scholarly journals Mating in Saccharomyces cerevisiae: The Role of the Pheromone Signal Transduction Pathway in the Chemotropic Response to Pheromone

Genetics ◽  
1997 ◽  
Vol 147 (1) ◽  
pp. 19-32 ◽  
Author(s):  
Kathrin Schrick ◽  
Barbara Garvik ◽  
Leland H Hartwell
Keyword(s):  
Signal Transduction ◽  
Map Kinase ◽  
Transcriptional Activation ◽  
Signal Transduction Pathway ◽  
Transduction Pathway ◽  
Wild Type ◽  
Mating Partner ◽  
Map Kinase Cascade ◽  
Kinase Cascade ◽  
Wild Type Control

Abstract The mating process in yeast has two distinct aspects. One is the induction and activation of proteins required for cell fusion in response to a pheromone signal; the other is chemotropism, i.e., detection of a pheromone gradient and construction of a fusion site available to the signaling cell. To determine whether components of the signal transduction pathway necessary for transcriptional activation also play a role in chemotropism, we examined strains with null mutations in components of the signal transduction pathway for diploid formation, prezygote formation and the chemotropic process of mating partner discrimination when transcription was induced downstream of the mutation. Cells mutant for components of the mitogen-activated protein (MAP) kinase cascade (ste5, ste20, ste11, ste7 or fus3 kss1) formed diploids at a frequency 1% that of the wild-type control, but formed prezygotes as efficiently as the wild-type control and showed good mating partner discrimination, suggesting that the MAP kinase cascade is not essential for chemotropism. In contrast, cells mutant for the receptor (ste2) or the β or γ subunit (ste4 and stel8) of the G protein were extremely defective in both diploid and prezygote formation and discriminated poorly between signaling and nonsignaling mating partners, implying that these components are important for chemotropism.

scholarly journals Activation of an MAP kinase cascade leads to Sir3p hyperphosphorylation and strengthens transcriptional silencing.

1996 ◽  
Vol 135 (3) ◽  
pp. 571-583 ◽  
Author(s):  
E M Stone ◽  
L Pillus
Keyword(s):  
Signal Transduction ◽  
Map Kinase ◽  
Transcriptional Repression ◽  
Transcriptional Control ◽  
Signal Transduction Pathway ◽  
Transcriptional Silencing ◽  
G1 Arrest ◽  
Map Kinase Cascade ◽  
Mitogen Activated Protein ◽  
Kinase Cascade

During cell division and growth, the nucleus and chromosomes are remodeled for DNA replication and cell type-specific transcriptional control. The yeast silencing protein Sir3p functions in both chromosome structure and in transcriptional regulation. Specifically, Sir3p is critical for the maintenance of telomere structure and for transcriptional repression at both the silent mating-type loci and telomeres. We demonstrate that Sir3p becomes hyperphosphorylated in response to mating pheromone, heat shock, and starvation. Cells exposed to pheromone arrest in G1 of the cell cycle, yet G1 arrest is neither necessary nor sufficient for pheromone-induced Sir3p hyperphosphorylation. Rather, hyperphosphorylation of Sir3p requires the mitogen-activated protein (MAP) kinase pathway genes STE11, STE7, FUS3/KSS1, and STE12, indicating that an intact signal transduction pathway is crucial for this Sir3p phosphorylation event. Constitutive activation of the pheromone-response MAP kinase cascade in an STE11-4 strain leads to hyperphosphorylation of Sir3p and increased Sir3p-dependent transcriptional silencing at telomeres. Regulated phosphorylation of Sir3p may thus be a mechanistically significant means for modulating silencing. Together, these observations suggest a novel role for MAP kinase signal transduction in coordinating chromatin structure and nuclear organization for transcriptional silencing.

scholarly journals Mapping of a Yeast G Protein βγ Signaling Interaction

Genetics ◽  
1998 ◽  
Vol 150 (4) ◽  
pp. 1407-1417 ◽  
Author(s):  
Simon J Dowell ◽  
Anne L Bishop ◽  
Susan L Dyos ◽  
Andrew J Brown ◽  
Malcolm S Whiteway
Keyword(s):  
Signal Transduction ◽  
Map Kinase ◽  
G Protein ◽  
Coiled Coil ◽  
Receptor Activation ◽  
Temperature Sensitive ◽  
Hydrophobic Residues ◽  
Map Kinase Cascade ◽  
Kinase Cascade

Abstract The mating pathway of Saccharomyces cerevisiae is widely used as a model system for G protein-coupled receptor-mediated signal transduction. Following receptor activation by the binding of mating pheromones, G protein βγ subunits transmit the signal to a MAP kinase cascade, which involves interaction of Gβ (Ste4p) with the MAP kinase scaffold protein Ste5p. Here, we identify residues in Ste4p required for the interaction with Ste5p. These residues define a new signaling interface close to the Ste20p binding site within the Gβγ coiled-coil. Ste4p mutants defective in the Ste5p interaction interact efficiently with Gpa1p (Gα) and Ste18p (Gγ) but cannot function in signal transduction because cells expressing these mutants are sterile. Ste4 L65S is temperature-sensitive for its interaction with Ste5p, and also for signaling. We have identified a Ste5p mutant (L196A) that displays a synthetic interaction defect with Ste4 L65S, providing strong evidence that Ste4p and Ste5p interact directly in vivo through an interface that involves hydrophobic residues. The correlation between disruption of the Ste4p-Ste5p interaction and sterility confirms the importance of this interaction in signal transduction. Identification of the Gβγ coiled-coil in Ste5p binding may set a precedent for Gβγ-effector interactions in more complex organisms.

The Mak2 MAP kinase signal transduction pathway is required for pathogenicity in Stagonospora nodorum

2005 ◽  
Vol 48 (1) ◽  
pp. 60-68 ◽  
Author(s):  
Peter S. Solomon ◽  
Ormonde D. C. Waters ◽  
Joanne Simmonds ◽  
Richard M. Cooper ◽  
Richard P. Oliver
Keyword(s):  
Signal Transduction ◽  
Map Kinase ◽  
Signal Transduction Pathway ◽  
Stagonospora Nodorum ◽  
Transduction Pathway

scholarly journals Activation of MK5/PRAK by the atypical MAP kinase ERK3 defines a novel signal transduction pathway

2004 ◽  
Vol 23 (24) ◽  
pp. 4780-4791 ◽  
Author(s):  
Ole-Morten Seternes ◽  
Theresa Mikalsen ◽  
Bjarne Johansen ◽  
Espen Michaelsen ◽  
Chris G Armstrong ◽  
...  
Keyword(s):  
Signal Transduction ◽  
Map Kinase ◽  
Signal Transduction Pathway ◽  
Transduction Pathway

Rho5p downregulates the yeast cell integrity pathway

2002 ◽  
Vol 115 (15) ◽  
pp. 3139-3148 ◽  
Author(s):  
Hans-Peter Schmitz ◽  
Stefanie Huppert ◽  
Anja Lorberg ◽  
Jürgen J. Heinisch
Keyword(s):  
Map Kinase ◽  
Signal Transduction Pathway ◽  
Eukaryotic Cell ◽  
Cell Integrity ◽  
Calcofluor White ◽  
Cell Functions ◽  
Map Kinase Cascade ◽  
Independent Functions ◽  
Dependent Signal ◽  
Kinase Cascade

The Rho family of proteins and their effectors are key regulators involved in many eukaryotic cell functions. In Saccharomyces cerevisiae the family consists of six members, Rho1p to Rho5p and Cdc42p. With the exception of Rho5p, these enzymes have been assigned different biological functions,including the regulation of polar growth, morphogenesis, actin cytoskeleton,budding and secretion. Here we show that a rho5 deletion results in an increased activity of the protein kinase C (Pkc1p)-dependent signal transduction pathway. Accordingly, the deletion shows an increased resistance to drugs such as caffeine, Calcofluor white and Congo red, which indicates activation of the pathway. In contrast, overexpression of an activated RHO5Q91H mutant renders cells more sensitive to these drugs. We conclude that Rho5p acts as an off-switch for the MAP-kinase cascade, which differentiates between MAP-kinase-dependent and -independent functions of Pkc1p. Kinetics of actin depolarisation and repolarisation after heat treatment of rho5 deletions as well as strains overexpressing the activated RHO5Q91H allele provide further evidence for such a function.

scholarly journals The Drosophila rolled locus encodes a MAP kinase required in the sevenless signal transduction pathway.

1994 ◽  
Vol 13 (7) ◽  
pp. 1628-1635 ◽  
Author(s):  
W.H. Biggs ◽  
K.H. Zavitz ◽  
B. Dickson ◽  
A. van der Straten ◽  
D. Brunner ◽  
...  
Keyword(s):  
Signal Transduction ◽  
Map Kinase ◽  
Signal Transduction Pathway ◽  
Transduction Pathway

scholarly journals Function of a Chemotaxis-Like Signal Transduction Pathway in Modulating Motility, Cell Clumping, and Cell Length in the Alphaproteobacterium Azospirillum brasilense

2008 ◽  
Vol 190 (19) ◽  
pp. 6365-6375 ◽  
Author(s):  
Amber N. Bible ◽  
Bonnie B. Stephens ◽  
Davi R. Ortega ◽  
Zhihong Xie ◽  
Gladys Alexandre
Keyword(s):  
Signal Transduction ◽  
Signal Transduction Pathway ◽  
Cell Aggregation ◽  
Cell Length ◽  
Transduction Pathway ◽  
Wild Type ◽  
Cellular Functions ◽  
Swimming Pattern ◽  
A Minor ◽  
Nutritional Imbalance

ABSTRACT A chemotaxis signal transduction pathway (hereafter called Che1) has been previously identified in the alphaproteobacterium Azospirillum brasilense. Previous experiments have demonstrated that although mutants lacking CheB and/or CheR homologs from this pathway are defective in chemotaxis, a mutant in which the entire chemotaxis pathway has been mutated displayed a chemotaxis phenotype mostly similar to that of the parent strain, suggesting that the primary function of this Che1 pathway is not the control of motility behavior. Here, we report that mutants carrying defined mutations in the cheA1 (strain AB101) and the cheY1 (strain AB102) genes and a newly constructed mutant lacking the entire operon [Δ(cheA1-cheR1)::Cm] (strain AB103) were defective, but not null, for chemotaxis and aerotaxis and had a minor defect in swimming pattern. We found that mutations in genes of the Che1 pathway affected the cell length of actively growing cells but not their growth rate. Cells of a mutant lacking functional cheB1 and cheR1 genes (strain BS104) were significantly longer than wild-type cells, whereas cells of mutants impaired in the cheA1 or cheY1 genes, as well as a mutant lacking a functional Che1 pathway, were significantly shorter than wild-type cells. Both the modest chemotaxis defects and the observed differences in cell length could be complemented by expressing the wild-type genes from a plasmid. In addition, under conditions of high aeration, cells of mutants lacking functional cheA1 or cheY1 genes or the Che1 operon formed clumps due to cell-to-cell aggregation, whereas the mutant lacking functional CheB1 and CheR1 (BS104) clumped poorly, if at all. Further analysis suggested that the nature of the exopolysaccharide produced, rather than the amount, may be involved in this behavior. Interestingly, mutants that displayed clumping behavior (lacking cheA1 or cheY1 genes or the Che1 operon) also flocculated earlier and quantitatively more than the wild-type cells, whereas the mutant lacking both CheB1 and CheR1 was delayed in flocculation. We propose that the Che1 chemotaxis-like pathway modulates the cell length as well as clumping behavior, suggesting a link between these two processes. Our data are consistent with a model in which the function of the Che1 pathway in regulating these cellular functions directly affects flocculation, a cellular differentiation process initiated under conditions of nutritional imbalance.

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