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Vol. 19, Issue 3, 865-876, March 2008

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Isc1p Plays a Key Role in Hydrogen Peroxide Resistance and Chronological Lifespan through Modulation of Iron Levels and Apoptosis

Teresa Almeida^*,,, Marta Marques^*,,, Dominik Mojzita, Maria A. Amorim^*,, Rui D. Silva^||, Bruno Almeida^¶, Pedro Rodrigues^*, Paula Ludovico^¶, Stefan Hohmann, Pedro Moradas-Ferreira^*,, Manuela Côrte-Real^||, and Vítor Costa^*,

*IBMC, Instituto de Biologia Molecular e Celular, Grupo de Microbiologia Celular e Aplicada, 4150-180 Porto, Portugal; ICBAS, Instituto de Ciências Biomédicas Abel Salazar, Departamento de Biologia Molecular, Universidade do Porto, 4099-003, Porto, Portugal; Department of Cell and Molecular Biology, Göteborg University, S-405 30 Göteborg, Sweden; ^||Departamento de Biologia-Centro de Biologia, Universidade do Minho, Campus de Gualtar, 4710-057 Braga, Portugal; and ^¶Instituto de Investigação em Ciências da Vida e Saúde (ICVS), Escola de Ciências da Saúde, Universidade do Minho, Campus de Gualtar, 4710-057 Braga, Portugal

Submitted June 26, 2007; Revised December 11, 2007; Accepted December 19, 2007
Monitoring Editor: Donald Newmeyer

The inositolphosphosphingolipid phospholipase C (Isc1p) of Saccharomyces cerevisiae belongs to the family of neutral sphingomyelinases that generates the bioactive sphingolipid ceramide. In this work the role of Isc1p in oxidative stress resistance and chronological lifespan was investigated. Loss of Isc1p resulted in a higher sensitivity to hydrogen peroxide that was associated with an increase in oxidative stress markers, namely intracellular oxidation, protein carbonylation, and lipid peroxidation. Microarray analysis showed that Isc1p deficiency up-regulated the iron regulon leading to increased levels of iron, which is known to catalyze the production of the highly reactive hydroxyl radicals via the Fenton reaction. In agreement, iron chelation suppressed hydrogen peroxide sensitivity of isc1 mutants. Cells lacking Isc1p also displayed a shortened chronological lifespan associated with oxidative stress markers and aging of parental cells was correlated with a decrease in Isc1p activity. The analysis of DNA fragmentation and caspase-like activity showed that Isc1p deficiency increased apoptotic cell death associated with oxidative stress and aging. Furthermore, deletion of Yca1p metacaspase suppressed the oxidative stress sensitivity and premature aging phenotypes of isc1 mutants. These results indicate that Isc1p plays an important role in the regulation of cellular redox homeostasis, through modulation of iron levels, and of apoptosis.

These authors contributed equally to this work.

Address correspondence to: Vítor Costa (vcosta{at}ibmc.up.pt)

Abbreviations used: ROS, reactive oxygen species; BPS, bathophenanthroline disulfonic acid; LCB, long-chain sphingoid base; H₂DCFDA, 2',7'-dichlorodihydrofluorescein diacetate; MDA, malondialdehyde.