Role for Sit4p-dependent mitochondrial dysfunction in mediating the shortened chronological lifespan and oxidative stress sensitivity of Isc1p-deficient cells

Authors

  • António Daniel Barbosa,

    1. IBMC, Instituto de Biologia Molecular e Celular, Grupo de Microbiologia Celular e Aplicada, Rua do Campo Alegre, 823, 4150-180 Porto, Portugal.
    2. ICBAS, Instituto de Ciências Biomédicas Abel Salazar, Departamento de Biologia Molecular, Universidade do Porto, Porto, Portugal.
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  • Hugo Osório,

    1. IBMC, Instituto de Biologia Molecular e Celular, Grupo de Microbiologia Celular e Aplicada, Rua do Campo Alegre, 823, 4150-180 Porto, Portugal.
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    • Present addresses: Instituto de Patologia e Imunologia Molecular da Universidade do Porto (IPATIMUP), Rua Dr Roberto Frias s/n, 4200-465 Porto, Portugal;

  • Kellie J. Sims,

    1. Department of Biochemistry and Molecular Biology, Medical University of South Carolina, 173 Ashley Avenue, Charleston, SC 29425, USA.
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  • Teresa Almeida,

    1. IBMC, Instituto de Biologia Molecular e Celular, Grupo de Microbiologia Celular e Aplicada, Rua do Campo Alegre, 823, 4150-180 Porto, Portugal.
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  • Mariana Alves,

    1. IBMC, Instituto de Biologia Molecular e Celular, Grupo de Microbiologia Celular e Aplicada, Rua do Campo Alegre, 823, 4150-180 Porto, Portugal.
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    • Centro de Genética Médica Jacinto Magalhães, INSA IP, Praça Pedro Nunes, 88, 4099-028 Porto, Portugal.

  • Jacek Bielawski,

    1. Department of Biochemistry and Molecular Biology, Medical University of South Carolina, 173 Ashley Avenue, Charleston, SC 29425, USA.
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  • Maria Amélia Amorim,

    1. IBMC, Instituto de Biologia Molecular e Celular, Grupo de Microbiologia Celular e Aplicada, Rua do Campo Alegre, 823, 4150-180 Porto, Portugal.
    2. ICBAS, Instituto de Ciências Biomédicas Abel Salazar, Departamento de Biologia Molecular, Universidade do Porto, Porto, Portugal.
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  • Pedro Moradas-Ferreira,

    1. IBMC, Instituto de Biologia Molecular e Celular, Grupo de Microbiologia Celular e Aplicada, Rua do Campo Alegre, 823, 4150-180 Porto, Portugal.
    2. ICBAS, Instituto de Ciências Biomédicas Abel Salazar, Departamento de Biologia Molecular, Universidade do Porto, Porto, Portugal.
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  • Yusuf A. Hannun,

    1. Department of Biochemistry and Molecular Biology, Medical University of South Carolina, 173 Ashley Avenue, Charleston, SC 29425, USA.
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  • Vítor Costa

    Corresponding author
    1. IBMC, Instituto de Biologia Molecular e Celular, Grupo de Microbiologia Celular e Aplicada, Rua do Campo Alegre, 823, 4150-180 Porto, Portugal.
    2. ICBAS, Instituto de Ciências Biomédicas Abel Salazar, Departamento de Biologia Molecular, Universidade do Porto, Porto, Portugal.
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Summary

Saccharomyces cerevisiae cells lacking Isc1p, an orthologue of mammalian neutral sphingomyelinase 2, display a shortened lifespan and an increased sensitivity to oxidative stress. A lipidomic analysis revealed specific changes in sphingolipids that accompanied the premature ageing of Isc1p-deficient cells under severe calorie restriction conditions, including a decrease of dihydrosphingosine levels and an increase of dihydro-C26-ceramide and phyto-C26-ceramide levels, the latter raising the possibility of activation of ceramide-dependent protein phosphatases. Consequently, deletion of the SIT4 gene, which encodes for the catalytic subunit of type 2A ceramide-activated protein phosphatase in yeast, abolished the premature ageing and hydrogen peroxide sensitivity of isc1Δ cells. SIT4 deletion also abolished the respiratory defects and catalase A deficiency exhibited by isc1Δ mutants. These results are consistent with catabolic derepression associated with the loss of Sit4p. The overall results show that Isc1p is an upstream regulator of Sit4p and implicate Sit4p activation in mitochondrial dysfunction leading to the shortened chronological lifespan and oxidative stress sensitivity of isc1Δ mutants.

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