Anti-apoptotic activity of Japanese encephalitis virus NS5 protein in human medulloblastoma cells treated with interferon-β

Background: Japanese encephalitis virus (JEV) non-structural protein 5(NS5)exhibits type I interferon (IFN) antagonists, contributing to immune escape, and even inducing viral anti-apoptosis. This study investigated the anti-apoptotic mechanism of JEV NS5 protein on type I IFN-induced apoptosis of human medulloblastoma cells. Methods: Vector control and NS5-expressing cells were treated with IFN-beta, and then harvested for analyzing apoptotic pathways with flow cytometry, Western blotting, subcellular localization, etc. Results: Annexin V-FITC/PI staining indicated that IFN-beta triggered apoptosis of human medulloblastoma cells, but JEV NS5 protein significantly inhibited IFN-beta-induced apoptosis. Phage display technology and co-immunoprecipitation assay identified the anti-apoptotic protein Hsp70 as a NS5-interacting protein. In addition, Western blotting demonstrated that NS5 protein up-regulated the Hsp70 expression, and reduced IFN-beta-induced phosphorylation of ERK2, p38 MAPK and STAT1. Hsp70 down-regulation by quercetin significantly recovered IFN-beta-