Activation of Rap1 by cytosolic GEFs

Signals from agonist receptors (such as GPVI) trigger the production of PIP3, DAG, cAMP and elevated Ca++ levels. This leads to the activation and translocation of active Rap1-GTP to the plasma membrane. Rap-GEFs stimulate the replacement of GDP for GTP, activating Rap1. Several Rap1 GEFs have been identified enabling Rap1 to respond to diverse stimuli. CalDAG-GEFs activate Rap1 in response to calcium and DAG, downstream of Phospholipase C. EPAC (exchange proteins directly activated by cAMP) GEFs are activated by binding cAMP.

激动剂受体（如GPVI）的信号触发PIP3、DAG、cAMP的产生以及Ca++水平升高。此过程导致活性Rap1-GTP向质膜的激活与转移。Rap-GEFs（Rap1激活因子）促进GDP与GTP的替换，从而激活Rap1。已鉴定出多种Rap1 GEFs，使得Rap1能够对多种刺激作出反应。CalDAG-GEFs在磷脂酶C下游，响应钙和DAG激活Rap1。EPAC（由cAMP直接激活的交换蛋白）GEFs通过结合cAMP而被激活。