Cardiovirus-Mediated PKR Inhibition Results from Nucleocytoplasmic Trafficking Disruption

ABSTRACT: Protein kinase R (PKR) is a key antiviral kinase activated by binding double-stranded RNA (dsRNA) produced during viral replication. Upon activation, PKR phosphorylates eIF2α, leading to the inhibition of translation and viral replication. However, many viruses have evolved mechanisms to counteract PKR activity. In Cardioviruses, the Leader protein (L), a short peptide cleaved from the N-terminus of the viral polyprotein, not only inhibits PKR but also blocks interferon production and disrupts nucleocytoplasmic trafficking (NCT). L disrupts NCT by recruiting host RSK kinases to the nuclear pore complex (NPC), where RSK phosphorylates FG-nucleoporins, thereby impairing NCT. L mutations that affect NCT disruption also impact its ability to inhibit PKR, suggesting a mechanistic link. Recombinant TMEV and EMCV viruses designed to disrupt NCT through different mechanisms exhibited some extent of PKR inhibition, supporting the link between NCT disruption and PKR inhibition. Immunostaining and live-cell imaging revealed that L-induced NCT disruption redistributes a fraction of PKR to the nucleoli, where PKR remains inactive. This suggests that nucleolar sequestration contributes to PKR inhibition. Additionally, L-mediated NCT disruption leads to the release of nuclear RNA-binding proteins (nRBPs) into the cytosol, which may bind or modify viral dsRNA, further preventing PKR activation. Collectively, these results highlight nucleocytoplasmic trafficking as a critical regulatory mechanism governing PKR activation. Thus, beyond the specific action of the Cardiovirus L protein, our study reveals a broader principle in which interference with host nucleocytoplasmic transport can significantly impact the subcellular localization and functional regulation of immune effectors, such as PKR

INSTRUMENT(S):

ORGANISM(S): Homo Sapiens (human)

TISSUE(S): Epithelial Cell, Cell Culture

SUBMITTER: Didier Vertommen  

LAB HEAD: Thomas Michiels

PROVIDER: PXD066206 | Pride | 2025-11-17

REPOSITORIES: Pride