SH2 domain function is essential for the role of the Lck tyrosine kinase in T cell receptor signal transduction.
Tyrosine kinase activity is required for signal transduction through the T cell antigen receptor (TCR). The Src family tyrosine kinase Lck appears to play a key role in the initiation of TCR signaling events. We have investigated the role of the phosphotyrosine-binding Src homology-2 (SH2), domain of Lck in TCR signaling. Lck containing a mutation in the phosphotyrosine binding pocket of the SH2 domain was expressed in an Lck-deficient cell line. We found that, in contrast to wild-type Lck, the SH2 domain mutant was unable to restore even the earliest TCR-mediated signaling events. To investigate the role of the Lck SH2 domain, we examined the association of tyrosine phosphoproteins with Lck. The predominant associated phosphoprotein was the ZAP-70 tyrosine kinase, which has also been implicated in the initiation of TCR signaling. In addition, the zeta subunit of the T cell receptor was found to weakly associate with Lck. Further analysis indicated that the SH2 domain of Lck can directly recognize both ZAP-70 and zeta in immunoprecipitates from TCR-stimulated cells. Our findings demonstrate that the SH2 domain of Lck is essential for the initiation of signaling events following TCR stimulation probably as a result of its ability to mediate an interaction between Lck and the ZAP-70 tyrosine kinase and/or the zeta subunit of the T cell receptor.
Straus
D B
DB
Department of Medicine, University of Chicago, Chicago, Illinois 60637,USA.
Chan
A C
AC
Patai
B
B
Weiss
A
A
D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D006801:Humans; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); D010750:Phosphoproteins / Q000378:metabolism; D019000:Phosphotyrosine / Q000378:metabolism; D011485:Protein Binding; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011948:Receptors, Antigen, T-Cell / Q000378:metabolism*; D017384:Sequence Deletion; D015398:Signal Transduction; D013329:Structure-Activity Relationship; D013601:T-Lymphocytes / Q000502:physiology*; D051746:ZAP-70 Protein-Tyrosine Kinase; D018909:src Homology Domains; D019061:src-Family Kinases / Q000378:metabolism*
D010750:Phosphoproteins; D011948:Receptors, Antigen, T-Cell; D019000:Phosphotyrosine; D011505:Protein-Tyrosine Kinases; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); D051746:ZAP-70 Protein-Tyrosine Kinase; C497261:ZAP70 protein, human; D019061:src-Family Kinases; D002118:Calcium