Rap1 activity is required for αIIbβ3 activation after talin recruitment to the plasma membrane. Lentivirus encoding Myc-tagged RapGAP was transduced into A5 cells stably expressing CRY2–mCherry–talin and CIBN–GFP–CAAX. Empty lentiviral vector was used as a control. A, expression of CRY2–mCherry–talin and Myc–RapGAP in the A5 cells was examined by Western blotting. β-Actin was monitored as a loading control. B, expression of RapGAP has no discernable effect on the optogenetic recruitment of talin to the plasma membrane as assessed by confocal microscopy. The scale bar represents 35 μm. C, RapGAP blocks activation of αIIbβ3 in response to optogenetic recruitment of talin to the plasma membrane. Data represent the means ± SEM of four experiments (double asterisk, p < 0.01; asterisk, p < 0.05). CRY2, Arabidopsis cryptochrome 2; N.S., not statistically significant; Rap1, Ras-related protein 1.