Caspase-9-dependent nuclear translocation of cytochrome c in hypoxic injury.

Objective: Hypoxia signals the release of cytochrome c from mitochondria as well as sequential activation of caspase-9 and caspase-3 in the pathway to apoptosis. In this report, we describe novel mechanisms governing the nuclear translocation of cytochrome c during hypoxia-induced apoptosis in neuroepithelioma, SK-N-MC cells. Methods: This work focuses on an investigation of the mechanism of cytochrome c translocation by means of immunocytochemistry, cell fractionation, Western blot and caspase assay. Results: Using immunocytochemistry and subcellular fractionation, we found that caspase-9 activation precedes cytochrome c release and translocation. Inhibition of caspase-9 activity blocked these responses to hypoxia. Previous studies suggest a key role for c-Jun N-terminal kinase (JNK) in apoptosis regulation and accordingly we found that JNK activation was essential for caspase-9 activation and nuclear translocation of cytochrome c. Conclusions: In this report, we describe novel mechanisms of caspase-9-dependent nuclear translocation of cytochrome c in hypoxic injury. Copyright (C) 2011 S. Karger AG, Basel