The function of ARHGEF4 (Rho guanine nucleotide exchange factor 4, Ensembl gene identifier ENSG00000136002) is as follows. Acts as a guanine nucleotide exchange factor (GEF) for RHOA, RAC1 and CDC42 GTPases. Binding of APC may activate RAC1 GEF activity. The APC-ARHGEF4 complex seems to be involved in cell migration as well as in E-cadherin-mediated cell-cell adhesion. Required for MMP9 up- regulation via the JNK signaling pathway in colorectal tumor cells. Involved in tumor angiogenesis and may play a role in intestinal adenoma formation and tumor progression. {ECO:0000269|PubMed:10947987, ECO:0000269|PubMed:12598901, ECO:0000269|PubMed:17145773, ECO:0000269|PubMed:17599059, ECO:0000269|PubMed:19893577}.