Enterovirus 71 protease 2Apro and 3Cpro differentially inhibit the cellular endoplasmic reticulum-associated degradation (ERAD) pathway via distinct mechanisms, and enterovirus 71 hijacks ERAD component p97 to promote its replication

Abstract

Endoplasmic reticulum-associated degradation (ERAD) is an important function for cellular homeostasis. The mechanism of how picornavirus infection interferes with ERAD remains unclear. In this study, we demonstrated that enterovirus 71 (EV71) infection significantly inhibits cellular ERAD by targeting multiple key ERAD molecules with its proteases 2Apro and 3Cpro using different mechanisms. Ubc6e was identified as the key E2 ubiquitin-conjugating enzyme in EV71 disturbed ERAD. EV71 3Cpro cleaves Ubc6e at Q219G, Q260S, and Q273G. EV71 2Apro mainly inhibits the de novo synthesis of key ERAD molecules Herp and VIMP at the protein translational level. Herp differentially participates in the degradation of different glycosylated ERAD substrates α-1 antitrypsin Null Hong Kong (NHK) and the C-terminus of sonic hedgehog (SHH-C) via unknown mechanisms. p97 was identified as a host factor in EV71 replication; it redistributed and co-exists with the viral protein and other known replication-related molecules in EV71-induced replication organelles. Electron microscopy and multiple-color confocal assays also showed that EV71-induced membranous vesicles were closely associated with the endoplasmic reticulum (ER), and the ER membrane molecule RTN3 was redistributed to the viral replication complex during EV71 infection. Therefore, we propose that EV71 rearranges ER membranes and hijacks p97 from cellular ERAD to benefit its replication. These findings add to our understanding of how viruses disturb ERAD and provide potential anti-viral targets for EV71 infection.

An update on enterovirus 71 infection and interferon type I response

“…80,81 EV71 proteases 2A and 3C are also responsible for inhibition of the cellular endoplasmic reticulum-associated degradation (ERAD) pathway. 82 Inhibition of NFkB activation by EV71 infection was reported through target transforming growth factor beta-activated kinase 1 (TAK1) and TGF-beta-activated kinase 1 (TAB) complex as TAK1/TAB1/TAB2/TAB3, cleaved by 3Cpro. 83…”

A nanobody that recognizes a 14-residue peptide epitope in the E2 ubiquitin-conjugating enzyme UBC6e modulates its activity

“…UBC6e is cleaved by Enterovirus 71 3C pro in its C-terminal region for release from the ER. This cleavage causes a disturbance of normal ERAD in the course of viral infection 10 . Genetic ablation of UBC6e is not lethal in mice but causes sterility in males homozygous for the deletion 11 .…”

Cleavage and degradation of EDEM1 promotes coxsackievirus B3 replication via ATF6a‐mediated unfolded protein response signalling

“…Thus, we hypothesized that VP1 quality is controlled by the EDEM1‐mediated non‐glycoprotein ERAD pathway. This speculation was based on the following: (a) several previous reports on studies of other positive strand RNA viruses discovered EDEM1 protein in the Golgi apparatus as well as in viral replication organelles formed during virus‐induced remodelling of ER‐Golgi membrane system (Belov & Sztul, ; Jackson, ; Reggiori et al, ; Wang et al, ). (b) EDEM1 is a transmembrane protein containing a hydrophobic N‐terminal signal sequence; but not like GRP78, EDEM1 exists in membrane‐bound and soluble free forms before and after its signal sequence is cleaved, respectively (Tamura, Cormier, & Hebert, ).…”