Two Transmembrane Aspartates in presenilin-1 Required for Presenilin Endoproteolysis and Gamma-Secretase Activity

Nature. 1999 Apr 8;398(6727):513-7. doi: 10.1038/19077.

Abstract

Accumulation of the amyloid-beta protein (Abeta) in the cerebral cortex is an early and invariant event in the pathogenesis of Alzheimer's disease. The final step in the generation of Abeta from the beta-amyloid precursor protein is an apparently intramembranous proteolysis by the elusive gamma-secretase(s). The most common cause of familial Alzheimer's disease is mutation of the genes encoding presenilins 1 and 2, which alters gamma-secretase activity to increase the production of the highly amyloidogenic Abeta42 isoform. Moreover, deletion of presenilin-1 in mice greatly reduces gamma-secretase activity, indicating that presenilin-1 mediates most of this proteolytic event. Here we report that mutation of either of two conserved transmembrane (TM) aspartate residues in presenilin-1, Asp 257 (in TM6) and Asp 385 (in TM7), substantially reduces Abeta production and increases the amounts of the carboxy-terminal fragments of beta-amyloid precursor protein that are the substrates of gamma-secretase. We observed these effects in three different cell lines as well as in cell-free microsomes. Either of the Asp --> Ala mutations also prevented the normal endoproteolysis of presenilin-1 in the TM6 --> TM7 cytoplasmic loop. In a functional presenilin-1 variant (carrying a deletion in exon 9) that is associated with familial Alzheimer's disease and which does not require this cleavage, the Asp 385 --> Ala mutation still inhibited gamma-secretase activity. Our results indicate that the two transmembrane aspartate residues are critical for both presenilin-1 endoproteolysis and gamma-secretase activity, and suggest that presenilin 1 is either a unique diaspartyl cofactor for gamma-secretase or is itself gamma-secretase, an autoactivated intramembranous aspartyl protease.

Publication types

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

MeSH terms

  • Alzheimer Disease / metabolism
  • Amyloid Precursor Protein Secretases
  • Amyloid beta-Peptides / metabolism*
  • Amyloid beta-Protein Precursor / metabolism
  • Animals
  • Aspartic Acid / metabolism*
  • Aspartic Acid Endopeptidases / metabolism
  • CHO Cells
  • COS Cells
  • Cell Line
  • Cell Membrane / metabolism
  • Cell-Free System
  • Coenzymes / metabolism
  • Cricetinae
  • Electrochemistry
  • Endopeptidases / metabolism*
  • Exons
  • Humans
  • Membrane Proteins / chemistry
  • Membrane Proteins / genetics
  • Membrane Proteins / metabolism*
  • Microsomes / metabolism
  • Mutagenesis, Site-Directed
  • Peptide Fragments / metabolism
  • Presenilin-1
  • Protein Folding
  • Recombinant Proteins / metabolism
  • Transfection

Substances

  • Amyloid beta-Peptides
  • Amyloid beta-Protein Precursor
  • Coenzymes
  • Membrane Proteins
  • PSEN1 protein, human
  • Peptide Fragments
  • Presenilin-1
  • Recombinant Proteins
  • Aspartic Acid
  • Amyloid Precursor Protein Secretases
  • Endopeptidases
  • Aspartic Acid Endopeptidases
  • BACE1 protein, human