The protease inhibitor, MG132, blocks maturation of the amyloid precursor protein Swedish mutant preventing cleavage by beta-Secretase

J Biol Chem. 2001 Feb 9;276(6):4476-84. doi: 10.1074/jbc.M008793200. Epub 2000 Nov 17.

Abstract

Amyloid (Abeta) peptides found aggregated into plaques in Alzheimer's disease are derived from the sequential cleavage of the amyloid precursor protein (APP) first by beta- and then by gamma-secretases. Peptide aldehydes, which inhibit cysteine proteases and proteasomes, reportedly block Abeta peptide secretion by interfering with gamma-secretase cleavage. Using a novel, specific, and sensitive enzyme-linked immunosorbent assay for the beta-secretase-cleaved fragment of the Swedish mutant of APP (APPSw), we determined that the peptide aldehyde, MG132, prevented beta-secretase cleavage. This block in beta-secretase cleavage was not observed with clasto-lactacystin beta-lactone and thus, cannot be attributed to proteasomal inhibition. MG132 inhibition of beta-secretase cleavage was compared with the serine protease inhibitor, 4-(2-aminoethyl)benzenesulfonyl fluoride hydrochloride (AEBSF). AEBSF inhibition of beta-secretase cleavage was immediate and did not affect alpha-secretase cleavage. With MG132, inhibition was delayed and it decreased secretion of alpha-cleaved APPSw as well. Furthermore, MG132 treatment impaired maturation of full-length APPSw. Both inhibited intracellular formation of the beta-cleaved product. These results suggest that peptide aldehydes such as MG132 have multiple effects on the maturation and processing of APP. We conclude that the MG132-induced decrease in beta-secretase cleavage of APPSw is due to a block in maturation. This is sufficient to explain the previously reported peptide aldehyde-induced decrease in Abeta peptide secretion.

Publication types

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

MeSH terms

  • Amino Acid Sequence
  • Amyloid Precursor Protein Secretases
  • Amyloid beta-Protein Precursor / chemistry
  • Amyloid beta-Protein Precursor / genetics
  • Amyloid beta-Protein Precursor / metabolism*
  • Cysteine Proteinase Inhibitors / pharmacology*
  • Endopeptidases / metabolism*
  • Enzyme-Linked Immunosorbent Assay
  • Golgi Apparatus / metabolism
  • Hydrolysis
  • Leupeptins / pharmacology*
  • Molecular Sequence Data
  • Mutation*

Substances

  • Amyloid beta-Protein Precursor
  • Cysteine Proteinase Inhibitors
  • Leupeptins
  • Amyloid Precursor Protein Secretases
  • Endopeptidases
  • benzyloxycarbonylleucyl-leucyl-leucine aldehyde