The role of integrins in human cytomegalovirus (HCMV)-infected monocytes.

We have established that human cytomegalovirus (HCMV) infection modulates the biology of target primary blood monocytes, allowing HCMV to use monocytes as vehicles for its systemic spread. HCMV infection of monocytes results in rapid induction of PI(3)K and NF-B activity. Integrins, which are upstream of the PI(3)K and NF-B pathways, were shown to be involved in HCMV binding to and entry into fibroblasts, suggesting that receptor-ligand-mediated signaling following viral binding to integrins on monocytes could trigger the functional changes seen in infected monocytes. We now show that integrin engagement and the activation of the integrin/Src-signaling pathway is essential for the induction of HCMV-infected monocyte motility. To investigate how integrin engagement by HCMV triggers monocyte motility, we examined the infected monocyte transcriptome and found that the integrin/Src-signaling pathway regulates the expression of paxillin, which is an important signal transducer in the regulation of actin rearrangement during cell adhesion and movement. Functionally, we observed that paxillin is activated via the integrin/Src-signaling pathway and is required for monocyte motility. Because motility is intimately connected to cellular cytoskeletal organization, a process that is also important in viral entry, we investigated the role paxillin regulation plays in the process of viral entry of monocytes. New results confirmed that HCMV`s ability to enter target monocytes is significantly inhibited in cells deficient in paxillin expression or that had their integrin/Src/paxillin signaling pathway blocked. From our data, HCMV-cell interactions emerge as an essential trigger for the cellular changes that allow for HCMV entry and hematogenous dissemination.

9