title: Low concentrations of the toxin ophiobolin A lead to an arrest of the cell cycle and alter the intracellular partitioning of glutathione between the nuclei and cytoplasm.
abstract: Ophiobolin A, a tetracyclic sesterpenoid produced by phytopathogenic fungi, is responsible for catastrophic losses in crop yield but its mechanism of action is not understood. The effects of ophiobolin A were therefore investigated on the growth and redox metabolism of Tobacco Bright Yellow-2 (TBY-2) cell cultures by applying concentrations of the toxin that did not promote cell death. At concentrations between 2 and 5 μM, ophiobolin A inhibited growth and proliferation of the TBY-2 cells, which remained viable. Microscopic and cytofluorimetric analyses showed that ophiobolin A treatment caused a rapid decrease in mitotic index, with a lower percentage of the cells at G1 and increased numbers of cells at the S/G2 phases. Cell size was not changed following treatment suggesting that the arrest of cell cycle progression was not the result of a block on cell growth. The characteristic glutathione redox state and the localization of glutathione in the nucleus during cell proliferation were not changed by ophiobolin A. However, subsequent decreases in glutathione and the re-distribution of glutathione between the cytoplasm and nuclei after mitosis occurring in control cells, as well as the profile of glutathionylated proteins, were changed in the presence of the toxin. The profile of poly ADP-ribosylated proteins were also modified by ophiobolin A. Taken together, these data provide evidence of the mechanism of ophiobolin A action as a cell cycle inhibitor and further demonstrate the link between nuclear glutathione and the cell cycle regulation, suggesting that glutathione-dependent redox controls in the nuclei prior to cell division are of pivotal importance.
authors.affiliation: Centro Integrato di Ricerca, Università Campus Bio-Medico, Via Alvaro del Portillo, 00128 Roma, Italy.
authors.forename: Vittoria
authors.initials: V
authors.lastname: Locato
authors.affiliation: Centro Integrato di Ricerca, Università Campus Bio-Medico, Via Alvaro del Portillo, 00128 Roma, Italy Departamento de Biología Vegetal, Universidad de Murcia, Campus Espinardo, Murcia, Spain.
authors.forename: Esther Novo
authors.initials: EN
authors.lastname: Uzal
authors.affiliation: Centro Integrato di Ricerca, Università Campus Bio-Medico, Via Alvaro del Portillo, 00128 Roma, Italy.
authors.forename: Sara
authors.initials: S
authors.lastname: Cimini
authors.affiliation: Istituto di Scienze delle Produzioni Alimentari, Consiglio Nazionale delle Ricerche, Via Amendola 122/O, 70125 Bari, Italy.
authors.forename: Maria Chiara
authors.initials: MC
authors.lastname: Zonno
authors.affiliation: Dipartimento di Scienze Chimiche, Università di Napoli Federico II, Complesso Universitario Monte S. Angelo, Via Cinthia 4, 80126 Napoli, Italy.
authors.forename: Antonio
authors.initials: A
authors.lastname: Evidente
authors.affiliation: IRCCS-G.B. Fondazione Bietti, Roma, Italy.
authors.forename: Alessandra
authors.initials: A
authors.lastname: Micera
authors.affiliation: Centre for Plant Sciences, Faculty of Biology, University of Leeds, Leeds LS2 9JT, UK.
authors.forename: Christine H
authors.initials: CH
authors.lastname: Foyer
authors.affiliation: Centro Integrato di Ricerca, Università Campus Bio-Medico, Via Alvaro del Portillo, 00128 Roma, Italy l.degara@unicampus.it.
authors.forename: Laura
authors.initials: L
authors.lastname: De Gara
mesh_terms: D001203:Ascomycota / Q000737:chemistry*; D002453:Cell Cycle; D002467:Cell Nucleus / Q000378:metabolism; D049109:Cell Proliferation; D003593:Cytoplasm / Q000378:metabolism; D005978:Glutathione / Q000378:metabolism*; D009183:Mycotoxins / Q000378:metabolism* / Q000633:toxicity; D010084:Oxidation-Reduction; D059828:Plant Cells; D010935:Plant Diseases / Q000382:microbiology*; D054830:Sesterterpenes / Q000378:metabolism* / Q000633:toxicity; D014026:Nicotiana / Q000382:microbiology / Q000502:physiology*
chemical_list: D009183:Mycotoxins; D054830:Sesterterpenes; C040764:ophiobolin A; D005978:Glutathione
keywords: Cell cycle; Tobacco Bright Yellow-2.; glutathione; glutathionylation; ophiobolin A; poly-ADP-ribosylation