The interaction of superoxide with nitric oxide destabilizes hypoxia-inducible factor-1alpha.
In renal carcinoma cells (RCC4) hypoxia inducible factor-1 (HIF-1) is constitutively expressed due to a von Hippel Lindau protein deficiency, but can be degraded by calpain, independently of the 26S proteasome, when exposed to hypoxia/nitric oxide (NO). In this study we examined molecular mechanisms to explain calpain activation. The inability of hypoxia/NO to degrade HIF-1alpha in respiratory-deficient RCC4-rho0 cells pointed to the requirement for mitochondria-derived reactive oxygen species. A prerequisite for O(2)(-) in combination with NO to destabilize HIF-1alpha was corroborated in RCC4-rho0 cells, when the redox cycler 2,3-dimethoxy-1,4-naphthoquinone was used as a source of superoxide. Degradation of HIF-1alpha required intracellular calcium transients and calpain activation. Using uric acid to interfere with signal transmission elicited by NO/O(2)(-) blocked HIF-1alpha degradation and attenuated a calcium increase. We conclude that an oxidative signal as a result of NO/O(2)(-) coformation triggers a calcium increase that activates calpain to degrade HIF-1alpha, independently of the proteasome.
Herr
B
B
Institute of Biochemistry I, Pathobiochemistry, Faculty of Medicine, Johann Wolfgang Goethe-University, Theodor-Stern-Kai 7, 60590, Frankfurt, Germany.
Zhou
J
J
Dröse
S
S
Brüne
B
B
D020013:Calcium Signaling / Q000187:drug effects; D002154:Calpain / Q000378:metabolism; D002478:Cells, Cultured; D015536:Down-Regulation; D004347:Drug Interactions / Q000502:physiology; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism*; D008954:Models, Biological; D009569:Nitric Oxide / Q000494:pharmacology*; D010084:Oxidation-Reduction / Q000187:drug effects; D011499:Protein Processing, Post-Translational / Q000187:drug effects*; D013481:Superoxides / Q000494:pharmacology*
D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D013481:Superoxides; D009569:Nitric Oxide; D002154:Calpain