Inhibition of CD4/p56lck signaling by a dominant negative mutant of the Shc adaptor protein.
T-cell antigen receptor stimulation results in phosphorylation of the SH2 containing Shc proteins and recruitment of the Grb2/mSos complex suggesting that Shc proteins are involved in transducing T-cell activating signals to Ras. We have measured the effects of the isolated Shc-SH2 domain and the dominant negative RasN17 protein on activation of the T-cell specific transcription factor NF-AT. The isolated Shc-SH2 domain was designed to compete with endogenous Shc binding to upstream tyrosine phosphorylated proteins and to interfere with coupling to regulators of Ras activation. We have demonstrated that both the Shc-SH2 domain and the RasN17 protein significantly inhibited NF-AT activation by the CD4 coreceptor and the CD4 associated tyrosine kinase p56lck. In contrast, only the RasN17 protein reduced NF-AT activation by the TCR/CD3 complex. Furthermore, tyrosine kinase activity and p56lck protein were found in complexes immunoprecipitated with Shc specific antisera after CD4 triggering but not after CD3 triggering. These results indicate that both CD4 and CD3 signal to Ras and that this signaling is mediated by independent pathways of activation of the Shc adaptor protein.
Baldari
C T
CT
Department of Evolutionary Biology, University of Siena, Italy.
Pelicci
G
G
Di Somma
M M
MM
Milia
E
E
Giuli
S
S
Pelicci
P G
PG
Telford
J L
JL
D001483:Base Sequence; D015704:CD4 Antigens / Q000378:metabolism*; D002460:Cell Line; D015500:Chloramphenicol O-Acetyltransferase / Q000235:genetics; D018076:DNA, Complementary; D004268:DNA-Binding Proteins / Q000378:metabolism; D005799:Genes, Dominant; D006801:Humans; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); D008969:Molecular Sequence Data; D009154:Mutation; D050778:NFATC Transcription Factors; D009687:Nuclear Proteins; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D015398:Signal Transduction; D014157:Transcription Factors / Q000378:metabolism; D014443:Tyrosine / Q000378:metabolism; D018631:ras Proteins / Q000378:metabolism
D015704:CD4 Antigens; D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D050778:NFATC Transcription Factors; D009687:Nuclear Proteins; D014157:Transcription Factors; D014443:Tyrosine; D015500:Chloramphenicol O-Acetyltransferase; D011505:Protein-Tyrosine Kinases; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); D018631:ras Proteins