The steroidal analog GW707 activates the SREBP pathway through disruption of intracellular cholesterol trafficking

J Lipid Res. 2004 Feb;45(2):223-31. doi: 10.1194/jlr.M300409-JLR200. Epub 2003 Nov 16.

Abstract

Recently, a new class of lipid-lowering agents has been described that upregulate LDL receptor (LDLr) activity. These agents are proposed to activate sterol-regulated gene expression through binding to the sterol regulatory element binding protein (SREBP) cleavage-activating protein (SCAP). Here, we show that the steroidal LDLr upregulator, GW707, induces accumulation of lysosomal free cholesterol and inhibits LDL-stimulated cholesterol esterification, similar to that observed in U18666A-treated cells and in Niemann-Pick type C1 (NPC1) mutants. Moreover, we demonstrate that induction of the NPC-like phenotype by GW707 is independent of SCAP function. We find that treatment with GW707 does not increase SREBP-dependent gene expression above that observed in lipoprotein-starved cells. Rather, we show that the apparent increase in SREBP-dependent activity in GW707-treated cells is attributable to a failure to appropriately suppress sterol-regulated gene expression, as has been shown previously for U18666A-treated cells and NPC mutant fibroblasts. We further demonstrate that cells treated with either GW707 or U18666A fail to appropriately generate 27-hydroxycholesterol in response to LDL cholesterol. Taken together, these findings support a mechanism in which GW707 exerts its hypolipidemic effects through disruption of late endosomal/lysosomal sterol trafficking and subsequent stimulation of LDLr activity.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Androstenes / chemistry
  • Androstenes / pharmacology
  • Animals
  • Biological Transport / drug effects
  • CCAAT-Enhancer-Binding Proteins / genetics
  • CCAAT-Enhancer-Binding Proteins / metabolism*
  • COS Cells / cytology
  • Cholesterol / metabolism*
  • Cholesterol, LDL / metabolism
  • Cricetinae
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism*
  • Enzyme Inhibitors / chemistry
  • Enzyme Inhibitors / pharmacology
  • Gene Expression Regulation, Enzymologic / drug effects
  • Luciferases / genetics
  • Luciferases / metabolism
  • Mutation
  • Niemann-Pick Diseases / metabolism
  • Promoter Regions, Genetic / genetics
  • Receptors, LDL / antagonists & inhibitors
  • Receptors, LDL / metabolism
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism
  • Signal Transduction / drug effects*
  • Signal Transduction / genetics
  • Steroids / pharmacology*
  • Sterol Regulatory Element Binding Protein 1
  • Transcription Factors*

Substances

  • Androstenes
  • CCAAT-Enhancer-Binding Proteins
  • Cholesterol, LDL
  • DNA-Binding Proteins
  • Enzyme Inhibitors
  • GW 707
  • Receptors, LDL
  • Recombinant Proteins
  • Steroids
  • Sterol Regulatory Element Binding Protein 1
  • Transcription Factors
  • 3-beta-(2-(diethylamino)ethoxy)androst-5-en-17-one
  • Cholesterol
  • Luciferases