Oxidative stress is an important pathogenic mechanism in degenerative diseases such as Alzheimer’s disease. Although ginsenoside compound K (CK) is protective against neuronal oxidative damage, the underlying mechanism remains to be understood. In this study, the protective effects of ginsenoside CK against oxidative stress damage induced by hydrogen peroxide in HT22 cells were investigated with 1H nuclear magnetic resonance (1H-NMR)-based metabolomics. The optimal CK concentration for decreasing oxidative stress damage in nerves was determined with MTT assays. CK (8 μM) significantly increased the HT22 cell survival rate after the model was established. Cell lysates were subjected to 1H-NMR metabolomics, western blotting, and ATP assays for verification. Metabolic perturbation occurred in HT22 cells in the model group but not the control group. Twenty biomarkers were identified and used to analyze metabolic pathways. CK reversed metabolic changes in HT22 cells by altering taurine, glutamate, glycine, and glutathione metabolism. Subsequently, CK increased ATP content and the expression of components of the PI3K/AKT signaling pathway in HT22 cells. These findings demonstrated that CK prevents oxidative stress damage and protects nerves by regulating energy-metabolism pathways, such as those of taurine, glutamate, and other amino acids, thus providing a rationale for the use of CK in Alzheimer’s disease treatment.

Pseudorabies (PR) is a domestic and wild animal infectious disease caused by the pseudorabies virus (PRV) and is one of the major infectious diseases that endanger the global swine industry. Studies have reported that PRV may achieve cross-species transmission from pigs to humans in recent years. Therefore, in-depth exploration of the relationship between PRV and host proteins is of great significance for elucidating the pathogenic mechanism of PRV and anti-PRV infection. Here, we report that heat shock protein 27 (HSP27) ubiquitinates and degrades cyclic GMP-AMP synthase (cGAS) and attenuates cGAS-mediated antiviral responses, thereby promoting PRV infection. Overexpression of HSP27 promoted PRV proliferation in vitro, while knockdown of HSP27 inhibited PRV infection. Importantly, we found that HSP27 inhibited PRV infection or poly(dA:dT)-activated IFN-β expression. Further studies found that HSP27 may inhibit cGAS-STING-mediated IFN-β expression through targeting cGAS. In addition, we found that HSP27 can suppress the expression of endogenous cGAS in different cells at both gene transcription and protein expression levels, and that HSP27 interacts with and ubiquitinates cGAS. In conclusion, we reveal for the first time that HSP27 is a novel negative regulator of the cGAS-STING signaling pathway induced by PRV infection or poly(dA:dT) activation and demonstrate that HSP27 plays a crucial role in PRV infection.

Heat shock proteins (HSPs) are a protein family that respond to physiological stress, such as heat, starvation, and infection. As cellular protein chaperones, they play an important role in protein folding, assembly, and degradation. Though it is well known that HSP27 is involved in a range of viral infections, its role during an encephalomyocarditis virus (EMCV) infection is not known. Here, we report that EMCV degrades HSP27 and that EMCV proteins 2Cpro and 3Apro are primarily responsible for its degradation. Consequently, loss of cellular HSP27 augmented EMCV proliferation, an effect that could be reversed upon HSP27 overexpression. Importantly, we found that HSP27 positively regulated EMCV-triggered type I interferon (IFN) production. Moreover, overexpression of 2Cpro and 3Apro significantly blocked type I IFN production. We also found for the first time that HSP27, as a molecular chaperone, can specifically interact with MDA5 and stabilize the expression of MDA5. Collectively, this study shows that HSP27 dampens EMCV infectivity by positively regulating EMCV-triggered retinoic acid-inducible gene (RIG)-I-like receptor (RLR)/melanoma differentiation-associated gene 5 (MDA5) signal pathway, while EMCV proteins 2Cpro and 3Apro interact with HSP27 and degrade HSP27 protein expression to allow EMCV proliferation. Our findings provide further mechanistic evidence for EMCV partaking in immune escape mechanisms, and that 2Cpro and 3Apro could serve as potential antiviral targets.

Pseudorabies virus (PRV) is an agent of Aujeszky's disease, and causes great economic losses to pig farming. Re-outburst of pseudorabies implies that new control measures are urgently needed. We show here that DDX56 possesses the ability to inhibit PRV replication in vitro, which may be an important factor for PRV infection. Overexpression of DDX56 inhibited PRV genomic DNA transcription and lower titers of PRV infection in PK15 cells, whereas down-regulation of the DDX56 expression had a promotion role on virus replication. Further study demonstrated that DDX56 exerted its proliferation-inhibitory effects of PRV through up-regulating cGAS-STING-induced IFN-β expression. Moreover, we found that DDX56 could promote cGAS expression and direct interaction also existed between DDX56 and cGAS. Based on this, DDX56-regulated IFN-β pathway may be targeted at cGAS. To verify this, down-regulated cGAS expression in DDX56 over-expression cells was performed. Results indicated that knockdown of cGAS expression could abrogate the inhibition role of DDX56 on PRV proliferation and weaken the effect of DDX56 on IFN-β expression. In addition, DDX56 played a promotion role in IRF3 phosphorylation and nucleus translocation. Altogether, our results highlight DDX56's antiviral role in PRV infection, and our findings contribute to a better understanding of host factors controlling PRV replication.