The anti-viral dynamin family member MxB participates in mitochondrial integrity

Unraveling extracellular vesicle DNA: Biogenesis, functions, and clinical implications

Extracellular Vesicles (EVs) have emerged as essential carriers of molecular biomarkers and mediators of intercellular communication. While previous studies have predominantly focused on EV proteins, lipids, and RNA, the role of EV-derived DNA (EV-DNA) remains relatively unexplored. Understanding EV-DNA is crucial, given its association with nearly all EV populations. This review aims to comprehensively summarize existing EV-DNA research, emphasizing its functional significance and potential as a disease biomarker. By bridging the gap in our understanding, we shed light on the origins, structure, localization, and distribution of EV-DNA. We analyze a wide range of studies, investigating EV-DNA across various pathological conditions. Our review encompasses experimental methods, theoretical approaches, and clinical observations, providing a holistic view of EV-DNA research. We discuss the biogenesis mechanisms of different EV subtypes, the available isolation methods for these subtypes, and consider their origins and variability under different conditions. EV-DNA exhibits remarkable stability and reflects genomic alterations, making it a promising candidate for liquid biopsy applications. From cancer diagnostics to treatment monitoring, EV-DNA holds significant potential. The findings underscore the importance of EV-DNA as an innovative biomarker. As research continues, EV-DNA may revolutionize disease detection, prognosis, and therapeutic strategies.

MX2 forms nucleoporin-comprising cytoplasmic biomolecular condensates that lure viral capsids

Human myxovirus resistance 2 (MX2) can restrict HIV-1 and herpesviruses at a post-entry step through a process requiring an interaction between MX2 and the viral capsids. The involvement of other host cell factors, however, remains poorly understood. Here, we mapped the proximity interactome of MX2, revealing strong enrichment of phenylalanine-glycine (FG)-rich proteins related to the nuclear pore complex as well as proteins that are part of cytoplasmic ribonucleoprotein granules. MX2 interacted with these proteins to form multiprotein cytoplasmic biomolecular condensates that were essential for its anti-HIV-1 and anti-herpes simplex virus 1 (HSV-1) activity. MX2 condensate formation required the disordered N-terminal region and MX2 dimerization. Incoming HIV-1 and HSV-1 capsids associated with MX2 at these dynamic cytoplasmic biomolecular condensates, preventing nuclear entry of their viral genomes. Thus, MX2 forms cytoplasmic condensates that likely act as nuclear pore decoys, trapping capsids and inducing premature viral genome release to interfere with nuclear targeting of HIV-1 and HSV-1.

STING in tumors: a focus on non-innate immune pathways

Cyclic GMP-AMP synthase (cGAS) and downstream stimulator of interferon genes (STING) are involved in mediating innate immunity by promoting the release of interferon and other inflammatory factors. Mitochondrial DNA (mtDNA) with a double-stranded structure has greater efficiency and sensitivity in being detected by DNA sensors and thus has an important role in the activation of the cGAS-STING pathway. Many previous findings suggest that the cGAS-STING pathway-mediated innate immune regulation is the most important aspect affecting tumor survival, not only in its anti-tumor role but also in shaping the immunosuppressive tumor microenvironment (TME) through a variety of pathways. However, recent studies have shown that STING regulation of non-immune pathways is equally profound and also involved in tumor cell progression. In this paper, we will focus on the non-innate immune system pathways, in which the cGAS-STING pathway also plays an important role in cancer.

You Shall Not Pass: MX2 Proteins Are Versatile Viral Inhibitors

Myxovirus resistance (MX) proteins are pivotal players in the innate immune response to viral infections. Less than 10 years ago, three independent groups simultaneously showed that human MX2 is an interferon (IFN)-stimulated gene (ISG) with potent anti-human immunodeficiency virus 1 (HIV-1) activity. Thenceforth, multiple research works have been published highlighting the ability of MX2 to inhibit RNA and DNA viruses. These growing bodies of evidence have identified some of the key determinants regulating its antiviral activity. Therefore, the importance of the protein amino-terminal domain, the oligomerization state, or the ability to interact with viral components is now well recognized. Nonetheless, there are still several unknown aspects of MX2 antiviral activity asking for further research, such as the role of cellular localization or the effect of post-translational modifications. This work aims to provide a comprehensive review of our current knowledge on the molecular determinants governing the antiviral activity of this versatile ISG, using human MX2 and HIV-1 inhibition as a reference, but drawing parallelisms and noting divergent mechanisms with other proteins and viruses when necessary.

IFIT3 Is Increased in Serum from Patients with Chronic Hepatitis B Virus (HBV) Infection and Promotes the Anti-HBV Effect of Interferon Alpha via JAK-STAT2 In Vitro

Increasing evidence indicates that interferon alpha (IFN-α) therapy is an effective treatment option for a subgroup of patients with chronic hepatitis B virus (HBV) infection. It has been confirmed that interferon-induced protein with tetratricopeptide repeats 3 (IFIT3), a member of the interferon-stimulated genes (ISGs), could inhibit the replication of various viruses. However, its effect on HBV replication is unclear. The present study sought to explore the role and mechanism of IFIT3 in IFN-α antiviral activities against HBV. IFIT3 mRNA levels in the peripheral blood of 108 treatment-naive patients and 70 healthy controls were analyzed first. The effect of IFIT3 on the Janus kinase-signal transducer and activator of transcription (JAK-STAT) signaling pathway under the dual intervention of IFN-α and HBV was also explored in vitro. Treatment-naive individuals exhibited elevated levels of IFIT3 mRNA compared to the controls (P < 0.0001). Mechanistically, the knockdown of IFIT3 inhibited the phosphorylation of signal transducer and activator of transcription 2 (STAT2), whereas the overexpression of IFIT3 produced the opposite effect in vitro. Meanwhile, the overexpression of IFIT3 enhanced the expression of IFN-α-triggered ISGs, including myxovirus resistance A (MxA), 2'-5'-oligoadenylate synthetase 1 (OAS1), and double-stranded RNA-activated protein kinase (PKR), while a weaker induction of IFN-α-triggered ISGs was observed in ruxolitinib-treated cells. After decreasing IFIT3 expression by validated small hairpin RNAs (shRNAs), the levels of hepatitis B surface antigen (HBsAg), hepatitis B e antigen (HBeAg), and HBV DNA secreted by HepG2 cells transiently transfected with the pHBV1.2 plasmid were increased. Our findings suggest that IFIT3 works in a STAT2-dependent manner to promote the antiviral effect of IFN-α through the JAK-STAT pathway in HBV infection in both human hepatocytes and hepatocarcinoma cells. IMPORTANCE Our study contributes new insights into the understanding of the functions and roles of interferon-induced protein with tetratricopeptide repeats 3 (IFIT3), which is one of the interferon-stimulated genes induced by hepatitis B virus infection in human hepatocytes and hepatocarcinoma cells, and may help to identify targeted genes promoting the efficacy of interferon alpha.

NFIC1 suppresses migration and invasion of breast cancer cells through interferon-mediated Jak-STAT pathway

NFIC1, the longest isoform of NFIC, is essential for the regulation on spatiotemporal expression of drug-metabolizing genes in liver. However, the role of NFIC1 in breast cancer is not clear. Here we showed that increased expression of NFIC1 suppressed the migration and invasion of MCF-7 cells. NFIC1 overexpression increased the expression of IFNB1, IFNL1, IFNL2 and IFNL3, and the activation of interferon-mediated Jak-STAT pathway was enhanced by NFIC1 overexpression. Treatment with Jak-STAT pathway inhibitors, Filgotinib or Ruxolitinib, reversed the suppressive effects of NFIC1 overexpression on migration and invasion of MCF-7 cells. In addition, we found that MX1 and MX2, two target genes of Jak-STAT pathway, mediated the migration and invasion of MCF-7 cells. These results demonstrated that NFIC1 inhibited the migration and invasion in MCF-7 cells through interferon-mediated activation of Jak-STAT pathway, indicating that Jak-STAT pathway might be a potential therapeutic target for preventing breast cancer metastasis.

Mitoquinone mesylate targets SARS-CoV-2 infection in preclinical models

To date, there is no effective oral antiviral against SARS-CoV-2 that is also anti-inflammatory. Herein, we show that the mitochondrial antioxidant mitoquinone/mitoquinol mesylate (Mito-MES), a dietary supplement, has potent antiviral activity against SARS-CoV-2 and its variants of concern in vitro and in vivo . Mito-MES had nanomolar in vitro antiviral potency against the Beta and Delta SARS-CoV-2 variants as well as the murine hepatitis virus (MHV-A59). Mito-MES given in SARS-CoV-2 infected K18-hACE2 mice through oral gavage reduced viral titer by nearly 4 log units relative to the vehicle group. We found in vitro that the antiviral effect of Mito-MES is attributable to its hydrophobic dTPP+ moiety and its combined effects scavenging reactive oxygen species (ROS), activating Nrf2 and increasing the host defense proteins TOM70 and MX1. Mito-MES was efficacious reducing increase in cleaved caspase-3 and inflammation induced by SARS-CoV2 infection both in lung epithelial cells and a transgenic mouse model of COVID-19. Mito-MES reduced production of IL-6 by SARS-CoV-2 infected epithelial cells through its antioxidant properties (Nrf2 agonist, coenzyme Q10 moiety) and the dTPP moiety. Given established safety of Mito-MES in humans, our results suggest that Mito-MES may represent a rapidly applicable therapeutic strategy that can be added in the therapeutic arsenal against COVID-19. Its potential long-term use by humans as diet supplement could help control the SARS-CoV-2 pandemic, especially in the setting of rapidly emerging SARS-CoV-2 variants that may compromise vaccine efficacy.

One-Sentence Summary

Mitoquinone/mitoquinol mesylate has potent antiviral and anti-inflammatory activity in preclinical models of SARS-CoV-2 infection.

The interferon-inducible GTPase MxB promotes capsid disassembly and genome release of herpesviruses

Host proteins sense viral products and induce defence mechanisms, particularly in immune cells. Using cell-free assays and quantitative mass spectrometry, we determined the interactome of capsid-host protein complexes of herpes simplex virus and identified the large dynamin-like GTPase myxovirus resistance protein B (MxB) as an interferon-inducible protein interacting with capsids. Electron microscopy analyses showed that cytosols containing MxB had the remarkable capability to disassemble the icosahedral capsids of herpes simplex viruses and varicella zoster virus into flat sheets of connected triangular faces. In contrast, capsids remained intact in cytosols with MxB mutants unable to hydrolyse GTP or to dimerize. Our data suggest that MxB senses herpesviral capsids, mediates their disassembly, and thereby restricts the efficiency of nuclear targeting of incoming capsids and/or the assembly of progeny capsids. The resulting premature release of viral genomes from capsids may enhance the activation of DNA sensors, and thereby amplify the innate immune responses.

MxB inhibits long interspersed element type 1 retrotransposition

Long interspersed element type 1 (LINE-1, also L1 for short) is the only autonomously transposable element in the human genome. Its insertion into a new genomic site may disrupt the function of genes, potentially causing genetic diseases. Cells have thus evolved a battery of mechanisms to tightly control LINE-1 activity. Here, we report that a cellular antiviral protein, myxovirus resistance protein B (MxB), restricts the mobilization of LINE-1. This function of MxB requires the nuclear localization signal located at its N-terminus, its GTPase activity and its ability to form oligomers. We further found that MxB associates with LINE-1 protein ORF1p and promotes sequestration of ORF1p to G3BP1-containing cytoplasmic granules. Since knockdown of stress granule marker proteins G3BP1 or TIA1 abolishes MxB inhibition of LINE-1, we conclude that MxB engages stress granule components to effectively sequester LINE-1 proteins within the cytoplasmic granules, thus hindering LINE-1 from accessing the nucleus to complete retrotransposition. Thus, MxB protein provides one mechanism for cells to control the mobility of retroelements.

Retrotransposons occupy more than 40% of human genome, and have co-evolved with humans for millions of years. Long interspersed element type 1 (LINE-1, or L1) is the only retrotransposon that is able to jump to a new locus. LINE-1 retrotransposition causes genome instability, and is associated with genetic diseases including autoimmune diseases and cancer. To suppress this genome toxicity caused by LINE-1, humans have developed multi-layered mechanisms to control LINE-1 activity. MxB has been previously shown to inhibit LINE-1 mobility, thus contributing to host restriction of LINE-1. Here, we further demonstrate that MxB effectively restricts LINE-1 retrotransposition by sequestering LINE-1 ribonucleoprotein (RNP) within the cytoplasmic stress granules, thus guards genome stability. Hence our data attribute the restriction function of MxB to sequestering LINE-1 RNP to stress granules.

Cytoplasmic DNA: sources, sensing, and role in aging and disease

Endogenous cytoplasmic DNA (cytoDNA) species are emerging as key mediators of inflammation in diverse physiological and pathological contexts. Although the role of endogenous cytoDNA in innate immune activation is well established, the cytoDNA species themselves are often poorly characterized and difficult to distinguish, and their mechanisms of formation, scope of function and contribution to disease are incompletely understood. Here, we summarize current knowledge in this rapidly progressing field with emphases on similarities and differences between distinct cytoDNAs, their underlying molecular mechanisms of formation and function, interactions between cytoDNA pathways, and therapeutic opportunities in the treatment of age-associated diseases.

The transcriptome profile of human trisomy 21 blood cells

BACKGROUND

Trisomy 21 (T21) is a genetic alteration characterised by the presence of an extra full or partial human chromosome 21 (Hsa21) leading to Down syndrome (DS), the most common form of intellectual disability (ID). It is broadly agreed that the presence of extra genetic material in T21 gives origin to an altered expression of genes located on Hsa21 leading to DS phenotype. The aim of this study was to analyse T21 and normal control blood cell gene expression profiles obtained by total RNA sequencing (RNA-Seq).

RESULTS

The results were elaborated by the TRAM (Transcriptome Mapper) software which generated a differential transcriptome map between human T21 and normal control blood cells providing the gene expression ratios for 17,867 loci. The obtained gene expression profiles were validated through real-time reverse transcription polymerase chain reaction (RT-PCR) assay and compared with previously published data. A post-analysis through transcriptome mapping allowed the identification of the segmental (regional) variation of the expression level across the whole genome (segment-based analysis of expression). Interestingly, the most over-expressed genes encode for interferon-induced proteins, two of them (MX1 and MX2 genes) mapping on Hsa21 (21q22.3). The altered expression of genes involved in mitochondrial translation and energy production also emerged, followed by the altered expression of genes encoding for the folate cycle enzyme, GART, and the folate transporter, SLC19A1.

CONCLUSIONS

The alteration of these pathways might be linked and involved in the manifestation of ID in DS.

The role of extracellular DNA in COVID-19: Clues from inflamm-aging

Epidemiological data convey severe prognosis and high mortality rate for COVID-19 in elderly men affected by age-related diseases. These subjects develop local and systemic hyper-inflammation, which are associated with thrombotic complications and multi-organ failure. Therefore, understanding SARS-CoV-2 induced hyper-inflammation in elderly men is a pressing need. Here we focus on the role of extracellular DNA, mainly mitochondrial DNA (mtDNA) and telomeric DNA (telDNA) in the modulation of systemic inflammation in these subjects. In particular, extracellular mtDNA is regarded as a powerful trigger of the inflammatory response. On the contrary, extracellular telDNA pool is estimated to be capable of inhibiting a variety of inflammatory pathways. In turn, we underpin that telDNA reservoir is progressively depleted during aging, and that it is scarcer in men than in women. We propose that an increase in extracellular mtDNA, concomitant with the reduction of the anti-inflammatory telDNA reservoir may explain hyper-inflammation in elderly male affected by COVID-19. This scenario is reminiscent of inflamm-aging, the portmanteau word that depicts how aging and aging related diseases are intimately linked to inflammation.