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Štepihar D, Florke Gee RR, Hoyos Sanchez MC, Fon Tacer K. Cell-specific secretory granule sorting mechanisms: the role of MAGEL2 and retromer in hypothalamic regulated secretion. Front Cell Dev Biol 2023; 11:1243038. [PMID: 37799273 PMCID: PMC10548473 DOI: 10.3389/fcell.2023.1243038] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2023] [Accepted: 08/31/2023] [Indexed: 10/07/2023] Open
Abstract
Intracellular protein trafficking and sorting are extremely arduous in endocrine and neuroendocrine cells, which synthesize and secrete on-demand substantial quantities of proteins. To ensure that neuroendocrine secretion operates correctly, each step in the secretion pathways is tightly regulated and coordinated both spatially and temporally. At the trans-Golgi network (TGN), intrinsic structural features of proteins and several sorting mechanisms and distinct signals direct newly synthesized proteins into proper membrane vesicles that enter either constitutive or regulated secretion pathways. Furthermore, this anterograde transport is counterbalanced by retrograde transport, which not only maintains membrane homeostasis but also recycles various proteins that function in the sorting of secretory cargo, formation of transport intermediates, or retrieval of resident proteins of secretory organelles. The retromer complex recycles proteins from the endocytic pathway back to the plasma membrane or TGN and was recently identified as a critical player in regulated secretion in the hypothalamus. Furthermore, melanoma antigen protein L2 (MAGEL2) was discovered to act as a tissue-specific regulator of the retromer-dependent endosomal protein recycling pathway and, by doing so, ensures proper secretory granule formation and maturation. MAGEL2 is a mammalian-specific and maternally imprinted gene implicated in Prader-Willi and Schaaf-Yang neurodevelopmental syndromes. In this review, we will briefly discuss the current understanding of the regulated secretion pathway, encompassing anterograde and retrograde traffic. Although our understanding of the retrograde trafficking and sorting in regulated secretion is not yet complete, we will review recent insights into the molecular role of MAGEL2 in hypothalamic neuroendocrine secretion and how its dysregulation contributes to the symptoms of Prader-Willi and Schaaf-Yang patients. Given that the activation of many secreted proteins occurs after they enter secretory granules, modulation of the sorting efficiency in a tissue-specific manner may represent an evolutionary adaptation to environmental cues.
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Affiliation(s)
- Denis Štepihar
- School of Veterinary Medicine, Texas Tech University, Amarillo, TX, United States
- Texas Center for Comparative Cancer Research (TC3R), Amarillo, TX, United States
- Biotechnical Faculty, University of Ljubljana, Ljubljana, Slovenia
| | - Rebecca R. Florke Gee
- School of Veterinary Medicine, Texas Tech University, Amarillo, TX, United States
- Texas Center for Comparative Cancer Research (TC3R), Amarillo, TX, United States
| | - Maria Camila Hoyos Sanchez
- School of Veterinary Medicine, Texas Tech University, Amarillo, TX, United States
- Texas Center for Comparative Cancer Research (TC3R), Amarillo, TX, United States
| | - Klementina Fon Tacer
- School of Veterinary Medicine, Texas Tech University, Amarillo, TX, United States
- Texas Center for Comparative Cancer Research (TC3R), Amarillo, TX, United States
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2
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Neuman SD, Lee AR, Selegue JE, Cavanagh AT, Bashirullah A. A novel function for Rab1 and Rab11 during secretory granule maturation. J Cell Sci 2021; 134:jcs259037. [PMID: 34342349 PMCID: PMC8353522 DOI: 10.1242/jcs.259037] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2021] [Accepted: 06/29/2021] [Indexed: 01/15/2023] Open
Abstract
Regulated exocytosis is an essential process whereby specific cargo proteins are secreted in a stimulus-dependent manner. Cargo-containing secretory granules are synthesized in the trans-Golgi network (TGN); after budding from the TGN, granules undergo modifications, including an increase in size. These changes occur during a poorly understood process called secretory granule maturation. Here, we leverage the Drosophila larval salivary glands as a model to characterize a novel role for Rab GTPases during granule maturation. We find that secretory granules increase in size ∼300-fold between biogenesis and release, and loss of Rab1 or Rab11 reduces granule size. Surprisingly, we find that Rab1 and Rab11 localize to secretory granule membranes. Rab11 associates with granule membranes throughout maturation, and Rab11 recruits Rab1. In turn, Rab1 associates specifically with immature granules and drives granule growth. In addition to roles in granule growth, both Rab1 and Rab11 appear to have additional functions during exocytosis; Rab11 function is necessary for exocytosis, while the presence of Rab1 on immature granules may prevent precocious exocytosis. Overall, these results highlight a new role for Rab GTPases in secretory granule maturation.
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Affiliation(s)
| | | | | | | | - Arash Bashirullah
- Division of Pharmaceutical Sciences, University of Wisconsin-Madison, Madison, WI 53705-2222, USA
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3
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Ma CIJ, Burgess J, Brill JA. Maturing secretory granules: Where secretory and endocytic pathways converge. Adv Biol Regul 2021; 80:100807. [PMID: 33866198 DOI: 10.1016/j.jbior.2021.100807] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2021] [Revised: 03/10/2021] [Accepted: 03/18/2021] [Indexed: 10/21/2022]
Abstract
Secretory granules (SGs) are specialized organelles responsible for the storage and regulated release of various biologically active molecules from the endocrine and exocrine systems. Thus, proper SG biogenesis is critical to normal animal physiology. Biogenesis of SGs starts at the trans-Golgi network (TGN), where immature SGs (iSGs) bud off and undergo maturation before fusing with the plasma membrane (PM). How iSGs mature is unclear, but emerging studies have suggested an important role for the endocytic pathway. The requirement for endocytic machinery in SG maturation blurs the line between SGs and another class of secretory organelles called lysosome-related organelles (LROs). Therefore, it is important to re-evaluate the differences and similarities between SGs and LROs.
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Affiliation(s)
- Cheng-I Jonathan Ma
- Cell Biology Program, The Hospital for Sick Children, PGCRL Building, Room 15.9716, 686 Bay Street, Toronto, Ontario, M5G 0A4, Canada; Institute of Medical Science, University of Toronto, Medical Sciences Building, Room 2374, 1 King's College Circle, Toronto, Ontario, M5S 1A8, Canada
| | - Jason Burgess
- Cell Biology Program, The Hospital for Sick Children, PGCRL Building, Room 15.9716, 686 Bay Street, Toronto, Ontario, M5G 0A4, Canada; Department of Molecular Genetics, University of Toronto, Medical Sciences Building, Room 4396, 1 King's College Circle, Toronto, Ontario, M5S 1A8, Canada
| | - Julie A Brill
- Cell Biology Program, The Hospital for Sick Children, PGCRL Building, Room 15.9716, 686 Bay Street, Toronto, Ontario, M5G 0A4, Canada; Institute of Medical Science, University of Toronto, Medical Sciences Building, Room 2374, 1 King's College Circle, Toronto, Ontario, M5S 1A8, Canada; Department of Molecular Genetics, University of Toronto, Medical Sciences Building, Room 4396, 1 King's College Circle, Toronto, Ontario, M5S 1A8, Canada.
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4
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Neuman SD, Terry EL, Selegue JE, Cavanagh AT, Bashirullah A. Mistargeting of secretory cargo in retromer-deficient cells. Dis Model Mech 2021; 14:dmm.046417. [PMID: 33380435 PMCID: PMC7847263 DOI: 10.1242/dmm.046417] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2020] [Accepted: 12/08/2020] [Indexed: 12/11/2022] Open
Abstract
Intracellular trafficking is a basic and essential cellular function required for delivery of proteins to the appropriate subcellular destination; this process is especially demanding in professional secretory cells, which synthesize and secrete massive quantities of cargo proteins via regulated exocytosis. The Drosophila larval salivary glands are composed of professional secretory cells that synthesize and secrete mucin proteins at the onset of metamorphosis. Using the larval salivary glands as a model system, we have identified a role for the highly conserved retromer complex in trafficking of secretory granule membrane proteins. We demonstrate that retromer-dependent trafficking via endosomal tubules is induced at the onset of secretory granule biogenesis, and that recycling via endosomal tubules is required for delivery of essential secretory granule membrane proteins to nascent granules. Without retromer function, nascent granules do not contain the proper membrane proteins; as a result, cargo from these defective granules is mistargeted to Rab7-positive endosomes, where it progressively accumulates to generate dramatically enlarged endosomes. Retromer complex dysfunction is strongly associated with neurodegenerative diseases, including Alzheimer's disease, characterized by accumulation of amyloid β (Aβ). We show that ectopically expressed amyloid precursor protein (APP) undergoes regulated exocytosis in salivary glands and accumulates within enlarged endosomes in retromer-deficient cells. These results highlight recycling of secretory granule membrane proteins as a critical step during secretory granule maturation and provide new insights into our understanding of retromer complex function in secretory cells. These findings also suggest that missorting of secretory cargo, including APP, may contribute to the progressive nature of neurodegenerative disease.
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Affiliation(s)
- Sarah D Neuman
- Division of Pharmaceutical Sciences, University of Wisconsin-Madison, Madison, WI 53705-2222, USA
| | - Erica L Terry
- Division of Pharmaceutical Sciences, University of Wisconsin-Madison, Madison, WI 53705-2222, USA
| | - Jane E Selegue
- Division of Pharmaceutical Sciences, University of Wisconsin-Madison, Madison, WI 53705-2222, USA
| | - Amy T Cavanagh
- Division of Pharmaceutical Sciences, University of Wisconsin-Madison, Madison, WI 53705-2222, USA
| | - Arash Bashirullah
- Division of Pharmaceutical Sciences, University of Wisconsin-Madison, Madison, WI 53705-2222, USA
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5
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Hoogstraaten RI, van Keimpema L, Toonen RF, Verhage M. Tetanus insensitive VAMP2 differentially restores synaptic and dense core vesicle fusion in tetanus neurotoxin treated neurons. Sci Rep 2020; 10:10913. [PMID: 32616842 PMCID: PMC7331729 DOI: 10.1038/s41598-020-67988-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2019] [Accepted: 06/11/2020] [Indexed: 01/10/2023] Open
Abstract
The SNARE proteins involved in the secretion of neuromodulators from dense core vesicles (DCVs) in mammalian neurons are still poorly characterized. Here we use tetanus neurotoxin (TeNT) light chain, which cleaves VAMP1, 2 and 3, to study DCV fusion in hippocampal neurons and compare the effects on DCV fusion to those on synaptic vesicle (SV) fusion. Both DCV and SV fusion were abolished upon TeNT expression. Expression of tetanus insensitive (TI)-VAMP2 restored SV fusion in the presence of TeNT, but not DCV fusion. Expression of TI-VAMP1 or TI-VAMP3 also failed to restore DCV fusion. Co-transport assays revealed that both TI-VAMP1 and TI-VAMP2 are targeted to DCVs and travel together with DCVs in neurons. Furthermore, expression of the TeNT-cleaved VAMP2 fragment or a protease defective TeNT in wild type neurons did not affect DCV fusion and therefore cannot explain the lack of rescue of DCV fusion by TI-VAMP2. Finally, to test if two different VAMPs might both be required in the DCV secretory pathway, Vamp1 null mutants were tested. However, VAMP1 deficiency did not reduce DCV fusion. In conclusion, TeNT treatment combined with TI-VAMP2 expression differentially affects the two main regulated secretory pathways: while SV fusion is normal, DCV fusion is absent.
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Affiliation(s)
- Rein I Hoogstraaten
- Department of Functional Genomics, Center for Neurogenomics and Cognitive Research, Vrije Universiteit (VU) Amsterdam and University Medical Center Amsterdam, de Boelelaan 1087, 1018 HV, Amsterdam, The Netherlands
| | - Linda van Keimpema
- Department of Functional Genomics, Center for Neurogenomics and Cognitive Research, Vrije Universiteit (VU) Amsterdam and University Medical Center Amsterdam, de Boelelaan 1087, 1018 HV, Amsterdam, The Netherlands.,Sylics (Synaptologics BV), PO Box 71033, 1008 BA, Amsterdam, The Netherlands
| | - Ruud F Toonen
- Department of Functional Genomics, Center for Neurogenomics and Cognitive Research, Vrije Universiteit (VU) Amsterdam and University Medical Center Amsterdam, de Boelelaan 1087, 1018 HV, Amsterdam, The Netherlands.
| | - Matthijs Verhage
- Department of Functional Genomics, Center for Neurogenomics and Cognitive Research, Vrije Universiteit (VU) Amsterdam and University Medical Center Amsterdam, de Boelelaan 1087, 1018 HV, Amsterdam, The Netherlands. .,Clinical Genetics, Center for Neurogenomics and Cognitive Research, Vrije Universiteit (VU) Amsterdam and University Medical Center Amsterdam, de Boelelaan 1087, 1018 HV, Amsterdam, The Netherlands.
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6
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Genetic dissection of neuropeptide cell biology at high and low activity in a defined sensory neuron. Proc Natl Acad Sci U S A 2018; 115:E6890-E6899. [PMID: 29959203 PMCID: PMC6055185 DOI: 10.1073/pnas.1714610115] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Neuropeptides are ubiquitous modulators of behavior and physiology. They are packaged in specialized secretory organelles called dense core vesicles (DCVs) that are released upon neural stimulation. Whereas local recycling of synaptic vesicles has been investigated intensively, there are few studies on recycling of DCV proteins. We set up a paradigm to study DCVs in a neuron whose activity we can control. We validate our model by confirming many previous observations on DCV cell biology. We identify a set of genes involved in recycling of DCV proteins. We also find evidence that different mechanisms of DCV priming and exocytosis may operate at high and low neural activity. Neuropeptides are ubiquitous modulators of behavior and physiology. They are packaged in specialized secretory organelles called dense core vesicles (DCVs) that are released upon neural stimulation. Unlike synaptic vesicles, which can be recycled and refilled close to release sites, DCVs must be replenished by de novo synthesis in the cell body. Here, we dissect DCV cell biology in vivo in a Caenorhabditis elegans sensory neuron whose tonic activity we can control using a natural stimulus. We express fluorescently tagged neuropeptides in the neuron and define parameters that describe their subcellular distribution. We measure these parameters at high and low neural activity in 187 mutants defective in proteins implicated in membrane traffic, neuroendocrine secretion, and neuronal or synaptic activity. Using unsupervised hierarchical clustering methods, we analyze these data and identify 62 groups of genes with similar mutant phenotypes. We explore the function of a subset of these groups. We recapitulate many previous findings, validating our paradigm. We uncover a large battery of proteins involved in recycling DCV membrane proteins, something hitherto poorly explored. We show that the unfolded protein response promotes DCV production, which may contribute to intertissue communication of stress. We also find evidence that different mechanisms of priming and exocytosis may operate at high and low neural activity. Our work provides a defined framework to study DCV biology at different neural activity levels.
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Cattin-Ortolá J, Topalidou I, Dosey A, Merz AJ, Ailion M. The dense-core vesicle maturation protein CCCP-1 binds RAB-2 and membranes through its C-terminal domain. Traffic 2017; 18:720-732. [PMID: 28755404 DOI: 10.1111/tra.12507] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2017] [Revised: 07/26/2017] [Accepted: 07/26/2017] [Indexed: 12/18/2022]
Abstract
Dense-core vesicles (DCVs) are secretory organelles that store and release modulatory neurotransmitters from neurons and endocrine cells. Recently, the conserved coiled-coil protein CCCP-1 was identified as a component of the DCV biogenesis pathway in the nematode Caenorhabditis elegans. CCCP-1 binds the small GTPase RAB-2 and colocalizes with it at the trans-Golgi. Here, we report a structure-function analysis of CCCP-1 to identify domains of the protein important for its localization, binding to RAB-2, and function in DCV biogenesis. We find that the CCCP-1 C-terminal domain (CC3) has multiple activities. CC3 is necessary and sufficient for CCCP-1 localization and for binding to RAB-2, and is required for the function of CCCP-1 in DCV biogenesis. In addition, CCCP-1 binds membranes directly through its CC3 domain, indicating that CC3 may comprise a previously uncharacterized lipid-binding motif. We conclude that CCCP-1 is a coiled-coil protein that binds an activated Rab and localizes to the Golgi via its C-terminus, properties similar to members of the golgin family of proteins. CCCP-1 also shares biophysical features with golgins; it has an elongated shape and forms oligomers.
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Affiliation(s)
| | - Irini Topalidou
- Department of Biochemistry, University of Washington, Seattle, Washington
| | - Annie Dosey
- Department of Biochemistry, University of Washington, Seattle, Washington
| | - Alexey J Merz
- Department of Biochemistry, University of Washington, Seattle, Washington.,Department of Physiology and Biophysics, University of Washington, Seattle, Washington
| | - Michael Ailion
- Department of Biochemistry, University of Washington, Seattle, Washington
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8
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Touz MC, Zamponi N. Sorting without a Golgi complex. Traffic 2017; 18:637-645. [DOI: 10.1111/tra.12500] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2017] [Revised: 07/01/2017] [Accepted: 07/06/2017] [Indexed: 12/22/2022]
Affiliation(s)
- Maria C. Touz
- Instituto de Investigación Médica Mercedes y Martín Ferreyra, INIMEC - CONICET; Universidad Nacional de Córdoba; Córdoba Argentina
| | - Nahuel Zamponi
- Instituto de Investigación Médica Mercedes y Martín Ferreyra, INIMEC - CONICET; Universidad Nacional de Córdoba; Córdoba Argentina
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9
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Du W, Zhou M, Zhao W, Cheng D, Wang L, Lu J, Song E, Feng W, Xue Y, Xu P, Xu T. HID-1 is required for homotypic fusion of immature secretory granules during maturation. eLife 2016; 5. [PMID: 27751232 PMCID: PMC5094852 DOI: 10.7554/elife.18134] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2016] [Accepted: 10/17/2016] [Indexed: 02/06/2023] Open
Abstract
Secretory granules, also known as dense core vesicles, are generated at the trans-Golgi network and undergo several maturation steps, including homotypic fusion of immature secretory granules (ISGs) and processing of prehormones to yield active peptides. The molecular mechanisms governing secretory granule maturation are largely unknown. Here, we investigate a highly conserved protein named HID-1 in a mouse model. A conditional knockout of HID-1 in pancreatic β cells leads to glucose intolerance and a remarkable increase in the serum proinsulin/insulin ratio caused by defective proinsulin processing. Large volume three-dimensional electron microscopy and immunofluorescence imaging reveal that ISGs are much more abundant in the absence of HID-1. We further demonstrate that HID-1 deficiency prevented secretory granule maturation by blocking homotypic fusion of immature secretory granules. Our data identify a novel player during the early maturation of immature secretory granules.
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Affiliation(s)
- Wen Du
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Maoge Zhou
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.,College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Wei Zhao
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.,College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Dongwan Cheng
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Lifen Wang
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Jingze Lu
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Eli Song
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Wei Feng
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Yanhong Xue
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Pingyong Xu
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China.,Key Laboratory of RNA Biology, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Tao Xu
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.,College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China
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10
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Topalidou I, Cattin-Ortolá J, Pappas AL, Cooper K, Merrihew GE, MacCoss MJ, Ailion M. The EARP Complex and Its Interactor EIPR-1 Are Required for Cargo Sorting to Dense-Core Vesicles. PLoS Genet 2016; 12:e1006074. [PMID: 27191843 PMCID: PMC4871572 DOI: 10.1371/journal.pgen.1006074] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2016] [Accepted: 04/30/2016] [Indexed: 12/15/2022] Open
Abstract
The dense-core vesicle is a secretory organelle that mediates the regulated release of peptide hormones, growth factors, and biogenic amines. Dense-core vesicles originate from the trans-Golgi of neurons and neuroendocrine cells, but it is unclear how this specialized organelle is formed and acquires its specific cargos. To identify proteins that act in dense-core vesicle biogenesis, we performed a forward genetic screen in Caenorhabditis elegans for mutants defective in dense-core vesicle function. We previously reported the identification of two conserved proteins that interact with the small GTPase RAB-2 to control normal dense-core vesicle cargo-sorting. Here we identify several additional conserved factors important for dense-core vesicle cargo sorting: the WD40 domain protein EIPR-1 and the endosome-associated recycling protein (EARP) complex. By assaying behavior and the trafficking of dense-core vesicle cargos, we show that mutants that lack EIPR-1 or EARP have defects in dense-core vesicle cargo-sorting similar to those of mutants in the RAB-2 pathway. Genetic epistasis data indicate that RAB-2, EIPR-1 and EARP function in a common pathway. In addition, using a proteomic approach in rat insulinoma cells, we show that EIPR-1 physically interacts with the EARP complex. Our data suggest that EIPR-1 is a new interactor of the EARP complex and that dense-core vesicle cargo sorting depends on the EARP-dependent trafficking of cargo through an endosomal sorting compartment. Animal cells package and store many important signaling molecules in specialized compartments called dense-core vesicles. Molecules stored in dense-core vesicles include peptide hormones like insulin and small molecule neurotransmitters like dopamine. Defects in the release of these compounds can lead to a wide range of metabolic and mental disorders in humans, including diabetes, depression, and drug addiction. However, it is not well understood how dense-core vesicles are formed in cells and package the appropriate molecules. Here we use a genetic screen in the microscopic worm C. elegans to identify proteins that are important for early steps in the generation of dense-core vesicles, such as packaging the correct molecular cargos in the vesicles. We identify several factors that are conserved between worms and humans and point to a new role for a protein complex that had previously been shown to be important for controlling trafficking in other cellular compartments. The identification of this complex suggests new cellular trafficking events that may be important for the generation of dense-core vesicles.
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Affiliation(s)
- Irini Topalidou
- Department of Biochemistry, University of Washington, Seattle, Washington, United States of America
| | - Jérôme Cattin-Ortolá
- Department of Biochemistry, University of Washington, Seattle, Washington, United States of America
| | - Andrea L. Pappas
- Department of Neurobiology, Duke University School of Medicine, Durham, North Carolina, United States of America
| | - Kirsten Cooper
- Department of Biochemistry, University of Washington, Seattle, Washington, United States of America
| | - Gennifer E. Merrihew
- Department of Genome Sciences, University of Washington, Seattle, Washington, United States of America
| | - Michael J. MacCoss
- Department of Genome Sciences, University of Washington, Seattle, Washington, United States of America
| | - Michael Ailion
- Department of Biochemistry, University of Washington, Seattle, Washington, United States of America
- * E-mail:
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11
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Katsumata-Kato O, Yokoyama M, Matsuki-Fukushima M, Narita T, Sugiya H, Fujita-Yoshigaki J. Secretory proteins without a transport signal are retained in secretory granules during maturation in rat parotid acinar cells. Arch Oral Biol 2015; 60:642-9. [PMID: 25703816 DOI: 10.1016/j.archoralbio.2015.01.006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2014] [Revised: 12/22/2014] [Accepted: 01/02/2015] [Indexed: 10/24/2022]
Abstract
OBJECTIVE The acinar cells of the parotid gland are filled with numerous secretory granules (SGs), which accumulate the digestion enzyme amylase. SGs mature accompanied with membrane remodelling such as fusion and budding of small vesicles. However, little is understood about the mechanism of the condensation of SG contents during maturation. In this study, we examined whether secretory proteins need a specific signal to be retained in SGs. DESIGN To induce internalization of the luminal membrane after exocytosis, we injected the β-adrenergic agonist isoproterenol into rats. Acinar cells were then incubated with Lucifer Yellow (LY) dye as a tracer for 3h for uptake into immature secretory granules (ISGs). To observe whether LY was retained in SGs after maturation, we continued incubating the cultured acinar cells for 2 days. RESULTS The localization of LY into ISGs was confirmed by the following four methods: (1) co-localization of the fluorescence of LY and amylase by confocal laser microscopy, (2) detection of the fluorescence from purified ISGs, (3) secretion of the fluorescence together with amylase upon stimulation, and (4) observation of the intracellular localization of LY by electron microscopy. Moreover, we observed co-localization of some of the SGs with the fluorescence of LY after cell culture. CONCLUSIONS Although the fusion and budding of small vesicles may contribute to the process of granule maturation, LY remained in the SGs even after maturation. These results suggest that secretory proteins that have no transport signal are not excluded from SGs, and they are retained in SGs during granule maturation in exocrine parotid glands.
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Affiliation(s)
- Osamu Katsumata-Kato
- Department of Physiology and Research Institute of Oral Science, Nihon University School of Dentistry at Matsudo, 2-870-1 Sakaecho-Nishi, Matsudo, Chiba 271-8587, Japan.
| | - Megumi Yokoyama
- Department of Physiology and Research Institute of Oral Science, Nihon University School of Dentistry at Matsudo, 2-870-1 Sakaecho-Nishi, Matsudo, Chiba 271-8587, Japan
| | - Miwako Matsuki-Fukushima
- Department of Physiology and Research Institute of Oral Science, Nihon University School of Dentistry at Matsudo, 2-870-1 Sakaecho-Nishi, Matsudo, Chiba 271-8587, Japan
| | - Takanori Narita
- Laboratory of Veterinary Biochemistry, Nihon University College of Bioresource Sciences, 1866 Kameino, Fujisawa, Kanagawa 252-0880, Japan
| | - Hiroshi Sugiya
- Laboratory of Veterinary Biochemistry, Nihon University College of Bioresource Sciences, 1866 Kameino, Fujisawa, Kanagawa 252-0880, Japan
| | - Junko Fujita-Yoshigaki
- Department of Physiology and Research Institute of Oral Science, Nihon University School of Dentistry at Matsudo, 2-870-1 Sakaecho-Nishi, Matsudo, Chiba 271-8587, Japan
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12
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Ailion M, Hannemann M, Dalton S, Pappas A, Watanabe S, Hegermann J, Liu Q, Han HF, Gu M, Goulding MQ, Sasidharan N, Schuske K, Hullett P, Eimer S, Jorgensen EM. Two Rab2 interactors regulate dense-core vesicle maturation. Neuron 2014; 82:167-80. [PMID: 24698274 DOI: 10.1016/j.neuron.2014.02.017] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/23/2014] [Indexed: 12/14/2022]
Abstract
Peptide neuromodulators are released from a unique organelle: the dense-core vesicle. Dense-core vesicles are generated at the trans-Golgi and then sort cargo during maturation before being secreted. To identify proteins that act in this pathway, we performed a genetic screen in Caenorhabditis elegans for mutants defective in dense-core vesicle function. We identified two conserved Rab2-binding proteins: RUND-1, a RUN domain protein, and CCCP-1, a coiled-coil protein. RUND-1 and CCCP-1 colocalize with RAB-2 at the Golgi, and rab-2, rund-1, and cccp-1 mutants have similar defects in sorting soluble and transmembrane dense-core vesicle cargos. RUND-1 also interacts with the Rab2 GAP protein TBC-8 and the BAR domain protein RIC-19, a RAB-2 effector. In summary, a pathway of conserved proteins controls the maturation of dense-core vesicles at the trans-Golgi network.
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Affiliation(s)
- Michael Ailion
- Howard Hughes Medical Institute, Department of Biology, University of Utah, Salt Lake City, UT 84112, USA; Department of Biochemistry, University of Washington, Seattle WA, 98195, USA.
| | - Mandy Hannemann
- European Neuroscience Institute, 37077 Göttingen, Germany; International Max Planck Research School Molecular Biology, 37077 Göttingen, Germany
| | - Susan Dalton
- Howard Hughes Medical Institute, Department of Biology, University of Utah, Salt Lake City, UT 84112, USA
| | - Andrea Pappas
- Howard Hughes Medical Institute, Department of Biology, University of Utah, Salt Lake City, UT 84112, USA
| | - Shigeki Watanabe
- Howard Hughes Medical Institute, Department of Biology, University of Utah, Salt Lake City, UT 84112, USA
| | - Jan Hegermann
- European Neuroscience Institute, 37077 Göttingen, Germany; DFG research Center for Molecular Physiology of the Brain (CMPB), 37077 Göttingen, Germany
| | - Qiang Liu
- Howard Hughes Medical Institute, Department of Biology, University of Utah, Salt Lake City, UT 84112, USA
| | - Hsiao-Fen Han
- Howard Hughes Medical Institute, Department of Biology, University of Utah, Salt Lake City, UT 84112, USA
| | - Mingyu Gu
- Howard Hughes Medical Institute, Department of Biology, University of Utah, Salt Lake City, UT 84112, USA
| | - Morgan Q Goulding
- Department of Biochemistry, University of Washington, Seattle WA, 98195, USA
| | | | - Kim Schuske
- Howard Hughes Medical Institute, Department of Biology, University of Utah, Salt Lake City, UT 84112, USA
| | - Patrick Hullett
- Howard Hughes Medical Institute, Department of Biology, University of Utah, Salt Lake City, UT 84112, USA
| | - Stefan Eimer
- European Neuroscience Institute, 37077 Göttingen, Germany; DFG research Center for Molecular Physiology of the Brain (CMPB), 37077 Göttingen, Germany
| | - Erik M Jorgensen
- Howard Hughes Medical Institute, Department of Biology, University of Utah, Salt Lake City, UT 84112, USA.
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Azouz NP, Zur N, Efergan A, Ohbayashi N, Fukuda M, Amihai D, Hammel I, Rothenberg ME, Sagi-Eisenberg R. Rab5 Is a Novel Regulator of Mast Cell Secretory Granules: Impact on Size, Cargo, and Exocytosis. THE JOURNAL OF IMMUNOLOGY 2014; 192:4043-53. [DOI: 10.4049/jimmunol.1302196] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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14
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Křepelová-DROR M, Hammel I, Meilijson I. Statistical analysis of the quantal basis of secretory granule formation. Microsc Res Tech 2013; 77:1-10. [DOI: 10.1002/jemt.22305] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2013] [Revised: 10/09/2013] [Accepted: 10/14/2013] [Indexed: 11/09/2022]
Affiliation(s)
- Marika Křepelová-DROR
- Department of Econometrics; Faculty of Informatics and Statistics, University of Economics; Nám. W. Churchilla 4, 13067 Praha 3 Czech Republic
| | - Ilan Hammel
- Department of Pathology; Sackler Faculty of Medicine; Tel Aviv University. Tel Aviv 6997801; Israel
| | - Isaac Meilijson
- School of Mathematical Sciences, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University; Tel Aviv 6997801 Israel
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15
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Kögel T, Rudolf R, Hodneland E, Copier J, Regazzi R, Tooze SA, Gerdes HH. Rab3D is critical for secretory granule maturation in PC12 cells. PLoS One 2013; 8:e57321. [PMID: 23526941 PMCID: PMC3602456 DOI: 10.1371/journal.pone.0057321] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2012] [Accepted: 01/21/2013] [Indexed: 11/19/2022] Open
Abstract
Neuropeptide- and hormone-containing secretory granules (SGs) are synthesized at the trans-Golgi network (TGN) as immature secretory granules (ISGs) and complete their maturation in the F-actin-rich cell cortex. This maturation process is characterized by acidification-dependent processing of cargo proteins, condensation of the SG matrix and removal of membrane and proteins not destined to mature secretory granules (MSGs). Here we addressed a potential role of Rab3 isoforms in these maturation steps by expressing their nucleotide-binding deficient mutants in PC12 cells. Our data show that the presence of Rab3D(N135I) decreases the restriction of maturing SGs to the F-actin-rich cell cortex, blocks the removal of the endoprotease furin from SGs and impedes the processing of the luminal SG protein secretogranin II. This strongly suggests that Rab3D is implicated in the subcellular localization and maturation of ISGs.
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Affiliation(s)
- Tanja Kögel
- Department of Biomedicine, University of Bergen, Bergen, Norway
| | - Rüdiger Rudolf
- Interdisciplinary Center of Neurobiology, University of Heidelberg, Heidelberg, Germany
| | | | - John Copier
- London Research Institute Cancer Research United Kingdom, Lincoln's Inn Fields Laboratories, London, United Kingdom
| | - Romano Regazzi
- Department of Fundamental Neurosciences, University of Lausanne, Lausanne, Switzerland
| | - Sharon A. Tooze
- London Research Institute Cancer Research United Kingdom, Lincoln's Inn Fields Laboratories, London, United Kingdom
| | - Hans-Hermann Gerdes
- Department of Biomedicine, University of Bergen, Bergen, Norway
- Interdisciplinary Center of Neurobiology, University of Heidelberg, Heidelberg, Germany
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16
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Bonnemaison ML, Eipper BA, Mains RE. Role of adaptor proteins in secretory granule biogenesis and maturation. Front Endocrinol (Lausanne) 2013; 4:101. [PMID: 23966980 PMCID: PMC3743005 DOI: 10.3389/fendo.2013.00101] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/10/2013] [Accepted: 07/31/2013] [Indexed: 12/29/2022] Open
Abstract
In the regulated secretory pathway, secretory granules (SGs) store peptide hormones that are released on demand. SGs are formed at the trans-Golgi network and must undergo a maturation process to become responsive to secretagogues. The production of mature SGs requires concentrating newly synthesized soluble content proteins in granules whose membranes contain the appropriate integral membrane proteins. The mechanisms underlying the sorting of soluble and integral membrane proteins destined for SGs from other proteins are not yet well understood. For soluble proteins, luminal pH and divalent metals can affect aggregation and interaction with surrounding membranes. The trafficking of granule membrane proteins can be controlled by both luminal and cytosolic factors. Cytosolic adaptor proteins (APs), which recognize the cytosolic domains of proteins that span the SG membrane, have been shown to play essential roles in the assembly of functional SGs. Adaptor protein 1A (AP-1A) is known to interact with specific motifs in its cargo proteins and with the clathrin heavy chain, contributing to the formation of a clathrin coat. AP-1A is present in patches on immature SG membranes, where it removes cargo and facilitates SG maturation. AP-1A recruitment to membranes can be modulated by Phosphofurin Acidic Cluster Sorting protein 1 (PACS-1), a cytosolic protein which interacts with both AP-1A and cargo that has been phosphorylated by casein kinase II. A cargo/PACS-1/AP-1A complex is necessary to drive the appropriate transport of several cargo proteins within the regulated secretory pathway. The Golgi-localized, γ-ear containing, ADP-ribosylation factor binding (GGA) family of APs serve a similar role. We review the functions of AP-1A, PACS-1, and GGAs in facilitating the retrieval of proteins from immature SGs and review examples of cargo proteins whose trafficking within the regulated secretory pathway is governed by APs.
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Affiliation(s)
- Mathilde L. Bonnemaison
- Department of Molecular, Microbial and Structural Biology, University of Connecticut Health Center, Farmington, CT, USA
| | - Betty A. Eipper
- Department of Molecular, Microbial and Structural Biology, University of Connecticut Health Center, Farmington, CT, USA
- Department of Neuroscience, University of Connecticut Health Center, Farmington, CT, USA
| | - Richard E. Mains
- Department of Neuroscience, University of Connecticut Health Center, Farmington, CT, USA
- *Correspondence: Richard E. Mains, Department of Neuroscience, University of Connecticut Health Center, 263 Farmington Avenue, Farmington, CT 06030-3401, USA e-mail:
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17
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Cellular Mechanisms for the Biogenesis and Transport of Synaptic and Dense-Core Vesicles. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2012; 299:27-115. [DOI: 10.1016/b978-0-12-394310-1.00002-3] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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18
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Chapleau CA, Larimore JL, Theibert A, Pozzo-Miller L. Modulation of dendritic spine development and plasticity by BDNF and vesicular trafficking: fundamental roles in neurodevelopmental disorders associated with mental retardation and autism. J Neurodev Disord 2011; 1:185-96. [PMID: 19966931 PMCID: PMC2788955 DOI: 10.1007/s11689-009-9027-6] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The process of axonal and dendritic development establishes the synaptic circuitry of the central nervous system (CNS) and is the result of interactions between intrinsic molecular factors and the external environment. One growth factor that has a compelling function in neuronal development is the neurotrophin brain-derived neurotrophic factor (BDNF). BDNF participates in axonal and dendritic differentiation during embryonic stages of neuronal development, as well as in the formation and maturation of dendritic spines during postnatal development. Recent studies have also implicated vesicular trafficking of BDNF via secretory vesicles, and both secretory and endosomal trafficking of vesicles containing synaptic proteins, such as neurotransmitter and neurotrophin receptors, in the regulation of axonal and dendritic differentiation, and in dendritic spine morphogenesis. Several genes that are either mutated or deregulated in neurodevelopmental disorders associated with mental retardation have now been identified, and several mouse models of these disorders have been generated and characterized. Interestingly, abnormalities in dendritic and synaptic structure are consistently observed in human neurodevelopmental disorders associated with mental retardation, and in mouse models of these disorders as well. Abnormalities in dendritic and synaptic differentiation are thought to underlie altered synaptic function and network connectivity, thus contributing to the clinical outcome. Here, we review the roles of BDNF and vesicular trafficking in axonal and dendritic differentiation in the context of dendritic and axonal morphological impairments commonly observed in neurodevelopmental disorders associated with mental retardation.
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Affiliation(s)
- Christopher A Chapleau
- Department of Neurobiology, Civitan International Research Center, Evelyn McKnight Brain Institute, The University of Alabama at Birmingham, Birmingham, AL 35294, USA
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19
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Abstract
hid-1 was originally identified as a Caenorhabditis elegans gene encoding a novel conserved protein that regulates the decision to enter into the enduring dauer larval stage. We isolated a novel allele of hid-1 in a forward genetic screen for mutants mislocalizing RBF-1 rabphilin, a RAB-27 effector. Here we demonstrate that HID-1 functions in the nervous system to regulate neuromuscular signaling and in the intestine to regulate the defecation motor program. We further show that a conserved N-terminal myristoylated motif of both invertebrate and vertebrate HID-1 is essential for its association with intracellular membranes in nematodes and PC12 cells. C. elegans neuronal HID-1 resides on intracellular membranes in neuronal cell somas; however, the kinesin UNC-104 also transports HID-1 to synaptic regions. HID-1 accumulates in the axons of unc-13 and unc-31 mutants, suggesting it is associated with neurosecretory vesicles. Consistent with this, genetic studies place HID-1 in a peptidergic signaling pathway. Finally, a hid-1 null mutation reduces the levels of endogenous neuropeptides and alters the secretion of fluorescent-tagged cargos derived from neuronal and intestinal dense core vesicles (DCVs). Taken together, our findings indicate that HID-1 is a novel component of a DCV-based neurosecretory pathway and that it regulates one or more aspects of the biogenesis, maturation, or trafficking of DCVs.
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20
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Kögel T, Gerdes HH. Roles of myosin Va and Rab3D in membrane remodeling of immature secretory granules. Cell Mol Neurobiol 2010; 30:1303-8. [PMID: 21080055 PMCID: PMC3008937 DOI: 10.1007/s10571-010-9597-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2010] [Accepted: 09/02/2010] [Indexed: 01/24/2023]
Abstract
Neuroendocrine secretory granules (SGs) are formed at the trans-Golgi network (TGN) as immature intermediates. In PC12 cells, these immature SGs (ISGs) are transported within seconds to the cell cortex, where they move along actin filaments and complete maturation. This maturation process comprises acidification-dependent processing of cargo proteins, condensation of the SG matrix, and removal of membrane and proteins not destined to mature SGs (MSGs) into ISG-derived vesicles (IDVs). We investigated the roles of myosin Va and Rab3 isoforms in the maturation of ISGs in neuroendocrine PC12 cells. The expression of dominant-negative mutants of myosin Va or Rab3D blocked the removal of the endoprotease furin from ISGs. Furthermore, expression of mutant Rab3D, but not of mutant myosin Va, impaired cargo processing of SGs. In conclusion, our data suggest an implication of myosin Va and Rab3D in the maturation of SGs where they participate in overlapping but not identical tasks.
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Affiliation(s)
- Tanja Kögel
- Department of Biomedicine, University of Bergen, Jonas Lies Vei 91, 5009 Bergen, Norway
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21
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Courel M, Soler-Jover A, Rodriguez-Flores JL, Mahata SK, Elias S, Montero-Hadjadje M, Anouar Y, Giuly RJ, O'Connor DT, Taupenot L. Pro-hormone secretogranin II regulates dense core secretory granule biogenesis in catecholaminergic cells. J Biol Chem 2010; 285:10030-10043. [PMID: 20061385 PMCID: PMC2843166 DOI: 10.1074/jbc.m109.064196] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2009] [Revised: 12/16/2009] [Indexed: 11/06/2022] Open
Abstract
Processes underlying the formation of dense core secretory granules (DCGs) of neuroendocrine cells are poorly understood. Here, we present evidence that DCG biogenesis is dependent on the secretory protein secretogranin (Sg) II, a member of the granin family of pro-hormone cargo of DCGs in neuroendocrine cells. Depletion of SgII expression in PC12 cells leads to a decrease in both the number and size of DCGs and impairs DCG trafficking of other regulated hormones. Expression of SgII fusion proteins in a secretory-deficient PC12 variant rescues a regulated secretory pathway. SgII-containing dense core vesicles share morphological and physical properties with bona fide DCGs, are competent for regulated exocytosis, and maintain an acidic luminal pH through the V-type H(+)-translocating ATPase. The granulogenic activity of SgII requires a pH gradient along this secretory pathway. We conclude that SgII is a critical factor for the regulation of DCG biogenesis in neuroendocrine cells, mediating the formation of functional DCGs via its pH-dependent aggregation at the trans-Golgi network.
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Affiliation(s)
- Maïté Courel
- Department of Medicine, University of California San Diego, La Jolla, California 92093-0838.
| | - Alex Soler-Jover
- Department of Medicine, University of California San Diego, La Jolla, California 92093-0838
| | | | - Sushil K Mahata
- Department of Medicine, University of California San Diego, La Jolla, California 92093-0838; Veteran Affairs San Diego Healthcare System, San Diego, California 92093
| | - Salah Elias
- INSERM U982, University of Rouen, 76821 Mont-St.-Aignan Cedex, France
| | | | - Youssef Anouar
- INSERM U982, University of Rouen, 76821 Mont-St.-Aignan Cedex, France
| | - Richard J Giuly
- National Center for Microscopy and Imaging Research, University of California San Diego, La Jolla, California 92093
| | - Daniel T O'Connor
- Department of Medicine, University of California San Diego, La Jolla, California 92093-0838; Veteran Affairs San Diego Healthcare System, San Diego, California 92093.
| | - Laurent Taupenot
- Department of Medicine, University of California San Diego, La Jolla, California 92093-0838; Veteran Affairs San Diego Healthcare System, San Diego, California 92093.
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22
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Kögel T, Rudolf R, Hodneland E, Hellwig A, Kuznetsov SA, Seiler F, Söllner TH, Barroso J, Gerdes HH. Distinct Roles of Myosin Va in Membrane Remodeling and Exocytosis of Secretory Granules. Traffic 2010; 11:637-50. [DOI: 10.1111/j.1600-0854.2010.01048.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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23
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Plattner H. Membrane Trafficking in Protozoa. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2010; 280:79-184. [DOI: 10.1016/s1937-6448(10)80003-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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Inomoto C, Osamura RY. Formation of secretory granules by chromogranins. Med Mol Morphol 2009; 42:201-3. [PMID: 20033364 DOI: 10.1007/s00795-009-0472-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2009] [Accepted: 10/05/2009] [Indexed: 11/28/2022]
Abstract
This review article covers the molecular mechanisms of secretory granule formation by chromogranin transfection. Recently, a few investigators have reported that the transfection of chromogranin A and B produces the structures of secretory granules. We used the GFP-chromogranin A transfection method to nonendocrine cells, COS-7 cells, which are not equipped with secretory granules. Despite the absence of endogenous secretory granules in nontransfected COS-7 cells, COS-7 cells transfected with chromogranin A contained granule-like structures in electron micrographs. The granules were composed of an outer limiting membrane with core structures that were interpreted as secretory granules. Human chromogranin A (CgA) labeled with 5-nm gold particles was present in several dense-core granules in our previous electron microscopy study. This review depicts the role of chromogranin A in the formation of secretory granules. It emphasizes the application of recently developed new technologies and the genesis of secretory granules.
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Affiliation(s)
- Chie Inomoto
- Department of Pathology, Tokai University School of Medicine, 143 Shimokasuya, Isehara, Kanagawa 259-1193, Japan.
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Kurrasch DM, Nevin LM, Wong JS, Baier H, Ingraham HA. Neuroendocrine transcriptional programs adapt dynamically to the supply and demand for neuropeptides as revealed in NSF mutant zebrafish. Neural Dev 2009; 4:22. [PMID: 19549326 PMCID: PMC2715394 DOI: 10.1186/1749-8104-4-22] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2009] [Accepted: 06/23/2009] [Indexed: 02/26/2023] Open
Abstract
BACKGROUND Regulated secretion of specialized neuropeptides in the vertebrate neuroendocrine system is critical for ensuring physiological homeostasis. Expression of these cell-specific peptide markers in the differentiating hypothalamus commences prior to birth, often predating the physiological demand for secreted neuropeptides. The conserved function and spatial expression of hypothalamic peptides in vertebrates prompted us to search for critical neuroendocrine genes in newly hatched zebrafish larvae. RESULTS We screened mutant 5 days post-fertilization zebrafish larvae that fail to undergo visually mediated background adaptation for disruption in hypothalamic pomc expression. To our surprise, the ATPase N-ethylmaleimide sensitive factor (nsf) was identified as an essential gene for maintenance of neuroendocrine transcriptional programs during the embryo-to-larva transition. Despite normal hypothalamic development in nsf(st53) mutants, neuropeptidergic cells exhibited a dramatic loss of cell-specific markers by 5 days post-fertilization that is accompanied by elevated intracellular neuropeptide protein. Consistent with the role of NSF in vesicle-membrane fusion events and intracellular trafficking, cytoplasmic endoplasmic reticulum-like membranes accumulate in nsf(-/-) hypothalamic neurons similar to that observed for SEC18 (nsf ortholog) yeast mutants. Our data support a model in which unspent neuropeptide cargo feedbacks to extinguish transcription in neuropeptidergic cells just as they become functionally required. In support of this model we found that gnrh3 transcripts remained unchanged in pre-migratory, non-functional gonadotropin-releasing hormone (GnRH) neurons in nsf(-/-) zebrafish. Furthermore, oxytocin-like (oxtl, intp) transcripts, which are found in osmoreceptive neurons and persist in mutant zebrafish, drop precipitously after mutant zebrafish are acutely challenged with high salt. CONCLUSION Our analyses of nsf mutant zebrafish reveal an unexpected role for NSF in hypothalamic development, with mutant 5 days post-fertilization larvae exhibiting a stage-dependent loss of neuroendocrine transcripts and a corresponding accumulation of neuropeptides in the soma. Based on our collective findings, we speculate that neuroendocrine transcriptional programs adapt dynamically to both the supply and demand for neuropeptides to ensure adequate homeostatic responses.
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Affiliation(s)
- Deborah M Kurrasch
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, California, USA.
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26
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Abstract
Acute insulin secretion from stimulated pancreatic beta-cells is derived from the intracellular pool of insulin secretory granules wherein insulin is packaged in a highly concentrated (and in some species, crystalline) state. Here we review experimental work, principally from our laboratory, on the question of biogenesis of mature secretory granules within the broader context of intracellular protein trafficking. Events occurring in the lumen of organelles at various stages of intracellular transport within the secretory pathway and events at the limiting membrane of newly forming secretory granules each contribute to formation of the insulin storage compartment comprising the readily releasable pool.
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Affiliation(s)
- Peter Arvan
- Divisions of Metabolism, Endocrinology, and Diabetes, University of Michigan, Ann Arbor, MI, USA.
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27
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Tajparast M, Glavinović MI. Extrusion of transmitter, water and ions generates forces to close fusion pore. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2009; 1788:993-1008. [PMID: 19366586 DOI: 10.1016/j.bbamem.2009.01.018] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/23/2008] [Revised: 01/07/2009] [Accepted: 01/30/2009] [Indexed: 11/16/2022]
Abstract
During exocytosis the fusion pore opens rapidly, then dilates gradually, and may subsequently close completely, but what controls its dynamics is not well understood. In this study we focus our attention on forces acting on the pore wall, and which are generated solely by the passage of transmitter, ions and water through the open fusion pore. The transport through the charged cylindrical nano-size pore is simulated using a coupled system of Poisson-Nernst-Planck and Navier-Stokes equations and the forces that act radially on the wall of the fusion pore are then estimated. Four forces are considered: a) inertial force, b) pressure, c) viscotic force, and d) electrostatic force. The inertial and viscotic forces are small, but the electrostatic force and the pressure are typically significant. High vesicular pressure tends to open the fusion pore, but the pressure induced by the transport of charged particles (glutamate, ions), which is predominant when the pore wall charge density is high tends to close the pore. The electrostatic force, which also depends on the charge density on the pore wall, is weakly repulsive before the pore dilates, but becomes attractive and pronounced as the pore dilates. Given that the vesicular concentration of free transmitter can change rapidly due to the release, or owing to the dissociation from the gel matrix, we evaluated how much and how rapidly a change of the vesicular K(+)-glutamate(-) concentration affects the concentration of glutamate(-) and ions in the pore and how such changes alter the radial force on the wall of the fusion pore. A step-like rise of the vesicular K(+)-glutamate(-) concentration leads to a chain of events. Pore concentration (and efflux) of both K(+) and glutamate(-) rise reaching their new steady-state values in less than 100 ns. Interestingly within a similar time interval the pore concentration of Na(+) also rises, whereas that of Cl(-) diminishes, although their extra-cellular concentration does not change. Finally such changes affect also the water movement. Water efflux changes bi-phasically, first increasing before decreasing to a new, but lower steady-state value. Nevertheless, even under such conditions an overall approximate neutrality of the pore is maintained remarkably well, and the electrostatic, but also inertial, viscotic and pressure forces acting on the pore wall remain constant. In conclusion the extrusion of the vesicular content generates forces, primarily the force due to the electro-kinetically induced pressure and electrostatic force (both influenced by the pore radius and even more by the charge density on the pore wall), which tend to close the fusion pore.
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Affiliation(s)
- M Tajparast
- Department of Civil Engineering, McGill University, Montreal, PQ, Canada
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28
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Abstract
Exocrine, endocrine, and neuroendocrine cells store hormones and neuropeptides in secretory granules (SGs), which undergo regulated exocytosis in response to an appropriate stimulus. These cargo proteins are sorted at the trans-Golgi network into forming immature secretory granules (ISGs). ISGs undergo maturation while they are transported to and within the F-actin-rich cortex. This process includes homotypic fusion of ISGs, acidification of their lumen, processing, and aggregation of cargo proteins as well as removal of excess membrane and missorted cargo. The resulting mature secretory granules (MSGs) are stored in the F-actin-rich cell cortex, perhaps as segregated pools exhibiting specific responses to stimuli for regulated exocytosis. During the last decade our understanding of the maturation of ISGs advanced substantially. The use of biochemical approaches led to the identification of membrane molecules mechanistically involved in this process. Furthermore, live cell imaging in combination with fluorescently tagged marker proteins of SGs provided insights into the dynamics of maturing ISGs, and the functional implications of cytoskeletal elements and motor proteins.
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29
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Biogenesis of Dense-Core Secretory Granules. TRAFFICKING INSIDE CELLS 2009. [PMCID: PMC7122546 DOI: 10.1007/978-0-387-93877-6_10] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Dense core granules (DCGs) are vesicular organelles derived from outbound traffic through the eukaryotic secretory pathway. As DCGs are formed, the secretory pathway can also give rise to other types of vesicles, such as those bound for endosomes, lysosomes, and the cell surface. DCGs differ from these other vesicular carriers in both content and function, storing highly concentrated cores’ of condensed cargo in vesicles that are stably maintained within the cell until a specific extracellular stimulus causes their fusion with the plasma membrane. These unique features are imparted by the activities of membrane and lumenal proteins that are specifically delivered to the vesicles during synthesis. This chapter will describe the DCG biogenesis pathway, beginning with the sorting of DCG proteins from proteins that are destined for other types of vesicle carriers. In the trans-Golgi network (TGN), sorting occurs as DCG proteins aggregate, causing physical separation from non-DCG proteins. Recent work addresses the nature of interactions that produce these aggregates, as well as potentially important interactions with membranes and membrane proteins. DCG proteins are released from the TGN in vesicles called immature secretory granules (ISGs). The mechanism of ISG formation is largely unclear but is not believed to rely on the assembly of vesicle coats like those observed in other secretory pathways. The required cytosolic factors are now beginning to be identified using in vitro systems with purified cellular components. ISG transformation into a mature fusion-competent, stimulus-dependent DCG occurs as endoproteolytic processing of many DCG proteins causes continued condensation of the lumenal contents. At the same time, proteins that fail to be incorporated into the condensing core are removed by a coat-mediated budding mechanism, which also serves to remove excess membrane and membrane proteins from the maturing vesicle. This chapter will summarize the work leading to our current view of granule synthesis, and will discuss questions that need to be addressed in order to gain a more complete understanding of the pathway.
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Morvan J, Tooze SA. Discovery and progress in our understanding of the regulated secretory pathway in neuroendocrine cells. Histochem Cell Biol 2008; 129:243-52. [PMID: 18197413 PMCID: PMC2248607 DOI: 10.1007/s00418-008-0377-z] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/04/2008] [Indexed: 01/24/2023]
Abstract
In this review we start with a historical perspective beginning with the early morphological work done almost 50 years ago. The importance of these pioneering studies is underscored by our brief summary of the key questions addressed by subsequent research into the mechanism of secretion. We then highlight important advances in our understanding of the formation and maturation of neuroendocrine secretory granules, first using in vitro reconstitution systems, then most recently biochemical approaches, and finally genetic manipulations in vitro and in vivo.
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Affiliation(s)
- Joëlle Morvan
- London Research Institute, Cancer Research UK, 44 Lincoln's Inn Fields, London, UK
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31
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Origins of the regulated secretory pathway. THE GOLGI APPARATUS 2008. [PMCID: PMC7121582 DOI: 10.1007/978-3-211-76310-0_30] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Modes of transport of soluble (or luminal) secretory proteins synthesized in the endoplasmic reticulum (ER) could be divided into two groups. The socalled constitutive secretory pathway (CSP) is common to all eukaryotic cells, constantly delivering constitutive soluble secretory proteins (CSSPs) linked to the rate of protein synthesis but largely independent of external stimuli. In regulated secretion, protein is sorted from the Golgi into storage/secretory granules (SGs) whose contents are released when stimuli trigger their final fusion with the plasma membrane (Hannah et al. 1999).
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Inomoto C, Umemura S, Egashira N, Minematsu T, Takekoshi S, Itoh Y, Itoh J, Taupenot L, O'Connor DT, Osamura RY. Granulogenesis in Non-neuroendocrine COS-7 Cells Induced by EGFP-tagged Chromogranin A Gene Transfection: Identical and Distinct Distribution of CgA and EGFP. J Histochem Cytochem 2007; 55:487-93. [PMID: 17242462 DOI: 10.1369/jhc.6a7110.2007] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We examined whether an enhanced green fluorescent protein (EGFP)-tagged chromogranin A (CgA) gene construct could serve as a marker protein to follow the synthesis of CgA and the process of granulogenesis in non-neuroendocrine (NE) cells. We transfected a CgA-EGFP expression vector into non-NE COS-7 cells and investigated the localization of a chimeric CgA-EGFP protein using confocal laser scanning microscopy (CLSM). The fluorescent signal of CgA-EGFP was distributed granularly in the cytoplasm. An immunocytochemical study using anti-CgA antibody with a quantum dot (Qd)525 shows colocalization of fluorescent signal of chimeric CgA-EGFP and CgA-Qd525 signals in granular structures, particularly at the periphery of the cytoplasm. We interpreted granules that were immunoreactive to CgA in electron micrographs as secretory. Spectral analysis of EGFP fluorescence revealed distinct EGFP signals without CgA colocalization. This is the first report to show that a granular structure can be induced by transfecting the EGFP-tagged human CgA gene into non-NE cells. The EGFP-tagged CgA gene could be a useful tool to investigate processes of the regulatory pathway. A more precise analysis of the fluorescence signal of EGFP by combination with the Qd system or by spectral analysis with CLSM can provide insight into biological phenomena.
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Affiliation(s)
- Chie Inomoto
- Dept of Pathology, Tokai University School of Medicine, Bohseidai, Isehara, Kanagawa, Japan.
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Kim T, Gondré-Lewis MC, Arnaoutova I, Loh YP. Dense-core secretory granule biogenesis. Physiology (Bethesda) 2006; 21:124-33. [PMID: 16565478 DOI: 10.1152/physiol.00043.2005] [Citation(s) in RCA: 141] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The dense-core secretory granule is a key organelle for secretion of hormones and neuropeptides in endocrine cells and neurons, in response to stimulation. Cholesterol and granins are critical for the assembly of these organelles at the trans-Golgi network, and their biogenesis is regulated quantitatively by posttranscriptional and posttranslational mechanisms.
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Affiliation(s)
- Taeyoon Kim
- Section on Cellular Neurobiology, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland, USA
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34
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Fujita-Yoshigaki J, Katsumata O, Matsuki M, Yoshigaki T, Furuyama S, Sugiya H. Difference in distribution of membrane proteins between low- and high-density secretory granules in parotid acinar cells. Biochem Biophys Res Commun 2006; 344:283-92. [PMID: 16630574 DOI: 10.1016/j.bbrc.2006.03.130] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2006] [Accepted: 03/17/2006] [Indexed: 10/24/2022]
Abstract
Secretory granules (SGs) are considered to be generated as immature granules and to mature by condensation of their contents. In this study, SGs of parotid gland were separated into low-, medium-, and high-density granule fractions by Percoll-density gradient centrifugation, since it was proposed that the density corresponds to the degree of maturation. The observation with electron microscopy showed that granules in the three fractions were very similar. The average diameter of high-density granules was a little but significantly larger than that of low-density granules. Although the three fractions contained amylase, suggesting that they are all SGs, distribution of membrane proteins was markedly different. Syntaxin6 and VAMP4 were localized in the low-density granule fraction, while VAMP2 was concentrated in the high-density granule fraction. Immunoprecipitation with anti-syntaxin6 antibody caused coprecipitation of VAMP2 from the medium-density granule fraction without solubilization, but not from Triton X-100-solubilized fraction, while VAMP4 was coprecipitated from both fractions. Therefore, VAMP2 is present on the same granules, but is separated from syntaxin6 and VAMP4, which are expected to be removed from immature granules. These results suggest that the medium-density granules are intermediates from low- to high-density granules, and that the membrane components of SGs dynamically change by budding and fusion during maturation.
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Affiliation(s)
- Junko Fujita-Yoshigaki
- Department of Physiology, Nihon University School of Dentistry at Matsudo, Matsudo, Chiba 271-8587, Japan.
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35
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Germain D, Maysinger D, Glavinovic MI. Vesicular roundness and compound release in PC-12 cells. J Neurosci Methods 2006; 153:27-42. [PMID: 16290198 DOI: 10.1016/j.jneumeth.2005.10.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2005] [Revised: 09/22/2005] [Accepted: 10/03/2005] [Indexed: 11/18/2022]
Abstract
The principal goals of this study were to establish a quantitative morphological analysis of spatial and regional properties of dense core vesicles, and to use this analysis to assess whether homotypic fusion is prominent in chronically treated PC-12 cells at elevated release levels. Simple computerized image processing of electron-micrographs provided the binary images of vesicular dense cores, whilst the artificial intelligence methods were needed to determine the vesicular membranes. As in the past, the presence of large, highly irregular vesicles, provided the morphological evidence of fused vesicles, but the irregularity of vesicular shape was assessed quantitatively-from its roundness. Free space of each vesicle was determined from the distance to its nearest-neighbor, or from the size of its Voronoi polygon. Within a Voronoi polygon, each point is closer to that vesicle than to any other vesicle. Large vesicles were not less round and did not have larger free space, as expected if they result from fusion of several smaller vesicles. In conclusion, we present a novel and rigorous morphological analysis of spatial and regional properties of dense core vesicles. The results demonstrate that the homotypic fusion is not prominent in PC-12 cells, before or following a chronic treatment that enhances release.
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Affiliation(s)
- D Germain
- Department of Computer Engineering, McGill University, Montreal, Canada
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36
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Ahras M, Otto GP, Tooze SA. Synaptotagmin IV is necessary for the maturation of secretory granules in PC12 cells. ACTA ACUST UNITED AC 2006; 173:241-51. [PMID: 16618809 PMCID: PMC2063815 DOI: 10.1083/jcb.200506163] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In neuroendocrine PC12 cells, immature secretory granules (ISGs) mature through homotypic fusion and membrane remodeling. We present evidence that the ISG-localized synaptotagmin IV (Syt IV) is involved in ISG maturation. Using an in vitro homotypic fusion assay, we show that the cytoplasmic domain (CD) of Syt IV, but not of Syt I, VII, or IX, inhibits ISG homotypic fusion. Moreover, Syt IV CD binds specifically to ISGs and not to mature secretory granules (MSGs), and Syt IV binds to syntaxin 6, a SNARE protein that is involved in ISG maturation. ISG homotypic fusion was inhibited in vivo by small interfering RNA–mediated depletion of Syt IV. Furthermore, the Syt IV CD, as well as Syt IV depletion, reduces secretogranin II (SgII) processing by prohormone convertase 2 (PC2). PC2 is found mostly in the proform, suggesting that activation of PC2 is also inhibited. Granule formation, and the sorting of SgII and PC2 from the trans-Golgi network into ISGs and MSGs, however, is not affected. We conclude that Syt IV is an essential component for secretory granule maturation.
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Affiliation(s)
- Malika Ahras
- Cancer Research UK, London Research Institute, London WC2A 3PX, England, UK
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Kakhlon O, Sakya P, Larijani B, Watson R, Tooze SA. GGA function is required for maturation of neuroendocrine secretory granules. EMBO J 2006; 25:1590-602. [PMID: 16601685 PMCID: PMC1440831 DOI: 10.1038/sj.emboj.7601067] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2005] [Accepted: 03/08/2006] [Indexed: 11/08/2022] Open
Abstract
Secretory granule (SG) maturation has been proposed to involve formation of clathrin-coated vesicles (CCVs) from immature SGs (ISGs). We tested the effect of inhibiting CCV budding by using the clathrin adaptor GGA (Golgi-associated, gamma-ear-containing, ADP-ribosylation factor-binding protein) on SG maturation in neuroendocrine cells. Overexpression of a truncated, GFP-tagged GGA, VHS (Vps27, Hrs, Stam)-GAT (GGA and target of myb (TOM))-GFP led to retention of MPR, VAMP4, and syntaxin 6 in mature SGs (MSGs), suggesting that CCV budding from ISGs is inhibited by the SG-localizing VHS-GAT-GFP. Furthermore, VHS-GAT-GFP-overexpression disrupts prohormone convertase 2 (PC2) autocatalytic cleavage, processing of secretogranin II to its product p18, and the correlation between PC2 and p18 levels. All these effects were not observed if full-length GGA1-GFP was overexpressed. Neither GGA1-GFP nor VHS-GAT-GFP perturbed SG protein budding from the TGN, or homotypic fusion of ISGs. Reducing GGA3 levels by using short interfering (si)RNA also led to VAMP4 retention in SGs, and inhibition of PC2 activity. Our results suggest that inhibition of CCV budding from ISGs downregulates the sorting from the ISGs and perturbs the intragranular activity of PC2.
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Affiliation(s)
- Or Kakhlon
- Secretory Pathway Laboratories, Cancer Research UK, London Research Institute, London, UK
| | - Prabhat Sakya
- Cell Biophysics, Cancer Research UK, London Research Institute, London, UK
| | - Banafshe Larijani
- Cell Biophysics, Cancer Research UK, London Research Institute, London, UK
| | - Rose Watson
- Electron Microscopy Laboratories, Cancer Research UK, London Research Institute, London, UK
| | - Sharon A Tooze
- Secretory Pathway Laboratories, Cancer Research UK, London Research Institute, London, UK
- Secretory Pathway Laboratories, Cancer Research UK, London Research Institute, 44 Lincoln's Inn Fields, London WC2A 3PX, UK. Tel.: +44 207 269 3122; Fax: +44 207 269 3417; E-mail:
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Meyer HH. Golgi reassembly after mitosis: the AAA family meets the ubiquitin family. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2005; 1744:108-19. [PMID: 15878210 DOI: 10.1016/j.bbamcr.2005.03.011] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2004] [Revised: 03/22/2005] [Accepted: 03/23/2005] [Indexed: 11/30/2022]
Abstract
The Golgi apparatus in animal cells breaks down at the onset of mitosis and is later rebuilt in the two daughter cells. Two AAA ATPases, NSF and p97/VCP, have been implicated in regulating membrane fusion steps that lead to regrowth of Golgi cisternae from mitotic fragments. NSF dissociates complexes of SNARE proteins, thereby reactivating them to mediate membrane fusion. However, NSF has a second function in regulating SNARE pairing together with the ubiquitin-like protein GATE-16. p97/VCP, on the other hand, is involved in a cycle of ubiquitination and deubiquitination of an unknown target that governs Golgi membrane dynamics. Here, these findings are reviewed and discussed in the context of the increasingly evident role of ubiquitin in membrane traffic processes.
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Affiliation(s)
- Hemmo H Meyer
- Swiss Federal School of Technology (ETH), Institute of Biochemistry, ETH Honggerberg HPM, Zurich.
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39
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Kebir S, Aristizabal F, Maysinger D, Glavinović MI. Rapid change of quantal size in PC-12 cells detected by neural networks. J Neurosci Methods 2005; 142:231-42. [PMID: 15698663 DOI: 10.1016/j.jneumeth.2004.08.014] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2004] [Revised: 08/12/2004] [Accepted: 08/19/2004] [Indexed: 11/17/2022]
Abstract
The basic building block of synaptic transmission-the number of molecules released per vesicle (quantal size (QS)) often changes with stimulation, but there is no agreement about what factors regulate it. To throw more light on this problem spontaneous quantal release was recorded amperometrically in PC-12 cells. Amperometric current spikes, representing single vesicle release, were detected by thresholding and were separated from spurious events on the basis of their amplitude and time course using a pattern recognition system based on the principal component neural network methods. The frequency of current spikes, their amplitude, quantal size, rise time and decay time were typically non-stationary, even in the absence of stimulation. Their running values changed much more than those of memoryless stationary random data with the same probability density distribution. Irrespective of how much the quantal size, rise and decay times varied, their amplitude dependence remained constant, or changed with a very different time course. In conclusion, the quantal size is highly labile in PC-12 cells. The lability does not appear to result from the changes of fusion pore dynamics or the mechanism of release of vesicular content, but because of the preferential release of large vesicles.
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Affiliation(s)
- S Kebir
- Department of Physiology, McGill University, Montreal, Canada
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40
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Abstract
Biogenesis of the regulated secretory pathway in the pancreatic beta-cell involves packaging of products, notably proinsulin, into immature secretory granules derived from the trans-Golgi network. Proinsulin is converted to insulin and C-peptide as granules mature. Secretory proteins not entering granules are conveyed by transport intermediates directly to the plasma membrane for constitutive secretion. One of the co-authors, Peter Arvan, has proposed that in addition, small vesicles bud from granules to traffic to the endosomal system. From there, some proteins are secreted by a (post-granular) constitutive-like pathway. He argues that retention in granules is facilitated by condensation, rendering soluble products (notably C-peptide and proinsulin) more available for constitutive-like secretion. Thus he argues that prohormone conversion is potentially important in secretory granule biogenesis. The other co-author, Philippe Halban, argues that the post-granular secretory pathway is not of physiological relevance in primary beta-cells, and contests the importance of proinsulin conversion for retention in granules. Both, however, agree that trafficking from granules to endosomes is important, purging granules of unwanted newly synthesized proteins and allowing their traffic to other destinations. In this Traffic Interchange, the two co-authors attempt to reconcile their differences, leading to a common vision of proinsulin trafficking in primary and transformed cells.
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Affiliation(s)
- Peter Arvan
- Division of Metabolism, University of Michigan Medical Center, Ann Arbor, MI 48109, USA
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41
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Meldolesi J, Chieregatti E, Luisa Malosio M. Requirements for the identification of dense-core granules. Trends Cell Biol 2004; 14:13-9. [PMID: 14729176 DOI: 10.1016/j.tcb.2003.11.006] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Dense-core granules (DCGs), cytoplasmic organelles competent for regulated exocytosis, show considerable heterogeneity depending upon the specificity of their expressing cells--primarily neurons and neurosecretory cells. DCGs have been mainly identified by detecting their cargo molecules, often members of the granin family, and using conventional electron microscopy and immunocytochemistry. However, by a critical analysis of the various stages of DCG "life" within neurosecretory cells, we have highlighted several specific molecular and functional properties that are common to all these organelles. We propose that these properties be considered as strict requirements for the identification of DCGs.
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Affiliation(s)
- Jacopo Meldolesi
- Vita-Salute San Raffaele University and Scientific Institute San Raffaele, Department of Neuroscience and Immunology, Centre of Excellence in Physiopathology of Cell Differentiation, via Olgettina 58, 20132 Milan, Italy.
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Wang Q, Song C, Li CCH. Molecular perspectives on p97–VCP: progress in understanding its structure and diverse biological functions. J Struct Biol 2004; 146:44-57. [PMID: 15037236 DOI: 10.1016/j.jsb.2003.11.014] [Citation(s) in RCA: 248] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2003] [Revised: 10/22/2003] [Indexed: 12/22/2022]
Abstract
The 97-kDa valosin-containing protein (p97 or VCP) is a type-II AAA ( ATPases associated with a variety of activities) ATPases, which are characterized by possessing two conserved ATPase domains. VCP forms a stable homo-hexameric structure, and this two-tier ring-shaped complex acts as a molecular chaperone that mediates many seemingly unrelated cellular activities. The involvement of VCP in the ubiquitin-proteasome degradation pathway and the identification of VCP cofactors provided us important clues to the understanding of how this molecular chaperone works. In this review, we summarize the reported biological functions of VCP and explore the molecular mechanisms underlying the diverse cellular functions. We discuss the structural and biochemical studies, and elucidate how this sophisticated enzymatic machine converts chemical energy into the mechanical forces required for the chaperone activity.
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Affiliation(s)
- Qing Wang
- Basic Research Laboratory, National Cancer Institute at Frederick, Frederick, MD 21702, USA
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Kuliawat R, Kalinina E, Bock J, Fricker L, McGraw TE, Kim SR, Zhong J, Scheller R, Arvan P. Syntaxin-6 SNARE involvement in secretory and endocytic pathways of cultured pancreatic beta-cells. Mol Biol Cell 2004; 15:1690-701. [PMID: 14742717 PMCID: PMC379267 DOI: 10.1091/mbc.e03-08-0554] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2003] [Revised: 12/01/2003] [Accepted: 01/06/2004] [Indexed: 01/16/2023] Open
Abstract
In pancreatic beta-cells, the syntaxin 6 (Syn6) soluble N-ethylmaleimide-sensitive factor attachment protein receptor is distributed in the trans-Golgi network (TGN) (with spillover into immature secretory granules) and endosomes. A possible Syn6 requirement has been suggested in secretory granule biogenesis, but the role of Syn6 in live regulated secretory cells remains unexplored. We have created an ecdysone-inducible gene expression system in the INS-1 beta-cell line and find that induced expression of a membrane-anchorless, cytosolic Syn6 (called Syn6t), but not full-length Syn6, causes a prominent defect in endosomal delivery to lysosomes, and the TGN, in these cells. The defect occurs downstream of the endosomal branchpoint involved in transferrin recycling, and upstream of the steady-state distribution of mannose 6-phosphate receptors. By contrast, neither acquisition of stimulus competence nor the ultimate size of beta-granules is affected. Biosynthetic effects of dominant-interfering Syn6 seem limited to slowed intragranular processing to insulin (achieving normal levels within 2 h) and minor perturbation of sorting of newly synthesized lysosomal proenzymes. We conclude that expression of the Syn6t mutant slows a rate-limiting step in endosomal maturation but provides only modest and potentially indirect interference with regulated and constitutive secretory pathways, and in TGN sorting of lysosomal enzymes.
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Affiliation(s)
- Regina Kuliawat
- Division of Endocrinology and Department of Developmental/Molecular Biology, Albert Einstein College of Medicine, Bronx, New York 10461, USA
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Martin TF, Grishanin RN. PC12 cells as a model for studies of regulated secretion in neuronal and endocrine cells. Methods Cell Biol 2004; 71:267-86. [PMID: 12884694 DOI: 10.1016/s0091-679x(03)01012-4] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Pheochromocytoma-derived cell lines such as PC12 cells maintain a differentiated neuroendocrine phenotype and have been widely used as a convenient model system for a wide variety of cell biological studies on neurotrophin action, monoamine biogenesis, protein trafficking, and secretory vesicle dynamics. This chapter reviews a number of methods that are useful for studies of the regulated dense core vesicle secretory pathway. This includes protocols for maintaining cells and preserving their phenotype. A variety of assays are discussed for monitoring secretion in intact or permeable cells and in transfected cells. Specific methods for immunocytochemical studies in permeable cells are discussed. Finally, protocols for high-efficiency PC12 cell transfections and the isolation of stably transfected cell lines are provided.
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Affiliation(s)
- T F Martin
- Department of Biochemistry, University of Wisconsin, Madison, Wisconsin 53706, USA
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45
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Arvan P. Secretory protein trafficking. Cell Biochem Biophys 2004. [DOI: 10.1007/bf02739021] [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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46
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Feng L, Arvan P. The trafficking of alpha 1-antitrypsin, a post-Golgi secretory pathway marker, in INS-1 pancreatic beta cells. J Biol Chem 2003; 278:31486-94. [PMID: 12796484 DOI: 10.1074/jbc.m305690200] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A sulfated alpha1-antitrypsin (AAT), thought to be a default secretory pathway marker, is not stored in secretory granules when expressed in neuroendocrine PC12 cells. In search of a constitutive secretory pathway marker for pancreatic beta cells, we produced INS-1 cells stably expressing wild-type AAT. Because newly synthesized AAT arrives very rapidly in the Golgi complex, kinetics alone cannot resolve AAT release via distinct secretory pathways, although most AAT is secreted within a few hours and virtually none is stored in mature granules. Nevertheless, from pulse-chase analyses, a major fraction of newly synthesized AAT transiently exhibits secretogogue-stimulated exocytosis and localizes within immature secretory granules (ISGs). This trafficking occurs without detectable AAT polymerization or binding to lipid rafts. Remarkably, in a manner not requiring its glycans, all of the newly synthesized AAT is then removed from granules during their maturation, leading mostly to constitutive-like AAT secretion, whereas a smaller fraction (approximately 10%) goes on to lysosomes. Secretogogue-stimulated ISG exocytosis reroutes newly synthesized AAT directly into the medium and prevents its arrival in lysosomes. These data are most consistent with the idea that soluble AAT abundantly enters ISGs and then is efficiently relocated to the endosomal system, from which many molecules undergo constitutive-like secretion while a smaller fraction advances to lysosomes.
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Affiliation(s)
- Lijun Feng
- Division of Endocrinology and Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, Bronx, New York 10461, USA
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47
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Perera HKI, Clarke M, Morris NJ, Hong W, Chamberlain LH, Gould GW. Syntaxin 6 regulates Glut4 trafficking in 3T3-L1 adipocytes. Mol Biol Cell 2003; 14:2946-58. [PMID: 12857877 PMCID: PMC165689 DOI: 10.1091/mbc.e02-11-0722] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2002] [Revised: 02/19/2003] [Accepted: 03/10/2003] [Indexed: 11/11/2022] Open
Abstract
Insulin stimulates the movement of glucose transporter-4 (Glut4)-containing vesicles to the plasma membrane of adipose cells. We investigated the role of post-Golgi t-soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) in the trafficking of Glut4 in 3T3-L1 adipocytes. Greater than 85% of syntaxin 6 was found in Glut4-containing vesicles, and this t-SNARE exhibited insulin-stimulated movement to the plasma membrane. In contrast, the colocalization of Glut4 with syntaxin 7, 8, or 12/13 was limited and these molecules did not translocate to the plasma membrane. We used adenovirus to overexpress the cytosolic domain of these syntaxin's and studied their effects on Glut4 traffic. Overexpression of the cytosolic domain of syntaxin 6 did not affect insulin-stimulated glucose transport, but increased basal deGlc transport and cell surface Glut4 levels. Moreover, the syntaxin 6 cytosolic domain significantly reduced the rate of Glut4 reinternalization after insulin withdrawal and perturbed subendosomal Glut4 sorting; the corresponding domains of syntaxins 8 and 12 were without effect. Our data suggest that syntaxin 6 is involved in a membrane-trafficking step that sequesters Glut4 away from traffic destined for the plasma membrane. We speculate that this is at the level of traffic of Glut4 into its unique storage compartment and that syntaxin 16 may be involved.
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Affiliation(s)
- H Kumudu I Perera
- The Henry Wellcome Laboratory of Cell Biology, Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, Scotland, United Kingdom
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48
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Abstract
Regulated exocytosis of secretory granules or dense-core granules has been examined in many well-characterized cell types including neurons, neuroendocrine, endocrine, exocrine, and hemopoietic cells and also in other less well-studied cell types. Secretory granule exocytosis occurs through mechanisms with many aspects in common with synaptic vesicle exocytosis and most likely uses the same basic protein components. Despite the widespread expression and conservation of a core exocytotic machinery, many variations occur in the control of secretory granule exocytosis that are related to the specialized physiological role of particular cell types. In this review we describe the wide range of cell types in which regulated secretory granule exocytosis occurs and assess the evidence for the expression of the conserved fusion machinery in these cells. The signals that trigger and regulate exocytosis are reviewed. Aspects of the control of exocytosis that are specific for secretory granules compared with synaptic vesicles or for particular cell types are described and compared to define the range of accessory control mechanisms that exert their effects on the core exocytotic machinery.
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Affiliation(s)
- Robert D Burgoyne
- The Physiological Laboratory, University of Liverpool, United Kingdom.
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49
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Ficarro S, Chertihin O, Westbrook VA, White F, Jayes F, Kalab P, Marto JA, Shabanowitz J, Herr JC, Hunt DF, Visconti PE. Phosphoproteome analysis of capacitated human sperm. Evidence of tyrosine phosphorylation of a kinase-anchoring protein 3 and valosin-containing protein/p97 during capacitation. J Biol Chem 2003; 278:11579-89. [PMID: 12509440 DOI: 10.1074/jbc.m202325200] [Citation(s) in RCA: 394] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Before fertilization can occur, mammalian sperm must undergo capacitation, a process that requires a cyclic AMP-dependent increase in tyrosine phosphorylation. To identify proteins phosphorylated during capacitation, two-dimensional gel analysis coupled to anti-phosphotyrosine immunoblots and tandem mass spectrometry (MS/MS) was performed. Among the protein targets, valosin-containing protein (VCP), a homolog of the SNARE-interacting protein NSF, and two members of the A kinase-anchoring protein (AKAP) family were found to be tyrosine phosphorylated during capacitation. In addition, immobilized metal affinity chromatography was used to investigate phosphorylation sites in whole protein digests from capacitated human sperm. To increase this chromatographic selectivity for phosphopeptides, acidic residues in peptide digests were converted to their respective methyl esters before affinity chromatography. More than 60 phosphorylated sequences were then mapped by MS/MS, including precise sites of tyrosine and serine phosphorylation of the sperm tail proteins AKAP-3 and AKAP-4. Moreover, differential isotopic labeling was developed to quantify phosphorylation changes occurring during capacitation. The phosphopeptide enrichment and quantification methodology coupled to MS/MS, described here for the first time, can be employed to map and compare phosphorylation sites involved in multiple cellular processes. Although we were unable to determine the exact site of phosphorylation of VCP, we did confirm, using a cross-immunoprecipitation approach, that this protein is tyrosine phosphorylated during capacitation. Immunolocalization of VCP showed fluorescent staining in the neck of noncapacitated sperm. However, after capacitation, staining in the neck decreased, and most of the sperm showed fluorescent staining in the anterior head.
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Affiliation(s)
- Scott Ficarro
- Department of Chmeistry, University of Virginia, Charlottesville, Virginia 22908, USA
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Ramalho-Santos J, Schatten G, Moreno RD. Control of membrane fusion during spermiogenesis and the acrosome reaction. Biol Reprod 2003; 67:1043-51. [PMID: 12297516 DOI: 10.1095/biolreprod67.4.1043] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
Membrane fusion is important to reproduction because it occurs in several steps during the process of fertilization. Many events of intracellular trafficking occur during both spermiogenesis and oogenesis. The acrosome reaction, a key feature during mammalian fertilization, is a secretory event involving the specific fusion of the outer acrosomal membrane and the sperm plasma membrane overlaying the principal piece of the acrosome. Once the sperm has crossed the zona pellucida, the gametes fuse, but in the case of the sperm this process takes place through a specific membrane domain in the head, the equatorial segment. The cortical reaction, a process that prevents polyspermy, involves the exocytosis of the cortical granules to the extracellular milieu. In lower vertebrates, the formation of the zygotic nucleus involves the fusion (syngamia) of the male pronucleus with the female pronucleus. Other undiscovered membrane trafficking processes may also be relevant for the formation of the zygotic centrosome or other zygotic structures. In this review, we focus on the recent discovery of molecular machinery components involved in intracellular trafficking during mammalian spermiogenesis, notably related to acrosome biogenesis. We also extend our discussion to the molecular mechanism of membrane fusion during the acrosome reaction. The data available so far suggest that proteins participating in the intracellular trafficking events leading to the formation of the acrosome during mammalian spermiogenesis are also involved in controlling the acrosome reaction during fertilization.
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Affiliation(s)
- João Ramalho-Santos
- Unit of Reproduction and Development, Physiology Department, Pontifical Catholic University of Chile, 340-213 Santiago, Chile
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