scholarly journals A Mep2-dependent Transcriptional Profile Links Permease Function to Gene Expression during Pseudohyphal Growth in Saccharomyces cerevisiae

2008 ◽  
Vol 19 (7) ◽  
pp. 3028-3039 ◽  
Author(s):  
Julian C. Rutherford ◽  
Gordon Chua ◽  
Timothy Hughes ◽  
Maria E. Cardenas ◽  
Joseph Heitman
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Map Kinase ◽  
Molecular Mechanisms ◽  
Nutrient Sensing ◽  
Transcriptional Profile ◽  
Regulatory Function ◽  
Pseudohyphal Growth ◽  
Epistasis Analysis ◽  
Map Kinase Pathway ◽  
Kinase Pathway

The ammonium permease Mep2 is required for the induction of pseudohyphal growth, a process in Saccharomyces cerevisiae that occurs in response to nutrient limitation. Mep2 has both a transport and a regulatory function, supporting models in which Mep2 acts as a sensor of ammonium availability. Potentially similar ammonium permease-dependent regulatory cascades operate in other fungi, and they may also function in animals via the homologous Rh proteins; however, little is known about the molecular mechanisms that mediate ammonium sensing. We show that Mep2 is localized to the cell surface during pseudohyphal growth, and it is required for both filamentous and invasive growth. Analysis of site-directed Mep2 mutants in residues lining the ammonia-conducting channel reveal separation of function alleles (transport and signaling defective; transport-proficient/signaling defective), indicating transport is necessary but not sufficient to sense ammonia. Furthermore, Mep2 overexpression enhances differentiation under normally repressive conditions and induces a transcriptional profile that is consistent with activation of the mitogen-activated protein (MAP) kinase pathway. This finding is supported by epistasis analysis establishing that the known role of the MAP kinase pathway in pseudohyphal growth is linked to Mep2 function. Together, these data strengthen the model that Mep2-like proteins are nutrient sensing transceptors that govern cellular differentiation.

Response to high osmotic conditions and elevated temperature in Saccharomyces cerevisiae is controlled by intracellular glycerol and involves coordinate activity of MAP kinase pathways

Microbiology ◽  
2003 ◽  
Vol 149 (5) ◽  
pp. 1193-1204 ◽  
Author(s):  
Iwona Wojda ◽  
Rebeca Alonso-Monge ◽  
Jan-Paul Bebelman ◽  
Willem H. Mager ◽  
Marco Siderius
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cell Wall ◽  
Osmotic Stress ◽  
Map Kinase ◽  
Growth Temperature ◽  
Wild Type ◽  
Hog Pathway ◽  
Map Kinase Pathway ◽  
Kinase Pathway ◽  
Intracellular Glycerol

In the yeast Saccharomyces cerevisiae, response to an increase in external osmolarity is mediated by the HOG (high osmolarity glycerol) MAP kinase pathway. HOG pathway mutant strains display osmosensitive phenotypes. Recently evidence has been obtained that the osmosensitivity of HOG pathway mutants is reduced during growth at elevated temperature (37 °C). A notable exception is the ste11ssk2ssk22 mutant, which displays hypersensitivity to osmotic stress at 37 °C. This paper reports that overexpression of FPS1 or GPD1 (encoding the glycerol transport facilitator and glycerol-3-phosphate dehydrogenase, respectively, and both affecting intracellular glycerol levels) reduces the hypersensitivity to osmotic stress of ste11ssk2ssk22 at 37 °C. Although in this particular HOG pathway mutant a correlation between suppression of the phenotype and glycerol content could be demonstrated, the absolute level of intracellular glycerol per se does not determine whether a strain is osmosensitive or not. Rather, evidence was obtained that the glycerol level may have an indirect effect, viz. by influencing signalling through the PKC (protein kinase C) MAP kinase pathway, which plays an important role in maintenance of cellular integrity. In order to validate the data obtained with a HOG pathway mutant strain for wild-type yeast cells, MAP kinase signalling under different growth conditions was examined in wild-type strains. PKC pathway signalling, which is manifest at elevated growth temperature by phosphorylation of MAP kinase Mpk1p, is rapidly lost when cells are shifted to high external osmolarity conditions. Expression of bck1-20 or overexpression of WSC3 in wild-type cells resulted in restoration of PKC signalling. Both PKC and HOG signalling, cell wall phenotypes and high osmotic stress responses in wild-type cells were found to be influenced by the growth temperature. The data taken together indicate the intricate interdependence of growth temperature, intracellular glycerol, cell wall structure and MAP kinase signalling in the hyperosmotic stress response of yeast.

scholarly journals Saccharomyces cerevisiae G1 Cyclins Are Differentially Involved in Invasive and Pseudohyphal Growth Independent of the Filamentation Mitogen-Activated Protein Kinase Pathway

Genetics ◽  
1999 ◽  
Vol 153 (4) ◽  
pp. 1535-1546 ◽  
Author(s):  
Jonathan D J Loeb ◽  
Tatiana A Kerentseva ◽  
Ting Pan ◽  
Marisa Sepulveda-Becerra ◽  
Haoping Liu
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Mitogen Activated Protein Kinase ◽  
Invasive Growth ◽  
Transcriptional Program ◽  
Epistasis Analysis ◽  
G1 Cyclin ◽  
Mitogen Activated Protein ◽  
Pathway Function ◽  
Map Kinase Pathway ◽  
Kinase Pathway

Abstract Several lines of evidence suggest that the morphogenetic transition from the yeast form to pseudohyphae in Saccharomyces cerevisiae may be regulated by the cyclin-dependent kinase (Cdk). To examine this hypothesis, we mutated all of the G1 cyclin genes in strains competent to form pseudohyphae. Interestingly, mutation of each G1 cyclin results in a different filamentation phenotype, varying from a significant defect in cln1/cln1 strains to enhancement of filament production in cln3/cln3 strains. cln1 cln2 double mutants are more defective in pseudohyphal development and haploid invasive growth than cln1 strains. FLO11 transcription, which correlates with the level of invasive growth, is low in cln1 cln2 mutants and high in grr1 cells (defective in proteolysis of Cln1,2), suggesting that Cln1,2/Cdks regulate the pseudohyphal transcriptional program. Epistasis analysis reveals that Cln1,2/Cdk and the filamentation MAP kinase pathway function in parallel in regulating filamentous and invasive growth. Cln1 and Cln2, but not Ste20 or Ste12, are responsible for most of the elevated FLO11 transcription in grr1 strains. Furthermore, phenotypic comparison of various filamentation mutants illustrates that cell elongation and invasion/cell-cell adhesion during filamentation are separable processes controlled by the pseudohyphal transcriptional program. Potential targets for G1 cyclin/Cdks during filamentous growth are discussed.

Response of Saccharomyces cerevisiae to severe osmotic stress: evidence for a novel activation mechanism of the HOG MAP kinase pathway

2000 ◽  
Vol 37 (2) ◽  
pp. 382-397 ◽  
Author(s):  
O. Van Wuytswinkel ◽  
V. Reiser ◽  
M. Siderius ◽  
M. C. Kelders ◽  
G. Ammerer ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Osmotic Stress ◽  
Map Kinase ◽  
Activation Mechanism ◽  
Map Kinase Pathway ◽  
Kinase Pathway

scholarly journals Activation of p38 Mitogen-Activated Protein Kinase In Vivo Selectively Induces Apoptosis of CD8+ but Not CD4+ T Cells

2000 ◽  
Vol 20 (3) ◽  
pp. 936-946 ◽  
Author(s):  
Chris Merritt ◽  
Hervé Enslen ◽  
Nicole Diehl ◽  
Dietrich Conze ◽  
Roger J. Davis ◽  
...  
Keyword(s):  
T Cells ◽  
Cell Death ◽  
T Cell ◽  
Map Kinase ◽  
Molecular Mechanisms ◽  
P38 Map Kinase ◽  
Mitogen Activated Protein ◽  
Map Kinase Pathway ◽  
Kinase Pathway

ABSTRACT CD4+ and CD8+ T cells play specific roles during an immune response. Different molecular mechanisms could regulate the proliferation, death, and effector functions of these two subsets of T cells. The p38 mitogen-activated protein (MAP) kinase pathway is induced by cytokines and environmental stress and has been associated with cell death and cytokine expression. Here we report that activation of the p38 MAP kinase pathway in vivo causes a selective loss of CD8+ T cells due to the induction of apoptosis. In contrast, activation of p38 MAP kinase does not induce CD4+T-cell death. The apoptosis of CD8+ T cells is associated with decreased expression of the antiapoptotic protein Bcl-2. Regulation of the p38 MAP kinase pathway in T cells is therefore essential for the maintenance of CD4/CD8 homeostasis in the peripheral immune system. Unlike cell death, gamma interferon production is regulated by the p38 MAP kinase pathway in both CD4+ and CD8+ T cells. Thus, specific aspects of CD4+and CD8+ T-cell function are differentially controlled by the p38 MAP kinase signaling pathway.

scholarly journals Fus3p and Kss1p Control G1 Arrest in Saccharomyces cerevisiae Through a Balance of Distinct Arrest and Proliferative Functions That Operate in Parallel With Far1p

Genetics ◽  
1999 ◽  
Vol 151 (3) ◽  
pp. 989-1004 ◽  
Author(s):  
Vera Cherkasova ◽  
David M Lyons ◽  
Elaine A Elion
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Map Kinase ◽  
Map Kinases ◽  
G1 Arrest ◽  
Multiple Functions ◽  
Map Kinase Cascade ◽  
Kinase Cascade ◽  
Map Kinase Pathway ◽  
Kinase Pathway ◽  
Cyclin Genes

AbstractIn Saccharomyces cerevisiae, mating pheromones activate two MAP kinases (MAPKs), Fus3p and Kss1p, to induce G1 arrest prior to mating. Fus3p is known to promote G1 arrest by activating Far1p, which inhibits three Clnp/Cdc28p kinases. To analyze the contribution of Fus3p and Kss1p to G1 arrest that is independent of Far1p, we constructed far1 CLN strains that undergo G1 arrest from increased activation of the mating MAP kinase pathway. We find that Fus3p and Kss1p both control G1 arrest through multiple functions that operate in parallel with Far1p. Fus3p and Kss1p together promote G1 arrest by repressing transcription of G1/S cyclin genes (CLN1, CLN2, CLB5) by a mechanism that blocks their activation by Cln3p/Cdc28p kinase. In addition, Fus3p and Kss1p counteract G1 arrest through overlapping and distinct functions. Fus3p and Kss1p together increase the expression of CLN3 and PCL2 genes that promote budding, and Kss1p inhibits the MAP kinase cascade. Strikingly, Fus3p promotes proliferation by a novel function that is not linked to reduced Ste12p activity or increased levels of Cln2p/Cdc28p kinase. Genetic analysis suggests that Fus3p promotes proliferation through activation of Mcm1p transcription factor that upregulates numerous genes in G1 phase. Thus, Fus3p and Kss1p control G1 arrest through a balance of arrest functions that inhibit the Cdc28p machinery and proliferative functions that bypass this inhibition.

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