Vav1 transduces T cell receptor signals to the activation of phospholipase C-gamma1 via phosphoinositide 3-kinase-dependent and -independent pathways.
Vav1 is a signal transducing protein required for T cell receptor (TCR) signals that drive positive and negative selection in the thymus. Furthermore, Vav1-deficient thymocytes show greatly reduced TCR-induced intracellular calcium flux. Using a novel genetic system which allows the study of signaling in highly enriched populations of CD4(+)CD8(+) double positive thymocytes, we have studied the mechanism by which Vav1 regulates TCR-induced calcium flux. We show that in Vav1-deficient double positive thymocytes, phosphorylation, and activation of phospholipase C-gamma1 (PLCgamma1) is defective. Furthermore, we demonstrate that Vav1 regulates PLCgamma1 phosphorylation by at least two distinct pathways. First, in the absence of Vav1 the Tec-family kinases Itk and Tec are no longer activated, most likely as a result of a defect in phosphoinositide 3-kinase (PI3K) activation. Second, Vav1-deficient thymocytes show defective assembly of a signaling complex containing PLCgamma1 and the adaptor molecule Src homology 2 domain-containing leukocyte phosphoprotein 76. We show that this latter function is independent of PI3K.
Reynolds
Lucinda F
LF
National Institute for Medical Research, London NW7 1AA, United Kingdom.
Smyth
Lesley A
LA
Norton
Trisha
T
Freshney
Norman
N
Downward
Julian
J
Kioussis
Dimitris
D
Tybulewicz
Victor L J
VL
D000818:Animals; D002118:Calcium / Q000502:physiology; D018797:Cell Cycle Proteins; D007527:Isoenzymes / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D008954:Models, Biological; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D051966:Phospholipase C gamma; D010766:Phosphorylation; D011518:Proto-Oncogene Proteins / Q000172:deficiency / Q000235:genetics / Q000276:immunology*; D051567:Proto-Oncogene Proteins c-vav; D011948:Receptors, Antigen, T-Cell / Q000276:immunology*; D015398:Signal Transduction; D013601:T-Lymphocytes / Q000276:immunology; D010738:Type C Phospholipases / Q000378:metabolism*
D018797:Cell Cycle Proteins; D007527:Isoenzymes; D011518:Proto-Oncogene Proteins; D051567:Proto-Oncogene Proteins c-vav; D011948:Receptors, Antigen, T-Cell; C496619:Vav1 protein, mouse; D019869:Phosphatidylinositol 3-Kinases; D010738:Type C Phospholipases; D051966:Phospholipase C gamma; D002118:Calcium