PMID: 25287889

Authors:

Visperas PR, Winger JA, Horton TM, Shah NH, Aum DJ, Tao A, Barros T, Yan Q, Wilson CG, Arkin MR, Weiss A, Kuriyan J

Title:

Modification by covalent reaction or oxidation of cysteine residues in the tandem-SH2 domains of ZAP-70 and Syk can block phosphopeptide binding.

Journal:

Biochem J. 2015 Jan 1;465(1):149-61. doi: 10.1042/BJ20140793.

Abstract:

Zeta-chain associated protein of 70 kDa (ZAP-70) and spleen tyrosine kinase (Syk) are non-receptor tyrosine kinases that are essential for T-cell and B-cell antigen receptor signalling respectively. They are recruited, via their tandem-SH2 (Src-homology domain 2) domains, to doubly phosphorylated immunoreceptor tyrosine-based activation motifs (ITAMs) on invariant chains of immune antigen receptors. Because of their critical roles in immune signalling, ZAP-70 and Syk are targets for the development of drugs for autoimmune diseases. We show that three thiol-reactive small molecules can prevent the tandem-SH2 domains of ZAP-70 and Syk from binding to phosphorylated ITAMs. We identify a specific cysteine residue in the phosphotyrosine-binding pocket of each protein (Cys39 in ZAP-70, Cys206 in Syk) that is necessary for inhibition by two of these compounds. We also find that ITAM binding to ZAP-70 and Syk is sensitive to the presence of H2O2 and these two cysteine residues are also necessary for inhibition by H2O2. Our findings suggest a mechanism by which the reactive oxygen species generated during responses to antigen could attenuate signalling through these kinases and may also inform the development of ZAP-70 and Syk inhibitors that bind covalently to their SH2 domains.