Hypoxia-mediated degradation of Na,K-ATPase via mitochondrial reactive oxygen species and the ubiquitin-conjugating system.

Abstract

We set out to determine whether cellular hypoxia, via mitochondrial reactive oxygen species, promotes Na,K-ATPase degradation via the ubiquitin-conjugating system. Cells exposed to 1.5% O2 had a decrease in Na,K-ATPase activity and oxygen consumption. The total cell pool of alpha1 Na,K-ATPase protein decreased on exposure to 1.5% O2 for 30 hours, whereas the plasma membrane Na,K-ATPase was 50% degraded after 2 hours of hypoxia, which was prevented by lysosome and proteasome inhibitors. When Chinese hamster ovary cells that exhibit a temperature-sensitive defect in E1 ubiquitin conjugation enzyme were incubated at 40 degrees C and 1.5% O2, the degradation of the alpha1 Na,K-ATPase was prevented. Exogenous reactive oxygen species increased the plasma membrane Na,K-ATPase degradation, whereas, in mitochondrial DNA deficient rho(0) cells and in cells transfected with small interfering RNA against Rieske iron sulfur protein, the hypoxia-mediated Na,K-ATPase degradation was prevented. The catalase/superoxide dismutase (SOD) mimetic (EUK-134) and glutathione peroxidase overexpression prevented the hypoxia-mediated Na,K-ATPase degradation and overexpression of SOD1, but not SOD2, partially inhibited the Na+ pump degradation. Accordingly, we provide evidence that during hypoxia, mitochondrial reactive oxygen species are necessary to degrade the plasma membrane Na,K-ATPase via the ubiquitin-conjugating system.

• Authors: Alejandro P Comellas, Laura A Dada, Emilia Lecuona, Liuska M Pesce, Navdeep S Chandel, Nancy Quesada, G R Scott Budinger, Ger J Strous, Aaron Ciechanover, Jacob I Sznajder
• Journal: Circulation research (Circ Res) Vol. 98 Issue 10 Pg. 1314-22 (May 26 2006) ISSN: 1524-4571 [Electronic] United States
• PMID: 16614303 (Publication Type: Journal Article, Research Support, N.I.H., Extramural)

Chemical References

• Reactive Oxygen Species
• Ubiquitin-Conjugating Enzymes
• Proteasome Endopeptidase Complex
• Sodium-Potassium-Exchanging ATPase

Topics

• Animals
• CHO Cells
• Cell Membrane (enzymology)
• Cells, Cultured
• Cricetinae
• Cricetulus
• Humans
• Hypoxia (enzymology, metabolism)
• Lysosomes (metabolism)
• Male
• Mitochondria (metabolism)
• Oxygen Consumption
• Proteasome Endopeptidase Complex (metabolism)
• Rats
• Rats, Sprague-Dawley
• Reactive Oxygen Species (metabolism)
• Sodium-Potassium-Exchanging ATPase (metabolism)
• Ubiquitin-Conjugating Enzymes (metabolism)