title: Caspase cleavage of exon 9 deleted presenilin-1 is an early event in apoptosis induced by calcium ionophore A 23187 in SH-SY5Y neuroblastoma cells.
abstract: Presenilins (PSs) are mutated in a majority of familial Alzheimer disease (FAD) cases. Mutated PSs may cause FAD by a number of pro-apoptotic mechanisms, or by regulating gamma-secretase activity, a protease involved in beta-amyloid precursor protein processing to the neurotoxic beta-amyloid peptide. Besides their normal endoproteolytic processing, PSs are substrates for caspases, being cleaved to alternative N-terminal and C-terminal fragments. So far little is known about the role of PSs cleavage in the apoptotic machinery. Here, we used SH-SY5Y neuroblastoma cells stably transfected with wild-type or exon 9 deleted presenilin 1 (PS1) in a time-course study after the exposure to the calcium ionophore A23187. During and after exposure to A 23187, intracellular calcium levels were higher in exon 9 deleted PS1 cells as compared with non-transfected and wild-type PS1 transfected cells. Cell death and the enrichment of apoptotic cells after A23187 exposure were increased by overexpression of exon 9 deleted PS1 as compared with the control cell lines. Wild-type PS1 cells were compared with exon 9 deleted PS1 cells and the temporal relationship between PS1 and other caspase substrates cleavages was analyzed. Exon 9 deleted PS1 cells exhibited a higher caspase-3 activation and a greater cleavage of PS1 and poly(ADP-ribose) polymerase (PARP) compared with wild-type PS1 cells. Exon 9 deleted PS1 cleavage occurred earlier than other caspase substrate cleavages (i.e., PARP and gelsolin), simultaneous with minimum detectable caspase-3 activation. Therefore, alternative cleavage of PS1 may play an important role for the regulation of the proteolytic cascade activated during apoptosis.
authors.affiliation: Karolinska Institute, NEUROTEC, Division of Geriatric Medicine, KFC, NOVUM, Huddinge, Sweden.
authors.forename: B O
authors.initials: BO
authors.lastname: Popescu
authors.forename: A
authors.initials: A
authors.lastname: Cedazo-Minguez
authors.forename: L M
authors.initials: LM
authors.lastname: Popescu
authors.forename: B
authors.initials: B
authors.lastname: Winblad
authors.forename: R F
authors.initials: RF
authors.lastname: Cowburn
authors.forename: M
authors.initials: M
authors.lastname: Ankarcrona
mesh_terms: D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D002021:Buffers; D000001:Calcimycin / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D020169:Caspases / Q000378:metabolism*; D002448:Cell Adhesion / Q000502:physiology; D005091:Exons / Q000235:genetics; D017353:Gene Deletion; D015870:Gene Expression / Q000502:physiology; D006706:Homeostasis / Q000187:drug effects / Q000502:physiology; D006801:Humans; D007476:Ionophores / Q000494:pharmacology*; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism*; D009447:Neuroblastoma; D009474:Neurons / Q000166:cytology / Q000201:enzymology; D053764:Presenilin-1; D014162:Transfection; D014407:Tumor Cells, Cultured / Q000166:cytology / Q000201:enzymology
chemical_list: D002021:Buffers; D007476:Ionophores; D008565:Membrane Proteins; C508853:PSEN1 protein, human; D053764:Presenilin-1; D000001:Calcimycin; D020169:Caspases; D002118:Calcium