Jun activation domain-binding protein 1 (JAB1) is required for the optimal response to interferons

Regulatory mechanisms and therapeutic potential of JAB1 in neurological development and disorders

c-Jun activation domain binding protein-1 (JAB1) is a multifunctional regulator that plays vital roles in diverse cellular processes. It regulates AP-1 transcriptional activity and also acts as the fifth component of the COP9 signalosome complex. While JAB1 is considered an oncoprotein that triggers tumor development, recent studies have shown that it also functions in neurological development and disorders. In this review, we summarize the general features of the JAB1 gene and protein, and present recent updates on the regulation of JAB1 expression. Moreover, we also highlight the functional roles and regulatory mechanisms of JAB1 in neurodevelopmental processes such as neuronal differentiation, synaptic morphogenesis, myelination, and hair cell development and in the pathogenesis of some neurological disorders such as Alzheimer's disease, multiple sclerosis, neuropathic pain, and peripheral nerve injury. Furthermore, current challenges and prospects are discussed, including updates on drug development targeting JAB1.

An Integrated View of Deubiquitinating Enzymes Involved in Type I Interferon Signaling, Host Defense and Antiviral Activities

Viral infectious diseases pose a great challenge to human health around the world. Type I interferons (IFN-Is) function as the first line of host defense and thus play critical roles during virus infection by mediating the transcriptional induction of hundreds of genes. Nevertheless, overactive cytokine immune responses also cause autoimmune diseases, and thus, tight regulation of the innate immune response is needed to achieve viral clearance without causing excessive immune responses. Emerging studies have recently uncovered that the ubiquitin system, particularly deubiquitinating enzymes (DUBs), plays a critical role in regulating innate immune responses. In this review, we highlight recent advances on the diverse mechanisms of human DUBs implicated in IFN-I signaling. These DUBs function dynamically to calibrate host defenses against various virus infections by targeting hub proteins in the IFN-I signaling transduction pathway. We also present a future perspective on the roles of DUB-substrate interaction networks in innate antiviral activities, discuss the promises and challenges of DUB-based drug development, and identify the open questions that remain to be clarified. Our review provides a comprehensive description of DUBs, particularly their differential mechanisms that have evolved in the host to regulate IFN-I-signaling-mediated antiviral responses.

Better together: the role of IFIT protein-protein interactions in the antiviral response

The interferon-induced proteins with tetratricopeptide repeats (IFITs) are a family of antiviral proteins conserved throughout all vertebrates. IFIT1 binds tightly to non-self RNA, particularly capped transcripts lacking methylation on the first cap-proximal nucleotide, and inhibits their translation by out-competing the cellular translation initiation apparatus. This exerts immense selection pressure on cytoplasmic RNA viruses to maintain mechanisms that protect their messenger RNA from IFIT1 recognition. However, it is becoming increasingly clear that protein-protein interactions are necessary for optimal IFIT function. Recently, IFIT1, IFIT2 and IFIT3 have been shown to form a functional complex in which IFIT3 serves as a central scaffold to regulate and/or enhance the antiviral functions of the other two components. Moreover, IFITs interact with other cellular proteins to expand their contribution to regulation of the host antiviral response by modulating innate immune signalling and apoptosis. Here, we summarize recent advances in our understanding of the IFIT complex and review how this impacts on the greater role of IFIT proteins in the innate antiviral response.

Ubiquitin C-terminal hydrolase-L3 promotes interferon antiviral activity by stabilizing type I-interferon receptor

Type-I interferons (IFN-I) are important antiviral drugs which are widely used in clinical therapy of diverse viral infections. However, understanding the detailed mechanisms for IFN-I antiviral signaling remains a major challenge, and may provide novel targets for IFN-based antiviral therapy. So far, the roles of deubiquitinases (DUBs) in regulating IFN-I antiviral activity are still largely unexplored. Here, we find that Ubiquitin C-terminal hydrolase-L3 (UCHL3) plays an important role in regulating type I-interferon (IFN-I) mediated antiviral response. Interestingly, we find that UCHL3 regulates COPS5-dependent deneddylation of Cullin1, which is an essential component of SCF^β-TrCP complex and associated with SCF^β-TrCP activities. Furthermore, we reveal that UCHL3 physically interacts with COPS5, and determines the level and protein stability of cellular COPS5 by deubiquitinating COPS5. We further demonstrate that UCHL3 upregulates the levels of SCF^β-TrCP substrates including IFN-I receptor IFNAR1, which enhances IFN-I mediated signaling pathway and antiviral activity. These findings identify COPS5 as a novel in vivo substrate of UCHL3, and uncover the deubiquitination-deneddylation mediated regulation for IFN-I signaling and antiviral function, which may provide a novel strategy for improving IFN-based antiviral therapy.

Estrous cycle stage-dependent manner of type I interferon-stimulated genes induction in the bovine endometrium

Interferon tau (IFN-τ) is a ruminant-specific type I IFN secreted by a conceptus before its attachment to the uterus. IFN-τ induces the expression of IFN-stimulated genes (ISGs) via the type I IFN receptor (IFNAR), which is composed of IFNAR1 and IFNAR2 subunits in the endometrium. However, expression patterns of IFNARs during the estrous cycle have not been reported. We hypothesized that the response to a type I IFN changes along with IFNARs and the IFN-regulatory factors (IRFs) driving transcription of IFN signal-related genes and modulating a type I IFN signal during the estrous cycle. We investigated the estrous cycle stage-dependent type I IFN induction of ISGs and expression patterns of IFN signal-related genes in bovine endometrial tissues. Endometrial tissue pieces collected from bovine uteri at each estrous stage (early, mid, and late) were cultured with or without recombinant bovine IFN-α or concentrated pregnant uterine flushing (PUF) on day 18 after confirming the presence of a conceptus. IFN-α and PUF each significantly increased the expression of ISGs in endometrial tissues. The induction levels of the typical ISGs (MX1-a and ISG15) were significantly higher at the mid stage and correlated with high expression of IRFs at the mid stage. The immunostaining of IFNARs showed strong fluorescence intensities in luminal and glandular epithelia at the early and mid stages. Collectively, these results suggest that the endometrium exhibits estrous cycle stage-dependent responsiveness to type I IFN that may be associated with the expression of IFNARs and IRFs for pregnancy recognition.

The oxoglutarate receptor 1 (OXGR1) modulates pressure overload-induced cardiac hypertrophy in mice

The G-protein-coupled receptors (GPCRs) family of proteins play essential roles in the heart, including in the regulation of cardiac hypertrophy. One member of this family, the oxoglutarate receptor 1 (OXGR1), may have a crucial role in the heart because it acts as a receptor for α-ketoglutarate, a metabolite that is elevated in heart failure patients. OXGR1 is expressed in the heart but its precise function during cardiac pathophysiological process is unknown. Here we used both in vivo and in vitro approaches to investigate the role of OXGR1 in cardiac hypertrophy. Genetic ablation of Oxgr1 in mice (OXGR1^-/-) resulted in a significant increase in hypertrophy following transverse aortic constriction (TAC). This was accompanied by reduction in contractile function as indicated by cardiac fractional shortening and ejection fraction. Conversely, adenoviral mediated overexpression of OXGR1 in neonatal rat cardiomyocytes significantly reduced phenylephrine-induced cardiomyocyte hypertrophy, a result that was consistent with the in vivo data. Using a combination of yeast two hybrid screening and phospho-antibody array analysis we identified novel interacting partner and downstream signalling pathway that might be regulated by the OXGR1. First, we found that OXGR1 forms a molecular complex with the COP9 signalosome complex subunit 5 (CSN5). Secondly, we observed that the STAT3 signalling pathway was upregulated in OXGR1^-/- hearts. Since CSN5 interacts with TYK2, a major upstream regulator of STAT3, OXGR1 might regulate the pro-hypertrophic STAT3 pathway via interaction with the CSN5-TYK2 complex. In conclusion, our study has identified OXGR1 as a novel regulator of pathological hypertrophy via the regulation of the STAT3. Identification of molecules that can specifically activate or inhibit this receptor may be very useful in the development of novel therapeutic approach for pathological cardiac hypertrophy.

IL-17A plays a central role in the expression of psoriasis signature genes through the induction of IκB-ζ in keratinocytes

In psoriasis lesions, a diverse mixture of cytokines is up-regulated that influence each other generating a complex inflammatory situation. Although this is the case, the inhibition of IL-17A alone showed unprecedented clinical results in patients, indicating that IL-17A is a critical inducer of psoriasis pathogenesis. To elucidate IL-17A-driven keratinocyte-intrinsic signaling pathways, we treated monolayers of normal human epidermal keratinocytes in vitro with a mixture of six cytokines (IL-17A, TNF-α, IL-17C, IL-22, IL-36γ and IFN-γ) involved in psoriasis to mimic the inflammatory milieu in psoriasis lesions. Microarray and gene set enrichment analysis revealed that this cytokine mixture induced similar gene expression changes with the previous transcriptome studies using psoriasis lesions. Importantly, we identified a set of IL-17A-regulated genes in keratinocytes, which recapitulate typical psoriasis genes exemplified by DEFB4A, S100A7, IL19 and CSF3, based on the differences in the expression profiles of cells stimulated with six cytokines versus cells stimulated with only five cytokines lacking IL-17A. Furthermore, a specific IL-17A-induced gene, NFKBIZ, which encodes IκB-ζ, a transcriptional regulator for NF-κB, was demonstrated to have a significant role for IL-17A-induced gene expression. Thus, we present novel in vitro data from normal human keratinocytes that would help elucidating the IL-17A-driven keratinocyte activation in psoriasis.