Giving ITK the SLP

Science's STKE  24 Apr 2007:
Vol. 2007, Issue 383, pp. tw145
DOI: 10.1126/stke.3832007tw145

Tyrosine phosphorylation and activation of phospholipase C-γ (PLC-γ) after stimulation of the T cell antigen receptor (TCR) is dependent on the activities of the tyrosine kinases Lck, ZAP-70 (ζ chain-associated protein kinase of 70 kD), and ITK (IL-2-inducible T cell kinase). Other important components are adaptor molecules, such as SLP-76 (SH2-domain-containing leukocyte protein of 76 kD), which couple Syk family kinases, such as ZAP-70, to PLC-γ activation. Two tyrosine residues important for TCR-mediated phosphorylation and activation of PLC-γ1 are Y783 and Y775. Although previous studies suggest that ZAP-70 and ITK act together to activate PLC-γ1, it is not known which is responsible for phosphorylating the critical tyrosines. Bogin et al. performed studies in a SLP-76-deficient T cell line called J14 (derived from the human CD4+ T cell line, Jurkat) to answer this question. In vitro kinase assays with ITK, but not ZAP-70, immunoprecipitated from TCR-stimulated J14 cells (transfected with a tagged form of SLP-76) resulted in the phosphorylation of both Y783 and Y775 in a recombinant form of PLC-γ1, whereas both kinases could phosphorylate SLP-76. The ability of ITK to phosphorylate PLC-γ1 was dependent on SLP-76. Studies with mutants of SLP-76 found that ITK phosphorylation of recombinant PLC-γ1 was dependent on the presence of tyrosines in the N-terminal region of SLP-76. Coimmunoprecipitation studies revealed that stimulation of the TCR resulted in the association of SLP-76 with ITK in J14 cells. Immunoprecipitated ITK in complex with SLP-76 was catalytically more active than uncomplexed ITK. These data suggest that SLP-76 is necessary to initiate and maintain the activity of ITK.

Y. Bogin, C. Ainey, D. Beach, D. Yablonski, SLP-76 mediates and maintains activation of the Tec family kinase ITK via the T cell antigen receptor-induced association between SLP-76 and ITK. Proc. Natl. Acad. Sci. U.S.A. 104, 6638-6643 (2007). [Abstract] [Full Text]