Metabolic control analysis (MCA) has been largely applied to the analysis of oxidative phosphorylation, in order to investigate the control exerted by each individual reaction step on the whole pathway. Using this approach, the control exerted by the electron transport chain complexes was shown to be higher in experimental systems closer to in vivo conditions than in mitochondria. To study the effect of the mitochondrial transmembrane proton electrochemical gradient (ΔμH+) on the control of respiration by cytochrome c oxidase (CcOX) in intact cells, we applied MCA to mitochondrial respiration of HepG2 cells. Both the overall O2 consumption and specific CcOX activity of actively phosphorylating cells were progressively inhibited by cyanide titration under conditions in which the electrical (Δψ) and/or the chemical (ΔpH) component of ΔμH+ was selectively modulated by addition of ionophores. Under endogenous conditions, i.e., in the absence of ionophores, CcOX displayed a high control coefficient value, thus representing an important site of regulation of mitochondrial oxidative phosphorylation. A high CcOX control coefficient value was also measured in the presence of nigericin, when Δψ is maximal, and in the presence of nigericin and valinomycin, when ΔμH+ is abolished. On the contrary and interestingly CcOX displayed a markedly lower control coefficient in the presence valinomycin converting Δψ into ΔpH. These results show that CcOX activity and its control over oxidative phosphorylation critically depend on Δψ in actively phosphorylating cells.

Role of membrane potential on the control of cytochrome c oxidase over respiration in intact hepatoma HepG2 cells / Forte, Elena; Maria Elena, Dalmonte; Maria Luisa, Genova; Arese, Marzia; Daniela, Mastronicola; Alessandro, Giuffrè; Giorgio, Lenaz; Sarti, Paolo. - In: BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS. - ISSN 0005-2728. - 1797, Supplement 1:(2010), pp. 95-95. (Intervento presentato al convegno 16th European Bioenergetics Conference tenutosi a Warsaw, Poland nel July, 17-22 2010) [10.1016/j.bbabio.2010.04.286].

Role of membrane potential on the control of cytochrome c oxidase over respiration in intact hepatoma HepG2 cells

FORTE, Elena;ARESE, Marzia;SARTI, Paolo
2010

Abstract

Metabolic control analysis (MCA) has been largely applied to the analysis of oxidative phosphorylation, in order to investigate the control exerted by each individual reaction step on the whole pathway. Using this approach, the control exerted by the electron transport chain complexes was shown to be higher in experimental systems closer to in vivo conditions than in mitochondria. To study the effect of the mitochondrial transmembrane proton electrochemical gradient (ΔμH+) on the control of respiration by cytochrome c oxidase (CcOX) in intact cells, we applied MCA to mitochondrial respiration of HepG2 cells. Both the overall O2 consumption and specific CcOX activity of actively phosphorylating cells were progressively inhibited by cyanide titration under conditions in which the electrical (Δψ) and/or the chemical (ΔpH) component of ΔμH+ was selectively modulated by addition of ionophores. Under endogenous conditions, i.e., in the absence of ionophores, CcOX displayed a high control coefficient value, thus representing an important site of regulation of mitochondrial oxidative phosphorylation. A high CcOX control coefficient value was also measured in the presence of nigericin, when Δψ is maximal, and in the presence of nigericin and valinomycin, when ΔμH+ is abolished. On the contrary and interestingly CcOX displayed a markedly lower control coefficient in the presence valinomycin converting Δψ into ΔpH. These results show that CcOX activity and its control over oxidative phosphorylation critically depend on Δψ in actively phosphorylating cells.
2010
16th European Bioenergetics Conference
04 Pubblicazione in atti di convegno::04c Atto di convegno in rivista
Role of membrane potential on the control of cytochrome c oxidase over respiration in intact hepatoma HepG2 cells / Forte, Elena; Maria Elena, Dalmonte; Maria Luisa, Genova; Arese, Marzia; Daniela, Mastronicola; Alessandro, Giuffrè; Giorgio, Lenaz; Sarti, Paolo. - In: BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS. - ISSN 0005-2728. - 1797, Supplement 1:(2010), pp. 95-95. (Intervento presentato al convegno 16th European Bioenergetics Conference tenutosi a Warsaw, Poland nel July, 17-22 2010) [10.1016/j.bbabio.2010.04.286].
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11573/463165
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