title: Potent γ-secretase inhibitors/modulators interact with amyloid-β fibrils but do not inhibit fibrillation: a high-resolution NMR study.
abstract: Recently, γ-secretase modulators (GSM) have been shown to interact directly with the amyloid precursor protein (APP) and simultaneously inhibit the activity of the Presenilin domain of γ-secretase. A clear understanding of the molecular recognition pathways by which GSM can target both γ-secretase and Aβ precursor protein can lead to the development of more effective inhibitors. To examine whether this direct interaction with APP affects the downstream Aβ fibril formation, we chose to investigate three different molecules in this study: Sulindac sulfide, Semagacestat and E2012 from the class of generation I GSMs, γ-secretase inhibitors (GSI), and generation II GSM molecules, respectively. Firstly, through NMR based ligand titration, we identified that Sulindac sulfide and Semagacestat interact strongly with Aβ40 monomers, whereas E2012 does not. Secondly, using saturation transfer difference (STD) NMR experiments, we found that all three molecules bind equally well with Aβ40 fibrils. To determine if these interactions with the monomer/fibril lead to a viable inhibition of the fibrillation process, we designed an NMR based time-dependent assay and accurately distinguished the inhibitors from the non-inhibitors within a short period of 12h. Based on this pre-seeded fibril assay, we conclude that none of these molecules inhibit the ongoing fibrillation, rather ligands such as Semagacestat and E2012 accelerated the rate of aggregation.
authors.affiliation: Department of Biotechnology, School of Bioengineering, SRM University, Kattankolathur 603203, India.
authors.forename: Ravichandran
authors.initials: R
authors.lastname: Yesuvadian
authors.affiliation: Department of Chemistry and Biophysics, University of Michigan, Ann Arbor, MI 48109-1055, United States.
authors.forename: Janarthanan
authors.initials: J
authors.lastname: Krishnamoorthy
authors.affiliation: Department of Chemistry and Biophysics, University of Michigan, Ann Arbor, MI 48109-1055, United States. Electronic address: ramamoor@umich.edu.
authors.forename: Ayyalusamy
authors.initials: A
authors.lastname: Ramamoorthy
authors.affiliation: Department of Biophysics, Bose Institute, P-1/12 CIT Scheme VII (M), Kolkata 700054, India. Electronic address: bhunia@jcbose.ac.in.
authors.forename: Anirban
authors.initials: A
authors.lastname: Bhunia
mesh_terms: D000409:Alanine / Q000031:analogs & derivatives / Q000494:pharmacology; D000682:Amyloid / Q000737:chemistry / Q000378:metabolism; D053829:Amyloid Precursor Protein Secretases / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D016229:Amyloid beta-Peptides / Q000737:chemistry* / Q000378:metabolism*; D016564:Amyloid beta-Protein Precursor / Q000737:chemistry / Q000378:metabolism; D001381:Azepines / Q000494:pharmacology; D001665:Binding Sites; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D007700:Kinetics; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism; D010880:Piperidines / Q000494:pharmacology; D011480:Protease Inhibitors / Q000494:pharmacology*; D011487:Protein Conformation; D055503:Protein Multimerization / Q000187:drug effects; D013467:Sulindac / Q000031:analogs & derivatives / Q000494:pharmacology
chemical_list: C555019:1-(1-(4-fluorophenyl)ethyl)-3-((3-methoxy-4-(4-methyl-1H-imidazol-1-yl)phenyl)methylene)-2-piperidinone; D000682:Amyloid; D016229:Amyloid beta-Peptides; D016564:Amyloid beta-Protein Precursor; D001381:Azepines; D007093:Imidazoles; C484278:N2-((2S)-2-(3,5-difluorophenyl)-2-hydroxyethanoyl)-N1-((7S)-5-methyl-6-oxo-6,7-dihydro-5H-dibenzo(b,d)azepin-7-yl)-L-alaninamide; D010446:Peptide Fragments; D010880:Piperidines; D011480:Protease Inhibitors; C078592:amyloid beta-protein (1-40); D013467:Sulindac; C025462:sulindac sulfide; D053829:Amyloid Precursor Protein Secretases; D000409:Alanine
keywords: Abeta40; GSM; STD NMR; Sulindac sulfide NMR fibril assay