FcγRIIa-mediated Rap1 and integrin αIIbβ3 activation are potentiated by 12-LOX. (A) Washed human platelets pretreated with ML355 or DMSO were stimulated by FcγRIIa crosslinking (IV.3 + GAM) and αIIbβ3 integrin activation (DMSO, n = 3; ML355, n = 6) and (B) Rap1 activation (n = 4) were assessed. (C) hFcR/ALOX12^+/+ and hFcR/ALOX12^−/− platelets were stimulated with 0.125 and 0.25 μg/mL of mouse anti-CD9 and replicates of n = 5 were assessed for Rap1 activation. PAC1-FITC was used to measure αIIbβ3 activation by flow cytometry. A composite bar graph of PAC1-FITC fold changes relative to the unstimulated PAC1-FITC fluoresence is shown. Activated Rap1 was pulled down using Ral-GDS and blotted with a Rap1 antibody. Active Rap1 was measured using LI-COR and then normalized to total Rap1 and unstimulated for fold change in Rap1 activity. Error bars indicate SEM. **P < .01.