Coordinate activation of c-Src by SH3- and SH2-binding sites on a novel, p130 super(Cas)-related protein, Sin

• Published in: Genes & development Vol. 10; no. 11; pp. 1341 - 1355
• Main Authors: Alexandropoulos, K, Baltimore, D
• Format: Journal Article
• Language: English
• Published: 01.01.1996
• ISSN: 0890-9369

To understand how protein-protein interactions mediated by the Src-SH3 domain affect c-Src signaling, we screened for proteins that interact with the Src-SH3. We found a novel protein, Sin (Src interacting or signal integrating protein), that binds to Src-SH3 with high affinity, contains numerous tyrosine residues in configurations suggestive of SH2-binding sites, and is related to the v-Src substrate p130 super(Cas). In cotransfection assays, a small fragment of Sin retaining the Src-SH3-binding site and one tyrosine-containing motif induced c-Src activation as measured by a transcriptional reporter. Phosphorylation of the peptide on tyrosine by c-Src, as a consequence of Src-SH3 binding, was necessary for its stable interaction with c-Src in vivo and for transcriptional activation. Phosphorylation of multiple tyrosine-containing motifs found on Sin correlated with c-Crk and cellular phosphoprotein binding to Sin as well as increased c-Src activity. These data suggest that (1) SH2 and SH3 ligand sites on Sin cooperatively activate the signaling potential of c-Src, (2) Sin acts as both an activator and a substrate for c-Src, and (3) phosphorylated Sin may serve as a signaling effector molecule for Src by binding to multiple cellular proteins. (DBO)