摘要
The human prion protein fragment, PrP (106-126), may contain a majority of the pathological features associated with the infectious scrapie isoform of PrP, known as PrPSc. Based on our previous findings that hypoxia protects neuronal cells from PrP (106-126)-induced apoptosis and increases cellular prion protein (PrPC) expression, we hypothesized that hypoxia-related genes, including hypoxia-inducible factor-1 alpha (HIF-1伪), may regulate PrPC expression and that these genes may be involved in prion-related neurodegenerative diseases. Hypoxic conditions are known to elicit cellular responses designed to improve cell survival through adaptive processes. Under normoxic conditions, a deferoxamine-mediated elevation of HIF-1伪 produced the same effect as hypoxia-inhibited neuron cell death. However, under hypoxic conditions, doxorubicin-suppressed HIF-1伪 attenuated the inhibitory effect on neuron cell death mediated by PrP (106-126). Knock-down of HIF-1伪 using lentiviral short hairpin (sh) RNA-induced downregulation of PrPC mRNA and protein expression under hypoxic conditions, and sensitized neuron cells to prion peptide-mediated cell death even in hypoxic conditions. In PrPC knockout hippocampal neuron cells, hypoxia increased the HIF-1伪 protein but the cells did not display the inhibitory effect of prion peptide-induced neuron cell death. Adenoviruses expressing the full length Prnp gene (Ad-Prnp) were utilized for overexpression of the Prnp gene in PrPC knockout hippocampal neuron cells. Adenoviral transfection of PrPC knockout cells with Prnp resulted in the inhibition of prion peptide-mediated cell death in these cells. This is the first report demonstrating that expression of normal PrPC is regulated by HIF-1伪, and PrPC overexpression induced by hypoxia plays a pivotal role in hypoxic inhibition of prion peptide-induced neuron cell death. These results suggest that hypoxia-related genes, including HIF-1伪, may be involved in the pathogenesis of prion-related diseases and as such may be a therapeutic target for prion-related neurodegenerative diseases.