1
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Terry LE, Alzayady KJ, Wahl AM, Malik S, Yule DI. Disease-associated mutations in inositol 1,4,5-trisphosphate receptor subunits impair channel function. J Biol Chem 2020; 295:18160-18178. [PMID: 33093175 PMCID: PMC7939385 DOI: 10.1074/jbc.ra120.015683] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [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: 08/17/2020] [Revised: 10/21/2020] [Indexed: 01/27/2023] Open
Abstract
The inositol 1,4,5-trisphosphate (IP3) receptors (IP3Rs), which form tetrameric channels, play pivotal roles in regulating the spatiotemporal patterns of intracellular calcium signals. Mutations in IP3Rs have been increasingly associated with many debilitating human diseases such as ataxia, Gillespie syndrome, and generalized anhidrosis. However, how these mutations affect IP3R function, and how the perturbation of as-sociated calcium signals contribute to the pathogenesis and severity of these diseases remains largely uncharacterized. Moreover, many of these diseases occur as the result of autosomal dominant inheritance, suggesting that WT and mutant subunits associate in heterotetrameric channels. How the in-corporation of different numbers of mutant subunits within the tetrameric channels affects its activities and results in different disease phenotypes is also unclear. In this report, we investigated representative disease-associated missense mutations to determine their effects on IP3R channel activity. Additionally, we designed concatenated IP3R constructs to create tetrameric channels with a predefined subunit composition to explore the functionality of heteromeric channels. Using calcium imaging techniques to assess IP3R channel function, we observed that all the mutations studied resulted in severely attenuated Ca2+ release when expressed as homotetramers. However, some heterotetramers retained varied degrees of function dependent on the composition of the tetramer. Our findings suggest that the effect of mutations depends on the location of the mutation in the IP3R structure, as well as on the stoichiometry of mutant subunits assembled within the tetrameric channel. These studies provide insight into the pathogenesis and penetrance of these devastating human diseases.
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Affiliation(s)
- Lara E Terry
- Department of Pharmacology and Physiology, University of Rochester, Rochester, New York, USA
| | - Kamil J Alzayady
- Department of Pharmacology and Physiology, University of Rochester, Rochester, New York, USA
| | - Amanda M Wahl
- Department of Pharmacology and Physiology, University of Rochester, Rochester, New York, USA
| | - Sundeep Malik
- Department of Pharmacology and Physiology, University of Rochester, Rochester, New York, USA
| | - David I Yule
- Department of Pharmacology and Physiology, University of Rochester, Rochester, New York, USA.
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2
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Argent L, Winter F, Prickett I, Carrasquero-Ordaz M, Olsen AL, Kramer H, Lancaster E, Becker EBE. Caspr2 interacts with type 1 inositol 1,4,5-trisphosphate receptor in the developing cerebellum and regulates Purkinje cell morphology. J Biol Chem 2020; 295:12716-12726. [PMID: 32675284 PMCID: PMC7476715 DOI: 10.1074/jbc.ra120.012655] [Citation(s) in RCA: 3] [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] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2020] [Revised: 07/01/2020] [Indexed: 12/18/2022] Open
Abstract
Contactin-associated protein-like 2 (Caspr2) is a neurexin-like protein that has been associated with numerous neurological conditions. However, the specific functional roles that Caspr2 plays in the central nervous system and their underlying mechanisms remain incompletely understood. Here, we report on a functional role for Caspr2 in the developing cerebellum. Using a combination of confocal microscopy, biochemical analyses, and behavioral testing, we show that loss of Caspr2 in the Cntnap2-/- knockout mouse results in impaired Purkinje cell dendritic development, altered intracellular signaling, and motor coordination deficits. We also find that Caspr2 is highly enriched at synaptic specializations in the cerebellum. Using a proteomics approach, we identify type 1 inositol 1,4,5-trisphosphate receptor (IP3R1) as a specific synaptic interaction partner of the Caspr2 extracellular domain in the molecular layer of the developing cerebellum. The interaction of the Caspr2 extracellular domain with IP3R1 inhibits IP3R1-mediated changes in cellular morphology. Together, our work defines a mechanism by which Caspr2 controls the development and function of the cerebellum and advances our understanding of how Caspr2 dysfunction might lead to specific brain disorders.
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Affiliation(s)
- Liam Argent
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - Friederike Winter
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - Imogen Prickett
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | | | - Abby L Olsen
- Department of Neurology, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Holger Kramer
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - Eric Lancaster
- Department of Neurology, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Esther B E Becker
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
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3
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Guo W, Sun B, Estillore JP, Wang R, Chen SRW. The central domain of cardiac ryanodine receptor governs channel activation, regulation, and stability. J Biol Chem 2020; 295:15622-15635. [PMID: 32878990 DOI: 10.1074/jbc.ra120.013512] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2020] [Revised: 08/25/2020] [Indexed: 11/06/2022] Open
Abstract
Structural analyses identified the central domain of ryanodine receptor (RyR) as a transducer converting conformational changes in the cytoplasmic platform to the RyR gate. The central domain is also a regulatory hub encompassing the Ca2+-, ATP-, and caffeine-binding sites. However, the role of the central domain in RyR activation and regulation has yet to be defined. Here, we mutated five residues that form the Ca2+ activation site and 10 residues with negatively charged or oxygen-containing side chains near the Ca2+ activation site. We also generated eight disease-associated mutations within the central domain of RyR2. We determined the effect of these mutations on Ca2+, ATP, and caffeine activation and Mg2+ inhibition of RyR2. Mutating the Ca2+ activation site markedly reduced the sensitivity of RyR2 to Ca2+ and caffeine activation. Unexpectedly, Ca2+ activation site mutation E3848A substantially enhanced the Ca2+-independent basal activity of RyR2, suggesting that E3848A may also affect the stability of the closed state of RyR2. Mutations in the Ca2+ activation site also abolished the effect of ATP/caffeine on the Ca2+-independent basal activity, suggesting that the Ca2+ activation site is also a critical determinant of ATP/caffeine action. Mutating residues with negatively charged or oxygen-containing side chains near the Ca2+ activation site significantly altered Ca2+ and caffeine activation and reduced Mg2+ inhibition. Furthermore, disease-associated RyR2 mutations within the central domain significantly enhanced Ca2+ and caffeine activation and reduced Mg2+ inhibition. Our data demonstrate that the central domain plays an important role in channel activation, channel regulation, and closed state stability.
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Affiliation(s)
- Wenting Guo
- Department of Physiology and Pharmacology, Libin Cardiovascular Institute, University of Calgary, Calgary, Alberta, Canada; Department of Biochemistry and Molecular Biology, Libin Cardiovascular Institute, University of Calgary, Calgary, Alberta, Canada
| | - Bo Sun
- Department of Physiology and Pharmacology, Libin Cardiovascular Institute, University of Calgary, Calgary, Alberta, Canada; Department of Biochemistry and Molecular Biology, Libin Cardiovascular Institute, University of Calgary, Calgary, Alberta, Canada; Medical School, Kunming University of Science and Technology, Kunming, China
| | - John Paul Estillore
- Department of Physiology and Pharmacology, Libin Cardiovascular Institute, University of Calgary, Calgary, Alberta, Canada; Department of Biochemistry and Molecular Biology, Libin Cardiovascular Institute, University of Calgary, Calgary, Alberta, Canada
| | - Ruiwu Wang
- Department of Physiology and Pharmacology, Libin Cardiovascular Institute, University of Calgary, Calgary, Alberta, Canada; Department of Biochemistry and Molecular Biology, Libin Cardiovascular Institute, University of Calgary, Calgary, Alberta, Canada
| | - S R Wayne Chen
- Department of Physiology and Pharmacology, Libin Cardiovascular Institute, University of Calgary, Calgary, Alberta, Canada; Department of Biochemistry and Molecular Biology, Libin Cardiovascular Institute, University of Calgary, Calgary, Alberta, Canada.
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4
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Alogaili F, Chinnarasu S, Jaeschke A, Kranias EG, Hui DY. Hepatic HAX-1 inactivation prevents metabolic diseases by enhancing mitochondrial activity and bile salt export. J Biol Chem 2020; 295:4631-4646. [PMID: 32079675 DOI: 10.1074/jbc.ra119.012361] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2019] [Revised: 02/04/2020] [Indexed: 12/26/2022] Open
Abstract
Increasing hepatic mitochondrial activity through pyruvate dehydrogenase and elevating enterohepatic bile acid recirculation are promising new approaches for metabolic disease therapy, but neither approach alone can completely ameliorate disease phenotype in high-fat diet-fed mice. This study showed that diet-induced hepatosteatosis, hyperlipidemia, and insulin resistance can be completely prevented in mice with liver-specific HCLS1-associated protein X-1 (HAX-1) inactivation. Mechanistically, we showed that HAX-1 interacts with inositol 1,4,5-trisphosphate receptor-1 (InsP3R1) in the liver, and its absence reduces InsP3R1 levels, thereby improving endoplasmic reticulum-mitochondria calcium homeostasis to prevent excess calcium overload and mitochondrial dysfunction. As a result, HAX-1 ablation activates pyruvate dehydrogenase and increases mitochondria utilization of glucose and fatty acids to prevent hepatosteatosis, hyperlipidemia, and insulin resistance. In contrast to the reduction of InsP3R1 levels, hepatic HAX-1 deficiency increases bile salt exporter protein levels, thereby promoting enterohepatic bile acid recirculation, leading to activation of bile acid-responsive genes in the intestinal ileum to augment insulin sensitivity and of cholesterol transport genes in the liver to suppress hyperlipidemia. The dual mechanisms of increased mitochondrial respiration and enterohepatic bile acid recirculation due to improvement of endoplasmic reticulum-mitochondria calcium homeostasis with hepatic HAX-1 inactivation suggest that this may be a potential therapeutic target for metabolic disease intervention.
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Affiliation(s)
- Fawzi Alogaili
- Department of Pathology and Laboratory Medicine, Metabolic Diseases Research Center, University of Cincinnati College of Medicine, Cincinnati, Ohio 45237.,Department of Pharmacology and Systems Physiology, University of Cincinnati College of Medicine, Cincinnati, Ohio 45267
| | - Sivaprakasam Chinnarasu
- Department of Pathology and Laboratory Medicine, Metabolic Diseases Research Center, University of Cincinnati College of Medicine, Cincinnati, Ohio 45237
| | - Anja Jaeschke
- Department of Pathology and Laboratory Medicine, Metabolic Diseases Research Center, University of Cincinnati College of Medicine, Cincinnati, Ohio 45237
| | - Evangelia G Kranias
- Department of Pharmacology and Systems Physiology, University of Cincinnati College of Medicine, Cincinnati, Ohio 45267
| | - David Y Hui
- Department of Pathology and Laboratory Medicine, Metabolic Diseases Research Center, University of Cincinnati College of Medicine, Cincinnati, Ohio 45237
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5
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Azumaya CM, Linton EA, Risener CJ, Nakagawa T, Karakas E. Cryo-EM structure of human type-3 inositol triphosphate receptor reveals the presence of a self-binding peptide that acts as an antagonist. J Biol Chem 2020; 295:1743-1753. [PMID: 31915246 PMCID: PMC7008357 DOI: 10.1074/jbc.ra119.011570] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [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: 10/22/2019] [Revised: 01/06/2020] [Indexed: 01/04/2023] Open
Abstract
Calcium-mediated signaling through inositol 1,4,5-triphosphate receptors (IP3Rs) is essential for the regulation of numerous physiological processes, including fertilization, muscle contraction, apoptosis, secretion, and synaptic plasticity. Deregulation of IP3Rs leads to pathological calcium signaling and is implicated in many common diseases, including cancer and neurodegenerative, autoimmune, and metabolic diseases. Revealing the mechanism of activation and inhibition of this ion channel will be critical to an improved understanding of the biological processes that are controlled by IP3Rs. Here, we report structural findings of the human type-3 IP3R (IP3R-3) obtained by cryo-EM (at an overall resolution of 3.8 Å), revealing an unanticipated regulatory mechanism where a loop distantly located in the primary sequence occupies the IP3-binding site and competitively inhibits IP3 binding. We propose that this inhibitory mechanism must differ qualitatively among IP3R subtypes because of their diverse loop sequences, potentially serving as a key molecular determinant of subtype-specific calcium signaling in IP3Rs. In summary, our structural characterization of human IP3R-3 provides critical insights into the mechanistic function of IP3Rs and into subtype-specific regulation of these important calcium-regulatory channels.
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MESH Headings
- Binding Sites
- Calcium Signaling
- Cryoelectron Microscopy
- Humans
- Inositol 1,4,5-Trisphosphate/metabolism
- Inositol 1,4,5-Trisphosphate Receptors/antagonists & inhibitors
- Inositol 1,4,5-Trisphosphate Receptors/chemistry
- Inositol 1,4,5-Trisphosphate Receptors/metabolism
- Inositol 1,4,5-Trisphosphate Receptors/ultrastructure
- Models, Molecular
- Peptides/metabolism
- Protein Conformation
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Affiliation(s)
- Caleigh M Azumaya
- Department of Molecular Physiology and Biophysics, Vanderbilt University, School of Medicine, Nashville, Tennessee 37232
| | - Emily A Linton
- Department of Molecular Physiology and Biophysics, Vanderbilt University, School of Medicine, Nashville, Tennessee 37232
| | - Caitlin J Risener
- Department of Molecular Physiology and Biophysics, Vanderbilt University, School of Medicine, Nashville, Tennessee 37232
| | - Terunaga Nakagawa
- Department of Molecular Physiology and Biophysics, Vanderbilt University, School of Medicine, Nashville, Tennessee 37232; Center for Structural Biology, Vanderbilt University, School of Medicine, Nashville, Tennessee 37232; Vanderbilt Brain Institute, Vanderbilt University, School of Medicine, Nashville, Tennessee 37232
| | - Erkan Karakas
- Department of Molecular Physiology and Biophysics, Vanderbilt University, School of Medicine, Nashville, Tennessee 37232; Center for Structural Biology, Vanderbilt University, School of Medicine, Nashville, Tennessee 37232.
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6
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Potapenko E, Negrão NW, Huang G, Docampo R. The acidocalcisome inositol-1,4,5-trisphosphate receptor of Trypanosoma brucei is stimulated by luminal polyphosphate hydrolysis products. J Biol Chem 2019; 294:10628-10637. [PMID: 31138655 DOI: 10.1074/jbc.ra119.007906] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2019] [Revised: 05/27/2019] [Indexed: 12/21/2022] Open
Abstract
Acidocalcisomes are acidic calcium stores rich in polyphosphate (polyP) and are present in trypanosomes and also in a diverse range of other organisms. Ca2+ is released from these organelles through a channel, inositol 1,4,5-trisphosphate receptor (TbIP3R), which is essential for growth and infectivity of the parasite Trypanosoma brucei However, the mechanism by which TbIP3R controls Ca2+ release is unclear. In this work, we expressed TbIP3R in a chicken B lymphocyte cell line in which the genes for all three vertebrate IP3Rs were stably ablated (DT40-3KO). We show that IP3-mediated Ca2+ release depends on Ca2+ but not on ATP concentration and is inhibited by heparin, caffeine, and 2-aminomethoxydiphenyl borate (2-APB). Excised patch clamp recordings from nuclear membranes of DT40 cells expressing only TbIP3R disclosed that luminal inorganic orthophosphate (Pi) or pyrophosphate (PPi), and neutral or alkaline pH can stimulate IP3-generated currents. In contrast, polyP or acidic pH did not induce these currents, and nuclear membranes obtained from cells expressing rat IP3R were unresponsive to polyP or its hydrolysis products. Our results are consistent with the notion that polyP hydrolysis products within acidocalcisomes or alkalinization of their luminal pH activate TbIP3R and Ca2+ release. We conclude that TbIP3R is well-adapted to its role as the major Ca2+ release channel of acidocalcisomes in T. brucei.
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Affiliation(s)
| | - Núria W Negrão
- From the Center for Tropical and Emerging Global Diseases and.,Department of Cellular Biology, University of Georgia, Athens, Georgia 30602
| | - Guozhong Huang
- From the Center for Tropical and Emerging Global Diseases and
| | - Roberto Docampo
- From the Center for Tropical and Emerging Global Diseases and .,Department of Cellular Biology, University of Georgia, Athens, Georgia 30602
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7
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Yamamoto WR, Bone RN, Sohn P, Syed F, Reissaus CA, Mosley AL, Wijeratne AB, True JD, Tong X, Kono T, Evans-Molina C. Endoplasmic reticulum stress alters ryanodine receptor function in the murine pancreatic β cell. J Biol Chem 2018; 294:168-181. [PMID: 30420428 DOI: 10.1074/jbc.ra118.005683] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2018] [Revised: 11/08/2018] [Indexed: 01/23/2023] Open
Abstract
Alterations in endoplasmic reticulum (ER) calcium (Ca2+) levels diminish insulin secretion and reduce β-cell survival in both major forms of diabetes. The mechanisms responsible for ER Ca2+ loss in β cells remain incompletely understood. Moreover, a specific role for either ryanodine receptor (RyR) or inositol 1,4,5-triphosphate receptor (IP3R) dysfunction in the pathophysiology of diabetes remains largely untested. To this end, here we applied intracellular and ER Ca2+ imaging techniques in INS-1 β cells and isolated islets to determine whether diabetogenic stressors alter RyR or IP3R function. Our results revealed that the RyR is sensitive mainly to ER stress-induced dysfunction, whereas cytokine stress specifically alters IP3R activity. Consistent with this observation, pharmacological inhibition of the RyR with ryanodine and inhibition of the IP3R with xestospongin C prevented ER Ca2+ loss under ER and cytokine stress conditions, respectively. However, RyR blockade distinctly prevented β-cell death, propagation of the unfolded protein response (UPR), and dysfunctional glucose-induced Ca2+ oscillations in tunicamycin-treated INS-1 β cells and mouse islets and Akita islets. Monitoring at the single-cell level revealed that ER stress acutely increases the frequency of intracellular Ca2+ transients that depend on both ER Ca2+ leakage from the RyR and plasma membrane depolarization. Collectively, these findings indicate that RyR dysfunction shapes ER Ca2+ dynamics in β cells and regulates both UPR activation and cell death, suggesting that RyR-mediated loss of ER Ca2+ may be an early pathogenic event in diabetes.
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Affiliation(s)
- Wataru R Yamamoto
- Departments of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Robert N Bone
- Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Paul Sohn
- Departments of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Farooq Syed
- Herman B. Wells Center for Pediatric Research, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Christopher A Reissaus
- Herman B. Wells Center for Pediatric Research, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Amber L Mosley
- Departments of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Aruna B Wijeratne
- Departments of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Jason D True
- Departments of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Xin Tong
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee 37235
| | - Tatsuyoshi Kono
- Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Carmella Evans-Molina
- Departments of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, Indiana 46202; Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana 46202; Departments of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana 46202; Herman B. Wells Center for Pediatric Research, Indiana University School of Medicine, Indianapolis, Indiana 46202; Roudebush Veterans Affairs Medical Center, Indianapolis, Indiana 46202.
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8
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Wright FA, Bonzerato CG, Sliter DA, Wojcikiewicz RJH. The erlin2 T65I mutation inhibits erlin1/2 complex-mediated inositol 1,4,5-trisphosphate receptor ubiquitination and phosphatidylinositol 3-phosphate binding. J Biol Chem 2018; 293:15706-15714. [PMID: 30135210 DOI: 10.1074/jbc.ra118.004547] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2018] [Revised: 07/19/2018] [Indexed: 12/11/2022] Open
Abstract
The erlin1/2 complex is a ∼2-MDa endoplasmic reticulum membrane-located ensemble of the ∼40-kDa type II membrane proteins erlin1 and erlin2. The best defined function of this complex is to mediate the ubiquitination of activated inositol 1,4,5-trisphosphate receptors (IP3Rs) and their subsequent degradation. However, it remains unclear how mutations of the erlin1/2 complex affect its cellular function and cause cellular dysfunction and diseases such as hereditary spastic paraplegia. Here, we used gene editing to ablate erlin1 or erlin2 expression to better define their individual roles in the cell and examined the functional effects of a spastic paraplegia-linked mutation to erlin2 (threonine to isoleucine at position 65; T65I). Our results revealed that erlin2 is the dominant player in mediating the interaction between the erlin1/2 complex and IP3Rs and that the T65I mutation dramatically inhibits this interaction and the ability of the erlin1/2 complex to promote IP3R ubiquitination and degradation. Remarkably, we also discovered that the erlin1/2 complex specifically binds to phosphatidylinositol 3-phosphate, that erlin2 binds this phospholipid much more strongly than does erlin1, that the binding is inhibited by T65I mutation of erlin2, and that multiple determinants within the erlin2 polypeptide comprise the phosphatidylinositol 3-phosphate-binding site. Overall, these results indicate that erlin2 is the primary mediator of the cellular roles of the erlin1/2 complex and that disease-linked mutations of erlin2 can affect both IP3R processing and lipid binding.
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Affiliation(s)
- Forrest A Wright
- From the Department of Pharmacology, State University of New York (SUNY) Upstate Medical University, Syracuse, New York 13210 and
| | - Caden G Bonzerato
- From the Department of Pharmacology, State University of New York (SUNY) Upstate Medical University, Syracuse, New York 13210 and
| | - Danielle A Sliter
- Biochemistry Section, Surgical Neurology Branch, NINDS, National Institutes of Health, Bethesda, Maryland 20892
| | - Richard J H Wojcikiewicz
- From the Department of Pharmacology, State University of New York (SUNY) Upstate Medical University, Syracuse, New York 13210 and
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9
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Choi S, Quan X, Bang S, Yoo H, Kim J, Park J, Park KS, Chung J. Mitochondrial calcium uniporter in Drosophila transfers calcium between the endoplasmic reticulum and mitochondria in oxidative stress-induced cell death. J Biol Chem 2017; 292:14473-14485. [PMID: 28726639 DOI: 10.1074/jbc.m116.765578] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Revised: 07/13/2017] [Indexed: 12/16/2022] Open
Abstract
Mitochondrial calcium plays critical roles in diverse cellular processes ranging from energy metabolism to cell death. Previous studies have demonstrated that mitochondrial calcium uptake is mainly mediated by the mitochondrial calcium uniporter (MCU) complex. However, the roles of the MCU complex in calcium transport, signaling, and dysregulation by oxidative stress still remain unclear. Here, we confirmed that Drosophila MCU contains evolutionarily conserved structures and requires essential MCU regulator (EMRE) for its calcium channel activities. We generated Drosophila MCU loss-of-function mutants, which lacked mitochondrial calcium uptake in response to caffeine stimulation. Basal metabolic activities were not significantly affected in these MCU mutants, as observed in examinations of body weight, food intake, body sugar level, and starvation-induced autophagy. However, oxidative stress-induced increases in mitochondrial calcium, mitochondrial membrane potential depolarization, and cell death were prevented in these mutants. We also found that inositol 1,4,5-trisphosphate receptor genetically interacts with Drosophila MCU and effectively modulates mitochondrial calcium uptake upon oxidative stress. Taken together, these results support the idea that Drosophila MCU is responsible for endoplasmic reticulum-to-mitochondrial calcium transfer and for cell death due to mitochondrial dysfunction under oxidative stress.
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Affiliation(s)
- Sekyu Choi
- From the National Creative Research Initiatives Center for Energy Homeostasis Regulation, Institute of Molecular Biology and Genetics and School of Biological Sciences, Seoul National University, Seoul 08826, Korea and
| | - Xianglan Quan
- the Department of Physiology, Yonsei University Wonju College of Medicine, Wonju, Gangwon-Do 26426, Korea
| | - Sunhoe Bang
- From the National Creative Research Initiatives Center for Energy Homeostasis Regulation, Institute of Molecular Biology and Genetics and School of Biological Sciences, Seoul National University, Seoul 08826, Korea and
| | - Heesuk Yoo
- From the National Creative Research Initiatives Center for Energy Homeostasis Regulation, Institute of Molecular Biology and Genetics and School of Biological Sciences, Seoul National University, Seoul 08826, Korea and
| | - Jiyoung Kim
- From the National Creative Research Initiatives Center for Energy Homeostasis Regulation, Institute of Molecular Biology and Genetics and School of Biological Sciences, Seoul National University, Seoul 08826, Korea and
| | - Jiwon Park
- From the National Creative Research Initiatives Center for Energy Homeostasis Regulation, Institute of Molecular Biology and Genetics and School of Biological Sciences, Seoul National University, Seoul 08826, Korea and
| | - Kyu-Sang Park
- the Department of Physiology, Yonsei University Wonju College of Medicine, Wonju, Gangwon-Do 26426, Korea
| | - Jongkyeong Chung
- From the National Creative Research Initiatives Center for Energy Homeostasis Regulation, Institute of Molecular Biology and Genetics and School of Biological Sciences, Seoul National University, Seoul 08826, Korea and
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10
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Butler MR, Ma H, Yang F, Belcher J, Le YZ, Mikoshiba K, Biel M, Michalakis S, Iuso A, Križaj D, Ding XQ. Endoplasmic reticulum (ER) Ca 2+-channel activity contributes to ER stress and cone death in cyclic nucleotide-gated channel deficiency. J Biol Chem 2017; 292:11189-11205. [PMID: 28495882 DOI: 10.1074/jbc.m117.782326] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2017] [Revised: 05/01/2017] [Indexed: 02/05/2023] Open
Abstract
Endoplasmic reticulum (ER) stress and mislocalization of improperly folded proteins have been shown to contribute to photoreceptor death in models of inherited retinal degenerative diseases. In particular, mice with cone cyclic nucleotide-gated (CNG) channel deficiency, a model for achromatopsia, display both early-onset ER stress and opsin mistrafficking. By 2 weeks of age, these mice show elevated signaling from all three arms of the ER-stress pathway, and by 1 month, cone opsin is improperly distributed away from its normal outer segment location to other retinal layers. This work investigated the role of Ca2+-release channels in ER stress, protein mislocalization, and cone death in a mouse model of CNG-channel deficiency. We examined whether preservation of luminal Ca2+ stores through pharmacological and genetic suppression of ER Ca2+ efflux protects cones by attenuating ER stress. We demonstrated that the inhibition of ER Ca2+-efflux channels reduced all three arms of ER-stress signaling while improving opsin trafficking to cone outer segments and decreasing cone death by 20-35%. Cone-specific gene deletion of the inositol-1,4,5-trisphosphate receptor type I (IP3R1) also significantly increased cone density in the CNG-channel-deficient mice, suggesting that IP3R1 signaling contributes to Ca2+ homeostasis and cone survival. Consistent with the important contribution of organellar Ca2+ signaling in this achromatopsia mouse model, significant differences in dynamic intraorganellar Ca2+ levels were detected in CNG-channel-deficient cones. These results thus identify a novel molecular link between Ca2+ homeostasis and cone degeneration, thereby revealing novel therapeutic targets to preserve cones in inherited retinal degenerative diseases.
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Affiliation(s)
| | | | - Fan Yang
- From the Departments of Cell Biology
| | | | - Yun-Zheng Le
- From the Departments of Cell Biology.,Internal Medicine, and.,Ophthalmology and.,the Harold Hamm Diabetes Center, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104
| | - Katsuhiko Mikoshiba
- the Laboratory for Developmental Neurobiology, RIKEN Brain Science Institute, Hirosawa Wako-shi, Saitama 351-0198, Japan
| | - Martin Biel
- the Center for Integrated Protein Science Munich (CIPSM) and Department of Pharmacy, Center for Drug Research, Ludwig-Maximilians-Universität München, 81377 Munich, Germany, and
| | - Stylianos Michalakis
- the Center for Integrated Protein Science Munich (CIPSM) and Department of Pharmacy, Center for Drug Research, Ludwig-Maximilians-Universität München, 81377 Munich, Germany, and
| | - Anthony Iuso
- the John A. Moran Eye Center, University of Utah, Salt Lake City, Utah 84132
| | - David Križaj
- the John A. Moran Eye Center, University of Utah, Salt Lake City, Utah 84132
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Schulman JJ, Wright FA, Han X, Zluhan EJ, Szczesniak LM, Wojcikiewicz RJH. The Stability and Expression Level of Bok Are Governed by Binding to Inositol 1,4,5-Trisphosphate Receptors. J Biol Chem 2016; 291:11820-8. [PMID: 27053113 DOI: 10.1074/jbc.m115.711242] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2015] [Indexed: 12/31/2022] Open
Abstract
Bok is a member of the Bcl-2 protein family that governs the intrinsic apoptosis pathway, although the role that Bok plays in this pathway is unclear. We have shown previously in cultured cell lines that Bok interacts strongly with inositol 1,4,5-trisphosphate receptors (IP3Rs), suggesting that it may contribute to the structural integrity or stability of IP3R tetramers. Here we report that Bok is similarly IP3R-assocated in mouse tissues, that essentially all cellular Bok is IP3R bound, that it is the helical nature of the Bok BH4 domain, rather than specific amino acids, that mediates binding to IP3Rs, that Bok is dramatically stabilized by binding to IP3Rs, that unbound Bok is ubiquitinated and degraded by the proteasome, and that binding to IP3Rs limits the pro-apoptotic effect of overexpressed Bok. Agents that stimulate IP3R activity, apoptosis, phosphorylation, and endoplasmic reticulum stress did not trigger the dissociation of mature Bok from IP3Rs or Bok degradation, indicating that the role of proteasome-mediated Bok degradation is to destroy newly synthesized Bok that is not IP3R associated. The existence of this unexpected proteolytic mechanism that is geared toward restricting Bok to that which is bound to IP3Rs, implies that unbound Bok is deleterious to cell viability and helps explain the current uncertainty regarding the cellular role of Bok.
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Affiliation(s)
- Jacqualyn J Schulman
- From the Department of Pharmacology, SUNY Upstate Medical University, Syracuse, New York 13210
| | - Forrest A Wright
- From the Department of Pharmacology, SUNY Upstate Medical University, Syracuse, New York 13210
| | - Xiaobing Han
- From the Department of Pharmacology, SUNY Upstate Medical University, Syracuse, New York 13210
| | - Eric J Zluhan
- From the Department of Pharmacology, SUNY Upstate Medical University, Syracuse, New York 13210
| | - Laura M Szczesniak
- From the Department of Pharmacology, SUNY Upstate Medical University, Syracuse, New York 13210
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Chandrasekhar R, Alzayady KJ, Wagner LE, Yule DI. Unique Regulatory Properties of Heterotetrameric Inositol 1,4,5-Trisphosphate Receptors Revealed by Studying Concatenated Receptor Constructs. J Biol Chem 2016; 291:4846-60. [PMID: 26755721 DOI: 10.1074/jbc.m115.705301] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2015] [Indexed: 02/02/2023] Open
Abstract
The ability of inositol 1,4,5-trisphosphate receptors (IP3R) to precisely initiate and generate a diverse variety of intracellular Ca(2+) signals is in part mediated by the differential regulation of the three subtypes (R1, R2, and R3) by key functional modulators (IP3, Ca(2+), and ATP). However, the contribution of IP3R heterotetramerization to Ca(2+) signal diversity has largely been unexplored. In this report, we provide the first definitive biochemical evidence of endogenous heterotetramer formation. Additionally, we examine the contribution of individual subtypes within defined concatenated heterotetramers to the shaping of Ca(2+) signals. Under conditions where key regulators of IP3R function are optimal for Ca(2+) release, we demonstrate that individual monomers within heteromeric IP3Rs contributed equally toward generating a distinct 'blended' sensitivity to IP3 that is likely dictated by the unique IP3 binding affinity of the heteromers. However, under suboptimal conditions where [ATP] were varied, we found that one subtype dictated the ATP regulatory properties of heteromers. We show that R2 monomers within a heterotetramer were both necessary and sufficient to dictate the ATP regulatory properties. Finally, the ATP-binding site B in R2 critical for ATP regulation was mutated and rendered non-functional to address questions relating to the stoichiometry of IP3R regulation. Two intact R2 monomers were sufficient to maintain ATP regulation in R2 homotetramers. In summary, we demonstrate that heterotetrameric IP3R do not necessarily behave as the sum of the constituent subunits, and these properties likely extend the versatility of IP3-induced Ca(2+) signaling in cells expressing multiple IP3R isoforms.
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Affiliation(s)
- Rahul Chandrasekhar
- From the Department of Pharmacology and Physiology, University of Rochester, Rochester, New York 14642
| | - Kamil J Alzayady
- From the Department of Pharmacology and Physiology, University of Rochester, Rochester, New York 14642
| | - Larry E Wagner
- From the Department of Pharmacology and Physiology, University of Rochester, Rochester, New York 14642
| | - David I Yule
- From the Department of Pharmacology and Physiology, University of Rochester, Rochester, New York 14642
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Wright FA, Lu JP, Sliter DA, Dupré N, Rouleau GA, Wojcikiewicz RJH. A Point Mutation in the Ubiquitin Ligase RNF170 That Causes Autosomal Dominant Sensory Ataxia Destabilizes the Protein and Impairs Inositol 1,4,5-Trisphosphate Receptor-mediated Ca2+ Signaling. J Biol Chem 2015; 290:13948-57. [PMID: 25882839 DOI: 10.1074/jbc.m115.655043] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2015] [Indexed: 12/11/2022] Open
Abstract
RNF170 is an endoplasmic reticulum membrane ubiquitin ligase that contributes to the ubiquitination of activated inositol 1,4,5-trisphosphate (IP3) receptors, and also, when point mutated (arginine to cysteine at position 199), causes autosomal dominant sensory ataxia (ADSA), a disease characterized by neurodegeneration in the posterior columns of the spinal cord. Here we demonstrate that this point mutation inhibits RNF170 expression and signaling via IP3 receptors. Inhibited expression of mutant RNF170 was seen in cells expressing exogenous RNF170 constructs and in ADSA lymphoblasts, and appears to result from enhanced RNF170 autoubiquitination and proteasomal degradation. The basis for these effects was probed via additional point mutations, revealing that ionic interactions between charged residues in the transmembrane domains of RNF170 are required for protein stability. In ADSA lymphoblasts, platelet-activating factor-induced Ca(2+) mobilization was significantly impaired, whereas neither Ca(2+) store content, IP3 receptor levels, nor IP3 production were altered, indicative of a functional defect at the IP3 receptor locus, which may be the cause of neurodegeneration. CRISPR/Cas9-mediated genetic deletion of RNF170 showed that RNF170 mediates the addition of all of the ubiquitin conjugates known to become attached to activated IP3 receptors (monoubiquitin and Lys(48)- and Lys(63)-linked ubiquitin chains), and that wild-type and mutant RNF170 have apparently identical ubiquitin ligase activities toward IP3 receptors. Thus, the Ca(2+) mobilization defect seen in ADSA lymphoblasts is apparently not due to aberrant IP3 receptor ubiquitination. Rather, the defect likely reflects abnormal ubiquitination of other substrates, or adaptation to the chronic reduction in RNF170 levels.
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Affiliation(s)
- Forrest A Wright
- From the Department of Pharmacology, SUNY Upstate Medical University, Syracuse, New York 13210
| | - Justine P Lu
- From the Department of Pharmacology, SUNY Upstate Medical University, Syracuse, New York 13210
| | | | - Nicolas Dupré
- the Neuromuscular and Neurogenetic Disease Clinic, CHU de Québec, Laval University, Quebec City, Quebec G1J 1Z4, Canada, and
| | - Guy A Rouleau
- the Montreal Neurological Institute and Hospital and Department of Neurology and Neurosurgery, McGill University, Montreal, Quebec H3A 2B4, Canada
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