title: Distinct mechanisms by mutant presenilin 1 and 2 leading to increased intracellular levels of amyloid beta-protein 42 in Chinese hamster ovary cells.
abstract: To characterize the properties of presenilin (PS) 1- and PS2-associated gamma-secretases, we established stable transfectants overexpressing amyloid precursor protein and wild-type (wt) or a number of mutant (mt) PS1 or PS2. Quantification of the intracellular amyloid beta-protein (Abeta) levels in mtPS1 and mtPS2 cell lines revealed the presence of two subtypes. One group consists of N141I, M239V, and T122P mutations of the PS2 gene and homologous mutations of PS1, N135D and M233T. These mutations led to an increase in the intracellular Abeta42 levels and a concomitant decrease in the intracellular Abeta40 levels. A cell-free assay for Abeta production using the membranes prepared from these transfectants exhibited predominant cleavage at position Abeta42 with marginal production of Abeta40. The other group consists of M146L, H163R, and G384A mutations of PS1, leading only to an increase in the intracellular Abeta42 levels. While the intracellular Abeta levels in M146L cells were consistent with the results from cell-free Abeta production, H163R and G384A cells showed significant discrepancies between the intracellular Abeta levels and cell-free Abeta production. Thus, all the mtPS1/2 examined here result in increases in the intracellular Abeta42 levels. This suggests that the underlying mechanisms for this shared phenotype may be diverse.
authors.affiliation: Department of Neuropathology, Faculty of Medicine, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: Yue
authors.initials: Y
authors.lastname: Qi
authors.forename: Maho
authors.initials: M
authors.lastname: Morishima-Kawashima
authors.forename: Toru
authors.initials: T
authors.lastname: Sato
authors.forename: Rie
authors.initials: R
authors.lastname: Mitsumori
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Ihara
mesh_terms: D019943:Amino Acid Substitution / Q000235:genetics; D053829:Amyloid Precursor Protein Secretases; D016229:Amyloid beta-Peptides / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000378:metabolism*; D000818:Animals; D001216:Asparagine / Q000235:genetics; D001224:Aspartic Acid / Q000235:genetics; D016282:Aspartic Acid Endopeptidases; D016466:CHO Cells; D002219:Carbamates / Q000494:pharmacology; D002460:Cell Line; D002474:Cell-Free System / Q000378:metabolism; D006224:Cricetinae; D003470:Culture Media / Q000378:metabolism; D004151:Dipeptides / Q000494:pharmacology; D010450:Endopeptidases / Q000378:metabolism; D006801:Humans; D007424:Intracellular Fluid / Q000378:metabolism*; D007532:Isoleucine / Q000235:genetics; D008565:Membrane Proteins / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D008715:Methionine / Q000235:genetics; D016297:Mutagenesis, Site-Directed; D010446:Peptide Fragments / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000378:metabolism*; D053764:Presenilin-1; D053766:Presenilin-2; D015842:Serine Proteinase Inhibitors / Q000494:pharmacology; D013912:Threonine / Q000235:genetics; D014162:Transfection; D015854:Up-Regulation / Q000235:genetics*; D014633:Valine / Q000235:genetics
chemical_list: D016229:Amyloid beta-Peptides; D002219:Carbamates; D003470:Culture Media; D004151:Dipeptides; C410009:L 685458; D008565:Membrane Proteins; C508853:PSEN1 protein, human; C508861:PSEN2 protein, human; D010446:Peptide Fragments; D053764:Presenilin-1; D053766:Presenilin-2; D015842:Serine Proteinase Inhibitors; C078592:amyloid beta-protein (1-40); C075222:amyloid beta-protein (1-42); D007532:Isoleucine; D013912:Threonine; D001224:Aspartic Acid; D001216:Asparagine; D008715:Methionine; D053829:Amyloid Precursor Protein Secretases; D010450:Endopeptidases; D016282:Aspartic Acid Endopeptidases; C509280:BACE1 protein, human; D014633:Valine