FYVE, RhoGEF and PH domain-containing protein 1 (FGD1) also known as faciogenital dysplasia 1 protein (FGDY), zinc finger FYVE domain-containing protein 3 (ZFYVE3), or Rho/Rac guanine nucleotide exchange factor FGD1 (Rho/Rac GEF) is a protein that in humans is encoded by the FGD1 gene that lies on the X chromosome.Orthologs of the FGD1 gene are found in dog, cow, mouse, rat, and zebrafish, and also budding yeast and C. elegans. It is a member of the FYVE, RhoGEF and PH domain containing family.
FGD1 is a guanine-nucleotide exchange factor (GEF) that can activate the Rho GTPase Cdc42. It localizes preferentially to the trans-Golgi network (TGN) of mammalian cells and regulates, for example, the secretory transport of bone-specific proteins from the Golgi complex. Thus Cdc42 and FGD1 regulate secretory membrane trafficking that occurs especially during bone growth and mineralization in humans. FGD1 promotes nucleotide exchange on the GTPase Cdc42, a key player in the establishment of cell polarity in all eukaryotic cells. The GEF activity of FGD1, which activates Cdc42, is harbored in its DH domain and causes the formation of filopodia, enabling the cells to migrate. FGD1 also activates the c-Jun N-terminal kinase (JNK) signaling cascade, important in cell differentiation and apoptosis. It also promotes the transition through G1 during the cell cycle and causes tumorgenic transformation of NIH/3T3 fibroblasts.