1
|
Campelo F, Tian M, von Blume J. Rediscovering the intricacies of secretory granule biogenesis. Curr Opin Cell Biol 2023; 85:102231. [PMID: 37657367 DOI: 10.1016/j.ceb.2023.102231] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2023] [Revised: 08/01/2023] [Accepted: 08/07/2023] [Indexed: 09/03/2023]
Abstract
Regulated secretion, an essential cellular process, relies on secretory granules (SGs) for the controlled release of a diverse range of cargo molecules, including proteins, peptides, hormones, enzymes, and neurotransmitters. SG biogenesis encompasses cargo selection, sorting, packaging, and trafficking, with the trans-Golgi Network (TGN) playing a central role. Research in the last three decades has revealed significant components required for SG biogenesis; however, no cargo receptor transferring granule cargo from the TGN to immature SGs (ISGs) has yet been identified. Consequently, recent research has devoted significant attention to studying receptor-independent cargo sorting mechanisms, shedding new light on the complexities of regulated secretion. Understanding the underlying molecular and biophysical mechanisms behind cargo sorting into ISGs holds great promise for advancing our knowledge of cellular communication and disease mechanisms.
Collapse
Affiliation(s)
- Felix Campelo
- ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, 08860, Castelldefels, Barcelona, Spain
| | - Meng Tian
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA
| | - Julia von Blume
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA.
| |
Collapse
|
2
|
Loh YP, Xiao L, Park JJ. Trafficking of hormones and trophic factors to secretory and extracellular vesicles: a historical perspective and new hypothesis. EXTRACELLULAR VESICLES AND CIRCULATING NUCLEIC ACIDS 2023; 4:568-587. [PMID: 38435713 PMCID: PMC10906782 DOI: 10.20517/evcna.2023.34] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 03/05/2024]
Abstract
It is well known that peptide hormones and neurotrophic factors are intercellular messengers that are packaged into secretory vesicles in endocrine cells and neurons and released by exocytosis upon the stimulation of the cells in a calcium-dependent manner. These secreted molecules bind to membrane receptors, which then activate signal transduction pathways to mediate various endocrine/trophic functions. Recently, there is evidence that these molecules are also in extracellular vesicles, including small extracellular vesicles (sEVs), which appear to be taken up by recipient cells. This finding raised the hypothesis that they may have functions differentiated from their classical secretory hormone/neurotrophic factor actions. In this article, the historical perspective and updated mechanisms for the sorting and packaging of hormones and neurotrophic factors into secretory vesicles and their transport in these organelles for release at the plasma membrane are reviewed. In contrast, little is known about the packaging of hormones and neurotrophic factors into extracellular vesicles. One proposal is that these molecules could be sorted at the trans-Golgi network, which then buds to form Golgi-derived vesicles that can fuse to endosomes and subsequently form intraluminal vesicles. They are then taken up by multivesicular bodies to form extracellular vesicles, which are subsequently released. Other possible mechanisms for packaging RSP proteins into sEVs are discussed. We highlight some studies in the literature that suggest the dual vesicular pathways for the release of hormones and neurotrophic factors from the cell may have some physiological significance in intercellular communication.
Collapse
Affiliation(s)
- Y. Peng Loh
- Section on Cellular Neurobiology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Lan Xiao
- Section on Cellular Neurobiology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Joshua J. Park
- Scientific Review Branch, National Institute on Aging, National Institutes of Health, Bethesda, MD 20892, USA
| |
Collapse
|
3
|
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.
Collapse
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
| |
Collapse
|
4
|
Parchure A, Tian M, Stalder D, Boyer CK, Bearrows SC, Rohli KE, Zhang J, Rivera-Molina F, Ramazanov BR, Mahata SK, Wang Y, Stephens SB, Gershlick DC, von Blume J. Liquid-liquid phase separation facilitates the biogenesis of secretory storage granules. J Cell Biol 2022; 221:e202206132. [PMID: 36173346 PMCID: PMC9526250 DOI: 10.1083/jcb.202206132] [Citation(s) in RCA: 21] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2022] [Revised: 08/30/2022] [Accepted: 09/01/2022] [Indexed: 02/03/2023] Open
Abstract
Insulin is synthesized by pancreatic β-cells and stored into secretory granules (SGs). SGs fuse with the plasma membrane in response to a stimulus and deliver insulin to the bloodstream. The mechanism of how proinsulin and its processing enzymes are sorted and targeted from the trans-Golgi network (TGN) to SGs remains mysterious. No cargo receptor for proinsulin has been identified. Here, we show that chromogranin (CG) proteins undergo liquid-liquid phase separation (LLPS) at a mildly acidic pH in the lumen of the TGN, and recruit clients like proinsulin to the condensates. Client selectivity is sequence-independent but based on the concentration of the client molecules in the TGN. We propose that the TGN provides the milieu for converting CGs into a "cargo sponge" leading to partitioning of client molecules, thus facilitating receptor-independent client sorting. These findings provide a new receptor-independent sorting model in β-cells and many other cell types and therefore represent an innovation in the field of membrane trafficking.
Collapse
Affiliation(s)
- Anup Parchure
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT
| | - Meng Tian
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT
| | - Danièle Stalder
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge, UK
| | - Cierra K. Boyer
- Departments of Pharmacology and Neuroscience, Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, IA
- Internal Medicine, Division of Endocrinology and Metabolism, University of Iowa, Iowa City, IA
| | - Shelby C. Bearrows
- Departments of Pharmacology and Neuroscience, Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, IA
- Internal Medicine, Division of Endocrinology and Metabolism, University of Iowa, Iowa City, IA
| | - Kristen E. Rohli
- Departments of Pharmacology and Neuroscience, Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, IA
- Internal Medicine, Division of Endocrinology and Metabolism, University of Iowa, Iowa City, IA
| | - Jianchao Zhang
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, MI
- Department of Neurology, University of Michigan School of Medicine, Ann Arbor, MI
| | - Felix Rivera-Molina
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT
| | - Bulat R. Ramazanov
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT
| | - Sushil K. Mahata
- Department of Medicine, University of California San Diego, La Jolla, CA
- VA San Diego Healthcare System, San Diego, CA
| | - Yanzhuang Wang
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, MI
- Department of Neurology, University of Michigan School of Medicine, Ann Arbor, MI
| | - Samuel B. Stephens
- Departments of Pharmacology and Neuroscience, Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, IA
| | - David C. Gershlick
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge, UK
| | - Julia von Blume
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT
| |
Collapse
|
5
|
Xu H, Chang F, Jain S, Heller BA, Han X, Liu Y, Edwards RH. SNX5 targets a monoamine transporter to the TGN for assembly into dense core vesicles by AP-3. J Cell Biol 2022; 221:e202106083. [PMID: 35426896 PMCID: PMC9016777 DOI: 10.1083/jcb.202106083] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2021] [Revised: 12/06/2021] [Accepted: 02/16/2022] [Indexed: 11/22/2022] Open
Abstract
The time course of signaling by peptide hormones, neural peptides, and other neuromodulators depends on their storage inside dense core vesicles (DCVs). Adaptor protein 3 (AP-3) assembles the membrane proteins that confer regulated release of DCVs and is thought to promote their trafficking from endosomes directly to maturing DCVs. We now find that regulated monoamine release from DCVs requires sorting nexin 5 (SNX5). Loss of SNX5 disrupts trafficking of the vesicular monoamine transporter (VMAT) to DCVs. The mechanism involves a role for SNX5 in retrograde transport of VMAT from endosomes to the TGN. However, this role for SNX5 conflicts with the proposed function of AP-3 in trafficking from endosomes directly to DCVs. We now identify a transient role for AP-3 at the TGN, where it associates with DCV cargo. Thus, retrograde transport from endosomes by SNX5 enables DCV assembly at the TGN by AP-3, resolving the apparent antagonism. A novel role for AP-3 at the TGN has implications for other organelles that also depend on this adaptor.
Collapse
Affiliation(s)
- Hongfei Xu
- Departments of Neurology and Physiology, University of California San Francisco, San Francisco, CA
- Jiangsu Key Laboratory of Xenotransplantation, School of Basic Medical Science, Nanjing Medical University, Nanjing, China
| | - Fei Chang
- Jiangsu Key Laboratory of Xenotransplantation, School of Basic Medical Science, Nanjing Medical University, Nanjing, China
| | - Shweta Jain
- Departments of Neurology and Physiology, University of California San Francisco, San Francisco, CA
| | - Bradley Austin Heller
- Departments of Neurology and Physiology, University of California San Francisco, San Francisco, CA
| | - Xu Han
- Jiangsu Key Laboratory of Xenotransplantation, School of Basic Medical Science, Nanjing Medical University, Nanjing, China
| | - Yongjian Liu
- Jiangsu Key Laboratory of Xenotransplantation, School of Basic Medical Science, Nanjing Medical University, Nanjing, China
- Departments of Pharmacology and Biological Chemistry, University of Pittsburgh, Pittsburgh, PA
| | - Robert H. Edwards
- Departments of Neurology and Physiology, University of California San Francisco, San Francisco, CA
| |
Collapse
|
6
|
Isolation and Proteomics of the Insulin Secretory Granule. Metabolites 2021; 11:metabo11050288. [PMID: 33946444 PMCID: PMC8147143 DOI: 10.3390/metabo11050288] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2021] [Revised: 04/28/2021] [Accepted: 04/28/2021] [Indexed: 12/21/2022] Open
Abstract
Insulin, a vital hormone for glucose homeostasis is produced by pancreatic beta-cells and when secreted, stimulates the uptake and storage of glucose from the blood. In the pancreas, insulin is stored in vesicles termed insulin secretory granules (ISGs). In Type 2 diabetes (T2D), defects in insulin action results in peripheral insulin resistance and beta-cell compensation, ultimately leading to dysfunctional ISG production and secretion. ISGs are functionally dynamic and many proteins present either on the membrane or in the lumen of the ISG may modulate and affect different stages of ISG trafficking and secretion. Previously, studies have identified few ISG proteins and more recently, proteomics analyses of purified ISGs have uncovered potential novel ISG proteins. This review summarizes the proteins identified in the current ISG proteomes from rat insulinoma INS-1 and INS-1E cell lines. Here, we also discuss techniques of ISG isolation and purification, its challenges and potential future directions.
Collapse
|
7
|
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.
Collapse
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.
| |
Collapse
|
8
|
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.
Collapse
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
| |
Collapse
|
9
|
Dembla E, Becherer U. Biogenesis of large dense core vesicles in mouse chromaffin cells. Traffic 2021; 22:78-93. [PMID: 33369005 DOI: 10.1111/tra.12783] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2020] [Revised: 12/21/2020] [Accepted: 12/21/2020] [Indexed: 12/14/2022]
Abstract
Large dense core vesicle (LDCVs) biogenesis in neuroendocrine cells involves: (a) production of cargo peptides processed in the Golgi; (b) fission of cargo loaded LDCVs undergoing maturation steps; (c) movement of these LDCVs to the plasma membrane. These steps have been resolved over several decades in PC12 cells and in bovine chromaffin cells. More recently, the molecular machinery involved in LDCV biogenesis has been examined using genetically modified mice, generating contradictory results. To address these contradictions, we have used NPY-mCherry electroporation combined with immunolabeling and super-resolution structured illumination microscopy. We show that LDCVs separate from an intermediate Golgi compartment, mature in its proximity for about 1 hour and then travel to the plasma membrane. The exocytotic machinery composed of vSNAREs and synaptotagmin1, which originate from either de novo synthesis or recycling, is most likely acquired via fusion with precursor vesicles during maturation. Finally, recycling of LDCV membrane protein is achieved in less than 2 hours. With this comprehensive scheme of LDCV biogenesis we have established a framework for future studies in mouse chromaffin cells.
Collapse
Affiliation(s)
- Ekta Dembla
- Cellular Neurophysiology, CIPMM, Saarland University, Homburg, Germany
| | - Ute Becherer
- Cellular Neurophysiology, CIPMM, Saarland University, Homburg, Germany
| |
Collapse
|
10
|
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] [Key Words] [MESH Headings] [Grants] [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.
Collapse
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.
| |
Collapse
|
11
|
Deng Y, Pakdel M, Blank B, Sundberg EL, Burd CG, von Blume J. Activity of the SPCA1 Calcium Pump Couples Sphingomyelin Synthesis to Sorting of Secretory Proteins in the Trans-Golgi Network. Dev Cell 2018; 47:464-478.e8. [PMID: 30393074 PMCID: PMC6261503 DOI: 10.1016/j.devcel.2018.10.012] [Citation(s) in RCA: 50] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2018] [Revised: 08/29/2018] [Accepted: 10/05/2018] [Indexed: 12/24/2022]
Abstract
How the principal functions of the Golgi apparatus-protein processing, lipid synthesis, and sorting of macromolecules-are integrated to constitute cargo-specific trafficking pathways originating from the trans-Golgi network (TGN) is unknown. Here, we show that the activity of the Golgi localized SPCA1 calcium pump couples sorting and export of secreted proteins to synthesis of new lipid in the TGN membrane. A secreted Ca2+-binding protein, Cab45, constitutes the core component of a Ca2+-dependent, oligomerization-driven sorting mechanism whereby secreted proteins bound to Cab45 are packaged into a TGN-derived vesicular carrier whose membrane is enriched in sphingomyelin, a lipid implicated in TGN-to-cell surface transport. SPCA1 activity is controlled by the sphingomyelin content of the TGN membrane, such that local sphingomyelin synthesis promotes Ca2+ flux into the lumen of the TGN, which drives secretory protein sorting and export, thereby establishing a protein- and lipid-specific secretion pathway.
Collapse
Affiliation(s)
- Yongqiang Deng
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA
| | - Mehrshad Pakdel
- Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany
| | - Birgit Blank
- Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany
| | - Emma L Sundberg
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA
| | - Christopher G Burd
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA.
| | - Julia von Blume
- Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany.
| |
Collapse
|
12
|
Li M, Du W, Zhou M, Zheng L, Song E, Hou J. Proteomic analysis of insulin secretory granules in INS-1 cells by protein correlation profiling. BIOPHYSICS REPORTS 2018; 4:329-338. [PMID: 30596141 PMCID: PMC6276070 DOI: 10.1007/s41048-018-0061-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2018] [Accepted: 07/08/2018] [Indexed: 11/30/2022] Open
Abstract
Abstract Insulin secretory granules (ISGs), a group of distinguishing organelles in pancreatic β cells, are responsible for the storage and secretion of insulin to maintain blood glucose homeostasis. The molecular mechanisms of ISG biogenesis, maturation, transportation, and exocytosis are still largely unknown because the proteins involved in these distinct steps have not been fully identified. Subcellular fractionation by density gradient centrifugation has been successfully employed to analyze the proteomes of numerous organelles. However, use of this method to elucidate the ISG proteome is limited by co-fractionated contaminants because ISGs are very dynamic and have abundant exchanges or contacts with other organelles, such as the Golgi apparatus, lysosomes, and endosomes. In this study, we developed a new strategy for identifying ISG proteins by protein correlation profiling (PCP)-based proteomics, which included ISG purification by OptiPrep density gradient centrifugation, label-free quantitative proteome, and identification of ISG proteins by correlating fractionation profiles between candidates and known ISG markers. Using this approach, we were able to identify 81 ISG proteins. Among them, TM9SF3, a nine-transmembrane protein, was considered a high confidence ISG candidate protein highlighted in the PCP network. Further biochemical and immunofluorescence assays indicated that TM9SF3 localized in ISGs, suggesting that it is a potential new ISG marker. Graphical abstract ![]()
Electronic supplementary material The online version of this article (10.1007/s41048-018-0061-3) contains supplementary material, which is available to authorized users.
Collapse
Affiliation(s)
- Min Li
- 1National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101 China.,2College of Life Sciences, University of Chinese Academy of Sciences, Beijing, 100049 China
| | - Wen Du
- 1National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101 China
| | - Maoge Zhou
- 1National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101 China
| | - Li Zheng
- 1National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101 China
| | - Eli Song
- 1National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101 China
| | - Junjie Hou
- 1National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101 China
| |
Collapse
|
13
|
Merighi A. Costorage of High Molecular Weight Neurotransmitters in Large Dense Core Vesicles of Mammalian Neurons. Front Cell Neurosci 2018; 12:272. [PMID: 30186121 PMCID: PMC6110924 DOI: 10.3389/fncel.2018.00272] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2018] [Accepted: 08/03/2018] [Indexed: 12/19/2022] Open
Abstract
It is today widely accepted that several types of high molecular weight (MW) neurotransmitters produced by neurons are synthesized at the cell body, selectively stored within large dense core vesicles (LDCVs) and anterogradely transported to terminals where they elicit their biological role(s). Among these molecules there are neuropeptides and neurotrophic factors, the main focus of this perspective article. I here first provide a brief resume of the state of art on neuronal secretion, with primary emphasis on the molecular composition and mechanism(s) of filling and release of LDCVs. Then, I discuss the perspectives and future directions of research in the field as regarding the synthesis and storage of multiple high MW transmitters in LDCVs and the possibility that a selective sorting of LDCVs occurs along different neuronal processes and/or their branches. I also consider the ongoing discussion that diverse types of neurons may contain LDCVs with different sets of integral proteins or dial in a different fashion with LDCVs containing the same cargo. In addition, I provide original data on the size of LDCVs in rat dorsal root ganglion neurons and their central terminals in the spinal cord after immunogold labeling for calcitonin gene-related peptide (CGRP), neuropeptide K, substance P, neurokinin A or somatostatin. These data corroborate the idea that, similarly to endocrine cells, LDCVs undergo a process of maturation which involves a homotypic fusion followed by a reduction in size and condensation of cargo. They also give support to the conjecture that release at terminals occurs by cavicapture, a process of partial fusion of the vesicle with the axolemma, accompanied by depletion of cargo and diminution of size.
Collapse
Affiliation(s)
- Adalberto Merighi
- Laboratory of Neurobiology, Department of Veterinary Sciences, University of Turin, Turin, Italy
| |
Collapse
|
14
|
Kowalska M, Rupik W. Ultrastructure of endocrine pancreatic granules during pancreatic differentiation in the grass snake, Natrix natrix L. (Lepidosauria, Serpentes). J Morphol 2017; 279:330-348. [PMID: 29148072 DOI: 10.1002/jmor.20775] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2017] [Revised: 10/30/2017] [Accepted: 11/01/2017] [Indexed: 01/12/2023]
Abstract
We used transmission electron microscopy to study the pancreatic main endocrine cell types in the embryos of the grass snake Natrix natrix L. with focus on the morphology of their secretory granules. The embryonic endocrine part of the pancreas in the grass snake contains four main types of cells (A, B, D, and PP), which is similar to other vertebrates. The B granules contained a moderately electron-dense crystalline-like core that was polygonal in shape and an electron-dense outer zone. The A granules had a spherical electron-dense eccentrically located core and a moderately electron-dense outer zone. The D granules were filled with a moderately electron-dense non-homogeneous content. The PP granules had a spherical electron-dense core with an electron translucent outer zone. Within the main types of granules (A, B, D, PP), different morphological subtypes were recognized that indicated their maturity, which may be related to the different content of these granules during the process of maturation. The sequence of pancreatic endocrine cell differentiation in grass snake embryos differs from that in many vertebrates. In the grass snake embryos, the B and D cells differentiated earlier than A and PP cells. The different sequence of endocrine cell differentiation in snakes and other vertebrates has been related to phylogenetic position and nutrition during early developmental stages.
Collapse
Affiliation(s)
- Magdalena Kowalska
- Department of Animal Histology and Embryology, University of Silesia, 9 Bankowa St, Katowice, 40-007, Poland
| | - Weronika Rupik
- Department of Animal Histology and Embryology, University of Silesia, 9 Bankowa St, Katowice, 40-007, Poland
| |
Collapse
|
15
|
Hummer BH, de Leeuw NF, Burns C, Chen L, Joens MS, Hosford B, Fitzpatrick JAJ, Asensio CS. HID-1 controls formation of large dense core vesicles by influencing cargo sorting and trans-Golgi network acidification. Mol Biol Cell 2017; 28:3870-3880. [PMID: 29074564 PMCID: PMC5739301 DOI: 10.1091/mbc.e17-08-0491] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2017] [Revised: 10/05/2017] [Accepted: 10/16/2017] [Indexed: 12/19/2022] Open
Abstract
The peripheral membrane protein HID-1 localizes to the trans-Golgi network, where it contributes to the formation of large dense core vesicles of neuroendocrine cells by influencing cargo sorting and trans-Golgi network acidification. Large dense core vesicles (LDCVs) mediate the regulated release of neuropeptides and peptide hormones. They form at the trans-Golgi network (TGN), where their soluble content aggregates to form a dense core, but the mechanisms controlling biogenesis are still not completely understood. Recent studies have implicated the peripheral membrane protein HID-1 in neuropeptide sorting and insulin secretion. Using CRISPR/Cas9, we generated HID-1 KO rat neuroendocrine cells, and we show that the absence of HID-1 results in specific defects in peptide hormone and monoamine storage and regulated secretion. Loss of HID-1 causes a reduction in the number of LDCVs and affects their morphology and biochemical properties, due to impaired cargo sorting and dense core formation. HID-1 KO cells also exhibit defects in TGN acidification together with mislocalization of the Golgi-enriched vacuolar H+-ATPase subunit isoform a2. We propose that HID-1 influences early steps in LDCV formation by controlling dense core formation at the TGN.
Collapse
Affiliation(s)
- Blake H Hummer
- Department of Biological Sciences, University of Denver, Denver, CO 80210
| | - Noah F de Leeuw
- Department of Biological Sciences, University of Denver, Denver, CO 80210
| | - Christian Burns
- Department of Biological Sciences, University of Denver, Denver, CO 80210
| | - Lan Chen
- Department of Biological Sciences, University of Denver, Denver, CO 80210
| | - Matthew S Joens
- Washington University Center for Cellular Imaging, Washington University School of Medicine, St. Louis, MO 63110
| | - Bethany Hosford
- Department of Biological Sciences, University of Denver, Denver, CO 80210
| | - James A J Fitzpatrick
- Washington University Center for Cellular Imaging, Washington University School of Medicine, St. Louis, MO 63110
| | - Cedric S Asensio
- Department of Biological Sciences, University of Denver, Denver, CO 80210
| |
Collapse
|
16
|
Molecular regulation of insulin granule biogenesis and exocytosis. Biochem J 2017; 473:2737-56. [PMID: 27621482 DOI: 10.1042/bcj20160291] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2016] [Accepted: 04/19/2016] [Indexed: 12/15/2022]
Abstract
Type 2 diabetes mellitus (T2DM) is a metabolic disorder characterized by hyperglycemia, insulin resistance and hyperinsulinemia in early disease stages but a relative insulin insufficiency in later stages. Insulin, a peptide hormone, is produced in and secreted from pancreatic β-cells following elevated blood glucose levels. Upon its release, insulin induces the removal of excessive exogenous glucose from the bloodstream primarily by stimulating glucose uptake into insulin-dependent tissues as well as promoting hepatic glycogenesis. Given the increasing prevalence of T2DM worldwide, elucidating the underlying mechanisms and identifying the various players involved in the synthesis and exocytosis of insulin from β-cells is of utmost importance. This review summarizes our current understanding of the route insulin takes through the cell after its synthesis in the endoplasmic reticulum as well as our knowledge of the highly elaborate network that controls insulin release from the β-cell. This network harbors potential targets for anti-diabetic drugs and is regulated by signaling cascades from several endocrine systems.
Collapse
|
17
|
Zhang X, Jiang S, Mitok KA, Li L, Attie AD, Martin TFJ. BAIAP3, a C2 domain-containing Munc13 protein, controls the fate of dense-core vesicles in neuroendocrine cells. J Cell Biol 2017. [PMID: 28626000 PMCID: PMC5496627 DOI: 10.1083/jcb.201702099] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Zhang et al. conducted a siRNA screen of C2 domain proteins involved in regulated peptide secretion. One of the hits, a Munc13 family member BAIAP3, was characterized as endosome localized involved in post-exocytic dense-core vesicle protein recycling to the TGN. BAIAP3 knockdown inhibited dense-core vesicle maturation/stability in neuroendocrine/endocrine cells. Dense-core vesicle (DCV) exocytosis is a SNARE (soluble N-ethylmaleimide–sensitive fusion attachment protein receptor)-dependent anterograde trafficking pathway that requires multiple proteins for regulation. Several C2 domain–containing proteins are known to regulate Ca2+-dependent DCV exocytosis in neuroendocrine cells. In this study, we identified others by screening all (∼139) human C2 domain–containing proteins by RNA interference in neuroendocrine cells. 40 genes were identified, including several encoding proteins with known roles (CAPS [calcium-dependent activator protein for secretion 1], Munc13-2, RIM1, and SYT10) and many with unknown roles. One of the latter, BAIAP3, is a secretory cell–specific Munc13-4 paralog of unknown function. BAIAP3 knockdown caused accumulation of fusion-incompetent DCVs in BON neuroendocrine cells and lysosomal degradation (crinophagy) of insulin-containing DCVs in INS-1 β cells. BAIAP3 localized to endosomes was required for Golgi trans-Golgi network 46 (TGN46) recycling, exhibited Ca2+-stimulated interactions with TGN SNAREs, and underwent Ca2+-stimulated TGN recruitment. Thus, unlike other Munc13 proteins, BAIAP3 functions indirectly in DCV exocytosis by affecting DCV maturation through its role in DCV protein recycling. Ca2+ rises that stimulate DCV exocytosis may stimulate BAIAP3-dependent retrograde trafficking to maintain DCV protein homeostasis and DCV function.
Collapse
Affiliation(s)
- Xingmin Zhang
- Department of Biochemistry, University of Wisconsin, Madison, WI.,Program in Cellular and Molecular Biology, University of Wisconsin, Madison, WI
| | - Shan Jiang
- School of Pharmacy, University of Wisconsin, Madison, WI
| | - Kelly A Mitok
- Department of Biochemistry, University of Wisconsin, Madison, WI
| | - Lingjun Li
- School of Pharmacy, University of Wisconsin, Madison, WI
| | - Alan D Attie
- Department of Biochemistry, University of Wisconsin, Madison, WI
| | | |
Collapse
|
18
|
Tanaka T, Goto K, Iino M. Diverse Functions and Signal Transduction of the Exocyst Complex in Tumor Cells. J Cell Physiol 2016; 232:939-957. [DOI: 10.1002/jcp.25619] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2016] [Accepted: 09/23/2016] [Indexed: 12/11/2022]
Affiliation(s)
- Toshiaki Tanaka
- Department of Anatomy and Cell Biology; School of Medicine; Yamagata University; Yamagata Japan
- Department of Dentistry, Oral and Maxillofacial Surgery; Plastic and Reconstructive Surgery; School of Medicine; Yamagata University; Yamagata Japan
| | - Kaoru Goto
- Department of Anatomy and Cell Biology; School of Medicine; Yamagata University; Yamagata Japan
| | - Mitsuyoshi Iino
- Department of Dentistry, Oral and Maxillofacial Surgery; Plastic and Reconstructive Surgery; School of Medicine; Yamagata University; Yamagata Japan
| |
Collapse
|
19
|
Peitsch CF, Beckmann S, Zuber B. iMEM: Isolation of Plasma Membrane for Cryoelectron Microscopy. Structure 2016; 24:2198-2206. [PMID: 27818102 DOI: 10.1016/j.str.2016.09.016] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2016] [Revised: 09/30/2016] [Accepted: 10/07/2016] [Indexed: 11/18/2022]
Abstract
The plasma membrane and the cell cortex are essential parts of the eukaryotic cell. The plasma membrane delimitates the cell and mediates communication with the outside. The cell cortex is the submembrane cytoskeleton shaping the cell and is able to reorganize for the passage of material. To study events at and near the plasma membrane, cryoelectron microscopy (cryo-EM) may be used. Most intact cells are too thick for direct cryo-EM imaging. Generating cell-free membrane patches could be a means to study features at the plasma membrane. Here we present an unroofing method, termed iMEM (isolation of membrane patches for cryo-EM) where the plasma membrane is isolated directly on an EM grid. The in situ isolation of membrane patches has several advantages: it is a one-step procedure providing a higher throughput than focused-ion beam cryomilling. It enables the time-precise control over biochemical events before cryofixation.
Collapse
Affiliation(s)
- Camille Françoise Peitsch
- Experimental Morphology, Institute of Anatomy, University of Bern, Baltzerstrasse 2, Bern 3012, Switzerland; Graduate School for Cellular and Biomedical Sciences, University of Bern, Bern 3012, Switzerland
| | - Sven Beckmann
- Experimental Morphology, Institute of Anatomy, University of Bern, Baltzerstrasse 2, Bern 3012, Switzerland
| | - Benoît Zuber
- Experimental Morphology, Institute of Anatomy, University of Bern, Baltzerstrasse 2, Bern 3012, Switzerland.
| |
Collapse
|
20
|
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: 26] [Impact Index Per Article: 3.3] [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.
Collapse
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
| |
Collapse
|
21
|
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.
Collapse
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:
| |
Collapse
|
22
|
Chen Y, Xia Z, Wang L, Yu Y, Liu P, Song E, Xu T. An efficient two-step subcellular fractionation method for the enrichment of insulin granules from INS-1 cells. BIOPHYSICS REPORTS 2015; 1:34-40. [PMID: 26942217 PMCID: PMC4762126 DOI: 10.1007/s41048-015-0008-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2015] [Accepted: 07/03/2015] [Indexed: 10/25/2022] Open
Abstract
Insulin is one of the key regulators for blood glucose homeostasis. More than 99% of insulin is secreted from the pancreatic β-cells. Within each β-cell, insulin is packaged and processed in insulin secretary granules (ISGs) before its exocytosis. Insulin secretion is a complicated but well-organized dynamic process that includes the budding of immature ISGs (iISGs) from the trans-Golgi network, iISG maturation, and mature ISG (mISG) fusion with plasma membrane. However, the molecular mechanisms involved in this process are largely unknown. It is therefore crucial to separate and enrich iISGs and mISGs before determining their distinct characteristics and protein contents. Here, we developed an efficient two-step subcellular fractionation method for the enrichment of iISGs and mISGs from INS-1 cells: OptiPrep gradient purification followed by Percoll solution purification. We demonstrated that by using this method, iISGs and mISGs can be successfully distinguished and enriched. This method can be easily adapted to investigate SGs in other cells or tissues, thereby providing a useful tool for elucidating the mechanisms of granule maturation and secretion.
Collapse
Affiliation(s)
- Yan Chen
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101 China.,University of Chinese Academy of Sciences, Beijing, 100049 China
| | - Zhiping Xia
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101 China.,University of Chinese Academy of Sciences, Beijing, 100049 China
| | - Lifen Wang
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101 China.,University of Chinese Academy of Sciences, Beijing, 100049 China
| | - Yong Yu
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101 China.,University of Chinese Academy of Sciences, Beijing, 100049 China
| | - Pingsheng Liu
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101 China
| | - Eli Song
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101 China
| | - Tao Xu
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101 China
| |
Collapse
|
23
|
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.
Collapse
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
| |
Collapse
|
24
|
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.
Collapse
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.
| |
Collapse
|
25
|
Self-assembly of VPS41 promotes sorting required for biogenesis of the regulated secretory pathway. Dev Cell 2013; 27:425-37. [PMID: 24210660 DOI: 10.1016/j.devcel.2013.10.007] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2012] [Revised: 08/06/2013] [Accepted: 10/11/2013] [Indexed: 12/22/2022]
Abstract
The regulated release of polypeptides has a central role in physiology, behavior, and development, but the mechanisms responsible for production of the large dense core vesicles (LDCVs) capable of regulated release have remained poorly understood. Recent work has implicated cytosolic adaptor protein AP-3 in the recruitment of LDCV membrane proteins that confer regulated release. However, AP-3 in mammals has been considered to function in the endolysosomal pathway and in the biosynthetic pathway only in yeast. We now find that the mammalian homolog of yeast VPS41, a member of the homotypic fusion and vacuole protein sorting (HOPS) complex that delivers biosynthetic cargo to the endocytic pathway in yeast, promotes LDCV formation through a common mechanism with AP-3, indicating a conserved role for these proteins in the biosynthetic pathway. VPS41 also self-assembles into a lattice, suggesting that it acts as a coat protein for AP-3 in formation of the regulated secretory pathway.
Collapse
|
26
|
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
| |
Collapse
|
27
|
Sirkis DW, Edwards RH, Asensio CS. Widespread dysregulation of peptide hormone release in mice lacking adaptor protein AP-3. PLoS Genet 2013; 9:e1003812. [PMID: 24086151 PMCID: PMC3784564 DOI: 10.1371/journal.pgen.1003812] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2013] [Accepted: 08/06/2013] [Indexed: 12/13/2022] Open
Abstract
The regulated secretion of peptide hormones, neural peptides and many growth factors depends on their sorting into large dense core vesicles (LDCVs) capable of regulated exocytosis. LDCVs form at the trans-Golgi network, but the mechanisms that sort proteins to this regulated secretory pathway and the cytosolic machinery that produces LDCVs remain poorly understood. Recently, we used an RNAi screen to identify a role for heterotetrameric adaptor protein AP-3 in regulated secretion and in particular, LDCV formation. Indeed, mocha mice lacking AP-3 have a severe neurological and behavioral phenotype, but this has been attributed to a role for AP-3 in the endolysosomal rather than biosynthetic pathway. We therefore used mocha mice to determine whether loss of AP-3 also dysregulates peptide release in vivo. We find that adrenal chromaffin cells from mocha animals show increased constitutive exocytosis of both soluble cargo and LDCV membrane proteins, reducing the response to stimulation. We also observe increased basal release of both insulin and glucagon from pancreatic islet cells of mocha mice, suggesting a global disturbance in the release of peptide hormones. AP-3 exists as both ubiquitous and neuronal isoforms, but the analysis of mice lacking each of these isoforms individually and together shows that loss of both is required to reproduce the effect of the mocha mutation on the regulated pathway. In addition, we show that loss of the related adaptor protein AP-1 has a similar effect on regulated secretion but exacerbates the effect of AP-3 RNAi, suggesting distinct roles for the two adaptors in the regulated secretory pathway.
Collapse
Affiliation(s)
- Daniel W. Sirkis
- Graduate Program in Pharmaceutical Sciences and Pharmacogenomics, University of California San Francisco, San Francisco, California, United States of America
- Departments of Physiology and Neurology, University of California San Francisco, San Francisco, California, United States of America
| | - Robert H. Edwards
- Graduate Program in Pharmaceutical Sciences and Pharmacogenomics, University of California San Francisco, San Francisco, California, United States of America
- Departments of Physiology and Neurology, University of California San Francisco, San Francisco, California, United States of America
- * E-mail:
| | - Cédric S. Asensio
- Departments of Physiology and Neurology, University of California San Francisco, San Francisco, California, United States of America
| |
Collapse
|
28
|
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.
Collapse
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
| |
Collapse
|
29
|
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.
Collapse
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:
| |
Collapse
|
30
|
Bogan JS, Xu Y, Hao M. Cholesterol accumulation increases insulin granule size and impairs membrane trafficking. Traffic 2012; 13:1466-80. [PMID: 22889194 DOI: 10.1111/j.1600-0854.2012.01407.x] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2012] [Revised: 08/09/2012] [Accepted: 08/13/2012] [Indexed: 11/28/2022]
Abstract
The formation of mature secretory granules is essential for proper storage and regulated release of hormones and neuropeptides. In pancreatic β cells, cholesterol accumulation causes defects in insulin secretion and may participate in the pathogenesis of type 2 diabetes. Using a novel cholesterol analog, we show for the first time that insulin granules are the major sites of intracellular cholesterol accumulation in live β cells. This is distinct from other, non-secretory cell types, in which cholesterol is concentrated in the recycling endosomes and the trans-Golgi network. Excess cholesterol was delivered specifically to insulin granules, which caused granule enlargement and retention of syntaxin 6 and VAMP4 in granule membranes, with concurrent depletion of these proteins from the trans-Golgi network. Clathrin also accumulated in the granules of cholesterol-overloaded cells, consistent with a possible defect in the last stage of granule maturation, during which clathrin-coated vesicles bud from the immature granules. Excess cholesterol also reduced the docking and fusion of insulin granules at the plasma membrane. Together, the data support a model in which cholesterol accumulation in insulin secretory granules impairs the ability of these vesicles to respond to stimuli, and thus reduces insulin secretion.
Collapse
Affiliation(s)
- Jonathan S Bogan
- Department of Internal Medicine, Yale University School of Medicine, New Haven, CT 06520, USA
| | | | | |
Collapse
|
31
|
Becherer U, Medart MR, Schirra C, Krause E, Stevens D, Rettig J. Regulated exocytosis in chromaffin cells and cytotoxic T lymphocytes: How similar are they? Cell Calcium 2012; 52:303-12. [DOI: 10.1016/j.ceca.2012.04.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2012] [Revised: 03/27/2012] [Accepted: 04/09/2012] [Indexed: 10/28/2022]
|
32
|
TBC-8, a putative RAB-2 GAP, regulates dense core vesicle maturation in Caenorhabditis elegans. PLoS Genet 2012; 8:e1002722. [PMID: 22654674 PMCID: PMC3359978 DOI: 10.1371/journal.pgen.1002722] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2011] [Accepted: 04/04/2012] [Indexed: 02/05/2023] Open
Abstract
Dense core vesicles (DCVs) are thought to be generated at the late Golgi apparatus as immature DCVs, which subsequently undergo a maturation process through clathrin-mediated membrane remodeling events. This maturation process is required for efficient processing of neuropeptides within DCVs and for removal of factors that would otherwise interfere with DCV release. Previously, we have shown that the GTPase, RAB-2, and its effector, RIC-19, are involved in DCV maturation in Caenorhabditis elegans motoneurons. In rab-2 mutants, specific cargo is lost from maturing DCVs and missorted into the endosomal/lysosomal degradation route. Cargo loss could be prevented by blocking endosomal delivery. This suggests that RAB-2 is involved in retention of DCV components during the sorting process at the Golgi-endosomal interface. To understand how RAB-2 activity is regulated at the Golgi, we screened for RAB-2-specific GTPase activating proteins (GAPs). We identified a potential RAB-2 GAP, TBC-8, which is exclusively expressed in neurons and which, when depleted, shows similar DCV maturation defects as rab-2 mutants. We could demonstrate that RAB-2 binds to its putative GAP, TBC-8. Interestingly, TBC-8 also binds to the RAB-2 effector, RIC-19. This interaction appears to be conserved as TBC-8 also interacted with the human ortholog of RIC-19, ICA69. Therefore, we propose that a dynamic ON/OFF cycling of RAB-2 at the Golgi induced by the GAP/effector complex is required for proper DCV maturation.
Collapse
|
33
|
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]
|
34
|
Matsuoka H, Harada K, Nakamura J, Fukuda M, Inoue M. Differential distribution of synaptotagmin-1, -4, -7, and -9 in rat adrenal chromaffin cells. Cell Tissue Res 2011; 344:41-50. [PMID: 21287204 DOI: 10.1007/s00441-011-1131-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2010] [Accepted: 01/12/2011] [Indexed: 11/27/2022]
Abstract
Neurons and certain kinds of endocrine cells, such as adrenal chromaffin cells, have large dense-core vesicles (LDCVs) and synaptic vesicles or synaptic-like microvesicles (SLMVs). These secretory vesicles exhibit differences in Ca(2+) sensitivity and contain diverse signaling substances. The present work was undertaken to identify the synaptotagmin (Syt) isoforms present in secretory vesicles. Fractionation analysis of lysates of the bovine adrenal medulla and immunocytochemistry in rat chromaffin cells indicated that Syt 1 was localized in LDCVs and SLMVs, whereas Syt 7 was the predominant isoform present in LDCVs. In contrast to PC12 cells and the pancreatic β cell line INS-1, Syt 9 was not immunodetected in LDCVs in rat chromaffin cells. Double-staining revealed that Syt 9-like immunoreactivity was nearly identical with fluorescent thapsigargin binding, suggesting the presence of Syt 9 in the endoplasmic reticulum (ER).The exogenous expression of Syt 1-GFP in INS-1 cells, which had a negligible level of endogenous Syt 1, resulted in an increase in the amount of Syt 9 in the ER, suggesting that Syt 9 competes with Syt 1 for trafficking from the ER to the Golgi complex. We conclude that LDCVs mainly contain Syt 7, whereas SLMVs contain Syt 1, but not Syt 7, in rat and bovine chromaffin cells.
Collapse
Affiliation(s)
- Hidetada Matsuoka
- Department of Cell and Systems Physiology, University of Occupational and Environmental Health School of Medicine, Kitakyushu, 807-8555, Japan
| | | | | | | | | |
Collapse
|
35
|
Asensio CS, Sirkis DW, Edwards RH. RNAi screen identifies a role for adaptor protein AP-3 in sorting to the regulated secretory pathway. ACTA ACUST UNITED AC 2011; 191:1173-87. [PMID: 21149569 PMCID: PMC3002028 DOI: 10.1083/jcb.201006131] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
AP-3 concentrates proteins within large dense-core vesicles to promote regulated exocytosis. The regulated release of proteins depends on their inclusion within large dense-core vesicles (LDCVs) capable of regulated exocytosis. LDCVs form at the trans-Golgi network (TGN), but the mechanism for protein sorting to this regulated secretory pathway (RSP) and the cytosolic machinery involved in this process have remained poorly understood. Using an RNA interference screen in Drosophila melanogaster S2 cells, we now identify a small number of genes, including several subunits of the heterotetrameric adaptor protein AP-3, which are required for sorting to the RSP. In mammalian neuroendocrine cells, loss of AP-3 dysregulates exocytosis due to a primary defect in LDCV formation. Previous work implicated AP-3 in the endocytic pathway, but we find that AP-3 promotes sorting to the RSP within the biosynthetic pathway at the level of the TGN. Although vesicles with a dense core still form in the absence of AP-3, they contain substantially less synaptotagmin 1, indicating that AP-3 concentrates the proteins required for regulated exocytosis.
Collapse
Affiliation(s)
- Cédric S Asensio
- Department of Physiology, University of California, San Francisco, San Francisco, CA 94158, USA
| | | | | |
Collapse
|
36
|
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.
Collapse
Affiliation(s)
- Tanja Kögel
- Department of Biomedicine, University of Bergen, Jonas Lies Vei 91, 5009 Bergen, Norway
| | | |
Collapse
|
37
|
Hammel I, Lagunoff D, Galli SJ. Regulation of secretory granule size by the precise generation and fusion of unit granules. J Cell Mol Med 2010; 14:1904-16. [PMID: 20406331 PMCID: PMC2909340 DOI: 10.1111/j.1582-4934.2010.01071.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2010] [Accepted: 04/08/2010] [Indexed: 12/31/2022] Open
Abstract
Morphometric evidence derived from studies of mast cells, pancreatic acinar cells and other cell types supports a model in which the post-Golgi processes that generate mature secretory granules can be resolved into three steps: (1) fusion of small, Golgi-derived progranules to produce immature secretory granules which have a highly constrained volume; (2) transformation of such immature granules into mature secretory granules, a process often associated with a reduction in the maturing granule's volume, as well as changes in the appearance of its content and (3) fusion of secretory granules of the smallest size, termed 'unit granules', forming granules whose volumes are multiples of the unit granule's volume. Mutations which perturb this process can cause significant pathology. For example, Chediak-Higashi syndrome / lysosomal trafficking regulator (CHS)/(Lyst) mutations result in giant secretory granules in a number of cell types in human beings with the Chediak-Higashi syndrome and in 'beige' (Lyst(bg)/Lyst(bg)) mice. Analysis of the secretory granules of mast cells and pancreatic acinar cells in Lyst-deficient beige mice suggests that beige mouse secretory granules retain the ability to fuse randomly with other secretory granules no matter what the size of the fusion partners. By contrast, in normal mice, the pattern of granule-granule fusion occurs exclusively by the addition of unit granules, either to each other or to larger granules. The normal pattern of fusion is termed unit addition and the fusion evident in cells with CHS/Lyst mutations is called random addition. The proposed model of secretory granule formation has several implications. For example, in neurosecretory cells, the secretion of small amounts of cargo in granules constrained to a very narrow size increases the precision of the information conveyed by secretion. By contrast, in pancreatic acinar cells and mast cells, large granules composed of multiple unit granules permit the cells to store large amounts of material without requiring the amount of membrane necessary to package the same amount of cargo into small granules. In addition, the formation of mature secretory granules that are multimers of unit granules provides a mechanism for mixing in large granules the contents of unit granules which differ in their content of cargo.
Collapse
Affiliation(s)
- Ilan Hammel
- Department of Pathology, Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel.
| | | | | |
Collapse
|
38
|
Harada K, Matsuoka H, Nakamura J, Fukuda M, Inoue M. Storage of GABA in chromaffin granules and not in synaptic-like microvesicles in rat adrenal medullary cells. J Neurochem 2010; 114:617-26. [DOI: 10.1111/j.1471-4159.2010.06792.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
39
|
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.
Collapse
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.
| |
Collapse
|
40
|
Versatile roles for myosin Va in dense core vesicle biogenesis and function. Biochem Soc Trans 2010; 38:199-204. [PMID: 20074059 DOI: 10.1042/bst0380199] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The motor protein myosin Va is involved in multiple successive steps in the development of dense-core vesicles, such as in the membrane remodelling during their maturation, their transport along actin filaments and the regulation of their exocytosis. In the present paper, we summarize the current knowledge on the roles of myosin Va in the different steps of dense-core vesicle biogenesis and exocytosis, and compare findings obtained from different cell types and experimental systems.
Collapse
|
41
|
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]
|
42
|
Hosaka M, Watanabe T. Secretogranin III: a bridge between core hormone aggregates and the secretory granule membrane. Endocr J 2010; 57:275-86. [PMID: 20203425 DOI: 10.1507/endocrj.k10e-038] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Secretory granules in endocrine cells selectively store bioactive peptide hormones and amines, which are secreted in a regulated manner upon appropriate stimulation. In addition to bioactive substances, various proteins and lipids characteristic of secretory granules are likely recruited to a restricted space at the trans-Golgi Network (TGN), and the space then matures to the secretory granule. Although experimental findings so far have strongly suggested that aggregation- and receptor-mediated processes are essential for the formation of secretory granules, the putative link between these two processes remains to be clarified. Recently, secretogranin III (SgIII) has been identified as a specific binding protein for chromogranin A (CgA), a representative constituent of the core aggregate within secretory granules, and it was later revealed that SgIII can also bind to the cholesterol-rich membrane domain at the TGN. Based on its multifaceted binding properties, SgIII may act as a central player in the formation of cholesterol-rich membrane platforms. Upon these platforms, essential processes for secretory granule biogenesis coordinately occur; that is, selective recruitment of prohormones, processing and modifying of prohormones, and condensation of mature hormones as an aggregate. This review summarizes the findings and theoretical concepts on the issue to date and then focuses on the putative role of SgIII in secretory granule biogenesis in endocrine cells.
Collapse
Affiliation(s)
- Masahiro Hosaka
- Department of Molecular Medicine, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Japan.
| | | |
Collapse
|
43
|
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.
Collapse
Affiliation(s)
- Chie Inomoto
- Department of Pathology, Tokai University School of Medicine, 143 Shimokasuya, Isehara, Kanagawa 259-1193, Japan.
| | | |
Collapse
|
44
|
Brunner Y, Schvartz D, Couté Y, Sanchez JC. Proteomics of regulated secretory organelles. MASS SPECTROMETRY REVIEWS 2009; 28:844-867. [PMID: 19301366 DOI: 10.1002/mas.20211] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Regulated secretory organelles are important subcellular structures of living cells that allow the release in the extracellular space of crucial compounds, such as hormones and neurotransmitters. Therefore, the regulation of biogenesis, trafficking, and exocytosis of regulated secretory organelles has been intensively studied during the last 30 years. However, due to the large number of different regulated secretory organelles, only a few of them have been specifically characterized. New insights into regulated secretory organelles open crucial perspectives for a better comprehension of the mechanisms that govern cell secretion. The combination of subcellular fractionation, protein separation, and mass spectrometry is also possible to study regulated secretory organelles at the proteome level. In this review, we present different strategies used to isolate regulated secretory organelles, separate their protein content, and identify the proteins by mass spectrometry. The biological significance of regulated secretory organelles-proteomic analysis is discussed as well.
Collapse
Affiliation(s)
- Yannick Brunner
- Biomedical Proteomics Research Group, University Medical Center, Geneva, Switzerland
| | | | | | | |
Collapse
|
45
|
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.
Collapse
|
46
|
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.
Collapse
|
47
|
Eshpeter A, Jiang J, Au M, Rajotte RV, Lu K, Lebkowski JS, Majumdar AS, Korbutt GS. In vivo characterization of transplanted human embryonic stem cell-derived pancreatic endocrine islet cells. Cell Prolif 2008; 41:843-858. [PMID: 19040565 PMCID: PMC6495805 DOI: 10.1111/j.1365-2184.2008.00564.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2007] [Accepted: 02/29/2008] [Indexed: 11/29/2022] Open
Abstract
OBJECTIVES Islet-like clusters (ILCs), differentiated from human embryonic stem cells (hESCs), were characterized both before and after transplantation under the kidney capsule of streptozotocin-induced diabetic immuno-incompetent mice. MATERIALS AND METHODS Multiple independent ILC preparations (n = 8) were characterized by immunohistochemistry, flow cytometry and cell insulin content, with six preparations transplanted into diabetic mice (n = 42), compared to controls, which were transplanted with either a human fibroblast cell line or undifferentiated hESCs (n = 28). RESULTS Prior to transplantation, ILCs were immunoreactive for the islet hormones insulin, C-peptide and glucagon, and for the ductal epithelial marker cytokeratin-19. ILCs also had cellular insulin contents similar to or higher than human foetal islets. Expression of islet and pancreas-specific cell markers was maintained for 70 days post-transplantation. The mean survival of recipients was increased by transplanted ILCs as compared to transplanted human fibroblast cells (P < 0.0001), or undifferentiated hESCs (P < 0.042). Graft function was confirmed by secretion of human C-peptide in response to an oral bolus of glucose. CONCLUSIONS hESC-derived ILC grafts continued to contain cells that were positive for islet endocrine hormones and were shown to be functional by their ability to secrete human C-peptide. Further enrichment and maturation of ILCs could lead to generation of a sufficient source of insulin-producing cells for transplantation into patients with type 1 diabetes.
Collapse
Affiliation(s)
- A. Eshpeter
- Alberta Diabetes Institute and
- Department of Surgery, University of Alberta, Edmonton, Canada, and
| | - J. Jiang
- Geron Corporation, Menlo Park, CA, USA
| | - M. Au
- Geron Corporation, Menlo Park, CA, USA
| | - R. V. Rajotte
- Alberta Diabetes Institute and
- Department of Surgery, University of Alberta, Edmonton, Canada, and
| | - K. Lu
- Geron Corporation, Menlo Park, CA, USA
| | | | | | - G. S. Korbutt
- Alberta Diabetes Institute and
- Department of Surgery, University of Alberta, Edmonton, Canada, and
| |
Collapse
|
48
|
Ma GQ, Wang B, Wang HB, Wang Q, Bao L. Short elements with charged amino acids form clusters to sort protachykinin into large dense-core vesicles. Traffic 2008; 9:2165-79. [PMID: 18939957 DOI: 10.1111/j.1600-0854.2008.00836.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The sorting of neuropeptide tachykinins into large dense-core vesicles (LDCVs) is a key step in their regulated secretion from neurons. However, the sorting mechanism for protachykinin has not yet to be clearly resolved. In this study, we report that the clustered short elements with charged amino acids regulate the efficiency of protachykinin sorting into LDCVs. A truncation experiment showed that the propeptide and the mature peptide-containing sequence of protachykinin were sorted into LDCVs. These two regions exhibit a polarized distribution of charged amino acids. The LDCV localization of the propeptide was gradually decreased with an increasing number of neutral amino acids. Furthermore, the short element with four to five amino acids containing two charged residues was found to be a basic unit for LDCV sorting that enables regulated secretion. In the native propeptide sequence, these charged short elements were clustered to enhance the intermolecular aggregation by electrostatic interaction and produce a gradual and additive effect on LDCV sorting. The optimal conditions for intermolecular aggregation of protachykinin were at millimolar Ca(2+) concentrations and pH 5.5-6.0. These results demonstrate that the charged short elements are clustered such that they serve as aggregative signals and regulate the efficiency of protachykinin sorting into LDCVs. These findings reveal a novel mechanism for the sorting of neuropeptides into a regulated secretory pathway.
Collapse
Affiliation(s)
- Guo-Qiang Ma
- Laboratory of Molecular Cell Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 320 Yue Yang Road, Shanghai 200031, China
| | | | | | | | | |
Collapse
|
49
|
Martelli AM, Baldini G, Tabellini G, Koticha D, Bareggi R, Baldini G. Rab3A and Rab3D Control the Total Granule Number and the Fraction of Granules Docked at the Plasma Membrane in PC12 Cells. Traffic 2008. [DOI: 10.1111/j.1600-0854.2000.11207.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
|
50
|
Fei H, Grygoruk A, Brooks ES, Chen A, Krantz DE. Trafficking of vesicular neurotransmitter transporters. Traffic 2008; 9:1425-36. [PMID: 18507811 DOI: 10.1111/j.1600-0854.2008.00771.x] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Vesicular neurotransmitter transporters are required for the storage of all classical and amino acid neurotransmitters in secretory vesicles. Transporter expression can influence neurotransmitter storage and release, and trafficking targets the transporters to different types of secretory vesicles. Vesicular transporters traffic to synaptic vesicles (SVs) as well as large dense core vesicles and are recycled to SVs at the nerve terminal. Some of the intrinsic signals for these trafficking events have been defined and include a dileucine motif present in multiple transporter subtypes, an acidic cluster in the neural isoform of the vesicular monoamine transporter (VMAT) 2 and a polyproline motif in the vesicular glutamate transporter (VGLUT) 1. The sorting of VMAT2 and the vesicular acetylcholine transporter to secretory vesicles is regulated by phosphorylation. In addition, VGLUT1 uses alternative endocytic pathways for recycling back to SVs following exocytosis. Regulation of these sorting events has the potential to influence synaptic transmission and behavior.
Collapse
Affiliation(s)
- Hao Fei
- Departments of Psychiatry and Neurobiology, Gonda Goldschmied Neuroscience and Genetics Research Center, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095-1761, USA
| | | | | | | | | |
Collapse
|