title: Coordinate activation of c-Src by SH3- and SH2-binding sites on a novel p130Cas-related protein, Sin.
abstract: 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 p130Cas. 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.
authors.affiliation: Massachusetts Institute of Technology, Cambridge, 02139, USA.
authors.forename: K
authors.initials: K
authors.lastname: Alexandropoulos
authors.forename: D
authors.initials: D
authors.lastname: Baltimore
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D002448:Cell Adhesion; D002460:Cell Line; D006801:Humans; D008969:Molecular Sequence Data; D010455:Peptides / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D050721:Proto-Oncogene Proteins c-cbl; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000378:metabolism*; D015398:Signal Transduction; D044767:Ubiquitin-Protein Ligases; D018909:src Homology Domains
chemical_list: D010455:Peptides; D011518:Proto-Oncogene Proteins; D050721:Proto-Oncogene Proteins c-cbl; D044767:Ubiquitin-Protein Ligases; D016392:Proto-Oncogene Proteins pp60(c-src); C067419:CBL protein, human