PAPEL DO PERÓXIDO DE HIDROGÉNIO NA ALTERAÇÃO DA PERMEABILIDADE DA MEMBRANA PLASMÁTICA

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Modulation of fatty acid synthase and plasma membrane microdomains by hydrogen peroxide

Publication . Matias, Ana Isabel Ayres de Mendonça Cardoso,1980-; Marinho,Helena Susana Pappámikail da Costa,1958-; Antunes,Fernando José Nunes,1969-

Adaptation of Saccharomyces cerevisiae cells to hydrogen peroxide (H2O2) decreases plasma membrane permeability, slowing H2O2 diffusion into cells and turning cells more resistant to H2O2. The mechanism responsible for this change remains largely unknown. Here this mechanism was addressed revealing that fatty acid synthase (Fas) plays a key role during the cellular response of S. cerevisiae to H2O2: Adaptation to H2O2 was associated with a decrease in both Fas expression and activity. However, cellular effects of H2O2 were shown to vary over a narrow range of concentrations. Therefore, a tight control of H2O2 exposure is essential for cellular studies of H2O2-dependent redox regulation. The importance of Fas in adaptation was reinforced by the observation that the decrease of Fas activity by 50 % through deletion of one of the FAS1 alleles increases the resistance to lethal doses of H2O2. The plasma membrane of fas1 cells presented a large increase lignoceric acid (C24:0) (40%) and cerotic acid (C26:0) (50%) levels, suggesting that alterations in the plasma membrane composition of very-long-chain fatty acids (VLCFA) occur with Fas downregulation. Through interdigitation or by modulating formation of lipid rafts, VLCFA may decrease the overall or localized plasma membrane permeability to H2O2, respectively, thus conferring a higher resistance to H2O2. In agreement, fluorescence studies with transparinaric acid showed that both H2O2 adaptation and Fas downregulation increase the formation of lipid domains in the plasma membrane. Also, microscopy studies revealed that changes in Fas activity lead to the reorganization of plasma membrane domains. Preliminary studies in Jurkat T cells showed a decrease in plasma membrane fluidity, alteration to digitonin sensitivity and reorganization of membrane microdomains after exposure to a nonlethal H2O2 dose for 4 h. However, no relation between these changes and fatty acid synthase activity could be established. In conclusion, these results reveal the key role of Fas in the modulation of plasma membrane permeability to H2O2 during adaptation in S. cerevisiae and suggest that downregulation of FAS1 is the molecular mechanism by which H2O2 leads to the reorganization of the plasma membrane by remodelling specific membrane microdomains.

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Entidade financiadora

Fundação para a Ciência e a Tecnologia

Programa de financiamento

PIDDAC

Número da atribuição

SFRH/BD/41421/2007