have been associated with Leber congenital amaurosis, a severe blinding disease. Here, we report the backbone and sidechain assignments of the N-terminal FKBPΔloop (with a loop deletion) of AIPL1 in complex with a farnesyl ligand. We also compare the predicted secondary structures of FKBPΔloop with those of a highly homologous AIP FKBP. These results show that the FKBP domains of AIP and AIPL1 have similar folds, but display subtle differences in structure and dynamics. Therefore, these assignments provide a framework for further elucidation of the mechanism of farnesyl binding and the function of AIPL1 FKBP.
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Affiliation(s)
- Liping Yu
- Departments of Biochemistry, Carver College of Medicine, University of Iowa, Iowa City, IA, 52242, USA.
- NMR Core Facility, Carver College of Medicine, University of Iowa, 285 Newton Road, Iowa City, IA, 52242, USA.
| | - Ravi P Yadav
- Molecular Physiology and Biophysics, Carver College of Medicine, University of Iowa, 51 Newton Road, Iowa City, IA, 52242, USA
| | - Nikolai O Artemyev
- Molecular Physiology and Biophysics, Carver College of Medicine, University of Iowa, 51 Newton Road, Iowa City, IA, 52242, USA.
- Ophthalmology and Visual Sciences, Carver College of Medicine, University of Iowa, Iowa City, IA, 52242, USA.
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22
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Zhang L, Du J, Justus S, Hsu CW, Bonet-Ponce L, Wu WH, Tsai YT, Wu WP, Jia Y, Duong JK, Mahajan VB, Lin CS, Wang S, Hurley JB, Tsang SH. Reprogramming metabolism by targeting sirtuin 6 attenuates retinal degeneration. J Clin Invest 2016; 126:4659-4673. [PMID: 27841758 DOI: 10.1172/jci86905] [Citation(s) in RCA: 68] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2016] [Accepted: 10/06/2016] [Indexed: 12/16/2022] Open
Abstract
Retinitis pigmentosa (RP) encompasses a diverse group of Mendelian disorders leading to progressive degeneration of rods and then cones. For reasons that remain unclear, diseased RP photoreceptors begin to deteriorate, eventually leading to cell death and, consequently, loss of vision. Here, we have hypothesized that RP associated with mutations in phosphodiesterase-6 (PDE6) provokes a metabolic aberration in rod cells that promotes the pathological consequences of elevated cGMP and Ca2+, which are induced by the Pde6 mutation. Inhibition of sirtuin 6 (SIRT6), a histone deacetylase repressor of glycolytic flux, reprogrammed rods into perpetual glycolysis, thereby driving the accumulation of biosynthetic intermediates, improving outer segment (OS) length, enhancing photoreceptor survival, and preserving vision. In mouse retinae lacking Sirt6, effectors of glycolytic flux were dramatically increased, leading to upregulation of key intermediates in glycolysis, TCA cycle, and glutaminolysis. Both transgenic and AAV2/8 gene therapy-mediated ablation of Sirt6 in rods provided electrophysiological and anatomic rescue of both rod and cone photoreceptors in a preclinical model of RP. Due to the extensive network of downstream effectors of Sirt6, this study motivates further research into the role that these pathways play in retinal degeneration. Because reprogramming metabolism by enhancing glycolysis is not gene specific, this strategy may be applicable to a wide range of neurodegenerative disorders.
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23
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Stephen LA, Ismail S. Shuttling and sorting lipid-modified cargo into the cilia. Biochem Soc Trans 2016; 44:1273-1280. [PMID: 27911709 DOI: 10.1042/bst20160122] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2016] [Revised: 07/22/2016] [Accepted: 07/26/2016] [Indexed: 11/17/2022]
Abstract
Primary cilia are hair-like microtubule-based organelles that can be found on almost all human cell types. Although the cilium is not separated from the cell by membranes, their content is different from that of the cell body and their membrane composition is distinct from that of the plasma membrane. Here, we will introduce a molecular machinery that shuttles and sorts lipid-modified proteins to the cilium, thus contributing in maintaining its distinct composition. The mechanism involves the binding of the GDI-like solubilising factors, uncoordinated (UNC)119a, UNC119b and PDE6D, to the lipid-modified ciliary cargo and the specific release of the cargo in the cilia by the ciliary small G-protein Arl3 in a GTP-dependent manner.
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Affiliation(s)
- Louise A Stephen
- CR-UK Beatson Institute, Garscube Estate Switchback Road, Glasgow G61 1BD, U.K
| | - Shehab Ismail
- CR-UK Beatson Institute, Garscube Estate Switchback Road, Glasgow G61 1BD, U.K
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24
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Wu WH, Tsai YT, Justus S, Lee TT, Zhang L, Lin CS, Bassuk AG, Mahajan VB, Tsang SH. CRISPR Repair Reveals Causative Mutation in a Preclinical Model of Retinitis Pigmentosa. Mol Ther 2016; 24:1388-94. [PMID: 27203441 PMCID: PMC5023380 DOI: 10.1038/mt.2016.107] [Citation(s) in RCA: 79] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2016] [Accepted: 05/07/2016] [Indexed: 02/04/2023] Open
Abstract
Massive parallel sequencing enables identification of numerous genetic variants in mutant organisms, but determining pathogenicity of any one mutation can be daunting. The most commonly studied preclinical model of retinitis pigmentosa called the "rodless" (rd1) mouse is homozygous for two mutations: a nonsense point mutation (Y347X) and an intronic insertion of a leukemia virus (Xmv-28). Distinguishing which mutation causes retinal degeneration is still under debate nearly a century after the discovery of this model organism. Here, we performed gene editing using the CRISPR/Cas9 system and demonstrated that the Y347X mutation is the causative variant of disease. Genome editing in the first generation produced animals that were mosaic for the corrected allele but still showed neurofunction preservation despite low repair frequencies. Furthermore, second-generation CRISPR-repaired mice showed an even more robust rescue and amelioration of the disease. This predicts excellent outcomes for gene editing in diseased human tissue, as Pde6b, the mutated gene in rd1 mice, has an orthologous intron-exon relationship comparable with the human PDE6B gene. Not only do these findings resolve the debate surrounding the source of neurodegeneration in the rd1 model, but they also provide the first example of homology-directed recombination-mediated gene correction in the visual system.
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Affiliation(s)
- Wen-Hsuan Wu
- Barbara and Donald Jonas Stem Cell and Regenerative Medicine Laboratory and Bernard and Shirlee Brown Glaucoma Laboratory, Department of Ophthalmology, Institute of Human Nutrition, Herbert Irving Comprehensive Cancer Center, Columbia University, New York, New York, USA
- Barbara and Donald Jonas Stem Cell and Regenerative Medicine Laboratory and Bernard and Shirlee Brown Glaucoma Laboratory, Department of Pathology and Cell Biology, Institute of Human Nutrition, Herbert Irving Comprehensive Cancer Center, Columbia University, New York, New York, USA
- Edward S. Harkness Eye Institute, New York-Presbyterian Hospital, New York, New York, USA
| | - Yi-Ting Tsai
- Barbara and Donald Jonas Stem Cell and Regenerative Medicine Laboratory and Bernard and Shirlee Brown Glaucoma Laboratory, Department of Ophthalmology, Institute of Human Nutrition, Herbert Irving Comprehensive Cancer Center, Columbia University, New York, New York, USA
- Barbara and Donald Jonas Stem Cell and Regenerative Medicine Laboratory and Bernard and Shirlee Brown Glaucoma Laboratory, Department of Pathology and Cell Biology, Institute of Human Nutrition, Herbert Irving Comprehensive Cancer Center, Columbia University, New York, New York, USA
- Edward S. Harkness Eye Institute, New York-Presbyterian Hospital, New York, New York, USA
| | - Sally Justus
- Barbara and Donald Jonas Stem Cell and Regenerative Medicine Laboratory and Bernard and Shirlee Brown Glaucoma Laboratory, Department of Ophthalmology, Institute of Human Nutrition, Herbert Irving Comprehensive Cancer Center, Columbia University, New York, New York, USA
- Barbara and Donald Jonas Stem Cell and Regenerative Medicine Laboratory and Bernard and Shirlee Brown Glaucoma Laboratory, Department of Pathology and Cell Biology, Institute of Human Nutrition, Herbert Irving Comprehensive Cancer Center, Columbia University, New York, New York, USA
- Edward S. Harkness Eye Institute, New York-Presbyterian Hospital, New York, New York, USA
| | - Ting-Ting Lee
- Barbara and Donald Jonas Stem Cell and Regenerative Medicine Laboratory and Bernard and Shirlee Brown Glaucoma Laboratory, Department of Ophthalmology, Institute of Human Nutrition, Herbert Irving Comprehensive Cancer Center, Columbia University, New York, New York, USA
- Barbara and Donald Jonas Stem Cell and Regenerative Medicine Laboratory and Bernard and Shirlee Brown Glaucoma Laboratory, Department of Pathology and Cell Biology, Institute of Human Nutrition, Herbert Irving Comprehensive Cancer Center, Columbia University, New York, New York, USA
- Edward S. Harkness Eye Institute, New York-Presbyterian Hospital, New York, New York, USA
| | - Lijuan Zhang
- Barbara and Donald Jonas Stem Cell and Regenerative Medicine Laboratory and Bernard and Shirlee Brown Glaucoma Laboratory, Department of Ophthalmology, Institute of Human Nutrition, Herbert Irving Comprehensive Cancer Center, Columbia University, New York, New York, USA
- Barbara and Donald Jonas Stem Cell and Regenerative Medicine Laboratory and Bernard and Shirlee Brown Glaucoma Laboratory, Department of Pathology and Cell Biology, Institute of Human Nutrition, Herbert Irving Comprehensive Cancer Center, Columbia University, New York, New York, USA
- Edward S. Harkness Eye Institute, New York-Presbyterian Hospital, New York, New York, USA
- Shanxi Eye Hospital, Shanxi Medical University, Taiyuan, Shanxi, China
| | - Chyuan-Sheng Lin
- Department of Pathology & Cell Biology, Columbia University Medical Center, New York, New York, USA
| | - Alexander G Bassuk
- Department of Pediatrics and Neurology, University of Iowa, Iowa City, Iowa, USA
| | - Vinit B Mahajan
- Omics Laboratory, University of Iowa, Iowa City, Iowa, USA
- Department of Ophthalmology and Visual Sciences, University of Iowa, Iowa City, Iowa, USA
| | - Stephen H Tsang
- Barbara and Donald Jonas Stem Cell and Regenerative Medicine Laboratory and Bernard and Shirlee Brown Glaucoma Laboratory, Department of Ophthalmology, Institute of Human Nutrition, Herbert Irving Comprehensive Cancer Center, Columbia University, New York, New York, USA
- Barbara and Donald Jonas Stem Cell and Regenerative Medicine Laboratory and Bernard and Shirlee Brown Glaucoma Laboratory, Department of Pathology and Cell Biology, Institute of Human Nutrition, Herbert Irving Comprehensive Cancer Center, Columbia University, New York, New York, USA
- Edward S. Harkness Eye Institute, New York-Presbyterian Hospital, New York, New York, USA
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25
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Kolesnikov SS, Bystrova MF. [Cyclic AMP: Second Messenger as the First Messenger]. Usp Fiziol Nauk 2016; 47:3-16. [PMID: 29283227] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Cell-to-cell communications and autocrine/paracrine regulations are mediated by an extracellular signaling network involving secretion of a variety of different factors, hormones, neurotransmitters, and other signaling molecules that are recognized in an extracellular medium by multiple molecular receptors operating in the plasma membrane of cells. Most of plasma membrane receptors belong to the superfamily of heptahelical receptors, many of which are coupled by G-proteins to adenylate cyclase responsible for cAMP production in the cell cytoplasm. The canonical role of cAMP in cell physiology is to serve as a second messenger and universal regulator of intracellular processes. Meanwhile, increasing body of evidence leaves little doubts that stimulated cells can release cAMP into intercellular space, where it may serve as signaling molecule in cell-to-cell communications and autocrine regulations. This review considers the basic concept on mechanisms of intracellular and extracellular signaling with cAMP as the second and first messenger.
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26
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Wang J, Saul A, Roon P, Smith SB. Activation of the molecular chaperone, sigma 1 receptor, preserves cone function in a murine model of inherited retinal degeneration. Proc Natl Acad Sci U S A 2016; 113:E3764-72. [PMID: 27298364 PMCID: PMC4932934 DOI: 10.1073/pnas.1521749113] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Retinal degenerative diseases are major causes of untreatable blindness, and novel approaches to treatment are being sought actively. Here we explored the activation of a unique protein, sigma 1 receptor (Sig1R), in the treatment of PRC loss because of its multifaceted role in cellular survival. We used Pde6β(rd10) (rd10) mice, which harbor a mutation in the rod-specific phosphodiesterase gene Pde6β and lose rod and cone photoreceptor cells (PRC) within the first 6 wk of life, as a model for severe retinal degeneration. Systemic administration of the high-affinity Sig1R ligand (+)-pentazocine [(+)-PTZ] to rd10 mice over several weeks led to the rescue of cone function as indicated by electroretinographic recordings using natural noise stimuli and preservation of cone cells upon spectral domain optical coherence tomography and retinal histological examination. The protective effect appears to result from the activation of Sig1R, because rd10/Sig1R(-/-) mice administered (+)-PTZ exhibited no cone preservation. (+)-PTZ treatment was associated with several beneficial cellular phenomena including attenuated reactive gliosis, reduced microglial activation, and decreased oxidative stress in mutant retinas. To our knowledge, this is the first report that activation of Sig1R attenuates inherited PRC loss. The findings may have far-reaching therapeutic implications for retinal neurodegenerative diseases.
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Affiliation(s)
- Jing Wang
- Department of Cellular Biology/Anatomy, Medical College of Georgia, Augusta University, Augusta, GA 30912; James and Jean Culver Vision Discovery Institute, Augusta University, Augusta, GA 30912
| | - Alan Saul
- James and Jean Culver Vision Discovery Institute, Augusta University, Augusta, GA 30912; Department of Ophthalmology, Medical College of Georgia, Augusta University, Augusta, GA 30912
| | - Penny Roon
- Department of Cellular Biology/Anatomy, Medical College of Georgia, Augusta University, Augusta, GA 30912
| | - Sylvia B Smith
- Department of Cellular Biology/Anatomy, Medical College of Georgia, Augusta University, Augusta, GA 30912; James and Jean Culver Vision Discovery Institute, Augusta University, Augusta, GA 30912; Department of Ophthalmology, Medical College of Georgia, Augusta University, Augusta, GA 30912
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27
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Papke B, Murarka S, Vogel HA, Martín-Gago P, Kovacevic M, Truxius DC, Fansa EK, Ismail S, Zimmermann G, Heinelt K, Schultz-Fademrecht C, Al Saabi A, Baumann M, Nussbaumer P, Wittinghofer A, Waldmann H, Bastiaens PI. Identification of pyrazolopyridazinones as PDEδ inhibitors. Nat Commun 2016; 7:11360. [PMID: 27094677 PMCID: PMC4843002 DOI: 10.1038/ncomms11360] [Citation(s) in RCA: 120] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2015] [Accepted: 03/17/2016] [Indexed: 12/21/2022] Open
Abstract
The prenyl-binding protein PDEδ is crucial for the plasma membrane localization of prenylated Ras. Recently, we have reported that the small-molecule Deltarasin binds to the prenyl-binding pocket of PDEδ, and impairs Ras enrichment at the plasma membrane, thereby affecting the proliferation of KRas-dependent human pancreatic ductal adenocarcinoma cell lines. Here, using structure-based compound design, we have now identified pyrazolopyridazinones as a novel, unrelated chemotype that binds to the prenyl-binding pocket of PDEδ with high affinity, thereby displacing prenylated Ras proteins in cells. Our results show that the new PDEδ inhibitor, named Deltazinone 1, is highly selective, exhibits less unspecific cytotoxicity than the previously reported Deltarasin and demonstrates a high correlation with the phenotypic effect of PDEδ knockdown in a set of human pancreatic cancer cell lines.
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Affiliation(s)
- Björn Papke
- Department of Systemic Cell Biology, Max Planck Institute of Molecular Physiology, D-44227 Dortmund, Germany
| | - Sandip Murarka
- Department of Chemical Biology, Max Planck Institute of Molecular Physiology, D-44227 Dortmund, Germany
| | - Holger A Vogel
- Department of Systemic Cell Biology, Max Planck Institute of Molecular Physiology, D-44227 Dortmund, Germany
| | - Pablo Martín-Gago
- Department of Chemical Biology, Max Planck Institute of Molecular Physiology, D-44227 Dortmund, Germany
| | - Marija Kovacevic
- Department of Systemic Cell Biology, Max Planck Institute of Molecular Physiology, D-44227 Dortmund, Germany
| | - Dina C Truxius
- Department of Systemic Cell Biology, Max Planck Institute of Molecular Physiology, D-44227 Dortmund, Germany
| | - Eyad K Fansa
- Structural Biology Group, Max Planck Institute for Molecular Physiology, D-44227 Dortmund, Germany
| | - Shehab Ismail
- Structural Biology Group, Max Planck Institute for Molecular Physiology, D-44227 Dortmund, Germany
- Beatson Institute for Cancer Research, Bearsden, Glasgow G61 1BD, UK
| | - Gunther Zimmermann
- Department of Chemical Biology, Max Planck Institute of Molecular Physiology, D-44227 Dortmund, Germany
| | - Kaatje Heinelt
- Department of Systemic Cell Biology, Max Planck Institute of Molecular Physiology, D-44227 Dortmund, Germany
| | | | - Alaa Al Saabi
- Lead Discovery Center GmbH, D-44227 Dortmund, Germany
| | | | | | - Alfred Wittinghofer
- Structural Biology Group, Max Planck Institute for Molecular Physiology, D-44227 Dortmund, Germany
| | - Herbert Waldmann
- Department of Chemical Biology, Max Planck Institute of Molecular Physiology, D-44227 Dortmund, Germany
- TU Dortmund, Faculty of Chemistry and Chemical Biology, D-44227 Dortmund, Germany
| | - Philippe I.H. Bastiaens
- Department of Systemic Cell Biology, Max Planck Institute of Molecular Physiology, D-44227 Dortmund, Germany
- TU Dortmund, Faculty of Chemistry and Chemical Biology, D-44227 Dortmund, Germany
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Fansa EK, Kösling SK, Zent E, Wittinghofer A, Ismail S. PDE6δ-mediated sorting of INPP5E into the cilium is determined by cargo-carrier affinity. Nat Commun 2016; 7:11366. [PMID: 27063844 PMCID: PMC5512577 DOI: 10.1038/ncomms11366] [Citation(s) in RCA: 65] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2015] [Accepted: 03/18/2016] [Indexed: 01/06/2023] Open
Abstract
The phosphodiesterase 6 delta subunit (PDE6δ) shuttles several farnesylated cargos between membranes. The cargo sorting mechanism between cilia and other compartments is not understood. Here we show using the inositol polyphosphate 5'-phosphatase E (INPP5E) and the GTP-binding protein (Rheb) that cargo sorting depends on the affinity towards PDE6δ and the specificity of cargo release. High-affinity cargo is exclusively released by the ciliary transport regulator Arl3, while low-affinity cargo is released by Arl3 and its non-ciliary homologue Arl2. Structures of PDE6δ/cargo complexes reveal the molecular basis of the sorting signal which depends on the residues at the -1 and -3 positions relative to farnesylated cysteine. Structure-guided mutation allows the generation of a low-affinity INPP5E mutant which loses exclusive ciliary localization. We postulate that the affinity to PDE6δ and the release by Arl2/3 in addition to a retention signal are the determinants for cargo sorting and enrichment at its destination.
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Affiliation(s)
- Eyad Kalawy Fansa
- Max Planck Institute of Molecular Physiology, Otto-Hahn-Strasse 11, 44227 Dortmund, Germany
| | | | - Eldar Zent
- Max Planck Institute of Molecular Physiology, Otto-Hahn-Strasse 11, 44227 Dortmund, Germany
| | - Alfred Wittinghofer
- Max Planck Institute of Molecular Physiology, Otto-Hahn-Strasse 11, 44227 Dortmund, Germany
| | - Shehab Ismail
- CR-UK Beatson Institute, Garscube Estate Switchback Road, Glasgow G61 1BD, UK
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Hippert C, Graca AB, Barber AC, West EL, Smith AJ, Ali RR, Pearson RA. Müller glia activation in response to inherited retinal degeneration is highly varied and disease-specific. PLoS One 2015; 10:e0120415. [PMID: 25793273 PMCID: PMC4368159 DOI: 10.1371/journal.pone.0120415] [Citation(s) in RCA: 93] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2014] [Accepted: 01/22/2015] [Indexed: 12/20/2022] Open
Abstract
Despite different aetiologies, most inherited retinal disorders culminate in photoreceptor loss, which induces concomitant changes in the neural retina, one of the most striking being reactive gliosis by Müller cells. It is typically assumed that photoreceptor loss leads to an upregulation of glial fibrilliary acidic protein (Gfap) and other intermediate filament proteins, together with other gliosis-related changes, including loss of integrity of the outer limiting membrane (OLM) and deposition of proteoglycans. However, this is based on a mix of both injury-induced and genetic causes of photoreceptor loss. There are very few longitudinal studies of gliosis in the retina and none comparing these changes across models over time. Here, we present a comprehensive spatiotemporal assessment of features of gliosis in the degenerating murine retina that involves Müller glia. Specifically, we assessed Gfap, vimentin and chondroitin sulphate proteoglycan (CSPG) levels and outer limiting membrane (OLM) integrity over time in four murine models of inherited photoreceptor degeneration that encompass a range of disease severities (Crb1rd8/rd8, Prph2+/Δ307, Rho-/-, Pde6brd1/rd1). These features underwent very different changes, depending upon the disease-causing mutation, and that these changes are not correlated with disease severity. Intermediate filament expression did indeed increase with disease progression in Crb1rd8/rd8 and Prph2+/Δ307, but decreased in the Prph2+/Δ307 and Pde6brd1/rd1 models. CSPG deposition usually, but not always, followed the trends in intermediate filament expression. The OLM adherens junctions underwent significant remodelling in all models, but with differences in the composition of the resulting junctions; in Rho-/- mice, the adherens junctions maintained the typical rod-Müller glia interactions, while in the Pde6brd1/rd1 model they formed predominantly between Müller cells in late stage of degeneration. Together, these results show that gliosis and its associated processes are variable and disease-dependent.
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Affiliation(s)
- Claire Hippert
- Department of Genetics, University College London Institute of Ophthalmology, 11–43 Bath Street, London, EC1V 9EL, United Kingdom
| | - Anna B. Graca
- Department of Genetics, University College London Institute of Ophthalmology, 11–43 Bath Street, London, EC1V 9EL, United Kingdom
| | - Amanda C. Barber
- Department of Genetics, University College London Institute of Ophthalmology, 11–43 Bath Street, London, EC1V 9EL, United Kingdom
| | - Emma L. West
- Department of Genetics, University College London Institute of Ophthalmology, 11–43 Bath Street, London, EC1V 9EL, United Kingdom
| | - Alexander J. Smith
- Department of Genetics, University College London Institute of Ophthalmology, 11–43 Bath Street, London, EC1V 9EL, United Kingdom
| | - Robin R. Ali
- Department of Genetics, University College London Institute of Ophthalmology, 11–43 Bath Street, London, EC1V 9EL, United Kingdom
- NIHR Biomedical Research Centre at Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, City Road, London, EC1V 2PD, United Kingdom
| | - Rachael A. Pearson
- Department of Genetics, University College London Institute of Ophthalmology, 11–43 Bath Street, London, EC1V 9EL, United Kingdom
- * E-mail:
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Cheguru P, Majumder A, Artemyev NO. Distinct patterns of compartmentalization and proteolytic stability of PDE6C mutants linked to achromatopsia. Mol Cell Neurosci 2014; 64:1-8. [PMID: 25461672 DOI: 10.1016/j.mcn.2014.10.007] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2014] [Revised: 10/08/2014] [Accepted: 10/20/2014] [Indexed: 11/19/2022] Open
Abstract
Phosphodiesterase-6 (PDE6) is an essential effector enzyme in vertebrate photoreceptor cells. Mutations in rod and cone PDE6 cause recessive retinitis pigmentosa and achromatopsia, respectively. The mechanisms of missense PDE6 mutations underlying severe visual disorders are poorly understood. To probe these mechanisms, we expressed seven known missense mutants of cone PDE6C in rods of transgenic Xenopus laevis and examined their stability and compartmentalization. PDE6C proteins with mutations in the catalytic domain, H602L and E790K, displayed modestly reduced proteolytic stability, but they were properly targeted to the outer segment of photoreceptor cells. Mutations in the regulatory GAF domains, R104W, Y323N, and P391L led to a proteolytic degradation of the proteins involving a cleavage in the GAFb domain. Lastly, the R29W and M455V mutations residing outside the conserved PDE6 domains produced a pattern of subcellular compartmentalization different from that of PDE6C. Thus, our results suggest a spectrum of mechanisms of missense PDE6C mutations in achromatopsia including catalytic defects, protein mislocalization, or a specific sequence of proteolytic degradation.
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Affiliation(s)
- Pallavi Cheguru
- Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, IA 52242, United States
| | - Anurima Majumder
- Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, IA 52242, United States
| | - Nikolai O Artemyev
- Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, IA 52242, United States; Department of Ophthalmology and Visual Sciences, University of Iowa, Iowa City, IA 52242, United States.
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Zeng-Elmore X, Gao XZ, Pellarin R, Schneidman-Duhovny D, Zhang XJ, Kozacka KA, Tang Y, Sali A, Chalkley RJ, Cote RH, Chu F. Molecular architecture of photoreceptor phosphodiesterase elucidated by chemical cross-linking and integrative modeling. J Mol Biol 2014; 426:3713-3728. [PMID: 25149264 DOI: 10.1016/j.jmb.2014.07.033] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2014] [Revised: 07/01/2014] [Accepted: 07/28/2014] [Indexed: 11/20/2022]
Abstract
Photoreceptor phosphodiesterase (PDE6) is the central effector enzyme in visual excitation pathway in rod and cone photoreceptors. Its tight regulation is essential for the speed, sensitivity, recovery and adaptation of visual detection. Although major steps in the PDE6 activation/deactivation pathway have been identified, mechanistic understanding of PDE6 regulation is limited by the lack of knowledge about the molecular organization of the PDE6 holoenzyme (αβγγ). Here, we characterize the PDE6 holoenzyme by integrative structural determination of the PDE6 catalytic dimer (αβ), based primarily on chemical cross-linking and mass spectrometric analysis. Our models built from high-density cross-linking data elucidate a parallel organization of the two catalytic subunits, with juxtaposed α-helical segments within the tandem regulatory GAF domains to provide multiple sites for dimerization. The two catalytic domains exist in an open configuration when compared to the structure of PDE2 in the apo state. Detailed structural elements for differential binding of the γ-subunit to the GAFa domains of the α- and β-subunits are revealed, providing insight into the regulation of the PDE6 activation/deactivation cycle.
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Affiliation(s)
- Xiaohui Zeng-Elmore
- Department of Molecular, Cellular & Biomedical Sciences, University of New Hampshire, Durham, NH 03824, USA; Hubbard Center for Genome Studies, University of New Hampshire, Durham, NH 03824, USA
| | - Xiong-Zhuo Gao
- Department of Molecular, Cellular & Biomedical Sciences, University of New Hampshire, Durham, NH 03824, USA
| | - Riccardo Pellarin
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, CA 94158, USA
| | - Dina Schneidman-Duhovny
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, CA 94158, USA
| | - Xiu-Jun Zhang
- Department of Molecular, Cellular & Biomedical Sciences, University of New Hampshire, Durham, NH 03824, USA
| | - Katie A Kozacka
- Department of Molecular, Cellular & Biomedical Sciences, University of New Hampshire, Durham, NH 03824, USA
| | - Yang Tang
- Department of Molecular, Cellular & Biomedical Sciences, University of New Hampshire, Durham, NH 03824, USA; Hubbard Center for Genome Studies, University of New Hampshire, Durham, NH 03824, USA
| | - Andrej Sali
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, CA 94158, USA; Department of Pharmaceutical Chemistry, University of California, San Francisco, CA 94143, USA; California Institute for Quantitative Biosciences, University of California, San Francisco, CA 94158, USA
| | - Robert J Chalkley
- Department of Pharmaceutical Chemistry, University of California, San Francisco, CA 94143, USA
| | - Rick H Cote
- Department of Molecular, Cellular & Biomedical Sciences, University of New Hampshire, Durham, NH 03824, USA
| | - Feixia Chu
- Department of Molecular, Cellular & Biomedical Sciences, University of New Hampshire, Durham, NH 03824, USA; Hubbard Center for Genome Studies, University of New Hampshire, Durham, NH 03824, USA.
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32
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Thomas S, Wright KJ, Le Corre S, Micalizzi A, Romani M, Abhyankar A, Saada J, Perrault I, Amiel J, Litzler J, Filhol E, Elkhartoufi N, Kwong M, Casanova JL, Boddaert N, Baehr W, Lyonnet S, Munnich A, Burglen L, Chassaing N, Encha-Ravazi F, Vekemans M, Gleeson JG, Valente EM, Jackson PK, Drummond IA, Saunier S, Attié-Bitach T. A homozygous PDE6D mutation in Joubert syndrome impairs targeting of farnesylated INPP5E protein to the primary cilium. Hum Mutat 2014; 35:137-46. [PMID: 24166846 DOI: 10.1002/humu.22470] [Citation(s) in RCA: 99] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2013] [Accepted: 10/10/2013] [Indexed: 11/09/2022]
Abstract
Joubert syndrome (JS) is characterized by a distinctive cerebellar structural defect, namely the << molar tooth sign >>. JS is genetically heterogeneous, involving 20 genes identified to date, which are all required for cilia biogenesis and/or function. In a consanguineous family with JS associated with optic nerve coloboma, kidney hypoplasia, and polydactyly, combined exome sequencing and mapping identified a homozygous splice-site mutation in PDE6D, encoding a prenyl-binding protein. We found that pde6d depletion in zebrafish leads to renal and retinal developmental anomalies and wild-type but not mutant PDE6D is able to rescue this phenotype. Proteomic analysis identified INPP5E, whose mutations also lead to JS or mental retardation, obesity, congenital retinal dystrophy, and micropenis syndromes, as novel prenyl-dependent cargo of PDE6D. Mutant PDE6D shows reduced binding to INPP5E, which fails to localize to primary cilia in patient fibroblasts and tissues. Furthermore, mutant PDE6D is unable to bind to GTP-bound ARL3, which acts as a cargo-release factor for PDE6D-bound INPP5E. Altogether, these results indicate that PDE6D is required for INPP5E ciliary targeting and suggest a broader role for PDE6D in targeting other prenylated proteins to the cilia. This study identifies PDE6D as a novel JS disease gene and provides the first evidence of prenyl-binding-dependent trafficking in ciliopathies.
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Zimmermann G, Schultz-Fademrecht C, Küchler P, Murarka S, Ismail S, Triola G, Nussbaumer P, Wittinghofer A, Waldmann H. Structure guided design and kinetic analysis of highly potent benzimidazole inhibitors targeting the PDEδ prenyl binding site. J Med Chem 2014; 57:5435-48. [PMID: 24884780 DOI: 10.1021/jm500632s] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
K-Ras is one of the most frequently mutated signal transducing human oncogenes. Ras signaling activity requires correct cellular localization of the GTPase. The spatial organization of K-Ras is controlled by the prenyl binding protein PDEδ, which enhances Ras diffusion in the cytosol. Inhibition of the Ras-PDEδ interaction by small molecules impairs Ras localization and signaling. Here we describe in detail the identification and structure guided development of Ras-PDEδ inhibitors targeting the farnesyl binding pocket of PDEδ with nanomolar affinity. We report kinetic data that characterize the binding of the most potent small molecule ligands to PDEδ and prove their binding to endogenous PDEδ in cell lysates. The PDEδ inhibitors provide promising starting points for the establishment of new drug discovery programs aimed at cancers harboring oncogenic K-Ras.
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Affiliation(s)
- Gunther Zimmermann
- Max Planck Institute of Molecular Physiology , Otto-Hahn-Strasse 11, 44227 Dortmund, Germany
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34
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Suladze S, Ismail S, Winter R. Thermodynamic, dynamic and solvational properties of PDEδ binding to farnesylated cystein: a model study for uncovering the molecular mechanism of PDEδ interaction with prenylated proteins. J Phys Chem B 2014; 118:966-75. [PMID: 24401043 DOI: 10.1021/jp411466r] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The protein PDEδ is an important solubilizing factor for several prenylated proteins including the Ras subfamily members. The binding occurs mainly through the farnesyl anchor of Ras proteins, which is recognized by a hydrophobic pocket of PDEδ. In this study, we carried out a detailed study of the thermodynamic and solvational properties of PDEδ binding to farnesyl-cystein, which serves as a model for PDEδ association to prenylated proteins. Using various biophysical approaches in conjunction with theoretical considerations, we show here that binding of the largely hydrophobic ligand surprisingly has enthalpy-driven signature, and the entropy change is largely controlled by the fine balance between the hydrational and conformational terms. Moreover, binding of PDEδ to farnesyl-cystein is accompanied by an increase in thermal stability, the release of about 150 water molecules from the interacting species, a decrease in solvent accessible surface area, and a marked decrease of the volume fluctuations and hence dynamics of the protein. Altogether, our results shed more light on the molecular mechanism of PDEδ interaction with prenylated Ras proteins, which is also prerequisite for an optimization of the structure-based molecular design of drugs against Ras related diseases and for understanding the multitude of biological functions of PDEδ.
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Affiliation(s)
- S Suladze
- TU Dortmund University , Department of Chemistry and Chemical Biology, D-44221 Dortmund, Germany
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35
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Abstract
PrBP/δ, encoded by the Pde6d gene, is an isoprenyl-binding protein that regulates trafficking of isoprenylated proteins, such as PDE6 and GRK1, from photoreceptor inner segments to outer segments. Trafficking of PDE6 and GRK1 to photoreceptor outer segments is impeded in Pde6d knockout mice. In Pde6d (-/-) cones, PDE6 and GRK1 are nearly undetectable and the b-wave amplitudes of photopic ERGs in Pde6d (-/-) mice are reduced by over 50 %. We reported recently that UNC119, a homolog of PrBP/δ highly expressed in photoreceptors, functions as an acyl-binding protein and regulates transport of G-proteins in sensory neurons. Since both PrBP/δ and UNC119 regulate peripheral protein trafficking in photoreceptors, we generated Pde6d; Unc119 double knockout mice in order to study how PrBP/δ and UNC119 may interact. Surprisingly, knockout of Unc119 partially reversed the transport defect of GRK1 in cone photoreceptors caused by deletion of Pde6d, and the b-wave amplitudes of photopic ERGs in the double knockout mice were significantly higher than those in the Pde6d (-/-) mice. These results suggest that cone transport of isoprenylated and acylated proteins is interdependent.
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Affiliation(s)
- Houbin Zhang
- Department of Ophthalmology, John A. Moran Eye Center, University of Utah Health Science Center, 65 Mario Capecchi Drive, 84132, Salt Lake City, UT, USA,
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36
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Mariani S, Dell'Orco D, Felline A, Raimondi F, Fanelli F. Network and atomistic simulations unveil the structural determinants of mutations linked to retinal diseases. PLoS Comput Biol 2013; 9:e1003207. [PMID: 24009494 PMCID: PMC3757061 DOI: 10.1371/journal.pcbi.1003207] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2013] [Accepted: 07/18/2013] [Indexed: 12/19/2022] Open
Abstract
A number of incurable retinal diseases causing vision impairments derive from alterations in visual phototransduction. Unraveling the structural determinants of even monogenic retinal diseases would require network-centered approaches combined with atomistic simulations. The transducin G38D mutant associated with the Nougaret Congenital Night Blindness (NCNB) was thoroughly investigated by both mathematical modeling of visual phototransduction and atomistic simulations on the major targets of the mutational effect. Mathematical modeling, in line with electrophysiological recordings, indicates reduction of phosphodiesterase 6 (PDE) recognition and activation as the main determinants of the pathological phenotype. Sub-microsecond molecular dynamics (MD) simulations coupled with Functional Mode Analysis improve the resolution of information, showing that such impairment is likely due to disruption of the PDEγ binding cavity in transducin. Protein Structure Network analyses additionally suggest that the observed slight reduction of theRGS9-catalyzed GTPase activity of transducin depends on perturbed communication between RGS9 and GTP binding site. These findings provide insights into the structural fundamentals of abnormal functioning of visual phototransduction caused by a missense mutation in one component of the signaling network. This combination of network-centered modeling with atomistic simulations represents a paradigm for future studies aimed at thoroughly deciphering the structural determinants of genetic retinal diseases. Analogous approaches are suitable to unveil the mechanism of information transfer in any signaling network either in physiological or pathological conditions.
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Affiliation(s)
- Simona Mariani
- Department of Life Sciences, University of Modena and Reggio Emilia, Modena, Italy
- Dulbecco Telethon Institute (DTI), Modena, Italy
| | - Daniele Dell'Orco
- Department of Life Sciences and Reproduction Sect. of Biological Chemistry and Center for BioMedical Computing, University of Verona, Verona, Italy
| | - Angelo Felline
- Department of Life Sciences, University of Modena and Reggio Emilia, Modena, Italy
- Dulbecco Telethon Institute (DTI), Modena, Italy
| | - Francesco Raimondi
- Department of Life Sciences, University of Modena and Reggio Emilia, Modena, Italy
- Dulbecco Telethon Institute (DTI), Modena, Italy
| | - Francesca Fanelli
- Department of Life Sciences, University of Modena and Reggio Emilia, Modena, Italy
- Dulbecco Telethon Institute (DTI), Modena, Italy
- * E-mail:
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37
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Abstract
Targeting the KRAS-PDEδ interaction inhibits KRAS-dependent signaling and tumor growth.
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38
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Bramall AN, Szego MJ, Pacione LR, Chang I, Diez E, D'Orleans-Juste P, Stewart DJ, Hauswirth WW, Yanagisawa M, McInnes RR. Endothelin-2-mediated protection of mutant photoreceptors in inherited photoreceptor degeneration. PLoS One 2013; 8:e58023. [PMID: 23469133 PMCID: PMC3585171 DOI: 10.1371/journal.pone.0058023] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2012] [Accepted: 01/30/2013] [Indexed: 12/21/2022] Open
Abstract
Expression of the Endothelin-2 (Edn2) mRNA is greatly increased in the photoreceptors (PRs) of mouse models of inherited PR degeneration (IPD). To examine the role of Edn2 in mutant PR survival, we generated Edn2−/− mice carrying homozygous Pde6brd1 alleles or the Tg(RHO P347S) transgene. In the Edn2−/− background, PR survival increased 110% in Pde6brd1/rd1 mice at post-natal (PN) day 15, and 60% in Tg(RHO P347S) mice at PN40. In contrast, PR survival was not increased in retinal explants of Pde6brd1/rd1; Edn2−/− mice. This finding, together with systemic abnormalities in Edn2−/− mice, suggested that the increased survival of mutant PRs in the Edn2−/− background resulted at least partly from the systemic EDN2 loss of function. To examine directly the role of EDN2 in mutant PRs, we used a scAAV5-Edn2 cDNA vector to restore Edn2 expression in Pde6brd1/rd1; Edn2−/− PRs and observed an 18% increase in PR survival at PN14. Importantly, PR survival was also increased after injection of scAAV5-Edn2 into Pde6brd1/rd1 retinas, by 31% at PN15. Together, these findings suggest that increased Edn2 expression is protective to mutant PRs. To begin to elucidate Edn2-mediated mechanisms that contribute to PR survival, we used microarray analysis and identified a cohort of 20 genes with >4-fold increased expression in Tg(RHO P347S) retinas, including Fgf2. Notably, increased expression of the FGF2 protein in Tg(RHO P347S) PRs was ablated in Tg(RHO P347S); Edn2−/− retinas. Our findings indicate that the increased expression of PR Edn2 increases PR survival, and suggest that the Edn2-dependent increase in PR expression of FGF2 may contribute to the augmented survival.
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Affiliation(s)
- Alexa N. Bramall
- Program in Developmental Biology, The Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
| | - Michael J. Szego
- Program in Developmental Biology, The Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
| | - Laura R. Pacione
- Program in Developmental Biology, The Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
| | - Inik Chang
- Department of Molecular Genetics and Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
| | - Eduardo Diez
- Lady Davis Research Institute, Jewish General Hospital, McGill University, Montreal, Quebec, Canada
| | - Pedro D'Orleans-Juste
- Department of Anatomy and Cell Biology, Faculty of Medicine, Université de Sherbrooke, Sherbrooke, Quebec, Canada
| | - Duncan J. Stewart
- The Regenerative Medicine Program, Ottawa Hospital Research Institute, University of Ottawa, Ottawa, Ontario, Canada
| | - William W. Hauswirth
- Department of Ophthalmology, College of Medicine, University of Florida, Gainesville, Florida, United States of America
| | - Masashi Yanagisawa
- Department of Molecular Genetics and Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
| | - Roderick R. McInnes
- Program in Developmental Biology, The Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
- Lady Davis Research Institute, Jewish General Hospital, McGill University, Montreal, Quebec, Canada
- * E-mail:
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Sahaboglu A, Paquet-Durand O, Dietter J, Dengler K, Bernhard-Kurz S, Ekström PAR, Hitzmann B, Ueffing M, Paquet-Durand F. Retinitis pigmentosa: rapid neurodegeneration is governed by slow cell death mechanisms. Cell Death Dis 2013; 4:e488. [PMID: 23392176 PMCID: PMC3593146 DOI: 10.1038/cddis.2013.12] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2012] [Revised: 12/21/2012] [Accepted: 01/03/2013] [Indexed: 12/31/2022]
Abstract
For most neurodegenerative diseases the precise duration of an individual cell's death is unknown, which is an obstacle when counteractive measures are being considered. To address this, we used the rd1 mouse model for retinal neurodegeneration, characterized by phosphodiesterase-6 (PDE6) dysfunction and photoreceptor death triggered by high cyclic guanosine-mono-phosphate (cGMP) levels. Using cellular data on cGMP accumulation, cell death, and survival, we created mathematical models to simulate the temporal development of the degeneration. We validated model predictions using organotypic retinal explant cultures derived from wild-type animals and exposed to the selective PDE6 inhibitor zaprinast. Together, photoreceptor data and modeling for the first time delineated three major cell death phases in a complex neuronal tissue: (1) initiation, taking up to 36 h, (2) execution, lasting another 40 h, and finally (3) clearance, lasting about 7 h. Surprisingly, photoreceptor neurodegeneration was noticeably slower than necrosis or apoptosis, suggesting a different mechanism of death for these neurons.
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Affiliation(s)
- A Sahaboglu
- Institute for Ophthalmic Research, University of Tübingen, Tübingen, Germany
| | - O Paquet-Durand
- Institute of Food Science and Biotechnology, University of Stuttgart Hohenheim, Stuttgart, Germany
| | - J Dietter
- Institute for Ophthalmic Research, University of Tübingen, Tübingen, Germany
| | - K Dengler
- Skin Clinic, University of Tübingen, Tübingen, Germany
| | - S Bernhard-Kurz
- Institute for Ophthalmic Research, University of Tübingen, Tübingen, Germany
| | - P AR Ekström
- Department of Clinical Sciences, Lund, University of Lund, Lund, Sweden
| | - B Hitzmann
- Institute of Food Science and Biotechnology, University of Stuttgart Hohenheim, Stuttgart, Germany
| | - M Ueffing
- Institute for Ophthalmic Research, University of Tübingen, Tübingen, Germany
| | - F Paquet-Durand
- Institute for Ophthalmic Research, University of Tübingen, Tübingen, Germany
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Zhang H, Constantine R, Frederick JM, Baehr W. The prenyl-binding protein PrBP/δ: a chaperone participating in intracellular trafficking. Vision Res 2012; 75:19-25. [PMID: 22960045 PMCID: PMC3514561 DOI: 10.1016/j.visres.2012.08.013] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2012] [Revised: 08/17/2012] [Accepted: 08/20/2012] [Indexed: 01/21/2023]
Abstract
Expressed ubiquitously, PrBP/δ functions as chaperone/co-factor in the transport of a subset of prenylated proteins. PrBP/δ features an immunoglobulin-like β-sandwich fold for lipid binding, and interacts with diverse partners. PrBP/δ binds both C-terminal C15 and C20 prenyl side chains of phototransduction polypeptides and small GTP-binding (G) proteins of the Ras superfamily. PrBP/δ also interacts with the small GTPases, ARL2 and ARL3, which act as release factors (GDFs) for prenylated cargo. Targeted deletion of the mouse Pde6d gene encoding PrBP/δ resulted in impeded trafficking to the outer segments of GRK1 and cone PDE6 which are predicted to be farnesylated and geranylgeranylated, respectively. Rod and cone transducin trafficking was largely unaffected. These trafficking defects produce progressive cone-rod dystrophy in the Pde6d(-/-) mouse.
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Affiliation(s)
- Houbin Zhang
- Department of Ophthalmology, John A. Moran Eye Center, University of Utah Health Science Center, 65 Mario Capecchi Dr., Salt Lake City UT 84132, USA
| | - Ryan Constantine
- Department of Ophthalmology, John A. Moran Eye Center, University of Utah Health Science Center, 65 Mario Capecchi Dr., Salt Lake City UT 84132, USA
- Graduate Program in Neuroscience, University of Utah Health Science Center, Salt Lake City UT 84132, USA
| | - Jeanne M. Frederick
- Department of Ophthalmology, John A. Moran Eye Center, University of Utah Health Science Center, 65 Mario Capecchi Dr., Salt Lake City UT 84132, USA
| | - Wolfgang Baehr
- Department of Ophthalmology, John A. Moran Eye Center, University of Utah Health Science Center, 65 Mario Capecchi Dr., Salt Lake City UT 84132, USA
- Department of Neurobiology and Anatomy, University of Utah Health Science Center, Salt Lake City UT 84132, USA
- Department of Biology, University of Utah, 257 South 1400 East, Salt Lake City, Utah 84112, USA
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Nakao T, Tsujikawa M, Notomi S, Ikeda Y, Nishida K. The role of mislocalized phototransduction in photoreceptor cell death of retinitis pigmentosa. PLoS One 2012; 7:e32472. [PMID: 22485131 PMCID: PMC3317642 DOI: 10.1371/journal.pone.0032472] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2011] [Accepted: 01/31/2012] [Indexed: 01/09/2023] Open
Abstract
Most of inherited retinal diseases such as retinitis pigmentosa (RP) cause photoreceptor cell death resulting in blindness. RP is a large family of diseases in which the photoreceptor cell death can be caused by a number of pathways. Among them, light exposure has been reported to induce photoreceptor cell death. However, the detailed mechanism by which photoreceptor cell death is caused by light exposure is unclear. In this study, we have shown that even a mild light exposure can induce ectopic phototransduction and result in the acceleration of rod photoreceptor cell death in some vertebrate models. In ovl, a zebrafish model of outer segment deficiency, photoreceptor cell death is associated with light exposure. The ovl larvae show ectopic accumulation of rhodopsin and knockdown of ectopic rhodopsin and transducin rescue rod photoreceptor cell death. However, knockdown of phosphodiesterase, the enzyme that mediates the next step of phototransduction, does not. So, ectopic phototransduction activated by light exposure, which leads to rod photoreceptor cell death, is through the action of transducin. Furthermore, we have demonstrated that forced activation of adenylyl cyclase in the inner segment leads to rod photoreceptor cell death. For further confirmation, we have also generated a transgenic fish which possesses a human rhodopsin mutation, Q344X. This fish and rd10 model mice show photoreceptor cell death caused by adenylyl cyclase. In short, our study indicates that in some RP, adenylyl cyclase is involved in photoreceptor cell death pathway; its inhibition is potentially a logical approach for a novel RP therapy.
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Affiliation(s)
- Takeshi Nakao
- Department of Ophthalmology, Osaka University Graduate School of Medicine, Suita, Osaka, Japan
| | - Motokazu Tsujikawa
- Department of Ophthalmology, Osaka University Graduate School of Medicine, Suita, Osaka, Japan
- * E-mail:
| | - Shoji Notomi
- Department of Ophthalmology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Yasuhiro Ikeda
- Department of Ophthalmology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Kohji Nishida
- Department of Ophthalmology, Osaka University Graduate School of Medicine, Suita, Osaka, Japan
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Chrenek MA, Dalal N, Gardner C, Grossniklaus H, Jiang Y, Boatright JH, Nickerson JM. Analysis of the RPE sheet in the rd10 retinal degeneration model. Adv Exp Med Biol 2012; 723:641-7. [PMID: 22183388 DOI: 10.1007/978-1-4614-0631-0_81] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
BACKGROUND The normal RPE sheet in the C57BL/6J mouse is subclassified into two major tiling patterns: a regular generally hexagonal array covering most of the surface and a “soft network” near the ciliary body made of irregularly shaped cells. Physics models predict these two patterns based on contractility and elasticity of the RPE cell, and strength of cellular adhesion between cells. HYPOTHESIS We hypothesized and identified major changes in RPE regular hexagonal tiling pattern in rd10 compared to C57BL/6J mice. RESULTS In rd10 mice, RPE sheet damage was extensive but occurred later than expected, after most retinal degeneration was complete. RPE sheet changes occur in zones with a bullseye pattern. In the posterior zone, around the optic nerve, RPE cells take on larger irregular and varied shapes to maintain an intact monolayer. In mid periphery, RPE cells have a compressed or convoluted morphology that progress into ingrown layers of RPE under the retina. Cells in the periphery maintain their shape and size until the late stages of the RPE reorganization. The number of neighboring cells varies widely depending on zone and progression. RPE morphology continues to deteriorate after the photoreceptors have degenerated. CONCLUSIONS The RPE cells are bystanders to photoreceptor degeneration in the rd10 model, and the collateral damage to the RPE results in changes in morphology as early as 30 days old. Quantitative measures of the tiling patterns and histopathology detected here were scripted in a pipeline written in Perl and Cell Profiler (an open source MatLab plugin) and are directly applicable to RPE sheet images from noninvasive fundus autofluorescence (FAF), adaptive optics confocal scanning laser ophthalmoscope (AO-cSLO), and spectral domain optical coherence tomography (SD-OCT) of patients with early stage AMD or RP.
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Affiliation(s)
- Micah A Chrenek
- Department of Ophthalmology, Emory University, 1365B Clifton Road NE, TEC-B5602, Atlanta, GA 30322, USA
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Temkitthawon P, Hinds TR, Beavo JA, Viyoch J, Suwanborirux K, Pongamornkul W, Sawasdee P, Ingkaninan K. Kaempferia parviflora, a plant used in traditional medicine to enhance sexual performance contains large amounts of low affinity PDE5 inhibitors. J Ethnopharmacol 2011; 137:1437-1441. [PMID: 21884777 PMCID: PMC4056445 DOI: 10.1016/j.jep.2011.08.025] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2011] [Revised: 07/05/2011] [Accepted: 08/12/2011] [Indexed: 05/31/2023]
Abstract
AIM OF THE STUDY A number of medicinal plants are used in traditional medicine to treat erectile dysfunction. Since cyclic nucleotide PDEs inhibitors underlie several current treatments for this condition, we sought to show whether these plants might contain substantial amounts of PDE5 inhibitors. MATERIALS AND METHODS Forty one plant extracts and eight 7-methoxyflavones from Kaempferia parviflora Wall. ex Baker were screened for PDE5 and PDE6 inhibitory activities using the two-step radioactive assay. The PDE5 and PDE6 were prepared from mice lung and chicken retinas, respectively. All plant extracts were tested at 50 μg/ml whereas the pure compounds were tested at 10 μM. RESULTS From forty one plant extracts tested, four showed the PDE5 inhibitory effect. The chemical constituents isolated from rhizomes of Kaempferia parviflora were further investigated on inhibitory activity against PDE5 and PDE6. The results showed that 7-methoxyflavones from this plant showed inhibition toward both enzymes. The most potent PDE5 inhibitor was 5,7-dimethoxyflavone (IC(50) = 10.64 ± 2.09 μM, selectivity on PDE5 over PDE6 = 3.71). Structure activity relationship showed that the methoxyl group at C-5 position of 7-methoxyflavones was necessary for PDE5 inhibition. CONCLUSIONS Kaempferia parviflora rhizome extract and its 7-methoxyflavone constituents had moderate inhibitory activity against PDE5. This finding provides an explanation for enhancing sexual performance in the traditional use of Kaempferia parviflora. Moreover, 5,7-dimethoxyflavones should make a useful lead compound to further develop clinically efficacious PDE5 inhibitors.
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Affiliation(s)
- Prapapan Temkitthawon
- Department of Pharmaceutical Chemistry and Pharmacognosy, Faculty of Pharmaceutical Sciences and Center of Excellence for Innovation in Chemistry, Naresuan University, Phitsanulok 65000, Thailand
| | - Thomas R. Hinds
- Department of Pharmacology, University of Washington, Seattle, USA
| | - Joseph A. Beavo
- Department of Pharmacology, University of Washington, Seattle, USA
| | - Jarupa Viyoch
- Department of Pharmaceutical Technology, Faculty of Pharmaceutical Sciences and Center of Excellence for Innovation in Chemistry, Naresuan University, Phitsanulok 65000, Thailand
| | - Khanit Suwanborirux
- Department of Pharmacognosy and Pharmaceutical Botany and Center for Bioactive Natural Products from Marine Organisms and Endophytic Fungi, Faculty of Pharmaceutical Sciences, Chulalongkorn University, Bangkok 10330, Thailand
| | | | - Pattara Sawasdee
- Natural Product Research Unit, Department of Chemistry, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand
| | - Kornkanok Ingkaninan
- Department of Pharmaceutical Chemistry and Pharmacognosy, Faculty of Pharmaceutical Sciences and Center of Excellence for Innovation in Chemistry, Naresuan University, Phitsanulok 65000, Thailand
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Tsang SH, Woodruff ML, Hsu CW, Naumann MC, Cilluffo M, Tosi J, Lin CS. Function of the asparagine 74 residue of the inhibitory γ-subunit of retinal rod cGMP-phophodiesterase (PDE) in vivo. Cell Signal 2011; 23:1584-9. [PMID: 21616145 PMCID: PMC3148328 DOI: 10.1016/j.cellsig.2011.05.007] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2011] [Accepted: 05/09/2011] [Indexed: 11/30/2022]
Abstract
The inhibitory subunit of rod cyclic guanosine monophosphate (cGMP) phosphodiesterase, PDE6γ, is a major component of rod transduction and is required to support photoreceptor integrity. The N74A allele of PDE6γ has previously been shown in experiments carried out in vitro to reduce the regulatory inhibition on the PDE6 catalytic core subunits, PDE6αβ. This should, in intact rods, lead to an increase in basal (dark) PDE6 activity producing a state equivalent to light adaptation in the rods and we have examined this possibility using ERG and suction-electrode measurements. The murine opsin promoter was used to drive the expression of a mutant N74A and a wild-type PDE6γ control transgene in the photoreceptors of +/Pde6g(tm1) mice. This transgenic line was crossed with Pde6g(tm1)/Pde6g(tm1) mice to generate animals able to synthesize only the transgenic mutant PDE6γ. We find that the N74A mutation did not produce a significant decrease in circulating current, a decrease in sensitivity or affect the kinetics of the light response, all hallmarks of the light-adapted state. In an in vitro assay of the PDE purified from the N74A transgenic mice and control mice we could find no increase in basal activity of the mutant PDE6. Both the results from the physiology and the biochemistry experiments are consistent with the interpretation that the mutation causes a much milder phenotype in vivo than was predicted from observations made using a cell-free assay system. The in vivo regulation of PDE6γ on PDE6αβ may be more dynamic and context-dependent than was replicated in vitro.
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Affiliation(s)
- Stephen H Tsang
- Bernard and Shirlee Brown Glaucoma Laboratory, Department of Pathology & Cell Biology, College of Physicians and Surgeons, Columbia University, New York, NY 10032, United States.
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Christiansen JR, Kolandaivelu S, Bergo MO, Ramamurthy V. RAS-converting enzyme 1-mediated endoproteolysis is required for trafficking of rod phosphodiesterase 6 to photoreceptor outer segments. Proc Natl Acad Sci U S A 2011; 108:8862-6. [PMID: 21555557 PMCID: PMC3102416 DOI: 10.1073/pnas.1103627108] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Prenylation is the posttranslational modification of a carboxyl-terminal cysteine residue of proteins that terminate with a CAAX motif. Following prenylation, the last three amino acids are cleaved off by the endoprotease, RAS-converting enzyme 1 (RCE1), and the prenylcysteine residue is methylated. Although it is clear that prenylation increases membrane affinity of CAAX proteins, less is known about the importance of the postprenylation processing steps. RCE1 function has been studied in a variety of tissues but not in neuronal cells. To approach this issue, we generated mice lacking Rce1 in the retina. Retinal development proceeded normally in the absence of Rce1, but photoreceptor cells failed to respond to light and subsequently degenerated in a rapid fashion. In contrast, the inner nuclear and ganglion cell layers were unaffected. We found that the multimeric rod phosphodiesterase 6 (PDE6), a prenylated protein and RCE1 substrate, was unable to be transported to the outer segments in Rce1-deficient photoreceptor cells. PDE6 present in the inner segment of Rce1-deficient photoreceptor cells was assembled and functional. Synthesis and transport of transducin, and rhodopsin kinase 1 (GRK1), also prenylated substrates of RCE1, was unaffected by Rce1 deficiency. We conclude that RCE1 is essential for the intracellular trafficking of PDE6 and survival of photoreceptor cells.
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Affiliation(s)
| | - Saravanan Kolandaivelu
- Center for Neuroscience and
- Departments of Ophthalmology and
- Biochemistry, Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, WV 26505; and
| | - Martin O. Bergo
- Cancer Center Sahlgrenska, University of Gothenburg, SE 413 45 Gothenburg, Sweden
| | - Visvanathan Ramamurthy
- Center for Neuroscience and
- Departments of Ophthalmology and
- Biochemistry, Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, WV 26505; and
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Sahaboglu A, Tanimoto N, Kaur J, Sancho-Pelluz J, Huber G, Fahl E, Arango-Gonzalez B, Zrenner E, Ekström P, Löwenheim H, Seeliger M, Paquet-Durand F. PARP1 gene knock-out increases resistance to retinal degeneration without affecting retinal function. PLoS One 2010; 5:e15495. [PMID: 21124852 PMCID: PMC2990765 DOI: 10.1371/journal.pone.0015495] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2010] [Accepted: 10/03/2010] [Indexed: 11/25/2022] Open
Abstract
Retinitis pigmentosa (RP) is a group of inherited neurodegenerative diseases affecting photoreceptors and causing blindness in humans. Previously, excessive activation of enzymes belonging to the poly-ADP-ribose polymerase (PARP) group was shown to be involved in photoreceptor degeneration in the human homologous rd1 mouse model for RP. Since there are at least 16 different PARP isoforms, we investigated the exact relevance of the predominant isoform - PARP1 - for photoreceptor cell death using PARP1 knock-out (KO) mice. In vivo and ex vivo morphological analysis using optic coherence tomography (OCT) and conventional histology revealed no major alterations of retinal phenotype when compared to wild-type (wt). Likewise, retinal function as assessed by electroretinography (ERG) was normal in PARP1 KO animals. We then used retinal explant cultures derived from wt, rd1, and PARP1 KO animals to test their susceptibility to chemically induced photoreceptor degeneration. Since photoreceptor degeneration in the rd1 retina is triggered by a loss-of-function in phosphodiesterase-6 (PDE6), we used selective PDE6 inhibition to emulate the rd1 situation on non-rd1 genotypes. While wt retina subjected to PDE6 inhibition showed massive photoreceptor degeneration comparable to rd1 retina, in the PARP1 KO situation, cell death was robustly reduced. Together, these findings demonstrate that PARP1 activity is in principle dispensable for normal retinal function, but is of major importance for photoreceptor degeneration under pathological conditions. Moreover, our results suggest that PARP dependent cell death or PARthanatos may play a major role in retinal degeneration and highlight the possibility to use specific PARP inhibitors for the treatment of RP.
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Affiliation(s)
- Ayse Sahaboglu
- Division of Experimental Ophthalmology, Institute for Ophthalmic Research, University of Tübingen, Tübingen, Germany
| | - Naoyuki Tanimoto
- Ocular Neurodegeneration Research Group, Centre for Ophthalmology, Institute for Ophthalmic Research, University of Tübingen, Tübingen, Germany
| | - Jasvir Kaur
- Division of Experimental Ophthalmology, Institute for Ophthalmic Research, University of Tübingen, Tübingen, Germany
| | - Javier Sancho-Pelluz
- Division of Experimental Ophthalmology, Institute for Ophthalmic Research, University of Tübingen, Tübingen, Germany
| | - Gesine Huber
- Ocular Neurodegeneration Research Group, Centre for Ophthalmology, Institute for Ophthalmic Research, University of Tübingen, Tübingen, Germany
| | - Edda Fahl
- Ocular Neurodegeneration Research Group, Centre for Ophthalmology, Institute for Ophthalmic Research, University of Tübingen, Tübingen, Germany
| | - Blanca Arango-Gonzalez
- Division of Experimental Ophthalmology, Institute for Ophthalmic Research, University of Tübingen, Tübingen, Germany
| | - Eberhart Zrenner
- Division of Experimental Ophthalmology, Institute for Ophthalmic Research, University of Tübingen, Tübingen, Germany
| | - Per Ekström
- Department of Ophthalmology, Clinical Sciences Lund, University of Lund, Lund, Sweden
| | - Hubert Löwenheim
- Otolaryngology Department, University of Tübingen, Tübingen, Germany
| | - Mathias Seeliger
- Ocular Neurodegeneration Research Group, Centre for Ophthalmology, Institute for Ophthalmic Research, University of Tübingen, Tübingen, Germany
| | - François Paquet-Durand
- Division of Experimental Ophthalmology, Institute for Ophthalmic Research, University of Tübingen, Tübingen, Germany
- * E-mail:
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Chu UB, Song J, Mavlyutov TA, Guo LW. In vitro interaction of tubulin with the photoreceptor cGMP phosphodiesterase gamma-subunit. Neurosci Lett 2010; 482:225-9. [PMID: 20655363 DOI: 10.1016/j.neulet.2010.07.044] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2010] [Revised: 06/24/2010] [Accepted: 07/16/2010] [Indexed: 11/18/2022]
Abstract
The alpha and beta tubulins compose the microtubule cytoskeleton which is involved in many cellular processes such as vesicular transport. The photoreceptor cells in the retina are neurons specialized for phototransduction. Here we report a novel interaction between tubulin and the photoreceptor cGMP phosphodiesterase (PDE6) gamma subunit (PDE gamma). The specificity and molecular details of the PDE gamma:tubulin interaction were analyzed through the experiments of pull down, microtubule co-sedimentation, and NMR spectroscopy. The tubulin-interacting site was identified to be in the PDE gamma C-terminal I67-G85 region, and the interaction interface appeared to be distinct from those with the other PDE gamma targets in phototransduction. We also observed that PDE gamma interacted with tubulin in a GTP-dependent manner. Our findings offer implications for non-phototransduction role(s) of PDE gamma in the photoreceptor neurons.
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Affiliation(s)
- Uyen B Chu
- Department of Pharmacology, University of Wisconsin School of Medicine and Public Health, Madison, WI 53706, USA
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Vinberg F, Koskelainen A. Calcium sets the physiological value of the dominant time constant of saturated mouse rod photoresponse recovery. PLoS One 2010; 5:e13025. [PMID: 20885958 PMCID: PMC2946398 DOI: 10.1371/journal.pone.0013025] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2010] [Accepted: 09/03/2010] [Indexed: 11/19/2022] Open
Abstract
Background The rate-limiting step that determines the dominant time constant (τD) of mammalian rod photoresponse recovery is the deactivation of the active phosphodiesterase (PDE6). Physiologically relevant Ca2+-dependent mechanisms that would affect the PDE inactivation have not been identified. However, recently it has been shown that τD is modulated by background light in mouse rods. Methodology/Principal Findings We used ex vivo ERG technique to record pharmacologically isolated photoreceptor responses (fast PIII component). We show a novel static effect of calcium on mouse rod phototransduction: Ca2+ shortens the dominant time constant (τD) of saturated photoresponse recovery, i.e., when extracellular free Ca2+ is decreased from 1 mM to ∼25 nM, the τD is reversibly increased ∼1.5–2-fold. Conclusions We conclude that the increase in τD during low Ca2+ treatment is not due to increased [cGMP], increased [Na+] or decreased [ATP] in rod outer segment (ROS). Also it cannot be due to protein translocation mechanisms. We suggest that a Ca2+-dependent mechanism controls the life time of active PDE.
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Affiliation(s)
- Frans Vinberg
- Department of Biomedical Engineering and Computational Science (BECS), Aalto University School of Science and Technology, Espoo, Finland
| | - Ari Koskelainen
- Department of Biomedical Engineering and Computational Science (BECS), Aalto University School of Science and Technology, Espoo, Finland
- * E-mail:
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Miranda M, Arnal E, Ahuja S, Alvarez-Nölting R, López-Pedrajas R, Ekström P, Bosch-Morell F, van Veen T, Romero FJ. Antioxidants rescue photoreceptors in rd1 mice: Relationship with thiol metabolism. Free Radic Biol Med 2010; 48:216-22. [PMID: 19854264 DOI: 10.1016/j.freeradbiomed.2009.10.042] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/07/2009] [Revised: 09/18/2009] [Accepted: 10/18/2009] [Indexed: 10/20/2022]
Abstract
We have previously shown that the use of a combination of antioxidants delayed the degeneration process in rd1 mouse retina. In an effort to understand the mechanism of action of these substances (zeaxanthin, lutein, alpha-lipoic acid, glutathione, and Lycium barbarum extract) the changes in the levels of several proteins and oxidative stress markers in the rd1 retina have been studied. The treatment increased glutathione peroxidase activity and glutathione levels and decreased cystine concentrations in rd1 retinas. Considering all the results obtained from treated and untreated animals, a high correlation was present between glutathione concentration and glutathione peroxidase activity, and there was a negative correlation between glutathione retinal concentration and number of TUNEL-positive cells. No difference was observed between the numbers of nNOS- and NADPH-diaphorase-positive cells in treated and untreated rd1 mice. Thiol contents and thiol-dependent peroxide metabolism seem to be directly related to the survival of photoreceptors in rd1 mouse retina.
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Affiliation(s)
- María Miranda
- Department of Physiology, University CEU-Cardenal Herrera, 46113 Moncada, Valencia, Spain
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Muradov H, Boyd KK, Haeri M, Kerov V, Knox BE, Artemyev NO. Characterization of human cone phosphodiesterase-6 ectopically expressed in Xenopus laevis rods. J Biol Chem 2009; 284:32662-9. [PMID: 19801642 PMCID: PMC2781681 DOI: 10.1074/jbc.m109.049916] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2009] [Revised: 09/14/2009] [Indexed: 11/06/2022] Open
Abstract
PDE6 (phosphodiesterase-6) is the effector molecule in the vertebrate phototransduction cascade. Progress in understanding the structure and function of PDE6 has been hindered by lack of an expression system of the enzyme. Here we report ectopic expression and analysis of compartmentalization and membrane dynamics of the enhanced green fluorescent protein (EGFP) fusion protein of human cone PDE6C in rods of transgenic Xenopus laevis. EGFP-PDE6C is correctly targeted to the rod outer segments in transgenic Xenopus, where it displayed a characteristic striated pattern of EGFP fluorescence. Immunofluorescence labeling indicated significant and light-independent co-localization of EGFP-PDE6C with the disc rim marker peripherin-2 and endogenous frog PDE6. The diffusion of EGFP-PDE6C on disc membranes investigated with fluorescence recovery after photobleaching was markedly slower than theoretically predicted. The enzymatic characteristics of immunoprecipitated recombinant PDE6C were similar to known properties of the native bovine PDE6C. PDE6C was potently inhibited by the cone- and rod-specific PDE6 gamma-subunits. Thus, transgenic Xenopus laevis is a unique expression system for PDE6 well suited for analysis of the mechanisms of visual diseases linked to PDE6 mutations.
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Affiliation(s)
- Hakim Muradov
- From the
Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, Iowa 52242 and
| | - Kimberly K. Boyd
- From the
Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, Iowa 52242 and
| | - Mohammad Haeri
- the Departments of
Biochemistry and Molecular Biology and
| | - Vasily Kerov
- From the
Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, Iowa 52242 and
| | - Barry E. Knox
- the Departments of
Biochemistry and Molecular Biology and
- Ophthalmology, SUNY Upstate Medical University, Syracuse, New York 13210
| | - Nikolai O. Artemyev
- From the
Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, Iowa 52242 and
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