T cell receptor-mediated tyrosine phosphorylation of Cas-L, a 105-kDa Crk-associated substrate-related protein, and its association of Crk and C3G.

Cas-L (pp105), a Crk-associated substrate (p130(Cas))-related protein, was first identified as a 105-kDa protein that is tyrosine-phosphorylated following beta1 integrin cross-linking in T cells. Cas-L contains possible multiple binding sites for the Src homology (SH) 2 domains of various signaling molecules, and appears to be involved in signal transduction through ...
phosphorylated tyrosine-mediated protein-protein interaction. Since Cas-L is preferentially expressed in lymphocytes, it is conceivable that Cas-L plays an important role in lymphocyte-specific signals. Here, we show the involvement of Cas-L in the T cell receptor (TCR)/CD3 signaling pathway. Cas-L is transiently phosphorylated following CD3 cross-linking, and tyrosine-phosphorylated Cas-L binds to Crk and C3G. Furthermore, a Cas-L mutant that lacks the SH3 domain, the binding site for focal adhesion kinase (FAK), is also tyrosine-phosphorylated upon CD3 cross-linking, but not upon beta1 integrin crosslinking, suggesting that FAK is not involved in CD3-dependent Cas-L phosphorylation. Taken together, the present study indicates a novel signaling pathway mediated by tyrosine-phosphorylated Cas-L upon the TCR/CD3 stimulation.
Mesh Terms:
Adaptor Proteins, Signal Transducing, Antibody Specificity, Antigens, CD3, Cell Adhesion Molecules, Cell Line, Focal Adhesion Kinase 1, Focal Adhesion Protein-Tyrosine Kinases, Guanine Nucleotide Exchange Factors, Humans, Immunologic Capping, Mutation, Phosphoproteins, Phosphorylation, Protein Binding, Protein-Tyrosine Kinases, Proteins, Proto-Oncogene Proteins, Proto-Oncogene Proteins c-cbl, Proto-Oncogene Proteins c-crk, Receptors, Antigen, T-Cell, Signal Transduction, Tyrosine, Ubiquitin-Protein Ligases
J. Biol. Chem.
Date: Mar. 13, 1998
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