15 results on '"Sandford, Gordon"'
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2. Rat cytomegalovirus (RCMV) English isolate and a newly identified Berlin isolate share similarities with but are separate as an anciently diverged clade from Mouse CMV and the Maastricht isolate of RCMV.
- Author
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Geyer H, Ettinger J, Möller L, Schmolz E, Nitsche A, Brune W, Heaggans S, Sandford GR, Hayward GS, and Voigt S
- Subjects
- Animals, Genome, Viral, Mice, Muromegalovirus isolation & purification, Phylogeny, Rats, Sequence Homology, Synteny, Genetic Variation, Muromegalovirus classification, Muromegalovirus genetics
- Abstract
The genome of the rat cytomegalovirus (RCMV) English isolate (MuHV-8) differs significantly from the RCMV Maastricht isolate (MuHV-2) and other cytomegaloviruses (CMVs) in its size, base composition and genomic content. Analysis of the RCMV-Berlin isolate, MuHV-8, revealed that the two MuHV-8 isolates are highly similar in genome size and content, indicating that the smaller genome size (202 946 bp) compared to other known CMVs was not the result of an accidental deletion during passage in tissue culture. Surprisingly, the proteins encoded in MuHV-8 shared more overall similarity with their orthologues from mouse CMV (MuHV-1) compared to their orthologues in rat CMV (MuHV-2). Phylogenetic analyses of conserved viral genes showed that the two MuHV-8 isolates are from the same species and represent a unique clade that is distinct from other rodent CMVs.
- Published
- 2015
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3. Human herpesvirus 8 viral interleukin-6 signaling through gp130 promotes virus replication in primary effusion lymphoma and endothelial cells.
- Author
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Cousins E, Gao Y, Sandford G, and Nicholas J
- Subjects
- Base Sequence, DNA Primers, Herpesvirus 8, Human physiology, Humans, Cytokine Receptor gp130 physiology, Endothelial Cells virology, Herpesvirus 8, Human metabolism, Interleukin-6 metabolism, Lymphoma, Primary Effusion virology, Signal Transduction, Virus Replication
- Abstract
The contributions of human herpesvirus 8 (HHV-8) viral interleukin-6 (vIL-6) to virus biology remain unclear. Here we examined the role of vIL-6/gp130 signaling in HHV-8 productive replication in primary effusion lymphoma and endothelial cells. Depletion and depletion-complementation experiments revealed that endoplasmic reticulum-localized vIL-6 activity via gp130 and gp130-activated signal transducer and activator of transcription (STAT) signaling, but not extracellular signal-regulated kinase (ERK) activation, was critical for vIL-6 proreplication activity. Our data significantly extend current understanding of vIL-6 function and associated mechanisms in HHV-8 biology., (Copyright © 2014, American Society for Microbiology. All Rights Reserved.)
- Published
- 2014
- Full Text
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4. Complete genome sequence of the english isolate of rat cytomegalovirus (Murid herpesvirus 8).
- Author
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Ettinger J, Geyer H, Nitsche A, Zimmermann A, Brune W, Sandford GR, Hayward GS, and Voigt S
- Subjects
- Animals, Molecular Sequence Data, Open Reading Frames, Rats, Cytomegalovirus genetics, Genome, Viral
- Abstract
The complete genome of the English isolate of rat cytomegalovirus (RCMV-E) was determined. RCMV-E has a 202,946-bp genome with noninverting repeats but without terminal repeats. Thus, it differs significantly in size and genomic arrangement from closely related rodent cytomegaloviruses (CMVs). To account for the differences between the rat CMV isolates of Maastricht and England, RCMV-E was classified as Murid herpesvirus 8 by the International Committee on Taxonomy of Viruses.
- Published
- 2012
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5. Human herpesvirus 8 viral interleukin-6 interacts with splice variant 2 of vitamin K epoxide reductase complex subunit 1.
- Author
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Chen D, Cousins E, Sandford G, and Nicholas J
- Subjects
- Amino Acid Sequence, Base Sequence, Cell Line, Electrophoresis, Polyacrylamide Gel, Humans, Microscopy, Fluorescence, Mixed Function Oxygenases chemistry, Molecular Sequence Data, Protein Binding, Two-Hybrid System Techniques, Vitamin K Epoxide Reductases, Herpesvirus 8, Human metabolism, Interleukin-6 metabolism, Mixed Function Oxygenases metabolism, RNA Splicing
- Abstract
Viral interleukin-6 (vIL-6) specified by human herpesvirus 8 is, unlike its cellular counterpart, secreted very inefficiently and can signal via vIL-6(2):gp130(2) signaling complexes from the endoplasmic reticulum (ER) compartment. Intracellular, autocrine activities of vIL-6 are important for proproliferative and prosurvival activities of the viral cytokine in latently infected primary effusion lymphoma (PEL) cells. However, the molecular determinants of vIL-6 ER localization and function are unclear. Using yeast two-hybrid analysis, we identified the database-documented but uncharacterized splice variant of vitamin K epoxide reductase complex subunit 1 (VKORC1), termed VKORC1 variant 2 (VKORC1v2), as a potential interaction partner of vIL-6. In transfected cells, epitope-tagged VKORC1v2 was found to localize to the ER, to adopt a single-transmembrane (TM) topology placing the C tail in the ER lumen, and to bind vIL-6 via these sequences. Deletion mutagenesis and coprecipitation assays mapped the vIL-6-binding domain (vBD) of VKORC1v2 to TM-proximal residues 31 to 39. However, while sufficient to confer vIL-6 binding to a heterologous protein, vBD was unable to induce vIL-6 secretion when fused to (secreted) hIL-6, suggesting a VKORC1v2-independent mechanism of vIL-6 ER retention. In functional assays, overexpression of ER-directed vBD led to suppression of PEL cell proliferation and viability, effects also mediated by VKORC1v2 depletion and, as reported previously, by vIL-6 suppression. The growth-inhibitory and proapoptotic effects of VKORC1v2 depletion could be rescued by transduced wild-type VKORC1v2 but not by a vIL-6-refractory vBD-altered variant, indicating the functional relevance of the vIL-6-VKORC1v2 interaction. Notably, gp130 signaling was unaffected by VKORC1v2 or vBD overexpression or by VKORC1v2 depletion, suggesting an alternative pathway of vIL-6 activity via VKORC1v2. Combined, our data identify a novel and functionally significant interaction partner of vIL-6 that could potentially be targeted for therapeutic benefit.
- Published
- 2012
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6. Human herpesvirus 8 interferon regulatory factor-mediated BH3-only protein inhibition via Bid BH3-B mimicry.
- Author
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Choi YB, Sandford G, and Nicholas J
- Subjects
- Amino Acid Sequence, Apoptosis physiology, Apoptosis Regulatory Proteins chemistry, Apoptosis Regulatory Proteins metabolism, BH3 Interacting Domain Death Agonist Protein chemistry, BH3 Interacting Domain Death Agonist Protein metabolism, Bcl-2-Like Protein 11, Cell Line, Fluorescent Antibody Technique, Humans, Immunoblotting, Immunoprecipitation, In Situ Nick-End Labeling, Membrane Proteins chemistry, Membrane Proteins metabolism, Molecular Sequence Data, Protein Structure, Secondary, Proto-Oncogene Proteins chemistry, Proto-Oncogene Proteins metabolism, Transfection, Herpesviridae Infections metabolism, Herpesvirus 8, Human metabolism, Immune Evasion, Interferon Regulatory Factors metabolism, Molecular Mimicry, Viral Proteins metabolism
- Abstract
Viral replication efficiency is in large part governed by the ability of viruses to counteract pro-apoptotic signals induced by infection of host cells. For HHV-8, viral interferon regulatory factor-1 (vIRF-1) contributes to this process in part via inhibitory interactions with BH3-only protein (BOP) Bim, recently identified as an interaction partner of vIRF-1. Here we recognize that the Bim-binding domain (BBD) of vIRF-1 resembles a region (BH3-B) of Bid, another BOP, which interacts intramolecularly with the functional BH3 domain of Bid to inhibit it pro-apoptotic activity. Indeed, vIRF-1 was found to target Bid in addition to Bim and to interact, via its BBD region, with the BH3 domain of each. In functional assays, BBD could substitute for BH3-B in the context of Bid, to suppress Bid-induced apoptosis in a BH3-binding-dependent manner, and vIRF-1 was able to protect transfected cells from apoptosis induced by Bid. While vIRF-1 can mediate nuclear sequestration of Bim, this was not the case for Bid, and inhibition of Bid and Bim by vIRF-1 could occur independently of nuclear localization of the viral protein. Consistent with this finding, direct BBD-dependent inactivation by vIRF-1 of Bid-induced mitochondrial permeabilization was demonstrable in vitro and isolated BBD sequences were also active in this assay. In addition to Bim and Bid BH3 domains, BH3s of BOPs Bik, Bmf, Hrk, and Noxa also were found to bind BBD, while those of both pro- and anti-apoptotic multi-BH domain Bcl-2 proteins were not. Finally, the significance of Bid to virus replication was demonstrated via Bid-depletion in HHV-8 infected cells, which enhanced virus production. Together, our data demonstrate and characterize BH3 targeting and associated inhibition of BOP pro-apoptotic activity by vIRF-1 via Bid BH3-B mimicry, identifying a novel mechanism of viral evasion from host cell defenses.
- Published
- 2012
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7. Recombinant luciferase-expressing human cytomegalovirus (CMV) for evaluation of CMV inhibitors.
- Author
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He R, Sandford G, Hayward GS, Burns WH, Posner GH, Forman M, and Arav-Boger R
- Subjects
- Cell Line, Cytomegalovirus genetics, Cytomegalovirus metabolism, Cytomegalovirus Infections drug therapy, Drug Evaluation, Preclinical instrumentation, Gene Expression drug effects, Humans, Luciferases metabolism, Promoter Regions, Genetic, Recombinant Proteins genetics, Recombinant Proteins metabolism, Antiviral Agents pharmacology, Cytomegalovirus drug effects, Cytomegalovirus Infections virology, Drug Evaluation, Preclinical methods, Luciferases genetics
- Abstract
Recombinant Towne CMV expressing luciferase under the control of CMV-DNA polymerase (POL) or the late pp28 (UL99) promoters were evaluated for potential application in high-throughput screening of anti-viral compounds. POL-and pp28-luciferase displayed maximal expression 48 and 72 hours post infection, respectively. The pp28-luciferase virus achieved a wider dynamic range of luciferase expression (6-7 logs) and was selected for testing of inhibition by five anti-viral compounds. Luciferase expression highly correlated with plaque reduction and real-time PCR. The pp28-luciferase reporter system is rapid, reproducible, and highly sensitive. It may be applied to screening of novel anti-CMV compounds.
- Published
- 2011
- Full Text
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8. Deletion of the rat cytomegalovirus immediate-early 1 gene results in a virus capable of establishing latency, but with lower levels of acute virus replication and latency that compromise reactivation efficiency.
- Author
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Sandford GR, Schumacher U, Ettinger J, Brune W, Hayward GS, Burns WH, and Voigt S
- Subjects
- Animals, Cells, Cultured, Fibroblasts virology, Herpesviridae Infections virology, In Vitro Techniques, Muromegalovirus genetics, Rats, Salivary Glands virology, Spleen virology, Virulence, Virus Activation, DNA, Viral genetics, Immediate-Early Proteins genetics, Muromegalovirus physiology, Sequence Deletion, Trans-Activators genetics, Virus Latency, Virus Replication
- Abstract
The immediate-early 1 (IE1) and IE2 proteins encoded by the major immediate-early (MIE) transcription unit of cytomegaloviruses are thought to play key roles in the switch between latent- and lytic-cycle infection. Whilst IE2 is essential for triggering the lytic cycle, the exact roles of IE1 have not been resolved. An MIE-exon 4-deleted rat cytomegalovirus (DeltaIE1) failed to synthesize the IE1 protein and did not disperse promyelocytic leukaemia bodies early post-infection, but was still capable of normal replication in fibroblast cell culture. However, DeltaIE1 had a diminished ability to infect salivary glands persistently in vivo and to reactivate from spleen explant cultures ex vivo. Quantification of viral genomes in spleens of infected animals revealed a reduced amount of DeltaIE1 virus produced during acute infection, suggesting a role for IE1 as a regulator in establishing a chronic or persistent infection, rather than in influencing the latency or reactivation processes more directly.
- Published
- 2010
- Full Text
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9. Role of ORF74-encoded viral G protein-coupled receptor in human herpesvirus 8 lytic replication.
- Author
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Sandford G, Choi YB, and Nicholas J
- Subjects
- Humans, Receptors, Chemokine genetics, Herpesvirus 8, Human physiology, Receptors, Chemokine physiology, Viral Proteins physiology, Virus Replication
- Abstract
The human herpesvirus 8 (HHV-8) viral G protein-coupled receptor (vGPCR) has been implicated in virus-associated disease pathogenesis due principally to its ability to induce the production of angiogenic cytokines involved in this process. However, the role of the vGPCR in normal virus biology is understudied and remains unknown. Here we provide evidence from vGPCR gene knockout and depletion experiments that vGPCR is a positive regulator of HHV-8 productive replication and, through experimental utilization of Galpha-coupling variants of vGPCR, that signaling via Galpha(q) activation and targeted mitogen-activated protein kinase pathways is of particular relevance to this activity.
- Published
- 2009
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10. Determinants of secretion and intracellular localization of human herpesvirus 8 interleukin-6.
- Author
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Chen D, Choi YB, Sandford G, and Nicholas J
- Subjects
- Amino Acid Sequence, Calnexin metabolism, Cell Line, Endoplasmic Reticulum metabolism, Glycosylation, Herpesvirus 8, Human genetics, Humans, Interleukin-6 genetics, Molecular Sequence Data, Point Mutation, Protein Folding, Cytokine Receptor gp130 metabolism, Endoplasmic Reticulum virology, Herpesvirus 8, Human physiology, Interleukin-6 metabolism
- Abstract
Human herpesvirus 8 (HHV-8) interleukin-6 (vIL-6) is distinct from human and other cellular IL-6 proteins in that it does not require the nonsignaling alpha-receptor subunit for the formation of gp130-based signal transducing complexes and also is largely retained intracellularly rather than being secreted. We and others have reported that vIL-6 is retained and is active in the endoplasmic reticulum (ER) compartment, and data from our laboratory have demonstrated that intracellular vIL-6 is functional in the autocrine promotion of proliferation and survival of HHV-8 latently infected primary effusion lymphoma cells. It has also been reported that vIL-6 secretion in gp130-deficient cells can be enhanced by introduced gp130, thereby implicating the signal transducer in vIL-6 trafficking to the cell surface. We examine here the requirements for intracellular retention and localization of vIL-6. Using vIL-6-hIL-6 chimeric and point-mutated vIL-6 proteins, we identified regions and residues of vIL-6 influencing vIL-6 secretion. However, there was no correlation between vIL-6 secretion and gp130 interaction. We found that vIL-6, but not hIL-6, could associate stably with ER-resident chaperone protein calnexin. Glycosylation-dependent interaction of vIL-6 with calnexin correlated with proper protein folding, but there was no direct relationship between vIL-6-calnexin interaction and intracellular retention. While calnexin depletion had little influence on absolute amounts of secreted vIL-6, it led to markedly reduced levels of intracellular cytokine. This was reversed by gp130 transduction, which had no detectable effect on vIL-6 secretion, but redistributed vIL-6 into ER-distinct locations in calnexin-depleted cells, specifically. Our data reveal that calnexin plays a role in ER localization of vIL-6 and that gp130 promotes ER exit, but not secretion, of the viral cytokine.
- Published
- 2009
- Full Text
- View/download PDF
11. Intracellular signaling mechanisms and activities of human herpesvirus 8 interleukin-6.
- Author
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Chen D, Sandford G, and Nicholas J
- Subjects
- Cell Line, Cytokine Receptor gp130 metabolism, Endoplasmic Reticulum chemistry, Gene Knockdown Techniques, Humans, Receptors, Interleukin-6 metabolism, Herpesvirus 8, Human physiology, Interleukin-6 metabolism, Signal Transduction, Viral Proteins metabolism
- Abstract
Human herpesvirus 8 (HHV-8)-encoded viral interleukin-6 (vIL-6) has been implicated as a key factor in virus-associated neoplasia because of its proproliferative and survival effects and also in view of its angiogenic properties. A major difference between vIL-6 and human IL-6 (hIL-6) is that vIL-6, uniquely, is largely retained and can signal intracellularly. While vIL-6 is generally considered to be a lytic gene, several reports have noted its low-level expression in latently infected primary effusion lymphoma (PEL) cultures, in the absence of other lytic gene expression. Thus, intracellular autocrine signal transduction by the viral cytokine may be of particular relevance to the growth and survival of latently infected cells and to pathogenesis. Here we report that most intracellular vIL-6 is located in the endoplasmic reticulum (ER), signals via the gp130 signal transducer in this compartment, and does so independently of the gp80 alpha-subunit of the IL-6 receptor, required for hIL-6 signal transduction. Signaling and biological assays incorporating ER-retained vIL-6 and hIL-6 confirmed vIL-6 activity, specifically, in this compartment. Knockdown of vIL-6 expression in PEL cells led to markedly reduced cell growth in normal culture, independently of extracellular cytokines. This could be reversed by reintroduction via virus vector of exclusively ER-retained vIL-6. These data indicate that in virus biology vIL-6 may act to support the growth and survival of cells latently infected with HHV-8 in an autocrine manner via intracrine signaling and that these activities may contribute to the maintenance of latently infected cells and to virus-induced neoplasia.
- Published
- 2009
- Full Text
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12. The English strain of rat cytomegalovirus (CMV) contains a novel captured CD200 (vOX2) gene and a spliced CC chemokine upstream from the major immediate-early region: further evidence for a separate evolutionary lineage from that of rat CMV Maastricht.
- Author
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Voigt S, Sandford GR, Hayward GS, and Burns WH
- Subjects
- Animals, Antigens, CD, DNA-Directed DNA Polymerase genetics, Evolution, Molecular, Immediate-Early Proteins genetics, Membrane Glycoproteins genetics, Molecular Mimicry, Molecular Sequence Data, Muromegalovirus classification, Open Reading Frames, Phylogeny, Rats, Receptors, Fc genetics, Trans-Activators genetics, Viral Proteins genetics, Antigens, Surface genetics, Chemokines, CC genetics, Genes, Viral, Muromegalovirus genetics
- Abstract
Sequence data for eight genes, together with time-course Northern blotting and 3'- and 5'-RACE (rapid amplification of cDNA ends) analysis for some mRNAs from a 12 kb region upstream from the major immediate-early (MIE) genes of the English isolate of rat cytomegalovirus (RCMV), are presented. The results identified important differences compared to both murine cytomegalovirus (MCMV) and the Maastricht isolate of RCMV. A striking finding is the presence of a highly conserved, rightwards-oriented homologue of the rat cellular CD200 (OX2) gene immediately to the right of the MIE region, which replaces either the leftwards-oriented AAV REP gene of RCMV (Maastricht) or the upstream spliced portions of the immediate-early 2 gene (ie2) in MCMV. From the presence of other homologues of MCMV- and RCMV-specific genes, such as the beta-chemokine MCK-2, SGG1 and an Fcgamma receptor gene, as reported here, the basic architecture of the MIE region (reported previously) and the level of IE2 and DNA polymerase (POL) protein conservation in phylogenetic analyses, it is clear that the English strain of RCMV is also a member of the genus Muromegalovirus, but is a beta-herpesvirus species that is very distinct from both MCMV and RCMV (Maastricht). Both the lack of a CD200 homologue in the other two rodent viruses and the depth of sequence divergence of the rodent CMV IE2 and POL proteins suggest that these three viruses have evolved as separate species in the genus Muromegalovirus since very early in the host rodent lineage.
- Published
- 2005
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13. CD200 is a novel p53-target gene involved in apoptosis-associated immune tolerance.
- Author
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Rosenblum MD, Olasz E, Woodliff JE, Johnson BD, Konkol MC, Gerber KA, Orentas RJ, Sandford G, and Truitt RL
- Subjects
- Animals, Antigens, CD, Base Sequence, Cells, Cultured, DNA Primers, Humans, Introns genetics, Lymphocyte Culture Test, Mixed, Lymphocytes immunology, Lymphocytes radiation effects, Mice, Mice, Inbred C57BL, Mice, Knockout, RNA, Messenger genetics, Transcription, Genetic, Tumor Cells, Cultured, Ultraviolet Rays, Antigens, Surface genetics, Apoptosis immunology, Dendritic Cells immunology, Genes, p53 immunology, Immune Tolerance immunology
- Abstract
During apoptotic cell death, biochemical processes modify self-proteins and create potential autoantigens. To maintain self-tolerance in the face of natural cell turnover, the immune system must prevent or control responses to apoptosis-associated autoantigens or risk autoimmunity. The molecular mechanisms governing this process remain largely unknown. Here, we show that expression of the immunoregulatory protein CD200 increases as murine dendritic cells (DCs) undergo apoptosis. We define CD200 as a p53-target gene and identify both p53- and caspase-dependent pathways that control CD200 expression during apoptosis. CD200 expression on apoptotic DCs diminishes proinflammatory cytokine production in response to self-antigens in vitro and is required for UVB-mediated tolerance to haptenated self-proteins in vivo. Up-regulation of CD200 may represent a novel mechanism, whereby immune reactivity to apoptosis-associated self-antigens is suppressed under steady state conditions.
- Published
- 2004
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14. Galpha protein selectivity determinant specified by a viral chemokine receptor-conserved region in the C tail of the human herpesvirus 8 g protein-coupled receptor.
- Author
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Liu C, Sandford G, Fei G, and Nicholas J
- Subjects
- Amino Acid Sequence, Calcium Signaling, Cell Line, GTP-Binding Protein alpha Subunits, Gq-G11 metabolism, Genes, Reporter genetics, Humans, MAP Kinase Signaling System, Mitogen-Activated Protein Kinases genetics, Mitogen-Activated Protein Kinases metabolism, Molecular Sequence Data, Mutagenesis, Site-Directed, Mutation genetics, NF-kappa B metabolism, Promoter Regions, Genetic genetics, Receptors, Chemokine genetics, Substrate Specificity, Vascular Endothelial Growth Factor A genetics, GTP-Binding Protein alpha Subunits metabolism, Herpesvirus 8, Human metabolism, Receptors, Chemokine chemistry, Receptors, Chemokine metabolism
- Abstract
The viral G-protein coupled receptor (vGPCR) specified by human herpesvirus 8 (HHV-8) open reading frame 74 (ORF74) is a ligand-independent chemokine receptor that has structural and functional homologues among other characterized gammaherpesviruses and related receptors in the betaherpesviruses. Sequence comparisons of the gammaherpesvirus vGPCRs revealed a highly conserved region in the C tail, just distal to the seventh transmembrane domain. Mutagenesis of the corresponding codons of HHV-8 ORF74 was carried out to provide C-tail-altered proteins for functional analyses. By measuring receptor-activated vascular endothelial growth factor promoter induction and NF-kappaB, mitogen-activated protein kinase, and Ca(2+) signaling, we found that while some altered receptors showed general signaling deficiencies, others had distinguishable activation profiles, suggestive of selective Galpha protein coupling. This was supported by the finding that vGPCR and representative functionally altered variants, vGPCR.8 (R322W) and vGPCR.15 (M325S), were affected differently by inhibitors of Galpha(i) (pertussis toxin), protein kinase C (GF109203X), and phosphatidylinositol 3-kinase (wortmannin). Consistent with the signaling data, [(35)S]GTPgammaS incorporation assays revealed preferential coupling of vGPCR.15 to Galpha(q) and an inability of vGPCR.8 to couple functionally to Galpha(q). However, both variants, wild-type vGPCR, and a C-tail deletion version of the receptor were equally able to associate physically with Galpha(q). Combined, our data demonstrate that HHV-8 vGPCR contains discrete sites of Galpha interaction and that receptor residues in the proximal region of the cytoplasmic tail are determinants of Galpha protein coupling specificity.
- Published
- 2004
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15. Molecular mechanisms for viral mimicry of a human cytokine: activation of gp130 by HHV-8 interleukin-6.
- Author
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Boulanger MJ, Chow DC, Brevnova E, Martick M, Sandford G, Nicholas J, and Garcia KC
- Subjects
- Amino Acid Sequence, Antigens, CD chemistry, Cytokine Receptor gp130, Humans, Interleukin-6 chemistry, Interleukin-6 genetics, Membrane Glycoproteins chemistry, Molecular Sequence Data, Protein Binding, Sarcoma, Kaposi, Sequence Homology, Amino Acid, Structure-Activity Relationship, Thermodynamics, Viral Proteins chemistry, Viral Proteins genetics, Antigens, CD metabolism, Herpesvirus 8, Human metabolism, Interleukin-6 metabolism, Membrane Glycoproteins metabolism, Molecular Mimicry, Receptors, Interleukin-6 physiology, Signal Transduction, Viral Proteins metabolism
- Abstract
Kaposi's sarcoma-associated herpesvirus (KSHV, or HHV-8) encodes a pathogenic viral homologue of human interleukin-6 (IL-6). In contrast to human IL-6 (hIL-6), viral IL-6 (vIL-6) binds directly to, and activates, the shared human cytokine signaling receptor gp130 without the requirement for pre-complexation to a specific alpha-receptor. Here, we dissect the biochemical and functional basis of vIL-6 mimicry of hIL-6. We find that, in addition to the "alpha-receptor-independent" tetrameric vIL-6/gp130 complex, the viral cytokine can engage the human alpha-receptor (IL-6Ralpha) to form a hexameric vIL-6/IL-6Ralpha/gp130 complex with enhanced signaling potency. In contrast to the assembly sequence of the hIL-6 hexamer, the preformed vIL-6/gp130 tetramer can be decorated with IL-6Ralpha, post facto, in a "vIL-6-dependent" fashion. A detailed comparison of the viral and human cytokine/gp130 interfaces indicates that vIL-6 has evolved a unique molecular strategy to interact with gp130, as revealed by an almost entirely divergent structural makeup of its receptor binding sites. Viral IL-6 appears to utilize an elegant combination of both convergent, and unexpectedly divergent, molecular strategies to oligomerize gp130 and activate similar downstream signaling cascades as its human counterpart.
- Published
- 2004
- Full Text
- View/download PDF
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