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Src kinase plays an essential role in integrin-mediated tyrosine phosphorylation of Crk-associated substrate p130Cas
K Hamasaki1, T Mimura, N Morino
1Third Department of Internal Medicine, University of Tokyo, Japan.
Abstract:
A novel signaling molecule p130Cas has been shown to undergo tyrosine phosphorylation in response to integrin-mediated cell adhesion. In this study, we have attempted to identify kinases that mediate Cas phosphorylation in integrin signaling by examining various mutant cell lines that do not express either p125FAK, c-Scr, c-Fyn or c-Abl. We found that deficiency of c-Src but not of other kinases completely abrogated integrin-mediated Cas phosphorylation. Importantly, paxillin phosphorylation was not compromised in each mutant cell line examined. These results suggest that c-Src primarily mediates adhesion-dependent Cas phosphorylation. As for paxillin phosphorylation, there may exist substantial redundancy amongst multiple kinases. Finally, adhesion-induced Cas phosphorylation resulted in its association with c-Crk adapter protein via the Crk-SH2 domain. Thus, Cas plays a role in the transmission of integrin-initiated signals through tyrosine phosphorylation and subsequent binding to c-Crk.
Insights
The study identifies c-Src as the primary kinase mediating p130Cas phosphorylation during integrin signaling. This phosphorylation is crucial for transmitting signals via association with the c-Crk adapter protein.
Area of Science:
- Cellular Biology
- Molecular Signaling
- Biochemistry
Background:
- Integrin-mediated cell adhesion triggers signaling pathways.
- p130Cas is a key substrate for tyrosine phosphorylation in response to adhesion.
- The kinases responsible for Cas phosphorylation in this context are not fully elucidated.
Purpose of the Study:
- To identify the specific kinases that mediate p130Cas tyrosine phosphorylation upon integrin engagement.
- To investigate the role of c-Src, c-Fyn, c-Abl, and p125FAK in this signaling pathway.
- To understand the downstream consequences of Cas phosphorylation, including its interaction with other proteins.
Main Methods:
- Utilized mutant cell lines lacking expression of specific kinases (p125FAK, c-Src, c-Fyn, c-Abl).
- Assessed integrin-mediated tyrosine phosphorylation of p130Cas and paxillin in these mutant cell lines.
- Examined the association of phosphorylated p130Cas with the c-Crk adapter protein.
Main Results:
- Deficiency in c-Src kinase completely abolished integrin-mediated p130Cas phosphorylation.
- Phosphorylation of paxillin was unaffected in all examined mutant cell lines, suggesting kinase redundancy.
- Adhesion-induced p130Cas phosphorylation led to its binding with the c-Crk adapter protein through the Crk-SH2 domain.
Conclusions:
- c-Src is the principal kinase responsible for mediating adhesion-dependent p130Cas phosphorylation.
- Paxillin phosphorylation appears to involve multiple redundant kinases.
- p130Cas facilitates integrin signal transduction by undergoing tyrosine phosphorylation and subsequently binding to c-Crk.