%0 Journal Article
%T In Vivo Consequences of Disrupting SH3-Mediated Interactions of the Inducible T-Cell Kinase
%A Roman M. Levytskyy
%A Nupura Hirve
%A David M. Guimond
%A Lie Min
%A Amy H. Andreotti
%A Constantine D. Tsoukas
%J Journal of Signal Transduction
%D 2012
%I Hindawi Publishing Corporation
%R 10.1155/2012/694386
%X ITK-SH3-mediated interactions, both with exogenous ligands and via intermolecular self-association with ITK-SH2, have been shown to be important for regulation of ITK activity. The biological significance of these competing SH3 interactions is not completely understood. A mutant of ITK where substitution of the SH3 domain with that of the related kinase BTK (ITK-BTK(SH3)) was used to disrupt intermolecular self-association of ITK while maintaining canonical binding to exogenous ligands such as SLP-76. ITK-BTK(SH3) displays reduced association with SLP-76 leading to inefficient transphosphorylation, reduced phosphorylation of PLC¦Ã1, and diminished Th2 cytokine production. In contrast, ITK-BTK(SH3) displays no defect in its localization to the T-cell-APC contact site. Another mutation, Y511F, in the activation loop of ITK, impairs ITK activation. T cells expressing ITK-Y511F display defective phosphorylation of ITK and its downstream target PLC¦Ã1, as well as significant inhibition of Th2 cytokines. In contrast, the inducible localization of ITK-Y511F to the T cell-APC contact site and its association with SLP-76 are not affected. The presented data lend further support to the hypothesis that precise interactions between ITK and its signaling partners are required to support ITK signaling downstream of the TCR. 1. Introduction Protein tyrosine kinases play a critical role in signaling through the T-cell Antigen Receptor/CD3 (TCR-CD3) molecular complex [1]. The Tec family of tyrosine kinases regulates lymphocyte development, differentiation, and activation [2]. Among them, the Inducible T-Cell Kinase (ITK) plays an important role in T-cell signaling and function [3]. ITK is the major Tec kinase expressed in T cells, regulating intracellular Ca++ mobilization by phosphorylation and activation of Phospholipase C¦Ã1 [4], TCR-induced actin polymerization [5], and production of Th2 cytokines [6]. Even though ITK does not appear to be important for the development of£¿£¿Th2 cells per se, it is critical for the expression of Th2 cell effector function, as evidenced by defective expression of Th2 cytokines in ITK-deficient animals [7]. ITK is structurally organized into domains that carry out its catalytic function, domains that regulate its catalytic activity, and domains that provide sites for interactions with other signaling partners [8]. Even though the crystal structure of full-length ITK has not been resolved, important insights into its structure have been provided by NMR-based analysis of individual ITK domains [2]. Previous in vitro observations provide some
%U http://www.hindawi.com/journals/jst/2012/694386/