Sterol regulatory element binding protein-mediated effect of fluvastatin on cytosolic 3-hydroxy-3-methylglutaryl-coenzyme A synthase transcription.
The effects of acute treatment with fluvastatin, a hypocholesteremic drug, on the mRNA levels of several regulatory enzymes of cholesterogenesis and of the LDL receptor were determined in rat liver. Fluvastatin increased the hepatic mRNA levels for HMG-CoA reductase up to 12-fold in 5 weeks of treatment at a daily dose of 6. 3 mg/kg. The effect was less marked in cytosolic HMG-CoA synthase, farnesyl-PP synthase, squalene synthetase, and LDL receptor. SREBP-2 mRNA levels were also increased, but SREBP-1 were not. De novo synthesis of cholesterol in several cultured cells was reduced by increasing concentrations of fluvastatin, and the IC(50) values of fluvastatin in HepG2, CV-1, and CHO cells were respectively 0.01, 0. 05, and 0.1 microM. When CHO cells stably transfected with a chimeric gene composed of the promoter of cytosolic HMG-CoA synthase and the CAT gene as a reporter were incubated with fluvastatin, the CAT gene was overexpressed, an effect which was similar to the cotransfection with the processed form of SREBP-1a. Both ALLN and fluvastatin increased the transcriptional activity of cytosolic HMG-CoA synthase. Mutation in either SRE or NF-Y boxes abolished the increase in transcriptional rate caused by fluvastatin in the promoter of cytosolic HMG-CoA synthase. These results indicate that the increase in transcriptional activity in the HMG-CoA synthase gene attributable to fluvastatin is a consequence of the activation of the proteolytic cleavage of SREBPs by reduced levels of intracellular cholesterol.
Mascaró
C
C
Department of Biochemistry and Molecular Biology, University of Barcelona, Barcelona, E-08028, Spain.
Ortiz
J A
JA
Ramos
M M
MM
Haro
D
D
Hegardt
F G
FG
D000818:Animals; D022762:CCAAT-Enhancer-Binding Proteins; D016466:CHO Cells; D002460:Cell Line; D015500:Chloramphenicol O-Acetyltransferase / Q000235:genetics; D006224:Cricetinae; D003600:Cytosol / Q000201:enzymology; D017931:DNA Primers; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005229:Fatty Acids, Monounsaturated / Q000494:pharmacology*; D000077340:Fluvastatin; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects*; D006801:Humans; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors / Q000494:pharmacology*; D006904:Hydroxymethylglutaryl-CoA Synthase / Q000235:genetics*; D007211:Indoles / Q000494:pharmacology*; D008099:Liver / Q000201:enzymology; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic / Q000187:drug effects; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D051780:Sterol Regulatory Element Binding Protein 1; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects* / Q000502:physiology; D015533:Transcriptional Activation / Q000187:drug effects; D014162:Transfection; D014407:Tumor Cells, Cultured
D022762:CCAAT-Enhancer-Binding Proteins; D017931:DNA Primers; D004268:DNA-Binding Proteins; D005229:Fatty Acids, Monounsaturated; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D007211:Indoles; D009687:Nuclear Proteins; D011993:Recombinant Fusion Proteins; C497387:SREBF1 protein, human; C497389:Srebf1 protein, rat; D051780:Sterol Regulatory Element Binding Protein 1; D014157:Transcription Factors; D000077340:Fluvastatin; D015500:Chloramphenicol O-Acetyltransferase; D006904:Hydroxymethylglutaryl-CoA Synthase