Guanine nucleotide exchange factor which activates Rho GTPases (PubMed:15601624). Strongly activates RHOA (PubMed:15601624). Also strongly activates RHOB, weakly activates RHOC and RHOG and shows no effect on RHOD, RHOV, RHOQ or RAC1 (By similarity). Involved in regulation of cell shape and actin cytoskeletal organization (PubMed:15601624). Plays a role in actin organization by generating a loss of actin stress fibers and the formation of membrane ruffles and filopodia (PubMed:14662653). Required for SRC-induced podosome formation (By similarity). Involved in positive regulation of immature dendritic cell migration (By similarity). Interacts with SRC (By similarity). Forms a ternary complex with SRC and the PI3K 85 kDa subunit (By similarity). Interacts with and is activated by the heterodimer formed by GNB1 and GNG2 (By similarity). Interacts with ODAM (via C-terminus) (PubMed:25911094). Interacts with RHOA (By similarity). A number of additional isoforms are detected in primary breast tumors but not in normal tissues. Ubiquitously expressed with highest levels in placenta. High levels are also found in colon, kidney, trachea, prostate, liver, pancreas, pituitary gland, thyroid gland and mammary gland. In fetal tissues, expressed at high levels in kidney, lung and liver (PubMed:15601624). Expressed at low levels in lung and heart (PubMed:14662653). The PH domain binds to phosphoinositides and is essential for podosome formation. Activation of SRC induces tyrosine phosphorylation of ARHGEF5. Extended N-terminus.