title: The role of presenilin cofactors in the gamma-secretase complex.
abstract: Mutations in presenilin genes account for the majority of the cases of the familial form of Alzheimer's disease (FAD). Presenilin is essential for gamma-secretase activity, a proteolytic activity involved in intramembrane cleavage of Notch and beta-amyloid precursor protein (betaAPP). Cleavage of betaAPP by FAD mutant presenilin results in the overproduction of highly amyloidogenic amyloid beta42 peptides. gamma-Secretase activity requires the formation of a stable, high-molecular-mass protein complex that, in addition to the endoproteolysed fragmented form of presenilin, contains essential cofactors including nicastrin, APH-1 (refs 15-18) and PEN-2 (refs 16, 19). However, the role of each protein in complex formation and the generation of enzymatic activity is unclear. Here we show that Drosophila APH-1 (Aph-1) increases the stability of Drosophila presenilin (Psn) holoprotein in the complex. Depletion of PEN-2 by RNA interference prevents endoproteolysis of presenilin and promotes stabilization of the holoprotein in both Drosophila and mammalian cells, including primary neurons. Co-expression of Drosophila Pen-2 with Aph-1 and nicastrin increases the formation of Psn fragments as well as gamma-secretase activity. Thus, APH-1 stabilizes the presenilin holoprotein in the complex, whereas PEN-2 is required for endoproteolytic processing of presenilin and conferring gamma-secretase activity to the complex.
authors.affiliation: Department of Neuropathology and Neuroscience, Graduate School of Pharmaceutical Sciences, University of Tokyo, 7-3-1 Hongo, Bunkyoku, Tokyo 113-0033, Japan.
authors.forename: Nobumasa
authors.initials: N
authors.lastname: Takasugi
authors.forename: Taisuke
authors.initials: T
authors.lastname: Tomita
authors.forename: Ikuo
authors.initials: I
authors.lastname: Hayashi
authors.forename: Makiko
authors.initials: M
authors.lastname: Tsuruoka
authors.forename: Manabu
authors.initials: M
authors.lastname: Niimura
authors.forename: Yasuko
authors.initials: Y
authors.lastname: Takahashi
authors.forename: Gopal
authors.initials: G
authors.lastname: Thinakaran
authors.forename: Takeshi
authors.initials: T
authors.lastname: Iwatsubo
mesh_terms: D000544:Alzheimer Disease / Q000201:enzymology / Q000235:genetics / Q000378:metabolism; D053829:Amyloid Precursor Protein Secretases; D000818:Animals; D016282:Aspartic Acid Endopeptidases; D002460:Cell Line; D002478:Cells, Cultured; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000201:enzymology / Q000235:genetics / Q000378:metabolism; D010450:Endopeptidases / Q000737:chemistry / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D046911:Macromolecular Substances; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism; D010447:Peptide Hydrolases; D053764:Presenilin-1; D011499:Protein Processing, Post-Translational; D034622:RNA Interference
chemical_list: D029721:Drosophila Proteins; D046911:Macromolecular Substances; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; C508853:PSEN1 protein, human; C469349:PSENEN protein, human; C473290:Pen-2 protein, Drosophila; D053764:Presenilin-1; C413604:nicastrin protein; C475154:APH1A protein, human; D053829:Amyloid Precursor Protein Secretases; D010450:Endopeptidases; D010447:Peptide Hydrolases; D016282:Aspartic Acid Endopeptidases; C509280:BACE1 protein, human