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

Leuk Res. 2007 Apr;31(4):541-5. doi: 10.1016/j.leukres.2006.07.010. Epub 2006 Aug 30.

Abstract

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.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Signal Transducing / metabolism*
  • Cells, Cultured
  • GRB2 Adaptor Protein / metabolism
  • Humans
  • Intracellular Signaling Peptides and Proteins / metabolism*
  • Jurkat Cells / metabolism
  • Kidney / cytology
  • Kidney / metabolism
  • Lymphocyte Activation
  • Lymphocyte Specific Protein Tyrosine Kinase p56(lck) / metabolism*
  • Membrane Proteins / metabolism*
  • Mitogen-Activated Protein Kinase 1 / metabolism
  • Mitogen-Activated Protein Kinase 3 / metabolism
  • Mitogen-Activated Protein Kinases / metabolism
  • Phospholipase C gamma / metabolism
  • Phosphorylation
  • Protein-Tyrosine Kinases / metabolism*
  • Proto-Oncogene Proteins c-cbl / metabolism
  • Signal Transduction
  • Syk Kinase
  • T-Lymphocytes / metabolism*

Substances

  • Adaptor Proteins, Signal Transducing
  • GRB2 Adaptor Protein
  • Intracellular Signaling Peptides and Proteins
  • LAT protein, human
  • Membrane Proteins
  • Proto-Oncogene Proteins c-cbl
  • Protein-Tyrosine Kinases
  • Lymphocyte Specific Protein Tyrosine Kinase p56(lck)
  • SYK protein, human
  • Syk Kinase
  • Mitogen-Activated Protein Kinase 1
  • Mitogen-Activated Protein Kinase 3
  • Mitogen-Activated Protein Kinases
  • Phospholipase C gamma
  • CBL protein, human