Rho3 and cdc42 function in polarized exocytosis.

摘要

Cell polarity requires the coordination of many different processes in eukaryotic cells. Spatial regulation of membrane traffic and polarization of the cytoskeleton are two factors that contribute to overall cell polarity in S. cerevisiae. We show that regulation of both the secretory pathway and the actin cytoskeleton is influenced by the same family of genes. Here we demonstrate that the Rho family of GTPases, which organizes and maintains the actin cytoskeleton, also has a central role in the exocytic pathway. Work presented in this dissertation will address the identification and characterization of rho alleles that have led to the elucidation of these roles.; Our analysis of the small Rho GTPase Rho3 identified several genetic interactions with components of the late exocytic pathway. Mutagenesis of the Rho3 effector domain generated rho3 mutants that were specifically defective either for exocytosis or for a polarized actin cytoskeleton. We show that one of the rho3 alleles is defective for secretion and accumulates post-Golgi vesicles. In addition, this mutant no longer interacts with components of the late secretory targeting and docking complex.; The second section of this work focuses on the Rho GTPase, Cdc42, a molecule extensively involved in cell polarity regulation and many diverse cellular processes. The generation of a novel allele, which genetically interacts with many secretory components, has uncovered additional functions for Cdc42. Specifically, we show that Cdc42 has a direct role in post-Golgi secretion, as this mutant accumulates vesicles and post-Golgi markers during specific times of the cell cycle. Additional work focused on the localization of the Cdc42 GTPase and components of the secretory apparatus in this mutant, to determine how Cdc42-6 was mediating its effects.