Acts as a RAC1 guanine nucleotide exchange factor (GEF) and can induce membrane ruffling. May function as a positive regulator of apoptosis. Functions in cell migration, attachment and cell spreading. Promotes targeting of RAC1 to focal adhesions. Downstream of NMDA receptors and CaMKK-CaMK1 signaling cascade, promotes the formation of spines and synapses in hippocampal neurons (By similarity). Interacts with PAK kinases through the SH3 domain. Interacts with unphosphorylated PAK1. Interacts with ITCH. Interacts with SCRIB; interaction is direct and may play a role in regulation of apoptosis (By similarity). Interacts with GIT1 and TGFB1I1. Interacts with FRMPD4 (via N-terminus). Interacts with CaMK1. Interacts with BIN2 (By similarity). Interacts with PTK2/FAK1 and RAC1. Interacts with PARVB. Interacts with YWHAZ (PubMed:16959763). Detected at cell adhesions. A small proportion is detected at focal adhesions. Seems to be expressed in the central nervous system. Isoform B, isoform C and isoform E are expressed with highest levels in brain and testis. Phosphorylated on Ser-673 by CaMK1; enhancement of GEF activity and downstream activation of RAC1 (By similarity). Phosphorylated by PTK2/FAK1; this promotes interaction with RAC1. Produced by alternative initiation at Met-158 of isoform G. Truncated N-terminus. Truncated N-terminus. Truncated N-terminus. Truncated N-terminus. Truncated N-terminus. Truncated N-terminus. Extended N-terminus.