1
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FKBP52 overexpression accelerates hippocampal-dependent memory impairments in a tau transgenic mouse model. NPJ Aging Mech Dis 2021; 7:9. [PMID: 33941782 PMCID: PMC8093247 DOI: 10.1038/s41514-021-00062-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2020] [Accepted: 02/17/2021] [Indexed: 01/31/2023] Open
Abstract
Abnormal accumulation of hyperphosphorylated tau induces pathogenesis in neurodegenerative diseases, like Alzheimer's disease. Molecular chaperones with peptidyl-prolyl cis/trans isomerase (PPIase) activity are known to regulate these processes. Previously, in vitro studies have shown that the 52 kDa FK506-binding protein (FKBP52) interacts with tau inducing its oligomerization and fibril formation to promote toxicity. Thus, we hypothesized that increased expression of FKBP52 in the brains of tau transgenic mice would alter tau phosphorylation and neurofibrillary tangle formation ultimately leading to memory impairments. To test this, tau transgenic (rTg4510) and wild-type mice received bilateral hippocampal injections of virus overexpressing FKBP52 or GFP control. We examined hippocampal-dependent memory, synaptic plasticity, tau phosphorylation status, and neuronal health. This work revealed that rTg4510 mice overexpressing FKBP52 had impaired spatial learning, accompanied by long-term potentiation deficits and hippocampal neuronal loss, which was associated with a modest increase in total caspase 12. Together with previous studies, our findings suggest that FKBP52 may sensitize neurons to tau-mediated dysfunction via activation of a caspase-dependent pathway, contributing to memory and learning impairments.
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2
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Buckley C, Wilson C, McCarron JG. FK506 regulates Ca 2+ release evoked by inositol 1,4,5-trisphosphate independently of FK-binding protein in endothelial cells. Br J Pharmacol 2020; 177:1131-1149. [PMID: 31705533 PMCID: PMC7042112 DOI: 10.1111/bph.14905] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2019] [Revised: 10/08/2019] [Accepted: 10/10/2019] [Indexed: 12/16/2022] Open
Abstract
Background and Purpose FK506 and rapamycin are modulators of FK‐binding proteins (FKBP) that are used to suppress immune function after organ and hematopoietic stem cell transplantations. The drugs share the unwanted side‐effect of evoking hypertension that is associated with reduced endothelial function and nitric oxide production. The underlying mechanisms are not understood. FKBP may regulate IP3 receptors (IP3R) and ryanodine receptors (RyR) to alter Ca2+ signalling in endothelial cells. Experimental Approach We investigated the effects of FK506 and rapamycin on Ca2+ release via IP3R and RyR in hundreds of endothelial cells, using the indicator Cal‐520, in intact mesenteric arteries from male Sprague‐Dawley rats. IP3Rs were activated by acetylcholine or localised photo‐uncaging of IP3, and RyR by caffeine. Key Results While FKBPs were present, FKBP modulation with rapamycin did not alter IP3‐evoked Ca2+ release. Conversely, FK506, which modulates FKBP and blocks calcineurin, increased IP3‐evoked Ca2+ release. Inhibition of calcineurin (okadiac acid or cypermethrin) also increased IP3‐evoked Ca2+ release and blocked FK506 effects. When calcineurin was inhibited, FK506 reduced IP3‐evoked Ca2+ release. These findings suggest that IP3‐evoked Ca2+ release is not modulated by FKBP, but by FK506‐mediated calcineurin inhibition. The RyR modulators caffeine and ryanodine failed to alter Ca2+ signalling suggesting that RyR is not functional in native endothelium. Conclusion and Implications The hypertensive effects of the immunosuppressant drugs FK506 and rapamycin, while mediated by endothelial cells, do not appear to be exerted at the documented cellular targets of Ca2+ release and altered FKBP binding to IP3 and RyR.
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Affiliation(s)
- Charlotte Buckley
- Strathclyde Institute of Pharmacy and Biomedical Science, University of Strathclyde, Glasgow, UK
| | - Calum Wilson
- Strathclyde Institute of Pharmacy and Biomedical Science, University of Strathclyde, Glasgow, UK
| | - John G McCarron
- Strathclyde Institute of Pharmacy and Biomedical Science, University of Strathclyde, Glasgow, UK
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3
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Haldar B, Hamilton CL, Solodushko V, Abney KA, Alexeyev M, Honkanen RE, Scammell JG, Cioffi DL. S100A6 is a positive regulator of PPP5C-FKBP51-dependent regulation of endothelial calcium signaling. FASEB J 2020; 34:3179-3196. [PMID: 31916625 DOI: 10.1096/fj.201901777r] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2019] [Revised: 10/18/2019] [Accepted: 12/19/2019] [Indexed: 11/11/2022]
Abstract
ISOC is a cation current permeating the ISOC channel. In pulmonary endothelial cells, ISOC activation leads to formation of inter-endothelial cell gaps and barrier disruption. The immunophilin FK506-binding protein 51 (FKBP51), in conjunction with the serine/threonine protein phosphatase 5C (PPP5C), inhibits ISOC . Free PPP5C assumes an autoinhibitory state, which has low "basal" catalytic activity. Several S100 protein family members bind PPP5C increasing PPP5C catalytic activity in vitro. One of these family members, S100A6, exhibits a calcium-dependent translocation to the plasma membrane. The goal of this study was to determine whether S100A6 activates PPP5C in pulmonary endothelial cells and contributes to ISOC inhibition by the PPP5C-FKBP51 axis. We observed that S100A6 activates PPP5C to dephosphorylate tau T231. Following ISOC activation, cytosolic S100A6 translocates to the plasma membrane and interacts with the TRPC4 subunit of the ISOC channel. Global calcium entry and ISOC are decreased by S100A6 in a PPP5C-dependent manner and by FKBP51 in a S100A6-dependent manner. Further, calcium entry-induced endothelial barrier disruption is decreased by S100A6 dependent upon PPP5C, and by FKBP51 dependent upon S100A6. Overall, these data reveal that S100A6 plays a key role in the PPP5C-FKBP51 axis to inhibit ISOC and protect the endothelial barrier against calcium entry-induced disruption.
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Affiliation(s)
- Barnita Haldar
- Departments of Biochemistry and Molecular Biology, University of South Alabama, Mobile, AL, USA.,Center for Lung Biology, University of South Alabama, Mobile, AL, USA
| | - Caleb L Hamilton
- Department of Anatomy and Molecular Medicine, Alabama College of Osteopathic Medicine, Dothan, AL, USA
| | - Viktoriya Solodushko
- Departments of Biochemistry and Molecular Biology, University of South Alabama, Mobile, AL, USA
| | - Kevin A Abney
- Departments of Biochemistry and Molecular Biology, University of South Alabama, Mobile, AL, USA
| | - Mikhail Alexeyev
- Center for Lung Biology, University of South Alabama, Mobile, AL, USA.,Physiology and Cell Biology, University of South Alabama, Mobile, AL, USA
| | - Richard E Honkanen
- Departments of Biochemistry and Molecular Biology, University of South Alabama, Mobile, AL, USA
| | | | - Donna L Cioffi
- Departments of Biochemistry and Molecular Biology, University of South Alabama, Mobile, AL, USA.,Center for Lung Biology, University of South Alabama, Mobile, AL, USA
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4
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Abstract
The FK506-binding protein 51 (FKBP51) has emerged as a key regulator of endocrine stress responses in mammals and as a potential therapeutic target for stress-related disorders (depression, post-traumatic stress disorder), metabolic disorders (obesity and diabetes) and chronic pain. Recently, FKBP51 has been implicated in several cellular pathways and numerous interacting protein partners have been reported. However, no consensus on the underlying molecular mechanisms has yet emerged. Here, we review the protein interaction partners reported for FKBP51, the proposed pathways involved, their relevance to FKBP51’s physiological function(s), the interplay with other FKBPs, and implications for the development of FKBP51-directed drugs.
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5
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Kusuda Y, Kondo Y, Miyagi Y, Munemasa T, Hori Y, Aonuma F, Tsuka S, Mukaibo T, Masaki C, Hosokawa R. Long-term dexamethasone treatment diminishes store-operated Ca 2+ entry in salivary acinar cells. Int J Oral Sci 2019; 11:1. [PMID: 30602784 PMCID: PMC6315037 DOI: 10.1038/s41368-018-0031-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2017] [Revised: 05/10/2018] [Accepted: 05/14/2018] [Indexed: 11/09/2022] Open
Abstract
Corticosteroids are used in the treatment of many diseases; however, they also induce various side effects. Dexamethasone is one of the most potent corticosteroids, and it has been reported to induce the side effect of impaired salivary gland function. This study aimed to evaluate the effects of dexamethasone on mouse submandibular gland function to gain insight into the mechanism of dexamethasone-induced salivary hypofunction. The muscarinic agonist carbachol (CCh) induced salivary secretion and was not affected by short-term dexamethasone treatment but was decreased following long-term dexamethasone administration. The expression levels of the membrane proteins Na+-K+-2Cl- cotransporter, transmembrane member 16A, and aquaporin 5 were comparable between the control and long-term dexamethasone treatment groups. The CCh-induced increase in calcium concentration was significantly lower in the presence of extracellular Ca2+ in the long-term dexamethasone treatment group compared to that in the control group. Furthermore, CCh-induced salivation in the absence of extracellular Ca2+ and Ca2+ ionophore A23187-induced salivation was comparable between the control and long-term dexamethasone treatment groups. Moreover, salivation induced by the Ca2+-ATPase inhibitor thapsigargin was diminished in the long-term dexamethasone treatment group. In summary, these results demonstrate that short-term dexamethasone treatment did not impair salivary gland function, whereas long-term dexamethasone treatment diminished store-operated Ca2+ entry, resulting in hyposalivation in mouse submandibular glands.
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Affiliation(s)
- Yuichiro Kusuda
- Division of Oral Reconstruction and Rehabilitation, Kyushu Dental University, Kitakyushu, Fukuoka, 803-8580, Japan
| | - Yusuke Kondo
- Division of Oral Reconstruction and Rehabilitation, Kyushu Dental University, Kitakyushu, Fukuoka, 803-8580, Japan.
| | - Yuta Miyagi
- Division of Oral Reconstruction and Rehabilitation, Kyushu Dental University, Kitakyushu, Fukuoka, 803-8580, Japan
| | - Takashi Munemasa
- Division of Oral Reconstruction and Rehabilitation, Kyushu Dental University, Kitakyushu, Fukuoka, 803-8580, Japan
| | - Yusuke Hori
- Division of Oral Reconstruction and Rehabilitation, Kyushu Dental University, Kitakyushu, Fukuoka, 803-8580, Japan
| | - Fumiko Aonuma
- Division of Oral Reconstruction and Rehabilitation, Kyushu Dental University, Kitakyushu, Fukuoka, 803-8580, Japan
| | - Shintaro Tsuka
- Division of Oral Reconstruction and Rehabilitation, Kyushu Dental University, Kitakyushu, Fukuoka, 803-8580, Japan
| | - Taro Mukaibo
- Division of Oral Reconstruction and Rehabilitation, Kyushu Dental University, Kitakyushu, Fukuoka, 803-8580, Japan
| | - Chihiro Masaki
- Division of Oral Reconstruction and Rehabilitation, Kyushu Dental University, Kitakyushu, Fukuoka, 803-8580, Japan
| | - Ryuji Hosokawa
- Division of Oral Reconstruction and Rehabilitation, Kyushu Dental University, Kitakyushu, Fukuoka, 803-8580, Japan
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6
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Criado-Marrero M, Rein T, Binder EB, Porter JT, Koren J, Blair LJ. Hsp90 and FKBP51: complex regulators of psychiatric diseases. Philos Trans R Soc Lond B Biol Sci 2018; 373:rstb.2016.0532. [PMID: 29203717 DOI: 10.1098/rstb.2016.0532] [Citation(s) in RCA: 81] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2017] [Accepted: 09/11/2017] [Indexed: 01/30/2023] Open
Abstract
Mood disorders affect nearly a quarter of the world's population. Therefore, understanding the molecular mechanisms underlying these conditions is of great importance. FK-506 binding protein 5 (FKBP5) encodes the FKBP51 protein, a heat shock protein 90 kDa (Hsp90) co-chaperone, and is a risk factor for several affective disorders. FKBP51, in coordination with Hsp90, regulates glucocorticoid receptor (GR) activity via a short negative feedback loop. This signalling pathway rapidly restores homeostasis in the hypothalamic-pituitary-adrenal (HPA) axis following stress. Expression of FKBP5 increases with age through reduced DNA methylation. High levels of FKBP51 are linked to GR resistance and reduced stress coping behaviour. Moreover, common allelic variants in the FKBP5 gene are associated with increased risk of developing affective disorders like anxiety, depression and post-traumatic stress disorder (PTSD). This review highlights the current understanding of the Hsp90 co-chaperone, FKBP5, in disease from both human and animal studies. In addition, FKBP5 genetic implications in the clinic involving life stress exposure, gender differences and treatment outcomes are discussed.This article is part of the theme issue 'Heat shock proteins as modulators and therapeutic targets of chronic disease: an integrated perspective'.
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Affiliation(s)
- Marangelie Criado-Marrero
- Department of Molecular Medicine, Byrd Alzheimer's Research Institute, University of South Florida, Tampa, FL 33613, USA
| | - Theo Rein
- Department of Translational Research in Psychiatry, Max Planck Institute of Psychiatry, 80804 Munich, Germany
| | - Elisabeth B Binder
- Department of Translational Research in Psychiatry, Max Planck Institute of Psychiatry, 80804 Munich, Germany.,Department of Psychiatry and Behavioral Sciences, Emory University School of Medicine, Atlanta, GA 30307, USA
| | - James T Porter
- Department of Basic Sciences, Ponce Health Sciences University-School of Medicine/Ponce Research Institute, Ponce, Puerto Rico 00732, USA
| | - John Koren
- Department of Molecular Medicine, Byrd Alzheimer's Research Institute, University of South Florida, Tampa, FL 33613, USA
| | - Laura J Blair
- Department of Molecular Medicine, Byrd Alzheimer's Research Institute, University of South Florida, Tampa, FL 33613, USA
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7
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Hamilton CL, Abney KA, Vasauskas AA, Alexeyev M, Li N, Honkanen RE, Scammell JG, Cioffi DL. Serine/threonine phosphatase 5 (PP5C/PPP5C) regulates the ISOC channel through a PP5C-FKBP51 axis. Pulm Circ 2017; 8:2045893217753156. [PMID: 29283027 PMCID: PMC6018905 DOI: 10.1177/2045893217753156] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Pulmonary endothelial cells express a store-operated calcium entry current (Isoc), which contributes to inter-endothelial cell gap formation. Isoc is regulated by a heterocomplex of proteins that includes the immunophilin FKBP51. FKBP51 inhibits Isoc by mechanisms that are not fully understood. In pulmonary artery endothelial cells (PAECs) we have shown that FKBP51 increases microtubule polymerization, an event that is critical for Isoc inhibition by FKBP51. In neurons, FKBP51 promotes microtubule stability through facilitation of tau dephosphorylation. However, FKBP51 does not possess phosphatase activity. Protein phosphatase 5 (PP5C/PPP5C) can dephosphorylate tau, and similar to FKBP51, PP5C possesses tetratricopeptide repeats (TPR) that mediate interaction with heat shock protein-90 (HSP90) chaperone/scaffolding complexes. We therefore tested whether PP5C contributes to FKBP51-mediated inhibition of Isoc. Both siRNA-mediated suppression of PP5C expression in PAECs and genetic disruption of PP5C in HEK293 cells attenuate FKBP51-mediated inhibition of Isoc. Reintroduction of catalytically competent, but not catalytically inactive PP5C, restored FKBP51-mediated inhibition of Isoc. PAEC cell fractionation studies identified both PP5C and the ISOC heterocomplex in the same membrane fractions. Further, PP5C co-precipitates with TRPC4, an essential subunit of ISOC channel. Finally, to determine if PP5C is required for FKBP51-mediated inhibition of calcium entry-induced inter-endothelial cell gap formation, we measured gap area by wide-field microscopy and performed biotin gap quantification assay and electric cell-substrate impedance sensing (ECIS®). Collectively, the data presented indicate that suppression of PP5C expression negates the protective effect of FKBP51. These observations identify PP5C as a novel member of the ISOC heterocomplex that is required for FKBP51-mediated inhibition of Isoc.
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Affiliation(s)
| | | | | | | | - Ni Li
- University of South Alabama
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8
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Hamilton CL, Kadeba PI, Vasauskas AA, Solodushko V, McClinton AK, Alexeyev M, Scammell JG, Cioffi DL. Protective role of FKBP51 in calcium entry-induced endothelial barrier disruption. Pulm Circ 2017; 8:2045893217749987. [PMID: 29261039 PMCID: PMC5798693 DOI: 10.1177/2045893217749987] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Pulmonary artery endothelial cells (PAECs) express a cation current, ISOC (store-operated calcium entry current), which when activated permits calcium entry leading to inter-endothelial cell gap formation. The large molecular weight immunophilin FKBP51 inhibits ISOC but not other calcium entry pathways in PAECs. However, it is unknown whether FKBP51-mediated inhibition of ISOC is sufficient to protect the endothelial barrier from calcium entry-induced disruption. The major objective of this study was to determine whether FKBP51-mediated inhibition of ISOC leads to decreased calcium entry-induced inter-endothelial gap formation and thus preservation of the endothelial barrier. Here, we measured the effects of thapsigargin-induced ISOC on the endothelial barrier in control and FKBP51 overexpressing PAECs. FKBP51 overexpression decreased actin stress fiber and inter-endothelial cell gap formation in addition to attenuating the decrease in resistance observed with control cells using electric cell-substrate impedance sensing. Finally, the thapsigargin-induced increase in dextran flux was abolished in FKBP51 overexpressing PAECs. We then measured endothelial permeability in perfused lungs of FKBP51 knockout (FKBP51–/–) mice and observed increased calcium entry-induced permeability compared to wild-type mice. To begin to dissect the mechanism underlying the FKBP51-mediated inhibition of ISOC, a second goal of this study was to determine the role of the microtubule network. We observed that FKBP51 overexpressing PAECs exhibited increased microtubule polymerization that is critical for inhibition of ISOC by FKBP51. Overall, we have identified FKBP51 as a novel regulator of endothelial barrier integrity, and these findings are significant as they reveal a protective mechanism for endothelium against calcium entry-induced disruption.
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Affiliation(s)
- Caleb L Hamilton
- 1 5557 Department of Biochemistry and Molecular Biology , University of South Alabama, Mobile, AL, USA.,2 Center for Lung Biology, University of South Alabama, Mobile, AL, USA
| | - Pierre I Kadeba
- 1 5557 Department of Biochemistry and Molecular Biology , University of South Alabama, Mobile, AL, USA.,2 Center for Lung Biology, University of South Alabama, Mobile, AL, USA
| | - Audrey A Vasauskas
- 3 376598 Department of Anatomical Sciences and Molecular Medicine , Alabama College of Osteopathic Medicine, Dothan, AL, USA
| | - Viktoriya Solodushko
- 1 5557 Department of Biochemistry and Molecular Biology , University of South Alabama, Mobile, AL, USA
| | - Anna K McClinton
- 2 Center for Lung Biology, University of South Alabama, Mobile, AL, USA.,4 Department of Pharmacology, University of South Alabama, Mobile, AL, USA
| | - Mikhail Alexeyev
- 2 Center for Lung Biology, University of South Alabama, Mobile, AL, USA.,5 Department of Physiology and Cell Biology, University of South Alabama, Mobile, AL, USA
| | - Jonathan G Scammell
- 6 Department of Comparative Medicine, 5557 University of South Alabama , Mobile, AL, USA
| | - Donna L Cioffi
- 1 5557 Department of Biochemistry and Molecular Biology , University of South Alabama, Mobile, AL, USA.,2 Center for Lung Biology, University of South Alabama, Mobile, AL, USA
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9
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Systems biology of ion channels and transporters in tumor angiogenesis: An omics view. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2015; 1848:2647-56. [DOI: 10.1016/j.bbamem.2014.10.031] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/2014] [Revised: 10/09/2014] [Accepted: 10/20/2014] [Indexed: 01/19/2023]
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10
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Nilius B, Szallasi A. Transient Receptor Potential Channels as Drug Targets: From the Science of Basic Research to the Art of Medicine. Pharmacol Rev 2014; 66:676-814. [DOI: 10.1124/pr.113.008268] [Citation(s) in RCA: 348] [Impact Index Per Article: 34.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
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11
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Abstract
TRPC4 proteins comprise six transmembrane domains, a putative pore-forming region, and an intracellularly located amino- and carboxy-terminus. Among eleven splice variants identified so far, TRPC4α and TRPC4β are the most abundantly expressed and functionally characterized. TRPC4 is expressed in various organs and cell types including the soma and dendrites of numerous types of neurons; the cardiovascular system including endothelial, smooth muscle, and cardiac cells; myometrial and skeletal muscle cells; kidney; and immune cells such as mast cells. Both recombinant and native TRPC4-containing channels differ tremendously in their permeability and other biophysical properties, pharmacological modulation, and mode of activation depending on the cellular environment. They vary from inwardly rectifying store-operated channels with a high Ca(2+) selectivity to non-store-operated channels predominantly carrying Na(+) and activated by Gαq- and/or Gαi-coupled receptors with a complex U-shaped current-voltage relationship. Thus, individual TRPC4-containing channels contribute to agonist-induced Ca(2+) entry directly or indirectly via depolarization and activation of voltage-gated Ca(2+) channels. The differences in channel properties may arise from variations in the composition of the channel complexes, in the specific regulatory pathways in the corresponding cell system, and/or in the expression pattern of interaction partners which comprise other TRPC proteins to form heteromultimeric channels. Additional interaction partners of TRPC4 that can mediate the activity of TRPC4-containing channels include (1) scaffolding proteins (e.g., NHERF) that may mediate interactions with signaling molecules in or in close vicinity to the plasma membrane such as Gα proteins or phospholipase C and with the cytoskeleton, (2) proteins in specific membrane microdomains (e.g., caveolin-1), or (3) proteins on cellular organelles (e.g., Stim1). The diversity of TRPC4-containing channels hampers the development of specific agonists or antagonists, but recently, ML204 was identified as a blocker of both recombinant and endogenous TRPC4-containing channels with an IC50 in the lower micromolar range that lacks activity on most voltage-gated channels and other TRPs except TRPC5 and TRPC3. Lanthanides are specific activators of heterologously expressed TRPC4- and TRPC5-containing channels but can block individual native TRPC4-containing channels. The biological relevance of TRPC4-containing channels was demonstrated by knockdown of TRPC4 expression in numerous native systems including gene expression, cell differentiation and proliferation, formation of myotubes, and axonal regeneration. Studies of TRPC4 single and TRPC compound knockout mice uncovered their role for the regulation of vascular tone, endothelial permeability, gastrointestinal contractility and motility, neurotransmitter release, and social exploratory behavior as well as for excitotoxicity and epileptogenesis. Recently, a single-nucleotide polymorphism (SNP) in the Trpc4 gene was associated with a reduced risk for experience of myocardial infarction.
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Affiliation(s)
- Marc Freichel
- Pharmakologisches Institut, Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer Feld 366, 69120, Heidelberg, Germany,
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12
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Bracher A, Kozany C, Hähle A, Wild P, Zacharias M, Hausch F. Crystal structures of the free and ligand-bound FK1-FK2 domain segment of FKBP52 reveal a flexible inter-domain hinge. J Mol Biol 2013; 425:4134-44. [PMID: 23933011 DOI: 10.1016/j.jmb.2013.07.041] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2013] [Revised: 07/30/2013] [Accepted: 07/31/2013] [Indexed: 12/11/2022]
Abstract
The human Hsp90 co-chaperone FKBP52 belongs to the family of FK506-binding proteins, which act as peptidyl-prolyl isomerases. FKBP52 specifically enhances the signaling of steroid hormone receptors, modulates ion channels and regulates neuronal outgrowth dynamics. In turn, small-molecule ligands of FKBP52 have been suggested as potential neurotrophic or anti-prostate cancer agents. The usefulness of available ligands is however limited by a lack of selectivity. The immunophilin FKBP52 is composed of three domains, an FK506-binding domain with peptidyl-prolyl isomerase activity, an FKBP-like domain of unknown function and a TPR-clamp domain, which recognizes the C-terminal peptide of Hsp90 with high affinity. The herein reported crystal structures of FKBP52 reveal that the short linker connecting the FK506-binding domain and the FKBP-like domain acts as a flexible hinge. This enhanced flexibility and its modulation by phosphorylation might explain some of the functional antagonism between the closely related homologs FKBP51 and FKBP52. We further present two co-crystal structures of FKBP52 in complex with the prototypic ligand FK506 and a synthetic analog thereof. These structures revealed the molecular interactions in great detail, which enabled in-depth comparison with the corresponding complexes of the other cytosolic FKBPs, FKBP51 and FKBP12. The observed subtle differences provide crucial insights for the rational design of ligands with improved selectivity for FKBP52.
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Affiliation(s)
- Andreas Bracher
- Department of Cellular Biochemistry, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany.
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13
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Abstract
FK506-binding proteins (FKBP) belong to the immunophilin family and are best known for their ability to enable the immunosuppressive properties of FK506 and rapamycin. For rapamycin, this is achieved by inducing inhibitory ternary complexes with the kinase mTOR. The essential accessory protein for this gain-of-function was thought to be FKBP12. We recently showed that this view might be too restricted, since larger FK506-binding proteins can functionally substitute for FKBP12 in mammalian cells. Recent studies have also shown that FK506-binding proteins can modulate Akt-mTOR signaling in the absence of rapamycin. Here we discuss the role of FK506-binding proteins for the mechanism of rapamycin as well as their intrinsic actions on the Akt/mTOR pathway.
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Affiliation(s)
- Felix Hausch
- Max Planck Institute of Psychiatry; Munich, Germany
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