title: Apaf-1-deficient fog mouse cell apoptosis involves hypo-polarization of the mitochondrial inner membrane, ATP depletion and citrate accumulation.
abstract: To explore how the intrinsic apoptosis pathway is controlled in the spontaneous fog (forebrain overgrowth) mutant mice with an Apaf1 splicing deficiency, we examined spleen and bone marrow cells from Apaf1(+/+) (+/+) and Apaf1(fog/fog) (fog/fog) mice for initiator caspase-9 activation by cellular stresses. When the mitochondrial inner membrane potential (Deltapsim) was disrupted by staurosporine, +/+ cells but not fog/fog cells activated caspase-9 to cause apoptosis, indicating the lack of apoptosome (apoptosis protease activating factor 1 (Apaf-1)/cytochrome c/(d)ATP/procaspase-9) function in fog/fog cells. However, when a marginal ( approximately 20%) decrease in Deltapsim was caused by hydrogen peroxide (0.1 mM), peroxynitritedonor 3-morpholinosydnonimine (0.1 mM) and UV-C irradiation (20 J/m(2)), both +/+ and fog/fog cells triggered procaspase-9 auto-processing and its downstream cascade activation. Supporting our previous results, procaspase-9 pre-existing in the mitochondria induced its auto-processing before the cytosolic caspase activation regardless of the genotypes. Cellular ATP concentration significantly decreased under the hypoactive Deltapsim condition. Furthermore, we detected accumulation of citrate, a kosmotrope known to facilitate procaspase-9 dimerization, probably due to a feedback control of the Krebs cycle by the electron transfer system. Thus, mitochondrial in situ caspase-9 activation may be caused by the major metabolic reactions in response to physiological stresses, which may represent a mode of Apaf-1-independent apoptosis hypothesized from recent genetic studies.
authors.affiliation: Department of Microbiology, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, Yamanashi 409-3898, Japan.
authors.forename: Iyoko
authors.initials: I
authors.lastname: Katoh
authors.forename: Shingo
authors.initials: S
authors.lastname: Sato
authors.forename: Nahoko
authors.initials: N
authors.lastname: Fukunishi
authors.forename: Hiroki
authors.initials: H
authors.lastname: Yoshida
authors.forename: Takasuke
authors.initials: T
authors.lastname: Imai
authors.forename: Shun-Ichi
authors.initials: S
authors.lastname: Kurata
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D017209:Apoptosis; D053477:Apoptotic Protease-Activating Factor 1 / Q000235:genetics* / Q000378:metabolism*; D001854:Bone Marrow Cells / Q000378:metabolism; D053453:Caspase 9 / Q000378:metabolism; D002478:Cells, Cultured; D019343:Citric Acid / Q000378:metabolism*; D005347:Fibroblasts / Q000378:metabolism; D051379:Mice; D008817:Mice, Mutant Strains; D051336:Mitochondrial Membranes / Q000378:metabolism*; D018384:Oxidative Stress; D013154:Spleen / Q000378:metabolism
chemical_list: C506593:Apaf1 protein, mouse; D053477:Apoptotic Protease-Activating Factor 1; D019343:Citric Acid; D000255:Adenosine Triphosphate; C506434:Casp9 protein, mouse; D053453:Caspase 9