Phosphorylation of the glycerol 3‐phosphate acyltransferase Gpt2 regulates the timing of TAG mobilization upon growth resumption
Notice bibliographique
Résumé
Glycerol‐3‐phosphate acyltransferases (GPATs) catalyze the first step of glycerol‐3‐phosphate acylation at the sn‐1 position producing lyso‐phosphatidic acid. This is the committed and rate limiting step in de‐novo synthesis of phosphatidic acid, the key intermediate in the glycerophospholipids and triacylglycerols (TAG) biosynthetic pathways. Two GPATs have been identified in S cerevisiae , Gpt2 and Sct1. Gpt2 (but not Sct1) becomes essential when cells are grown with oleic acid as the only carbon source. While oleic acid induced large accumulation of lipid droplets (LDs) in wild‐type cells, cells lacking GPT2 failed to accumulate these storage compartments of TAG and other neutral lipids. This lead to a growth defect and significant reduction of cell viability. We were intrigued by the fact that the intracellular distribution of Gpt2 and its phosphorylation status changed under these growth conditions compared to growth on glucose. We identified several phosphoresidues in Gpt2 by mass spectrometry analysis, localized to a serine rich region in the carboxy‐terminus of the protein. To investigate the role of phosphorylation in the regulation of Gpt2, the phosphorylation status of the protein was manipulated by introducing Ser to Ala or to Asp mutations in the GPT2 locus. Importantly, all phosphorylation mutants were expressed at physiological levels and could support life in the absence of Sct1, indicating these mutants are functional. During characterization studies of these mutants, we have discovered that changes in the phosphorylation status of Gpt2 affect its ER distribution, with the protein concentrating at points of contact with lipid droplets in actively growing cells. Staining of neutral lipids with BODIPY™ 493/503 or Nile red, indicated that specific serine to alanine mutations result in larger lipid droplets compare to those in wild type cells. We determined that this phenotype was indeed accompanied by a significant increase in TAG levels, mostly notorious during exponential growth. The differences in LD size and TAG accumulation became milder during stationary phase. SDS‐PAGE analysis of wild type Gpt2 indicated that the phosphorylation pattern of the protein changes in stationary phase, with the appearance of a faster migrating band that resembles that observed for the S to A mutants. Interestingly, this second band vanishes upon growth resumption, coinciding with TAG mobilization and lipolysis. Microscopy inspection of S to A phosphomutant strains showed a clear delay in LD size reduction up to 5 hours after resuspension of 5‐days stationary phase cells in fresh medium. This was also accompanied by a delay in TAG consumption. These results highlight the role of Gpt2 in coordinating synthesis and glycerolipid turnover in response to nutrients. Altogether, it appears that phosphorylation regulates Gpt2 interaction with lipid droplets, allowing TAG mobilization upon growth resumption from a quiescent state. Support or Funding Information This work has been financially supported by NSERC (to V.Z. and B.S.) and the Austrian Science Fund (FWF; Project P21251 to K.A.)
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
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 | 0,001 | 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) | 0,001 | 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 ».