Repression of SUMOylation pathway by grass carp reovirus contributes to the upregulation of PKR in an IFN-independent manner

The crosstalk between SUMOylation and immune system in host-pathogen interactions

Pathogens can not only cause infectious diseases, immune system diseases, and chronic diseases, but also serve as potential triggers or initiators for certain tumors. They directly or indirectly damage human health and are one of the leading causes of global deaths. Small ubiquitin-like modifier (SUMO) modification, a type of protein post-translational modification (PTM) that occurs when SUMO groups bond covalently to particular lysine residues on substrate proteins, plays a crucial role in both innate and adaptive immunologic responses, as well as pathogen-host immune system crosstalk. SUMOylation participates in the host's defense against pathogens by regulating immune responses, while numerically vast and taxonomically diverse pathogens have evolved to exploit the cellular SUMO modification system to break through innate defenses. Here, we describe the characteristics and multiple functions of SUMOylation as a pivotal PTM mechanism, the tactics employed by various pathogens to counteract the immune system through targeting host SUMOylation, and the character of the SUMOylation system in the fight between pathogens and the host immune system. We have also included a summary of the potential anti-pathogen SUMO enzyme inhibitors. This review serves as a reference for basic research and clinical practice in the diagnosis, prognosis, and treatment of pathogenic microorganism-caused disorders.

Lufenuron treatment temporarily represses gene expression and affects the SUMO pathway in liver of Atlantic salmon

Lufenuron is a benzoylurea insecticide currently in use to combat sea lice infestation in salmon aquaculture in Chile. With pending approval in Norway, the aim of this work was to study the uptake and toxicity of lufenuron in liver tissue of Atlantic salmon. Juvenile salmon weighing 40 g were given a standard 7-day oral dose, and bioaccumulation and transcriptional responses in the liver were examined 1 day after the end-of-treatment (day 8) and after 1 week of elimination (day 14). Bioaccumulation levels of lufenuron were 29 ± 3 mg/kg at day 8 and 14 ± 1 mg/kg at day 14, indicating relatively rapid clearance. However, residues of lufenuron were still present in the liver after 513 days of depuration. The exposure gave a transient inhibition of transcription in the liver at day 8 (2437 significant DEGs, p-adj < .05), followed by a weaker compensatory response at day 14 (169 significant DEGs). Pathways associated with RNA metabolism such as the sumoylation pathway were most strongly affected at day 8, while the apelin pathway was most profoundly affected at day 14. In conclusion, this study shows that lufenuron easily bioaccumulates and that a standard 7-day oral dose induces a transient inhibition of transcription in liver of salmon.

The subgroup of 2'-hydroxy-flavonoids: Molecular diversity, mechanism of action, and anticancer properties

Flavonoids are abundant in nature, structurally very diversified and largely investigated. However, the subgroup of 2'-hydroxyflavonoids is much less known and not frequently studied. The present review identifies the major naturally-occurring and synthetic 2'-hydroxyflavonoid derivatives and discusses their structural characteristics and biological properties, with a focus on anticancer activities. The pharmacological properties of 2'-hydroxyflavone (2'-HF) and 2'-hydroxyflavanone (2'-HFa) are detailed. Upon binding to the Ral-interacting protein Rlip implicated in the transport of glutathione conjugates, 2'-HFa inhibits tumor cell proliferation and restrict tumor growth, in particular in breast cancer models. Among the synthetic derivatives, the characteristics of the anticancer product 2D08 (2',3',4'-trihydroxy flavone) are detailed to shed light on the molecular mechanism of action of this compound, as a regulator of protein SUMOylation. Inhibition of protein SUMOylation by 2D08 blocks cancer cell migration and invasion, and the compound greatly enhances the anticancer effects of conventional cytotoxic drugs like etoposide. The structural role of the 2'-hydroxyl group on the phenyl C-ring of the flavonoid is discussed, notably the capacity to engage intramolecular H-bonding interactions with the O1 atom on the B-ring of the chromone unit (or the oxygen of a 3-OH group when it is presents). The 2'-hydroxyl group of flavonoid appears as a regulator of the conformational freedom between the bicyclic A-B unit and the appended phenyl C-ring, favoring the planarity of the molecule. It is an essential group accounting for the biological properties of 2'-HF, 2'-HFa and structurally related compounds. This review shed light on 2'-hydroxyflavonoids to encourage their use and chemical development.

Interleukin-17 suppresses grass carp reovirus infection in Ctenopharyngodon idellus kidney cells by activating NF-κB signaling

The grass carp accounts for a large proportion of aquacultural production in China, but the hemorrhagic disease caused by grass carp reovirus (GCRV) infection often causes huge economic losses to the industry. Interleukin 17 (IL-17) is an important cytokine that plays a critical role in the inflammatory and immune responses. Although IL-17 family members have been extensively studied in mammals, our knowledge of the activity of IL-17 proteins in teleosts in response to viral infection is still limited. In this study, the role of IL-17 in GCRV infection and its mechanism were investigated. The expression levels of IL-17AF1, IL-17AF2, and IL-17AF3 in Ctenopharyngodon idella kidney (CIK) cells gradually increased from 6 h after infection with GCRV. The nuclear translocation of p65, which acts in the NF-κB signaling pathway, was also increased by GCRV infection. The overexpression of IL-17AF1, IL-17AF2, or IL-17AF3 also promoted the nuclear translocation of p65 and the levels of phospho-IκBα in CIK cells, and reduced the expression of the viral structural protein VP7. An NF-κB signal inhibitor abolished the inhibition of GCRV infection by IL-17 proteins. These results suggested that the NF-κB signaling pathway was activated by the overexpression of IL-17 proteins, resulting in the inhibition of viral infection. In conclusion, in this study, we demonstrated that IL-17AF1, IL-17AF2, and IL-17AF3 acted as immune cytokines, exerting an antiviral effect by activating the NF-κB signaling pathway.

Characterization of the interaction between outer-fiber protein VP55 of genotype III grass carp reovirus and Fibulin-4 of grass carp

Genotype III grass carp reovirus (GCRV; representative strain, GCRV-104) belongs to the subfamily Spinareovirinae and encodes an outer-fiber protein, VP55, responsible for mediating the infection of target tissues by the virus and assisting the virus into cells. Fibulin-4/EFEMP2 protein was previously identified as a putative binding partner for VP55 in a yeast two-hybrid screening. Here, we have further characterized the association between Fibulin-4 and VP55 by using protein interaction assays. An intracellular co-localization assay showed that RFP-Fibulin-4 co-localized with GFP-VP55 in grass carp ovary (GCO) cells. Bacterially expressed GST-tagged Fibulin-4 was shown to associate with baculovirus-expressed His-tagged VP55 in a dot-blot overlay assay; moreover, baculovirus-expressed His-tagged VP55 was able to pull down GFP-Fibulin-4 expressed in the GCO cells. We performed real-time PCR and immunoblotting analysis and showed that endogenous Fibulin-4, although suppressed to a lower level in the late infection phase, is present throughout the infection course of GCRV-104 in CIK cells. In conclusion, our results indicate that grass carp Fibulin-4 interacts with VP55. The presence of Fibulin-4, a well-known secreted protein, during the infection course of GCRV-104 in grass carp cells implies its potential role during viral egression through interaction with VP55.

Infection of grass carp reovirus induced the expressional suppression of pro-viral Fibulin-4 in host cells

Fibulin-4 is not only involved in connective tissue development and elastic fiber formation, but also plays critical neoplastic roles in tumor growth by activating Wnt/β-Catenin signaling in human. Recently, Fibulin-4 was shown to associate with grass carp reovirus (GCRV) outer capsid proteins and might relate to viral hemorrhagic disease in grass carp Ctenopharyngodon idella. Here, we monitored the expression pattern of Fibulin-4 during the infection course of GCRV at both translational and transcriptional levels, and found that Fibulin-4 was significantly suppressed upon the viral challenge in grass cap GCO cells. Over expression of Fibulin-4 was achieved by transduction of pEGFP-Fibulin-4 plasmids into GCO cells, which was confirmed by both Western blot and Real time RT-PCR analysis. In GCO cells with over-expression of Fibulin-4, significantly increase of viral protein synthesis and progeny virus production was detected. Our study indicated that Fibulin-4 displayed pro-viral function and was inhibited during viral challenge. Thus, repression of Fibulin-4 expression seemed to be involved in anti-viral response in grass carp Ctenopharyngodon idella.