Association of p130(CAS) with phosphatidylinositol-3-OH kinase mediates adenovirus cell entry

The Crk-associated substrate, p130(CAS), has been implicated in the regulat ion of the actin cytoskeleton following ligation of cell integrins with the extracellular matrix. Integrin-mediated cell adhesion involves p130(CAS) a ssociation with focal adhesion kinase (p125(FAK)). Internalization/cell ent ry of type 2 and type 5 adenoviruses (Ad) is also mediated by alpha(v) inte grins. However, expression of dominant negative forms of p125FAK does not a lter virus entry, and Ad entry occurs normally in p125(FAK)-deficient fibro blasts. We now provide evidence that Ad internalization, a process which is mediated by LY,integrins, also requires p130(CAS) and phosphatidylinositol -3-OH kinase (PI 3-kinase). Ad induces p130(CAS) phosphorylation and inhibi tion of p130(CAS) phosphorylation by tyrphostin and genistein, or expressio n of the substrate domain deleted p130(CAS) blocks Ad internalization. p130 (CAS) was also found to associate with the p85 subunit of PI 3-kinase throu gh its proline-rich domain during virus internalization and expression of p 130(CAS) containing a deleted proline-rich domain (PRD) inhibited adenoviru s cell entry. We showed further that the RPLPSPP motif in the proline-rich region of p130(CAS) interacts with the SH3 domain of p85/PI 3-kinase. These studies reveal the molecular basis by which p130(CAS) coordinates the sign aling pathways involved in integrin-mediated Ad endocytosis.