Abstract
Western blot analysis of 3T3-L1 adipocyte proteins using an anti-C/EBPalpha antibody detected a 24kD polypeptide in addition to the expected 42 and 30kD isoforms of C/EBPalpha. Mass spectrometric sequencing of the protein following its purification by HPLC and preparative 2D gel electrophoresis identified it as glutathione S-transferase zeta/maleylacetoacetate isomerase (GSTzeta/MAAI). Expression of GSTzeta/MAAI mRNA and protein was induced during the terminal phase of adipogenesis in 3T3-L1 preadipocytes. Ectopic expression of PPARgamma2 in NIH-3T3 fibroblasts exposed to insulin and troglitazone-induced perilipin production, but was incapable of activating GSTzeta/MAAI unless C/EBPalpha was also expressed. Similarly, ectopic expression of C/EBPalpha in PPARgamma +/- or PPARgamma -/- MEFs demonstrated that the C/EBPalpha-dependent induction of GSTzeta/MAAI production was dependent on expression of endogenous PPARgamma. These data suggest a role for GSTzeta/MAAI in mature adipocytes that may be responsive to the thiazolidinedione class of insulin sensitizing PPARgamma ligands.
Publication types
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Research Support, N.I.H., Extramural
MeSH terms
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3T3-L1 Cells
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Adipocytes / cytology
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Adipocytes / enzymology*
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Adipocytes / metabolism
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Animals
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Antioxidants / metabolism
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Blotting, Western
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CCAAT-Enhancer-Binding Protein-alpha / metabolism*
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Cell Differentiation
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Cells, Cultured
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Chromatography, High Pressure Liquid
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DNA, Complementary / metabolism
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Electrophoresis, Gel, Two-Dimensional
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Fibroblasts / cytology
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Fibroblasts / enzymology*
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Gene Expression Regulation, Enzymologic*
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Genetic Vectors
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Glutathione Transferase / biosynthesis*
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Glutathione Transferase / metabolism
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Ligands
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Lipid Metabolism
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Mass Spectrometry
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Mice
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Mice, Transgenic
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PPAR gamma / metabolism
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Peroxisome Proliferator-Activated Receptors / metabolism
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Plasmids / metabolism
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Protein Isoforms
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Protein Structure, Tertiary
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RNA, Messenger / metabolism
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Reverse Transcriptase Polymerase Chain Reaction
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Time Factors
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cis-trans-Isomerases / metabolism*
Substances
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Antioxidants
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CCAAT-Enhancer-Binding Protein-alpha
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DNA, Complementary
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Ligands
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PPAR gamma
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Peroxisome Proliferator-Activated Receptors
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Protein Isoforms
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RNA, Messenger
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Gstz1 protein, mouse
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Glutathione Transferase
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cis-trans-Isomerases
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maleylacetoacetate isomerase