title: Caspase activation in etoposide-treated fibroblasts is correlated to ERK phosphorylation and both events are blocked by polyamine depletion.
abstract: Activation of the extracellular signal-regulated kinases (ERKs) 1 and 2 is correlated to cell survival, but in some cases ERKs can act in signal transduction pathways leading to apoptosis. Treatment of mouse fibroblasts with 20 microM etoposide elicited a sustained phosphorylation of ERK 1/2, that increased until 24 h from the treatment in parallel with caspase activity. The inhibitor of ERK activation PD98059 abolished caspase activation, but caspase inhibition did not reduce ERK 1/2 phosphorylation, suggesting that ERK activation is placed upstream of caspases. Both ERK and caspase activation were blocked in cells depleted of polyamines by the ornithine decarboxylase inhibitor alpha-difluoromethylornithine (DFMO). In etoposide-treated cells, DFMO also abolished phosphorylation of c-Jun NH(2)-terminal kinases triggered by the drug. Polyamine replenishment with exogenous putrescine restored the ability of the cells to undergo caspase activation and ERK 1/2 phosphorylation in response to etoposide. Ornithine decarboxylase activity decreased after etoposide, indicating that DFMO exerts its effect by depleting cellular polyamines before induction of apoptosis. These results reveal a role for polyamines in the transduction of the death signal triggered by etoposide.
authors.affiliation: Department of Biochemistry 'G. Moruzzi', University of Bologna, Via Irnerio, 48, 40126, Bologna, Italy. cstefan@biocfarm.unibo
authors.forename: Claudio
authors.initials: C
authors.lastname: Stefanelli
authors.forename: Benedetta
authors.initials: B
authors.lastname: Tantini
authors.forename: Monia
authors.initials: M
authors.lastname: Fattori
authors.forename: Ivana
authors.initials: I
authors.lastname: Stanic'
authors.forename: Carla
authors.initials: C
authors.lastname: Pignatti
authors.forename: Carlo
authors.initials: C
authors.lastname: Clo
authors.forename: Carlo
authors.initials: C
authors.lastname: Guarnieri
authors.forename: Claudio M
authors.initials: CM
authors.lastname: Caldarera
authors.forename: Caroline A
authors.initials: CA
authors.lastname: Mackintosh
authors.forename: Anthony E
authors.initials: AE
authors.lastname: Pegg
authors.forename: Flavio
authors.initials: F
authors.lastname: Flamigni
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D061945:Caspase Inhibitors; D020169:Caspases / Q000187:drug effects / Q000378:metabolism*; D003374:Coumarins / Q000494:pharmacology; D000518:Eflornithine / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005047:Etoposide / Q000494:pharmacology*; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000187:drug effects / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000187:drug effects / Q000378:metabolism*; D009842:Oligopeptides / Q000494:pharmacology; D065108:Ornithine Decarboxylase Inhibitors; D010766:Phosphorylation; D011073:Polyamines / Q000378:metabolism*; D011700:Putrescine / Q000494:pharmacology; D015398:Signal Transduction
chemical_list: C112287:Ac-aspartyl-glutamyl-valyl-aspartyl-aminomethylcoumarin; D061945:Caspase Inhibitors; D003374:Coumarins; D004791:Enzyme Inhibitors; D009842:Oligopeptides; D065108:Ornithine Decarboxylase Inhibitors; D011073:Polyamines; C099158:acetyl-aspartyl-glutamyl-valyl-aspartal; D005047:Etoposide; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D020169:Caspases; D011700:Putrescine; D000518:Eflornithine