1
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Liu RJY, Al-Molieh Y, Chen SZ, Drobac M, Urban D, Chen CH, Yao HHY, Geng RSQ, Li L, Pluthero FG, Benlekbir S, Rubinstein JL, Kahr WHA. The Sec1/Munc18 protein VPS33B forms a uniquely bidirectional complex with VPS16B. J Biol Chem 2023; 299:104718. [PMID: 37062417 DOI: 10.1016/j.jbc.2023.104718] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2023] [Revised: 03/03/2023] [Accepted: 04/07/2023] [Indexed: 04/18/2023] Open
Abstract
Loss of function variants of VPS33B and VIPAS39 (encoding VPS16B) are causative for arthrogryposis, renal dysfunction and cholestasis (ARC) syndrome, where early lethality of patients indicates that VPS33B and VPS16B play essential cellular roles. VPS33B is a member of the Sec1/Munc18 (SM) protein family, and thus thought to facilitate vesicular fusion via interaction with SNARE complexes, as does its paralog VPS33A in the homotypic fusion and vacuole sorting (HOPS) complex. VPS33B and VPS16B have been shown to associate, but little is known about the composition, structure or function of the VPS33B/VPS16B complex. We show here that human VPS33B/VPS16B is a high molecular weight complex, which we expressed in yeast to obtain material for structural, composition and stability analysis. Circular dichroism data indicate VPS33B/VPS16B has a well-folded α-helical secondary structure, for which size exclusion chromatography-multi angle light scattering revealed a MW of ∼315 kDa. Quantitative immunoblotting indicated the complex has a VPS33B:VPS16B ratio of 2:3. Expression of ARC syndrome-causing VPS33B missense variants showed that L30P disrupts complex formation, but not S243F or H344D. Truncated VPS16B containing amino acids 143-316 was sufficient to form a complex with VPS33B. Small angle X-ray scattering and negative staining electron microscopy revealed a two-lobed shape for VPS33B/VPS16B. Avidin tagging indicated that each lobe contains a VPS33B molecule, and they are oriented in opposite directions. From this we propose a structure for VPS33B/VPS16B that allows the copies of VPS33B at each end to interact with separate SNARE bundles and/or SNAREpins, plus their associated membrane components. Thus our observations reveal the only known potentially bidirectional SM protein complex.
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Affiliation(s)
- Richard J Y Liu
- Department of Biochemistry, University of Toronto, Toronto, ON, M5S 1A8, Canada
| | - Yusef Al-Molieh
- Department of Biochemistry, University of Toronto, Toronto, ON, M5S 1A8, Canada
| | - Shao Z Chen
- Department of Biochemistry, University of Toronto, Toronto, ON, M5S 1A8, Canada
| | - Marko Drobac
- Department of Biochemistry, University of Toronto, Toronto, ON, M5S 1A8, Canada
| | - Denisa Urban
- Department of Biochemistry, University of Toronto, Toronto, ON, M5S 1A8, Canada
| | - Chang H Chen
- Department of Biochemistry, University of Toronto, Toronto, ON, M5S 1A8, Canada
| | - Helen H Y Yao
- Department of Biochemistry, University of Toronto, Toronto, ON, M5S 1A8, Canada
| | - Ryan S Q Geng
- Department of Biochemistry, University of Toronto, Toronto, ON, M5S 1A8, Canada
| | - Ling Li
- Cell Biology Program, Research Institute, Hospital for Sick Children, Toronto, ON, M5G 0A4, Canada
| | - Fred G Pluthero
- Cell Biology Program, Research Institute, Hospital for Sick Children, Toronto, ON, M5G 0A4, Canada
| | - Samir Benlekbir
- Molecular Medicine Program, Research Institute, Hospital for Sick Children, Toronto, ON, M5G 0A4, Canada
| | - John L Rubinstein
- Department of Biochemistry, University of Toronto, Toronto, ON, M5S 1A8, Canada; Molecular Medicine Program, Research Institute, Hospital for Sick Children, Toronto, ON, M5G 0A4, Canada
| | - Walter H A Kahr
- Department of Biochemistry, University of Toronto, Toronto, ON, M5S 1A8, Canada; Cell Biology Program, Research Institute, Hospital for Sick Children, Toronto, ON, M5G 0A4, Canada; Division of Haematology/Oncology, Department of Paediatrics, University of Toronto and The Hospital for Sick Children, Toronto, ON, M5G 1X8, Canada.
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2
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Schoppe J, Schubert E, Apelbaum A, Yavavli E, Birkholz O, Stephanowitz H, Han Y, Perz A, Hofnagel O, Liu F, Piehler J, Raunser S, Ungermann C. Flexible open conformation of the AP-3 complex explains its role in cargo recruitment at the Golgi. J Biol Chem 2021; 297:101334. [PMID: 34688652 PMCID: PMC8591511 DOI: 10.1016/j.jbc.2021.101334] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2021] [Revised: 09/15/2021] [Accepted: 09/21/2021] [Indexed: 01/17/2023] Open
Abstract
Vesicle formation at endomembranes requires the selective concentration of cargo by coat proteins. Conserved adapter protein complexes at the Golgi (AP-3), the endosome (AP-1), or the plasma membrane (AP-2) with their conserved core domain and flexible ear domains mediate this function. These complexes also rely on the small GTPase Arf1 and/or specific phosphoinositides for membrane binding. The structural details that influence these processes, however, are still poorly understood. Here we present cryo-EM structures of the full-length stable 300 kDa yeast AP-3 complex. The structures reveal that AP-3 adopts an open conformation in solution, comparable to the membrane-bound conformations of AP-1 or AP-2. This open conformation appears to be far more flexible than AP-1 or AP-2, resulting in compact, intermediate, and stretched subconformations. Mass spectrometrical analysis of the cross-linked AP-3 complex further indicates that the ear domains are flexibly attached to the surface of the complex. Using biochemical reconstitution assays, we also show that efficient AP-3 recruitment to the membrane depends primarily on cargo binding. Once bound to cargo, AP-3 clustered and immobilized cargo molecules, as revealed by single-molecule imaging on polymer-supported membranes. We conclude that its flexible open state may enable AP-3 to bind and collect cargo at the Golgi and could thus allow coordinated vesicle formation at the trans-Golgi upon Arf1 activation.
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Affiliation(s)
- Jannis Schoppe
- Department of Biology/Chemistry, Biochemistry Section, Osnabrück University, Osnabrück, Germany
| | - Evelyn Schubert
- Department of Structural Biochemistry, Max-Planck Institute of Molecular Physiology, Dortmund, Germany
| | - Amir Apelbaum
- Department of Structural Biochemistry, Max-Planck Institute of Molecular Physiology, Dortmund, Germany
| | - Erdal Yavavli
- Department of Biology/Chemistry, Biochemistry Section, Osnabrück University, Osnabrück, Germany
| | - Oliver Birkholz
- Department of Biology/Chemistry, Biophysics Section, Osnabrück University, Osnabrück, Germany
| | - Heike Stephanowitz
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Campus Berlin-Buch, Berlin, Germany
| | - Yaping Han
- Department of Biology/Chemistry, Biochemistry Section, Osnabrück University, Osnabrück, Germany
| | - Angela Perz
- Department of Biology/Chemistry, Biochemistry Section, Osnabrück University, Osnabrück, Germany
| | - Oliver Hofnagel
- Department of Structural Biochemistry, Max-Planck Institute of Molecular Physiology, Dortmund, Germany
| | - Fan Liu
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Campus Berlin-Buch, Berlin, Germany
| | - Jacob Piehler
- Department of Biology/Chemistry, Biophysics Section, Osnabrück University, Osnabrück, Germany; Center of Cellular Nanoanalytics Osnabrück (CellNanOs), Osnabrück University, Osnabrück, Germany
| | - Stefan Raunser
- Department of Structural Biochemistry, Max-Planck Institute of Molecular Physiology, Dortmund, Germany.
| | - Christian Ungermann
- Department of Biology/Chemistry, Biochemistry Section, Osnabrück University, Osnabrück, Germany; Center of Cellular Nanoanalytics Osnabrück (CellNanOs), Osnabrück University, Osnabrück, Germany.
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3
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Schoppe J, Mari M, Yavavli E, Auffarth K, Cabrera M, Walter S, Fröhlich F, Ungermann C. AP-3 vesicle uncoating occurs after HOPS-dependent vacuole tethering. EMBO J 2020; 39:e105117. [PMID: 32840906 PMCID: PMC7560216 DOI: 10.15252/embj.2020105117] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2020] [Revised: 07/16/2020] [Accepted: 07/22/2020] [Indexed: 11/09/2022] Open
Abstract
Heterotetrameric adapter (AP) complexes cooperate with the small GTPase Arf1 or lipids in cargo selection, vesicle formation, and budding at endomembranes in eukaryotic cells. While most AP complexes also require clathrin as the outer vesicle shell, formation of AP-3-coated vesicles involved in Golgi-to-vacuole transport in yeast has been postulated to depend on Vps41, a subunit of the vacuolar HOPS tethering complex. HOPS has also been identified as the tether of AP-3 vesicles on vacuoles. To unravel this conundrum of a dual Vps41 function, we anchored Vps41 stably to the mitochondrial outer membrane. By monitoring AP-3 recruitment, we now show that Vps41 can tether AP-3 vesicles to mitochondria, yet AP-3 vesicles can form in the absence of Vps41 or clathrin. By proximity labeling and mass spectrometry, we identify the Arf1 GTPase-activating protein (GAP) Age2 at the AP-3 coat and show that tethering, but not fusion at the vacuole can occur without complete uncoating. We conclude that AP-3 vesicles retain their coat after budding and that their complete uncoating occurs only after tethering at the vacuole.
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Affiliation(s)
- Jannis Schoppe
- Department of Biology/Chemistry, Biochemistry Section, University of Osnabrück, Osnabrück, Germany
| | - Muriel Mari
- Department of Biomedical Sciences of Cells and Systems, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Erdal Yavavli
- Department of Biology/Chemistry, Biochemistry Section, University of Osnabrück, Osnabrück, Germany
| | - Kathrin Auffarth
- Department of Biology/Chemistry, Biochemistry Section, University of Osnabrück, Osnabrück, Germany
| | - Margarita Cabrera
- Departament de Ciències Experimentals i de la Salut, Universitat Pompeu Farba, Barcelona, Spain
| | - Stefan Walter
- Center of Cellular Nanoanalytic Osnabrück (CellNanOs), University of Osnabrück, Osnabrück, Germany
| | - Florian Fröhlich
- Center of Cellular Nanoanalytic Osnabrück (CellNanOs), University of Osnabrück, Osnabrück, Germany.,Department of Biology/Chemistry, Molecular Membrane Biology Section, University of Osnabrück, Osnabrück, Germany
| | - Christian Ungermann
- Department of Biology/Chemistry, Biochemistry Section, University of Osnabrück, Osnabrück, Germany.,Center of Cellular Nanoanalytic Osnabrück (CellNanOs), University of Osnabrück, Osnabrück, Germany
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4
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Mechanism of platelet α-granule biogenesis: study of cargo transport and the VPS33B-VPS16B complex in a model system. Blood Adv 2020; 3:2617-2626. [PMID: 31501156 DOI: 10.1182/bloodadvances.2018028969] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2018] [Accepted: 07/30/2019] [Indexed: 12/29/2022] Open
Abstract
Platelet α-granules play important roles in platelet function. They contain hundreds of proteins that are synthesized by the megakaryocyte or taken up by endocytosis. The trafficking pathways that mediate platelet α-granule biogenesis are incompletely understood, especially with regard to cargo synthesized by the megakaryocyte. Vacuolar-protein sorting 33B (VPS33B) and VPS16B are essential proteins for α-granule biogenesis, but they are largely uncharacterized. Here, we adapted a powerful method to directly map the pathway followed by newly synthesized cargo proteins to reach α-granules. Using this method, we revealed the recycling endosome as a key intermediate compartment in α-granule biogenesis. We then used CRISPR/Cas9 gene editing to knock out VPS33B in pluripotent stem cell-derived immortalized megakaryocyte cells (imMKCLs). Consistent with the observations in platelets from patients with VPS33B mutation, VPS33B-knockout (KO) imMKCLs have drastically reduced levels of α-granule proteins platelet factor 4, von Willebrand factor, and P-selectin. VPS33B and VPS16B form a distinct and small complex in imMKCLs with the same hydrodynamic radius as the recombinant VPS33B-VPS16B heterodimer purified from bacteria. Mechanistically, the VPS33B-VPS16B complex ensures the correct trafficking of α-granule proteins. VPS33B deficiency results in α-granule cargo degradation in lysosomes. VPS16B steady-state levels are significantly lower in VPS33B-KO imMKCLs, suggesting that VPS16B is destabilized in the absence of its partner. Exogenous expression of green fluorescent protein-VPS33B in VPS33B-KO imMKCLs reconstitutes the complex, which localizes to the recycling endosome, further defining this compartment as a key intermediate in α-granule biogenesis. These results advance our understanding of platelet α-granule biogenesis and open new avenues for the study of these organelles.
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5
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Tower-Gilchrist C, Zlatic SA, Yu D, Chang Q, Wu H, Lin X, Faundez V, Chen P. Adaptor protein-3 complex is required for Vangl2 trafficking and planar cell polarity of the inner ear. Mol Biol Cell 2019; 30:2422-2434. [PMID: 31268833 PMCID: PMC6741063 DOI: 10.1091/mbc.e16-08-0592] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Planar cell polarity (PCP) regulates coordinated cellular polarity among neighboring cells to establish a polarity axis parallel to the plane of the tissue. Disruption in PCP results in a range of developmental anomalies and diseases. A key feature of PCP is the polarized and asymmetric localization of several membrane PCP proteins, which is essential to establish the polarity axis to orient cells coordinately. However, the machinery that regulates the asymmetric partition of PCP proteins remains largely unknown. In the present study, we show Van gogh-like 2 (Vangl2) in early and recycling endosomes as made evident by colocalization with diverse endosomal Rab proteins. Vangl2 biochemically interacts with adaptor protein-3 complex (AP-3). Using short hairpin RNA knockdown, we found that Vangl2 subcellular localization was modified in AP-3–depleted cells. Moreover, Vangl2 membrane localization within the cochlea is greatly reduced in AP-3–deficient mocha mice, which exhibit profound hearing loss. In inner ears from AP-3–deficient mocha mice, we observed PCP-dependent phenotypes, such as misorientation and deformation of hair cell stereociliary bundles and disorganization of hair cells characteristic of defects in convergent extension that is driven by PCP. These findings demonstrate a novel role of AP-3–mediated sorting mechanisms in regulating PCP proteins.
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Affiliation(s)
| | - Stephanie A Zlatic
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA 30322
| | - Dehong Yu
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA 30322.,Department of Otolaryngology-Head and Neck Surgery, Xinhua Hospital and Ear Institute, Shanghai Jiaotong University School of Medicine, Shanghai 200125, China
| | - Qing Chang
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA 30322.,Department of Otolaryngology, Emory University School of Medicine, Atlanta, GA 30322
| | - Hao Wu
- Department of Otolaryngology-Head and Neck Surgery, Xinhua Hospital and Ear Institute, Shanghai Jiaotong University School of Medicine, Shanghai 200125, China
| | - Xi Lin
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA 30322.,Department of Otolaryngology, Emory University School of Medicine, Atlanta, GA 30322
| | - Victor Faundez
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA 30322
| | - Ping Chen
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA 30322
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6
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Morlon-Guyot J, El Hajj H, Martin K, Fois A, Carrillo A, Berry L, Burchmore R, Meissner M, Lebrun M, Daher W. A proteomic analysis unravels novel CORVET and HOPS proteins involved in Toxoplasma gondii
secretory organelles biogenesis. Cell Microbiol 2018; 20:e12870. [DOI: 10.1111/cmi.12870] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2018] [Revised: 05/23/2018] [Accepted: 06/05/2018] [Indexed: 01/10/2023]
Affiliation(s)
- Juliette Morlon-Guyot
- Dynamique des Interactions Membranaires Normales et Pathologiques, UMR5235 CNRS, INSERM; Université de Montpellier; Montpellier France
| | - Hiba El Hajj
- Departments of Internal Medicine and Experimental Pathology, Immunology and Microbiology; American University of Beirut; Beirut Lebanon
| | - Kevin Martin
- Dynamique des Interactions Membranaires Normales et Pathologiques, UMR5235 CNRS, INSERM; Université de Montpellier; Montpellier France
| | - Adrien Fois
- Dynamique des Interactions Membranaires Normales et Pathologiques, UMR5235 CNRS, INSERM; Université de Montpellier; Montpellier France
| | - Amandine Carrillo
- Dynamique des Interactions Membranaires Normales et Pathologiques, UMR5235 CNRS, INSERM; Université de Montpellier; Montpellier France
| | - Laurence Berry
- Dynamique des Interactions Membranaires Normales et Pathologiques, UMR5235 CNRS, INSERM; Université de Montpellier; Montpellier France
| | | | - Markus Meissner
- Wellcome Centre for Molecular Parasitology; University of Glasgow; Glasgow UK
- Department of Veterinary Sciences, Experimental Parasitology; Ludwig-Maximilians-Universität München; Munich Germany
| | - Maryse Lebrun
- Dynamique des Interactions Membranaires Normales et Pathologiques, UMR5235 CNRS, INSERM; Université de Montpellier; Montpellier France
| | - Wassim Daher
- Dynamique des Interactions Membranaires Normales et Pathologiques, UMR5235 CNRS, INSERM; Université de Montpellier; Montpellier France
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7
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Gengyo-Ando K, Kage-Nakadai E, Yoshina S, Otori M, Kagawa-Nagamura Y, Nakai J, Mitani S. Distinct roles of the two VPS33 proteins in the endolysosomal system in Caenorhabditis elegans. Traffic 2016; 17:1197-1213. [PMID: 27558849 DOI: 10.1111/tra.12430] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Revised: 08/18/2016] [Accepted: 08/18/2016] [Indexed: 02/02/2023]
Abstract
Sec1/Munc-18 (SM) family proteins are essential regulators in intracellular transport in eukaryotic cells. The SM protein Vps33 functions as a core subunit of two tethering complexes, class C core vacuole/endosome tethering (CORVET) and homotypic fusion and vacuole protein sorting (HOPS) in the endocytic pathway in yeast. Metazoan cells possess two Vps33 proteins, VPS33A and VPS33B, but their precise roles remain unknown. Here, we present a comparative analysis of Caenorhabditis elegans null mutants for these proteins. We found that the vps-33.1 (VPS33A) mutants exhibited severe defects in both endocytic function and endolysosomal biogenesis in scavenger cells. Furthermore, vps-33.1 mutations caused endocytosis defects in other tissues, and the loss of maternal and zygotic VPS-33.1 resulted in embryonic lethality. By contrast, vps-33.2 mutants were viable but sterile, with terminally arrested spermatocytes. The spermatogenesis phenotype suggests that VPS33.2 is involved in the formation of a sperm-specific organelle. The endocytosis defect in the vps-33.1 mutant was not restored by the expression of VPS-33.2, which indicates that these proteins have nonredundant functions. Together, our data suggest that VPS-33.1 shares most of the general functions of yeast Vps33 in terms of tethering complexes in the endolysosomal system, whereas VPS-33.2 has tissue/organelle specific functions in C. elegans.
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Affiliation(s)
- Keiko Gengyo-Ando
- Department of Physiology, Tokyo Women's Medical University School of Medicine, Tokyo, Japan. .,Brain and Body System Science Institute, Saitama University, Saitama, Japan. .,Graduate School of Science and Engineering, Saitama University, Saitama, Japan.
| | - Eriko Kage-Nakadai
- Department of Physiology, Tokyo Women's Medical University School of Medicine, Tokyo, Japan.,The OCU Advanced Research Institute for Natural Science and Technology, Osaka City University, Osaka, Japan
| | - Sawako Yoshina
- Department of Physiology, Tokyo Women's Medical University School of Medicine, Tokyo, Japan
| | - Muneyoshi Otori
- Department of Physiology, Tokyo Women's Medical University School of Medicine, Tokyo, Japan
| | - Yuko Kagawa-Nagamura
- Brain and Body System Science Institute, Saitama University, Saitama, Japan.,Graduate School of Science and Engineering, Saitama University, Saitama, Japan
| | - Junichi Nakai
- Brain and Body System Science Institute, Saitama University, Saitama, Japan.,Graduate School of Science and Engineering, Saitama University, Saitama, Japan
| | - Shohei Mitani
- Department of Physiology, Tokyo Women's Medical University School of Medicine, Tokyo, Japan.
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8
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Schroeter S, Beckmann S, Schmitt HD. Coat/Tether Interactions-Exception or Rule? Front Cell Dev Biol 2016; 4:44. [PMID: 27243008 PMCID: PMC4868844 DOI: 10.3389/fcell.2016.00044] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2016] [Accepted: 04/25/2016] [Indexed: 12/02/2022] Open
Abstract
Coat complexes are important for cargo selection and vesicle formation. Recent evidence suggests that they may also be involved in vesicle targeting. Tethering factors, which form an initial bridge between vesicles and the target membrane, may bind to coat complexes. In this review, we ask whether these coat/tether interactions share some common mechanisms, or whether they are special adaptations to the needs of very specific transport steps. We compare recent findings in two multisubunit tethering complexes, the Dsl1 complex and the HOPS complex, and put them into context with the TRAPP I complex as a prominent example for coat/tether interactions. We explore where coat/tether interactions are found, compare their function and structure, and comment on a possible evolution from a common ancestor of coats and tethers.
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Affiliation(s)
- Saskia Schroeter
- Neurobiology, Max Planck Institute for Biophysical Chemistry Göttingen, Germany
| | - Sabrina Beckmann
- Neurobiology, Max Planck Institute for Biophysical Chemistry Göttingen, Germany
| | - Hans Dieter Schmitt
- Neurobiology, Max Planck Institute for Biophysical Chemistry Göttingen, Germany
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9
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Kuhlee A, Raunser S, Ungermann C. Functional homologies in vesicle tethering. FEBS Lett 2015; 589:2487-97. [PMID: 26072291 DOI: 10.1016/j.febslet.2015.06.001] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2015] [Revised: 05/30/2015] [Accepted: 06/01/2015] [Indexed: 11/24/2022]
Abstract
The HOPS multisubunit tethering factor (MTC) is a macromolecular protein complex composed of six different subunits. It is one of the key components in the perception and subsequent fusion of multivesicular bodies and vacuoles. Electron microscopy studies indicate structural flexibility of the purified HOPS complex. Inducing higher rigidity into HOPS by biochemically modifying the complex declines the potential to mediate SNARE-driven membrane fusion. Thus, we propose that integral flexibility seems to be not only a feature, but of essential need for the function of HOPS. This review focuses on the general features of membrane tethering and fusion. For this purpose, we compare the structure and mode of action of different tethering factors to highlight their common central features and mechanisms.
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Affiliation(s)
- Anne Kuhlee
- Department of Structural Biochemistry, Max-Planck Institute of Molecular Physiology, Otto-Hahn-Strasse 11, 44227 Dortmund, Germany.
| | - Stefan Raunser
- Department of Structural Biochemistry, Max-Planck Institute of Molecular Physiology, Otto-Hahn-Strasse 11, 44227 Dortmund, Germany
| | - Christian Ungermann
- Department of Biology, University of Osnabrück, Barbarastrasse 13, 49076 Osnabrück, Germany
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10
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Perini ED, Schaefer R, Stöter M, Kalaidzidis Y, Zerial M. Mammalian CORVET Is Required for Fusion and Conversion of Distinct Early Endosome Subpopulations. Traffic 2014; 15:1366-89. [DOI: 10.1111/tra.12232] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2014] [Revised: 09/26/2014] [Accepted: 09/26/2014] [Indexed: 12/22/2022]
Affiliation(s)
- Enrico D. Perini
- Max Planck Institute of Molecular Cell Biology and Genetics; Pfotenhauerstrasse 108 01307 Dresden Germany
| | - Ramona Schaefer
- Max Planck Institute of Molecular Cell Biology and Genetics; Pfotenhauerstrasse 108 01307 Dresden Germany
| | - Martin Stöter
- Max Planck Institute of Molecular Cell Biology and Genetics; Pfotenhauerstrasse 108 01307 Dresden Germany
| | - Yannis Kalaidzidis
- Max Planck Institute of Molecular Cell Biology and Genetics; Pfotenhauerstrasse 108 01307 Dresden Germany
- Faculty of Bioengineering and Bioinformatics; Moscow State University; 119991 Moscow Russia
| | - Marino Zerial
- Max Planck Institute of Molecular Cell Biology and Genetics; Pfotenhauerstrasse 108 01307 Dresden Germany
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11
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Zlatic SA, Tornieri K, L'hernault SW, Faundez V. Metazoan cell biology of the HOPS tethering complex. CELLULAR LOGISTICS 2014; 1:111-117. [PMID: 21922076 DOI: 10.4161/cl.1.3.17279] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/19/2011] [Revised: 07/18/2011] [Accepted: 07/20/2011] [Indexed: 01/09/2023]
Abstract
Membrane fusion with vacuoles, the lysosome equivalent of the yeast Saccharomyces cerevisiae, is among the best understood membrane fusion events. Our precise understanding of this fusion machinery stems from powerful genetics and elegant in vitro reconstitution assays. Central to vacuolar membrane fusion is the multi-subunit tether the HO motypic fusion and Protein Sorting (HOPS) complex, a complex of proteins that organizes other necessary components of the fusion machinery. We lack a similarly detailed molecular understanding of membrane fusion with lysosomes or lysosome-related organelles in metazoans. However, it is likely that fundamental principles of how rabs, SNAREs and HOPS tethers work to fuse membranes with lysosomes and related organelles are conserved between Saccharomyces cerevisiae and metazoans. Here, we discuss emerging differences in the coat-dependent mechanisms that govern HOPS complex subcellular distribution between Saccharomyces cerevisiae and metazoans. These differences reside upstream of the membrane fusion event. We propose that the differences in how coats segregate class C Vps/HOPS tethers to organelles and domains of metazoan cells are adaptations to complex architectures that characterize metazoan cells such as those of neuronal and epithelial tissues.
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Affiliation(s)
- Stephanie A Zlatic
- Graduate Program in Biochemistry, Cell and Developmental Biology; Emory University; Atlanta, GA USA
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12
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Lachmann J, Glaubke E, Moore PS, Ungermann C. The Vps39-like TRAP1 is an effector of Rab5 and likely the missing Vps3 subunit of human CORVET. CELLULAR LOGISTICS 2014; 4:e970840. [PMID: 25750764 DOI: 10.4161/21592780.2014.970840] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2014] [Accepted: 09/25/2014] [Indexed: 12/22/2022]
Abstract
Membrane fusion in the endocytic pathway is mediated by a protein machinery consistent of Rab GTPases, tethering factors and SNAREs. In yeast, the endosomal CORVET and lysosomal HOPS tethering complexes share 4 of their 6 subunits. The 2 additional subunits in each complex - Vps3 and Vps8 for CORVET, and the homologous Vps39 and Vps41 for HOPS - bind directly to Rab5 and Rab7, respectively. In humans, all subunits for HOPS have been described. However, human CORVET remains poorly characterized and a homolog of Vps3 is still missing. Here we characterize 2 previously identified Vps39 isoforms, hVps39-1/hVam6/TLP and hVps39-2/TRAP1, in yeast and HEK293 cells. None of them can compensate the loss of the endogenous yeast Vps39, though the specific interaction of hVps39-1 with the virus-specific LT protein was reproduced. Both human Vps39 proteins show a cytosolic localization in yeast and mammalian cells. However, hVps39-2/TRAP1 strongly co-localizes with co-expressed Rab5 and interacts directly with Rab5-GTP in vitro. We conclude that hVps39-2/TRAP1 is an endosomal protein and an effector of Rab5, suggesting a role of the protein as a subunit of the putative human CORVET complex.
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Affiliation(s)
- Jens Lachmann
- Department of Biology/Chemistry; Biochemistry Section; University of Osnabruck ; Osnabrück, Germany
| | - Elina Glaubke
- Department of Biology/Chemistry; Biochemistry Section; University of Osnabruck ; Osnabrück, Germany
| | - Patrick S Moore
- University of Pittsburgh Cancer Institute; Cancer Virology Program ; Pittsburgh, PA USA
| | - Christian Ungermann
- Department of Biology/Chemistry; Biochemistry Section; University of Osnabruck ; Osnabrück, Germany
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13
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Delahaye JL, Foster OK, Vine A, Saxton DS, Curtin TP, Somhegyi H, Salesky R, Hermann GJ. Caenorhabditis elegans HOPS and CCZ-1 mediate trafficking to lysosome-related organelles independently of RAB-7 and SAND-1. Mol Biol Cell 2014; 25:1073-96. [PMID: 24501423 PMCID: PMC3967972 DOI: 10.1091/mbc.e13-09-0521] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
As early endosomes mature, the SAND-1/CCZ-1 complex acts as a guanine nucleotide exchange factor (GEF) for RAB-7 to promote the activity of its effector, HOPS, which facilitates late endosome-lysosome fusion and the consumption of AP-3-containing vesicles. We show that CCZ-1 and the HOPS complex are essential for the biogenesis of gut granules, cell type-specific, lysosome-related organelles (LROs) that coexist with conventional lysosomes in Caenorhabditis elegans intestinal cells. The HOPS subunit VPS-18 promotes the trafficking of gut granule proteins away from lysosomes and functions downstream of or in parallel to the AP-3 adaptor. CCZ-1 also acts independently of AP-3, and ccz-1 mutants mistraffic gut granule proteins. Our results indicate that SAND-1 does not participate in the formation of gut granules. In the absence of RAB-7 activity, gut granules are generated; however, their size and protein composition are subtly altered. These observations suggest that CCZ-1 acts in partnership with a protein other than SAND-1 as a GEF for an alternate Rab to promote gut granule biogenesis. Point mutations in GLO-1, a Rab32/38-related protein, predicted to increase spontaneous guanine nucleotide exchange, specifically suppress the loss of gut granules by ccz-1 and glo-3 mutants. GLO-3 is known to be required for gut granule formation and has homology to SAND-1/Mon1-related proteins, suggesting that CCZ-1 functions with GLO-3 upstream of the GLO-1 Rab, possibly as a GLO-1 GEF. These results support LRO formation occurring via processes similar to conventional lysosome biogenesis, albeit with key molecular differences.
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Affiliation(s)
- Jared L Delahaye
- Department of Biology, Lewis & Clark College, Portland, OR 97219 Program in Biochemistry and Molecular Biology, Lewis & Clark College, Portland, OR 97219
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14
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Ahmed S, Xie J, Horne D, Williams JC. Photocleavable dimerizer for the rapid reversal of molecular trap antagonists. J Biol Chem 2014; 289:4546-52. [PMID: 24421317 DOI: 10.1074/jbc.c113.513622] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Herein, we report the development of a photocleavable analog of AP20187, a cell-permeable molecule used to dimerize FK506-binding protein (FKBP) fusion proteins and initiate biological signaling cascades and gene expression or disrupt protein-protein interactions. We demonstrate that this reagent permits the unique ability to rapidly and specifically antagonize a molecular interaction in vitro and follow a biological process due to this acute antagonism (e.g. endosome dispersion) and to release the trap upon photocleavage to follow the cell's return to homeostasis. In addition, this photocleavable AP20187 analog can be used in other systems where the dimerization of FKBP has been used to initiate signaling pathways, offering the ability to correlate the duration of a signaling event and a cellular response.
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Affiliation(s)
- Shubbir Ahmed
- From the Department of Molecular Medicine, Beckman Research Institute of City of Hope, Duarte, California 91010
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15
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Balderhaar HJK, Ungermann C. CORVET and HOPS tethering complexes - coordinators of endosome and lysosome fusion. J Cell Sci 2013; 126:1307-16. [PMID: 23645161 DOI: 10.1242/jcs.107805] [Citation(s) in RCA: 394] [Impact Index Per Article: 32.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Protein and lipid transport along the endolysosomal system of eukaryotic cells depends on multiple fusion and fission events. Over the past few years, the molecular constituents of both fission and fusion machineries have been identified. Here, we focus on the mechanism of membrane fusion at endosomes, vacuoles and lysosomes, and in particular on the role of the two homologous tethering complexes called CORVET and HOPS. Both complexes are heterohexamers; they share four subunits, interact with Rab GTPases and soluble NSF attachment protein receptors (SNAREs) and can tether membranes. Owing to the presence of specific subunits, CORVET is a Rab5 effector complex, whereas HOPS can bind efficiently to late endosomes and lysosomes through Rab7. Based on the recently described overall structure of the HOPS complex and a number of in vivo and in vitro analyses, important insights into their function have been obtained. Here, we discuss the general function of both complexes in yeast and in metazoan cells in the context of endosomal biogenesis and maturation.
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Affiliation(s)
- Henning J kleine Balderhaar
- University of Osnabrück, Department of Biology/Chemistry, Biochemistry Section, Barbarastrasse 13, 49076 Osnabrück, Germany
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16
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Morgan JR, Comstra HS, Cohen M, Faundez V. Presynaptic membrane retrieval and endosome biology: defining molecularly heterogeneous synaptic vesicles. Cold Spring Harb Perspect Biol 2013; 5:a016915. [PMID: 24086045 DOI: 10.1101/cshperspect.a016915] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The release and uptake of neurotransmitters by synaptic vesicles is a tightly controlled process that occurs in response to diverse stimuli at morphologically disparate synapses. To meet these architectural and functional synaptic demands, it follows that there should be diversity in the mechanisms that control their secretion and retrieval and possibly in the composition of synaptic vesicles within the same terminal. Here we pay particular attention to areas where such diversity is generated, such as the variance in exocytosis/endocytosis coupling, SNAREs defining functionally diverse synaptic vesicle populations and the adaptor-dependent sorting machineries capable of generating vesicle diversity. We argue that there are various synaptic vesicle recycling pathways at any given synapse and discuss several lines of evidence that support the role of the endosome in synaptic vesicle recycling.
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Affiliation(s)
- Jennifer R Morgan
- Eugene Bell Center for Regenerative Biology and Tissue Engineering, Marine Biological Laboratory, Woods Hole, Massachusetts 02543
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17
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Tornieri K, Zlatic SA, Mullin AP, Werner E, Harrison R, L'hernault SW, Faundez V. Vps33b pathogenic mutations preferentially affect VIPAS39/SPE-39-positive endosomes. Hum Mol Genet 2013; 22:5215-28. [PMID: 23918659 DOI: 10.1093/hmg/ddt378] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Mutations in Vps33 isoforms cause pigment dilution in mice (Vps33a, buff) and Drosophila (car) and the neurogenic arthrogryposis, renal dysfunction and cholestasis syndrome in humans (ARC1, VPS33B). The later disease is also caused by mutations in VIPAS39, (Vps33b interacting protein, apical-basolateral polarity regulator, SPE-39 homolog; ARC2), a protein that interacts with the HOmotypic fusion and Protein Sorting (HOPS) complex, a tether necessary for endosome-lysosome traffic. These syndromes offer insight into fundamental endosome traffic processes unique to metazoans. However, the molecular and cellular mechanisms underlying these mutant phenotypes remain poorly understood. Here we investigate interactions of wild-type and disease-causing mutations in VIPAS39/SPE-39 and Vps33b by yeast two hybrid, immunoprecipitation and quantitative fluorescent microscopy. We find that although few mutations prevent interaction between VIPAS39/SPE-39 and Vps33b, some mutants fragment VIPAS39/SPE-39-positive endosomes, but all mutants alter the subcellular localization of Vps33b to VIPAS39/SPE-39-positive endosomes. Our data suggest that the ARC syndrome may result through impaired VIPAS39/SPE-39 and Vps33b-dependent endosomal maturation or fusion.
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18
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Zlatic SA, Grossniklaus EJ, Ryder PV, Salazar G, Mattheyses AL, Peden AA, Faundez V. Chemical-genetic disruption of clathrin function spares adaptor complex 3-dependent endosome vesicle biogenesis. Mol Biol Cell 2013; 24:2378-88. [PMID: 23761069 PMCID: PMC3727930 DOI: 10.1091/mbc.e12-12-0860] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Clathrin–AP-3 association is dispensable for AP-3 vesicle budding from endosomes, which suggests that AP-3–clathrin interactions differ from those by which AP-1 and AP-2 adaptors productively engage clathrin in vesicle biogenesis. A role for clathrin in AP-3–dependent vesicle biogenesis has been inferred from biochemical interactions and colocalization between this adaptor and clathrin. The functionality of these molecular associations, however, is controversial. We comprehensively explore the role of clathrin in AP-3–dependent vesicle budding, using rapid chemical-genetic perturbation of clathrin function with a clathrin light chain–FKBP chimera oligomerizable by the drug AP20187. We find that AP-3 interacts and colocalizes with endogenous and recombinant FKBP chimeric clathrin polypeptides in PC12-cell endosomes. AP-3 displays, however, a divergent behavior from AP-1, AP-2, and clathrin chains. AP-3 cofractionates with clathrin-coated vesicle fractions isolated from PC12 cells even after clathrin function is acutely inhibited by AP20187. We predicted that AP20187 would inhibit AP-3 vesicle formation from endosomes after a brefeldin A block. AP-3 vesicle formation continued, however, after brefeldin A wash-out despite impairment of clathrin function by AP20187. These findings indicate that AP-3–clathrin association is dispensable for endosomal AP-3 vesicle budding and suggest that endosomal AP-3–clathrin interactions differ from those by which AP-1 and AP-2 adaptors productively engage clathrin in vesicle biogenesis.
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19
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Wei AH, Li W. Hermansky-Pudlak syndrome: pigmentary and non-pigmentary defects and their pathogenesis. Pigment Cell Melanoma Res 2012; 26:176-92. [DOI: 10.1111/pcmr.12051] [Citation(s) in RCA: 91] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2012] [Accepted: 11/16/2012] [Indexed: 10/27/2022]
Affiliation(s)
| | - Wei Li
- State Key Laboratory of Molecular Developmental Biology; Institute of Genetics & Developmental Biology; Chinese Academy of Sciences; Beijing; China
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20
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Smith H, Galmes R, Gogolina E, Straatman-Iwanowska A, Reay K, Banushi B, Bruce CK, Cullinane AR, Romero R, Chang R, Ackermann O, Baumann C, Cangul H, Cakmak Celik F, Aygun C, Coward R, Dionisi-Vici C, Sibbles B, Inward C, Ae Kim C, Klumperman J, Knisely AS, Watson SP, Gissen P. Associations among genotype, clinical phenotype, and intracellular localization of trafficking proteins in ARC syndrome. Hum Mutat 2012; 33:1656-1664. [PMID: 22753090 PMCID: PMC3746110 DOI: 10.1002/humu.22155] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2012] [Accepted: 06/12/2012] [Indexed: 12/31/2022]
Abstract
Arthrogryposis-renal dysfunction-cholestasis (ARC) syndrome is a rare autosomal recessive multisystem disorder caused by mutations in vacuolar protein sorting 33 homologue B (VPS33B) and VPS33B interacting protein, apical-basolateral polarity regulator (VIPAR). Cardinal features of ARC include congenital joint contractures, renal tubular dysfunction, cholestasis, severe failure to thrive, ichthyosis, and a defect in platelet alpha-granule biogenesis. Most patients with ARC do not survive past the first year of life. We report two patients presenting with a mild ARC phenotype, now 5.5 and 3.5 years old. Both patients were compound heterozygotes with the novel VPS33B donor splice-site mutation c.1225+5G>C in common. Immunoblotting and complementary DNA analysis suggest expression of a shorter VPS33B transcript, and cell-based assays show that c.1225+5G>C VPS33B mutant retains some ability to interact with VIPAR (and thus partial wild-type function). This study provides the first evidence of genotype-phenotype correlation in ARC and suggests that VPS33B c.1225+5G>C mutation predicts a mild ARC phenotype. We have established an interactive online database for ARC (https://grenada.lumc.nl/LOVD2/ARC) comprising all known variants in VPS33B and VIPAR. Also included in the database are 15 novel pathogenic variants in VPS33B and five in VIPAR.
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Affiliation(s)
- Holly Smith
- Medical and Molecular Genetics, School of Clinical and Experimental Medicine, College of Medical and Dental Sciences, University of BirminghamBirmingham, United Kingdom
- University College London Institute of Child Health, University College LondonLondon, United Kingdom
| | - Romain Galmes
- Department of Cell Biology, University Medical CenterUtrecht, the Netherlands
| | - Ekaterina Gogolina
- Medical Research Council Laboratory for Molecular Cell Biology, University College LondonLondon, United Kingdom
- University College London Institute of Child Health, University College LondonLondon, United Kingdom
- Medical School, Edinburgh UniversityEdinburgh, United Kingdom
| | - Anna Straatman-Iwanowska
- Medical Research Council Laboratory for Molecular Cell Biology, University College LondonLondon, United Kingdom
- University College London Institute of Child Health, University College LondonLondon, United Kingdom
| | - Kim Reay
- West Midlands Regional Genetics Laboratory, Birmingham Women's HospitalBirmingham, United Kingdom
| | - Blerida Banushi
- Medical and Molecular Genetics, School of Clinical and Experimental Medicine, College of Medical and Dental Sciences, University of BirminghamBirmingham, United Kingdom
- University College London Institute of Child Health, University College LondonLondon, United Kingdom
| | - Christopher K Bruce
- Medical and Molecular Genetics, School of Clinical and Experimental Medicine, College of Medical and Dental Sciences, University of BirminghamBirmingham, United Kingdom
| | - Andrew R Cullinane
- Medical Genetics Branch, National Human Genome Research Institute, National Institutes of HealthBethesda, Maryland
| | - Rene Romero
- Emory Children's Center Division of Gastroenterology, Hepatology, and NutritionAtlanta, Georgia
| | - Richard Chang
- Division of Metabolic Disorders, Children's Hospital of Orange CountyOrange, California
| | | | | | - Hakan Cangul
- Medical and Molecular Genetics, School of Clinical and Experimental Medicine, College of Medical and Dental Sciences, University of BirminghamBirmingham, United Kingdom
| | | | - Canan Aygun
- Neonatology Unit, Mayis UniversitySamsun, Turkey
| | - Richard Coward
- Bristol Royal Hospital for Sick ChildrenBristol, United Kingdom
| | - Carlo Dionisi-Vici
- Division of Metabolism, Bambino Gesú Children's Hospital IRCCSRome, Italy
| | - Barbara Sibbles
- Erasmus University Medical Center, Sophia Children's HospitalRotterdam, the Netherlands
| | - Carol Inward
- Bristol Royal Hospital for Sick ChildrenBristol, United Kingdom
| | - Chong Ae Kim
- Department of Pediatrics, Instituto da Criança, University of Sao PauloSao Paulo, Brazil
| | - Judith Klumperman
- Department of Cell Biology, University Medical CenterUtrecht, the Netherlands
| | - A S Knisely
- Institute of Liver Studies/Histopathology, King's College HospitalLondon, United Kingdom
| | - Steven P Watson
- The Platelet Group, School of Clinical and Experimental Medicine, College of Medical and Dental Sciences, University of BirminghamBirmingham, United Kingdom
| | - Paul Gissen
- Medical Research Council Laboratory for Molecular Cell Biology, University College LondonLondon, United Kingdom
- University College London Institute of Child Health, University College LondonLondon, United Kingdom
- Inherited Metabolic Diseases, Great Ormond Street HospitalLondon, United Kingdom
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21
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Zheng L, Saunders CA, Sorensen EB, Waxmonsky NC, Conner SD. Notch signaling from the endosome requires a conserved dileucine motif. Mol Biol Cell 2012; 24:297-307. [PMID: 23171551 PMCID: PMC3564540 DOI: 10.1091/mbc.e12-02-0081] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Notch signaling is reliant on γ-secretase–mediated processing, although the subcellular location where it cleaves Notch to initiate signaling remains unresolved. Findings here support a model in which Notch signaling in mammalian systems is initiated from either the plasma membrane or lysosome, but not the early endosome. Notch signaling is reliant on γ-secretase–mediated processing, although the subcellular location where γ-secretase cleaves Notch to initiate signaling remains unresolved. Accumulating evidence demonstrates that Notch signaling is modulated by endocytosis and endosomal transport. In this study, we investigated the relationship between Notch transport itinerary and signaling capacity. In doing so, we discovered a highly conserved dileucine sorting signal encoded within the cytoplasmic tail that directs Notch to the limiting membrane of the lysosome for signaling. Mutating the dileucine motif led to receptor accumulation in cation-dependent mannose-phosphate receptor–positive tubular early endosomes and a reduction in Notch signaling capacity. Moreover, truncated receptor forms that mimic activated Notch were readily cleaved by γ-secretase within the endosome; however, the cleavage product was proteasome-sensitive and failed to contribute to robust signaling. Collectively these results indicate that Notch signaling from the lysosome limiting membrane is conserved and that receptor targeting to this compartment is an active process. Moreover, the data support a model in which Notch signaling in mammalian systems is initiated from either the plasma membrane or lysosome, but not the early endosome.
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Affiliation(s)
- Li Zheng
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, MN 55455, USA
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22
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Ivan V, Martinez-Sanchez E, Sima LE, Oorschot V, Klumperman J, Petrescu SM, van der Sluijs P. AP-3 and Rabip4' coordinately regulate spatial distribution of lysosomes. PLoS One 2012; 7:e48142. [PMID: 23144738 PMCID: PMC3483219 DOI: 10.1371/journal.pone.0048142] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2012] [Accepted: 09/20/2012] [Indexed: 11/19/2022] Open
Abstract
The RUN and FYVE domain proteins rabip4 and rabip4' are encoded by RUFY1 and differ in a 108 amino acid N-terminal extension in rabip4'. Their identical C terminus binds rab5 and rab4, but the function of rabip4s is incompletely understood. We here found that silencing RUFY1 gene products promoted outgrowth of plasma membrane protrusions, and polarized distribution and clustering of lysosomes at their tips. An interactor screen for proteins that function together with rabip4' yielded the adaptor protein complex AP-3, of which the hinge region in the β3 subunit bound directly to the FYVE domain of rabip4'. Rabip4' colocalized with AP-3 on a tubular subdomain of early endosomes and the extent of colocalization was increased by a dominant negative rab4 mutant. Knock-down of AP-3 had an ever more dramatic effect and caused accumulation of lysosomes in protrusions at the plasma membrane. The most peripheral lysosomes were localized beyond microtubules, within the cortical actin network. Our results uncover a novel function for AP-3 and rabip4' in regulating lysosome positioning through an interorganellar pathway.
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Affiliation(s)
- Viorica Ivan
- Department of Cell Biology, University Medical Center Utrecht, Utrecht, The Netherlands
- Department of Molecular Cell Biology, Institute of Biochemistry of the Romanian Academy, Bucharest, Romania
| | - Emma Martinez-Sanchez
- Department of Cell Biology, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Livia E. Sima
- Department of Molecular Cell Biology, Institute of Biochemistry of the Romanian Academy, Bucharest, Romania
| | - Viola Oorschot
- Department of Cell Biology, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Judith Klumperman
- Department of Cell Biology, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Stefana M. Petrescu
- Department of Molecular Cell Biology, Institute of Biochemistry of the Romanian Academy, Bucharest, Romania
| | - Peter van der Sluijs
- Department of Cell Biology, University Medical Center Utrecht, Utrecht, The Netherlands
- * E-mail:
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23
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Molecular architecture of the multisubunit homotypic fusion and vacuole protein sorting (HOPS) tethering complex. Proc Natl Acad Sci U S A 2012; 109:1991-6. [PMID: 22308417 DOI: 10.1073/pnas.1117797109] [Citation(s) in RCA: 220] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Membrane fusion within the eukaryotic endomembrane system depends on the initial recognition of Rab GTPase on transport vesicles by multisubunit tethering complexes and subsequent coupling to SNARE-mediated fusion. The conserved vacuolar/lysosomal homotypic fusion and vacuole protein sorting (HOPS) tethering complex combines both activities. Here we present the overall structure of the fusion-active HOPS complex. Our data reveal a flexible ≈30-nm elongated seahorse-like structure, which can adopt contracted and elongated shapes. Surprisingly, both ends of the HOPS complex contain a Rab-binding subunit: Vps41 and Vps39. The large head contains in addition to Vps41 the SNARE-interacting Vps33, whereas Vps39 is found in the bulky tip of its tail. Vps11 and Vps18 connect head and tail. Our data suggest that HOPS bridges Ypt7-positive membranes and chaperones SNAREs at fusion sites.
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