Activation of the autophagy pathway by Torovirus infection is irrelevant for virus replication

PLoS One. 2019 Jul 15;14(7):e0219428. doi: 10.1371/journal.pone.0219428. eCollection 2019.

Abstract

Autophagy is a conserved eukaryotic process that mediates lysosomal degradation of cytoplasmic macromolecules and damaged organelles, also exerting an important role in the elimination of intracellular pathogens. Despite the antiviral role of autophagy, many studies suggest that some positive-stranded RNA viruses exploit this pathway to facilitate their own replication. In this study, we demonstrate that the equine torovirus Berne virus (BEV), the prototype member of the Torovirus genus (Coronaviridae Family, Nidovirales Order), induces autophagy at late times post-infection. Conversion of microtubule associated protein 1B light chain 3 (LC3) from cytosolic (LC3 I) to the membrane associated form (LC3 II), a canonical marker of autophagosome formation, is enhanced in BEV infected cells. However, neither autophagy induction, via starvation, nor pharmacological blockade significantly affect BEV replication. Similarly, BEV infection is not altered in autophagy deficient cells lacking either Beclin 1 or LC3B protein expression. Unexpectedly, the cargo receptor p62, a selective autophagy receptor, aggregates within the region where the BEV main protease (Mpro) localizes. This finding, coupled with observation that BEV replication also induces ER stress at the time when selective autophagy is taking place, suggests that the autophagy pathway is activated in response to the hefty accumulation of virus-encoded polypeptides during the late phase of BEV infection.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Autophagosomes
  • Autophagy*
  • Beclin-1 / metabolism
  • Green Fluorescent Proteins / metabolism
  • HEK293 Cells
  • Horses
  • Humans
  • Lysosomes / metabolism
  • Microtubule-Associated Proteins / metabolism
  • Phagosomes / metabolism
  • Signal Transduction
  • Torovirus / physiology*
  • Torovirus Infections / physiopathology
  • Torovirus Infections / virology*
  • Virus Replication*

Substances

  • Beclin-1
  • MAP1LC3A protein, human
  • Microtubule-Associated Proteins
  • Green Fluorescent Proteins

Grants and funding

This work was supported by AEI/FEDER (EU) under grants AGL2010-15495 and AGL2014-60095-P to D.R and J.F.R. G.A-P was supported by a FPU fellowship from the Spanish Ministry of Education, Culture and Sport, L.L.C was supported by a pre-doctoral research contract from the International Fellowship Program from La Caixa Foundation and G.N.M. was supported by a pre-doctoral research contract from the Junta para Ampliación de Estudios (JAE-Predoc) which was cofinanced by the Spanish Research Council (CSIC) and FEDER (UE). The funders had no role in study design, data collection and interpretation, or decision to submit the work for publication.