# Disrupted glycosylphosphatidylinositol anchoring induces ER stress and restricts enterovirus infection

## TL;DR

This study shows that disrupting a cellular process called GPI anchoring causes stress in the endoplasmic reticulum, which limits the replication of certain viruses like echovirus 7.

## Contribution

The study reveals a novel role of GPI anchoring in ER stress and antiviral defense, independent of CD55, and identifies new host targets for broad-spectrum antiviral therapy.

## Key findings

- Disruption of GPI anchor transfer causes ER stress and activates the IRE1α and RIDD pathways.
- Enterovirus RNA is specifically degraded during ER stress due to sequences in its untranslated region.
- GPI anchoring supports replication organelle biogenesis and viral protein translation in a CD55-independent manner.

## Abstract

Many positive-sense RNA viruses, including viruses from the Picornaviridae, Coronaviridae and Flaviviridae family, exploit endoplasmic reticulum (ER)-derived membrane structures as sites of genome replication. Here we use a pooled CRISPR genetic screening strategy to identify glycosylphosphatidylinositol (GPI) anchor biosynthesis and transfer genes as host factors for echovirus 7 infection. In addition to supporting the biogenesis of CD55, which is a GPI anchor protein and an entry factor for some echoviruses, the GPI anchor synthesis machinery also supports several other enterovirus infections by enhancing viral replication and replication organelle biogenesis. Disruption of GPI anchor transfer machinery compromises ER integrity and causes ER stress. Consistent with these findings, ER-resident sensor, inositol-requiring protein 1α (IRE1α) is activated and regulated IRE1-dependent decay of mRNA (RIDD) is detected to reduce ER stress. Interestingly, enterovirus viral RNA, but not Hepatitis C Virus RNA, is degraded during this process due to specific sequences in the Untranslated Region (UTR). This study revealed novel links between GPI anchoring, ER stress and enterovirus infection, and illuminates new host targets for antiviral therapy.

Viruses are experts at hijacking cellular machinery to replicate. Many positive-sense RNA viruses, such as enteroviruses, remodel host membranes to establish replication organelles (ROs). We here discovered that a group of genes responsible for a cellular process called GPI-anchoring as critical host factors for echovirus 7 (Echo7) infection. While this pathway supports the expression of the GPI-anchored attachment factor CD55, we found it plays a more fundamental, CD55-independent role in enteroviral protein translation and the biogenesis of ROs. Mechanistically, we demonstrate that disruption of GPI anchor transfer, but not its early-stage synthesis, compromises endoplasmic reticulum (ER) integrity, inducing ER stress. This triggers the unfolded protein response (UPR), activating the IRE1α sensor and its downstream Regulated IRE1-Dependent Decay (RIDD) pathway. Intriguingly, this defense also specifically targets enteroviruses due to specific sequences in the viral untranslated regions. Our work reveals a novel link between a fundamental cellular process and the cell’s ability to fight off specific viral infections, opening new avenues for developing broad-spectrum antiviral drugs.