FIG. 2.
Activation of αIIbβ3 results in the activation of Rap1. Platelets isolated from a healthy volunteer (left) or platelets deficient in integrin αIIbβ3 expression, isolated from patients with Glanzmann's thrombasthenia (two right panels), were preincubated with 30 μM indomethacin for 30 min to inhibit TxA2 formation. After that time they were stimulated with Fab fragments of monoclonal antibody LIBS-6 at a concentration of 4 μM for 5 min under nonaggregating conditions. After lysis, active, GTP-bound Rap1 was precipitated. Indicated beneath the panel is the fold induction of Rap1 activity by LIBS-6 compared to unstimulated platelets. The same result was achieved in one additional experiment.