P130Cas, a substrate associated with v-Src and v-Crk, localizes to focal adhesions and binds to focal adhesion kinase

Abstract

p130Cas (crk associated substrate) has the structural characteristics of an adapter protein, containing multiple consensus SH2 binding sites, an SH3 domain, and a proline-rich domain. The structure of p130Cas suggests that it may act to provide a framework for protein-protein interactions; however, as yet, its functional role in cells is unknown. In this report we show that p130Cas is localized to focal adhesions. We demonstrate that p130Cas associates both in vitro and in vivo with pp125FAK (focal adhesion kinase), a kinase implicated in signaling by the integrin family of cell adhesion receptors. p130Cas also associates with pp41/43FRNK (pp125FAK-related, non-kinase), an autonomously expressed form of pp125FAK composed of only the C-terminal noncatalytic domain. We show that the association of p130Cas with pp125Fak and pp41/43FRNK is direct, and is mediated by the binding of the SH3 domain of p130Cas to a proline-rich sequence present in both the C terminus of pp125FAK and in pp41/43FRNK. In agreement with recent studies we show that p130Cas is tyrosine-phosphorylated upon integrin mediated cell adhesion. The association of p130Cas with pp125FAK, a kinase which is activated upon cell adhesion, is likely to be functionally important in integrin mediated signal transduction.