title: Truncated carboxyl-terminal fragments of beta-amyloid precursor protein are processed to amyloid beta-proteins 40 and 42.
abstract: We previously showed that beta-amyloid precursor protein (APP) is cleaved not only in the middle of the membrane (gamma-cleavage) but also at novel cleavage sites close to the membrane/cytoplasmic boundary (epsilon-cleavage), releasing APP intracellular domains (AICDs) 49-99 and 50-99. To learn more about the relationship between gamma- and epsilon-cleavage, C-terminally truncated carboxyl-terminal fragments (CTFs) of APP, especially CTFs1-48 and 1-49 (the postulated products that are generated by epsilon-cleavage), were transiently expressed in CHO cells. Most importantly, the cells expressing CTF1-49 secreted predominantly amyloid beta-protein (Abeta) 40, while those expressing CTF1-48 secreted preferentially Abeta42. This supports our assumption that epsilon-cleavage precedes Alphabeta production and that preceding epsilon-cleavage determines the preference for the final Abeta species. The gamma-secretase inhibitors, L-685,458 and DAPT, suppressed Abeta production from CTF1-49. Regarding Abeta production from CTF1-48, L-685,458 suppressed it, but DAPT failed to do so. A dominant negative mutant of presenilin 1 suppressed the production of Abeta40 and 42 from both CTFs1-48 and 1-49. These data should shed significant light into the mechanism of Abeta production.
authors.affiliation: Department of Neuropathology, Faculty of Medicine, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: Satoru
authors.initials: S
authors.lastname: Funamoto
authors.forename: Maho
authors.initials: M
authors.lastname: Morishima-Kawashima
authors.forename: Yu
authors.initials: Y
authors.lastname: Tanimura
authors.forename: Naoko
authors.initials: N
authors.lastname: Hirotani
authors.forename: Takaomi C
authors.initials: TC
authors.lastname: Saido
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Ihara
mesh_terms: D000595:Amino Acid Sequence; D053829:Amyloid Precursor Protein Secretases; D016229:Amyloid beta-Peptides / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D016564:Amyloid beta-Protein Precursor / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D010450:Endopeptidases / Q000378:metabolism; D006868:Hydrolysis; D008565:Membrane Proteins / Q000737:chemistry; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D053764:Presenilin-1; D011480:Protease Inhibitors / Q000737:chemistry; D011499:Protein Processing, Post-Translational; D017384:Sequence Deletion; D013379:Substrate Specificity; D014162:Transfection
chemical_list: D016229:Amyloid beta-Peptides; D016564:Amyloid beta-Protein Precursor; D008565:Membrane Proteins; D010446:Peptide Fragments; D053764:Presenilin-1; D011480:Protease Inhibitors; C078592:amyloid beta-protein (1-40); C075222:amyloid beta-protein (1-42); D053829:Amyloid Precursor Protein Secretases; D010450:Endopeptidases