Stromal cell–derived factor-1α/CXCL12–induced chemotaxis of T cells involves activation of the RasGAP-associated docking protein p62Dok-1

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Abstract
Events mediating stromal cell–derived factor-1 (SDF-1α/CXCL12) chemotaxis of lymphocytes are not completely known. We evaluated intracellular signaling through RasGAP-associated protein p62Dok-1 (downstream of tyrosine kinase [Dok-1]) and associated proteins. SDF-1α/CXCL12 stimulated Dok-1 tyrosine phosphorylation and association with RasGAP, adaptor protein p46Nck, and Crk-L in Jurkat T cells. The phosphorylation of Dok-1 was blocked by pretreatment of cells with the src kinase inhibitor PP2. Src kinase family member Lck was implicated. SDF-1α/CXCL12 did not phosphorylate Dok-1 in J.CaM1.6 cells, a Jurkat derivative not expressing Lck, but did phosphorylate Dok-1 in J.CaM1.6 cells expressing Lck. SDF-1α/CXCL12 induced the tyrosine phosphorylation of Pyk2 and the association of Pyk2 with zeta chain–associated protein-70 kilodaltons (Zap-70) and Vav. SDF-1α/CXCL12 enhanced the association of RasGAP with Pyk2. CXCR4–expressing NIH3T3 and Baf3 cells transfected with full-length Dok-1 cDNA were suppressed in their responses to SDF-1α/CXCL12–induced chemotaxis; mitogen-activated protein (MAP) kinase activity was also decreased. Chemotaxis to SDF-1/CXCL12 was significantly enhanced in Dok-1–/– CD4+ and CD8+ splenic T cells. These results implicate Dok-1, Nck, Crk-L, and Src kinases—especially Lck, Pyk2, Zap-70, Vav, and Ras-GAP—in intracellular signaling by SDF-1α/CXCL12, and they suggest that Dok-1 plays an important role in SDF-1α/CXCL12–induced chemotaxis in T cells.