Thymocyte activation induces the association of the proto-oncoprotein c-cbl and ras GTPase-activating protein with CD5.

Studies of knockout mice indicate that the glycoprotein CD5, which is expressed on Tcells, most thymocytes and a subset of B cells, down-regulates TCR- and B cell receptor (BCR)-mediated signaling. CD5 is associated with the TCR and BCR, and is phosphorylated on cytoplasmic tyrosine residues following antigen receptor ligation. Cross-linking ...
of CD5 or pervanadate stimulation of thymocytes induces the association of a 120-kDa tyrosine-phosphorylated protein with CD5. The proto-oncoprotein c-cbl associates with CD5 in pervanadate-stimulated thymocytes, and reprecipitation analysis demonstrates that the major proportion of CD5-associated pp120 is c-cbl. The GTPase-activating protein for ras (ras GAP), which is not tyrosine phosphorylated following CD5 cross-linking, associates with CD5 in pervanadate-stimulated thymocytes. Using tyrosine-phosphorylated peptides we show that ras GAP interacts in an SH2-mediated manner with the phosphorylated Y429SQP sequence of CD5. Both c-cbl and ras GAP have been proposed to suppress receptor-mediated signaling, and may contribute to CD5-mediated suppression of TCR or BCR signaling.
Mesh Terms:
Amino Acid Sequence, Animals, Antigens, CD5, Cell Adhesion Molecules, Focal Adhesion Kinase 1, Focal Adhesion Protein-Tyrosine Kinases, GTP Phosphohydrolases, GTPase-Activating Proteins, Humans, Lymphocyte Activation, Mice, Mice, Knockout, Molecular Sequence Data, Phosphopeptides, Phosphorylation, Protein-Tyrosine Kinases, Proteins, Proto-Oncogene Proteins, Proto-Oncogene Proteins c-cbl, Rats, Rats, Inbred Strains, T-Lymphocytes, Tyrosine, Ubiquitin-Protein Ligases, ras GTPase-Activating Proteins, ras Proteins, src Homology Domains
Eur. J. Immunol.
Date: May. 01, 1998
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