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Sitbon J, Nestvogel D, Kappeler C, Nicolas A, Maciuba S, Henrion A, Troudet R, Courtois E, Grannec G, Latapie V, Barau C, Le Corvoisier P, Pietrancosta N, Henry C, Leboyer M, Etain B, Nosten-Bertrand M, Martin TFJ, Rhee J, Jamain S. CADPS functional mutations in patients with bipolar disorder increase the sensitivity to stress. Mol Psychiatry 2022; 27:1145-1157. [PMID: 35169262 DOI: 10.1038/s41380-021-01151-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/07/2019] [Revised: 04/19/2021] [Accepted: 04/29/2021] [Indexed: 11/09/2022]
Abstract
Bipolar disorder is a severe and chronic psychiatric disease resulting from a combination of genetic and environmental risk factors. Here, we identified a significant higher mutation rate in a gene encoding the calcium-dependent activator protein for secretion (CADPS) in 132 individuals with bipolar disorder, when compared to 184 unaffected controls or to 21,070 non-psychiatric and non-Finnish European subjects from the Exome Aggregation Consortium. We found that most of these variants resulted either in a lower abundance or a partial impairment in one of the basic functions of CADPS in regulating neuronal exocytosis, synaptic plasticity and vesicular transporter-dependent uptake of catecholamines. Heterozygous mutant mice for Cadps+/- revealed that a decreased level of CADPS leads to manic-like behaviours, changes in BDNF level and a hypersensitivity to stress. This was consistent with more childhood trauma reported in families with mutation in CADPS, and more specifically in mutated individuals. Furthermore, hyperactivity observed in mutant animals was rescued by the mood-stabilizing drug lithium. Overall, our results suggest that dysfunction in calcium-dependent vesicular exocytosis may increase the sensitivity to environmental stressors enhancing the risk of developing bipolar disorder.
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Affiliation(s)
- Jérémy Sitbon
- Univ Paris Est Créteil, INSERM, IMRB, Translational Neuropsychiatry, Créteil, France.,Fondation FondaMental, Créteil, France
| | - Dennis Nestvogel
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Caroline Kappeler
- Univ Paris Est Créteil, INSERM, IMRB, Translational Neuropsychiatry, Créteil, France.,Fondation FondaMental, Créteil, France
| | - Aude Nicolas
- Univ Paris Est Créteil, INSERM, IMRB, Translational Neuropsychiatry, Créteil, France.,Fondation FondaMental, Créteil, France
| | - Stephanie Maciuba
- Department of Biochemistry, University of Wisconsin, Madison, WI, USA
| | - Annabelle Henrion
- Univ Paris Est Créteil, INSERM, IMRB, Translational Neuropsychiatry, Créteil, France.,Fondation FondaMental, Créteil, France
| | - Réjane Troudet
- Univ Paris Est Créteil, INSERM, IMRB, Translational Neuropsychiatry, Créteil, France.,Fondation FondaMental, Créteil, France
| | - Elisa Courtois
- Univ Paris Est Créteil, INSERM, IMRB, Translational Neuropsychiatry, Créteil, France.,Fondation FondaMental, Créteil, France
| | - Gaël Grannec
- INSERM U1270, Sorbonne Université, Institut du Fer à Moulin, Paris, France
| | - Violaine Latapie
- Univ Paris Est Créteil, INSERM, IMRB, Translational Neuropsychiatry, Créteil, France.,Fondation FondaMental, Créteil, France
| | - Caroline Barau
- AP-HP, Hôpital H. Mondor - A. Chenevier, Plateforme de Ressources Biologiques, Créteil, France
| | | | - Nicolas Pietrancosta
- Sorbonne University, École Normale Supérieure, PSL University, CNRS, Laboratoire des biomolécules (LBM), Paris, France.,Neuroscience Paris Seine - Institut de Biologie Paris Seine (NPS - IBPS) INSERM, CNRS, Sorbonne Université, Paris, France
| | - Chantal Henry
- Univ Paris Est Créteil, INSERM, IMRB, Translational Neuropsychiatry, Créteil, France.,Fondation FondaMental, Créteil, France.,AP-HP, Hôpitaux Universitaires H. Mondor, DMU IMPACT, Créteil, France
| | - Marion Leboyer
- Univ Paris Est Créteil, INSERM, IMRB, Translational Neuropsychiatry, Créteil, France.,Fondation FondaMental, Créteil, France.,AP-HP, Hôpitaux Universitaires H. Mondor, DMU IMPACT, Créteil, France
| | - Bruno Etain
- Fondation FondaMental, Créteil, France.,Département de Psychiatrie et de Médecine Addictologique, AP-HP, GH Saint-Louis - Lariboisière - F. Widal, Paris, France.,Université de Paris, Sorbonne Paris Cité, Paris, France.,Inserm, UMR-S1144, Paris, France
| | | | - Thomas F J Martin
- Department of Biochemistry, University of Wisconsin, Madison, WI, USA
| | - JeongSeop Rhee
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Stéphane Jamain
- Univ Paris Est Créteil, INSERM, IMRB, Translational Neuropsychiatry, Créteil, France. .,Fondation FondaMental, Créteil, France.
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Barak-Broner N, Singer-Lahat D, Chikvashvili D, Lotan I. CK2 Phosphorylation Is Required for Regulation of Syntaxin 1A Activity in Ca 2+-Triggered Release in Neuroendocrine Cells. Int J Mol Sci 2021; 22:ijms222413556. [PMID: 34948351 PMCID: PMC8708312 DOI: 10.3390/ijms222413556] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2021] [Revised: 12/12/2021] [Accepted: 12/13/2021] [Indexed: 12/29/2022] Open
Abstract
The polybasic juxtamembrane region (5RK) of the plasma membrane neuronal SNARE, syntaxin1A (Syx), was previously shown by us to act as a fusion clamp in PC12 cells, as charge neutralization of 5RK promotes spontaneous and inhibits Ca2+-triggered release. Using a Syx-based FRET probe (CSYS), we demonstrated that 5RK is required for a depolarization-induced Ca+2-dependent opening (close-to-open transition; CDO) of Syx, which involves the vesicular SNARE synaptobrevin2 and occurs concomitantly with Ca2+-triggered release. Here, we investigated the mechanism underlying the CDO requirement for 5RK and identified phosphorylation of Syx at Ser-14 (S14) by casein kinase 2 (CK2) as a crucial molecular determinant. Thus, following biochemical verification that both endogenous Syx and CSYS are constitutively S14 phosphorylated in PC12 cells, dynamic FRET analysis of phospho-null and phospho-mimetic mutants of CSYS and the use of a CK2 inhibitor revealed that the S14 phosphorylation confers the CDO requirement for 5RK. In accord, amperometric analysis of catecholamine release revealed that the phospho-null mutant does not support Ca2+-triggered release. These results identify a functionally important CK2 phosphorylation of Syx that is required for the 5RK-regulation of CDO and for concomitant Ca2+-triggered release. Further, also spontaneous release, conferred by charge neutralization of 5RK, was abolished in the phospho-null mutant.
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Affiliation(s)
- Noa Barak-Broner
- Department of Neurobiology Biochemistry & Biophysics, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Ramat Aviv, Tel Aviv-Yafo 69978, Israel;
| | - Dafna Singer-Lahat
- Department of Physiology and Pharmacology, Sackler School of Medicine, Tel Aviv University, Ramat Aviv, Tel Aviv-Yafo 69978, Israel; (D.S.-L.); (D.C.)
| | - Dodo Chikvashvili
- Department of Physiology and Pharmacology, Sackler School of Medicine, Tel Aviv University, Ramat Aviv, Tel Aviv-Yafo 69978, Israel; (D.S.-L.); (D.C.)
| | - Ilana Lotan
- Department of Physiology and Pharmacology, Sackler School of Medicine, Tel Aviv University, Ramat Aviv, Tel Aviv-Yafo 69978, Israel; (D.S.-L.); (D.C.)
- Sagol School of Neuroscience, Tel Aviv University, Ramat Aviv, Tel Aviv-Yafo 69978, Israel
- Correspondence:
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3
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Crummy E, Mani M, Thellman JC, Martin TFJ. The priming factor CAPS1 regulates dense-core vesicle acidification by interacting with rabconnectin3β/WDR7 in neuroendocrine cells. J Biol Chem 2019; 294:9402-9415. [PMID: 31004036 PMCID: PMC6579465 DOI: 10.1074/jbc.ra119.007504] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2019] [Revised: 03/21/2019] [Indexed: 12/20/2022] Open
Abstract
Vacuolar-type H+-ATPases (V-ATPases) contribute to pH regulation and play key roles in secretory and endocytic pathways. Dense-core vesicles (DCVs) in neuroendocrine cells are maintained at an acidic pH, which is part of the electrochemical driving force for neurotransmitter loading and is required for hormonal propeptide processing. Genetic loss of CAPS1 (aka calcium-dependent activator protein for secretion, CADPS), a vesicle-bound priming factor required for DCV exocytosis, dissipates the pH gradient across DCV membranes and reduces neurotransmitter loading. However, the basis for CAPS1 binding to DCVs and for its regulation of vesicle pH has not been determined. Here, MS analysis of CAPS1 immunoprecipitates from brain membrane fractions revealed that CAPS1 associates with a rabconnectin3 (Rbcn3) complex comprising Dmx-like 2 (DMXL2) and WD repeat domain 7 (WDR7) proteins. Using immunofluorescence microscopy, we found that Rbcn3α/DMXL2 and Rbcn3β/WDR7 colocalize with CAPS1 on DCVs in human neuroendocrine (BON) cells. The shRNA-mediated knockdown of Rbcn3β/WDR7 redistributed CAPS1 from DCVs to the cytosol, indicating that Rbcn3β/WDR7 is essential for optimal DCV localization of CAPS1. Moreover, cell-free experiments revealed direct binding of CAPS1 to Rbcn3β/WDR7, and cell assays indicated that Rbcn3β/WDR7 recruits soluble CAPS1 to membranes. As anticipated by the reported association of Rbcn3 with V-ATPase, we found that knocking down CAPS1, Rbcn3α, or Rbcn3β in neuroendocrine cells impaired rates of DCV reacidification. These findings reveal a basis for CAPS1 binding to DCVs and for CAPS1 regulation of V-ATPase activity via Rbcn3β/WDR7 interactions.
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Affiliation(s)
- Ellen Crummy
- From the Department of Biochemistry, University of Wisconsin, Madison, Wisconsin 53706
| | - Muralidharan Mani
- From the Department of Biochemistry, University of Wisconsin, Madison, Wisconsin 53706
| | - John C Thellman
- From the Department of Biochemistry, University of Wisconsin, Madison, Wisconsin 53706
| | - Thomas F J Martin
- From the Department of Biochemistry, University of Wisconsin, Madison, Wisconsin 53706
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Petrie M, Esquibel J, Kabachinski G, Maciuba S, Takahashi H, Edwardson JM, Martin TFJ. The Vesicle Priming Factor CAPS Functions as a Homodimer via C2 Domain Interactions to Promote Regulated Vesicle Exocytosis. J Biol Chem 2016; 291:21257-21270. [PMID: 27528604 PMCID: PMC5076532 DOI: 10.1074/jbc.m116.728097] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2016] [Revised: 07/29/2016] [Indexed: 11/06/2022] Open
Abstract
Neurotransmitters and peptide hormones are secreted by regulated vesicle exocytosis. CAPS (also known as CADPS) is a 145-kDa cytosolic and peripheral membrane protein required for vesicle docking and priming steps that precede Ca2+-triggered vesicle exocytosis. CAPS binds phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) and SNARE proteins and is proposed to promote SNARE protein complex assembly for vesicle docking and priming. We characterized purified soluble CAPS as mainly monomer in equilibrium with small amounts of dimer. However, the active form of CAPS bound to PC12 cell membranes or to liposomes containing PI(4,5)P2 and Q-SNARE proteins was mainly dimer. CAPS dimer formation required its C2 domain based on mutation or deletion studies. Moreover, C2 domain mutations or deletions resulted in a loss of CAPS function in regulated vesicle exocytosis, indicating that dimerization is essential for CAPS function. Comparison of the CAPS C2 domain to a structurally defined Munc13-1 C2A domain dimer revealed conserved residues involved in CAPS dimerization. We conclude that CAPS functions as a C2 domain-mediated dimer in regulated vesicle exocytosis. The unique tandem C2-PH domain of CAPS may serve as a PI(4,5)P2-triggered switch for dimerization. CAPS dimerization may be coupled to oligomeric SNARE complex assembly for vesicle docking and priming.
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Affiliation(s)
- Matt Petrie
- From the Department of Biochemistry, Integrated Program in Biochemistry, University of Wisconsin, Madison, Wisconsin 53706, and
| | - Joseph Esquibel
- From the Department of Biochemistry, Program of Molecular and Cellular Pharmacology, and
| | - Greg Kabachinski
- From the Department of Biochemistry, Integrated Program in Biochemistry, University of Wisconsin, Madison, Wisconsin 53706, and
| | - Stephanie Maciuba
- From the Department of Biochemistry, Integrated Program in Biochemistry, University of Wisconsin, Madison, Wisconsin 53706, and
| | - Hirohide Takahashi
- the Department of Pharmacology, University of Cambridge, Cambridge CB2 1PD, United Kingdom
| | - J Michael Edwardson
- the Department of Pharmacology, University of Cambridge, Cambridge CB2 1PD, United Kingdom
| | - Thomas F J Martin
- From the Department of Biochemistry, Integrated Program in Biochemistry, University of Wisconsin, Madison, Wisconsin 53706, and Program of Molecular and Cellular Pharmacology, and
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5
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Xue R, Tang W, Dong P, Weng S, Ma L, Chen S, Liu T, Shen X, Huang X, Zhang S, Dong L. CAPS1 Negatively Regulates Hepatocellular Carcinoma Development through Alteration of Exocytosis-Associated Tumor Microenvironment. Int J Mol Sci 2016; 17:E1626. [PMID: 27689999 PMCID: PMC5085659 DOI: 10.3390/ijms17101626] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2016] [Revised: 08/30/2016] [Accepted: 09/05/2016] [Indexed: 12/28/2022] Open
Abstract
The calcium-dependent activator protein for secretion 1 (CAPS1) regulates exocytosis of dense-core vesicles (DCVs) in neurons and neuroendocrine cells. The role of CAPS1 in cancer biology remains unknown. The purpose of this study was to investigate the role of CAPS1 in hepatocellular carcinoma (HCC). We determined the levels of CAPS1 in eight hepatoma cell lines and 141 HCC specimens. We evaluated the prognostic value of CAPS1 expression and its association with clinical parameters. We investigated the biological consequences of CAPS1 overexpression in two hepatoma cell lines in vitro and in vivo. The results showed that loss of CAPS1 expression in HCC tissues was markedly correlated with aggressive tumor phenotypes, such as high-grade tumor node metastasis (TNM) stage (p = 0.003) and absence of tumor encapsulation (p = 0.016), and was associated with poor overall survival (p = 0.008) and high recurrence (p = 0.015). CAPS1 overexpression inhibited cell proliferation and migration by changing the exocytosis-associated tumor microenvironment in hepatoma cells in vitro. The in vivo study showed that CAPS1 overexpression inhibited xenograft tumor growth. Together, these results identified a previously unrecognized tumor suppressor role for CAPS1 in HCC development.
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Affiliation(s)
- Ruyi Xue
- Department of Gastroenterology and Hepatology, Shanghai Institute of Liver Diseases, Zhongshan Hospital of Fudan University, Shanghai 200032, China.
| | - Wenqing Tang
- Department of Gastroenterology and Hepatology, Shanghai Institute of Liver Diseases, Zhongshan Hospital of Fudan University, Shanghai 200032, China.
| | - Pingping Dong
- Department of Gastroenterology and Hepatology, Shanghai Institute of Liver Diseases, Zhongshan Hospital of Fudan University, Shanghai 200032, China.
| | - Shuqiang Weng
- Department of Gastroenterology and Hepatology, Shanghai Institute of Liver Diseases, Zhongshan Hospital of Fudan University, Shanghai 200032, China.
| | - Lijie Ma
- Department of Hepatic Surgery of Liver Cancer Institute, Zhongshan Hospital, Fudan University, Shanghai 200032, China.
| | - She Chen
- Key Laboratory of Glycoconjugate Research Ministry of Public Health, Department of Biochemistry and Molecular Biology, Shanghai Medical College, Fudan University, Shanghai 200032, China.
| | - Taotao Liu
- Department of Gastroenterology and Hepatology, Shanghai Institute of Liver Diseases, Zhongshan Hospital of Fudan University, Shanghai 200032, China.
| | - Xizhong Shen
- Department of Gastroenterology and Hepatology, Shanghai Institute of Liver Diseases, Zhongshan Hospital of Fudan University, Shanghai 200032, China.
| | - Xiaowu Huang
- Department of Hepatic Surgery of Liver Cancer Institute, Zhongshan Hospital, Fudan University, Shanghai 200032, China.
| | - Si Zhang
- Key Laboratory of Glycoconjugate Research Ministry of Public Health, Department of Biochemistry and Molecular Biology, Shanghai Medical College, Fudan University, Shanghai 200032, China.
| | - Ling Dong
- Department of Gastroenterology and Hepatology, Shanghai Institute of Liver Diseases, Zhongshan Hospital of Fudan University, Shanghai 200032, China.
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Kabachinski G, Kielar-Grevstad DM, Zhang X, James DJ, Martin TFJ. Resident CAPS on dense-core vesicles docks and primes vesicles for fusion. Mol Biol Cell 2016; 27:654-68. [PMID: 26700319 PMCID: PMC4750925 DOI: 10.1091/mbc.e15-07-0509] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2015] [Revised: 12/12/2015] [Accepted: 12/18/2015] [Indexed: 11/11/2022] Open
Abstract
The Ca(2+)-dependent exocytosis of dense-core vesicles in neuroendocrine cells requires a priming step during which SNARE protein complexes assemble. CAPS (aka CADPS) is one of several factors required for vesicle priming; however, the localization and dynamics of CAPS at sites of exocytosis in live neuroendocrine cells has not been determined. We imaged CAPS before, during, and after single-vesicle fusion events in PC12 cells by TIRF micro-scopy. In addition to being a resident on cytoplasmic dense-core vesicles, CAPS was present in clusters of approximately nine molecules near the plasma membrane that corresponded to docked/tethered vesicles. CAPS accompanied vesicles to the plasma membrane and was present at all vesicle exocytic events. The knockdown of CAPS by shRNA eliminated the VAMP-2-dependent docking and evoked exocytosis of fusion-competent vesicles. A CAPS(ΔC135) protein that does not localize to vesicles failed to rescue vesicle docking and evoked exocytosis in CAPS-depleted cells, showing that CAPS residence on vesicles is essential. Our results indicate that dense-core vesicles carry CAPS to sites of exocytosis, where CAPS promotes vesicle docking and fusion competence, probably by initiating SNARE complex assembly.
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Affiliation(s)
- Greg Kabachinski
- Department of Biochemistry, University of Wisconsin, Madison, WI 53706
| | | | - Xingmin Zhang
- Department of Biochemistry, University of Wisconsin, Madison, WI 53706
| | - Declan J James
- Department of Biochemistry, University of Wisconsin, Madison, WI 53706
| | - Thomas F J Martin
- Department of Biochemistry, University of Wisconsin, Madison, WI 53706
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7
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Nguyen Truong CQ, Nestvogel D, Ratai O, Schirra C, Stevens DR, Brose N, Rhee J, Rettig J. Secretory vesicle priming by CAPS is independent of its SNARE-binding MUN domain. Cell Rep 2014; 9:902-9. [PMID: 25437547 DOI: 10.1016/j.celrep.2014.09.050] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2014] [Revised: 09/12/2014] [Accepted: 09/28/2014] [Indexed: 01/27/2023] Open
Abstract
Priming of secretory vesicles is a prerequisite for their Ca(2+)-dependent fusion with the plasma membrane. The key vesicle priming proteins, Munc13s and CAPSs, are thought to mediate vesicle priming by regulating the conformation of the t-SNARE syntaxin, thereby facilitating SNARE complex assembly. Munc13s execute their priming function through their MUN domain. Given that the MUN domain of Ca(2+)-dependent activator protein for secretion (CAPS) also binds syntaxin, it was assumed that CAPSs prime vesicles through the same mechanism as Munc13s. We studied naturally occurring splice variants of CAPS2 in CAPS1/CAPS2-deficient cells and found that CAPS2 primes vesicles independently of its MUN domain. Instead, the pleckstrin homology domain of CAPS2 seemingly is essential for its priming function. Our findings indicate a priming mode for secretory vesicles. This process apparently requires membrane phospholipids, does not involve the binding or direct conformational regulation of syntaxin by MUN domains of CAPSs, and is therefore not redundant with Munc13 action.
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Affiliation(s)
| | - Dennis Nestvogel
- Neurophysiology Group, Max-Planck-Institute of Experimental Medicine, 37075 Göttingen, Germany; Department of Molecular Neurobiology, Max-Planck-Institute of Experimental Medicine, 37075 Göttingen, Germany
| | - Olga Ratai
- Institute of Physiology, Saarland University, Building 59, 66421 Homburg/Saar, Germany
| | - Claudia Schirra
- Institute of Physiology, Saarland University, Building 59, 66421 Homburg/Saar, Germany
| | - David R Stevens
- Institute of Physiology, Saarland University, Building 59, 66421 Homburg/Saar, Germany
| | - Nils Brose
- Department of Molecular Neurobiology, Max-Planck-Institute of Experimental Medicine, 37075 Göttingen, Germany
| | - JeongSeop Rhee
- Neurophysiology Group, Max-Planck-Institute of Experimental Medicine, 37075 Göttingen, Germany; Department of Molecular Neurobiology, Max-Planck-Institute of Experimental Medicine, 37075 Göttingen, Germany
| | - Jens Rettig
- Institute of Physiology, Saarland University, Building 59, 66421 Homburg/Saar, Germany.
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8
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James DJ, Martin TFJ. CAPS and Munc13: CATCHRs that SNARE Vesicles. Front Endocrinol (Lausanne) 2013; 4:187. [PMID: 24363652 PMCID: PMC3849599 DOI: 10.3389/fendo.2013.00187] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/03/2013] [Accepted: 11/18/2013] [Indexed: 11/13/2022] Open
Abstract
CAPS (Calcium-dependent Activator Protein for Secretion, aka CADPS) and Munc13 (Mammalian Unc-13) proteins function to prime vesicles for Ca(2+)-triggered exocytosis in neurons and neuroendocrine cells. CAPS and Munc13 proteins contain conserved C-terminal domains that promote the assembly of SNARE complexes for vesicle priming. Similarities of the C-terminal domains of CAPS/Munc13 proteins with Complex Associated with Tethering Containing Helical Rods domains in multi-subunit tethering complexes (MTCs) have been reported. MTCs coordinate multiple interactions for SNARE complex assembly at constitutive membrane fusion steps. We review aspects of these diverse tethering and priming factors to identify common operating principles.
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Affiliation(s)
- Declan J. James
- Department of Biochemistry, University of Wisconsin, Madison, WI, USA
| | - Thomas F. J. Martin
- Department of Biochemistry, University of Wisconsin, Madison, WI, USA
- *Correspondence: Thomas F. J. Martin, Department of Biochemistry, University of Wisconsin, 433 Babcock Drive, Madison, WI 53706, USA e-mail:
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Khodthong C, Kabachinski G, James DJ, Martin TFJ. Munc13 homology domain-1 in CAPS/UNC31 mediates SNARE binding required for priming vesicle exocytosis. Cell Metab 2011; 14:254-63. [PMID: 21803295 PMCID: PMC3148490 DOI: 10.1016/j.cmet.2011.07.002] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/17/2010] [Revised: 04/09/2011] [Accepted: 06/21/2011] [Indexed: 01/11/2023]
Abstract
Neuropeptide and peptide hormone secretion from neural and endocrine cells occurs by Ca(2+)-triggered dense-core vesicle exocytosis. The membrane fusion machinery consisting of vesicle and plasma membrane SNARE proteins needs to be assembled for Ca(2+)-triggered vesicle exocytosis. The related Munc13 and CAPS/UNC31 proteins that prime vesicle exocytosis are proposed to promote SNARE complex assembly. CAPS binds SNARE proteins and stimulates SNARE complex formation on liposomes, but the relevance of SNARE binding to CAPS function in cells had not been determined. Here we identify a core SNARE-binding domain in CAPS as corresponding to Munc13 homology domain-1 (MHD1). CAPS lacking a single helix in MHD1 was unable to bind SNARE proteins or to support the Ca(2+)-triggered exocytosis of either docked or newly arrived dense-core vesicles. The results show that MHD1 is a SNARE-binding domain and that SNARE protein binding is essential for CAPS function in dense-core vesicle exocytosis.
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10
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Kluetzman KS, Thomas RM, Nechamen CA, Dias JA. Decreased degradation of internalized follicle-stimulating hormone caused by mutation of aspartic acid 6.30(550) in a protein kinase-CK2 consensus sequence in the third intracellular loop of human follicle-stimulating hormone receptor. Biol Reprod 2011; 84:1154-63. [PMID: 21270425 DOI: 10.1095/biolreprod.110.087965] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
A naturally occurring mutation in follicle-stimulating hormone receptor (FSHR) gene has been reported: an amino acid change to glycine occurs at a conserved aspartic acid 550 (D550, D567, D6.30(567)). This residue is contained in a protein kinase-CK2 consensus site present in human FSHR (hFSHR) intracellular loop 3 (iL3). Because CK2 has been reported to play a role in trafficking of some receptors, the potential roles for CK2 and D550 in FSHR function were evaluated by generating a D550A mutation in the hFSHR. The hFSHR-D550A binds hormone similarly to WT-hFSHR when expressed in HEK293T cells. Western blot analyses showed lower levels of mature hFSHR-D550A. Maximal cAMP production of both hFSHR-D550A as well as the naturally occurring mutation hFSHR-D550G was diminished, but constitutive activity was not observed. Unexpectedly, when (125)I-hFSH bound to hFSHR-D550A or hFSHR-D550G, intracellular accumulation of radiolabeled FSH was observed. Both sucrose and dominant-negative dynamin blocked internalization of radiolabeled FSH and its commensurate intracellular accumulation. Accumulation of radiolabeled FSH in cells transfected with hFSHR-D550A is due to a defect in degradation of hFSH as measured in pulse chase studies, and confocal microscopy imaging revealed that FSH accumulated in large intracellular structures. CK2 kinase activity is not required for proper degradation of internalized FSH because inhibition of CK2 kinase activity in cells expressing hFSHR did not uncouple degradation of internalized radiolabeled FSH. Additionally, the CK2 consensus site in FSHR iL3 is not required for binding because CK2alpha coimmunoprecipitated with hFSHR-D550A. Thus, mutation of D550 uncouples the link between internalization and degradation of hFSH.
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11
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Daily NJ, Boswell KL, James DJ, Martin TFJ. Novel interactions of CAPS (Ca2+-dependent activator protein for secretion) with the three neuronal SNARE proteins required for vesicle fusion. J Biol Chem 2010; 285:35320-9. [PMID: 20826818 DOI: 10.1074/jbc.m110.145169] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
CAPS (aka CADPS) is required for optimal vesicle exocytosis in neurons and endocrine cells where it functions to prime the exocytic machinery for Ca(2+)-triggered fusion. Fusion is mediated by trans complexes of the SNARE proteins VAMP-2, syntaxin-1, and SNAP-25 that bridge vesicle and plasma membrane. CAPS promotes SNARE complex formation on liposomes, but the SNARE binding properties of CAPS are unknown. The current work revealed that CAPS exhibits high affinity binding to syntaxin-1 and SNAP-25 and moderate affinity binding to VAMP-2. CAPS binding is specific for a subset of exocytic SNARE protein isoforms and requires membrane integration of the SNARE proteins. SNARE protein binding by CAPS is novel and mediated by interactions with the SNARE motifs in the three proteins. The C-terminal site for CAPS binding on syntaxin-1 does not overlap the Munc18-1 binding site and both proteins can co-reside on membrane-integrated syntaxin-1. As expected for a C-terminal binding site on syntaxin-1, CAPS stimulates SNARE-dependent liposome fusion with N-terminal truncated syntaxin-1 but exhibits impaired activity with C-terminal syntaxin-1 mutants. Overall the results suggest that SNARE complex formation promoted by CAPS may be mediated by direct interactions of CAPS with each of the three SNARE proteins required for vesicle exocytosis.
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Affiliation(s)
- Neil J Daily
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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Gao J, Takeuchi H, Umebayashi H, Zhang Z, Matsuda M, Hirata M. Assay of dense-core vesicle exocytosis using permeabilized PC12 cells. ACTA ACUST UNITED AC 2009; 50:237-46. [PMID: 19895839 DOI: 10.1016/j.advenzreg.2009.10.011] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Affiliation(s)
- Jing Gao
- Laboratory of Molecular and Cellular Biochemistry, Faculty of Dental Science and Station for Collaborative Research, Kyushu University, Fukuoka 812-8582, Japan
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