title: Activation of CPP32-like protease in tumor necrosis factor-induced apoptosis is dependent on mitochondrial function.
abstract: Mitochondria have been implicated in apoptosis, however, the precise mechanisms whereby mitochondria exert their effect are not clear. To gain further insights, we generated a panel of cells from ML-1a cells that were rendered respiration deficient by ethidium bromide treatment. Two respiration-deficient clones were subsequently reconstituted by fusion with platelets. Respiration-deficient clones were resistant to TNF-induced apoptosis, whereas ML-1a and reconstituted clones were sensitive. In contrast, inhibition of proliferation and induction of differentiation by TNF were still observed in respiration deficient clones, suggesting a selective requirement of respiration in TNF-induced apoptosis. Furthermore the apoptosis machinery is not completely altered in respiration-deficient cells because they underwent apoptosis after staurosporine treatment. Next, we showed that apoptosis induced by TNF and staurosporine were blocked by z-DEVD-CH2F, an inhibitor of CPP32-like cysteine protease, suggesting the involvement of CPP32-like protease in both apoptosis signaling pathways. Interestingly, TNF activated CPP32-like protease in the parental and reconstituted clones but not in respiration-deficient clones, and staurosporine in all clones. Thus, the apoptosis signaling block in respiration-deficient clones is located at a step before CPP32-like protease activation, which can be bypassed by staurosporine.
authors.affiliation: Department of Internal Medicine, The University of Texas-Houston Health Science Center, 77030, USA. masahiro.higuchi@uth.tmc.edu
authors.forename: M
authors.initials: M
authors.lastname: Higuchi
authors.forename: B B
authors.initials: BB
authors.lastname: Aggarwal
authors.forename: E T
authors.initials: ET
authors.lastname: Yeh
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D004579:Electron Transport / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D008928:Mitochondria / Q000502:physiology*; D019311:Staurosporine / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
chemical_list: D014409:Tumor Necrosis Factor-alpha; D003546:Cysteine Endopeptidases; D019311:Staurosporine