Crucial step in cholesterol homeostasis: sterols promote binding of SCAP to INSIG-1, a membrane protein that facilitates retention of SREBPs in ER

Cell. 2002 Aug 23;110(4):489-500. doi: 10.1016/s0092-8674(02)00872-3.

Abstract

Using coimmunoprecipitation and tandem mass spectrometry, we identify INSIG-1 as an ER protein that binds the sterol-sensing domain of SREBP cleavage-activating protein (SCAP) and facilitates retention of the SCAP/SREBP complex in the ER. In sterol-depleted cells, SCAP escorts SREBPs from ER to Golgi for proteolytic processing, thereby allowing SREBPs to stimulate cholesterol synthesis. Sterols induce binding of SCAP to INSIG-1, as determined by blue native-PAGE, and this is correlated with the inhibition of SCAP exit from the ER. Overexpression of INSIG-1 increases the sensitivity of cells to sterol-mediated inhibition of SREBP processing. Mutant SCAP(Y298C) fails to bind INSIG-1 and is resistant to sterol-mediated inhibition of ER exit. By facilitating sterol-dependent ER retention of SCAP, INSIG-1 plays a central role in cholesterol homeostasis.

Publication types

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

MeSH terms

  • CCAAT-Enhancer-Binding Proteins / metabolism*
  • Cell Membrane / metabolism*
  • Cell Membrane / ultrastructure
  • Cells, Cultured
  • Cholesterol / biosynthesis*
  • DNA-Binding Proteins / metabolism*
  • Endoplasmic Reticulum / metabolism*
  • Endoplasmic Reticulum / ultrastructure
  • Eukaryotic Cells / cytology
  • Eukaryotic Cells / metabolism
  • Gene Expression Regulation / physiology
  • Genetic Vectors / physiology
  • Golgi Apparatus / metabolism
  • Golgi Apparatus / ultrastructure
  • Homeostasis / genetics*
  • Humans
  • Intracellular Signaling Peptides and Proteins
  • Membrane Proteins / genetics
  • Membrane Proteins / metabolism*
  • Mutation / genetics
  • Peptide Hydrolases / metabolism
  • Protein Binding / physiology
  • Protein Structure, Tertiary / physiology
  • Protein Transport / physiology
  • Proteins / genetics
  • Proteins / metabolism*
  • Sterol Regulatory Element Binding Protein 1
  • Sterols / metabolism
  • Transcription Factors*
  • Transfection

Substances

  • CCAAT-Enhancer-Binding Proteins
  • DNA-Binding Proteins
  • INSIG1 protein, human
  • Intracellular Signaling Peptides and Proteins
  • Membrane Proteins
  • Proteins
  • SREBF1 protein, human
  • SREBP cleavage-activating protein
  • Sterol Regulatory Element Binding Protein 1
  • Sterols
  • Transcription Factors
  • Cholesterol
  • Peptide Hydrolases