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.

The role of Nrf2 in oxidative stress-induced endothelial injuries

“…CK2 interacts with two phosphorylated forms of Nrf2, specifically Nrf2-118 and Nrf2-98, the latter of which has transcription activity, which makes it easier for it to degrade (Pi et al 2007). Additionally, glycogen synthesis kinase 3 (GSK3; Chowdhry et al 2013, Mobasher et al 2013) and RNA-dependent protein kinase endoplasmic reticulum enzyme also phosphorylate Nrf2 (Zhang et al 2014b).…”

Synthesis and evaluation of isatin-β-thiosemicarbazones as novel agents against antibiotic-resistant Gram-positive bacterial species

“…Cif file for 3-1 is also given in the supplemental data. Generally, the structure of IBT is similar to other reported isatin derivatives, forming an intramolecular H-bond (O1 and the H atom linked to N3) [17,23]. Thus, the IBT structures are not E isomers, but Z isomers.…”

Synthesis, Characterization and DPPH Scavenging Assay of Isatin Related Spiroheterocyclic Compounds

“…Isatin (1-H-indole-2,3-dione) and its derivatives possess diverse biological and pharmacological activities and are widely used as a starting material for the synthesis of a broad range of heterocyclic compound substrates for drug synthesis [1] . Isatin is a heterocyclic compound and derivatives of isatin possess biological activities such as antimicrobial [2] , antibacterial, antifungal [3] , antiviral [4] , antiHIV [5] , anticancer [6,7] , antiproliferative [8] , antioxidant activity [9] . Spirocyclic systems containing one common carbon atom to two rings are structurally interesting [10] and naturally occurring substances being known for their wide range of biological activities [11,12] .…”