Activation of Hsp90/NOS and increased NO generation does not impair mitochondrial respiratory chain by competitive binding at cytochrome c oxidase in low oxygen concentrations.
Nitric oxide (NO) is known to regulate mitochondrial respiration, especially during metabolic stress and disease, by nitrosation of the mitochondrial electron transport chain (ETC) complexes (irreversible) and by a competitive binding at O2 binding site of cytochrome c oxidase (CcO) in complex IV (reversible). In this study, by using bovine aortic endothelial cells, we demonstrate that the inhibitory effect of endogenously generated NO by nitric oxide synthase (NOS) activation, by either NOS stimulators or association with heat shock protein 90 (Hsp90), is significant only at high prevailing pO2 through nitrosation of mitochondrial ETC complexes, but it does not inhibit the respiration by competitive binding at CcO at very low pO2. ETC complexes activity measurements confirmed that significant reduction in complex IV activity was noticed at higher pO2, but it was unaffected at low pO2 in these cells. This was further extended to heat-shocked cells, where NOS was activated by the induction/activation of (Hsp90) through heat shock at an elevated temperature of 42 degrees C. From these results, we conclude that the entire attenuation of respiration by endogenous NO is due to irreversible inhibition by nitrosation of ETC complexes but not through reversible inhibition by competing with O2 binding at CcO at complex IV.
The Center for Biomedical EPR Spectroscopy and Imaging, Biophysics Program, Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH, USA.
Tennille
T
Presley
Kaushik
K
Vedam
Xiaoping
X
Liu
Jay L
JL
Zweier
Govindasamy
G
Ilangovan
D000818:Animals; D001011:Aorta; D001667:Binding, Competitive; D002417:Cattle; D019069:Cell Respiration / Q000502:physiology*; D003576:Electron Transport Complex IV / Q000378:metabolism*; D042783:Endothelial Cells / Q000378:metabolism*; D018841:HSP90 Heat-Shock Proteins / Q000378:metabolism*; D018869:Heat-Shock Response / Q000502:physiology; D008928:Mitochondria / Q000378:metabolism*; D009566:Nitrates; D009569:Nitric Oxide / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000378:metabolism; D015538:Nitrosation; D010100:Oxygen / Q000378:metabolism*
D018841:HSP90 Heat-Shock Proteins; D009566:Nitrates; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D003576:Electron Transport Complex IV; D010100:Oxygen