UMMS Affiliation

Department of Biochemistry and Molecular Biology; Program in Molecular Medicine

Date

7-1-1995

Document Type

Article

Subjects

1-Phosphatidylinositol 3-Kinase; *Adaptor Proteins, Signal Transducing; Antigens, CD3; Base Sequence; Blotting, Western; GRB2 Adaptor Protein; Lymphocyte Activation; Membrane Proteins; Molecular Sequence Data; Phosphotransferases (Alcohol Group Acceptor); Precipitin Tests; Protein Binding; Proteins; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-cbl; Receptors, Antigen, T-Cell; Recombinant Fusion Proteins; *Signal Transduction; Son of Sevenless Proteins; T-Lymphocytes; *Ubiquitin-Protein Ligases

Disciplines

Life Sciences | Medicine and Health Sciences

Abstract

T-cell receptor (TCR) cross-linking increases tyrosine phosphorylation of multiple proteins, only a few of which have been identified. One of the most rapidly tyrosine-phosphorylated polypeptides is the 120-kDa product of the proto-oncogene c-cbl, a cytosolic and cytoskeletal protein containing multiple proline-rich motifs that are potential binding sites for proteins containing Src homology 3 (SH3) domains. We report here that in cultured Jurkat T cells, Cbl is coprecipitated with antibody against the adapter protein Grb2. Upon activation of Jurkat T cells via the TCR-CD3 complex, we find that high-affinity binding of Cbl requires the N-terminal SH3 domain of GST-Grb2 fusion protein but after cross-linking of the TCR-CD3 and CD4 receptors, Cbl binds equally to its SH2 domain. Grb2 antisera also precipitated p85 from serum-starved cells, while TCR activation increased p85 and tyrosine-phosphorylated Cbl but not Cbl protein in Grb2 immunocomplexes. Phosphatidylinositol (PI) 3-kinase activity was immunoprecipitated from serum-starved cells with Cbl and to a lesser extent with Grb2 antisera, and TCR cross-linking increased this activity severalfold. The PI 3-kinase activity associated with Cbl amounted to 5 to 10% of the total cellular activity that could be precipitated by p85 antisera. The Ras exchange factor Son-of-sevenless 1 (Sos-1) was not found in anti-Cbl immunoprecipitates from activated cells, and Cbl was not detectable in anti-Sos-1 precipitates, supporting the likelihood that Sos-Grb2 and Cbl-Grb2 are present as distinct complexes. Taken together, these data suggest that Cbl function in Jurkat T cells involves its constitutive association with Grb2 and its recruitment of PI 3-kinase in response to TCR activation.

Rights and Permissions

Citation: Mol Cell Biol. 1995 Jul;15(7):3571-8.

Related Resources

Link to Article in PubMed

Journal Title

Molecular and cellular biology

PubMed ID

7791764

Share

COinS
 
 

To view the content in your browser, please download Adobe Reader or, alternately,
you may Download the file to your hard drive.

NOTE: The latest versions of Adobe Reader do not support viewing PDF files within Firefox on Mac OS and if you are using a modern (Intel) Mac, there is no official plugin for viewing PDF files within the browser window.