1
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Chai Q, Li S, Collins MK, Li R, Ahmad I, Johnson SF, Frabutt DA, Yang Z, Shen X, Sun L, Hu J, Hultquist JF, Peterlin BM, Zheng YH. HIV-1 Nef interacts with the cyclin K/CDK13 complex to antagonize SERINC5 for optimal viral infectivity. Cell Rep 2021; 36:109514. [PMID: 34380030 PMCID: PMC8385645 DOI: 10.1016/j.celrep.2021.109514] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Revised: 06/17/2021] [Accepted: 07/20/2021] [Indexed: 11/03/2022] Open
Abstract
HIV-1-negative factor (Nef) protein antagonizes serine incorporator 5 (SERINC5) by redirecting this potent restriction factor to the endosomes and lysosomes for degradation. However, the precise mechanism remains unclear. Using affinity purification/mass spectrometry, we identify cyclin K (CycK) and cyclin-dependent kinase 13 (CDK13) as a Nef-associated kinase complex. CycK/CDK13 phosphorylates the serine at position 360 (S360) in SERINC5, which is required for Nef downregulation of SERINC5 from the cell surface and its counteractivity of the SERINC5 antiviral activity. To understand the role of S360 phosphorylation, we generate chimeric proteins between CD8 and SERINC5 to study their response to Nef. Nef not only downregulates but, importantly, also binds to this chimera in an S360-dependent manner. Thus, S360 phosphorylation increases interactions between Nef and SERINC5 and initiates the destruction of SERINC5 by the endocytic machinery.
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Affiliation(s)
- Qingqing Chai
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI, USA
| | - Sunan Li
- Harbin Veterinary Research Institute, CAAS-Michigan State University Joint Laboratory of Innate Immunity, State Key Laboratory of Veterinary Biotechnology, Chinese Academy of Agricultural Sciences, Harbin, China
| | - Morgan K Collins
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI, USA
| | - Rongrong Li
- Harbin Veterinary Research Institute, CAAS-Michigan State University Joint Laboratory of Innate Immunity, State Key Laboratory of Veterinary Biotechnology, Chinese Academy of Agricultural Sciences, Harbin, China
| | - Iqbal Ahmad
- Harbin Veterinary Research Institute, CAAS-Michigan State University Joint Laboratory of Innate Immunity, State Key Laboratory of Veterinary Biotechnology, Chinese Academy of Agricultural Sciences, Harbin, China
| | - Silas F Johnson
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI, USA; Department of Biology, Hillsdale College, Hillsdale, MI, USA
| | - Dylan A Frabutt
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI, USA
| | - Zhichang Yang
- Department of Chemistry, Michigan State University, East Lansing, MI, USA
| | - Xiaojing Shen
- Department of Chemistry, Michigan State University, East Lansing, MI, USA
| | - Liangliang Sun
- Department of Chemistry, Michigan State University, East Lansing, MI, USA
| | - Jian Hu
- Department of Chemistry, Michigan State University, East Lansing, MI, USA; Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI, USA
| | - Judd F Hultquist
- Division of Infectious Diseases, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
| | - B Matija Peterlin
- Department of Medicine, University of California, San Francisco, San Francisco, CA, USA; Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, CA, USA
| | - Yong-Hui Zheng
- Harbin Veterinary Research Institute, CAAS-Michigan State University Joint Laboratory of Innate Immunity, State Key Laboratory of Veterinary Biotechnology, Chinese Academy of Agricultural Sciences, Harbin, China; Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI, USA.
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2
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Liu X, Li F, Zhang J, Wang L, Wang J, Wen Z, Wang Z, Shuai L, Wang X, Ge J, Zhao D, Bu Z. The ATPase ATP6V1A facilitates rabies virus replication by promoting virion uncoating and interacting with the viral matrix protein. J Biol Chem 2021; 296:100096. [PMID: 33208464 PMCID: PMC7949080 DOI: 10.1074/jbc.ra120.014190] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2020] [Revised: 11/12/2020] [Accepted: 11/18/2020] [Indexed: 12/25/2022] Open
Abstract
Rabies virus (RABV) matrix protein (M) plays crucial roles in viral transcription, replication, assembly, and budding; however, its function during the early stage of virus replication remains unknown. Here, we mapped the protein interactome between RABV M and human host factors using a proteomic approach, finding a link to the V-type proton ATPase catalytic subunit A (ATP6V1A), which is located in the endosomes where RABV first enters. By downregulating or upregulating ATP6V1A expression in HEK293T cells, we found that ATP6V1A facilitated RABV replication. We further found that ATP6V1A was involved in the dissociation of incoming viral M proteins during viral uncoating. Coimmunoprecipitation demonstrated that M interacted with the full length or middle domain of ATP6V1A, which was dependent on the lysine residue at position 256 and the glutamic acid residue at position 279. RABV growth and uncoating in ATP6V1A-depleted cells was restored by trans-complementation with the full length or interaction domain of ATP6V1A. Moreover, stably overexpressed ATP6V1A enhanced RABV growth in Vero cells, which are used for the production of rabies vaccine. Our findings identify a new partner for RABV M proteins and establish a new role of ATP6V1A by promoting virion uncoating during RABV replication.
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Affiliation(s)
- Xing Liu
- State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, People's Republic of China
| | - Fang Li
- State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, People's Republic of China
| | - Jiwen Zhang
- State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, People's Republic of China
| | - Lulu Wang
- State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, People's Republic of China
| | - Jinliang Wang
- State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, People's Republic of China
| | - Zhiyuan Wen
- State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, People's Republic of China
| | - Zilong Wang
- State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, People's Republic of China
| | - Lei Shuai
- State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, People's Republic of China
| | - Xijun Wang
- State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, People's Republic of China
| | - Jinying Ge
- State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, People's Republic of China
| | - Dongming Zhao
- State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, People's Republic of China; National High Containment Laboratory for Animal Diseases Control and Prevention, Harbin, People's Republic of China.
| | - Zhigao Bu
- State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, People's Republic of China; National High Containment Laboratory for Animal Diseases Control and Prevention, Harbin, People's Republic of China.
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3
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Painter MM, Zimmerman GE, Merlino MS, Robertson AW, Terry VH, Ren X, McLeod MR, Gomez-Rodriguez L, Garcia KA, Leonard JA, Leopold KE, Neevel AJ, Lubow J, Olson E, Piechocka-Trocha A, Collins DR, Tripathi A, Raghavan M, Walker BD, Hurley JH, Sherman DH, Collins KL. Concanamycin A counteracts HIV-1 Nef to enhance immune clearance of infected primary cells by cytotoxic T lymphocytes. Proc Natl Acad Sci U S A 2020; 117:23835-23846. [PMID: 32900948 PMCID: PMC7519347 DOI: 10.1073/pnas.2008615117] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Nef is an HIV-encoded accessory protein that enhances pathogenicity by down-regulating major histocompatibility class I (MHC-I) expression to evade killing by cytotoxic T lymphocytes (CTLs). A potent Nef inhibitor that restores MHC-I is needed to promote immune-mediated clearance of HIV-infected cells. We discovered that the plecomacrolide family of natural products restored MHC-I to the surface of Nef-expressing primary cells with variable potency. Concanamycin A (CMA) counteracted Nef at subnanomolar concentrations that did not interfere with lysosomal acidification or degradation and were nontoxic in primary cell cultures. CMA specifically reversed Nef-mediated down-regulation of MHC-I, but not CD4, and cells treated with CMA showed reduced formation of the Nef:MHC-I:AP-1 complex required for MHC-I down-regulation. CMA restored expression of diverse allotypes of MHC-I in Nef-expressing cells and inhibited Nef alleles from divergent clades of HIV and simian immunodeficiency virus, including from primary patient isolates. Lastly, we found that restoration of MHC-I in HIV-infected cells was accompanied by enhanced CTL-mediated clearance of infected cells comparable to genetic deletion of Nef. Thus, we propose CMA as a lead compound for therapeutic inhibition of Nef to enhance immune-mediated clearance of HIV-infected cells.
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Affiliation(s)
- Mark M Painter
- Graduate Program in Immunology, University of Michigan, Ann Arbor, MI 48109
| | | | - Madeline S Merlino
- Department of Internal Medicine, University of Michigan, Ann Arbor, MI 48109
| | - Andrew W Robertson
- Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109
- Natural Products Discovery Core, Life Sciences Institute, University of Michigan Ann Arbor, MI 48109
| | - Valeri H Terry
- Department of Internal Medicine, University of Michigan, Ann Arbor, MI 48109
| | - Xuefeng Ren
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720
- California Institute for Quantitative Biosciences, University of California, Berkeley, CA 94720
| | - Megan R McLeod
- Department of Internal Medicine, University of Michigan, Ann Arbor, MI 48109
| | - Lyanne Gomez-Rodriguez
- Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109
- Graduate Program in Chemical Biology, University of Michigan, Ann Arbor, MI 48109
| | - Kirsten A Garcia
- Department of Internal Medicine, University of Michigan, Ann Arbor, MI 48109
| | - Jolie A Leonard
- Department of Internal Medicine, University of Michigan, Ann Arbor, MI 48109
| | - Kay E Leopold
- Department of Internal Medicine, University of Michigan, Ann Arbor, MI 48109
| | - Andrew J Neevel
- Department of Internal Medicine, University of Michigan, Ann Arbor, MI 48109
| | - Jay Lubow
- Department of Microbiology and Immunology, University of Michigan, Ann Arbor, MI 48109
| | - Eli Olson
- Graduate Program in Immunology, University of Michigan, Ann Arbor, MI 48109
| | - Alicja Piechocka-Trocha
- Ragon Institute of MGH, MIT and Harvard, Cambridge, MA 02139
- Howard Hughes Medical Institute, Chevy Chase, MD 20815
| | - David R Collins
- Ragon Institute of MGH, MIT and Harvard, Cambridge, MA 02139
- Howard Hughes Medical Institute, Chevy Chase, MD 20815
| | - Ashootosh Tripathi
- Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109
- Natural Products Discovery Core, Life Sciences Institute, University of Michigan Ann Arbor, MI 48109
- Department of Medicinal Chemistry, University of Michigan, Ann Arbor, MI 48109
| | - Malini Raghavan
- Department of Microbiology and Immunology, University of Michigan, Ann Arbor, MI 48109
| | - Bruce D Walker
- Ragon Institute of MGH, MIT and Harvard, Cambridge, MA 02139
- Howard Hughes Medical Institute, Chevy Chase, MD 20815
| | - James H Hurley
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720
- California Institute for Quantitative Biosciences, University of California, Berkeley, CA 94720
| | - David H Sherman
- Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109
- Department of Microbiology and Immunology, University of Michigan, Ann Arbor, MI 48109
- Department of Medicinal Chemistry, University of Michigan, Ann Arbor, MI 48109
| | - Kathleen L Collins
- Graduate Program in Immunology, University of Michigan, Ann Arbor, MI 48109;
- Department of Internal Medicine, University of Michigan, Ann Arbor, MI 48109
- Department of Microbiology and Immunology, University of Michigan, Ann Arbor, MI 48109
- Cellular and Molecular Biology Graduate Program, University of Michigan, Ann Arbor, MI 48109
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4
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Waheed AA, Swiderski M, Khan A, Gitzen A, Majadly A, Freed EO. The viral protein U (Vpu)-interacting host protein ATP6V0C down-regulates cell-surface expression of tetherin and thereby contributes to HIV-1 release. J Biol Chem 2020; 295:7327-7340. [PMID: 32291285 PMCID: PMC7247306 DOI: 10.1074/jbc.ra120.013280] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2020] [Revised: 04/09/2020] [Indexed: 12/11/2022] Open
Abstract
Host proteins with antiviral activity have evolved as first-line defenses to suppress viral replication. The HIV-1 accessory protein viral protein U (Vpu) enhances release of the virus from host cells by down-regulating the cell-surface expression of the host restriction factor tetherin. However, the exact mechanism of Vpu-mediated suppression of antiviral host responses is unclear. To further understand the role of host proteins in Vpu's function, here we carried out yeast two-hybrid screening and identified the V0 subunit C of vacuolar ATPase (ATP6V0C) as a Vpu-binding protein. To examine the role of ATP6V0C in Vpu-mediated tetherin degradation and HIV-1 release, we knocked down ATP6V0C expression in HeLa cells and observed that ATP6V0C depletion impairs Vpu-mediated tetherin degradation, resulting in defective HIV-1 release. We also observed that ATP6V0C overexpression stabilizes tetherin expression. This stabilization effect was specific to ATP6V0C, as overexpression of another subunit of the vacuolar ATPase, ATP6V0C″, had no effect on tetherin expression. ATP6V0C overexpression did not stabilize CD4, another target of Vpu-mediated degradation. Immunofluorescence localization experiments revealed that the ATP6V0C-stabilized tetherin is sequestered in a CD63- and lysosome-associated membrane protein 1 (LAMP1)-positive intracellular compartment. These results indicate that the Vpu-interacting protein ATP6V0C plays a role in down-regulating cell-surface expression of tetherin and thereby contributes to HIV-1 assembly and release.
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Affiliation(s)
- Abdul A Waheed
- Virus-Cell Interaction Section, HIV Dynamics and Replication Program, Center for Cancer Research, NCI, National Institutes of Health, Frederick, Maryland 21702.
| | - Maya Swiderski
- Virus-Cell Interaction Section, HIV Dynamics and Replication Program, Center for Cancer Research, NCI, National Institutes of Health, Frederick, Maryland 21702
| | - Ali Khan
- Virus-Cell Interaction Section, HIV Dynamics and Replication Program, Center for Cancer Research, NCI, National Institutes of Health, Frederick, Maryland 21702
| | - Ariana Gitzen
- Virus-Cell Interaction Section, HIV Dynamics and Replication Program, Center for Cancer Research, NCI, National Institutes of Health, Frederick, Maryland 21702
| | - Ahlam Majadly
- Virus-Cell Interaction Section, HIV Dynamics and Replication Program, Center for Cancer Research, NCI, National Institutes of Health, Frederick, Maryland 21702
| | - Eric O Freed
- Virus-Cell Interaction Section, HIV Dynamics and Replication Program, Center for Cancer Research, NCI, National Institutes of Health, Frederick, Maryland 21702
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5
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Marrero-Hernández S, Márquez-Arce D, Cabrera-Rodríguez R, Estévez-Herrera J, Pérez-Yanes S, Barroso-González J, Madrid R, Machado JD, Blanco J, Valenzuela-Fernández A. HIV-1 Nef Targets HDAC6 to Assure Viral Production and Virus Infection. Front Microbiol 2019; 10:2437. [PMID: 31736889 PMCID: PMC6831784 DOI: 10.3389/fmicb.2019.02437] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2019] [Accepted: 10/10/2019] [Indexed: 12/11/2022] Open
Abstract
HIV Nef is a central auxiliary protein in HIV infection and pathogenesis. Our results indicate that HDAC6 promotes the aggresome/autophagic degradation of the viral polyprotein Pr55Gag to inhibit HIV-1 production. Nef counteracts this antiviral activity of HDAC6 by inducing its degradation and subsequently stabilizing Pr55Gag and Vif viral proteins. Nef appears to neutralize HDAC6 by an acidic/endosomal-lysosomal processing and does not need the downregulation function, since data obtained with the non-associated cell-surface Nef-G2A mutant - the cytoplasmic location of HDAC6 - together with studies with chemical inhibitors and other Nef mutants, point to this direction. Hence, the polyproline rich region P72xxP75 (69-77 aa) and the di-Leucin motif in the Nef-ExxxLL160-165 sequence of Nef, appear to be responsible for HDAC6 clearance and, therefore, required for this novel Nef proviral function. Nef and Nef-G2A co-immunoprecipitate with HDAC6, whereas the Nef-PPAA mutant showed a reduced interaction with the anti-HIV-1 enzyme. Thus, the P72xxP75 motif appears to be responsible, directly or indirectly, for the interaction of Nef with HDAC6. Remarkably, by neutralizing HDAC6, Nef assures Pr55Gag location and aggregation at plasma membrane, as observed by TIRFM, promotes viral egress, and enhances the infectivity of viral particles. Consequently, our results suggest that HDAC6 acts as an anti-HIV-1 restriction factor, limiting viral production and infection by targeting Pr55Gag and Vif. This function is counteracted by functional HIV-1 Nef, in order to assure viral production and infection capacities. The interplay between HIV-1 Nef and cellular HDAC6 may determine viral infection and pathogenesis, representing both molecules as key targets to battling HIV.
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Affiliation(s)
- Sara Marrero-Hernández
- Laboratorio de Inmunología Celular y Viral, Unidad de Farmacología, Sección de Medicina, Facultad de Medicina, Universidad de La Laguna (ULL), La Laguna, Spain.,Unidad Virología y Microbiología del IUETSPC, Universidad de La Laguna (ULL), La Laguna, Spain
| | - Daniel Márquez-Arce
- Laboratorio de Inmunología Celular y Viral, Unidad de Farmacología, Sección de Medicina, Facultad de Medicina, Universidad de La Laguna (ULL), La Laguna, Spain.,Unidad Virología y Microbiología del IUETSPC, Universidad de La Laguna (ULL), La Laguna, Spain
| | - Romina Cabrera-Rodríguez
- Laboratorio de Inmunología Celular y Viral, Unidad de Farmacología, Sección de Medicina, Facultad de Medicina, Universidad de La Laguna (ULL), La Laguna, Spain.,Unidad Virología y Microbiología del IUETSPC, Universidad de La Laguna (ULL), La Laguna, Spain
| | - Judith Estévez-Herrera
- Laboratorio de Inmunología Celular y Viral, Unidad de Farmacología, Sección de Medicina, Facultad de Medicina, Universidad de La Laguna (ULL), La Laguna, Spain.,Unidad Virología y Microbiología del IUETSPC, Universidad de La Laguna (ULL), La Laguna, Spain
| | - Silvia Pérez-Yanes
- Laboratorio de Inmunología Celular y Viral, Unidad de Farmacología, Sección de Medicina, Facultad de Medicina, Universidad de La Laguna (ULL), La Laguna, Spain.,Unidad Virología y Microbiología del IUETSPC, Universidad de La Laguna (ULL), La Laguna, Spain
| | - Jonathan Barroso-González
- Laboratorio de Inmunología Celular y Viral, Unidad de Farmacología, Sección de Medicina, Facultad de Medicina, Universidad de La Laguna (ULL), La Laguna, Spain
| | - Ricardo Madrid
- BioAssays SL, Campus de Cantoblanco, Madrid, Spain.,Departmento de Genética, Fisiología y Microbiología, Facultad de Biología, Universidad Complutense de Madrid (UCM), Madrid, Spain
| | - José-David Machado
- Laboratorio de Inmunología Celular y Viral, Unidad de Farmacología, Sección de Medicina, Facultad de Medicina, Universidad de La Laguna (ULL), La Laguna, Spain
| | - Julià Blanco
- AIDS Research Institute IrsiCaixa, Institut de Recerca en Ciències de la Salut Germans Trias i Pujol (IGTP), Badalona, Spain.,Universitat de Vic-Central de Catalunya, UVIC-UCC, Catalonia, Spain
| | - Agustín Valenzuela-Fernández
- Laboratorio de Inmunología Celular y Viral, Unidad de Farmacología, Sección de Medicina, Facultad de Medicina, Universidad de La Laguna (ULL), La Laguna, Spain.,Unidad Virología y Microbiología del IUETSPC, Universidad de La Laguna (ULL), La Laguna, Spain
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6
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Vacuolar H+-ATPase: An Essential Multitasking Enzyme in Physiology and Pathophysiology. ACTA ACUST UNITED AC 2014. [DOI: 10.1155/2014/675430] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Vacuolar H+-ATPases (V-ATPases) are large multisubunit proton pumps that are required for housekeeping acidification of membrane-bound compartments in eukaryotic cells. Mammalian V-ATPases are composed of 13 different subunits. Their housekeeping functions include acidifying endosomes, lysosomes, phagosomes, compartments for uncoupling receptors and ligands, autophagosomes, and elements of the Golgi apparatus. Specialized cells, including osteoclasts, intercalated cells in the kidney and pancreatic beta cells, contain both the housekeeping V-ATPases and an additional subset of V-ATPases, which plays a cell type specific role. The specialized V-ATPases are typically marked by the inclusion of cell type specific isoforms of one or more of the subunits. Three human diseases caused by mutations of isoforms of subunits have been identified. Cancer cells utilize V-ATPases in unusual ways; characterization of V-ATPases may lead to new therapeutic modalities for the treatment of cancer. Two accessory proteins to the V-ATPase have been identified that regulate the proton pump. One is the (pro)renin receptor and data is emerging that indicates that V-ATPase may be intimately linked to renin/angiotensin signaling both systemically and locally. In summary, V-ATPases play vital housekeeping roles in eukaryotic cells. Specialized versions of the pump are required by specific organ systems and are involved in diseases.
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7
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Weiser K, Barton M, Gershoony D, DasGupta R, Cardozo T. HIV's Nef interacts with β-catenin of the Wnt signaling pathway in HEK293 cells. PLoS One 2013; 8:e77865. [PMID: 24130899 PMCID: PMC3795062 DOI: 10.1371/journal.pone.0077865] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2012] [Accepted: 09/13/2013] [Indexed: 11/18/2022] Open
Abstract
The Wnt signaling pathway is implicated in major physiologic cellular functions, such as proliferation, migration, cell fate specification, maintenance of pluripotency and induction of tumorigenicity. Proliferation and migration are important responses of T-cells, which are major cellular targets of HIV infection. Using an informatics screen, we identified a previously unsuspected interaction between HIV’s Nef protein and β-catenin, a key component of the Wnt pathway. A segment in Nef contains identical amino acids at key positions and structurally mimics the β-catenin binding sites on endogenous β-catenin ligands. The interaction between Nef and β-catenin was confirmed in vitro and in a co-immunoprecipitation from HEK293 cells. Moreover, the introduction of Nef into HEK293 cells specifically inhibited a Wnt pathway reporter.
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Affiliation(s)
- Keren Weiser
- Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, New York, United States of America
| | - Meredith Barton
- Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, New York, United States of America
| | - Dafna Gershoony
- Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, New York, United States of America
| | - Ramanuj DasGupta
- Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, New York, United States of America
| | - Timothy Cardozo
- Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, New York, United States of America
- * E-mail:
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8
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Cruz NVG, Amorim R, Oliveira FE, Speranza FAC, Costa LJ. Mutations in the nef and vif genes associated with progression to AIDS in elite controller and slow-progressor patients. J Med Virol 2013; 85:563-74. [PMID: 23417613 DOI: 10.1002/jmv.23512] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/26/2012] [Indexed: 11/07/2022]
Abstract
Progression towards AIDS can vary from 5 to 10 years from the establishment of the primary infection by HIV-1 to more than 10 years in the complete absence of antiretroviral therapy. Several factors can contribute to the outcome of HIV infection, including host genetic and viral replicating characteristics. Historically, nef-deleted viral genomes have been associated with disease progression. Therefore, the lentiviral Nef protein is regarded as a progression factor. The objective of this work was to characterize the nef gene from a group of treatment naive patients infected with HIV-1 for more than 10 years. These patients were classified as long-term non-progressors, elite controller, and slow-progressors according to clinical and laboratorial data. A premature stop codon within the nef gene leading to the expression of a truncated peptide was observed on samples from the elite controller patient. For the slow-progressor patients, several degrees of deletions at the C-terminal of Nef were observed predicting a loss of function of this protein. The vif gene was characterized for these patients and a rare mutation that predicts a miss localization of the Vif protein to the nucleus of infected cells that could prevent its function as an APOBEC neutralization factor was also observed. These data indicate the importance of the HIV accessory proteins as factors that contribute to the outcome of AIDS.
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Affiliation(s)
- Nadia V G Cruz
- Department of Virology, Institute of Microbiology Paulo de Góes, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
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9
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Mwimanzi P, Markle TJ, Ueno T, Brockman MA. Human leukocyte antigen (HLA) class I down-regulation by human immunodeficiency virus type 1 negative factor (HIV-1 Nef): what might we learn from natural sequence variants? Viruses 2012; 4:1711-30. [PMID: 23170180 PMCID: PMC3499827 DOI: 10.3390/v4091711] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2012] [Revised: 09/18/2012] [Accepted: 09/21/2012] [Indexed: 12/12/2022] Open
Abstract
HIV-1 causes a chronic infection in humans that is characterized by high plasma viremia, progressive loss of CD4+ T lymphocytes, and severe immunodeficiency resulting in opportunistic disease and AIDS. Viral persistence is mediated in part by the ability of the Nef protein to down-regulate HLA molecules on the infected cell surface, thereby allowing HIV-1 to evade recognition by antiviral CD8+ T lymphocytes. Extensive research has been conducted on Nef to determine protein domains that are required for its immune evasion activities and to identify critical cellular co-factors, and our mechanistic understanding of this process is becoming more complete. This review highlights our current knowledge of Nef-mediated HLA class I down-regulation and places this work in the context of naturally occurring sequence variation in this protein. We argue that efforts to fully understand the critical role of Nef for HIV-1 pathogenesis will require greater analysis of patient-derived sequences to elucidate subtle differences in immune evasion activity that may alter clinical outcome.
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Affiliation(s)
- Philip Mwimanzi
- Department of Molecular Biology and Biochemistry, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia V5A 1S6, Canada; (P.M.); (T.J.M.)
| | - Tristan J. Markle
- Department of Molecular Biology and Biochemistry, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia V5A 1S6, Canada; (P.M.); (T.J.M.)
| | - Takamasa Ueno
- Center for AIDS Research, Kumamoto University, 2-2-1 Honjo, Chuo-ku, Kumamoto 860-0811, Japan;
| | - Mark A. Brockman
- Department of Molecular Biology and Biochemistry, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia V5A 1S6, Canada; (P.M.); (T.J.M.)
- Faculty of Health Sciences, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia V5A 1S6, Canada
- Author to whom correspondence should be addressed; ; Tel.: +1-778-782-3341; Fax: +1-778-782-5583
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10
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Cai C, Rodepeter FR, Rossmann A, Teymoortash A, Lee JS, Quint K, Di Fazio P, Ocker M, Werner JA, Mandic R. Nef from SIV(mac239) decreases proliferation and migration of adenoid-cystic carcinoma cells and inhibits angiogenesis. Oral Oncol 2011; 47:847-54. [PMID: 21763177 DOI: 10.1016/j.oraloncology.2011.06.502] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2011] [Revised: 06/20/2011] [Accepted: 06/21/2011] [Indexed: 02/07/2023]
Abstract
The HIV/SIV accessory protein Nef is known to down-modulate cell surface receptors that are required for virus entry such as CD4, CCR5 and CXCR4 to block lethal viral superinfection of the infected cell. The chemokine receptor CXCR4 also plays an important role in promoting cell proliferation, metastasis and tumor angiogenesis. Therefore it was of interest to evaluate if Nef can down-regulate CXCR4 in tumor cells since this could affect these critical prognostic parameters. The CXCR4-expressing cell line ACC3 that was derived from a salivary gland adenoid cystic carcinoma (ACC) of the head and neck was transfected with Nef from SIV(mac239) and cell surface expression of the receptor was monitored by FACS analysis. Real time proliferation of cells was measured with the xCELLigence system (Roche, Mannheim, Germany). Cell migration was detected by an in vitro scratch assay. Similarly, COS-7 cells were co-transfected with CXCR4 and Nef and were treated as described for ACC3. In vitro tube formation was deployed to assess the effect of Nef on angiogenesis. siRNA was used for CXCR4 knockdown. Cell surface down-modulation of endogenous CXCR4 could be observed in ACC3 cells after Nef-transfection as well as in COS-7 cells after co-transfection of CXCR4 and Nef. Proliferation as well as migration of Nef-transfected ACC3 tumor cells appeared significantly reduced. In vitro tube formation was significantly lowered after Nef-transfection or CXCR4 knockdown with siRNA. SIV-Nef could serve as an interesting tool to study the biologic behavior of CXCR4-expressing tumors such as ACC. Deploying SIV-Nef thereby could help in the discovery of new therapeutic approaches for the treatment of ACC and other CXCR4-expressing tumors.
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Affiliation(s)
- Chengzhong Cai
- Department of Otorhinolaryngology, Head and Neck Surgery, University Hospital Giessen and Marburg, Campus Marburg, Baldingerstrasse, D-35033 Marburg, Germany
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11
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Jesus da Costa L, Lopes Dos Santos A, Mandic R, Shaw K, Santana de Aguiar R, Tanuri A, Luciw PA, Peterlin BM. Interactions between SIVNef, SIVGagPol and Alix correlate with viral replication and progression to AIDS in rhesus macaques. Virology 2009; 394:47-56. [PMID: 19748111 DOI: 10.1016/j.virol.2009.08.024] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2009] [Revised: 05/26/2009] [Accepted: 08/12/2009] [Indexed: 11/25/2022]
Abstract
Infection with Simian Immunodeficiency Virus (SIV) leads to high viral loads and progression to Simian AIDS (SAIDS) in rhesus macaques. The viral accessory protein Nef is required for this phenotype in monkeys as well as in HIV-infected humans. Previously, we determined that HIVNef binds HIVGagPol and Alix for optimal viral replication in cells. In this study, we demonstrated that these interactions could correlate with high viral loads leading to SAIDS in the infected host. By infecting rhesus macaques with a mutant SIV(mac239), where sequences in the nef gene that are required for these interactions were mutated, we observed robust viral replication and disease in two out of four monkeys, where they reverted to the wild type genotype and phenotype. These two rhesus macaques also died of SAIDS. Two other monkeys did not progress to disease and continued to harbor mutant nef sequences. We conclude that interactions between Nef, GagPol and Alix contribute to optimal viral replication and progression to disease in the infected host.
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12
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Marshansky V, Futai M. The V-type H+-ATPase in vesicular trafficking: targeting, regulation and function. Curr Opin Cell Biol 2008; 20:415-26. [PMID: 18511251 PMCID: PMC7111286 DOI: 10.1016/j.ceb.2008.03.015] [Citation(s) in RCA: 374] [Impact Index Per Article: 23.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2008] [Revised: 03/27/2008] [Accepted: 03/31/2008] [Indexed: 12/31/2022]
Abstract
Vacuolar-type H+-ATPase (V-ATPase)-driven proton pumping and organellar acidification is essential for vesicular trafficking along both the exocytotic and endocytotic pathways of eukaryotic cells. Deficient function of V-ATPase and defects of vesicular acidification have been recently recognized as important mechanisms in a variety of human diseases and are emerging as potential therapeutic targets. In the past few years, significant progress has been made in our understanding of function, regulation, and the cell biological role of V-ATPase. Here, we will review these studies with emphasis on novel direct roles of V-ATPase in the regulation of vesicular trafficking events.
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Affiliation(s)
- Vladimir Marshansky
- Program in Membrane Biology, Center for Systems Biology, Simches Research Center, CPZN No. 8212, Massachusetts General Hospital, 185 Cambridge Street, Boston, MA 02114, USA.
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13
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Qi M, Aiken C. Nef enhances HIV-1 infectivity via association with the virus assembly complex. Virology 2008; 373:287-97. [PMID: 18191978 DOI: 10.1016/j.virol.2007.12.001] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2007] [Revised: 10/12/2007] [Accepted: 12/01/2007] [Indexed: 11/24/2022]
Abstract
The HIV-1 accessory protein Nef enhances virus infectivity by facilitating an early post-entry step of infection. Nef acts in the virus producer cell, leading to a beneficial modification to HIV-1 particles. Nef itself is incorporated into HIV-1 particles, where it is cleaved by the viral protease during virion maturation. To probe the role of virion-associated Nef in HIV-1 infection, we generated a fusion protein consisting of the host protein cyclophilin A (CypA) linked to the amino terminus of Nef. The resulting CypA-Nef protein enhanced the infectivity of Nef-defective HIV-1 particles and was specifically incorporated into the virions via association with Gag during particle assembly. Pharmacologic or genetic inhibition of CypA-Nef binding to Gag prevented incorporation of CypA-Nef into virions and inhibited infectivity enhancement. Our results indicate that infectivity enhancement by Nef requires its association with a component of the assembling HIV-1 particle.
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Affiliation(s)
- Mingli Qi
- Department of Microbiology and Immunology, Vanderbilt University School of Medicine, A-5301 Medical Center North, Nashville, TN 37232-2363, USA
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14
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Wolf D, Giese SI, Witte V, Krautkrämer E, Trapp S, Sass G, Haller C, Blume K, Fackler OT, Baur AS. Novel (n)PKC kinases phosphorylate Nef for increased HIV transcription, replication and perinuclear targeting. Virology 2007; 370:45-54. [PMID: 17904606 DOI: 10.1016/j.virol.2007.08.015] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2007] [Revised: 05/28/2007] [Accepted: 08/08/2007] [Indexed: 10/22/2022]
Abstract
The N-terminus of the human immunodeficiency virus (HIV) pathogenicity factor Nef associates with a protein complex (NAKC for Nef-associated kinase complex) that contains at least two kinases: the tyrosine kinase Lck and a serine kinase activity which was found to phosphorylate Lck and the Nef N-terminus. Here we show that this serine kinase activity is mediated by members of the novel Protein Kinase C (nPKC) subfamily, PKCdelta and theta. Association with the Nef N-terminus was sufficient to activate PKC leading to phosphorylation of Nef in vitro on a conserved serine residue at position 6. Mutation of serine 6 or coexpression of a transdominant negative PKC mutant significantly reduced Nef-stimulated HIV transcription and replication in resting PBMC. When analyzing the molecular mechanisms, we found that mutating serine 6 moderately affected myristoylation of Nef and its association with Pak2 activity, whereas CD4 downmodulation was not inhibited. More interestingly, this mutation abolished the typical perinuclear localization of Nef in T cells. We conclude that the activation of nPKCs by Nef is required to increase viral replication/infectivity and direct the subcellular localization of Nef.
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Affiliation(s)
- Dietlinde Wolf
- University of Miami, Miller School of Medicine, Department of Microbiology and Immunology, BCRI 739, Miami, FL 33136, USA
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15
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Walker PR, Ketunuti M, Choge IA, Meyers T, Gray G, Holmes EC, Morris L. Polymorphisms in Nef associated with different clinical outcomes in HIV type 1 subtype C-infected children. AIDS Res Hum Retroviruses 2007; 23:204-15. [PMID: 17331028 DOI: 10.1089/aid.2006.0080] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The human immunodeficiency virus type 1 (HIV-1) negative factor, or Nef, has a variety of functions that are important in viral pathogenesis. Sequence analysis has identified nef mutations that are linked to the rate of disease progression in adults and children infected with HIV-1 subtype B. Here we have sequenced and analyzed HIV-1 subtype C nef sequences from 34 children with rapid (RP) or slow progressing (SP) disease and identified polymorphisms associated with disease stage including motifs involved in specific pathogenic functions. Unlike subtype B, insertions and deletions in the N-terminal variable region were observed exclusively in SP children (8 out of 25). Strong positive selection pressures were found in sites of known functional importance among SP sequences, whereas RP had strong negative selection across the gene. A lineage analysis of selection pressures indicated weaker pressure across the nef gene in SP sequences bearing a deletion in region 8-12, suggesting this deletion has functional importance in vivo. Together these results suggest a differential adaptation of certain Nef functions related to disease progression, some of which may be attributable to immune-imposed pressures. These data broadly reflect previous studies on subtype B, corroborate the decreased cytopathicity of SP viruses, but also highlight potential subtype differences that require further investigation.
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Affiliation(s)
- Polly R Walker
- Department of Zoology, University of Oxford, South Parks Road, Oxford, OX1 3PS, UK
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16
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Roeth JF, Collins KL. Human immunodeficiency virus type 1 Nef: adapting to intracellular trafficking pathways. Microbiol Mol Biol Rev 2006; 70:548-63. [PMID: 16760313 PMCID: PMC1489538 DOI: 10.1128/mmbr.00042-05] [Citation(s) in RCA: 154] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
The Nef protein of primate lentiviruses is a unique protein that has evolved in several ways to manipulate the biology of an infected cell to support viral replication, immune evasion, pathogenesis, and viral spread. Nef is a small (25- to 34-kDa), myristoylated protein that binds to a collection of cellular factors and acts as an adaptor to generate novel protein interactions to accomplish specific functions. Of the many biological activities attributed to Nef, the reduction of surface levels of the viral receptor (CD4) and antigen-presenting molecules (major histocompatibility complex class I) has been intensely examined; recent evidence demonstrates that Nef utilizes multiple, distinct pathways to affect these proteins. To accomplish this, Nef promotes the formation of multiprotein complexes, recruiting host adaptor proteins to commandeer intracellular vesicular trafficking routes. The altered trafficking of several other host molecules has also been reported, and an emerging theory suggests that Nef generates pleiotrophic effects in the secretory and endocytic pathways that reprogram intracellular protein trafficking and may ultimately provide an efficient platform for viral assembly. This review critically discusses some of the major findings regarding the impact of human immunodeficiency virus type 1 Nef on host protein transport and addresses some emerging directions in this area of human immunodeficiency virus biology.
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Affiliation(s)
- Jeremiah F Roeth
- Graduate Program in Cellular and Molecular Biology, University of Michigan, Ann Arbor, MI 48109, USA
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17
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Abstract
Relatively small genomes and high replication rates allow viruses and bacteria to accumulate mutations. This continuously presents the host immune system with new challenges. On the other side of the trenches, an increasingly well-adjusted host immune response, shaped by coevolutionary history, makes a pathogen's life a rather complicated endeavor. It is, therefore, no surprise that pathogens either escape detection or modulate the host immune response, often by redirecting normal cellular pathways to their advantage. For the purpose of this chapter, we focus mainly on the manipulation of the class I and class II major histocompatibility complex (MHC) antigen presentation pathways and the ubiquitin (Ub)-proteasome system by both viral and bacterial pathogens. First, we describe the general features of antigen presentation pathways and the Ub-proteasome system and then address how they are manipulated by pathogens. We discuss the many human cytomegalovirus (HCMV)-encoded immunomodulatory genes that interfere with antigen presentation (immunoevasins) and focus on the HCMV immunoevasins US2 and US11, which induce the degradation of class I MHC heavy chains by the proteasome by catalyzing their export from the endoplasmic reticulum (ER)-membrane into the cytosol, a process termed ER dislocation. US2- and US11-mediated subversion of ER dislocation ensures proteasomal degradation of class I MHC molecules and presumably allows HCMV to avoid recognition by cytotoxic T cells, whilst providing insight into general aspects of ER-associated degradation (ERAD) which is used by eukaryotic cells to purge their ER of defective proteins. We discuss the similarities and differences between the distinct pathways co-opted by US2 and US11 for dislocation and degradation of human class I MHC molecules and also a putatively distinct pathway utilized by the murine herpes virus (MHV)-68 mK3 immunoevasin for ER dislocation of murine class I MHC. We speculate on the implications of the three pathogen-exploited dislocation pathways to cellular ER quality control. Moreover, we discuss the ubiquitin (Ub)-proteasome system and its position at the core of antigen presentation as proteolysis and intracellular trafficking rely heavily on Ub-dependent processes. We add a few examples of manipulation of the Ub-proteasome system by pathogens in the context of the immune system and such diverse aspects of the host-pathogen relationship as virus budding, bacterial chromosome integration, and programmed cell death, to name a few. Finally, we speculate on newly found pathogen-encoded deubiquitinating enzymes (DUBs) and their putative roles in modulation of host-pathogen interactions.
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Affiliation(s)
- Joana Loureiro
- Whitehead Institute, 9 Cambridge Center, Cambridge, Massachusetts, USA
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18
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Sultana H, Rivero F, Blau-Wasser R, Schwager S, Balbo A, Bozzaro S, Schleicher M, Noegel AA. Cyclase-Associated Protein is Essential for the Functioning of the Endo-Lysosomal System and Provides a Link to the Actin Cytoskeleton. Traffic 2005; 6:930-46. [PMID: 16138906 DOI: 10.1111/j.1600-0854.2005.00330.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Data from mutant analysis in yeast and Dictyostelium indicate a role for the cyclase-associated protein (CAP) in endocytosis and vesicle transport. We have used genetic and biochemical approaches to identify novel interacting partners of Dictyostelium CAP to help explain its molecular interactions in these processes. Cyclase-associated protein associates and interacts with subunits of the highly conserved vacuolar H(+)-ATPase (V-ATPase) and co-localizes to some extent with the V-ATPase. Furthermore, CAP is essential for maintaining the structural organization, integrity and functioning of the endo-lysosomal system, as distribution and morphology of V-ATPase- and Nramp1-decorated membranes were disturbed in a CAP mutant (CAP bsr) accompanied by an increased endosomal pH. Moreover, concanamycin A (CMA), a specific inhibitor of the V-ATPase, had a more severe effect on CAP bsr than on wild-type cells, and the mutant did not show adaptation to the drug. Also, the distribution of green fluorescent protein-CAP was affected upon CMA treatment in the wildtype and recovered after adaptation. Distribution of the V-ATPase in CAP bsr was drastically altered upon hypo-osmotic shock, and growth was slower and reached lower saturation densities in the mutant under hyper-osmotic conditions. Taken together, our data unravel a link of CAP with the actin cytoskeleton and endocytosis and suggest that CAP is an essential component of the endo-lysosomal system in Dictyostelium.
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Affiliation(s)
- Hameeda Sultana
- Center for Biochemistry and Center for Molecular Medicine Cologne, Medical Faculty, University of Cologne, 50931 Köln, Germany
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19
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Cluet D, Bertsch C, Beyer C, Gloeckler L, Erhardt M, Gut JP, Galzi JL, Aubertin AM. Detection of human immunodeficiency virus type 1 Nef and CD4 physical interaction in living human cells by using bioluminescence resonance energy transfer. J Virol 2005; 79:8629-36. [PMID: 15956605 PMCID: PMC1143710 DOI: 10.1128/jvi.79.13.8629-8636.2005] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2005] [Accepted: 02/21/2005] [Indexed: 11/20/2022] Open
Abstract
CD4 down-regulation by human immunodeficiency virus type 1 (HIV-1) Nef protein is a key function for virus virulence. This activity may be mediated by a direct Nef-CD4 interaction. We investigated the formation, in situ, of such a complex between proteins using bioluminescence resonance energy transfer technology and co-immunoprecipitations. Our data clearly demonstrate that Nef and CD4 interact in intact human cells. Moreover, our results clearly indicate that the dileucine motif of the CD4 cytoplasmic domain, critical for the Nef-induced CD4 down-regulation, is not implicated in the Nef/CD4 complex formation in the cellular context.
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Affiliation(s)
- David Cluet
- INSERM-ULP U544, Université Louis Pasteur, Institut de Virologie, 3 Rue Koeberlé, 67000 Strasbourg, France
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20
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Sharova N, Swingler C, Sharkey M, Stevenson M. Macrophages archive HIV-1 virions for dissemination in trans. EMBO J 2005; 24:2481-9. [PMID: 15920469 PMCID: PMC1173148 DOI: 10.1038/sj.emboj.7600707] [Citation(s) in RCA: 154] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2005] [Accepted: 05/12/2005] [Indexed: 01/25/2023] Open
Abstract
Viruses have evolved various strategies in order to persist within the host. To date, most information on mechanisms of HIV-1 persistence has been derived from studies with lymphocytes, but there is little information regarding mechanisms that govern HIV-1 persistence in macrophages. It has previously been demonstrated that virus assembly in macrophages occurs in cytoplasmic vesicles, which exhibit the characteristics of multivesicular bodies or late endosomes. The infectious stability of virions that assemble intracellularly in macrophages has not been evaluated. We demonstrate that virions assembling intracellularly in primary macrophages retain infectivity for extended intervals. Infectious virus was recovered directly from cytoplasmic lysates of macrophages and could be transmitted from macrophages to peripheral blood lymphocytes in trans 6 weeks after ongoing viral replication was blocked. Cell-associated virus decayed significantly from 1 to 2 weeks post infection, but decreased minimally thereafter. The persistence of intracellular virions did not require the viral accessory proteins Vpu or Nef. The stable sequestration of infectious virions within cytoplasmic compartments of macrophages may represent an additional mechanism for viral persistence in HIV-1-infected individuals.
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Affiliation(s)
- Natalia Sharova
- Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, MA, USA
| | - Catherine Swingler
- Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, MA, USA
| | - Mark Sharkey
- Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, MA, USA
| | - Mario Stevenson
- Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, MA, USA
- Program in Molecular Medicine, University of Massachusetts Medical School, Two Biotech, Suite 319, 373 Plantation Street, Worcester, MA 01605, USA. Tel.: +1 508 856 3645; Fax: +1 508 856 4075; E-mail:
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21
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Sun-Wada GH, Wada Y, Futai M. Diverse and essential roles of mammalian vacuolar-type proton pump ATPase: toward the physiological understanding of inside acidic compartments. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2004; 1658:106-14. [PMID: 15282181 DOI: 10.1016/j.bbabio.2004.04.013] [Citation(s) in RCA: 98] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/09/2004] [Revised: 04/19/2004] [Accepted: 04/20/2004] [Indexed: 11/19/2022]
Abstract
The vacuolar-type H(+)-ATPases (V-ATPase) are a family of multi-subunit ATP-dependent proton pumps involved in a wide variety of physiological processes. They are present in endomembrane organelles such as vacuoles, lysosomes, endosomes, the Golgi apparatus, chromaffin granules and coated vesicles, and acidify the luminal pH of these intracellular compartments. They also pump protons across the plasma membranes of specialized cells including osteoclasts and epithelial cells in kidneys and male genital tracts. Here, we briefly summarize our recent studies on the diverse and essential roles of mammalian V-ATPase.
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Affiliation(s)
- Ge-Hong Sun-Wada
- Division of Biological Sciences and Nanoscience, Institute of Scientific and Industrial Research, Osaka University, Mihogaoka 8-1, Ibaraki, Osaka 567-0047, Japan
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22
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Michael B, Nair A, Lairmore MD. Role of accessory proteins of HTLV-1 in viral replication, T cell activation, and cellular gene expression. FRONT BIOSCI-LANDMRK 2004; 9:2556-76. [PMID: 15358581 PMCID: PMC2829751 DOI: 10.2741/1417] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Human T-cell lymphotropic virus type 1 (HTLV-1), causes adult T cell leukemia/lymphoma (ATLL), and initiates a variety of immune mediated disorders. The viral genome encodes common structural and enzymatic proteins characteristic of all retroviruses and utilizes alternative splicing and alternate codon usage to make several regulatory and accessory proteins encoded in the pX region (pX ORF I to IV). Recent studies indicate that the accessory proteins p12I, p27I, p13II, and p30II, encoded by pX ORF I and II, contribute to viral replication and the ability of the virus to maintain typical in vivo expression levels. Proviral clones that are mutated in either pX ORF I or II, while fully competent in cell culture, are severely limited in their replicative capacity in a rabbit model. These HTLV-1 accessory proteins are critical for establishment of viral infectivity, enhance T-lymphocyte activation and potentially alter gene transcription and mitochondrial function. HTLV-1 pX ORF I expression is critical to the viral infectivity in resting primary lymphocytes suggesting a role for the calcineurin-binding protein p12I in lymphocyte activation. The endoplasmic reticulum and cis-Golgi localizing p12I activates NFAT, a key T cell transcription factor, through calcium-mediated signaling pathways and may lower the threshold of lymphocyte activation via the JAK/STAT pathway. In contrast p30II localizes to the nucleus and represses viral promoter activity, but may regulate cellular gene expression through p300/CBP or related co-activators of transcription. The mitochondrial localizing p13II induces morphologic changes in the organelle and may influence energy metabolism infected cells. Future studies of the molecular details HTLV-1 "accessory" proteins interactions will provide important new directions for investigations of HTLV-1 and related viruses associated with lymphoproliferative diseases. Thus, the accessory proteins of HTLV-1, once thought to be dispensable for viral replication, have proven to be directly involved in viral spread in vivo and represent potential targets for therapeutic intervention against HTLV-1 infection and disease.
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Affiliation(s)
- Bindhu Michael
- Center for Retrovirus Research and Department of Veterinary Biosciences, The Ohio State University, Columbus, Ohio 43210
| | - Amithraj Nair
- Center for Retrovirus Research and Department of Veterinary Biosciences, The Ohio State University, Columbus, Ohio 43210
| | - Michael D. Lairmore
- Center for Retrovirus Research and Department of Veterinary Biosciences, The Ohio State University, Columbus, Ohio 43210
- Department of Molecular Virology, Immunology and Medical Genetics, The Ohio State University, Columbus, Ohio 43210
- Comprehensive Cancer Center, The Arthur G. James Cancer Hospital and Solove Research Institute, The Ohio State University, Columbus, Ohio 43210
- Corresponding Author: Dr. Michael D. Lairmore, The Ohio State University, Department of Veterinary Biosciences, 1925 Coffey Road, Columbus, OH 43210-1093, Phone: (614) 292-4489. Fax: (614) 292-6473.
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23
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Lundquist CA, Zhou J, Aiken C. Nef stimulates human immunodeficiency virus type 1 replication in primary T cells by enhancing virion-associated gp120 levels: coreceptor-dependent requirement for Nef in viral replication. J Virol 2004; 78:6287-96. [PMID: 15163722 PMCID: PMC416500 DOI: 10.1128/jvi.78.12.6287-6296.2004] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Nef protein enhances human immunodeficiency virus type 1 (HIV-1) replication through an unknown mechanism. We and others have previously reported that efficient HIV-1 replication in activated primary CD4(+) T cells depends on the ability of Nef to downregulate CD4 from the cell surface. Here we demonstrate that Nef greatly enhances the infectivity of HIV-1 particles produced in primary T cells. Nef-defective HIV-1 particles contained significantly reduced quantities of gp120 on their surface; however, Nef did not affect the levels of virion-associated gp41, indicating that Nef indirectly stabilizes the association of gp120 with gp41. Surprisingly, Nef was not required for efficient replication of viruses that use CCR5 for entry, nor did Nef influence the infectivity or gp120 content of these virions. Nef also inhibited the incorporation of CD4 into HIV-1 particles released from primary T cells. We propose that Nef, by downregulating cell surface CD4, enhances HIV-1 replication by inhibiting CD4-induced dissociation of gp120 from gp41. The preferential requirement for Nef in the replication of X4-tropic HIV-1 suggests that the ability of Nef to downregulate CD4 may be most important at later stages of disease when X4-tropic viruses emerge.
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Affiliation(s)
- Christopher A Lundquist
- Department of Microbiology and Immunology, Vanderbilt University School of Medicine, A-5301 Medical Center North, Nashville, TN 37232-2363, USA
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24
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Costa LJ, Zheng YH, Sabotic J, Mak J, Fackler OT, Peterlin BM. Nef binds p6* in GagPol during replication of human immunodeficiency virus type 1. J Virol 2004; 78:5311-23. [PMID: 15137387 PMCID: PMC400368 DOI: 10.1128/jvi.78.10.5311-5323.2004] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The atypical Nef protein (NefF12) from human immunodeficiency virus type 1 strain F12 (HIV-1(F12)) interferes with virion production and infectivity via a mysterious mechanism. The correlation of these effects with the unusual perinuclear subcellular localization of NefF12 suggested that the wild-type Nef protein could bind to assembly intermediates in late stages of viral replication. To test this hypothesis, Nef from HIV-1(NL4-3) was fused to an endoplasmic reticulum (ER) retention signal (NefKKXX). This mutant NefKKXX protein recapitulated fully the effects of NefF12 on on Gag processing and virion production, either alone or as a CD8 fusion protein. Importantly, the mutant NefKKXX protein also localized to the intermediate compartment, between the ER and the trans-Golgi network. Furthermore, Nef bound the GagPol polyprotein in vitro and in vivo. This binding mapped to the C-terminal flexible loop in Nef and the transframe p6* protein in GagPol. The significance of this interaction was demonstrated by a genetic assay in which the release of a mutant HIV-1 provirus lacking the PTAP motif in the late domain that no longer binds Tsg101 was rescued by a Nef.Tsg101 chimera. Importantly, this rescue as well as incorporation of Nef into HIV-1 virions correlated with the ability of Nef to interact with GagPol. Our data demonstrate that the retention of Nef in the intermediate compartment interferes with viral replication and suggest a new role for Nef in the production of HIV-1.
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Affiliation(s)
- Luciana J Costa
- Department of Medicine, University of California-San Francisco, UCSF-Mt. Zion Cancer Center, 2340 Sutter Street, San Francisco, CA 94115, USA
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25
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Djordjevic JT, Schibeci SD, Stewart GJ, Williamson P. HIV type 1 Nef increases the association of T cell receptor (TCR)-signaling molecules with T cell rafts and promotes activation-induced raft fusion. AIDS Res Hum Retroviruses 2004; 20:547-55. [PMID: 15186530 DOI: 10.1089/088922204323087804] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
HIV-1 Nef (Nef) is a myristoylated protein that contributes to HIV disease pathogenesis. Nef has a modulatory effect on T cell receptor (TCR) signaling, resulting in up-regulation of interleukin-2 (IL-2) production in stimulated T cells. Recent studies have shown that efficient TCR signaling requires enhanced association of TCR-signaling molecules with plasma membrane microdomains (lipid rafts) and fusion of rafts into larger structures. We utilized Jurkat T cell lines expressing wild-type Nef (Nef(wt)) and a myristoylation-deficient form of Nef (Nef(G)2(A)), from an inducible promoter, to determine the effects of Nef on the association of TCR-signaling molecules with rafts in nonstimulated T cells. In addition, the effect of Nef on raft size, before and after TCR activation by CD3 cross-linking, was also examined. Following induction, Nef(wt) was associated with both rafts and nonrafts, while Nef(G)2(A) was almost exclusively cytosolic. Induction of Nef(wt), but not Nef(G)2(A), coincided with an increased association of the src family tyrosine kinase, Lck, and TCRzeta with rafts, but not with nonrafts. Further, rafts were found to be significantly larger in CD3-activated T cells in the presence of Nef(wt) when compared to nonexpressing cells. We propose that myristoylated, raft-localized Nef primes resting T cells for activation by increasing the levels of signaling molecules within rafts, and that TCR activation is enhanced by the capacity of Nef to promote raft fusion.
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Affiliation(s)
- Julianne T Djordjevic
- Institute for Immunology and Allergy Research, Westmead Millennium Institute, NSW 2145, Australia
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Sun AQ, Balasubramaniyan N, Liu CJ, Shahid M, Suchy FJ. Association of the 16-kDa subunit c of vacuolar proton pump with the ileal Na+-dependent bile acid transporter: protein-protein interaction and intracellular trafficking. J Biol Chem 2004; 279:16295-300. [PMID: 14752118 DOI: 10.1074/jbc.m312838200] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The rat ileal apical sodium-dependent bile acid transporter (Asbt) transports conjugated bile acids in a Na+-dependent fashion and localizes specifically to the apical surface of ileal enterocytes. The mechanisms that target organic anion transporters to different domains of the ileal enterocyte plasma membrane have not been well defined. Previous studies (Sung, A.-Q., Arresa, M. A., Zeng, L., Swaby, I'K., Zhou, M. M., and Suchy, F. J. (2001) J. Biol. Chem. 276, 6825-6833) from our laboratory demonstrated that rat Asbt follows an apical sorting pathway that is brefeldin A-sensitive and insensitive to protein glycosylation, monensin treatment, and low temperature shift. Furthermore, a 14-mer signal sequence that adopts a beta-turn conformation is required for apical localization of rat Asbt. In this study, a vacuolar proton pump subunit (VPP-c, the 16-kDa subunit c of vacuolar H+-ATPase) has been identified as an interacting partner of Asbt by a bacterial two-hybrid screen. A direct protein-protein interaction between Asbt and VPP-c was confirmed in an in vitro pull-down assay and in an in vivo mammalian two-hybrid analysis. Indirect immunofluorescence confocal microscopy demonstrated that the Asbt and VPP-c colocalized in transfected COS-7 and MDCK cells. Moreover, bafilomycin A1 (a specific inhibitor of VPP) interrupted the colocalization of Asbt and VPP-c. A taurocholate influx assay and membrane biotinylation analysis showed that treatment with bafilomycin A1 resulted in a significant decrease in bile acid transport activity and the apical membrane localization of Asbt in transfected cells. Thus, these results suggest that the apical membrane localization of Asbt is mediated in part by the vacuolar proton pump associated apical sorting machinery.
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Affiliation(s)
- An-Qiang Sun
- Department of Pediatrics, Mount Sinai School of Medicine, New York, New York 10029, USA.
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Vitavska O, Wieczorek H, Merzendorfer H. A novel role for subunit C in mediating binding of the H+-V-ATPase to the actin cytoskeleton. J Biol Chem 2003; 278:18499-505. [PMID: 12606563 DOI: 10.1074/jbc.m212844200] [Citation(s) in RCA: 118] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Primary proton transport by V-ATPases is regulated via the reversible dissociation of the V(1)V(0) holoenzyme into its V(1) and V(0) subcomplexes. Laser scanning microscopy of different tissues from the tobacco hornworm revealed co-localization of the holoenzyme and F-actin close to the apical membranes of the epithelial cells. In midgut goblet cells, no co-localization was observed under conditions where the V(1) complex detaches from the apical membrane. Binding studies, however, demonstrated that both the V(1) complex and the holoenzyme interact with F-actin, the latter with an apparently higher affinity. To identify F-actin binding subunits, we performed overlay blots that revealed two V(1) subunits as binding partners, namely subunit B, resembling the situation in the osteoclast V-ATPase (Holliday, L. S., Lu, M., Lee, B. S., Nelson, R. D., Solivan, S., Zhang, L., and Gluck, S. L. (2000) J. Biol. Chem. 275, 32331-32337), but, in addition, subunit C, which gets released during reversible dissociation of the holoenzyme. Overlay blots and co-pelleting assays showed that the recombinant subunit C also binds to F-actin. When the V(1) complex was reconstituted with recombinant subunit C, enhanced binding to F-actin was observed. Thus, subunit C may function as an anchor protein regulating the linkage between V-ATPase and the actin-based cytoskeleton.
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Affiliation(s)
- Olga Vitavska
- Department of Biology/Chemistry, Division of Animal Physiology, University of Osnabrück, D-49069 Osnabrück, Germany
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28
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Albrecht B, Lairmore MD. Critical role of human T-lymphotropic virus type 1 accessory proteins in viral replication and pathogenesis. Microbiol Mol Biol Rev 2002; 66:396-406, table of contents. [PMID: 12208996 PMCID: PMC120794 DOI: 10.1128/mmbr.66.3.396-406.2002] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Human T-cell lymphotropic virus type 1 (HTLV-1) infection is associated with a diverse range of lymphoproliferative and neurodegenerative diseases, yet pathogenic mechanisms induced by the virus remain obscure. This complex retrovirus contains typical structural and enzymatic genes but also unique regulatory and accessory genes in four open reading frames (ORFs) of the pX region of the viral genome (pX ORFs I to IV). The regulatory proteins encoded by pX ORFs III and IV, Tax and Rex, respectively, have been extensively characterized. In contrast the contribution of the four accessory proteins p12(I), p27(I), p13(II), and p30(II), encoded by pX ORFs I and II, to viral replication and pathogenesis remained unclear. Proviral clones that are mutated in either pX ORF I or II, while fully competent in cell culture, are severely limited in their replicative capacity in a rabbit model. Emerging evidence indicates that the HTLV-1 accessory proteins are critical for establishment of viral infectivity, enhance T-lymphocyte activation, and potentially alter gene transcription and mitochondrial function. HTLV-1 pX ORF I expression is critical to the viral infectivity in resting primary lymphocytes, suggesting a role for p12(I) in lymphocyte activation. The endoplasmic reticulum and cis-Golgi localizing p12(I), encoded from pX ORF I, activates NFAT, a key T-cell transcription factor, through calcium-mediated signaling pathways and may lower the threshold of lymphocyte activation via the JAK/STAT pathway. In contrast p30(II) localizes to the nucleus and represses viral promoter activity, but may regulate cellular gene expression through p300/CBP or related coactivators of transcription. p13(II) targets mitochondrial proteins, where it alters the organelle morphology and may influence energy metabolism. Collectively, studies of the molecular functions of the HTLV-1 accessory proteins provide insight into strategies used by retroviruses that are associated with lymphoproliferative diseases.
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Affiliation(s)
- Björn Albrecht
- Center for Retrovirus Research, Department of Veterinary Biosciences, The Ohio State University, Columbus, Ohio 43210, USA
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Geyer M, Yu H, Mandic R, Linnemann T, Zheng YH, Fackler OT, Peterlin BM. Subunit H of the V-ATPase binds to the medium chain of adaptor protein complex 2 and connects Nef to the endocytic machinery. J Biol Chem 2002; 277:28521-9. [PMID: 12032142 DOI: 10.1074/jbc.m200522200] [Citation(s) in RCA: 84] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Nef is an accessory protein of human and simian immunodeficiency viruses (HIV and SIV) that is required for efficient viral infectivity and pathogenicity. It decreases the expression of CD4 on the surface of infected cells. V1H is the regulatory subunit H of the vacuolar membrane ATPase (V-ATPase). Previously, the interaction between Nef and V1H has been found to facilitate the internalization of CD4, suggesting that V1H could connect Nef to the endocytic machinery. In this study, we demonstrate that V1H binds to the C-terminal flexible loop in Nef from HIV-1 and to the medium chain (mu2) of the adaptor protein complex 2 (AP-2) in vitro and in vivo. The interaction sites of V1H and mu2 were mapped to a central region in V1H from positions 133 to 363, which contains 4 armadillo repeats, and to the N-terminal adaptin-binding domain in mu2 from positions 1 to 145. Fusing Nef to V1H reproduced the appropriate trafficking of Nef. This chimera internalized CD4 even in the absence of the C-terminal flexible loop in Nef. Finally, blocking the expression of V1H decreased the enhancement of virion infectivity by Nef. Thus, V1H can function as an adaptor for interactions between Nef and AP-2.
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Affiliation(s)
- Matthias Geyer
- Department of Medicine, University of California, San Francisco, California 94143-0703, USA
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Geyer M, Fackler OT, Peterlin BM. Subunit H of the V-ATPase involved in endocytosis shows homology to beta-adaptins. Mol Biol Cell 2002; 13:2045-56. [PMID: 12058068 PMCID: PMC117623 DOI: 10.1091/mbc.02-02-0026] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The vacuolar ATPase (V-ATPase) is a multisubunit enzyme that facilitates the acidification of intracellular compartments in eukaryotic cells and plays an important role in receptor-mediated endocytosis, intracellular trafficking processes, and protein degradation. In this study we show that the C-terminal fragment of 350 residues of the regulatory subunit H (V1H) of the V-ATPase shares structural and functional homologies with the beta-chains of adaptor protein complexes. Moreover, the fragment is similar to a region in the beta-subunit of COPI coatomer complexes, which suggests the existence of a shared domain in these three different families of proteins. For beta-adaptins, this fragment binds to cytoplasmic di-leucine-based sorting motifs such as in HIV-1 Nef that mediate endocytic trafficking. Expression of this fragment in cells blocks the internalization of transmembrane proteins, which depend on di-leucine-based motifs, whereas mutation of the consensus sequence GEY only partly diminishes the recognition of the sorting motif. Based on recent structural analysis, our results suggest that the di-leucine-binding domain consists of a HEAT or ARM repeat protein fold.
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Affiliation(s)
- Matthias Geyer
- Howard Hughes Medical Institute, Department of Medicine, University of California at San Francisco, California 94143-0703, USA.
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Preusser A, Briese L, Willbold D. Presence of a helix in human CD4 cytoplasmic domain promotes binding to HIV-1 Nef protein. Biochem Biophys Res Commun 2002; 292:734-40. [PMID: 11922627 DOI: 10.1006/bbrc.2002.6700] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The Nef proteins of simian and human immunodeficiency viruses are known to directly bind and downregulate the CD4 receptor of infected cells. Recent results suggest that residues forming an alpha-helix N-cap in the CD4 cytoplasmic domain play a role in binding of CD4 to human immunodeficiency virus type 1 Nef protein. We determined the dissociation constants between Nef and several CD4 peptides that contain or do not contain the respective alpha-helix N-cap. Further, we compared helical secondary structure content of these CD4 peptide variants by circular dichroism spectroscopy. We conclude that presence of an alpha-helix in CD4 cytoplasmic domain increases CD4 affinity to Nef. In addition, the amino acid sequence of residues forming the helix N-cap influences CD4 affinity to Nef, too. Finally, the structural changes induced in Nef and CD4 upon binding to each other are investigated.
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Affiliation(s)
- Andrea Preusser
- Institut für Molekulare Biotechnologie, Beutenbergstrasse 11, D-07745 Jena, Germany
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32
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Torigoe T, Izumi H, Ise T, Murakami T, Uramoto H, Ishiguchi H, Yoshida Y, Tanabe M, Nomoto M, Kohno K. Vacuolar H(+)-ATPase: functional mechanisms and potential as a target for cancer chemotherapy. Anticancer Drugs 2002; 13:237-43. [PMID: 11984067 DOI: 10.1097/00001813-200203000-00005] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Tumor cells in vivo often exist in a hypoxic microenvironment with a lower extracellular pH than that surrounding normal cells. Ability to upregulate proton extrusion may be important for tumor cell survival. Such microenvironmental factors may be involved in the development of resistant subpopulations of tumor cells. In solid tumors, both intracellular and extracellular pH differ between drug-sensitive and -resistant cells, and pH appears critical to the therapeutic effectiveness of anticancer agents. Four major types of pH regulators have been identified in tumor cells: the sodium-proton antiporter, the bicarbonate transporter, the proton-lactate symporter and proton pumps. Understanding mechanisms regulating tumor acidity opens up novel opportunities for cancer chemotherapy. In this minireview, we describe the structure and function of certain proton pumps overexpressed in many tumors--vacuolar H(+)-ATPases--and consider their potential as targets for cancer chemotherapy.
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Affiliation(s)
- Takayuki Torigoe
- Department of Molecular Biology, University of Occupational and Environmental Health, Yahatanishi-ku, Kitakyushu, Fukuoka 807-8555, Japan
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Abstract
Primate lentiviruses encode a small protein designated Nef that has been shown to be a major determinant of virus pathogenicity. Nef regulates multiple host factors in order to optimize the cellular environment for virus replication. The mechanisms by which this small protein modulates distinct host cell properties provide intriguing insight into the intricate interaction between virus and host.
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Affiliation(s)
- Vivek K Arora
- Department of Internal Medicine, Division of Infectious Diseases Y9.206, University of Texas Southwestern Medical Center at Dallas, 5323 Harry Hines Blvd., Dallas, TX 75390-9113, USA.
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