Apolipoprotein A-I directly interacts with amyloid precursor protein and inhibits A beta aggregation and toxicity

Biochemistry. 2001 Mar 27;40(12):3553-60. doi: 10.1021/bi002186k.

Abstract

Amyloid precursor protein (APP) is the source of the neurotoxic amyloid beta (Abeta) peptide associated with Alzheimer's disease. Apolipoprotein A-I (apoA-I), a constituent of high-density lipoprotein complexes, was identified by a yeast two-hybrid system as a strong and specific binding partner of full-length APP (APPfl). This association between apoA-I and APPfl was localized to the extracellular domain of APP (APPextra). Furthermore, the interaction between apoA-I and APPfl was confirmed by coprecipitation using recombinant epitope-tagged APPextra and purified apoA-I. Several functional domains have been identified in APPextra, and we focused on a possible interaction between apoA-1 and the pathologically important Abeta peptide, because APPextra contains the nontransmembrane domain of Abeta. The binding between apoA-I and Abeta was saturable (K(d) = 6 nM), specific, and reversible. APPextra also competed with apoA-I for binding to Abeta. Direct evidence for this interaction was obtained by the formation of an SDS-resistant Abeta-apoA-I complex in polyacrylamide gels. Competitive experiments with apolipoprotein E (isoforms E2 and E4) showed that apoA-I had a higher binding affinity for Abeta. We also found that apoA-I inhibited the beta-sheet formation of Abeta with a mean inhibitory concentration close to that of alpha2-macroglobulin. Finally, we demonstrated that apoA-I attenuated Abeta-induced cytotoxicity. These results suggest apoA-I binds to at least one extracellular domain of APP and has a functional role in controlling Abeta aggregation and toxicity.

Publication types

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

MeSH terms

  • Amyloid beta-Peptides / antagonists & inhibitors*
  • Amyloid beta-Peptides / metabolism
  • Amyloid beta-Peptides / toxicity*
  • Amyloid beta-Protein Precursor / genetics
  • Amyloid beta-Protein Precursor / metabolism*
  • Animals
  • Apolipoprotein A-I / metabolism*
  • Apolipoprotein A-I / pharmacology*
  • Enzyme-Linked Immunosorbent Assay
  • Extracellular Space / metabolism
  • Humans
  • Mutagenesis, Site-Directed
  • Oxidation-Reduction
  • PC12 Cells / drug effects
  • PC12 Cells / metabolism
  • Protein Structure, Tertiary / genetics
  • Rats
  • Sodium Dodecyl Sulfate
  • Tetrazolium Salts / metabolism
  • Thiazoles / metabolism
  • Two-Hybrid System Techniques

Substances

  • Amyloid beta-Peptides
  • Amyloid beta-Protein Precursor
  • Apolipoprotein A-I
  • Tetrazolium Salts
  • Thiazoles
  • Sodium Dodecyl Sulfate
  • thiazolyl blue