Cdc42 Background Information
Rho GTPases are molecular switches that regulate many essential cellular processes, including Actin dynamics, cell adhesion, cell-cycle progression and transcription. The Rho-type guanosine triphosphatase (GTPase), Cdc42, has been implicated in a variety of functions in the yeast life cycle, including septin organization for cytokinesis, pheromone response, haploid invasive growth and the establishment and maintenance of cell polarity. In yeast, the role of Cdc42 in polarization of cell growth includes polarization of the Actin cytoskeleton, which delivers secretory vesicles to growth sites at the plasma membrane. A group of proteins (Rga1, Rga2 and Bem3) called GTPase-activating proteins (GAPs) catalyze the hydrolysis of GTP to GDP, thereby inactivating Cdc42. Phosphorylation states of Cdc42 regulate its interaction with Rho GDP dissociation inhibitor and its extraction from biological membranes. Yeast Cdc42 functions at a late step in exocytosis, specifically during polarized growth of the emerging bud.
