Guanine nucleotide exchange factor that catalyzes guanine nucleotide exchange on RHOA and CDC42, and thereby contributes to the regulation of RHOA and CDC42 signaling pathways (By similarity). Seems to lack activity with RAC1. Becomes activated and highly tumorigenic by truncation of the N-terminus (By similarity). Isoform 5 activates CDC42 (PubMed:15157669). Does not catalyze guanine nucleotide exchange on CDC42 (PubMed:15157669). Interacts with GTP-bound RAC1 (By similarity). Interacts with CDC42 (PubMed:15157669). Interacts with RHOA. Interacts with CCPG1, which results in specific inhibition of its exchange activity toward RHOA, but does not affect its activity on CDC42 (By similarity). Interaction with membranes enriched in phosphoinositides is mediated by the CRAL-TRIO domain. A number of isoforms are produced. According to EST sequences. Experimental confirmation may be lacking for some isoforms. The CRAL-TRIO domain mediates interaction with various inositol phospholipids, such as phosphatidylinositol 3-phosphate (PI3P), phosphatidylinositol 4-phosphate (PI4P) and phosphatidylinositol 5-phosphate (PI5P). The DH domain is involved in interaction with CCPG1. Belongs to the MCF2 family. Extended N-terminus.