KSHV-TK is a tyrosine kinase that disrupts focal adhesions and induces Rhomediated cell contraction

This is the accepted manuscript. The final version is available from Wiley at http://onlinelibrary.wiley.com/doi/10.15252/embj.201490358/abstract.Paradoxically, the thymidine kinase (TK) encoded by Kaposi sarcoma-associated herpesvirus (KSHV) is an extremely inefficient nucleoside kinase, when compared to TKs from related herpesviruses. We now show that KSHV-TK, in contrast to HSV1-TK, associates with the actin cytoskeleton, induces extensive cell contraction followed by membrane blebbing. These dramatic changes in cell morphology depend on the autophosphorylation of tyrosine 65, 85 and 120 in the N-terminus of KSHV-TK. Phosphorylation of Tyrosine 65/85 and 120 results in an interaction with Crk family proteins and the p85 regulatory subunit of PI3-Kinase respectively. The interaction with KSHV-TK leads to tyrosine phoshorylation of Crk. Auto-phosphorylation of KSHV-TK also induces a loss of FAK and paxillin from focal adhesions, resulting in activation of RhoA-ROCK signalling to myosin II and cell contraction. In the absence of FAK or paxillin, KSHV-TK has no effect on focal adhesion integrity or cell morphology. Our observations demonstrate that by acting as a tyrosine kinase KSHV-TK modulates signalling and cell morphology.This work was supported by Medical Research Council grant G0701185 to PGS and MBG. M.W is supported by Cancer Research UK