title: Inhibiting amyloid precursor protein C-terminal cleavage promotes an interaction with presenilin 1.
abstract: Presenilin 1 (PS1) plays a pivotal role in the production of the amyloid-beta protein, which is central to the pathogenesis of Alzheimer's disease. It has been demonstrated that PS1 regulates the gamma-secretase proteolysis of the amyloid precursor protein (APP) C-terminal fragment (APP-C100), which is the final step in amyloid-beta 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 NH(4)Cl, 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 gamma-secretase cleavage through a direct interaction.
authors.affiliation: Sir James McCusker Alzheimer's Disease Research Unit and Department of Surgery, University of Western Australia, Hollywood Private Hospital, Nedlands, Western Australia 6009.
authors.forename: G
authors.initials: G
authors.lastname: Verdile
authors.forename: R N
authors.initials: RN
authors.lastname: Martins
authors.forename: M
authors.initials: M
authors.lastname: Duthie
authors.forename: E
authors.initials: E
authors.lastname: Holmes
authors.forename: P H
authors.initials: PH
authors.lastname: St George-Hyslop
authors.forename: P E
authors.initials: PE
authors.lastname: Fraser
mesh_terms: D000544:Alzheimer Disease / Q000378:metabolism; D000643:Ammonium Chloride / Q000494:pharmacology; D053829:Amyloid Precursor Protein Secretases; D016564:Amyloid beta-Protein Precursor / Q000378:metabolism*; D000818:Animals; D016282:Aspartic Acid Endopeptidases; D002460:Cell Line; D002499:Centrifugation, Density Gradient; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D004285:Dogs; D010450:Endopeptidases / Q000378:metabolism; D006801:Humans; D007976:Leupeptins / Q000494:pharmacology; D008565:Membrane Proteins / Q000378:metabolism*; D010446:Peptide Fragments / Q000378:metabolism*; D011233:Precipitin Tests; D053764:Presenilin-1; D014162:Transfection
chemical_list: D016564:Amyloid beta-Protein Precursor; D015853:Cysteine Proteinase Inhibitors; D007976:Leupeptins; D008565:Membrane Proteins; C508853:PSEN1 protein, human; D010446:Peptide Fragments; D053764:Presenilin-1; C092826:amyloid precursor protein, carboxy-terminal 100 residues; D000643:Ammonium Chloride; C063261:acetylleucyl-leucyl-norleucinal; D053829:Amyloid Precursor Protein Secretases; D010450:Endopeptidases; D016282:Aspartic Acid Endopeptidases; C509280:BACE1 protein, human