101
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Mehrtash AB, Hochstrasser M. Ubiquitin-dependent protein degradation at the endoplasmic reticulum and nuclear envelope. Semin Cell Dev Biol 2018; 93:111-124. [PMID: 30278225 DOI: 10.1016/j.semcdb.2018.09.013] [Citation(s) in RCA: 78] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2018] [Revised: 09/26/2018] [Accepted: 09/27/2018] [Indexed: 01/01/2023]
Abstract
Numerous nascent proteins undergo folding and maturation within the luminal and membrane compartments of the endoplasmic reticulum (ER). Despite the presence of various factors in the ER that promote protein folding, many proteins fail to properly fold and assemble and are subsequently degraded. Regulatory proteins in the ER also undergo degradation in a way that is responsive to stimuli or the changing needs of the cell. As in most cellular compartments, the ubiquitin-proteasome system (UPS) is responsible for the majority of the degradation at the ER-in a process termed ER-associated degradation (ERAD). Autophagic processes utilizing ubiquitin-like protein-conjugating systems also play roles in protein degradation at the ER. The ER is continuous with the nuclear envelope (NE), which consists of the outer nuclear membrane (ONM) and inner nuclear membrane (INM). While ERAD is known also to occur at the NE, only some of the ERAD ubiquitin-ligation pathways function at the INM. Protein degradation machineries in the ER/NE target a wide variety of substrates in multiple cellular compartments, including the cytoplasm, nucleoplasm, ER lumen, ER membrane, and the NE. Here, we review the protein degradation machineries of the ER and NE and the underlying mechanisms dictating recognition and processing of substrates by these machineries.
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Affiliation(s)
- Adrian B Mehrtash
- Department of Molecular, Cellular, & Developmental Biology, Yale University, New Haven, 06520, CT, USA.
| | - Mark Hochstrasser
- Department of Molecular Biophysics & Biochemistry, Yale University, New Haven, CT, 06520, USA; Department of Molecular, Cellular, & Developmental Biology, Yale University, New Haven, 06520, CT, USA.
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102
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McCullough J, Frost A, Sundquist WI. Structures, Functions, and Dynamics of ESCRT-III/Vps4 Membrane Remodeling and Fission Complexes. Annu Rev Cell Dev Biol 2018; 34:85-109. [PMID: 30095293 PMCID: PMC6241870 DOI: 10.1146/annurev-cellbio-100616-060600] [Citation(s) in RCA: 167] [Impact Index Per Article: 27.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The endosomal sorting complexes required for transport (ESCRT) pathway mediates cellular membrane remodeling and fission reactions. The pathway comprises five core complexes: ALIX, ESCRT-I, ESCRT-II, ESCRT-III, and Vps4. These soluble complexes are typically recruited to target membranes by site-specific adaptors that bind one or both of the early-acting ESCRT factors: ALIX and ESCRT-I/ESCRT-II. These factors, in turn, nucleate assembly of ESCRT-III subunits into membrane-bound filaments that recruit the AAA ATPase Vps4. Together, ESCRT-III filaments and Vps4 remodel and sever membranes. Here, we review recent advances in our understanding of the structures, activities, and mechanisms of the ESCRT-III and Vps4 machinery, including the first high-resolution structures of ESCRT-III filaments, the assembled Vps4 enzyme in complex with an ESCRT-III substrate, the discovery that ESCRT-III/Vps4 complexes can promote both inside-out and outside-in membrane fission reactions, and emerging mechanistic models for ESCRT-mediated membrane fission.
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Affiliation(s)
- John McCullough
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, Utah 84112, USA;
| | - Adam Frost
- Department of Biochemistry and Biophysics, University of California, San Francisco, California 94158, USA
- Chan Zuckerberg Biohub, San Francisco, California 94158, USA
| | - Wesley I Sundquist
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, Utah 84112, USA;
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103
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Arii J, Watanabe M, Maeda F, Tokai-Nishizumi N, Chihara T, Miura M, Maruzuru Y, Koyanagi N, Kato A, Kawaguchi Y. ESCRT-III mediates budding across the inner nuclear membrane and regulates its integrity. Nat Commun 2018; 9:3379. [PMID: 30139939 PMCID: PMC6107581 DOI: 10.1038/s41467-018-05889-9] [Citation(s) in RCA: 72] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Accepted: 07/28/2018] [Indexed: 11/30/2022] Open
Abstract
Vesicle-mediated nucleocytoplasmic transport is a nuclear pore-independent mechanism for the nuclear export of macromolecular complexes, but the molecular basis for this transport remains largely unknown. Here we show that endosomal sorting complex required for transport-III (ESCRT-III) is recruited to the inner nuclear membrane (INM) during the nuclear export of herpes simplex virus 1 (HSV-1). Scission during HSV-1 budding through the INM is prevented by depletion of ESCRT-III proteins. Interestingly, in uninfected human cells, the depletion of ESCRT-III proteins induces aberrant INM proliferation. Our results show that HSV-1 expropriates the ESCRT-III machinery in infected cells for scission of the INM to produce vesicles containing progeny virus nucleocapsids. In uninfected cells, ESCRT-III regulates INM integrity by downregulating excess INM. The endosomal sorting complex required for transport-III (ESCRT-III) has been implicated in the packaging of HIV and HSV-1 viruses in the cytoplasm. Here the authors show that ESCRT-III proteins are required for the transport of HSV-1 nucleocapsids from nucleoplasm to cytosol through the nuclear envelope and confirm that the same mechanism is also used for the nucleocytoplasmic transport of RNP in Drosophila cells.
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Affiliation(s)
- Jun Arii
- Division of Molecular Virology, Department of Microbiology and Immunology, The Institute of Medical Science, The University of Tokyo, Minato-ku, Tokyo, 108-8639, Japan.,Department of Infectious Disease Control, International Research Center for Infectious Diseases, The Institute of Medical Science, The University of Tokyo, Minato-ku, Tokyo, 108-8639, Japan
| | - Mizuki Watanabe
- Division of Molecular Virology, Department of Microbiology and Immunology, The Institute of Medical Science, The University of Tokyo, Minato-ku, Tokyo, 108-8639, Japan.,Department of Infectious Disease Control, International Research Center for Infectious Diseases, The Institute of Medical Science, The University of Tokyo, Minato-ku, Tokyo, 108-8639, Japan
| | - Fumio Maeda
- Division of Molecular Virology, Department of Microbiology and Immunology, The Institute of Medical Science, The University of Tokyo, Minato-ku, Tokyo, 108-8639, Japan.,Department of Infectious Disease Control, International Research Center for Infectious Diseases, The Institute of Medical Science, The University of Tokyo, Minato-ku, Tokyo, 108-8639, Japan
| | - Noriko Tokai-Nishizumi
- Microscope Core Laboratory, The Institute of Medical Science, The University of Tokyo, Minato-ku, Tokyo, 108-8639, Japan
| | - Takahiro Chihara
- Department of Genetics, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, 113-0033, Japan.,Graduate School of Science, Hiroshima University, Higashi-Hiroshima, Hiroshima, 739-8526, Japan
| | - Masayuki Miura
- Department of Genetics, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, 113-0033, Japan
| | - Yuhei Maruzuru
- Division of Molecular Virology, Department of Microbiology and Immunology, The Institute of Medical Science, The University of Tokyo, Minato-ku, Tokyo, 108-8639, Japan.,Department of Infectious Disease Control, International Research Center for Infectious Diseases, The Institute of Medical Science, The University of Tokyo, Minato-ku, Tokyo, 108-8639, Japan
| | - Naoto Koyanagi
- Division of Molecular Virology, Department of Microbiology and Immunology, The Institute of Medical Science, The University of Tokyo, Minato-ku, Tokyo, 108-8639, Japan.,Department of Infectious Disease Control, International Research Center for Infectious Diseases, The Institute of Medical Science, The University of Tokyo, Minato-ku, Tokyo, 108-8639, Japan
| | - Akihisa Kato
- Division of Molecular Virology, Department of Microbiology and Immunology, The Institute of Medical Science, The University of Tokyo, Minato-ku, Tokyo, 108-8639, Japan.,Department of Infectious Disease Control, International Research Center for Infectious Diseases, The Institute of Medical Science, The University of Tokyo, Minato-ku, Tokyo, 108-8639, Japan
| | - Yasushi Kawaguchi
- Division of Molecular Virology, Department of Microbiology and Immunology, The Institute of Medical Science, The University of Tokyo, Minato-ku, Tokyo, 108-8639, Japan. .,Department of Infectious Disease Control, International Research Center for Infectious Diseases, The Institute of Medical Science, The University of Tokyo, Minato-ku, Tokyo, 108-8639, Japan.
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104
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Fantastic nuclear envelope herniations and where to find them. Biochem Soc Trans 2018; 46:877-889. [PMID: 30026368 DOI: 10.1042/bst20170442] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2018] [Revised: 05/02/2018] [Accepted: 05/04/2018] [Indexed: 12/19/2022]
Abstract
Morphological abnormalities of the bounding membranes of the nucleus have long been associated with human diseases from cancer to premature aging to neurodegeneration. Studies over the past few decades support that there are both cell intrinsic and extrinsic factors (e.g. mechanical force) that can lead to nuclear envelope 'herniations', a broad catch-all term that reveals little about the underlying molecular mechanisms that contribute to these morphological defects. While there are many genetic perturbations that could ultimately change nuclear shape, here, we focus on a subset of nuclear envelope herniations that likely arise as a consequence of disrupting physiological nuclear membrane remodeling pathways required to maintain nuclear envelope homeostasis. For example, stalling of the interphase nuclear pore complex (NPC) biogenesis pathway and/or triggering of NPC quality control mechanisms can lead to herniations in budding yeast, which are remarkably similar to those observed in human disease models of early-onset dystonia. By also examining the provenance of nuclear envelope herniations associated with emerging nuclear autophagy and nuclear egress pathways, we will provide a framework to help understand the molecular pathways that contribute to nuclear deformation.
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105
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Mast FD, Herricks T, Strehler KM, Miller LR, Saleem RA, Rachubinski RA, Aitchison JD. ESCRT-III is required for scissioning new peroxisomes from the endoplasmic reticulum. J Cell Biol 2018; 217:2087-2102. [PMID: 29588378 PMCID: PMC5987711 DOI: 10.1083/jcb.201706044] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2017] [Revised: 01/23/2018] [Accepted: 03/05/2018] [Indexed: 12/11/2022] Open
Abstract
Dynamic control of peroxisome proliferation is integral to the peroxisome's many functions. The endoplasmic reticulum (ER) serves as a source of preperoxisomal vesicles (PPVs) that mature into peroxisomes during de novo peroxisome biogenesis and support growth and division of existing peroxisomes. However, the mechanism of PPV formation and release from the ER remains poorly understood. In this study, we show that endosomal sorting complexes required for transport (ESCRT)-III are required to release PPVs budding from the ER into the cytosol. Absence of ESCRT-III proteins impedes de novo peroxisome formation and results in an aberrant peroxisome population in vivo. Using a cell-free PPV budding assay, we show that ESCRT-III proteins Vps20 and Snf7 are necessary to release PPVs from the ER. ESCRT-III is therefore a positive effector of membrane scission for vesicles budding both away from and toward the cytosol. These findings have important implications for the evolutionary timing of emergence of peroxisomes and the rest of the internal membrane architecture of the eukaryotic cell.
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Affiliation(s)
- Fred D. Mast
- Center for Infectious Disease Research, Seattle, WA
- Institute for Systems Biology, Seattle, WA
| | - Thurston Herricks
- Center for Infectious Disease Research, Seattle, WA
- Institute for Systems Biology, Seattle, WA
| | - Kathleen M. Strehler
- Center for Infectious Disease Research, Seattle, WA
- Institute for Systems Biology, Seattle, WA
| | - Leslie R. Miller
- Center for Infectious Disease Research, Seattle, WA
- Institute for Systems Biology, Seattle, WA
| | - Ramsey A. Saleem
- Center for Infectious Disease Research, Seattle, WA
- Institute for Systems Biology, Seattle, WA
| | | | - John D. Aitchison
- Center for Infectious Disease Research, Seattle, WA
- Institute for Systems Biology, Seattle, WA
- Department of Cell Biology, University of Alberta, Edmonton, Alberta, Canada
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106
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A SUMO-dependent feedback loop senses and controls the biogenesis of nuclear pore subunits. Nat Commun 2018; 9:1665. [PMID: 29695777 PMCID: PMC5916902 DOI: 10.1038/s41467-018-03673-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2017] [Accepted: 03/05/2018] [Indexed: 11/29/2022] Open
Abstract
While the activity of multiprotein complexes is crucial for cellular metabolism, little is known about the mechanisms that collectively control the expression of their components. Here, we investigate the regulations targeting the biogenesis of the nuclear pore complex (NPC), the macromolecular assembly mediating nucleocytoplasmic exchanges. Systematic analysis of RNA-binding proteins interactomes, together with in vivo and in vitro assays, reveal that a subset of NPC mRNAs are specifically bound by Hek2, a yeast hnRNP K-like protein. Hek2-dependent translational repression and protein turnover are further shown to finely tune the levels of NPC subunits. Strikingly, mutations or physiological perturbations altering pore integrity decrease the levels of the NPC-associated SUMO protease Ulp1, and trigger the accumulation of sumoylated versions of Hek2 unable to bind NPC mRNAs. Our results support the existence of a quality control mechanism involving Ulp1 as a sensor of NPC integrity and Hek2 as a repressor of NPC biogenesis. The nuclear pore complex is crucial for mediating nucleocytoplasmic exchanges. Here the authors use budding yeast to reveal a mechanism responsible of maintaining nucleoporin homeostasis by sensing changes in the complex integrity and further altering the metabolism of the corresponding mRNAs.
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107
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Increasing Diversity of Biological Membrane Fission Mechanisms. Trends Cell Biol 2018; 28:274-286. [DOI: 10.1016/j.tcb.2017.12.001] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2017] [Revised: 12/06/2017] [Accepted: 12/12/2017] [Indexed: 12/19/2022]
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108
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Penfield L, Wysolmerski B, Mauro M, Farhadifar R, Martinez MA, Biggs R, Wu HY, Broberg C, Needleman D, Bahmanyar S. Dynein pulling forces counteract lamin-mediated nuclear stability during nuclear envelope repair. Mol Biol Cell 2018; 29:852-868. [PMID: 29386297 PMCID: PMC5905298 DOI: 10.1091/mbc.e17-06-0374] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Transient nuclear envelope (NE) ruptures in the Caenorhabditis elegans zygote are caused by a weakened nuclear lamina during nuclear positioning. Dynein-pulling forces enhance the severity of ruptures, while lamin restricts nucleocytoplasmic mixing and allows stable NE repair. This work is the first mechanistic analysis of NE rupture and repair in an organism. Recent work done exclusively in tissue culture cells revealed that the nuclear envelope (NE) ruptures and repairs in interphase. The duration of NE ruptures depends on lamins; however, the underlying mechanisms and relevance to in vivo events are not known. Here, we use the Caenorhabditis elegans zygote to analyze lamin’s role in NE rupture and repair in vivo. Transient NE ruptures and subsequent NE collapse are induced by weaknesses in the nuclear lamina caused by expression of an engineered hypomorphic C. elegans lamin allele. Dynein-generated forces that position nuclei enhance the severity of transient NE ruptures and cause NE collapse. Reduction of dynein forces allows the weakened lamin network to restrict nucleo–cytoplasmic mixing and support stable NE recovery. Surprisingly, the high incidence of transient NE ruptures does not contribute to embryonic lethality, which is instead correlated with stochastic chromosome scattering resulting from premature NE collapse, suggesting that C. elegans tolerates transient losses of NE compartmentalization during early embryogenesis. In sum, we demonstrate that lamin counteracts dynein forces to promote stable NE repair and prevent catastrophic NE collapse, and thus provide the first mechanistic analysis of NE rupture and repair in an organismal context.
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Affiliation(s)
- Lauren Penfield
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT 06520
| | - Brian Wysolmerski
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT 06520
| | - Michael Mauro
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT 06520
| | - Reza Farhadifar
- Department of Molecular and Cellular Biology, School of Engineering and Applied Sciences, FAS Center for Systems Biology, Harvard University, Cambridge, MA 02138
| | - Michael A Martinez
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT 06520
| | - Ronald Biggs
- Department of Cellular & Molecular Medicine, Ludwig Institute for Cancer Research, University of California, San Diego, La Jolla, CA 92093
| | - Hai-Yin Wu
- Department of Molecular and Cellular Biology, School of Engineering and Applied Sciences, FAS Center for Systems Biology, Harvard University, Cambridge, MA 02138
| | - Curtis Broberg
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT 06520
| | - Daniel Needleman
- Department of Molecular and Cellular Biology, School of Engineering and Applied Sciences, FAS Center for Systems Biology, Harvard University, Cambridge, MA 02138
| | - Shirin Bahmanyar
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT 06520
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109
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110
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Abstract
A better understanding of proteostasis in health and disease requires robust methods to determine protein half-lives. Here we improve the precision and accuracy of peptide ion intensity-based quantification, enabling more accurate protein turnover determination in non-dividing cells by dynamic SILAC-based proteomics. This approach allows exact determination of protein half-lives ranging from 10 to >1000 h. We identified 4000-6000 proteins in several non-dividing cell types, corresponding to 9699 unique protein identifications over the entire data set. We observed similar protein half-lives in B-cells, natural killer cells and monocytes, whereas hepatocytes and mouse embryonic neurons show substantial differences. Our data set extends and statistically validates the previous observation that subunits of protein complexes tend to have coherent turnover. Moreover, analysis of different proteasome and nuclear pore complex assemblies suggests that their turnover rate is architecture dependent. These results illustrate that our approach allows investigating protein turnover and its implications in various cell types.
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111
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Zhang W, Neuner A, Rüthnick D, Sachsenheimer T, Lüchtenborg C, Brügger B, Schiebel E. Brr6 and Brl1 locate to nuclear pore complex assembly sites to promote their biogenesis. J Cell Biol 2018; 217:877-894. [PMID: 29439116 PMCID: PMC5839787 DOI: 10.1083/jcb.201706024] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2017] [Revised: 11/21/2017] [Accepted: 01/10/2018] [Indexed: 12/30/2022] Open
Abstract
The conserved paralogous Brr6 and Brl1 promote NPC biogenesis in an unclear manner. Here, Zhang et al. show that both transmembrane proteins transiently associate with NPC assembly intermediates and directly promote NPC biogenesis. The paralogous Brr6 and Brl1 are conserved integral membrane proteins of the nuclear envelope (NE) with an unclear role in nuclear pore complex (NPC) biogenesis. Here, we analyzed double-degron mutants of Brr6/Brl1 to understand this function. Depletion of Brr6 and Brl1 caused defects in NPC biogenesis, whereas the already assembled NPCs remained unaffected. This NPC biogenesis defect was not accompanied by a change in lipid composition. However, Brl1 interacted with Ndc1 and Nup188 by immunoprecipitation, and with transmembrane and outer and inner ring NPC components by split yellow fluorescent protein analysis, indicating a direct role in NPC biogenesis. Consistently, we found that Brr6 and Brl1 associated with a subpopulation of NPCs and emerging NPC assembly sites. Moreover, BRL1 overexpression affected NE morphology without a change in lipid composition and completely suppressed the nuclear pore biogenesis defect of nup116Δ and gle2Δ cells. We propose that Brr6 and Brl1 transiently associate with NPC assembly sites where they promote NPC biogenesis.
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Affiliation(s)
- Wanlu Zhang
- Zentrum für Molekulare Biologie der Universität Heidelberg, DKFZ-ZMBH Allianz, Heidelberg, Germany
| | - Annett Neuner
- Zentrum für Molekulare Biologie der Universität Heidelberg, DKFZ-ZMBH Allianz, Heidelberg, Germany
| | - Diana Rüthnick
- Zentrum für Molekulare Biologie der Universität Heidelberg, DKFZ-ZMBH Allianz, Heidelberg, Germany
| | | | | | - Britta Brügger
- Heidelberg University Biochemistry Center, Heidelberg, Germany
| | - Elmar Schiebel
- Zentrum für Molekulare Biologie der Universität Heidelberg, DKFZ-ZMBH Allianz, Heidelberg, Germany
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112
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Otsuka S, Ellenberg J. Mechanisms of nuclear pore complex assembly - two different ways of building one molecular machine. FEBS Lett 2018; 592:475-488. [PMID: 29119545 PMCID: PMC6220763 DOI: 10.1002/1873-3468.12905] [Citation(s) in RCA: 79] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2017] [Revised: 10/27/2017] [Accepted: 11/02/2017] [Indexed: 12/16/2022]
Abstract
The nuclear pore complex (NPC) mediates all macromolecular transport across the nuclear envelope. In higher eukaryotes that have an open mitosis, NPCs assemble at two points in the cell cycle: during nuclear assembly in late mitosis and during nuclear growth in interphase. How the NPC, the largest nonpolymeric protein complex in eukaryotic cells, self-assembles inside cells remained unclear. Recent studies have started to uncover the assembly process, and evidence has been accumulating that postmitotic and interphase NPC assembly use fundamentally different mechanisms; the duration, structural intermediates, and regulation by molecular players are different and different types of membrane deformation are involved. In this Review, we summarize the current understanding of these two modes of NPC assembly and discuss the structural and regulatory steps that might drive the assembly processes. We furthermore integrate understanding of NPC assembly with the mechanisms for rapid nuclear growth in embryos and, finally, speculate on the evolutionary origin of the NPC implied by the presence of two distinct assembly mechanisms.
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Affiliation(s)
- Shotaro Otsuka
- Cell Biology and Biophysics UnitEuropean Molecular Biology LaboratoryHeidelbergGermany
| | - Jan Ellenberg
- Cell Biology and Biophysics UnitEuropean Molecular Biology LaboratoryHeidelbergGermany
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113
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114
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Integration of the Endocytic System into the Network of Cellular Functions. PROGRESS IN MOLECULAR AND SUBCELLULAR BIOLOGY 2018; 57:39-63. [PMID: 30097771 DOI: 10.1007/978-3-319-96704-2_2] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Maintenance of physiologic cellular functions and homeostasis requires highly coordinated interactions between different cellular compartments. In this regard, the endocytic system, which plays a key role in cargo internalization and trafficking within the cell, participates in upkeep of intracellular dynamics, while communicating with multiple organelles. This chapter will discuss the function of endosomes from a standpoint of cellular integration. We will present examples of different types of interactions between endosomes and other cellular compartments, such as the endoplasmic reticulum (ER), mitochondria, the plasma membrane (PM), and the nuclear envelope. In addition, we will describe the incorporation of endocytic components, such as endosomal sorting complexes required for transport (ESCRT) proteins and Rab small GTPases, into cellular processes that operate outside of the endolysosomal pathway. The significance of endosomal interactions for processes such as signaling regulation, intracellular trafficking, organelle dynamics, metabolic control, and homeostatic responses will be reviewed. Accumulating data indicate that beyond its involvement in cargo transport, the endocytic pathway is comprehensively integrated into other systems of the cell and plays multiple roles in the complex net of cellular functions.
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115
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Distinct Roles of Cellular ESCRT-I and ESCRT-III Proteins in Efficient Entry and Egress of Budded Virions of Autographa californica Multiple Nucleopolyhedrovirus. J Virol 2017; 92:JVI.01636-17. [PMID: 29046462 DOI: 10.1128/jvi.01636-17] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2017] [Accepted: 10/06/2017] [Indexed: 11/20/2022] Open
Abstract
The endosomal sorting complex required for transport (ESCRT) machinery is necessary for budding of many enveloped viruses. Recently, it was demonstrated that Vps4, the key regulator for recycling of the ESCRT-III complex, is required for efficient infection by the baculovirus Autographa californica multiple nucleopolyhedrovirus (AcMNPV). However, ESCRT assembly, regulation, and function are complex, and little is known regarding the details of participation of specific ESCRT complexes in AcMNPV infection. In this study, the core components of ESCRT-I (Tsg101 and Vps28) and ESCRT-III (Vps2B, Vps20, Vps24, Snf7, Vps46, and Vps60) were cloned from Spodoptera frugiperda Using a viral complementation system and RNA interference (RNAi) assays, we found that ESCRT-I and ESCRT-III complexes are required for efficient entry of AcMNPV into insect cells. In cells knocking down or overexpressing dominant negative (DN) forms of the components of ESCRT-I and ESCRT-III complexes, entering virions were partially trapped within the cytosol. To examine only egress, cells were transfected with the double-stranded RNA (dsRNA) targeting an individual ESCRT-I or ESCRT-III gene and viral bacmid DNA or viral bacmid DNA that expressed DN forms of ESCRT-I and ESCRT-III components. We found that ESCRT-III components (but not ESCRT-I components) are required for efficient nuclear egress of progeny nucleocapsids. In addition, we found that several baculovirus core or conserved proteins (Ac11, Ac76, Ac78, GP41, Ac93, Ac103, Ac142, and Ac146) interact with Vps4 and components of ESCRT-III. We propose that these viral proteins may form an "egress complex" that is involved in recruiting ESCRT-III components to a virus egress domain on the nuclear membrane.IMPORTANCE The ESCRT system is hijacked by many enveloped viruses to mediate budding and release. Recently, it was found that Vps4, the key regulator of the cellular ESCRT machinery, is necessary for efficient entry and egress of Autographa californica multiple nucleopolyhedrovirus (AcMNPV). However, little is known about the roles of specific ESCRT complexes in AcMNPV infection. In this study, we demonstrated that ESCRT-I and ESCRT-III complexes are required for efficient entry of AcMNPV into insect cells. The components of ESCRT-III (but not ESCRT-I) are also necessary for efficient nuclear egress of progeny nucleocapsids. Several baculovirus core or conserved proteins were found to interact with Vps4 and components of ESCRT-III, and these interactions may suggest the formation of an "egress complex" involved in the nuclear release or transport of viral nucleocapsids.
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116
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Parchure A, Munson M, Budnik V. Getting mRNA-Containing Ribonucleoprotein Granules Out of a Nuclear Back Door. Neuron 2017; 96:604-615. [PMID: 29096075 DOI: 10.1016/j.neuron.2017.10.020] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2017] [Revised: 10/15/2017] [Accepted: 10/16/2017] [Indexed: 12/21/2022]
Abstract
A pivotal feature of long-lasting synaptic plasticity is the localization of RNAs and the protein synthesis machinery at synaptic sites. How and where ribonucleoprotein (RNP) transport granules that support this synthetic activity are formed is of fundamental importance. The prevailing model poses that the nuclear pore complex (NPC) is the sole gatekeeper for transit of cellular material in and out of the nucleus. However, insights from the nuclear assembly of large viral capsids highlight a back door route for nuclear escape, a process referred to nuclear envelope (NE) budding. Recent studies indicate that NE budding might be an endogenous cellular process for the nuclear export of very large RNPs and protein aggregates. In Drosophila, this mechanism is required for synaptic plasticity, but its role may extend beyond the nervous system, in tissues where local changes in translation are required. Here we discuss these recent findings and a potential relationship between NE budding and the NPC.
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Affiliation(s)
- Anup Parchure
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, MA, USA
| | - Mary Munson
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA, USA
| | - Vivian Budnik
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, MA, USA.
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117
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Kim HJ, Taylor JP. Lost in Transportation: Nucleocytoplasmic Transport Defects in ALS and Other Neurodegenerative Diseases. Neuron 2017; 96:285-297. [PMID: 29024655 DOI: 10.1016/j.neuron.2017.07.029] [Citation(s) in RCA: 177] [Impact Index Per Article: 25.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2017] [Revised: 07/21/2017] [Accepted: 07/25/2017] [Indexed: 12/12/2022]
Abstract
Amyotrophic lateral sclerosis (ALS) is a progressive, fatal neurodegenerative disease characterized by degeneration of upper and lower motor neurons in the brain and spinal cord. The hallmark pathological feature in most cases of ALS is nuclear depletion and cytoplasmic accumulation of the protein TDP-43 in degenerating neurons. Consistent with this pattern of intracellular protein redistribution, impaired nucleocytoplasmic trafficking has emerged as a mechanism contributing to ALS pathology. Dysfunction in nucleocytoplasmic transport is also an emerging theme in physiological aging and other related neurodegenerative diseases, such as Huntington's and Alzheimer's diseases. Here we review transport through the nuclear pore complex, pointing out vulnerabilities that may underlie ALS and potentially contribute to this and other age-related neurodegenerative diseases.
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Affiliation(s)
- Hong Joo Kim
- Department of Cell and Molecular Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - J Paul Taylor
- Department of Cell and Molecular Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA; Howard Hughes Medical Institute, Chevy Chase, MD 20815, USA.
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118
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Roles of Cellular NSF Protein in Entry and Nuclear Egress of Budded Virions of Autographa californica Multiple Nucleopolyhedrovirus. J Virol 2017; 91:JVI.01111-17. [PMID: 28747507 DOI: 10.1128/jvi.01111-17] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2017] [Accepted: 07/20/2017] [Indexed: 02/03/2023] Open
Abstract
In eukaryotic cells, the soluble N-ethylmaleimide-sensitive factor (NSF) attachment protein receptor (SNARE) proteins comprise the minimal machinery that triggers fusion of transport vesicles with their target membranes. Comparative studies revealed that genes encoding the components of the SNARE system are highly conserved in yeast, insect, and human genomes. Upon infection of insect cells by the virus Autographa californica multiple nucleopolyhedrovirus (AcMNPV), the transcript levels of most SNARE genes initially were upregulated. We found that overexpression of dominant-negative (DN) forms of NSF or knockdown of the expression of NSF, the key regulator of the SNARE system, significantly affected infectious AcMNPV production. In cells expressing DN NSF, entering virions were trapped in the cytoplasm or transported to the nucleus with low efficiency. The presence of DN NSF also moderately reduced trafficking of the viral envelope glycoprotein GP64 to the plasma membrane but dramatically inhibited production of infectious budded virions (BV). Transmission electron microscopy analysis of infections in cells expressing DN NSF revealed that progeny nucleocapsids were retained in a perinuclear space surrounded by inner and outer nuclear membranes. Several baculovirus conserved (core) proteins (Ac76, Ac78, GP41, Ac93, and Ac103) that are important for infectious budded virion production were found to associate with NSF, and NSF was detected within the assembled BV. Together, these data indicate that the cellular SNARE system is involved in AcMNPV infection and that NSF is required for efficient entry and nuclear egress of budded virions of AcMNPV.IMPORTANCE Little is known regarding the complex interplay between cellular factors and baculoviruses during viral entry and egress. Here, we examined the cellular SNARE system, which mediates the fusion of vesicles in healthy cells, and its relation to baculovirus infection. Using a DN approach and RNA interference knockdown, we demonstrated that a general disruption of the SNARE machinery significantly inhibited the production of infectious BV of AcMNPV. The presence of a DN NSF protein resulted in low-efficiency entry of BV and the retention of progeny nucleocapsids in the perinuclear space during egress. Combined with these effects, we also found that several conserved (core) baculovirus proteins closely associate with NSF, and these results suggest their involvement in the egress of BV. Our findings are the first to demonstrate that the SNARE system is required for efficient entry of BV and nuclear egress of progeny nucleocapsids of baculoviruses.
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119
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Stoten CL, Carlton JG. ESCRT-dependent control of membrane remodelling during cell division. Semin Cell Dev Biol 2017; 74:50-65. [PMID: 28843980 PMCID: PMC6015221 DOI: 10.1016/j.semcdb.2017.08.035] [Citation(s) in RCA: 70] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2017] [Revised: 08/07/2017] [Accepted: 08/18/2017] [Indexed: 12/16/2022]
Abstract
The Endosomal Sorting Complex Required for Transport (ESCRT) proteins form an evolutionarily conserved membrane remodelling machinery. Identified originally for their role in cargo sorting and remodelling of endosomal membranes during yeast vacuolar sorting, an extensive body of work now implicates a sub-complex of this machinery (ESCRT-III), as a transplantable membrane fission machinery that is dispatched to various cellular locations to achieve a topologically unique membrane separation. Surprisingly, several ESCRT-III-regulated processes occur during cell division, when cells undergo a dramatic and co-ordinated remodelling of their membranes to allow the physical processes of division to occur. The ESCRT machinery functions in regeneration of the nuclear envelope during open mitosis and in the abscission phase of cytokinesis, where daughter cells are separated from each other in the last act of division. Roles for the ESCRT machinery in cell division are conserved as far back as Archaea, suggesting that the ancestral role of these proteins was as a membrane remodelling machinery that facilitated division and that was co-opted throughout evolution to perform a variety of other cell biological functions. Here, we will explore the function and regulation of the ESCRT machinery in cell division.
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120
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Sadoul R, Laporte MH, Chassefeyre R, Chi KI, Goldberg Y, Chatellard C, Hemming FJ, Fraboulet S. The role of ESCRT during development and functioning of the nervous system. Semin Cell Dev Biol 2017; 74:40-49. [PMID: 28811263 DOI: 10.1016/j.semcdb.2017.08.013] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2017] [Revised: 07/21/2017] [Accepted: 08/04/2017] [Indexed: 12/12/2022]
Abstract
The endosomal sorting complex required for transport (ESCRT) is made of subcomplexes (ESCRT 0-III), crucial to membrane remodelling at endosomes, nuclear envelope and cell surface. ESCRT-III shapes membranes and in most cases cooperates with the ATPase VPS4 to mediate fission of membrane necks from the inside. The first ESCRT complexes mainly serve to catalyse the formation of ESCRT-III but can be bypassed by accessory proteins like the Alg-2 interacting protein-X (ALIX). In the nervous system, ALIX/ESCRT controls the survival of embryonic neural progenitors and later on the outgrowth and pruning of axons and dendrites, all necessary steps to establish a functional brain. In the adult brain, ESCRTs allow the endosomal turn over of synaptic vesicle proteins while stable ESCRT complexes might serve as scaffolds for the postsynaptic parts. The necessity of ESCRT for the harmonious function of the brain has its pathological counterpart, the mutations in CHMP2B of ESCRT-III giving rise to several neurodegenerative diseases.
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Affiliation(s)
- Rémy Sadoul
- Institut National de la Santé et de la Recherche Médicale (INSERM), U1216, F-38042 Grenoble, France; Université Grenoble Alpes, Institut des Neurosciences, F-38042 Grenoble, France.
| | - Marine H Laporte
- Institut National de la Santé et de la Recherche Médicale (INSERM), U1216, F-38042 Grenoble, France; Université Grenoble Alpes, Institut des Neurosciences, F-38042 Grenoble, France
| | - Romain Chassefeyre
- Institut National de la Santé et de la Recherche Médicale (INSERM), U1216, F-38042 Grenoble, France; Université Grenoble Alpes, Institut des Neurosciences, F-38042 Grenoble, France
| | - Kwang Il Chi
- Institut National de la Santé et de la Recherche Médicale (INSERM), U1216, F-38042 Grenoble, France; Université Grenoble Alpes, Institut des Neurosciences, F-38042 Grenoble, France
| | - Yves Goldberg
- Institut National de la Santé et de la Recherche Médicale (INSERM), U1216, F-38042 Grenoble, France; Université Grenoble Alpes, Institut des Neurosciences, F-38042 Grenoble, France
| | - Christine Chatellard
- Institut National de la Santé et de la Recherche Médicale (INSERM), U1216, F-38042 Grenoble, France; Université Grenoble Alpes, Institut des Neurosciences, F-38042 Grenoble, France
| | - Fiona J Hemming
- Institut National de la Santé et de la Recherche Médicale (INSERM), U1216, F-38042 Grenoble, France; Université Grenoble Alpes, Institut des Neurosciences, F-38042 Grenoble, France
| | - Sandrine Fraboulet
- Institut National de la Santé et de la Recherche Médicale (INSERM), U1216, F-38042 Grenoble, France; Université Grenoble Alpes, Institut des Neurosciences, F-38042 Grenoble, France
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121
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Growing functions of the ESCRT machinery in cell biology and viral replication. Biochem Soc Trans 2017; 45:613-634. [PMID: 28620025 DOI: 10.1042/bst20160479] [Citation(s) in RCA: 65] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2016] [Revised: 02/17/2017] [Accepted: 02/21/2017] [Indexed: 01/31/2023]
Abstract
The vast expansion in recent years of the cellular processes promoted by the endosomal sorting complex required for transport (ESCRT) machinery has reinforced its identity as a modular system that uses multiple adaptors to recruit the core membrane remodelling activity at different intracellular sites and facilitate membrane scission. Functional connections to processes such as the aurora B-dependent abscission checkpoint also highlight the importance of the spatiotemporal regulation of the ESCRT machinery. Here, we summarise the role of ESCRTs in viral budding, and what we have learned about the ESCRT pathway from studying this process. These advances are discussed in the context of areas of cell biology that have been transformed by research in the ESCRT field, including cytokinetic abscission, nuclear envelope resealing and plasma membrane repair.
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122
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Chiaruttini N, Roux A. Dynamic and elastic shape transitions in curved ESCRT-III filaments. Curr Opin Cell Biol 2017; 47:126-135. [PMID: 28728013 DOI: 10.1016/j.ceb.2017.07.002] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
The ESCRT-III complex is an evolutionary ancient and conserved complex that catalyzes fission of lipid membranes from the lumen of the neck in many, if not all processes requiring this specific fission reaction. The ESCRT-III membrane remodeling complex is unique as its molecular and polymeric structures do not intuitively suggests how it could deform and break lipid membranes. Here we review the common structural features of the ESCRT-III subunits, and the shape diversity of the various filamentous forms. We propose a simple geometry and elasticity framework that could help to isolate which features of the ESCRT-III filaments are common to all filamentous forms as well as to explain their diversity. We speculate on how these features could provide mechanistic insights into the many functions of the ESCRT-III complex.
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Affiliation(s)
- Nicolas Chiaruttini
- Department of Biochemistry, University of Geneva, CH-1211 Geneva, Switzerland
| | - Aurélien Roux
- Department of Biochemistry, University of Geneva, CH-1211 Geneva, Switzerland; Swiss National Centre for Competence in Research Programme Chemical Biology, CH-1211 Geneva, Switzerland.
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123
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Zhu L, Jorgensen JR, Li M, Chuang YS, Emr SD. ESCRTs function directly on the lysosome membrane to downregulate ubiquitinated lysosomal membrane proteins. eLife 2017; 6:e26403. [PMID: 28661397 PMCID: PMC5507667 DOI: 10.7554/elife.26403] [Citation(s) in RCA: 72] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2017] [Accepted: 06/23/2017] [Indexed: 11/23/2022] Open
Abstract
The lysosome plays an important role in maintaining cellular nutrient homeostasis. Regulation of nutrient storage can occur by the ubiquitination of certain transporters that are then sorted into the lysosome lumen for degradation. To better understand the underlying mechanism of this process, we performed genetic screens to identify components of the sorting machinery required for vacuole membrane protein degradation. These screens uncovered genes that encode a ubiquitin ligase complex, components of the PtdIns 3-kinase complex, and the ESCRT machinery. We developed a novel ubiquitination system, Rapamycin-Induced Degradation (RapiDeg), to test the sorting defects caused by these mutants. These tests revealed that ubiquitinated vacuole membrane proteins recruit ESCRTs to the vacuole surface, where they mediate cargo sorting and direct cargo delivery into the vacuole lumen. Our findings demonstrate that the ESCRTs can function at both the late endosome and the vacuole membrane to mediate cargo sorting and intra-luminal vesicle formation.
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Affiliation(s)
- Lu Zhu
- Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, United States
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, United States
| | - Jeff R Jorgensen
- Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, United States
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, United States
| | - Ming Li
- Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, United States
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, United States
| | - Ya-Shan Chuang
- Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, United States
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, United States
| | - Scott D Emr
- Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, United States
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124
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Chase AR, Laudermilch E, Schlieker C. Torsin ATPases: Harnessing Dynamic Instability for Function. Front Mol Biosci 2017; 4:29. [PMID: 28553638 PMCID: PMC5425593 DOI: 10.3389/fmolb.2017.00029] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2017] [Accepted: 04/25/2017] [Indexed: 12/11/2022] Open
Abstract
Torsins are essential, disease-relevant AAA+ (ATPases associated with various cellular activities) proteins residing in the endoplasmic reticulum and perinuclear space, where they are implicated in a variety of cellular functions. Recently, new structural and functional details about Torsins have emerged that will have a profound influence on unraveling the precise mechanistic details of their yet-unknown mode of action in the cell. While Torsins are phylogenetically related to Clp/HSP100 proteins, they exhibit comparatively weak ATPase activities, which are tightly controlled by virtue of an active site complementation through accessory cofactors. This control mechanism is offset by a TorsinA mutation implicated in the severe movement disorder DYT1 dystonia, suggesting a critical role for the functional Torsin-cofactor interplay in vivo. Notably, TorsinA lacks aromatic pore loops that are both conserved and critical for the processive unfolding activity of Clp/HSP100 proteins. Based on these distinctive yet defining features, we discuss how the apparent dynamic nature of the Torsin-cofactor system can inform emerging models and hypotheses for Torsin complex formation and function. Specifically, we propose that the dynamic assembly and disassembly of the Torsin/cofactor system is a critical property that is required for Torsins' functional roles in nuclear trafficking and nuclear pore complex assembly or homeostasis that merit further exploration. Insights obtained from these future studies will be a valuable addition to our understanding of disease etiology of DYT1 dystonia.
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Affiliation(s)
- Anna R Chase
- Department of Molecular Biophysics and Biochemistry, Yale UniversityNew Haven, CT, USA
| | - Ethan Laudermilch
- Department of Molecular Biophysics and Biochemistry, Yale UniversityNew Haven, CT, USA
| | - Christian Schlieker
- Department of Molecular Biophysics and Biochemistry, Yale UniversityNew Haven, CT, USA.,Department of Cell Biology, Yale School of MedicineNew Haven, CT, USA
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125
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LEM2 recruits CHMP7 for ESCRT-mediated nuclear envelope closure in fission yeast and human cells. Proc Natl Acad Sci U S A 2017; 114:E2166-E2175. [PMID: 28242692 PMCID: PMC5358359 DOI: 10.1073/pnas.1613916114] [Citation(s) in RCA: 125] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The molecular mechanism for sealing newly formed nuclear envelopes was unclear until the recent discovery that endosomal sorting complexes required for transport III (ESCRT-III) proteins mediate this process. Cmp7p (CHMP7), in particular, was identified as an early acting factor that recruits other ESCRT-III proteins to the nuclear envelope. A fundamental aspect of the varied roles of ESCRT factors is their recruitment by site-specific adaptors, yet the central question of how the ESCRT machinery is targeted to nuclear membranes has remained outstanding. Our study identifies the inner nuclear membrane protein LEM2 as a key, conserved factor that recruits CHMP7 and downstream ESCRT-III proteins to breaches in the nuclear envelope. Endosomal sorting complexes required for transport III (ESCRT-III) proteins have been implicated in sealing the nuclear envelope in mammals, spindle pole body dynamics in fission yeast, and surveillance of defective nuclear pore complexes in budding yeast. Here, we report that Lem2p (LEM2), a member of the LEM (Lap2-Emerin-Man1) family of inner nuclear membrane proteins, and the ESCRT-II/ESCRT-III hybrid protein Cmp7p (CHMP7), work together to recruit additional ESCRT-III proteins to holes in the nuclear membrane. In Schizosaccharomyces pombe, deletion of the ATPase vps4 leads to severe defects in nuclear morphology and integrity. These phenotypes are suppressed by loss-of-function mutations that arise spontaneously in lem2 or cmp7, implying that these proteins may function upstream in the same pathway. Building on these genetic interactions, we explored the role of LEM2 during nuclear envelope reformation in human cells. We found that CHMP7 and LEM2 enrich at the same region of the chromatin disk periphery during this window of cell division and that CHMP7 can bind directly to the C-terminal domain of LEM2 in vitro. We further found that, during nuclear envelope formation, recruitment of the ESCRT factors CHMP7, CHMP2A, and IST1/CHMP8 all depend on LEM2 in human cells. We conclude that Lem2p/LEM2 is a conserved nuclear site-specific adaptor that recruits Cmp7p/CHMP7 and downstream ESCRT factors to the nuclear envelope.
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126
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LaJoie D, Ullman KS. Coordinated events of nuclear assembly. Curr Opin Cell Biol 2017; 46:39-45. [PMID: 28189102 DOI: 10.1016/j.ceb.2016.12.008] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2016] [Revised: 12/22/2016] [Accepted: 12/30/2016] [Indexed: 12/01/2022]
Abstract
Each time a metazoan cell undergoes open mitosis, the nucleus is dismantled in order to partition DNA content to the daughter cells. After chromosomes separate, changes at the chromatin surface usher in reestablishment of nuclear architecture. Proteins destined for the nuclear envelope are attracted to chromatin and concomitantly recruit membrane. As nuclear envelope and protein constituents spread to coat chromatin, distinct regions emerge-some rich in rapid pore formation, others occupied by microtubules that remain attached to kinetochores. Microtubule connections present physical barriers that must be remodeled in order for the nuclear envelope to seal. Regions of the nascent nuclear envelope that are initially characterized by contrasting repertoires of nuclear envelope proteins rapidly coalesce as nuclei expand and enter interphase.
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Affiliation(s)
- Dollie LaJoie
- Department of Oncological Sciences, Huntsman Cancer Institute, University of Utah, Salt Lake City, UT 84112, USA
| | - Katharine S Ullman
- Department of Oncological Sciences, Huntsman Cancer Institute, University of Utah, Salt Lake City, UT 84112, USA.
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127
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Abstract
As a compartment border, the nuclear envelope (NE) needs to serve as both a protective membrane shell for the genome and a versatile communication interface between the nucleus and the cytoplasm. Despite its important structural role in sheltering the genome, the NE is a dynamic and highly adaptable boundary that changes composition during differentiation, deforms in response to mechanical challenges, can be repaired upon rupture and even rapidly disassembles and reforms during open mitosis. NE remodelling is fundamentally involved in cell growth, division and differentiation, and if perturbed can lead to devastating diseases such as muscular dystrophies or premature ageing.
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128
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Johnson N, West M, Odorizzi G. Regulation of yeast ESCRT-III membrane scission activity by the Doa4 ubiquitin hydrolase. Mol Biol Cell 2017; 28:661-672. [PMID: 28057764 PMCID: PMC5328624 DOI: 10.1091/mbc.e16-11-0761] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2016] [Revised: 12/15/2016] [Accepted: 12/30/2016] [Indexed: 11/23/2022] Open
Abstract
Doa4 is the ubiquitin hydrolase in yeast that deubiquitinates transmembrane proteins sorted by ESCRTs. Results support a model for bidirectional regulation between Doa4 and the ESCRT-III complex. ESCRT-III executes membrane scission during the budding of intralumenal vesicles (ILVs) at endosomes. The scission mechanism is unknown but appears to be linked to the cycle of assembly and disassembly of ESCRT-III complexes at membranes. Regulating this cycle is therefore expected to be important for determining the timing of ESCRT-III–mediated membrane scission. We show that in Saccharomyces cerevisiae, ESCRT-III complexes are stabilized and ILV membrane scission is delayed by Doa4, which is the ubiquitin hydrolase that deubiquitinates transmembrane proteins sorted as cargoes into ILVs. These results suggest a mechanism to delay ILV budding while cargoes undergo deubiquitination. We further show that deubiquitination of ILV cargoes is inhibited via Doa4 binding to Vps20, which is the subunit of ESCRT-III that initiates assembly of the complex. Current models suggest that ESCRT-III complexes surround ubiquitinated cargoes to trap them at the site of ILV budding while the cargoes undergo deubiquitination. Thus our results also propose a mechanism to prevent the onset of ILV cargo deubiquitination at the initiation of ESCRT-III complex assembly.
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Affiliation(s)
- Natalie Johnson
- Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, CO 80309
| | - Matt West
- Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, CO 80309
| | - Greg Odorizzi
- Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, CO 80309
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129
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Christ L, Raiborg C, Wenzel EM, Campsteijn C, Stenmark H. Cellular Functions and Molecular Mechanisms of the ESCRT Membrane-Scission Machinery. Trends Biochem Sci 2017; 42:42-56. [DOI: 10.1016/j.tibs.2016.08.016] [Citation(s) in RCA: 300] [Impact Index Per Article: 42.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2016] [Revised: 08/24/2016] [Accepted: 08/31/2016] [Indexed: 12/22/2022]
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130
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Laudermilch E, Tsai PL, Graham M, Turner E, Zhao C, Schlieker C. Dissecting Torsin/cofactor function at the nuclear envelope: a genetic study. Mol Biol Cell 2016; 27:3964-3971. [PMID: 27798237 PMCID: PMC5156537 DOI: 10.1091/mbc.e16-07-0511] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2016] [Revised: 10/18/2016] [Accepted: 10/20/2016] [Indexed: 01/12/2023] Open
Abstract
Torsins are essential, disease-relevant ATPases, but their function is unknown. Monitoring of nuclear envelope morphology after deletion of multiple Torsins or their cofactors reveals a robust inner nuclear membrane–blebbing phenotype in HeLa cells. Nucleoporins and ubiquitin are defining molecular components of these omega-shaped blebs. The human genome encodes four Torsin ATPases, the functions of which are poorly understood. In this study, we use CRISPR/Cas9 engineering to delete all four Torsin ATPases individually and in combination. Using nuclear envelope (NE) blebbing as a phenotypic measure, we establish a direct correlation between the number of inactivated Torsin alleles and the occurrence of omega-shaped herniations within the lumen of the NE. A similar, although not identical, redundancy is observed for LAP1 and LULL1, which serve as regulatory cofactors for a subset of Torsin ATPases. Unexpectedly, deletion of Tor2A in a TorA/B/3A-deficient background results in a stark increase of bleb formation, even though Tor2A does not respond to LAP1/LULL1 stimulation. The robustness of the observed phenotype in Torsin-deficient cells enables a structural analysis via electron microscopy tomography and a compositional analysis via immunogold labeling. Ubiquitin and nucleoporins were identified as distinctively localizing components of the omega-shaped bleb structure. These findings suggest a functional link between the Torsin/cofactor system and NE/nuclear pore complex biogenesis or homeostasis and establish a Torsin-deficient cell line as a valuable experimental platform with which to decipher Torsin function.
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Affiliation(s)
- Ethan Laudermilch
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520
| | - Pei-Ling Tsai
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520
| | - Morven Graham
- Department of Cell Biology, Yale School of Medicine, New Haven, CT 06520
| | - Elizabeth Turner
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520
| | - Chenguang Zhao
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520
| | - Christian Schlieker
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520 .,Department of Cell Biology, Yale School of Medicine, New Haven, CT 06520
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131
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Webster BM, Thaller DJ, Jäger J, Ochmann SE, Borah S, Lusk CP. Chm7 and Heh1 collaborate to link nuclear pore complex quality control with nuclear envelope sealing. EMBO J 2016; 35:2447-2467. [PMID: 27733427 DOI: 10.15252/embj.201694574] [Citation(s) in RCA: 90] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2016] [Revised: 09/21/2016] [Accepted: 09/22/2016] [Indexed: 11/09/2022] Open
Abstract
The integrity of the nuclear envelope barrier relies on membrane remodeling by the ESCRTs, which seal nuclear envelope holes and contribute to the quality control of nuclear pore complexes (NPCs); whether these processes are mechanistically related remains poorly defined. Here, we show that the ESCRT-II/III chimera, Chm7, is recruited to a nuclear envelope subdomain that expands upon inhibition of NPC assembly and is required for the formation of the storage of improperly assembled NPCs (SINC) compartment. Recruitment to sites of NPC assembly is mediated by its ESCRT-II domain and the LAP2-emerin-MAN1 (LEM) family of integral inner nuclear membrane proteins, Heh1 and Heh2. We establish direct binding between Heh2 and the "open" forms of both Chm7 and the ESCRT-III, Snf7, and between Chm7 and Snf7. Interestingly, Chm7 is required for the viability of yeast strains where double membrane seals have been observed over defective NPCs; deletion of CHM7 in these strains leads to a loss of nuclear compartmentalization suggesting that the sealing of defective NPCs and nuclear envelope ruptures could proceed through similar mechanisms.
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Affiliation(s)
- Brant M Webster
- Department of Cell Biology, Yale School of Medicine, New Haven, CT, USA
| | - David J Thaller
- Department of Cell Biology, Yale School of Medicine, New Haven, CT, USA
| | - Jens Jäger
- Department of Cell Biology, Yale School of Medicine, New Haven, CT, USA
| | - Sarah E Ochmann
- Department of Cell Biology, Yale School of Medicine, New Haven, CT, USA
| | - Sapan Borah
- Department of Cell Biology, Yale School of Medicine, New Haven, CT, USA
| | - C Patrick Lusk
- Department of Cell Biology, Yale School of Medicine, New Haven, CT, USA
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132
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The Ubiquitin Ligase Itch and Ubiquitination Regulate BFRF1-Mediated Nuclear Envelope Modification for Epstein-Barr Virus Maturation. J Virol 2016; 90:8994-9007. [PMID: 27466427 DOI: 10.1128/jvi.01235-16] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2016] [Accepted: 07/19/2016] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED The cellular endosomal sorting complex required for transport (ESCRT) was recently found to mediate important morphogenesis processes at the nuclear envelope (NE). We previously showed that the Epstein-Barr virus (EBV) BFRF1 protein recruits the ESCRT-associated protein Alix to modulate NE structure and promote EBV nuclear egress. Here, we uncover new cellular factors and mechanisms involved in this process. BFRF1-induced NE vesicles are similar to those observed following EBV reactivation. BFRF1 is ubiquitinated, and elimination of possible ubiquitination by either lysine mutations or fusion of a deubiquitinase hampers NE-derived vesicle formation and virus maturation. While it interacts with multiple Nedd4-like ubiquitin ligases, BFRF1 preferentially binds Itch ligase. We show that Itch associates with Alix and BFRF1 and is required for BFRF1-induced NE vesicle formation. Our data demonstrate that Itch, ubiquitin, and Alix control the BFRF1-mediated modulation of the NE and EBV maturation, uncovering novel regulatory mechanisms of nuclear egress of viral nucleocapsids. IMPORTANCE The nuclear envelope (NE) of eukaryotic cells not only serves as a transverse scaffold for cellular processes, but also as a natural barrier for most DNA viruses that assemble their nucleocapsids in the nucleus. Previously, we showed that the cellular endosomal sorting complex required for transport (ESCRT) machinery is required for the nuclear egress of EBV. Here, we further report the molecular interplay among viral BFRF1, the ESCRT adaptor Alix, and the ubiquitin ligase Itch. We found that BFRF1-induced NE vesicles are similar to those observed following EBV reactivation. The lysine residues and the ubiquitination of BFRF1 regulate the formation of BFRF1-induced NE-derived vesicles and EBV maturation. During the process, a ubiquitin ligase, Itch, preferably associates with BFRF1 and is required for BFRF1-induced NE vesicle formation. Therefore, our data indicate that Itch, ubiquitin, and Alix control the BFRF1-mediated modulation of the NE, suggesting novel regulatory mechanisms for ESCRT-mediated NE modulation.
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133
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Vesicular Nucleo-Cytoplasmic Transport-Herpesviruses as Pioneers in Cell Biology. Viruses 2016; 8:v8100266. [PMID: 27690080 PMCID: PMC5086602 DOI: 10.3390/v8100266] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2016] [Revised: 09/12/2016] [Accepted: 09/20/2016] [Indexed: 11/16/2022] Open
Abstract
Herpesviruses use a vesicle-mediated transfer of intranuclearly assembled nucleocapsids through the nuclear envelope (NE) for final maturation in the cytoplasm. The molecular basis for this novel vesicular nucleo-cytoplasmic transport is beginning to be elucidated in detail. The heterodimeric viral nuclear egress complex (NEC), conserved within the classical herpesviruses, mediates vesicle formation from the inner nuclear membrane (INM) by polymerization into a hexagonal lattice followed by fusion of the vesicle membrane with the outer nuclear membrane (ONM). Mechanisms of capsid inclusion as well as vesicle-membrane fusion, however, are largely unclear. Interestingly, a similar transport mechanism through the NE has been demonstrated in nuclear export of large ribonucleoprotein complexes during Drosophila neuromuscular junction formation, indicating a widespread presence of a novel concept of cellular nucleo-cytoplasmic transport.
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134
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Otsuka S, Bui KH, Schorb M, Hossain MJ, Politi AZ, Koch B, Eltsov M, Beck M, Ellenberg J. Nuclear pore assembly proceeds by an inside-out extrusion of the nuclear envelope. eLife 2016; 5. [PMID: 27630123 PMCID: PMC5065316 DOI: 10.7554/elife.19071] [Citation(s) in RCA: 117] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2016] [Accepted: 09/13/2016] [Indexed: 01/01/2023] Open
Abstract
The nuclear pore complex (NPC) mediates nucleocytoplasmic transport through the nuclear envelope. How the NPC assembles into this double membrane boundary has remained enigmatic. Here, we captured temporally staged assembly intermediates by correlating live cell imaging with high-resolution electron tomography and super-resolution microscopy. Intermediates were dome-shaped evaginations of the inner nuclear membrane (INM), that grew in diameter and depth until they fused with the flat outer nuclear membrane. Live and super-resolved fluorescence microscopy revealed the molecular maturation of the intermediates, which initially contained the nuclear and cytoplasmic ring component Nup107, and only later the cytoplasmic filament component Nup358. EM particle averaging showed that the evagination base was surrounded by an 8-fold rotationally symmetric ring structure from the beginning and that a growing mushroom-shaped density was continuously associated with the deforming membrane. Quantitative structural analysis revealed that interphase NPC assembly proceeds by an asymmetric inside-out extrusion of the INM.
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Affiliation(s)
- Shotaro Otsuka
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Khanh Huy Bui
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Martin Schorb
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany.,Electron Microscopy Core Facility, European Molecular Biology Laboratory, Heidelberg, Germany
| | - M Julius Hossain
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Antonio Z Politi
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Birgit Koch
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Mikhail Eltsov
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Martin Beck
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Jan Ellenberg
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, Heidelberg, Germany
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135
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Campsteijn C, Vietri M, Stenmark H. Novel ESCRT functions in cell biology: spiraling out of control? Curr Opin Cell Biol 2016; 41:1-8. [DOI: 10.1016/j.ceb.2016.03.008] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2016] [Revised: 03/08/2016] [Accepted: 03/11/2016] [Indexed: 01/05/2023]
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136
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Makarova M, Oliferenko S. Mixing and matching nuclear envelope remodeling and spindle assembly strategies in the evolution of mitosis. Curr Opin Cell Biol 2016; 41:43-50. [PMID: 27062548 PMCID: PMC7100904 DOI: 10.1016/j.ceb.2016.03.016] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2016] [Revised: 03/20/2016] [Accepted: 03/23/2016] [Indexed: 12/11/2022]
Abstract
In eukaryotes, cellular genome is enclosed inside a membrane-bound organelle called the nucleus. The nucleus compartmentalizes genome replication, repair and expression, keeping these activities separated from protein synthesis and other metabolic processes. Each proliferative division, the duplicated chromosomes must be equipartitioned between the daughter cells and this requires precise coordination between assembly of the microtubule-based mitotic spindle and nuclear remodeling. Here we review a surprising variety of strategies used by modern eukaryotes to manage these processes and discuss possible mechanisms that might have led to the emergence of this diversity in evolution.
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Affiliation(s)
- Maria Makarova
- Randall Division of Cell and Molecular Biophysics, King's College London, London SE1 1UL, UK
| | - Snezhana Oliferenko
- Randall Division of Cell and Molecular Biophysics, King's College London, London SE1 1UL, UK.
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137
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Tsai PL, Zhao C, Turner E, Schlieker C. The Lamin B receptor is essential for cholesterol synthesis and perturbed by disease-causing mutations. eLife 2016; 5:e16011. [PMID: 27336722 PMCID: PMC4951196 DOI: 10.7554/elife.16011] [Citation(s) in RCA: 59] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2016] [Accepted: 06/20/2016] [Indexed: 12/23/2022] Open
Abstract
Lamin B receptor (LBR) is a polytopic membrane protein residing in the inner nuclear membrane in association with the nuclear lamina. We demonstrate that human LBR is essential for cholesterol synthesis. LBR mutant derivatives implicated in Greenberg skeletal dysplasia or Pelger-Huët anomaly fail to rescue the cholesterol auxotrophy of a LBR-deficient human cell line, consistent with a loss-of-function mechanism for these congenital disorders. These disease-causing variants fall into two classes: point mutations in the sterol reductase domain perturb enzymatic activity by reducing the affinity for the essential cofactor NADPH, while LBR truncations render the mutant protein metabolically unstable, leading to its rapid degradation at the inner nuclear membrane. Thus, metabolically unstable LBR variants may serve as long-sought-after model substrates enabling previously impossible investigations of poorly understood protein turnover mechanisms at the inner nuclear membrane of higher eukaryotes.
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Affiliation(s)
- Pei-Ling Tsai
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, United States
| | - Chenguang Zhao
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, United States
| | - Elizabeth Turner
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, United States
| | - Christian Schlieker
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, United States
- Department of Cell Biology, Yale School of Medicine, New Haven, United States
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138
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Abstract
Two recent publications in Science report on frequent rupturing events of the nuclear envelope induced by migration of cells through narrow openings. Nuclear envelope "wounds" are repaired by the ESCRT-III machinery to limit DNA damage, nuclear fragmentation, and cell death.
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Affiliation(s)
| | - Ulrike Kutay
- Institute of Biochemistry, ETH Zurich, 8093 Zurich, Switzerland.
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139
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Hagen C, Dent KC, Zeev-Ben-Mordehai T, Grange M, Bosse JB, Whittle C, Klupp BG, Siebert CA, Vasishtan D, Bäuerlein FJB, Cheleski J, Werner S, Guttmann P, Rehbein S, Henzler K, Demmerle J, Adler B, Koszinowski U, Schermelleh L, Schneider G, Enquist LW, Plitzko JM, Mettenleiter TC, Grünewald K. Structural Basis of Vesicle Formation at the Inner Nuclear Membrane. Cell 2016; 163:1692-701. [PMID: 26687357 PMCID: PMC4701712 DOI: 10.1016/j.cell.2015.11.029] [Citation(s) in RCA: 149] [Impact Index Per Article: 18.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2015] [Revised: 09/11/2015] [Accepted: 11/06/2015] [Indexed: 12/22/2022]
Abstract
Vesicular nucleo-cytoplasmic transport is becoming recognized as a general cellular mechanism for translocation of large cargoes across the nuclear envelope. Cargo is recruited, enveloped at the inner nuclear membrane (INM), and delivered by membrane fusion at the outer nuclear membrane. To understand the structural underpinning for this trafficking, we investigated nuclear egress of progeny herpesvirus capsids where capsid envelopment is mediated by two viral proteins, forming the nuclear egress complex (NEC). Using a multi-modal imaging approach, we visualized the NEC in situ forming coated vesicles of defined size. Cellular electron cryo-tomography revealed a protein layer showing two distinct hexagonal lattices at its membrane-proximal and membrane-distant faces, respectively. NEC coat architecture was determined by combining this information with integrative modeling using small-angle X-ray scattering data. The molecular arrangement of the NEC establishes the basic mechanism for budding and scission of tailored vesicles at the INM. Multimodal imaging reveals mechanism of vesicle formation at inner nuclear membrane Nucleo-cytoplasmic cargo vesicle coat in situ comprises two distinct lattices Lattices are formed by hexameric building blocks made of the nuclear egress complex Induction of membrane curvature based solely on heterodimeric interactions
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Affiliation(s)
- Christoph Hagen
- Oxford Particle Imaging Centre, Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford OX3 7BN, UK
| | - Kyle C Dent
- Oxford Particle Imaging Centre, Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford OX3 7BN, UK; Diamond Light Source Ltd., Harwell Science and Innovation Campus, Didcot OX11 0DE, UK
| | - Tzviya Zeev-Ben-Mordehai
- Oxford Particle Imaging Centre, Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford OX3 7BN, UK
| | - Michael Grange
- Oxford Particle Imaging Centre, Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford OX3 7BN, UK
| | - Jens B Bosse
- Department of Molecular Biology, Princeton Neuroscience Institute, Princeton University, Washington Road, Princeton, NJ 08544, USA
| | - Cathy Whittle
- Oxford Particle Imaging Centre, Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford OX3 7BN, UK
| | - Barbara G Klupp
- Institute of Molecular Virology and Cell Biology, Friedrich-Loeffler-Institut, 17493 Greifswald-Insel Riems, Germany
| | - C Alistair Siebert
- Oxford Particle Imaging Centre, Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford OX3 7BN, UK
| | - Daven Vasishtan
- Oxford Particle Imaging Centre, Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford OX3 7BN, UK
| | - Felix J B Bäuerlein
- Department of Molecular Structural Biology, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany
| | - Juliana Cheleski
- Oxford Particle Imaging Centre, Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford OX3 7BN, UK
| | - Stephan Werner
- Helmholtz Zentrum Berlin für Materialien und Energie GmbH, Wilhelm-Conrad-Röntgen Campus, 12489 Berlin, Germany
| | - Peter Guttmann
- Helmholtz Zentrum Berlin für Materialien und Energie GmbH, Wilhelm-Conrad-Röntgen Campus, 12489 Berlin, Germany
| | - Stefan Rehbein
- Helmholtz Zentrum Berlin für Materialien und Energie GmbH, Wilhelm-Conrad-Röntgen Campus, 12489 Berlin, Germany
| | - Katja Henzler
- Helmholtz Zentrum Berlin für Materialien und Energie GmbH, Wilhelm-Conrad-Röntgen Campus, 12489 Berlin, Germany
| | - Justin Demmerle
- Micron Oxford, Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Barbara Adler
- Max von Pettenkofer-Institut, Ludwig-Maximilians-Universität München, Pettenkoferstr. 9a, 80336 Munich, Germany
| | - Ulrich Koszinowski
- Max von Pettenkofer-Institut, Ludwig-Maximilians-Universität München, Pettenkoferstr. 9a, 80336 Munich, Germany
| | - Lothar Schermelleh
- Micron Oxford, Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Gerd Schneider
- Helmholtz Zentrum Berlin für Materialien und Energie GmbH, Wilhelm-Conrad-Röntgen Campus, 12489 Berlin, Germany
| | - Lynn W Enquist
- Department of Molecular Biology, Princeton Neuroscience Institute, Princeton University, Washington Road, Princeton, NJ 08544, USA
| | - Jürgen M Plitzko
- Department of Molecular Structural Biology, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany
| | - Thomas C Mettenleiter
- Institute of Molecular Virology and Cell Biology, Friedrich-Loeffler-Institut, 17493 Greifswald-Insel Riems, Germany.
| | - Kay Grünewald
- Oxford Particle Imaging Centre, Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford OX3 7BN, UK.
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140
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A model for coordinating nuclear mechanics and membrane remodeling to support nuclear integrity. Curr Opin Cell Biol 2016; 41:9-17. [PMID: 27031045 DOI: 10.1016/j.ceb.2016.03.009] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2016] [Revised: 03/10/2016] [Accepted: 03/11/2016] [Indexed: 11/20/2022]
Abstract
A polymer network of intranuclear lamin filaments underlies the nuclear envelope and provides mechanical stability to the nucleus in metazoans. Recent work demonstrates that the expression of A-type lamins scales positively with the stiffness of the cellular environment, thereby coupling nuclear and extracellular mechanics. Using the spectrin-actin network at the erythrocyte plasma membrane as a model, we contemplate how the relative stiffness of the nuclear scaffold impinges on the growing number of interphase-specific nuclear envelope remodeling events, including recently discovered, nuclear envelope-specialized quality control mechanisms. We suggest that a stiffer lamina impedes these remodeling events, necessitating local lamina remodeling and/or concomitant scaling of the efficacy of membrane-remodeling machineries that act at the nuclear envelope.
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141
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Closing a gap in the nuclear envelope. Curr Opin Cell Biol 2016; 40:90-97. [PMID: 27016712 DOI: 10.1016/j.ceb.2016.03.001] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2015] [Revised: 02/13/2016] [Accepted: 03/05/2016] [Indexed: 11/22/2022]
Abstract
The nuclear envelope (NE) ensures nucleo-cytoplasmic compartmentalization, with trafficking of macromolecules across this double membrane controlled by embedded nuclear pore complexes (NPCs). The NE and associated proteins are dismantled during open mitosis and reestablishment of this barrier during mitotic exit requires dynamic remodeling of endoplasmic reticulum (ER) membranes and coordination with NPC reformation, with NPC deposition continuing during subsequent interphase. In this review, we discuss recent progress in our understanding of NE reformation and nuclear pore complex generation, with special focus on work implicating the endosomal sorting complex required for transport (ESCRT) membrane remodeling machinery in these events.
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142
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Abstract
Long terminal repeat (LTR) retrotransposons constitute significant fractions of many eukaryotic genomes. Two ancient families are Ty1/Copia (Pseudoviridae) and Ty3/Gypsy (Metaviridae). The Ty3/Gypsy family probably gave rise to retroviruses based on the domain order, similarity of sequences, and the envelopes encoded by some members. The Ty3 element of Saccharomyces cerevisiae is one of the most completely characterized elements at the molecular level. Ty3 is induced in mating cells by pheromone stimulation of the mitogen-activated protein kinase pathway as cells accumulate in G1. The two Ty3 open reading frames are translated into Gag3 and Gag3-Pol3 polyprotein precursors. In haploid mating cells Gag3 and Gag3-Pol3 are assembled together with Ty3 genomic RNA into immature virus-like particles in cellular foci containing RNA processing body proteins. Virus-like particle Gag3 is then processed by Ty3 protease into capsid, spacer, and nucleocapsid, and Gag3-Pol3 into those proteins and additionally, protease, reverse transcriptase, and integrase. After haploid cells mate and become diploid, genomic RNA is reverse transcribed into cDNA. Ty3 integration complexes interact with components of the RNA polymerase III transcription complex resulting in Ty3 integration precisely at the transcription start site. Ty3 activation during mating enables proliferation of Ty3 between genomes and has intriguing parallels with metazoan retrotransposon activation in germ cell lineages. Identification of nuclear pore, DNA replication, transcription, and repair host factors that affect retrotransposition has provided insights into how hosts and retrotransposons interact to balance genome stability and plasticity.
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143
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Alonso Y Adell M, Migliano SM, Teis D. ESCRT-III and Vps4: a dynamic multipurpose tool for membrane budding and scission. FEBS J 2016; 283:3288-302. [PMID: 26910595 DOI: 10.1111/febs.13688] [Citation(s) in RCA: 75] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2015] [Revised: 01/19/2016] [Accepted: 02/17/2016] [Indexed: 12/11/2022]
Abstract
Complex molecular machineries bud, scission and repair cellular membranes. Components of the multi-subunit endosomal sorting complex required for transport (ESCRT) machinery are enlisted when multivesicular bodies are generated, extracellular vesicles are formed, the plasma membrane needs to be repaired, enveloped viruses bud out of host cells, defective nuclear pores have to be cleared, the nuclear envelope must be resealed after mitosis and for final midbody abscission during cytokinesis. While some ESCRT components are only required for specific processes, the assembly of ESCRT-III polymers on target membranes and the action of the AAA-ATPase Vps4 are mandatory for every process. In this review, we summarize the current knowledge of structural and functional features of ESCRT-III/Vps4 assemblies in the growing pantheon of ESCRT-dependent pathways. We describe specific recruitment processes for ESCRT-III to different membranes, which could be useful to selectively inhibit ESCRT function during specific processes, while not affecting other ESCRT-dependent processes. Finally, we speculate how ESCRT-III and Vps4 might function together and highlight how the characterization of their precise spatiotemporal organization will improve our understanding of ESCRT-mediated membrane budding and scission in vivo.
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Affiliation(s)
| | - Simona M Migliano
- Division of Cell Biology, Biocenter, Medical University of Innsbruck, Austria
| | - David Teis
- Division of Cell Biology, Biocenter, Medical University of Innsbruck, Austria.
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144
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Lefebvre C, Largeau C, Michelet X, Fourrage C, Maniere X, Matic I, Legouis R, Culetto E. The ESCRT-II proteins are involved in shaping the sarcoplasmic reticulum in C. elegans. J Cell Sci 2016; 129:1490-9. [PMID: 26906413 DOI: 10.1242/jcs.178467] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2015] [Accepted: 02/15/2016] [Indexed: 12/22/2022] Open
Abstract
The sarcoplasmic reticulum is a network of tubules and cisternae localized in close association with the contractile apparatus, and regulates Ca(2+)dynamics within striated muscle cell. The sarcoplasmic reticulum maintains its shape and organization despite repeated muscle cell contractions, through mechanisms which are still under investigation. The ESCRT complexes are essential to organize membrane subdomains and modify membrane topology in multiple cellular processes. Here, we report for the first time that ESCRT-II proteins play a role in the maintenance of sarcoplasmic reticulum integrity inC. elegans ESCRT-II proteins colocalize with the sarcoplasmic reticulum marker ryanodine receptor UNC-68. The localization at the sarcoplasmic reticulum of ESCRT-II and UNC-68 are mutually dependent. Furthermore, the characterization of ESCRT-II mutants revealed a fragmentation of the sarcoplasmic reticulum network, associated with an alteration of Ca(2+)dynamics. Our data provide evidence that ESCRT-II proteins are involved in sarcoplasmic reticulum shaping.
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Affiliation(s)
- Christophe Lefebvre
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ. Paris-Sud, Université Paris-Saclay, Gif-sur-Yvette cedex 91198, France
| | - Céline Largeau
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ. Paris-Sud, Université Paris-Saclay, Gif-sur-Yvette cedex 91198, France
| | - Xavier Michelet
- Brigham and Women's Hospital, 1 Jimmy Fund Way, Boston, MA 02115, USA
| | - Cécile Fourrage
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ. Paris-Sud, Université Paris-Saclay, Gif-sur-Yvette cedex 91198, France
| | - Xavier Maniere
- Faculté de médecine Paris Descartes, Inserm U1001 - 24, rue du Faubourg St-Jacques, Paris 75014, France
| | - Ivan Matic
- Faculté de médecine Paris Descartes, Inserm U1001 - 24, rue du Faubourg St-Jacques, Paris 75014, France
| | - Renaud Legouis
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ. Paris-Sud, Université Paris-Saclay, Gif-sur-Yvette cedex 91198, France
| | - Emmanuel Culetto
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ. Paris-Sud, Université Paris-Saclay, Gif-sur-Yvette cedex 91198, France
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145
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Olmos Y, Carlton JG. The ESCRT machinery: new roles at new holes. Curr Opin Cell Biol 2016; 38:1-11. [PMID: 26775243 PMCID: PMC5023845 DOI: 10.1016/j.ceb.2015.12.001] [Citation(s) in RCA: 68] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2015] [Revised: 12/14/2015] [Accepted: 12/21/2015] [Indexed: 01/04/2023]
Abstract
The ESCRT machinery drives a diverse collection of membrane remodeling events, including multivesicular body biogenesis, release of enveloped retroviruses and both reformation of the nuclear envelope and cytokinetic abscission during mitotic exit. These events share the requirement for a topologically equivalent membrane remodeling for their completion and the cells deployment of the ESCRT machinery in these different contexts highlights its functionality as a transposable membrane-fission machinery. Here, we will examine recent data describing ESCRT-III dependent membrane remodeling and explore new roles for the ESCRT-III complex at the nuclear envelope.
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Affiliation(s)
- Y Olmos
- Division of Cancer Studies, Section of Cell Biology and Imaging, King's College London, London SE1 1UL, United Kingdom
| | - J G Carlton
- Division of Cancer Studies, Section of Cell Biology and Imaging, King's College London, London SE1 1UL, United Kingdom.
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146
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Hilscher J, Kapusi E, Stoger E, Ibl V. Cell layer-specific distribution of transiently expressed barley ESCRT-III component HvVPS60 in developing barley endosperm. PROTOPLASMA 2016; 253:137-53. [PMID: 25796522 PMCID: PMC4712231 DOI: 10.1007/s00709-015-0798-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/28/2014] [Accepted: 03/09/2015] [Indexed: 05/29/2023]
Abstract
The significance of the endosomal sorting complexes required for transport (ESCRT)-III in cereal endosperm has been shown by the identification of the recessive mutant supernumerary aleurone layer1 (SAL1) in maize. ESCRT-III is indispensable in the final membrane fission step during biogenesis of multivesicular bodies (MVBs), responsible for protein sorting to vacuoles and to the cell surface. Here, we annotated barley ESCRT-III members in the (model) crop Hordeum vulgare and show that all identified members are expressed in developing barley endosperm. We used fluorescently tagged core ESCRT-III members HvSNF7a/CHMP4 and HvVPS24/CHMP3 and the associated ESCRT-III component HvVPS60a/CHMP5 for transient localization studies in barley endosperm. In vivo confocal microscopic analyses show that the localization of recombinantly expressed HvSNF7a, HvVPS24 and HvVPS60a differs within barley endosperm. Whereas HvSNF7a induces large agglomerations, HvVPS24 shows mainly cytosolic localization in aleurone and subaleurone. In contrast, HvVPS60a localizes strongly at the plasma membrane in aleurone. In subaleurone, HvVPS60a was found to a lesser extent at the plasma membrane and at vacuolar membranes. These results indicate that the steady-state association of ESCRT-III may be influenced by cell layer-specific protein deposition or trafficking and remodelling of the endomembrane system in endosperm. We show that sorting of an artificially mono-ubiquitinated Arabidopsis plasma membrane protein is inhibited by HvVPS60a in aleurone. The involvement of HvVPS60a in different cell layer-specific trafficking pathways, reflected by localization of HvVPS60a at the plasma membrane in aleurone and at the PSV membrane in subaleurone, is discussed.
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Affiliation(s)
- Julia Hilscher
- Department of Applied Genetics and Cell Biology, Division of Molecular Cell Biology and Glycobiotechnology, University of Natural Resources and Life Sciences, Muthgasse 18, 1190, Vienna, Austria
| | - Eszter Kapusi
- Department of Applied Genetics and Cell Biology, Division of Molecular Cell Biology and Glycobiotechnology, University of Natural Resources and Life Sciences, Muthgasse 18, 1190, Vienna, Austria
| | - Eva Stoger
- Department of Applied Genetics and Cell Biology, Division of Molecular Cell Biology and Glycobiotechnology, University of Natural Resources and Life Sciences, Muthgasse 18, 1190, Vienna, Austria
| | - Verena Ibl
- Department of Applied Genetics and Cell Biology, Division of Molecular Cell Biology and Glycobiotechnology, University of Natural Resources and Life Sciences, Muthgasse 18, 1190, Vienna, Austria.
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147
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Zhang Y, Li W, Chu M, Chen H, Yu H, Fang C, Sun N, Wang Q, Luo T, Luo K, She X, Zhang M, Yang D. The AAA ATPase Vps4 Plays Important Roles in Candida albicans Hyphal Formation and is Inhibited by DBeQ. Mycopathologia 2015; 181:329-39. [PMID: 26700222 DOI: 10.1007/s11046-015-9979-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2015] [Accepted: 12/16/2015] [Indexed: 10/22/2022]
Abstract
Candida albicans is an opportunistic human pathogen, and its pathogenicity is associated with hyphal formation. Previous studies have shown that at neutral-to-alkaline pH, hyphal growth is dependent on the Rim101 pathway whose activation requires Snf7, a member of the ESCRT system. In this work, we described the purification and characterization of the C. albicans Vps4, an AAA ATPase required for recycling of the ESCRTs. Its role on hyphal growth has been investigated. Our data suggest deletion of Vps4 decreases overall hyphal growth at pH 7 and increases the growth of multiple hyphae induced by serum, which indicates that the ESCRTs may make a Rim101-independent contribution to hyphal growth. Furthermore, DBeQ, an inhibitor of the AAA ATPase p97, was shown to inhibit the ATPase activity of Vps4 with an IC50 of about 11.5 μM. To a less degree, it also inhibits hyphal growth. Our work may provide a new strategy to control C. albicans infection.
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Affiliation(s)
- Yahui Zhang
- Gene Engineering and Biotechnology Beijing Key Laboratory, College of Life Sciences, Beijing Normal University, Beijing, 100875, China
| | - Wanjie Li
- Key Laboratory of Cell Proliferation and Regulation Biology, Ministry of Education, College of Life Sciences, Beijing Normal University, Beijing, 100875, China
| | - Mi Chu
- Gene Engineering and Biotechnology Beijing Key Laboratory, College of Life Sciences, Beijing Normal University, Beijing, 100875, China
| | - Hengye Chen
- Gene Engineering and Biotechnology Beijing Key Laboratory, College of Life Sciences, Beijing Normal University, Beijing, 100875, China
| | - Haoyuan Yu
- Gene Engineering and Biotechnology Beijing Key Laboratory, College of Life Sciences, Beijing Normal University, Beijing, 100875, China
| | - Chaoguang Fang
- Gene Engineering and Biotechnology Beijing Key Laboratory, College of Life Sciences, Beijing Normal University, Beijing, 100875, China
| | - Ningze Sun
- Gene Engineering and Biotechnology Beijing Key Laboratory, College of Life Sciences, Beijing Normal University, Beijing, 100875, China
| | - Qiming Wang
- Gene Engineering and Biotechnology Beijing Key Laboratory, College of Life Sciences, Beijing Normal University, Beijing, 100875, China
| | - Tian Luo
- Gene Engineering and Biotechnology Beijing Key Laboratory, College of Life Sciences, Beijing Normal University, Beijing, 100875, China
| | - Kaiju Luo
- Gene Engineering and Biotechnology Beijing Key Laboratory, College of Life Sciences, Beijing Normal University, Beijing, 100875, China
| | - Xueping She
- Gene Engineering and Biotechnology Beijing Key Laboratory, College of Life Sciences, Beijing Normal University, Beijing, 100875, China
| | - Mengqian Zhang
- Gene Engineering and Biotechnology Beijing Key Laboratory, College of Life Sciences, Beijing Normal University, Beijing, 100875, China
| | - Dong Yang
- Gene Engineering and Biotechnology Beijing Key Laboratory, College of Life Sciences, Beijing Normal University, Beijing, 100875, China.
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148
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Tang S, Henne WM, Borbat PP, Buchkovich NJ, Freed JH, Mao Y, Fromme JC, Emr SD. Structural basis for activation, assembly and membrane binding of ESCRT-III Snf7 filaments. eLife 2015; 4:e12548. [PMID: 26670543 PMCID: PMC4720517 DOI: 10.7554/elife.12548] [Citation(s) in RCA: 93] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2015] [Accepted: 12/13/2015] [Indexed: 12/14/2022] Open
Abstract
The endosomal sorting complexes required for transport (ESCRTs) constitute hetero-oligomeric machines that catalyze multiple topologically similar membrane-remodeling processes. Although ESCRT-III subunits polymerize into spirals, how individual ESCRT-III subunits are activated and assembled together into a membrane-deforming filament remains unknown. Here, we determine X-ray crystal structures of the most abundant ESCRT-III subunit Snf7 in its active conformation. Using pulsed dipolar electron spin resonance spectroscopy (PDS), we show that Snf7 activation requires a prominent conformational rearrangement to expose protein-membrane and protein-protein interfaces. This promotes the assembly of Snf7 arrays with ~30 Å periodicity into a membrane-sculpting filament. Using a combination of biochemical and genetic approaches, both in vitro and in vivo, we demonstrate that mutations on these protein interfaces halt Snf7 assembly and block ESCRT function. The architecture of the activated and membrane-bound Snf7 polymer provides crucial insights into the spatially unique ESCRT-III-mediated membrane remodeling.
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Affiliation(s)
- Shaogeng Tang
- Weill Institute of Cell and Molecular Biology, Cornell University, Ithaca, United States
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, United States
| | - W Mike Henne
- Weill Institute of Cell and Molecular Biology, Cornell University, Ithaca, United States
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, United States
| | - Peter P Borbat
- National Biomedical Center for Advanced Electron Spin Resonance Technology, Cornell University, Ithaca, United States
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, United States
| | - Nicholas J Buchkovich
- Weill Institute of Cell and Molecular Biology, Cornell University, Ithaca, United States
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, United States
| | - Jack H Freed
- National Biomedical Center for Advanced Electron Spin Resonance Technology, Cornell University, Ithaca, United States
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, United States
| | - Yuxin Mao
- Weill Institute of Cell and Molecular Biology, Cornell University, Ithaca, United States
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, United States
| | - J Christopher Fromme
- Weill Institute of Cell and Molecular Biology, Cornell University, Ithaca, United States
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, United States
| | - Scott D Emr
- Weill Institute of Cell and Molecular Biology, Cornell University, Ithaca, United States
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, United States
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149
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Monroe N, Hill CP. Meiotic Clade AAA ATPases: Protein Polymer Disassembly Machines. J Mol Biol 2015; 428:1897-911. [PMID: 26555750 DOI: 10.1016/j.jmb.2015.11.004] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2015] [Revised: 11/03/2015] [Accepted: 11/04/2015] [Indexed: 12/20/2022]
Abstract
Meiotic clade AAA ATPases (ATPases associated with diverse cellular activities), which were initially grouped on the basis of phylogenetic classification of their AAA ATPase cassette, include four relatively well characterized family members, Vps4, spastin, katanin and fidgetin. These enzymes all function to disassemble specific polymeric protein structures, with Vps4 disassembling the ESCRT-III polymers that are central to the many membrane-remodeling activities of the ESCRT (endosomal sorting complexes required for transport) pathway and spastin, katanin p60 and fidgetin affecting multiple aspects of cellular dynamics by severing microtubules. They share a common domain architecture that features an N-terminal MIT (microtubule interacting and trafficking) domain followed by a single AAA ATPase cassette. Meiotic clade AAA ATPases function as hexamers that can cycle between the active assembly and inactive monomers/dimers in a regulated process, and they appear to disassemble their polymeric substrates by translocating subunits through the central pore of their hexameric ring. Recent studies with Vps4 have shown that nucleotide-induced asymmetry is a requirement for substrate binding to the pore loops and that recruitment to the protein lattice via MIT domains also relieves autoinhibition and primes the AAA ATPase cassettes for substrate binding. The most striking, unifying feature of meiotic clade AAA ATPases may be their MIT domain, which is a module that is found in a wide variety of proteins that localize to ESCRT-III polymers. Spastin also displays an adjacent microtubule binding sequence, and the presence of both ESCRT-III and microtubule binding elements may underlie the recent findings that the ESCRT-III disassembly function of Vps4 and the microtubule-severing function of spastin, as well as potentially katanin and fidgetin, are highly coordinated.
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Affiliation(s)
- Nicole Monroe
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT 84112-5650, USA
| | - Christopher P Hill
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT 84112-5650, USA.
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150
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Saarikangas J, Barral Y. Protein aggregates are associated with replicative aging without compromising protein quality control. eLife 2015; 4. [PMID: 26544680 PMCID: PMC4635334 DOI: 10.7554/elife.06197] [Citation(s) in RCA: 102] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2014] [Accepted: 10/19/2015] [Indexed: 12/12/2022] Open
Abstract
Differentiation of cellular lineages is facilitated by asymmetric segregation of fate determinants between dividing cells. In budding yeast, various aging factors segregate to the aging (mother)-lineage, with poorly understood consequences. In this study, we show that yeast mother cells form a protein aggregate during early replicative aging that is maintained as a single, asymmetrically inherited deposit over the remaining lifespan. Surprisingly, deposit formation was not associated with stress or general decline in proteostasis. Rather, the deposit-containing cells displayed enhanced degradation of cytosolic proteasome substrates and unimpaired clearance of stress-induced protein aggregates. Deposit formation was dependent on Hsp42, which collected non-random client proteins of the Hsp104/Hsp70-refolding machinery, including the prion Sup35. Importantly, loss of Hsp42 resulted in symmetric inheritance of its constituents and prolonged the lifespan of the mother cell. Together, these data suggest that protein aggregation is an early aging-associated differentiation event in yeast, having a two-faceted role in organismal fitness. DOI:http://dx.doi.org/10.7554/eLife.06197.001 Aging is a complex process. Studies involving a single-celled organism called budding yeast are commonly used to investigate the factors that contribute to aging. When these yeast cells divide, a small daughter cell buds out from a large mother cell. A mother cell has a limited lifespan and produces a finite number of daughter cells and then dies (a phenomenon referred to ‘replicative aging’). However, when a daughter cell forms, the daughter's age is reset to zero, giving it the full potential to produce new offspring. Previous research on budding yeast has shown that damaged or aggregated proteins accumulate in the mother cells but not the daughter cells, and that this accumulation of proteins contributes to shortening the lifespan of the mother cell. Furthermore, protein aggregation has also been associated with a number of age-related diseases in humans, including neurodegenerative disorders such as Alzheimer's and Parkinson's disease. However, it remains unclear how cells respond to protein aggregation that occurs during aging. Many studies that have previously investigated this question have relied on exposing cells to stressful conditions, such as high temperatures, in order to trigger proteins to aggregate. But now, Saarikangas and Barral have studied how proteins aggregate under normal, unstressed conditions in budding yeast as they age. The experiments revealed that most unstressed yeast cells develop a single deposit of aggregated proteins already during early aging. This age-associated structure proved to be a different type of response than the protein aggregation that occurs during stress. Furthermore, the deposit did not form as a consequence of the cell having obvious problems with folding its proteins, nor did the deposit hinder cells from coping with stressful conditions that trigger protein misfolding. Rather, this deposit supported the ability of the cell to degrade defective proteins. This suggests that the deposit represents an early adaptive response to aging, which might consequently provide aged cells some advantage over their younger counterparts. Saarikangas and Barral also found that this protein deposit was always retained in the mother cell and not passed onto the daughters at cell division. Further experiments showed that an enzyme called heat shock protein 42 was responsible for collecting target proteins and bring them together to form the single deposit. Reducing the levels of this enzyme prevented the deposit from forming and extended the lifespan of the mother cells. Thus, these findings suggest that mother cells collect harmful protein aggregates into a single deposit and prevent them from entering the daughter cells. Further work is needed to understand how the deposit is preferentially retained within the mother cell. DOI:http://dx.doi.org/10.7554/eLife.06197.002
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Affiliation(s)
- Juha Saarikangas
- Institute of Biochemistry, Eidgenössische Technische Hochschule Zürich, Zürich, Switzerland
| | - Yves Barral
- Institute of Biochemistry, Eidgenössische Technische Hochschule Zürich, Zürich, Switzerland
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