It has become increasingly appreciated that receptors coupled to Gα i family members can
stimulate platelet aggregation, but the mechanism for this has remained unclear. One
possible mediator is the small GTPase, Rap1, which has been shown to contribute to
integrin activation in several cell lines and to be activated by a calcium-dependent
mechanism in platelets. Here, we demonstrate that Rap1 is also activated by Gα i family
members in platelets. First, we show that platelets from mice lacking the Gα i family member …