bims-mevinf 2023-09-10 papers

Issue of 2023‒09‒10
seven papers selected by
Alexander Ivanov, Engelhardt Institute of Molecular Biology

Front Immunol. 2023 ;14 1213180

Two-photon fluorescence lifetime imaging microscopy of NADH metabolism in HIV-1 infected cells and tissues.

Greg A Snyder, Sameer Kumar, George K Lewis, Krishanu Ray.

Rapid detection of microbial-induced cellular changes during the course of an infection is critical to understanding pathogenesis and immunological homeostasis. In the last two decades, fluorescence imaging has received significant attention for its ability to help characterize microbial induced cellular and tissue changes in in vitro and in vivo settings. However, most of these methods rely on the covalent conjugation of large exogenous probes and detection methods based on intensity-based imaging. Here, we report a quantitative, intrinsic, label-free, and minimally invasive method based on two-photon fluorescence lifetime (FLT) imaging microscopy (2p-FLIM) for imaging 1,4-dihydro-nicotinamide adenine dinucleotide (NADH) metabolism of virally infected cells and tissue sections. To better understand virally induced cellular and tissue changes in metabolism we have used 2p-FLIM to study differences in NADH intensity and fluorescence lifetimes in HIV-1 infected cells and tissues. Differences in NADH fluorescence lifetimes are associated with cellular changes in metabolism and changes in cellular metabolism are associated with HIV-1 infection. NADH is a critical co-enzyme and redox regulator and an essential biomarker in the metabolic processes. Label-free 2p-FLIM application and detection of NADH fluorescence using viral infection systems are in their infancy. In this study, the application of the 2p-FLIM assay and quantitative analyses of HIV-1 infected cells and tissue sections reveal increased fluorescence lifetime and higher enzyme-bound NADH fraction suggesting oxidative phosphorylation (OxPhos) compared to uninfected cells and tissues. 2p-FLIM measurements improve signal to background, fluorescence specificity, provide spatial and temporal resolution of intracellular structures, and thus, are suitable for quantitative studies of cellular functions and tissue morphology. Furthermore, 2p-FLIM allows distinguishing free and bound populations of NADH by their different fluorescence lifetimes within single infected cells. Accordingly, NADH fluorescence measurements of individual single cells should provide necessary insight into the heterogeneity of metabolic activity of infected cells. Implementing 2p-FLIM to viral infection systems measuring NADH fluorescence at the single or subcellular level within a tissue can provide visual evidence, localization, and information in a real-time diagnostic or therapeutic metabolic workflow.

Keywords: HIV-1; NADH metabolism; infected cells and tissues; oxidative phosphorylation; two-photon fluorescence lifetime imaging microscopy

DOI: https://doi.org/10.3389/fimmu.2023.1213180

Life Sci Alliance. 2023 Nov;pii: e202302049. [Epub ahead of print]6(11):

Inhibition of the SREBP pathway prevents SARS-CoV-2 replication and inflammasome activation.

Vinicius Cardoso Soares, Suelen Silva Gomes Dias, Julia Cunha Santos, Isaclaudia G Azevedo-Quintanilha, Isabela Batista Gonçalves Moreira, Carolina Q Sacramento, Natalia Fintelman-Rodrigues, Jairo R Temerozo, Marcos Alexandre Nunes da Silva, Debora Ferreira Barreto-Vieira, Thiago Ml Souza, Patricia T Bozza.

SARS-CoV-2 induces major cellular lipid rearrangements, exploiting the host's metabolic pathways to replicate. Sterol regulatory element binding proteins (SREBPs) are a family of transcription factors that control lipid metabolism. SREBP1 is associated with the regulation of fatty acids, whereas SREBP2 controls cholesterol metabolism, and both isoforms are associated with lipid droplet (LD) biogenesis. Here, we evaluated the effect of SREBP in a SARS-CoV-2-infected lung epithelial cell line (Calu-3). We showed that SARS-CoV-2 infection induced the activation of SREBP1 and SREBP2 and LD accumulation. Genetic knockdown of both SREBPs and pharmacological inhibition with the dual SREBP activation inhibitor fatostatin promote the inhibition of SARS-CoV-2 replication, cell death, and LD formation in Calu-3 cells. In addition, we demonstrated that SARS-CoV-2 induced inflammasome-dependent cell death by pyroptosis and release of IL-1β and IL-18, with activation of caspase-1, cleavage of gasdermin D1, was also reduced by SREBP inhibition. Collectively, our findings help to elucidate that SREBPs are crucial host factors required for viral replication and pathogenesis. These results indicate that SREBP is a host target for the development of antiviral strategies.

DOI: https://doi.org/10.26508/lsa.202302049

Int J Mol Sci. 2023 Aug 28. pii: 13354. [Epub ahead of print]24(17):

Hydrogen Peroxide Inhibits Hepatitis B Virus Replication by Downregulating HBx Levels via Siah-1-Mediated Proteasomal Degradation in Human Hepatoma Cells.

Hyunyoung Yoon, Hye-Kyoung Lee, Kyung Lib Jang.

The hepatitis B virus (HBV) is constantly exposed to significant oxidative stress characterized by elevated levels of reactive oxygen species (ROS), such as H2O2, during infection in hepatocytes of patients. In this study, we demonstrated that H2O2 inhibits HBV replication in a p53-dependent fashion in human hepatoma cell lines expressing sodium taurocholate cotransporting polypeptide. Interestingly, H2O2 failed to inhibit the replication of an HBV X protein (HBx)-null HBV mutant, but this defect was successfully complemented by ectopic expression of HBx. Additionally, H2O2 upregulated p53 levels, leading to increased expression of seven in absentia homolog 1 (Siah-1) levels. Siah-1, an E3 ligase, induced the ubiquitination-dependent proteasomal degradation of HBx. The inhibitory effect of H2O2 was nearly abolished not only by treatment with a representative antioxidant, N-acetyl-L-cysteine but also by knockdown of either p53 or Siah-1 using specific short hairpin RNA, confirming the role of p53 and Siah-1 in the inhibition of HBV replication by H2O2. The present study provides insights into the mechanism that regulates HBV replication under conditions of oxidative stress in patients.

Keywords: HBx; Siah-1; hepatitis B virus; hydrogen peroxide; p53; proteasome

DOI: https://doi.org/10.3390/ijms241713354

Stress Biol. 2022 Apr 15. 2(1): 10

Polyamine-metabolizing enzymes are activated to promote the proper assembly of rice stripe mosaic virus in insect vectors.

Dongsheng Jia, Huan Liu, Jian Zhang, Wenqiang Wan, Zongwen Wang, Xiaofeng Zhang, Qian Chen, Taiyun Wei.

Both viruses and host cells compete for intracellular polyamines for efficient propagation. Currently, how the key polyamine-metabolizing enzymes, including ornithine decarboxylase 1 (ODC1) and its antizyme 1 (OAZ1), are activated to co-ordinate viral propagation and polyamine biosynthesis remains unknown. Here, we report that the matrix protein of rice stripe mosaic virus (RSMV), a cytorhabdovirus, directly hijacks OAZ1 to ensure the proper assembly of rigid bacilliform non-enveloped virions in leafhopper vector. Viral matrix protein effectively competes with ODC1 to bind to OAZ1, and thus, the ability of OAZ1 to target and mediate the degradation of ODC1 is significantly inhibited during viral propagation, which finally promotes polyamines production. Thus, OAZ1 and ODC1 are activated to synergistically promote viral persistent propagation and polyamine biosynthesis in viruliferous vectors. Our data suggest that it is a novel mechanism for rhabdovirus to exploit OAZ1 for facilitating viral assembly.

Keywords: Insect vector; OAZ1; ODC1; Polyamines; Rhabdovirus; Rice stripe mosaic virus; Viral assembly

DOI: https://doi.org/10.1007/s44154-021-00032-z

Kobe J Med Sci. 2023 Aug 31. 69(3): E86-E95

Transcription Factor JunB Suppresses Hepatitis C Virus Replication.

Adi Ariffianto, Lin Deng, Saki Harada, Yujiao Liang, Chieko Matsui, Takayuki Abe, Ikuo Shoji.

We previously reported that hepatitis C virus (HCV) infection activates the reactive oxygen species (ROS)/c-Jun N-terminal kinase (JNK) signaling pathway. Activation of JNK contributes to the development of liver diseases, including metabolic disorders, steatosis, liver cirrhosis and hepatocellular carcinoma. JNK is known to have numerous target genes, including JunB, a member of activator protein-1 transcription factor family. However, the roles of JunB in the HCV life cycle and HCV-associated pathogenesis remain unclear. To clarify a physiological role of JunB in HCV infection, we investigated the phosphorylation of JunB in HCV J6/JFH1-infected Huh-7.5 cells. Immunoblot analysis revealed that HCV-induced ROS/JNK activation promoted phosphorylation of JunB. The small interfering RNA (siRNA) knockdown of JunB significantly increased the amount of intracellular HCV RNA as well as the intracellular and extracellular HCV infectivity titers. Conversely, overexpression of JunB significantly reduced the amount of intracellular HCV RNA and the intracellular and extracellular HCV infectivity titers. These results suggest that JunB plays a role in inhibiting HCV propagation. Additionally, HCV-mediated JunB activation promoted hepcidin promoter activity and hepcidin mRNA levels, a key factor in modulating iron homeostasis, suggesting that JunB is involved in HCV-induced transcriptional upregulation of hepcidin. Taken together, we propose that the HCV-induced ROS/JNK/JunB signaling pathway plays roles in inhibiting HCV replication and contributing to HCV-mediated iron metabolism disorder.

Keywords: Hepatitis C virus; ROS/JNK/JunB; Viral propagation

Dev Cell. 2023 Aug 28. pii: S1534-5807(23)00409-4. [Epub ahead of print]

Usp25-Erlin1/2 activity limits cholesterol flux to restrict virus infection.

Qi Wen Teo, Ho Him Wong, Tiaan Heunis, Viktoriya Stancheva, Asmaa Hachim, Huibin Lv, Lewis Siu, Julian Ho, Yun Lan, Chris Ka Pun Mok, Rachel Ulferts, Sumana Sanyal.

Reprogramming lipid metabolic pathways is a critical feature of activating immune responses to infection. However, how these reconfigurations occur is poorly understood. Our previous screen to identify cellular deubiquitylases (DUBs) activated during influenza virus infection revealed Usp25 as a prominent hit. Here, we show that Usp25-deleted human lung epithelial A549 cells display a >10-fold increase in pathogenic influenza virus production, which was rescued upon reconstitution with the wild type but not the catalytically deficient (C178S) variant. Proteomic analysis of Usp25 interactors revealed a strong association with Erlin1/2, which we confirmed as its substrate. Newly synthesized Erlin1/2 were degraded in Usp25-/- or Usp25C178S cells, activating Srebp2, with increased cholesterol flux and attenuated TLR3-dependent responses. Our study therefore defines the function of a deubiquitylase that serves to restrict a range of viruses by reprogramming lipid biosynthetic flux to install appropriate inflammatory responses.

Keywords: Erlin1/2; Usp25; autophagy; cholesterol; influenza; innate immunity; lipid homeostasis

DOI: https://doi.org/10.1016/j.devcel.2023.08.013

Front Pharmacol. 2023 ;14 1248873

Obesity exacerbates influenza-induced respiratory disease via the arachidonic acid-p38 MAPK pathway.

Ravishankar Chandrasekaran, Carolyn R Morris, Isabella M Butzirus, Zoe F Mark, Amit Kumar, Dhemerson Souza De Lima, Nirav Daphtary, Minara Aliyeva, Matthew E Poynter, Vikas Anathy, Anne E Dixon.

Obesity is a risk factor for severe influenza, and asthma exacerbations caused by respiratory viral infections. We investigated mechanisms that increase the severity of airway disease related to influenza in obesity using cells derived from obese and lean individuals, and in vitro and in vivo models. Primary human nasal epithelial cells (pHNECs) derived from obese compared with lean individuals developed increased inflammation and injury in response to influenza A virus (IAV). Obese mice infected with influenza developed increased airway inflammation, lung injury and elastance, but had a decreased interferon response, compared with lean mice. Lung arachidonic acid (AA) levels increased in obese mice infected with IAV; arachidonic acid increased inflammatory cytokines and injury markers in response to IAV in human bronchial epithelial (HBE) cells. Obesity in mice, and AA in HBE cells, increased activation of p38 MAPK signaling following IAV infection; inhibiting this pathway attenuated inflammation, injury and tissue elastance responses, and improved survival. In summary, obesity increases disease severity in response to influenza infection through activation of the p38 MAPK pathway in response to altered arachidonic acid signaling.

Keywords: arachidonic acid; influenza A virus; lung inflammation; lung injury; obesity; p38 MAPK

DOI: https://doi.org/10.3389/fphar.2023.1248873