Molecular chaperone Hsp70 protects neuroblastoma SK-N-SH cells from hypoxic stress

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Cellular response to hypoxic stress is based on the activation of the HIF-1 protein factor (hypoxia-inducible factor) composed of two subunits, α and β. HIF-1α is expressed constantly; however, under conditions of normoxia, due to hydroxylation of certain protein sites, its degradation occurs. During hypoxia, hydroxylation is blocked and HIF-1α forms dimers with HIF-1β and acts as a transcription factor for genes whose products provide various cellular processes. The molecular chaperone Hsp70 protects neuronal cells from hypoxic stress; however, the mechanism of its protective action remains unclear. To understand how Hsp70 protects cells under hypoxic conditions, we designed, based on neuroblastoma SK-N-SH cells, a cell line containing hsp70 gene under the induced promoter, SK-N-SH-hsp. Cells of this line turned out to be more resistant to the action of CoCl2 imitating action of hypoxia in our experiments. The lifetime of HIF-1α was increased in these cells as compared with the parental line cells becase, for a long time, Hsp70 was in a complex with HIF-1α. According to our data, Hsp70 interferes with signal pathways of the cell's response to hypoxic stress at the level of regulation of the stability of HIF-1α.

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