title: Homologues of oxysterol-binding proteins affect Cdc42p- and Rho1p-mediated cell polarization in Saccharomyces cerevisiae.
abstract: Polarized cell growth requires the establishment of an axis of growth along which secretion can be targeted to a specific site on the cell cortex. How polarity establishment and secretion are choreographed is not fully understood, though Rho GTPase- and Rab GTPase-mediated signaling is required. Superimposed on this regulation are the functions of specific lipids and their cognate binding proteins. In a screen for Saccharomyces cerevisiae genes that interact with Rho family CDC42 to promote polarity establishment, we identified KES1/OSH4, which encodes a homologue of mammalian oxysterol-binding protein (OSBP). Other yeast OSH genes (OSBP homologues) had comparable genetic interactions with CDC42, implicating OSH genes in the regulation of CDC42-dependent polarity establishment. We found that the OSH gene family (OSH1-OSH7) promotes cell polarization by maintaining the proper localization of septins, the Rho GTPases Cdc42p and Rho1p, and the Rab GTPase Sec4p. Disruption of all OSH gene function caused specific defects in polarized exocytosis, indicating that the Osh proteins are collectively required for a secretory pathway implicated in the maintenance of polarized growth.
authors.affiliation: Department of Biology, University of Virginia, Charlottesville, VA 22904, USA.
authors.forename: Keith G
authors.initials: KG
authors.lastname: Kozminski
authors.forename: Gabriel
authors.initials: G
authors.lastname: Alfaro
authors.forename: Shubha
authors.initials: S
authors.lastname: Dighe
authors.forename: Christopher T
authors.initials: CT
authors.lastname: Beh
mesh_terms: D016764:Cell Polarity / Q000235:genetics / Q000502:physiology*; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics / Q000502:physiology*; D009154:Mutation; D011987:Receptors, Steroid / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000502:physiology*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000502:physiology*; D020846:cdc42 GTP-Binding Protein, Saccharomyces cerevisiae / Q000502:physiology*; D020741:rho GTP-Binding Proteins / Q000502:physiology*; D000098825:Oxysterol Binding Proteins
chemical_list: C087901:KES1 protein, S cerevisiae; D008565:Membrane Proteins; D011987:Receptors, Steroid; D029701:Saccharomyces cerevisiae Proteins; D000098825:Oxysterol Binding Proteins; C051302:RHO1 protein, S cerevisiae; D020846:cdc42 GTP-Binding Protein, Saccharomyces cerevisiae; D020741:rho GTP-Binding Proteins