Bexarotene Binds to the Amyloid Precursor Protein Transmembrane Domain, Alters Its α-Helical Conformation, and Inhibits γ-Secretase Nonselectively in Liposomes

ACS Chem Neurosci. 2018 Jul 18;9(7):1702-1713. doi: 10.1021/acschemneuro.8b00068. Epub 2018 May 11.


Bexarotene is a pleiotropic molecule that has been proposed as an amyloid-β (Aβ)-lowering drug for the treatment of Alzheimer's disease (AD). It acts by upregulation of an apolipoprotein E (apoE)-mediated Aβ clearance mechanism. However, whether bexarotene induces removal of Aβ plaques in mouse models of AD has been controversial. Here, we show by NMR and CD spectroscopy that bexarotene directly interacts with and stabilizes the transmembrane domain α-helix of the amyloid precursor protein (APP) in a region where cholesterol binds. This effect is not mediated by changes in membrane lipid packing, as bexarotene does not share with cholesterol the property of inducing phospholipid condensation. Bexarotene inhibited the intramembrane cleavage by γ-secretase of the APP C-terminal fragment C99 to release Aβ in cell-free assays of the reconstituted enzyme in liposomes, but not in cells, and only at very high micromolar concentrations. Surprisingly, in vitro, bexarotene also inhibited the cleavage of Notch1, another major γ-secretase substrate, demonstrating that its inhibition of γ-secretase is not substrate specific and not mediated by acting via the cholesterol binding site of C99. Our data suggest that bexarotene is a pleiotropic molecule that interfere with Aβ metabolism through multiple mechanisms.

Keywords: 2H NMR; CD spectroscopy; cholesterol-protein interaction; intramembrane proteolysis; order parameter; γ-secretase cleavage.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amyloid Precursor Protein Secretases / antagonists & inhibitors*
  • Amyloid Precursor Protein Secretases / metabolism
  • Amyloid beta-Protein Precursor / metabolism*
  • Bexarotene / chemistry
  • Bexarotene / pharmacology*
  • Cholesterol / metabolism
  • HEK293 Cells
  • Humans
  • Liposomes / metabolism*
  • Molecular Structure
  • Neuroprotective Agents / chemistry
  • Neuroprotective Agents / pharmacology*
  • Phosphatidylcholines / chemistry
  • Protein Conformation, alpha-Helical
  • Protein Domains
  • Receptor, Notch1 / metabolism
  • Static Electricity


  • Amyloid beta-Protein Precursor
  • Liposomes
  • Neuroprotective Agents
  • Phosphatidylcholines
  • Receptor, Notch1
  • Cholesterol
  • Bexarotene
  • Amyloid Precursor Protein Secretases
  • 1-palmitoyl-2-oleoylphosphatidylcholine