title: Generation of C-terminally truncated amyloid-beta peptides is dependent on gamma-secretase activity.
abstract: Aberrant production of amyloid-beta peptides by processing of the beta-amyloid precursor protein leads to the formation of characteristic extracellular protein deposits which are thought to be the cause of Alzheimer's disease. Therefore, inhibiting the key enzymes responsible for amyloid-beta peptide generation, beta- and gamma-secretase may offer an opportunity to intervene with the progression of the disease. In human brain and cell culture systems a heterogeneous population of amyloid-beta peptides with various truncations is detected and at present, it is unclear how they are produced. We have used a combination of surface enhanced laser desorption/ionization time-of-flight mass spectrometry (SELDI-TOF MS) and a specific inhibitor of gamma-secretase to investigate whether the production of all amyloid-beta peptide species requires the action of gamma-secretase. Using this approach, we demonstrate that the production of all truncated amyloid-beta peptides except those released by the action of the nonamyloidogenic alpha-secretase enzyme or potentially beta-site betaAPP cleaving enzyme 2 depends on gamma-secretase activity. This indicates that none of these peptides are generated by a separate enzyme entity and a specific inhibitor of the gamma-secretase enzyme should havethe potential to block the generation of all amyloidogenicpeptides. Furthermore in the presence of gamma-secretase inhibitors, the observation of increased cleavage of the membrane-bound betaAPP C-terminal fragment C99 by alpha-secretase suggests that during its trafficking C99 encounters compartments in which alpha-secretase activity resides.
authors.affiliation: Department of Biochemistry & Molecular Biology, Merck Sharp & Dohme Research Laboratories, Harlow, Essex, UK. dirk_beher@merck.com
authors.forename: Dirk
authors.initials: D
authors.lastname: Beher
authors.forename: Jonathan D J
authors.initials: JD
authors.lastname: Wrigley
authors.forename: Andrew P
authors.initials: AP
authors.lastname: Owens
authors.forename: Mark S
authors.initials: MS
authors.lastname: Shearman
mesh_terms: D000544:Alzheimer Disease / Q000378:metabolism*; D000595:Amino Acid Sequence; D053829:Amyloid Precursor Protein Secretases; D016229:Amyloid beta-Peptides / Q000737:chemistry / Q000378:metabolism*; D016564:Amyloid beta-Protein Precursor / Q000235:genetics / Q000378:metabolism; D000911:Antibodies, Monoclonal / Q000737:chemistry; D000918:Antibody Specificity; D016282:Aspartic Acid Endopeptidases; D002460:Cell Line; D017077:Culture Media, Conditioned / Q000737:chemistry / Q000378:metabolism; D010450:Endopeptidases / Q000187:drug effects* / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000494:pharmacology*; D005464:Fluorobenzenes / Q000494:pharmacology; D006801:Humans; D007668:Kidney / Q000166:cytology / Q000378:metabolism; D013058:Mass Spectrometry; D008666:Metalloendopeptidases / Q000037:antagonists & inhibitors; D008969:Molecular Sequence Data; D009447:Neuroblastoma / Q000378:metabolism; D010421:Pentanoic Acids / Q000494:pharmacology; D010446:Peptide Fragments / Q000032:analysis / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D010455:Peptides; D010649:Phenylalanine / Q000031:analogs & derivatives* / Q000494:pharmacology; D011994:Recombinant Proteins; D013876:Thiophenes / Q000494:pharmacology; D014162:Transfection
chemical_list: C464588:1,2(S)-(2(S)-(2-(3,5-difluorophenyl)acetylamino)propionylamino)-4-methylpentanoic acid methyl ester; D016229:Amyloid beta-Peptides; D016564:Amyloid beta-Protein Precursor; D000911:Antibodies, Monoclonal; D017077:Culture Media, Conditioned; D004791:Enzyme Inhibitors; D005464:Fluorobenzenes; C432344:MW167; D010421:Pentanoic Acids; D010446:Peptide Fragments; D010455:Peptides; D011994:Recombinant Proteins; C120368:SPA4CT protein, recombinant; D013876:Thiophenes; D010649:Phenylalanine; C080985:batimastat; D053829:Amyloid Precursor Protein Secretases; D010450:Endopeptidases; D016282:Aspartic Acid Endopeptidases; C509280:BACE1 protein, human; D008666:Metalloendopeptidases