Molecular role of the Ste50 adaptor protein in regulating mating-pheromone signaling specificity in «Saccharomyces cerevisiae»
Notice bibliographique
Résumé
Living cells are continuously receiving stimuli from their external environments to bring out biological responses required for growth, maintenance and safety.Cells realize this through a network of signaling pathways that are dedicated to produce precise biological responses.Because pathways often share components, a fundamental question in the field of signal transduction is how the myriads of inputs are sensed, integrated and transduced accurately so that each elicits a specific and proper biological response.In the yeast Saccharomyces cerevisiae, three major mitogen activated protein kinase (MAPK) pathways, which control the mating process in response to pheromone, the glycerol production in response to hyperosmotic stress and the filamentous growth in response to nutrient deprivation, share a common Ste11MAP3K and an adaptor protein Ste50, which has an N-terminal SAM (sterile alpha motif) domain and a C-terminal RA (Rasassociation) domain.Ste11 and Ste50 interact through their respective SAM domains.The role of C-terminal Ste50-RA domain in conferring signaling specificity in the hyperosmolar glycerol and filamentous growth pathways has been established, however, the mechanism through which the Ste50-RA domain connects the mating pathway remains unknown.In this dissertation, I have demonstrated that RA domain of Ste50 adaptor protein uses genetically separable surfaces to differentially connect to distinct MAPK signaling pathways.Using random mutagenesis, I built and screened Ste50-RA domain mutant libraries and identified mutants with interesting phenotypes.The mutants were grouped into three classes displaying defects specific to the mating pathway, or to the HOG pathway, or to both signaling pathways.The RA domain residues involved in these different mutant classes, when mapped onto the solution structure of the folded RA domain, showed distinct structural localizations and clustering according to their phenotypic traits.Analyses with structural meta-prediction tools indicate that all these residues showed a high propensity to engage in protein-protein interactions.I further performed microscopic studies with GFP fusions of the different Ste50 alleles in cells under pheromone stimulation, and iii showed that wild type Ste50 accumulates at the polarization front of the shmoo structure, while the specifically pheromone response defective mutants are unable to form shmoos and fail to accumulate Ste50 at the polarized shmoo tip, indicating a loss of association of the ste50 mutants with the shmoo polarization complex.These results suggest that Ste50-RA domain uses differential interactions to connect different MAPK pathways to exert early layer control of signaling specificity.Subsequently, in detailed microscopic studies, I showed the dynamic cellular localization of the wild type Ste50 protein, as well as the location of the specifically-pheromone-signalingdefective Ste50 mutant protein.The mutant showed a strong defect in its dynamic cellular localization, suggesting a link between this localization and proper function of Ste50 in mating pheromone signaling.Finally, I performed a suppressor study to find genetic suppressor of the specificallypheromone-response-defective mutants.I expected that overexpressing some regulator(s) of Ste50 might identify suppressors that can compensate for the functional defects of these mutants.The genetic screen identified RIE1 as a Ste50 mutant dependent suppressor of the pheromone signaling pathway.Deleting RIE1 caused defective pheromone signaling, aberrant shmoo morphology and defective cell cycle arrest.These results suggest that RIE1 is a new component of the mating-pheromone response pathway.
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Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,003 | 0,001 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».