title: Interactions of Cbl with two adapter proteins, Grb2 and Crk, upon T cell activation.
abstract: Several recent studies have demonstrated that Grb2, composed entirely of SH2 and SH3 domains, serves as an adaptor protein in tyrosine kinase signaling pathways. Cb1, the protein product of c-cbl proto-oncogene, has been reported to be phosphorylated on tyrosine residues upon T cell receptor (TCR) engagement. Here we show that in unstimulated Jurkat cells Cbl is co-immunoprecipitated with monoclonal antibody against Grb2. However, in lymphocytes activated through the TCR, Cbl loses its ability to bind to Grb2 precipitated either with anti-Grb2 antibody or with an immobilized tyrosine phosphopeptide, Y1068-P, derived from the epidermal growth factor receptor. In vitro studies confirm that the ability of Cb1 to bind to both SH3 domains of Grb2 is strongly reduced in activated T lymphocytes. Investigation of the time course of Cbl dissociation from Grb2 reveals that it is transient and correlates with the kinetics of tyrosine phosphorylation of Cbl. Moreover, Cb1 is co-immunoprecipitated with Crk, another SH2/SH3 domain-containing protein, upon TCR stimulation. Tyrosine-phosphorylated Cbl binds exclusively to the SH2 domain of Crk. These results suggest that different adaptor proteins may have different roles in the regulation of c-cbl proto-oncogene product.
authors.affiliation: 1st Institute of Biochemistry, Semmelweis University Medical School, Budapest, Hungary.
authors.forename: L
authors.initials: L
authors.lastname: Buday
authors.forename: A
authors.initials: A
authors.lastname: Khwaja
authors.forename: S
authors.initials: S
authors.lastname: Sipeki
authors.forename: A
authors.initials: A
authors.lastname: Faragó
authors.forename: J
authors.initials: J
authors.lastname: Downward
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000595:Amino Acid Sequence; D001665:Binding Sites; D002460:Cell Line; D051380:GRB2 Adaptor Protein; D006801:Humans; D007700:Kinetics; D008213:Lymphocyte Activation; D008969:Molecular Sequence Data; D010766:Phosphorylation; D011506:Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D050721:Proto-Oncogene Proteins c-cbl; D050737:Proto-Oncogene Proteins c-crk; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D013601:T-Lymphocytes / Q000276:immunology* / Q000378:metabolism*; D014443:Tyrosine / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases; D018909:src Homology Domains
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D051380:GRB2 Adaptor Protein; C495948:GRB2 protein, human; C000715470:MAS1 protein, human; D011506:Proteins; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins; D050737:Proto-Oncogene Proteins c-crk; D011993:Recombinant Fusion Proteins; D014443:Tyrosine; D050721:Proto-Oncogene Proteins c-cbl; D044767:Ubiquitin-Protein Ligases; C067419:CBL protein, human