Phosphatidylinositol 3,4,5-trisphosphate-dependent Rac exchanger 1 protein is a protein in humans that is encoded by PREX1 gene. Functions as a RAC guanine nucleotide exchange factor (GEF), which activates the Rac proteins by exchanging bound GDP for free GTP. Its activity is synergistically activated by phosphatidylinositol 3,4,5-trisphosphate and the beta gamma subunits of heterotrimeric G protein. May function downstream of heterotrimeric G proteins in neutrophils.