Abstract
Influenza A virus (IAV) infection perturbs metabolic pathways such as autophagy, a stress-induced catabolic pathway that crosstalks with cellular inflammatory responses. However, the impact of autophagy perturbation on IAV gene expression or host cell responses remains disputed. Discrepant results may be a reflection of in vivo studies using cell-specific autophagy-related (Atg) gene-deficient mouse strains, which do not delineate modification of developmental programmes from more proximal effects on inflammatory response. In vitro experiments can be confounded by gene expression divergence in wild-type cultivated cell lines, as compared to those experiencing long-term absence of autophagy. With the goal to investigate cellular processes within cells that are competent or incompetent for autophagy, we generated a novel experimental cell line in which autophagy can be restored by ATG5 protein stabilization in an otherwise Atg5-deficient background. We confirmed that IAV induced autophagosome formation and p62 accumulation in infected cells and demonstrated that perturbation of autophagy did not impact viral infection or replication in ATG5-stablized cells. Notably, the induction of interferon-stimulated genes (ISGs) by IAV was diminished when cells were autophagy competent. We further demonstrated that, in the absence of ATG5, IAV-induced interferon-β (IFN-β) expression was increased as compared to levels in autophagy-competent lines, a mechanism that was independent of IAV non-structural protein 1. In sum, we report that induction of autophagy by IAV infection reduces ISG expression in infected cells by limiting IFN-β expression, which may benefit viral replication and spread.
Highlights
Macroautophagy is a catabolic pathway conserved among eukaryotes by which cytoplasmic elements are isolated within doublemembrane autophagosomes that mature by fusing with the endo-lysosomal compartment[1]
We generated clonal populations of Atg5–/– mouse embryonic fibroblasts (MEFs) that stably expressed the autophagy-related 5 (ATG5) protein fused to a destabilization domain (ATG5DD), which is known to be rapidly degraded by the proteasome (Fig. 1a)[34]
Cells in which ATG5DD was stabilized through Shield[1] had autophagy levels that were comparable to that of WT MEFs, and untreated cells exhibited a marked decrease in autophagic activity
Summary
Macroautophagy (hereafter referred to as autophagy) is a catabolic pathway conserved among eukaryotes by which cytoplasmic elements are isolated within doublemembrane autophagosomes that mature by fusing with the endo-lysosomal compartment[1]. The elongation of is conjugated to ATG12, which is required for formation of the second complex composed of phosphatidylethanolamine (PE) conjugated to microtubule-associated protein 1 light chain-3 (LC3). Free cytosolic LC3 is referred to as LC3-I, whereas the PE-conjugated form is termed LC3-II. Autophagy occurs in all nucleated cells, playing a key role in maintaining homeostasis[2]. In stress conditions, such as viral infection, autophagic activity may increase[3,4,5]. Official journal of the Cell Death Differentiation Association
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have