An activated epidermal growth factor receptor/Lck chimera restores early T cell receptor-mediated calcium response in a CD45-deficient T cell line.
In T cells, cell surface expression of CD45, a transmembrane tyrosine phosphatase, is required for T cell receptor (TCR) signal transduction. Indirect evidence suggests that CD45 function in TCR signaling involves the dephosphorylation of the C-terminal negative regulatory site of p56(lck), Tyr-505. To evaluate the importance of CD45-mediated dephosphorylation of p56(lck) Tyr-505 in TCR signaling, we established CD45(-) Jurkat cell lines expressing various forms of a chimera containing the extracellular and transmembrane domains of the epidermal growth factor receptor (EGFR) fused to p56(lck). We report that an activated EGFR/Lck chimera is able to reconstitute a Ca2+ response after CD3 stimulation in the absence of CD45 expression. In addition, the wild-type and kinase inactive versions of the EGFR/Lck chimera fail to restore early signaling. Restoration of the response by EGFR/LckF505 required EGF binding to the chimeric kinase. Altogether, these results provide the first direct evidence that the lack of efficient dephosphorylation of p56(lck) Tyr-505 is, in part, responsible for the unresponsiveness of CD45(-) cells. They also indicate that a second event is required for p56(lck) function in TCR signaling in addition to its dephosphorylation at Tyr-505.
Duplay
P
P
Department of Biochemistry, McIntyre Medical Sciences Building, McGill University, Montréal, Québec H3G 1Y6, Canada.
Alcover
A
A
Fargeas
C
C
Sékaly
R P
RP
Branton
P E
PE
D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D004815:Epidermal Growth Factor / Q000494:pharmacology; D066246:ErbB Receptors / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D017493:Leukocyte Common Antigens / Q000378:metabolism*; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); D010766:Phosphorylation; D011948:Receptors, Antigen, T-Cell / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D015398:Signal Transduction; D013601:T-Lymphocytes / Q000502:physiology*; D014443:Tyrosine / Q000378:metabolism; D019061:src-Family Kinases / Q000235:genetics / Q000378:metabolism*
D011948:Receptors, Antigen, T-Cell; D011993:Recombinant Fusion Proteins; D014443:Tyrosine; D004815:Epidermal Growth Factor; D066246:ErbB Receptors; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); D019061:src-Family Kinases; D017493:Leukocyte Common Antigens; D002118:Calcium