Functions as a calcium-regulated nucleotide exchange factor activating both Ras and rac1 through the exchange of bound GDP for GTP. May function in synaptic plasticity. The Ras-GEF domain and the N-terminal Ras-GEF domain mediate Ras activation. The IQ domain is dispensable for the Ras-GEF activity. The DH (DBL-homology) domain is required for rac1 activation.