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Yamaga M, Kielar-Grevstad DM, Martin TFJ. Phospholipase Cη2 Activation Redirects Vesicle Trafficking by Regulating F-actin. J Biol Chem 2015; 290:29010-21. [PMID: 26432644 PMCID: PMC4661413 DOI: 10.1074/jbc.m115.658328] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2015] [Revised: 09/30/2015] [Indexed: 02/02/2023] Open
Abstract
PI(4,5)P2 localizes to sites of dense core vesicle exocytosis in neuroendocrine cells and is required for Ca(2+)-triggered vesicle exocytosis, but the impact of local PI(4,5)P2 hydrolysis on exocytosis is poorly understood. Previously, we reported that Ca(2+)-dependent activation of phospholipase Cη2 (PLCη2) catalyzes PI(4,5)P2 hydrolysis, which affected vesicle exocytosis by regulating the activities of the lipid-dependent priming factors CAPS (also known as CADPS) and ubiquitous Munc13-2 in PC12 cells. Here we describe an additional role for PLCη2 in vesicle exocytosis as a Ca(2+)-dependent regulator of the actin cytoskeleton. Depolarization of neuroendocrine PC12 cells with 56 or 95 mm KCl buffers increased peak Ca(2+) levels to ~400 or ~800 nm, respectively, but elicited similar numbers of vesicle exocytic events. However, 56 mm K(+) preferentially elicited the exocytosis of plasma membrane-resident vesicles, whereas 95 mm K(+) preferentially elicited the exocytosis of cytoplasmic vesicles arriving during stimulation. Depolarization with 95 mm K(+) but not with 56 mm K(+) activated PLCη2 to catalyze PI(4,5)P2 hydrolysis. The decrease in PI(4,5)P2 promoted F-actin disassembly, which increased exocytosis of newly arriving vesicles. Consistent with its role as a Ca(2+)-dependent regulator of the cortical actin cytoskeleton, PLCη2 localized with F-actin filaments. The results highlight the importance of PI(4,5)P2 for coordinating cytoskeletal dynamics with vesicle exocytosis and reveal a new role for PLCη2 as a Ca(2+)-dependent regulator of F-actin dynamics and vesicle trafficking.
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Affiliation(s)
- Masaki Yamaga
- From the Department of Biochemistry, University of Wisconsin, Madison, Wisconsin 53706
| | | | - Thomas F J Martin
- From the Department of Biochemistry, University of Wisconsin, Madison, Wisconsin 53706
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2
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Gandasi NR, Vestö K, Helou M, Yin P, Saras J, Barg S. Survey of Red Fluorescence Proteins as Markers for Secretory Granule Exocytosis. PLoS One 2015; 10:e0127801. [PMID: 26091288 PMCID: PMC4474633 DOI: 10.1371/journal.pone.0127801] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2015] [Accepted: 04/18/2015] [Indexed: 12/18/2022] Open
Abstract
Fluorescent proteins (FPs) have proven to be valuable tools for high-resolution imaging studies of vesicle transport processes, including exo- and endocytosis. Since the pH of the vesicle lumen changes between acidic and neutral during these events, pH-sensitive FPs with near neutral pKa, such as pHluorin, are particularly useful. FPs with pKa>6 are readily available in the green spectrum, while red-emitting pH-sensitive FPs are rare and often not well characterized as reporters of exo- or endocytosis. Here we tested a panel of ten orange/red and two green FPs in fusions with neuropeptide Y (NPY) for use as secreted vesicle marker and reporter of dense core granule exocytosis and release. We report relative brightness, bleaching rate, targeting accuracy, sensitivity to vesicle pH, and their performance in detecting exocytosis in live cells. Tandem dimer (td)-mOrange2 was identified as well-targeted, bright, slowly bleaching and pH-sensitive FP that performed similar to EGFP. Single exocytosis events were readily observed, which allowed measurements of fusion pore lifetime and the dynamics of the exocytosis protein syntaxin at the release site during membrane fusion and cargo release.
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Affiliation(s)
- Nikhil R. Gandasi
- Institute of Medical Cell Biology, Uppsala University, Box 571, Husargatan 3, 75123, Uppsala, Sweden
| | - Kim Vestö
- Institute of Medical Cell Biology, Uppsala University, Box 571, Husargatan 3, 75123, Uppsala, Sweden
| | - Maria Helou
- Institute of Medical Cell Biology, Uppsala University, Box 571, Husargatan 3, 75123, Uppsala, Sweden
| | - Peng Yin
- Institute of Medical Cell Biology, Uppsala University, Box 571, Husargatan 3, 75123, Uppsala, Sweden
| | - Jan Saras
- Institute of Medical Cell Biology, Uppsala University, Box 571, Husargatan 3, 75123, Uppsala, Sweden
| | - Sebastian Barg
- Institute of Medical Cell Biology, Uppsala University, Box 571, Husargatan 3, 75123, Uppsala, Sweden
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3
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Moving RNA moves RNA forward. SCIENCE CHINA-LIFE SCIENCES 2013; 56:914-20. [DOI: 10.1007/s11427-013-4545-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2013] [Accepted: 08/23/2013] [Indexed: 12/11/2022]
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4
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Blanco EH, Lagos CF, Andrés ME, Gysling K. An amphipathic alpha-helix in the prodomain of cocaine and amphetamine regulated transcript peptide precursor serves as its sorting signal to the regulated secretory pathway. PLoS One 2013; 8:e59695. [PMID: 23527253 PMCID: PMC3602189 DOI: 10.1371/journal.pone.0059695] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2012] [Accepted: 02/17/2013] [Indexed: 11/18/2022] Open
Abstract
Cocaine and Amphetamine Regulated Transcript (CART) peptides are anorexigenic neuropeptides. The L34F mutation in human CART peptide precursor (proCART) has been linked to obesity (Yanik et al. Endocrinology 147: 39, 2006). Decrease in CART peptide levels in individuals carrying the L34F mutation was attributed to proCART subcellular missorting. We studied proCART features required to enter the regulated secretory pathway. The subcellular localization and the secretion mode of monomeric EGFP fused to the full-length or truncated forms of human proCART transiently transfected in PC12 cells were analyzed. Our results showed that the N-terminal 1-41 fragment of proCART was necessary and sufficient to sort proCART to the regulated secretory pathway. In silico modeling predicted an alpha-helix structure located between residues 24-37 of proCART. Helical wheel projection of proCART alpha-helix showed an amphipathic configuration. The L34F mutation does not modify the amphipathicity of proCART alpha-helix and consistently proCARTL34F was efficiently sorted to the regulated secretory pathway. However, four additional mutations to proCARTL34F that reduced its alpha-helix amphipathicity resulted in the missorting of the mutated proCART toward the constitutive secretory pathway. These findings show that an amphipathic alpha-helix is a key cis-structure for the proCART sorting mechanism. In addition, our results indicate that the association between L34F mutation and obesity is not explained by proCART missorting.
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Affiliation(s)
- Elías H. Blanco
- Millennium Science Nucleus in Stress and Addiction, Department of Cell and Molecular Biology, Faculty of Biological Sciences, Pontificia Universidad Católica de Chile, Santiago, Chile
- * E-mail: (EHB); (KG)
| | - Carlos F. Lagos
- Department of Pharmacy, Faculty of Chemistry, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - María Estela Andrés
- Millennium Science Nucleus in Stress and Addiction, Department of Cell and Molecular Biology, Faculty of Biological Sciences, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Katia Gysling
- Millennium Science Nucleus in Stress and Addiction, Department of Cell and Molecular Biology, Faculty of Biological Sciences, Pontificia Universidad Católica de Chile, Santiago, Chile
- * E-mail: (EHB); (KG)
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5
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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.
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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
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6
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Delazari dos Santos L, Aparecido dos Santos Pinto JR, Ribeiro da Silva Menegasso A, Menezes Saidemberg D, Caviquioli Garcia AM, Sergio Palma M. Proteomic profiling of the molecular targets of interactions of the mastoparan peptide Protopolybia MP-III at the level of endosomal membranes from rat mast cells. Proteomics 2012; 12:2682-93. [DOI: 10.1002/pmic.201200030] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2012] [Revised: 04/13/2012] [Accepted: 04/16/2012] [Indexed: 01/30/2023]
Affiliation(s)
- Lucilene Delazari dos Santos
- Center for the Study of Venoms and Venomous Animals (CEVAP); University of São Paulo State (UNESP); Botucatu SP Brazil
- Instituto Nacional de Ciência e Tecnologia (INCT) em Imunologia/iii; Rio Claro SP Brazil
| | - José Roberto Aparecido dos Santos Pinto
- Instituto Nacional de Ciência e Tecnologia (INCT) em Imunologia/iii; Rio Claro SP Brazil
- Institute of Biosciences/Department of Biology; Center for the Study of Social Insects; University of São Paulo State (UNESP); Rio Claro SP Brazil
| | - Anally Ribeiro da Silva Menegasso
- Instituto Nacional de Ciência e Tecnologia (INCT) em Imunologia/iii; Rio Claro SP Brazil
- Institute of Biosciences/Department of Biology; Center for the Study of Social Insects; University of São Paulo State (UNESP); Rio Claro SP Brazil
| | - Daniel Menezes Saidemberg
- Instituto Nacional de Ciência e Tecnologia (INCT) em Imunologia/iii; Rio Claro SP Brazil
- Institute of Biosciences/Department of Biology; Center for the Study of Social Insects; University of São Paulo State (UNESP); Rio Claro SP Brazil
| | - Ana Maria Caviquioli Garcia
- Instituto Nacional de Ciência e Tecnologia (INCT) em Imunologia/iii; Rio Claro SP Brazil
- Institute of Biosciences/Department of Biology; Center for the Study of Social Insects; University of São Paulo State (UNESP); Rio Claro SP Brazil
| | - Mario Sergio Palma
- Instituto Nacional de Ciência e Tecnologia (INCT) em Imunologia/iii; Rio Claro SP Brazil
- Institute of Biosciences/Department of Biology; Center for the Study of Social Insects; University of São Paulo State (UNESP); Rio Claro SP Brazil
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7
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Feng W, Liang T, Yu J, Zhou W, Zhang Y, Wu Z, Xu T. RAB-27 and its effector RBF-1 regulate the tethering and docking steps of DCV exocytosis in C. elegans. SCIENCE CHINA. LIFE SCIENCES 2012; 55:228-35. [PMID: 22527519 DOI: 10.1007/s11427-012-4296-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/24/2011] [Accepted: 01/18/2012] [Indexed: 10/28/2022]
Abstract
The molecular mechanisms by which dense core vesicles (DCVs) translocate, tether, dock and prime are poorly understood. In this study, Caenorhabditis elegans was used as a model organism to study the function of Rab proteins and their effectors in DCV exocytosis. RAB-27/AEX-6, but not RAB-3, was found to be required for peptide release from neurons. By analyzing the movement of DCVs approaching the plasma membrane using total internal reflection fluorescence microscopy, we demonstrated that RAB-27/AEX-6 is involved in the tethering of DCVs and that its effector rabphilin/RBF-1 is required for the initial tethering and subsequent stabilization by docking.
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Affiliation(s)
- WanJuan Feng
- College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan 430074, China
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8
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DCVs Exocytosis is Damaged in The Dominant Allele of β-G Spectrin Mutant in <I>C. elegans</I>*. PROG BIOCHEM BIOPHYS 2010. [DOI: 10.3724/sp.j.1206.2009.00365] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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9
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Li J, Xiao Y, Zhou W, Wu Z, Zhang R, Xu T. Silence of Synaptotagmin VII inhibits release of dense core vesicles in PC12 cells. ACTA ACUST UNITED AC 2009; 52:1156-63. [PMID: 20016973 DOI: 10.1007/s11427-009-0160-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2009] [Accepted: 08/27/2009] [Indexed: 11/27/2022]
Abstract
Synaptotagmin VII (Syt VII), which has a higher Ca(2+) affinity and slower disassembly kinetics with lipid than Syt I and Syt IX, was regarded as being uninvolved in synaptic vesicle (SV) exocytosis but instead possibly as a calcium sensor for the slower kinetic phase of dense core vesicles (DCVs) release. By using high temporal resolution capacitance and amperometry measurements, it was demonstrated that the knockdown of endogenous Syt VII attenuated the fusion of DCV with the plasma membrane, reduced the amplitude of the exocytotic burst of the Ca(2+)-triggered DCV release without affecting the slope of the sustained component, and blocked the fusion pore expansion. This suggests that Syt VII is the Ca(2+) sensor of DCV fusion machinery and is an essential factor for the establishment and maintenance of the pool size of releasable DCVs in PC12 cells.
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Affiliation(s)
- JiangLi Li
- Key Laboratory of Molecular Biophysics of the Ministry of Education, Institute of Biophysics and Biochemistry, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, China
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10
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Xue R, Zhao Y, Su L, Ye F, Chen P. PKC epsilon facilitates recovery of exocytosis after an exhausting stimulation. Pflugers Arch 2009; 458:1137-49. [PMID: 19593582 DOI: 10.1007/s00424-009-0697-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2009] [Revised: 06/22/2009] [Accepted: 06/26/2009] [Indexed: 01/18/2023]
Abstract
It has been well documented that protein kinase Cs (PKCs) play multifaceted roles in regulating exocytosis of neurotransmitters and hormones. But the isoform-specific PKC effects are still poorly elucidated mainly because of the large variety of PKC isoforms and the dubious specificity of the commonly used pharmacological agents. In the present study, based on overexpression of wild-type or dominant negative PKC epsilon, we demonstrate in neuroendocrine PC12 cells that PKC epsilon, but not PKC alpha, facilitates recovery of exocytosis after an exhausting stimulation. Specifically, PKC epsilon mediates fast recovery of the extent of exocytosis in a phosphatidylinositol biphosphate-dependent manner, likely through enhancing the rate of vesicle delivery and reorganization of cortical actin network. In addition, PKC epsilon promotes fast recovery of vesicle release kinetics that is slowed after a strong stimulation. These experimental results may suggest a PKC-dependent mechanism relevant to the short-term plasticity of exocytosis in both neurons and neuroendocrine cells.
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Affiliation(s)
- Renhao Xue
- Division of Bioengineering, Nanyang Technological University, Singapore, 637457, Singapore
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11
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Mechanisms, locations, and kinetics of synaptic BDNF secretion: an update. Neurosci Res 2009; 65:11-22. [PMID: 19523993 DOI: 10.1016/j.neures.2009.06.004] [Citation(s) in RCA: 224] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2009] [Revised: 06/01/2009] [Accepted: 06/03/2009] [Indexed: 01/12/2023]
Abstract
Brain-derived neurotrophic factor (BDNF) and other members of the protein family of neurotrophins have been implicated in a multitude of processes that are important for neuronal development and synaptic plasticity in the rodent central nervous system. In comparison to the wealth of information available with respect to the biological functions of neurotrophins, our knowledge regarding the processes that govern synaptic secretion of neurotrophins is scarce. Using live cell imaging of GFP-tagged neurotrophins in primary neurons, immunocytochemical detection of endogenous BDNF in fixed cells, and by blocking the action of endogenously released BDNF by means of TrkB receptor bodies in living neurons, several studies in recent years have allowed to better understand the time course and the mechanisms of synaptic secretion of neurotrophins. This review will summarize the current knowledge regarding the intracellular processing of proneurotrophins, the targeting of neurotrophin vesicles to axons and dendrites, and the mechanisms of activity-dependent secretion of BDNF at synapses. Since these processes are known to be cell type dependent, special emphasis is given to observations gained from experiments in primary neurons.
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Hu ZT, Chen MR, Ping Z, Dong YM, Zhang RY, Xu T, Wu ZX. Synaptotagmin IV regulates dense core vesicle (DCV) release in LbetaT2 cells. Biochem Biophys Res Commun 2008; 371:781-6. [PMID: 18468511 DOI: 10.1016/j.bbrc.2008.04.174] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2008] [Accepted: 04/28/2008] [Indexed: 11/17/2022]
Abstract
Synaptotagmins (Syts) are calcium-binding proteins which are conserved from nematodes to humans. Fifteen Syts have been identified in mammalian species. Syt I is recognized as a Ca(2+) sensor for the synchronized release of synaptic vesicles in some types of neurons, but its role in the secretion of dense core vesicles (DCVs) remains unclear. The function of Syt IV is of particular interest because it is rapidly up-regulated by chronic depolarization and seizures. Using RNAi-mediated gene silencing, we have explored the role of Syt I and IV on secretion in a pituitary gonadotrope cell line. Downregulation of Syt IV clearly reduced Ca(2+)-triggered exocytosis of dense core vesicles (DCVs) in LbetaT2 cells. Syt I silencing, however, had no effect on vesicular release.
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Affiliation(s)
- Zhi-Tao Hu
- Key Laboratory of Molecular Biophysics, Ministry of Education, and Joint Laboratory of Institute of Biophysics & Huazhong University of Science and Technology, Huazhong University of Science and Technology, Luoyu Road 1037#, Wuhan 430074, PR China
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13
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Tomas A, Meda P, Regazzi R, Pessin JE, Halban PA. Munc 18-1 and granuphilin collaborate during insulin granule exocytosis. Traffic 2008; 9:813-32. [PMID: 18208509 DOI: 10.1111/j.1600-0854.2008.00709.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Munc 18-1 is a member of the Sec/Munc family of syntaxin-binding proteins known to bind to the plasma membrane Q-SNARE syntaxin1 and whose precise role in regulated exocytosis remains controversial. Here, we show that Munc 18-1 plays a positive role in regulated insulin secretion from pancreatic beta cells. Munc 18-1 depletion caused a loss in the secretory capacity of both transiently transfected INS 1E cells and a stable clone with tetracycline-regulated Munc 18-1 RNA interference. In addition, Munc 18-1-depleted cells exhibited defective docking of insulin granules to the plasma membrane and accumulated insulin in the trans Golgi network. Furthermore, glucose stimulation after Munc 18-1 depletion resulted in the rapid formation of autophagosomes. In contrast, overexpression of Munc 18-1 had no effect on insulin secretion. Although there was no detectable interaction between Munc 18-1 and Munc-18-interacting protein 1 or calcium/calmodulin-dependent serine protein kinase, Munc 18-1 associated with the granular protein granuphilin. This association was regulated by glucose and was required for the specific interaction of insulin granules with syntaxin1. We conclude that Munc 18-1 and granuphilin collaborate in the docking of insulin granules to the plasma membrane in an initial fusion-incompetent state, with Munc 18-1 subsequently playing a positive role in a later stage of insulin granule exocytosis.
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Affiliation(s)
- Alejandra Tomas
- Department of Genetic Medicine and Development, University of Geneva Medical School, 1211 Geneva 4, Switzerland.
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14
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Zhou KM, Dong YM, Ge Q, Zhu D, Zhou W, Lin XG, Liang T, Wu ZX, Xu T. PKA Activation Bypasses the Requirement for UNC-31 in the Docking of Dense Core Vesicles from C. elegans Neurons. Neuron 2007; 56:657-69. [DOI: 10.1016/j.neuron.2007.09.015] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2006] [Revised: 03/07/2007] [Accepted: 09/06/2007] [Indexed: 10/22/2022]
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15
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Zhou W, Zhu D, Liang T, Li C, Wu Z. Characterization of docking and fusion of synaptic-like microvesicles in PC12 cells using TIRFM. CHINESE SCIENCE BULLETIN-CHINESE 2007. [DOI: 10.1007/s11434-007-0469-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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16
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Zhu D, Zhou W, Liang T, Yang F, Zhang RY, Wu ZX, Xu T. Synaptotagmin I and IX function redundantly in controlling fusion pore of large dense core vesicles. Biochem Biophys Res Commun 2007; 361:922-7. [PMID: 17686463 DOI: 10.1016/j.bbrc.2007.07.083] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2007] [Accepted: 07/17/2007] [Indexed: 11/28/2022]
Abstract
Synaptotagmins (Syts) constitute a large family of at least 16 members and individual Syt isoforms exhibit distinct Ca(2+)-binding properties and subcellular localization. It remains to be demonstrated whether multiple Syt isoforms can function independently or cooperatively on certain type of vesicle. In the current study, we have developed NPY-pHluorin to specifically assess exocytosis of large dense core vesicles (LDCVs) and studied the requirement of Syt I and Syt IX for LDCV exocytosis in PC12 cells. We found that down-regulation of both Syt I and Syt IX resulted in a significant loss of Ca(2+)-dependent LDCV exocytosis. Moreover, our results suggest Syt I and Syt IX play redundant role in controlling the choice of fusion modes. Down-regulation of both Syt I and Syt IX renders more fusion in the kiss-and-run mode. We conclude that Syt I and Syt IX function redundantly in Ca(2+)-sensing and fusion pore dilation on LDCVs in PC12 cells.
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Affiliation(s)
- Dan Zhu
- Key Laboratory of Molecular Biophysics (Huazhong University of Science and Technology), Ministry of Education, and Joint Laboratory of Institute of Biophysics, Huazhong University of Science and Technology, Wuhan 430074, PR China
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17
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Xu P, Lu J, Li Z, Yu X, Chen L, Xu T. Aggregation of STIM1 underneath the plasma membrane induces clustering of Orai1. Biochem Biophys Res Commun 2006; 350:969-76. [PMID: 17045966 DOI: 10.1016/j.bbrc.2006.09.134] [Citation(s) in RCA: 185] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2006] [Accepted: 09/26/2006] [Indexed: 11/30/2022]
Abstract
STIM1 and Orai1 have recently been identified to be crucial in the regulation of store-operated Ca(2+) entry. However, it remains to be established how STIM1 couples store depletion to the functioning of Orai1 in the plasma membrane. Using quantitative measurement, we find little STIM1 on the surface membrane which is not increased by store depletion. We further demonstrate that Orai1 assembles into clusters that co-localize with STIM1 aggregations upon store depletion. The clustering of Orai1 is only seen when Oari1 are co-expressed with STIM1, but not when expressed alone. Moreover, ER retreat from cell periphery leads to mismatching of Orai1 and STIM1 puncta. Therefore, we propose that store depletion causes aggregation and translocation of STIM1 in close apposition to the plasma membrane, which in turn recruits Orai1 in the plasma membrane to the sites of STIM1 aggregates to assemble functional units of CRAC channels in a stoichiometric manner.
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Affiliation(s)
- Pingyong Xu
- National Key Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Science, Beijing 100101, PR China
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18
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Kang L, He Z, Xu P, Fan J, Betz A, Brose N, Xu T. Munc13-1 is required for the sustained release of insulin from pancreatic beta cells. Cell Metab 2006; 3:463-8. [PMID: 16697276 DOI: 10.1016/j.cmet.2006.04.012] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/04/2006] [Revised: 04/03/2006] [Accepted: 04/27/2006] [Indexed: 11/30/2022]
Abstract
Munc13-1 is a presynaptic protein that is essential for synaptic vesicle priming. Deletion of Munc13-1/unc13 causes total arrest of synaptic transmission due to a complete loss of fusion-competent synaptic vesicles. The requirement of Munc13-1 for large dense-core vesicles (LDCVs), however, has not been established. In the present study, we use Munc13-1 knockout (KO) and diacylglycerol (DAG) binding-deficient Munc13-1(H567K) mutant knockin (KI) mice to determine the role of Munc13-1 in the secretion of insulin-containing LDCVs from primary cultured pancreatic beta cells. We show that Munc13-1 is required for the sustained insulin release upon prolonged stimulation. The sustained release involves signaling of DAG second messenger, since it is also reduced in KI mice. Insulin secretion in response to glucose stimulation is characterized by a biphasic time course. Our data show that Munc13-1 plays an essential role in the development of the second phase of insulin secretion by priming insulin-containing LDCVs.
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Affiliation(s)
- Lijun Kang
- Joint Laboratory of Huazhong University of Science and Technology and Institute of Biophysics, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan 430074, China
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