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CXCR3‐mediated T‐cell chemotaxis involves ZAP‐70 and is regulated by signalling through the T‐cell receptor
Author(s) -
Dar Wasim A.,
Knechtle Stuart J.
Publication year - 2007
Publication title -
immunology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.297
H-Index - 133
eISSN - 1365-2567
pISSN - 0019-2805
DOI - 10.1111/j.1365-2567.2006.02534.x
Subject(s) - jurkat cells , tyrosine phosphorylation , cxcr3 , microbiology and biotechnology , t cell , phosphorylation , biology , tyrosine kinase , chemotaxis , receptor tyrosine kinase , sh2 domain , tyrosine , zap70 , chemokine receptor , signal transduction , chemistry , receptor , biochemistry , t cell receptor , chemokine , immunology , immune system
Summary The chemokine receptor CXCR3 is critical for the function of activated T cells. We studied the molecular mechanisms of CXCR3 signalling. The addition of CXCR3 ligands to normal human T cells expressing CXCR3 led to the tyrosine phosphorylation of multiple proteins. Addition of the same ligands to Jurkat T cells engineered to express CXCR3 induced tyrosine phosphorylation of proteins with molecular weights similar to those in normal cells. Immunoblotting with phosphotyrosine‐specific antibodies identified Zeta‐associated protein of 70 000 molecular weight (ZAP‐70), linker for the activation of T cells (LAT), and phospholipase‐C‐γ1 (PLCγ1) to be among the proteins that become phosphorylated upon CXCR3 activation. ZAP‐70 was phosphorylated on tyrosine 319, LAT on tyrosines 171 and 191, and PLCγ1 on tyrosine 783. The ZAP‐70 inhibitor piceatannol reduced CXCR3‐mediated tyrosine phosphorylation of ZAP‐70, LAT, PLCγ1 and mitogen‐activated protein kinase Erk and it reduced CXCL10‐mediated chemotaxis of both CXCR3‐transfected Jurkat T cells and normal T cells expressing CXCR3. These results are consistent with the involvement of ZAP‐70 in CXCR3‐mediated protein tyrosine phosphorylation and CXCR3‐induced T‐cell chemotaxis. Studies with the Lck‐deficient Jurkat T‐cell line, JCAM1.6, demonstrated that phosphorylation of ZAP‐70 after CXCR3 activation is a Lck‐dependent process. Finally, stimulating CXCR3‐expressing Jurkat T cells and normal T cells expressing CXCR3 through the T‐cell receptor attenuated CXCR3‐induced tyrosine phosphorylation and CXCR3‐mediated T‐cell migration, indicating the occurrence of cross‐talk between T‐cell receptor and CXCR3‐signalling pathways. These results shed light on the mechanisms of CXCR3 signalling. Such information could be useful when designing therapeutic strategies to regulate T‐cell function.