title: Polarity establishment by Cdc42: Key roles for positive feedback and differential mobility.
abstract: Cell polarity is fundamental to the function of most cells. The evolutionarily conserved molecular machinery that controls cell polarity is centered on a family of GTPases related to Cdc42. Cdc42 becomes activated and concentrated at polarity sites, but studies in yeast model systems led to controversy on the mechanisms of polarization. Here we review recent studies that have clarified how Cdc42 becomes polarized in yeast. On one hand, findings that appeared to support a key role for the actin cytoskeleton and vesicle traffic in polarity establishment now appear to reflect the action of stress response pathways induced by cytoskeletal perturbations. On the other hand, new findings strongly support hypotheses on the polarization mechanism whose origins date back to the mathematician Alan Turing. The key features of the polarity establishment mechanism in yeasts include a positive feedback pathway in which active Cdc42 recruits a Cdc42 activator to polarity sites, and differential mobility of polarity "activators" and "substrates."
authors.affiliation: a Department of Pharmacology and Cancer Biology , Duke University Medical Center , Durham , NC , USA.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Woods
authors.affiliation: a Department of Pharmacology and Cancer Biology , Duke University Medical Center , Durham , NC , USA.
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Lew
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism; D016764:Cell Polarity; D025461:Feedback, Physiological; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000378:metabolism; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism*
chemical_list: D020764:cdc42 GTP-Binding Protein
keywords: Bem1; Cdc42; GDI; GEF; PAK; diffusion; polarity; positive feedback