CDC42 (Cell division cycle 42 isoform 1) is a small GTPase of the Rho-subfamily that regulates signaling pathways which control various cellular functions including cell morphology, migration, endocytosis and cell cycle progression. CDC42 is a plasma membrane-associated small GTPase which cycles between an active GTP-bound and an inactive GDP-bound state. In the active state, CDC42 binds to a variety of effector proteins to regulate cellular responses. CDC42 is involved in epithelial cell polarization processes. CDC42 causes the formation of thin, actin-rich surface projections called filopodia. Also, CDC42 regulates actin polymerization through its direct binding to N-WASP (Neural Wiskott-Aldrich syndrome protein), which subsequently activates Arp2/3 complex. Loss of CDC42 function raises endocytotic uptake of apical proteins, as well as apical polarity factors such as Crumbs. The product of oncogene Dbl was described to specifically catalyze the dissociation of GDP from CDC42 protein Synonyms: Cell division control protein 42 homolog, G25K GTP-binding protein, CDC42, G25K, CDC42Hs