title: A model for cell wall dissolution in mating yeast cells: polarized secretion and restricted diffusion of cell wall remodeling enzymes induces local dissolution.
abstract: Mating of the budding yeast, Saccharomyces cerevisiae, occurs when two haploid cells of opposite mating types signal using reciprocal pheromones and receptors, grow towards each other, and fuse to form a single diploid cell. To fuse, both cells dissolve their cell walls at the point of contact. This event must be carefully controlled because the osmotic pressure differential between the cytoplasm and extracellular environment causes cells with unprotected plasma membranes to lyse. If the cell wall-degrading enzymes diffuse through the cell wall, their concentration would rise when two cells touched each other, such as when two pheromone-stimulated cells adhere to each other via mating agglutinins. At the surfaces that touch, the enzymes must diffuse laterally through the wall before they can escape into the medium, increasing the time the enzymes spend in the cell wall, and thus raising their concentration at the point of attachment and restricting cell wall dissolution to points where cells touch each other. We tested this hypothesis by studying pheromone treated cells confined between two solid, impermeable surfaces. This confinement increases the frequency of pheromone-induced cell death, and this effect is diminished by reducing the osmotic pressure difference across the cell wall or by deleting putative cell wall glucanases and other genes necessary for efficient cell wall fusion. Our results support the model that pheromone-induced cell death is the result of a contact-driven increase in the local concentration of cell wall remodeling enzymes and suggest that this process plays an important role in regulating cell wall dissolution and fusion in mating cells.
authors.affiliation: Molecular and Cellular Biology, Harvard University, Cambridge, MA, United States of America; Faculty of Arts and Sciences Center for Systems Biology, Harvard University, Cambridge, MA, United States of America.
authors.forename: Lori B
authors.initials: LB
authors.lastname: Huberman
authors.affiliation: Molecular and Cellular Biology, Harvard University, Cambridge, MA, United States of America; Faculty of Arts and Sciences Center for Systems Biology, Harvard University, Cambridge, MA, United States of America.
authors.forename: Andrew W
authors.initials: AW
authors.lastname: Murray
mesh_terms: D002448:Cell Adhesion / Q000187:drug effects; D002473:Cell Wall / Q000201:enzymology / Q000378:metabolism*; D004058:Diffusion; D008954:Models, Biological; D009995:Osmosis; D010675:Pheromones / Q000494:pharmacology; D012098:Reproduction; D012441:Saccharomyces cerevisiae / Q000166:cytology* / Q000201:enzymology / Q000378:metabolism / Q000502:physiology*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism; D013499:Surface Properties
chemical_list: D010675:Pheromones; D029701:Saccharomyces cerevisiae Proteins