title: Src-induced activation of inducible T cell kinase (ITK) requires phosphatidylinositol 3-kinase activity and the Pleckstrin homology domain of inducible T cell kinase.
abstract: The Tec family of tyrosine kinases are involved in signals emanating from cytokine receptors, antigen receptors, and other lymphoid cell surface receptors. One family member, ITK (inducible T cell kinase), is involved in T cell activation and can be activated by the T cell receptor and the CD28 cell surface receptor. This stimulation of tyrosine phosphorylation and activation of ITK can be mimicked by the Src family kinase Lck. We have explored the mechanism of this requirement for Src family kinases in the activation of ITK. We found that coexpression of ITK and Src results in increased membrane association, tyrosine phosphorylation and activation of ITK, which could be blocked by inhibitors of the lipid kinase phosphatidylinositol 3-kinase (PI 3-kinase) as well as overexpression of the p85 subunit of PI 3-kinase. Removal of the Pleckstrin homology domain (PH) of ITK resulted in a kinase that could no longer be induced to localize to the membrane or be activated by Src. The PH of ITK was also able to bind inositol phosphates phosphorylated at the D3 position. Membrane targeting of ITK without the PH recovered its ability to be activated by Src. These results suggest that ITK can be activated by a combination of Src and PI 3-kinase.
authors.affiliation: Laboratory of Molecular Oncology, The Rockefeller University, 1230 York Avenue, New York, NY 10021, USA.
authors.forename: A
authors.initials: A
authors.lastname: August
authors.forename: A
authors.initials: A
authors.lastname: Sadra
authors.forename: B
authors.initials: B
authors.lastname: Dupont
authors.forename: H
authors.initials: H
authors.lastname: Hanafusa
mesh_terms: D000818:Animals; D001798:Blood Proteins / Q000737:chemistry; D019556:COS Cells; D002867:Chromones / Q000494:pharmacology; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D051379:Mice; D008954:Models, Biological; D009025:Morpholines / Q000494:pharmacology; D016297:Mutagenesis, Site-Directed; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010750:Phosphoproteins; D010766:Phosphorylation; D019000:Phosphotyrosine / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000737:chemistry* / Q000378:metabolism*; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D014162:Transfection; D018909:src Homology Domains; D019061:src-Family Kinases / Q000378:metabolism*
chemical_list: D001798:Blood Proteins; D002867:Chromones; D004791:Enzyme Inhibitors; D009025:Morpholines; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010750:Phosphoproteins; D019000:Phosphotyrosine; D011505:Protein-Tyrosine Kinases; D016392:Proto-Oncogene Proteins pp60(c-src); D011993:Recombinant Fusion Proteins; D019061:src-Family Kinases; C039077:platelet protein P47; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C080813:emt protein-tyrosine kinase