Endoplasmic reticulum (ER) stress and autophagy are key cellular responses to RNA virus infection. Recent studies have shown that Japanese encephalitis virus (JEV)-induced autophagy negatively influences virus replication in mouse neuronal cells and embryonic fibroblasts, and delays virus-induced cell death. Here, we evaluated the role of ER stress pathways in inducing autophagy during JEV infection. We observed that JEV infection of neuronal cells led to activation of all three sensors of ER stress mediated by eIF2α/PERK, IRE1/XBP1 and ATF6. The kinetics of autophagy induction as monitored by levels of SQSTM1 and LC3-II paralleled activation of ER stress. Inhibition of the eIF2α/PERK pathway by siRNA-mediated depletion of proteins and by the PERK inhibitor had no effect on autophagy and JEV replication. However, depletion of XBP1 and ATF6, alone or in combination, prevented autophagy induction and significantly enhanced JEV-induced cell death. JEV-infected cells depleted of XBP1 or ATF6 showed reduced transcription of ER chaperones, ERAD components and autophagy genes, resulting in reduced protein levels of the crucial autophagy effectors ATG3 and BECLIN-1. Conversely, pharmacological induction of ER stress in JEV-infected cells further enhanced autophagy and reduced virus titres. Our study thus demonstrates that a crucial link exists between the ER stress pathways and autophagy in virus-infected cells, and that these processes are highly regulated during virus infection.

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CXCR4 is a G-protein coupled receptor which mediates signalling for diverse functions such as cell proliferation and migration, hematopoiesis and plays a role in embryogenesis and development. Signal transduction occurs primarily through transmembrane helices that function in the multicomponent lipid environment of the plasma membrane. Elevated levels of plasma membrane oxysterols occur in cardiovascular and metabolic disorders, physiological stress and inflammatory conditions. We use experimental and simulation approaches to study the impact of oxysterol chemistry and composition on CXCL12-mediated CXCR4 signalling. Experiments on HeLa cells show a pronounced decrease in calcium oscillation response for the tail oxidized sterols in comparison with the ring oxidized sterols with 22(R) hydroxycholesterol showing a near complete loss of signalling followed by 27-hydroxycholesterol and 25-hydroxycholesterol. All-atom molecular dynamics simulations reveal that tail oxidized, 27-hydroxycholesterol, displaces cholesterol and ubiquitously binds to several critical signalling residues, as well as the dimer interface. Enhanced 27-hydroxycholesterol binding alters CXCR4 residue conformations, disrupts the toggle switch and induces secondary structure changes at both N and C termini. Our study provides a molecular view of the observed mitigated CXCR4 signalling in the presence of oxysterols revealing that disruption of cholesterol-protein interactions, important for regulating the active state, is a key factor in the loss of CXCR4 signalling. Additionally, a signalling class switching from Gαito Gαsas revealed by increased CREB and ERK phosphorylation is observed in the experiments.