Characterization of the murine gammaherpesvirus 68 ORF74 product: a novel oncogenic G protein-coupled receptor.
Murine gammaherpesvirus (MHV-68) is well established as a small animal model for the study of gammaherpesviruses. The MHV-68 genome contains an open reading frame (ORF74) that has significant sequence homology with mammalian G-protein coupled receptors (GPCRs) and the GPCR from the related Kaposi's sarcoma-associated herpesvirus (KSHV). Here we show that the MHV-68 ORF74 is predicted to encode a GPCR since it has seven potential transmembrane helices and that it has other sequence motifs in common with GPCRS: Of interest is the observation that the sequence around a conserved arginine at the start of the second intracellular loop suggests that the ORF74 product may signal constitutively (agonist independent). Given that the ORF74 product is predicted to encode a GPCR we named it MHV-GPCR. In studies on the transcription of the MHV-GPCR, we determined that it was encoded on multiple early transcripts of 3.4, 4.4, 6.6 and 8.7 kb in size. At least one of these transcripts was bicistronic, containing the ORF encoding the Bcl-2 homologue also. In vivo, we found that MHV GPCR was expressed during acute infection but also during persistence, particularly in the lungs of infected mice. Immunofluorescence studies indicated that the MHV GPCR protein was expressed on the surface of cells in patches. Finally, like the KSHV GPCR, expression of the MHV GPCR resulted in transformation of NIH 3T3 cells. We surmise, therefore, that the MHV GPCR may act in concert with genes with which it is expressed such as vBcl-2 to enhance the growth and survival of MHV-68-infected cells.
Wakeling
Madeleine N
MN
Laboratory for Clinical and Molecular Virology, The University of Edinburgh, Summerhall, Edinburgh EH9 1QH, UK1.
Roy
Douglas J
DJ
Laboratory for Clinical and Molecular Virology, The University of Edinburgh, Summerhall, Edinburgh EH9 1QH, UK1.
Nash
Anthony A
AA
Laboratory for Clinical and Molecular Virology, The University of Edinburgh, Summerhall, Edinburgh EH9 1QH, UK1.
Stewart
James P
JP
Laboratory for Clinical and Molecular Virology, The University of Edinburgh, Summerhall, Edinburgh EH9 1QH, UK1.
D016475:3T3 Cells; D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D002472:Cell Transformation, Viral; D006224:Cricetinae; D005260:Female; D019204:GTP-Binding Proteins / Q000378:metabolism*; D018142:Gammaherpesvirinae / Q000235:genetics; D015870:Gene Expression; D020869:Gene Expression Profiling; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D015513:Oncogene Proteins / Q000235:genetics / Q000502:physiology*; D016366:Open Reading Frames; D011956:Receptors, Cell Surface / Q000235:genetics / Q000502:physiology*; D014158:Transcription, Genetic; D014764:Viral Proteins / Q000235:genetics / Q000502:physiology*
D015513:Oncogene Proteins; D011956:Receptors, Cell Surface; D014764:Viral Proteins; D019204:GTP-Binding Proteins