# The genetic driver of Acute Necrotizing Encephalopathy, RANBP2, regulates the inflammatory response to Influenza A virus infection

## TL;DR

This study shows that a genetic mutation in RANBP2 increases influenza virus replication and inflammation, leading to a severe brain condition called Acute Necrotizing Encephalopathy.

## Contribution

The study reveals how RANBP2 regulates influenza replication and inflammation, linking its mislocalization to Acute Necrotizing Encephalopathy.

## Key findings

- RANBP2 depletion increases influenza viral replication by aiding viral polymerase import.
- RANBP2 knockdown enhances viral RNA export and pro-inflammatory chemokine production.
- The RANBP2-T585M mutation causes mislocalization, mimicking RANBP2 knockdown effects.

## Abstract

Influenza virus infections can cause severe complications such as Acute Necrotizing Encephalopathy (ANE), which is characterised by a rapid onset of pathological inflammation following febrile infection. Heterozygous dominant mutations in the nucleoporin RANBP2/Nup358 predispose to influenza-triggered ANE1. The aim of our study was to determine whether RANBP2 plays a role in IAV-triggered inflammatory responses. We found that the depletion of RANBP2 in a human airway epithelial cell line increases IAV genomic replication by favouring the import of the viral polymerase subunits, PB1, PB2, and PA, following viral transcription and translation. Additionally, RANBP2 knockdown enhances the cytoplasmic export of viral genomic RNA (vRNA) and disrupts segment stoichiometry, which is associated with elevated production of the pro-inflammatory chemokines CXCL8, CXCL10, CCL2, CCL3, and CCL4 in human primary macrophages. Using CRISPR-Cas9 knock-in for the ANE1 disease variant RANBP2-T585M, we further demonstrate that this point mutation causes a loss-of-localisation phenotype that excludes RANBP2 from the nuclear envelope, which phenocopies RANBP2 knockdown by increasing IAV replication and driving pro-inflammatory cytokine expression following infection. Together, our results reveal that RANBP2 regulates influenza RNA replication and nuclear export, thereby restraining virus-induced hyperinflammation, and further suggest that ANE1 pathogenesis results from the impaired localisation of RANBP2 at the nuclear envelope.

Influenza can cause Acute Necrotizing Encephalopathy (ANE), a rare brain inflammatory disease. This study shows that loss or mislocalisation of RANBP2, as seen with ANE-linked mutations, boosts viral replication and triggers excessive inflammation.