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. Seems to lack activity with RAC1. Becomes activated and highly tumorigenic by truncation of the N-terminus. Interacts with GTP-bound RAC1 (PubMed:7957046). Interacts with CDC42. 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). Highest expression in the brain, where it is found in neurons and alpha-tanycytes (at protein level). Detected in brain, and at lower levels in the heart. 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. Mainly phosphorylated on serine. Belongs to the MCF2 family. Probable cloning artifact.