Selected non-steroidal anti-inflammatory drugs and their derivatives target gamma-secretase at a novel site. Evidence for an allosteric mechanism.
Gamma-secretase is a multi-component enzyme complex that performs an intramembranous cleavage, releasing amyloid-beta (Abeta) peptides from processing intermediates of the beta-amyloid precursor protein. Because Abeta peptides are thought to be causative for Alzheimer's disease, inhibiting gamma-secretase represents a potential treatment for this neurodegenerative condition. Whereas inhibitors directed at the active center of gamma-secretase inhibit the cleavage of all its substrates, certain non-steroidal antiinflammatory drugs (NSAIDs) have been shown to selectively reduce the production of the more amyloidogenic Abeta(1-42) peptide without inhibiting alternative cleavages. In contrast to the majority of previous studies, however, we demonstrate that in cell-free systems the mode of action of selected NSAIDs and their derivatives, depending on the concentrations used, can either be classified as modulatory or inhibitory. At modulatory concentrations, a selective and, with respect to the substrate, noncompetitive inhibition of Abeta(1-42) production was observed. At inhibitory concentrations, on the other hand, biochemical readouts reminiscent of a nonselective gamma-secretase inhibition were obtained. When these compounds were analyzed for their ability to displace a radiolabeled, transition-state analog inhibitor from solubilized enzyme, noncompetitive antagonism was observed. The allosteric nature of radioligand displacement suggests that NSAID-like inhibitors change the conformation of the gamma-secretase enzyme complex by binding to a novel site, which is discrete from the binding site for transition-state analogs and therefore distinct from the catalytic center. Consequently, drug discovery efforts aimed at this site may identify novel allosteric inhibitors that could benefit from a wider window for inhibition of gamma (42)-cleavage over alternative cleavages in the beta-amyloid precursor protein and, more importantly, alternative substrates.
Department of Molecular and Cellular Neuroscience, Merck Sharp & Dohme Research Laboratories, The Neuroscience Research Centre, Terlings Park, Harlow, Essex CM20 2QR, UK. dirk_beher@merck.com
Dirk
D
Beher
Earl E
EE
Clarke
Jonathan D J
JD
Wrigley
Agnes C L
AC
Martin
Alan
A
Nadin
Ian
I
Churcher
Mark S
MS
Shearman
D000494:Allosteric Regulation; D053829:Amyloid Precursor Protein Secretases; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology*; D001665:Binding Sites; D010450:Endopeptidases / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*; D005480:Flurbiprofen / Q000494:pharmacology; D007700:Kinetics; D008024:Ligands; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism; D013467:Sulindac / Q000494:pharmacology
D000894:Anti-Inflammatory Agents, Non-Steroidal; D008024:Ligands; D010446:Peptide Fragments; D013467:Sulindac; D005480:Flurbiprofen; D053829:Amyloid Precursor Protein Secretases; D010450:Endopeptidases