title: Distinct roles for Arp2/3 regulators in actin assembly and endocytosis.
abstract: The Arp2/3 complex is essential for actin assembly and motility in many cell processes, and a large number of proteins have been found to bind and regulate it in vitro. A critical challenge is to understand the actions of these proteins in cells, especially in settings where multiple regulators are present. In a systematic study of the sequential multicomponent actin assembly processes that accompany endocytosis in yeast, we examined and compared the roles of WASp, two type-I myosins, and two other Arp2/3 activators, along with that of coronin, which is a proposed inhibitor of Arp2/3. Quantitative analysis of high-speed fluorescence imaging revealed individual functions for the regulators, manifested in part by novel phenotypes. We conclude that Arp2/3 regulators have distinct and overlapping roles in the processes of actin assembly that drive endocytosis in yeast. The formation of the endocytic actin patch, the creation of the endocytic vesicle, and the movement of the vesicle into the cytoplasm display distinct dependencies on different Arp2/3 regulators. Knowledge of these roles provides insight into the in vivo relevance of the dendritic nucleation model for actin assembly.
authors.affiliation: Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri, United States of America.
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Galletta
authors.forename: Dennis Y
authors.initials: DY
authors.lastname: Chuang
authors.forename: John A
authors.initials: JA
authors.lastname: Cooper
mesh_terms: D051377:Actin-Related Protein 2 / Q000378:metabolism; D051376:Actin-Related Protein 2-3 Complex / Q000378:metabolism*; D051378:Actin-Related Protein 3 / Q000378:metabolism; D000199:Actins / Q000378:metabolism*; D003598:Cytoskeletal Proteins / Q000502:physiology*; D004705:Endocytosis; D024461:Myosin Type I / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism
chemical_list: D051377:Actin-Related Protein 2; D051376:Actin-Related Protein 2-3 Complex; D051378:Actin-Related Protein 3; D000199:Actins; D003598:Cytoskeletal Proteins; D029701:Saccharomyces cerevisiae Proteins; D024461:Myosin Type I