1
|
Synaptic Secretion and Beyond: Targeting Synapse and Neurotransmitters to Treat Neurodegenerative Diseases. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2022; 2022:9176923. [PMID: 35923862 PMCID: PMC9343216 DOI: 10.1155/2022/9176923] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/10/2022] [Revised: 05/16/2022] [Accepted: 06/04/2022] [Indexed: 11/17/2022]
Abstract
The nervous system is important, because it regulates the physiological function of the body. Neurons are the most basic structural and functional unit of the nervous system. The synapse is an asymmetric structure that is important for neuronal function. The chemical transmission mode of the synapse is realized through neurotransmitters and electrical processes. Based on vesicle transport, the abnormal information transmission process in the synapse can lead to a series of neurorelated diseases. Numerous proteins and complexes that regulate the process of vesicle transport, such as SNARE proteins, Munc18-1, and Synaptotagmin-1, have been identified. Their regulation of synaptic vesicle secretion is complicated and delicate, and their defects can lead to a series of neurodegenerative diseases. This review will discuss the structure and functions of vesicle-based synapses and their roles in neurons. Furthermore, we will analyze neurotransmitter and synaptic functions in neurodegenerative diseases and discuss the potential of using related drugs in their treatment.
Collapse
|
2
|
Fadil SA, Janetopoulos C. The Polarized Redistribution of the Contractile Vacuole to the Rear of the Cell is Critical for Streaming and is Regulated by PI(4,5)P2-Mediated Exocytosis. Front Cell Dev Biol 2022; 9:765316. [PMID: 35928786 PMCID: PMC9344532 DOI: 10.3389/fcell.2021.765316] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2021] [Accepted: 10/20/2021] [Indexed: 12/05/2022] Open
Abstract
Dictyostelium discoideum amoebae align in a head to tail manner during the process of streaming during fruiting body formation. The chemoattractant cAMP is the chemoattractant regulating cell migration during this process and is released from the rear of cells. The process by which this cAMP release occurs has eluded investigators for many decades, but new findings suggest that this release can occur through expulsion during contractile vacuole (CV) ejection. The CV is an organelle that performs several functions inside the cell including the regulation of osmolarity, and discharges its content via exocytosis. The CV localizes to the rear of the cell and appears to be part of the polarity network, with the localization under the influence of the plasma membrane (PM) lipids, including the phosphoinositides (PIs), among those is PI(4,5)P2, the most abundant PI on the PM. Research on D. discoideum and neutrophils have shown that PI(4,5)P2 is enriched at the rear of migrating cells. In several systems, it has been shown that the essential regulator of exocytosis is through the exocyst complex, mediated in part by PI(4,5)P2-binding. This review features the role of the CV complex in D. discoideum signaling with a focus on the role of PI(4,5)P2 in regulating CV exocytosis and localization. Many of the regulators of these processes are conserved during evolution, so the mechanisms controlling exocytosis and membrane trafficking in D. discoideum and mammalian cells will be discussed, highlighting their important functions in membrane trafficking and signaling in health and disease.
Collapse
Affiliation(s)
- Sana A. Fadil
- Department of Biological Sciences, University of the Sciences in Philadelphia, Philadelphia, PA, United States
- Department of Natural product, Faculty of Pharmacy, King Abdulaziz University, Saudia Arabia
| | - Chris Janetopoulos
- Department of Biological Sciences, University of the Sciences in Philadelphia, Philadelphia, PA, United States
- The Science Research Institute, Albright College, Reading, PA, United States
- The Department of Cell Biology at Johns Hopkins University School of Medicine, Baltimore, MD, United States
- *Correspondence: Chris Janetopoulos,
| |
Collapse
|
3
|
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.
Collapse
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.
| |
Collapse
|
4
|
Shumate KM, Tas ST, Kavalali ET, Emeson RB. RNA editing-mediated regulation of calcium-dependent activator protein for secretion (CAPS1) localization and its impact on synaptic transmission. J Neurochem 2021; 158:182-196. [PMID: 33894004 DOI: 10.1111/jnc.15372] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2021] [Revised: 03/16/2021] [Accepted: 04/07/2021] [Indexed: 12/12/2022]
Abstract
Calcium-dependent activator protein for secretion 1 (CAPS1) is a SNARE accessory protein that facilitates formation of the SNARE complex to enable neurotransmitter release. Messenger RNAs encoding CAPS1 are subject to a site-specific adenosine-to-inosine (A-to-I) editing event resulting in a glutamate-to-glycine (E-to-G) substitution in the C-terminal domain of the encoded protein product. The C-terminal domain of CAPS1 is necessary for its synaptic enrichment and Cadps RNA editing has been shown previously to enhance the release of neuromodulatory transmitters. Using mutant mouse lines engineered to solely express CAPS1 protein isoforms encoded by either the non-edited or edited Cadps transcript, primary neuronal cultures from mouse hippocampus were used to explore the effect of Cadps editing on neurotransmission and CAPS1 synaptic localization at both glutamatergic and GABAergic synapses. While the editing of Cadps does not alter baseline evoked neurotransmission, it enhances short-term synaptic plasticity, specifically short-term depression, at inhibitory synapses. Cadps editing also alters spontaneous inhibitory neurotransmission. Neurons that solely express edited Cadps have a greater proportion of synapses that contain CAPS1 than neurons that solely express non-edited Cadps for both glutamatergic and GABAergic synapses. Editing of Cadps transcripts is regulated by neuronal activity, as global network stimulation increases the extent of transcripts edited in wild-type hippocampal neurons, whereas chronic network silencing decreases the level of Cadps editing. Taken together, these results provide key insights into the importance of Cadps editing in modulating its own synaptic localization, as well as the modulation of neurotransmission at inhibitory synapses in hippocampal neurons.
Collapse
Affiliation(s)
- Kayla M Shumate
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Sadik T Tas
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Ege T Kavalali
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN, USA.,Training Program in Neuroscience, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Ronald B Emeson
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN, USA.,Training Program in Neuroscience, Vanderbilt University School of Medicine, Nashville, TN, USA
| |
Collapse
|
5
|
Structural and Functional Analysis of the CAPS SNARE-Binding Domain Required for SNARE Complex Formation and Exocytosis. Cell Rep 2020; 26:3347-3359.e6. [PMID: 30893606 DOI: 10.1016/j.celrep.2019.02.064] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2018] [Revised: 01/18/2019] [Accepted: 02/15/2019] [Indexed: 12/29/2022] Open
Abstract
Exocytosis of synaptic vesicles and dense-core vesicles requires both the Munc13 and CAPS (Ca2+-dependent activator proteins for secretion) proteins. CAPS contains a soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE)-binding region (called the DAMH domain), which has been found to be essential for SNARE-mediated exocytosis. Here we report a crystal structure of the CAPS-1 DAMH domain at 2.9-Å resolution and reveal a dual role of CAPS-1 in SNARE complex formation. CAPS-1 plays an inhibitory role dependent on binding of the DAMH domain to the MUN domain of Munc13-1, which hinders the ability of Munc13 to catalyze opening of syntaxin-1, inhibiting SNARE complex formation, and a chaperone role dependent on interaction of the DAMH domain with the syntaxin-1/SNAP-25 complex, which stabilizes the open conformation of Syx1, facilitating SNARE complex formation. Our results suggest that CAPS-1 facilitates SNARE complex formation via the DAMH domain in a manner dependent on sequential and cooperative interaction with Munc13-1 and SNARE proteins.
Collapse
|
6
|
CAPS1 Suppresses Tumorigenesis in Cholangiocarcinoma. Dig Dis Sci 2020; 65:1053-1063. [PMID: 31562609 DOI: 10.1007/s10620-019-05843-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/20/2019] [Accepted: 08/02/2019] [Indexed: 12/09/2022]
Abstract
BACKGROUND CAPS1 (calcium-dependent activator protein for secretion) is a multi-domain protein involved in regulating exocytosis of synaptic vesicles and dense-core vesicles. However, the expression and function of CAPS1 in cholangiocarcinoma (CCA) remains unclear. In the present study, we explored the role of CAPS1 in CCA carcinogenesis. METHODS CAPS1 expression was explored using western blotting and immunohistochemistry in four CCA cell lines and clinical samples from 90 cases of CCA. The clinical significance of CAPS1 was analyzed. The biological function of CAPS1 in CCA cells was detected in vitro and in vivo. The underlying mechanism of CAPS1 function was explored by detecting the expression of critical molecules in its associated signaling pathways. The mechanism of CAPS1 downregulation in tumor tissues was explored using in silico prediction and luciferase reporter assays. RESULTS CAPS1 expression was reduced in CCA cell lines and human tumor tissues. Loss of CAPS1 in tumor tissues was closely associated with poor prognosis of patients with CCA. Moreover, CAPS1 expression correlated significantly with tumor-node-metastasis stage, lymph node metastasis, and vascular invasion. Lentivirus-mediated CAPS1 overexpression substantially prevented clone formation, cell proliferation, and cell cycle progression. CAPS1 overexpression also suppressed carcinogenesis in nude mice. Mechanistically, CAPS1 overexpression greatly accelerated the ERK and p38 MAPK signal pathways. In addition, microRNA miR-30e-5p negatively regulated CAPS1 expression. CONCLUSION These data showed that CAPS1 functions as a tumor suppressor in CCA. Reduced CAPS1 expression could indicate poor prognosis of patients with CCA.
Collapse
|
7
|
Asadi F, Dhanvantari S. Stathmin-2 Mediates Glucagon Secretion From Pancreatic α-Cells. Front Endocrinol (Lausanne) 2020; 11:29. [PMID: 32117057 PMCID: PMC7011091 DOI: 10.3389/fendo.2020.00029] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/06/2019] [Accepted: 01/14/2020] [Indexed: 01/26/2023] Open
Abstract
Inhibition of glucagon hypersecretion from pancreatic α-cells is an appealing strategy for the treatment of diabetes. Our hypothesis is that proteins that associate with glucagon within alpha cell secretory granules will regulate glucagon secretion, and may provide druggable targets for controlling abnormal glucagon secretion in diabetes. Recently, we identified a dynamic glucagon interactome within the secretory granules of the α cell line, αTC1-6, and showed that select proteins within the interactome could modulate glucagon secretion. In the present study, we show that one of these interactome proteins, the neuronal protein stathmin-2, is expressed in αTC1-6 cells and in mouse pancreatic alpha cells, and is a novel regulator of glucagon secretion. The secretion of both glucagon and Stmn2 was significantly enhanced in response to 55 mM K+, and immunofluorescence confocal microscopy showed co-localization of stathmin-2 with glucagon and the secretory granule markers chromogranin A and VAMP-2 in αTC1-6 cells. In mouse pancreatic islets, Stathmin-2 co-localized with glucagon, but not with insulin, and co-localized with secretory pathway markers. To show a function for stathmin-2 in regulating glucagon secretion, we showed that siRNA-mediated depletion of stathmin-2 in αTC1-6 cells caused glucagon secretion to become constitutive without any effect on proglucagon mRNA levels, while overexpression of stathmin-2 completely abolished both basal and K+-stimulated glucagon secretion. Overexpression of stathmin-2 increased the localization of glucagon into the endosomal-lysosomal compartment, while depletion of stathmin-2 reduced the endosomal localization of glucagon. Therefore, we describe stathmin-2 as having a novel role as an alpha cell secretory granule protein that modulates glucagon secretion via trafficking through the endosomal-lysosomal system. These findings describe a potential new pathway for the regulation of glucagon secretion, and may have implications for controlling glucagon hypersecretion in diabetes.
Collapse
Affiliation(s)
- Farzad Asadi
- Department of Pathology and Laboratory Medicine, Schulich School of Medicine & Dentistry, Western University, London, ON, Canada
| | - Savita Dhanvantari
- Department of Pathology and Laboratory Medicine, Schulich School of Medicine & Dentistry, Western University, London, ON, Canada
- Department of Medical Biophysics, Western University, London, ON, Canada
- Lawson Health Research Institute, London, ON, Canada
- *Correspondence: Savita Dhanvantari
| |
Collapse
|
8
|
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.
Collapse
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
| |
Collapse
|
9
|
An Alternative Exon of CAPS2 Influences Catecholamine Loading into LDCVs of Chromaffin Cells. J Neurosci 2019; 39:18-27. [PMID: 30389842 DOI: 10.1523/jneurosci.2040-18.2018] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2018] [Revised: 10/01/2018] [Accepted: 10/27/2018] [Indexed: 11/21/2022] Open
Abstract
The calcium-dependent activator proteins for secretion (CAPS) are priming factors for synaptic and large dense-core vesicles (LDCVs), promoting their entry into and stabilizing the release-ready state. A modulatory role of CAPS in catecholamine loading of vesicles has been suggested. Although an influence of CAPS on monoamine transporter function and on vesicle acidification has been reported, a role of CAPS in vesicle loading is disputed. Using expression of naturally occurring splice variants of CAPS2 into chromaffin cells from CAPS1/CAPS2 double-deficient mice of both sexes, we show that an alternative exon of 40 aa is responsible for enhanced catecholamine loading of LDCVs in mouse chromaffin cells. The presence of this exon leads to increased activity of both vesicular monoamine transporters. Deletion of CAPS does not alter acidification of vesicles. Our results establish a splice-variant-dependent modulatory effect of CAPS on catecholamine content in LDCVs.SIGNIFICANCE STATEMENT The calcium activator protein for secretion (CAPS) promotes and stabilizes the entry of catecholamine-containing vesicles of the adrenal gland into a release-ready state. Expression of an alternatively spliced exon in CAPS leads to enhanced catecholamine content in chromaffin granules. This exon codes for 40 aa with a high proline content, consistent with an unstructured loop present in the portion of the molecule generally thought to be involved in vesicle priming. CAPS variants containing this exon promote serotonin uptake into Chinese hamster ovary cells expressing either vesicular monoamine transporter. Epigenetic tuning of CAPS variants may allow modulation of endocrine adrenaline and noradrenaline release. This mechanism may extend to monoamine release in central neurons or in the enteric nervous system.
Collapse
|
10
|
Abstract
This review summarizes current knowledge of synaptic proteins that are central to synaptic vesicle fusion in presynaptic active zones, including SNAREs (soluble N-ethylmaleimide sensitive factor attachment protein receptors), synaptotagmin, complexin, Munc18 (mammalian uncoordinated-18), and Munc13 (mammalian uncoordinated-13), and highlights recent insights in the cooperation of these proteins for neurotransmitter release. Structural and functional studies of the synaptic fusion machinery suggest new molecular models of synaptic vesicle priming and Ca2+-triggered fusion. These studies will be a stepping-stone toward answering the question of how the synaptic vesicle fusion machinery achieves such high speed and sensitivity.
Collapse
Affiliation(s)
- Axel T Brunger
- Department of Molecular and Cellular Physiology, Department of Neurology and Neurological Sciences, Department of Structural Biology, Department of Photon Science, Howard Hughes Medical Institute, Stanford University, Stanford, California 94305, USA;
| | - Ucheor B Choi
- Department of Molecular and Cellular Physiology, Department of Neurology and Neurological Sciences, Department of Structural Biology, Department of Photon Science, Howard Hughes Medical Institute, Stanford University, Stanford, California 94305, USA;
| | - Ying Lai
- Department of Molecular and Cellular Physiology, Department of Neurology and Neurological Sciences, Department of Structural Biology, Department of Photon Science, Howard Hughes Medical Institute, Stanford University, Stanford, California 94305, USA;
| | - Jeremy Leitz
- Department of Molecular and Cellular Physiology, Department of Neurology and Neurological Sciences, Department of Structural Biology, Department of Photon Science, Howard Hughes Medical Institute, Stanford University, Stanford, California 94305, USA;
| | - Qiangjun Zhou
- Department of Molecular and Cellular Physiology, Department of Neurology and Neurological Sciences, Department of Structural Biology, Department of Photon Science, Howard Hughes Medical Institute, Stanford University, Stanford, California 94305, USA;
| |
Collapse
|
11
|
Xu R, Zhou J, Zhou XD, Li Q, Perelman JM, Kolosov VP. Munc13‑4 mediates human neutrophil elastase‑induced airway mucin5AC hypersecretion by interacting with syntaxin2. Mol Med Rep 2018; 18:1015-1024. [PMID: 29767240 DOI: 10.3892/mmr.2018.9015] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2017] [Accepted: 03/27/2018] [Indexed: 11/06/2022] Open
Abstract
The overexpression and hypersecretion of mucus is a hallmark of chronic pulmonary inflammatory disease. Mucin5AC (MUC5AC) is a major component of airway gel‑forming mucin. Members of the Unc13 (Munc13) protein family act as important activators of granule exocytosis from various types of mammalian cells. The present study aimed to determine the role of Munc13 family proteins in MUC5AC secretion via an in vitro study with BEAS‑2B and Calu‑3 cell lines. Reverse transcription‑quantitative polymerase chain reaction and western blotting indicated that stimulation of the cells with 100 nM human neutrophil elastase (hNE) for 1 h did not affect the expression of either unc13 homolog B (Munc13‑2) or unc13 homolog D (Munc13‑4), but immunofluorescence analysis demonstrated that hNE treatment was associated with the recruitment of Munc13‑4 to the plasma membrane. Co‑immunoprecipitation analysis indicated increased binding between Munc13‑4 and syntaxin2 followingh NE stimulation; however, Munc13‑2 formed a stable interaction with syntaxin2 with or without hNE stimulation. Subsequently, Munc13‑2 and Munc13‑4 expression levels were downregulated in BEAS‑2B and Calu‑3 cells using small interfering RNA (siRNA). ELISAs and immunofluorescence analysis were performed to assess MUC5AC secretion and intracellular retention, respectively. Munc13‑2 siRNA transfection did not alter the expression levels of intracellular or secreted MUC5AC following hNE stimulation in either cell line; however, it increased the baseline intracellular levels of MUC5AC and decreased the amount of secreted MUC5AC. Conversely, Munc13‑4 siRNA transfection increased the intracellular levels of MUC5AC and decreased the amount of secreted MUC5AC following hNE stimulation, but did not affect their baseline quantities. The results of the present study indicate that Munc13‑2 may be an essential regulator of basal MUC5AC exocytosis, while Munc13‑4 appears to be a Munc13 protein subtype that may to be sensitive to hNE stimulation during airway MUC5AC hypersecretion.
Collapse
Affiliation(s)
- Rui Xu
- Department of Respiratory Medicine, The Second Affiliated Hospital of Chongqing Medical University, Chongqing 400010, P.R. China
| | - Jia Zhou
- Department of Respiratory Medicine, The First Affiliated Hospital of Chongqing Medical University, Chongqing 400016, P.R. China
| | - Xiang-Dong Zhou
- Department of Respiratory Medicine, The First Affiliated Hospital of Hainan Medical University, Haikou, Hainan 570102, P.R. China
| | - Qi Li
- Department of Respiratory Medicine, The First Affiliated Hospital of Hainan Medical University, Haikou, Hainan 570102, P.R. China
| | - Juliy M Perelman
- Far Eastern Scientific Center of Physiology and Pathology of Respiration, Russian Academy of Medical Sciences, Blagoveshchensk 675000, Russia
| | - Victor P Kolosov
- Far Eastern Scientific Center of Physiology and Pathology of Respiration, Russian Academy of Medical Sciences, Blagoveshchensk 675000, Russia
| |
Collapse
|
12
|
Meijer M, Dörr B, Lammertse HC, Blithikioti C, van Weering JR, Toonen RF, Söllner TH, Verhage M. Tyrosine phosphorylation of Munc18-1 inhibits synaptic transmission by preventing SNARE assembly. EMBO J 2017; 37:300-320. [PMID: 29150433 PMCID: PMC5770875 DOI: 10.15252/embj.201796484] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2017] [Revised: 10/12/2017] [Accepted: 10/16/2017] [Indexed: 11/17/2022] Open
Abstract
Tyrosine kinases are important regulators of synaptic strength. Here, we describe a key component of the synaptic vesicle release machinery, Munc18‐1, as a phosphorylation target for neuronal Src family kinases (SFKs). Phosphomimetic Y473D mutation of a SFK phosphorylation site previously identified by brain phospho‐proteomics abolished the stimulatory effect of Munc18‐1 on SNARE complex formation (“SNARE‐templating”) and membrane fusion in vitro. Furthermore, priming but not docking of synaptic vesicles was disrupted in hippocampal munc18‐1‐null neurons expressing Munc18‐1Y473D. Synaptic transmission was temporarily restored by high‐frequency stimulation, as well as by a Munc18‐1 mutation that results in helix 12 extension, a critical conformational step in vesicle priming. On the other hand, expression of non‐phosphorylatable Munc18‐1 supported normal synaptic transmission. We propose that SFK‐dependent Munc18‐1 phosphorylation may constitute a potent, previously unknown mechanism to shut down synaptic transmission, via direct occlusion of a Synaptobrevin/VAMP2 binding groove and subsequent hindrance of conformational changes in domain 3a responsible for vesicle priming. This would strongly interfere with the essential post‐docking SNARE‐templating role of Munc18‐1, resulting in a largely abolished pool of releasable synaptic vesicles.
Collapse
Affiliation(s)
- Marieke Meijer
- Department of Clinical Genetics, Center for Neurogenomics and Cognitive Research (CNCR), Neuroscience Campus Amsterdam (NCA) VU University Medical Center, Amsterdam, The Netherlands
| | - Bernhard Dörr
- Heidelberg University Biochemistry Center (BZH), Heidelberg, Germany
| | - Hanna Ca Lammertse
- Department of Functional Genomics, Center for Neurogenomics and Cognitive Research (CNCR), Neuroscience Campus Amsterdam (NCA) VU University Amsterdam, Amsterdam, The Netherlands
| | - Chrysanthi Blithikioti
- Department of Functional Genomics, Center for Neurogenomics and Cognitive Research (CNCR), Neuroscience Campus Amsterdam (NCA) VU University Amsterdam, Amsterdam, The Netherlands
| | - Jan Rt van Weering
- Department of Clinical Genetics, Center for Neurogenomics and Cognitive Research (CNCR), Neuroscience Campus Amsterdam (NCA) VU University Medical Center, Amsterdam, The Netherlands
| | - Ruud Fg Toonen
- Department of Functional Genomics, Center for Neurogenomics and Cognitive Research (CNCR), Neuroscience Campus Amsterdam (NCA) VU University Amsterdam, Amsterdam, The Netherlands
| | - Thomas H Söllner
- Heidelberg University Biochemistry Center (BZH), Heidelberg, Germany
| | - Matthijs Verhage
- Department of Clinical Genetics, Center for Neurogenomics and Cognitive Research (CNCR), Neuroscience Campus Amsterdam (NCA) VU University Medical Center, Amsterdam, The Netherlands .,Department of Functional Genomics, Center for Neurogenomics and Cognitive Research (CNCR), Neuroscience Campus Amsterdam (NCA) VU University Amsterdam, Amsterdam, The Netherlands
| |
Collapse
|
13
|
Cai P, Liu S, Piao X, Hou N, You H, McManus DP, Chen Q. A next-generation microarray further reveals stage-enriched gene expression pattern in the blood fluke Schistosoma japonicum. Parasit Vectors 2017; 10:19. [PMID: 28069074 PMCID: PMC5223471 DOI: 10.1186/s13071-016-1947-x] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2016] [Accepted: 12/21/2016] [Indexed: 01/22/2023] Open
Abstract
BACKGROUND Schistosomiasis is caused by infection with blood flukes of the genus Schistosoma, and ranks, in terms of disability-adjusted life years (DALYs), as the third most important neglected tropical disease. Schistosomes have several discrete life stages involving dramatic morphological changes during their development, which require subtle gene expression modulations to complete the complex life-cycle. RESULTS In the current study, we employed a second generation schistosome DNA chip printed with the most comprehensive probe array for studying the Schistosoma japonicum transcriptome, to explore stage-associated gene expression in different developmental phases of S. japonicum. A total of 328, 95, 268 and 532 mRNA transcripts were enriched in cercariae, hepatic schistosomula, adult worms and eggs, respectively. In general, genes associated with transcriptional regulation, cell signalling and motor activity were readily expressed in cercariae; the expression of genes involved in neuronal activities, apoptosis and renewal was modestly upregulated in hepatic schistosomula; transcripts involved in egg production, nutrition metabolism and glycosylation were enriched in adult worms; while genes involved in cell division, microtubule-associated mobility, and host-parasite interplay were relatively highly expressed in eggs. CONCLUSIONS The study further highlights the expressional features of stage-associated genes in schistosomes with high accuracy. The results provide a better perspective of the biological characteristics among different developmental stages, which may open new avenues for identification of novel vaccine candidates and the development of novel control interventions against schistosomiasis.
Collapse
Affiliation(s)
- Pengfei Cai
- MOH Key Laboratory of Systems Biology of Pathogens, Institute of Pathogen Biology, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, People's Republic of China. .,Molecular Parasitology Laboratory, QIMR Berghofer Medical Research Institute, Queensland, Australia.
| | - Shuai Liu
- MOH Key Laboratory of Systems Biology of Pathogens, Institute of Pathogen Biology, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, People's Republic of China
| | - Xianyu Piao
- MOH Key Laboratory of Systems Biology of Pathogens, Institute of Pathogen Biology, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, People's Republic of China
| | - Nan Hou
- MOH Key Laboratory of Systems Biology of Pathogens, Institute of Pathogen Biology, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, People's Republic of China
| | - Hong You
- Molecular Parasitology Laboratory, QIMR Berghofer Medical Research Institute, Queensland, Australia
| | - Donald P McManus
- Molecular Parasitology Laboratory, QIMR Berghofer Medical Research Institute, Queensland, Australia.
| | - Qijun Chen
- MOH Key Laboratory of Systems Biology of Pathogens, Institute of Pathogen Biology, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, People's Republic of China. .,Key Laboratory of Zoonosis, Shenyang Agriculture University, Shenyang, People's Republic of China.
| |
Collapse
|
14
|
Pérez-Lara Á, Thapa A, Nyenhuis SB, Nyenhuis DA, Halder P, Tietzel M, Tittmann K, Cafiso DS, Jahn R. PtdInsP 2 and PtdSer cooperate to trap synaptotagmin-1 to the plasma membrane in the presence of calcium. eLife 2016; 5. [PMID: 27791979 PMCID: PMC5123861 DOI: 10.7554/elife.15886] [Citation(s) in RCA: 71] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2016] [Accepted: 10/25/2016] [Indexed: 12/16/2022] Open
Abstract
The Ca2+-sensor synaptotagmin-1 that triggers neuronal exocytosis binds to negatively charged membrane lipids (mainly phosphatidylserine (PtdSer) and phosphoinositides (PtdIns)) but the molecular details of this process are not fully understood. Using quantitative thermodynamic, kinetic and structural methods, we show that synaptotagmin-1 (from Rattus norvegicus and expressed in Escherichia coli) binds to PtdIns(4,5)P2 via a polybasic lysine patch in the C2B domain, which may promote the priming or docking of synaptic vesicles. Ca2+ neutralizes the negative charges of the Ca2+-binding sites, resulting in the penetration of synaptotagmin-1 into the membrane, via binding of PtdSer, and an increase in the affinity of the polybasic lysine patch to phosphatidylinositol-4,5-bisphosphate (PtdIns(4,5)P2). These Ca2+-induced events decrease the dissociation rate of synaptotagmin-1 membrane binding while the association rate remains unchanged. We conclude that both membrane penetration and the increased residence time of synaptotagmin-1 at the plasma membrane are crucial for triggering exocytotic membrane fusion. DOI:http://dx.doi.org/10.7554/eLife.15886.001 The human nervous system contains billions of neurons that communicate with each other across junctions called synapses. When a neuron is activated, the levels of calcium ions inside the cell rise. This causes molecules called neurotransmitters to be released from the neuron at a synapse to make contact with the second neuron. The neurotransmitters are stored inside cells within compartments known as synaptic vesicles and are released when these vesicles fuse with the membrane surrounding the cell. Proteins called SNAREs regulate the membrane fusion process. These proteins assemble into bundles that help to drive vesicle and cell membranes together. Another protein called synaptotagmin-1 sticks out from the vesicle membrane and senses the levels of calcium ions in the cell to trigger membrane fusion at the right time. Synaptotagmin-1 has two regions that can bind to calcium ions, known as the C2 domains. When calcium ion levels rise, these domains insert into the cell membrane by binding to two fat molecules in the membrane called phosphatidylserine (PtdSer) and phosphatidylinositol 4,5-bisphosphate (PtdInsP2). Synaptotagmin-1 also interacts with the SNARE proteins, but it is not known whether synaptotagmin-1 triggers fusion by binding directly to SNAREs, or by the way it inserts into the cell membrane. Pérez-Lara et al. used several biophysical methods to investigate how synaptotagmin-1 binds to PtdSer and PtdInsP2. The experiments show that these molecules bind to different regions of synaptotagmin-1 and work together to attach the protein to the cell membrane and insert the C2 domains. Calcium ions increase the affinity of synaptotagmin-1 binding to the cell membrane by making it harder for synaptotagmin-1 to separate from the membrane, rather than by increasing its ability to bind to it. Further experiments show that synaptotagmin-1 prefers to bind to membranes that contain PtdInsP2 over binding to the SNARE proteins. Together, the findings of Pérez-Lara et al. suggest that calcium ions may trigger the release of neurotransmitters by trapping synaptotagmin-1 at the cell membrane rather than by directly affecting how it interacts with SNARE proteins. Further work will be needed to establish exactly how the SNARE proteins, PtdInsP2 and synaptotagmin-1 interact. DOI:http://dx.doi.org/10.7554/eLife.15886.002
Collapse
Affiliation(s)
- Ángel Pérez-Lara
- Department of Neurobiology, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Anusa Thapa
- Department of Chemistry and Center for Membrane Biology, University of Virginia, Charlottesville, United States
| | - Sarah B Nyenhuis
- Department of Chemistry and Center for Membrane Biology, University of Virginia, Charlottesville, United States
| | - David A Nyenhuis
- Department of Chemistry and Center for Membrane Biology, University of Virginia, Charlottesville, United States
| | - Partho Halder
- Department of Neurobiology, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Michael Tietzel
- Department of Molecular Enzymology, Göttingen Center for Molecular Biosciences, Georg-August University Göttingen, Göttingen, Germany
| | - Kai Tittmann
- Department of Molecular Enzymology, Göttingen Center for Molecular Biosciences, Georg-August University Göttingen, Göttingen, Germany
| | - David S Cafiso
- Department of Chemistry and Center for Membrane Biology, University of Virginia, Charlottesville, United States
| | - Reinhard Jahn
- Department of Neurobiology, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| |
Collapse
|
15
|
Male-specific association between MT-ND4 11719 A/G polymorphism and ulcerative colitis: a mitochondria-wide genetic association study. BMC Gastroenterol 2016; 16:118. [PMID: 27716073 PMCID: PMC5048482 DOI: 10.1186/s12876-016-0509-1] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/22/2016] [Accepted: 08/02/2016] [Indexed: 12/17/2022] Open
Abstract
Background Ulcerative colitis (UC) is a chronic inflammatory disorder of still unknown pathogenesis. Increasing evidence indicates that alterations in mitochondrial respiration and thus adenosine triphosphate (ATP) production are involved. This may contribute to mucosal energy deficiency and subsequently intestinal barrier malfunction, which is accepted to be a major hallmark of UC. Genetic alterations of the mitochondrial genome are one cause of mitochondrial dysfunction. However, less is known about mitochondrial gene polymorphisms in UC. Therefore, we aimed at identifying genetic associations between mitochondrial polymorphisms and UC. Methods German UC cases (n = 1062) and German healthy controls (n = 3030) were genotyped using the Affymetrix Genome-Wide Human SNP Array 6.0. The primary association analysis was to test for associations between mitochondrial single nucleotide polymorphisms (SNPs) and UC using Fisher’s exact test in the total sample and stratified by sex. In addition, we tested for associations between mitochondrial haplogroups and UC and for interactions between the most promising mitochondrial SNPs and nuclear SNPs. An independent set of German subjects with 1625 UC cases and 3575 controls was used for replication. Results We identified a genetic association between the MT-ND4 11719 A/G polymorphism and UC in the subgroup of males (rs2853495; odds ratio, 1.40; 95 % confidence interval, 1.13 to 1.73; p = 0.002). This association was replicated in the second independent cohort. In the association analysis based on mitochondrial haplogroups the lowest p values were reached for haplogroups HV and T (p = 0.029 and 0.035). Haplogroup HV is determined by the mitochondrial 11719 A/G polymorphism. Accordingly, this association was only found in the subgroup of males (p = 0.009). Conclusions For the first time, we observed an association between the MT-ND4 11719 A/G polymorphism and UC. The gene MT-ND4 encodes for a subunit of the mitochondrial electron transport chain complex I, which is pivotal for ATP production and might therefore contribute to mucosal energy deficiency. The male-specific association indicates differences between males and females concerning the impact of mitochondrial gene polymorphisms on the development of UC. Further investigations of the functional mechanism underlying this association and the relevance of the gender-specificity are highly warranted. Electronic supplementary material The online version of this article (doi:10.1186/s12876-016-0509-1) contains supplementary material, which is available to authorized users.
Collapse
|
16
|
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.
Collapse
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
| |
Collapse
|
17
|
Interaction of Ca(2+)-dependent activator protein for secretion 1 (CAPS1) with septin family proteins in mouse brain. Neurosci Lett 2016; 617:232-5. [PMID: 26917099 DOI: 10.1016/j.neulet.2016.02.035] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2015] [Revised: 02/18/2016] [Accepted: 02/19/2016] [Indexed: 01/22/2023]
Abstract
The Ca(2+)-dependent activator protein for secretion 1 (CAPS1) protein plays a regulatory role in the dense-core vesicle exocytosis pathway. To clarify the functions of this protein in the brain, we searched for novel interaction partners of CAPS1 by mass spectrometry. We identified a specific interaction of CAPS1 with septin family proteins. We also demonstrated that the C-terminal region of the CAPS1 protein binds to part of the deduced GTP-binding domain of septin proteins. It is possible that a tertiary complex of septin, CAPS, and syntaxin contributes to dense-core vesicle trafficking and exocytosis in neurons.
Collapse
|
18
|
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.
Collapse
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
| |
Collapse
|
19
|
Man KNM, Imig C, Walter AM, Pinheiro PS, Stevens DR, Rettig J, Sørensen JB, Cooper BH, Brose N, Wojcik SM. Identification of a Munc13-sensitive step in chromaffin cell large dense-core vesicle exocytosis. eLife 2015; 4. [PMID: 26575293 PMCID: PMC4798968 DOI: 10.7554/elife.10635] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2015] [Accepted: 11/16/2015] [Indexed: 01/16/2023] Open
Abstract
It is currently unknown whether the molecular steps of large dense-core vesicle (LDCV) docking and priming are identical to the corresponding reactions in synaptic vesicle (SV) exocytosis. Munc13s are essential for SV docking and priming, and we systematically analyzed their role in LDCV exocytosis using chromaffin cells lacking individual isoforms. We show that particularly Munc13-2 plays a fundamental role in LDCV exocytosis, but in contrast to synapses lacking Munc13s, the corresponding chromaffin cells do not exhibit a vesicle docking defect. We further demonstrate that ubMunc13-2 and Munc13-1 confer Ca(2+)-dependent LDCV priming with similar affinities, but distinct kinetics. Using a mathematical model, we identify an early LDCV priming step that is strongly dependent upon Munc13s. Our data demonstrate that the molecular steps of SV and LDCV priming are very similar while SV and LDCV docking mechanisms are distinct.
Collapse
Affiliation(s)
- Kwun Nok M Man
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Cordelia Imig
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | | | - Paulo S Pinheiro
- Department of Neuroscience and Pharmacology, Faculty of Health and Medical Sciences and Lundbeck Foundation Center for Biomembranes in Nanomedicine, University of Copenhagen, Copenhagen, Denmark
| | - David R Stevens
- Department of Physiology, Saarland University, Homburg, Germany
| | - Jens Rettig
- Department of Physiology, Saarland University, Homburg, Germany
| | - Jakob B Sørensen
- Department of Neuroscience and Pharmacology, Faculty of Health and Medical Sciences and Lundbeck Foundation Center for Biomembranes in Nanomedicine, University of Copenhagen, Copenhagen, Denmark
| | - Benjamin H Cooper
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Nils Brose
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Sonja M Wojcik
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| |
Collapse
|
20
|
Redina OE, Smolenskaya SE, Klimov LO, Markel AL. Candidate genes in quantitative trait loci associated with absolute and relative kidney weight in rats with Inherited Stress Induced Arterial Hypertension. BMC Genet 2015; 16 Suppl 1:S1. [PMID: 25707311 PMCID: PMC4331803 DOI: 10.1186/1471-2156-16-s1-s1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND The kidney mass is significantly increased in hypertensive ISIAH rats with Inherited Stress Induced Arterial Hypertension as compared with normotensive WAG rats. The QTL/microarray approach was carried out to determine the positional candidate genes in the QTL for absolute and relative kidney weight. RESULTS Several known and predicted genes differentially expressed in ISIAH and WAG kidney were mapped to genetic loci associated with the absolute and relative kidney weight in 6-month old F2 hybrid (ISIAHxWAG) males. The knowledge-driven filtering of the list of candidates helped to suggest several positional candidate genes, which may be related to the structural and mass changes in hypertensive ISIAH kidney. CONCLUSIONS The further experimental validation of causative genes and detection of polymorphisms will provide opportunities to advance our understanding of the underlying nature of structural and mass changes in hypertensive ISIAH kidney.
Collapse
|
21
|
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.
Collapse
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.
| |
Collapse
|
22
|
Martin TFJ. PI(4,5)P₂-binding effector proteins for vesicle exocytosis. Biochim Biophys Acta Mol Cell Biol Lipids 2014; 1851:785-93. [PMID: 25280637 DOI: 10.1016/j.bbalip.2014.09.017] [Citation(s) in RCA: 97] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2014] [Revised: 09/20/2014] [Accepted: 09/23/2014] [Indexed: 12/27/2022]
Abstract
PI(4,5)P₂participates directly in priming and possibly in fusion steps of Ca²⁺-triggered vesicle exocytosis. High concentration nanodomains of PI(4,5)P₂reside on the plasma membrane of neuroendocrine cells. A subset of vesicles that co-localize with PI(4,5)P₂ domains appear to undergo preferential exocytosis in stimulated cells. PI(4,5)P₂directly regulates vesicle exocytosis by recruiting and activating PI(4,5)P₂-binding proteins that regulate SNARE protein function including CAPS, Munc13-1/2, synaptotagmin-1, and other C2 domain-containing proteins. These PI(4,5)P₂effector proteins are coincidence detectors that engage in multiple interactions at vesicle exocytic sites. The SNARE protein syntaxin-1 also binds to PI(4,5)P₂, which promotes clustering, but an activating role for PI(4,5)P₂in syntaxin-1 function remains to be fully characterized. Similar principles underlie polarized constitutive vesicle fusion mediated in part by the PI(4,5)P₂-binding subunits of the exocyst complex (Sec3, Exo70). Overall, focal vesicle exocytosis occurs at sites landmarked by PI(4,5)P2, which serves to recruit and/or activate multifunctional PI(4,5)P₂-binding proteins. This article is part of a Special Issue entitled Phosphoinositides.
Collapse
Affiliation(s)
- Thomas F J Martin
- Biochemistry Department, University of Wisconsin, 433 Babcock Drive, Madison, WI 53706, USA.
| |
Collapse
|
23
|
Kabachinski G, Yamaga M, Kielar-Grevstad DM, Bruinsma S, Martin TFJ. CAPS and Munc13 utilize distinct PIP2-linked mechanisms to promote vesicle exocytosis. Mol Biol Cell 2013; 25:508-21. [PMID: 24356451 PMCID: PMC3923642 DOI: 10.1091/mbc.e12-11-0829] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Phosphoinositides provide compartment-specific signals for membrane trafficking. Plasma membrane phosphatidylinositol 4,5-bisphosphate (PIP2) is required for Ca(2+)-triggered vesicle exocytosis, but whether vesicles fuse into PIP2-rich membrane domains in live cells and whether PIP2 is metabolized during Ca(2+)-triggered fusion were unknown. Ca(2+)-dependent activator protein in secretion 1 (CAPS-1; CADPS/UNC31) and ubMunc13-2 (UNC13B) are PIP2-binding proteins required for Ca(2+)-triggered vesicle exocytosis in neuroendocrine PC12 cells. These proteins are likely effectors for PIP2, but their localization during exocytosis had not been determined. Using total internal reflection fluorescence microscopy in live cells, we identify PIP2-rich membrane domains at sites of vesicle fusion. CAPS is found to reside on vesicles but depends on plasma membrane PIP2 for its activity. Munc13 is cytoplasmic, but Ca(2+)-dependent translocation to PIP2-rich plasma membrane domains is required for its activity. The results reveal that vesicle fusion into PIP2-rich membrane domains is facilitated by sequential PIP2-dependent activation of CAPS and PIP2-dependent recruitment of Munc13. PIP2 hydrolysis only occurs under strong Ca(2+) influx conditions sufficient to activate phospholipase Cη2 (PLCη2). Such conditions reduce CAPS activity and enhance Munc13 activity, establishing PLCη2 as a Ca(2+)-dependent modulator of exocytosis. These studies provide a direct view of the spatial distribution of PIP2 linked to vesicle exocytosis via regulation of lipid-dependent protein effectors CAPS and Munc13.
Collapse
Affiliation(s)
- Greg Kabachinski
- Department of Biochemistry, University of Wisconsin, Madison, WI 53706
| | | | | | | | | |
Collapse
|
24
|
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.
Collapse
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:
| |
Collapse
|
25
|
Schwaibold EMC, Zoll B, Burfeind P, Hobbiebrunken E, Wilken B, Funke R, Shoukier M. A 3p interstitial deletion in two monozygotic twin brothers and an 18-year-old man: further characterization and review. Am J Med Genet A 2013; 161A:2634-40. [PMID: 23949945 DOI: 10.1002/ajmg.a.36129] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2013] [Accepted: 06/13/2013] [Indexed: 01/02/2023]
Abstract
An increasing number of patients with 3p proximal deletions were reported in the previous decade, but the region responsible for the main features such as intellectual disability (ID) and developmental delay is not yet characterized. Here we report on two monozygotic twin brothers of 2 10/12 years and an 18-year-old man, all three of them displaying severe ID, psychomotoric delay, autistic features, and only mild facial dysmorphisms. Array CGH (aCGH), revealed a 6.55 Mb de novo interstitial deletion of 3p14.1p14.3 in the twin brothers and a 4.76 Mb interstitial deletion of 3p14.1p14.2 in the 18-year-old patient, respectively. We compared the malformation spectrum with previous molecularly well-defined patients in the literature and in the DECIPHER database (Database of Chromosomal Imbalance and Phenotype in Humans using Ensembl Resources; http://decipher.sanger.ac.uk/). In conclusion, the deletion of a region containing 3p14.2 seems to be associated with a relative concise phenotype including ID and developmental delay. Thus, we hypothesize that 3p14.2 is the potential core region in 3p proximal deletions. The knowledge of this potential core region could be helpful in the genetic counselling of patients with 3p proximal deletions, especially concerning their phenotype.
Collapse
|
26
|
Parsaud L, Li L, Jung CH, Park S, Saw NMN, Park S, Kim MY, Sugita S. Calcium-dependent activator protein for secretion 1 (CAPS1) binds to syntaxin-1 in a distinct mode from Munc13-1. J Biol Chem 2013; 288:23050-63. [PMID: 23801330 DOI: 10.1074/jbc.m113.494088] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Calcium-dependent activator protein for secretion 1 (CAPS1) is a multidomain protein containing a Munc13 homology domain 1 (MHD1). Although CAPS1 and Munc13-1 play crucial roles in the priming stage of secretion, their functions are non-redundant. Similar to Munc13-1, CAPS1 binds to syntaxin-1, a key t-SNARE protein in neurosecretion. However, whether CAPS1 interacts with syntaxin-1 in a similar mode to Munc13-1 remains unclear. Here, using yeast two-hybrid assays followed by biochemical binding experiments, we show that the region in CAPS1 consisting of the C-terminal half of the MHD1 with the corresponding C-terminal region can bind to syntaxin-1. Importantly, the binding mode of CAPS1 to syntaxin-1 is distinct from that of Munc13-1; CAPS1 binds to the full-length of cytoplasmic syntaxin-1 with preference to its "open" conformation, whereas Munc13-1 binds to the first 80 N-terminal residues of syntaxin-1. Unexpectedly, the majority of the MHD1 of CAPS1 is dispensable, whereas the C-terminal 69 residues are crucial for the binding to syntaxin-1. Functionally, a C-terminal truncation of 69 or 134 residues in CAPS1 abolishes its ability to reconstitute secretion in permeabilized PC12 cells. Our results reveal a novel mode of binding between CAPS1 and syntaxin-1, which play a crucial role in neurosecretion. We suggest that the distinct binding modes between CAPS1 and Munc13-1 can account for their non-redundant functions in neurosecretion. We also propose that the preferential binding of CAPS1 to open syntaxin-1 can contribute to the stabilization of the open state of syntaxin-1 during its transition from "closed" state to the SNARE complex formation.
Collapse
Affiliation(s)
- Leon Parsaud
- Division of Fundamental Neurobiology, University Health Network, Toronto, Ontario M5T 2S8, Canada
| | | | | | | | | | | | | | | |
Collapse
|
27
|
Caldwell L, Harries P, Sydlik S, Schwiening CJ. Presynaptic pH and vesicle fusion in Drosophila larvae neurones. Synapse 2013; 67:729-40. [PMID: 23649934 PMCID: PMC4282566 DOI: 10.1002/syn.21678] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2013] [Accepted: 04/22/2013] [Indexed: 11/11/2022]
Abstract
Both intracellular pH (pHi) and synaptic cleft pH change during neuronal activity yet little is known about how these pH shifts might affect synaptic transmission by influencing vesicle fusion. To address this we imaged pH- and Ca2+-sensitive fluorescent indicators (HPTS, Oregon green) in boutons at neuromuscular junctions. Electrical stimulation of motor nerves evoked presynaptic Ca2+i rises and pHi falls (∼0.1 pH units) followed by recovery of both Ca2+i and pHi. The plasma-membrane calcium ATPase (PMCA) inhibitor, 5(6)-carboxyeosin diacetate, slowed both the calcium recovery and the acidification. To investigate a possible calcium-independent role for the pHi shifts in modulating vesicle fusion we recorded post-synaptic miniature end-plate potential (mEPP) and current (mEPC) frequency in Ca2+-free solution. Acidification by propionate superfusion, NH4+ withdrawal, or the inhibition of acid extrusion on the Na+/H+ exchanger (NHE) induced a rise in miniature frequency. Furthermore, the inhibition of acid extrusion enhanced the rise induced by propionate addition and NH4+ removal. In the presence of NH4+, 10 out of 23 cells showed, after a delay, one or more rises in miniature frequency. These findings suggest that Ca2+-dependent pHi shifts, caused by the PMCA and regulated by NHE, may stimulate vesicle release. Furthermore, in the presence of membrane permeant buffers, exocytosed acid or its equivalents may enhance release through positive feedback. This hitherto neglected pH signalling, and the potential feedback role of vesicular acid, could explain some important neuronal excitability changes associated with altered pH and its buffering. Synapse 67:729–740, 2013.
Collapse
Affiliation(s)
- Lesley Caldwell
- Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge, CB2 3EG, United Kingdom
| | | | | | | |
Collapse
|
28
|
MARCKS protein is phosphorylated and regulates calcium mobilization during human acrosomal exocytosis. PLoS One 2013; 8:e64551. [PMID: 23704996 PMCID: PMC3660367 DOI: 10.1371/journal.pone.0064551] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2012] [Accepted: 04/17/2013] [Indexed: 12/01/2022] Open
Abstract
Acrosomal exocytosis is a calcium-regulated exocytosis that can be triggered by PKC activators. The involvement of PKC in acrosomal exocytosis has not been fully elucidated, and it is unknown if MARCKS, the major substrate for PKC, participates in this exocytosis. Here, we report that MARCKS is expressed in human spermatozoa and localizes to the sperm head and the tail. Calcium- and phorbol ester-triggered acrosomal exocytosis in permeabilized sperm was abrogated by different anti-MARCKS antibodies raised against two different domains, indicating that the protein participates in acrosomal exocytosis. Interestingly, an anti-phosphorylated MARCKS antibody was not able to inhibit secretion. Similar results were obtained using recombinant proteins and phospho-mutants of MARCKS effector domain (ED), indicating that phosphorylation regulates MARCKS function in acrosomal exocytosis. It is known that unphosphorylated MARCKS sequesters PIP2. This phospholipid is the precursor for IP3, which in turn triggers release of calcium from the acrosome during acrosomal exocytosis. We found that PIP2 and adenophostin, a potent IP3-receptor agonist, rescued MARCKS inhibition in permeabilized sperm, suggesting that MARCKS inhibits acrosomal exocytosis by sequestering PIP2 and, indirectly, MARCKS regulates the intracellular calcium mobilization. In non-permeabilized sperm, a permeable peptide of MARCKS ED also inhibited acrosomal exocytosis when stimulated by a natural agonist such as progesterone, and pharmacological inducers such as calcium ionophore and phorbol ester. The preincubation of human sperm with the permeable MARCKS ED abolished the increase in calcium levels caused by progesterone, demonstrating that MARCKS regulates calcium mobilization. In addition, the phosphorylation of MARCKS increased during acrosomal exocytosis stimulated by the same activators. Altogether, these results show that MARCKS is a negative modulator of the acrosomal exocytosis, probably by sequestering PIP2, and that it is phosphorylated during acrosomal exocytosis.
Collapse
|
29
|
Zhang Z, Takeuchi H, Gao J, Wang D, James DJ, Martin TFJ, Hirata M. PRIP (phospholipase C-related but catalytically inactive protein) inhibits exocytosis by direct interactions with syntaxin 1 and SNAP-25 through its C2 domain. J Biol Chem 2013; 288:7769-7780. [PMID: 23341457 DOI: 10.1074/jbc.m112.419317] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Membrane fusion for exocytosis is mediated by SNAREs, forming trans-ternary complexes to bridge vesicle and target membranes. There is an array of accessory proteins that directly interact with and regulate SNARE proteins. PRIP (phospholipase C-related but catalytically inactive protein) is likely one of these proteins; PRIP, consisting of multiple functional modules including pleckstrin homology and C2 domains, inhibited exocytosis, probably via the binding to membrane phosphoinositides through the pleckstrin homology domain. However, the roles of the C2 domain have not yet been investigated. In this study, we found that the C2 domain of PRIP directly interacts with syntaxin 1 and SNAP-25 but not with VAMP2. The C2 domain promoted PRIP to co-localize with syntaxin 1 and SNAP-25 in PC12 cells. The binding profile of the C2 domain to SNAP-25 was comparable with that of synaptotagmin I, and PRIP inhibited synaptotagmin I in binding to SNAP-25 and syntaxin 1. It was also shown that the C2 domain was required for PRIP to suppress SDS-resistant ternary SNARE complex formation and inhibit high K(+)-induced noradrenalin release from PC12 cells. These results suggest that PRIP inhibits regulated exocytosis through the interaction of its C2 domain with syntaxin 1 and SNAP-25, potentially competing with other SNARE-binding, C2 domain-containing accessory proteins such as synaptotagmin I and by directly inhibiting trans-SNARE complex formation.
Collapse
Affiliation(s)
- Zhao Zhang
- Laboratory of Molecular and Cellular Biochemistry, Faculty of Dental Science, Kyushu University, Fukuoka 812-8582, Japan; Stomatological Hospital of Hebei Medical University, Shijiazhuang 050017, China
| | - Hiroshi Takeuchi
- Laboratory of Molecular and Cellular Biochemistry, Faculty of Dental Science, Kyushu University, Fukuoka 812-8582, Japan; Division of Applied Pharmacology, Kyushu Dental College, Kitakyushu 803-8580, Japan.
| | - Jing Gao
- Laboratory of Molecular and Cellular Biochemistry, Faculty of Dental Science, Kyushu University, Fukuoka 812-8582, Japan
| | - DaGuang Wang
- Laboratory of Molecular and Cellular Biochemistry, Faculty of Dental Science, Kyushu University, Fukuoka 812-8582, Japan
| | - Declan J James
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706
| | - Thomas F J Martin
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706
| | - Masato Hirata
- Laboratory of Molecular and Cellular Biochemistry, Faculty of Dental Science, Kyushu University, Fukuoka 812-8582, Japan.
| |
Collapse
|
30
|
Rizo J, Südhof TC. The Membrane Fusion Enigma: SNAREs, Sec1/Munc18 Proteins, and Their Accomplices—Guilty as Charged? Annu Rev Cell Dev Biol 2012; 28:279-308. [DOI: 10.1146/annurev-cellbio-101011-155818] [Citation(s) in RCA: 318] [Impact Index Per Article: 26.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Josep Rizo
- Departments of Biophysics, Biochemistry and Pharmacology, University of Texas Southwestern Medical Center, Dallas, Texas 75390;
| | - Thomas C. Südhof
- Department of Molecular and Cellular Physiology and Howard Hughes Medical Institute, Stanford University Medical School, Stanford, California 94305;
| |
Collapse
|
31
|
Kasai H, Takahashi N, Tokumaru H. Distinct Initial SNARE Configurations Underlying the Diversity of Exocytosis. Physiol Rev 2012; 92:1915-64. [DOI: 10.1152/physrev.00007.2012] [Citation(s) in RCA: 120] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The dynamics of exocytosis are diverse and have been optimized for the functions of synapses and a wide variety of cell types. For example, the kinetics of exocytosis varies by more than five orders of magnitude between ultrafast exocytosis in synaptic vesicles and slow exocytosis in large dense-core vesicles. However, in all cases, exocytosis is mediated by the same fundamental mechanism, i.e., the assembly of soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins. It is often assumed that vesicles need to be docked at the plasma membrane and SNARE proteins must be preassembled before exocytosis is triggered. However, this model cannot account for the dynamics of exocytosis recently reported in synapses and other cells. For example, vesicles undergo exocytosis without prestimulus docking during tonic exocytosis of synaptic vesicles in the active zone. In addition, epithelial and hematopoietic cells utilize cAMP and kinases to trigger slow exocytosis of nondocked vesicles. In this review, we summarize the manner in which the diversity of exocytosis reflects the initial configurations of SNARE assembly, including trans-SNARE, binary-SNARE, unitary-SNARE, and cis-SNARE configurations. The initial SNARE configurations depend on the particular SNARE subtype (syntaxin, SNAP25, or VAMP), priming proteins (Munc18, Munc13, CAPS, complexin, or snapin), triggering proteins (synaptotagmins, Doc2, and various protein kinases), and the submembraneous cytomatrix, and they are the key to determining the kinetics of subsequent exocytosis. These distinct initial configurations will help us clarify the common SNARE assembly processes underlying exocytosis and membrane trafficking in eukaryotic cells.
Collapse
Affiliation(s)
- Haruo Kasai
- Laboratory of Structural Physiology, Center for Disease Biology and Integrative Medicine, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan; and Faculty of Pharmaceutical Sciences at Kagawa, Tokushima Bunri University, Kagawa, Japan
| | - Noriko Takahashi
- Laboratory of Structural Physiology, Center for Disease Biology and Integrative Medicine, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan; and Faculty of Pharmaceutical Sciences at Kagawa, Tokushima Bunri University, Kagawa, Japan
| | - Hiroshi Tokumaru
- Laboratory of Structural Physiology, Center for Disease Biology and Integrative Medicine, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan; and Faculty of Pharmaceutical Sciences at Kagawa, Tokushima Bunri University, Kagawa, Japan
| |
Collapse
|
32
|
Bar-On D, Wolter S, van de Linde S, Heilemann M, Nudelman G, Nachliel E, Gutman M, Sauer M, Ashery U. Super-resolution imaging reveals the internal architecture of nano-sized syntaxin clusters. J Biol Chem 2012; 287:27158-67. [PMID: 22700970 DOI: 10.1074/jbc.m112.353250] [Citation(s) in RCA: 101] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Key synaptic proteins from the soluble SNARE (N-ethylmaleimide-sensitive factor attachment protein receptor) family, among many others, are organized at the plasma membrane of cells as clusters containing dozens to hundreds of protein copies. However, the exact membranal distribution of proteins into clusters or as single molecules, the organization of molecules inside the clusters, and the clustering mechanisms are unclear due to limitations of the imaging and analytical tools. Focusing on syntaxin 1 and SNAP-25, we implemented direct stochastic optical reconstruction microscopy together with quantitative clustering algorithms to demonstrate a novel approach to explore the distribution of clustered and nonclustered molecules at the membrane of PC12 cells with single-molecule precision. Direct stochastic optical reconstruction microscopy images reveal, for the first time, solitary syntaxin/SNAP-25 molecules and small clusters as well as larger clusters. The nonclustered syntaxin or SNAP-25 molecules are mostly concentrated in areas adjacent to their own clusters. In the clusters, the density of the molecules gradually decreases from the dense cluster core to the periphery. We further detected large clusters that contain several density gradients. This suggests that some of the clusters are formed by unification of several clusters that preserve their original organization or reorganize into a single unit. Although syntaxin and SNAP-25 share some common distributional features, their clusters differ markedly from each other. SNAP-25 clusters are significantly larger, more elliptical, and less dense. Finally, this study establishes methodological tools for the analysis of single-molecule-based super-resolution imaging data and paves the way for revealing new levels of membranal protein organization.
Collapse
Affiliation(s)
- Dana Bar-On
- Laser Laboratory for Fast Reactions in Biology, Department of Biochemistry, Tel Aviv University, Tel Aviv 69978, Israel
| | | | | | | | | | | | | | | | | |
Collapse
|
33
|
Boswell KL, James DJ, Esquibel JM, Bruinsma S, Shirakawa R, Horiuchi H, Martin TFJ. Munc13-4 reconstitutes calcium-dependent SNARE-mediated membrane fusion. ACTA ACUST UNITED AC 2012; 197:301-12. [PMID: 22508512 PMCID: PMC3328385 DOI: 10.1083/jcb.201109132] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Munc13-4 is a Ca2+-dependent membrane- and SNARE-binding protein that promotes membrane fusion. Munc13-4 is a widely expressed member of the CAPS/Munc13 protein family proposed to function in priming secretory granules for exocytosis. Munc13-4 contains N- and C-terminal C2 domains (C2A and C2B) predicted to bind Ca2+, but Ca2+-dependent regulation of Munc13-4 activity has not been described. The C2 domains bracket a predicted SNARE-binding domain, but whether Munc13-4 interacts with SNARE proteins is unknown. We report that Munc13-4 bound Ca2+ and restored Ca2+-dependent granule exocytosis to permeable cells (platelets, mast, and neuroendocrine cells) dependent on putative Ca2+-binding residues in C2A and C2B. Munc13-4 exhibited Ca2+-stimulated SNARE interactions dependent on C2A and Ca2+-dependent membrane binding dependent on C2B. In an apparent coupling of membrane and SNARE binding, Munc13-4 stimulated SNARE-dependent liposome fusion dependent on putative Ca2+-binding residues in both C2A and C2B domains. Munc13-4 is the first priming factor shown to promote Ca2+-dependent SNARE complex formation and SNARE-mediated liposome fusion. These properties of Munc13-4 suggest its function as a Ca2+ sensor at rate-limiting priming steps in granule exocytosis.
Collapse
Affiliation(s)
- Kristin L Boswell
- Department of Biochemistry, University of Wisconsin, Madison, WI 53706, USA
| | | | | | | | | | | | | |
Collapse
|
34
|
Tobin V, Schwab Y, Lelos N, Onaka T, Pittman QJ, Ludwig M. Expression of exocytosis proteins in rat supraoptic nucleus neurones. J Neuroendocrinol 2012; 24:629-41. [PMID: 21988098 PMCID: PMC3569506 DOI: 10.1111/j.1365-2826.2011.02237.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
In magnocellular neurones of the supraoptic nucleus (SON), the neuropeptides vasopressin and oxytocin are synthesised and packaged into large dense-cored vesicles (LDCVs). These vesicles undergo regulated exocytosis from nerve terminals in the posterior pituitary gland and from somata/dendrites in the SON. Regulated exocytosis of LDCVs is considered to involve the soluble N-ethylmaleimide sensitive fusion protein attachment protein receptor (SNARE) complex [comprising vesicle associated membrane protein 2 (VAMP-2), syntaxin-1 and soluble N-ethylmaleimide attachment protein-25 (SNAP-25)] and regulatory proteins [such as synaptotagmin-1, munc-18 and Ca(2+) -dependent activator protein for secretion (CAPS-1)]. Using fluorescent immunocytochemistry and confocal microscopy, in both oxytocin and vasopressin neurones, we observed VAMP-2, SNAP-25 and syntaxin-1-immunoreactivity in axon terminals. The somata and dendrites contained syntaxin-1 and other regulatory exocytosis proteins, including munc-18 and CAPS-1. However, the distribution of VAMP-2 and synaptotagmin-1 in the SON was limited to putative pre-synaptic contacts because they co-localised with synaptophysin (synaptic vesicle marker) and had no co-localisation with either oxytocin or vasopressin. SNAP-25 immunoreactivity in the SON was limited to glial cell processes and was not detected in oxytocin or vasopressin somata/dendrites. The present results indicate differences in the expression and localisation of exocytosis proteins between the axon terminals and somata/dendritic compartment. The absence of VAMP-2 and SNAP-25 immunoreactivity from the somata/dendrites suggests that there might be different SNARE protein isoforms expressed in these compartments. Alternatively, exocytosis of LDCVs from somata/dendrites may use a different mechanism from that described by the SNARE complex theory.
Collapse
Affiliation(s)
- V. Tobin
- Centre for Integrative Physiology, University of Edinburgh, Edinburgh, UK
| | - Y. Schwab
- Hotchkiss Brain Institute, Department of Physiology and Pharmacology, University of Calgary, Calgary, Canada
| | - N. Lelos
- Centre for Integrative Physiology, University of Edinburgh, Edinburgh, UK
| | - T. Onaka
- Department of Physiology, Jichi Medical University, Tochigi, Japan
| | - Q. J. Pittman
- Hotchkiss Brain Institute, Department of Physiology and Pharmacology, University of Calgary, Calgary, Canada
| | - M. Ludwig
- Centre for Integrative Physiology, University of Edinburgh, Edinburgh, UK
| |
Collapse
|
35
|
Sebollela A, Freitas-Correa L, Oliveira FF, Paula-Lima AC, Saraiva LM, Martins SM, Mota LD, Torres C, Alves-Leon S, de Souza JM, Carraro DM, Brentani H, De Felice FG, Ferreira ST. Amyloid-β oligomers induce differential gene expression in adult human brain slices. J Biol Chem 2012; 287:7436-45. [PMID: 22235132 PMCID: PMC3293600 DOI: 10.1074/jbc.m111.298471] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2011] [Revised: 12/27/2011] [Indexed: 01/01/2023] Open
Abstract
Cognitive decline in Alzheimer disease (AD) is increasingly attributed to the neuronal impact of soluble oligomers of the amyloid-β peptide (AβOs). Current knowledge on the molecular and cellular mechanisms underlying the toxicity of AβOs stems largely from rodent-derived cell/tissue culture experiments or from transgenic models of AD, which do not necessarily recapitulate the complexity of the human disease. Here, we used DNA microarray and RT-PCR to investigate changes in transcription in adult human cortical slices exposed to sublethal doses of AβOs. The results revealed a set of 27 genes that showed consistent differential expression upon exposure of slices from three different donors to AβOs. Functional classification of differentially expressed genes revealed that AβOs impact pathways important for neuronal physiology and known to be dysregulated in AD, including vesicle trafficking, cell adhesion, actin cytoskeleton dynamics, and insulin signaling. Most genes (70%) were down-regulated by AβO treatment, suggesting a predominantly inhibitory effect on the corresponding pathways. Significantly, AβOs induced down-regulation of synaptophysin, a presynaptic vesicle membrane protein, suggesting a mechanism by which oligomers cause synapse failure. The results provide insight into early mechanisms of pathogenesis of AD and suggest that the neuronal pathways affected by AβOs may be targets for the development of novel diagnostic or therapeutic approaches.
Collapse
Affiliation(s)
- Adriano Sebollela
- From the Institute of Medical Biochemistry, Federal University of Rio de Janeiro, Rio de Janeiro, RJ 21944-590, Brazil
| | - Leo Freitas-Correa
- From the Institute of Medical Biochemistry, Federal University of Rio de Janeiro, Rio de Janeiro, RJ 21944-590, Brazil
| | - Fabio F. Oliveira
- From the Institute of Medical Biochemistry, Federal University of Rio de Janeiro, Rio de Janeiro, RJ 21944-590, Brazil
| | - Andrea C. Paula-Lima
- From the Institute of Medical Biochemistry, Federal University of Rio de Janeiro, Rio de Janeiro, RJ 21944-590, Brazil
| | - Leonardo M. Saraiva
- From the Institute of Medical Biochemistry, Federal University of Rio de Janeiro, Rio de Janeiro, RJ 21944-590, Brazil
| | - Samantha M. Martins
- From the Institute of Medical Biochemistry, Federal University of Rio de Janeiro, Rio de Janeiro, RJ 21944-590, Brazil
| | - Louise D. Mota
- the International Center of Education and Research, A. C. Camargo Hospital, São Paulo SP 01509, Brazil, and
| | - Cesar Torres
- the International Center of Education and Research, A. C. Camargo Hospital, São Paulo SP 01509, Brazil, and
| | | | - Jorge M. de Souza
- the Division of Neurosurgery, Clementino Fraga Filho University Hospital, Federal University of Rio de Janeiro, Rio de Janeiro RJ 21941-913, Brazil
| | - Dirce M. Carraro
- the International Center of Education and Research, A. C. Camargo Hospital, São Paulo SP 01509, Brazil, and
| | - Helena Brentani
- the International Center of Education and Research, A. C. Camargo Hospital, São Paulo SP 01509, Brazil, and
| | - Fernanda G. De Felice
- From the Institute of Medical Biochemistry, Federal University of Rio de Janeiro, Rio de Janeiro, RJ 21944-590, Brazil
| | - Sergio T. Ferreira
- From the Institute of Medical Biochemistry, Federal University of Rio de Janeiro, Rio de Janeiro, RJ 21944-590, Brazil
| |
Collapse
|
36
|
Abstract
A role for phosphatidylinositol 4,5-bisphosphate (PI(4,5)P(2)) in membrane fusion was originally identified for regulated dense-core vesicle exocytosis in neuroendocrine cells. Subsequent studies demonstrated essential roles for PI(4,5)P(2) in regulated synaptic vesicle and constitutive vesicle exocytosis. For regulated dense-core vesicle exocytosis, PI(4,5)P(2) appears to be primarily required for priming, a stage in vesicle exocytosis that follows vesicle docking and precedes Ca(2) (+)-triggered fusion. The priming step involves the organization of SNARE protein complexes for fusion. A central issue concerns the mechanisms by which PI(4,5)P(2) exerts an essential role in membrane fusion events at the plasma membrane. The observed microdomains of PI(4,5)P(2) in the plasma membrane of neuroendocrine cells at fusion sites has suggested possible direct effects of the phosphoinositide on membrane curvature and tension. More likely, PI(4,5)P(2) functions in vesicle exocytosis as in other cellular processes to recruit and activate PI(4,5)P(2)-binding proteins. CAPS and Munc13 proteins, which bind PI(4,5)P(2) and function in vesicle priming to organize SNARE proteins, are key candidates as effectors for the role of PI(4,5)P(2) in vesicle priming. Consistent with roles prior to fusion that affect SNARE function, subunits of the exocyst tethering complex involved in constitutive vesicle exocytosis also bind PI(4,5)P(2). Additional roles for PI(4,5)P(2) in fusion pore dilation have been described, which may involve other PI(4,5)P(2)-binding proteins such as synaptotagmin. Lastly, the SNARE proteins that mediate exocytic vesicle fusion contain highly basic membrane-proximal domains that interact with acidic phospholipids that likely affect their function.
Collapse
Affiliation(s)
- Thomas F J Martin
- Department of Biochemistry, University of Wisconsin-Madison, 433 Babcock Drive, 53706, Madison, WI, U.S.A,
| |
Collapse
|
37
|
Gadi D, Wagenknecht-Wiesner A, Holowka D, Baird B. Sequestration of phosphoinositides by mutated MARCKS effector domain inhibits stimulated Ca(2+) mobilization and degranulation in mast cells. Mol Biol Cell 2011; 22:4908-17. [PMID: 22013076 PMCID: PMC3237632 DOI: 10.1091/mbc.e11-07-0614] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
A new strategy for interfering with phosphoinositide-dependent processes at the plasma membrane uses high-avidity association of the polybasic MARCKS effector domain with negatively charged phospholipids to provide new insights into roles for phosphoinositides in IgE receptor signaling leading to exocytosis. Protein kinase C β (PKCβ) participates in antigen-stimulated mast cell degranulation mediated by the high-affinity receptor for immunoglobulin E, FcεRI, but the molecular basis is unclear. We investigated the hypothesis that the polybasic effector domain (ED) of the abundant intracellular substrate for protein kinase C known as myristoylated alanine-rich protein kinase C substrate (MARCKS) sequesters phosphoinositides at the inner leaflet of the plasma membrane until MARCKS dissociates after phosphorylation by activated PKC. Real-time fluorescence imaging confirms synchronization between stimulated oscillations of intracellular Ca2+ concentrations and oscillatory association of PKCβ–enhanced green fluorescent protein with the plasma membrane. Similarly, MARCKS-ED tagged with monomeric red fluorescent protein undergoes antigen-stimulated oscillatory dissociation and rebinding to the plasma membrane with a time course that is synchronized with reversible plasma membrane association of PKCβ. We find that MARCKS-ED dissociation is prevented by mutation of four serine residues that are potential sites of phosphorylation by PKC. Cells expressing this mutated MARCKS-ED SA4 show delayed onset of antigen-stimulated Ca2+ mobilization and substantial inhibition of granule exocytosis. Stimulation of degranulation by thapsigargin, which bypasses inositol 1,4,5-trisphosphate production, is also substantially reduced in the presence of MARCKS-ED SA4, but store-operated Ca2+ entry is not inhibited. These results show the capacity of MARCKS-ED to regulate granule exocytosis in a PKC-dependent manner, consistent with regulated sequestration of phosphoinositides that mediate granule fusion at the plasma membrane.
Collapse
Affiliation(s)
- Deepti Gadi
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, USA
| | | | | | | |
Collapse
|
38
|
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.
Collapse
|
39
|
Stevens DR, Schirra C, Becherer U, Rettig J. Vesicle pools: lessons from adrenal chromaffin cells. Front Synaptic Neurosci 2011; 3:2. [PMID: 21423410 PMCID: PMC3059608 DOI: 10.3389/fnsyn.2011.00002] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2010] [Accepted: 01/17/2011] [Indexed: 11/30/2022] Open
Abstract
The adrenal chromaffin cell serves as a model system to study fast Ca2+-dependent exocytosis. Membrane capacitance measurements in combination with Ca2+ uncaging offers a temporal resolution in the millisecond range and reveals that catecholamine release occurs in three distinct phases. Release of a readily releasable (RRP) and a slowly releasable (SRP) pool are followed by sustained release, due to maturation, and release of vesicles which were not release-ready at the start of the stimulus. Trains of depolarizations, a more physiological stimulus, induce release from a small immediately releasable pool of vesicles residing adjacent to calcium channels, as well as from the RRP. The SRP is poorly activated by depolarization. A sequential model, in which non-releasable docked vesicles are primed to a slowly releasable state, and then further mature to the readily releasable state, has been proposed. The docked state, dependent on membrane proximity, requires SNAP-25, synaptotagmin, and syntaxin. The ablation or modification of SNAP-25 and syntaxin, components of the SNARE complex, as well as of synaptotagmin, the calcium sensor, and modulators such complexins and Snapin alter the properties and/or magnitudes of different phases of release, and in particular can ablate the RRP. These results indicate that the composition of the SNARE complex and its interaction with modulatory molecules drives priming and provides a molecular basis for different pools of releasable vesicles.
Collapse
Affiliation(s)
- David R Stevens
- Physiologisches Institut, Universität des Saarlandes Homburg, Saarland, Germany
| | | | | | | |
Collapse
|
40
|
Furuichi T, Shiraishi-Yamaguchi Y, Sato A, Sadakata T, Huang J, Shinoda Y, Hayashi K, Mishima Y, Tomomura M, Nishibe H, Yoshikawa F. Systematizing and cloning of genes involved in the cerebellar cortex circuit development. Neurochem Res 2011; 36:1241-52. [PMID: 21243430 DOI: 10.1007/s11064-011-0398-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/04/2011] [Indexed: 10/18/2022]
Abstract
The cerebellar cortical circuit of mammals develops via a series of magnificent cellular events in the postnatal stage of development to accomplish the formation of functional circuit architectures. The contribution of genetic factors is thought to be crucial to cerebellar development. Therefore, it is essential to analyze the underlying transcriptome during development to understand the genetic blueprint of the cerebellar cortical circuit. In this review, we introduce the profiling of large numbers of spatiotemporal gene expression data obtained by developmental time-series microarray analyses and in situ hybridization cellular mRNA mapping, and the creation of a neuroinformatics database called the Cerebellar Development Transcriptome Database. Using this database, we have identified thousands of genes that are classified into various functional categories and are expressed coincidently with related cellular developmental stages. We have also suggested the molecular mechanisms of cerebellar development by functional characterization of several identified genes (Cupidin, p130Cas, very-KIND, CAPS2) responsible for distinct cellular events of developing cerebellar granule cells. Taken together, the gene expression profiling during the cerebellar development demonstrates that the development of cerebellar cortical circuit is attributed to the complex but orchestrated transcriptome.
Collapse
Affiliation(s)
- Teiichi Furuichi
- Laboratory for Molecular Neurogenesis, RIKEN Brain Science Institute, 2-1 Hirosawa, Wako, 351-0198, Saitama, Japan.
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|