title: Longer forms of amyloid beta protein: implications for the mechanism of intramembrane cleavage by gamma-secretase.
abstract: Gamma-cleavage of beta-amyloid precursor protein (APP) in the middle of the cell membrane generates amyloid beta protein (Abeta), and epsilon-cleavage, approximately 10 residues downstream of the gamma-cleavage site, releases the APP intracellular domain (AICD). A significant link between generation of Abeta and AICD and failure to detect AICD41-99 led us to hypothesize that epsilon-cleavage generates longer Abetas, which are then processed to Abeta40/42. Using newly developed gel systems and an N-end-specific monoclonal antibody, we have identified the longer Abetas (Abeta1-43, Abeta1-45, Abeta1-46, and Abeta1-48) within the cells and in brain tissues. The production of these longer Abetas as well as Abeta40/42 is presenilin dependent and is suppressed by {1S-benzyl-4R-[1S-carbamoyl-2-phenylethylcarbamoyl-1S-3-methylbutylcarbamoyl]-2R-hydroxy-5-phenylpentyl}carbamic acid tert-butyl ester, a transition state analog inhibitor for aspartyl protease. In contrast, N-[N-(3,5-difluorophenacetyl)-L-alanyl]-S-phenylglycine t-butyl ester, a potent dipeptide gamma-secretase inhibitor, builds up Abeta1-43 and Abeta1-46 intracellularly, which was also confirmed by mass spectrometry. Notably, suppression of Abeta40 appeared to lead to an increase in Abeta43, which in turn brings an increase in Abeta46, in a dose-dependent manner. We therefore propose an alpha-helical model in which longer Abeta species generated by epsilon-cleavage is cleaved at every three residues in its carboxyl portion.
authors.affiliation: Department of Neuropathology, Faculty of Medicine, University of Tokyo, Tokyo 113-0033, Japan.
authors.forename: Yue
authors.initials: Y
authors.lastname: Qi-Takahara
authors.forename: Maho
authors.initials: M
authors.lastname: Morishima-Kawashima
authors.forename: Yu
authors.initials: Y
authors.lastname: Tanimura
authors.forename: Georgia
authors.initials: G
authors.lastname: Dolios
authors.forename: Naoko
authors.initials: N
authors.lastname: Hirotani
authors.forename: Yuko
authors.initials: Y
authors.lastname: Horikoshi
authors.forename: Fuyuki
authors.initials: F
authors.lastname: Kametani
authors.forename: Masahiro
authors.initials: M
authors.lastname: Maeda
authors.forename: Takaomi C
authors.initials: TC
authors.lastname: Saido
authors.forename: Rong
authors.initials: R
authors.lastname: Wang
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Ihara
mesh_terms: D000544:Alzheimer Disease / Q000235:genetics / Q000378:metabolism; D020816:Amino Acid Motifs; D053829:Amyloid Precursor Protein Secretases; D016229:Amyloid beta-Peptides / Q000737:chemistry* / Q000378:metabolism*; D016564:Amyloid beta-Protein Precursor / Q000378:metabolism; D000818:Animals; D016282:Aspartic Acid Endopeptidases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D001921:Brain / Q000378:metabolism; D002460:Cell Line; D006224:Cricetinae; D003412:Cricetulus; D004151:Dipeptides / Q000494:pharmacology; D010450:Endopeptidases; D006801:Humans; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D053764:Presenilin-1; D053766:Presenilin-2; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D013347:Subcellular Fractions / Q000378:metabolism
chemical_list: D016229:Amyloid beta-Peptides; D016564:Amyloid beta-Protein Precursor; D004151:Dipeptides; D008565:Membrane Proteins; C419410:N-(N-(3,5-difluorophenacetyl)alanyl)phenylglycine tert-butyl ester; C508853:PSEN1 protein, human; C508861:PSEN2 protein, human; D053764:Presenilin-1; D053766:Presenilin-2; D053829:Amyloid Precursor Protein Secretases; D010450:Endopeptidases; D016282:Aspartic Acid Endopeptidases; C509280:BACE1 protein, human; C509282:Bace1 protein, mouse