scholarly journals PSMB1 Negatively Regulates the Innate Antiviral Immunity by Facilitating Degradation of IKK-ε

Viruses ◽  
2019 ◽  
Vol 11 (2) ◽  
pp. 99
Author(s):  
Fangyi Wu ◽  
Zhenmin Niu ◽  
Bin Zhou ◽  
Pengcheng Li ◽  
Feng Qian
Keyword(s):  
Viral Infection ◽  
Rna Virus ◽  
Cell Cycle Control ◽  
Ubiquitin Proteasome System ◽  
Innate Immune ◽  
Negative Regulator ◽  
Viral Immunity ◽  
Chemokine Production ◽  
Cellular Processes ◽  
Innate Immune Signaling

Proteasome is a large protein complex, which degrades most intracellular proteins. It regulates numerous cellular processes, including the removal of misfolded or unfolded proteins, cell cycle control, and regulation of apoptosis. However, the function of proteasome subunits in viral immunity has not been well characterized. In this study, we identified PSMB1, a member of the proteasome β subunits (PSMB) family, as a negative regulator of innate immune responses during viral infection. Knockdown of PSMB1 enhanced the RNA virus-induced cytokine and chemokine production. Overexpression of PSMB1 abolished virus-induced activation of the interferon-stimulated response element (ISRE) and interferon beta (IFNβ) promoters. Mechanistically, PSMB1 inhibited the activation of RIG-I-like receptor (RLR) and Toll-like receptor 3 (TLR3) signaling pathways. PSMB1 was induced after viral infection and its interaction with IKK-ε promoted degradation of IKK-ε through the ubiquitin-proteasome system. Collectively, our study demonstrates PSMB1 is an important regulator of innate immune signaling.

scholarly journals Spatiotemporal dynamics of innate immune signaling via RIG-I–like receptors

2020 ◽  
Vol 117 (27) ◽  
pp. 15778-15788 ◽  
Author(s):  
Katharina Esser-Nobis ◽  
Lauren D. Hatfield ◽  
Michael Gale
Keyword(s):  
Innate Immunity ◽  
Virus Infection ◽  
Rna Virus ◽  
Adaptor Protein ◽  
Innate Immune ◽  
Negative Regulator ◽  
Resting Cells ◽  
Immune Signaling ◽  
Innate Immune Signaling ◽  
Irf3 Activation

RIG-I, MDA5, and LGP2 comprise the RIG-I–like receptors (RLRs). RIG-I and MDA5 are essential pathogen recognition receptors sensing viral infections while LGP2 has been described as both RLR cofactor and negative regulator. After sensing and binding to viral RNA, including double-stranded RNA (dsRNA), RIG-I and MDA5 undergo cytosol-to-membrane relocalization to bind and signal through the MAVS adaptor protein on intracellular membranes, thus directing downstream activation of IRF3 and innate immunity. Here, we report examination of the dynamic subcellular localization of all three RLRs within the intracellular response to dsRNA and RNA virus infection. Observations from high resolution biochemical fractionation and electron microscopy, coupled with analysis of protein interactions and IRF3 activation, show that, in resting cells, microsome but not mitochondrial fractions harbor the central components to initiate innate immune signaling. LGP2 interacts with MAVS in microsomes, blocking the RIG-I/MAVS interaction. Remarkably, in response to dsRNA treatment or RNA virus infection, LGP2 is rapidly released from MAVS and redistributed to mitochondria, temporally correlating with IRF3 activation. We reveal that IRF3 activation does not take place on mitochondria but instead occurs at endoplasmic reticulum (ER)-derived membranes. Our observations suggest ER-derived membranes as key RLR signaling platforms controlled through inhibitory actions of LGP2 binding to MAVS wherein LGP2 translocation to mitochondria releases MAVS inhibition to facilitate RLR-mediated signaling of innate immunity.

scholarly journals N6-methyladenosine RNA modification suppresses antiviral innate sensing pathways via reshaping double-stranded RNA

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Weinan Qiu ◽  
Qingyang Zhang ◽  
Rui Zhang ◽  
Yangxu Lu ◽  
Xin Wang ◽  
...  
Keyword(s):  
Rna Virus ◽  
Negative Regulator ◽  
Rna Modification ◽  
Type I ◽  
Viral Immunity ◽  
Potential Therapeutic Target ◽  
Viral Dsrna ◽  
Double Stranded Rna ◽  
Genetic Ablation ◽  
Vesicular Stomatitis

AbstractDouble-stranded RNA (dsRNA) is a virus-encoded signature capable of triggering intracellular Rig-like receptors (RLR) to activate antiviral signaling, but whether intercellular dsRNA structural reshaping mediated by the N6-methyladenosine (m6A) modification modulates this process remains largely unknown. Here, we show that, in response to infection by the RNA virus Vesicular Stomatitis Virus (VSV), the m6A methyltransferase METTL3 translocates into the cytoplasm to increase m6A modification on virus-derived transcripts and decrease viral dsRNA formation, thereby reducing virus-sensing efficacy by RLRs such as RIG-I and MDA5 and dampening antiviral immune signaling. Meanwhile, the genetic ablation of METTL3 in monocyte or hepatocyte causes enhanced type I IFN expression and accelerates VSV clearance. Our findings thus implicate METTL3-mediated m6A RNA modification on viral RNAs as a negative regulator for innate sensing pathways of dsRNA, and also hint METTL3 as a potential therapeutic target for the modulation of anti-viral immunity.

scholarly journals Interferon-Stimulated Genes as Enhancers of Antiviral Innate Immune Signaling

2017 ◽  
Vol 10 (2) ◽  
pp. 85-93 ◽  
Author(s):  
Keaton M. Crosse ◽  
Ebony A. Monson ◽  
Michael R. Beard ◽  
Karla J. Helbig
Keyword(s):  
Immune Response ◽  
Viral Infection ◽  
Innate Immune Response ◽  
Innate Immune ◽  
Regulatory Factor ◽  
Interferon Stimulated Genes ◽  
Innate Immune Signaling ◽  
Recent Advancement ◽  
Antiviral Function

The ability of a host to curb a viral infection is heavily reliant on the effectiveness of an initial antiviral innate immune response, resulting in the upregulation of interferon (IFN) and, subsequently, IFN-stimulated genes (ISGs). ISGs serve to mount an antiviral state within a host cell, and although the specific antiviral function of a number of ISGs has been characterized, the function of many of these ISGs remains to be determined. Recent research has uncovered a novel role for a handful of ISGs, some of them directly induced by IFN regulatory factor 3 in the absence of IFN itself. These ISGs, most with potent antiviral activity, are also able to augment varying arms of the innate immune response to viral infection, thereby strengthening this response. This new understanding of the role of ISGs may, in turn, help the recent advancement of novel therapeutics aiming to augment innate signaling pathways in an attempt to control viral infection and pathogenesis.

scholarly journals MAVS Self-Association Mediates Antiviral Innate Immune Signaling

2009 ◽  
Vol 83 (8) ◽  
pp. 3420-3428 ◽  
Author(s):  
Eric D. Tang ◽  
Cun-Yu Wang
Keyword(s):  
Rna Virus ◽  
Innate Immune ◽  
Type I Interferons ◽  
Mitochondrial Outer Membrane ◽  
Type I ◽  
Rna Helicases ◽  
Downstream Effector ◽  
Innate Immune Signaling ◽  
Self Association ◽  
Tm Domain

ABSTRACT The innate immune system recognizes nucleic acids during viral infection and stimulates cellular antiviral responses. Intracellular detection of RNA virus infection is mediated by the RNA helicases RIG-I (retinoic acid inducible gene I) and MDA-5, which recognize viral RNA and signal through the adaptor molecule MAVS (mitochondrial antiviral signaling) to stimulate the phosphorylation and activation of the transcription factors IRF3 (interferon regulatory factor 3) and IRF7. Once activated, IRF3 and IRF7 turn on the expression of type I interferons, such as beta interferon. Interestingly, unlike other signaling molecules identified in this pathway, MAVS contains a C-terminal transmembrane (TM) domain that is essential for both type I interferon induction and localization of MAVS to the mitochondrial outer membrane. However, the role the MAVS TM domain plays in signaling remains unclear. Here we report the identification of a function for the TM domain in mediating MAVS self-association. The activation of RIG-I/MDA-5 leads to the TM-dependent dimerization of the MAVS N-terminal caspase recruitment domain, thereby providing an interface for direct binding to and activation of the downstream effector TRAF3 (tumor necrosis factor receptor-associated factor 3). Our results reveal a role for MAVS self-association in antiviral innate immunity signaling and provide a molecular mechanism for downstream signal transduction.

scholarly journals Regulation of antiviral innate immune signaling and viral evasion following viral genome sensing

2021 ◽  
Author(s):  
Kiramage Chathuranga ◽  
Asela Weerawardhana ◽  
Niranjan Dodantenna ◽  
Jong-Soo Lee
Keyword(s):  
Viral Infection ◽  
Innate Immune ◽  
Host Immune System ◽  
Immune Signaling ◽  
Antiviral Responses ◽  
Current State ◽  
Innate Immune Signaling ◽  
Genes Encoding ◽  
Host Antiviral Response ◽  
Recognition Receptor

AbstractA harmonized balance between positive and negative regulation of pattern recognition receptor (PRR)-initiated immune responses is required to achieve the most favorable outcome for the host. This balance is crucial because it must not only ensure activation of the first line of defense against viral infection but also prevent inappropriate immune activation, which results in autoimmune diseases. Recent studies have shown how signal transduction pathways initiated by PRRs are positively and negatively regulated by diverse modulators to maintain host immune homeostasis. However, viruses have developed strategies to subvert the host antiviral response and establish infection. Viruses have evolved numerous genes encoding immunomodulatory proteins that antagonize the host immune system. This review focuses on the current state of knowledge regarding key host factors that regulate innate immune signaling molecules upon viral infection and discusses evidence showing how specific viral proteins counteract antiviral responses via immunomodulatory strategies.

scholarly journals Keratinocytes contribute intrinsically to psoriasis upon loss of Tnip1 function

2016 ◽  
Vol 113 (41) ◽  
pp. E6162-E6171 ◽  
Author(s):  
Sirish K. Ippagunta ◽  
Ruchika Gangwar ◽  
David Finkelstein ◽  
Peter Vogel ◽  
Stephane Pelletier ◽  
...  
Keyword(s):  
Immune Cells ◽  
Inflammatory Process ◽  
Immune Cell ◽  
Genetic Alterations ◽  
Innate Immune ◽  
Negative Regulator ◽  
Specific Gene ◽  
Innate Immune Cells ◽  
Chemokine Production

Psoriasis is a chronic inflammatory skin disease with a clear genetic contribution, characterized by keratinocyte proliferation and immune cell infiltration. Various closely interacting cell types, including innate immune cells, T cells, and keratinocytes, are known to contribute to inflammation. Innate immune cells most likely initiate the inflammatory process by secretion of IL-23. IL-23 mediates expansion of T helper 17 (Th17) cells, whose effector functions, including IL-17A, activate keratinocytes. Keratinocyte activation in turn results in cell proliferation and chemokine expression, the latter of which fuels the inflammatory process through further immune cell recruitment. One question that remains largely unanswered is how genetic susceptibility contributes to this process and, specifically, which cell type causes disease due to psoriasis-specific genetic alterations. Here we describe a mouse model based on the human psoriasis susceptibility locus TNIP1, also referred to as ABIN1, whose gene product is a negative regulator of various inflammatory signaling pathways, including the Toll-like receptor pathway in innate immune cells. We find that Tnip1-deficient mice recapitulate major features of psoriasis on pathological, genomic, and therapeutic levels. Different genetic approaches, including tissue-specific gene deletion and the use of various inflammatory triggers, reveal that Tnip1 controls not only immune cells, but also keratinocyte biology. Loss of Tnip1 in keratinocytes leads to deregulation of IL-17–induced gene expression and exaggerated chemokine production in vitro and overt psoriasis-like inflammation in vivo. Together, the data establish Tnip1 as a critical regulator of IL-17 biology and reveal a causal role of keratinocytes in the pathogenesis of psoriasis.

scholarly journals Interleukin-37 regulates innate immune signaling in human and mouse colonic organoids

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Joannie M. Allaire ◽  
Anita Poon ◽  
Shauna M. Crowley ◽  
Xiao Han ◽  
Zohreh Sharafian ◽  
...  
Keyword(s):  
Inflammatory Responses ◽  
Individual Variability ◽  
Innate Immune ◽  
Negative Regulator ◽  
Intestinal Epithelial ◽  
Immune Signaling ◽  
Strong Expression ◽  
Innate Immune Signaling ◽  
Close Proximity ◽  
Species Specific

AbstractIntestinal epithelial cells (IEC) reside in close proximity to the gut microbiota and are hypo-responsive to bacterial products, likely to prevent maladaptive inflammatory responses. This is in part due to their strong expression of Single Ig IL-1 related receptor (SIGIRR), a negative regulator of interleukin (IL)-1 and toll-like receptor signaling. IL-37 is an anti-inflammatory cytokine that inhibits innate signaling in diverse cells by signaling through SIGIRR. Despite the strong expression of SIGIRR by IEC, few studies have examined whether IL-37 can suppress their innate immune signaling. We characterized innate immune responses of human and murine colonoids to bacteria (FliC, LPS) and host (IL-1β) products and the role of IL-37/SIGIRR in regulating these responses. We demonstrated that human colonoids responded only to FliC, but not to LPS or IL-1β. While colonoids derived from different donors displayed significant inter-individual variability in the magnitude of their innate responses to FliC stimulation, all colonoids released a variety of chemokines. Interestingly, IL-37 attenuated these responses through inhibition of p38 and NFκB signaling pathways. We determined that this suppression by IL-37 was SIGIRR dependent, in murine organoids. Along with species-specific differences in IEC innate responses, we show that IL-37 can promote IEC hypo-responsiveness by suppressing inflammatory signaling.

scholarly journals Interleukin-37 Regulates Innate Immune Signaling in Human and Mouse Colonic Organoids

2020 ◽  
Author(s):  
Joannie Allaire ◽  
Anita Poon ◽  
Shauna Crowley ◽  
Xiao Han ◽  
Navjit Moore ◽  
...  
Keyword(s):  
Inflammatory Responses ◽  
Individual Variability ◽  
Innate Immune ◽  
Negative Regulator ◽  
Intestinal Epithelial ◽  
Immune Signaling ◽  
Strong Expression ◽  
Innate Immune Signaling ◽  
Close Proximity ◽  
Species Specific

Abstract Intestinal epithelial cells (IEC) reside in close proximity to the gut microbiota and are hypo-responsive to bacterial products, likely to prevent maladaptive inflammatory responses. This is in part due to their strong expression of Single Ig IL-1 related receptor (SIGIRR), a negative regulator of interleukin (IL)-1 and toll-like receptor signaling. IL-37, an anti-inflammatory cytokine that inhibits innate signaling in diverse cells by signaling through SIGIRR. Despite the strong expression of SIGIRR by IEC, few studies have examined whether IL-37 can suppress their innate immune signaling. We characterized innate immune responses of human and murine colonoids to bacteria (FliC, LPS) and host (IL-1β) products and the role of IL-37/SIGIRR in regulating these responses. We demonstrated that human colonoids responded only to FliC, but not to LPS or IL-1β. While colonoids derived from different donors displayed significant inter-individual variability in the magnitude of their innate responses to FliC stimulation, all colonoids released a variety of chemokines. Interestingly, IL-37 attenuated these responses through inhibition of p38 and NFκB signaling pathways. We determined that this suppression by IL-37 was SIGIRR dependent, in murine organoids. Along with species-specific differences in IEC innate responses, we show that IL-37 can promote IEC hypo-responsiveness by supressing inflammatory signaling.

scholarly journals Defining the Immune Responses for SARS-CoV-2-Human Macrophage Interactions

2021 ◽  
Author(s):  
Mai Mostafa ◽  
Pravin Yeapuri ◽  
Jatin Machhi ◽  
Katherine Olson ◽  
Farah Shahjin ◽  
...  
Keyword(s):  
Immune Response ◽  
Viral Infection ◽  
Innate Immune Response ◽  
Human Monocyte ◽  
Innate Immune ◽  
Mononuclear Phagocytes ◽  
Human Macrophage ◽  
Type I ◽  
Innate Immune Signaling ◽  
Organ Tissue

Host innate immune response follows severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, and it is the driver of the acute respiratory distress syndrome (ARDS) amongst other inflammatory end-organ morbidities. Such life-threatening coronavirus disease 2019 (COVID-19) is heralded by virus-induced activation of mononuclear phagocytes (MPs; monocytes, macrophages, and dendritic cells). MPs play substantial roles in aberrant immune secretory activities affecting profound systemic inflammation and end organ malfunctions. All follow an abortive viral infection. To elucidate SARS-CoV-2-MP interactions we investigated transcriptomic and proteomic profiles of human monocyte-derived macrophages. While expression of the SARS-CoV-2 receptor, the angiotensin-converting enzyme 2, paralleled monocyte-macrophage differentiation it failed to affect productive viral infection. In contrast, simple macrophage viral exposure led to robust pro-inflammatory cytokine and chemokine expression but attenuated type I interferon (IFN) activity. Both paralleled dysregulation of innate immune signaling pathways specifically those linked to IFN. We conclude that the SARS-CoV-2-infected host mounts a robust innate immune response characterized by a pro-inflammatory storm heralding consequent end-organ tissue damage.

scholarly journals PPM1G restricts innate immune signaling mediated by STING and MAVS and is hijacked by KSHV for immune evasion

2020 ◽  
Vol 6 (47) ◽  
pp. eabd0276
Author(s):  
Kuai Yu ◽  
Huabin Tian ◽  
Hongyu Deng
Keyword(s):  
Immune Evasion ◽  
Adaptor Proteins ◽  
Antiviral Response ◽  
Innate Immune ◽  
Negative Regulator ◽  
Host Protein ◽  
Type I ◽  
Dna And Rna ◽  
Innate Immune Signaling ◽  
Interferon Pathway

The adaptor proteins, STING and MAVS, are components of critical pathogen-sensing pathways that induce innate immunity. Phosphorylation of either adaptor results in activation of the type I interferon pathway. How this phosphorylation is regulated and how it is manipulated by pathogens remain largely unknown. Here, we identified host protein phosphatase, Mg2+/Mn2+ dependent 1G (PPM1G) as a negative regulator of innate immune pathways and showed that this host system is hijacked by Kaposi’s sarcoma-associated herpesvirus (KSHV). Mechanistically, KSHV tegument protein ORF33 interacts with STING/MAVS and enhances recruitment of PPM1G to dephosphorylate p-STING/p-MAVS for immunosuppression. Inhibition of PPM1G expression improves the antiviral response against both DNA and RNA viruses. Collectively, our study shows that PPM1G restricts both cytosolic DNA– and RNA–sensing pathways to naturally balance the intensity of the antiviral response. Manipulation of PPM1G by KSHV provides an important strategy for immune evasion.

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