Elevated levels of plasma low density lipoprotein (LDL) cholesterol are important in the development of atherosclerosis and coronary heart disease. Down-regulation of LDL receptor gene expression, in response to dietary intake of saturated fats and cholesterol, leads to an increase in plasma LDL cholesterol and contributes to the development of atherosclerosis. Non-sterol signals transduced during mitogenic stimulation apparently override the normal down-regulatory effects of exogenous LDL cholesterol on LDL receptor expression. The proposed studies are focused on understanding the molecular basis whereby these non-sterol mitogenic signals regulate LDL receptor gene transcription. The hypotheses to be tested in the proposed studies are that: 1). the mechanism(s) that increase LDL receptor gene transcription with mitogenic stimulation are distinct from those involved in sterol regulation; and 2). signals transmitted by growth factors and cytokines increase LDL receptor expression in a variety of cells involved in regulation of plasma LDL cholesterol levels and metabolism of LDL cholesterol in atherosclerotic lesions. The plan of approach entails initial utilization of Jurkat cells, a continuously proliferating T lymphocyte cell line that retains mitogen responsiveness. The elements that control LDL receptor gene expression with mitogenic stimulation will be identified by electrophoretic mobility shift analysis and confirmed by transfection of wild-type and mutant fragments from the 5' flanking region of the LDL receptor gene linked to a reporter gene. Additional studies will examine whether similar regions and mechanisms determine regulation of LDL receptor gene transcription in hepatocyte, monocyte/macrophage and fibroblast cell lines. DNA sequences that are important in regulation of LDL receptor gene expression but are not associated with known nuclear factors will be further characterized by gel mobility shift analysis and DNase protection assays. The results should provide insight into the means by which LDL receptor expression is increased by activation signals, suggest mechanisms whereby plasma LDL cholesterol levels might decrease during the acute phase response and also suggest possible approaches to regulate LDL cholesterol levels therapeutically.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Research Project (R01)
Project #
5R01AI017653-13
Application #
2517166
Study Section
Metabolism Study Section (MET)
Project Start
1981-05-01
Project End
1999-08-31
Budget Start
1997-09-01
Budget End
1999-08-31
Support Year
13
Fiscal Year
1997
Total Cost
Indirect Cost
Name
University of Texas Sw Medical Center Dallas
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
City
Dallas
State
TX
Country
United States
Zip Code
75390
Makar, R S; Lipsky, P E; Cuthbert, J A (1998) Sterol-independent, sterol response element-dependent, regulation of low density lipoprotein receptor gene expression. J Lipid Res 39:1647-54
Cuthbert, J A; Lipsky, P E (1995) Suppression of the proliferation of Ras-transformed cells by fluoromevalonate, an inhibitor of mevalonate metabolism. Cancer Res 55:1732-40
Makar, R S; Lipsky, P E; Cuthbert, J A (1994) Non-sterol regulation of low density lipoprotein receptor gene expression in T cells. J Lipid Res 35:1888-95
Spady, D K; Cuthbert, J A (1992) Regulation of hepatic sterol metabolism in the rat. Parallel regulation of activity and mRNA for 7 alpha-hydroxylase but not 3-hydroxy-3-methylglutaryl-coenzyme A reductase or low density lipoprotein receptor. J Biol Chem 267:5584-91
Cuthbert, J A; Lipsky, P E (1991) A product of mevalonate proximal to isoprenoids is the source of both a necessary growth factor and an inhibitor of cell proliferation. Trans Assoc Am Physicians 104:97-106
Cuthbert, J A; Lipsky, P E (1991) Negative regulation of cell proliferation by mevalonate or one of the mevalonate phosphates. J Biol Chem 266:17966-71
Cuthbert, J A; Lipsky, P E (1990) Inhibition by 6-fluoromevalonate demonstrates that mevalonate or one of the mevalonate phosphates is necessary for lymphocyte proliferation. J Biol Chem 265:18568-75
Cuthbert, J A; Lipsky, P E (1990) Tissue-specific regulation of low density lipoprotein receptor gene expression. Trans Assoc Am Physicians 103:271-80
Cuthbert, J A; Lipsky, P E (1990) Mitogenic stimulation alters the regulation of LDL receptor gene expression in human lymphocytes. J Lipid Res 31:2067-78
Cuthbert, J A; Lipsky, P E (1989) Identification of low density lipoprotein receptor abnormalities by assaying functional receptors on proliferating lymphocytes. Arteriosclerosis 9:I43-9

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