Open AccessBinding of ZAP-70 to Phosphorylated T-Cell Receptor ζ and η Enhances Its Autophosphorylation and Generates Specific Binding Sites for SH2 Domain-Containing Proteins
Author(s) -
Ellen N. Neumeister,
Yuexin Zhu,
Stéphane Richard,
Cox Terhorst,
Andrew C. Chan,
A S Shaw
Publication year - 1995
Publication title -
molecular and cellular biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.14
H-Index - 327
eISSN - 1067-8824
pISSN - 0270-7306
DOI - 10.1128/mcb.15.6.3171
Subject(s) - autophosphorylation , immunoreceptor tyrosine based activation motif , sh2 domain , biology , phosphorylation , phosphotyrosine binding domain , tyrosine phosphorylation , tyrosine , receptor tyrosine kinase , tyrosine kinase , t cell receptor , microbiology and biotechnology , proto oncogene tyrosine protein kinase src , signal transduction , biochemistry , t cell , protein kinase a , immune system , immunology
ZAP-70 is a protein tyrosine kinase thought to play a critical role in T-cell receptor (TCR) signal transduction. During T-cell activation, ZAP-70 binds to a conserved signalling motif known as the immune receptor tyrosine activating motif (ITAM) and becomes tyrosine phosphorylated. To determine whether binding of ZAP-70 to the phosphorylated ITAM was able to activate its kinase activity, we measured the kinase activity of ZAP-70 both when it was bound and when it was unbound to phosphorylated TCR subunits. The ability of ZAP-70 to phosphorylate itself, but not exogenous substrates, was enhanced when it was bound to the tyrosine-phosphorylated TCR zeta and eta chains or to a construct that contained duplicated epsilon ITAMs. No enhanced ZAP-70 autophosphorylation was noted when it was bound to tyrosine-phosphorylated CD3 gamma or epsilon. In addition, autophosphorylation of ZAP-70 when bound to zeta or eta resulted in the generation of multiple distinct ZAP-70 phosphorylated tyrosine residues which had the capacity to bind the SH2 domains of fyn, lck, GAP, and abl. As the effect was noted only when ZAP-70 was bound to TCR subunits containing multiple ITAMs, we propose that one of the roles of the tandem ITAMs is to facilitate the autophosphorylation of ZAP-70. Tyrosine-phosphorylated ZAP-70 then mediates downstream signalling by recruiting SH2 domain-containing signalling proteins.