Deficiency in either 4E-BP1 or 4E-BP2 augments innate antiviral immune responses.
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ABSTRACT:
SUBMITTER: Nehdi A
PROVIDER: S-EPMC4273997 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:BackgroundSarcopenia is the loss of muscle mass/function that occurs during the aging process. The links between mechanistic target of rapamycin (mTOR) activity and muscle development are largely documented, but the role of its downstream targets in the development of sarcopenia is poorly understood. Eukaryotic initiation factor 4E-binding proteins (4E-BPs) are targets of mTOR that repress mRNA translation initiation and are involved in the control of several physiological processes. However, their role in skeletal muscle is still poorly understood. The goal of this study was to assess how loss of 4E-BP1 and 4E-BP2 expression impacts skeletal muscle function and homeostasis in aged mice and to characterize the associated metabolic changes by metabolomic and lipidomic profiling.MethodsTwenty-four-month-old wild-type and whole body 4E-BP1/4E-BP2 double knockout (DKO) mice were used to measure muscle mass and function. Protein homeostasis was measured ex vivo in extensor digitorum longus by incorporation of l-[U-14 C]phenylalanine, and metabolomic and lipidomic profiling of skeletal muscle was performed by Metabolon, Inc.ResultsThe 4E-BP1/2 DKO mice exhibited an increase in muscle mass that was associated with increased grip strength (P < 0.05). Protein synthesis was higher under both basal (+102%, P < 0.05) and stimulated conditions (+65%, P < 0.05) in DKO skeletal muscle. Metabolomic and complex lipid analysis of skeletal muscle revealed robust differences pertaining to amino acid homeostasis, carbohydrate abundance, and certain aspects of lipid metabolism. In particular, levels of most free amino acids were lower within the 4E-BP1/2 DKO muscle. Interestingly, although glucose levels were unchanged, differences were observed in the isobaric compound maltitol/lactitol (33-fold increase, P < 0.01) and in several additional carbohydrate compounds. 4E-BP1/2 depletion also resulted in accumulation of medium-chain acylcarnitines and a 20% lower C2/C0 acylcarnitine ratio (P < 0.01) indicative of reduced β-oxidation.ConclusionsTaken together, these findings demonstrate that deletion of 4E-BPs is associated with perturbed energy metabolism in skeletal muscle and could have beneficial effects on skeletal muscle mass and function in aging mice. They also identify 4E-BPs as potential targets for the treatment of sarcopenia.
| S-EPMC6596930 | biostudies-literature
Project description:The most common pathology associated with obesity is insulin resistance, which results in the onset of type 2 diabetes mellitus. Several studies have implicated the mammalian target of rapamycin (mTOR) signaling pathway in obesity. Eukaryotic translation initiation factor 4E-binding (eIF4E-binding) proteins (4E-BPs), which repress translation by binding to eIF4E, are downstream effectors of mTOR. We report that the combined disruption of 4E-BP1 and 4E-BP2 in mice increased their sensitivity to diet-induced obesity. Increased adiposity was explained at least in part by accelerated adipogenesis driven by increased expression of CCAAT/enhancer-binding protein delta (C/EBPdelta), C/EBPalpha, and PPARgamma coupled with reduced energy expenditure, reduced lipolysis, and greater fatty acid reesterification in the adipose tissue of 4E-BP1 and 4E-BP2 double KO mice. Increased insulin resistance in 4E-BP1 and 4E-BP2 double KO mice was associated with increased ribosomal protein S6 kinase (S6K) activity and impairment of Akt signaling in muscle, liver, and adipose tissue. These data clearly demonstrate the role of 4E-BPs as a metabolic brake in the development of obesity and reinforce the idea that deregulated mTOR signaling is associated with the development of the metabolic syndrome.
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Project description:Pattern-recognition receptors (PRRs), including Toll-like receptors (TLRs) and RIG-like helicase (RLH) receptors, are involved in innate immune antiviral responses. Here we show that nucleotide-binding oligomerization domain 2 (Nod2) can also function as a cytoplasmic viral PRR by triggering activation of interferon-regulatory factor 3 (IRF3) and production of interferon-beta (IFN-beta). After recognition of a viral ssRNA genome, Nod2 used the adaptor protein MAVS to activate IRF3. Nod2-deficient mice failed to produce interferon efficiently and showed enhanced susceptibility to virus-induced pathogenesis. Thus, the function of Nod2 as a viral PRR highlights the important function of Nod2 in host antiviral defense mechanisms.
| S-EPMC2752345 | biostudies-other
Project description:Autophagy is an essential process for physiological homeostasis, but its role in viral infection is only beginning to be elucidated. We show here that the Atg5-Atg12 conjugate, a key regulator of the autophagic process, plays an important role in innate antiviral immune responses. Atg5-deficient mouse embryonic fibroblasts (MEFs) were resistant to vesicular stomatitis virus replication, which was largely due to hyperproduction of type I interferons in response to immunostimulatory RNA (isRNA), such as virus-derived, double-stranded, or 5'-phosphorylated RNA. Similar hyperresponse to isRNA was also observed in Atg7-deficient MEFs, in which Atg5-Atg12 conjugation is impaired. Overexpression of Atg5 or Atg12 resulted in Atg5-Atg12 conjugate formation and suppression of isRNA-mediated signaling. Molecular interaction studies indicated that the Atg5-Atg12 conjugate negatively regulates the type I IFN production pathway by direct association with the retinoic acid-inducible gene I (RIG-I) and IFN-beta promoter stimulator 1 (IPS-1) through the caspase recruitment domains (CARDs). Thus, in contrast to its role in promoting the bactericidal process, a component of the autophagic machinery appears to block innate antiviral immune responses, thereby contributing to RNA virus replication in host cells.
| S-EPMC1955809 | biostudies-other
Project description:ObjectiveCyclin-dependent kinase 1 (CDK1)/cyclin B1 phosphorylates many of the same substrates as mTORC1 (a key regulator of glucose metabolism), including the eukaryotic initiation factor 4E-binding protein 1 (4E-BP1). Only mitotic CDK1 phosphorylates 4E-BP1 at residue S82 in mice (S83 in humans), in addition to the common 4E-BP1 phospho-acceptor sites phosphorylated by both CDK1 and mTORC1. We examined glucose metabolism in mice having a single aspartate phosphomimetic amino acid knock in substitution at the 4E-BP1 serine 82 (4E-BP1S82D) mimicking constitutive CDK1 phosphorylation.MethodsKnock-in homozygous 4E-BP1S82D and 4E-BP1S82A C57Bl/6N mice were assessed for glucose tolerance testing (GTT) and metabolic cage analysis on regular and on high-fat chow diets. Gastrocnemius tissues from 4E-BP1S82D and WT mice were subject to Reverse Phase Protein Array analysis. Since the bone marrow is one of the few tissues typically having cycling cells that transit mitosis, reciprocal bone-marrow transplants were performed between male 4E-BP1S82D and WT mice, followed by metabolic assessment, to determine the role of actively cycling cells on glucose homeostasis.ResultsHomozygous knock-in 4E-BP1S82D mice showed glucose intolerance that was markedly accentuated with a diabetogenic high-fat diet (p = 0.004). In contrast, homozygous mice with the unphosphorylatable alanine substitution (4E-BP1S82A) had normal glucose tolerance. Protein profiling of lean muscle tissues, largely arrested in G0, did not show protein expression or signaling changes that could account for these results. Reciprocal bone-marrow transplantation between 4E-BP1S82D and wild-type littermates revealed a trend for wild-type mice with 4E-BP1S82D marrow engraftment on high-fat diets to become hyperglycemic after glucose challenge.Conclusions4E-BP1S82D is a single amino acid substitution that induces glucose intolerance in mice. These findings indicate that glucose metabolism may be regulated by CDK1 4E-BP1 phosphorylation independent from mTOR and point towards an unexpected role for cycling cells that transit mitosis in diabetic glucose control.
| S-EPMC10004604 | biostudies-literature
Project description:The galectin 3 binding protein (LGALS3BP, also known as 90K) is a ubiquitous multifunctional secreted glycoprotein originally identified in cancer progression. It remains unclear how 90K functions in innate immunity during viral infections. In this study, we found that viral infections resulted in elevated levels of 90K. Further studies demonstrated that 90K expression suppressed virus replication by inducing IFN and pro-inflammatory cytokine production. Upon investigating the mechanisms behind this event, we found that 90K functions as a scaffold/adaptor protein to interact with TRAF6, TRAF3, TAK1 and TBK1. Furthermore, 90K enhanced TRAF6 and TRAF3 ubiquitination and served as a specific ubiquitination substrate of TRAF6, leading to transcription factor NF-κB, IRF3 and IRF7 translocation from the cytoplasm to the nucleus. Conclusions: 90K is a virus-induced protein capable of binding with the TRAF6 and TRAF3 complex, leading to IFN and pro-inflammatory production.
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Project description:Highly pathogenic coronavirus (CoV) infection induces a defective innate antiviral immune response coupled with the dysregulated release of proinflammatory cytokines and finally results in acute respiratory distress syndrome (ARDS). A timely and appropriate triggering of innate antiviral response is crucial to inhibit viral replication and prevent ARDS. However, current medical countermeasures can rarely meet this urgent demand. Here, an antiviral nanobiologic named CoVR-MV is developed, which is polymerized of CoVs receptors based on a biomimetic membrane vesicle system. The designed CoVR-MV interferes with the viral infection by absorbing the viruses with maximized viral spike target interface, and mediates the clearance of the virus through its inherent interaction with macrophages. Furthermore, CoVR-MV coupled with the virus promotes a swift production and signaling of endogenous type I interferon via deregulating 7-dehydrocholesterol reductase (DHCR7) inhibition of interferon regulatory factor 3 (IRF3) activation in macrophages. These sequential processes re-modulate the innate immune responses to the virus, trigger spontaneous innate antiviral defenses, and rescue infected Syrian hamsters from ARDS caused by SARS-CoV-2 and all tested variants.
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Project description:Rationale: Hosts defend against viral infection by sensing viral pathogen-associated molecular patterns and activating antiviral innate immunity through TBK1-IRF3 signaling. However, the underlying molecular mechanism remains unclear. Methods: SiRNAs targeting Sirt1-7 were transfected into macrophages to screen the antiviral function. Sirt5 deficient mice or macrophages were subjected to viral infection to assess in vivo and in vitro function of Sirt5 by detecting cytokines, viral replicates and survival rate. Immunoprecipitation, WesternBlot and luciferase reporter assay were used to reveal molecular mechanism. Results: In this study, we functionally screened seven Sirtuin family members, and found that Sirtuin5 (Sirt5) promotes antiviral signaling and responses. Sirt5 deficiency leads to attenuated antiviral innate immunity in vivo and in vitro upon viral infection by decreasing TBK1-IRF3 activation and type I IFN production. Sirt5 overexpression increased antiviral innate immunity. Mechanism investigation revealed that Sirt5 interacts with DDX3 and demalonylates DDX3, which is critical for TBK1-IRF3 activation. Mutation of the demalonylation lysine sites (K66, K130, and K162) of DDX3 increased ifnβ transcription. Furthermore, the acetylation on lysine 118 of DDX3 positively regulated ifnβ transcription, whereas Sirt5 could not deacetylate this site. Conclusion: Sirt5 promotes anti- RNA and DNA virus innate immune responses by increasing TBK1 signaling through demalonylating DDX3, which identifies a novel regulatory pathway of antiviral innate immune response.
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Project description:Bats are important hosts for various zoonotic viral diseases. However, they rarely show signs of disease infection with such viruses. As the first line for virus control, the innate immune system of bats attracted our full attention. In this study, the Tadarida brasiliensis MDA5 gene (batMDA5), a major sensor for anti-RNA viral infection, was first cloned, and its biological functions in antiviral innate immunity were identified. Bioinformatics analysis shows that the amino acid sequence of batMDA5 is poorly conserved among species, and it is evolutionarily closer to humans. The mRNA of batMDA5 was significantly upregulated in Newcastle disease virus (NDV), avian influenza virus (AIV), and vesicular stomatitis virus (VSV)-infected bat TB 1 Lu cells. Overexpression of batMDA5 could activate IFNβ and inhibit vesicular stomatitis virus (VSV-GFP) replication in TB 1 Lu cells, while knockdown of batMDA5 yielded the opposite result. In addition, we found that the CARD domain was essential for MDA5 to activate IFNβ by constructing MDA5 domain mutant plasmids. These results indicated that bat employs a conserved MDA5 gene to trigger anti-RNA virus innate immune response. This study helps understand the biological role of MDA5 in innate immunity during evolution.
| S-EPMC9168228 | biostudies-literature
Project description:Rotavirus infection is a major cause of severe dehydrating diarrhea in infants younger than 5 y old and in particular cases of immunocompromised patients irrespective to the age of the patients. Although vaccines have been developed, antiviral therapy is an important complement that cannot be substituted. Because of the lack of specific approved treatment, it is urgent to facilitate the cascade of further understanding of the infection biology, identification of druggable targets and the final development of effective antiviral therapies. PI3K-Akt-mTOR signaling pathway plays a vital role in regulating the infection course of many viruses. In this study, we have dissected the effects of PI3K-Akt-mTOR signaling pathway on rotavirus infection using both conventional cell culture models and a 3D model of human primary intestinal organoids. We found that PI3K-Akt-mTOR signaling is essential in sustaining rotavirus infection. Thus, blocking the key elements of this pathway, including PI3K, mTOR and 4E-BP1, has resulted in potent anti-rotavirus activity. Importantly, a clinically used mTOR inhibitor, rapamycin, potently inhibited both experimental and patient-derived rotavirus strains. This effect involves 4E-BP1 mediated induction of autophagy, which in turn exerts anti-rotavirus effects. These results revealed new insights on rotavirus-host interactions and provided new avenues for antiviral drug development.
| S-EPMC5955461 | biostudies-literature