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.

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.

Caveolin-mediated regulation of signaling along the p42/44 MAP kinase cascade in vivo

FEBS Letters ◽  
1998 ◽  
Vol 428 (3) ◽  
pp. 205-211 ◽  
Author(s):  
Jeffrey A. Engelman ◽  
Caryn Chu ◽  
Anning Lin ◽  
Hanjoong Jo ◽  
Tsuneya Ikezu ◽  
...  
Keyword(s):  
Map Kinase ◽  
Map Kinase Cascade ◽  
Kinase Cascade

scholarly journals Requirement of Pyk2 for the activation of the MAP kinase cascade induced by Ca2+ (but not by PKC or G protein) in PC12 cells

FEBS Letters ◽  
1999 ◽  
Vol 461 (3) ◽  
pp. 273-276 ◽  
Author(s):  
Rico Barsacchi ◽  
Harald Heider ◽  
Jean-Antoine Girault ◽  
Jacopo Meldolesi
Keyword(s):  
Map Kinase ◽  
G Protein ◽  
Pc12 Cells ◽  
Map Kinase Cascade ◽  
Kinase Cascade

MAPKAP kinase 2 is activated by heat shock and TNF-α: In vivo phosphorylation of small heat shock protein results from stimulation of the MAP kinase cascade

1995 ◽  
Vol 57 (2) ◽  
pp. 321-330 ◽  
Author(s):  
Katrin Engel ◽  
Annette Ahlers ◽  
Marion A. Brach ◽  
Friedhelm Herrmann ◽  
Matthias Gaestel
Keyword(s):  
Heat Shock ◽  
Heat Shock Protein ◽  
Map Kinase ◽  
Small Heat Shock Protein ◽  
Map Kinase Cascade ◽  
Tnf Α ◽  
Kinase Cascade ◽  
Stimulation Of

scholarly journals The G-Protein β Subunit GPB1 Is Required for Mating and Haploid Fruiting in Cryptococcus neoformans

2000 ◽  
Vol 20 (1) ◽  
pp. 352-362 ◽  
Author(s):  
Ping Wang ◽  
John R. Perfect ◽  
Joseph Heitman
Keyword(s):  
Map Kinase ◽  
Cryptococcus Neoformans ◽  
G Protein ◽  
Nutrient Sensing ◽  
Β Subunit ◽  
A Cells ◽  
Map Kinase Cascade ◽  
Mutant Strains ◽  
Kinase Cascade ◽  
Monokaryotic Fruiting

ABSTRACT Cryptococcus neoformans is an opportunistic fungal pathogen with a defined sexual cycle. The gene encoding a heterotrimeric G-protein β subunit, GPB1, was cloned and disrupted.gpb1 mutant strains are sterile, indicating a role for this gene in mating. GPB1 plays an active role in mediating responses to pheromones in early mating steps (conjugation tube formation and cell fusion) and signals via a mitogen-activated protein (MAP) kinase cascade in both MATα and MATa cells. The functions of GPB1 are distinct from those of the Gα protein GPA1, which functions in a nutrient-sensing cyclic AMP (cAMP) pathway required for mating, virulence factor induction, and virulence.gpb1 mutant strains are also defective in monokaryotic fruiting in response to nitrogen starvation. We show thatMATa cells stimulate monokaryotic fruiting ofMATα cells, possibly in response to mating pheromone, which may serve to disperse cells and spores to locate mating partners. In summary, the Gβ subunit GPB1 and the Gα subunit GPA1 function in distinct signaling pathways: one (GPB1) senses pheromones and regulates mating and haploid fruiting via a MAP kinase cascade, and the other (GPA1) senses nutrients and regulates mating, virulence factors, and pathogenicity via a cAMP cascade.

scholarly journals Loss of sustained Fus3p kinase activity and the G1 arrest response in cells expressing an inappropriate pheromone receptor.

1996 ◽  
Vol 16 (8) ◽  
pp. 4478-4485 ◽  
Author(s):  
A Couve ◽  
J P Hirsch
Keyword(s):  
Map Kinase ◽  
G Protein ◽  
Kinase Activity ◽  
G1 Arrest ◽  
Wild Type ◽  
Pheromone Response Pathway ◽  
Cycle Arrest ◽  
Map Kinase Cascade ◽  
Receptor Inhibition ◽  
Kinase Cascade

The yeast pheromone response pathway is mediated by two G protein-linked receptors, each of which is expressed only in its specific cell type. The STE3DAF mutation results in inappropriate expression of the a-factor receptor in MATa cells. Expression of this receptor in the inappropriate cell type confers resistance to pheromone-induced G1 arrest, a phenomenon that we have termed receptor inhibition. The ability of STE3DAF cells to cycle in the presence of pheromone was found to correlate with reduced phosphorylation of the cyclin-dependent kinase inhibitor Far1p. Measurement of Fus3p mitogen-activated protein (MAP) kinase activity in wild-type and STE3DAF cells showed that induction of Fus3p activity was the same in both strains at times of up to 1 h after pheromone treatment. However, after 2 or more hours, Fus3p activity declined in STE3DAF cells but remained high in wild-type cells. The level of inducible FUS1 RNA paralleled the changes seen in Fus3p activity. Short-term activation of the Fus3p MAP kinase is therefore sufficient for the early transcriptional induction response to pheromone, but sustained activation is required for cell cycle arrest. Escape from the cell cycle arrest response was not seen in wild-type cells treated with low doses of pheromone, indicating that receptor inhibition is not simply a result of weak signaling but rather acts selectively at late times during the response. STE3DAF was found to inhibit the pheromone response pathway at a step between the G beta subunit and Ste5p, the scaffolding protein that binds the components of the MAP kinase phosphorylation cascade. Overexpression of Ste20p, a kinase thought to act between the G protein and the MAP kinase cascade, suppressed the STE3DAF phenotype. These findings are consistent with a model in which receptor inhibition acts by blocking the signaling pathway downstream of G protein dissociation and upstream of MAP kinase cascade activation, at a step that could directly involve Ste20p.

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.

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