Evidence of LAT as a dual substrate for Lck and Syk in T lymphocytes.

LAT is a linker protein essential for activation of T lymphocytes. Its rapid tyrosine-phosphorylation upon T cell receptor (TCR) stimulation recruits downstream signaling molecules for membrane targeting and activation. LAT is physically concentrated in cholesterol-enriched membrane microdomains and is known a substrate for Syk/Zap70 kinase. In this study, we demonstrate ...
that LAT serves as a dual substrate for both Lck and Syk kinases. LAT phosphorylation is absent in Lck-deficient J.CaM1.6 cells and Lck is co-precipitated with LAT in pervanadate-activated Jurkat cells. Further, the in vitro kinase assay using purified Lck and LAT shows that Lck directly phosphorylates LAT. Both Lck and Syk, phosphorylate the ITAM-like motifs on LAT at Y171Y191, which is essential for induction of the interaction of LAT with downstream signaling molecules such as Grb2, PLC-gamma1 and c-Cbl, and for activation of MAPK-ERK. Collectively, our data indicate that LAT is an immediate substrate for Lck in one of the earliest events of T cell activation.
Mesh Terms:
Adaptor Proteins, Signal Transducing, Cells, Cultured, GRB2 Adaptor Protein, Humans, Intracellular Signaling Peptides and Proteins, Jurkat Cells, Kidney, Lymphocyte Activation, Lymphocyte Specific Protein Tyrosine Kinase p56(lck), Membrane Proteins, Mitogen-Activated Protein Kinase 1, Mitogen-Activated Protein Kinase 3, Mitogen-Activated Protein Kinases, Phospholipase C gamma, Phosphorylation, Protein-Tyrosine Kinases, Proto-Oncogene Proteins c-cbl, Signal Transduction, T-Lymphocytes
Leuk. Res.
Date: Apr. 01, 2007
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