Chemokines Induce Wnt-Frizzled Gene Expression in Human T Cells

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Chemokines have been shown to induce and direct adhesion, chemotaxis, activation, and degranulation of human and rodent leukocytes both in vitro and in vivo. CXCL12 and CCL19 are two important chemokines that regulate T cell motility and activation under normal and inflammatory conditions. Despite numerous reports examining the function of chemokines, little is known about the transcriptional events involved therein. Here, we performed microarray analysis on CXCL12- treated T-cells, and found that the Wnt family of proteins was significantly upregulated during CXCL12 treatment. Confirmation of these results by real-time PCR and Western analysis revealed that the expression of Wnt5A and other members of the non-canonical Wnt pathway were specifically upregulated during CXCL12 stimulation, while -catenin and canonical Wnt family members were selectively downregulated. Wnt5A was found to augment signaling through the CXCL12-CXCR4 axis via the activation of protein kinase C (PKC). Moreover, our data has revealed that Wnt5A expression is required to mediate directional T-cell migration in response to CXCL12, and that the treatment of human T-cells with recombinant Wnt5A sensitized T-cells to CXCL12-induced migration. Furthermore,Wnt5A expression was also required for the sustained expression of CXCR4, both transcriptionally and translationally. These results were further supported in vivo using EL4 thymoma metastasis as a model of T-cell migration. Together, these data demonstrate, for the first time, that Wnt5A is a critical mediator in CXCL12-CXCR4 signaling and migration in human and murine T cells. Interestingly, we also found that Wnt10A plays a role in CCL19 chemotaxis and in the maintenance of CCR7 expression on T cells. These findings may reveal a novel cooperative signaling network between various chemokine and Wnt receptors and ligands that may control cell polarization and directional migration. Moreover, we are also currently verifying and characterizing several additional gene families that are highly expressed in T cells after migration in response to or simply stimulation with CXCL12, CCL19, gp120 and HIV-1 virus. Moreover, the role of lipid rafts in chemokine biology and HIV infectivity are also under examination using microarray analysis. A greater understanding of the transcriptional signals differentially induced by the ligation of various chemokine receptors may provide a means to dissect the pathways by which these chemoattractants induce cell migration and activation as well as any host transcriptional signals important in HIV entry and replication.