The involvement of the proto-oncogene p120 c-Cbl and ZAP-70 in CD2-mediated T cell activation.
The CD2 co-receptor expressed on the surface of T lymphocytes is able to stimulate T cell activation, proliferation and cytokine production in the absence of direct engagement of the antigen-specific TCR. Engagement of human CD2 by mitogenic pairs of anti-CD2 mAb induces tyrosine phosphorylation of a number of intracellular proteins including a 120 kDa phosphoprotein that we identify as the proto-oncogene c-Cbl. Rapidly tyrosine phosphorylated following stimulation of a number of cell surface receptors, c-Cbl is an adaptor protein that has been shown to associate with a complex of intracellular signaling molecules, and to mediate both positive and negative regulatory effects. Here we show that, like TCR-CD3 stimulation, stimulation of CD2 enhanced the association of c-Cbl with both Crk(L) and the p85 subunit of phosphatidylinositol-3 kinase. Overexpression of wild-type c-Cbl protein inhibited both CD2and CD3-induced NF-AT transcriptional activity, suggesting that CD2 signaling is also negatively regulated by c-Cbl. The inhibitory effect of c-Cbl depended upon its N-terminal phosphotyrosine-binding domain, the domain that has been shown to be required for inhibition of the Syk/ZAP-70 family kinases. In Syk(-) Jurkat T cells stably expressing wild-type ZAP-70, CD2 stimulation induced only a minimal increase in ZAP-70 tyrosine phosphorylation. Nevertheless, ZAP-70 kinase was required for CD2-mediated NF-AT transcriptional activity. Thus, CD2-mediated NF-AT transcriptional activity appears to depend upon ZAP-70/Syk kinases and to be negatively regulated by c-Cbl.
Lin
H
H
Department of Pediatric Oncology, Dana-Farber Cancer Institute, Boston, MA 02115, USA.
Martelli
M P
MP
Bierer
B E
BE
D000595:Amino Acid Sequence; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D018801:CD2 Antigens / Q000276:immunology / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D006801:Humans; D019169:Jurkat Cells; D008213:Lymphocyte Activation; D008969:Molecular Sequence Data; D050778:NFATC Transcription Factors; D009687:Nuclear Proteins; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D019000:Phosphotyrosine / Q000378:metabolism; D017434:Protein Structure, Tertiary; D011505:Protein-Tyrosine Kinases / Q000502:physiology*; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins / Q000502:physiology*; D050721:Proto-Oncogene Proteins c-cbl; D015398:Signal Transduction / Q000276:immunology; D013601:T-Lymphocytes / Q000201:enzymology / Q000276:immunology* / Q000378:metabolism*; D014157:Transcription Factors / Q000037:antagonists & inhibitors / Q000378:metabolism; D014443:Tyrosine / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases; D051746:ZAP-70 Protein-Tyrosine Kinase; D016335:Zinc Fingers / Q000276:immunology
D000911:Antibodies, Monoclonal; D018801:CD2 Antigens; D004268:DNA-Binding Proteins; C000715470:MAS1 protein, human; D050778:NFATC Transcription Factors; D009687:Nuclear Proteins; D010750:Phosphoproteins; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins; D014157:Transcription Factors; D019000:Phosphotyrosine; D014443:Tyrosine; D050721:Proto-Oncogene Proteins c-cbl; D044767:Ubiquitin-Protein Ligases; D011505:Protein-Tyrosine Kinases; D051746:ZAP-70 Protein-Tyrosine Kinase; C497261:ZAP70 protein, human; C067419:CBL protein, human