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. {ECO:0000269|PubMed:10918068, ECO:0000269|PubMed:14702343, ECO:0000269|PubMed:17576779, ECO:0000269|PubMed:17702895, ECO:0000269|PubMed:24958846, ECO:0000269|PubMed:27235135}. This is the function of ENSG00000068831 (RASGRP2, RAS guanyl releasing protein 2).