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A novel signaling molecule, p130, forms stable complexes in vivo with v-Crk and v-Src in a tyrosine
R Sakai1, A Iwamatsu, N Hirano
1Molecular Biology Division, Jichi Medical School, Tochigi, Japan.
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.
Insights
v-Crk and v-Src oncoproteins phosphorylate p130, a novel signaling molecule. This protein, now named p130Cas, acts as a common cellular target, potentially assembling signals from multiple SH2-containing molecules.
Area of Science:
- Molecular Biology
- Cell Signaling
- Oncogenesis
Background:
- v-Crk is a transforming protein that elevates tyrosine phosphorylation.
- p130 is a cellular protein strongly associated with and phosphorylated by v-Crk.
Purpose of the Study:
- To identify and characterize the p130 protein.
- To understand the role of p130 in signaling pathways involving v-Crk and v-Src.
Main Methods:
- Immunoaffinity purification to isolate rat p130.
- Immunochemical analyses and peptidase mapping.
- Subcellular fractionation.
Main Results:
- p130 was cloned and identified as a novel SH3-containing signaling molecule with SH2-binding motifs.
- p130 is highly tyrosine phosphorylated and forms complexes with v-Crk and v-Src oncoproteins.
- p130 acts as a potent substrate for Src kinase and translocates to the membrane upon phosphorylation.
Conclusions:
- p130 (p130Cas) is a common cellular target for v-Crk and v-Src signaling.
- Its structure suggests a role in signal assembly from SH2-containing molecules.