Japanese encephalitis virus nonstructural protein NS5 interacts with mitochondrial trifunctional protein and impairs fatty acid β-oxidation

PLoS Pathog. 2015 Mar 27;11(3):e1004750. doi: 10.1371/journal.ppat.1004750. eCollection 2015 Mar.

Abstract

Infection with Japanese encephalitis virus (JEV) can induce the expression of pro-inflammatory cytokines and cause acute encephalitis in humans. β-oxidation breaks down fatty acids for ATP production in mitochondria, and impaired β-oxidation can induce pro-inflammatory cytokine expression. To address the role of fatty-acid β-oxidation in JEV infection, we measured the oxygen consumption rate of mock- and JEV-infected cells cultured with or without long chain fatty acid (LCFA) palmitate. Cells with JEV infection showed impaired LCFA β-oxidation and increased interleukin 6 (IL-6) and tumor necrosis factor α (TNF-α) expression. JEV nonstructural protein 5 (NS5) interacted with hydroxyacyl-CoA dehydrogenase α and β subunits, two components of the mitochondrial trifunctional protein (MTP) involved in LCFA β-oxidation, and NS5 proteins were detected in mitochondria and co-localized with MTP. LCFA β-oxidation was impaired and higher cytokines were induced in cells overexpressing NS5 protein as compared with control cells. Deletion and mutation studies showed that the N-terminus of NS5 was involved in the MTP association, and a single point mutation of NS5 residue 19 from methionine to alanine (NS5-M19A) reduced its binding ability with MTP. The recombinant JEV with NS5-M19A mutation (JEV-NS5-M19A) was less able to block LCFA β-oxidation and induced lower levels of IL-6 and TNF-α than wild-type JEV. Moreover, mice challenged with JEV-NS5-M19A showed less neurovirulence and neuroinvasiveness. We identified a novel function of JEV NS5 in viral pathogenesis by impairing LCFA β-oxidation and inducing cytokine expression by association with MTP.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Encephalitis Virus, Japanese / genetics
  • Encephalitis Virus, Japanese / metabolism*
  • Encephalitis, Japanese / genetics
  • Encephalitis, Japanese / metabolism*
  • Fatty Acids / genetics
  • Fatty Acids / metabolism*
  • HEK293 Cells
  • Humans
  • Mice
  • Mitochondrial Trifunctional Protein, alpha Subunit / genetics
  • Mitochondrial Trifunctional Protein, alpha Subunit / metabolism*
  • Mitochondrial Trifunctional Protein, beta Subunit / genetics
  • Mitochondrial Trifunctional Protein, beta Subunit / metabolism*
  • Oxidation-Reduction
  • Point Mutation
  • Viral Nonstructural Proteins / genetics
  • Viral Nonstructural Proteins / metabolism*

Substances

  • Fatty Acids
  • NS5 protein, flavivirus
  • Viral Nonstructural Proteins
  • Mitochondrial Trifunctional Protein, alpha Subunit
  • Mitochondrial Trifunctional Protein, beta Subunit

Grants and funding

This work was supported by grants from the National Science Council, Taiwan (NSC 101-2321-B-001-028-MY3 and NSC 103-2321-B-001-047) and from Academia Sinica, Taiwan. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.