Pi 3-Kinase and Cxcr4 Chemokine Receptor Signaling in Jurkat Cells

Objectives:Chemokines can induce rapid changes in integrin-dependent adhesion. Although activation of phosphatidylinositol 3-kinase (PI 3-K) is critical to integrin activation induced by Ig superfamily members such as CD2, CD3 and CD28, the role of PI 3-K in chemokine-induced integrin activation is unclear. We examined the role of PI 3-K in several functional responses induced by ligation of the CXCR4 chemokine receptor expressed on Jurkat cells with the CXC chemokine stromal cell-derived factor-1 a (CXCL12).Methods: and Results:FN coated with 96 well plate and blocked with 2.5 %BSA. Jurakat cells were added, incubated, wash out nonadherent cells, and then measured adherent cells. CXCL12 treatment induced increased adhesion of Jurkat cells to fibronectin that peaked within 3 minutes of stimulation. Enhanced Jurkat cell adhesion induced by CXCL12 was inhibited by pertussis toxin and the PI 3-K inhibitors wortmannin and LY294002, but not by a dominant-negative form of the p85 subunit of PI 3-K. CXCL12 also induced F-actin polymerization on Jurkat cells that was only partially inhibited by PI 3-K inhibitors. In contrast, CXCL12-mediated phosphorylation of the PI 3-K-dependent enzyme Akt was markedly prolonged, with Akt activation being detectable as late as 60 min. following CXCL12 stimulation. Conclusion:These results suggest that CXCR4 can initiate PI 3-K-dependent signaling events that affect T cell adhesion and cytoskeletal reorganization. However, these responses do not appear to require the p85 subunit of PI 3-K. In addition, there are dramatic differences in the kinetics of CXCR4-mediated activation of Akt versus CXCR4-mediated effects on adhesion.