| Mitochondrial glycerol phosphate acyltransferase directs the incorporation of exogenous fatty acids into triacylglycerol. | |
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MedLine Citation:
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PMID: 11546763 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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The mitochondrial isoform of glycerol-3-phosphate acyltransferase (GPAT), the first step in glycerolipid synthesis, is up-regulated by insulin and by high carbohydrate feeding via SREBP-1c, suggesting that it plays a role in triacylglycerol synthesis. To test this hypothesis, we overexpressed mitochondrial GPAT in Chinese hamster ovary (CHO) cells. When GPAT was overexpressed 3.8-fold, triacylglycerol mass was 2.7-fold higher than in control cells. After incubation with trace [(14)C]oleate ( approximately 3 microm), control cells incorporated 4.7-fold more label into phospholipid than triacylglycerol, but GPAT-overexpressing cells incorporated equal amounts of label into phospholipid and triacylglycerol. In GPAT-overexpressing cells, the incorporation of label into phospholipid, particularly phosphatidylcholine, decreased 30%, despite normal growth rate and phospholipid content, suggesting that exogenous oleate was directed primarily toward triacylglycerol synthesis. Transiently transfected HEK293 cells that expressed a 4.4-fold increase in GPAT activity incorporated 9.7-fold more [(14)C]oleate into triacylglycerol compared with control cells, showing that the effect of GPAT overexpression was similar in two different cell types that had been transfected by different methods. When the stable, GPAT-overexpressing CHO cells were incubated with 100 microm oleate to stimulate triacylglycerol synthesis, they incorporated 1.9-fold more fatty acid into triacylglycerol than did the control cells. Confocal microscopy of CHO and HEK293 cells transfected with the GPAT-FLAG construct showed that GPAT was located correctly in mitochondria and was not present elsewhere in the cell. These studies indicate that overexpressed mitochondrial GPAT directs incorporation of exogenous fatty acid into triacylglycerol rather than phospholipid and imply that (a) mitochondrial GPAT and lysophosphatidic acid acyltransferase produce a separate pool of lysophosphatidic acid and phosphatidic acid that must be transported to the endoplasmic reticulum where the terminal enzymes of triacylglycerol synthesis are located, and (b) this pool remains relatively separate from the pool of lysophosphatidic acid and phosphatidic acid that contributes to the synthesis of the major phospholipid species. |
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Authors:
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R A Igal; S Wang; M Gonzalez-Baró; R A Coleman |
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Publication Detail:
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Type: Journal Article; Research Support, U.S. Gov't, P.H.S. Date: 2001-08-23 |
Journal Detail:
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Title: The Journal of biological chemistry Volume: 276 ISSN: 0021-9258 ISO Abbreviation: J. Biol. Chem. Publication Date: 2001 Nov |
Date Detail:
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Created Date: 2001-11-05 Completed Date: 2001-12-05 Revised Date: 2007-11-14 |
Medline Journal Info:
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Nlm Unique ID: 2985121R Medline TA: J Biol Chem Country: United States |
Other Details:
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Languages: eng Pagination: 42205-12 Citation Subset: IM |
Affiliation:
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Instituto de Investigaciones Bioquimicas de La Plata, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, CC 455, calles 60 y 120, 1900 La Plata, Argentina. |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Animals CCAAT-Enhancer-Binding Proteins / analysis CHO Cells Cricetinae DNA-Binding Proteins / analysis Fatty Acids / metabolism* Glycerol-3-Phosphate O-Acyltransferase / physiology* Mitochondria / enzymology* Oleic Acid / metabolism Receptors, Cytoplasmic and Nuclear / analysis Sterol Regulatory Element Binding Protein 1 Transcription Factors / analysis Triglycerides / biosynthesis* |
| Grant Support | |
ID/Acronym/Agency:
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DK56598/DK/NIDDK NIH HHS; TW00891/TW/FIC NIH HHS |
| Chemical | |
Reg. No./Substance:
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0/CCAAT-Enhancer-Binding Proteins; 0/DNA-Binding Proteins; 0/Fatty Acids; 0/Receptors, Cytoplasmic and Nuclear; 0/Sterol Regulatory Element Binding Protein 1; 0/Transcription Factors; 0/Triglycerides; 112-80-1/Oleic Acid; EC 2.3.1.15/Glycerol-3-Phosphate O-Acyltransferase |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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