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Zhao X, Chen A, Wang Z, Xu XH, Tao Y. Biological functions and potential therapeutic applications of huntingtin-associated protein 1: progress and prospects. Clin Transl Oncol 2021; 24:203-214. [PMID: 34564830 DOI: 10.1007/s12094-021-02702-w] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2021] [Accepted: 08/19/2021] [Indexed: 11/28/2022]
Abstract
Huntington disease (HD) is a single-gene autosomal dominant inherited neurodegenerative disease caused by a polyglutamine expansion of the protein huntingtin (HTT). Huntingtin-associated protein 1 (HAP1) is the first protein identified as an interacting partner of huntingtin, which is directly associated with HD. HAP1 is mainly expressed in the nervous system and is also found in the endocrine system and digestive system, and then involves in the occurrence of the related endocrine diseases, digestive system diseases, and cancer. Understanding the function of HAP1 could help elucidate the pathogenesis that HTT plays in the disease process. Therefore, this article attempts to summarize the latest research progress of the role of HAP1 and its application for diseases in recent years, aiming to clarify the functions of HAP1 and its interacting proteins, and provide new research ideas and new therapeutic targets for the treatment of cancer and related diseases.
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Affiliation(s)
- X Zhao
- School of Medical Laboratory, Weifang Medical University, Weifang, Shandong, 261053, People's Republic of China
| | - A Chen
- School of Medical Laboratory, Weifang Medical University, Weifang, Shandong, 261053, People's Republic of China.,Department of Central Lab, Weihai Municipal Hospital, Cheeloo College of Medicine, Shandong University. Weihai, Shandong, 264200, People's Republic of China
| | - Z Wang
- School of Medical Laboratory, Weifang Medical University, Weifang, Shandong, 261053, People's Republic of China
| | - Xiao-Han Xu
- School of Medical Laboratory, Weifang Medical University, Weifang, Shandong, 261053, People's Republic of China
| | - Y Tao
- Department of Laboratory Medicine, Affiliated Hospital of Weifang Medical University, Weifang, Shandong, 261031, People's Republic of China.
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2
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Torii S, Orba Y, Sasaki M, Tabata K, Wada Y, Carr M, Hobson-Peters J, Hall RA, Takada A, Fukuhara T, Matsuura Y, Hall WW, Sawa H. Host ESCRT factors are recruited during chikungunya virus infection and are required for the intracellular viral replication cycle. J Biol Chem 2020; 295:7941-7957. [PMID: 32341071 DOI: 10.1074/jbc.ra119.012303] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Revised: 04/23/2020] [Indexed: 11/06/2022] Open
Abstract
Chikungunya fever is a re-emerging zoonotic disease caused by chikungunya virus (CHIKV), a member of the Alphavirus genus in the Togaviridae family. Only a few studies have reported on the host factors required for intracellular CHIKV trafficking. Here, we conducted an imaging-based siRNA screen to identify human host factors for intracellular trafficking that are involved in CHIKV infection, examined their interactions with CHIKV proteins, and investigated the contributions of these proteins to CHIKV infection. The results of the siRNA screen revealed that host endosomal sorting complexes required for transport (ESCRT) proteins are recruited during CHIKV infection. Co-immunoprecipitation analyses revealed that both structural and nonstructural CHIKV proteins interact with hepatocyte growth factor-regulated tyrosine kinase substrate (HGS), a component of the ESCRT-0 complex. We also observed that HGS co-localizes with the E2 protein of CHIKV and with dsRNA, a marker of the replicated CHIKV genome. Results from gene knockdown analyses indicated that, along with other ESCRT factors, HGS facilitates both genome replication and post-translational steps during CHIKV infection. Moreover, we show that ESCRT factors are also required for infections with other alphaviruses. We conclude that during CHIKV infection, several ESCRT factors are recruited via HGS and are involved in viral genome replication and post-translational processing of viral proteins.
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Affiliation(s)
- Shiho Torii
- Division of Molecular Pathobiology, Research Center for Zoonosis Control, Hokkaido University, Sapporo, Japan
| | - Yasuko Orba
- Division of Molecular Pathobiology, Research Center for Zoonosis Control, Hokkaido University, Sapporo, Japan
| | - Michihito Sasaki
- Division of Molecular Pathobiology, Research Center for Zoonosis Control, Hokkaido University, Sapporo, Japan
| | - Koshiro Tabata
- Division of Molecular Pathobiology, Research Center for Zoonosis Control, Hokkaido University, Sapporo, Japan
| | - Yuji Wada
- Department of Pathology, National Institute of Infectious Diseases, Shinjuku, Japan
| | - Michael Carr
- National Virus Reference Laboratory, School of Medicine, University College Dublin, Dublin, Ireland.,Global Institution for Collaborative Research and Education (GI-CoRE), Hokkaido University, Sapporo, Japan
| | - Jody Hobson-Peters
- Australian Infectious Diseases Research Centre, School of Chemistry and Molecular Biosciences, University of Queensland, St. Lucia, Queensland, Australia
| | - Roy A Hall
- Australian Infectious Diseases Research Centre, School of Chemistry and Molecular Biosciences, University of Queensland, St. Lucia, Queensland, Australia
| | - Ayato Takada
- Global Institution for Collaborative Research and Education (GI-CoRE), Hokkaido University, Sapporo, Japan.,Division of Global Epidemiology, Research Center for Zoonosis Control, Hokkaido University, Sapporo, Japan
| | - Takasuke Fukuhara
- Department of Molecular Virology, Research Institute for Microbial Diseases, Osaka University, Suita, Japan
| | - Yoshiharu Matsuura
- Department of Molecular Virology, Research Institute for Microbial Diseases, Osaka University, Suita, Japan
| | - William W Hall
- National Virus Reference Laboratory, School of Medicine, University College Dublin, Dublin, Ireland.,Global Institution for Collaborative Research and Education (GI-CoRE), Hokkaido University, Sapporo, Japan.,Centre for Research in Infectious Diseases, School of Medicine, University College Dublin, Dublin, Ireland.,Global Virus Network, Baltimore, Maryland, USA
| | - Hirofumi Sawa
- Division of Molecular Pathobiology, Research Center for Zoonosis Control, Hokkaido University, Sapporo, Japan .,Global Institution for Collaborative Research and Education (GI-CoRE), Hokkaido University, Sapporo, Japan.,Global Virus Network, Baltimore, Maryland, USA
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3
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The ESCRT-0 Protein HRS Interacts with the Human T Cell Leukemia Virus Type 2 Antisense Protein APH-2 and Suppresses Viral Replication. J Virol 2019; 94:JVI.01311-19. [PMID: 31597781 DOI: 10.1128/jvi.01311-19] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2019] [Accepted: 10/01/2019] [Indexed: 01/18/2023] Open
Abstract
The divergent clinical outcomes of human T cell leukemia virus type 1 (HTLV-1) and HTLV-2 infections have been attributed to functional differences in their antisense proteins. In contrast to HTLV-1 bZIP factor (HBZ), the role of the antisense protein of HTLV-2 (APH-2) in HTLV-2 infection is poorly understood. In previous studies, we identified the endosomal sorting complex required for transport 0 (ESCRT-0) subunit HRS as a novel interaction partner of APH-2 but not HBZ. HRS is a master regulator of endosomal protein sorting for lysosomal degradation and is hijacked by many viruses to promote replication. However, no studies to date have shown a link between HTLVs and HRS. In this study, we sought to characterize the interaction between HRS and APH-2 and to investigate the impact of HRS on the life cycle of HTLV-2. We confirmed a direct specific interaction between APH-2 and HRS and showed that the CC2 domain of HRS and the N-terminal domain of APH-2 mediate their interaction. We demonstrated that HRS recruits APH-2 to early endosomes, possibly furnishing an entry route into the endosomal/lysosomal pathway. We demonstrated that inhibition of this pathway using either bafilomycin or HRS overexpression substantially extends the half-life of APH-2 and stabilizes Tax2B expression levels. We found that HRS enhances Tax2B-mediated long terminal repeat (LTR) activation, while depletion of HRS enhances HTLV-2 production and release, indicating that HRS may have a negative impact on HTLV-2 replication. Overall, our study provides important new insights into the role of the ESCRT-0 HRS protein, and by extension the ESCRT machinery and the endosomal/lysosomal pathway, in HTLV-2 infection.IMPORTANCE While APH-2 is the only viral protein consistently expressed in infected carriers, its role in HTLV-2 infection is poorly understood. In this study, we characterized the interaction between the ESCRT-0 component HRS and APH-2 and explored the role of HRS in HTLV-2 replication. HRS is a master regulator of protein sorting for lysosomal degradation, a feature that is manipulated by several viruses to promote replication. Unexpectedly, we found that HRS targets APH-2 and possibly Tax2B for lysosomal degradation and has an overall negative impact on HTLV-2 replication and release. The negative impact of interactions between HTLV-2 regulatory proteins and HRS, and by extension the ESCRT machinery, may represent an important strategy used by HTLV-2 to limit virus production and to promote persistence, features that may contribute to the limited pathogenic potential of this infection.
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Abstract
Calcitonin gene-related peptide (CGRP) is a promiscuous peptide, similar to many other members of the calcitonin family of peptides. The potential of CGRP to act on many different receptors with differing affinities and efficacies makes deciphering the signalling from the CGRP receptor a challenging task for researchers.Although it is not a typical G protein-coupled receptor (GPCR), in that it is composed not just of a GPCR, the CGRP receptor activates many of the same signalling pathways common for other GPCRs. This includes the family of G proteins and a variety of protein kinases and transcription factors. It is now also clear that in addition to the initiation of cell-surface signalling, GPCRs, including the CGRP receptor, also activate distinct signalling pathways as the receptor is trafficking along the endocytic conduit.Given CGRP's characteristic of activating multiple GPCRs, we will first consider the complex of calcitonin receptor-like receptor (CLR) and receptor activity-modifying protein 1 (RAMP1) as the CGRP receptor. We will discuss the discovery of the CGRP receptor components, the molecular mechanisms controlling its internalization and post-endocytic trafficking (recycling and degradation) and the diverse signalling cascades that are elicited by this receptor in model cell lines. We will then discuss CGRP-mediated signalling pathways in primary cells pertinent to migraine including neurons, glial cells and vascular smooth muscle cells.Investigation of all the CGRP- and CGRP receptor-mediated signalling cascades is vital if we are to fully understand CGRP's role in migraine and will no doubt unearth new targets for the treatment of migraine and other CGRP-driven diseases.
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5
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Mycobacterium tuberculosis Type VII Secretion System Effectors Differentially Impact the ESCRT Endomembrane Damage Response. mBio 2018; 9:mBio.01765-18. [PMID: 30482832 PMCID: PMC6282207 DOI: 10.1128/mbio.01765-18] [Citation(s) in RCA: 64] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Intracellular pathogens have varied strategies to breach the endolysosomal barrier so that they can deliver effectors to the host cytosol, access nutrients, replicate in the cytoplasm, and avoid degradation in the lysosome. In the case of Mycobacterium tuberculosis, the bacterium perforates the phagosomal membrane shortly after being taken up by macrophages. Phagosomal damage depends upon the mycobacterial ESX-1 type VII secretion system (T7SS). Sterile insults, such as silica crystals or membranolytic peptides, can also disrupt phagosomal and endolysosomal membranes. Recent work revealed that the host endosomal sorting complex required for transport (ESCRT) machinery rapidly responds to sterile endolysosomal damage and promotes membrane repair. We hypothesized that ESCRTs might also respond to pathogen-induced phagosomal damage and that M. tuberculosis could impair this host response. Indeed, we found that ESCRT-III proteins were recruited to M. tuberculosis phagosomes in an ESX-1-dependent manner. We previously demonstrated that the mycobacterial effectors EsxG/TB9.8 and EsxH/TB10.4, both secreted by the ESX-3 T7SS, can inhibit ESCRT-dependent trafficking of receptors to the lysosome. Here, we additionally show that ESCRT-III recruitment to sites of endolysosomal damage is antagonized by EsxG and EsxH, both within the context of M. tuberculosis infection and sterile injury. Moreover, EsxG and EsxH themselves respond within minutes to membrane damage in a manner that is independent of calcium and ESCRT-III recruitment. Thus, our study reveals that T7SS effectors and ESCRT participate in a series of measures and countermeasures for control of phagosome integrity.IMPORTANCE Mycobacterium tuberculosis causes tuberculosis, which kills more people than any other infection. M. tuberculosis grows in macrophages, cells that specialize in engulfing and degrading microorganisms. Like many intracellular pathogens, in order to cause disease, M. tuberculosis damages the membrane-bound compartment (phagosome) in which it is enclosed after macrophage uptake. Recent work showed that when chemicals damage this type of intracellular compartment, cells rapidly detect and repair the damage, using machinery called the endosomal sorting complex required for transport (ESCRT). Therefore, we hypothesized that ESCRT might also respond to pathogen-induced damage. At the same time, our previous work showed that the EsxG-EsxH heterodimer of M. tuberculosis can inhibit ESCRT, raising the possibility that M. tuberculosis impairs this host response. Here, we show that ESCRT is recruited to damaged M. tuberculosis phagosomes and that EsxG-EsxH undermines ESCRT-mediated endomembrane repair. Thus, our studies demonstrate a battle between host and pathogen over endomembrane integrity.
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6
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A Critical Role for Sorting Nexin 1 in the Trafficking of Metabotropic Glutamate Receptors. J Neurosci 2018; 38:8605-8620. [PMID: 30143569 DOI: 10.1523/jneurosci.0454-18.2018] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2018] [Revised: 07/22/2018] [Accepted: 08/16/2018] [Indexed: 11/21/2022] Open
Abstract
Group I metabotropic glutamate receptors (mGluRs) function as modulators of neuronal physiology and they have also been implicated in various neuropsychiatric disorders. Trafficking of mGluRs plays important roles in controlling the precise localization of these receptors at specific region of the cell, as well as it regulates the activity of these receptors. Despite this obvious significance, we know very little about the cellular machineries that control the trafficking of these receptors in the CNS. Sorting nexin 1 (SNX1) has been shown to regulate the endosomal sorting of few cell surface receptors either to lysosomes where they are downregulated or back to the cell surface. Using "molecular replacement" approach in hippocampal neurons derived from mice of both sexes, we show here that SNX1 plays critical role in the trafficking of mGluR1, a member of the group I mGluR family. Overexpression of dominant-negative SNX1 or knockdown of endogenous SNX1 resulted in the rapid recycling of the receptor. Importantly, recycling via the rapid recycling route, did not allow the resensitization of the receptors. Our data suggest that both, N-terminal and C-terminal region of SNX1 play critical role in the normal trafficking of the receptor. In addition, we also show here that SNX1 regulates the trafficking of mGluR1 through the interaction with Hrs (hepatocyte growth factor-regulated tyrosine kinase substrate), a protein that has been implicated in both signaling and vesicular trafficking. Thus, these studies reveal a mechanistic role of SNX1 in the trafficking of group I mGluRs and its physiological implications.SIGNIFICANCE STATEMENT Group I mGluRs are activated by the neurotransmitter glutamate in the CNS, and play various important roles in the brain. Similar to many other receptors, trafficking plays crucial roles in controlling the precise localization as well as activity of these receptors. Despite this obvious significance very little is known about the cellular machineries that control the trafficking of these receptors. We demonstrate here, that SNX1 plays a critical role in the trafficking of mGluR1, a member of the group I mGluR family. SNX1-mediated trafficking is critical for the resensitization of the receptor. SNX1 controls the trafficking of the receptor through the interaction with another protein, Hrs. The results suggest a role for SNX1 in the regulation of group I mGluRs.
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7
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Naslavsky N, Caplan S. The enigmatic endosome - sorting the ins and outs of endocytic trafficking. J Cell Sci 2018; 131:131/13/jcs216499. [PMID: 29980602 DOI: 10.1242/jcs.216499] [Citation(s) in RCA: 195] [Impact Index Per Article: 32.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The early endosome (EE), also known as the sorting endosome (SE) is a crucial station for the sorting of cargoes, such as receptors and lipids, through the endocytic pathways. The term endosome relates to the receptacle-like nature of this organelle, to which endocytosed cargoes are funneled upon internalization from the plasma membrane. Having been delivered by the fusion of internalized vesicles with the EE or SE, cargo molecules are then sorted to a variety of endocytic pathways, including the endo-lysosomal pathway for degradation, direct or rapid recycling to the plasma membrane, and to a slower recycling pathway that involves a specialized form of endosome known as a recycling endosome (RE), often localized to the perinuclear endocytic recycling compartment (ERC). It is striking that 'the endosome', which plays such essential cellular roles, has managed to avoid a precise description, and its characteristics remain ambiguous and heterogeneous. Moreover, despite the rapid advances in scientific methodologies, including breakthroughs in light microscopy, overall, the endosome remains poorly defined. This Review will attempt to collate key characteristics of the different types of endosomes and provide a platform for discussion of this unique and fascinating collection of organelles. Moreover, under-developed, poorly understood and important open questions will be discussed.
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Affiliation(s)
- Naava Naslavsky
- The Department of Biochemistry and Molecular Biology, The University of Nebraska Medical Center, Omaha, NE 68198, USA
| | - Steve Caplan
- The Department of Biochemistry and Molecular Biology, The University of Nebraska Medical Center, Omaha, NE 68198, USA .,The Fred and Pamela Buffett Cancer Center, The University of Nebraska Medical Center, Omaha, NE 68198, USA
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8
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Endosomal binding kinetics of Eps15 and Hrs specifically regulate the degradation of RTKs. Sci Rep 2017; 7:17962. [PMID: 29269784 PMCID: PMC5740074 DOI: 10.1038/s41598-017-17320-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2017] [Accepted: 10/25/2017] [Indexed: 01/25/2023] Open
Abstract
Activation of EGF-R and PDGF-R triggers autophosphorylation and the recruitment of Eps15 and Hrs. These two endosomal proteins are important for specific receptor sorting. Hrs is recruiting ubiquitinated receptors to early endosomes to further facilitate degradation through the ESCRT complex. Upon receptor activation Hrs becomes phosphorylated and is relocated to the cytosol, important for receptor degradation. In this work we have studied the endosomal binding dynamics of Eps15 and Hrs upon EGF-R and PDGF-R stimulation. By analysing the fluorescence intensity on single endosomes after ligand stimulation we measured a time-specific decrease in the endosomal fluorescence level of Eps15-GFP and Hrs-YFP. Through FRAP experiments we could further register a specific change in the endosomal-membrane to cytosol binding properties of Eps15-GFP and Hrs-YFP. This specific change in membrane fractions proved to be a redistribution of the immobile fraction, which was not shown for the phosphorylation deficient mutants. We here describe a mechanism that can explain the previously observed relocation of Hrs from the endosomes to cytosol after EGF stimulation and show that Eps15 follows a similar mechanism. Moreover, this specific redistribution of the endosomal protein binding dynamics proved to be of major importance for receptor degradation.
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9
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Roux BT, Bauer CC, McNeish AJ, Ward SG, Cottrell GS. The Role of Ubiquitination and Hepatocyte Growth Factor-Regulated Tyrosine Kinase Substrate in the Degradation of the Adrenomedullin Type I Receptor. Sci Rep 2017; 7:12389. [PMID: 28959041 PMCID: PMC5620052 DOI: 10.1038/s41598-017-12585-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2017] [Accepted: 09/06/2017] [Indexed: 01/27/2023] Open
Abstract
Calcitonin receptor-like receptor (CLR) and the receptor activity-modifying protein 2 (RAMP2) comprise a receptor for adrenomedullin (AM). Although it is known that AM induces internalization of CLR•RAMP2, little is known about the molecular mechanisms that regulate the trafficking of CLR•RAMP2. Using HEK and HMEC-1 cells, we observed that AM-induced activation of CLR•RAMP2 promoted ubiquitination of CLR. A mutant (CLRΔ9KR), lacking all intracellular lysine residues was functional and trafficked similar to the wild-type receptor, but was not ubiquitinated. Degradation of CLR•RAMP2 and CLRΔ9KR•RAMP2 was not dependent on the duration of AM stimulation or ubiquitination and occurred via a mechanism that was partially prevented by peptidase inhibitors. Degradation of CLR•RAMP2 was sensitive to overexpression of hepatocyte growth factor-regulated tyrosine kinase substrate (HRS), but not to HRS knockdown, whereas CLRΔ9KR•RAMP2 degradation was unaffected. Overexpression, but not knockdown of HRS, promoted hyperubiquitination of CLR under basal conditions. Thus, we propose a role for ubiquitin and HRS in the regulation of AM-induced degradation of CLR•RAMP2.
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Affiliation(s)
- Benoît T Roux
- Department of Pharmacy and Pharmacology, University of Bath, Claverton Down, Bath, BA2 7AY, UK
| | - Claudia C Bauer
- Cellular and Molecular Neuroscience, Reading School of Pharmacy, University of Reading, Reading, RG6 6UB, UK
| | - Alister J McNeish
- Cellular and Molecular Neuroscience, Reading School of Pharmacy, University of Reading, Reading, RG6 6UB, UK
| | - Stephen G Ward
- Department of Pharmacy and Pharmacology, University of Bath, Claverton Down, Bath, BA2 7AY, UK
| | - Graeme S Cottrell
- Cellular and Molecular Neuroscience, Reading School of Pharmacy, University of Reading, Reading, RG6 6UB, UK.
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Huntingtin-associated protein-1 (HAP1) regulates endocytosis and interacts with multiple trafficking-related proteins. Cell Signal 2017; 35:176-187. [DOI: 10.1016/j.cellsig.2017.02.023] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2017] [Revised: 02/16/2017] [Accepted: 02/28/2017] [Indexed: 12/24/2022]
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11
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Watson JA, Bhattacharyya BJ, Vaden JH, Wilson JA, Icyuz M, Howard AD, Phillips E, DeSilva TM, Siegal GP, Bean AJ, King GD, Phillips SE, Miller RJ, Wilson SM. Motor and Sensory Deficits in the teetering Mice Result from Mutation of the ESCRT Component HGS. PLoS Genet 2015; 11:e1005290. [PMID: 26115514 PMCID: PMC4482608 DOI: 10.1371/journal.pgen.1005290] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2014] [Accepted: 05/18/2015] [Indexed: 11/18/2022] Open
Abstract
Neurons are particularly vulnerable to perturbations in endo-lysosomal transport, as several neurological disorders are caused by a primary deficit in this pathway. In this report, we used positional cloning to show that the spontaneously occurring neurological mutation teetering (tn) is a single nucleotide substitution in hepatocyte growth factor-regulated tyrosine kinase substrate (Hgs/Hrs), a component of the endosomal sorting complex required for transport (ESCRT). The tn mice exhibit hypokenesis, muscle weakness, reduced muscle size and early perinatal lethality by 5-weeks of age. Although HGS has been suggested to be essential for the sorting of ubiquitinated membrane proteins to the lysosome, there were no alterations in receptor tyrosine kinase levels in the central nervous system, and only a modest decrease in tropomyosin receptor kinase B (TrkB) in the sciatic nerves of the tn mice. Instead, loss of HGS resulted in structural alterations at the neuromuscular junction (NMJ), including swellings and ultra-terminal sprouting at motor axon terminals and an increase in the number of endosomes and multivesicular bodies. These structural changes were accompanied by a reduction in spontaneous and evoked release of acetylcholine, indicating a deficit in neurotransmitter release at the NMJ. These deficits in synaptic transmission were associated with elevated levels of ubiquitinated proteins in the synaptosome fraction. In addition to the deficits in neuronal function, mutation of Hgs resulted in both hypermyelinated and dysmyelinated axons in the tn mice, which supports a growing body of evidence that ESCRTs are required for proper myelination of peripheral nerves. Our results indicate that HGS has multiple roles in the nervous system and demonstrate a previously unanticipated requirement for ESCRTs in the maintenance of synaptic transmission. Endocytic trafficking involves the internalization, endosomal sorting and lysosomal degradation of cell surface cargo. Many factors involved in endosomal sorting in mammalian cells have been identified, and mutations in these components are associated with a variety of neurological disorders. While the function of endosomal sorting components has been intensely studied in immortalized cell lines, it is not known what role these factors play in endosomal sorting in the nervous system. In this study, we show that the teetering (tn) gene encodes the hepatocytegrowth factor regulated tyrosine kinasesubstrate (Hgs), a core component of the endosomal sorting pathway. The tn mice exhibit several signs of motor neuron disease, including reduced muscle mass, muscle weakness and motor abnormalities. Although HGS is predicted to be required for the lysosomal degradation of receptor tyrosine kinases, there was no change in the levels of receptor tyrosine kinases in the spinal cords of the tn mice. Instead, we found that HGS is required for synaptic transmission at the neuromuscular junction and for the proper myelination of the peripheral nervous system.
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Affiliation(s)
- Jennifer A. Watson
- Department of Neurobiology, University of Alabama at Birmingham, Evelyn F. McKnight Brain Institute, Civitan International Research Center, Birmingham, Alabama, United States of America
| | - Bula J. Bhattacharyya
- Department of Molecular Pharmacology and Biological Chemistry, Northwestern University, Evanston, Illinois, United States of America
| | - Jada H. Vaden
- Department of Neurobiology, University of Alabama at Birmingham, Evelyn F. McKnight Brain Institute, Civitan International Research Center, Birmingham, Alabama, United States of America
| | - Julie A. Wilson
- Department of Neurobiology, University of Alabama at Birmingham, Evelyn F. McKnight Brain Institute, Civitan International Research Center, Birmingham, Alabama, United States of America
| | - Mert Icyuz
- Department of Neurobiology, University of Alabama at Birmingham, Evelyn F. McKnight Brain Institute, Civitan International Research Center, Birmingham, Alabama, United States of America
- Department of Genetics, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Alan D. Howard
- Department of Neurobiology, University of Alabama at Birmingham, Evelyn F. McKnight Brain Institute, Civitan International Research Center, Birmingham, Alabama, United States of America
| | - Edward Phillips
- Department of Neurobiology, University of Alabama at Birmingham, Evelyn F. McKnight Brain Institute, Civitan International Research Center, Birmingham, Alabama, United States of America
| | - Tara M. DeSilva
- Department of Physical Medicine and Rehabilitation, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Gene P. Siegal
- Departments of Pathology, Surgery and Cell, Developmental and Integrative Biology, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Andrew J. Bean
- Department of Neurobiology and Anatomy and Graduate School of Biomedical Sciences, The University of Texas Health Science Center at Houston, Houston, Texas, United States of America
- Division of Pediatrics, The University of Texas M.D. Anderson Cancer Center, Houston, Texas, United States of America
| | - Gwendalyn D. King
- Department of Neurobiology, University of Alabama at Birmingham, Evelyn F. McKnight Brain Institute, Civitan International Research Center, Birmingham, Alabama, United States of America
| | - Scott E. Phillips
- Department of Neurobiology, University of Alabama at Birmingham, Evelyn F. McKnight Brain Institute, Civitan International Research Center, Birmingham, Alabama, United States of America
| | - Richard J. Miller
- Department of Molecular Pharmacology and Biological Chemistry, Northwestern University, Evanston, Illinois, United States of America
| | - Scott M. Wilson
- Department of Neurobiology, University of Alabama at Birmingham, Evelyn F. McKnight Brain Institute, Civitan International Research Center, Birmingham, Alabama, United States of America
- * E-mail:
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12
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Vogel GF, Ebner HL, de Araujo MEG, Schmiedinger T, Eiter O, Pircher H, Gutleben K, Witting B, Teis D, Huber LA, Hess MW. Ultrastructural Morphometry Points to a New Role for LAMTOR2 in Regulating the Endo/Lysosomal System. Traffic 2015; 16:617-34. [DOI: 10.1111/tra.12271] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2014] [Revised: 02/09/2015] [Accepted: 02/09/2015] [Indexed: 12/13/2022]
Affiliation(s)
- Georg F. Vogel
- Division of Histology and Embryology; Medical University of Innsbruck; Müllerstrasse 59 A-6020 Innsbruck Austria
- Division of Cell Biology, Biocenter; Medical University of Innsbruck; Innrain 80-82 A-6020 Innsbruck Austria
| | - Hannes L. Ebner
- Division of Histology and Embryology; Medical University of Innsbruck; Müllerstrasse 59 A-6020 Innsbruck Austria
- Current address: Department for Trauma Surgery; Medical University of Innsbruck; Anichstrasse 35 A-6020 Innsbruck Austria
| | - Mariana E. G. de Araujo
- Division of Cell Biology, Biocenter; Medical University of Innsbruck; Innrain 80-82 A-6020 Innsbruck Austria
| | - Thomas Schmiedinger
- Department of Therapeutic Radiology and Oncology; Medical University of Innsbruck; Anichstrasse 35 A-6020 Innsbruck Austria
| | - Oliver Eiter
- Department of Therapeutic Radiology and Oncology; Medical University of Innsbruck; Anichstrasse 35 A-6020 Innsbruck Austria
| | - Haymo Pircher
- Research Institute for Biomedical Aging Research; University of Innsbruck; Rennweg 10 A-6020 Innsbruck Austria
| | - Karin Gutleben
- Division of Histology and Embryology; Medical University of Innsbruck; Müllerstrasse 59 A-6020 Innsbruck Austria
| | - Barbara Witting
- Division of Histology and Embryology; Medical University of Innsbruck; Müllerstrasse 59 A-6020 Innsbruck Austria
| | - David Teis
- Division of Cell Biology, Biocenter; Medical University of Innsbruck; Innrain 80-82 A-6020 Innsbruck Austria
| | - Lukas A. Huber
- Division of Cell Biology, Biocenter; Medical University of Innsbruck; Innrain 80-82 A-6020 Innsbruck Austria
| | - Michael W. Hess
- Division of Histology and Embryology; Medical University of Innsbruck; Müllerstrasse 59 A-6020 Innsbruck Austria
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13
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Reincke M, Sbiera S, Hayakawa A, Theodoropoulou M, Osswald A, Beuschlein F, Meitinger T, Mizuno-Yamasaki E, Kawaguchi K, Saeki Y, Tanaka K, Wieland T, Graf E, Saeger W, Ronchi CL, Allolio B, Buchfelder M, Strom TM, Fassnacht M, Komada M. Mutations in the deubiquitinase gene USP8 cause Cushing's disease. Nat Genet 2014; 47:31-8. [PMID: 25485838 DOI: 10.1038/ng.3166] [Citation(s) in RCA: 361] [Impact Index Per Article: 36.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2014] [Accepted: 11/17/2014] [Indexed: 12/13/2022]
Abstract
Cushing's disease is caused by corticotroph adenomas of the pituitary. To explore the molecular mechanisms of endocrine autonomy in these tumors, we performed exome sequencing of 10 corticotroph adenomas. We found somatic mutations in the USP8 deubiquitinase gene in 4 of 10 adenomas. The mutations clustered in the 14-3-3 protein binding motif and enhanced the proteolytic cleavage and catalytic activity of USP8. Cleavage of USP8 led to increased deubiqutination of the EGF receptor, impairing its downregulation and sustaining EGF signaling. USP8 mutants enhanced promoter activity of the gene encoding proopiomelanocortin. In summary, our data show that dominant mutations in USP8 cause Cushing's disease via activation of EGF receptor signaling.
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Affiliation(s)
- Martin Reincke
- Medizinische Klinik und Poliklinik IV, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Silviu Sbiera
- 1] Medizinische Klinik und Poliklinik IV, Ludwig-Maximilians-Universität München, Munich, Germany. [2] Department of Medicine I, Endocrine and Diabetes Unit, University Hospital, University of Würzburg, Würzburg, Germany
| | - Akira Hayakawa
- Department of Biological Sciences, Tokyo Institute of Technology, Yokohama, Japan
| | | | - Andrea Osswald
- Medizinische Klinik und Poliklinik IV, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Felix Beuschlein
- Medizinische Klinik und Poliklinik IV, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Thomas Meitinger
- 1] Institute of Human Genetics, Helmholtz Zentrum München, Neuherberg, Germany. [2] Institute of Human Genetics, Technische Universität München, Munich, Germany. [3] DZHK (German Centre for Cardiovascular Research) partner site, Munich Heart Alliance, Munich, Germany
| | - Emi Mizuno-Yamasaki
- Department of Biological Sciences, Tokyo Institute of Technology, Yokohama, Japan
| | - Kohei Kawaguchi
- Department of Biological Sciences, Tokyo Institute of Technology, Yokohama, Japan
| | - Yasushi Saeki
- Laboratory of Protein Metabolism, Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan
| | - Keiji Tanaka
- Laboratory of Protein Metabolism, Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan
| | - Thomas Wieland
- Institute of Human Genetics, Helmholtz Zentrum München, Neuherberg, Germany
| | - Elisabeth Graf
- Institute of Human Genetics, Helmholtz Zentrum München, Neuherberg, Germany
| | - Wolfgang Saeger
- Institut für Neuropathologie der Universität Hamburg, Hamburg, Germany
| | - Cristina L Ronchi
- Comprehensive Cancer Center Mainfranken, University of Würzburg, Würzburg, Germany
| | - Bruno Allolio
- 1] Department of Medicine I, Endocrine and Diabetes Unit, University Hospital, University of Würzburg, Würzburg, Germany. [2] Comprehensive Heart Failure Center, University of Würzburg, Würzburg, Germany
| | - Michael Buchfelder
- Neurochirurgische Klinik, Klinikum der Universität Erlangen, Erlangen, Germany
| | - Tim M Strom
- 1] Institute of Human Genetics, Helmholtz Zentrum München, Neuherberg, Germany. [2] Institute of Human Genetics, Technische Universität München, Munich, Germany
| | - Martin Fassnacht
- 1] Medizinische Klinik und Poliklinik IV, Ludwig-Maximilians-Universität München, Munich, Germany. [2] Department of Medicine I, Endocrine and Diabetes Unit, University Hospital, University of Würzburg, Würzburg, Germany. [3] Comprehensive Cancer Center Mainfranken, University of Würzburg, Würzburg, Germany
| | - Masayuki Komada
- Department of Biological Sciences, Tokyo Institute of Technology, Yokohama, Japan
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14
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Logue MW, Schu M, Vardarajan BN, Farrell J, Lunetta KL, Jun G, Baldwin CT, DeAngelis MM, Farrer LA. Search for age-related macular degeneration risk variants in Alzheimer disease genes and pathways. Neurobiol Aging 2014; 35:1510.e7-18. [PMID: 24439028 PMCID: PMC3961547 DOI: 10.1016/j.neurobiolaging.2013.12.007] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2013] [Revised: 11/22/2013] [Accepted: 12/12/2013] [Indexed: 12/17/2022]
Abstract
Several lines of inquiry point to overlapping molecular mechanisms between late-onset Alzheimer disease (AD) and age-related macular degeneration (AMD). We evaluated summarized results from large genome-wide association studies for AD and AMD to test the hypothesis that AD susceptibility loci are also associated with AMD. We observed association of both disorders with genes in a region of chromosome 7, including PILRA and ZCWPW1 (peak AMD SNP rs7792525, minor allele frequency [MAF] = 19%, odds ratio [OR] = 1.14, p = 2.34 × 10(-6)), and with ABCA7 (peak AMD SNP rs3752228, MAF = 0.054, OR = 1.22, p = 0.00012). Next, we evaluated association of AMD with genes in AD-related pathways identified by canonical pathway analysis of AD-associated genes. Significant associations were observed with multiple previously identified AMD risk loci and 2 novel genes: HGS (peak SNP rs8070488, MAF = 0.23, OR = 0.91, p = 7.52 × 10(-5)), which plays a role in the clathrin-mediated endocytosis signaling pathway, and TNF (peak SNP rs2071590, MAF = 0.34, OR = 0.89, p = 1.17 × 10(-5)), which is a member of the atherosclerosis signaling and the LXR/RXR activation pathways. Our results suggest that AMD and AD share genetic mechanisms.
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Affiliation(s)
- Mark W. Logue
- Department of Medicine (Biomedical Genetics), Boston University Schools of Medicine and Public Health, Boston, MA, 02118, USA.,Department of Biostatistics, Boston University Schools of Medicine and Public Health, Boston, MA, 02118, USA
| | - Matthew Schu
- Department of Medicine (Biomedical Genetics), Boston University Schools of Medicine and Public Health, Boston, MA, 02118, USA
| | - Badri N. Vardarajan
- Department of Medicine (Biomedical Genetics), Boston University Schools of Medicine and Public Health, Boston, MA, 02118, USA
| | - John Farrell
- Department of Medicine (Biomedical Genetics), Boston University Schools of Medicine and Public Health, Boston, MA, 02118, USA
| | - Kathryn L. Lunetta
- Department of Biostatistics, Boston University Schools of Medicine and Public Health, Boston, MA, 02118, USA
| | - Gyungah Jun
- Department of Medicine (Biomedical Genetics), Boston University Schools of Medicine and Public Health, Boston, MA, 02118, USA.,Department of Ophthalmology, Boston University Schools of Medicine and Public Health, Boston, MA, 02118, USA.,Department of Biostatistics, Boston University Schools of Medicine and Public Health, Boston, MA, 02118, USA
| | - Clinton T. Baldwin
- Department of Medicine (Biomedical Genetics), Boston University Schools of Medicine and Public Health, Boston, MA, 02118, USA
| | | | - Lindsay A. Farrer
- Department of Medicine (Biomedical Genetics), Boston University Schools of Medicine and Public Health, Boston, MA, 02118, USA.,Department of Neurology, Boston University Schools of Medicine and Public Health, Boston, MA, 02118, USA.,Department of Ophthalmology, Boston University Schools of Medicine and Public Health, Boston, MA, 02118, USA.,Department of Epidemiology, Boston University Schools of Medicine and Public Health, Boston, MA, 02118, USA.,Department of Biostatistics, Boston University Schools of Medicine and Public Health, Boston, MA, 02118, USA.,Corresponding Author: Dr. Lindsay A. Farrer, Boston University School of Medicine, Biomedical Genetics L320, 72 East Concord Street, Boston, MA 02118, Tel: (617) 638-5393, Fax: (617) 638-4275,
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15
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Kolb AR, Needham PG, Rothenberg C, Guerriero CJ, Welling PA, Brodsky JL. ESCRT regulates surface expression of the Kir2.1 potassium channel. Mol Biol Cell 2013; 25:276-89. [PMID: 24227888 PMCID: PMC3890348 DOI: 10.1091/mbc.e13-07-0394] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The Kir2.1 potassium channel is targeted by endoplasmic reticulum–associated degradation in yeast. To identify other Kir2.1 quality control factors, a novel yeast screen was performed. ESCRT components were among the strongest hits from the screen. Consistent with these data, ESCRT also regulates Kir2.1 stability in human cells. Protein quality control (PQC) is required to ensure cellular health. PQC is recognized for targeting the destruction of defective polypeptides, whereas regulated protein degradation mechanisms modulate the concentration of specific proteins in concert with physiological demands. For example, ion channel levels are physiologically regulated within tight limits, but a system-wide approach to define which degradative systems are involved is lacking. We focus on the Kir2.1 potassium channel because altered Kir2.1 levels lead to human disease and Kir2.1 restores growth on low-potassium medium in yeast mutated for endogenous potassium channels. Using this system, first we find that Kir2.1 is targeted for endoplasmic reticulum–associated degradation (ERAD). Next a synthetic gene array identifies nonessential genes that negatively regulate Kir2.1. The most prominent gene family that emerges from this effort encodes members of endosomal sorting complex required for transport (ESCRT). ERAD and ESCRT also mediate Kir2.1 degradation in human cells, with ESCRT playing a more prominent role. Thus multiple proteolytic pathways control Kir2.1 levels at the plasma membrane.
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Affiliation(s)
- Alexander R Kolb
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15261 Department of Physiology, University of Maryland School of Medicine, Baltimore, MD 21201
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16
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Korkut C, Li Y, Koles K, Brewer C, Ashley J, Yoshihara M, Budnik V. Regulation of postsynaptic retrograde signaling by presynaptic exosome release. Neuron 2013; 77:1039-46. [PMID: 23522040 DOI: 10.1016/j.neuron.2013.01.013] [Citation(s) in RCA: 182] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/04/2013] [Indexed: 12/18/2022]
Abstract
Retrograde signals from postsynaptic targets are critical during development and plasticity of synaptic connections. These signals serve to adjust the activity of presynaptic cells according to postsynaptic cell outputs and to maintain synaptic function within a dynamic range. Despite their importance, the mechanisms that trigger the release of retrograde signals and the role of presynaptic cells in this signaling event are unknown. Here we show that a retrograde signal mediated by Synaptotagmin 4 (Syt4) is transmitted to the postsynaptic cell through anterograde delivery of Syt4 via exosomes. Thus, by transferring an essential component of retrograde signaling through exosomes, presynaptic cells enable retrograde signaling.
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Affiliation(s)
- Ceren Korkut
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, MA 01605, USA
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17
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Distinct roles for β-arrestin2 and arrestin-domain-containing proteins in β2 adrenergic receptor trafficking. EMBO Rep 2012. [PMID: 23208550 DOI: 10.1038/embor.2012.187] [Citation(s) in RCA: 97] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
β-arrestin 1 and 2 (also known as arrestin 2 and 3) are homologous adaptor proteins that regulate seven-transmembrane receptor trafficking and signalling. Other proteins with predicted 'arrestin-like' structural domains but lacking sequence homology have been indicated to function like β-arrestin in receptor regulation. We demonstrate that β-arrestin2 is the primary adaptor that rapidly binds agonist-activated β(2) adrenergic receptors (β(2)ARs) and promotes clathrin-dependent internalization, E3 ligase Nedd4 recruitment and ubiquitin-dependent lysosomal degradation of the receptor. The arrestin-domain-containing (ARRDC) proteins 2, 3 and 4 are secondary adaptors recruited to internalized β(2)AR-Nedd4 complexes on endosomes and do not affect the adaptor roles of β-arrestin2. Rather, the role of ARRDC proteins is to traffic Nedd4-β(2)AR complexes to a subpopulation of early endosomes.
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18
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Dodson MW, Zhang T, Jiang C, Chen S, Guo M. Roles of the Drosophila LRRK2 homolog in Rab7-dependent lysosomal positioning. Hum Mol Genet 2011; 21:1350-63. [PMID: 22171073 DOI: 10.1093/hmg/ddr573] [Citation(s) in RCA: 169] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
LRRK2 (PARK8) is the most common genetic determinant of Parkinson's disease (PD), with dominant mutations in LRRK2 causing inherited PD and sequence variation at the LRRK2 locus associated with increased risk for sporadic PD. Although LRRK2 has been implicated in diverse cellular processes encompassing almost all cellular compartments, the precise functions of LRRK2 remain unclear. Here, we show that the Drosophila homolog of LRRK2 (Lrrk) localizes to the membranes of late endosomes and lysosomes, physically interacts with the crucial mediator of late endosomal transport Rab7 and negatively regulates rab7-dependent perinuclear localization of lysosomes. We also show that a mutant form of lrrk analogous to the pathogenic LRRK2(G2019S) allele behaves oppositely to wild-type lrrk in that it promotes rather than inhibits rab7-dependent perinuclear lysosome clustering, with these effects of mutant lrrk on lysosome position requiring both microtubules and dynein. These data suggest that LRRK2 normally functions in Rab7-dependent lysosomal positioning, and that this function is disrupted by the most common PD-causing LRRK2 mutation, linking endolysosomal dysfunction to the pathogenesis of LRRK2-mediated PD.
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Affiliation(s)
- Mark W Dodson
- Department of Neurology, The David Geffen School of Medicine, University of California, Los Angeles, CA 90095, USA
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19
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Kulkarni V, Khadilkar RJ, M. S. S, Inamdar MS. Asrij maintains the stem cell niche and controls differentiation during Drosophila lymph gland hematopoiesis. PLoS One 2011; 6:e27667. [PMID: 22110713 PMCID: PMC3215734 DOI: 10.1371/journal.pone.0027667] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2011] [Accepted: 10/21/2011] [Indexed: 02/02/2023] Open
Abstract
Several signaling pathways control blood cell (hemocyte) development in the Drosophila lymph gland. Mechanisms that modulate and integrate these signals are poorly understood. Here we report that mutation in a conserved endocytic protein Asrij affects signal transmission and causes aberrant lymph gland hematopoiesis. Mammalian Asrij (Ociad1) is expressed in stem cells of the blood vascular system and is implicated in several cancers. We found that Drosophila Asrij is a pan-hemocyte marker and localizes to a subset of endocytic vesicles. Loss of asrij causes hyperproliferation of lymph gland lobes coupled with increased hemocyte differentiation, thereby depleting the pool of quiescent hemocyte precursors. This co-relates with fewer Col+ cells in the hematopoietic stem cell niche of asrij mutants. Asrij null mutants also show excess specification of crystal cells that express the RUNX factor Lozenge (Lz), a target of Notch signaling. Asrij mutant lymph glands show increased N in sorting endosomes suggesting aberrant trafficking. In vitro assays also show impaired traffic of fluorescent probes in asrij null hemocytes. Taken together our data suggest a role for Asrij in causing increased Notch signaling thereby affecting hemocyte differentiation. Thus, conserved endocytic functions may control blood cell progenitor quiescence and differentiation.
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Affiliation(s)
- Vani Kulkarni
- Molecular Biology and Genetics Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore, India
| | - Rohan J. Khadilkar
- Molecular Biology and Genetics Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore, India
| | - Srivathsa M. S.
- Molecular Biology and Genetics Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore, India
| | - Maneesha S. Inamdar
- Molecular Biology and Genetics Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore, India
- * E-mail:
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20
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Miura S, Mishina Y. Hepatocyte growth factor-regulated tyrosine kinase substrate (Hgs) is involved in BMP signaling through phosphorylation of SMADS and TAK1 in early mouse embryo. Dev Dyn 2011; 240:2474-81. [PMID: 21953618 DOI: 10.1002/dvdy.22750] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/04/2011] [Indexed: 12/15/2022] Open
Abstract
Hepatocyte growth factor-regulated tyrosine kinase substrate that is encoded by Hgs promotes degradation of ubiquitinated signaling molecule in the early endosome. We previously reported that a targeted mutation in Hgs results in embryonic lethality soon after gastrulation in the mouse. Here, we report that downstream target genes for BMP signaling were highly down-regulated in the Hgs mutant embryos. We also showed that Hgs is required for phosphorylation of SMAD1/5/8 and TAK1/p38 to transduce BMP signaling. Furthermore, we found that HGS functions to localize TAK1 in early endosome for its activation. These results suggest that HGS is critical to localize TAK1 to early endosome for transducing BMP signaling for proper development. Our data revealed a new mechanism to modify BMP signaling by Hgs during early mouse development.
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Affiliation(s)
- Shigeto Miura
- Laboratory of Reproductive and Developmental Toxicology, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, USA
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21
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Santonico E, Belleudi F, Panni S, Torrisi MR, Cesareni G, Castagnoli L. Multiple modification and protein interaction signals drive the Ring finger protein 11 (RNF11) E3 ligase to the endosomal compartment. Oncogene 2010; 29:5604-18. [PMID: 20676133 DOI: 10.1038/onc.2010.294] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Ring finger protein 11 (RNF11) is a small RING E3-ligase overexpressed in numerous human prostate, colon and invasive breast cancers. Although functional studies have implicated RNF11 in a variety of biological processes, including signal transduction and apoptosis, the molecular mechanisms underlying its function are still poorly understood. In this study we show that RNF11 is a membrane-associated E3 ligase co-localizing with markers of both the early and the recycling endosomes. Several modification and protein interaction signals in the RNF11 sequence are shown to affect its compartmentalization. Membrane binding requires two acylation motifs driving the myristoylation of Gly2 and the S-palmitoylation of Cys4. Accordingly, genetic removal of the myristoylating signal results in diffuse staining, whereas an RNF11 protein mutated in the palmitoylation signal is retained in compartments of the early secretory pathway. However, amino-terminal fusion to green fluorescent protein of a 10-residue peptide containing both acylation signals re-localizes the chimera to the plasma membrane, but it is not sufficient to direct it to the recycling compartment suggesting that additional signals contribute to the correct localization. In addition, we show that membrane anchoring through acylation is necessary for RNF11 to be post-translationally modified by the addition of several ubiquitin moieties and that loss of acylation severely impairs the in vivo ubiquitination mediated by the HECT E3-ligases Itch and Nedd4. Finally, in cells transfected with RNF11 we observe a correlation between high RNF11 expression, as in tumor cells, and a swelling of the endosomal compartment suggesting a possible role of the dysregulation of the endosome compartment in tumorigenesis.
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Affiliation(s)
- E Santonico
- Department of Molecular Biology, Tor Vergata University of Rome, Rome, Italy.
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22
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Calore F, Genisset C, Casellato A, Rossato M, Codolo G, Esposti MD, Scorrano L, de Bernard M. Endosome-mitochondria juxtaposition during apoptosis induced by H. pylori VacA. Cell Death Differ 2010; 17:1707-16. [PMID: 20431599 DOI: 10.1038/cdd.2010.42] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The vacuolating cytotoxin (VacA) is an important virulence factor of Helicobacter pylori with pleiotropic effects on mammalian cells, including the ability to trigger mitochondria-dependent apoptosis. However, the mechanism by which VacA exerts its apoptotic function is unclear. Using a genetic approach, in this study we show that killing by VacA requires the proapoptotic Bcl-2 family members BAX and BAK at the mitochondrial level, but not adequate endoplasmic reticulum Ca²(+) levels, similarly controlled by BAX and BAK. A combination of subcellular fractionation and imaging shows that wild-type VacA, but not mutants in its channel-forming region, induces the accumulation of BAX on endosomes and endosome-mitochondria juxtaposition that precedes the retrieval of active BAX on mitochondria. It is noteworthy that in Bax- and Bak-deficient cells, VacA is unable to cause endosome-mitochondria juxtaposition and is not retrieved in mitochondria. Thus, VacA causes BAX/BAK-dependent juxtaposition of endosomes and mitochondria early in the process of cell death, revealing a new function for these proapoptotic proteins in the regulation of relative position of organelles.
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Affiliation(s)
- F Calore
- Venetian Institute of Molecular Medicine, Padova, Italy
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23
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Omelyanchuk LV, Pertseva JA, Burns SS, Chang LS. Evolution and origin of HRS, a protein interacting with Merlin, the Neurofibromatosis 2 gene product. GENE REGULATION AND SYSTEMS BIOLOGY 2009; 3:143-57. [PMID: 20054405 PMCID: PMC2796970 DOI: 10.4137/grsb.s3106] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Hepatocyte growth factor receptor tyrosine kinase substrate (HRS) is an endosomal protein required for trafficking receptor tyrosine kinases from the early endosome to the lysosome. HRS interacts with Merlin, the Neurofibromatosis 2 (NF2) gene product, and this interaction may be important for Merlin’s tumor suppressor activity. Understanding the evolution, origin, and structure of HRS may provide new insight into Merlin function. We show that HRS homologs are present across a wide range of Metazoa with the yeast Vps27 protein as their most distant ancestor. The phylogenetic tree of the HRS family coincides with species evolution and divergence, suggesting a unique function for HRS. Sequence alignment shows that various protein domains of HRS, including the VHS domain, the FYVE domain, the UIM domain, and the clathrin-binding domain, are conserved from yeast to multicellular organisms. The evolutionary transition from unicellular to multicellular organisms was accompanied by the appearance of a binding site for Merlin, which emerges in the early Metazoa after its separation from flatworms. In addition to the region responsible for growth suppression, the Merlin-binding and STAM-binding domains of HRS are conserved among multicellular organisms. The residue equivalent to tyrosine-377, which is phosphorylated in the human HRS protein, is highly conserved throughout the HRS family. Three additional conserved boxes lacking assigned functions are found in the HRS proteins of Metazoa. While boxes 1 and 3 may constitute the Eps-15-and Snx1-binding sites, respectively, box 2, containing the residue equivalent to tyrosine-377, is likely to be important for HRS phosphorylation. While several functional domains are conserved throughout the HRS family, the STAM-binding, Merlin-binding, and growth suppression domains evolved in the early Metazoa around the time the Merlin protein emerged. As these domains appear during the transition to multicellularity, their functional roles may be related to cell-cell interaction.
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Affiliation(s)
- Leonid V Omelyanchuk
- Institute of Cytology and Genetics, Russian Academy of Sciences, 10 Lavrent'ev Ave., 630090, Novosibirsk, Russia.
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24
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Abe M, Setoguchi Y, Tanaka T, Awano W, Takahashi K, Ueda R, Nakamura A, Goto S. Membrane protein location-dependent regulation by PI3K (III) and rabenosyn-5 in Drosophila wing cells. PLoS One 2009; 4:e7306. [PMID: 19798413 PMCID: PMC2749332 DOI: 10.1371/journal.pone.0007306] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2009] [Accepted: 09/11/2009] [Indexed: 11/19/2022] Open
Abstract
The class III phosphatidylinositol-3 kinase (PI3K (III)) regulates intracellular vesicular transport at multiple steps through the production of phosphatidylinositol-3-phosphate (PI(3)P). While the localization of proteins at distinct membrane domains are likely regulated in different ways, the roles of PI3K (III) and its effectors have not been extensively investigated in a polarized cell during tissue development. In this study, we examined in vivo functions of PI3K (III) and its effector candidate Rabenosyn-5 (Rbsn-5) in Drosophila wing primordial cells, which are polarized along the apical-basal axis. Knockdown of the PI3K (III) subunit Vps15 resulted in an accumulation of the apical junctional proteins DE-cadherin and Flamingo and also the basal membrane protein beta-integrin in intracellular vesicles. By contrast, knockdown of PI3K (III) increased lateral membrane-localized Fasciclin III (Fas III). Importantly, loss-of-function mutation of Rbsn-5 recapitulated the aberrant localization phenotypes of beta-integrin and Fas III, but not those of DE-cadherin and Flamingo. These results suggest that PI3K (III) differentially regulates localization of proteins at distinct membrane domains and that Rbsn-5 mediates only a part of the PI3K (III)-dependent processes.
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Affiliation(s)
- Masato Abe
- Glycobiology and Glycotechnology Research Group, Mitsubishi Kagaku Institute of Life Sciences, Tokyo, Japan
| | - Yuka Setoguchi
- Glycobiology and Glycotechnology Research Group, Mitsubishi Kagaku Institute of Life Sciences, Tokyo, Japan
| | - Tsubasa Tanaka
- Laboratory for Germline Development, RIKEN Center for Development Biology, Hyogo, Japan
| | - Wakae Awano
- Mutant Flies Laboratory, Mitsubishi Kagaku Institute of Life Sciences, Tokyo, Japan
| | - Kuniaki Takahashi
- Invertebrate Genetics Laboratory, National Institute of Genetics, Shizuoka, Japan
| | - Ryu Ueda
- Invertebrate Genetics Laboratory, National Institute of Genetics, Shizuoka, Japan
| | - Akira Nakamura
- Laboratory for Germline Development, RIKEN Center for Development Biology, Hyogo, Japan
| | - Satoshi Goto
- Glycobiology and Glycotechnology Research Group, Mitsubishi Kagaku Institute of Life Sciences, Tokyo, Japan
- Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency, Saitama, Japan
- * E-mail:
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25
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Nakada-Tsukui K, Okada H, Mitra BN, Nozaki T. Phosphatidylinositol-phosphates mediate cytoskeletal reorganization during phagocytosis via a unique modular protein consisting of RhoGEF/DH and FYVE domains in the parasitic protozoonEntamoeba histolytica. Cell Microbiol 2009; 11:1471-91. [DOI: 10.1111/j.1462-5822.2009.01341.x] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
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26
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Belleudi F, Leone L, Maggio M, Torrisi MR. Hrs regulates the endocytic sorting of the fibroblast growth factor receptor 2b. Exp Cell Res 2009; 315:2181-91. [DOI: 10.1016/j.yexcr.2009.03.022] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2009] [Revised: 03/27/2009] [Accepted: 03/29/2009] [Indexed: 11/28/2022]
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Truschel ST, Simoes S, Setty SRG, Harper DC, Tenza D, Thomas PC, Herman KE, Sackett SD, Cowan DC, Theos AC, Raposo G, Marks MS. ESCRT-I function is required for Tyrp1 transport from early endosomes to the melanosome limiting membrane. Traffic 2009; 10:1318-36. [PMID: 19624486 DOI: 10.1111/j.1600-0854.2009.00955.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Melanosomes are lysosome-related organelles that coexist with lysosomes within melanocytes. The pathways by which melanosomal proteins are diverted from endocytic organelles toward melanosomes are incompletely defined. In melanocytes from mouse models of Hermansky-Pudlak syndrome that lack BLOC-1, melanosomal proteins such as tyrosinase-related protein 1 (Tyrp1) accumulate in early endosomes. Whether this accumulation represents an anomalous pathway or an arrested normal intermediate in melanosome protein trafficking is not clear. Here, we show that early endosomes are requisite intermediates in the trafficking of Tyrp1 from the Golgi to late stage melanosomes in normal melanocytic cells. Kinetic analyses show that very little newly synthesized Tyrp1 traverses the cell surface and that internalized Tyrp1 is inefficiently sorted to melanosomes. Nevertheless, nearly all Tyrp1 traverse early endosomes since it becomes trapped within enlarged, modified endosomes upon overexpression of Hrs. Although Tyrp1 localization is not affected by Hrs depletion, depletion of the ESCRT-I component, Tsg101, or inhibition of ESCRT function by dominant-negative approaches results in a dramatic redistribution of Tyrp1 to aberrant endosomal membranes that are largely distinct from those harboring traditional ESCRT-dependent, ubiquitylated cargoes such as MART-1. The lysosomal protein content of some of these membranes and the lack of Tyrp1 recycling to the plasma membrane in Tsg101-depleted cells suggests that ESCRT-I functions downstream of BLOC-1. Our data delineate a novel pathway for Tyrp1 trafficking and illustrate a requirement for ESCRT-I function in controlling protein sorting from vacuolar endosomes to the limiting membrane of a lysosome-related organelle.
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Affiliation(s)
- Steven T Truschel
- Department of Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
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28
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Huang SH, Zhao L, Sun ZP, Li XZ, Geng Z, Zhang KD, Chao MV, Chen ZY. Essential role of Hrs in endocytic recycling of full-length TrkB receptor but not its isoform TrkB.T1. J Biol Chem 2009; 284:15126-36. [PMID: 19351881 DOI: 10.1074/jbc.m809763200] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Brain-derived neurotrophic factor (BDNF) signaling through its receptor, TrkB, modulates survival, differentiation, and synaptic activity of neurons. Both full-length TrkB (TrkB-FL) and its isoform T1 (TrkB.T1) receptors are expressed in neurons; however, whether they follow the same endocytic pathway after BDNF treatment is not known. In this study we report that TrkB-FL and TrkB.T1 receptors traverse divergent endocytic pathways after binding to BDNF. We provide evidence that in neurons TrkB.T1 receptors predominantly recycle back to the cell surface by a "default" mechanism. However, endocytosed TrkB-FL receptors recycle to a lesser extent in a hepatocyte growth factor-regulated tyrosine kinase substrate (Hrs)-dependent manner which relies on its tyrosine kinase activity. The distinct role of Hrs in promoting recycling of internalized TrkB-FL receptors is independent of its ubiquitin-interacting motif. Moreover, Hrs-sensitive TrkB-FL recycling plays a role in BDNF-induced prolonged mitogen-activated protein kinase (MAPK) activation. These observations provide evidence for differential postendocytic sorting of TrkB-FL and TrkB.T1 receptors to alternate intracellular pathways.
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Affiliation(s)
- Shu-Hong Huang
- Department of Neurobiology, Key Laboratory of Medical Neurobiology, School of Medicine, Jinan, Shandong 250012, China
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29
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MacAskill AF, Brickley K, Stephenson FA, Kittler JT. GTPase dependent recruitment of Grif-1 by Miro1 regulates mitochondrial trafficking in hippocampal neurons. Mol Cell Neurosci 2009; 40:301-12. [DOI: 10.1016/j.mcn.2008.10.016] [Citation(s) in RCA: 130] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2008] [Revised: 10/28/2008] [Accepted: 10/31/2008] [Indexed: 11/16/2022] Open
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30
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Abstract
Huntington disease (HD) is caused by a polyglutamine expansion in the protein huntingtin (Htt). Several studies suggest that Htt and huntingtin associated protein 1 (HAP1) participate in intracellular trafficking and that polyglutamine expansion affects vesicular transport. Understanding the function of HAP1 and its related proteins could help elucidate the pathogenesis of HD. The present review focuses on HAP1, which has proved to be involved in intracellular trafficking. Unlike huntingtin, which is expressed ubiquitously throughout the brain and body, HAP1 is enriched in neurons, suggesting that its dysfunction could contribute to the selective neuropathology in HD. We discuss recent evidence for the involvement of HAP1 and its binding proteins in potential functions.
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Affiliation(s)
- Linda Lin-yan Wu
- Department of Human Physiology, Flinders University, Adelaide, South Australia, Australia
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31
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Aoh QL, Castle AM, Hubbard CH, Katsumata O, Castle JD. SCAMP3 negatively regulates epidermal growth factor receptor degradation and promotes receptor recycling. Mol Biol Cell 2009; 20:1816-32. [PMID: 19158374 DOI: 10.1091/mbc.e08-09-0894] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
The epidermal growth factor receptor (EGFR) is targeted for lysosomal degradation by ubiquitin-mediated interactions with the ESCRTs (endosomal-sorting complexes required for transport) in multivesicular bodies (MVBs). We show that secretory carrier membrane protein, SCAMP3, localizes in part to early endosomes and negatively regulates EGFR degradation through processes that involve its ubiquitylation and interactions with ESCRTs. SCAMP3 is multimonoubiquitylated and is able to associate with Nedd4 HECT ubiquitin ligases and the ESCRT-I subunit Tsg101 via its PY and PSAP motifs, respectively. SCAMP3 also associates with the ESCRT-0 subunit Hrs. Depletion of SCAMP3 in HeLa cells by inhibitory RNA accelerated degradation of EGFR and EGF while inhibiting recycling. Conversely, overexpression enhanced EGFR recycling unless ubiquitylatable lysines, PY or PSAP motifs in SCAMP3 were mutated. Notably, dual depletions of SCAMP3 and ESCRT subunits suggest that SCAMP3 has a distinct function in parallel with the ESCRTs that regulates receptor degradation. This function may affect trafficking of receptors from prelysosomal compartments as SCAMP3 depletion appeared to sustain the incidence of EGFR-containing MVBs detected by immunoelectron microscopy. Together, our results suggest that SCAMP3, its modification with ubiquitin, and its interactions with ESCRTs coordinately regulate endosomal pathways and affect the efficiency of receptor down-regulation.
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Affiliation(s)
- Quyen L Aoh
- Department of Cell Biology, University of Virginia, Charlottesville, VA 22908, USA
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32
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Mukai A, Mizuno E, Kobayashi K, Matsumoto M, Nakayama KI, Kitamura N, Komada M. Dynamic regulation of ubiquitylation and deubiquitylation at the central spindle during cytokinesis. J Cell Sci 2008; 121:1325-33. [PMID: 18388320 DOI: 10.1242/jcs.027417] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
During cytokinesis, the central spindle, a bundle of interdigitated anti-parallel microtubules between separating chromosomes, recruits various cytokinetic regulator proteins to the cleavage region. Here, we show that the level of protein ubiquitylation is strikingly and transiently elevated in Aurora B kinase-positive double-band regions of the central spindle during cytokinesis. Two deubiquitylating enzymes UBPY and AMSH, which act on endosomes in interphase, were also recruited to the cleavage region. Whereas UBPY was detected only in the final stage of cytokinesis at the midbody, AMSH localized to a ring structure surrounding the mitotic kinesin MKLP1-positive region of the central spindle and midbody throughout cytokinesis. Depletion of cellular UBPY or AMSH led to defects in cytokinesis. VAMP8, a v-SNARE required for vesicle fusion in cytokinesis, localized to the central spindle region positive for ubiquitylated proteins, and underwent ubiquitylation and deubiquitylation by both UBPY and AMSH. Our results thus implicate the ubiquitylation/deubiquitylation of proteins including VAMP8 in cytokinesis.
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Affiliation(s)
- Akiko Mukai
- Department of Biological Sciences, Tokyo Institute of Technology, 4259-B-16 Nagatsuta, Yokohama 226-8501, Japan
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33
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Kanwar R, Fortini ME. The big brain aquaporin is required for endosome maturation and notch receptor trafficking. Cell 2008; 133:852-63. [PMID: 18510929 DOI: 10.1016/j.cell.2008.04.038] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2007] [Revised: 03/10/2008] [Accepted: 04/29/2008] [Indexed: 11/26/2022]
Abstract
Activity of the big brain (bib) gene influences Notch signaling during Drosophila nervous system development. We demonstrate that Bib, which belongs to the aquaporin family of channel proteins, is required for endosome maturation in Drosophila epithelial cells. In the absence of Bib, early endosomes arrest and form abnormal clusters, and cells exhibit reduced acidification of endocytic trafficking organelles. Bib acts downstream of Hrs in early endosome morphogenesis and regulates biogenesis of endocytic compartments prior to the formation of Rab7-containing late endosomes. Abnormal endosome morphology caused by loss of Bib is accompanied by overaccumulation of Notch, Delta, and other signaling molecules as well as reduced intracellular trafficking of Notch to nuclei. Analysis of several endosomal trafficking mutants reveals a correlation between endosomal acidification and levels of Notch signaling. Our findings reveal an unprecedented role for an aquaporin in endosome maturation, trafficking, and acidification.
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Affiliation(s)
- Ritu Kanwar
- Cancer and Developmental Biology Laboratory, National Cancer Institute, 1050 Boyles Street, Building 560, Room 22-12, Frederick, MD 21701, USA
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34
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Yanagida-Ishizaki Y, Takei T, Ishizaki R, Imakagura H, Takahashi S, Shin HW, Katoh Y, Nakayama K. Recruitment of Tom1L1/Srcasm to endosomes and the midbody by Tsg101. Cell Struct Funct 2008; 33:91-100. [PMID: 18367816 DOI: 10.1247/csf.07037] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Tom1 (target of Myb 1) and its related proteins (Tom1L1/Srcasm and Tom1L2) constitute a protein family, which share an N-terminal VHS (Vps27, Hrs and STAM) domain and a following GAT (GGA and Tom1) domain. Tom1L1 has potential binding sequences for Tsg101, which is one of key regulators of the multivesicular body (MVB) formation. To obtain a clue to the role of Tom1L1 in the MVB formation, we have characterized the Tom1L1-Tsg101 interaction. We have found that not only the PTAP sequence in the GAT domain but also the PSAP sequence in the C-terminal region of Tom1L1 is responsible for its interaction with the UEV domain of Tsg101 and competes with the HIV-1 Gag protein for the Tsg101 interaction. Furthermore, we show that, by means of Tsg101, Tom1L1 associates with the midbody during cytokinesis as well as endosomes. Taken into account the topological equivalency among the events of the MVB formation, viral egress from the cell, and cytokinesis, the data obtained here suggest that Tom1L1 is implicated in these three distinct cellular processes.
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35
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Laifenfeld D, Patzek LJ, McPhie DL, Chen Y, Levites Y, Cataldo AM, Neve RL. Rab5 mediates an amyloid precursor protein signaling pathway that leads to apoptosis. J Neurosci 2007; 27:7141-53. [PMID: 17611268 PMCID: PMC6794581 DOI: 10.1523/jneurosci.4599-06.2007] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Alzheimer's disease (AD) involves activation of apoptotic pathways that may be regulated through signaling cascades initiated by the amyloid precursor protein (APP). Enlarged endosomes have been observed in postmortem AD brains at very early stages of the disease. We show here that exogenous expression of a familial AD (FAD) mutant of APP or of the APP binding protein APP-BP1 in neurons causes enlargement of early endosomes, increased receptor-mediated endocytosis via a pathway dependent on APP-BP1 binding to APP, and apoptosis. Levels of both APP-BP1 and Rab5 are elevated in early endosomes in cortical embryonic neurons expressing APP(V642I) or APP-BP1, in cultured skin fibroblast cells from Down syndrome subjects, and in postmortem hippocampal tissue of individuals with AD. Indeed, Rab5 was found to bind specifically to APP-BP1, between amino acids 443 and 479. Inhibition of Rab5 or dynamin activity, but not of Eps15 (epidermal growth factor receptor pathway substrate 15) activity, rescued neurons from apoptosis induced by either APP(V642I) or APP-BP1, without affecting levels of intracellular or secreted amyloid-beta (Abeta). Induction of Rab5 activity via expression of a constitutively active mutant led to an increase in neuronal apoptosis more than twice that attributable to induction of endosome enlargement via a Rab5-independent mechanism, regardless of Abeta production. Together, these findings suggest that Rab5 activation via an APP/APP-BP1-initiated signaling pathway mediates neuronal apoptosis caused by FAD mutants of APP and that, within this pathway, Rab5 has a specific role in signaling that is distinct from, although not independent of, its role in trafficking.
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Affiliation(s)
- Daphna Laifenfeld
- Department of Psychiatry, Harvard Medical School, McLean Hospital, Belmont, Massachusetts 02478
| | - Lucas J. Patzek
- Department of Psychiatry, Harvard Medical School, McLean Hospital, Belmont, Massachusetts 02478
| | - Donna L. McPhie
- Department of Psychiatry, Harvard Medical School, McLean Hospital, Belmont, Massachusetts 02478
| | - Yuzhi Chen
- Department of Geriatrics, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205, and
| | - Yona Levites
- Department of Neuroscience, Mayo Clinic College of Medicine, Jacksonville, Florida 32224
| | - Anne M. Cataldo
- Department of Psychiatry, Harvard Medical School, McLean Hospital, Belmont, Massachusetts 02478
| | - Rachael L. Neve
- Department of Psychiatry, Harvard Medical School, McLean Hospital, Belmont, Massachusetts 02478
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36
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Tamai K, Tanaka N, Nara A, Yamamoto A, Nakagawa I, Yoshimori T, Ueno Y, Shimosegawa T, Sugamura K. Role of Hrs in maturation of autophagosomes in mammalian cells. Biochem Biophys Res Commun 2007; 360:721-7. [PMID: 17624298 DOI: 10.1016/j.bbrc.2007.06.105] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2007] [Accepted: 06/16/2007] [Indexed: 12/30/2022]
Abstract
Autophagy is an evolutionarily conserved system responsible for the degradation of cellular components and contributes to the increasing of amino acid pool, organelle turnover, and elimination of intracellular bacteria. The molecular process of autophagy is still unclear. Here we demonstrate that Hrs, a master regulator in endosomal protein sorting, plays critical roles for the autophagic degradation of non-specific proteins and Streptococcus pyogenes. We found that Hrs containing FYVE domain is localized to autophagosomes. Hrs depletion resulted in a significant decrease in the number of mature autophagosomes (autophagolysosomes) detected by the co-localization of autophagosome marker LC3 and lysosome marker LAMP-1. In contrast, formation of the primary autophagosome, detected by LC3 immunoblotting and lysosomal degradation of non-specific proteins, were not significantly altered by Hrs depletion. Based on these results, we propose a novel function of Hrs, as a crucial player in the maturation of autophagosomes.
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Affiliation(s)
- Keiichi Tamai
- Department of Microbiology and Immunology, Tohoku University Graduate School of Medicine, 2-1 Seiryo-machi, Aoba-ku, Sendai 980-8575, Japan
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37
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Abstract
Cilia are endowed with membrane receptors, channels, and signaling components whose localization and function must be tightly controlled. In primary cilia of mammalian kidney epithelia and sensory cilia of Caenorhabditis elegans neurons, polycystin-1 (PC1) and transient receptor polycystin-2 channel (TRPP2 or PC2), function together as a mechanosensory receptor-channel complex. Despite the importance of the polycystins in sensory transduction, the mechanisms that regulate polycystin activity and localization, or ciliary membrane receptors in general, remain poorly understood. We demonstrate that signal transduction adaptor molecule STAM-1A interacts with C. elegans LOV-1 (PC1), and that STAM functions with hepatocyte growth factor-regulated tyrosine kinase substrate (Hrs) on early endosomes to direct the LOV-1-PKD-2 complex for lysosomal degradation. In a stam-1 mutant, both LOV-1 and PKD-2 improperly accumulate at the ciliary base. Conversely, overexpression of STAM or Hrs promotes the removal of PKD-2 from cilia, culminating in sensory behavioral defects. These data reveal that the STAM-Hrs complex, which down-regulates ligand-activated growth factor receptors from the cell surface of yeast and mammalian cells, also regulates the localization and signaling of a ciliary PC1 receptor-TRPP2 complex.
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Affiliation(s)
- Jinghua Hu
- Division of Pharmaceutical Sciences, School of Pharmacy, University of Wisconsin, Madison, WI 53705, USA
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38
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Fritzius T, Frey AD, Schweneker M, Mayer D, Moelling K. WD-repeat-propeller-FYVE protein, ProF, binds VAMP2 and protein kinase Czeta. FEBS J 2007; 274:1552-66. [PMID: 17313651 DOI: 10.1111/j.1742-4658.2007.05702.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We have recently identified a protein, consisting of seven WD repeats, presumably forming a beta-propeller, and a domain identified in Fab1p, YOTB, VAC1p, and EEA1 (FYVE) domain, ProF. The FYVE domain targets the protein to vesicular membranes, while the WD repeats allow binding of the activated kinases Akt and protein kinase (PK)Czeta. Here, we describe the vesicle-associated membrane protein 2 (VAMP2) as interaction partner of ProF. The interaction is demonstrated with overexpressed and endogenous proteins in mammalian cells. ProF and VAMP2 partially colocalize on vesicular structures with PKCzeta and the proteins form a ternary complex. VAMP2 can be phosphorylated by activated PKCzeta in vitro and the presence of ProF increases the PKCzeta-dependent phosphorylation of VAMP2 in vitro. ProF is an adaptor protein that brings together a kinase with its substrate. VAMP2 is known to regulate docking and fusion of vesicles and to play a role in targeting vesicles to the plasma membrane. The complex may be involved in vesicle cycling in various secretory pathways.
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Affiliation(s)
- Thorsten Fritzius
- Institute of Medical Virology, University of Zurich, Gloriastrasse 30, Zurich CH-8006, Switzerland
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39
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Ren J, Kee Y, Huibregtse JM, Piper RC. Hse1, a component of the yeast Hrs-STAM ubiquitin-sorting complex, associates with ubiquitin peptidases and a ligase to control sorting efficiency into multivesicular bodies. Mol Biol Cell 2007; 18:324-35. [PMID: 17079730 PMCID: PMC1751313 DOI: 10.1091/mbc.e06-06-0557] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2006] [Revised: 10/16/2006] [Accepted: 10/19/2006] [Indexed: 11/11/2022] Open
Abstract
Ubiquitinated integral membrane proteins are delivered to the interior of the lysosome/vacuole for degradation. This process relies on specific ubiquitination of potential cargo and recognition of that Ub-cargo by sorting receptors at multiple compartments. We show that the endosomal Hse1-Vps27 sorting receptor binds to ubiquitin peptidases and the ubiquitin ligase Rsp5. Hse1 is linked to Rsp5 directly via a PY element within its C-terminus and through a novel protein Hua1, which recruits a complex of Rsp5, Rup1, and Ubp2. The SH3 domain of Hse1 also binds to the deubiquitinating protein Ubp7. Functional analysis shows that when both modes of Rsp5 association with Hse1 are altered, sorting of cargo that requires efficient ubiquitination for entry into the MVB is blocked, whereas sorting of cargo containing an in-frame addition of ubiquitin is normal. Further deletion of Ubp7 restores sorting of cargo when the Rsp5:Hse1 interaction is compromised suggesting that both ubiquitin ligases and peptidases associate with the Hse1-Vps27 sorting complex to control the ubiquitination status and sorting efficiency of cargo proteins. Additionally, we find that disruption of UBP2 and RUP1 inhibits MVB sorting of some cargos suggesting that Rsp5 requires association with Ubp2 to properly ubiquitinate cargo for efficient MVB sorting.
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Affiliation(s)
- Jihui Ren
- *Department of Physiology and Biophysics, University of Iowa, Iowa City, IA 52242; and
| | - Younghoon Kee
- Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, TX 78712
| | - Jon M. Huibregtse
- Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, TX 78712
| | - Robert C. Piper
- *Department of Physiology and Biophysics, University of Iowa, Iowa City, IA 52242; and
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40
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Bouamr F, Houck-Loomis BR, De Los Santos M, Casaday RJ, Johnson MC, Goff SP. The C-terminal portion of the Hrs protein interacts with Tsg101 and interferes with human immunodeficiency virus type 1 Gag particle production. J Virol 2006; 81:2909-22. [PMID: 17182674 PMCID: PMC1865988 DOI: 10.1128/jvi.01413-06] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
The human immunodeficiency virus type 1 (HIV-1) Gag protein recruits Tsg101 to facilitate HIV-1 particle budding and release. In uninfected cells, the Hrs protein recruits the ESCRT-I complex to the endosome, also through an interaction with Tsg101, to promote the sorting of host proteins into endosomal vesicles and multivesicular bodies. Here, we show that the overexpression of the C-terminal fragment of Hrs (residues 391 to 777) or Hrs mutants lacking either the N-terminal FYVE domain (mutant dFYVE) or the PSAP (residues 348 to 351) motif (mutant ASAA) all efficiently inhibit HIV-1 Gag particle production. Expression of the dFYVE or ASAA mutants of Hrs had no effect on the release of Moloney murine leukemia virus. Coimmunoprecipitation analysis showed that the expression of Hrs mutant dFYVE or ASAA significantly reduced or abolished the HIV-1 Gag-Tsg101 interaction. Yeast-two hybrid assays were used to identify two new and independent Tsg101 binding sites, one in the Hrs coiled-coil domain and one in the proline/glutamic acid-rich domain. Scanning electron microscopy of HeLa cells expressing HIV-1 Gag and the Hrs ASAA mutant showed viral particles arrested in "lump-like" structures that remained attached to the cell surface. Together, these data indicate that fragments of Hrs containing the C-terminal portion of the protein can potently inhibit HIV-1 particle release by efficiently sequestering Tsg101 away from the Gag polyprotein.
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Affiliation(s)
- Fadila Bouamr
- Howard Hughes Medical Institute, Department of Biochemistry and Molecular Biophysics, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA
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41
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Stern KA, Visser Smit GD, Place TL, Winistorfer S, Piper RC, Lill NL. Epidermal growth factor receptor fate is controlled by Hrs tyrosine phosphorylation sites that regulate Hrs degradation. Mol Cell Biol 2006; 27:888-98. [PMID: 17101784 PMCID: PMC1800687 DOI: 10.1128/mcb.02356-05] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Hepatocyte growth factor-regulated tyrosine kinase substrate (Hrs) is an endosomal protein essential for the efficient sorting of activated growth factor receptors into the lysosomal degradation pathway. Hrs undergoes ligand-induced tyrosine phosphorylation on residues Y329 and Y334 downstream of epidermal growth factor receptor (EGFR) activation. It has been difficult to investigate the functional roles of phosphoHrs, as only a small proportion of the cellular Hrs pool is detectably phosphorylated. Using an HEK 293 model system, we found that ectopic expression of the protein Cbl enhances Hrs ubiquitination and increases Hrs phosphorylation following cell stimulation with EGF. We exploited Cbl's expansion of the phosphoHrs pool to determine whether Hrs tyrosine phosphorylation controls EGFR fate. In structure-function studies of Cbl and EGFR mutants, the level of Hrs phosphorylation and rapidity of apparent Hrs dephosphorylation correlated directly with EGFR degradation. Differential expression of wild-type versus Y329,334F mutant Hrs in Hrs-depleted cells revealed that one or both tyrosines regulate ligand-dependent Hrs degradation, as well as EGFR degradation. By modulating Hrs ubiquitination, phosphorylation, and protein levels, Cbl may control the composition of the endosomal sorting machinery and its ability to target EGFR for lysosomal degradation.
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Affiliation(s)
- Kathryn A Stern
- Department of Pharmacology, Roy J. and Lucille A Carver College of Medicine, University of Iowa, 51 Newton Road, Iowa City, IA 52242, USA
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42
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Childress JL, Acar M, Tao C, Halder G. Lethal giant discs, a novel C2-domain protein, restricts notch activation during endocytosis. Curr Biol 2006; 16:2228-33. [PMID: 17088062 PMCID: PMC2683616 DOI: 10.1016/j.cub.2006.09.031] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2006] [Revised: 09/07/2006] [Accepted: 09/14/2006] [Indexed: 11/27/2022]
Abstract
The Notch signaling pathway plays a central role in animal growth and patterning, and its deregulation leads to many human diseases, including cancer. Mutations in the tumor suppressor lethal giant discs (lgd) induce strong Notch activation and hyperplastic overgrowth of Drosophila imaginal discs. However, the gene that encodes Lgd and its function in the Notch pathway have not yet been identified. Here, we report that Lgd is a novel, conserved C2-domain protein that regulates Notch receptor trafficking. Notch accumulates on early endosomes in lgd mutant cells and signals in a ligand-independent manner. This phenotype is similar to that seen when cells lose endosomal-pathway components such as Erupted and Vps25. Interestingly, Notch activation in lgd mutant cells requires the early endosomal component Hrs, indicating that Hrs is epistatic to Lgd. These data suggest that Lgd affects Notch trafficking between the actions of Hrs and the late endosomal component Vps25. Taken together, our data identify Lgd as a novel tumor-suppressor protein that regulates Notch signaling by targeting Notch for degradation or recycling.
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Affiliation(s)
- Jennifer L. Childress
- Department of Biochemistry and Molecular Biology, M.D. Anderson Cancer Center, University of Texas, Houston, Texas 77030 USA
- Program in Genes and Development, M.D. Anderson Cancer Center, University of Texas, Houston, Texas 77030 USA
| | - Melih Acar
- Program in Developmental Biology, Baylor College of Medicine, Houston, TX 77030 USA
| | - Chunyao Tao
- Department of Biochemistry and Molecular Biology, M.D. Anderson Cancer Center, University of Texas, Houston, Texas 77030 USA
| | - Georg Halder
- Department of Biochemistry and Molecular Biology, M.D. Anderson Cancer Center, University of Texas, Houston, Texas 77030 USA
- Program in Genes and Development, M.D. Anderson Cancer Center, University of Texas, Houston, Texas 77030 USA
- Program in Developmental Biology, Baylor College of Medicine, Houston, TX 77030 USA
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43
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Kirk E, Chin LS, Li L. GRIF1 binds Hrs and is a new regulator of endosomal trafficking. J Cell Sci 2006; 119:4689-701. [PMID: 17062640 DOI: 10.1242/jcs.03249] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Endosomal sorting of internalized cell surface receptors to the lysosomal pathway plays a crucial role in the control of cell signaling and function. Here we report the identification of GABA(A) receptor interacting factor-1 (GRIF1), a recently discovered protein of unknown function, as a new regulator of endosome-to-lysosome trafficking. Yeast two-hybrid screen and co-immunoprecipitation analysis reveal that GRIF1 interacts with hepatocyte growth factor-regulated tyrosine kinase substrate (Hrs), an essential component of the endosomal sorting machinery. We have mapped the binding domains of GRIF1 and Hrs that mediate their association and shown the colocalization of GRIF1 with Hrs on early endosomes. Like Hrs, both overexpression and siRNA-mediated depletion of GRIF1 inhibit the degradation of internalized epidermal growth factor receptors and block the trafficking of the receptors from early endosomes to the lysosomal pathway. Our results indicate, for the first time, a functional role for GRIF1 in the regulation of endosomal trafficking. Interestingly, overexpression of full-length GRIF1, but not the Hrs- or kinesin-interacting GRIF1 deletion mutants, causes a perinuclear clustering of early endosomes. Our findings suggest that GRIF1 may also participate in microtubule-based transport of early endosomes by acting as an adaptor linking Hrs-containing endosomes to kinesin.
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Affiliation(s)
- Elizabeth Kirk
- Department of Pharmacology, Emory University School of Medicine, Atlanta, GA 30322, USA
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Welsch S, Habermann A, Jäger S, Müller B, Krijnse-Locker J, Kräusslich HG. Ultrastructural analysis of ESCRT proteins suggests a role for endosome-associated tubular-vesicular membranes in ESCRT function. Traffic 2006; 7:1551-66. [PMID: 17014699 DOI: 10.1111/j.1600-0854.2006.00489.x] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The endosomal sorting complex required for transport (ESCRT) is thought to support the formation of intralumenal vesicles of multivesicular bodies (MVBs). The ESCRT is also required for the budding of HIV and has been proposed to be recruited to the HIV-budding site, the plasma membrane of T cells and MVBs in macrophages. Despite increasing data on the function of ESCRT, the ultrastructural localization of its components has not been determined. We therefore localized four proteins of the ESCRT machinery in human T cells and macrophages by quantitative electron microscopy. All the proteins were found throughout the endocytic pathway, including the plasma membrane, with only around 10 and 3% of the total labeling in the cytoplasm and on the MVBs, respectively. The majority of the labeling (45%) was unexpectedly found on tubular-vesicular endosomal membranes rather than on endosomes themselves. The ESCRT labeling was twice as concentrated on early and late endosomes/lysosomes in macrophages compared with that in T cells, where it was twice more abundant at the plasma membrane. The ESCRT proteins were not redistributed on HIV infection, suggesting that the amount of ESCRT proteins located at the budding site suffices for HIV release. These results represent the first systematic ultrastructural localization of ESCRT and provide insights into its role in uninfected and HIV-infected cells.
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Affiliation(s)
- Sonja Welsch
- Department of Virology, Heidelberg University, Im Neuenheimer Feld 324, 69120 Heidelberg, Germany
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Nakamura M, Tanaka N, Kitamura N, Komada M. Clathrin anchors deubiquitinating enzymes, AMSH and AMSH-like protein, on early endosomes. Genes Cells 2006; 11:593-606. [PMID: 16716190 DOI: 10.1111/j.1365-2443.2006.00963.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Endosomal sorting of ubiquitinated membrane proteins for trafficking to lysosomes is executed by a complex of two ubiquitin-binding proteins, Hrs and STAM, that localizes on a microdomain of early endosomes with a flat clathrin coat. AMSH is a deubiquitinating enzyme that interacts with STAM and is implicated in the down-regulation of epidermal growth factor receptor. AMSH has a close homolog, AMSH-like protein (AMSH-LP). Here we show that AMSH-LP is also a deubiquitinating enzyme that acts on early endosomes. We further show that AMSH and AMSH-LP bind to the terminal domain of clathrin heavy chain via a novel clathrin-binding site conserved between these proteins. Exogenously expressed AMSH and AMSH-LP co-localized with clathrin on early endosomes. However, deletion of the clathrin-binding site from the proteins, as well as RNA interference-mediated depletion of clathrin heavy chain, resulted in a failure of AMSH and AMSH-LP to localize on endosomes. In contrast, a mutant of AMSH that lacks the ability to bind STAM localized normally on endosomes. We suggest that AMSH and AMSH-LP are anchored on the early endosomal membrane via interaction with the clathrin coat.
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Affiliation(s)
- Michihiko Nakamura
- Department of Biological Sciences, Tokyo Institute of Technology, Yokohama 226-8501, Japan
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Mizuno E, Kobayashi K, Yamamoto A, Kitamura N, Komada M. A deubiquitinating enzyme UBPY regulates the level of protein ubiquitination on endosomes. Traffic 2006; 7:1017-31. [PMID: 16771824 DOI: 10.1111/j.1600-0854.2006.00452.x] [Citation(s) in RCA: 93] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Monoubiquitination of endocytosed cell surface receptors serves as a sorting signal for their trafficking from endosomes to lysosomes. The sorting of ubiquitinated proteins is executed by concerted actions of class E vacuolar protein sorting (Vps) proteins. Some proteins in the sorting machinery undergo monoubiquitination, suggesting that their functions are also regulated by ubiquitination. The Hrs-STAM complex, a class E Vps protein complex essential for the initial step of the sorting pathway, binds two deubiquitinating enzymes, UBPY and AMSH. Here we examined the effects of inactivating UBPY on protein ubiquitination at endosomes. Overexpression of a catalytically inactive UBPY mutant or depletion of UBPY by RNA interference resulted in the accumulation of ubiquitinated proteins on morphologically aberrant endosomes. Electron microscopy showed that they are aggregates of multivesicular endosomes. Among the sorting machinery proteins that undergo ubiquitination, Eps15 was monoubiquitinated at an elevated level in UBPY-inactivated cells. UBPY also deubiquitinated Eps15 in vitro, suggesting that Eps15 is a cellular substrate for UBPY. Furthermore, inactivation of UBPY caused the accumulation of Eps15 on the endosomal aggregates. These results suggest that UBPY regulates the level of protein ubiquitination on endosomes, which is required for maintaining the morphology of the organelle.
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Affiliation(s)
- Emi Mizuno
- Department of Biological Sciences, Tokyo Institute of Technology, Yokohama 226-8501, Japan
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Offe K, Dodson SE, Shoemaker JT, Fritz JJ, Gearing M, Levey AI, Lah JJ. The lipoprotein receptor LR11 regulates amyloid beta production and amyloid precursor protein traffic in endosomal compartments. J Neurosci 2006; 26:1596-603. [PMID: 16452683 PMCID: PMC2638122 DOI: 10.1523/jneurosci.4946-05.2006] [Citation(s) in RCA: 223] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Alzheimer's disease (AD) is a neurodegenerative disorder characterized by progressive cognitive decline and neuropathological changes, including the deposition of amyloid beta (Abeta) in senile plaques. The mechanisms causing the disease and Abeta accumulation are not well understood, but important genetic associations with apolipoprotein E genotype and involvement of lipoprotein receptors have become apparent. LR11 (also known as SorLA), a member of the low-density lipoprotein receptor family, has been identified previously as an altered transcript in microarray analyses of samples from human AD cases. Here, we show neuronal expression of the lipoprotein receptor LR11 in control brain in regions vulnerable to AD neuropathology and marked reduction of LR11 expression in these regions in AD brains before cell death. Overexpression of LR11 drastically reduces levels of extracellular Abeta and also lowers levels of total cellular amyloid precursor protein (APP). LR11 colocalizes with APP and regulates its trafficking in endocytic compartments, which are important intracellular sites for APP processing and Abeta generation. Endogenous LR11 localizes to neuronal multivesicular bodies in both rat and human brain. The robust correlation between reduced LR11 expression and AD neuropathology and its potent effects on extracellular Abeta levels suggest that this neuronal lipoprotein receptor could play an important role in AD pathogenesis.
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Haag J, Chubinskaya S, Aigner T. Hgs physically interacts with Smad5 and attenuates BMP signaling. Exp Cell Res 2006; 312:1153-63. [PMID: 16516194 DOI: 10.1016/j.yexcr.2006.01.019] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2005] [Revised: 01/13/2006] [Accepted: 01/18/2006] [Indexed: 11/25/2022]
Abstract
Signaling by members of the bone morphogenetic protein family plays a critical role in cartilage development and differentiation. Recently, the potential involvement of BMPs in the maintenance and repair of damaged adult articular cartilage has initiated an interest in the role of BMP signaling and the involved signaling pathways in the adult tissue. In this study, we identified Hgs as a novel Smad5 interactor using a cDNA expression library constructed from human adult cartilage. This interaction was confirmed by coimmunoprecipitation experiments in 293 EBNA cells and the chondrocytic cell line T/C-28a2. Overexpression of Hgs resulted in an attenuation of BMP-dependent transcriptional responses suggesting that Hgs acts as an inhibitor of BMP signaling. Of note, osteoarthritic chondrocytes which have been suggested previously to show increased reactivity to BMP-stimulation showed less expression of Hgs. Thus, it is tempting to speculate that both might be related to each other given the suppressive effect of BMP signaling on Hgs shown in this study.
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Affiliation(s)
- Jochen Haag
- Osteoarticular and Arthritis Research, Department of Pathology, Friedrich-Alexander University of Erlangen-Nuremberg, Krankenhausstr. 8-10, D-91054 Erlangen, Germany
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Abella JV, Peschard P, Naujokas MA, Lin T, Saucier C, Urbé S, Park M. Met/Hepatocyte growth factor receptor ubiquitination suppresses transformation and is required for Hrs phosphorylation. Mol Cell Biol 2005; 25:9632-45. [PMID: 16227611 PMCID: PMC1265818 DOI: 10.1128/mcb.25.21.9632-9645.2005] [Citation(s) in RCA: 153] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Met receptor tyrosine kinase (RTK) regulates epithelial remodeling, dispersal, and invasion and is deregulated in many human cancers. It is now accepted that impaired down-regulation, as well as sustained activation, of RTKs could contribute to their deregulation. Down-regulation of the Met receptor involves ligand-induced internalization, ubiquitination by Cbl ubiquitin ligases, and lysosomal degradation. Here we report that a ubiquitination-deficient Met receptor mutant (Y1003F) is tumorigenic in vivo. The Met Y1003F mutant is internalized, and undergoes endosomal trafficking with kinetics similar to the wild-type Met receptor, yet is inefficiently targeted for degradation. This results in sustained activation of Met Y1003F and downstream signals involving the Ras-mitogen-activated protein kinase pathway, cell transformation, and tumorigenesis. Although Met Y1003F undergoes endosomal trafficking and localizes with the cargo-sorting protein Hrs, it is unable to induce phosphorylation of Hrs. Fusion of monoubiquitin to Met Y1003F is sufficient to decrease Met receptor stability and prevent sustained MEK1/2 activation. In addition, this rescues Hrs tyrosine phosphorylation and decreases transformation in a focus-forming assay. These results demonstrate that Cbl-dependent ubiquitination is dispensable for Met internalization but is critical to target the Met receptor to components of the lysosomal sorting machinery and to suppress its inherent transforming activity.
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Affiliation(s)
- Jasmine V Abella
- Molecular Oncology Group H5.21, Department of Biochemistry, McGill University Health Centre, 687 Pine Avenue West, Montréal, Québec, Canada H3A 1A1
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Merkulova M, Huynh H, Radchenko V, Saito K, Lipkin V, Shuvaeva T, Mustelin T. Secretion of the mammalian Sec14p-like phosphoinositide-binding p45 protein. FEBS J 2005; 272:5595-605. [PMID: 16262698 DOI: 10.1111/j.1742-4658.2005.04955.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Protein-lipid interactions are important for protein targeting, signal transduction, lipid transport, and the maintenance of cellular compartments and membranes. Specific lipid-binding protein domains, such as PH, FYVE, PX, PHD, C2 and SEC14 homology domains, mediate interactions between proteins and specific phospholipids. We recently cloned a 45-kDa protein from rat olfactory epithelium, which is homologous to the yeast Sec14p phosphatidylinositol (PtdIns) transfer protein and we report here that this protein binds to PtdIns(3,4,5)P3 and far weaker to less phosphorylated derivatives of PtdIns. Expression of the p45 protein in COS-1 cells resulted in accumulation of the protein in secretory vesicles and in the extracellular space. The secreted material contained PtdIns(3,4,5)P3. Our findings are the first report of a Sec14p-like protein involved in transport out of a cell and, to the best of our knowledge, inositol-containing phospholipids have not previously been detected in the extracellular space. Our findings suggest that p45 and phosphoinositides may participate in the formation of the protective mucus on nasal epithelium.
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Affiliation(s)
- Maria Merkulova
- Shemyakin and Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia
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