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Augustine T, Chaudhary P, Gupta K, Islam S, Ghosh P, Santra MK, Mitra D. Cyclin F/FBXO1 Interacts with HIV-1 Viral Infectivity Factor (Vif) and Restricts Progeny Virion Infectivity by Ubiquitination and Proteasomal Degradation of Vif Protein through SCF cyclin F E3 Ligase Machinery. J Biol Chem 2017; 292:5349-5363. [PMID: 28184007 PMCID: PMC5392680 DOI: 10.1074/jbc.m116.765842] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2016] [Revised: 02/09/2017] [Indexed: 12/22/2022] Open
Abstract
Cyclin F protein, also known as FBXO1, is the largest among all cyclins and oscillates in the cell cycle like other cyclins. Apart from being a G2/M cyclin, cyclin F functions as the substrate-binding subunit of SCFcyclin F E3 ubiquitin ligase. In a gene expression analysis performed to identify novel gene modulations associated with cell cycle dysregulation during HIV-1 infection in CD4+ T cells, we observed down-regulation of the cyclin F gene (CCNF). Later, using gene overexpression and knockdown studies, we identified cyclin F as negatively influencing HIV-1 viral infectivity without any significant impact on virus production. Subsequently, we found that cyclin F negatively regulates the expression of viral protein Vif (viral infectivity factor) at the protein level. We also identified a novel host-pathogen interaction between cyclin F and Vif protein in T cells during HIV-1 infection. Mutational analysis of a cyclin F-specific amino acid motif in the C-terminal region of Vif indicated rescue of the protein from cyclin F-mediated down-regulation. Subsequently, we showed that Vif is a novel substrate of the SCFcyclin F E3 ligase, where cyclin F mediates the ubiquitination and proteasomal degradation of Vif through physical interaction. Finally, we showed that cyclin F augments APOBEC3G expression through degradation of Vif to regulate infectivity of progeny virions. Taken together, our results demonstrate that cyclin F is a novel F-box protein that functions as an intrinsic cellular regulator of HIV-1 Vif and has a negative regulatory effect on the maintenance of viral infectivity by restoring APOBEC3G expression.
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Affiliation(s)
- Tracy Augustine
- From the National Centre for Cell Science, Pune, Maharashtra 411007, India and
| | - Priyanka Chaudhary
- From the National Centre for Cell Science, Pune, Maharashtra 411007, India and
| | - Kailash Gupta
- From the National Centre for Cell Science, Pune, Maharashtra 411007, India and
| | - Sehbanul Islam
- From the National Centre for Cell Science, Pune, Maharashtra 411007, India and
| | - Payel Ghosh
- the Bioinformatics Centre, Savitribai Phule Pune University, Pune, Maharashtra 411007, India
| | - Manas Kumar Santra
- From the National Centre for Cell Science, Pune, Maharashtra 411007, India and
| | - Debashis Mitra
- From the National Centre for Cell Science, Pune, Maharashtra 411007, India and
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Yoshida K, Komai K, Shiozawa K, Mashida A, Horiuchi T, Tanaka Y, Nose M, Hashiramoto A, Shiozawa S. Role of the MICA polymorphism in systemic lupus erythematosus. ACTA ACUST UNITED AC 2013; 63:3058-66. [PMID: 21702010 DOI: 10.1002/art.30501] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
OBJECTIVE To study the genetic contribution of major histocompatibility complex class I polypeptide-related sequence A (MICA), important in natural killer (NK) cell function, in patients with systemic lupus erythematosus (SLE). METHODS Japanese patients with SLE (n=716), those with rheumatoid arthritis (RA) (n=327), and healthy control subjects (n=351) were genotyped for the Val129 Met polymorphism (rs1051792) and transmembrane (TM) alanine-encoding GCT repeats, termed A4, A5, A5.1, A6, and A9, in the MICA gene. Recombinant human MICA-GST fusion proteins were tested on the NK cell line NK92MI for the expression of NK group 2, member D (NKG2-D), NK cell-mediated cytotoxicity, and interferon-γ (IFNγ) production. RESULTS The MICA 129Met allele, TMA9 allele, and 129Met/Met genotype were positively associated with SLE (corrected P [Pcorr]=0.01 and odds ratio [OR] 1.3, Pcorr=0.003 and OR 1.6, and Pcorr=0.02 and OR 1.8, respectively), while the MICA 129Val allele was negatively associated with SLE (Pcorr=0.01, OR 0.8). The MICA 129Met;A9 haplotype was also associated with SLE (Pcorr=0.0006, OR 1.8), and there was an additive genetic effect between the MICA 129Met;A9 haplotype and HLA-DRB1*15:01. When NK92MI cells were incubated in vitro with recombinant human disease-associated 129Met;A9 (the combination of polymorphisms at 129Met and TMA9), expression of NKG2-D on NK92MI cells and cytotoxicity of the NK cells were inhibited, but production of IFNγ from NK92MI cells was enhanced. CONCLUSION The MICA polymorphism is genetically associated with SLE, and MICA appears to contribute to the pathogenesis of SLE by modulating NK cell function.
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Affiliation(s)
- Kohsuke Yoshida
- Department of Medicine, Kobe University Graduate School of Health Sciences, and Center for Rheumatic Diseases, Kobe University Hospital, Kobe, Japan
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Mi T, Merlin JC, Deverasetty S, Gryk MR, Bill TJ, Brooks AW, Lee LY, Rathnayake V, Ross CA, Sargeant DP, Strong CL, Watts P, Rajasekaran S, Schiller MR. Minimotif Miner 3.0: database expansion and significantly improved reduction of false-positive predictions from consensus sequences. Nucleic Acids Res 2012; 40:D252-60. [PMID: 22146221 PMCID: PMC3245078 DOI: 10.1093/nar/gkr1189] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2011] [Revised: 11/14/2011] [Accepted: 11/15/2011] [Indexed: 12/21/2022] Open
Abstract
Minimotif Miner (MnM available at http://minimotifminer.org or http://mnm.engr.uconn.edu) is an online database for identifying new minimotifs in protein queries. Minimotifs are short contiguous peptide sequences that have a known function in at least one protein. Here we report the third release of the MnM database which has now grown 60-fold to approximately 300,000 minimotifs. Since short minimotifs are by their nature not very complex we also summarize a new set of false-positive filters and linear regression scoring that vastly enhance minimotif prediction accuracy on a test data set. This online database can be used to predict new functions in proteins and causes of disease.
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Affiliation(s)
- Tian Mi
- Department of Computer Science and Engineering, University of Connecticut, Storrs, CT 06269-2155, School of Life Sciences, University of Nevada Las Vegas, 4505 Maryland Pkwy., Las Vegas, NV 89154-4004 and Department of Molecular, Microbial, and Structural Biology, University of Connecticut Health Center, 263 Farmington Ave., Farmington, CT 06030-3305, USA
| | - Jerlin Camilus Merlin
- Department of Computer Science and Engineering, University of Connecticut, Storrs, CT 06269-2155, School of Life Sciences, University of Nevada Las Vegas, 4505 Maryland Pkwy., Las Vegas, NV 89154-4004 and Department of Molecular, Microbial, and Structural Biology, University of Connecticut Health Center, 263 Farmington Ave., Farmington, CT 06030-3305, USA
| | - Sandeep Deverasetty
- Department of Computer Science and Engineering, University of Connecticut, Storrs, CT 06269-2155, School of Life Sciences, University of Nevada Las Vegas, 4505 Maryland Pkwy., Las Vegas, NV 89154-4004 and Department of Molecular, Microbial, and Structural Biology, University of Connecticut Health Center, 263 Farmington Ave., Farmington, CT 06030-3305, USA
| | - Michael R. Gryk
- Department of Computer Science and Engineering, University of Connecticut, Storrs, CT 06269-2155, School of Life Sciences, University of Nevada Las Vegas, 4505 Maryland Pkwy., Las Vegas, NV 89154-4004 and Department of Molecular, Microbial, and Structural Biology, University of Connecticut Health Center, 263 Farmington Ave., Farmington, CT 06030-3305, USA
| | - Travis J. Bill
- Department of Computer Science and Engineering, University of Connecticut, Storrs, CT 06269-2155, School of Life Sciences, University of Nevada Las Vegas, 4505 Maryland Pkwy., Las Vegas, NV 89154-4004 and Department of Molecular, Microbial, and Structural Biology, University of Connecticut Health Center, 263 Farmington Ave., Farmington, CT 06030-3305, USA
| | - Andrew W. Brooks
- Department of Computer Science and Engineering, University of Connecticut, Storrs, CT 06269-2155, School of Life Sciences, University of Nevada Las Vegas, 4505 Maryland Pkwy., Las Vegas, NV 89154-4004 and Department of Molecular, Microbial, and Structural Biology, University of Connecticut Health Center, 263 Farmington Ave., Farmington, CT 06030-3305, USA
| | - Logan Y. Lee
- Department of Computer Science and Engineering, University of Connecticut, Storrs, CT 06269-2155, School of Life Sciences, University of Nevada Las Vegas, 4505 Maryland Pkwy., Las Vegas, NV 89154-4004 and Department of Molecular, Microbial, and Structural Biology, University of Connecticut Health Center, 263 Farmington Ave., Farmington, CT 06030-3305, USA
| | - Viraj Rathnayake
- Department of Computer Science and Engineering, University of Connecticut, Storrs, CT 06269-2155, School of Life Sciences, University of Nevada Las Vegas, 4505 Maryland Pkwy., Las Vegas, NV 89154-4004 and Department of Molecular, Microbial, and Structural Biology, University of Connecticut Health Center, 263 Farmington Ave., Farmington, CT 06030-3305, USA
| | - Christian A. Ross
- Department of Computer Science and Engineering, University of Connecticut, Storrs, CT 06269-2155, School of Life Sciences, University of Nevada Las Vegas, 4505 Maryland Pkwy., Las Vegas, NV 89154-4004 and Department of Molecular, Microbial, and Structural Biology, University of Connecticut Health Center, 263 Farmington Ave., Farmington, CT 06030-3305, USA
| | - David P. Sargeant
- Department of Computer Science and Engineering, University of Connecticut, Storrs, CT 06269-2155, School of Life Sciences, University of Nevada Las Vegas, 4505 Maryland Pkwy., Las Vegas, NV 89154-4004 and Department of Molecular, Microbial, and Structural Biology, University of Connecticut Health Center, 263 Farmington Ave., Farmington, CT 06030-3305, USA
| | - Christy L. Strong
- Department of Computer Science and Engineering, University of Connecticut, Storrs, CT 06269-2155, School of Life Sciences, University of Nevada Las Vegas, 4505 Maryland Pkwy., Las Vegas, NV 89154-4004 and Department of Molecular, Microbial, and Structural Biology, University of Connecticut Health Center, 263 Farmington Ave., Farmington, CT 06030-3305, USA
| | - Paula Watts
- Department of Computer Science and Engineering, University of Connecticut, Storrs, CT 06269-2155, School of Life Sciences, University of Nevada Las Vegas, 4505 Maryland Pkwy., Las Vegas, NV 89154-4004 and Department of Molecular, Microbial, and Structural Biology, University of Connecticut Health Center, 263 Farmington Ave., Farmington, CT 06030-3305, USA
| | - Sanguthevar Rajasekaran
- Department of Computer Science and Engineering, University of Connecticut, Storrs, CT 06269-2155, School of Life Sciences, University of Nevada Las Vegas, 4505 Maryland Pkwy., Las Vegas, NV 89154-4004 and Department of Molecular, Microbial, and Structural Biology, University of Connecticut Health Center, 263 Farmington Ave., Farmington, CT 06030-3305, USA
| | - Martin R. Schiller
- Department of Computer Science and Engineering, University of Connecticut, Storrs, CT 06269-2155, School of Life Sciences, University of Nevada Las Vegas, 4505 Maryland Pkwy., Las Vegas, NV 89154-4004 and Department of Molecular, Microbial, and Structural Biology, University of Connecticut Health Center, 263 Farmington Ave., Farmington, CT 06030-3305, USA
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Keating JA, Striker R. Phosphorylation events during viral infections provide potential therapeutic targets. Rev Med Virol 2011; 22:166-81. [PMID: 22113983 PMCID: PMC3334462 DOI: 10.1002/rmv.722] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2011] [Revised: 10/07/2011] [Accepted: 10/10/2011] [Indexed: 01/21/2023]
Abstract
For many medically relevant viruses, there is now considerable evidence that both viral and cellular kinases play important roles in viral infection. Ultimately, these kinases, and the cellular signaling pathways that they exploit, may serve as therapeutic targets for treating patients. Currently, small molecule inhibitors of kinases are under investigation as therapy for herpes viral infections. Additionally, a number of cellular or host-directed tyrosine kinase inhibitors that have been previously FDA approved for cancer treatment are under study in animal models and clinical trials, as they have shown promise for the treatment of various viral infections as well. This review will highlight the wide range of viral proteins phosphorylated by viral and cellular kinases, and the potential for variability of kinase recognition sites within viral substrates to impact phosphorylation and kinase prediction. Research studying kinase-targeting prophylactic and therapeutic treatments for a number of viral infections will also be discussed.
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Affiliation(s)
- Julie A Keating
- Department of Medicine, University of Wisconsin-Madison, Madison, WI 53706, USA
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Wolf D, Giese SI, Witte V, Krautkrämer E, Trapp S, Sass G, Haller C, Blume K, Fackler OT, Baur AS. Novel (n)PKC kinases phosphorylate Nef for increased HIV transcription, replication and perinuclear targeting. Virology 2007; 370:45-54. [PMID: 17904606 DOI: 10.1016/j.virol.2007.08.015] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2007] [Revised: 05/28/2007] [Accepted: 08/08/2007] [Indexed: 10/22/2022]
Abstract
The N-terminus of the human immunodeficiency virus (HIV) pathogenicity factor Nef associates with a protein complex (NAKC for Nef-associated kinase complex) that contains at least two kinases: the tyrosine kinase Lck and a serine kinase activity which was found to phosphorylate Lck and the Nef N-terminus. Here we show that this serine kinase activity is mediated by members of the novel Protein Kinase C (nPKC) subfamily, PKCdelta and theta. Association with the Nef N-terminus was sufficient to activate PKC leading to phosphorylation of Nef in vitro on a conserved serine residue at position 6. Mutation of serine 6 or coexpression of a transdominant negative PKC mutant significantly reduced Nef-stimulated HIV transcription and replication in resting PBMC. When analyzing the molecular mechanisms, we found that mutating serine 6 moderately affected myristoylation of Nef and its association with Pak2 activity, whereas CD4 downmodulation was not inhibited. More interestingly, this mutation abolished the typical perinuclear localization of Nef in T cells. We conclude that the activation of nPKCs by Nef is required to increase viral replication/infectivity and direct the subcellular localization of Nef.
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Affiliation(s)
- Dietlinde Wolf
- University of Miami, Miller School of Medicine, Department of Microbiology and Immunology, BCRI 739, Miami, FL 33136, USA
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Mann J, Patrick CN, Cragg MS, Honeychurch J, Mann DA, Harris M. Functional analysis of HIV type 1 Nef reveals a role for PAK2 as a regulator of cell phenotype and function in the murine dendritic cell line, DC2.4. THE JOURNAL OF IMMUNOLOGY 2006; 175:6560-9. [PMID: 16272310 DOI: 10.4049/jimmunol.175.10.6560] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The HIV-1 Nef protein plays a critical role in viral pathogenesis. Nef has been shown to modulate dendritic cell (DC) function, in particular perturbing their ability to present Ag. To further characterize the effects of Nef on DCs, we established a panel of transfectants of the murine DC line, DC2.4, stably expressing differing levels of either wild-type Nef, or a number of Nef mutants lacking key functional motifs. Transfectants expressing increasing levels of wild-type Nef demonstrated a dose-dependent shrinkage and loss of dendrites. Nef expression levels also correlated with increased proliferative ability but did not confer resistance to proapoptotic stimuli. Importantly, Nef expression resulted in an impairment of Ag presentation to T cells correlating with a reduction in the cell surface expression of molecules involved in Ag presentation such as MHC class I, CD80/86, and ICAM-1. Nef expression also rendered DC2.4 cells resistant to the maturation stimulus provided by an anti-CD40 Ab. Mutations in either the myristoylation site or Src homology 3-domain binding polyproline motif of Nef abolished these effects. Previous studies had shown that these mutations also abolished the ability of Nef to activate the p21-activated kinase, PAK2. Consistent with this, stable expression of constitutively active PAK2 in DC2.4 mimicked the effects of Nef. We conclude that Nef, acting via activation of PAK2, inhibits both DC maturation and Ag presentation. These data have clear implications for the role of Nef in early stages of HIV-1 infection and validate Nef as a valid target for development of antiviral chemotherapeutics.
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Affiliation(s)
- Jelena Mann
- Liver Group, Division of Infection, Inflammation and Repair, University of Southampton, Southampton General Hospital, Southampton, United Kingdom
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7
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Barber SA, Maughan MF, Roos JW, Clements JE. Two amino acid substitutions in the SIV Nef protein mediate associations with distinct cellular kinases. Virology 2000; 276:329-38. [PMID: 11040124 DOI: 10.1006/viro.2000.0558] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
A functional Nef protein is crucial in vivo for viral replication leading to pathogenesis in SIV-infected macaques. Moreover, a full-length Nef protein is required for optimal virus replication in primary cells, and both HIV and SIV Nef proteins enhance virion infectivity. Enhanced infectivity may result in part from the ability of Nef to incorporate cellular kinases into virions. In two previous reports, we compared in vitro kinase profiles of SIV recombinant clones that express nef genes derived either from the prototypic lymphocyte-tropic SIVmac239, clone SIV/Fr-2, or from our neurovirulent clone SIV/17E-Fr. While the SIV/Fr-2 Nef protein associated with the previously described PAK-related kinase and an unidentified serine kinase present in a Nef-associated kinase complex (NAKC), SIV/17E-Fr Nef was found to associate with a novel serine kinase activity that was biochemically distinct from both PAK and NAKC. Interestingly, while both Nef proteins were incorporated into virus particles, Nef-associated kinase activity was detected only in virions containing the SIV/17E-Fr Nef protein. Because sequence analysis identified only five amino acids that differed between the Nef proteins of SIV/Fr-2 and SIV/17E-Fr, we were able to evaluate the contribution of each amino acid to Nef-associated kinase activity as well as virus infectivity by constructing a panel of SIV clones containing individual reversions of each differing amino acid in SIV/17E-Fr Nef to the corresponding amino acid in SIV/Fr-2 Nef. In this report, we identify previously uncharacterized amino acids in the N terminus and the conserved core domain of Nef that are essential for the detection of Nef/kinase interactions as well as Nef phosphorylation during SIV infection. Further, via a novel infectivity assay recently developed in our laboratory that utilizes CEMX174 reporter cells stably expressing an SIV/LTR-luciferase construct, we find no direct correlation between specific Nef kinase associations and enhanced virion infectivity.
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Affiliation(s)
- S A Barber
- Division of Comparative Medicine, Johns Hopkins University School of Medicine, 720 Rutland Avenue, Baltimore, Maryland, 21205, USA
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Ambrosini E, Slepko N, Kohleisen B, Shumay E, Erfle V, Aloisi F, Levi G. HIV-1 Nef alters the expression of ?II and ? isoforms of protein kinase c and the activation of the long terminal repeat promoter in human astrocytoma cells. Glia 1999. [DOI: 10.1002/(sici)1098-1136(199908)27:2<143::aid-glia4>3.0.co;2-v] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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9
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Cartier C, Sivard P, Tranchat C, Decimo D, Desgranges C, Boyer V. Identification of three major phosphorylation sites within HIV-1 capsid. Role of phosphorylation during the early steps of infection. J Biol Chem 1999; 274:19434-40. [PMID: 10383459 DOI: 10.1074/jbc.274.27.19434] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We previously reported the presence of two cellular serine/threonine protein kinases incorporated in human immunodeficiency virus type 1 (HIV-1) particles. One protein kinase is MAPK ERK2 (mitogen-activated protein kinase), whereas the other one, a 53-kDa protein, still needs to be identified. Furthermore, we demonstrated that the capsid protein CAp24 is phosphorylated by one of those two virion-associated protein kinases (Cartier, C., Deckert, M., Grangeasse, C., Trauger, R., Jensen, F., Bernard, A., Cozzone, A., Desgranges, C., and Boyer, V. (1997) J. Virol. 71, 4832-4837). In this study, we showed that CAp24 is not a direct substrate of MAPK ERK2. Moreover, using site-directed mutagenesis of each of the 9 serine residues of CAp24, we demonstrated the phosphorylation of 3 serine residues (Ser-109, Ser-149, and Ser-178) in the CAp24. Substitution of each serine residue did not affect viral budding, nor viral structure. By contrast, substitution of Ser-109, Ser-149, or Ser-178 affects viral infectivity by preventing the reverse transcription process to be completely achieved. Our results suggest that CAp24 serine phosphorylation is essential for viral uncoating process.
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Affiliation(s)
- C Cartier
- Virus des Hépatites, Rétrovirus Humains et Pathologies Associées, INSERM U271, 151 Cours. A. Thomas, 69 424 Lyon Cedex 03, France.
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Carl S, Iafrate AJ, Lang SM, Stahl-Hennig C, Kuhn EM, Fuchs D, Mätz-Rensing K, ten Haaft P, Heeney JL, Skowronski J, Kirchhoff F. The acidic region and conserved putative protein kinase C phosphorylation site in Nef are important for SIV replication in rhesus macaques. Virology 1999; 257:138-55. [PMID: 10208928 DOI: 10.1006/viro.1999.9645] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Variants of the pathogenic SIVmac239 clone with changes in Nef were analyzed to assess the functional relevance of two highly conserved regions in Nef in vitro and in vivo. Changes in a region with an acidic charge (Aci-Nef), or a potential protein kinase C phosphorylation site (PKC-Nef), impaired the ability of Nef to down-regulate CD4 and MHC class I surface expression and to alter CD3-initiated signal transduction in Jurkat T cells. The Aci-Nef, but not the PKC-Nef, associated with the previously described p65 phosphoprotein. SIV containing Aci-Nef, but not SIV containing PKC-Nef, showed reduced infectivity and replication in cell culture systems. One of two rhesus macaques infected with the PKC-Nef mutant virus showed rapid reversion and progressed to disease. In the second animal no reversions and nonprogressive infection was observed. In one of two macaques infected with the Aci-Nef variant, the mutations were stable during the first 40 weeks after infection. Thereafter, variants evolved in which up to six of the eight mutated positions in Nef were reverted and functional activity in vitro was partially restored. These changes occurred concomitantly with increasing viral load and disease progression. The second animal infected with the Aci-Nef variant showed no reversions and remained asymptomatic. Our study suggests that the acidic region and conserved PKC phosphorylation site in Nef are important for SIV replication in rhesus macaques and for several in vitro Nef functions. An almost wild-type activity in in vitro infectivity and replication assays seems insufficient to confer a full nef-positive phenotype in vivo.
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Affiliation(s)
- S Carl
- Institute for Clinical and Molecular Virology, University of Erlangen-Nuernberg, Schlossgarten 4, Erlangen, 91054, Germany
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11
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Barber SA, Flaherty MT, Plafker SM, Clements JE. A novel kinase activity associated with Nef derived from neurovirulent simian immunodeficiency virus. Virology 1998; 251:165-75. [PMID: 9813212 DOI: 10.1006/viro.1998.9408] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The Nef proteins of Simian immunodeficiency virus (SIV) and human immunodeficiency virus (HIV) have been shown to associate with several cellular kinases. Further, the ability of SIVmac239 Nef to associate with a p21-activated kinase (PAK)-related kinase has been correlated with pathogenic progression to AIDS in rhesus macaques. Because the ability of Nef to associate with the PAK-related kinase is viral isolate dependent, we reasoned that viral isolates derived from distinct physiological locations may encode Nef proteins that exhibit distinct kinase association profiles. In this study, we compared kinase activities associated with Nef proteins derived from the prototypic lymphocyte-tropic SIVmac239 and a macrophage-tropic, neurovirulent clone, SIV/17E-Fr. Our findings not only support previous studies that have documented the association of SIVmac239 Nef with a PAK-related kinase and a Nef-associated kinase complex (NAKC) but describe a novel serine kinase activity detectable only in conjunction with the Nef protein derived from the neurovirulent clone, SIV/17E-Fr. The latter Nef protein does not associate with PAK, and unlike PAK or NAKC, this novel kinase activity is enhanced in association with nonmyristoylated forms of Nef and can utilize both ATP and GTP as phosphodonors. We also show that at least one substrate for the kinase is Nef itself and demonstrate that the SIV/17E-Fr Nef protein is phosphorylated in SIV-infected cells. These results suggest that the ability to associate with cellular kinases in general may be a conserved feature of Nef, but particular kinase/Nef associations may evolve with changes in the host environment concomitant with viral spread.
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Affiliation(s)
- S A Barber
- Division of Comparative Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, 21205, USA
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12
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Dutartre H, Harris M, Olive D, Collette Y. The human immunodeficiency virus type 1 Nef protein binds the Src-related tyrosine kinase Lck SH2 domain through a novel phosphotyrosine independent mechanism. Virology 1998; 247:200-11. [PMID: 9705913 DOI: 10.1006/viro.1998.9244] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Primate lentiviruses encode for an unique nef gene with an essential function in both viral replication and pathogenicity in the host. The molecular basis for this function remains however poorly defined. Several Nef-binding cellular proteins are thought to be instrumental in its function. Indeed, Nef contains a proline-rich motif implicated in the binding to the Src-like tyrosine kinase Hck and also to a Ser/Thr kinase of molecular weight 62 kDa. The disruption of this motif affects the binding to both these kinases as well as viral replication. Whereas Hck is expressed in the myeloid lineage and hence may account for the nef function in infected monocytes, we and others have reported previously that Nef also interacts with the T-lymphocyte Src-kinase Lck, leading to specific cell signaling impairment. This interaction occurs through the binding of Nef to both Lck SH2 and SH3 domains. Both the proline motif and phosphorylation of Nef on tyrosine residue were proposed to account for these interactions. Here, we investigate the mechanism of Lck SH2 binding by HIV-1 Nef. Using recombinant fusion proteins to precipitate lysates, we show that although SH2 binding is dependent on phosphorylation events, it occurs in a tyrosine independent manner because it requires neither tyrosine residues in Nef nor the phosphotyrosine binding pocket from the Lck SH2 domain, hence suggesting a role for a phosphoserine or a phosphothreonine residue. Further, we show that Hck SH2 does not interact with Nef, indicating that Hck SH3 binding is sufficient for Nef binding, whereas Lck SH2 cooperate together with SH3 to allow Nef binding to a level similar to Hck SH3. Together, our results establish different mechanisms for Hck and Lck binding by HIV-1 Nef protein, and identify a novel mechanism for Src-like tyrosine kinase targeting by a viral protein.
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Affiliation(s)
- H Dutartre
- Unité 119 Instituto National de la Santé et de la Recherche Médicale, Marseille, France
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Fackler OT, Kienzle N, Kremmer E, Boese A, Schramm B, Klimkait T, Kücherer C, Mueller-Lantzsch N. Association of human immunodeficiency virus Nef protein with actin is myristoylation dependent and influences its subcellular localization. EUROPEAN JOURNAL OF BIOCHEMISTRY 1997; 247:843-51. [PMID: 9288906 DOI: 10.1111/j.1432-1033.1997.00843.x] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Human immunodeficiency virus (HIV) Nef functions are thought to be mediated via interactions with cellular proteins. Utilizing zone velocity sedimentation in glycerol gradients we found that recombinant HIV-1 Nef non-covalently associates with actin forming a high-molecular-mass complex of 150-300 kDa. This Nef/actin complex was present in human B and T lymphocytes but not in insect cells and was dependent on the N-terminal myristoylation of Nef, whereas the SH3-binding proline motif of Nef was not involved. Despite being myristoylated, HIV-2 Nef did not associate with actin. This might reflect differences in the subcellular localization of Nef since cell-fractionation experiments revealed that HIV-1 Nef was virtually exclusively localized in the cytoskeletal (detergent-insoluble) fraction whereas HIV-2 Nef had significantly reduced affinity for the cytoskeleton. Colocalization experiments in HIV-1-infected CD4+ fibroblasts revealed that Nef/actin complexes may also exist in HIV-infected cells. This novel interaction of HIV-1 Nef with actin provides insight into the association of Nef with cellular structures and reveals general differences in the interactions of the Nef proteins from HIV-1 and HIV-2.
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Affiliation(s)
- O T Fackler
- Universitätskliniken des Saarlandes, Institut für Med. Mikrobiologie und Hygiene, Abt. Virologie, Homburg/Saar, Germany
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Coates K, Cooke SJ, Mann DA, Harris MP. Protein kinase C-mediated phosphorylation of HIV-I nef in human cell lines. J Biol Chem 1997; 272:12289-94. [PMID: 9139671 DOI: 10.1074/jbc.272.19.12289] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Stable human cell lines expressing the human immunodeficiency virus type I (HIV-I) Nef protein from inducible promoters were used to analyze the phosphorylation status of Nef in vivo. Nef phosphorylation in both HeLa and Jurkat cells was stimulated by phorbol ester treatment. Phosphoamino acid analysis revealed a predominance of phosphoserine with a small proportion of phosphothreonine. Treatment of cells with selective protein kinase inhibitors revealed that Nef phosphorylation was markedly reduced by bisindolylmaleimide, an inhibitor of protein kinase C, but was unaffected by inhibitors of mitogen-activated protein kinase kinase or cAMP-dependent kinase. These data implicate protein kinase C in Nef phosphorylation in vivo, and thus confirm and extend earlier in vitro data. Phosphorylation of a nonmyristoylated Nef mutant was impaired, suggesting that membrane targeting of Nef was required for phosphorylation. This was expected given that activated protein kinase C translocates from the cytosol to the plasma membrane. However, analysis of the subcellular localization of phosphorylated wild-type Nef revealed that both the cytosolic and membrane-associated pools of Nef were phosphorylated to an equivalent extent. Thus the significance of myristoylation for Nef function may be in influencing protein conformation, although these data could be explained by a transient and dynamic interaction between myristoylated Nef and the plasma membrane.
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Affiliation(s)
- K Coates
- MRC Retrovirus Research Laboratory, Department of Veterinary Pathology, University of Glasgow, Glasgow G61 1QH, Scotland, United Kingdom
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Smith BL, Krushelnycky BW, Mochly-Rosen D, Berg P. The HIV nef protein associates with protein kinase C theta. J Biol Chem 1996; 271:16753-7. [PMID: 8663223 DOI: 10.1074/jbc.271.28.16753] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Expression of the human immunodeficiency virus (HIV) Nef protein has been linked to both decreased cell surface expression of CD4 and an impairment of signal transduction. The recently reported association of Nef with an unidentified serine kinase provides a clue as to how Nef might exert its effects. Considering the key role of protein kinase C (PKC) in T cell activation, we investigated the possibility that Nef interacts with PKC. Our results, using two approaches for detecting interactions between Nef and PKC isozymes in Jurkat cells, show that Nef interacts preferentially with thetaPKC. The interaction of Nef and thetaPKC is independent of calcium, enhanced by phospholipid activators of PKC and not affected by a PKC pseudosubstrate peptide. Phorbol 12-myristate 13-acetate and phytohemagglutinin stimulation of Jurkat cells expressing Nef fails to produce the usual translocation of thetaPKC from the cytosol to the particulate fraction; translocation of betaPKC and epsilonPKC was unaffected. Indeed, there appears to be a net loss of thetaPKC in Nef-expressing cells following stimulation. The loss of thetaPKC, which may be a result of inhibition of its binding to RACKs due to Nef binding, could contribute to the various impairments of T cell function associated with HIV infection and Nef expression.
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Affiliation(s)
- B L Smith
- Department of Biochemistry, Beckman Center and Stanford University School of Medicine, Stanford, California 94305, USA
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