RNase L induces autophagy via c-Jun N-terminal kinase and double-stranded RNA-dependent protein kinase signaling pathways.

Abstract

Autophagy is a tightly regulated mechanism that mediates sequestration, degradation, and recycling of cellular proteins, organelles, and pathogens. Several proteins associated with autophagy regulate host responses to viral infections. Ribonuclease L (RNase L) is activated during viral infections and cleaves cellular and viral single-stranded RNAs, including rRNAs in ribosomes. Here we demonstrate that direct activation of RNase L coordinates the activation of c-Jun N-terminal kinase (JNK) and double-stranded RNA-dependent protein kinase (PKR) to induce autophagy with hallmarks as accumulation of autophagic vacuoles, p62(SQSTM1) degradation and conversion of Microtubule-associated Protein Light Chain 3-I (LC3-I) to LC3-II. Accordingly, treatment of cells with pharmacological inhibitors of JNK or PKR and mouse embryonic fibroblasts (MEFs) lacking JNK1/2 or PKR showed reduced autophagy levels. Furthermore, RNase L-induced JNK activity promoted Bcl-2 phosphorylation, disrupted the Beclin1-Bcl-2 complex and stimulated autophagy. Viral infection with Encephalomyocarditis virus (EMCV) or Sendai virus led to higher levels of autophagy in wild-type (WT) MEFs compared with RNase L knock out (KO) MEFs. Inhibition of RNase L-induced autophagy using Bafilomycin A1 or 3-methyladenine suppressed viral growth in initial stages; in later stages autophagy promoted viral replication dampening the antiviral effect. Induction of autophagy by activated RNase L is independent of the paracrine effects of interferon (IFN). Our findings suggest a novel role of RNase L in inducing autophagy affecting the outcomes of viral pathogenesis.

• Authors: Mohammad Adnan Siddiqui, Krishnamurthy Malathi
• Journal: The Journal of biological chemistry (J Biol Chem) Vol. 287 Issue 52 Pg. 43651-64 (Dec 21 2012) ISSN: 1083-351X [Electronic] United States
• PMID: 23109342 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)

Chemical References

• Adaptor Proteins, Signal Transducing
• Heat-Shock Proteins
• MAP1LC3A protein, human
• Map1lc3b protein, mouse
• Microtubule-Associated Proteins
• Proto-Oncogene Proteins c-bcl-2
• RNA, Double-Stranded
• SQSTM1 protein, human
• Sequestosome-1 Protein
• Sqstm1 protein, mouse
• Mitogen-Activated Protein Kinase 9
• eIF-2 Kinase
• Mitogen-Activated Protein Kinase 8
• Endoribonucleases
• 2-5A-dependent ribonuclease

Topics

• Adaptor Proteins, Signal Transducing (genetics, metabolism)
• Animals
• Autophagy
• Cardiovirus Infections (genetics, metabolism, pathology)
• Cell Line, Tumor
• Embryo, Mammalian (metabolism, pathology)
• Encephalomyocarditis virus (physiology)
• Endoribonucleases (genetics, metabolism)
• Fibroblasts (metabolism, pathology)
• Heat-Shock Proteins (genetics, metabolism)
• Humans
• MAP Kinase Signaling System
• Mice
• Mice, Knockout
• Microtubule-Associated Proteins (genetics, metabolism)
• Mitogen-Activated Protein Kinase 8 (genetics, metabolism)
• Mitogen-Activated Protein Kinase 9 (genetics, metabolism)
• Proto-Oncogene Proteins c-bcl-2 (genetics, metabolism)
• RNA, Double-Stranded (genetics, metabolism)
• Respirovirus Infections (genetics, metabolism, pathology)
• Sendai virus (physiology)
• Sequestosome-1 Protein
• Virus Replication (physiology)
• eIF-2 Kinase (genetics, metabolism)