A novel signaling molecule, p130, forms stable complexes in vivo with v-Crk and v-Src in a tyrosine phosphorylation-dependent manner.

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Abstract
P47v‐crk (v‐Crk), a transforming gene product containing Src homology (SH)‐2 and ‐3 domains, induces an elevated level of tyrosine phosphorylation of several cellular proteins. Among these proteins, a 125‐135 kDa protein (p130) shows marked phosphorylation at tyrosines and tight association with v‐Crk, suggesting a direct signal mediator of v‐Crk. Here we report the molecular cloning of rat p130 by immunoaffinity purification. The p130 is a novel SH3‐containing signaling molecule with a cluster of multiple putative SH2‐binding motifs of v‐Crk. Immunochemical analyses revealed that p130 is highly phosphorylated at tyrosines during transformation by p60v‐src (v‐Src), as well as by v‐Crk, forming stable complexes with these oncoproteins. The p130 behaves as an extremely potent substrate of kinase activity included in the complexes and it is a major v‐Src‐associated substrate of the Src kinase by partial peptidase mapping. Subcellular fractionation demonstrated that the cytoplasmic p130 could move to the membrane upon tyrosine phosphorylation. The p130 (designated Cas for Crk‐associated substrate) is a common cellular target of phosphorylation signal via v‐Crk and v‐Src oncoproteins, and its unique structure indicates the possible role of p130Cas in assembling signals from multiple SH2‐containing molecules.