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Wang Y, Lan Q, Cheng X, Gao Y, Chang L, Xu P, Li Y. Quantitative Proteomics-Based Substrate Screening Revealed Cyclophilin Stabilization Regulated by Deubiquitinase Ubp7. J Proteome Res 2023; 22:2281-2292. [PMID: 37341107 DOI: 10.1021/acs.jproteome.2c00853] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/22/2023]
Abstract
Quantitative proteomics has emerged as a crucial approach to identifying ubiquitinated substrates to investigate the functions of ubiquitination in cells. In this regard, although the substrate screening of certain enzymes in the ubiquitin system has been based on proteome or ubiquitinome level measurements, the direct comparison of these two approaches has not been determined to date. To quantitatively compare the efficiency and effectiveness of substrate screening from the entire proteomics to the ubiquitinomics filter, we used yeast deubiquitinating enzyme, Ubp7, as an example to evaluate it in this study. A total of 112 potential ubiquitinated substrates were identified from the ubiquitinomics level, whereas only 27 regulated substrates were identified from the entire proteomic screening, demonstrating the increased efficiency of ubiquitinomics quantitative analysis. Subsequently, we selected cyclophilin A (Cpr1) protein as an example, which was filtered out at the proteomics level but was a promising candidate according to the ubiquitinomics filter. Additional investigations revealed that Cpr1 possessed a K48-linked ubiquitin chain regulated by Ubp7, which may affect its homeostasis and, consequently, sensitivity to the therapeutic drug cyclosporine (CsA).
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Affiliation(s)
- Yonghong Wang
- Department of Biomedicine, School of Medicine, Guizhou University, Guiyang 550025, China
- State Key Laboratory of Proteomics, Beijing Proteome Research Center, National Center for Protein Sciences Beijing, Research Unit of Proteomics & Research and Development of New Drug of Chinese Academy of Medical Sciences, Institute of Lifeomics, 38 Science Park Road, Changping District, Beijing 102206, China
| | - Qiuyan Lan
- State Key Laboratory of Proteomics, Beijing Proteome Research Center, National Center for Protein Sciences Beijing, Research Unit of Proteomics & Research and Development of New Drug of Chinese Academy of Medical Sciences, Institute of Lifeomics, 38 Science Park Road, Changping District, Beijing 102206, China
| | - Xinyu Cheng
- School of Basic Medicine, Anhui Medical University, Hefei 230032, China
| | - Yuan Gao
- Central Laboratory of College of Horticulture, Nanjing Agricultural University, Nanjing 210095, People's Republic of China
| | - Lei Chang
- State Key Laboratory of Proteomics, Beijing Proteome Research Center, National Center for Protein Sciences Beijing, Research Unit of Proteomics & Research and Development of New Drug of Chinese Academy of Medical Sciences, Institute of Lifeomics, 38 Science Park Road, Changping District, Beijing 102206, China
| | - Ping Xu
- Department of Biomedicine, School of Medicine, Guizhou University, Guiyang 550025, China
- State Key Laboratory of Proteomics, Beijing Proteome Research Center, National Center for Protein Sciences Beijing, Research Unit of Proteomics & Research and Development of New Drug of Chinese Academy of Medical Sciences, Institute of Lifeomics, 38 Science Park Road, Changping District, Beijing 102206, China
- School of Basic Medicine, Anhui Medical University, Hefei 230032, China
- Key Laboratory of Microbial Diversity Research and Application of Hebei Province, School of Life Sciences, Hebei University, Baoding 071002, China
| | - Yanchang Li
- State Key Laboratory of Proteomics, Beijing Proteome Research Center, National Center for Protein Sciences Beijing, Research Unit of Proteomics & Research and Development of New Drug of Chinese Academy of Medical Sciences, Institute of Lifeomics, 38 Science Park Road, Changping District, Beijing 102206, China
- School of Basic Medicine, Anhui Medical University, Hefei 230032, China
- Key Laboratory of Microbial Diversity Research and Application of Hebei Province, School of Life Sciences, Hebei University, Baoding 071002, China
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α-Arrestins and Their Functions: From Yeast to Human Health. Int J Mol Sci 2022; 23:ijms23094988. [PMID: 35563378 PMCID: PMC9105457 DOI: 10.3390/ijms23094988] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2022] [Revised: 04/26/2022] [Accepted: 04/27/2022] [Indexed: 12/10/2022] Open
Abstract
α-Arrestins, also called arrestin-related trafficking adaptors (ARTs), constitute a large family of proteins conserved from yeast to humans. Despite their evolutionary precedence over their extensively studied relatives of the β-arrestin family, α-arrestins have been discovered relatively recently, and thus their properties are mostly unexplored. The predominant function of α-arrestins is the selective identification of membrane proteins for ubiquitination and degradation, which is an important element in maintaining membrane protein homeostasis as well as global cellular metabolisms. Among members of the arrestin clan, only α-arrestins possess PY motifs that allow canonical binding to WW domains of Rsp5/NEDD4 ubiquitin ligases and the subsequent ubiquitination of membrane proteins leading to their vacuolar/lysosomal degradation. The molecular mechanisms of the selective substrate’s targeting, function, and regulation of α-arrestins in response to different stimuli remain incompletely understood. Several functions of α-arrestins in animal models have been recently characterized, including redox homeostasis regulation, innate immune response regulation, and tumor suppression. However, the molecular mechanisms of α-arrestin regulation and substrate interactions are mainly based on observations from the yeast Saccharomyces cerevisiae model. Nonetheless, α-arrestins have been implicated in health disorders such as diabetes, cardiovascular diseases, neurodegenerative disorders, and tumor progression, placing them in the group of potential therapeutic targets.
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Ubiquitination of the ubiquitin-binding machinery: how early ESCRT components are controlled. Essays Biochem 2022; 66:169-177. [PMID: 35352804 PMCID: PMC9400068 DOI: 10.1042/ebc20210042] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2022] [Revised: 03/04/2022] [Accepted: 03/16/2022] [Indexed: 12/22/2022]
Abstract
To be able to quickly and accurately respond to the environment, cells need to tightly control the amount and localization of plasma membrane proteins. The post-translation modification by the protein modifier ubiquitin is the key signal for guiding membrane-associated cargo to the lysosome/vacuole for their degradation. The machinery responsible for such sorting contains several subunits that function as ubiquitin receptors, many of which are themselves subjected to ubiquitination. This review will focus on what is currently known about the modulation of the machinery itself by ubiquitination and how this might affect its function with a special emphasis on current findings from the plant field.
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Adaptors as the regulators of HECT ubiquitin ligases. Cell Death Differ 2021; 28:455-472. [PMID: 33402750 DOI: 10.1038/s41418-020-00707-6] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2020] [Revised: 11/04/2020] [Accepted: 11/04/2020] [Indexed: 12/15/2022] Open
Abstract
The HECT (homologous to E6AP C-terminus) ubiquitin ligases (E3s) are a small family of highly conserved enzymes involved in diverse cellular functions and pathological conditions. Characterised by a C-terminal HECT domain that accepts ubiquitin from E2 ubiquitin conjugating enzymes, these E3s regulate key signalling pathways. The activity and functional regulation of HECT E3s are controlled by several factors including post-translational modifications, inter- and intramolecular interactions and binding of co-activators and adaptor proteins. In this review, we focus on the regulation of HECT E3s by accessory proteins or adaptors and discuss various ways by which adaptors mediate their regulatory roles to affect physiological outcomes. We discuss common features that are conserved from yeast to mammals, regardless of the type of E3s as well as shed light on recent discoveries explaining some existing enigmas in the field.
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Hoban K, Lux SY, Poprawski J, Zhang Y, Shepherdson J, Castiñeira PG, Pesari S, Yao T, Prosser DC, Norris C, Wendland B. ESCRT-dependent protein sorting is required for the viability of yeast clathrin-mediated endocytosis mutants. Traffic 2020; 21:430-450. [PMID: 32255230 DOI: 10.1111/tra.12731] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2019] [Revised: 03/31/2020] [Accepted: 04/01/2020] [Indexed: 12/11/2022]
Abstract
Endocytosis regulates many processes, including signaling pathways, nutrient uptake, and protein turnover. During clathrin-mediated endocytosis (CME), adaptors bind to cytoplasmic regions of transmembrane cargo proteins, and many endocytic adaptors are also directly involved in the recruitment of clathrin. This clathrin-associated sorting protein family includes the yeast epsins, Ent1/2, and AP180/PICALM homologs, Yap1801/2. Mutant strains lacking these four adaptors, but expressing an epsin N-terminal homology (ENTH) domain necessary for viability (4Δ+ENTH), exhibit endocytic defects, such as cargo accumulation at the plasma membrane (PM). This CME-deficient strain provides a sensitized background ideal for revealing cellular components that interact with clathrin adaptors. We performed a mutagenic screen to identify alleles that are lethal in 4Δ+ENTH cells using a colony-sectoring reporter assay. After isolating candidate synthetic lethal genes by complementation, we confirmed that mutations in VPS4 led to inviability of a 4Δ+ENTH strain. Vps4 mediates the final step of endosomal sorting complex required for transport (ESCRT)-dependent trafficking, and we found that multiple ESCRTs are also essential in 4Δ+ENTH cells, including Snf7, Snf8 and Vps36. Deletion of VPS4 from an end3Δ strain, another CME mutant, similarly resulted in inviability, and upregulation of a clathrin-independent endocytosis pathway rescued 4Δ+ENTH vps4Δ cells. Loss of Vps4 from an otherwise wild-type background caused multiple cargoes to accumulate at the PM because of an increase in Rcy1-dependent recycling of internalized protein to the cell surface. Additionally, vps4Δ rcy1Δ mutants exhibited deleterious growth phenotypes. Together, our findings reveal previously unappreciated effects of disrupted ESCRT-dependent trafficking on endocytic recycling and the PM.
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Affiliation(s)
- Kyle Hoban
- Department of Biology, Johns Hopkins University, Baltimore, Maryland, USA
| | - Samantha Y Lux
- Department of Biology, Johns Hopkins University, Baltimore, Maryland, USA
| | - Joanna Poprawski
- Department of Biology, Johns Hopkins University, Baltimore, Maryland, USA
| | - Yorke Zhang
- Department of Biology, Johns Hopkins University, Baltimore, Maryland, USA
| | - James Shepherdson
- Department of Biology, Johns Hopkins University, Baltimore, Maryland, USA
| | - Pedro G Castiñeira
- Department of Biology, Johns Hopkins University, Baltimore, Maryland, USA
| | - Sanjana Pesari
- Department of Biology, Johns Hopkins University, Baltimore, Maryland, USA
| | - Tony Yao
- Department of Biology, Johns Hopkins University, Baltimore, Maryland, USA
| | - Derek C Prosser
- Department of Biology, Virginia Commonwealth University, Richmond, Virginia, USA
| | - Carolyn Norris
- Department of Biology, Johns Hopkins University, Baltimore, Maryland, USA
| | - Beverly Wendland
- Department of Biology, Johns Hopkins University, Baltimore, Maryland, USA
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MacDonald C, Shields SB, Williams CA, Winistorfer S, Piper RC. A Cycle of Ubiquitination Regulates Adaptor Function of the Nedd4-Family Ubiquitin Ligase Rsp5. Curr Biol 2020; 30:465-479.e5. [PMID: 31956026 PMCID: PMC7197006 DOI: 10.1016/j.cub.2019.11.086] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2019] [Revised: 10/28/2019] [Accepted: 11/29/2019] [Indexed: 10/25/2022]
Abstract
In yeast, the main ubiquitin ligase responsible for the sorting of proteins to the lysosomal vacuole is Rsp5, a member of the Nedd4 family of ligases whose distinguishing features are a catalytic homologous to E6AP C terminus (HECT) domain and 3 central WW domains that bind PY motifs in target proteins. Many substrates do not bind Rsp5 directly and instead rely on PY-containing adaptor proteins that interact with Rsp5. Recent studies indicate that the activities of these adaptors are elevated when they undergo ubiquitination, yet the mechanism whereby ubiquitination activates the adaptors and how this process is regulated remain unclear. Here, we report on a mechanism that explains how ubiquitination stimulates adaptor function and how this process can be regulated by the Rsp5-associated deubiquitinase, Ubp2. Our overexpression experiments revealed that several adaptors compete for Rsp5 in vivo. We found that the ability of the adaptors to compete effectively was enhanced by their ubiquitination and diminished by a block of their ubiquitination. Ubiquitination-dependent adaptor activation required a ubiquitin-binding surface within the Rsp5 catalytic HECT domain. Finally, like constitutively ubiquitinated adaptors, a Ubp2 deficiency increased both the adaptor activity and the ability to compete for Rsp5. Our data support a model whereby ubiquitinated Rsp5 adaptors are more active when "locked" onto Rsp5 via its N-lobe ubiquitin-binding surface and less active when they are "unlocked" by Ubp2-mediated deubiquitination.
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Affiliation(s)
- Chris MacDonald
- Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, IA USA, 52242,Current Address: Department of Biology, University of York, York, UK YO10 5DD
| | - S. Brookhart Shields
- Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, IA USA, 52242,Current Address: Gustavus Adolphus College, 800 West College Ave. Saint Peter, MN USA, 56082
| | - Charlotte A. Williams
- Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, IA USA, 52242
| | - Stanley Winistorfer
- Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, IA USA, 52242
| | - Robert C. Piper
- Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, IA USA, 52242,Lead Contact:
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Sardana R, Zhu L, Emr SD. Rsp5 Ubiquitin ligase-mediated quality control system clears membrane proteins mistargeted to the vacuole membrane. J Cell Biol 2018; 218:234-250. [PMID: 30361468 PMCID: PMC6314561 DOI: 10.1083/jcb.201806094] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2018] [Revised: 09/06/2018] [Accepted: 10/01/2018] [Indexed: 11/22/2022] Open
Abstract
Sardana et al. show that protein quality control systems on multiple endocytic organelles cooperate to prevent aberrant protein accumulation and maintain proteostasis. By mistargeting PM proteins de novo to the yeast vacuolar membrane, they uncover a “fail-safe” mechanism that ensures degradation of diverse endocytic cargos. Maintenance of organelle identity is profoundly dependent on the coordination between correct targeting of proteins and removal of mistargeted and damaged proteins. This task is mediated by organelle-specific protein quality control (QC) systems. In yeast, the endocytosis and QC of most plasma membrane (PM) proteins requires the Rsp5 ubiquitin ligase and ART adaptor network. We show that intracellular adaptors of Rsp5, Ear1, and Ssh4 mediate recognition and vacuolar degradation of PM proteins that escape or bypass PM QC systems. This second tier of surveillance helps to maintain cell integrity upon heat stress and protects from proteotoxicity. To understand the mechanism of the recognition of aberrant PM cargos by Ssh4–Rsp5, we mistarget multiple PM proteins de novo to the vacuolar membrane. We found that Ssh4–Rsp5 can target and ubiquitinate multiple lysines within a restricted distance from the membrane, providing a fail-safe mechanism for a diverse cargo repertoire. The mistargeting or misfolding of PM proteins likely exposes these lysines or shifts them into the “ubiquitination zone” accessible to the Ssh4–Rsp5 complex.
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Affiliation(s)
- Richa Sardana
- Department of Molecular Biology and Genetics, Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY
| | - Lu Zhu
- Department of Molecular Biology and Genetics, Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY
| | - Scott D Emr
- Department of Molecular Biology and Genetics, Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY
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Abstract
Ubiquitin ligases (E3s) are basic components of the eukaryotic ubiquitination system. In this work, the emergence and diversification of fungal HECT ubiquitin ligases is described. Phylogenetic and structural data indicate that six HECT subfamilies (RSP5, TOM1, UFD4, HUL4, HUL4A and HUL5) existed in the common ancestor of all fungi. These six subfamilies have evolved very conservatively, with only occasional losses and duplications in particular fungal lineages. However, an early, drastic reduction in the number of HECT genes occurred in microsporidians, in parallel to the reduction of their genomes. A significant correlation between the total number of genes and the number of HECT-encoding genes present in fungi has been observed. However, transitions from unicellularity to multicellularity or vice versa apparently had no effect on the evolution of this family. Likely orthologs or co-orthologs of all fungal HECT genes have been detected in animals. Four genes are deduced to be present in the common ancestor of fungi, animals and plants. Protein-protein interactions detected in both the yeast Saccharomyces cerevisiae and humans suggest that some ancient functions of HECT proteins have been conserved since the animals/fungi split.
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Shao G, Wang R, Sun A, Wei J, Peng K, Dai Q, Yang W, Lin Q. The E3 ubiquitin ligase NEDD4 mediates cell migration signaling of EGFR in lung cancer cells. Mol Cancer 2018; 17:24. [PMID: 29455656 PMCID: PMC5817799 DOI: 10.1186/s12943-018-0784-2] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2017] [Accepted: 02/01/2018] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND EGFR-dependent cell migration plays an important role in lung cancer progression. Our previous study observed that the HECT E3 ubiquitin ligase NEDD4 is significantly correlated with tumor metastasis and required for migration and invasion signaling of EGFR in gastric cancer cells. However, how NEDD4 promotes the EGFR-dependent lung cancer cell migration is unknown. This study is to elucidate the mechanism by which NEDD4 mediates the EGFR lung cancer migration signaling. METHODS Lentiviral vector-loaded NEDD4 shRNA was used to deplete endogenous NEDD4 in lung cancer cell lines. Effects of the NEDD4 knockdown on the EGFR-dependent or independent lung cancer cell migration were determined using the wound-healing and transwell assays. Association of NEDD4 with activated EGFR was assayed by co-immunoprecipitation. Co-expression of NEDD4 with EGFR or PTEN was determined by immunohistochemical (IHC) staining in 63 lung adenocarcinoma tissue samples. Effects of NEDD4 ectopic expression or knockdown on PTEN ubiquitination and down-regulation, AKT activation and lysosomal secretion were examined using the GST-Uba pulldown assay, immunoblotting, immunofluorescent staining and a human cathepsin B ELISA assay respectively. The specific cathepsin B inhibitor CA-074Me was used for assessing the role of cathepsin B in lung cancer cell migration. RESULTS Knockdown of NEDD4 significantly reduced EGF-stimulated cell migration in non-small cell lung carcinoma (NSCLC) cells. Co-immunoprecipitation assay found that NEDD4 is associated with EGFR complex upon EGF stimulation, and IHC staining indicates that NEDD4 is co-expressed with EGFR in lung adenocarcinoma tumor tissues, suggesting that NEDD4 might mediate lung cancer cell migration by interaction with the EGFR signaling complex. Interestingly, NEDD4 promotes the EGF-induced cathepsin B secretion, possibly through lysosomal exocytosis, as overexpression of the ligase-dead mutant of NEDD4 impedes lysosomal secretion, and knockdown of NEDD4 significantly reduced extracellular amount of cathepsin B induced by EGF. Consistent with the role of NEDD4, cathepsin B is pivotal for both basal and the EGF-stimulated lung cancer cell migration. Our studies propose a novel mechanism underlying the EGFR-promoted lung cancer cell migration that is mediated by NEDD4 through regulation of cathepsin B secretion. CONCLUSION NEDD4 mediates the EGFR lung cancer cell migration signaling through promoting lysosomal secretion of cathepsin B.
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Affiliation(s)
- Genbao Shao
- School of Medicine, Jiangsu University, Zhenjiang, Jiangsu, 212013, China
| | - Ranran Wang
- School of Medicine, Jiangsu University, Zhenjiang, Jiangsu, 212013, China
| | - Aiqin Sun
- School of Medicine, Jiangsu University, Zhenjiang, Jiangsu, 212013, China
| | - Jing Wei
- School of Medicine, Jiangsu University, Zhenjiang, Jiangsu, 212013, China
| | - Ke Peng
- School of Medicine, Jiangsu University, Zhenjiang, Jiangsu, 212013, China
| | - Qian Dai
- School of Medicine, Jiangsu University, Zhenjiang, Jiangsu, 212013, China
| | - Wannian Yang
- School of Medicine, Jiangsu University, Zhenjiang, Jiangsu, 212013, China
| | - Qiong Lin
- School of Medicine, Jiangsu University, Zhenjiang, Jiangsu, 212013, China.
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Oku M, Maeda Y, Kagohashi Y, Kondo T, Yamada M, Fujimoto T, Sakai Y. Evidence for ESCRT- and clathrin-dependent microautophagy. J Cell Biol 2017; 216:3263-3274. [PMID: 28838958 PMCID: PMC5626533 DOI: 10.1083/jcb.201611029] [Citation(s) in RCA: 113] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2016] [Revised: 04/27/2017] [Accepted: 07/24/2017] [Indexed: 12/20/2022] Open
Abstract
Microautophagy is a mode of autophagy in which the lysosomal or vacuolar membrane invaginates and engulfs target components. Oku et al. show that, upon a diauxic shift, yeast microautophagy involves recruitment of ESCRT proteins to the vacuolar membrane, including clathrin-interacting Vps27, and uptake of lipid droplets by the vacuole. Microautophagy refers to a mode of autophagy in which the lysosomal or vacuolar membrane invaginates and directly engulfs target components. The molecular machinery of membrane dynamics driving microautophagy is still elusive. Using immunochemical monitoring of yeast vacuolar transmembrane proteins, Vph1 and Pho8, fused to fluorescent proteins, we obtained evidence showing an induction of microautophagy after a diauxic shift in the yeast Saccharomyces cerevisiae. Components of the endosomal sorting complex required for transport machinery were found to be required for this process, and the gateway protein of the machinery, Vps27, was observed to change its localization onto the vacuolar membrane after a diauxic shift. We revealed the functional importance of Vps27’s interaction with clathrin in this microautophagy that also contributed to uptake of lipid droplets into the vacuole. This study sheds light on the molecular mechanism of microautophagy, which does not require the core Atg proteins.
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Affiliation(s)
- Masahide Oku
- Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kyoto, Japan
| | - Yuichiro Maeda
- Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kyoto, Japan
| | - Yoko Kagohashi
- Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kyoto, Japan
| | - Takeshi Kondo
- Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kyoto, Japan
| | - Mai Yamada
- Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kyoto, Japan
| | - Toyoshi Fujimoto
- Department of Anatomy and Molecular Cell Biology, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Yasuyoshi Sakai
- Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kyoto, Japan .,Research Unit for Physiological Chemistry, Center for the Promotion of Interdisciplinary Education and Research, Kyoto University, Kyoto, Japan
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An ubiquitin-dependent balance between mitofusin turnover and fatty acids desaturation regulates mitochondrial fusion. Nat Commun 2017; 8:15832. [PMID: 28607491 PMCID: PMC5474747 DOI: 10.1038/ncomms15832] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2016] [Accepted: 04/27/2017] [Indexed: 01/22/2023] Open
Abstract
Mitochondrial integrity relies on homotypic fusion between adjacent outer membranes, which is mediated by large GTPases called mitofusins. The regulation of this process remains nonetheless elusive. Here, we report a crosstalk between the ubiquitin protease Ubp2 and the ubiquitin ligases Mdm30 and Rsp5 that modulates mitochondrial fusion. Ubp2 is an antagonist of Rsp5, which promotes synthesis of the fatty acids desaturase Ole1. We show that Ubp2 also counteracts Mdm30-mediated turnover of the yeast mitofusin Fzo1 and that Mdm30 targets Ubp2 for degradation thereby inducing Rsp5-mediated desaturation of fatty acids. Exogenous desaturated fatty acids inhibit Ubp2 degradation resulting in higher levels of Fzo1 and maintenance of efficient mitochondrial fusion. Our results demonstrate that the Mdm30-Ubp2-Rsp5 crosstalk regulates mitochondrial fusion by coordinating an intricate balance between Fzo1 turnover and the status of fatty acids saturation. This pathway may link outer membrane fusion to lipids homeostasis. Mitochondrial fusion is crucial for cellular homeostasis but its regulation is still not fully understood. Here the authors report that a cross-talk between ubiquitin protease Ubp2 and ligases Mdm30 and Rsp5 modulates mitofusin Fzo1 levels and fatty acids saturation and thus mitochondrial fusion.
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12
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Deubiquitylating enzymes in receptor endocytosis and trafficking. Biochem J 2017; 473:4507-4525. [PMID: 27941029 DOI: 10.1042/bcj20160826] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2016] [Revised: 09/15/2016] [Accepted: 09/16/2016] [Indexed: 12/25/2022]
Abstract
In recent times, our knowledge of the roles ubiquitin plays in multiple cellular processes has expanded exponentially, with one example being the role of ubiquitin in receptor endocytosis and trafficking. This has prompted a multitude of studies examining how the different machinery involved in the addition and removal of ubiquitin can influence this process. Multiple deubiquitylating enzymes (DUBs) have been implicated either in facilitating receptor endocytosis and lysosomal degradation or in rescuing receptor levels by preventing endocytosis and/or promoting recycling to the plasma membrane. In this review, we will discuss in detail what is currently known about the role of DUBs in regulating the endocytosis of various transmembrane receptors and ion channels. We will also expand upon the role DUBs play in receptor sorting at the multivesicular body to determine whether a receptor is recycled or trafficked to the lysosome for degradation. Finally, we will briefly discuss how the DUBs implicated in these processes may contribute to the pathogenesis of a range of diseases, and thus the potential these have as therapeutic targets.
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Ho HC, MacGurn JA, Emr SD. Deubiquitinating enzymes Ubp2 and Ubp15 regulate endocytosis by limiting ubiquitination and degradation of ARTs. Mol Biol Cell 2017; 28:1271-1283. [PMID: 28298493 PMCID: PMC5415021 DOI: 10.1091/mbc.e17-01-0008] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2017] [Revised: 02/27/2017] [Accepted: 02/28/2017] [Indexed: 12/18/2022] Open
Abstract
Endocytic down-regulation of cell-surface proteins is a fundamental cellular process for cell survival and adaptation to environmental stimuli. Ubiquitination of cargo proteins serves as the sorting signal for downstream trafficking and relies on the arrestin-related trafficking adaptor (ART)-Rsp5 ubiquitin ligase adaptor network in yeast. Hence proper regulation of the abundance and activity of these ligase-adaptor complexes is critical for main-tenance of optimal plasma membrane protein composition. Here we report that the stability of ARTs is regulated by the deubiquitinating enzymes (DUBs) Ubp2 and Ubp15. By counteracting the E3 ubiquitin ligase Rsp5, Ubp2 and Ubp15 prevent hyperubiquitination and proteasomal degradation of ARTs. Specifically, we show that loss of both Ubp2 and Ubp15 results in a defect in Hxt6 endocytosis associated with Art4 instability. Our results uncover a novel function for DUBs in the endocytic pathway by which Ubp2 and Ubp15 positively regulate the ART-Rsp5 network.
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Affiliation(s)
- Hsuan-Chung Ho
- Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY 14853
| | - Jason A MacGurn
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37240
| | - Scott D Emr
- Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY 14853
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Deubiquitinase activity is required for the proteasomal degradation of misfolded cytosolic proteins upon heat-stress. Nat Commun 2016; 7:12907. [PMID: 27698423 PMCID: PMC5059457 DOI: 10.1038/ncomms12907] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2016] [Accepted: 08/12/2016] [Indexed: 12/25/2022] Open
Abstract
Elimination of misfolded proteins is crucial for proteostasis and to prevent proteinopathies. Nedd4/Rsp5 emerged as a major E3-ligase involved in multiple quality control pathways that target misfolded plasma membrane proteins, aggregated polypeptides and cytosolic heat-induced misfolded proteins for degradation. It remained unclear how in one case cytosolic heat-induced Rsp5 substrates are destined for proteasomal degradation, whereas other Rsp5 quality control substrates are otherwise directed to lysosomal degradation. Here we find that Ubp2 and Ubp3 deubiquitinases are required for the proteasomal degradation of cytosolic misfolded proteins targeted by Rsp5 after heat-shock (HS). The two deubiquitinases associate more with Rsp5 upon heat-stress to prevent the assembly of K63-linked ubiquitin on Rsp5 heat-induced substrates. This activity was required to promote the K48-mediated proteasomal degradation of Rsp5 HS-induced substrates. Our results indicate that ubiquitin chain editing is key to the cytosolic protein quality control under stress conditions. Ubiquitination of misfolded proteins usually results in protein degradation. Here, the authors show that two deubiquitinases—enzymes that remove ubiquitin—are required for the proteasomal degradation of misfolded proteins in response to heat-shock in yeast.
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15
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Böhm S, Szakal B, Herken BW, Sullivan MR, Mihalevic MJ, Kabbinavar FF, Branzei D, Clark NL, Bernstein KA. The Budding Yeast Ubiquitin Protease Ubp7 Is a Novel Component Involved in S Phase Progression. J Biol Chem 2016; 291:4442-52. [PMID: 26740628 DOI: 10.1074/jbc.m115.671057] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2015] [Indexed: 11/06/2022] Open
Abstract
DNA damage must be repaired in an accurate and timely fashion to preserve genome stability. Cellular mechanisms preventing genome instability are crucial to human health because genome instability is considered a hallmark of cancer. Collectively referred to as the DNA damage response, conserved pathways ensure proper DNA damage recognition and repair. The function of numerous DNA damage response components is fine-tuned by posttranslational modifications, including ubiquitination. This not only involves the enzyme cascade responsible for conjugating ubiquitin to substrates but also requires enzymes that mediate directed removal of ubiquitin. Deubiquitinases remove ubiquitin from substrates to prevent degradation or to mediate signaling functions. The Saccharomyces cerevisiae deubiquitinase Ubp7 has been characterized previously as an endocytic factor. However, here we identify Ubp7 as a novel factor affecting S phase progression after hydroxyurea treatment and demonstrate an evolutionary and genetic interaction of Ubp7 with DNA damage repair pathways of homologous recombination and nucleotide excision repair. We find that deletion of UBP7 sensitizes cells to hydroxyurea and cisplatin and demonstrate that factors that stabilize replication forks are critical under these conditions. Furthermore, ubp7Δ cells exhibit an S phase progression defect upon checkpoint activation by hydroxyurea treatment. ubp7Δ mutants are epistatic to factors involved in histone maintenance and modification, and we find that a subset of Ubp7 is chromatin-associated. In summary, our results suggest that Ubp7 contributes to S phase progression by affecting the chromatin state at replication forks, and we propose histone H2B ubiquitination as a potential substrate of Ubp7.
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Affiliation(s)
- Stefanie Böhm
- From the Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, University of Pittsburgh Cancer Institute, Pittsburgh, Pennsylvania 15213
| | - Barnabas Szakal
- the Department of Molecular Oncology, Fondazione Istituto Fondazione Italiana per la Ricerca sul Cancro di Oncologia Molecolare, Milan 20139, Italy
| | - Benjamin W Herken
- From the Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, University of Pittsburgh Cancer Institute, Pittsburgh, Pennsylvania 15213
| | - Meghan R Sullivan
- From the Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, University of Pittsburgh Cancer Institute, Pittsburgh, Pennsylvania 15213
| | - Michael J Mihalevic
- From the Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, University of Pittsburgh Cancer Institute, Pittsburgh, Pennsylvania 15213
| | - Faiz F Kabbinavar
- From the Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, University of Pittsburgh Cancer Institute, Pittsburgh, Pennsylvania 15213
| | - Dana Branzei
- the Department of Molecular Oncology, Fondazione Istituto Fondazione Italiana per la Ricerca sul Cancro di Oncologia Molecolare, Milan 20139, Italy
| | - Nathan L Clark
- the Department of Computational and Systems Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15213, and
| | - Kara A Bernstein
- From the Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, University of Pittsburgh Cancer Institute, Pittsburgh, Pennsylvania 15213,
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16
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Erpapazoglou Z, Walker O, Haguenauer-Tsapis R. Versatile roles of k63-linked ubiquitin chains in trafficking. Cells 2014; 3:1027-88. [PMID: 25396681 PMCID: PMC4276913 DOI: 10.3390/cells3041027] [Citation(s) in RCA: 131] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2014] [Revised: 10/14/2014] [Accepted: 10/21/2014] [Indexed: 12/11/2022] Open
Abstract
Modification by Lys63-linked ubiquitin (UbK63) chains is the second most abundant form of ubiquitylation. In addition to their role in DNA repair or kinase activation, UbK63 chains interfere with multiple steps of intracellular trafficking. UbK63 chains decorate many plasma membrane proteins, providing a signal that is often, but not always, required for their internalization. In yeast, plants, worms and mammals, this same modification appears to be critical for efficient sorting to multivesicular bodies and subsequent lysosomal degradation. UbK63 chains are also one of the modifications involved in various forms of autophagy (mitophagy, xenophagy, or aggrephagy). Here, in the context of trafficking, we report recent structural studies investigating UbK63 chains assembly by various E2/E3 pairs, disassembly by deubiquitylases, and specifically recognition as sorting signals by receptors carrying Ub-binding domains, often acting in tandem. In addition, we address emerging and unanticipated roles of UbK63 chains in various recycling pathways that function by activating nucleators required for actin polymerization, as well as in the transient recruitment of signaling molecules at the plasma or ER membrane. In this review, we describe recent advances that converge to elucidate the mechanisms underlying the wealth of trafficking functions of UbK63 chains.
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Affiliation(s)
- Zoi Erpapazoglou
- Institut Jacques Monod-CNRS, UMR 7592, Université-Paris Diderot, Sorbonne Paris Cité, F-75205 Paris, France.
| | - Olivier Walker
- Institut des Sciences Analytiques, UMR5280, Université de Lyon/Université Lyon 1, 69100 Villeurbanne, France.
| | - Rosine Haguenauer-Tsapis
- Institut Jacques Monod-CNRS, UMR 7592, Université-Paris Diderot, Sorbonne Paris Cité, F-75205 Paris, France.
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17
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Efficient mRNA polyadenylation requires a ubiquitin-like domain, a zinc knuckle, and a RING finger domain, all contained in the Mpe1 protein. Mol Cell Biol 2014; 34:3955-67. [PMID: 25135474 DOI: 10.1128/mcb.00077-14] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Almost all eukaryotic mRNAs must be polyadenylated at their 3' ends to function in protein synthesis. This modification occurs via a large nuclear complex that recognizes signal sequences surrounding a poly(A) site on mRNA precursor, cleaves at that site, and adds a poly(A) tail. While the composition of this complex is known, the functions of some subunits remain unclear. One of these is a multidomain protein called Mpe1 in the yeast Saccharomyces cerevisiae and RBBP6 in metazoans. The three conserved domains of Mpe1 are a ubiquitin-like (UBL) domain, a zinc knuckle, and a RING finger domain characteristic of some ubiquitin ligases. We show that mRNA 3'-end processing requires all three domains of Mpe1 and that more than one region of Mpe1 is involved in contact with the cleavage/polyadenylation factor in which Mpe1 resides. Surprisingly, both the zinc knuckle and the RING finger are needed for RNA-binding activity. Consistent with a role for Mpe1 in ubiquitination, mutation of Mpe1 decreases the association of ubiquitin with Pap1, the poly(A) polymerase, and suppressors of mpe1 mutants are linked to ubiquitin ligases. Furthermore, an inhibitor of ubiquitin-mediated interactions blocks cleavage, demonstrating for the first time a direct role for ubiquitination in mRNA 3'-end processing.
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18
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Babst M. Quality control: quality control at the plasma membrane: one mechanism does not fit all. ACTA ACUST UNITED AC 2014; 205:11-20. [PMID: 24733583 PMCID: PMC3987138 DOI: 10.1083/jcb.201310113] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The plasma membrane quality control system of eukaryotic cells is able to recognize and degrade damaged cell surface proteins. Recent studies have identified two mechanisms involved in the recognition of unfolded transmembrane proteins. One system uses chaperones to detect unfolded cytoplasmic domains of transmembrane proteins, whereas the second mechanism relies on an internal quality control system of the protein, which can trigger degradation when the protein deviates from the folded state. Both quality control mechanisms are key to prevent proteotoxic effects at the cell surface and to ensure cell integrity.
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Affiliation(s)
- Markus Babst
- Department of Biology, Center for Cell and Genome Science, University of Utah, Salt Lake City, UT 84112
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19
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Schuh AL, Audhya A. The ESCRT machinery: from the plasma membrane to endosomes and back again. Crit Rev Biochem Mol Biol 2014; 49:242-61. [PMID: 24456136 DOI: 10.3109/10409238.2014.881777] [Citation(s) in RCA: 102] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
The manipulation and reorganization of lipid bilayers are required for diverse cellular processes, ranging from organelle biogenesis to cytokinetic abscission, and often involves transient membrane disruption. A set of membrane-associated proteins collectively known as the endosomal sorting complex required for transport (ESCRT) machinery has been implicated in membrane scission steps, which transform a single, continuous bilayer into two distinct bilayers, while simultaneously segregating cargo throughout the process. Components of the ESCRT pathway, which include 5 distinct protein complexes and an array of accessory factors, each serve discrete functions. This review focuses on the molecular mechanisms by which the ESCRT proteins facilitate cargo sequestration and membrane remodeling and highlights their unique roles in cellular homeostasis.
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Affiliation(s)
- Amber L Schuh
- Department of Biomolecular Chemistry, University of Wisconsin-Madison School of Medicine and Public Health , Madison, WI , USA
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20
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Lam MHY, Emili A. Ubp2 regulates Rsp5 ubiquitination activity in vivo and in vitro. PLoS One 2013; 8:e75372. [PMID: 24069405 PMCID: PMC3777918 DOI: 10.1371/journal.pone.0075372] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2012] [Accepted: 08/15/2013] [Indexed: 11/19/2022] Open
Abstract
The yeast HECT-family E3 ubiquitin ligase Rsp5 has been implicated in diverse cell functions. Previously, we and others [1], [2] reported the physical and functional interaction of Rsp5 with the deubiquitinating enzyme Ubp2, and the ubiquitin associated (UBA) domain-containing cofactor Rup1. To investigate the mechanism and significance of the Rsp5-Rup1-Ubp2 complex, we examined Rsp5 ubiquitination status in the presence or absence of these cofactors. We found that, similar to its mammalian homologues, Rsp5 is auto-ubiquitinated in vivo. Association with a substrate or Rup1 increased Rsp5 self-ubiquitination, whereas Ubp2 efficiently deubiquitinates Rsp5 in vivo and in vitro. The data reported here imply an auto-modulatory mechanism of Rsp5 regulation common to other E3 ligases.
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Affiliation(s)
- Mandy H. Y. Lam
- Banting and Best Department of Medical Research, Donnelly Centre for Cellular and Biomolecular Research, Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
| | - Andrew Emili
- Banting and Best Department of Medical Research, Donnelly Centre for Cellular and Biomolecular Research, Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
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21
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Erpapazoglou Z, Dhaoui M, Pantazopoulou M, Giordano F, Mari M, Léon S, Raposo G, Reggiori F, Haguenauer-Tsapis R. A dual role for K63-linked ubiquitin chains in multivesicular body biogenesis and cargo sorting. Mol Biol Cell 2012; 23:2170-83. [PMID: 22493318 PMCID: PMC3364180 DOI: 10.1091/mbc.e11-10-0891] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
In yeast, the sorting of transmembrane proteins into the multivesicular body (MVB) internal vesicles requires their ubiquitylation by the ubiquitin ligase Rsp5. This allows their recognition by the ubiquitin-binding domains (UBDs) of several endosomal sorting complex required for transport (ESCRT) subunits. K63-linked ubiquitin (K63Ub) chains decorate several MVB cargoes, and accordingly we show that they localize prominently to the class E compartment, which accumulates ubiquitylated cargoes in cells lacking ESCRT components. Conversely, yeast cells unable to generate K63Ub chains displayed MVB sorting defects. These properties are conserved among eukaryotes, as the mammalian melanosomal MVB cargo MART-1 is modified by K63Ub chains and partly missorted when the genesis of these chains is inhibited. We show that all yeast UBD-containing ESCRT proteins undergo ubiquitylation and deubiquitylation, some being modified through the opposing activities of Rsp5 and the ubiquitin isopeptidase Ubp2, which are known to assemble and disassemble preferentially K63Ub chains, respectively. A failure to generate K63Ub chains in yeast leads to an MVB ultrastructure alteration. Our work thus unravels a double function of K63Ub chains in cargo sorting and MVB biogenesis.
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Affiliation(s)
- Zoi Erpapazoglou
- Institut Jacques Monod, Centre National de la Recherche Scientifique, Unité Mixte de Recherche 7592, Université Paris-Diderot, Sorbonne Paris Cité, Paris, France
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22
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Abstract
From the moment of cotranslational insertion into the lipid bilayer of the endoplasmic reticulum (ER), newly synthesized integral membrane proteins are subject to a complex series of sorting, trafficking, quality control, and quality maintenance systems. Many of these processes are intimately controlled by ubiquitination, a posttranslational modification that directs trafficking decisions related to both the biosynthetic delivery of proteins to the plasma membrane (PM) via the secretory pathway and the removal of proteins from the PM via the endocytic pathway. Ubiquitin modification of integral membrane proteins (or "cargoes") generally acts as a sorting signal, which is recognized, captured, and delivered to a specific cellular destination via specialized trafficking events. By affecting the quality, quantity, and localization of integral membrane proteins in the cell, defects in these processes contribute to human diseases, including cystic fibrosis, circulatory diseases, and various neuropathies. This review summarizes our current understanding of how ubiquitin modification influences cargo trafficking, with a special emphasis on mechanisms of quality control and quality maintenance in the secretory and endocytic pathways.
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Affiliation(s)
- Jason A MacGurn
- Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, New York 14853, USA.
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23
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Malik R, Soh UJK, Trejo J, Marchese A. Novel roles for the E3 ubiquitin ligase atrophin-interacting protein 4 and signal transduction adaptor molecule 1 in G protein-coupled receptor signaling. J Biol Chem 2012; 287:9013-27. [PMID: 22275353 DOI: 10.1074/jbc.m111.336792] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The CXCL12/CXCR4 signaling axis plays an important role in human health and disease; however, the molecular mechanisms mediating CXCR4 signaling remain poorly understood. Ubiquitin modification of CXCR4 by the E3 ubiquitin ligase AIP4 is required for lysosomal sorting and degradation, which is mediated by the endosomal sorting complex required for transport (ESCRT) machinery. CXCR4 sorting is regulated by an interaction between endosomal localized arrestin-2 and STAM-1, an ESCRT-0 component. Here, we report a novel role for AIP4 and STAM-1 in regulation of CXCR4 signaling that is distinct from their function in CXCR4 trafficking. Depletion of AIP4 and STAM-1 by siRNA caused significant inhibition of CXCR4-induced ERK-1/2 activation, whereas overexpression of these proteins enhanced CXCR4 signaling. We further show that AIP4 and STAM-1 physically interact and that the proline-rich region in AIP4 and the SH3 domain in STAM-1 are essential for the interaction. Overexpression of an AIP4 catalytically inactive mutant and a mutant that shows poor binding to STAM-1 fails to enhance CXCR4-induced ERK-1/2 signaling, as compared with wild-type AIP4, suggesting that the interaction between AIP4 and STAM-1 and the ligase activity of AIP4 are essential for ERK-1/2 activation. Remarkably, a discrete subpopulation of AIP4 and STAM-1 resides in caveolar microdomains with CXCR4 and appears to mediate ERK-1/2 signaling. We propose that AIP4-mediated ubiquitination of STAM-1 in caveolae coordinates activation of ERK-1/2 signaling. Thus, our study reveals a novel function for ubiquitin in the regulation of CXCR4 signaling, which may be broadly applicable to other G protein-coupled receptors.
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Affiliation(s)
- Rohit Malik
- Program in Molecular Biology, Stritch School of Medicine, Loyola University Chicago, Maywood, Illinois 60153, USA
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24
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Wright MH, Berlin I, Nash PD. Regulation of endocytic sorting by ESCRT-DUB-mediated deubiquitination. Cell Biochem Biophys 2011; 60:39-46. [PMID: 21448666 DOI: 10.1007/s12013-011-9181-9] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Endocytosis of cell surface receptors mediates cellular homeostasis by coordinating receptor distribution with downstream signal transduction and attenuation. Post-translational modification with ubiquitin of these receptors, as well as the proteins that comprise the endocytic machinery, modulates cargo progression along the endocytic pathway. The interplay between ubiquitination states of cargo and sorting proteins drives trafficking outcomes by directing endocytosed material toward either lysosomal degradation or recycling. Deubiquitination by specific proteinases creates a reversible system that promotes spatial and temporal organization of endosomal sorting complexes required for transport (ESCRTs) and supports regulated cargo trafficking. Two dubiquitinating enzymes--ubiquitin-specific protease 8 (USP8/Ubpy) and associated molecule with the SH3 domain of STAM (AMSH)--interact with ESCRT components to modulate the ubiquitination status of receptors and relevant sorting proteins. In doing so, these ESCRT-DUBs control receptor fate and sorting complex function through a variety of mechanisms described herein.
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Affiliation(s)
- Michelle H Wright
- Ben May Department for Cancer Research, The University of Chicago, Chicago, IL 60637, USA
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25
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Abstract
Over the past 14 years, ubiquitination has emerged as a centrally important mechanism governing the subcellular trafficking of proteins. Ubiquitination, interaction with sorting factors that contain ubiquitin-binding domains, and deubiquitination govern the itineraries of cargo proteins that include yeast carboxypeptidase S, the epithelial sodium channel ENaC, and epidermal growth factor receptor. The molecular structures and mechanisms of the paradigmatic HECT and RING domain ubiquitin ligases, of JAMM- and USP-domain-deubiquitinating enzymes, and of numerous ubiquitin-binding domains involved in these pathways have been worked out in recent years and are described.
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Affiliation(s)
- James H Hurley
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892-0580, USA.
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26
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Abstract
The endosomal-sorting complex required for transport (ESCRT) apparatus has multiple ubiquitin (Ub)-binding domains and participates in a wide variety of cellular processes. Many of these ESCRT-dependent processes are keenly regulated by Ub, which serves as a lysosomal-sorting signal for membrane proteins targeted into multivesicular bodies (MVBs) and which may serve as a mediator of viral budding from the cell surface. Hints that both ESCRTs and Ub work together in the processes such as cytokinesis, transcription and autophagy are beginning to emerge. Here, we explore the relationship between ESCRTs and Ub in MVB sorting and viral budding.
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Affiliation(s)
- S Brookhart Shields
- Department of Molecular Physiology and Biophysics, Carver College of Medicine, University of Iowa, Iowa City, IA 52246, USA
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27
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Wang S, Thibault G, Ng DTW. Routing misfolded proteins through the multivesicular body (MVB) pathway protects against proteotoxicity. J Biol Chem 2011; 286:29376-29387. [PMID: 21708947 DOI: 10.1074/jbc.m111.233346] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
The secretory pathway maintains multiple quality control checkpoints. Initially, endoplasmic reticulum-associated degradation pathways monitor protein folding to retain and eliminate aberrant products. Despite its broad client range, some molecules escape detection and traffic to Golgi membranes. There, a poorly understood mechanism termed Golgi quality control routes aberrant proteins for lysosomal/vacuolar degradation. To better understand Golgi quality control, we examined the processing of the obligate substrate Wsc1p. Misfolded Wsc1p does not use routes of typical vacuolar membrane proteins. Instead, it partitions into intralumenal vesicles of the multivesicular body (MVB) pathway, mediated by the E3 ubiquitin ligase Rsp5p. Its subsequent transport to the vacuolar lumen is essential for complete molecule breakdown. Surprisingly, the transport mode plays a second crucial function in neutralizing potential substrate toxicity. Eliminating the MVB sorting signal diverted molecules to the vacuolar limiting membrane, resulting in the generation of toxic by-products. These data demonstrate a new role of the MVB pathway in protein quality control.
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Affiliation(s)
- Songyu Wang
- Temasek Life Sciences Laboratory, National University of Singapore, Singapore 117604, Singapore; Department of Biological Sciences, National University of Singapore, Singapore 117604, Singapore
| | - Guillaume Thibault
- Temasek Life Sciences Laboratory, National University of Singapore, Singapore 117604, Singapore
| | - Davis T W Ng
- Temasek Life Sciences Laboratory, National University of Singapore, Singapore 117604, Singapore; Department of Biological Sciences, National University of Singapore, Singapore 117604, Singapore.
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28
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Grabbe C, Husnjak K, Dikic I. The spatial and temporal organization of ubiquitin networks. Nat Rev Mol Cell Biol 2011; 12:295-307. [PMID: 21448225 DOI: 10.1038/nrm3099] [Citation(s) in RCA: 279] [Impact Index Per Article: 21.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
In the past decade, the diversity of signals generated by the ubiquitin system has emerged as a dominant regulator of biological processes and propagation of information in the eukaryotic cell. A wealth of information has been gained about the crucial role of spatial and temporal regulation of ubiquitin species of different lengths and linkages in the nuclear factor-κB (NF-κB) pathway, endocytic trafficking, protein degradation and DNA repair. This spatiotemporal regulation is achieved through sophisticated mechanisms of compartmentalization and sequential series of ubiquitylation events and signal decoding, which control diverse biological processes not only in the cell but also during the development of tissues and entire organisms.
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Affiliation(s)
- Caroline Grabbe
- Department of Molecular Biology, Umeå University, Umeå, Sweden
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29
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Stringer DK, Piper RC. A single ubiquitin is sufficient for cargo protein entry into MVBs in the absence of ESCRT ubiquitination. ACTA ACUST UNITED AC 2011; 192:229-42. [PMID: 21242292 PMCID: PMC3172180 DOI: 10.1083/jcb.201008121] [Citation(s) in RCA: 107] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
While ESCRT-0 is ubiquitinated by the Rsp5 E3 ligase, loss of Rsp5 does not disrupt monoubiquitin-dependent sorting into multivesicular bodies. ESCRTs (endosomal sorting complexes required for transport) bind and sequester ubiquitinated membrane proteins and usher them into multivesicular bodies (MVBs). As Ubiquitin (Ub)-binding proteins, ESCRTs themselves become ubiquitinated. However, it is unclear whether this regulates a critical aspect of their function or is a nonspecific consequence of their association with the Ub system. We investigated whether ubiquitination of the ESCRTs was required for their ability to sort cargo into the MVB lumen. Although we found that Rsp5 was the main Ub ligase responsible for ubiquitination of ESCRT-0, elimination of Rsp5 or elimination of the ubiquitinatable lysines within ESCRT-0 did not affect MVB sorting. Moreover, by fusing the catalytic domain of deubiquitinating peptidases onto ESCRTs, we could block ESCRT ubiquitination and the sorting of proteins that undergo Rsp5-dependent ubiquitination. Yet, proteins fused to a single Ub moiety were efficiently delivered to the MVB lumen, which strongly indicates that a single Ub is sufficient in sorting MVBs in the absence of ESCRT ubiquitination.
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Affiliation(s)
- Daniel K Stringer
- Molecular Physiology and Biophysics, University of Iowa, Iowa City, IA 52246, USA
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30
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Mayers JR, Fyfe I, Schuh AL, Chapman ER, Edwardson JM, Audhya A. ESCRT-0 assembles as a heterotetrameric complex on membranes and binds multiple ubiquitinylated cargoes simultaneously. J Biol Chem 2010; 286:9636-45. [PMID: 21193406 DOI: 10.1074/jbc.m110.185363] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The ESCRT machinery consists of multiple protein complexes that collectively participate in the biogenesis of multivesicular endosomes (MVEs). The ESCRT-0 complex is composed of two subunits, Hrs and STAM, both of which can engage ubiquitinylated substrates destined for lysosomal degradation. Here, we conduct a comprehensive analysis of ESCRT-0:ubiquitin interactions using isothermal titration calorimetry and define the affinity of each ubiquitin-binding domain (UBD) within the intact ESCRT-0 complex. Our data demonstrate that ubiquitin binding is non-cooperative between the ESCRT-0 UBDs. Additionally, our findings show that the affinity of the Hrs double ubiquitin interacting motif (DUIM) for ubiquitin is more than 2-fold greater than that of UBDs found in STAM, suggesting that Hrs functions as the major ubiquitin-binding protein in ESCRT-0. In vivo, Hrs and STAM localize to endosomal membranes. To study recombinant ESCRT-0 assembly on lipid bilayers, we used atomic force microscopy. Our data show that ESCRT-0 forms mostly heterodimers and heterotetramers of Hrs and STAM when analyzed in the presence of membranes. Consistent with these findings, hydrodynamic analysis of endogenous ESCRT-0 indicates that it exists largely as a heterotetrameric complex of its two subunits. Based on these data, we present a revised model for ESCRT-0 function in cargo recruitment and concentration at the endosome.
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Affiliation(s)
- Jonathan R Mayers
- Department of Biomolecular Chemistry, University of Wisconsin-Madison Medical School, Madison, Wisconsin 53706, USA
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31
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Berlin I, Higginbotham KM, Dise RS, Sierra MI, Nash PD. The deubiquitinating enzyme USP8 promotes trafficking and degradation of the chemokine receptor 4 at the sorting endosome. J Biol Chem 2010; 285:37895-908. [PMID: 20876529 PMCID: PMC2988392 DOI: 10.1074/jbc.m110.129411] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2010] [Revised: 08/30/2010] [Indexed: 01/08/2023] Open
Abstract
Reversible ubiquitination orchestrated by the opposition of ubiquitin ligases and deubiquitinating enzymes mediates endocytic trafficking of cell surface receptors for lysosomal degradation. Ubiquitin-specific protease 8 (USP8) has previously been implicated in endocytosis of several receptors by virtue of their deubiquitination. The present study explores an indirect role for USP8 in cargo trafficking through its regulation of the chemokine receptor 4 (CXCR4). Contrary to the effects of USP8 loss on enhanced green fluorescent protein, we find that USP8 depletion stabilizes CXCR4 on the cell surface and attenuates receptor degradation without affecting its ubiquitination status. In the presence of ligand, diminished CXCR4 turnover is accompanied by receptor accumulation on enlarged early endosomes and leads to enhancement of phospho-ERK signaling. Perturbation in CXCR4 trafficking, resulting from USP8 inactivation, occurs at the ESCRT-0 checkpoint, and catalytic mutation of USP8 specifically targeted to the ESCRT-0 complex impairs the spatial and temporal organization of the sorting endosome. USP8 functionally opposes the ubiquitin ligase AIP4 with respect to ESCRT-0 ubiquitination, thereby promoting trafficking of CXCR4. Collectively, our findings demonstrate a functional cooperation between USP8, AIP4, and the ESCRT-0 machinery at the early sorting phase of CXCR4 and underscore the versatility of USP8 in shaping trafficking events at the early-to-late endosome transition.
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Affiliation(s)
- Ilana Berlin
- From the Ben May Department for Cancer Research, University of Chicago, Chicago, Illinois 60637
| | | | - Rebecca S. Dise
- From the Ben May Department for Cancer Research, University of Chicago, Chicago, Illinois 60637
| | - Maria I. Sierra
- From the Ben May Department for Cancer Research, University of Chicago, Chicago, Illinois 60637
| | - Piers D. Nash
- From the Ben May Department for Cancer Research, University of Chicago, Chicago, Illinois 60637
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32
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Hood-DeGrenier JK. Identification of phosphatase 2A-like Sit4-mediated signalling and ubiquitin-dependent protein sorting as modulators of caffeine sensitivity in S. cerevisiae. Yeast 2010; 28:189-204. [DOI: 10.1002/yea.1830] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2010] [Accepted: 10/23/2010] [Indexed: 11/07/2022] Open
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33
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Berlin I, Schwartz H, Nash PD. Regulation of epidermal growth factor receptor ubiquitination and trafficking by the USP8·STAM complex. J Biol Chem 2010; 285:34909-21. [PMID: 20736164 PMCID: PMC2966105 DOI: 10.1074/jbc.m109.016287] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2009] [Revised: 08/02/2010] [Indexed: 11/06/2022] Open
Abstract
Reversible ubiquitination of activated receptor complexes signals their sorting between recycling and degradation and thereby dictates receptor fate. The deubiquitinating enzyme ubiquitin-specific protease 8 (USP8/UBPy) has been previously implicated in the regulation of the epidermal growth factor receptor (EGFR); however, the molecular mechanisms governing its recruitment and activity in this context remain unclear. Herein, we investigate the role of USP8 in countering ligand-induced ubiquitination and down-regulation of EGFR and characterize a subset of protein-protein interaction determinants critical for this function. USP8 depletion accelerates receptor turnover, whereas loss of hepatocyte growth factor-regulated substrate (Hrs) rescues this phenotype, indicating that USP8 protects EGFR from degradation via an Hrs-dependent pathway. Catalytic inactivation of USP8 incurs EGFR hyperubiquitination and promotes receptor localization to endosomes marked by high ubiquitin content. These phenotypes require the central region of USP8, containing three extended Arg-X-X-Lys (RXXK) motifs that specify direct low affinity interactions with the SH3 domain(s) of ESCRT-0 proteins, STAM1/2. The USP8·STAM complex critically impinges on receptor ubiquitination status and modulates ubiquitin dynamics on EGFR-positive endosomes. Consequently, USP8-mediated deubiquitination slows progression of EGFR past the early-to-recycling endosome circuit in a manner dependent upon the RXXK motifs. Collectively, these findings demonstrate a role for the USP8·STAM complex as a protective mechanism regulating early endosomal sorting of EGFR between pathways destined for lysosomal degradation and recycling.
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Affiliation(s)
- Ilana Berlin
- From the Ben May Department for Cancer Research, The University of Chicago, Chicago, Illinois 60637
| | - Heather Schwartz
- From the Ben May Department for Cancer Research, The University of Chicago, Chicago, Illinois 60637
| | - Piers D. Nash
- From the Ben May Department for Cancer Research, The University of Chicago, Chicago, Illinois 60637
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Zhou R, Kabra R, Olson DR, Piper RC, Snyder PM. Hrs controls sorting of the epithelial Na+ channel between endosomal degradation and recycling pathways. J Biol Chem 2010; 285:30523-30. [PMID: 20675381 DOI: 10.1074/jbc.m110.150755] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Epithelial Na(+) absorption is regulated by Nedd4-2, an E3 ubiquitin ligase that reduces expression of the epithelial Na(+) channel (ENaC) at the cell surface. Defects in this regulation cause Liddle syndrome, an inherited form of hypertension. Previous work found that Nedd4-2 functions through two distinct effects on trafficking, enhancing both ENaC endocytosis and ENaC degradation in lysosomes. To investigate the mechanism by which Nedd4-2 targets ENaC to lysosomes, we tested the role of hepatocyte growth factor-regulated tyrosine kinase substrate (Hrs), a component of the endosomal sorting complexes required for transport (ESCRT)-0 complex. We found that α-, β-, and γENaC each interact with Hrs. These interactions were enhanced by Nedd4-2 and were dependent on the catalytic function of Nedd4-2 as well as its WW domains. Mutation of ENaC PY motifs, responsible for inherited hypertension (Liddle syndrome), decreased Hrs binding to ENaC. Moreover, binding of ENaC to Hrs was reduced by dexamethasone/serum- and glucocorticoid-inducible kinase and cAMP, which are signaling pathways that inhibit Nedd4-2. Nedd4-2 bound to Hrs and catalyzed Hrs ubiquitination but did not alter Hrs protein levels. Expression of a dominant negative Hrs lacking its ubiquitin-interacting motif (Hrs-ΔUIM) increased ENaC surface expression and current. This occurred through reduced degradation of the cell surface pool of proteolytically activated ENaC, which enhanced its recycling to the cell surface. In contrast, Hrs-ΔUIM had no effect on degradation of uncleaved inactive channels. The data support a model in which Nedd4-2 induces binding of ENaC to Hrs, which mediates the sorting decision between ENaC degradation and recycling.
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Affiliation(s)
- Ruifeng Zhou
- Department of Internal Medicine, Roy J and Lucille A Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242, USA
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Abstract
The ESCRT machinery consists of the peripheral membrane protein complexes ESCRT-0, -I, -II, -III, and Vps4-Vta1, and the ALIX homodimer. The ESCRT system is required for degradation of unneeded or dangerous plasma membrane proteins; biogenesis of the lysosome and the yeast vacuole; the budding of most membrane enveloped viruses; the membrane abscission step in cytokinesis; macroautophagy; and several other processes. From their initial discovery in 2001-2002, the literature on ESCRTs has grown exponentially. This review will describe the structure and function of the six complexes noted above and summarize current knowledge of their mechanistic roles in cellular pathways and in disease.
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Affiliation(s)
- James H Hurley
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, US Department of Health and Human Services, Bethesda, MD 20892, USA.
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37
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Lauwers E, Erpapazoglou Z, Haguenauer-Tsapis R, André B. The ubiquitin code of yeast permease trafficking. Trends Cell Biol 2010; 20:196-204. [PMID: 20138522 DOI: 10.1016/j.tcb.2010.01.004] [Citation(s) in RCA: 198] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2009] [Revised: 12/24/2009] [Accepted: 01/05/2010] [Indexed: 11/26/2022]
Abstract
Yeast permeases, that act as transporters for nutrients including amino acids, nucleobases and metals, provide a powerful model system for dissecting the physiological control of membrane protein trafficking. Modification of these transporters by ubiquitin is known to target them for degradation in the vacuole, the degradation organelle of fungi. Recent studies have uncovered the role of specific adaptors for recruiting the Rsp5 ubiquitin ligase to these proteins. In addition, the role of ubiquitin at different trafficking steps including early endocytosis, sorting into the multivesicular body (MVB) pathway and Golgi-to-endosome transit is now becoming clear. In particular, K63-linked ubiquitin chains now emerge as a specific signal for protein sorting into the MVB pathway. A complete view of the ubiquitin code governing yeast permease trafficking might not be far off.
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Affiliation(s)
- Elsa Lauwers
- Physiologie Moléculaire de la Cellule, Institut de Biologie et de Médecine Moléculaires (IBMM), Université Libre de Bruxelles (ULB), Gosselies, Belgium
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38
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Homoserine toxicity in Saccharomyces cerevisiae and Candida albicans homoserine kinase (thr1Delta) mutants. EUKARYOTIC CELL 2010; 9:717-28. [PMID: 20305002 DOI: 10.1128/ec.00044-10] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
In addition to threonine auxotrophy, mutation of the Saccharomyces cerevisiae threonine biosynthetic genes THR1 (encoding homoserine kinase) and THR4 (encoding threonine synthase) results in a plethora of other phenotypes. We investigated the basis for these other phenotypes and found that they are dependent on the toxic biosynthetic intermediate homoserine. Moreover, homoserine is also toxic for Candida albicans thr1Delta mutants. Since increasing levels of threonine, but not other amino acids, overcome the homoserine toxicity of thr1Delta mutants, homoserine may act as a toxic threonine analog. Homoserine-mediated lethality of thr1Delta mutants is blocked by cycloheximide, consistent with a role for protein synthesis in this lethality. We identified various proteasome and ubiquitin pathway components that either when mutated or present in high copy numbers suppressed the thr1Delta mutant homoserine toxicity. Since the doa4Delta and proteasome mutants identified have reduced ubiquitin- and/or proteasome-mediated proteolysis, the degradation of a particular protein or subset of proteins likely contributes to homoserine toxicity.
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Abstract
Components of the ESCRT (endosomal sorting complex required for transport) machinery mediate endosomal sorting of ubiquitinated membrane proteins. They are key regulators of biological processes important for cell growth and survival, such as growth-factor-mediated signalling and cytokinesis. In addition, enveloped viruses, such as HIV-1, hijack and utilize the ESCRTs for budding during virus release and infection. Obviously, the ESCRT-facilitated pathways require tight regulation, which is partly mediated by a group of interacting proteins, for which our knowledge is growing. In this review we discuss the different ESCRT-modulating proteins and how they influence ESCRT-dependent processes, for example, by acting as positive or negative regulators or by providing temporal and spatial control. A number of the interactors influence the classical ESCRT-mediated process of endosomal cargo sorting, for example, by modulating the interaction between ubiquitinated cargo and the ESCRTs. Certain accessory proteins have been implicated in regulating the activity or steady-state expression levels of the ESCRT components, whereas other interactors control the cellular localization of the ESCRTs, for example, by inducing shuttling between cytosol and nucleus or endosomes. In conclusion, the discovery of novel interactors has and will extend our knowledge of the biological roles of ESCRTs.
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Multiple proteins and phosphorylations regulate Saccharomyces cerevisiae Cdc24p localization. FEBS Lett 2009; 583:3339-43. [PMID: 19782078 DOI: 10.1016/j.febslet.2009.09.033] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2009] [Revised: 09/16/2009] [Accepted: 09/19/2009] [Indexed: 11/23/2022]
Abstract
Targeting of Saccharomyces cerevisiae Cdc24p to polarized growth sites is essential for its function. Localization of GFP-tagged Cdc24 proteins or fragments was assayed in deletion mutants of Cdc24p-interacting proteins. The boi2Delta, ent2Delta, and hua1Delta mutants showed localization defects. The tos2Delta skg6Delta double mutant displayed aberrant pre-anaphase localization to the mother-bud neck region. The same aberrant pattern was seen when potential phosphorylation sites Ser697, Thr704, and Tyr200 were mutated. The S697A mutation also resulted in phosphorylation defects in vivo. These data support roles for Boi2p, Ent2p, Hua1p, Tos2p, and for Cdc24p phosphorylation in targeting Cdc24p to growth sites.
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41
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Lee JRE, Oestreich AJ, Payne JA, Gunawan MS, Norgan AP, Katzmann DJ. The HECT domain of the ubiquitin ligase Rsp5 contributes to substrate recognition. J Biol Chem 2009; 284:32126-37. [PMID: 19744925 DOI: 10.1074/jbc.m109.048629] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Ubiquitin modification of endosomal membrane proteins is a signal for active inclusion into the Multivesicular Body (MVB) pathway, resulting in lysosomal degradation. However, the endosome represents a dynamic site of protein sorting with a majority of proteins destined for recycling, rather than MVB targeting. Substrate recognition by ubiquitin ligases is therefore highly regulated. We have investigated substrate recognition by the Nedd4 ortholog Rsp5 as a model for understanding ligase-substrate interactions. Rsp5 interacts directly with its substrate Cps1 via a novel interaction mode. Perturbation of this mode of interaction revealed a compensatory role for the Rsp5 adaptor Bsd2. These results highlight the ability of Rsp5 to interact with substrates via multiple modalities, suggesting additional mechanisms of regulating this interaction and relevant outcomes.
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Affiliation(s)
- Jacqueline R E Lee
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, Rochester, Minnesota 55905, USA
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42
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Abstract
Tissue patterning during development relies on cell communication by secreted proteins and receptors that engage in complex signaling crosstalk to induce distinct cell behaviors in a context-dependent fashion. Here I summarize recent insights into basic mechanisms that control the distribution and activities of transforming growth factor beta, Wnt, Hedgehog, and Notch proteins, by regulating trafficking decisions during secretion and endocytosis.
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Affiliation(s)
- Daniel B Constam
- Swiss Institute for Experimental Cancer Research (ISREC), School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne (EPFL) CH 1015 Lausanne, Switzerland USA.
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43
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Ren X, Kloer DP, Kim YC, Ghirlando R, Saidi LF, Hummer G, Hurley JH. Hybrid structural model of the complete human ESCRT-0 complex. Structure 2009; 17:406-16. [PMID: 19278655 DOI: 10.1016/j.str.2009.01.012] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2008] [Revised: 01/16/2009] [Accepted: 01/23/2009] [Indexed: 10/21/2022]
Abstract
The human Hrs and STAM proteins comprise the ESCRT-0 complex, which sorts ubiquitinated cell surface receptors to lysosomes for degradation. Here we report a model for the complete ESCRT-0 complex based on the crystal structure of the Hrs-STAM core complex, previously solved domain structures, hydrodynamic measurements, and Monte Carlo simulations. ESCRT-0 expressed in insect cells has a hydrodynamic radius of RH = 7.9 nm and is a 1:1 heterodimer. The 2.3 Angstroms crystal structure of the ESCRT-0 core complex reveals two domain-swapped GAT domains and an antiparallel two-stranded coiled-coil, similar to yeast ESCRT-0. ESCRT-0 typifies a class of biomolecular assemblies that combine structured and unstructured elements, and have dynamic and open conformations to ensure versatility in target recognition. Coarse-grained Monte Carlo simulations constrained by experimental RH values for ESCRT-0 reveal a dynamic ensemble of conformations well suited for diverse functions.
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Affiliation(s)
- Xuefeng Ren
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Department of Health and Human Services, Bethesda, MD 20892, USA
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Shields SB, Oestreich AJ, Winistorfer S, Nguyen D, Payne JA, Katzmann DJ, Piper R. ESCRT ubiquitin-binding domains function cooperatively during MVB cargo sorting. ACTA ACUST UNITED AC 2009; 185:213-24. [PMID: 19380877 PMCID: PMC2700381 DOI: 10.1083/jcb.200811130] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Ubiquitin (Ub) sorting receptors facilitate the targeting of ubiquitinated membrane proteins into multivesicular bodies (MVBs). Ub-binding domains (UBDs) have been described in several endosomal sorting complexes required for transport (ESCRT). Using available structural information, we have investigated the role of the multiple UBDs within ESCRTs during MVB cargo selection. We found a novel UBD within ESCRT-I and show that it contributes to MVB sorting in concert with the known UBDs within the ESCRT complexes. These experiments reveal an unexpected level of coordination among the ESCRT UBDs, suggesting that they collectively recognize a diverse set of cargo rather than act sequentially at discrete steps.
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Affiliation(s)
- S Brookhart Shields
- Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, IA 52240, USA
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45
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Davies BA, Lee JRE, Oestreich AJ, Katzmann DJ. Membrane protein targeting to the MVB/lysosome. Chem Rev 2009; 109:1575-86. [PMID: 19243135 PMCID: PMC3911787 DOI: 10.1021/cr800473s] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Brian A. Davies
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, Rochester, Minnesota 55905
| | - Jacqueline R. E. Lee
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, Rochester, Minnesota 55905
| | - Andrea J. Oestreich
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, Rochester, Minnesota 55905
| | - David J. Katzmann
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, Rochester, Minnesota 55905
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46
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Lam MHY, Urban-Grimal D, Bugnicourt A, Greenblatt JF, Haguenauer-Tsapis R, Emili A. Interaction of the deubiquitinating enzyme Ubp2 and the e3 ligase Rsp5 is required for transporter/receptor sorting in the multivesicular body pathway. PLoS One 2009; 4:e4259. [PMID: 19165343 PMCID: PMC2626285 DOI: 10.1371/journal.pone.0004259] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2008] [Accepted: 12/10/2008] [Indexed: 11/30/2022] Open
Abstract
Protein ubiquitination is essential for many events linked to intracellular protein trafficking. We sought to elucidate the possible involvement of the S. cerevisiae deubiquitinating enzyme Ubp2 in transporter and receptor trafficking after we (this study) and others established that affinity purified Ubp2 interacts stably with the E3 ubiquitin ligase Rsp5 and the (ubiquitin associated) UBA domain containing protein Rup1. UBP2 interacts genetically with RSP5, while Rup1 facilitates the tethering of Ubp2 to Rsp5 via a PPPSY motif. Using the uracil permease Fur4 as a model reporter system, we establish a role for Ubp2 in membrane protein turnover. Similar to hypomorphic rsp5 alleles, cells deleted for UBP2 exhibited a temporal stabilization of Fur4 at the plasma membrane, indicative of perturbed protein trafficking. This defect was ubiquitin dependent, as a Fur4 N-terminal ubiquitin fusion construct bypassed the block and restored sorting in the mutant. Moreover, the defect was absent in conditions where recycling was absent, implicating Ubp2 in sorting at the multivesicular body. Taken together, our data suggest a previously overlooked role for Ubp2 as a positive regulator of Rsp5-mediated membrane protein trafficking subsequent to endocytosis.
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Affiliation(s)
- Mandy H. Y. Lam
- Banting and Best Department of Medical Research, Donnelly Centre for Cellular and Biomolecular Research, Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
| | | | - Amandine Bugnicourt
- Institut Jacques Monod-CNRS, Universités Paris VI and Paris VII, Paris, France
| | - Jack F. Greenblatt
- Banting and Best Department of Medical Research, Donnelly Centre for Cellular and Biomolecular Research, Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
| | | | - Andrew Emili
- Banting and Best Department of Medical Research, Donnelly Centre for Cellular and Biomolecular Research, Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
- * E-mail:
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Ren J, Pashkova N, Winistorfer S, Piper RC. DOA1/UFD3 plays a role in sorting ubiquitinated membrane proteins into multivesicular bodies. J Biol Chem 2008; 283:21599-611. [PMID: 18508771 PMCID: PMC2490793 DOI: 10.1074/jbc.m802982200] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2008] [Revised: 05/19/2008] [Indexed: 12/23/2022] Open
Abstract
Ubiquitin (Ub) is a sorting signal that targets integral membrane proteins to the interior of the vacuole/lysosome by directing them into lumenal vesicles of multivesicular bodies (MVBs). The Vps27-Hse1 complex, which is homologous to the Hrs-STAM complex in mammalian cells, serves as a Ub-sorting receptor at the surface of early endosomes. We have found that Hse1 interacts with Doa1/Ufd3. Doa1 is known to interact with Cdc48/p97 and Ub and is required for maintaining Ub levels. We find that the Hse1 Src homology 3 domain binds directly to the central PFU domain of Doa1. Mutations in Doa1 that block Hse1 binding but not Ub binding do not alter Ub levels but do result in the missorting of the MVB cargo GFP-Cps1. Loss of Doa1 also causes a synthetic growth defect when combined with loss of Vps27. Unlike the loss of Doa1 alone, the doa1Delta vps27Delta double mutant phenotype is not suppressed by Ub overexpression, demonstrating that the effect is not due to indirect consequence of lowered Ub levels. Loss of Doa1 results in a defect in the accumulation of GFP-Ub within yeast vacuoles, implying that there is a reduction in the flux of ubiquitinated membrane proteins through the MVB pathway. This defect was also reflected by an inability to properly sort Vph1-GFP-Ub, a modified subunit of the multiprotein vacuolar ATPase complex, which carries an in-frame fusion of Ub as an MVB sorting signal. These results reveal novel roles for Doa1 in helping to process ubiquitinated membrane proteins for sorting into MVBs.
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Affiliation(s)
- Jihui Ren
- Molecular Physiology and Biophysics, University of Iowa, Iowa City, IA 52242, USA
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48
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Tanaka N, Kyuuma M, Sugamura K. Endosomal sorting complex required for transport proteins in cancer pathogenesis, vesicular transport, and non-endosomal functions. Cancer Sci 2008; 99:1293-303. [PMID: 18429951 PMCID: PMC11158640 DOI: 10.1111/j.1349-7006.2008.00825.x] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2007] [Revised: 02/27/2008] [Accepted: 02/29/2008] [Indexed: 12/18/2022] Open
Abstract
Endosomal sorting complex required for transport (ESCRT) proteins form a multicomplex sorting machinery that controls multivesicular body (MVB) formation and the sorting of ubiquitinated membrane proteins to the endosomes. Being sorted to the MVB generally results in the lysosome-dependent degradation of cell-surface receptors, and defects in this machinery induce dysregulated receptor traffic and turnover. Recent lessons from gene targeting and silencing methodologies have implicated the ESCRT in normal development, cell differentiation, and growth, as well as in the budding of certain enveloped viruses. Furthermore, it is becoming apparent that the dysregulation of ESCRT proteins is involved in the development of various human diseases, including many types of cancers and neurodegenerative disorders. Here, we summarize the roles of ESCRT proteins in MVB sorting processes and the regulation of tumor cells, and we discuss some of their other functions that are unrelated to vesicular transport.
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Affiliation(s)
- Nobuyuki Tanaka
- Department of Microbiology, Tohoku University Graduate School of Medicine, 2-1 Seiryo-machi, Aoba-ku, Sendai 980-8575, Japan.
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49
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Erpapazoglou Z, Froissard M, Nondier I, Lesuisse E, Haguenauer-Tsapis R, Belgareh-Touzé N. Substrate- and ubiquitin-dependent trafficking of the yeast siderophore transporter Sit1. Traffic 2008; 9:1372-91. [PMID: 18489705 DOI: 10.1111/j.1600-0854.2008.00766.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Eukaryotic plasma membrane transporters are subjected to a tightly regulated intracellular trafficking. The yeast siderophore iron transporter1 (Sit1) displays substrate-regulated trafficking. It is targeted to the plasma membrane or to a vacuolar degradative pathway when synthesized in the presence or absence of external substrate, respectively. Sorting of Sit1 to the vacuolar pathway is dependent on the clathrin adaptor Gga2, and more specifically on its C-GAT subdomain. Plasma membrane undergoes substrate-induced ubiquitylation dependent on the Rsp5 ubiquitin protein ligase. Sit1 is also ubiquitylated in an Rsp5-dependent manner in internal compartments when expressed in the absence of substrate. In several rsp5 mutants including cells deleted for RSP5, Sit1 expressed in the absence of substrate is correctly targeted to the endosomal pathway but its sorting to multivesicular bodies (MVBs) is impaired. Consequently, it displays endosome to plasma membrane targeting, with kinetics similar to those observed in vps mutants defective for MVB sorting. Plasma membrane Sit1 is modified by Lys63-linked ubiquitin chains. We also show for the first time in yeast that modification by this latter type of ubiquitin chains is required directly or indirectly for efficient MVB sorting, as it is for efficient internalization at the plasma membrane.
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Affiliation(s)
- Zoi Erpapazoglou
- Département de Biologie Cellulaire, Laboratoire Trafic Intracellulaire des Protéines dans la Levure, Institut Jacques Monod, UMR 7592 CNRS-Universités Paris 6 et 7, 75251 Paris cedex 05, France
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50
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Hurley JH. ESCRT complexes and the biogenesis of multivesicular bodies. Curr Opin Cell Biol 2008; 20:4-11. [PMID: 18222686 DOI: 10.1016/j.ceb.2007.12.002] [Citation(s) in RCA: 369] [Impact Index Per Article: 23.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2007] [Revised: 11/30/2007] [Accepted: 12/07/2007] [Indexed: 10/22/2022]
Abstract
Multivesicular bodies (MVBs) are crucial intermediates in the trafficking of ubiquitinated receptors and other cargo destined for lysosomes. The formation of MVBs by invagination of the endosomal limiting membrane is catalyzed by the endosomal sorting complex required for transport (ESCRT) complexes, a process that has recently been visualized in three-dimensional detail by electron tomography. Structural and biochemical analysis of the upstream components, Vps27-Hse1, ESCRT-I, and ESCRT-II, shows how these complexes assemble and cluster cargo. Rapid progress has been made in understanding the assembly and disassembly of the ESCRT-III complex and the interactions of its subunits with MIT domain and other proteins. A key role for deubiquitination in the regulation of the system has been demonstrated. One central question remains largely unanswered, which is how the ESCRTs actually promote the invagination of the endosomal membrane.
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Affiliation(s)
- James H Hurley
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, NIH, US Department of Health and Human Services, Bethesda, MD 20892, USA.
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