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Yoo SW, Waheed AA, Deme P, Tohumeken S, Rais R, Smith MD, DeMarino C, Calabresi PA, Kashanchi F, Freed EO, Slusher BS, Haughey NJ. Inhibition of neutral sphingomyelinase 2 impairs HIV-1 envelope formation and substantially delays or eliminates viral rebound. Proc Natl Acad Sci U S A 2023; 120:e2219543120. [PMID: 37406092 PMCID: PMC10334757 DOI: 10.1073/pnas.2219543120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2022] [Accepted: 04/03/2023] [Indexed: 07/07/2023] Open
Abstract
Although HIV-1 Gag is known to drive viral assembly and budding, the precise mechanisms by which the lipid composition of the plasma membrane is remodeled during assembly are incompletely understood. Here, we provide evidence that the sphingomyelin hydrolase neutral sphingomyelinase 2 (nSMase2) interacts with HIV-1 Gag and through the hydrolysis of sphingomyelin creates ceramide that is necessary for proper formation of the viral envelope and viral maturation. Inhibition or depletion of nSMase2 resulted in the production of noninfectious HIV-1 virions with incomplete Gag lattices lacking condensed conical cores. Inhibition of nSMase2 in HIV-1-infected humanized mouse models with a potent and selective inhibitor of nSMase2 termed PDDC [phenyl(R)-(1-(3-(3,4-dimethoxyphenyl)-2, 6-dimethylimidazo[1,2-b]pyridazin-8-yl) pyrrolidin-3-yl)-carbamate] produced a linear reduction in levels of HIV-1 in plasma. If undetectable plasma levels of HIV-1 were achieved with PDDC treatment, viral rebound did not occur for up to 4 wk when PDDC was discontinued. In vivo and tissue culture results suggest that PDDC selectively kills cells with actively replicating HIV-1. Collectively, this work demonstrates that nSMase2 is a critical regulator of HIV-1 replication and suggests that nSMase2 could be an important therapeutic target with the potential to kill HIV-1-infected cells.
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Affiliation(s)
- Seung-Wan Yoo
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD21210
| | - Abdul A. Waheed
- Virus-Cell Interaction Section, HIV-1 Dynamics and Replication Program, Center for Cancer Research, National Cancer Institute-Frederick, Frederick, MD21702
| | - Pragney Deme
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD21210
| | - Sehmus Tohumeken
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD21210
| | - Rana Rais
- Johns Hopkins Drug Discovery, Johns Hopkins University School of Medicine, Baltimore, MD21205
| | - Matthew D. Smith
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD21210
| | - Catherine DeMarino
- Laboratory of Molecular Virology, George Mason University, Manassas, VA20110
| | - Peter A. Calabresi
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD21210
| | - Fatah Kashanchi
- Laboratory of Molecular Virology, George Mason University, Manassas, VA20110
| | - Eric O. Freed
- Virus-Cell Interaction Section, HIV-1 Dynamics and Replication Program, Center for Cancer Research, National Cancer Institute-Frederick, Frederick, MD21702
| | - Barbara S. Slusher
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD21210
- Johns Hopkins Drug Discovery, Johns Hopkins University School of Medicine, Baltimore, MD21205
- Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, MD21210
- Pharmacology and Molecular Sciences, Johns Hopkins University School of Medicine, Baltimore, MD21210
- Department of Oncology, Johns Hopkins University School of Medicine, Baltimore, MD21224
- Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD21205
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD21210
| | - Norman J. Haughey
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD21210
- Pharmacology and Molecular Sciences, Johns Hopkins University School of Medicine, Baltimore, MD21210
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2
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Waheed AA, Zhu Y, Agostino E, Naing L, Hikichi Y, Soheilian F, Yoo SW, Song Y, Zhang P, Slusher BS, Haughey NJ, Freed EO. Neutral sphingomyelinase 2 is required for HIV-1 maturation. Proc Natl Acad Sci U S A 2023; 120:e2219475120. [PMID: 37406093 PMCID: PMC10334776 DOI: 10.1073/pnas.2219475120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2022] [Accepted: 04/11/2023] [Indexed: 07/07/2023] Open
Abstract
HIV-1 assembly occurs at the inner leaflet of the plasma membrane (PM) in highly ordered membrane microdomains. The size and stability of membrane microdomains is regulated by activity of the sphingomyelin hydrolase neutral sphingomyelinase 2 (nSMase2) that is localized primarily to the inner leaflet of the PM. In this study, we demonstrate that pharmacological inhibition or depletion of nSMase2 in HIV-1-producer cells results in a block in the processing of the major viral structural polyprotein Gag and the production of morphologically aberrant, immature HIV-1 particles with severely impaired infectivity. We find that disruption of nSMase2 also severely inhibits the maturation and infectivity of other primate lentiviruses HIV-2 and simian immunodeficiency virus, has a modest or no effect on nonprimate lentiviruses equine infectious anemia virus and feline immunodeficiency virus, and has no effect on the gammaretrovirus murine leukemia virus. These studies demonstrate a key role for nSMase2 in HIV-1 particle morphogenesis and maturation.
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Affiliation(s)
- Abdul A. Waheed
- Virus-Cell Interaction Section, HIV Dynamics and Replication Program, Center for Cancer Research, National Cancer Institute, Frederick, MD21702
| | - Yanan Zhu
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, OxfordOX3 7BN, United Kingdom
| | - Eva Agostino
- Virus-Cell Interaction Section, HIV Dynamics and Replication Program, Center for Cancer Research, National Cancer Institute, Frederick, MD21702
| | - Lwar Naing
- Virus-Cell Interaction Section, HIV Dynamics and Replication Program, Center for Cancer Research, National Cancer Institute, Frederick, MD21702
| | - Yuta Hikichi
- Virus-Cell Interaction Section, HIV Dynamics and Replication Program, Center for Cancer Research, National Cancer Institute, Frederick, MD21702
| | - Ferri Soheilian
- Electron Microscopy Laboratory, Cancer Research Technology Program, Frederick National Laboratory for Cancer Research, Frederick, MD21702
| | - Seung-Wan Yoo
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD21287
| | - Yun Song
- Electron Bio-Imaging Centre, Diamond Light Source, Harwell Science and Innovation Campus, DidcotOX11 0DE, United Kingdom
| | - Peijun Zhang
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, OxfordOX3 7BN, United Kingdom
- Electron Bio-Imaging Centre, Diamond Light Source, Harwell Science and Innovation Campus, DidcotOX11 0DE, United Kingdom
- Chinese Academy of Medical Sciences Oxford Institute, University of Oxford, OxfordOX3 7BN, United Kingdom
| | - Barbara S. Slusher
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD21287
- Johns Hopkins Drug Discovery, Johns Hopkins University School of Medicine, Baltimore, MD21287
- Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, MD21287
| | - Norman J. Haughey
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD21287
- Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, MD21287
| | - Eric O. Freed
- Virus-Cell Interaction Section, HIV Dynamics and Replication Program, Center for Cancer Research, National Cancer Institute, Frederick, MD21702
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Zeng C, Waheed AA, Li T, Yu J, Zheng YM, Yount JS, Wen H, Freed EO, Liu SL. SERINC proteins potentiate antiviral type I IFN production and proinflammatory signaling pathways. Sci Signal 2021; 14:eabc7611. [PMID: 34520227 DOI: 10.1126/scisignal.abc7611] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
[Figure: see text].
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Affiliation(s)
- Cong Zeng
- Center for Retrovirus Research, Ohio State University, Columbus, OH 43210, USA.,Department of Veterinary Biosciences, Ohio State University, Columbus, OH 43210, USA
| | - Abdul A Waheed
- Virus-Cell Interaction Section, HIV Dynamics and Replication Program, National Cancer Institute, Frederick, Frederick, MD 21702, USA
| | - Tianliang Li
- Department of Microbial Infection and Immunity, Ohio State University, Columbus, OH 43210, USA
| | - Jingyou Yu
- Center for Retrovirus Research, Ohio State University, Columbus, OH 43210, USA.,Department of Veterinary Biosciences, Ohio State University, Columbus, OH 43210, USA
| | - Yi-Min Zheng
- Center for Retrovirus Research, Ohio State University, Columbus, OH 43210, USA.,Department of Veterinary Biosciences, Ohio State University, Columbus, OH 43210, USA
| | - Jacob S Yount
- Department of Microbial Infection and Immunity, Ohio State University, Columbus, OH 43210, USA
| | - Haitao Wen
- Department of Microbial Infection and Immunity, Ohio State University, Columbus, OH 43210, USA
| | - Eric O Freed
- Virus-Cell Interaction Section, HIV Dynamics and Replication Program, National Cancer Institute, Frederick, Frederick, MD 21702, USA
| | - Shan-Lu Liu
- Center for Retrovirus Research, Ohio State University, Columbus, OH 43210, USA.,Department of Veterinary Biosciences, Ohio State University, Columbus, OH 43210, USA.,Department of Microbial Infection and Immunity, Ohio State University, Columbus, OH 43210, USA.,Viruses and Emerging Pathogens Program, Infectious Diseases Institute, Ohio State University, Columbus, OH 43210, USA
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Lun CM, Waheed AA, Majadly A, Powell N, Freed EO. Mechanism of Viral Glycoprotein Targeting by Membrane-associated-RING-CH Proteins. bioRxiv 2021:2021.01.25.428025. [PMID: 33532773 PMCID: PMC7852266 DOI: 10.1101/2021.01.25.428025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
An emerging class of cellular inhibitory proteins has been identified that targets viral glycoproteins. These include the membrane-associated RING-CH (MARCH) family of E3 ubiquitin ligases that, among other functions, downregulate cell-surface proteins involved in adaptive immunity. The RING-CH domain of MARCH proteins is thought to function by catalyzing the ubiquitination of the cytoplasmic tails (CTs) of target proteins, leading to their degradation. MARCH proteins have recently been reported to target retroviral envelope glycoproteins (Env) and vesicular stomatitis virus G glycoprotein (VSV-G). However, the mechanism of antiviral activity remains poorly defined. Here we show that MARCH8 antagonizes the full-length forms of HIV-1 Env, VSV-G, Ebola virus glycoprotein (EboV-GP), and the spike (S) protein of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) thereby impairing the infectivity of virions pseudotyped with these viral glycoproteins. This MARCH8-mediated targeting of viral glycoproteins requires the E3 ubiquitin ligase activity of the RING-CH domain. We observe that MARCH8 protein antagonism of VSV-G is CT dependent. In contrast, MARCH8-mediated targeting of HIV-1 Env, EboV-GP and SARS-CoV-2 S protein by MARCH8 does not require the CT, suggesting a novel mechanism of MARCH-mediated antagonism of these viral glycoproteins. Confocal microscopy data demonstrate that MARCH8 traps the viral glycoproteins in an intracellular compartment. We observe that the endogenous expression of MARCH8 in several relevant human cell types is rapidly inducible by type I interferon. These results help to inform the mechanism by which MARCH proteins exert their antiviral activity and provide insights into the role of cellular inhibitory factors in antagonizing the biogenesis, trafficking, and virion incorporation of viral glycoproteins.
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Affiliation(s)
- Cheng Man Lun
- Virus-Cell Interaction Section, HIV Dynamics and Replication Program, Center for Cancer Research, National Cancer Institute
| | - Abdul A. Waheed
- Virus-Cell Interaction Section, HIV Dynamics and Replication Program, Center for Cancer Research, National Cancer Institute
| | - Alhlam Majadly
- Virus-Cell Interaction Section, HIV Dynamics and Replication Program, Center for Cancer Research, National Cancer Institute
| | - Nicole Powell
- Virus-Cell Interaction Section, HIV Dynamics and Replication Program, Center for Cancer Research, National Cancer Institute
| | - Eric O. Freed
- Virus-Cell Interaction Section, HIV Dynamics and Replication Program, Center for Cancer Research, National Cancer Institute
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5
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He S, Waheed AA, Hetrick B, Dabbagh D, Akhrymuk IV, Kehn-Hall K, Freed EO, Wu Y. PSGL-1 Inhibits the Incorporation of SARS-CoV and SARS-CoV-2 Spike Glycoproteins into Pseudovirions and Impairs Pseudovirus Attachment and Infectivity. Viruses 2020; 13:E46. [PMID: 33396594 PMCID: PMC7824426 DOI: 10.3390/v13010046] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2020] [Revised: 12/25/2020] [Accepted: 12/27/2020] [Indexed: 12/22/2022] Open
Abstract
P-selectin glycoprotein ligand-1 (PSGL-1) is a cell surface glycoprotein that binds to P-, E-, and L-selectins to mediate the tethering and rolling of immune cells on the surface of the endothelium for cell migration into inflamed tissues. PSGL-1 has been identified as an interferon-γ (INF-γ)-regulated factor that restricts HIV-1 infectivity, and has recently been found to possess broad-spectrum antiviral activities. Here we report that the expression of PSGL-1 in virus-producing cells impairs the incorporation of SARS-CoV and SARS-CoV-2 spike (S) glycoproteins into pseudovirions and blocks pseudovirus attachment and infection of target cells. These findings suggest that PSGL-1 may potentially inhibit coronavirus replication in PSGL-1+ cells.
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Affiliation(s)
- Sijia He
- National Center for Biodefense and Infectious Diseases, School of Systems Biology, George Mason University, Manassas, VA 20110, USA; (S.H.); (B.H.); (D.D.)
| | - Abdul A. Waheed
- Virus-Cell Interaction Section, HIV Dynamics and Replication Program, Center for Cancer Research, National Cancer Institute-Frederick, Frederick, MD 21702, USA;
| | - Brian Hetrick
- National Center for Biodefense and Infectious Diseases, School of Systems Biology, George Mason University, Manassas, VA 20110, USA; (S.H.); (B.H.); (D.D.)
| | - Deemah Dabbagh
- National Center for Biodefense and Infectious Diseases, School of Systems Biology, George Mason University, Manassas, VA 20110, USA; (S.H.); (B.H.); (D.D.)
| | - Ivan V. Akhrymuk
- Department of Biomedical Sciences and Pathobiology, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA; (I.V.A.); (K.K.-H.)
| | - Kylene Kehn-Hall
- Department of Biomedical Sciences and Pathobiology, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA; (I.V.A.); (K.K.-H.)
| | - Eric O. Freed
- Virus-Cell Interaction Section, HIV Dynamics and Replication Program, Center for Cancer Research, National Cancer Institute-Frederick, Frederick, MD 21702, USA;
| | - Yuntao Wu
- National Center for Biodefense and Infectious Diseases, School of Systems Biology, George Mason University, Manassas, VA 20110, USA; (S.H.); (B.H.); (D.D.)
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6
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He S, Waheed AA, Hetrick B, Dabbagh D, Akhrymuk IV, Kehn-Hall K, Freed EO, Wu Y. PSGL-1 inhibits the virion incorporation of SARS-CoV and SARS-CoV-2 spike glycoproteins and impairs virus attachment and infectivity. bioRxiv 2020. [PMID: 32511349 DOI: 10.1101/2020.05.01.073387] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
P-selectin glycoprotein ligand-1 (PSGL-1) is a cell surface glycoprotein that binds to P-, E-, and L-selectins to mediate the tethering and rolling of immune cells on the surface of the endothelium for cell migration into inflamed tissues. PSGL-1 has been identified as an interferon-γ (INF-γ)-regulated factor that restricts HIV-1 infectivity, and has recently been found to possess broad-spectrum antiviral activities. Here we report that the expression of PSGL-1 in virus-producing cells impairs the incorporation of SARS-CoV and SARS-CoV-2 spike (S) glycoproteins into pseudovirions and blocks virus attachment and infection of target cells. These findings suggest that PSGL-1 may potentially inhibit coronavirus replication in PSGL-1+ cells.
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7
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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Mailler E, Waheed AA, Park SY, Gershlick DC, Freed EO, Bonifacino JS. The autophagy protein ATG9A promotes HIV-1 infectivity. Retrovirology 2019; 16:18. [PMID: 31269971 PMCID: PMC6607583 DOI: 10.1186/s12977-019-0480-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2019] [Accepted: 06/24/2019] [Indexed: 01/09/2023] Open
Abstract
BACKGROUND Nef is a multifunctional accessory protein encoded by HIV-1, HIV-2 and SIV that plays critical roles in viral pathogenesis, contributing to viral replication, assembly, budding, infectivity and immune evasion, through engagement of various host cell pathways. RESULTS To gain a better understanding of the role of host proteins in the functions of Nef, we carried out tandem affinity purification-mass spectrometry analysis, and identified over 70 HIV-1 Nef-interacting proteins, including the autophagy-related 9A (ATG9A) protein. ATG9A is a transmembrane component of the machinery for autophagy, a catabolic process in which cytoplasmic components are degraded in lysosomal compartments. Pulldown experiments demonstrated that ATG9A interacts with Nef from not only HIV-1 and but also SIV (cpz, smm and mac). However, expression of HIV-1 Nef had no effect on the levels and localization of ATG9A, and on autophagy, in the host cells. To investigate a possible role for ATG9A in virus replication, we knocked out ATG9A in HeLa cervical carcinoma and Jurkat T cells, and analyzed virus release and infectivity. We observed that ATG9A knockout (KO) had no effect on the release of wild-type (WT) or Nef-defective HIV-1 in these cells. However, the infectivity of WT virus produced from ATG9A-KO HeLa and Jurkat cells was reduced by ~ fourfold and eightfold, respectively, relative to virus produced from WT cells. This reduction in infectivity was independent of the interaction of Nef with ATG9A, and was not due to reduced incorporation of the viral envelope (Env) glycoprotein into the virus. The loss of HIV-1 infectivity was rescued by pseudotyping HIV-1 virions with the vesicular stomatitis virus G glycoprotein. CONCLUSIONS These studies indicate that ATG9A promotes HIV-1 infectivity in an Env-dependent manner. The interaction of Nef with ATG9A, however, is not required for Nef to enhance HIV-1 infectivity. We speculate that ATG9A could promote infectivity by participating in either the removal of a factor that inhibits infectivity or the incorporation of a factor that enhances infectivity of the viral particles. These studies thus identify a novel host cell factor implicated in HIV-1 infectivity, which may be amenable to pharmacologic manipulation for treatment of HIV-1 infection.
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Affiliation(s)
- Elodie Mailler
- Cell Biology and Neurobiology Branch, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Abdul A Waheed
- HIV Dynamics and Replication Program, National Cancer Institute, National Institutes of Health, Frederick, MD, 21702, USA
| | - Sang-Yoon Park
- Cell Biology and Neurobiology Branch, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, 20892, USA
| | - David C Gershlick
- Cell Biology and Neurobiology Branch, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, 20892, USA
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge, UK
| | - Eric O Freed
- HIV Dynamics and Replication Program, National Cancer Institute, National Institutes of Health, Frederick, MD, 21702, USA.
| | - Juan S Bonifacino
- Cell Biology and Neurobiology Branch, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, 20892, USA.
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Uhl J, Gujarathi S, Waheed AA, Gordon A, Freed EO, Gousset K. Myosin-X is essential to the intercellular spread of HIV-1 Nef through tunneling nanotubes. J Cell Commun Signal 2018; 13:209-224. [PMID: 30443895 DOI: 10.1007/s12079-018-0493-z] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2018] [Accepted: 11/01/2018] [Indexed: 12/18/2022] Open
Abstract
Tunneling nanotubes (TNTs) are intercellular structures that allow for the passage of vesicles, organelles, genomic material, pathogenic proteins and pathogens. The unconventional actin molecular motor protein Myosin-X (Myo10) is a known inducer of TNTs in neuronal cells, yet its role in other cell types has not been examined. The Nef HIV-1 accessory protein is critical for HIV-1 pathogenesis and can self-disseminate in culture via TNTs. Understanding its intercellular spreading mechanism could reveal ways to control its damaging effects during HIV-1 infection. Our goal in this study was to characterize the intercellular transport mechanism of Nef from macrophages to T cells. We demonstrate that Nef increases TNTs in a Myo10-dependent manner in macrophages and observed the transfer of Nef via TNTs from macrophages to T cells. To quantify this transfer mechanism, we established an indirect flow cytometry assay. Since Nef expression in T cells down-regulates the surface receptor CD4, we correlated the decrease in CD4 to the transfer of Nef between these cells. Thus, we co-cultured macrophages expressing varying levels of Nef with a T cell line expressing high levels of CD4 and quantified the changes in CD4 surface expression resulting from Nef transfer. We demonstrate that Nef transfer occurs via a cell-to-cell dependent mechanism that directly correlates with the presence of Myo10-dependent TNTs. Thus, we show that Nef can regulate Myo10 expression, thereby inducing TNT formation, resulting in its own transfer from macrophages to T cells. In addition, we demonstrate that up-regulation of Myo10 induced by Nef also occurs in human monocyte derived macrophages during HIV-1 infection.
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Affiliation(s)
- Jaime Uhl
- Biology Department, California State University Fresno, Fresno, 93740, USA
| | - Shivalee Gujarathi
- Biology Department, California State University Fresno, Fresno, 93740, USA
| | - Abdul A Waheed
- HIV Dynamics and Replication Program, National Cancer Institute-Frederick, Frederick, MD, 21702, USA
| | - Ana Gordon
- Biology Department, California State University Fresno, Fresno, 93740, USA
| | - Eric O Freed
- HIV Dynamics and Replication Program, National Cancer Institute-Frederick, Frederick, MD, 21702, USA
| | - Karine Gousset
- Biology Department, California State University Fresno, Fresno, 93740, USA.
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Waheed AA, Gitzen A, Swiderski M, Freed EO. High-Mannose But Not Complex-Type Glycosylation of Tetherin Is Required for Restriction of HIV-1 Release. Viruses 2018; 10:v10010026. [PMID: 29303997 PMCID: PMC5795439 DOI: 10.3390/v10010026] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2017] [Revised: 12/28/2017] [Accepted: 12/31/2017] [Indexed: 11/16/2022] Open
Abstract
Tetherin is an interferon-inducible antiviral protein that inhibits the release of a broad spectrum of enveloped viruses by retaining virions at the surface of infected cells. While the role of specific tetherin domains in antiviral activity is clearly established, the role of glycosylation in tetherin function is not clear. In this study, we carried out a detailed investigation of this question by using tetherin variants in which one or both sites of N-linked glycosylation were mutated (N65A, N92A, and N65,92A), and chemical inhibitors that prevent glycosylation at specific stages of oligosaccharide were added or modified. The single N-linked glycosylation mutants, N65A and N92A, efficiently inhibited the release of Vpu-defective human immunodeficiency virus type 1 (HIV-1). In contrast, the non-glycosylated double mutant, N65,92A, lost its ability to block HIV-1 release. The inability of the N65,92A mutant to inhibit HIV-1 release is associated with a lack of cell-surface expression. A role for glycosylation in cell-surface tetherin expression is supported by tunicamycin treatment, which inhibits the first step of N-linked glycosylation and impairs both cell-surface expression and antiviral activity. Inhibition of complex-type glycosylation with kifunensine, an inhibitor of the oligosaccharide processing enzyme mannosidase 1, had no effect on either the cell-surface expression or antiviral activity of tetherin. These results demonstrate that high-mannose modification of a single asparagine residue is necessary and sufficient, while complex-type glycosylation is dispensable, for cell-surface tetherin expression and antiviral activity.
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Affiliation(s)
- Abdul A Waheed
- Virus-Cell Interaction Section, HIV Dynamics and Replication Program, National Cancer Institute, Bldg. 535, Room 108B, 1050 Boyles St., Frederick, MD 21702-1201, USA.
| | - Ariana Gitzen
- Virus-Cell Interaction Section, HIV Dynamics and Replication Program, National Cancer Institute, Bldg. 535, Room 108B, 1050 Boyles St., Frederick, MD 21702-1201, USA.
| | - Maya Swiderski
- Virus-Cell Interaction Section, HIV Dynamics and Replication Program, National Cancer Institute, Bldg. 535, Room 108B, 1050 Boyles St., Frederick, MD 21702-1201, USA.
| | - Eric O Freed
- Virus-Cell Interaction Section, HIV Dynamics and Replication Program, National Cancer Institute, Bldg. 535, Room 108B, 1050 Boyles St., Frederick, MD 21702-1201, USA.
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11
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Waheed AA, Tachedjian G. Current and Emerging Drug Targets for Human Immunodeficiency Virus. Curr Top Med Chem 2016; 16:1072-3. [PMID: 26381413 DOI: 10.2174/1568026616999150918145541] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- Abdul A Waheed
- Virus-Cell Interaction Section, HIV-DRP National Cancer Institute at Frederick, NIH, Frederick, MD 21702-1201 USA.
| | - Gilda Tachedjian
- Centre for Biomedical Research Burnet Institute, 85 Commercial Rd., Melbourne, VIC, 3004 Australia.
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12
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Abstract
The biomedical intervention that has had a major impact on the natural history of HIV and on the global HIV epidemic is antiretroviral therapy (ART). However, the emergence of drug-resistant HIV, an inevitable consequence of increasing use of antiretroviral drugs, poses a major threat to ART success. At the turn of this century, access to life-saving ART was accelerated in low and middle-income countries with the Millennium Development Goal of 15 million individuals receiving ART by 2015 expected to be achieved. However, ART access needs to continue to expand to help bring HIV under control by 2030. The standard of care for people living with HIV in resource- limited settings differs dramatically compared to high-income countries, and not unexpectedly, ART rollout in these settings has resulted in an increase in acquired and transmitted drug resistance. Also of concern, the same drug classes used for ART have been approved or are being progressed for HIV prevention and drug resistance could mitigate their effectiveness for treatment and prevention. In the absence of an effective HIV vaccine and cure, it is imperative that the antiretroviral drug pipeline contains new classes of HIV inhibitors that are active against circulating drug-resistant strains. Studies to advance our fundamental understanding of HIV replication needs to continue, including the interplay between virus and host cell factors, to identify and characterize new drug targets for chemotherapeutic intervention.
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Affiliation(s)
| | - Gilda Tachedjian
- Retroviral Biology and Antivirals Laboratory, Centre for Biomedical Research, Burnet Institute, GPO Box: 2284, Melbourne, Australia.
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13
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Waheed AA, Kuruppu ND, Felton KL, D’Souza D, Freed EO. In COS cells Vpu can both stabilize tetherin expression and counteract its antiviral activity. PLoS One 2014; 9:e111628. [PMID: 25360760 PMCID: PMC4216104 DOI: 10.1371/journal.pone.0111628] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2014] [Accepted: 10/03/2014] [Indexed: 01/12/2023] Open
Abstract
The interferon-inducible cellular protein tetherin (CD317/BST-2) inhibits the release of a broad range of enveloped viruses. The HIV-1 accessory protein Vpu enhances virus particle release by counteracting this host restriction factor. While the antagonism of human tetherin by Vpu has been associated with both proteasomal and lysosomal degradation, the link between Vpu-mediated tetherin degradation and the ability of Vpu to counteract the antiviral activity of tetherin remains poorly understood. Here, we show that human tetherin is expressed at low levels in African green monkey kidney (COS) cells. However, Vpu markedly increases tetherin expression in this cell line, apparently by sequestering it in an internal compartment that bears lysosomal markers. This stabilization of tetherin by Vpu requires the transmembrane sequence of human tetherin. Although Vpu stabilizes human tetherin in COS cells, it still counteracts the ability of tetherin to suppress virus release. The enhancement of virus release by Vpu in COS cells is associated with a modest reduction in cell-surface tetherin expression, even though the overall expression of tetherin is higher in the presence of Vpu. This study demonstrates that COS cells provide a model system in which Vpu-mediated enhancement of HIV-1 release is uncoupled from Vpu-mediated tetherin degradation.
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Affiliation(s)
- Abdul A. Waheed
- Virus-Cell Interaction Section, HIV Drug Resistance Program, NCI-Frederick, Frederick, Maryland, United States of America
- * E-mail:
| | - Nishani D. Kuruppu
- Virus-Cell Interaction Section, HIV Drug Resistance Program, NCI-Frederick, Frederick, Maryland, United States of America
| | - Kathryn L. Felton
- Virus-Cell Interaction Section, HIV Drug Resistance Program, NCI-Frederick, Frederick, Maryland, United States of America
| | - Darren D’Souza
- Virus-Cell Interaction Section, HIV Drug Resistance Program, NCI-Frederick, Frederick, Maryland, United States of America
| | - Eric O. Freed
- Virus-Cell Interaction Section, HIV Drug Resistance Program, NCI-Frederick, Frederick, Maryland, United States of America
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14
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Park SY, Waheed AA, Zhang ZR, Freed EO, Bonifacino JS. HIV-1 Vpu accessory protein induces caspase-mediated cleavage of IRF3 transcription factor. J Biol Chem 2014; 289:35102-10. [PMID: 25352594 DOI: 10.1074/jbc.m114.597062] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Vpu is an accessory protein encoded by HIV-1 that interferes with multiple host-cell functions. Herein we report that expression of Vpu by transfection into 293T cells causes partial proteolytic cleavage of interferon regulatory factor 3 (IRF3), a key transcription factor in the innate anti-viral response. Vpu-induced IRF3 cleavage is mediated by caspases and occurs mainly at Asp-121. Cleavage produces a C-terminal fragment of ∼37 kDa that comprises the IRF dimerization and transactivation domains but lacks the DNA-binding domain. A similar cleavage is observed upon infection of the Jurkat T-cell line with vesicular stomatitis virus G glycoprotein (VSV-G)-pseudotyped HIV-1. Two other HIV-1 accessory proteins, Vif and Vpr, also contribute to the induction of IRF3 cleavage in both the transfection and the infection systems. The C-terminal IRF3 fragment interferes with the transcriptional activity of full-length IRF3. Cleavage of IRF3 under all of these conditions correlates with cleavage of poly(ADP-ribose) polymerase, an indicator of apoptosis. We conclude that Vpu contributes to the attenuation of the anti-viral response by partial inactivation of IRF3 while host cells undergo apoptosis.
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Affiliation(s)
- Sang Yoon Park
- From the Cell Biology and Metabolism Program, Eunice Kennedy Shriver NICHD, National Institutes of Health, Bethesda, Maryland 20892 and
| | - Abdul A Waheed
- the HIV Drug Resistance Program, Center for Cancer Research, NCI, National Institutes of Health, Frederick, Maryland 21702
| | - Zai-Rong Zhang
- From the Cell Biology and Metabolism Program, Eunice Kennedy Shriver NICHD, National Institutes of Health, Bethesda, Maryland 20892 and
| | - Eric O Freed
- the HIV Drug Resistance Program, Center for Cancer Research, NCI, National Institutes of Health, Frederick, Maryland 21702
| | - Juan S Bonifacino
- From the Cell Biology and Metabolism Program, Eunice Kennedy Shriver NICHD, National Institutes of Health, Bethesda, Maryland 20892 and
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15
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Gonzalez-Suarez ML, Waheed AA, Andrews DM, Ascherman DP, Zeng X, Nayer A. Lupus vasculopathy: Diagnostic, pathogenetic and therapeutic considerations. Lupus 2014; 23:421-7. [DOI: 10.1177/0961203313520340] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
A rare form of vascular disease in systemic lupus erythematosus (SLE), lupus vasculopathy is characterized by necrosis and accumulation of immunoglobulins (IGs) and complements in the wall of arterioles and small arteries resulting in luminal narrowing. Lupus vasculopathy often accompanies lupus nephritis and portends a poor prognosis. Although there is general agreement on the treatment of lupus nephritis, effective treatment strategies for lupus vasculopathy remain to be defined. We report a 20-year-old woman with SLE who presented with generalized tonic-clonic seizure. Her immunosuppressive regimen consisted of mycophenolate mofetil, prednisone and hydroxychloroquine. On physical examination, she was Cushingoid in appearance and hypertensive. Laboratory tests indicated renal disease. Coagulation studies disclosed de novo lupus anticoagulant. Magnetic resonance imaging of the brain demonstrated acute focal cerebral hemorrhage. Echocardiography revealed reduced ejection fraction and severe mitral regurgitation. Despite high-dose glucocorticoids and mycophenolate mofetil, renal function remained poor. Kidney biopsy demonstrated lupus vasculopathy and glomerulonephritis. Plasma exchange therapy and intravenous cyclophosphamide were administered. Over the ensuing four weeks, renal function improved, complement levels increased, autoantibody titers decreased and lupus anticoagulant disappeared. In conclusion, lupus vasculopathy can occur in SLE despite a heavy immunosuppressive regimen. Antiphospholipid antibodies might be involved in the pathogenesis of lupus vasculopathy. Plasma exchange therapy in conjunction with intravenous cyclophosphamide may represent an effective treatment strategy for lupus vasculopathy.
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Affiliation(s)
| | - AA Waheed
- Division of Nephrology and Hypertension, University of Miami, FL, USA
| | - DM Andrews
- Department of Pathology, University of Miami, FL, USA
| | - DP Ascherman
- Division of Rheumatology, University of Miami, FL, USA
| | - X Zeng
- Nephrocor-Bostwick Laboratories, FL, USA
| | - A Nayer
- Division of Nephrology and Hypertension, University of Miami, FL, USA
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16
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Zhang H, Curreli F, Waheed AA, Mercredi PY, Mehta M, Bhargava P, Scacalossi D, Tong X, Lee S, Cooper A, Summers MF, Freed EO, Debnath AK. Dual-acting stapled peptides target both HIV-1 entry and assembly. Retrovirology 2013; 10:136. [PMID: 24237936 PMCID: PMC3842668 DOI: 10.1186/1742-4690-10-136] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2013] [Accepted: 11/03/2013] [Indexed: 01/20/2023] Open
Abstract
Background Previously, we reported the conversion of the 12-mer linear and cell-impermeable peptide CAI to a cell-penetrating peptide NYAD-1 by using an i,i + 4 hydrocarbon stapling technique and confirmed its binding to the C-terminal domain (CTD) of the HIV-1 capsid (CA) protein with an improved affinity (Kd ~ 1 μM) compared to CAI (Kd ~ 15 μM). NYAD-1 disrupts the formation of both immature- and mature-like virus particles in in vitro and cell-based assembly assays. In addition, it displays potent anti-HIV-1 activity in cell culture against a range of laboratory-adapted and primary HIV-1 isolates. Results In this report, we expanded the study to i,i + 7 hydrocarbon-stapled peptides to delineate their mechanism of action and antiviral activity. We identified three potent inhibitors, NYAD-36, -66 and -67, which showed strong binding to CA in NMR and isothermal titration calorimetry (ITC) studies and disrupted the formation of mature-like particles. They showed typical α-helical structures and penetrated cells; however, the cell penetration was not as efficient as observed with the i,i + 4 peptides. Unlike NYAD-1, the i,i + 7 peptides did not have any effect on virus release; however, they impaired Gag precursor processing. HIV-1 particles produced in the presence of these peptides displayed impaired infectivity. Consistent with an effect on virus entry, selection for viral resistance led to the emergence of two mutations in the gp120 subunit of the viral envelope (Env) glycoprotein, V120Q and A327P, located in the conserved region 1 (C1) and the base of the V3 loop, respectively. Conclusion The i,i + 7 stapled peptides derived from CAI unexpectedly target both CA and the V3 loop of gp120. This dual-targeted activity is dependent on their ability to penetrate cells as well as their net charge. This mechanistic revelation will be useful in further modifying these peptides as potent anti-HIV-1 agents.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | | | | | | | - Asim K Debnath
- Laboratory of Molecular Modeling, Drug Design, Lindsley F, Kimball Research Institute of the New York Blood Center, 310 E 67th Street, New York, NY 10065, USA.
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17
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Daniels SI, Soule EE, Davidoff KS, Bernbaum JG, Hu D, Maeda K, Stahl SJ, Naiman NE, Waheed AA, Freed EO, Wingfield P, Yarchoan R, Davis DA. Activation of virus uptake through induction of macropinocytosis with a novel polymerizing peptide. FASEB J 2013; 28:106-16. [PMID: 24097312 DOI: 10.1096/fj.13-238113] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
A 27-aa peptide (P27) was previously shown to decrease the accumulation of human immunodeficiency virus type 1 (HIV-1) in the supernatant of chronically infected cells; however, the mechanism was not understood. Here, we show that P27 prevents virus accumulation by inducing macropinocytosis (MPC). Treatment of HIV-1- and human T-cell lymphotropic virus type 1 (HTLV-1)-infected cells with 2-10 μM P27 caused cell membrane ruffling and uptake of virus and polymerized forms of the peptide into large vacuoles. As demonstrated by electron microscopy, activation of MPC did not require virus or cells infected with virus, as P27 initiated its own uptake in the absence of virus. Inhibitors of MPC, Cytochalasin D and amiloride, decreased P27-mediated uptake of soluble dextran and inhibited P27-induced virus uptake by >60%, which provides further evidence that P27 induces MPC. In CD4(+) HeLa cells, HIV-1 infection was enhanced by P27 up to 4-fold, and P27 increased infection at concentrations as low as 20 nM. The 5-aa C-terminal domain of P27 was necessary for virus uptake and may be responsible for the polymerization of P27 into fibrils. These forms of P27 may play a key role in triggering MPC, making this peptide a useful tool for studying virus uptake and infection, as well as MPC of other macromolecules.
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Affiliation(s)
- Sarah I Daniels
- 110 Center Dr., Bldg 10, Rm. 6N106, MSC 1868, NIH, Bethesda MD 20892-1868, USA.
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18
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Abstract
The Gag proteins of HIV-1 are central players in virus particle assembly, release, and maturation, and also function in the establishment of a productive infection. Despite their importance throughout the replication cycle, there are currently no approved antiretroviral therapies that target the Gag precursor protein or any of the mature Gag proteins. Recent progress in understanding the structural and cell biology of HIV-1 Gag function has revealed a number of potential Gag-related targets for possible therapeutic intervention. In this review, we summarize our current understanding of HIV-1 Gag and suggest some approaches for the development of novel antiretroviral agents that target Gag.
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Affiliation(s)
- Abdul A. Waheed
- Virus-Cell Interaction Section, HIV Drug Resistance Program, National Cancer Institute, Frederick, Maryland
| | - Eric O. Freed
- Virus-Cell Interaction Section, HIV Drug Resistance Program, National Cancer Institute, Frederick, Maryland
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19
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Kim SE, Liu F, Im YJ, Stephen AG, Fivash MJ, Waheed AA, Freed EO, Fisher RJ, Hurley JH, Burke TR. Elucidation of New Binding Interactions with the Tumor Susceptibility Gene 101 (Tsg101) Protein Using Modified HIV-1 Gag-p6 Derived Peptide Ligands. ACS Med Chem Lett 2011; 2:337-341. [PMID: 21643473 DOI: 10.1021/ml1002579] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Targeting protein-protein interactions is gaining greater recognition as an attractive approach to therapeutic development. An example of this may be found with the human cellular protein encoded by the tumor susceptibility gene 101 (Tsg101), where interaction with the p6 C-terminal domain of the nascent viral Gag protein is required for HIV-1 particle budding and release. This association of Gag with Tsg101 is highly dependent on a "Pro-Thr-Ala-Pro" ("PTAP") peptide sequence within the p6 protein. Although p6-derived peptides offer potential starting points for developing Tsg101-binding inhibitors, the affinities of canonical peptides are outside the useful range (K(d) values greater than 50 μM). Reported herein are crystal structures of Tsg101 in complex with two structurally-modified PTAP-derived peptides. This data define new regions of ligand interaction not previously identified with canonical peptide sequences. This information could be highly useful in the design of Tsg101-binding antagonists.
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Affiliation(s)
- Sung-Eun Kim
- Chemical Biology Laboratory, Molecular, Discovery Program, CCR, NCI-Frederick, Frederick, Maryland 21702, United States
| | - Fa Liu
- Chemical Biology Laboratory, Molecular, Discovery Program, CCR, NCI-Frederick, Frederick, Maryland 21702, United States
| | | | | | - Matthew J. Fivash
- Data Management Systems, Inc., NCI-Frederick, Frederick, Maryland 21702, United States
| | - Abdul A. Waheed
- HIV Drug Resistance Program, CCR, NCI-Frederick, Frederick, Maryland 21702, United States
| | - Eric O. Freed
- HIV Drug Resistance Program, CCR, NCI-Frederick, Frederick, Maryland 21702, United States
| | | | | | - Terrence R. Burke
- Chemical Biology Laboratory, Molecular, Discovery Program, CCR, NCI-Frederick, Frederick, Maryland 21702, United States
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20
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Zhang H, Curreli F, Zhang X, Bhattacharya S, Waheed AA, Cooper A, Cowburn D, Freed EO, Debnath AK. Antiviral activity of α-helical stapled peptides designed from the HIV-1 capsid dimerization domain. Retrovirology 2011; 8:28. [PMID: 21539734 PMCID: PMC3097154 DOI: 10.1186/1742-4690-8-28] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2010] [Accepted: 05/03/2011] [Indexed: 01/11/2023] Open
Abstract
Background The C-terminal domain (CTD) of HIV-1 capsid (CA), like full-length CA, forms dimers in solution and CTD dimerization is a major driving force in Gag assembly and maturation. Mutations of the residues at the CTD dimer interface impair virus assembly and render the virus non-infectious. Therefore, the CTD represents a potential target for designing anti-HIV-1 drugs. Results Due to the pivotal role of the dimer interface, we reasoned that peptides from the α-helical region of the dimer interface might be effective as decoys to prevent CTD dimer formation. However, these small peptides do not have any structure in solution and they do not penetrate cells. Therefore, we used the hydrocarbon stapling technique to stabilize the α-helical structure and confirmed by confocal microscopy that this modification also made these peptides cell-penetrating. We also confirmed by using isothermal titration calorimetry (ITC), sedimentation equilibrium and NMR that these peptides indeed disrupt dimer formation. In in vitro assembly assays, the peptides inhibited mature-like virus particle formation and specifically inhibited HIV-1 production in cell-based assays. These peptides also showed potent antiviral activity against a large panel of laboratory-adapted and primary isolates, including viral strains resistant to inhibitors of reverse transcriptase and protease. Conclusions These preliminary data serve as the foundation for designing small, stable, α-helical peptides and small-molecule inhibitors targeted against the CTD dimer interface. The observation that relatively weak CA binders, such as NYAD-201 and NYAD-202, showed specificity and are able to disrupt the CTD dimer is encouraging for further exploration of a much broader class of antiviral compounds targeting CA. We cannot exclude the possibility that the CA-based peptides described here could elicit additional effects on virus replication not directly linked to their ability to bind CA-CTD.
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Affiliation(s)
- Hongtao Zhang
- Laboratory of Molecular Modeling & Drug Design; Lindsley F, Kimball Research Institute of the New York Blood Center, 310 E 67th Street, New York, NY 10065, USA
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21
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Liu F, Stephen AG, Waheed AA, Freed EO, Fisher RJ, Burke TR. Application of ring-closing metathesis macrocyclization to the development of Tsg101-binding antagonists. Bioorg Med Chem Lett 2010; 20:318-21. [PMID: 19914066 PMCID: PMC2818493 DOI: 10.1016/j.bmcl.2009.10.105] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2009] [Revised: 10/23/2009] [Accepted: 10/26/2009] [Indexed: 11/18/2022]
Abstract
HIV-1 viral budding involves binding of the viral Gag(p6) protein to the ubiquitin E2 variant domain of the human tumor susceptibility gene 101 protein (Tsg101). Recognition of p6 by Tsg101 is mediated in part by a proline-rich motif that contains the sequence 'Pro-Thr-Ala-Pro' ('PTAP'). Using the p6-derived 9-mer sequence 'PEPTAPPEE', we had previously improved peptide binding affinity by employing N-alkylglycine ('peptoid') residues. The current study applies ring-closing metathesis macrocyclization strategies to Tsg101-binding peptide-peptoid hybrids as an approach to stabilize binding conformations and to observe the effects of such macrocyclization on Tsg101-binding affinity and bioavailability.
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Affiliation(s)
- Fa Liu
- Laboratory of Medicinal Chemistry, Center for Cancer Research, National Cancer Institute-Frederick, National Institutes of Health Frederick, MD 21702
| | - Andrew G. Stephen
- Protein Chemistry Laboratory, Advanced Technology Program, SAIC-Frederick, Inc. NCI-Frederick, Frederick, MD 21702
| | - Abdul A. Waheed
- HIV Drug Resistance Program, National Cancer Institute-Frederick, National Institutes of Health Frederick, MD 21702
| | - Eric O. Freed
- HIV Drug Resistance Program, National Cancer Institute-Frederick, National Institutes of Health Frederick, MD 21702
| | - Robert J. Fisher
- Protein Chemistry Laboratory, Advanced Technology Program, SAIC-Frederick, Inc. NCI-Frederick, Frederick, MD 21702
| | - Terrence R. Burke
- Laboratory of Medicinal Chemistry, Center for Cancer Research, National Cancer Institute-Frederick, National Institutes of Health Frederick, MD 21702
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22
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Abstract
Several critical steps in the replication cycle of human immunodeficiency virus type 1 (HIV-1) - entry, assembly and budding - are complex processes that take place at the plasma membrane of the host cell. A growing body of data indicates that these early and late steps in HIV-1 replication take place in specialized plasma membrane microdomains, and that many of the viral and cellular components required for entry, assembly, and budding are concentrated in these microdomains. In particular, a number of studies have shown that cholesterol- and sphingolipid-enriched microdomains known as lipid rafts play important roles in multiple steps in the virus replication cycle. In this review, we provide an overview of what is currently known about the involvement of lipids and membrane microdomains in HIV-1 replication.
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Affiliation(s)
- Abdul A Waheed
- Virus-Cell Interaction Section, HIV Drug Resistance Program, National Cancer Institute, Frederick, MD 21702, USA.
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23
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Abstract
HIV-1 release requires a direct interaction between the p6 domain of the Gag protein and Tsg101, a component of the cellular endosomal sorting complex required for transport I (ESCRT-I). Disruption of the binding between Gag and Tsg101 is highly detrimental to particle release, making this viral-host cell interaction a potential target for the development of novel anti-HIV-1 agents. An article in this issue reports on the application of a bacterial reverse two-hybrid strategy to identify a cyclic peptide that disrupts Gag-Tsg101 binding and suppresses HIV-1 particle release.
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Affiliation(s)
- Abdul A. Waheed
- Virus-Cell Interaction Section, HIV Drug Resistance Program, National Cancer Institute, Frederick, Maryland 21702
| | - Eric O. Freed
- Virus-Cell Interaction Section, HIV Drug Resistance Program, National Cancer Institute, Frederick, Maryland 21702
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24
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Liu F, Stephen AG, Waheed AA, Aman MJ, Freed EO, Fisher RJ, Burke TR. SAR by oxime-containing peptide libraries: application to Tsg101 ligand optimization. Chembiochem 2008; 9:2000-4. [PMID: 18655064 PMCID: PMC2581409 DOI: 10.1002/cbic.200800281] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2008] [Indexed: 11/10/2022]
Abstract
HIV-1 viral assembly requires a direct interaction between a Pro-Thr-Ala-Pro ("PTAP") motif in the viral protein Gag-p6 and the cellular endosomal sorting factor Tsg101. In an effort to develop competitive inhibitors of this interaction, an SAR study was conducted based on the application of post solid-phase oxime formation involving the sequential insertion of aminooxy-containing residues within a nonamer parent peptide followed by reaction with libraries of aldehydes. Approximately 15-20-fold enhancement in binding affinity was achieved by this approach.
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Affiliation(s)
- Fa Liu
- Dr. F. Liu, Dr. T. R. Burke, Jr., Laboratory of Medicinal Chemistry, CCR, NCI-Frederick, Building 376 Boyles Street, Frederick, MD 21702 (USA)
| | - Andrew G. Stephen
- Dr. A. G. Stephen, Dr. R. J. Fisher, Protein Chemistry Laboratory, Advanced Technology Program, SAIC-Frederick, Inc. NCI-Frederick, Frederick, MD 21702 (USA)
| | - Abdul A. Waheed
- Dr. A. A. Waheed, Dr. E. O. Freed, HIV Drug Resistance Program, CCR, NCI-Frederick, Frederick, MD 21702 (USA)
| | - M. Javad Aman
- Dr. M. J. Aman, U.S. Army Medical Research Institute for Infectious Diseases, Frederick, MD 21702 (USA)
| | - Eric O. Freed
- Dr. A. A. Waheed, Dr. E. O. Freed, HIV Drug Resistance Program, CCR, NCI-Frederick, Frederick, MD 21702 (USA)
| | - Robert J. Fisher
- Dr. A. G. Stephen, Dr. R. J. Fisher, Protein Chemistry Laboratory, Advanced Technology Program, SAIC-Frederick, Inc. NCI-Frederick, Frederick, MD 21702 (USA)
| | - Terrence R. Burke
- Dr. F. Liu, Dr. T. R. Burke, Jr., Laboratory of Medicinal Chemistry, CCR, NCI-Frederick, Building 376 Boyles Street, Frederick, MD 21702 (USA)
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25
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Zhang H, Zhao Q, Bhattacharya S, Waheed AA, Tong X, Hong A, Heck S, Curreli F, Goger M, Cowburn D, Freed EO, Debnath AK. A cell-penetrating helical peptide as a potential HIV-1 inhibitor. J Mol Biol 2008; 378:565-80. [PMID: 18374356 DOI: 10.1016/j.jmb.2008.02.066] [Citation(s) in RCA: 155] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2007] [Revised: 02/27/2008] [Accepted: 02/28/2008] [Indexed: 10/22/2022]
Abstract
The capsid domain of the human immunodeficiency virus type 1 (HIV-1) Gag polyprotein is a critical determinant of virus assembly, and is therefore a potential target for developing drugs for AIDS therapy. Recently, a 12-mer alpha-helical peptide (CAI) was reported to disrupt immature- and mature-like capsid particle assembly in vitro; however, it failed to inhibit HIV-1 in cell culture due to its inability to penetrate cells. The same group reported the X-ray crystal structure of CAI in complex with the C-terminal domain of capsid (C-CA) at a resolution of 1.7 A. Using this structural information, we have utilized a structure-based rational design approach to stabilize the alpha-helical structure of CAI and convert it to a cell-penetrating peptide (CPP). The modified peptide (NYAD-1) showed enhanced alpha-helicity. Experiments with laser scanning confocal microscopy indicated that NYAD-1 penetrated cells and colocalized with the Gag polyprotein during its trafficking to the plasma membrane where virus assembly takes place. NYAD-1 disrupted the assembly of both immature- and mature-like virus particles in cell-free and cell-based in vitro systems. NMR chemical shift perturbation analysis mapped the binding site of NYAD-1 to residues 169-191 of the C-terminal domain of HIV-1 capsid encompassing the hydrophobic cavity and the critical dimerization domain with an improved binding affinity over CAI. Furthermore, experimental data indicate that NYAD-1 most likely targets capsid at a post-entry stage. Most significantly, NYAD-1 inhibited a large panel of HIV-1 isolates in cell culture at low micromolar potency. Our study demonstrates how a structure-based rational design strategy can be used to convert a cell-impermeable peptide to a cell-permeable peptide that displays activity in cell-based assays without compromising its mechanism of action. This proof-of-concept cell-penetrating peptide may aid validation of capsid as an anti-HIV-1 drug target and may help in designing peptidomimetics and small molecule drugs targeted to this protein.
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Affiliation(s)
- Hongtao Zhang
- Laboratory of Molecular Modeling and Drug Design, Lindsley F. Kimball Research Institute of the New York Blood Center, 310 E 67th Street, New York, NY 10021, USA
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Abstract
Virus assembly constitutes a key phase of the HIV-1 replication cycle. The assembly process is initiated by the synthesis of the Gag precursor protein, Pr55(Gag), in the cytosol of the infected cell. After its synthesis, Pr55(Gag) is rapidly transported in most cell types to the plasma membrane (PM) where it associates with the inner leaflet of the lipid bilayer. Gag-Gag interactions lead to the assembly of an electron-dense patch of Gag proteins at the membrane. The viral envelope (Env) glycoproteins associate with Gag during the assembly process. The highly multimerized Gag complex begins to bud outwardly from the PM and eventually pinches off from the cell surface. Concomitant with release, the viral protease cleaves Pr55(Gag) to the mature Gag proteins matrix, capsid, nucleocapsid and p6, leading to core condensation. The mature infectious virus particle is now able to initiate a new round of infection in a fresh target cell. Techniques have been developed in many laboratories to study each of the distinct phases of the HIV-1 assembly and release pathway. A number of these techniques are described in detail in this chapter.
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Affiliation(s)
- Abdul A Waheed
- Virus-Cell Interaction Section, HIV Drug Resistance Program NCI-Frederick, National Institutes of Health, Frederick MD, USA
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27
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Abstract
Interferons elicit antiviral responses by inducing the expression of a large number of host cell genes. In this issue of Cell Host & Microbe, Wang and colleagues report that the interferon-inducible protein viperin inhibits influenza A virus release by impairing the formation of cholesterol-enriched plasma membrane microdomains, or lipid rafts. Viperin appears to disrupt lipid rafts by suppressing the activity of farnesyl diphosphate synthase, a key enzyme in isoprenoid biosynthesis.
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Affiliation(s)
- Abdul A Waheed
- Virus-Cell Interaction Section, HIV Drug Resistance Program, National Cancer Institute, Frederick, MD 21702, USA
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Nini L, Waheed AA, Panicker LM, Czapiga M, Zhang JH, Simonds WF. R7-binding protein targets the G protein beta 5/R7-regulator of G protein signaling complex to lipid rafts in neuronal cells and brain. BMC Biochem 2007; 8:18. [PMID: 17880698 PMCID: PMC2048962 DOI: 10.1186/1471-2091-8-18] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/11/2007] [Accepted: 09/19/2007] [Indexed: 12/02/2022]
Abstract
Background Heterotrimeric guanine nucleotide-binding regulatory proteins (G proteins), composed of Gα, Gβ, and Gγ subunits, are positioned at the inner face of the plasma membrane and relay signals from activated G protein-coupled cell surface receptors to various signaling pathways. Gβ5 is the most structurally divergent Gβ isoform and forms tight heterodimers with regulator of G protein signalling (RGS) proteins of the R7 subfamily (R7-RGS). The subcellular localization of Gβ 5/R7-RGS protein complexes is regulated by the palmitoylation status of the associated R7-binding protein (R7BP), a recently discovered SNARE-like protein. We investigate here whether R7BP controls the targeting of Gβ5/R7-RGS complexes to lipid rafts, cholesterol-rich membrane microdomains where conventional heterotrimeric G proteins and some effector proteins are concentrated in neurons and brain. Results We show that endogenous Gβ5/R7-RGS/R7BP protein complexes are present in native neuron-like PC12 cells and that a fraction is targeted to low-density, detergent-resistant membrane lipid rafts. The buoyant density of endogenous raft-associated Gβ5/R7-RGS protein complexes in PC12 cells was similar to that of lipid rafts containing the palmitoylated marker proteins PSD-95 and LAT, but distinct from that of the membrane microdomain where flotillin was localized. Overexpression of wild-type R7BP, but not its palmitoylation-deficient mutant, greatly enriched the fraction of endogenous Gβ5/R7-RGS protein complexes in the lipid rafts. In HEK-293 cells the palmitoylation status of R7BP also regulated the lipid raft targeting of co-expressed Gβ5/R7-RGS/R7BP proteins. A fraction of endogenous Gβ5/R7-RGS/R7BP complexes was also present in lipid rafts in mouse brain. Conclusion A fraction of Gβ5/R7-RGS/R7BP protein complexes is targeted to low-density, detergent-resistant membrane lipid rafts in PC12 cells and brain. In cultured cells, the palmitoylation status of R7BP regulated the lipid raft targeting of endogenous or co-expressed Gβ5/R7-RGS proteins. Taken together with recent evidence that the kinetic effects of the Gβ5 complex on GPCR signaling are greatly enhanced by R7BP palmitoylation through a membrane-anchoring mechanism, our data suggest the targeting of the Gβ5/R7-RGS/R7BP complex to lipid rafts in neurons and brain, where G proteins and their effectors are concentrated, may be central to the G protein regulatory function of the complex.
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Affiliation(s)
- Lylia Nini
- Metabolic Diseases Branch, 10/8C-101, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - Abdul A Waheed
- Virus-Cell Interaction Section, HIV Drug Resistance Program, National Cancer Institute at Frederick, Frederick, MD 21702, USA
| | - Leelamma M Panicker
- Metabolic Diseases Branch, 10/8C-101, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - Meggan Czapiga
- Research Technologies Branch, Bldg. 4Room B2-30B, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - Jian-Hua Zhang
- Metabolic Diseases Branch, 10/8C-101, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - William F Simonds
- Metabolic Diseases Branch, 10/8C-101, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA
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Waheed AA, Ablan SD, Roser JD, Sowder RC, Schaffner CP, Chertova E, Freed EO. HIV-1 escape from the entry-inhibiting effects of a cholesterol-binding compound via cleavage of gp41 by the viral protease. Proc Natl Acad Sci U S A 2007; 104:8467-71. [PMID: 17483482 PMCID: PMC1895973 DOI: 10.1073/pnas.0701443104] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
HIV-1 virions are highly enriched in cholesterol relative to the cellular plasma membrane. We recently reported that a cholesterol-binding compound, amphotericin B methyl ester (AME), blocks HIV-1 entry and that single amino acid substitutions in the cytoplasmic tail of the transmembrane envelope glycoprotein gp41 confer resistance to AME. In this study, we defined the mechanism of resistance to AME. We observed that the gp41 in AME-resistant virions is substantially smaller than wild-type gp41. Remarkably, we found that this shift in gp41 size is due to cleavage of the gp41 cytoplasmic tail by the viral protease. We mapped the protease-mediated cleavage to two sites in the cytoplasmic tail and showed that gp41 truncations in this region also confer AME resistance. Thus, to escape the inhibitory effects of AME, HIV-1 evolved a mechanism of protease-mediated envelope glycoprotein cleavage used by several other retroviruses to activate envelope glycoprotein fusogenicity. In contrast to the mechanism of AME resistance observed for HIV-1, we demonstrate that simian immunodeficiency virus can escape from AME via the introduction of premature termination codons in the gp41 cytoplasmic tail coding region. These findings demonstrate that in human T cell lines, HIV-1 and simian immunodeficiency virus can evolve distinct strategies for evading AME, reflecting their differential requirements for the gp41 cytoplasmic tail in virus replication. These data reveal that HIV-1 can escape from an inhibitor of viral entry by acquiring mutations that cause the cytoplasmic tail of gp41 to be cleaved by the viral protease.
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Affiliation(s)
- Abdul A. Waheed
- *Virus–Cell Interaction Section, HIV Drug Resistance Program, National Cancer Institute–Frederick, Frederick, MD 21702
| | - Sherimay D. Ablan
- *Virus–Cell Interaction Section, HIV Drug Resistance Program, National Cancer Institute–Frederick, Frederick, MD 21702
| | - James D. Roser
- AIDS Vaccine Program, Basic Research Program, Science Applications International Corporation, National Cancer Institute–Frederick, Frederick, MD 21702; and
| | - Raymond C. Sowder
- AIDS Vaccine Program, Basic Research Program, Science Applications International Corporation, National Cancer Institute–Frederick, Frederick, MD 21702; and
| | - Carl P. Schaffner
- Department of Microbiology and Biochemistry, Waksman Institute, Rutgers, The State University of New Jersey, New Brunswick, NJ 08903
| | - Elena Chertova
- AIDS Vaccine Program, Basic Research Program, Science Applications International Corporation, National Cancer Institute–Frederick, Frederick, MD 21702; and
| | - Eric O. Freed
- *Virus–Cell Interaction Section, HIV Drug Resistance Program, National Cancer Institute–Frederick, Frederick, MD 21702
- To whom correspondence should be addressed. E-mail:
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Berkane AA, Nguyen HTT, Tranchida F, Waheed AA, Deyris V, Tchiakpe L, Fasano C, Nicoletti C, Desseaux V, Ajandouz EH, Comeau D, Comeau L, Hiol A. Proteomic of lipid rafts in the exocrine pancreas from diet-induced obese rats. Biochem Biophys Res Commun 2007; 355:813-9. [PMID: 17320817 DOI: 10.1016/j.bbrc.2007.02.037] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2007] [Accepted: 02/08/2007] [Indexed: 01/18/2023]
Abstract
In the present work, we induced obesity in rats with high-energy-starch diet and studied exocrine pancreas response. The zymogen granule (ZG) or purified plasma membrane (PM) from the exocrine pancreas was used for the isolation of the detergent-resistant membranes (DRMs). Based on high content of cholesterol, GM1, the bile salt dependent lipase (BSDL), and GP2 enrichment, the low-density fractions were defined as lipid rafts. Additionally, the rafts vesicles were determined by immunogold labeling with anti BSDL. By combining MALDI-TOF/MS and nano-LC ESI Q-TOF MS/MS proteomic identification we have selected 33 proteins from the lipid rafts which were classified into at least four functional families. Our data suggest that the acinar PM from the diet-induced obesity rats may be organized into lipid rafts, and characterization of rafts proteome can contribute to improve our understanding of food digestion under obesity.
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Affiliation(s)
- Amine Adda Berkane
- Université Paul Cézanne, FST-Institut Méditerranéen de Recherche en Nutrition IMRN, UMR INRA 1111/PNV UMR 6153 1147, Marseille, France
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31
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Ono A, Waheed AA, Freed EO. Depletion of cellular cholesterol inhibits membrane binding and higher-order multimerization of human immunodeficiency virus type 1 Gag. Virology 2007; 360:27-35. [PMID: 17095032 PMCID: PMC1945131 DOI: 10.1016/j.virol.2006.10.011] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2006] [Revised: 09/14/2006] [Accepted: 10/05/2006] [Indexed: 12/30/2022]
Abstract
Recent studies have suggested that the plasma membrane contains cholesterol-enriched microdomains known as lipid rafts. HIV-1 Gag binds raft-rich regions of the plasma membrane, and cholesterol depletion impairs HIV-1 particle production. In this study, we sought to define the block imposed by cholesterol depletion. We observed that membrane binding and higher-order multimerization of Gag were markedly reduced upon cholesterol depletion. Fusing to Gag a highly efficient, heterologous membrane-binding sequence reversed the defects in Gag-membrane binding and multimerization caused by cholesterol depletion, indicating that the impact of reducing the membrane cholesterol content on Gag-membrane binding and multimerization can be circumvented by increasing the affinity of Gag for membrane. Virus release efficiency of this Gag derivative was minimally affected by cholesterol depletion. Altogether, these results are consistent with the hypothesis that cholesterol-enriched membrane microdomains promote HIV-1 particle production by facilitating both Gag-membrane binding and Gag multimerization.
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Affiliation(s)
- Akira Ono
- Virus-Cell Interaction Section, HIV Drug Resistance Program, National Cancer Institute at Frederick, Frederick, MD 21702-1201, USA.
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32
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Waheed AA, Ablan SD, Mankowski MK, Cummins JE, Ptak RG, Schaffner CP, Freed EO. Inhibition of HIV-1 replication by amphotericin B methyl ester: selection for resistant variants. J Biol Chem 2006; 281:28699-711. [PMID: 16882663 DOI: 10.1074/jbc.m603609200] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Membrane cholesterol plays an important role in human immunodeficiency virus type 1 (HIV-1) particle production and infectivity. Here, we have investigated the target and mechanism of action of a cholesterol-binding compound, the polyene antifungal antibiotic amphotericin B methyl ester (AME). We found that AME potently inhibited the replication of a highly divergent panel of HIV-1 isolates in various T-cell lines and primary cells irrespective of clade or target cell tropism. The defects in HIV-1 replication caused by AME were due to profoundly impaired viral infectivity as well as a defect in viral particle production. To elucidate further the mechanism of action of AME, we selected for and characterized AME-resistant HIV-1 variants. Mutations responsible for AME resistance mapped to a highly conserved and functionally important endocytosis motif in the cytoplasmic tail of the transmembrane glycoprotein gp41. Interestingly, truncation of the gp41 cytoplasmic tail in the context of either HIV-1 or rhesus macaque simian immunodeficiency virus also conferred resistance to AME. The infectivity of HIV-1 virions bearing murine leukemia virus or vesicular stomatitis virus glycoproteins was unaffected by AME. Our data define the target and mechanism of action of AME and provide support for the concept that cholesterol-binding compounds should be pursued as antiretroviral drugs to disrupt HIV-1 replication.
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Affiliation(s)
- Abdul A Waheed
- Virus-Cell Interaction Section, HIV Drug Resistance Program, NCI-Frederick, National Institutes of Health, Frederick, Maryland 21702-1201, USA
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33
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Nguyen HTT, Amine AB, Lafitte D, Waheed AA, Nicoletti C, Villard C, Létisse M, Deyris V, Rozière M, Tchiakpe L, Danielle CD, Comeau L, Hiol A. Proteomic characterization of lipid rafts markers from the rat intestinal brush border. Biochem Biophys Res Commun 2006; 342:236-44. [PMID: 16480947 DOI: 10.1016/j.bbrc.2006.01.141] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2006] [Accepted: 01/26/2006] [Indexed: 11/22/2022]
Abstract
To assess intestinal lipid rafts functions through the characterization of their protein markers, we have isolated lipid rafts of rat mucosa either from the total membrane or purified brush-border membrane (BBM) by sucrose gradient fractionation after detergent treatment. In both membrane preparations, the floating fractions (4-5) were enriched in cholesterol, ganglioside GM1, and N aminopeptidase (NAP) known as intestinal lipid rafts markers. Based on MALDI-TOF/MS identification and simultaneous detection by immunoblotting, 12 proteins from BBM cleared from contaminants were selected as rafts markers. These proteins include several signaling/trafficking proteins belonging to the G protein family and the annexins as well as GPI-anchored proteins. Remarkably GP2, previously described as the pancreatic granule GPI-anchored protein, was found in intestinal lipid rafts. The proteomic strategy assayed on the intestine leads to the characterization of known (NAP, alkaline phosphatase, dipeptidyl aminopeptidase, annexin II, and galectin-4) and new (GP2, annexin IV, XIIIb, Galpha(q), Galpha(11), glutamate receptor, and GPCR 7) lipid rafts markers. Together our results indicate that some digestive enzymes, trafficking and signaling proteins may be functionally distributed in the intestine lipid rafts.
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Affiliation(s)
- Hang Thi Thu Nguyen
- Université Paul Cézanne, Aix-Marseille III, Faculté des Sciences et Techniques de St Jérôme, Institut Méditerranéen de Recherche en Nutrition IMRN, UMR-INRA 1111, LCBA-LBBN, 13397 Marseille Cedex 20, France
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34
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Ono A, Waheed AA, Joshi A, Freed EO. Association of human immunodeficiency virus type 1 gag with membrane does not require highly basic sequences in the nucleocapsid: use of a novel Gag multimerization assay. J Virol 2005; 79:14131-40. [PMID: 16254348 PMCID: PMC1280195 DOI: 10.1128/jvi.79.22.14131-14140.2005] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2005] [Accepted: 08/30/2005] [Indexed: 12/30/2022] Open
Abstract
Human immunodeficiency virus type 1 (HIV-1) particle production, a process driven by the Gag polyprotein precursor, occurs on the plasma membrane in most cell types. The plasma membrane contains cholesterol-enriched microdomains termed lipid rafts, which can be isolated as detergent-resistant membrane (DRM). Previously, we and others demonstrated that HIV-1 Gag is associated with DRM and that disruption of Gag-raft interactions impairs HIV-1 particle production. However, the determinants of Gag-raft association remain undefined. In this study, we developed a novel epitope-based Gag multimerization assay to examine whether Gag assembly is essential for its association with lipid rafts. We observed that membrane-associated, full-length Gag is poorly detected by immunoprecipitation relative to non-membrane-bound Gag. This poor detection is due to assembly-driven masking of Gag epitopes, as denaturation greatly improves immunoprecipitation. Gag mutants lacking the Gag-Gag interaction domain located in the N terminus of the nucleocapsid (NC) were efficiently immunoprecipitated without denaturation, indicating that the epitope masking is caused by higher-order Gag multimerization. We used this assay to examine the relationship between Gag assembly and Gag binding to total cellular membrane and DRM. Importantly, a multimerization-defective NC mutant displayed wild-type levels of membrane binding and DRM association, indicating that NC-mediated Gag multimerization is dispensable for association of Gag with membrane or DRM. We also demonstrate that different properties of sucrose and iodixanol membrane flotation gradients may explain some discrepancies regarding Gag-raft interactions. This report offers new insights into the association of HIV-1 Gag with membrane and with lipid rafts.
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Affiliation(s)
- Akira Ono
- Virus-Cell Interaction Section, HIV Drug Resistance Program, National Cancer Institute at Frederick, Frederick, Maryland, USA.
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35
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36
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Johnson EN, Seasholtz TM, Waheed AA, Kreutz B, Suzuki N, Kozasa T, Jones TLZ, Brown JH, Druey KM. RGS16 inhibits signalling through the G alpha 13-Rho axis. Nat Cell Biol 2003; 5:1095-103. [PMID: 14634662 DOI: 10.1038/ncb1065] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2003] [Accepted: 09/30/2003] [Indexed: 11/09/2022]
Abstract
G alpha 13 stimulates the guanine nucleotide exchange factors (GEFs) for Rho, such as p115Rho-GEF. Activated Rho induces numerous cellular responses, including actin polymerization, serum response element (SRE)-dependent gene transcription and transformation. p115Rho-GEF contains a Regulator of G protein Signalling domain (RGS box) that confers GTPase activating protein (GAP) activity towards G alpha 12 and G alpha 13 (ref. 3). In contrast, classical RGS proteins (such as RGS16 and RGS4) exhibit RGS domain-dependent GAP activity on G alpha i and G alpha q, but not G alpha 12 or G alpha 13 (ref 4). Here, we show that RGS16 inhibits G alpha 13-mediated, RhoA-dependent reversal of stellation and SRE activation. The RGS16 amino terminus binds G alpha 13 directly, resulting in translocation of G alpha 13 to detergent-resistant membranes (DRMs) and reduced p115Rho-GEF binding. RGS4 does not bind G alpha 13 or attenuate G alpha 13-dependent responses, and neither RGS16 nor RGS4 affects G alpha 12-mediated signalling. These results elucidate a new mechanism whereby a classical RGS protein regulates G alpha 13-mediated signal transduction independently of the RGS box.
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Affiliation(s)
- Eric N Johnson
- Molecular Signal Transduction Section, Laboratory of Allergic Diseases, National Institute of Allergy and Infectious Diseases/National Institute of Health, Rockville, MD 20852, USA
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37
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Nakamura M, Kondo H, Shimada Y, Waheed AA, Ohno-Iwashita Y. Cellular aging-dependent decrease in cholesterol in membrane microdomains of human diploid fibroblasts. Exp Cell Res 2003; 290:381-90. [PMID: 14567995 DOI: 10.1016/s0014-4827(03)00343-4] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Recently it has been shown that cholesterol plays indispensable roles in the function of cholesterol-rich microdomains (rafts), such as in ligand-mediated signal transduction. Using a perfringolysin O derivative (BCtheta) that binds selectively to cholesterol in rafts without causing membrane damage (Proc. Natl. Acad. Sci. USA 98 (2001) 4926), we have investigated the effect of in vitro replicative aging of human diploid fibroblasts, TIG-1, on the distribution of plasma membrane cholesterol. The amount of BCtheta-labeled membrane cholesterol decreased during replicative aging of TIG-1 cells, whereas total cholesterol increased somewhat. The relationship was confirmed by double staining with BCtheta and senescence-associated-beta-galactosidase, a biomarker of senescent cells. Cell fractionation experiments revealed decreases in both cholesterol in rafts and a raft marker, flotillin, during replicative aging. In addition, hydroxyurea-induced prematurely senescent cells also showed a lower level of BCtheta-labeled cholesterol than untreated cells, despite maintaining the total amount of cholesterol. When TIG-1 cells were cultured in cholesterol-deficient medium, BCtheta labeling was first diminished and then premature senescence was induced. Taken together with the reduced signaling capacity of aged cells, these results suggest that plasma membrane cholesterol in raft microdomains is more sensitive to senescence than total cholesterol and is a primary target in aging.
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Affiliation(s)
- Megumi Nakamura
- Department of Protein Biochemistry, Tokyo Metropolitan Institute of Gerontology, 35-2 Sakae-cho, Itabashi-ku, Tokyo 173-0015, Japan.
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Heijnen HFG, Van Lier M, Waaijenborg S, Ohno-Iwashita Y, Waheed AA, Inomata M, Gorter G, Möbius W, Akkerman JWN, Slot JW. Concentration of rafts in platelet filopodia correlates with recruitment of c-Src and CD63 to these domains. J Thromb Haemost 2003; 1:1161-73. [PMID: 12871315 DOI: 10.1046/j.1538-7836.2003.00316.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
The molecular mechanism that causes non-adhesive, discoid platelets to transform into sticky dendritic bodies that form blood clumps is a complex series of events. Recently it has become clear that lipid microdomains--also known as rafts--play a crucial role in this process. We have used a non-cytolytic derivative of perfringolysin-O, a cholesterol binding cytolysin, that binds selectively to cholesterol-rich membrane domains, combined with confocal- and immunoelectron microscopy to visualize cholesterol-raft dynamics during platelet adhesion. In resting platelets cholesterol was uniformly distributed on the cell surface and confined to distinct intracellular compartments (i.e. multivesicular bodies, dense granules, and the internal membranes of alpha-granules). Upon interaction with fibrinogen, cholesterol accumulated at the tips of filopodia and at the leading edge of spreading cells. Stimulation with thrombin receptor activating peptide (TRAP) resulted in a similar redistribution of cholesterol towards filopodia. The adhesion-dependent raft aggregation was accompanied by concentration of the tyrosine kinase c-Src and the tetraspanin CD63 in these domains, whereas glycoprotein Ib (GPIb) was not selectively targeted to the raft clusters. c-Src, the tetraspanin CD63, and GPIb were recovered in biochemically isolated low-density membrane fractions. Disruption of rafts by depleting membrane cholesterol had no effect on platelet shape change but inhibited platelet spreading on fibrinogen and TRAP-induced aggregation. Our results demonstrate that cholesterol rafts in platelets are dynamic entities in the membrane that co-cluster with the tyrosine kinase c-Src and the costimulatory molecule CD63 in specialized domains at the cell surface, thereby providing a possible mechanism in functioning as signaling centres.
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Affiliation(s)
- H F G Heijnen
- Department of Hematology, Division of Thrombosis and Hemostasis, University Medical Center Utrecht, Heidelberglaan 100, 3584 CX Utrecht, the Netherlands.
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39
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Hiol A, Davey PC, Osterhout JL, Waheed AA, Fischer ER, Chen CK, Milligan G, Druey KM, Jones TLZ. Palmitoylation regulates regulators of G-protein signaling (RGS) 16 function. I. Mutation of amino-terminal cysteine residues on RGS16 prevents its targeting to lipid rafts and palmitoylation of an internal cysteine residue. J Biol Chem 2003; 278:19301-8. [PMID: 12642593 DOI: 10.1074/jbc.m210123200] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Regulators of G-protein signaling (RGS) proteins down-regulate signaling by heterotrimeric G-proteins by accelerating GTP hydrolysis on the G alpha subunits. Palmitoylation, the reversible addition of palmitate to cysteine residues, occurs on several RGS proteins and is critical for their activity. For RGS16, mutation of Cys-2 and Cys-12 blocks its incorporation of [3H]palmitate and ability to turn-off Gi and Gq signaling and significantly inhibited its GTPase activating protein activity toward aG alpha subunit fused to the 5-hydroxytryptamine receptor 1A, but did not reduce its plasma membrane localization based on cell fractionation studies and immunoelectron microscopy. Palmitoylation can target proteins, including many signaling proteins, to membrane microdomains, called lipid rafts. A subpopulation of endogenous RGS16 in rat liver membranes and overexpressed RGS16 in COS cells, but not the nonpalmitoylated cysteine mutant of RGS16, localized to lipid rafts. However, disruption of lipid rafts by treatment with methyl-beta-cyclodextrin did not decrease the GTPase activating protein activity of RGS16. The lipid raft fractions were enriched in protein acyltransferase activity, and RGS16 incorporated [3H]palmitate into a peptide fragment containing Cys-98, a highly conserved cysteine within the RGS box. These results suggest that the amino-terminal palmitoylation of an RGS protein promotes its lipid raft targeting that allows palmitoylation of a poorly accessible cysteine residue that we show in the accompanying article (Osterhout, J. L., Waheed, A. A., Hiol, A., Ward, R. J., Davey, P. C., Nini, L., Wang, J., Milligan, G., Jones, T. L. Z., and Druey, K. M. (2003) J. Biol. Chem. 278, 19309-19316) was critical for RGS16 and RGS4 GAP activity.
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Affiliation(s)
- Abel Hiol
- Metabolic Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA
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Osterhout JL, Waheed AA, Hiol A, Ward RJ, Davey PC, Nini L, Wang J, Milligan G, Jones TLZ, Druey KM. Palmitoylation regulates regulator of G-protein signaling (RGS) 16 function. II. Palmitoylation of a cysteine residue in the RGS box is critical for RGS16 GTPase accelerating activity and regulation of Gi-coupled signalling. J Biol Chem 2003; 278:19309-16. [PMID: 12642592 DOI: 10.1074/jbc.m210124200] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Palmitoylation is a reversible post-translational modification used by cells to regulate protein activity. The regulator of G-protein signaling (RGS) proteins RGS4 and RGS16 share conserved cysteine (Cys) residues that undergo palmitoylation. In the accompanying article (Hiol, A., Davey, P. C., Osterhout, J. L., Waheed, A. A., Fischer, E. R., Chen, C. K., Milligan, G., Druey, K. M., and Jones, T. L. Z. (2003) J. Biol. Chem. 278, 19301-19308), we determined that mutation of NH2-terminal cysteine residues in RGS16 (Cys-2 and Cys-12) reduced GTPase accelerating (GAP) activity toward a 5-hydroxytryptamine (5-HT1A)/G alpha o1 receptor fusion protein in cell membranes. NH2-terminal acylation also permitted palmitoylation of a cysteine residue in the RGS box of RGS16 (Cys-98). Here we investigated the role of internal palmitoylation in RGS16 localization and GAP activity. Mutation of RGS16 Cys-98 or RGS4 Cys-95 to alanine reduced GAP activity on the 5-HT1A/G alpha o1 fusion protein and regulation of adenylyl cyclase inhibition. The C98A mutation had no effect on RGS16 localization or GAP activity toward purified G-protein alpha subunits. Enzymatic palmitoylation of RGS16 resulted in internal palmitoylation on residue Cys-98. Palmitoylated RGS16 or RGS4 WT but not C98A or C95A preincubated with membranes expressing 5-HT1a/G alpha o1 displayed increased GAP activity over time. These results suggest that palmitoylation of a Cys residue in the RGS box is critical for RGS16 and RGS4 GAP activity and their ability to regulate Gi-coupled signaling in mammalian cells.
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Affiliation(s)
- James L Osterhout
- Molecular Signal Transduction Section, Laboratory of Allergic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland 20892, USA
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Abstract
The heterotrimeric G proteins, G(12) and G(13), are closely related in their sequences, signaling partners, and cellular effects such as oncogenic transformation and cytoskeletal reorganization. Yet G(12) and G(13) can act through different pathways, bind different proteins, and show opposing actions on some effectors. We investigated the compartmentalization of G(12) and G(13) at the membrane because other G proteins reside in lipid rafts, membrane microdomains enriched in cholesterol and sphingolipids. Lipid rafts were isolated after cold, nonionic detergent extraction of cells and gradient centrifugation. Galpha(12) was in the lipid raft fractions, whereas Galpha(13) was not associated with lipid rafts. Mutation of Cys-11 on Galpha(12), which prevents its palmitoylation, partially shifted Galpha(12) from the lipid rafts. Geldanamycin treatment, which specifically inhibits Hsp90, caused a partial loss of wild-type Galpha(12) and a complete loss of the Cys-11 mutant from the lipid rafts and the appearance of a higher molecular weight form of Galpha(12) in the soluble fractions. These results indicate that acylation and Hsp90 interactions localized Galpha(12) to lipid rafts. Hsp90 may act as both a scaffold and chaperone to maintain a functional Galpha(12) only in discrete membrane domains and thereby explain some of the nonoverlapping functions of G(12) and G(13) and control of these potent cell regulators.
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Affiliation(s)
- Abdul A Waheed
- Metabolic Diseases Branch, NIDDK, National Institutes of Health, Bethesda, Maryland 20892, USA
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Abstract
Biomedical publications listed in Medline were analyzed based on publisher's location and first author's country of origin. In the present analysis I wished to determine the languages of biomedical publications and the publishers' locations.
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Waheed AA, Shimada Y, Heijnen HF, Nakamura M, Inomata M, Hayashi M, Iwashita S, Slot JW, Ohno-Iwashita Y. Selective binding of perfringolysin O derivative to cholesterol-rich membrane microdomains (rafts). Proc Natl Acad Sci U S A 2001; 98:4926-31. [PMID: 11309501 PMCID: PMC33140 DOI: 10.1073/pnas.091090798] [Citation(s) in RCA: 180] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
There is increasing evidence that sphingolipid- and cholesterol-rich microdomains (rafts) exist in the plasma membrane. Specific proteins assemble in these membrane domains and play a role in signal transduction and many other cellular events. Cholesterol depletion causes disassembly of the raft-associated proteins, suggesting an essential role of cholesterol in the structural maintenance and function of rafts. However, no tool has been available for the detection and monitoring of raft cholesterol in living cells. Here we show that a protease-nicked and biotinylated derivative (BCtheta) of perfringolysin O (theta-toxin) binds selectively to cholesterol-rich microdomains of intact cells, the domains that fulfill the criteria of rafts. We fractionated the homogenates of nontreated and Triton X-100-treated platelets after incubation with BCtheta on a sucrose gradient. BCtheta was predominantly localized in the floating low-density fractions (FLDF) where cholesterol, sphingomyelin, and Src family kinases are enriched. Immunoelectron microscopy demonstrated that BCtheta binds to a subpopulation of vesicles in FLDF. Depletion of 35% cholesterol from platelets with cyclodextrin, which accompanied 76% reduction in cholesterol from FLDF, almost completely abolished BCtheta binding to FLDF. The staining patterns of BCtheta and filipin in human epidermoid carcinoma A431 cells with and without cholesterol depletion suggest that BCtheta binds to specific membrane domains on the cell surface, whereas filipin binding is indiscriminate to cell cholesterol. Furthermore, BCtheta binding does not cause any damage to cell membranes, indicating that BCtheta is a useful probe for the detection of membrane rafts in living cells.
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Affiliation(s)
- A A Waheed
- Department of Protein Biochemistry, Tokyo Metropolitan Institute of Gerontology, 35-2 Sakae-cho, Itabashi-ku, Tokyo 173-0015, Japan.
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Abstract
Eosin B and eosin Y have been used to estimate micro- and submicrogram quantities of proteins respectively as shown in our previous reports. In the present study we describe the mechanism of eosin binding to proteins. At pH lower than 3.0 the absorbance of unbound dye is greatly reduced. After the dye binds to protein, the absorption maximum of the dye changes from 514 to 530 +/- 5 nm. The absorbance and bathochromatic shift in absorption maximum of the protein-dye complex are proportional to the concentration of protein. The pH of the assay solution does not change due to protein. Arginine, histidine, and lysine (at both acidic and neutral pH) and tryptophan (at acidic pH) residues of a protein bind electrostatically to carboxylic and phenolic groups of the dye to produce a stable water-soluble protein-dye complex. The binding constants of eosin B with poly-L-arginine, poly-L-histidine, poly-L-lysine, and poly-L-tryptophan at pH 1.96 are 0.37, 0.32, 0.33 and 0.33 nmol/nmol of amino acid, respectively. The binding constants of eosin B and eosin Y with bovine serum albumin (BSA) at pH 1.96 are essentially the same, i.e., 0.82 nmol/nmol of reactive amino acid of BSA. The binding constant varies with solution pH so that a wide range of protein concentrations can be estimated. The reason for the higher absorbance of protein-eosin Y complex compared to that of protein-eosin B complex is discussed.
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Affiliation(s)
- A A Waheed
- Department of Protein Biochemistry, Tokyo Metropolitan Institute of Gerontology, 35-2 Sakae-cho, Itabashi-ku, Tokyo, 173-0015, Japan.
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Abstract
Eosin B is used to estimate proteins above 1 microg/ml concentration [Waheed AA, Gupta, PD. Anal. Biochem. 1996:233:249-256; Waheed AA, Gupta PD. J. Biochem. Biophys. Meth. 1996;33:187-196]. In the present report we describe a method for estimating submicrogram quantities of proteins using the dye eosin Y. The increase in sensitivity of this assay is approximately two fold under optimal assay condition. The optimum concentration of eosin Y and citric acid for submicrogram assay is 0.01 and 0.05%; (final concentration) respectively. The protein-dye complex formation is completed within 2 min and its absorbance is stable up to 60 main with a variation of +/-4.0%. The interference due to sugars, reducing agents, glycerol and some neutral detergents like Triton X-100, NP-40 and Tween-20 is less than 12% whereas Brij-35, ethanol, acetone and chelators like EGTA and EDTA suppress the absorbance by about 12-18%. However, basic buffers like Tris, urea, CHAPS and NaN, interfere with the formation of the protein-dye complex. The increase in absorbance of protein-eosin Y complex compared to that of protein-eosin B complex is due to the higher extinction co-efficient of eosin Y compared to eosin B.
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Affiliation(s)
- A A Waheed
- Centre for Cellular and Molecular Biology, Hyderabad, India.
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Affiliation(s)
- A A Waheed
- Centre for Cellular and Molecular Biology, Hyderabad, 500 007, India.
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Waheed AA, Toyama Y, Yasuzumi F, Gupta PD. Decreased densities of intramembranous particles and cytochemically detectable cholesterol in microvilli of starved rat enterocytes. Cell Biol Int 1999; 22:177-83. [PMID: 9974211 DOI: 10.1006/cbir.1998.0227] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The densities of intramembranous particles (IMPs) and of sterol complexes induced by treatment of filipin were studied by freeze-fracture replication of intact intestine and/or isolated brush border membranes (BBM) of well-fed and starved rats. The density of IMPs and filipin-sterol complexes (FSCs) decrease considerably during starvation. Biochemical estimations show a decrease in the levels of cholesterol and proteins with respect to phospholipids during starvation which is in agreement with morphological findings. It is suggested that these changes may play a role in regulating membrane fluidity which in turn affects absorption of nutrients through BBM.
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Affiliation(s)
- A A Waheed
- Centre for Cellular and Molecular Biology, Hyderabad, India
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Abstract
Alterations in the lipid and fatty acid composition of brush border membrane (BBM) of small intestine were studied in well-fed, starved, and refed rats. The ratios of cholesterol/phospholipid (mol/mol), sphingomyelin/phosphatidylcholine (mol/mol), protein/lipid (w/w), and free fatty acids (w/w) decreased whereas the total phospholipid (w/w) ratio and the double-bond index increased in BBM of the intestine of the starved rat compared to that of the well-fed rat. Analyses of fatty acids showed higher percentage of stearic and arachidonic acids whereas oleic and linoleic acids decreased under starvation. The acyl chain of starved rat BBM was less ordered compared with that of well-fed rat BBM. On refeeding, these changes were restored to well-fed levels. The change in membrane state under starvation is associated with alterations in the lipid and fatty acid composition of BBM and may be responsible for functional changes that occur under nutritional stress.
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Affiliation(s)
- A A Waheed
- Centre for Cellular and Molecular Biology, Hyderabad, India
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Abstract
Changes in surface area of microvilli, fluidity of brush border membrane and transport of L-amino acids through intestinal epithelial cells were studied in wellfed and starved (2,4 and 6 days) rats. The surface area of microvilli per unit area of intestinal epithelial cells increased during starvation. Studies with fluoroprobes - pyrene, 1-anilinonaphthalene-8-sulphonate and 1,6-diphenyl-1,3,5-hexatriene, showed increased fluidity of brush border membrane on progressive starvation. Transport of five amino acids representing five different transport systems was studied during starvation in everted intestinal sleeves. Transport of L-proline, glycine and L-glutamic acid which represent imino, glycine and acidic systems respectively increased significantly in Na+-dependent pathway whereas transport of L-lysine representing basic system increased significantly in Na+-independent pathway during starvation.
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Affiliation(s)
- A A Waheed
- Centre for Cellular and Molecular Biology, Hyderabad, India
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