The long range objective of the proposed research is to understand the regulation of cholesterol biosynthesis and in particular to determine the mechanism involved in the hormonal and dietary regulation of 3-hydroxy-3-methylglutaryl coenzyme A reductase, the enzyme which catalyzes the rate-limiting reaction of cholesterol biosynthesis. The rate of cholesterol biosynthesis is one of several factors contributing to the regulation serum cholesterol levels. Elevated serum cholesterol is a significant risk factor in the development of vascular diseases. In this proposal, we seek to determine the extent to which changes in 1) enzyme quantity 2) rates of enzyme synthesis and degradation and 3) mRNA levels for HMG-CoA reductase contribute to various hormonal and dietary changes in HMG-CoA reductase activity. Of particular interest are the changes due to thyroid hormones and insulin. The methodology to be used will include immunotitration, immunoblotting, in vitro translation using a rabbit reticulocyte lysate system, immunoprecipitation and enzyme purification. We also plan to investigate certain properties of native HMG-CoA reductase. These include intracellular location of the reductase by immunoelectron microscopy, isolation of native reductase by immuno affinity chromatography and determination of the subunit and overall molecular weight, amino acid composition, whether it is synthesized as a proenzyme, whether it is glycoslated, its Kms for substrates etc.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL018094-11
Application #
3335552
Study Section
Physiological Chemistry Study Section (PC)
Project Start
1978-05-01
Project End
1989-04-30
Budget Start
1985-05-01
Budget End
1986-04-30
Support Year
11
Fiscal Year
1985
Total Cost
Indirect Cost
Name
University of South Florida
Department
Type
Schools of Medicine
DUNS #
City
Tampa
State
FL
Country
United States
Zip Code
33612
Li, Hai; Chen, Frank; Shang, Quan et al. (2005) FXR-activating ligands inhibit rabbit ASBT expression via FXR-SHP-FTF cascade. Am J Physiol Gastrointest Liver Physiol 288:G60-6
Xu, Guorong; Li, Hai; Pan, Lu-Xing et al. (2003) FXR-mediated down-regulation of CYP7A1 dominates LXRalpha in long-term cholesterol-fed NZW rabbits. J Lipid Res 44:1956-62
Xu, Guorong; Pan, Lu-xing; Erickson, Sandra K et al. (2002) Removal of the bile acid pool upregulates cholesterol 7alpha-hydroxylase by deactivating FXR in rabbits. J Lipid Res 43:45-50
Xu, Guorong; Pan, Lu-Xing; Li, Hai et al. (2002) Regulation of the farnesoid X receptor (FXR) by bile acid flux in rabbits. J Biol Chem 277:50491-6
Xu, G; Salen, G; Shneider, B L et al. (2001) Cholecystectomy prevents expansion of the bile acid pool and inhibition of cholesterol 7alpha-hydroxylase in rabbits fed cholesterol. J Lipid Res 42:1438-43
Xu, G; Salen, G; Shefer, S et al. (2001) Plant stanol fatty acid esters inhibit cholesterol absorption and hepatic hydroxymethyl glutaryl coenzyme A reductase activity to reduce plasma levels in rabbits. Metabolism 50:1106-12
Xu, G; Shneider, B L; Shefer, S et al. (2000) Ileal bile acid transport regulates bile acid pool, synthesis, and plasma cholesterol levels differently in cholesterol-fed rats and rabbits. J Lipid Res 41:298-304
Xu, G; Salen, G; Shefer, S et al. (1999) Increasing dietary cholesterol induces different regulation of classic and alternative bile acid synthesis. J Clin Invest 103:89-95
Xu, G; Salen, G; Shefer, S et al. (1998) Regulation of classic and alternative bile acid synthesis in hypercholesterolemic rabbits: effects of cholesterol feeding and bile acid depletion. J Lipid Res 39:1608-15
Xu, G; Servatius, R J; Shefer, S et al. (1998) Relationship between abnormal cholesterol synthesis and retarded learning in rats. Metabolism 47:878-82

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