Kaposi's sarcoma-associated herpesvirus glycoproteins B and K8.1 regulate virion egress and synthesis of vascular endothelial growth factor and viral interleukin-6 in BCBL-1 cells.

Abstract

Kaposi's sarcoma-associated herpesvirus (KSHV) viral glycoproteins play important roles in the infectious life cycle and have been implicated in KSHV-associated endothelial cell transformation, angiogenesis, and KS-induced malignancies. KSHV-associated primary effusion lymphomas (PELs) secrete high levels of vascular endothelial growth factor (VEGF) and viral interleukin-6 (vIL-6) in vitro and VEGF, vIL-6, and basic-fibroblast growth factor (b-FGF) in mouse xenografts. KSHV-encoded glycoproteins B (gB) and K8.1 stimulate VEGF secretion, most likely mediated by direct or indirect binding to cell surface receptors, including the gB-specific alphaVbeta3 and alpha3beta1 integrins. In this study, the short interfering RNA (siRNA)-mediated inhibition of either gB or K8.1 transcription by anti-gB or -K8.1 siRNAs caused a substantial reduction in virion egress and a decrease in both vIL-6 and VEGF production. Similarly, the treatment of BCBL-1 cells with anti-gB or anti-K8.1 antibodies caused a substantial reduction in vIL-6 and VEGF production. Codon-optimized versions of either wild-type gB, mutant gB having the RGD amino acid motif changed to RAA, or K8.1 efficiently rescued virion egress and VEGF and vIL-6 production. These results suggest that the binding of gB via its RGD motif to integrin receptors was not responsible for the observed gB-associated regulation of VEGF and vIL-6 transcription. Conditioned medium collected from BCBL-1 cells transfected with anti-gB and anti-K8.1 siRNAs or treated with anti-gB and anti-K8.1 antibodies exhibited a significantly reduced ability to induce the formation of the capillary network of endothelial cells compared to the ability of medium from mock-infected BCBl-1 cells. Furthermore, medium obtained from BCBL-1 cells expressing smaller amounts of gB and K8.1 produced a substantial reduction in endothelial cell migration in a vertical migration assay compared to that of control medium containing wild-type levels of gB and K8.1. These results suggest a functional linkage between gB/K8.1 synthesis and VEGF/vIL-6 transcriptional regulation via paracrine and/or autocrine signaling pathways.

• Authors: R Subramanian, I Sehgal, O D'Auvergne, K G Kousoulas
• Journal: Journal of virology (J Virol) Vol. 84 Issue 4 Pg. 1704-14 (Feb 2010) ISSN: 1098-5514 [Electronic] United States
• PMID: 19955303 (Publication Type: Journal Article, Research Support, N.I.H., Extramural)

Chemical References

• DNA Primers
• Glycoproteins
• Interleukin-6
• K8.1 protein, Human herpesvirus 8
• RNA, Messenger
• RNA, Small Interfering
• Recombinant Proteins
• Vascular Endothelial Growth Factor A
• Viral Envelope Proteins
• Viral Proteins
• glycoprotein B, human herpesvirus 8

Topics

• Amino Acid Substitution
• Animals
• Base Sequence
• Cell Line, Tumor
• Cells, Cultured
• DNA Primers (genetics)
• Endothelial Cells (virology)
• Genes, Viral
• Glycoproteins (antagonists & inhibitors, genetics, physiology)
• Herpesvirus 8, Human (genetics, pathogenicity, physiology)
• Humans
• Interleukin-6 (biosynthesis, genetics)
• Mice
• Mutagenesis, Site-Directed
• Neovascularization, Pathologic
• RNA, Messenger (genetics, metabolism)
• RNA, Small Interfering (genetics)
• Recombinant Proteins (genetics, metabolism)
• Transfection
• Vascular Endothelial Growth Factor A (biosynthesis, genetics)
• Viral Envelope Proteins (antagonists & inhibitors, genetics, physiology)
• Viral Proteins (antagonists & inhibitors, genetics, physiology)