Hypoglycemia enhances the expression of prion protein and heat-shock protein 70 in a mouse neuroblastoma cell line.

Cellular prion protein (PrP(C)) expression can be regulated by heat-shock stress, and we designed the present study to determine whether hypoglycemia could affect PrP(C) expression. RT-PCR and Western blotting were used to measure the expression of PrP(C) and heat-shock protein (Hsp70) in mouse neuroblastoma (N18) cells cultured 3 hr to 3 days in media deprived of 97.5% (L) or 75% (M) of its glucose. Hypoglycemia caused a concomitant time-dependent and glucose dose-dependent increase in PrP(C) and Hsp70. In addition, hypoglycemia also increased phosphorylated c-Jun N-terminal kinase (JNK) protein levels in a time-dependent manner. The upregulation of PrP(C) and Hsp70 under hypoglycemic conditions was disrupted by the specific JNK inhibitor SP600125. It was also found from in vitro studies that hypoglycemic conditions induced higher levels of PrP(C) promoter activity in PrP(C) promoters containing a heat-shock element (HSE) than in PrP(C) promoters lacking HSE. We propose that hypoglycemia-increased PrP(C) expression might be due to JNK phosphorylation of a heat-shock transcriptional factor, which then interacts with HSE in the promoter of PrP(C). Copyright 2005 Wiley-Liss, Inc.