Autophagy induction by the pathogen receptor NECTIN4 and sustained autophagy contribute to peste des petits ruminants virus infectivity.

ABSTRACT

Macroautophagy/autophagy is an essential cellular response in the fight against intracellular pathogens. Although some viruses can escape from or utilize autophagy to ensure their own replication, the responses of autophagy pathways to viral invasion remain poorly documented. Here, we show that peste des petits ruminants virus (PPRV) infection induces successive autophagic signalling in host cells via distinct and uncoupled molecular pathways. Immediately upon invasion, PPRV induced a first transient wave of autophagy via a mechanism involving the cellular pathogen receptor NECTIN4 and an AKT-MTOR-dependent pathway. Autophagic detection showed that early PPRV infection not only increased the amounts of autophagosomes and LC3-II but also downregulated the phosphorylation of AKT-MTOR. Subsequently, we found that the binding of viral protein H to NECTIN4 ultimately induced a wave of autophagy and inactivated the AKT-MTOR pathway, which is a critical step for the control of infection. Soon after infection, new autophagic signalling was initiated that required viral replication and protein expression. Interestingly, expression of IRGM and HSPA1A was significantly upregulated following PPRV replication. Strikingly, knockdown of IRGM and HSPA1A expression using small interfering RNAs impaired the PPRV-induced second autophagic wave and viral particle production. Moreover, IRGM-interacting PPRV-C and HSPA1A-interacting PPRV-N expression was sufficient to induce autophagy through an IRGM-HSPA1A-dependent pathway. Importantly, syncytia formation could facilitate sustained autophagy and the replication of PPRV. Overall, our work reveals distinct molecular pathways underlying the induction of self-beneficial sustained autophagy by attenuated PPRV, which will contribute to improving the use of vaccines for therapy.Abbreviations ACTB actin beta; ANOVA analysis of variance; ATG autophagy-related; BECN1 beclin 1; CDV canine distemper virus; Co-IP coimmunoprecipitation; FIP fusion inhibitory peptide; GFP green fluorescent protein; GST glutathione S-transferase; HMOX1 heme oxygenase 1; hpi hours post infection; HSPA1A heat shock protein family A (Hsp70) member 1A; HSP90AA1 heat shock protein 90 kDa alpha (cytosolic), class A member 1; IFN interferon; IgG immunoglobulin G; INS insulin; IRGM immunity related GTPase M; MAP1LC3/LC3 microtubule associated protein 1 light chain 3; MeV measles virus; MOI multiplicity of infection; MTOR mechanistic target of rapamycin kinase; PI3K phosphoinositide-3 kinase; PIK3C3 phosphatidylinositol 3-kinase catalytic subunit type 3; SDS sodium dodecyl sulfate; siRNA small interfering RNA; SQSTM1/p62 sequestosome 1; UV ultraviolet.