Membrane Physical Properties Regulate the Rate and Acyl Chain Specificity of One of the Steps of the Phosphatidylinositol Cycle
Notice bibliographique
Résumé
The plethora of biological functions regulated by phosphatidylinositol (PI) and its phosphorylated forms makes this lipid class one of the most important in cell physiology. The major metabolic pathway for the synthesis of this lipid class is the PI‐cycle. One of the steps of the PI‐cycle is the ATP‐dependent phosphorylation of diacylglycerol (DAG) to produce phosphatidic acid (PA), a reaction catalyzed by the epsilon isoform of diacylglycerol kinases (DGKɛ). The enzyme when assayed with mixed‐micelles exhibits a high degree of acyl chain specificity for its DAG substrate, with 1‐stearoyl‐2‐arachidonoyl glycerol (SAG) being the preferred substrate. These acyl chains are the same as those found in the lipid intermediates of the PI‐cycle, which was proposed to be in part due to the action of DGKɛ. Opposite to other metabolic cycles, steps of the PI‐cycle spans two different locations (membranes) within a cell, the plasma membrane (PM) and endoplasmic reticulum (ER), the same membranes where DGKɛ has been reported to be found. However, it is currently unknown whether DGKɛ catalyze its reaction within the PI‐cycle in the PM and/or ER. Since DGKɛ lacks a putative regulatory domain and these two membranes have several different physical and chemical properties, we hypothesized that either DGKɛ is constitutively active or it is regulated by the properties of the membrane it's bound to. To address this question we use an assay with purified DGKɛ and liposomes. This strategy allowed us to systematically vary the membrane physical and chemical properties while avoiding complications coming from other levels of regulation. In the present work we show that the rate of DGKɛ ‐ catalyzed reaction and its substrate acyl chain specificity are regulated by membrane physical properties. In a locally flat membrane (in relation to the size of the enzyme and its membrane binding platform) the enzyme works at very low basal levels without discriminating the nature of the substrate acyl chains. In these membrane structures the majority of biological negatively charged phospholipids showed an inhibitory effect on the enzyme. However, its product (PA), which is also negatively charged, exhibited the contrary effect leading to an enhancement in enzyme activity and acyl chain specificity. This result suggested a positive feedback mechanism, contrary to what is currently believed. Likewise, the presence of highly curved membranes, specifically those membrane structures bearing negative Gaussian (saddle‐point like) curvature greatly enhanced the rate of reaction as well as the enzyme substrate acyl chain specificity, which was also dependent on the degree of curvature. To sum up, our results indicate that DGKɛ is not likely to catalyze its reaction within the PI‐cycle in stable regions of either the ER or the PM, but rather at the junction between these two organelles where highly curved membrane structures have been reported and/or at PA‐enriched domains. Support or Funding Information This work was supported by the Canadian Natural Sciences and Engineering Research Council grant RGPIN‐2018‐05585. This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .
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 | 0,001 |
| 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 ».