title: The chemokine CXCL12 generates costimulatory signals in T cells to enhance phosphorylation and clustering of the adaptor protein SLP-76.
abstract: The CXC chemokine CXCL12 mediates the chemoattraction of T cells and enhances the stimulation of T cells through the T cell receptor (TCR). The adaptor SLP-76 [Src homology 2 (SH2) domain-containing leukocyte protein of 76 kD] has two key tyrosine residues, Tyr(113) and Tyr(128), that mediate signaling downstream of the TCR. We investigated the effect of CXCL12 on SLP-76 phosphorylation and the TCR-dependent formation of SLP-76 microclusters. Although CXCL12 alone failed to induce SLP-76 cluster formation, it enhanced the number, stability, and phosphorylation of SLP-76 microclusters formed in response to stimulation of the TCR by an activating antibody against CD3, a component of the TCR complex. Addition of CXCL12 to anti-CD3-stimulated cells resulted in F-actin polymerization that stabilized SLP-76 microclusters in the cells' periphery at the interface with antibody-coated coverslips and increased the interaction between SLP-76 clusters and those containing ZAP-70, the TCR-associated kinase that phosphorylates SLP-76, as well as increased TCR-dependent gene expression. Costimulation with CXCL12 and anti-CD3 increased the extent of phosphorylation of SLP-76 at Tyr(113) and Tyr(128), but not that of other TCR-proximal components, and mutation of either one of these residues impaired the CXCL12-dependent effect on SLP-76 microcluster formation, F-actin polymerization, and TCR-dependent gene expression. The effects of CXCL12 on SLP-76 microcluster formation were dependent on the coupling of its receptor CXCR4 to G(i)-family G proteins (heterotrimeric guanine nucleotide-binding proteins). Thus, we identified a costimulatory mechanism by which CXCL12 and antigen converge at SLP-76 microcluster formation to enhance T cell responses.
authors.affiliation: Cambridge Institute for Medical Research, Hills Road, Cambridge CB2 OXY, UK.
authors.forename: Xin
authors.initials: X
authors.lastname: Smith
authors.forename: Helga
authors.initials: H
authors.lastname: Schneider
authors.forename: Karsten
authors.initials: K
authors.lastname: Köhler
authors.forename: Hebin
authors.initials: H
authors.lastname: Liu
authors.forename: Yuning
authors.initials: Y
authors.lastname: Lu
authors.forename: Christopher E
authors.initials: CE
authors.lastname: Rudd
mesh_terms: D000199:Actins / Q000378:metabolism; D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D000818:Animals; D017252:CD3 Complex / Q000378:metabolism; D049109:Cell Proliferation; D054377:Chemokine CXCL12 / Q000378:metabolism*; D016000:Cluster Analysis; D004797:Enzyme-Linked Immunosorbent Assay; D015870:Gene Expression; D006801:Humans; D019169:Jurkat Cells; D051379:Mice; D008856:Microscopy, Fluorescence; D009154:Mutation; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D019718:Receptors, CXCR4 / Q000378:metabolism; D015398:Signal Transduction; D013154:Spleen / Q000166:cytology; D013601:T-Lymphocytes / Q000166:cytology / Q000378:metabolism*; D014443:Tyrosine / Q000737:chemistry; D051746:ZAP-70 Protein-Tyrosine Kinase / Q000378:metabolism
chemical_list: D000199:Actins; D048868:Adaptor Proteins, Signal Transducing; D017252:CD3 Complex; C515255:CXCL12 protein, human; C527276:CXCR4 protein, human; D054377:Chemokine CXCL12; D010750:Phosphoproteins; D019718:Receptors, CXCR4; C092947:SLP-76 signal Transducing adaptor proteins; D014443:Tyrosine; D051746:ZAP-70 Protein-Tyrosine Kinase