Fyn and Lck tyrosine kinases regulate tyrosine phosphorylation of p105CasL, a member of the p130Cas docking protein family, in T-cell receptor-mediated signalling.
We have previously shown that engagement of the T-cell receptor (TCR)/CD3 complex with anti-CD3 antibody induces tyrosine phosphorylation of p105CasL (CasL), a member of the p130Cas docking protein family. In the present work, we attempted to determine which protein tyrosine kinases (PTKs) regulate TCR-mediated phosphorylation of CasL. We show here that an association between CasL and two types of Src family PTKs, Fyn and Lck, is induced by anti-CD3 cross-linking of human H9 T cells. In contrast, ZAP-70, another PTK that also plays a critical role in the TCR signalling, failed to bind CasL, even after anti-CD3 stimulation. In vitro kinase assays revealed that Fyn and Lck, but not ZAP-70, were capable of phosphorylating CasL. Moreover, we found that CasL was constitutively hyperphosphorylated in vivo in splenocytes of MRL-MP-lpr/lpr mice, in which overproduction and excessive activation of Fyn and Lck have previously been shown to occur. Constitutive in vivo binding of CasL to both kinases was also demonstrated in lpr splenocytes. These results strongly suggest that CasL is a substrate for Fyn and Lck PTKs in TCR signal transduction.
Kanda
H
H
The Third Department of Internal Medicine, University of Tokyo, Japan.
Mimura
T
T
Hamasaki
K
K
Yamamoto
K
K
Yazaki
Y
Y
Hirai
H
H
Nojima
Y
Y
D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D017252:CD3 Complex / Q000276:immunology; D018929:Cell Culture Techniques; D002460:Cell Line; D006801:Humans; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck) / Q000502:physiology*; D051379:Mice; D019463:Mice, Inbred MRL lpr; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000502:physiology*; D051076:Proto-Oncogene Proteins c-fyn; D011948:Receptors, Antigen, T-Cell / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology*; D013154:Spleen / Q000378:metabolism; D014443:Tyrosine / Q000378:metabolism; D051746:ZAP-70 Protein-Tyrosine Kinase
D048868:Adaptor Proteins, Signal Transducing; D000911:Antibodies, Monoclonal; D017252:CD3 Complex; C099942:NEDD9 protein, human; D010750:Phosphoproteins; D011518:Proto-Oncogene Proteins; D011948:Receptors, Antigen, T-Cell; D014443:Tyrosine; D011505:Protein-Tyrosine Kinases; C494957:FYN protein, human; C494960:Fyn protein, mouse; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); D051076:Proto-Oncogene Proteins c-fyn; D051746:ZAP-70 Protein-Tyrosine Kinase; C497261:ZAP70 protein, human; C497262:Zap70 protein, mouse