Functions as a calcium- and DAG-regulated nucleotide exchange factor specifically activating Rap through the exchange of bound GDP for GTP. May also activate other GTPases such as RRAS, RRAS2, NRAS, KRAS but not HRAS. Functions in aggregation of platelets and adhesion of T-lymphocytes and neutrophils probably through inside-out integrin activation. May function in the muscarinic acetylcholine receptor M1/CHRM1 signaling pathway. Forms a signaling complex with RAP1 and BRAF. Interacts with RAP1. Interacts with F-actin (By similarity). Found both in the cytosol and associated with membranes. Enriched at juxtamembrane areas and membrane ruffles. Localizes to the cell bodies and axons of striatal neurons. The N-terminal Ras-GEF domain mediates association with F-actin. Defects in RASGRP2 may be the cause of Simmental thrombopathia. An inherited platelet disorder first described in Simmental cattle and characterized by mild to severe bleeding episodes. Belongs to the RASGRP family.