bims-rebvin 2023-03-19 papers

Issue of 2023‒03‒19
five papers selected by
Alexander Ivanov

Arch Virol. 2023 Mar 15. 168(4): 113

Hepatitis C virus nonstructural protein 4B induces lipogenesis via the Hippo pathway.

Chen Zou, Hongxi Tan, Jun Zeng, Minqi Liu, Guangping Zhang, Yi Zheng, Zhanfeng Zhang.

Hepatitis C virus (HCV) infection causes abnormal lipid metabolism in hepatocytes, which leads to hepatic steatosis and even hepatocellular carcinoma. HCV nonstructural protein 4B (NS4B) has been reported to induce lipogenesis, but the underlying mechanism is unclear. In this study, western blots were performed to investigate the effect of NS4B protein levels on key effectors of the Hippo and AKT signaling pathways. Yes-associated protein (YAP) and moesin-ezrin-radixin-like protein (Merlin) are effectors of the Hippo pathway. NS4B downregulated Merlin and phosphorylated YAP (p-YAP) protein expression while increasing the expression of the key AKT pathway proteins p-AKT and NF-κB. By observing the levels of AKT pathway proteins when Merlin was overexpressed or silenced, it was determined that Merlin mediates the AKT pathway. We suggest that HCV NS4B may mediate the AKT signaling pathway by inhibiting the Hippo pathway. Lipid droplets were observed in Huh7.5 cells overexpressing NS4B, and they increased significantly in number when Merlin was silenced. Overexpression of NS4B and Merlin silencing enhanced the expression of sterol regulatory element binding proteins (SREBPs), which have been demonstrated to be key regulatory factors controlling fatty acid synthesis. NS4B and Merlin silencing also enhanced the in vitro proliferative capacity of hepatocellular carcinoma cells. In conclusion, NS4B induces lipogenesis via the effect of the Hippo-YAP pathway on the AKT signaling pathway and thereby plays a significant role in the pathogenesis of HCV-associated diseases.

DOI: https://doi.org/10.1007/s00705-023-05743-4

Inflammopharmacology. 2023 Mar 15.

Nutritional deficiencies that may predispose to long COVID.

John V Schloss.

Multiple nutritional deficiencies (MND) confound studies designed to assess the role of a single nutrient in contributing to the initiation and progression of disease states. Despite the perception of many healthcare practitioners, up to 25% of Americans are deficient in five-or-more essential nutrients. Stress associated with the COVID-19 pandemic further increases the prevalence of deficiency states. Viral infections compete for crucial nutrients with immune cells. Viral replication and proliferation of immunocompetent cells critical to the host response require these essential nutrients, including zinc. Clinical studies have linked levels of more than 22 different dietary components to the likelihood of COVID-19 infection and the severity of the disease. People at higher risk of infection due to MND are also more likely to have long-term sequelae, known as Long COVID.

Keywords: Glutathione peroxidase isozyme 4; Lymphocyte proliferation assay; Multiple nutritional deficiencies; Myeloperoxidase; NADPH oxidase 2

DOI: https://doi.org/10.1007/s10787-023-01183-3

J Med Virol. 2023 Mar 17.

KSHV Hijacks FoxO1 to Promote Cell Proliferation and Cellular Transformation by Antagonizing Oxidative Stress.

Tingting Li, Shou-Jiang Gao.

Reactive oxygen species (ROS) are a group of a highly short-lived molecules that control diverse behaviors of cells. Normal cells maintain ROS balance to ensure their functions. Because of oncogenic stress, cancer cells often have excessive ROS, also known as oxidative stress, which are often counteracted by enhanced antioxidant systems in order to maintain redox homeostasis. Kaposi's sarcoma-associated herpesvirus (KSHV) is an oncogenic virus associated with Kaposi's sarcoma (KS), which manifests hyper inflammation and oxidative stress as the hallmarks. We have previously shown that excessive ROS can disrupt KSHV latency by inducing viral lytic replication, leading to cell death. Paradoxically, most KS tumor cells are latently infected by KSHV in a highly inflammatory and oxidative stress tumor microenvironment, which is in part due to the activation of alternative complement and TLR4 pathways, indicating the existence of an enhanced antioxidant defense system in KS tumor cells. In this study, we show that KSHV upregulates antioxidant genes, including SOD2 and CAT by hijacking the forkhead box protein O1 (FoxO1), to maintain intracellular ROS level. Moreover, the fine-tuned balance of ROS level in KSHV-transformed cells is essential for cell survival. Consequently, KSHV-transformed cells are extremely sensitive to exogenous ROS insult such as treatment with a low level of hydrogen peroxide (H2 O2 ). Either chemical inhibition or knockdown of FoxO1 by siRNAs decreases the expression of antioxidant genes and subsequently increases the intracellular ROS level in KSHV-transformed cells, resulting in the inhibition of cell proliferation and colony formation in soft agar. Mechanistically, KSHV-encoded microRNAs and vFLIP upregulate FoxO1 by activating the NF-κB pathway. These results reveal a novel mechanism by which an oncogenic virus counteracts oxidative stress by upregulating FoxO1, which is essential for KSHV-induced cell proliferation and cellular transformation. Therefore, FoxO1 might be a potential therapeutic target for KSHV-related malignancies. This article is protected by copyright. All rights reserved.

Keywords: FoxO1; KS; KSHV; Kaposi's sarcoma; Kaposi's sarcoma-associated herpesvirus; NF-κB; ROS; Reactive oxygen species; Viral miRNAs; vFLIP

DOI: https://doi.org/10.1002/jmv.28676

Vet Res. 2023 Mar 14. 54(1): 22

Orf virus induces complete autophagy to promote viral replication via inhibition of AKT/mTOR and activation of the ERK1/2/mTOR signalling pathway in OFTu cells.

Lijun Lv, Jiyu Guan, Ruixue Zhen, Pin Lv, Mengshi Xu, Xingyuan Liu, Shishi He, Ziyu Fang, Zi Li, Yungang Lan, Huijun Lu, Wenqi He, Feng Gao, Kui Zhao.

Orf virus (ORFV) is the causative agent of contagious ecthyma, which is an important zoonotic pathogen with a widespread distribution affecting sheep, goats and humans. Our previous research showed that autophagy can be induced in host cells by ORFV infection. However, the exact mechanism of ORFV-induced autophagy remains unknown. In this study, we investigated the underlying mechanisms of autophagy induced by ORFV in OFTu cells and the impact of autophagy on ORFV replication. By using specific autophagy inhibitors and activators, Western blotting, immunofluorescence and transmission electron microscopy imaging, we confirmed that ORFV infection triggered intracellular autophagosome accumulation and the activation of autophagic flux. Moreover, ORFV-induced autophagic activity was found to rely on an increase in the phosphorylation of tuberous sclerosis complex 2 (TSC2) and a decrease in the phosphorylation of mammalian target of rapamycin (mTOR), which is mediated by the suppression of the PI3K/AKT/mTOR signalling pathway and activation of the ERK1/2/mTOR signalling pathway. Furthermore, we investigated the role of mTOR-mediated autophagy during ORFV replication using pharmacological agents and demonstrated that ORFV-induced autophagy correlated positively with viral replication. Taken together, our data reveal the pathways of ORFV-induced autophagy and the impact of autophagy on ORFV replication, providing new insights into ORFV pathogenesis.

Keywords: ERK1/2/mTOR; ORFV; PI3K/AKT/mTOR; autophagy; replication

DOI: https://doi.org/10.1186/s13567-023-01153-1

Front Cell Dev Biol. 2023 ;11 1110271

Ectopic expression of SARS-CoV-2 S and ORF-9B proteins alters metabolic profiles and impairs contractile function in cardiomyocytes.

Peng Zhang, Yu Liu, Chunfeng Li, Lindsay D Stine, Pei-Hui Wang, Matthew W Turnbull, Haodi Wu, Qing Liu.

Coronavirus disease 2019 (COVID-19) is associated with adverse impacts in the cardiovascular system, but the mechanisms driving this response remain unclear. In this study, we conducted "pseudoviral infection" of SARS-CoV-2 subunits to evaluate their toxic effects in cardiomyocytes (CMs), that were derived from human induced pluripotent stem cells (hiPSCs). We found that the ectopic expression of S and ORF-9B subunits significantly impaired the contractile function and altered the metabolic profiles in human cardiomyocytes. Further mechanistic study has shown that the mitochondrial oxidative phosphorylation (OXPHOS), membrane potential, and ATP production were significantly decreased two days after the overexpression of S and ORF-9B subunits, while S subunits induced higher level of reactive oxygen species (ROS). Two weeks after overexpression, glycolysis was elevated in the ORF-9B group. Based on the transcriptomic analysis, both S and ORF-9B subunits dysregulated signaling pathways associated with metabolism and cardiomyopathy, including upregulated genes involved in HIF-signaling and downregulated genes involved in cholesterol biosynthetic processes. The ORF-9B subunit also enhanced glycolysis in the CMs. Our results collectively provide an insight into the molecular mechanisms underlying SARS-CoV-2 subunits-induced metabolic alterations and cardiac dysfunctions in the hearts of COVID-19 patients.

Keywords: 9b; S; SARS-CoV-2; cardiomyocyte; metabolism

DOI: https://doi.org/10.3389/fcell.2023.1110271