Acidification and glucocorticoids independently regulate branched-chain alpha-ketoacid dehydrogenase subunit genes.
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.
Wang
X
X
Renal Division, Emory University School of Medicine, Atlanta, Georgia 30322, USA.
Chinsky
J M
JM
Costeas
P A
PA
Price
S R
SR
D042942:3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide); D000818:Animals; D002460:Cell Line; D003907:Dexamethasone / Q000494:pharmacology*; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects / Q000502:physiology*; D005938:Glucocorticoids / Q000494:pharmacology*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007658:Ketone Oxidoreductases / Q000235:genetics*; D008156:Luciferases / Q000235:genetics; D008163:Luminescent Measurements; D051379:Mice; D009097:Multienzyme Complexes / Q000235:genetics*; D016328:NF-kappa B / Q000378:metabolism; D011401:Promoter Regions, Genetic; D021122:Protein Subunits; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D014162:Transfection
D005938:Glucocorticoids; D009097:Multienzyme Complexes; D016328:NF-kappa B; D021122:Protein Subunits; D011993:Recombinant Fusion Proteins; D003907:Dexamethasone; D008156:Luciferases; D007658:Ketone Oxidoreductases; D042942:3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide)