Differential susceptibility of mitochondrial complex II to inhibition by oxaloacetate in brain and heart
| Autor: | Anna, Stepanova, Yevgeniya, Shurubor, Federica, Valsecchi, Giovanni, Manfredi, Alexander, Galkin |
|---|---|
| Rok vydání: | 2016 |
| Předmět: |
Oxaloacetic Acid
Q1 2 3-dimethoxy-5-methyl-6-(3-methyl-2-butenyl)-1 4-benzoquinone I/R ischemia/reperfusion Article A/D active/de-active transition Oxaloacetate Mice Ischemia Animals DDM n-Dodecyl β-d-maltoside GOT1 glutamic/oxaloacetate transaminase Type 1 HAR hexaammineruthenium SMP submitochondrial particles Electron Transport Complex II Myocardium Brain FAD flavin adenine dinucleotide Mitochondria Mitochondrial complex II Succinate dehydrogenase SET medium sucrose/EDTA/Tris medium RET reverse electron transfer SDH succinate dehydrogenase OAA oxaloacetate Krebs cycle TCA tricarboxylic acid cycle |
| Zdroj: | Biochimica et Biophysica Acta |
| ISSN: | 0006-3002 |
| Popis: | Mitochondrial Complex II is a key mitochondrial enzyme connecting the tricarboxylic acid (TCA) cycle and the electron transport chain. Studies of complex II are clinically important since new roles for this enzyme have recently emerged in cell signalling, cancer biology, immune response and neurodegeneration. Oxaloacetate (OAA) is an intermediate of the TCA cycle and at the same time is an inhibitor of complex II with high affinity (Kd ~ 10− 8 M). Whether or not OAA inhibition of complex II is a physiologically relevant process is a significant, but still controversial topic. We found that complex II from mouse heart and brain tissue has similar affinity to OAA and that only a fraction of the enzyme in isolated mitochondrial membranes (30.2 ± 6.0% and 56.4 ± 5.6% in the heart and brain, respectively) is in the free, active form. Since OAA could bind to complex II during isolation, we established a novel approach to deplete OAA in the homogenates at the early stages of isolation. In heart, this treatment significantly increased the fraction of free enzyme, indicating that OAA binds to complex II during isolation. In brain the OAA-depleting system did not significantly change the amount of free enzyme, indicating that a large fraction of complex II is already in the OAA-bound inactive form. Furthermore, short-term ischemia resulted in a dramatic decline of OAA in tissues, but it did not change the amount of free complex II. Our data show that in brain OAA is an endogenous effector of complex II, potentially capable of modulating the activity of the enzyme. Highlights • Complex II in mitochondrial membranes is inhibited by tightly-bound oxaloacetate. • Oxaloacetate binds to the heart enzyme during isolation. • In brain a large fraction of Complex II is present in oxaloacetate-bound form. • Short-time tissue ischemia does not affect the content of the free Complex II in brain. |
| Databáze: | OpenAIRE |
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