CXCR4 internalization and Gαi signaling are impaired after CXCR4 conformational change on Rac1 inhibition. (A) Jurkat T cells were pretreated with or without NSC23766 and subsequently incubated with or without CXCL12. The CXCR4 (detected by mAb 4G10) surface signal was then measured (n = 3). Bars show the mean fluorescence intensity determined by flow cytometry and expressed as percentage ± SEM compared with untreated conditions. (B) HEK 293T cells expressing CXCR4 and CRE-Luc were stimulated with forskolin and different concentrations of CXCL12 (varied from 1pM to 100nM) in the absence or presence of NSC23766 or the Rac1 inhibitory peptide. After 8 hours, CXCL12-mediated inhibition of cyclic AMP synthesis was analyzed by the luciferase assay as indicated in “CRE-luciferose reporter gene assay.” The graph shows normalized data of 3 independent experiments where 100% represents the luciferase activity of untreated cells at the lowest CXCL12 concentration (**P < .01).
