Guanine nucleotide exchange factor which activates Rho GTPases (PubMed:19713215, PubMed:21525037). Strongly activates RHOA (PubMed:19713215, PubMed:21525037). Also strongly activates RHOB, weakly activates RHOC and RHOG and shows no effect on RHOD, RHOV, RHOQ or RAC1 (PubMed:19713215). Involved in regulation of cell shape and actin cytoskeletal organization (PubMed:21525037). Plays a role in actin organization by generating a loss of actin stress fibers and the formation of membrane ruffles and filopodia (By similarity). Required for SRC-induced podosome formation (PubMed:21525037). Involved in positive regulation of immature dendritic cell migration (PubMed:19713215). Interacts with SRC (PubMed:21525037). Forms a ternary complex with SRC and the PI3K 85 kDa subunit (PubMed:21525037). Interacts with and is activated by the heterodimer formed by GNB1 and GNG2 (PubMed:19713215). Interacts with ODAM (via C-terminus) (By similarity). Interacts with RHOA (PubMed:19713215). The PH domain binds to phosphoinositides and is essential for podosome formation. Activation of SRC induces tyrosine phosphorylation of ARHGEF5. Chemotaxis of macrophages, T and B lymphocytes and bone marrow-derived mature dendritic cells from mutant mice is not affected but chemotaxis of immature dendritic cells is abolished.