CHOLESTEROL TRANSPORT FROM PLASMA MEMBRANES TO INTRACELLULAR MEMBRANES IS INHIBITED BY 3-BETA-[2-(DIETHYLAMINO)ETHOXY]ANDROST-5-EN-17-ONE

A1 Journal article (refereed)


Internal Authors/Editors


Publication Details

List of Authors: HÄRMÄLÄ AS, PÖRN MI, MATTJUS P, SLOTTE JP
Publication year: 1994
Journal: BIOCHIMICA ET BIOPHYSICA ACTA-LIPIDS AND LIPID METABOLISM
Journal acronym: BBA-LIPID LIPID MET
Volume number: 1211
Issue number: 3
Start page: 317
End page: 325
Number of pages: 9
ISSN: 0005-2760


Abstract

The compound U18666A (3beta-[2-(diethylamino)ethoxylandrost-5-en-17-one) has been shown to inhibit the cellular transfer of low-density lipoprotein-derived cholesterol from lysosomes to plasma membranes (Liscum and Faust (1989) J. Biol. Chem. 264, 11796-806). We have in this study examined the effects of U18666A on cholesterol translocation from plasma membranes to intracellular membranes. Translocation of plasma membrane cholesterol was induced by degradation of plasma membrane sphingomyelin. The sphingomyelinase-induced activation of the acyl-CoA cholesterol acyl transferase (ACAT) reaction was completely inhibited in a dose-dependent manner by U18666A, both in cultured human skin fibroblasts and baby hamster kidney cells. Half-maximal inhibition (within 60 min) was obtained with 0.5-1 mug/ml of U18666A. A time-course study indicated that the onset of inhibition was rapid (within 10-15 min), and reversible if U18666A was removed from the incubation mixture. Using a cholesterol oxidase assay, we observed that the extent of plasma membrane cholesterol translocation in sphingomyelinase-treated HSF cells was significantly lowered in the presence of U18666A (at 3 mug/ml). The effect of U18666A on cholesterol translocation was also fully reversible when the drug was withdrawn. In mouse Leydig tumor cells, labeled to constant specific activity with [H-3]cholesterol, the compound U18666A inhibited in a dose-dependent manner the cyclic AMP-stimulated secretion of [H-3]steroid hormones. The effects seen with compound U18666A appeared to be specific for this molecule, since another hydrophobic amine, imipramine, did not in our experiments affect cholesterol translocation or ACAT activation. Since different cell types display sensitivity to U18666A in various intracellular cholesterol transfer processes, they appear to have a common U18666A-sensitive regulatory mechanism.


Keywords

CHOLESTEROL ESTERIFICATION, CHOLESTEROL TRANSLOCATION, FIBROBLAST, (HUMAN), LEYDIG CELL, LIPID TRANSFER, (MOUSE), STEROID HORMONE, U18666A

Last updated on 2019-17-10 at 04:27