title: Yeast G-proteins mediate directional sensing and polarization behaviors in response to changes in pheromone gradient direction.
abstract: Yeast cells polarize by projecting up mating pheromone gradients, a classic cell polarity behavior. However, these chemical gradients may shift direction. We examine how yeast cells sense and respond to a 180(o) switch in the direction of microfluidically generated pheromone gradients. We identify two behaviors: at low concentrations of α-factor, the initial projection grows by bending, whereas at high concentrations, cells form a second projection toward the new source. Mutations that increase heterotrimeric G-protein activity expand the bending-growth morphology to high concentrations; mutations that increase Cdc42 activity result in second projections at low concentrations. Gradient-sensing projection bending requires interaction between Gβγ and Cdc24, whereas gradient-nonsensing projection extension is stimulated by Bem1 and hyperactivated Cdc42. Of interest, a mutation in Gα affects both bending and extension. Finally, we find a genetic perturbation that exhibits both behaviors. Overexpression of the formin Bni1, a component of the polarisome, makes both bending-growth projections and second projections at low and high α-factor concentrations, suggesting a role for Bni1 downstream of the heterotrimeric G-protein and Cdc42 during gradient sensing and response. Thus we demonstrate that G-proteins modulate in a ligand-dependent manner two fundamental cell-polarity behaviors in response to gradient directional change.
authors.affiliation: Department of Developmental and Cell Biology, University of California, Irvine, Irvine, CA 92697, USA.
authors.forename: Travis I
authors.initials: TI
authors.lastname: Moore
authors.forename: Hiromasa
authors.initials: H
authors.lastname: Tanaka
authors.forename: Hyung Joon
authors.initials: HJ
authors.lastname: Kim
authors.forename: Noo Li
authors.initials: NL
authors.lastname: Jeon
authors.forename: Tau-Mu
authors.initials: TM
authors.lastname: Yi
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000235:genetics* / Q000378:metabolism; D016764:Cell Polarity; D002633:Chemotaxis / Q000187:drug effects; D015966:Gene Expression Regulation, Fungal / Q000187:drug effects; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics* / Q000378:metabolism; D000072235:Mating Factor; D008840:Microfilament Proteins / Q000235:genetics / Q000378:metabolism; D044085:Microfluidics; D009154:Mutation; D010455:Peptides / Q000378:metabolism / Q000494:pharmacology*; D010675:Pheromones / Q000378:metabolism / Q000494:pharmacology*; D011485:Protein Binding; D012441:Saccharomyces cerevisiae / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics* / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D020846:cdc42 GTP-Binding Protein, Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C105191:Bni1 protein, S cerevisiae; C073594:CDC24 protein, S cerevisiae; D018797:Cell Cycle Proteins; D020662:Guanine Nucleotide Exchange Factors; D008840:Microfilament Proteins; D010455:Peptides; D010675:Pheromones; D029701:Saccharomyces cerevisiae Proteins; C073129:BEM1 protein, S cerevisiae; D000072235:Mating Factor; D020846:cdc42 GTP-Binding Protein, Saccharomyces cerevisiae