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Updated: Sep 1, 2025
Monitoring Activation of the Antiviral Pattern Recognition Receptors RIG-I And PKR By Limited Protease Digestion and Native PAGE
Published on: July 29, 2014
PKR and TLR3 trigger distinct signals that coordinate the induction of antiviral apoptosis
Wenjie Zuo1,2, Mai Wakimoto1,2, Noriyasu Kozaiwa1,2
1Division of Integrated Life Science, Graduate School of Biostudies, Kyoto University, Sakyo-ku, Kyoto, 606-8507, Japan.
Abstract:
RIG-I-like receptors (RLRs), protein kinase R (PKR), and endosomal Toll-like receptor 3 (TLR3) sense viral non-self RNA and are involved in cell fate determination. However, the mechanisms by which intracellular RNA induces apoptosis, particularly the role of each RNA sensor, remain unclear. We performed cytoplasmic injections of different types of RNA and elucidated the molecular mechanisms underlying viral dsRNA-induced apoptosis. The results obtained revealed that short 5'-triphosphate dsRNA, the sole ligand of RIG-I, induced slow apoptosis in a fraction of cells depending on IRF-3 transcriptional activity and IFN-I production. However, intracellular long dsRNA was sensed by PKR and TLR3, which activate distinct signals, and synergistically induced rapid apoptosis. PKR essentially induced translational arrest, resulting in reduced levels of cellular FLICE-like inhibitory protein and functioned in the TLR3/TRIF-dependent activation of caspase 8. The present results demonstrated that PKR and TLR3 were both essential for inducing the viral RNA-mediated apoptosis of infected cells and the arrest of viral production.
Insights
Viral RNA sensing by protein kinase R (PKR) and Toll-like receptor 3 (TLR3) synergistically triggers rapid apoptosis in infected cells. This pathway is crucial for eliminating viral RNA and halting virus production.
Area of Science:
- Immunology
- Molecular Biology
- Virology
Background:
- RIG-I-like receptors (RLRs), protein kinase R (PKR), and Toll-like receptor 3 (TLR3) are key sensors of viral RNA.
- The precise mechanisms by which intracellular RNA triggers apoptosis and the specific roles of these sensors remain incompletely understood.
Purpose of the Study:
- To elucidate the molecular mechanisms of viral double-stranded RNA (dsRNA)-induced apoptosis.
- To differentiate the roles of various intracellular RNA sensors in triggering apoptotic pathways.
Main Methods:
- Cytoplasmic injection of different RNA types into cells.
- Analysis of apoptosis induction and signaling pathways.
- Assessment of interferon (IFN) production and transcriptional activity.
Main Results:
- Short 5'-triphosphate dsRNA, a RIG-I ligand, induced slow apoptosis dependent on IRF-3 and IFN-I.
- Long intracellular dsRNA, sensed by PKR and TLR3, induced rapid, synergistic apoptosis.
- PKR mediated translational arrest and TLR3/TRIF-dependent caspase 8 activation, crucial for apoptosis and viral inhibition.
Conclusions:
- PKR and TLR3 are essential for viral RNA-mediated apoptosis in infected cells.
- This combined sensing mechanism effectively halts viral replication and production.
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