A p130Cas tyrosine phosphorylated substrate domain decoy disrupts v-Crk signaling
1 Immunology Research Laboratories, Department of Veterinary Science, Penn State University, 115 Henning Building, University Park, PA 16802, USA
2 Laboratory of Molecular Oncology, The Rockefeller University, NY, NY, 10021, USA
3 Department of Biochemistry, Boston University School of Medicine, 715 Albany Street, K-225, Boston, MA 02118, USA
4 Osaka Bioscience Institute, 6-2-4 Furuedai, Suita, Osaka 565-0874, Japan
BMC Cell Biology 2002, 3:18 doi:10.1186/1471-2121-3-18Published: 15 July 2002
The adaptor protein p130Cas (Cas) has been shown to be involved in different cellular processes including cell adhesion, migration and transformation. This protein has a substrate domain with up to 15 tyrosines that are potential kinase substrates, able to serve as docking sites for proteins with SH2 or PTB domains. Cas interacts with focal adhesion plaques and is phosphorylated by the tyrosine kinases FAK and Src. A number of effector molecules have been shown to interact with Cas and play a role in its function, including c-crk and v-crk, two adaptor proteins involved in intracellular signaling. Cas function is dependent on tyrosine phosphorylation of its substrate domain, suggesting that tyrosine phosphorylation of Cas in part regulates its control of adhesion and migration. To determine whether the substrate domain alone when tyrosine phosphorylated could signal, we have constructed a chimeric Cas molecule that is phosphorylated independently of upstream signals.
We found that a tyrosine phosphorylated Cas substrate domain acts as a dominant negative mutant by blocking Cas-mediated signaling events, including JNK activation by the oncogene v-crk in transient and stable lines and v-crk transformation. This block was the result of competition for binding partners as the chimera competed for binding to endogenous c-crk and exogenously expressed v-crk.
Our approach suggests a novel method to study adaptor proteins that require phosphorylation, and indicates that mere tyrosine phosphorylation of the substrate domain of Cas is not sufficient for its function.