Couture C, Songyang Z, Jascur T, Williams S, Tailor P, Cantley L C, Mustelin T
Division of Cell Biology, La Jolla Institute for Allergy and Immunology, La Jolla, California 92037, USA.
J Biol Chem. 1996 Oct 4;271(40):24880-4. doi: 10.1074/jbc.271.40.24880.
Src homology 2 (SH2) domains bind to phosphotyrosine (Tyr(P)) residues in specific sequence contexts in other proteins and thereby mediate tyrosine phosphorylationdependent protein-protein interactions. The SH2 domain of the Src family kinase Lck is phosphorylated at tyrosine 192 in T cells upon T cell antigen receptor triggering. We have studied the consequences of this phosphorylation on the properties of the SH2 domain and on the function of Lck in T cell activation. We report that phosphorylation at Tyr192 reduced the capacity of the isolated SH2 domain to bind a high affinity peptide ligand and Tyr(P)-containing cellular proteins. This effect was mimicked by mutation of Tyr192 to an acidic residue. In intact T cells, where Lck participates in T cell antigen receptor signal transduction in an SH2 domain-dependent manner, phosphorylation of Tyr192 correlated with reduced downstream signaling. Our results indicate that tyrosine phosphorylation of the SH2 domain of Lck terminates its high affinity binding to ligands, thereby negatively regulating its participation in T cell antigen receptor signaling. This represents a novel mechanism for the regulation of the function of SH2 domains.
Src同源2（SH2）结构域可与其他蛋白质特定序列环境中的磷酸酪氨酸（Tyr(P)）残基结合，从而介导酪氨酸磷酸化依赖性的蛋白质-蛋白质相互作用。在T细胞抗原受体触发后，Src家族激酶Lck的SH2结构域在T细胞中的酪氨酸192位点发生磷酸化。我们研究了这种磷酸化对SH2结构域特性以及Lck在T细胞活化中功能的影响。我们报告称，酪氨酸192位点的磷酸化降低了分离的SH2结构域结合高亲和力肽配体和含Tyr(P)的细胞蛋白的能力。将酪氨酸192突变为酸性残基可模拟这种效应。在完整的T细胞中，Lck以SH2结构域依赖性方式参与T细胞抗原受体信号转导，酪氨酸192的磷酸化与下游信号传导减弱相关。我们的数据表明，Lck的SH2结构域的酪氨酸磷酸化终止了其与配体的高亲和力结合，从而对其参与T细胞抗原受体信号传导产生负调控作用。这代表了一种调节SH2结构域功能的新机制。
