Sterol-induced dislocation of 3-hydroxy-3-methylglutaryl coenzyme A reductase from membranes of permeabilized cells

Rania Elsabrouty, Youngah Jo, Tammy T. Dinh, Russell A. DeBose-Boyd

Research output: Contribution to journalArticlepeer-review

24 Scopus citations


The polytopic endoplasmic reticulum (ER)-localized enzyme 3-hydroxy-3-methylglutaryl CoA reductase catalyzes a rate-limiting step in the synthesis of cholesterol and non-sterol isoprenoids. Excess sterols cause the reductase to bind to ER membrane proteins called Insig-1 and Insig-2, which are carriers for the ubiquitin ligases gp78 and Trc8. The resulting gp78/Trc8-mediated ubiquitination of reductase marks it for recognition by VCP/p97, an ATPase that mediates subsequent dislocation of reductase from ER membranes into the cytosol for proteasomal degradation. Here we report that in vitro additions of the oxysterol 25-hydroxycholesterol (25-HC), exogenous cytosol, and ATP trigger dislocation of ubiquit-inated and full-length forms of reductase from membranes of permeabilized cells. In addition, the sterol-regulated reaction requires the action of Insigs, is stimulated by reagents that replace 25-HC in accelerating reductase degradation in intact cells, and is augmented by the nonsterol isoprenoid geranylgeraniol. Finally, pharmacologic inhibition of deubiquitinating enzymes markedly enhances sterol-dependent ubiquitination of reductase in membranes of permeabilized cells, leading to enhanced dislocation of the enzyme. Considered together, these results establish permeabilized cells as a viable system in which to elucidate mechanisms for postubiquitination steps in sterol-accelerated degradation of reductase.

Original languageEnglish (US)
Pages (from-to)3300-3308
Number of pages9
JournalMolecular biology of the cell
Issue number21
StatePublished - Nov 1 2013

ASJC Scopus subject areas

  • Molecular Biology
  • Cell Biology


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