1
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Roberts BS, Mitra D, Abishek S, Beher R, Satpute-Krishnan P. The p24-family and COPII subunit SEC24C facilitate the clearance of alpha1-antitrypsin Z from the endoplasmic reticulum to lysosomes. Mol Biol Cell 2024; 35:ar45. [PMID: 38294851 PMCID: PMC10916869 DOI: 10.1091/mbc.e23-06-0257] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2023] [Revised: 01/16/2024] [Accepted: 01/24/2024] [Indexed: 02/01/2024] Open
Abstract
A subpopulation of the alpha-1-antitrypsin misfolding Z mutant (ATZ) is cleared from the endoplasmic reticulum (ER) via an ER-to-lysosome-associated degradation (ERLAD) pathway. Here, we report that the COPII subunit SEC24C and the p24-family of proteins facilitate the clearance of ATZ via ERLAD. In addition to the previously reported ERLAD components calnexin and FAM134B, we discovered that ATZ coimmunoprecipitates with the p24-family members TMP21 and TMED9. This contrasts with wild type alpha1-antitrypsin, which did not coimmunoprecipitate with FAM134B, calnexin or the p24-family members. Live-cell imaging revealed that ATZ and the p24-family members traffic together from the ER to lysosomes. Using chemical inhibitors to block ER exit or autophagy, we demonstrated that p24-family members and ATZ co-accumulate at SEC24C marked ER-exit sites or in ER-derived compartments, respectively. Furthermore, depletion of SEC24C, TMP21, or TMED9 inhibited lysosomal trafficking of ATZ and resulted in the increase of intracellular ATZ levels. Conversely, overexpression of these p24-family members resulted in the reduction of ATZ levels. Intriguingly, the p24-family members coimmunoprecipitate with ATZ, FAM134B, and SEC24C. Thus, we propose a model in which the p24-family functions in an adaptor complex linking SEC24C with the ERLAD machinery for the clearance of ATZ.
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Affiliation(s)
| | - Debashree Mitra
- Uniformed Services University of the Health Sciences, Bethesda, MD 20814
| | - Sudhanshu Abishek
- Uniformed Services University of the Health Sciences, Bethesda, MD 20814
| | - Richa Beher
- Uniformed Services University of the Health Sciences, Bethesda, MD 20814
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2
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Seiler DK, Hay JC. Genetically encoded fluorescent tools: Shining a little light on ER-to-Golgi transport. Free Radic Biol Med 2022; 183:14-24. [PMID: 35272000 PMCID: PMC9097910 DOI: 10.1016/j.freeradbiomed.2022.03.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/14/2021] [Revised: 03/03/2022] [Accepted: 03/05/2022] [Indexed: 12/11/2022]
Abstract
Since the first fluorescent proteins (FPs) were identified and isolated over fifty years ago, FPs have become commonplace yet indispensable tools for studying the constitutive secretory pathway in live cells. At the same time, genetically encoded chemical tags have provided a new use for much older fluorescent dyes. Innovation has also produced several specialized methods to allow synchronous release of cargo proteins from the endoplasmic reticulum (ER), enabling precise characterization of sequential trafficking steps in the secretory pathway. Without the constant innovation of the researchers who design these tools to control, image, and quantitate protein secretion, major discoveries about ER-to-Golgi transport and later stages of the constitutive secretory pathway would not have been possible. We review many of the tools and tricks, some 25 years old and others brand new, that have been successfully implemented to study ER-to-Golgi transport in intact and living cells.
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Affiliation(s)
- Danette Kowal Seiler
- Division of Biological Sciences, Center for Structural & Functional Neuroscience, University of Montana, Missoula, MT, 59812, USA
| | - Jesse C Hay
- Division of Biological Sciences, Center for Structural & Functional Neuroscience, University of Montana, Missoula, MT, 59812, USA.
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3
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Yan R, Chen K, Wang B, Xu K. SURF4-induced tubular ERGIC selectively expedites ER-to-Golgi transport. Dev Cell 2022; 57:512-525.e8. [PMID: 35051356 PMCID: PMC8891076 DOI: 10.1016/j.devcel.2021.12.018] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2021] [Revised: 12/09/2021] [Accepted: 12/17/2021] [Indexed: 11/25/2022]
Abstract
The endoplasmic reticulum (ER)-to-Golgi transport is critical to protein secretion and intracellular sorting. Here, we report a highly elongated tubular ER-Golgi intermediate compartment (t-ERGIC) that selectively expedites the ER-to-Golgi transport for soluble cargoes of the receptor SURF4. Lacking the canonical ERGIC marker ERGIC-53 yet positive for the small GTPases Rab1A/B, the t-ERGIC is further marked by its extraordinarily elongated and thinned shape. With its large surface-to-volume ratio, high intracellular traveling speeds, and ER-Golgi recycling capabilities, the t-ERGIC accelerates the trafficking of SURF4-bound cargoes. The biogenesis and cargo selectivity of t-ERGIC both depend on SURF4, which recognizes the N terminus of soluble cargoes and co-clusters with the selected cargoes to expand the ER-exit site. In the steady state, the t-ERGIC-mediated fast ER-to-Golgi transport is antagonized by the KDEL-mediated ER retrieval. Together, our results argue that specific cargo-receptor interactions give rise to distinct transport carriers that regulate the trafficking kinetics.
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Affiliation(s)
- Rui Yan
- Department of Chemistry & California Institute for Quantitative Biosciences, University of California, Berkeley, Berkeley, CA 94720, USA; Chan Zuckerberg Biohub, San Francisco, CA 94158, USA.
| | - Kun Chen
- Department of Chemistry & California Institute for Quantitative Biosciences, University of California, Berkeley, Berkeley, CA, USA, 94720,Chan Zuckerberg Biohub, San Francisco, CA, USA, 94158
| | - Bowen Wang
- Department of Chemistry & California Institute for Quantitative Biosciences, University of California, Berkeley, Berkeley, CA, USA, 94720,Chan Zuckerberg Biohub, San Francisco, CA, USA, 94158
| | - Ke Xu
- Department of Chemistry & California Institute for Quantitative Biosciences, University of California, Berkeley, Berkeley, CA 94720, USA; Chan Zuckerberg Biohub, San Francisco, CA 94158, USA.
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4
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Shomron O, Nevo-Yassaf I, Aviad T, Yaffe Y, Zahavi EE, Dukhovny A, Perlson E, Brodsky I, Yeheskel A, Pasmanik-Chor M, Mironov A, Beznoussenko GV, Mironov AA, Sklan EH, Patterson GH, Yonemura Y, Sannai M, Kaether C, Hirschberg K. COPII collar defines the boundary between ER and ER exit site and does not coat cargo containers. J Cell Biol 2021; 220:211990. [PMID: 33852719 PMCID: PMC8054201 DOI: 10.1083/jcb.201907224] [Citation(s) in RCA: 44] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2019] [Revised: 01/14/2021] [Accepted: 03/11/2021] [Indexed: 12/13/2022] Open
Abstract
COPII and COPI mediate the formation of membrane vesicles translocating in opposite directions within the secretory pathway. Live-cell and electron microscopy revealed a novel mode of function for COPII during cargo export from the ER. COPII is recruited to membranes defining the boundary between the ER and ER exit sites, facilitating selective cargo concentration. Using direct observation of living cells, we monitored cargo selection processes, accumulation, and fission of COPII-free ERES membranes. CRISPR/Cas12a tagging, the RUSH system, and pharmaceutical and genetic perturbations of ER-Golgi transport demonstrated that the COPII coat remains bound to the ER–ERES boundary during protein export. Manipulation of the cargo-binding domain in COPII Sec24B prohibits cargo accumulation in ERES. These findings suggest a role for COPII in selecting and concentrating exported cargo rather than coating Golgi-bound carriers. These findings transform our understanding of coat proteins’ role in ER-to-Golgi transport.
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Affiliation(s)
- Olga Shomron
- Department of Pathology, Sackler School of Medicine, Tel-Aviv University, Tel Aviv, Israel
| | - Inbar Nevo-Yassaf
- Department of Pathology, Sackler School of Medicine, Tel-Aviv University, Tel Aviv, Israel
| | - Tamar Aviad
- Department of Pathology, Sackler School of Medicine, Tel-Aviv University, Tel Aviv, Israel
| | - Yakey Yaffe
- Department of Pathology, Sackler School of Medicine, Tel-Aviv University, Tel Aviv, Israel
| | - Eitan Erez Zahavi
- Department of Physiology and Pharmacology, Sackler School of Medicine, Tel-Aviv University, Tel Aviv, Israel
| | - Anna Dukhovny
- Department of Clinical Immunology and Microbiology, Sackler School of Medicine, Tel-Aviv University, Tel Aviv, Israel
| | - Eran Perlson
- Department of Physiology and Pharmacology, Sackler School of Medicine, Tel-Aviv University, Tel Aviv, Israel
| | - Ilya Brodsky
- Lomonosov Moscow State University, Andrey N. Belozersky Institute for Physico-Chemical Biology, Moscow, Russia
| | - Adva Yeheskel
- Bioinformatics Unit, George S. Wise Faculty of Life Sciences, Tel-Aviv University, Tel Aviv, Israel
| | - Metsada Pasmanik-Chor
- Bioinformatics Unit, George S. Wise Faculty of Life Sciences, Tel-Aviv University, Tel Aviv, Israel
| | - Anna Mironov
- Istituto Firc di Oncologia Molecolare, Fondazione Istituto Fondazione Italiana per la Ricerca sul Cancro di Oncologia Molecolare, Milan, Italy
| | - Galina V Beznoussenko
- Istituto Firc di Oncologia Molecolare, Fondazione Istituto Fondazione Italiana per la Ricerca sul Cancro di Oncologia Molecolare, Milan, Italy
| | - Alexander A Mironov
- Istituto Firc di Oncologia Molecolare, Fondazione Istituto Fondazione Italiana per la Ricerca sul Cancro di Oncologia Molecolare, Milan, Italy
| | - Ella H Sklan
- Department of Clinical Immunology and Microbiology, Sackler School of Medicine, Tel-Aviv University, Tel Aviv, Israel
| | - George H Patterson
- Section on Biophotonics, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, Rockville, MD
| | - Yoji Yonemura
- Leibniz Institute on Aging, Fritz Lipmann Institute, Jena, Germany
| | - Mara Sannai
- Leibniz Institute on Aging, Fritz Lipmann Institute, Jena, Germany
| | | | - Koret Hirschberg
- Department of Pathology, Sackler School of Medicine, Tel-Aviv University, Tel Aviv, Israel
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5
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Patella F, Cutler DF. RGS4 controls secretion of von Willebrand factor to the subendothelial matrix. J Cell Sci 2020; 133:jcs247312. [PMID: 32576664 DOI: 10.1242/jcs.247312] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2020] [Accepted: 06/11/2020] [Indexed: 11/20/2022] Open
Abstract
The haemostatic protein von Willebrand factor (VWF) exists in plasma and subendothelial pools. The plasma pools are secreted from endothelial storage granules, Weibel-Palade bodies (WPBs), by basal secretion with a contribution from agonist-stimulated secretion, and the subendothelial pool is secreted into the subendothelial matrix by a constitutive pathway not involving WPBs. We set out to determine whether the constitutive release of subendothelial VWF is actually regulated and, if so, what functional consequences this might have. Constitutive VWF secretion can be increased by a range of factors, including changes in VWF expression, levels of TNF and other environmental cues. An RNA-seq analysis revealed that expression of regulator of G protein signalling 4 (RGS4) was reduced in endothelial cells (HUVECs) grown under these conditions. siRNA RGS4 treatment of HUVECs increased constitutive basolateral secretion of VWF, probably by affecting the anterograde secretory pathway. In a simple model of endothelial damage, we show that RGS4-silenced cells increased platelet recruitment onto the subendothelial matrix under flow. These results show that changes in RGS4 expression alter levels of subendothelial VWF, affecting platelet recruitment. This introduces a novel control over VWF function.
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Affiliation(s)
- Francesca Patella
- MRC Laboratory for Molecular Cell Biology, University College London, London WC1E 6BT, UK
| | - Daniel F Cutler
- MRC Laboratory for Molecular Cell Biology, University College London, London WC1E 6BT, UK
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6
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Yao Q, Wang C, Fu M, Dai L, Li J, Gao Y. Dynamic Detection of Active Enzyme Instructed Supramolecular Assemblies In Situ via Super-Resolution Microscopy. ACS NANO 2020; 14:4882-4889. [PMID: 32233450 DOI: 10.1021/acsnano.0c00883] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Inspired by the self-assembly phenomena in nature, the instructed self-assembly of exogenous small molecules in a biological environment has become a prevalent process to control cell fate. Despite mounting examples of versatile bioactivities, the underlying mechanism remains less understood, which is in large hindered by the difficulties in the identification of those dynamic assemblies in situ. Here, with direct stochastic optical reconstruction microscopy, we are able to elucidate the dynamic morphology transformation of the enzyme-instructed supramolecular assemblies in situ inside cancer cells with a resolution below 50 nm. It indicates that the assembling molecules endure drastically different pathways between cell lines with different phosphatase activities and distribution. In HeLa cells, the direct formation of intracellular supramolecular nanofibers showed slight cytotoxicity, which was due to the possible cellular secretory pathway to excrete those exogenous molecules assemblies. In contrast, in Saos-2 cells with active phosphatase on the cell surface, assemblies with granular morphology first formed on the cell membranes, followed by a transformation into nanofibers and accumulation in cells, which induced Saos-2 cell death eventually. Overall, we provided a convenient method to reveal the in situ dynamic nanomorphology transformation of the supramolecular assemblies in a biological environment, in order to decipher their diverse biological activities.
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Affiliation(s)
- Qingxin Yao
- CAS Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Chenlei Wang
- Beijing National Laboratory for Molecular Sciences (BNLMS), CAS Key Lab of Colloid, Interface and Thermodynamics Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Meifang Fu
- Beijing National Laboratory for Molecular Sciences (BNLMS), CAS Key Lab of Colloid, Interface and Thermodynamics Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
| | - Luru Dai
- CAS Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Chinese Academy of Sciences, Beijing 100190, China
| | - Junbai Li
- Beijing National Laboratory for Molecular Sciences (BNLMS), CAS Key Lab of Colloid, Interface and Thermodynamics Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
| | - Yuan Gao
- CAS Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Sciences, Beijing 100049, China
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7
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Martinez VG, Pankova V, Krasny L, Singh T, Makris S, White IJ, Benjamin AC, Dertschnig S, Horsnell HL, Kriston-Vizi J, Burden JJ, Huang PH, Tape CJ, Acton SE. Fibroblastic Reticular Cells Control Conduit Matrix Deposition during Lymph Node Expansion. Cell Rep 2019; 29:2810-2822.e5. [PMID: 31775047 PMCID: PMC6899512 DOI: 10.1016/j.celrep.2019.10.103] [Citation(s) in RCA: 43] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2019] [Revised: 10/09/2019] [Accepted: 10/25/2019] [Indexed: 12/11/2022] Open
Abstract
Lymph nodes (LNs) act as filters, constantly sampling peripheral cues. This is facilitated by the conduit network, a tubular structure of aligned extracellular matrix (ECM) fibrils ensheathed by fibroblastic reticular cells (FRCs). LNs undergo rapid 3- to 5-fold expansion during adaptive immune responses, but these ECM-rich structures are not permanently damaged. Whether conduit flow or filtering function is affected during LN expansion is unknown. Here, we show that conduits are partially disrupted during acute LN expansion, but FRC-FRC contacts remain connected. We reveal that polarized FRCs deposit ECM basolaterally using LL5-β and that ECM production is regulated at transcriptional and secretory levels by the C-type lectin CLEC-2, expressed by dendritic cells. Inflamed LNs maintain conduit size exclusion, and flow is disrupted but persists, indicating the robustness of this structure despite rapid tissue expansion. We show how dynamic communication between peripheral tissues and LNs provides a mechanism to prevent inflammation-induced fibrosis in lymphoid tissue.
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Affiliation(s)
- Victor G Martinez
- Stromal Immunology Group, MRC Laboratory for Molecular Cell Biology, University College London, Gower Street, London WC1E 6BT, UK
| | - Valeriya Pankova
- Stromal Immunology Group, MRC Laboratory for Molecular Cell Biology, University College London, Gower Street, London WC1E 6BT, UK
| | - Lukas Krasny
- Division of Molecular Pathology, Institute of Cancer Research, 237 Fulham Road, London SW3 6JB, UK
| | - Tanya Singh
- Bioinformatics Image Core, MRC Laboratory for Molecular Cell Biology, University College London, London WC1E 6BT, UK
| | - Spyridon Makris
- Stromal Immunology Group, MRC Laboratory for Molecular Cell Biology, University College London, Gower Street, London WC1E 6BT, UK
| | - Ian J White
- Electron Microscopy Facility, MRC Laboratory for Molecular Cell Biology, University College London, London WC1E 6BT, UK
| | - Agnesska C Benjamin
- Stromal Immunology Group, MRC Laboratory for Molecular Cell Biology, University College London, Gower Street, London WC1E 6BT, UK
| | - Simone Dertschnig
- UCL Institute of Immunity and Transplantation, University College London, London NW3 2PF, UK
| | - Harry L Horsnell
- Stromal Immunology Group, MRC Laboratory for Molecular Cell Biology, University College London, Gower Street, London WC1E 6BT, UK
| | - Janos Kriston-Vizi
- Bioinformatics Image Core, MRC Laboratory for Molecular Cell Biology, University College London, London WC1E 6BT, UK
| | - Jemima J Burden
- Electron Microscopy Facility, MRC Laboratory for Molecular Cell Biology, University College London, London WC1E 6BT, UK
| | - Paul H Huang
- Division of Molecular Pathology, Institute of Cancer Research, 237 Fulham Road, London SW3 6JB, UK
| | - Christopher J Tape
- Cell Communication Lab, Department of Oncology, University College London Cancer Institute, 72 Huntley Street, London WC1E 6DD, UK
| | - Sophie E Acton
- Stromal Immunology Group, MRC Laboratory for Molecular Cell Biology, University College London, Gower Street, London WC1E 6BT, UK.
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8
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Lopes-da-Silva M, McCormack JJ, Burden JJ, Harrison-Lavoie KJ, Ferraro F, Cutler DF. A GBF1-Dependent Mechanism for Environmentally Responsive Regulation of ER-Golgi Transport. Dev Cell 2019; 49:786-801.e6. [PMID: 31056345 PMCID: PMC6764485 DOI: 10.1016/j.devcel.2019.04.006] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2018] [Revised: 02/19/2019] [Accepted: 04/04/2019] [Indexed: 12/17/2022]
Abstract
How can anterograde membrane trafficking be modulated by physiological cues? A screen of Golgi-associated proteins revealed that the ARF-GEF GBF1 can selectively modulate the ER-Golgi trafficking of prohaemostatic von Willebrand factor (VWF) and extracellular matrix (ECM) proteins in human endothelial cells and in mouse fibroblasts. The relationship between levels of GBF1 and the trafficking of VWF into forming secretory granules confirmed GBF1 is a limiting factor in this process. Further, GBF1 activation by AMPK couples its control of anterograde trafficking to physiological cues; levels of glucose control GBF1 activation in turn modulating VWF trafficking into secretory granules. GBF1 modulates both ER and TGN exit, the latter dramatically affecting the size of the VWF storage organelles, thereby influencing the hemostatic capacity of the endothelium. The role of AMPK as a central integrating element of cellular pathways with intra- and extra-cellular cues can now be extended to modulation of the anterograde secretory pathway. The Arf-GEF GBF1 modulates anterograde trafficking of VWF and ECM proteins Loss of GBF1 slows ER and TGN exit, producing swollen ER and giant WPBs Activation of GBF1 via AMPK reduces endothelial WPB size and secretion Metabolic change alters anterograde trafficking and cargo secretion via AMPK-GBF1
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Affiliation(s)
- Mafalda Lopes-da-Silva
- Endothelial Cell Biology Laboratory, MRC Laboratory for Molecular Cell Biology, University College London, London, UK.
| | - Jessica J McCormack
- Endothelial Cell Biology Laboratory, MRC Laboratory for Molecular Cell Biology, University College London, London, UK
| | - Jemima J Burden
- Electron Microscopy Laboratory, MRC Laboratory for Molecular Cell Biology, University College London, London, UK
| | - Kimberly J Harrison-Lavoie
- Endothelial Cell Biology Laboratory, MRC Laboratory for Molecular Cell Biology, University College London, London, UK
| | - Francesco Ferraro
- Endothelial Cell Biology Laboratory, MRC Laboratory for Molecular Cell Biology, University College London, London, UK
| | - Daniel F Cutler
- Endothelial Cell Biology Laboratory, MRC Laboratory for Molecular Cell Biology, University College London, London, UK.
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9
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Saraste J, Marie M. Intermediate compartment (IC): from pre-Golgi vacuoles to a semi-autonomous membrane system. Histochem Cell Biol 2018; 150:407-430. [PMID: 30173361 PMCID: PMC6182704 DOI: 10.1007/s00418-018-1717-2] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/27/2018] [Indexed: 12/19/2022]
Abstract
Despite its discovery more than three decades ago and well-established role in protein sorting and trafficking in the early secretory pathway, the intermediate compartment (IC) has remained enigmatic. The prevailing view is that the IC evolved as a specialized organelle to mediate long-distance endoplasmic reticulum (ER)–Golgi communication in metazoan cells, but is lacking in other eukaryotes, such as plants and fungi. However, this distinction is difficult to reconcile with the high conservation of the core machineries that regulate early secretory trafficking from yeast to man. Also, it has remained unclear whether the pleiomorphic IC components—vacuoles, tubules and vesicles—represent transient transport carriers or building blocks of a permanent pre-Golgi organelle. Interestingly, recent studies have revealed that the IC maintains its compositional, structural and spatial properties throughout the cell cycle, supporting a model that combines the dynamic and stable aspects of the organelle. Moreover, the IC has been assigned novel functions, such as cell signaling, Golgi-independent trafficking and autophagy. The emerging permanent nature of the IC and its connections with the centrosome and the endocytic recycling system encourage reconsideration of its relationship with the Golgi ribbon, role in Golgi biogenesis and ubiquitous presence in eukaryotic cells.
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Affiliation(s)
- Jaakko Saraste
- Department of Biomedicine and Molecular Imaging Center (MIC), University of Bergen, Jonas Lies vei 91, 5009, Bergen, Norway.
| | - Michaël Marie
- Department of Biomedicine and Molecular Imaging Center (MIC), University of Bergen, Jonas Lies vei 91, 5009, Bergen, Norway
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10
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von Willebrand factor multimerization and the polarity of secretory pathways in endothelial cells. Blood 2016; 128:277-85. [PMID: 27106123 DOI: 10.1182/blood-2015-10-677054] [Citation(s) in RCA: 71] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2015] [Accepted: 04/14/2016] [Indexed: 01/09/2023] Open
Abstract
The von Willebrand factor (VWF) synthesized and secreted by endothelial cells is central to hemostasis and thrombosis, providing a multifunctional adhesive platform that brings together components needed for these processes. VWF secretion can occur from both apical and basolateral sides of endothelial cells, and from constitutive, basal, and regulated secretory pathways, the latter two via Weibel-Palade bodies (WPB). Although the amount and structure of VWF is crucial to its function, the extent of VWF release, multimerization, and polarity of the 3 secretory pathways have only been addressed separately, and with conflicting results. We set out to clarify these relationships using polarized human umbilical vein endothelial cells (HUVECs) grown on Transwell membranes. We found that regulated secretion of ultra-large (UL)-molecular-weight VWF predominantly occurred apically, consistent with a role in localized platelet capture in the vessel lumen. We found that constitutive secretion of low-molecular-weight (LMW) VWF is targeted basolaterally, toward the subendothelial matrix, using the adaptor protein complex 1 (AP-1), where it may provide the bulk of collagen-bound subendothelial VWF. We also found that basally-secreted VWF is composed of UL-VWF, released continuously from WPBs in the absence of stimuli, and occurs predominantly apically, suggesting this could be the main source of circulating plasma VWF. Together, we provide a unified dataset reporting the amount and multimeric state of VWF secreted from the constitutive, basal, and regulated pathways in polarized HUVECs, and have established a new role for AP-1 in the basolateral constitutive secretion of VWF.
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11
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Saraste J, Marie M. Intermediate Compartment: A Sorting Station between the Endoplasmic Reticulum and the Golgi Apparatus. ENCYCLOPEDIA OF CELL BIOLOGY 2016. [PMCID: PMC7150006 DOI: 10.1016/b978-0-12-394447-4.20013-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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12
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The Directional Observation of Highly Dynamic Membrane Tubule Formation Induced by Engulfed Liposomes. Sci Rep 2015; 5:16559. [PMID: 26548331 PMCID: PMC4637876 DOI: 10.1038/srep16559] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2015] [Accepted: 10/01/2015] [Indexed: 11/09/2022] Open
Abstract
Highly dynamic tubular structures in cells are responsible for exchanges between organelles. Compared with bacterial invasion, the most affordable and least toxic lipids were found in this study to be gentle and safe exogenous stimuli for the triggering of membrane tubules. A specific lipid system was internalized by NIH3T3 cells. Following cellular uptake, the constructed liposomes traveled towards the nucleus in aggregations and were gradually distributed into moving vesicles and tubules in the cytosol. The triggered tubules proceeded, retreated or fluctuated along the cytoskeleton and were highly dynamic, moving quickly (up to several microns per second), and breaking and fusing frequently. These elongated tubules could also fuse with one another, giving rise to polygonal membrane networks. These lipid systems, with the novel property of accelerating intracellular transport, provide a new paradigm for investigating cellular dynamics.
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13
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Beznoussenko GV, Parashuraman S, Rizzo R, Polishchuk R, Martella O, Di Giandomenico D, Fusella A, Spaar A, Sallese M, Capestrano MG, Pavelka M, Vos MR, Rikers YGM, Helms V, Mironov AA, Luini A. Transport of soluble proteins through the Golgi occurs by diffusion via continuities across cisternae. eLife 2014; 3:e02009. [PMID: 24867214 PMCID: PMC4070021 DOI: 10.7554/elife.02009] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2013] [Accepted: 05/25/2014] [Indexed: 12/18/2022] Open
Abstract
The mechanism of transport through the Golgi complex is not completely understood, insofar as no single transport mechanism appears to account for all of the observations. Here, we compare the transport of soluble secretory proteins (albumin and α1-antitrypsin) with that of supramolecular cargoes (e.g., procollagen) that are proposed to traverse the Golgi by compartment progression-maturation. We show that these soluble proteins traverse the Golgi much faster than procollagen while moving through the same stack. Moreover, we present kinetic and morphological observations that indicate that albumin transport occurs by diffusion via intercisternal continuities. These data provide evidence for a transport mechanism that applies to a major class of secretory proteins and indicate the co-existence of multiple intra-Golgi trafficking modes.
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Affiliation(s)
- Galina V Beznoussenko
- Fondazione IFOM, Istituto FIRC di Oncologia Molecolare (IFOM-IEO Campus), Milan, Italy
- Department of Cell Biology and Oncology, Consorzio Mario Negri Sud, Santa Maria Imbaro, Italy
| | - Seetharaman Parashuraman
- Department of Cell Biology and Oncology, Consorzio Mario Negri Sud, Santa Maria Imbaro, Italy
- Institute of Protein Biochemistry, Consiglio Nazionale Delle Ricerche (CNR-IBP), Naples, Italy
| | - Riccardo Rizzo
- Institute of Protein Biochemistry, Consiglio Nazionale Delle Ricerche (CNR-IBP), Naples, Italy
| | - Roman Polishchuk
- Department of Cell Biology and Oncology, Consorzio Mario Negri Sud, Santa Maria Imbaro, Italy
- Telethon Institute for Genetics and Medicine (TIGEM), Naples, Italy
| | - Oliviano Martella
- Department of Cell Biology and Oncology, Consorzio Mario Negri Sud, Santa Maria Imbaro, Italy
| | - Daniele Di Giandomenico
- Department of Cell Biology and Oncology, Consorzio Mario Negri Sud, Santa Maria Imbaro, Italy
| | - Aurora Fusella
- Department of Cell Biology and Oncology, Consorzio Mario Negri Sud, Santa Maria Imbaro, Italy
| | - Alexander Spaar
- Department of Cell Biology and Oncology, Consorzio Mario Negri Sud, Santa Maria Imbaro, Italy
| | - Michele Sallese
- Department of Cell Biology and Oncology, Consorzio Mario Negri Sud, Santa Maria Imbaro, Italy
| | - Maria Grazia Capestrano
- Department of Cell Biology and Oncology, Consorzio Mario Negri Sud, Santa Maria Imbaro, Italy
| | - Margit Pavelka
- Department of Cell Biology and Ultrastructure Research, Center for Anatomy and Cell Biology, Medical University of Vienna, Vienna, Austria
| | | | | | - Volkhard Helms
- Center for Bioinformatics, Saarland University, Saarbruecken, Germany
| | - Alexandre A Mironov
- Fondazione IFOM, Istituto FIRC di Oncologia Molecolare (IFOM-IEO Campus), Milan, Italy
| | - Alberto Luini
- Department of Cell Biology and Oncology, Consorzio Mario Negri Sud, Santa Maria Imbaro, Italy
- Institute of Protein Biochemistry, Consiglio Nazionale Delle Ricerche (CNR-IBP), Naples, Italy
- Telethon Institute for Genetics and Medicine (TIGEM), Naples, Italy
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14
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Andreska T, Aufmkolk S, Sauer M, Blum R. High abundance of BDNF within glutamatergic presynapses of cultured hippocampal neurons. Front Cell Neurosci 2014; 8:107. [PMID: 24782711 PMCID: PMC3990111 DOI: 10.3389/fncel.2014.00107] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2014] [Accepted: 03/25/2014] [Indexed: 11/23/2022] Open
Abstract
In the mammalian brain, the neurotrophin brain-derived neurotrophic factor (BDNF) has emerged as a key factor for synaptic refinement, plasticity and learning. Although BDNF-induced signaling cascades are well known, the spatial aspects of the synaptic BDNF localization remained unclear. Recent data provide strong evidence for an exclusive presynaptic location and anterograde secretion of endogenous BDNF at synapses of the hippocampal circuit. In contrast, various studies using BDNF overexpression in cultured hippocampal neurons support the idea that postsynaptic elements and other dendritic structures are the preferential sites of BDNF localization and release. In this study we used rigorously tested anti-BDNF antibodies and achieved a dense labeling of endogenous BDNF close to synapses. Confocal microscopy showed natural BDNF close to many, but not all glutamatergic synapses, while neither GABAergic synapses nor postsynaptic structures carried a typical synaptic BDNF label. To visualize the BDNF distribution within the fine structure of synapses, we implemented super resolution fluorescence imaging by direct stochastic optical reconstruction microscopy (dSTORM). Two-color dSTORM images of neurites were acquired with a spatial resolution of ~20 nm. At this resolution, the synaptic scaffold proteins Bassoon and Homer exhibit hallmarks of mature synapses and form juxtaposed bars, separated by a synaptic cleft. BDNF imaging signals form granule-like clusters with a mean size of ~60 nm and are preferentially found within the fine structure of the glutamatergic presynapse. Individual glutamatergic presynapses carried up to 90% of the synaptic BDNF immunoreactivity, and only a minor fraction of BDNF molecules was found close to the postsynaptic bars. Our data proof that hippocampal neurons are able to enrich and store high amounts of BDNF in small granules within the mature glutamatergic presynapse, at a principle site of synaptic plasticity.
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Affiliation(s)
- Thomas Andreska
- Institute for Clinical Neurobiology, University Hospital, Julius-Maximilians-University Würzburg Würzburg, Germany
| | - Sarah Aufmkolk
- Department of Biotechnology and Biophysics, Biocenter, Julius-Maximilians-University Würzburg Würzburg, Germany
| | - Markus Sauer
- Department of Biotechnology and Biophysics, Biocenter, Julius-Maximilians-University Würzburg Würzburg, Germany
| | - Robert Blum
- Institute for Clinical Neurobiology, University Hospital, Julius-Maximilians-University Würzburg Würzburg, Germany
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15
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Neto H, Kaupisch A, Collins LL, Gould GW. Syntaxin 16 is a master recruitment factor for cytokinesis. Mol Biol Cell 2013; 24:3663-74. [PMID: 24109596 PMCID: PMC3842993 DOI: 10.1091/mbc.e13-06-0302] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Syntaxin 16 is a key regulator of cytokinesis, as it is required for the recruitment of both recycling endosome–associated Exocyst and ESCRT machinery during late telophase. Therefore these two distinct facets of cytokinesis are inextricably linked. Recently it was shown that both recycling endosome and endosomal sorting complex required for transport (ESCRT) components are required for cytokinesis, in which they are believed to act in a sequential manner to bring about secondary ingression and abscission, respectively. However, it is not clear how either of these complexes is targeted to the midbody and whether their delivery is coordinated. The trafficking of membrane vesicles between different intracellular organelles involves the formation of soluble N-ethylmaleimide–sensitive factor attachment protein receptor (SNARE) complexes. Although membrane traffic is known to play an important role in cytokinesis, the contribution and identity of intracellular SNAREs to cytokinesis remain unclear. Here we demonstrate that syntaxin 16 is a key regulator of cytokinesis, as it is required for recruitment of both recycling endosome–associated Exocyst and ESCRT machinery during late telophase, and therefore that these two distinct facets of cytokinesis are inextricably linked.
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Affiliation(s)
- Hélia Neto
- Henry Wellcome Laboratory of Cell Biology, Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, United Kingdom
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16
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Abstract
The Golgi complex is considered the central station of the secretory pathway where cargo proteins and lipids are properly modified, classified, packed into specific carriers and delivered to their final destinations. Early electron microscope studies showed the extraordinary structural complexity of this organelle. However, despite the large volume of incoming and outgoing traffic, it is able to maintain its architecture, although it is also flexible enough to adapt to the functional status of the cell. Many components of the molecular machinery involved in membrane traffic and other Golgi functions have been identified. However, some basic aspects of Golgi functioning remain unsolved. For instance, how cargo moves through the stack remains controversial and two classical models have been proposed: vesicular transport and cisternal maturation. Since neither of these models explains all the experimental data, a combination of these models as well as new models have been proposed. In this context, the specific role of the cisternae, vesicles and tubules needs to be clarified. In this review, we summarize our current knowledge of the Golgi organization and function, focusing on the mechanisms of intra-Golgi transport.
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17
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Yadav S, Puthenveedu MA, Linstedt AD. Golgin160 recruits the dynein motor to position the Golgi apparatus. Dev Cell 2012; 23:153-65. [PMID: 22814606 DOI: 10.1016/j.devcel.2012.05.023] [Citation(s) in RCA: 77] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2012] [Revised: 04/19/2012] [Accepted: 05/29/2012] [Indexed: 11/26/2022]
Abstract
Membrane motility is a fundamental characteristic of all eukaryotic cells. One of the best-known examples is that of the mammalian Golgi apparatus, where constant inward movement of Golgi membranes results in its characteristic position near the centrosome. While it is clear that the minus-end-directed motor dynein is required for this process, the mechanism and regulation of dynein recruitment to Golgi membranes remains unknown. Here, we show that the Golgi protein golgin160 recruits dynein to Golgi membranes. This recruitment confers centripetal motility to membranes and is regulated by the GTPase Arf1. Further, during cell division, motor association with membranes is regulated by the dissociation of the receptor-motor complex from membranes. These results identify a cell-cycle-regulated membrane receptor for a molecular motor and suggest a mechanistic basis for achieving the dramatic changes in organelle positioning seen during cell division.
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Affiliation(s)
- Smita Yadav
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, PA 15213, USA
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18
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Rannou Y, Salaun P, Benaud C, Khan J, Dutertre S, Giet R, Prigent C. MNK1 kinase activity is required for abscission. J Cell Sci 2012; 125:2844-52. [PMID: 22454512 DOI: 10.1242/jcs.058081] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
MNK1 is a serine/threonine kinase identified as a target for MAP kinase pathways. Using chemical drug, kinase-dead expression or knockdown by RNA interference, we show that inhibition of MNK1 induces the formation of multinucleated cells, which can be rescued by expressing a form of MNK1 that is resistant to RNA interference. We found that the active human form of MNK1 localises to centrosomes, spindle microtubules and the midbody. Time-lapse recording of MNK1-depleted cells displays cytokinesis defects, as daughter cells fuse back together. When MNK1 activity was inhibited, no microtubule defect at the midbody was detected, however, anchorage of the membrane vesicle at the midbody was impaired as lumenal GFP-positive vesicles did not accumulate at the midbody. At the molecular level, we found that centriolin localisation was impaired at the midbody in MNK1-depleted cells. As a consequence, endobrevin - a v-SNARE protein implicated in the abscission step - was not properly localised to the midbody. Altogether, our data show that MNK1 activity is required for abscission.
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Affiliation(s)
- Yoann Rannou
- CNRS UMR 6290, IGDR, Rennes, CS34317, 35043 Rennes, France
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19
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Ben-Tekaya H, Kahn RA, Hauri HP. ADP ribosylation factors 1 and 4 and group VIA phospholipase A₂ regulate morphology and intraorganellar traffic in the endoplasmic reticulum-Golgi intermediate compartment. Mol Biol Cell 2010; 21:4130-40. [PMID: 20881058 PMCID: PMC2993742 DOI: 10.1091/mbc.e10-01-0022] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
In search of morphological determinants for the endoplasmic reticulum-Golgi intermediate compartment (ERGIC), we found that a concerted action of Arf1, Arf4, and PLA2G6-A controls the architecture of the ERGIC by regulating tubular carriers. This is predicted to impact the rate of transport and destination of cargos in the ERGIC. Organelle morphology of the endomembrane system is critical for optimal organelle function. ADP ribosylation factors (Arfs), a family of small GTPases, are required for maintaining the structure of the Golgi and endosomes. What determines the discontinuous nature of the endoplasmic reticulum (ER)–Golgi intermediate compartment (ERGIC) as tubulovesicular clusters is unknown. In search of morphological determinants for the ERGIC, we found that a double knockdown of Arf1+Arf4 induced dynamic ERGIC tubules that connect ERGIC clusters, indicating that the tubules mediated lateral intraERGIC traffic. Tubule formation was inhibited by an antagonist of group VI calcium-independent phospholipase A2 (PLA2G6) and by silencing the A isoform of PLA2G6 (PLA2G6-A). Arf1+Arf4 depletion altered the expression of PLA2G6-A splice variants and relocalized PLA2G6-A from the cytosol to ERGIC clusters and tubules, suggesting that the enzyme became locally active. We show that changes in Arf1 can modulate the activity of PLA2G6-A. We propose that a concerted action of Arf1, Arf4, and PLA2G6-A controls the architecture of the ERGIC in a way that is predicted to impact the rate and possibly the destination of cargos. Our findings have identified key components in the molecular mechanism underlying the regulation of tubules in the ERGIC and uncover tubular carriers as tightly controlled machinery.
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20
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Nevalainen M, Kaisto T, Metsikkö K. Mobile ER-to-Golgi but not post-Golgi membrane transport carriers disappear during the terminal myogenic differentiation. Cell Tissue Res 2010; 342:107-16. [DOI: 10.1007/s00441-010-1041-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2010] [Accepted: 08/16/2010] [Indexed: 11/29/2022]
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21
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Abstract
Endothelial cells are reported to contain several distinct populations of regulated secretory organelles, including Weibel-Palade bodies (WPBs), the tissue plasminogen activator (tPA) organelle, and the type-2 chemokine-containing organelle. We show that the tPA and type-2 organelles in human endothelial cells represent a single compartment primarily responsible for unstimulated secretion of tPA or, in cells exposed to interleukin-1β (IL-1β), the cytokines IL-8, IL-6, monocyte chemoattractant protein-1 (MCP-1), and growth-regulated oncogene-α (GRO-α). This compartment was distinct from WPBs in that it lacked detectable von Willebrand factor, P-selectin, Rab27a, or CD63 immunoreactivity, displayed no time-dependent decrease in intragranule pH, underwent detectable unstimulated exocytosis, and was very poorly responsive to Ca(2+)-elevating secretagogues. WPBs could also contain tPA, and in IL-1β-treated cells, IL-8, IL-6, MCP-1, and GRO-α, and were the primary source for histamine or ionomycin-stimulated secretion of these molecules. However, analysis of the storage efficiency of cytokines and tPA revealed that all were very poorly stored compared with von Willebrand factor. The nonmammalian, nonsecretory protein EGFP, when expressed in the secretory pathway, also entered WPBs and had a storage efficiency similar to tPA and the cytokines tested. Based on these data, we proposed a revised model for storage and secretion of cytokines and tPA.
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22
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Saraste J, Dale HA, Bazzocco S, Marie M. Emerging new roles of the pre-Golgi intermediate compartment in biosynthetic-secretory trafficking. FEBS Lett 2009; 583:3804-10. [PMID: 19887068 DOI: 10.1016/j.febslet.2009.10.084] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2009] [Revised: 10/21/2009] [Accepted: 10/30/2009] [Indexed: 12/30/2022]
Abstract
The intermediate compartment (IC) between the endoplasmic reticulum (ER) and the Golgi apparatus appears to constitute an autonomous organelle composed of spatially and functionally distinct, but interconnected, vacuolar and tubular subdomains. In mammalian cells the IC network is stably anchored at the cell center, communicating directly with the endocytic pathway via a pericentrosomal membrane system (PCMS). This finding suggests that the secretory pathway divides at the level of the IC, which functions as a sorting station both in Golgi-dependent and -independent trafficking. The tubular subdomain of the IC is capable of expansion in accordance with its proposed biosynthetic functions such as cholesterol synthesis.
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Affiliation(s)
- Jaakko Saraste
- Department of Biomedicine and Molecular Imaging Center, University of Bergen, Jonas Lies Vei 91, N-5009 Bergen, Norway.
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23
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Shaping tubular carriers for intracellular membrane transport. FEBS Lett 2009; 583:3847-56. [DOI: 10.1016/j.febslet.2009.10.031] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2009] [Revised: 10/09/2009] [Accepted: 10/13/2009] [Indexed: 12/22/2022]
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24
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Steigemann P, Gerlich DW. Cytokinetic abscission: cellular dynamics at the midbody. Trends Cell Biol 2009; 19:606-16. [PMID: 19733077 DOI: 10.1016/j.tcb.2009.07.008] [Citation(s) in RCA: 107] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2009] [Revised: 07/18/2009] [Accepted: 07/20/2009] [Indexed: 10/20/2022]
Abstract
The intercellular canal containing the midbody is one of the most prominent structures in dividing animal cells, yet its function in the completion of cytokinesis by abscission remains largely unknown. This is because of its small size, which makes it difficult to investigate the cytoskeletal and membrane dynamics underlying abscission by standard light microscopy. The advent of new fluorescent probes and imaging technologies, along with sophisticated perturbation tools, provides new possibilities to elucidate the molecular control of this essential cell biological process. Here we discuss the control of midbody assembly and current models for the mechanism of abscission in animal cells. We highlight new methodologies that will facilitate testing and refining of these models.
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Affiliation(s)
- Patrick Steigemann
- Institute of Biochemistry, Swiss Federal Institute of Technology Zurich (ETHZ), Schafmattstr. 18, CH-8093 Zurich, Switzerland
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25
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A new non-disruptive strategy to target calcium indicator dyes to the endoplasmic reticulum. Cell Calcium 2008; 44:386-99. [DOI: 10.1016/j.ceca.2008.02.002] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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26
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Blum R, Lepier A. The Luminal Domain of p23 (Tmp21) Plays a Critical Role in p23 Cell Surface Trafficking. Traffic 2008; 9:1530-50. [DOI: 10.1111/j.1600-0854.2008.00784.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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27
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Szul T, Grabski R, Lyons S, Morohashi Y, Shestopal S, Lowe M, Sztul E. Dissecting the role of the ARF guanine nucleotide exchange factor GBF1 in Golgi biogenesis and protein trafficking. J Cell Sci 2007; 120:3929-40. [PMID: 17956946 DOI: 10.1242/jcs.010769] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
COPI recruitment to membranes appears to be essential for the biogenesis of the Golgi and for secretory trafficking. Preventing COPI recruitment by expressing inactive forms of the ADP-ribosylation factor (ARF) or the ARF-activating guanine nucleotide exchange factor GBF1, or by treating cells with brefeldin A (BFA), causes the collapse of the Golgi into the endoplasmic reticulum (ER) and arrests trafficking of soluble and transmembrane proteins at the ER. Here, we assess COPI function in Golgi biogenesis and protein trafficking by preventing COPI recruitment to membranes by removing GBF1. We report that siRNA-mediated depletion of GBF1 causes COPI dispersal but does not lead to collapse of the Golgi. Instead, it causes extensive tubulation of the cis-Golgi. The Golgi-derived tubules target to peripheral ER-Golgi intermediate compartment (ERGIC) sites and create dynamic continuities between the ERGIC and the cis-Golgi compartment. COPI dispersal in GBF1-depleted cells causes dramatic inhibition of the trafficking of transmembrane proteins. Unexpectedly, soluble proteins continue to be secreted from GBF1-depleted cells. Our findings suggest that a secretory pathway capable of trafficking soluble proteins can be maintained in cells in which COPI recruitment is compromised by GBF1 depletion. However, the trafficking of transmembrane proteins through the existing pathway requires GBF1-mediated ARF activation and COPI recruitment.
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Affiliation(s)
- Tomasz Szul
- Department of Cell Biology, University of Alabama at Birmingham, 1918 University Blvd, Birmingham, AL 35924, USA
| | - Robert Grabski
- Department of Cell Biology, University of Alabama at Birmingham, 1918 University Blvd, Birmingham, AL 35924, USA
| | - Susan Lyons
- Department of Cell Biology, University of Alabama at Birmingham, 1918 University Blvd, Birmingham, AL 35924, USA
| | - Yuichi Morohashi
- University of Manchester, Faculty of Life Sciences, Manchester M13 9PT, UK
| | - Svetlana Shestopal
- Department of Cell Biology, University of Alabama at Birmingham, 1918 University Blvd, Birmingham, AL 35924, USA
| | - Martin Lowe
- University of Manchester, Faculty of Life Sciences, Manchester M13 9PT, UK
| | - Elizabeth Sztul
- Department of Cell Biology, University of Alabama at Birmingham, 1918 University Blvd, Birmingham, AL 35924, USA
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28
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Kirk SJ, Ward TH. COPII under the microscope. Semin Cell Dev Biol 2007; 18:435-47. [PMID: 17693103 DOI: 10.1016/j.semcdb.2007.07.007] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2007] [Revised: 07/05/2007] [Accepted: 07/09/2007] [Indexed: 11/19/2022]
Abstract
Transport through the secretory pathway begins with COPII regulation of ER export. Driven by the Sar1 GTPase cycle, cytosolic COPII proteins exchange on and off the membrane at specific sites on the ER to regulate cargo exit. Here recent developments in COPII research are discussed, particularly the use of live-cell imaging, which has revealed surprising insights into the coat's role. The seemingly static ER exit sites are in fact highly dynamic, and the ability to visualise trafficking processes in intact living cells has highlighted the adaptable nature of COPII in cargo transport and the emerging roles of auxiliary factors.
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Affiliation(s)
- Semra J Kirk
- Immunology Unit, London School of Hygiene & Tropical Medicine, Keppel Street, London WC1E 7HT, UK.
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29
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Gromley A, Yeaman C, Rosa J, Redick S, Chen CT, Mirabelle S, Guha M, Sillibourne J, Doxsey SJ. Centriolin anchoring of exocyst and SNARE complexes at the midbody is required for secretory-vesicle-mediated abscission. Cell 2005; 123:75-87. [PMID: 16213214 DOI: 10.1016/j.cell.2005.07.027] [Citation(s) in RCA: 342] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2004] [Revised: 06/03/2005] [Accepted: 07/27/2005] [Indexed: 12/28/2022]
Abstract
The terminal step in cytokinesis, called abscission, requires resolution of the membrane connection between two prospective daughter cells. Our previous studies demonstrated that the coiled-coil protein centriolin localized to the midbody during cytokinesis and was required for abscission. Here we show that centriolin interacts with proteins of vesicle-targeting exocyst complexes and vesicle-fusion SNARE complexes. These complexes require centriolin for localization to a unique midbody-ring structure, and disruption of either complex inhibits abscission. Exocyst disruption induces accumulation of v-SNARE-containing vesicles at the midbody ring. In control cells, these v-SNARE vesicles colocalize with a GFP-tagged secreted polypeptide. The vesicles move to the midbody ring asymmetrically from one prospective daughter cell; the GFP signal is rapidly lost, suggesting membrane fusion; and subsequently the cell cleaves at the site of vesicle delivery/fusion. We propose that centriolin anchors protein complexes required for vesicle targeting and fusion and integrates membrane-vesicle fusion with abscission.
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Affiliation(s)
- Adam Gromley
- Program in Molecular Medicine, University of Massachusetts Medical Center, Worcester, Massachusetts 01605, USA
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30
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Simpson JC, Nilsson T, Pepperkok R. Biogenesis of tubular ER-to-Golgi transport intermediates. Mol Biol Cell 2005; 17:723-37. [PMID: 16314391 PMCID: PMC1356583 DOI: 10.1091/mbc.e05-06-0580] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Tubular transport intermediates (TTIs) have been described as one class of transport carriers in endoplasmic reticulum (ER)-to-Golgi transport. In contrast to vesicle budding and fusion, little is known about the molecular regulation of TTI synthesis, transport and fusion with target membranes. Here we have used in vivo imaging of various kinds of GFP-tagged proteins to start to address these questions. We demonstrate that under steady-state conditions TTIs represent approximately 20% of all moving transport carriers. They increase in number and length when more transport cargo becomes available at the donor membrane, which we induced by either temperature-related transport blocks or increased expression of the respective GFP-tagged transport markers. The formation and motility of TTIs is strongly dependent on the presence of intact microtubules. Microinjection of GTPgammaS increases the frequency of TTI synthesis and the length of these carriers. When Rab proteins are removed from membranes by microinjection of recombinant Rab-GDI, the synthesis of TTIs is completely blocked. Microinjection of the cytoplasmic tails of the p23 and p24 membrane proteins also abolishes formation of p24-containing TTIs. Our data suggest that TTIs are ER-to-Golgi transport intermediates that form preferentially when transport-competent cargo exists in excess at the donor membrane. We propose a model where the interaction of the cytoplasmic tails of membrane proteins with microtubules are key determinants for TTI synthesis and may also serve as a so far unappreciated model for aspects of transport carrier formation.
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Affiliation(s)
- Jeremy C Simpson
- Cell Biology and Biophysics Programme, European Molecular Biology Laboratory, 69117 Heidelberg, Germany.
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31
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Levine T, Rabouille C. Endoplasmic reticulum: one continuous network compartmentalized by extrinsic cues. Curr Opin Cell Biol 2005; 17:362-8. [PMID: 15975783 DOI: 10.1016/j.ceb.2005.06.005] [Citation(s) in RCA: 102] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2005] [Accepted: 06/06/2005] [Indexed: 11/19/2022]
Abstract
The endoplasmic reticulum (ER) is an extensive three-dimensional network that stretches from the inner nuclear envelope to the cell cortex with a single, continuous membrane and a single, continuous lumen. Yet the ER contains specialized regions that carry out unique functions. The question that immediately arises is how the ER can be compartmentalized if it is continuous, and the answer to this is that cellular landmarks with unique sub-cellular distributions impose non-uniformity on the ER from outside, creating structural and functional sub-domains of the ER.
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Affiliation(s)
- Tim Levine
- Division of Cell Biology, Institute of Ophthalmology, 11-43 Bath Street, London EC1V 9EL, UK
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32
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Tang BL, Wang Y, Ong YS, Hong W. COPII and exit from the endoplasmic reticulum. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2005; 1744:293-303. [PMID: 15979503 DOI: 10.1016/j.bbamcr.2005.02.007] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2004] [Revised: 02/16/2005] [Accepted: 02/23/2005] [Indexed: 01/06/2023]
Abstract
First discovered by genetic analysis of yeast secretion mutants, the evolutionarily conserved vesicular coat protein II (COPII) complex is responsible for membrane transport from the endoplasmic reticulum (ER) to the Golgi apparatus. In recent years, extensive efforts in structural, morphological, genetic and molecular analysis have greatly enhanced our understanding of the structural and molecular basis of COPII subunit assembly and selective cargo packaging during ER export. Very recent data have also indicated that a more "classical" picture of vesicle formation from ER exit sites (ERES) followed by their transport to the Golgi is far from accurate. Proteins modulating the function of COPII have also emerged in recent analysis. They either affect COPII-based cargo selection, the formation of vesicle/transport carrier, or subsequent targeting of the transport carrier. Together, elucidation of COPII-mediated ER export has painted a fascinating picture of molecular complexity for an essential process in all eukaryotic cells.
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Affiliation(s)
- Bor Luen Tang
- Department of Biochemistry, National University of Singapore, 8 Medical Drive, Singapore 117597, Singapore.
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33
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Stephens DJ, Pepperkok R. Differential effects of a GTP-restricted mutant of Sar1p on segregation of cargo during export from the endoplasmic reticulum. J Cell Sci 2005; 117:3635-44. [PMID: 15252131 DOI: 10.1242/jcs.01269] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Export of cargo from the endoplasmic reticulum (ER) is the first membrane trafficking step in the secretory pathway. To date, all cargo proteins appear to use a common set of machinery for the initial stages of export, namely the COPII coat complex. Recent data from both yeast and mammalian systems have emerged suggesting that specific cargoes could be sorted from one another at the point of exit from the endoplasmic reticulum or immediately afterwards. Here, we have examined the mechanisms used for export of different types of cargo molecule from the endoplasmic reticulum. All cargoes examined utilise the COPII machinery, but specific differences are seen in the accumulation of cargo into ER-derived pre-budding complexes following expression of a GTP-restricted mutant of the Sar1p GTPase. Glycosylphosphatidylinositol (GPI)-anchored GFP is seen to be restricted to the ER under these conditions whereas other cargoes, including ts045-G and lumFP accumulate in pre-budding complexes. Following exit, GPI-FP, lumFP and ts045-G-FP all travel to the Golgi in the same vesicular tubular clusters (VTCs). These data show a differential requirement for efficient GTP hydrolysis by the Sar1p GTPase in export of cargo from the ER.
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Affiliation(s)
- David J Stephens
- Department of Biochemistry, University of Bristol, School of Medical Sciences, University Walk, Bristol BS8 1TD, UK.
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Ben-Tekaya H, Miura K, Pepperkok R, Hauri HP. Live imaging of bidirectional traffic from the ERGIC. J Cell Sci 2005; 118:357-67. [PMID: 15632110 DOI: 10.1242/jcs.01615] [Citation(s) in RCA: 126] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022] Open
Abstract
The endoplasmic reticulum-Golgi intermediate compartment (ERGIC) defined by the cycling lectin ERGIC-53 consists of tubulovesicular clusters, but it is unknown if these membranes are transport vehicles or stationary entities. Here, we show by live imaging that GFP-ERGIC-53 mainly localizes to long-lived stationary and some short-lived highly mobile elements. Unlike the anterograde marker VSV-G-GFP, GFP-ERGIC-53 does not vectorially move to the Golgi upon exit from the ERGIC, as assessed by a novel quantitative vector field method. Dual-color imaging of GFP-ERGIC-53 and a secretory protein (signal-sequence-tagged dsRed) reveals that the stationary elements are sites of repeated sorting of retrograde and anterograde cargo, and are interconnected by highly mobile elements. These results suggest that the ERGIC is stationary and not simply a collection of mobile carriers that mediate protein traffic from endoplasmic reticulum to Golgi.
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Affiliation(s)
- Houchaima Ben-Tekaya
- Department of Pharmacology and Neurobiology, Biozentrum, University of Basel, Klingelbergstrasse 70, 4056 Basel, Switzerland
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Palmer KJ, Stephens DJ. Biogenesis of ER-to-Golgi transport carriers: complex roles of COPII in ER export. Trends Cell Biol 2004; 14:57-61. [PMID: 15106609 DOI: 10.1016/j.tcb.2003.12.001] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
It is widely believed that membrane traffic occurs by vesicular transport between successive compartments of the secretory pathway. Coat complexes function to collect cargo from donor membranes and deform them to generate transport vesicles with a diameter of 60-80 nm. Recent data argue in favour of a new model for export of secretory cargo from the endoplasmic reticulum, in which tubular extensions are protruded and subsequently matured into independent ER-to-Golgi transport carriers. Here, we examine the evidence for this controversial hypothesis.
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Affiliation(s)
- Krysten J Palmer
- Department of Biochemistry, University of Bristol, School of Medical Sciences, University Walk, Bristol, UK BS8 1TD
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Nies AT, König J, Cui Y, Brom M, Spring H, Keppler D. Structural requirements for the apical sorting of human multidrug resistance protein 2 (ABCC2). EUROPEAN JOURNAL OF BIOCHEMISTRY 2002; 269:1866-76. [PMID: 11952788 DOI: 10.1046/j.1432-1033.2002.02832.x] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The human multidrug resistance protein 2 (MRP2, symbol ABCC2) is a polytopic membrane glycoprotein of 1545 amino acids which exports anionic conjugates across the apical membrane of polarized cells. A chimeric protein composed of C-proximal MRP2 and N-proximal MRP1 localized to the apical membrane of polarized Madin-Darby canine kidney cells (MDCKII) indicating involvement of the carboxy-proximal part of human MRP2 in apical sorting. When compared to other MRP family members, MRP2 has a seven-amino-acid extension at its C-terminus with the last three amino acids (TKF) comprising a PDZ-interacting motif. In order to analyze whether this extension is required for apical sorting of MRP2, we generated MRP2 constructs mutated and stepwise truncated at their C-termini. These constructs were fused via their N-termini to green fluorescent protein (GFP) and were transiently transfected into polarized, liver-derived human HepG2 cells. Quantitative analysis showed that full-length GFP-MRP2 was localized to the apical membrane in 73% of transfected, polarized cells, whereas it remained on intracellular membranes in 27% of cells. Removal of the C-terminal TKF peptide and stepwise deletion of up to 11 amino acids did not change this predominant apical distribution. However, apical localization was largely impaired when GFP-MRP2 was C-terminally truncated by 15 or more amino acids. Thus, neither the PDZ-interacting TKF motif nor the full seven-amino-acid extension were necessary for apical sorting of MRP2. Instead, our data indicate that a deletion of at least 15 C-terminal amino acids impairs the localization of MRP2 to the apical membrane of polarized cells.
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Affiliation(s)
- Anne T Nies
- Division of Tumor Biochemistry, Deutsches Krebsforschungszentrum, Heidelberg, Germany.
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Shinotsuka C, Yoshida Y, Kawamoto K, Takatsu H, Nakayama K. Overexpression of an ADP-ribosylation factor-guanine nucleotide exchange factor, BIG2, uncouples brefeldin A-induced adaptor protein-1 coat dissociation and membrane tubulation. J Biol Chem 2002; 277:9468-73. [PMID: 11777925 DOI: 10.1074/jbc.m112427200] [Citation(s) in RCA: 91] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
BIG2 is a guanine nucleotide exchange factor (GEF) for the ADP-ribosylation factor (ARF) family of small GTPases, which regulate membrane association of COPI and adaptor protein (AP)-1 coat protein complexes. A fungal metabolite, brefeldin A (BFA), inhibits ARF-GEFs and leads to redistribution of coat proteins from membranes to the cytoplasm and membrane tubulation of the Golgi complex and the trans-Golgi network (TGN). To investigate the function of BIG2, we examined the effects of BIG2-overexpression on the BFA-induced redistribution of ARF, coat proteins, and organelle markers. The BIG2 overexpression blocked BFA-induced redistribution from membranes of ARF1 and the AP-1 complex but not that of the COPI complex. These observations indicate that BIG2 is implicated in membrane association of AP-1, but not that of COPI, through activating ARF. Furthermore, not only BIG2 but also ARF1 and AP-1 were found as queues of spherical swellings along the BFA-induced membrane tubules emanating from the TGN. These observations indicate that BFA-induced AP-1 dissociation from TGN membranes and tubulation of TGN membranes are not coupled events and suggest that a BFA target other than ARF-GEFs exists in the cell.
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Affiliation(s)
- Chisa Shinotsuka
- Institute of Biological Sciences and Gene Research Center, University of Tsukuba, 1-1-1 Tennohdai, Tsukuba Science City, Ibaraki 305-8572, Japan
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Stephens DJ, Pepperkok R. Imaging of procollagen transport reveals COPI-dependent cargo sorting during ER-to-Golgi transport in mammalian cells. J Cell Sci 2002; 115:1149-60. [PMID: 11884515 DOI: 10.1242/jcs.115.6.1149] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We have examined the ER-to-Golgi transport of procollagen, which, when assembled in the lumen of the ER, is thought to be physically too large to fit in classically described 60-80 nm COPI- and COPII-coated transport vesicles. We found that procollagen exits the ER via COPII- coated ER exit sites and is transported to the Golgi along microtubules in defined transport complexes. These procollagen-containing transport complexes are, however, distinct from those containing other cargo proteins like ERGIC-53 and ts-045-G. Furthermore,they do not label for the COPI coat complex in contrast to those containing ts-045-G. Inhibition of COPII or COPI function before addition of ascorbate,which is required for the folding of procollagen, inhibits export of procollagen from the ER. Inactivation of COPI coat function after addition of ascorbate results in the localisation of procollagen to transport complexes that now also contain ERGIC-53 and are inhibited in their transport to the Golgi complex. These data reveal the existence of an early COPI-dependent,pre-Golgi cargo sorting step in mammalian cells.
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Affiliation(s)
- David J Stephens
- Cell Biology and Cell Biophysics Programme, EMBL Heidelberg, Meyerhofstrasse 1, 69117 Heidelberg, Germany.
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Barr FA, Preisinger C, Kopajtich R, Körner R. Golgi matrix proteins interact with p24 cargo receptors and aid their efficient retention in the Golgi apparatus. J Cell Biol 2001; 155:885-91. [PMID: 11739402 PMCID: PMC2150891 DOI: 10.1083/jcb.200108102] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The Golgi apparatus is a highly complex organelle comprised of a stack of cisternal membranes on the secretory pathway from the ER to the cell surface. This structure is maintained by an exoskeleton or Golgi matrix constructed from a family of coiled-coil proteins, the golgins, and other peripheral membrane components such as GRASP55 and GRASP65. Here we find that TMP21, p24a, and gp25L, members of the p24 cargo receptor family, are present in complexes with GRASP55 and GRASP65 in vivo. GRASPs interact directly with the cytoplasmic domains of specific p24 cargo receptors depending on their oligomeric state, and mutation of the GRASP binding site in the cytoplasmic tail of one of these, p24a, results in it being transported to the cell surface. These results suggest that one function of the Golgi matrix is to aid efficient retention or sequestration of p24 cargo receptors and other membrane proteins in the Golgi apparatus.
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Affiliation(s)
- F A Barr
- Department of Cell Biology, Max-Planck-Institute of Biochemistry, 82152 Martinsried, Germany.
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Marra P, Maffucci T, Daniele T, Tullio GD, Ikehara Y, Chan EK, Luini A, Beznoussenko G, Mironov A, De Matteis MA. The GM130 and GRASP65 Golgi proteins cycle through and define a subdomain of the intermediate compartment. Nat Cell Biol 2001; 3:1101-13. [PMID: 11781572 DOI: 10.1038/ncb1201-1101] [Citation(s) in RCA: 123] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Integrating the pleomorphic membranes of the intermediate compartment (IC) into the array of Golgi cisternae is a crucial step in membrane transport, but it is poorly understood. To gain insight into this step, we investigated the dynamics by which cis-Golgi matrix proteins such as GM130 and GRASP65 associate with, and incorporate, incoming IC elements. We found that GM130 and GRASP65 cycle via membranous tubules between the Golgi complex and a constellation of mobile structures that we call late IC stations. These stations are intermediate between the IC and the cis-Golgi in terms of composition, and they receive cargo from earlier IC elements and deliver it to the Golgi complex. Late IC elements are transient in nature and sensitive to fixatives; they are seen in only a fraction of fixed cells, whereas they are always visible in living cells. Finally, late IC stations undergo homotypic fusion and establish tubular connections between themselves and the Golgi. Overall, these features indicate that late IC stations mediate the transition between IC elements and the cis-Golgi face.
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Affiliation(s)
- P Marra
- Department of Cell Biology and Oncology, Istituto di Ricerche Farmacologiche Mario Negri, Consorzio Mario Negri Sud, 66030 Santa Maria Imbaro (Chieti), Italy
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