Work

GRP75 blocks hepatitis E virus infection by targeting HEV-ORF2 for degradation through chaperone-mediated autophagy and promoting IRF3 activation

Year: 2025

Type: article

Abstract: Hepatitis E virus (HEV) is a viral hepatitis pathogen that poses a significant threat to global human health, representing a serious yet long-overlooked public health concern. In this study, we identified glucose-regulated protein 75 (GRP75) as an interaction partner of HEV-ORF2 using recombinant ORF2 truncation as bait. The substrate-binding domain of GRP75 interacted with HEV-ORF2 and inhibited HEV replication by facilitating HEV-ORF2 degradation. Further analysis revealed that HEV-ORF2 contains three KFERQ-like motifs, the key signature sequence required for chaperone-mediated autophagy (CMA). Our data demonstrated that GRP75-mediated degradation of HEV-ORF2 was heat-shock cognate protein 70 (HSC70)-dependent, although no direct interaction between HSC70 and ORF2 was detected. Instead, GRP75, together with HEV-ORF2 and HSC70, formed a complex that mediated CMA-dependent degradation of HEV-ORF2, whereas deletion of all three KFERQ-like motifs from ORF2 conferred resistance to such processes. Additionally, GRP75 blocked mitochondrial transport of HEV-ORF2, potentially mitigating ORF2's function as an interferon (IFN) induction antagonist. Furthermore, GRP75 enhanced the interaction between mitochondrial antiviral signaling protein (MAVS) and TANK-binding kinase 1 (TBK1), promoting IFN-β production and ultimately inhibiting HEV infection. In conclusion, our findings identify GRP75 as a novel restriction factor for HEV infection and provide new insights into its role in CMA and antiviral innate immunity. IMPORTANCE: model, the viral-host interaction of HEV remains largely elusive. This study uncovers a novel mechanism by which GRP75 inhibits HEV infection. On one hand, the GRP75 protein facilitates the degradation of HEV-ORF2 through the lysosome-associated, chaperone-mediated autophagy by recognizing KFERQ-like motif presented on HEV-ORF2. On the other hand, GRP75 enhances the production of IFN-β by promoting interaction between MAVS and TBK1, thereby establishing an antiviral state and suppressing HEV infection. This research expands our current understanding of host resistance to HEV and provides a new function of GRP75, suggesting that GRP75 might be a novel antiviral factor against virus infection.

Source: Journal of Virology

DOI: 10.1128/jvi.01344-25