Beta-catenin inhibits bovine parainfluenza virus type 3 replication via innate immunity pathway

A comparative analysis of Marburg virus-infected bat and human models from public high-throughput sequencing data

Marburg virus (MARV) disease (MVD) is an uncommon yet serious viral hemorrhagic fever that impacts humans and non-human primates. In humans, infection by the MARV is marked by rapid onset, high transmissibility, and elevated mortality rates, presenting considerable obstacles to the development of vaccines and treatments. Bats, particularly Rousettus aegyptiacus, are suspected to be natural hosts of MARV. Previous research reported asymptomatic MARV infection in bats, in stark contrast to the severe responses observed in humans and other primates. Recent MARV outbreaks highlight significant public health concerns, underscoring the need for gene expression studies during MARV progression. To investigate this, we employed two models from the Gene Expression Omnibus, including kidney cells from Rousettus aegyptiacus and primary proximal tubular cells from Homo sapiens. These models were chosen to identify changes in gene expression profiles and to examine co-regulated genes and pathways involved in MARV disease progression. Our analysis of differentially expressed genes (DEGs) revealed that these genes are mainly associated with pathways related to the complement system, innate immune response via interferons (IFNs), Wnt/β-catenin signaling, and Hedgehog signaling, which played crucial roles in MARV infection across both models. Furthermore, we also identified several potential compounds that may be useful against MARV infection. These findings offer valuable insights into the mechanisms underlying MARV's pathophysiology and suggest potential strategies for preventing transmission, managing post-infection effects, and developing future vaccines.

β-catenin facilitates fowl adenovirus serotype 4 replication through enhancing virus-induced autophagy

β-catenin is a key component of the Wnt/β-catenin signal transduction cascade which is a highly conserved signaling pathway in eukaryotes. Increasing evidence suggests that the Wnt/β-catenin signaling pathway is involved in the infection of many viruses. However, its role in fowl adenovirus serotype 4 (FAdV-4) replication remains unclear. In the present study, we showed that FAdV-4 infection increased the expression of β-catenin and promoted the nuclear translocation of β-catenin. Overexpression of β-catenin and LiCl treatment stimulated the accumulation of β-catenin in the nucleus, and then facilitated FAdV-4 replication. Conversely, repression of β-catenin by inhibitors and siRNA significantly inhibited FAdV-4 replication. Furthermore, inhibition of autophagy by 3-Methyladenine (3-MA) suppressed the FAdV-4 replication, and repression of β-catenin inhibited the FAdV-4-triggered autophagy. In conclusion, the nuclear translocation of β-catenin benefits FAdV-4 replication, and suppression of β-catenin limits FAdV-4 production by inhibiting FAdV-4-induced autophagy. These findings indicated that β-catenin is an important regulator of FAdV-4 replication which can serve as a potential target for anti-FAdV-4 agents.

The canonical Wnt/β-catenin signaling pathway facilitates pseudorabies virus proliferation and enhances virus-induced autophagy

Pseudorabies virus (PRV) is a swine herpesvirus with a broad host range that causes significant economic losses worldwide. The Wnt/β-catenin signaling pathway is reportedly involved in multiple viruses' proliferation. In this study, we demonstrated that PRV infection significantly activated the Wnt/β-catenin signaling and promoted the nuclear translocation of β-catenin. Applying specific chemical inhibitors (FH535 and iCRT14) caused a remarkable decrease in PRV titers in various cell lines. Knockdown of β-catenin by siRNA also reduced the proliferation of PRV. On the contrary, treatment with lithium chloride (LiCl), an inhibitor of GSK3β, stimulated the Wnt/β-catenin signaling pathway and enhanced the PRV proliferation. Similarly, overexpression of β-catenin promoted PRV proliferation and reversed the antiviral effect of FH535. Moreover, LiCl promoted PRV-induced autophagy, whereas FH535 and iCRT14 showed converse effects. These findings suggest that PRV infection stimulates the canonical Wnt/β-catenin signaling pathway, facilitating PRV proliferation and regulating virus-induced autophagy. These data also provide potential targets for developing antiviral agents against PRV.

Revisiting the Role of GSK3, A Modulator of Innate Immunity, in Idiopathic Inclusion Body Myositis

Idiopathic or sporadic inclusion body myositis (IBM) is the leading age-related (onset >50 years of age) autoimmune muscular pathology, resulting in significant debilitation in affected individuals. Once viewed as primarily a degenerative disorder, it is now evident that much like several other neuro-muscular degenerative disorders, IBM has a major autoinflammatory component resulting in chronic inflammation-induced muscle destruction. Thus, IBM is now considered primarily an inflammatory pathology. To date, there is no effective treatment for sporadic inclusion body myositis, and little is understood about the pathology at the molecular level, which would offer the best hopes of at least slowing down the degenerative process. Among the previously examined potential molecular players in IBM is glycogen synthase kinase (GSK)-3, whose role in promoting TAU phosphorylation and inclusion bodies in Alzheimer’s disease is well known. This review looks to re-examine the role of GSK3 in IBM, not strictly as a promoter of TAU and Abeta inclusions, but as a novel player in the innate immune system, discussing some of the recent roles discovered for this well-studied kinase in inflammatory-mediated pathology.

Heparanase-Induced Activation of AKT Stabilizes β-Catenin and Modulates Wnt/β-Catenin Signaling during Herpes Simplex Virus 1 Infection

Under pathological conditions like herpes simplex virus 1 (HSV-1) infection, host-pathogen interactions lead to major reconstruction of the host protein network, which contributes to the dysregulation of signaling pathways and disease onset. Of note is the upregulation of a multifunctional host protein, heparanase (HPSE), following infection, which serves as a mediator in HSV-1 replication. In this study, we identify a novel function of HPSE and highlight it as a key regulator of β-catenin signal transduction. The regulatory role of HPSE on the activation, nuclear translocation, and signal transduction of β-catenin disrupts cellular homeostasis and establishes a pathogenic environment that promotes viral replication. Under normal physiological conditions, β-catenin is bound to a group of proteins, referred to as the destruction complex, and targeted for ubiquitination and, ultimately, degradation. We show that virus-induced upregulation of HPSE leads to the activation of Akt and subsequent stabilization and activation of β-catenin through (i) the release of β-catenin from the destruction complex, and (ii) direct phosphorylation of β-catenin at Ser552. This study also provides an in-depth characterization of the proviral role of β-catenin signaling during HSV-1 replication using physiologically relevant cell lines and in vivo models of ocular infection. Furthermore, pharmacological inhibitors of this pathway generated a robust antiviral state against multiple laboratory and clinical strains of HSV-1. Collectively, our findings assign a novel regulatory role to HPSE as a driver of β-catenin signaling in HSV-1 infection. IMPORTANCE Heparanase (HPSE) and β-catenin have independently been implicated in regulating key pathophysiological processes, including neovascularization, angiogenesis, and inflammation; however, the relationship between the two proteins has remained elusive thus far. For that reason, characterizing this relationship is crucial and can lead to the development of novel therapeutics. For HSV-1 specifically, current antivirals are not able to abolish the virus from the host, leaving patients susceptible to episodes of viral reactivation. Identifying a host-based intervention can provide a better alternative with enhanced efficacy and sustained relief.

Cytosolic β-catenin is involved in macrophage M2 activation and antiviral defense in teleosts: Delineation through molecular characterization of β-catenin homolog from redlip mullet (Planiliza haematocheila)

β-catenin is a structural protein that makes the cell-cell connection in adherence junctions. Besides the structural functions, it also plays a role as a central transducer of the canonical Wnt signaling cascade, regulating nearly four hundred genes related to various cellular processes. Recently the immune functions of β-catenin during pathogenic invasion have gained more attention. In the present study, we elucidated the immune function of fish β-catenin by identifying and characterizing the β-catenin homolog (PhCatβ) from redlip mullet, Planiliza haematocheila. The complete open reading frame of PhCatβ consists of 2352 bp, which encodes a putative β-catenin homolog (molecular weight: 85.7 kDa). Multiple sequence alignment analysis revealed that β-catenin is highly conserved in vertebrates. Phylogenetic reconstruction demonstrated the close evolutionary relationship between PhCatβ and other fish β-catenin counterparts. The tissue distribution analysis showed the highest mRNA expression of PhCatβ in heart tissues of the redlip mullet under normal physiological conditions. While in response to pathogenic stress, the PhCatβ transcription level was dramatically increased in the spleen and gill tissues. The overexpression of PhCatβ stimulated M2 polarization and cell proliferation of murine RAW 264.7 macrophage. In fish cells, the overexpression of PhCatβ resulted in a significant upregulation of antiviral gene transcription and vice versa. Moreover, the overexpression of PhCatβ could inhibit the replication of VHSV in FHM cells. Our results strongly suggest that PhCatβ plays a role in macrophage activation and antiviral immune response in redlip mullet.

Regulation of Avian Leukosis Virus Subgroup J Replication by Wnt/β-Catenin Signaling Pathway

Wnt/β-catenin signaling is a highly conserved pathway related to a variety of biological processes in different cells. The regulation of replication of various viruses by Wnt/β-catenin signaling pathway has been reported. However, the interaction between the Wnt/β-catenin pathway and avian leukosis virus is unknown. In the present study, we investigated the effect of modulating the Wnt/β-catenin pathway during avian leukosis virus subgroup J (ALV-J) infection. The activation of the Wnt/β-catenin pathway by GSK-3 inhibitor increased ALV-J mRNA, viral protein expression, and virus production in CEF cells. This increase was suppressed by iCRT14, one of the specific inhibitors of the Wnt/β-catenin signaling pathway. Moreover, treatment with iCRT14 reduced virus titer and viral gene expression significantly in CEF and LMH cells in a dose-dependent manner. Inhibition Wnt/β-catenin signaling pathway by knockdown of β-catenin reduced virus proliferation in CEF cells also. Collectively, these results suggested that the status of Wnt/β-catenin signaling pathway modulated ALV-J replication. These studies extend our understanding of the role of Wnt/β-catenin signaling pathway in ALV-J replication and make a new contribution to understanding the virus–host interactions of avian leukosis virus.

Bta-miR-101 suppresses BEFV replication via targeting NKRF

MicroRNAs (miRNAs), as a kind of small noncoding RNAs, have been proved to play a regulatory role in virus infection. However, the role and mechanism of cellular miRNAs in bovine transient fever virus (BEFV) infection are largely unknown. In the present study, we found that bta-miR-101 was significantly up-regulated in the Madin-Darby Bovine Kidney (MDBK) cells upon BEFV infection. Notably, bta-miR-101 mimic dramatically inhibited BEFV replication, while bta-miR-101 inhibitor facilitated BEFV replication, suggesting that bta-miR-101 acted as an anti-viral host factor restraining BEFV replication. Subsequently, NF-κB repressing factor (NKRF) was identified as a target gene of bta-miR-101 by dual luciferase reporter assay, and bta-miR-101 mimic significantly down-regulated expression of NKRF, while bta-miR-101 inhibitor up-regulated its expression, respectively. Furthermore, NKRF could induce apoptosis, and favored the replication of BEFV. Finally, bta-miR-101 inhibited BEFV-induced apoptosis via targeting NKRF to suppress virus replication. In general, our study provides a novel mechanism for bta-miR-101 to exert its antiviral function, which provides a theoretical basis for the development of antiviral strategy.

RACK1 degrades MAVS to promote bovine ephemeral fever virus replication via upregulating E3 ubiquitin ligase STUB1

Receptors for activated C kinase 1 (RACK1) could competitively combine with mitochondrial antiviral signaling protein (MAVS) to inhibit the type I interferon (IFN) signaling pathway during viral infection in vitro. However, whether RACK1 can degrade MAVS to enhance viral replication is still unknown. In this study, we found that bovine epidemic fever virus (BEFV) infection triggered the expression of RACK1. Overexpression of RACK1 promoted BEFV replication, while knockdown of RACK1 inhibited the replication of BEFV. Further research showed that RACK1 inhibited the type I IFN signaling pathway during BEFV infection by degrading MAVS, and RACK1 degraded MAVS via the ubiquitin-proteasome system. Mechanistically, RACK1 up-regulated the expression of E3 ubiquitin ligase STIP1 homology and U-box containing protein 1 (STUB1), thereby promoting the ubiquitination and degradation of MAVS. In addition, RACK1 degraded MAVS by enhancing the interaction between STUB1 and MAVS but not via its interaction with STUB1. Overall, our study reveals a novel mechanism by which RACK1 inhibits the type I IFN signaling pathway to BEFV infection through degradation of MAVS, thereby promoting viral infection. These findings provide a new perspective for the MAVS degradation regulated by RACK1.

Induction of the Unfolded Protein Response during Bovine Alphaherpesvirus 1 Infection

Bovine herpesvirus 1 (BoHV-1) is an alphaherpesvirus that causes great economic losses in the cattle industry. Herpesvirus infection generally induces endoplasmic reticulum (ER) stress, and the unfolded protein response (UPR) in infected cells. However, it is not clear whether ER stress and UPR can be induced by BoHV-1 infection. Here, we found that ER stress induced by BoHV-1 infection could activate all three UPR sensors (the activating transcription factor 6 (ATF6), the inositol-requiring enzyme 1 (IRE1), and the protein kinase RNA-like ER kinase (PERK)) in MDBK cells. During BoHV-1 infection, the ATF6 pathway of UPR did not affect viral replication. However, both knockdown and specific chemical inhibition of PERK attenuated the BoHV-1 proliferation, and chemical inhibition of PERK significantly reduced the viral replication at the post-entry step of the BoHV-1 life cycle. Furthermore, knockdown of IRE1 inhibits BoHV-1 replication, indicating that the IRE1 pathway may promote viral replication. Further study revealed that BoHV-1 replication was enhanced by IRE1 RNase activity inhibition at the stage of virus post-entry in MDBK cells. Furthermore, IRE1 kinase activity inhibition and RNase activity enhancement decrease BoHV1 replication via affecting the virus post-entry step. Our study revealed that BoHV-1 infection activated all three UPR signaling pathways in MDBK cells, and BoHV-1-induced PERK and IRE1 pathways may promote viral replication. This study provides a new perspective for the interactions of BoHV-1 and UPR, which is helpful to further elucidate the mechanism of BoHV-1 pathogenesis.

Roles of GSK-3 and β-Catenin in Antiviral Innate Immune Sensing of Nucleic Acids

The rapid activation of the type I interferon (IFN) antiviral innate immune response relies on ubiquitously expressed RNA and DNA sensors. Once engaged, these nucleotide-sensing receptors use distinct signaling modules for the rapid and robust activation of mitogen-activated protein kinases (MAPKs), the IκB kinase (IKK) complex, and the IKK-related kinases IKKε and TANK-binding kinase 1 (TBK1), leading to the subsequent activation of the activator protein 1 (AP1), nuclear factor-kappa B (NF-κB), and IFN regulatory factor 3 (IRF3) transcription factors, respectively. They, in turn, induce immunomodulatory genes, allowing for a rapid antiviral cellular response. Unlike the MAPKs, the IKK complex and the IKK-related kinases, ubiquitously expressed glycogen synthase kinase 3 (GSK-3) α and β isoforms are active in unstimulated resting cells and are involved in the constitutive turnover of β-catenin, a transcriptional coactivator involved in cell proliferation, differentiation, and lineage commitment. Interestingly, studies have demonstrated the regulatory roles of both GSK-3 and β-catenin in type I IFN antiviral innate immune response, particularly affecting the activation of IRF3. In this review, we summarize current knowledge on the mechanisms by which GSK-3 and β-catenin control the antiviral innate immune response to RNA and DNA virus infections.