bims-mevinf 2024-11-03 papers

bims-mevinf

Biomed News

on Metabolism in viral infections

Issue of 2024–11–03
eight papers selected by
Alexander Ivanov, Engelhardt Institute of Molecular Biology

Stimulation of neutral lipid synthesis via viral growth factor signaling and ATP citrate lyase during vaccinia virus infection.
Hepatitis B Virus X Protein Induces Reactive Oxygen Species Generation via Activation of p53 in Human Hepatoma Cells.
Asparagine Availability Is a Critical Limiting Factor for Infectious Spleen and Kidney Necrosis Virus Replication.
Glucose and glutamine drive hepatitis E virus replication.
Small hepatitis B virus surface antigen (SHBs) induces dyslipidemia by suppressing apolipoprotein-AII expression through ER stress-mediated modulation of HNF4α and C/EBPγ.
GC-MS-based metabonomic analysis of silkworm haemolymph reveals four-stage metabolic responses to nucleopolyhedrovirus infection.
Viral Infections and Their Ability to Modulate Endoplasmic Reticulum Stress Response Pathways.
Antiviral role of cholesterol 25-hydroxylase in inhibiting porcine circovirus 3 replication.

J Virol. 2024 Oct 30. e0110324

Stimulation of neutral lipid synthesis via viral growth factor signaling and ATP citrate lyase during vaccinia virus infection.

Anil Pant, Djamal Brahim Belhaouari, Lara Dsouza, Zhilong Yang.

  Fatty acid metabolism can provide various products essential for viral infections. How vaccinia virus (VACV), the prototype of poxviruses, modulates fatty acid metabolism is not well understood. Here, we show that VACV infection results in increased neutral lipid droplet synthesis, the organelles that play a crucial role in storing and mobilizing fatty acids for energy production via β-oxidation. Citrate is the first tricarboxylic acid (TCA) cycle intermediate that can be transported to the cytosol to be converted to acetyl-CoA for de novo fatty acid biosynthesis. We found that VACV infection stimulates the S455 phosphorylation of ATP citrate lyase (ACLY), a pivotal enzyme that links citrate metabolism with lipid metabolism. We demonstrate that the inhibition of neutral lipid droplet synthesis and ACLY severely suppresses VACV replication. Remarkably, we found that virus growth factor (VGF)-induced signaling is essential for the VACV-mediated upregulation of ACLY phosphorylation and neutral lipid droplets. Finally, we report that VGF-induced EGFR-Akt pathway and ACLY phosphorylation are important for VACV stimulation of neutral lipid synthesis. These findings identified a new way of rewiring cell metabolism by a virus and a novel function for VGF in the governance of virus-host interactions through the induction of a key enzyme at the crossroads of the TCA cycle and fatty acid metabolism. Our study also provides a mechanism for the role played by VGF and its downstream signaling cascades in the modulation of lipid metabolism in VACV-infected cells.IMPORTANCENeutral lipid droplets are vital players in cellular metabolism. Here, we showed that VACV induces neutral lipid droplet synthesis in infected primary human foreskin fibroblasts and identified the cellular and viral factors needed. We identified VACV encoded growth factor (VGF) as an essential viral factor that induces cellular EGFR-Akt signaling to increase lipid droplets. Interestingly, VACV increases the S455 phosphorylation of ACLY, a key metabolic enzyme that sits at the crossroads of carbohydrate and lipid metabolism in a VGF-EGFR-Akt-dependent manner. We also found that ACLY is vital for VACV-induced lipid droplet synthesis. Our findings identified the modulation of ACLY by a virus and identified it as a potential target for antiviral development against pathogenic poxviruses. Our study also expands the role of growth factor signaling in boosting VACV replication by targeting fatty acid metabolism.

Keywords:  ATP citrate lyase; EGFR; fatty acids; lipid droplets; metabolism; poxvirus; vaccinia virus

DOI:  https://doi.org/10.1128/jvi.01103-24
Biomolecules. 2024 Sep 24. pii: 1201. [Epub ahead of print]14(10):

Hepatitis B Virus X Protein Induces Reactive Oxygen Species Generation via Activation of p53 in Human Hepatoma Cells.

Seungyeon Kim, Jimin Park, Jiwoo Han, Kyung Lib Jang.

  Hepatitis B virus (HBV), particularly through the HBx protein, induces oxidative stress during liver infections. This study reveals that HBx increases reactive oxygen species (ROS) via two distinct mechanisms. The first mechanism is p53-independent, likely involving mitochondrial dysfunction, as demonstrated by elevated ROS levels in p53-deficient Hep3B cells and p53-knocked-down HepG2 cells after HBx expression or HBV infection. The increase in ROS persisted even when p53 transcriptional activity was inhibited by pifithrin-α (PFT-α), a p53 inhibitor. The second mechanism is p53-dependent, wherein HBx activates p53, which then amplifies ROS production through a feedback loop involving ROS and p53. The ability of HBx to elevate ROS levels was higher in HepG2 than in Hep3B cells. Knocking down p53 in HepG2 cells lowered ROS levels, while ectopic p53 expression in Hep3B cells raised ROS. HBx-activated p53 downregulated catalase and upregulated manganese-dependent superoxide dismutase, contributing to ROS amplification. The transcriptional activity of p53 was crucial for these effects, as cells with a p53 R175H mutation or those treated with PFT-α generated less ROS. Additionally, HBx variants with Ser-101 increased p53 and ROS levels, whereas variants with Pro-101 did not. These dual mechanisms of HBx-induced ROS generation are likely significant in the pathogenesis of HBV and may contribute to liver diseases, including hepatocellular carcinoma.

Keywords:  HBx; hepatitis B virus; p53; proteasome; reactive oxygen species

DOI:  https://doi.org/10.3390/biom14101201
Viruses. 2024 Sep 29. pii: 1540. [Epub ahead of print]16(10):

Asparagine Availability Is a Critical Limiting Factor for Infectious Spleen and Kidney Necrosis Virus Replication.

Baofu Ma, Fangying Li, Xiaozhe Fu, Xia Luo, Qiang Lin, Hongru Liang, Yinjie Niu, Ningqiu Li.

  Infectious spleen and kidney necrosis virus (ISKNV) has brought huge economic loss to the aquaculture industry. Through interfering with the viral replication and proliferation process that depends on host cells, its pathogenicity can be effectively reduced. In this study, we investigated the role of asparagine metabolites in ISKNV proliferation. The results showed that ISKNV infection up-regulated the expression of some key enzymes of the asparagine metabolic pathway in Chinese perch brain (CPB) cells. These key enzymes, including glutamic oxaloacetic transaminase 1/2 (GOT1/2) and malate dehydrogenase1/2 (MDH1/2) associated with the malate-aspartate shuttle (MAS) pathway and asparagine synthetase (ASNS) involved in the asparagine biosynthesis pathway, were up-regulated during ISKNV replication and release stages. In addition, results showed that the production of ISKNV was significantly reduced by inhibiting the MAS pathway or reducing the expression of ASNS by 1.3-fold and 0.6-fold, respectively, indicating that asparagine was a critical limiting metabolite for ISKNV protein synthesis. Furthermore, when asparagine was added to the medium without glutamine, ISKNV copy number was restored to 92% of that in the complete medium, indicating that ISKNV could be fully rescued from the absence of glutamine by supplementing asparagine. The above results indicated that asparagine was a critical factor in limiting the effective replication of ISKNV, which provided a new idea for the treatment of aquatic viral diseases.

Keywords:  ISKNV; Siniperca chuatsi; asparagine; asparagine synthetase; aspartate-malate shuttle

DOI:  https://doi.org/10.3390/v16101540
Arch Virol. 2024 Oct 30. 169(11): 233

Glucose and glutamine drive hepatitis E virus replication.

Shaheen Khan, Suruchi Aggarwal, Pooja Bhatia, Amit Kumar Yadav, Yashwant Kumar, Naga Suresh Veerapu.

  Viruses have undergone evolutionary adaptations to tune their utilization of carbon sources, enabling them to extract specific cellular substrates necessary for their replication. The lack of a reliable cell culture system and a small-animal model has hampered our understanding of the molecular mechanism of replication of hepatitis E virus (HEV) genotype 1. Our recent identification of a replicative ensemble of mutant HEV RNA libraries has allowed us to study the metabolic prerequisites for HEV replication. Initial assessments revealed increased glucose and glutamine utilization during HEV replication. Inhibition of glycolysis and glycolysis + glutaminolysis reduced the levels of HEV replication to similar levels. An integrated analysis of protein-metabolite pathways suggests that HEV replication markedly alters glycolysis, the TCA cycle, and glutamine-associated metabolic pathways. Cells supporting HEV replication showed a requirement for fructose-6-phosphate and glutamine utilization through the hexosamine biosynthetic pathway (HBP), stimulating HSP70 expression to facilitate virus replication. Observations of mannose utilization and glutamine dependence suggest a crucial role of the HBP in supporting HEV replication. Inhibition of glycolysis and HSP70 activity or knockdown of glutamine fructose-6-phosphate amidotransferase expression led to a substantial reduction in HEV RNA and ORF2 expression accompanied by a significant decrease in HSP70 levels. This study demonstrates that glucose and glutamine play critical roles in facilitating HEV replication.

Keywords:  Glutaminolysis; Glycolysis; HSP70; HSP90; Hepatitis E virus; Hexosamine biosynthetic pathway

DOI:  https://doi.org/10.1007/s00705-024-06160-x
J Virol. 2024 Oct 29. e0123924

Small hepatitis B virus surface antigen (SHBs) induces dyslipidemia by suppressing apolipoprotein-AII expression through ER stress-mediated modulation of HNF4α and C/EBPγ.

Yunli Wu, Lan Ren, Chenglei Mao, Zhiqing Shen, Wenyu Zhu, Zhijun Su, Xinjian Lin, Xu Lin.

  Persistent infection with hepatitis B virus (HBV) often leads to disruptions in lipid metabolism. Apolipoprotein AII (apoAII) plays a crucial role in lipid metabolism and is implicated in various metabolic disorders. However, whether HBV could regulate apoAII and contribute to HBV-related dyslipidemia and the underlying mechanism remain unclear. This study revealed significant reductions in apoAII expression in HBV-expressing cell lines, the serum, and liver tissues of HBV-transgenic mice. The impact of HBV on apoAII is related to small hepatitis B virus surface antigen (SHBs). Overexpression of SHBs decreased apoAII levels in SHBs-expressing hepatoma cells, transgenic mice, and the serum of HBV-infected patients, whereas suppression of SHBs increased apoAII expression. Mechanistic investigations demonstrated that SHBs repressed the apoAII promoter activity through a HNF4α- and C/EBPγ-dependent manner; SHBs simultaneously upregulated C/EBPγ and downregulated HNF4α by inhibiting the PI3K/AKT signaling pathway through activating endoplasmic reticulum (ER) stress. Serum lipid profile assessments revealed notable decreases in high-density lipoprotein cholesterol (HDL-C), total cholesterol (TC), and triglycerides (TG) in SHBs-transgenic mice compared to control mice. However, concurrent overexpression of apoAII in these mice effectively counteracted these reductions in lipid levels. In HBV patients, SHBs levels were negatively correlated with serum levels of HDL-C, LDL-C, TC, and TG, whereas apoAII levels positively correlated with lipid content. This study underscores that SHBs contributes to dyslipidemia by suppressing the PI3K/AKT pathway via inducing ER stress, leading to altered expression of HNF4α and C/EBPγ, and subsequently reducing apoAII expression.IMPORTANCEThe significance of this study lies in its comprehensive examination of how the hepatitis B virus (HBV), specifically through its small hepatitis B virus surface antigen (SHBs), impacts lipid metabolism-a key aspect often disrupted by chronic HBV infection. By elucidating the role of SHBs in regulating apolipoprotein AII (apoAII), a critical player in lipid processes and associated metabolic disorders, this research provides insights into the molecular pathways contributing to HBV-related dyslipidemia. Discovering that SHBs downregulates apoAII through mechanisms involving the repression of the apoAII promoter via HNF4α and C/EBPγ, and the modulation of the PI3K/AKT signaling pathway via endoplasmic reticulum (ER) stress, adds critical knowledge to HBV pathogenesis. The research also shows an inverse correlation between SHBs expression and key lipid markers in HBV-infected individuals, suggesting that apoAII overexpression could counteract the lipid-altering effects of SHBs, offering new avenues for understanding and managing the metabolic implications of HBV infection.

Keywords:  C/EBPγ; ER stress; HNF4α; PI3K/AKT signaling; apolipoprotein AII; small hepatitis B virus surface antigen

DOI:  https://doi.org/10.1128/jvi.01239-24
Insect Mol Biol. 2024 Oct 31.

GC-MS-based metabonomic analysis of silkworm haemolymph reveals four-stage metabolic responses to nucleopolyhedrovirus infection.

Zhenyue Su, Yi Li, Zihan Lin, Qing Huang, Xinyu Fan, Zhaoming Dong, Qingyou Xia, Ping Zhao, Xin Wang.

  Silkworm, Bombyx mori, an economically significant insect, plays a crucial role in silk production. However, silkworm breeding is highly susceptible to various pathogens, particularly the Bombyx mori nucleopolyhedrovirus (BmNPV), which poses a serious threat. Recent metabonomic studies have provided insights into the metabolic changes associated with BmNPV infection. BmNPV infection has obvious temporal characteristics. However, few studies have investigated the silkworms infected in different periods. This study employed gas chromatography-mass spectrometry (GC-MS) to perform a comprehensive analysis of haemolymph metabolites in silkworms at 48, 72, 96 and 120 h post-infection (h.p.i.). Through the integration of time-course analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment, the study revealed distinct four-stage metabolic characteristics in the silkworm's response to BmNPV infection. At Stage 1 (48 h.p.i.), silkworms activate antioxidant defence mechanisms, with significant enrichment in metabolic pathways involving key antioxidants such as glutathione, to mitigate oxidative stress induced by viral invasion. By Stage 2 (72 h.p.i.), pathways related to amino acid metabolism and protein synthesis become active, indicating an increase in protein synthesis. In Stage 3 (96 h.p.i.), energy metabolism and substance transport pathways are significantly upregulated to support the rapid viral replication and the enhanced locomotor behaviour of silkworm. Finally, at Stage 4 (120 h.p.i.), there is a further enhancement of pathways related to energy metabolism, nucleic acid synthesis, and substance transport, which align with peak viral assembly and release. These findings contribute to an in-depth understanding of the biochemical basis of silkworm resistance to NPV.

Keywords:  Bombyx mori; metabonomics; nucleopolyhedrovirus; time‐course analysis

DOI:  https://doi.org/10.1111/imb.12972
Viruses. 2024 Sep 30. pii: 1555. [Epub ahead of print]16(10):

Viral Infections and Their Ability to Modulate Endoplasmic Reticulum Stress Response Pathways.

Flávio Guimarães da Fonseca, Ângela Vieira Serufo, Thiago Lima Leão, Karine Lima Lourenço.

  In eukaryotic cells, the endoplasmic reticulum is particularly important in post-translational modification of proteins before they are released extracellularly or sent to another endomembrane system. The correct three-dimensional folding of most proteins occurs in the ER lumen, which has an oxidative environment that is essential for the formation of disulfide bridges, which are important in maintaining protein structure. The ER is a versatile organelle that ensures the correct structure of proteins and is essential in the synthesis of lipids and sterols, in addition to offering support in the maintenance of intracellular calcium. Consequently, the cells needed to respond to demands caused by physiological conditions and pathological disturbances in the organelle homeostasis, leading to proper functioning of the cell or even programmed cell death. Disturbances to the ER function trigger a response to the accumulation of unfolded or misfolded proteins, known as the unfolded protein response. Such disturbances include abiotic stress, pharmacological agents, and intracellular pathogens, such as viruses. When misfolded proteins accumulate in the ER, they can undergo ubiquitination and proteasomal degradation through components of the ER-associated degradation system. Once a prolonged activity of the UPR pathway occurs, indicating that homeostasis cannot be reestablished, components of this pathway induce cell death by apoptosis. Here, we discuss how viruses have evolved ways to counteract UPR responses to maximize replication. This evolutionary viral ability is important to understand cell pathology and should be taken into account when designing therapeutic interventions and vaccines.

Keywords:  cell stress; endoplasmic reticulum stress; poxvirus; unfolded protein response

DOI:  https://doi.org/10.3390/v16101555
Vet Microbiol. 2024 Oct 22. pii: S0378-1135(24)00306-7. [Epub ahead of print]298 110284

Antiviral role of cholesterol 25-hydroxylase in inhibiting porcine circovirus 3 replication.

Baoge Zhang, Lumen Chao, Zhendong Wang, Hao Yu, Yufeng Li.

  Cholesterol 25-hydroxylase (CH25H) has significant antiviral effects through the production of 25-hydroxycholesterol (25HC). In this study, we investigated the effects of CH25H, its catalytic product 25HC, and its catalytic mutant lacking hydroxylase activity (CH25H-M) on porcine circovirus 3 (PCV3) replication. By transfecting PCV3 persistently infected PK-15 cells with the pCAGGS-CH25H-Flag plasmid, the results demonstrated that overexpression of CH25H significantly inhibited PCV3 Cap protein expression, Cap mRNA levels, and viral titers in a dose-dependent manner. Moreover, its catalytic product 25HC inhibited PCV3 replication in PK-15 cells at concentrations below 10 µM without affecting cell viability. In contrast, knockdown of endogenous CH25H using small interfering RNA (siRNA) enhanced PCV3 replication, further confirming its antiviral role. Interestingly, the CH25H-M mutant also exhibited inhibitory effects on PCV3 replication, although the inhibition was much less effective compared with CH25H. In conclusion, CH25H plays a critical role in regulating PCV3 replication, and its antiviral effect is not entirely dependent on its enzymatic activity. These findings provide new insights into both the enzymatic and non-enzymatic antiviral mechanisms of CH25H and revealed some mechanistic immune evasion for PCV3.

Keywords:  25-hydroxycholesterol; Antiviral effects; CH25H catalytic mutant; Cholesterol 25-hydroxylase; Porcine circovirus type 3

DOI:  https://doi.org/10.1016/j.vetmic.2024.110284