Bmp8a is an essential positive regulator of antiviral immunity in zebrafish

IRF11 synergizes with STAT1 and STAT2 to promote type I IFN production

Interferon regulatory factor 11 (IRF11), a fish specific member of IRF family, is a transcription factor known for its positive role in teleost antiviral defense by regulating IFN expression. Despite its recognized function, the precise mechanism of IRF11 in type I IFNs production remains largely unknown. In this study, we identified IRF11 in Japanese eel, Anguilla japonica, (AjIRF11) and determined its involvement in the later phase of fish IFN production. Our results demonstrate that IRF11-induced IFN production operates through ISRE binding. Mutations in each ISRE site within the promoter of AjIFN2 or AjIFN4 abolished IRF11-mediated activation of IFN promoters. In addition, the overexpression of AjIRF11 does not significantly impact the activation of AjIFN promoters induced by RLR-related signaling pathway proteins. Furthermore, IRF11-knockdown in ZFLs (zebrafish liver cells) has no effect on the RLRs-induced expression of zebrafish IFN-φ1 and IFN-φ3, indicating that IRF11 is not involved in the RLR-mediated IFN production. However, AjIRF11 can form transcription complexes with AjSTAT1 or AjSTAT2, or form homo- or heterodimers with AjIRF1 to stimulate the transcription of type I IFNs. Overall, it is shown in this study that IRF11 can act synergistically with STAT1 and/or STAT2 for the induction of IFN.

Novel role of bone morphogenetic protein 9 in innate host responses to HCMV infection

Herpesviruses modulate immune control to secure lifelong infection. The mechanisms Human Cytomegalovirus (HCMV) employs in this regard can reveal unanticipated aspects of cellular signaling involved in antiviral immunity. Here, we describe a novel relationship between the TGF-β family cytokine BMP9 and HCMV infection. We identify a cross-talk between BMP9-induced and IFN receptor-mediated signaling, showing that BMP9 boosts the transcriptional response to and antiviral activity of IFNβ, thereby enhancing viral restriction. We also show that BMP9 is secreted by human fibroblasts upon HCMV infection. However, HCMV infection impairs BMP9-induced enhancement of the IFNβ response, indicating that this signaling role of BMP9 is actively targeted by HCMV. Indeed, transmembrane proteins US18 and US20, which downregulate type I BMP receptors, are necessary and sufficient to cause inhibition of BMP9-mediated boosting of the antiviral response to IFNβ. HCMV lacking US18 and US20 is more sensitive to IFNβ. Thus, HCMV has a mutually antagonistic relationship with BMP9, which extends the growing body of evidence that BMP signaling is an underappreciated modulator of innate immunity in response to viral infection.

The Role of the CD28 Family Receptors in T-Cell Immunomodulation

The CD28 family receptors include the CD28, ICOS (inducible co-stimulator), CTLA-4 (cytotoxic T-lymphocyte antigen-4), PD-1 (programmed cell death protein 1), and BTLA (B- and T-lymphocyte attenuator) molecules. They characterize a group of molecules similar to immunoglobulins that control the immune response through modulating T-cell activity. Among the family members, CD28 and ICOS act as enhancers of T-cell activity, while three others-BTLA, CTLA-4, and PD-1-function as suppressors. The receptors of the CD28 family interact with the B7 family of ligands. The cooperation between these molecules is essential for controlling the course of the adaptive response, but it also significantly impacts the development of immune-related diseases. This review introduces the reader to the molecular basis of the functioning of CD28 family receptors and their impact on T-cell activity.

Bmp4 in Zebrafish Enhances Antiviral Innate Immunity through p38 MAPK (Mitogen-Activated Protein Kinases) Pathway

Bone morphogenetic proteins (BMPs) are a group of structurally and functionally related signaling molecules that comprise a subfamily, belonging to the TGF-β superfamily. Most BMPs play roles in the regulation of embryonic development, stem cell differentiation, tumor growth and some cardiovascular and cerebrovascular diseases. Although evidence is emerging for the antiviral immunity of a few BMPs, more BMPs are needed to determine whether this function is universal. Here, we identified the zebrafish bmp4 ortholog, whose expression is up-regulated through challenge with grass carp reovirus (GCRV) or its mimic poly(I:C). The overexpression of bmp4 in epithelioma papulosum cyprini (EPC) cells significantly decreased the viral titer of GCRV-infected cells. Moreover, compared to wild-type zebrafish, viral load and mortality were significantly increased in both larvae and adults of bmp4-/- mutant zebrafish infected with GCRV virus. We further demonstrated that Bmp4 promotes the phosphorylation of Tbk1 and Irf3 through the p38 MAPK pathway, thereby inducing the production of type I IFNs in response to virus infection. These data suggest that Bmp4 plays an important role in the host defense against virus infection. Our study expands the understanding of BMP protein functions and opens up new targets for the control of viral infection.

Bmp8a deletion leads to obesity through regulation of lipid metabolism and adipocyte differentiation

The role of bone morphogenetic proteins (BMPs) in regulating adipose has recently become a field of interest. However, the underlying mechanism of this effect has not been elucidated. Here we show that the anti-fat effect of Bmp8a is mediated by promoting fatty acid oxidation and inhibiting adipocyte differentiation. Knocking out the bmp8a gene in zebrafish results in weight gain, fatty liver, and increased fat production. The bmp8a-/- zebrafish exhibits decreased phosphorylation levels of AMPK and ACC in the liver and adipose tissues, indicating reduced fatty acid oxidation. Also, Bmp8a inhibits the differentiation of 3T3-L1 preadipocytes into mature adipocytes by activating the Smad2/3 signaling pathway, in which Smad2/3 binds to the central adipogenic factor PPARγ promoter to inhibit its transcription. In addition, lentivirus-mediated overexpression of Bmp8a in 3T3-L1 cells significantly increases NOD-like receptor, TNF, and NF-κB signaling pathways. Furthermore, NF-κB interacts with PPARγ, blocking PPARγ's activation of its target gene Fabp4, thereby inhibiting adipocyte differentiation. These data bring a signal bridge between immune regulation and adipocyte differentiation. Collectively, our findings indicate that Bmp8a plays a critical role in regulating lipid metabolism and adipogenesis, potentially providing a therapeutic approach for obesity and its comorbidities.

Recent progress in the biology and physiology of BMP-8a

PURPOSE

BMP-8a is a member of bone morphogenetic proteins (BMPs) and plays a regulatory role in human growth and development as a transcription regulator. This review aims to summarize the current research on the impact and mechanism of BMP-8a in female and male reproduction, formation and eruption of teeth, bone and cartilage development, tissue differentiation, disease occurrence, progression and prognosis.

METHODS

The phrases "BMP-8a," "BMPs," "regulator," "mechanism," "osteoblast," "cartilage," "cancer," "disease," and "inflammation" were searched in the PubMed database. The abstracts were evaluated, and a series of original publications and reviews were examined.

RESULTS

According to the search, BMP-8a affects the development of the uterus by inhibiting luteinization and plays an important role in late spermatogenesis. It is highly expressed in osteogenesis and differentially expressed in chondrogenesis. Furthermore, BMP-8a has a significant impact on the occurrence, development and prognosis of various diseases.

CONCLUSIONS

BMP-8a regulates important factors and pathways, such as SMAD2/3 and SMAD1/5/8, to promote or inhibit the developmental processes of human reproductive organs. BMP-8a is also a member of the BMP family of proteins that regulates chondrogenesis and osteogenesis. In addition to its osteoinductive capabilities, BMP-8a is involved in the progression of diverse cancers.

Immune checkpoint proteins: Signaling mechanisms and molecular interactions in cancer immunotherapy

Immune checkpoint proteins (ICP) are currently one of the most novel and promising areas of immune-oncology research. This novel way of targeting tumor cells has shown favorable success over the past few years with some FDA approvals such as Ipilimumab, Nivolumab, Pembrolizumab etc. Currently, more than 3000 clinical trials of immunotherapeutic agents are ongoing with majority being ICPs. However, as the number of trials increase so do the challenges. Some challenges such as adverse side effects, non-specific binding on healthy tissues and absence of response in some subset populations are critical obstacles. For a safe and effective further therapeutic development of molecules targeting ICPs, understanding their mechanism at molecular level is crucial. Since ICPs are mostly membrane bound receptors, a number of downstream signaling pathways divaricate following ligand-receptor binding. Most ICPs are expressed on more than one type of immune cell populations. Further, the expression varies within a cell type. This naturally varied expression pattern adds to the difficulty of targeting specific effector immune cell types against cancer. Hence, understanding the expression pattern and cellular mechanism helps lay out the possible effect of any immunotherapy. In this review, we discuss the signaling mechanism, expression pattern among various immune cells and molecular interactions derived using interaction database analysis (BioGRID).

Zebrafish Ism1 is a novel antiviral factor that positively regulates antiviral immune responses

Isthmin1 (Ism1), first identified as a secreted protein in Xenopus embryos in 2002, has been shown to perform multiple biological functions, but little is known currently regarding its role in immunity. Here we show that the expression of ism1 is inducible by challenge with Grass carp reovirus (GCRV) in zebrafish, suggesting involvement of Ism1 in antiviral response. We then demonstrate that recombinant Ism1 (rIsm1) reduces the cytopathic effect in the cells infected by GCRV, promotes the expression of type I IFN gene and IFN-inducible antiviral protein Mxa gene, and reduces the virus quantity in virus-infected cells and host. We also show that rIsm1 promotes the expression of tbk1, irf3 and irf7, suggesting it promotes the expression of type I IFN gene and Mxa gene via induction of Tbk1-Irf3-Ifn pathway. These data together indicate that Ism1 is a new immune-relevant factor functioning in antiviral immune response, and provides a target for controlling viral infection.