title: Foot-and-mouth disease virus induces autophagosomes during cell entry via a class III phosphatidylinositol 3-kinase-independent pathway.
abstract: Autophagy is an intracellular pathway that can contribute to innate antiviral immunity by delivering viruses to lysosomes for degradation or can be beneficial for viruses by providing specialized membranes for virus replication. Here, we show that the picornavirus foot-and-mouth disease virus (FMDV) induces the formation of autophagosomes. Induction was dependent on Atg5, involved processing of LC3 to LC3II, and led to a redistribution of LC3 from the cytosol to punctate vesicles indicative of authentic autophagosomes. Furthermore, FMDV yields were reduced in cells lacking Atg5, suggesting that autophagy may facilitate FMDV infection. However, induction of autophagosomes by FMDV appeared to differ from starvation, as the generation of LC3 punctae was not inhibited by wortmannin, implying that FMDV-induced autophagosome formation does not require the class III phosphatidylinositol 3-kinase (PI3-kinase) activity of vps34. Unlike other picornaviruses, for which there is strong evidence that autophagosome formation is linked to expression of viral nonstructural proteins, FMDV induced autophagosomes very early during infection. Furthermore, autophagosomes could be triggered by either UV-inactivated virus or empty FMDV capsids, suggesting that autophagosome formation was activated during cell entry. Unlike other picornaviruses, FMDV-induced autophagosomes did not colocalize with the viral 3A or 3D protein. In contrast, ∼50% of the autophagosomes induced by FMDV colocalized with VP1. LC3 and VP1 also colocalized with the cellular adaptor protein p62, which normally targets ubiquitinated proteins to autophagosomes. These results suggest that FMDV induces autophagosomes during cell entry to facilitate infection, but not to provide membranes for replication.
authors.affiliation: Institute for Animal Health, Pirbright Laboratories, Woking, Surrey, United Kingdom.
authors.forename: Stephen
authors.initials: S
authors.lastname: Berryman
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Brooks
authors.forename: Alison
authors.initials: A
authors.lastname: Burman
authors.forename: Philippa
authors.initials: P
authors.lastname: Hawes
authors.forename: Rebecca
authors.initials: R
authors.lastname: Roberts
authors.forename: Christopher
authors.initials: C
authors.lastname: Netherton
authors.forename: Paul
authors.initials: P
authors.lastname: Monaghan
authors.forename: Matthew
authors.initials: M
authors.lastname: Whelband
authors.forename: Eleanor
authors.initials: E
authors.lastname: Cottam
authors.forename: Zvulun
authors.initials: Z
authors.lastname: Elazar
authors.forename: Terry
authors.initials: T
authors.lastname: Jackson
authors.forename: Thomas
authors.initials: T
authors.lastname: Wileman
mesh_terms: D000730:Androstadienes; D000818:Animals; D001343:Autophagy / Q000502:physiology*; D000071187:Autophagy-Related Protein 5; D015153:Blotting, Western; D016466:CHO Cells; D058546:Class III Phosphatidylinositol 3-Kinases / Q000378:metabolism; D006224:Cricetinae; D003412:Cricetulus; D029544:Foot-and-Mouth Disease Virus / Q000502:physiology*; D049452:Green Fluorescent Proteins; D051379:Mice; D008856:Microscopy, Fluorescence; D008869:Microtubule-Associated Proteins / Q000172:deficiency / Q000378:metabolism*; D010588:Phagosomes / Q000821:virology*; D053586:Virus Internalization; D000077191:Wortmannin
chemical_list: D000730:Androstadienes; C495773:Atg5 protein, mouse; D000071187:Autophagy-Related Protein 5; C480860:Map1lc3b protein, mouse; D008869:Microtubule-Associated Proteins; D049452:Green Fluorescent Proteins; D058546:Class III Phosphatidylinositol 3-Kinases; D000077191:Wortmannin