title: Identification of caspase-10 in human neutrophils and its role in spontaneous apoptosis.
abstract: In the present study, we investigated the molecular mechanisms of spontaneous and tumor necrosis factor alpha (TNF-alpha)-mediated apoptosis of human polymorphonuclear neutrophils (PMN). Whereas TNF-alpha-mediated apoptosis was almost absent in the presence of the caspase-8 inhibitor Z-Ac-Ala-Glu-Val-Asp-7-fluoromethyl ketone (Z-AEVD-FMK), the inhibitor had no effect on spontaneous apoptosis, suggesting that spontaneous apoptosis was independent of caspase-8. Subsequently, we identified different isoforms of caspase-10 in human PMN and found high expression of caspase-10/b and/or -10/d and low expression of caspase-10/a and -10/c at the mRNA level. At the protein level, freshly isolated PMN showed high expression of caspase-10/b and -10/d as well as moderate expression of caspase-10/a and -10/c. Upon spontaneous apoptosis, caspase-10/b was down-regulated, which was accompanied by the appearance of a specific 47-kDa caspase-10/b cleavage product and an increased caspase-10 activity. In contrast, no down-regulation of caspase-10/a, -10/c, or -10/d was observed, suggesting that spontaneous apoptosis was associated with a differential activation of caspase-10/b. This was confirmed by the finding that spontaneous apoptosis was inhibited in the presence of Z-Ile-Glu-Thr-Asp (Z-IETD)-FMK, which blocks caspase-10. However, no down-regulation of caspase-10 isoforms was observed in the presence of TNF-alpha, suggesting that caspase-10 was not involved in TNF-alpha-induced apoptosis. Taken together, our study demonstrates that spontaneous and TNF-alpha-mediated apoptosis of PMN have different molecular requirements. Whereas TNF-alpha-mediated apoptosis depends on the activation of caspase-8, spontaneous apoptosis requires the activation of caspase-10/b. This finding may reveal that PMN apoptosis in different (patho-) physiological settings results from distinct molecular mechanisms.
authors.affiliation: Department of Physiology, Freie Universität, Berlin, Germany.
authors.forename: Friederike
authors.initials: F
authors.lastname: Goepel
authors.forename: Pamela
authors.initials: P
authors.lastname: Weinmann
authors.forename: Jürgen
authors.initials: J
authors.lastname: Schymeinsky
authors.forename: Barbara
authors.initials: B
authors.lastname: Walzog
mesh_terms: D017209:Apoptosis; D053455:Caspase 10; D053181:Caspase 8; D020169:Caspases / Q000032:analysis / Q000235:genetics / Q000502:physiology*; D002478:Cells, Cultured; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015971:Gene Expression Regulation, Enzymologic; D006801:Humans; D009504:Neutrophils / Q000166:cytology / Q000201:enzymology*; D020033:Protein Isoforms / Q000235:genetics / Q000502:physiology; D012333:RNA, Messenger / Q000032:analysis; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
chemical_list: D004791:Enzyme Inhibitors; D020033:Protein Isoforms; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; C505530:CASP8 protein, human; D053455:Caspase 10; D053181:Caspase 8; D020169:Caspases; C506438:CASP10 protein, human