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The unique proteasomal processing of viral ORF1 drives HEV-induced liver fibrosis

ABSTRACT: Hepatitis E virus (HEV) is a globally prevalent pathogen that causes 20 million infections and 60,000 fatalities annually, endangering particularly pregnant women and immunosuppressed individuals. Liver cirrhosis, which results from advanced fibrosis, is the primary symptom and leading mortality cause in chronic hepatitis E patients. However, the causation and process of liver fibrosis triggered by chronic HEV infection remain poorly understood. Here, we unexpectedly discovered that the viral multiple-domain replicase (ORF1) undergoes unique ubiquitin-proteasomal processing in HEV replicon hepatocytes, HEV-infected gerbil livers, and HEV-infected patient livers, which follows a CHIP-mediated K48 ubiquitination and produces the HEV-Derived Smad Activator (HDSA). Lacking putative helicase and RNA polymerase domains, this enriched viral polypeptide in hepatocytes and gerbil livers is non-HSP90-bound, stable, and exhibits exclusively nuclear localization. Surprisingly, HDSA markedly potentiates the fibrogenic TGF-β/Smad pathway in livers by facilitating promoter binding and coactivator recruitment of SMAD3, leading to profound liver fibrotic symptoms and damage. Thus, we have identified the first viral protein derived from the unique proteasomal processing of the host, defined its notable role in liver fibrosis, and highlighted the nature of complex host-HEV interactions that drives HEV pathogenesis.

ORGANISM(S): Homo sapiens

PROVIDER: GSE251924 | GEO | 2024/08/01

REPOSITORIES: GEO

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Project description:Background & Aims: Other than hepatitis B or C virus infection, Hepatitis E virus (HEV) infection is generally asymptomatic or leads to acute and self-limiting hepatitis. However, the mechanism of host cell defense against HEV is unclear. Viruses are known to perturb host cellular metabolism to enable their replication and spread. AMP-activated protein kinase (AMPK) activation is crucial for the regulation of cell homeostasis. We thus investigated the role of AMPK in HEV infection. Methods: Huh7, THP1 and HepG2 cells inoculated with infectious HEV viral particle or Huh7 and organoids transfected with in vitro generated subgenomic or full-length GT3 (Kernow-C1 p6 strain) HEV RNA, namely, p6Luc or p6 were used to model HEV infection. Viral replication and genes expression were quantified. Activation of AMPK, innate immune response and autophagy process were assessed. Results: We found HEV infection can trigger AMPK activation by phosphorylation of AMPK at threonine 172 by transfecting HEV viral RNA into host cells or inoculating host cells with infectious HEV viral particle. The activation of AMPK is associated with HEV induced mitochondrial damage and ATP deficiency. Pharmacological activation of AMPK using 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR) attenuated HEV replication, which was reversed by an AMPK inhibitor (compound C). Lentivirus-mediated knockdown of AMPK provided further evidence that AMPK has an antiviral effect on HEV replication. These results suggested that AMPK activation is a potent strategy of host cells for HEV clearance. Consistent with its antiviral effect, AMPK activation potentiated the expression of genes with antiviral properties (e.g., IFNs, ISG15, and IRF9) and inhibited inflammatory response (e.g., NF-KB NLRP3 and IL-1β). Meanwhile, HEV and activated AMPK also decreased autophagosome accumulation by decreasing induction of autophagy and autophagic degradation. Consistently, we found inhibition of AMPK efficiently augmented HEV induced autophagosome accumulation, evidenced by a marked increase in LC3II. Our previous study showed that rapamycin, an activator of autophagic induction by inhibiting mTOR, and Bafilomycin A1, an inhibitor of autophagic degradation, has a potent pro-HEV effect under AICAR treatment. Moreover, Wortmannin inhibiting autophagic induction recover AMPK inhibitor induced HEV replication. Together, these results suggested that HEV induced AMPK activation can serve to protect HEV infected cells from HEV infection by attenuating autophagosome and promoting innate immunity. Conclusions: Here we show that HEV infection can activate AMPK phosphorylation, which attenuates autophagosome accumulation and increases innate immune signaling. Thus, the AMPK activation in response to HEV infection is critical in host cells for rapid viral clearance by coordinating autophagic process and establishing persistent antiviral immunity.

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The unique proteasomal processing of viral ORF1 drives HEV-induced liver fibrosis

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