Mechanisms of cholesterol and sterol regulatory element binding protein regulation of the sterol 12alpha-hydroxylase gene (CYP8B1)

Biochemical and Biophysical Research Communications
Yizeng YangJohn Y L Chiang

Abstract

Sterol 12alpha-hydroxylase (CYP8B1) is an obligatory enzyme for the synthesis of cholic acid and regulation of liver bile acid synthesis and intestine cholesterol absorption. The present study evaluates the roles for sterol regulatory element binding proteins (SREBPs) in the regulation of the CYP8B1 gene. Cholesterol feeding of mice and rats decreased the activity of CYP8B1, contrary to the up-regulation of cholesterol 7alpha-hydroxylase (CYP7A1). Cholesterol feeding also reduced mRNA levels for SREBP-1 but not for SREBP-2 in rat livers. Cholesterol and 25-hydroxycholesterol decreased the CYP8B1/luciferase reporter activity. Co-transfection of SREBP-1a and -1c stimulated CYP8B1 promoter activity, while SREBP-2 did not have any effects. Electrophoretic mobility shift assay and mutagenesis analyses identified several functional sterol regulatory elements (SRE) and E-box motifs in the rat CYP8B1 promoter. Our results indicate that SREBP-1a and -1c enhance transcription of the CYP8B1 gene through binding to SRE. Cholesterol loading reduces SREBP-1 mRNA expression in addition to reducing functional SREBP-1 protein, and results in decreasing CYP8B1 gene transcription.

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Citations

Aug 31, 2006·Hepatology : Official Journal of the American Association for the Study of Liver Diseases·Takeshi HirayamaGerald Salen
Oct 30, 2008·Journal of Immunotoxicology·Kirsten A BakenHenk van Loveren
Oct 1, 2020·Journal of Biological Inorganic Chemistry : JBIC : a Publication of the Society of Biological Inorganic Chemistry·Xiaoxiang ZhengKaixun Huang
Jul 23, 2021·Liver Research·John Y L Chiang, Jessica M Ferrell
Jul 5, 2005·Biochimica Et Biophysica Acta·Charlotte MurphyMats Gåfvels

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