Levytskyy Roman M, Hirve Nupura, Guimond David M, Min Lie, Andreotti Amy H, Tsoukas Constantine D
Department of Biology, Molecular Biology Institute and Center for Microbial Sciences, San Diego State University, San Diego, CA 92182, USA.
J Signal Transduct. 2012;2012:694386. doi: 10.1155/2012/694386. Epub 2012 May 9.
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 PLCγ1, and diminished Th(2) 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 PLCγ1, as well as significant inhibition of Th(2) 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.
ITK-SH3介导的与外源性配体的相互作用，以及通过与ITK-SH2的分子间自缔合，已被证明对ITK活性的调节很重要。这些相互竞争的SH3相互作用的生物学意义尚未完全了解。一种ITK突变体，其中用相关激酶BTK的SH3结构域替换ITK的SH3结构域（ITK-BTK((SH3))），用于破坏ITK的分子间自缔合，同时保持与外源性配体如SLP-76的典型结合。ITK-BTK((SH3))与SLP-76的结合减少，导致转磷酸化效率低下、PLCγ1磷酸化减少以及Th(2)细胞因子产生减少。相比之下，ITK-BTK((SH3))在其定位于T细胞-抗原呈递细胞接触位点方面没有缺陷。ITK激活环中的另一个突变Y511F损害ITK激活。表达ITK-Y511F的T细胞显示ITK及其下游靶标PLCγ1的磷酸化缺陷，以及对Th(2)细胞因子的显著抑制。相比之下，ITK-Y511F向T细胞-抗原呈递细胞接触位点的诱导定位及其与SLP-76的缔合不受影响。所呈现的数据进一步支持了这样的假设，即ITK与其信号传导伙伴之间的精确相互作用是支持TCR下游ITK信号传导所必需的。
