Inhibiting the Recruitment of PLCγ1 to Kaposi’s Sarcoma Herpesvirus K15 Protein Reduces the Invasiveness and Angiogenesis of Infected Endothelial Cells

Kaposi's sarcoma (KS), caused by Kaposi's sarcoma herpesvirus (KSHV), is a highly vascularised tumour of endothelial origin. KSHV infected endothelial cells show increased invasiveness and angiogenesis. Here, we report that the KSHV K15 protein, which we showed previously to contribute to KSHV-induced angiogenesis, is also involved in KSHV-mediated invasiveness in a PLC gamma 1-dependent manner. We identified beta PIX, GIT1 and cdc42, downstream effectors of PLC gamma 1 in cell migration, as K15 interacting partners and as contributors to KSHV-triggered invasiveness. We mapped the interaction between PLC gamma 1, PLC gamma 2 and their individual domains with two K15 alleles, P and M. We found that the PLC gamma 2 cSH2 domain, by binding to K15P, can be used as dominant negative inhibitor of the K15P-PLC gamma 1 interaction, K15P-dependent PLC gamma 1 phosphorylation, NFAT-dependent promoter activation and the increased invasiveness and angiogenic properties of KSHV infected endothelial cells. We increased the binding of the PLC gamma 2 cSH2 domain for K15P by substituting two amino acids, thereby creating an improved dominant negative inhibitor of the K15P-dependent PLC gamma 1 activation. Taken together, these results demonstrate a necessary role of K15 in the increased invasiveness and angiogenesis of KSHV infected endothelial cells and suggest the K15-PLC gamma 1 interaction as a possible new target for inhibiting the angiogenic and invasive properties of KSHV.