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Self-acetylation at the active site of phosphoenolpyruvate carboxykinase (PCK1) controls enzyme activity.

ABSTRACT: Acetylation is known to regulate the activity of cytosolic phosphoenolpyruvate carboxykinase (PCK1), a key enzyme in gluconeogenesis, by promoting the reverse reaction of the enzyme (converting phosphoenolpyruvate to oxaloacetate). It is also known that the histone acetyltransferase p300 can induce PCK1 acetylation in cells, but whether that is a direct or indirect function was not known. Here we initially set out to determine whether p300 can acetylate directly PCK1 in vitro. We report that p300 weakly acetylates PCK1, but surprisingly, using several techniques including protein crystallization, mass spectrometry, isothermal titration calorimetry, saturation-transfer difference nuclear magnetic resonance and molecular docking, we found that PCK1 is also able to acetylate itself using acetyl-CoA independently of p300. This reaction yielded an acetylated recombinant PCK1 with a 3-fold decrease in k_cat without changes in K_m for all substrates. Acetylation stoichiometry was determined for 14 residues, including residues lining the active site. Structural and kinetic analyses determined that site-directed acetylation of K244, located inside the active site, altered this site and rendered the enzyme inactive. In addition, we found that acetyl-CoA binding to the active site is specific and metal dependent. Our findings provide direct evidence for acetyl-CoA binding and chemical reaction with the active site of PCK1 and suggest a newly discovered regulatory mechanism of PCK1 during metabolic stress.

SUBMITTER: Latorre-Muro P

PROVIDER: S-EPMC7948413 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Dynamic Acetylation of Phosphoenolpyruvate Carboxykinase Toggles Enzyme Activity between Gluconeogenic and Anaplerotic Reactions.

Project description:Cytosolic phosphoenolpyruvate carboxykinase (PCK1) is considered a gluconeogenic enzyme; however, its metabolic functions and regulatory mechanisms beyond gluconeogenesis are poorly understood. Here, we describe that dynamic acetylation of PCK1 interconverts the enzyme between gluconeogenic and anaplerotic activities. Under high glucose, p300-dependent hyperacetylation of PCK1 did not lead to protein degradation but instead increased the ability of PCK1 to perform the anaplerotic reaction, converting phosphoenolpyruvate to oxaloacetate. Lys91 acetylation destabilizes the active site of PCK1 and favors the reverse reaction. At low energy input, we demonstrate that SIRT1 deacetylates PCK1 and fully restores the gluconeogenic ability of PCK1. Additionally, we found that GSK3?-mediated phosphorylation of PCK1 decreases acetylation and increases ubiquitination. Biochemical evidence suggests that serine phosphorylation adjacent to Lys91 stimulates SIRT1-dependent deacetylation of PCK1. This work reveals an unexpected capacity of hyperacetylated PCK1 to promote anaplerotic activity, and the intersection of post-translational control of PCK1 involving acetylation, phosphorylation, and ubiquitination.

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Project description:The aim of this study was to investigate the role of the cytosolic form of phosphoenolpyruvate carboxykinase (Pck1) in the development of insulin resistance. Previous studies have shown that the roles of Pck1 in white adipose tissue (WAT) in glyceroneogenesis and reesterification of free fatty acids (FFA) to generate triglyceride are vital for the prevention of diabetes. We hypothesized that insulin resistance develops when dysregulation of Pck1 occurs in the triglyceride/fatty acid cycle, which regulates lipid synthesis and transport between adipose tissue and the liver. We examined this by analyzing mice with a deletion of the PPARgamma binding site in the promoter of Pck1 (PPARE(-/-)). This mutation reduced the fasting Pck1 mRNA expression in WAT in brown adipose tissue (BAT). To analyze insulin resistance, we performed hyperinsulinemic-euglycemic glucose clamp analyses. PPARE(-/-) mice were profoundly insulin resistant and had more FFA and glycerol released during the hyperinsulinemic-euglycemic clamp compared with wild-type mice (WT). Finally, we analyzed insulin secretion in isolated islets. We found a 2-fold increase in insulin secretion in the PPARE(-/-) mice at 16.7 mM glucose. Thus, the PPARE site in the Pck1 promoter is essential for maintenance of lipid metabolism and glucose homeostasis and disease prevention.

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Neddylation of phosphoenolpyruvate carboxykinase 1 controls glucose metabolism

Project description:Neddylation is a post-translational mechanism that adds a ubiquitin-like protein, namely neural precursor cell expressed developmentally down-regulated protein 8, to target proteins, with yet-unknown consequences. Here we show in mice that neddylation in liver is modulated by nutrient availability. Inhibition of neddylation in mouse liver (either pharmacologically or genetically) reduces gluconeogenic capacity and the hyperglycemic actions of counterregulatory hormones (glucagon, adrenaline and glucocorticoids). Further, people with obesity and type 2 diabetes (compared to people with obesity and normoglycemia) display elevated hepatic neddylation levels that correlate positively with fasting glucose levels. Mechanistically, we determined that fasting or caloric restriction of mice leads to neddylation of phosphoenolpyruvate carboxykinase 1 (PCK1) at three lysine residues—K278, K342 and K387. PCK1 is a key control point for gluconeogenesis regulation that can be post-translationally modified by acetylation and phosphorylation, but to date no modifications are known to affect its gluconeogenic capacity. Of note, we find that mutating the three PCK1 lysines that are neddylated reduces its gluconeogenic activity rate. Molecular dynamics simulations show that neddylation of PCK1 could re-position two loops surrounding the catalytic center into an open configuration, rendering the catalytic center more accessible. Our study reveals that neddylation of PCK1 provides a finely-tuned mechanism of controlling glucose metabolism by linking whole nutrient availability to metabolic homeostasis.

2023-10-08 | PXD043054 | Pride

Phosphoenolpyruvate Carboxykinase, a Key Enzyme That Controls Blood Glucose, Is a Target of Retinoic Acid Receptor-Related Orphan Receptor ?.

Project description:Phosphoenolpyruvate carboxykinase (PEPCK) catalyzes a committed and rate-limiting step in hepatic gluconeogenesis, and its activity is tightly regulated to maintain blood glucose levels within normal limits. PEPCK activity is primarily regulated through hormonal control of gene transcription. Transcription is additionally regulated via a cAMP response unit, which includes a cAMP response element and four binding sites for CCAAT/enhancer-binding protein (C/EBP). Notably, the cAMP response unit also contains a putative response element for retinoic acid receptor-related orphan receptor ? (ROR?). In this paper, we characterize the effect of the ROR? response element on cAMP-induced transcription. Electrophoresis mobility shift assay indicates that ROR? binds this response element in a sequence-specific manner. Furthermore, luciferase reporter assays indicate that ROR? interacts with C/EBP at the PEPCK promoter to synergistically enhance transcription. We also found that cAMP-induced transcription depends in part on ROR? and its response element. In addition, we show that suppression of ROR? by siRNA significantly decreased PEPCK transcription. Finally, we found that a ROR? antagonist inhibits hepatic gluconeogenesis in an in vitro glucose production assay. Taken together, the data strongly suggest that PEPCK is a direct ROR? target. These results define possible new roles for ROR? in hepatic gluconeogenesis.

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O-GlcNAcylation mediates the control of cytosolic phosphoenolpyruvate carboxykinase activity via Pgc1?.

Project description:PGC1? is a coactivator of many transcription factors and cytosolic phosphoenolpyruvate carboxykinase (PCK1) is a key enzyme for gluconeogenesis. PGC1? interacts with the transcription factor PPAR? to stimulate PCK1 expression and thus de novo glucose synthesis. These proteins are not only important for central energy metabolism but also for supplying intermediates for other metabolic pathways, including lipidogenesis and protein synthesis and might therefore be important factors in the ethiopathogenesis of metabolic disorders like diabetes but also in other pathologies like cancer. Since polymorphisms in these proteins have been related to some phenotypic traits in animals like pigs and PGC1? G482S polymorphism increases fat deposition in humans, we have investigated the molecular basis of such effects focusing on a commonly studied polymorphism in pig Pgc1?, which changes a cysteine at position 430 (WT) of the protein to a serine (C430S). Biochemical analyses show that Pgc1? WT stimulates higher expression of human PCK1 in HEK293T and HepG2 cells. Paradoxically, Pgc1? WT is less stable than Pgc1? p.C430S in HEK293T cells. However, the study of different post-translational modifications shows a higher O-GlcNAcylation level of Pgc1? p.C430S. This higher O-GlcNAcylation level significantly decreases the interaction between Pgc1? and PPAR? demonstrating the importance of post-translational glycosylation of PGC1? in the regulation of PCK1 activity. This, furthermore, could explain at least in part the observed epistatic effects between PGC1? and PCK1 in pigs.

| S-EPMC5482481 | biostudies-literature

Phosphoenolpyruvate cycling via mitochondrial phosphoenolpyruvate carboxykinase links anaplerosis and mitochondrial GTP with insulin secretion.

Project description:Pancreatic beta-cells couple the oxidation of glucose to the secretion of insulin. Apart from the canonical K(ATP)-dependent glucose-stimulated insulin secretion (GSIS), there are important K(ATP)-independent mechanisms involving both anaplerosis and mitochondrial GTP (mtGTP). How mtGTP that is trapped within the mitochondrial matrix regulates the cytosolic calcium increases that drive GSIS remains a mystery. Here we have investigated whether the mitochondrial isoform of phosphoenolpyruvate carboxykinase (PEPCK-M) is the GTPase linking hydrolysis of mtGTP made by succinyl-CoA synthetase (SCS-GTP) to an anaplerotic pathway producing phosphoenolpyruvate (PEP). Although cytosolic PEPCK (PEPCK-C) is absent, PEPCK-M message and protein were detected in INS-1 832/13 cells, rat islets, and mouse islets. PEPCK enzymatic activity is half that of primary hepatocytes and is localized exclusively to the mitochondria. Novel (13)C-labeling strategies in INS-1 832/13 cells and islets measured substantial contribution of PEPCK-M to the synthesis of PEP. As high as 30% of PEP in INS-1 832/13 cells and 41% of PEP in rat islets came from PEPCK-M. The contribution of PEPCK-M to overall PEP synthesis more than tripled with glucose stimulation. Silencing the PEPCK-M gene completely inhibited GSIS underscoring its central role in mitochondrial metabolism-mediated insulin secretion. Given that mtGTP synthesized by SCS-GTP is an indicator of TCA flux that is crucial for GSIS, PEPCK-M is a strong candidate to link mtGTP synthesis with insulin release through anaplerotic PEP cycling.

| S-EPMC2785346 | biostudies-literature

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