1. Acidification and glucocorticoids independently regulate branched-chain alpha-ketoacid dehydrogenase subunit genes.
- Author
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Wang X, Chinsky JM, Costeas PA, and Price SR
- Subjects
- 3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide), Animals, Cell Line, Gene Expression Regulation, Enzymologic drug effects, Humans, Luciferases genetics, Luminescent Measurements, Mice, NF-kappa B metabolism, Protein Subunits, Recombinant Fusion Proteins biosynthesis, Transfection, Dexamethasone pharmacology, Gene Expression Regulation, Enzymologic physiology, Glucocorticoids pharmacology, Hydrogen-Ion Concentration, Ketone Oxidoreductases genetics, Multienzyme Complexes genetics, Promoter Regions, Genetic
- Abstract
Acidification or glucocorticoids increase the maximal activity and subunit mRNA levels of branched chain alpha-ketoacid dehydrogenase (BCKAD) in various cell types. We examined whether these stimuli increase transcription of BCKAD subunit genes by transfecting BCKAD subunit promoter-luciferase plasmids containing the mouse E2 or human E1alpha-subunit promoter into LLC-PK(1) cells, which do not express glucocorticoid receptors, or LLC-PK(1)-GR101 cells, which we have engineered to constitutively express the glucocorticoid receptor gene. Dexamethasone or acidification increased luciferase activity in LLC-PK(1)-GR101 cells transfected with the E2 or E1alpha-minigenes; acidification augmented luciferase activity in LLC-PK(1) cells transfected with these minigenes but dexamethasone did not. A pH-responsive element in the E2 subunit promoter was mapped to a region >4.0 kb upstream of the transcription start site. Dexamethasone concurrently stimulated E2 subunit promoter activity and reduced the binding of nuclear factor-kappaB (NF-kappaB) to a site in the E2 promoter. Thus acidification and glucocorticoids independently enhance BCKAD subunit gene expression, and the glucocorticoid response in the E2 subunit involves interference with NF-kappaB, which may act as a transrepressor. more...
- Published
- 2001
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