title: p53-Dependent Aph-1 and Pen-2 anti-apoptotic phenotype requires the integrity of the gamma-secretase complex but is independent of its activity.
abstract: The presenilin-dependent gamma-secretase activity, which is responsible for the generation of amyloid beta-peptide, is a high molecular weight complex composed of at least four components, namely, presenilin-1 (or presenilin-2), nicastrin, Aph-1, and Pen-2. Previous data indicated that presenilins, which are thought to harbor the catalytic core of the complex, also control p53-dependent cell death. Whether the other components of the gamma-secretase complex could also modulate the cell death process in mammalian neurons remained to be established. Here, we examined the putative contribution of Aph-1 and Pen-2 in the control of apoptosis in TSM1 cells from a neuronal origin. We show by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling and DNA fragmentation analyses that the overexpression of Aph-1a, Aph-1b, or Pen-2 drastically lowered staurosporine-induced cellular toxicity. In support of an apoptosis rather than necrosis process, Aph-1 and Pen-2 also lower staurosporine- and etoposide-induced caspase-3 expression and diminished caspase-3 activity and poly(ADP-ribose) polymerase inactivation. The Aph-1 and Pen-2 anti-apoptotic phenotype was associated with a drastic reduction of p53 expression and activity and lowered p53 mRNA transcription. Furthermore, the Aph-1- and Pen-2-associated reduction of staurosporine-induced caspase-3 activation was fully abolished by p53 deficiency. Conversely, Aph-1a, Aph-1b, and Pen-2 gene inactivation increases both caspase-3 activity and p53 mRNA levels. Finally, we show that Aph-1 and Pen-2 did not trigger an anti-apoptotic response in cells devoid of presenilins or nicastrin, whereas the protective response was still observed in fibroblasts devoid of beta-amyloid precursor protein and amyloid precursor protein like-protein 2. Furthermore, Aph-1- and Pen-2-associated protection against staurosporine-induced caspase-3 activation was not affected by the gamma-secretase inhibitors N-[N-(3,5-difluorophenacetyl)-l-alanyl]-S-phenylglycine t-butyl ester and difluoromethylketone. Altogether, our study indicates that Aph-1 and Pen-2 trigger an anti-apoptotic response by lowering p53-dependent control of caspase-3. Our work also demonstrates that this phenotype is strictly dependent on the molecular integrity of the gamma-secretase complex but remains independent of the gamma-secretase catalytic activity.
authors.affiliation: Institut de Pharmacologie Moléculaire et Cellulaire, UMR 6097 CNRS/UNSA, Equipe labellisée, Fondation pour la Recherche Médicale, 660 Route des Lucioles, 06560 Valbonne, France.
authors.forename: Julie
authors.initials: J
authors.lastname: Dunys
authors.forename: Toshitaka
authors.initials: T
authors.lastname: Kawarai
authors.forename: Jean
authors.initials: J
authors.lastname: Sevalle
authors.forename: Virginia
authors.initials: V
authors.lastname: Dolcini
authors.forename: Peter St
authors.initials: PS
authors.lastname: George-Hyslop
authors.forename: Cristine Alves
authors.initials: CA
authors.lastname: Da Costa
authors.forename: Frédéric
authors.initials: F
authors.lastname: Checler
mesh_terms: D053829:Amyloid Precursor Protein Secretases / Q000378:metabolism*; D016229:Amyloid beta-Peptides / Q000096:biosynthesis*; D017209:Apoptosis; D053148:Caspase 3 / Q000378:metabolism; D002460:Cell Line; D010450:Endopeptidases; D004791:Enzyme Inhibitors / Q000633:toxicity; D006801:Humans; D008562:Membrane Glycoproteins / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism*; D046912:Multiprotein Complexes / Q000378:metabolism*; D010447:Peptide Hydrolases; D010641:Phenotype; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D053763:Presenilins / Q000378:metabolism; D019311:Staurosporine / Q000633:toxicity; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*
chemical_list: D016229:Amyloid beta-Peptides; D004791:Enzyme Inhibitors; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D046912:Multiprotein Complexes; C469349:PSENEN protein, human; D053763:Presenilins; D016159:Tumor Suppressor Protein p53; C413604:nicastrin protein; D011065:Poly(ADP-ribose) Polymerases; C475154:APH1A protein, human; D053829:Amyloid Precursor Protein Secretases; D010450:Endopeptidases; D010447:Peptide Hydrolases; D053148:Caspase 3; D019311:Staurosporine