Human Cytomegalovirus Chemokine Receptor US28-induced Smooth Muscle Cell Migration is Mediated by Focal Adhesion Kinase and Src

The human cytomegalovirus-encoded chemokine receptor US28 induces arterial smooth muscle cell (SMC) migration; however, the underlying mechanisms involved in this process are unclear. We have previously shown that US28-mediated SMC migration occurs by a ligand-dependent process that is sensitive to protein-tyrosine kinase inhibitors. We demonstrate here that US28 signals through the non-receptor protein-tyrosine kinases Src and focal adhesion kinase (FAK) and that this activity is necessary for US28-mediated SMC migration. In the presence of RANTES (regulated on activation normal T cell expressed and secreted), US28 stimulates the production of a FAK·Src kinase complex. Interestingly, Src co-immunoprecipitates with US28 in a ligand-dependent manner. This association occurs earlier than the formation of the FAK·Src kinase complex, suggesting that US28 activates Src before FAK. US28 binding to RANTES also promotes the formation of a Grb2·FAK complex, which is sensitive to treatment with the Src inhibitor PP2, further highlighting the critical role of Src in US28 activation of FAK. Human cytomegalovirus US28-mediated SMC migration is inhibited by treatment with PP2 and through the expression of either of two dominant negative inhibitors of FAK (F397Y and NH₂-terminal amino acids 1-401). These findings demonstrate that activation of FAK and Src plays a critical role in US28-mediated signaling and SMC migration.