Characterization of the Bar Proteinase, An Extracellular Enzyme from the Yeast Saccharomyces Cerevisiae

MacKay, Vivian L.; Armstrong, J. McD.; Yip, Carli; Welch, Susan K.; Walker, Kathy; Osborn, Sherri G.; Sheppard, Paul O.; Forstrom, John W.

doi:10.1007/978-1-4684-6012-4_21

Cited by 27 publications

(22 citation statements)

References 18 publications

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“…In S. cerevisiae, BAR1 (SST1), which encodes an ␣-pheromone-degrading aspartyl proteinase (22,23,38), is mating type specific (i.e., a specific) and pheromone induced. In C. albicans, SAP9, a member of the family of secreted aspartyl proteinases, was most homologous to BAR1 of S. cerevisiae (http://genolist.pasteur.fr/CandidaDB).…”

Section: Vol 2 2003 ␣-Pheromone Induction In C Albicans 851mentioning

confidence: 99%

α-Pheromone-Induced “Shmooing” and Gene Regulation Require White-Opaque Switching during Candida albicans Mating

et al. 2003

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A 14-mer ␣-pheromone peptide of Candida albicans was chemically synthesized and used to analyze the role of white-opaque switching in the mating process. The ␣-pheromone peptide blocked cell multiplication and induced "shmooing" in a/a cells expressing the opaque-phase phenotype but not in a/a cells expressing the white-phase phenotype. The ␣-pheromone peptide induced these effects at 25°C but not at 37°C. An analysis of mating-associated gene expression revealed several categories of gene regulation, including (i) MTL-homozygous-specific, pheromone stimulated, switching-independent (CAG1 and STE4); (ii) mating type-specific, pheromone-induced, switching-independent (STE2); and (iii) pheromone-induced, switching-dependent (FIG1, KAR4, and HWP1). An analysis of switching-regulated genes revealed an additional category of opaque-phasespecific genes that are downregulated by ␣-pheromone only in a/a cells (OP4, SAP1, and SAP3). These results demonstrate that ␣-pheromone causes shmooing, the initial step in the mating process, only in a/a cells expressing the opaque phenotype and only at temperatures below that in the human host. These results further demonstrate that although some mating-associated genes are stimulated by the ␣-pheromone peptide in both white-and opaque-phase cells, others are stimulated only in opaque-phase cells, revealing a category of gene regulation unique to C. albicans in which ␣-pheromone induction requires the white-opaque transition. These results demonstrate that in C. albicans, the mating process and associated gene regulation must be examined within the context of white-opaque switching.Approximately 97% of clinical isolates of Candida albicans are heterozygous (20) at the single mating-type locus (MTL) containing the gene MTLa1 in the MTLa copy of the locus on one homolog of chromosome 5 and the genes MTL␣1 and MTL␣2 in the MTL␣ copy on the other homolog (12). A minority of these a/␣ strains undergo homozygosis to both a/a and ␣/␣ at a high frequency (20,33). Approximately 3% of the clinical isolates are homozygous (a/a or ␣/␣) (20) and capable of mating (21). However, for MTL-homozygous cells to become mating competent, they must first switch from the white to the opaque phenotype (21, 26). White-opaque switching (36) is repressed in MTL heterozygotes by the Mtla1p-Mtl␣2p complex and activated in MTL homozygotes (21, 26). When opaque-phase a/a and ␣/␣ cells are mixed, they progress through a sequence of mating stages that parallel those in the mating process of Saccharomyces cerevisiae, including "shmooing," growth of the shmoo projection (conjugation tube), chemotropism, fusion of conjugation tubes to form a zygote, daughter cell formation from the conjugation bridge of the zygote, and nuclear migration from parent cells to the fusion junction (16,26,37).The requirements of shmooing and growth of the conjugation tube, therefore, are (i) MTL homozygosity, (ii) a switch from the white to the opaque phase, and (iii) the presence of opaque-phase cells of the opposite mating type. Further...

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Section: Vol 2 2003 ␣-Pheromone Induction In C Albicans 851mentioning

confidence: 99%

α-Pheromone-Induced “Shmooing” and Gene Regulation Require White-Opaque Switching during Candida albicans Mating

et al. 2003

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“…15,1995 YEAST DESENSITIZATION MUTANTS 3637 Fig. 1A), YDK499 exhibits large clear halos that do not fill in (because of the absence of BAR1, the ␣-factor-specific protease) (8)(9)(10)33). To avoid the confounding effects of BAR1 expression, strain YDK499 was used for most of the experiments described below.…”

Section: Overexpression Of Gpa1 Restores Recovery In Sst2 Mutantsmentioning

confidence: 99%

Inhibition of G-Protein Signaling by Dominant Gain-of-Function Mutations in Sst2p, a Pheromone Desensitization Factor in Saccharomyces cerevisiae

Dohlman

Apaniesk

Chen

et al. 1995

Molecular and Cellular Biology

195

164

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Genetic analysis of cell-cell signaling in Saccharomyces cerevisiae has led to the identification of a novel factor, known as Sst2p, that promotes recovery after pheromone-induced growth arrest (R. K. Chan and C. A. Otte, Mol. Cell. Biol. 2:11-20, 1982). Loss-of-function mutations lead to increased pheromone sensitivity, but this phenotype is partially suppressed by overexpression of the G protein ␣ subunit gene (GPA1). Suppression is allele specific, however, suggesting that there is direct interaction between the two gene products. To test this model directly, we isolated and characterized several dominant gain-of-function mutants of SST2. These mutations block the normal pheromone response, including a loss of pheromone-stimulated gene transcription, cell cycle growth arrest, and G protein myristoylation. Although the SST2 mutations confer a pheromoneresistant phenotype, they do not prevent downstream activation by overexpression of G␤ (STE4), a constitutively active G␤ mutation (STE4 Hpl ), or a disruption of GPA1. None of the SST2 alleles affects the expression or stability of G␣. These results point to the G protein ␣ subunit as being the direct target of Sst2p action and underscore the importance of this novel desensitization factor in G-protein-mediated signaling.The yeast Saccharomyces cerevisiae is a unicellular eukaryote that can grow vegetatively either as a diploid or as one of two haploid cell types, known as the mating types a and ␣. Haploid cells secrete specific peptide pheromones (a and ␣ mating factors) that act on cells of the opposite type to promote cell fusion, leading to the formation of an a/␣ diploid (28, 46).Pheromone signaling is mediated through receptors of the seven-transmembrane-segment class (other examples include the ␤-adrenergic receptor and rhodopsin) and is coupled to downstream events via a guanine nucleotide-binding regulatory protein (G protein) (28). Agonist binding to these receptors promotes exchange of GDP for GTP on the G-protein ␣ subunit and dissociation of G␣ from the G protein ␤ and ␥ subunits (4, 6, 11). In yeast cells, it is the ␤/␥ moiety that activates downstream signaling events leading to mating, which include alterations in gene transcription, morphological and cytoskeletal changes, and growth arrest in the G 1 phase of the cell cycle. Indeed, overexpression of the ␤ subunit or loss of the ␣ subunit leads to mating even in the absence of pheromone or receptor (13,17,25,36,39,53).A property of signal-response systems in general, and of G-protein-coupled receptors in particular, is that prolonged stimulation often results in a loss of responsiveness over time (desensitization) (23). The molecular basis for this phenomenon has been extensively characterized for vertebrate G-protein-coupled receptors (2, 32) and has also been described for S. cerevisiae (3, 8-10, 12, 16, 19, 27, 33, 37, 40, 41, 47). Despite the profound physiological and morphological changes that yeast cells undergo in preparation for mating, cells that fail to mate become desensitized to the...

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“…Bar1 is a highly specific aspartyl-protease10, that is diffusible11 and mostly found in the culture medium12, with only a small fraction remaining cell-wall associated13. Although production of Bar1 is further induced by α-factor14, it is already secreted by non-stimulated MAT a cells1215. An early study by Jackson and Hartwell has shown that Bar1 can enhance mating on a solid surface by improving partner discrimination16.…”

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confidence: 99%

Sensory input attenuation allows predictive sexual response in yeast

et al. 2016

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Animals are known to adjust their sexual behaviour depending on mate competition. Here we report similar regulation for mating behaviour in a sexual unicellular eukaryote, the budding yeast Saccharomyces cerevisiae. We demonstrate that pheromone-based communication between the two mating types, coupled to input attenuation by recipient cells, enables yeast to robustly monitor relative mate abundance (sex ratio) within a mixed population and to adjust their commitment to sexual reproduction in proportion to their estimated chances of successful mating. The mechanism of sex-ratio sensing relies on the diffusible peptidase Bar1, which is known to degrade the pheromone signal produced by mating partners. We further show that such a response to sexual competition within a population can optimize the fitness trade-off between the costs and benefits of mating response induction. Our study thus provides an adaptive explanation for the known molecular mechanism of pheromone degradation in yeast.

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Characterization of the Bar Proteinase, An Extracellular Enzyme from the Yeast Saccharomyces Cerevisiae

Cited by 27 publications

References 18 publications

α-Pheromone-Induced “Shmooing” and Gene Regulation Require White-Opaque Switching during Candida albicans Mating

α-Pheromone-Induced “Shmooing” and Gene Regulation Require White-Opaque Switching during Candida albicans Mating

Inhibition of G-Protein Signaling by Dominant Gain-of-Function Mutations in Sst2p, a Pheromone Desensitization Factor in Saccharomyces cerevisiae

Sensory input attenuation allows predictive sexual response in yeast

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