Inhibiting Amyloid Precursor Protein C-terminal Cleavage Promotes an Interaction with Presenilin 1

• Published in: The Journal of biological chemistry 2000-07, Vol.275 (27), p.20794-20798
• Main Authors: Verdile, Giuseppe, Martins, Ralph N., Duthie, Monika, Holmes, Erin, St George-Hyslop, Peter H., Fraser, Paul E.
• Format: Article
• Language: English
• Subjects: Alzheimer Disease - metabolism; Ammonium Chloride - pharmacology; Amyloid beta-Protein Precursor - metabolism; Amyloid Precursor Protein Secretases; Animals; Aspartic Acid Endopeptidases; Cell Line; Centrifugation, Density Gradient; Cysteine Proteinase Inhibitors - pharmacology; Dogs; Endopeptidases - metabolism; Humans; Leupeptins - pharmacology; Membrane Proteins - metabolism; Peptide Fragments - metabolism; Precipitin Tests; Presenilin-1; Transfection
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.C000208200

Presenilin 1 (PS1) plays a pivotal role in the production of the amyloid-β protein, which is central to the pathogenesis of Alzheimer's disease. It has been demonstrated that PS1 regulates the γ-secretase proteolysis of the amyloid precursor protein (APP) C-terminal fragment (APP-C100), which is the final step in amyloid-β protein production. The mechanism and detailed pathway of this PS1 activity has yet to be fully resolved, but it may be due to a presenilin-controlled trafficking of the APP fragment or possibly an inherent PS1 proteolytic activity. We have investigated the possibility of a direct interaction of PS1 and the APP-C100 within the high molecular mass presenilin complex. However, the APP-C100 is rapidly degraded, and if it forms, then any PS1·APP complex is likely to be very transitory. To circumvent this problem, we have utilized the protease inhibitor N-acetyl-leucyl-norleucinal (LLnL) and the lysosomotropic agent NH4Cl, which inhibits the turnover of the APP-C100. Under these conditions, levels of the fragment increased appreciably, and as shown by glycerol gradient analysis, the APP-C100 shifted to a higher molecular mass complex that overlapped with PS1. Immunoprecipitation studies demonstrated that a significant population of the APP-C100 co-precipitated with PS1. These findings suggest that PS1 may mediate the shuttling of APP fragments and/or facilitate their presentation for γ-secretase cleavage through a direct interaction.