title: Antiviral activity of an isatin derivative via induction of PERK-Nrf2-mediated suppression of cap-independent translation.
abstract: We report here an isatin derivative 45 (ID45) against coxsackievirus B3 (CVB3) replication, which was synthesized based on a high-throughput screen of a unique natural product library. ID45 showed the most potent anti-CVB3 activity among the four synthesized compounds. Treatment of cells with ID45 before or after infection significantly reduced viral particle formation, resulting in protection of cells from virus-induced apoptosis. In addition, ID45 treatment caused remarkable up-regulation of glucose-regulated protein 78 (GRP78), a hallmark of endoplasmic reticulum (ER) stress and an indicator of enhanced cell viability. In identifying the ER stress response pathway induced by ID45, we found that ID45 activated PKR-like ER protein kinase (PERK) but failed to up-regulate eIF2α phosphorylation. Instead ID45 activated transcription factor Nrf2 (NF-E2-related factor-2), which is evidenced by its nuclear translocation and upregulation of its downstream target genes NQO1 (NAD(P)H quinone-oxidoreductase 1) and GCLM (glutamate-cysteine ligase, modifier subunit). This observation was further verified by using siRNAs of GRP78 or Nrf2, which blocked both the translocation of Nrf2 and up-regulation of its target genes, leading to aggressive viral replication and enhanced cell apoptosis. Finally, we found that ID45-induced up-regulation of NQO1 protected eIF4GI, a eukaryotic cap-dependent translation initiation factor, from cleavage by CVB3 protease and degradation by proteasomes. Taken together, our findings established that a novel antiviral mechanism of isatin derivative ID45 inhibits CVB3 replication by promoting cell survival through a PERK/Nrf2-dependent ER stress pathway, which benefits host cap-dependent translation but suppresses CVB3 cap-independent translation.
authors.affiliation: Department of Pathology and Laboratory Medicine, University of British Columbia, Institute for Heart and Lung Health, St. Paul's Hospital , Vancouver, BC V6Z 1Y6, Canada.
authors.forename: Huifang M
authors.initials: HM
authors.lastname: Zhang
authors.forename: Huanqin
authors.initials: H
authors.lastname: Dai
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Hanson
authors.forename: Huidong
authors.initials: H
authors.lastname: Li
authors.forename: Hui
authors.initials: H
authors.lastname: Guo
authors.forename: Xin
authors.initials: X
authors.lastname: Ye
authors.forename: Maged G
authors.initials: MG
authors.lastname: Hemida
authors.forename: Luoqiang
authors.initials: L
authors.lastname: Wang
authors.forename: Yaojun
authors.initials: Y
authors.lastname: Tong
authors.forename: Ye
authors.initials: Y
authors.lastname: Qiu
authors.forename: Selina
authors.initials: S
authors.lastname: Liu
authors.forename: Fengping
authors.initials: F
authors.lastname: Wang
authors.forename: Fuhang
authors.initials: F
authors.lastname: Song
authors.forename: Buchang
authors.initials: B
authors.lastname: Zhang
authors.forename: Jian-Guo
authors.initials: JG
authors.lastname: Wang
authors.forename: Li-Xin
authors.initials: LX
authors.lastname: Zhang
authors.forename: Decheng
authors.initials: D
authors.lastname: Yang
mesh_terms: D000998:Antiviral Agents / Q000494:pharmacology*; D015153:Blotting, Western; D002470:Cell Survival / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D000091342:Endoplasmic Reticulum Chaperone BiP; D015967:Gene Expression Regulation, Viral / Q000187:drug effects*; D006367:HeLa Cells; D006801:Humans; D007510:Isatin / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology; D008954:Models, Biological; D051267:NF-E2-Related Factor 2 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014176:Protein Biosynthesis / Q000187:drug effects; D014779:Virus Replication / Q000187:drug effects; D019892:eIF-2 Kinase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D000998:Antiviral Agents; D000091342:Endoplasmic Reticulum Chaperone BiP; D007510:Isatin; D051267:NF-E2-Related Factor 2; D019892:eIF-2 Kinase; C000717247:HSPA5 protein, human