Inhibition of IP3, but not PKC, abrogates fMLP- and SDF-1–induced LDV-FITC binding. (A) LDV-FITC binding to U937-FPR cells pretreated with 2-APB and stimulated at time 0 with fMLP, SDF-1, Mn²⁺, or buffer was analyzed in real time. One of 3 independent experiments is shown. Dose responses for inhibition of fMLP-induced peak intracellular calcium flux (determined by fluorimetry) and LDV-FITC binding by 2-APB are shown. (B) U937-FPR cells pretreated with DMSO (0.1%, 30 minutes), GFX109203X (1 μM, 30 minutes), or PMA (50 nM, 18 hours) were stimulated at time 0 with Mn²⁺, buffer, fMLP, or PMA, and LDV-FITC binding was analyzed in real time. One of 3 independent experiments is shown.