High efficiency of energy flux controls within mitochondrial interactosome in cardiac intracellular energetic units

Kersti Tepp, Igor Shevchuk, Vladimir Chekulayev, Natalja Timohhina, Andrey V. Kuznetsov, Rita Guzun, Valdur Saks, Tuuli Kaambre

Index: Biochim. Biophys. Acta 1807(12) , 1549-61, (2011)

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Abstract

The aim of our study was to analyze a distribution of metabolic flux controls of all mitochondrial complexes of ATP-Synthasome and mitochondrial creatine kinase (MtCK) in situ in permeabilized cardiac cells. For this we used their specific inhibitors to measure flux control coefficients (CviJATP) in two different systems: A) direct stimulation of respiration by ADP and B) activation of respiration by coupled MtCK reaction in the presence of MgATP and creatine. In isolated mitochondria the CviJATP were for system A: Complex I - 0.19, Complex III – 0.06, Complex IV 0.18, adenine nucleotide translocase (ANT) – 0.11, ATP synthase – 0.01, Pi carrier - 0.20, and the sum of CviJATP was 0.75. In the presence of 10mM creatine (system B) the CviJATP were 0.38 for ANT and 0.80 for MtCK. In the permeabilized cardiomyocytes inhibitors had to be added in much higher final concentration, and the following values of CviJATP were determined for condition A and B, respectively: Complex I - 0.20 and 0.64, Complex III - 0.41 and 0.40, Complex IV - 0.40 and 0.49, ANT - 0.20 and 0.92, ATP synthase - 0.065 and 0.38, Pi carrier - 0.06 and 0.06, MtCK 0.95. The sum of CviJATP was 1.33 and 3.84, respectively. Thus, CviJATP were specifically increased under conditions B only for steps involved in ADP turnover and for Complex I in permeabilized cardiomyocytes within Mitochondrial Interactosome, a supercomplex consisting of MtCK, ATP-Synthasome, voltage dependent anion channel associated with tubulin βII which restricts permeability of the mitochondrial outer membrane.