Differential impact of various reactive oxygen species (ROS) on HIF-1α/p53 direct interaction in SK-N-MC neuroblastoma cells

BACKGROUND: A vital property of eukaryotic cells physiology is their rather quick response to variation of oxygen tension, mainly by a transcription factor known as hypoxia-inducible factor-1 (HIF-1). Aside from its transcriptional regulation, other mechanisms, such as post translational modifications and protein–protein interactions, the interaction between HIF-1α and p53 has attracted more attention mainly due to simultaneous enhancement in the protein levels of these two anti- and pro-apoptotic vital transcriptional factors within the ROS-stressed cells. METHODS: In this study, we measured cell viability following exposure of the cells to H(2)O(2), menadione and Cobalt Chloride by MTT, and ROS content was measured under the same condition. The immunoblotting technique has been used to establish the presence and amount of Caspase, HIF-1α and p53 proteins. Then, the effect of different ROS on interaction between HIF-1α and p53 proteins was examined by co-immunoprecipitation. RESULTS: The results showed that cells viability and intracellular ROS content were modulated in response to menadione, H(2)O(2) and Cobalt Chloride. These agents had different influence on HIF-1α signaling pathways as well as its interactions with p53 protein. It appeared that direct communication between HIF-1α and p53 proteins by ROS stresses, under both normoxic and hypoxic conditions, was governed by HIF-1α at a certain induced level. CONCLUSIONS: Our data indicated that stabilization, a prerequisite for communication, of HIF-1α is dependent to the types of free radicals.