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

Authors: Stark, R  Pasquel, F  Turcu, A  Pongratz, RL  Roden, M  Cline, GW  Shulman, GI  Kibbey, RG 
Citation: Stark R, etal., J Biol Chem. 2009 Sep 25;284(39):26578-90. doi: 10.1074/jbc.M109.011775. Epub 2009 Jul 27.
Pubmed: (View Article at PubMed) PMID:19635791
DOI: Full-text: DOI:10.1074/jbc.M109.011775

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.

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CRRD Object Information
CRRD ID: 7242950
Created: 2013-04-29
Species: All species
Last Modified: 2013-04-29
Status: ACTIVE



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RGD is funded by grant HL64541 from the National Heart, Lung, and Blood Institute on behalf of the NIH.