Specific combinations of presenilins and Aph1s affect the substrate specificity and activity of γ-secretase

Biochem Biophys Res Commun. 2016 Sep 30;478(4):1751-7. doi: 10.1016/j.bbrc.2016.09.018. Epub 2016 Sep 5.

Abstract

The γ-secretase complex comprises presenilin (PS), nicastrin (NCT), anterior pharynx-defective 1 (Aph1), and presenilin enhancer 2 (Pen2). PS has two homologues, PS1 and PS2. Aph1 has two isoforms, Aph1a and Aph1b, with the former existing as two splice variants Aph1aL and Aph1aS. Each complex consists of one subunit each, resulting in six different γ-secretases. To better understand the functional differences among the γ-secretases, we reconstituted them using a yeast system and compared Notch1-cleavage and amyloid precursor protein (APP)-cleavage activities. Intriguingly, PS2/Aph1b had a clear substrate specificity: APP-Gal4, but not Notch-Gal4, was cleaved. In HEK cell lines expressing defined γ-secretase subunits, we showed that PS1/Aph1b, PS2/Aph1aL, PS2/Aph1aS and PS2/Aph1b γ-secretase produced amyloid β peptide (Aβ) with a higher Aβ42+Aβ43-to-Aβ40 (Aβ42(43)/Aβ40) ratio than the other γ-secretases. In addition, PS2/Aph1aS γ-secretase produced less Notch intracellular domain (NICD) than did the other 5 γ-secretases. Considering that the Aβ42(43)/Aβ40 ratio is relevant in the pathogenesis of Alzheimer's disease (AD), and that inhibition of Notch cleavage causes severe side effect, these results suggest that the PS2/Aph1aS γ-secretase complex is a potential therapeutic target in AD.

Keywords: Alzheimer's disease; Aβ; Notch; γ-secretase.

MeSH terms

  • Amyloid Precursor Protein Secretases / genetics
  • Amyloid Precursor Protein Secretases / metabolism*
  • Amyloid beta-Peptides / genetics
  • Amyloid beta-Peptides / metabolism*
  • Blotting, Western
  • Endopeptidases
  • HEK293 Cells
  • Humans
  • Membrane Proteins / genetics
  • Membrane Proteins / metabolism*
  • Peptide Fragments / metabolism
  • Peptide Hydrolases / genetics
  • Peptide Hydrolases / metabolism*
  • Presenilin-1 / genetics
  • Presenilin-1 / metabolism*
  • Presenilin-2 / genetics
  • Presenilin-2 / metabolism*
  • Protein Isoforms / genetics
  • Protein Isoforms / metabolism
  • Protein Subunits / genetics
  • Protein Subunits / metabolism
  • Receptors, Notch / genetics
  • Receptors, Notch / metabolism
  • Saccharomyces cerevisiae / genetics
  • Saccharomyces cerevisiae / metabolism
  • Substrate Specificity

Substances

  • Amyloid beta-Peptides
  • Membrane Proteins
  • Peptide Fragments
  • Presenilin-1
  • Presenilin-2
  • Protein Isoforms
  • Protein Subunits
  • Receptors, Notch
  • amyloid beta-protein (1-40)
  • amyloid beta-protein (1-42)
  • amyloid beta-protein (1-43)
  • APH1A protein, human
  • APH1B protein, human
  • Amyloid Precursor Protein Secretases
  • Endopeptidases
  • Peptide Hydrolases