scholarly journals Haploinsufficiency of A20 impairs protein–protein interactome and leads into caspase-8-dependent enhancement of NLRP3 inflammasome activation

RMD Open ◽  
2018 ◽  
Vol 4 (2) ◽  
pp. e000740 ◽  
Author(s):  
Kristiina Rajamäki ◽  
Salla Keskitalo ◽  
Mikko Seppänen ◽  
Outi Kuismin ◽  
Paula Vähäsalo ◽  
...  
Keyword(s):  
Protein Interactions ◽  
Immune Cells ◽  
Nlrp3 Inflammasome ◽  
Molecular Mechanisms ◽  
Luciferase Reporter ◽  
Caspase 8 ◽  
Inflammasome Activation ◽  
Loss Of Function ◽  
Pyrin Domain ◽  
Protein Interactome

ObjectivesTNFAIP3 encodes A20 that negatively regulates nuclear factor kappa light chain enhancer of activated B cells (NF-κB), the major transcription factor coordinating inflammatory gene expression. TNFAIP3 polymorphisms have been linked with a spectrum of inflammatory and autoimmune diseases and, recently, loss-of-function mutations in A20 were found to cause a novel inflammatory disease ‘haploinsufficiency of A20’ (HA20). Here we describe a family with HA20 caused by a novel TNFAIP3 loss-of-function mutation and elucidate the upstream molecular mechanisms linking HA20 to dysregulation of NF-κB and the related inflammasome pathway.MethodsNF-κB activation was studied in a mutation-expressing cell line using luciferase reporter assay. Physical and close-proximity protein–protein interactions of wild-type and TNFAIP3 p.(Lys91*) mutant A20 were analysed using mass spectrometry. NF-κB -dependent transcription, cytokine secretion and inflammasome activation were compared in immune cells of the HA20 patients and control subjects.ResultsThe protein–protein interactome of p.(Lys91*) mutant A20 was severely impaired, including interactions with proteins regulating NF-κB activation, DNA repair responses and the NLR family pyrin domain containing 3 (NLRP3) inflammasome. The p.(Lys91*) mutant A20 failed to suppress NF-κB signalling, which led to increased NF-κB -dependent proinflammatory cytokine transcription. Functional experiments in the HA20 patients’ immune cells uncovered a novel caspase-8-dependent mechanism of NLRP3 inflammasome hyperresponsiveness that mediated the excessive secretion of interleukin-1β and interleukin-18.ConclusionsThe current findings significantly deepen our understanding of the molecular mechanisms underlying HA20 and other diseases associated with reduced A20 expression or function, paving the way for future therapeutic targeting of the pathway.

scholarly journals Haploinsufficiency of A20 impairs protein-protein interactome and leads into caspase-8-dependent enhancement of NLRP3 inflammasome activation

2018 ◽  
Author(s):  
Kristiina Rajamäki ◽  
Salla Keskitalo ◽  
Mikko Seppänen ◽  
Outi Kuismin ◽  
Paula Vähäsalo ◽  
...  
Keyword(s):  
Protein Interactions ◽  
Immune Cells ◽  
Nlrp3 Inflammasome ◽  
Molecular Mechanisms ◽  
Luciferase Reporter ◽  
Caspase 8 ◽  
Inflammasome Activation ◽  
Loss Of Function ◽  
Pyrin Domain ◽  
Protein Interactome

ABSTRACTObjectivesTNFAIP3 encodes A20 that negatively regulates nuclear factor kappa light chain enhancer of activated B cells (NF-κB), the major transcription factor coordinating inflammatory gene expression. TNFAIP3 polymorphisms have been linked with a spectrum of inflammatory and autoimmune diseases and recently, loss-of-function mutations in A20 were found to cause a novel inflammatory disease ‘haploinsufficiency of A20’ (HA20). Here we describe a family with HA20 caused by a novel TNFAIP3 loss-of-function mutation and elucidate the upstream molecular mechanisms linking HA20 to dysregulation of NF-κB and the related inflammasome pathway.MethodsNF-κB activation was studied in a mutation-expressing cell line using luciferase reporter assay. Physical and close-proximity protein-protein interactions of wild-type and TNFAIP3 p.(Lys91*) mutant A20 were analyzed using mass spectrometry. NF-κB –dependent transcription, cytokine secretion, and inflammasome activation were compared in immune cells of the HA20 patients and control subjects.ResultsThe protein-protein interactome of p.(Lys91*) mutant A20 was severely impaired, including inter-actions with proteins regulating NF-κB activation, DNA repair responses, and the NLR family pyrin domain containing 3 (NLRP3) inflammasome. The p.(Lys91*) mutant A20 failed to suppress NF-κB signaling, which led to increased NF-κB –dependent proinflammatory cytokine transcription. Functional experiments in the HA20 patients’ immune cells uncovered a novel caspase-8-dependent mechanism of NLRP3 inflammasome hyperresponsiveness that mediated the excessive secretion of interleukin-1β and -18.ConclusionsThe current findings significantly deepen our understanding of the molecular mechanisms underlying HA20 and other diseases associated with reduced A20 expression or function, paving the way for future therapeutic targeting of the pathway.

scholarly journals An update on the regulatory mechanisms of NLRP3 inflammasome activation

2021 ◽  
Author(s):  
Seungwha Paik ◽  
Jin Kyung Kim ◽  
Prashanta Silwal ◽  
Chihiro Sasakawa ◽  
Eun-Kyeong Jo
Keyword(s):  
Protein Interactions ◽  
Posttranslational Modifications ◽  
Nlrp3 Inflammasome ◽  
Molecular Mechanisms ◽  
Inflammasome Activation ◽  
Protein Protein Interactions ◽  
Regulatory Pathways ◽  
Pyrin Domain ◽  
Spatiotemporal Regulation ◽  
Nlrp3 Inflammasome Activation

AbstractThe NOD-, LRR-, and pyrin domain-containing protein 3 (NLRP3) inflammasome is a multiprotein complex involved in the release of mature interleukin-1β and triggering of pyroptosis, which is of paramount importance in a variety of physiological and pathological conditions. Over the past decade, considerable advances have been made in elucidating the molecular mechanisms underlying the priming/licensing (Signal 1) and assembly (Signal 2) involved in NLRP3 inflammasome activation. Recently, a number of studies have indicated that the priming/licensing step is regulated by complicated mechanisms at both the transcriptional and posttranslational levels. In this review, we discuss the current understanding of the mechanistic details of NLRP3 inflammasome activation with a particular emphasis on protein-protein interactions, posttranslational modifications, and spatiotemporal regulation of the NLRP3 inflammasome machinery. We also present a detailed summary of multiple positive and/or negative regulatory pathways providing upstream signals that culminate in NLRP3 inflammasome complex assembly. A better understanding of the molecular mechanisms underlying NLRP3 inflammasome activation will provide opportunities for the development of methods for the prevention and treatment of NLRP3 inflammasome-related diseases.

scholarly journals The NLRP3 inflammasome mediates DSS-induced intestinal inflammation in Nod2 knockout mice

2019 ◽  
Vol 25 (2) ◽  
pp. 132-143 ◽  
Author(s):  
Benjamin Umiker ◽  
Hyun-Hee Lee ◽  
Julia Cope ◽  
Nadim J. Ajami ◽  
Jean-Philippe Laine ◽  
...  
Keyword(s):  
Nlrp3 Inflammasome ◽  
Intestinal Inflammation ◽  
Inflammasome Activation ◽  
Intestinal Epithelial ◽  
Loss Of Function ◽  
Pyrin Domain ◽  
Nlrp3 Inflammasome Activation ◽  
Chronic Disorder ◽  
Molecule Inhibitor ◽  
Pathway Inhibition

Crohn’s disease (CD) is a chronic disorder of the gastrointestinal tract characterized by inflammation and intestinal epithelial injury. Loss of function mutations in the intracellular bacterial sensor NOD2 are major risk factors for the development of CD. In the absence of robust bacterial recognition by NOD2 an inflammatory cascade is initiated through alternative PRRs leading to CD. In the present study, MCC950, a specific small molecule inhibitor of NLR pyrin domain-containing protein 3 (NLRP3), abrogated dextran sodium sulfate (DSS)-induced intestinal inflammation in Nod2−/− mice. NLRP3 inflammasome formation was observed at a higher rate in NOD2-deficient small intestinal lamina propria cells after insult by DSS. NLRP3 complex formation led to an increase in IL-1β secretion in both the small intestine and colon of Nod2ko mice. This increase in IL-1β secretion in the intestine was attenuated by MCC950 leading to decreased disease severity in Nod2ko mice. Our work suggests that NLRP3 inflammasome activation may be a key driver of intestinal inflammation in the absence of functional NOD2. NLRP3 pathway inhibition can prevent intestinal inflammation in the absence of robust NOD2 signaling.

scholarly journals Targeting NLRP3 Inflammasome Activation in Severe Asthma

2019 ◽  
Vol 8 (10) ◽  
pp. 1615 ◽  
Author(s):  
Efthymia Theofani ◽  
Maria Semitekolou ◽  
Ioannis Morianos ◽  
Konstantinos Samitas ◽  
Georgina Xanthou
Keyword(s):  
Severe Asthma ◽  
Nlrp3 Inflammasome ◽  
Molecular Mechanisms ◽  
Inflammatory Responses ◽  
Pulmonary Inflammation ◽  
Airflow Obstruction ◽  
Inflammasome Activation ◽  
Pyrin Domain ◽  
Nlrp3 Inflammasome Activation ◽  
Reversible Airflow Obstruction

Severe asthma (SA) is a chronic lung disease characterized by recurring symptoms of reversible airflow obstruction, airway hyper-responsiveness (AHR), and inflammation that is resistant to currently employed treatments. The nucleotide-binding oligomerization domain-like Receptor Family Pyrin Domain Containing 3 (NLRP3) inflammasome is an intracellular sensor that detects microbial motifs and endogenous danger signals and represents a key component of innate immune responses in the airways. Assembly of the NLRP3 inflammasome leads to caspase 1-dependent release of the pro-inflammatory cytokines IL-1β and IL-18 as well as pyroptosis. Accumulating evidence proposes that NLRP3 activation is critically involved in asthma pathogenesis. In fact, although NLRP3 facilitates the clearance of pathogens in the airways, persistent NLRP3 activation by inhaled irritants and/or innocuous environmental allergens can lead to overt pulmonary inflammation and exacerbation of asthma manifestations. Notably, administration of NLRP3 inhibitors in asthma models restrains AHR and pulmonary inflammation. Here, we provide an overview of the pathophysiology of SA, present molecular mechanisms underlying aberrant inflammatory responses in the airways, summarize recent studies pertinent to the biology and functions of NLRP3, and discuss the role of NLRP3 in the pathogenesis of asthma. Finally, we contemplate the potential of targeting NLRP3 as a novel therapeutic approach for the management of SA.

scholarly journals ER Stress Activates the NLRP3 Inflammasome: A Novel Mechanism of Atherosclerosis

2019 ◽  
Vol 2019 ◽  
pp. 1-18 ◽  
Author(s):  
Xinnong Chen ◽  
Xiaochen Guo ◽  
Qihui Ge ◽  
Yixuan Zhao ◽  
Huaiyu Mu ◽  
...  
Keyword(s):  
Er Stress ◽  
Nlrp3 Inflammasome ◽  
Molecular Mechanisms ◽  
Ros Generation ◽  
Macromolecular Complex ◽  
Inflammasome Activation ◽  
Cellular Processes ◽  
Pyrin Domain ◽  
Nlrp3 Inflammasome Activation ◽  
The Unfolded Protein Response

The endoplasmic reticulum (ER) is an important organelle that regulates several fundamental cellular processes, and ER dysfunction has implications for many intracellular events. The nucleotide-binding oligomerization domain-like receptor family, pyrin domain-containing 3 (NLRP3) inflammasome is an intracellularly produced macromolecular complex that can trigger pyroptosis and inflammation, and its activation is induced by a variety of signals. ER stress has been found to affect NLRP3 inflammasome activation through multiple effects including the unfolded protein response (UPR), calcium or lipid metabolism, and reactive oxygen species (ROS) generation. Intriguingly, the role of ER stress in inflammasome activation has not attracted a great deal of attention. In addition, increasing evidence highlights that both ER stress and NLRP3 inflammasome activation contribute to atherosclerosis (AS). AS is a common cardiovascular disease with complex pathogenesis, and the precise mechanisms behind its pathogenesis remain to be determined. Both ER stress and the NLRP3 inflammasome have emerged as critical individual contributors of AS, and owing to the multiple associations between these two events, we speculate that they contribute to the mechanisms of pathogenesis in AS. In this review, we aim to summarize the molecular mechanisms of ER stress, NLRP3 inflammasome activation, and the cross talk between these two pathways in AS in the hopes of providing new pharmacological targets for AS treatment.

scholarly journals NLRP3 Inflammasome and Allergic Contact Dermatitis: A Connection to Demystify

Pharmaceutics ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 867
Author(s):  
Ana Isabel Sebastião ◽  
Isabel Ferreira ◽  
Gonçalo Brites ◽  
Ana Silva ◽  
Bruno Miguel Neves ◽  
...  
Keyword(s):  
Contact Dermatitis ◽  
Allergic Contact Dermatitis ◽  
Nlrp3 Inflammasome ◽  
Molecular Mechanisms ◽  
Alternative Methods ◽  
Inflammasome Activation ◽  
Pyrin Domain ◽  
And Migration ◽  
Novel Therapeutic Strategies ◽  
Allergic Contact

Allergic contact dermatitis is a common occupational disease that manifests as a cell-mediated hypersensitivity reaction following skin exposure to small reactive chemicals termed haptens. Haptens penetrate the stratum corneum and covalently modify proteins in the epidermis, inducing intracellular stress, which further leads to the release of damage-associated molecular patterns (DAMPs), such as uric acid, reactive oxygen species, hyaluronic acid fragments and extracellular adenosine triphosphate (ATP). These DAMPs are recognized by pattern recognition receptors (PRRs) in innate immune cells, namely dendritic cells (DCs), leading to their maturation and migration to the draining lymph nodes where they activate naïve T lymphocytes. Among all PRRs, several studies emphasize the role of NOD-, LRR- and pyrin domain-containing protein 3 (NLRP3) inflammasome on the allergic contact dermatitis (ACD) sensitization phase. However, skin allergens—danger signals—NLRP3 inflammasome axis is yet to be completely elucidated. Therefore, in this review, we sought to discuss the molecular mechanisms underlying DAMPs release and NLRP3 inflammasome activation triggered by skin allergens. The elucidation of these key events might help to identify novel therapeutic strategies for ACD, as well as the development of nonanimal alternative methods for the identification and potency categorization of skin sensitizers.

scholarly journals Circular RNA mmu_circ_0005019 inhibits fibrosis of cardiac fibroblasts and reverses electrical remodeling of cardiomyocytes

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Na Wu ◽  
Chengying Li ◽  
Bin Xu ◽  
Ying Xiang ◽  
Xiaoyue Jia ◽  
...  
Keyword(s):  
Molecular Mechanisms ◽  
Cardiac Fibroblasts ◽  
Circular Rna ◽  
Protective Role ◽  
Luciferase Reporter ◽  
Loss Of Function ◽  
Candidate Target ◽  
Paired Control ◽  
Reporter Assays ◽  
And Migration

Abstract Background Circular RNA (circRNA) have been reported to play important roles in cardiovascular diseases including myocardial infarction and heart failure. However, the role of circRNA in atrial fibrillation (AF) has rarely been investigated. We recently found a circRNA hsa_circ_0099734 was significantly differentially expressed in the AF patients atrial tissues compared to paired control. We aim to investigate the functional role and molecular mechanisms of mmu_circ_0005019 which is the homologous circRNA in mice of hsa_circ_0099734 in AF. Methods In order to investigate the effect of mmu_circ_0005019 on the proliferation, migration, differentiation into myofibroblasts and expression of collagen of cardiac fibroblasts, and the effect of mmu_circ_0005019 on the apoptosis and expression of Ito, INA and SK3 of cardiomyocytes, gain- and loss-of-function of cell models were established in mice cardiac fibroblasts and HL-1 atrial myocytes. Dual-luciferase reporter assays and RIP were performed to verify the binding effects between mmu_circ_0005019 and its target microRNA (miRNA). Results In cardiac fibroblasts, mmu_circ_0005019 showed inhibitory effects on cell proliferation and migration. In cardiomyocytes, overexpression of mmu_circ_0005019 promoted Kcnd1, Scn5a and Kcnn3 expression. Knockdown of mmu_circ_0005019 inhibited the expression of Kcnd1, Kcnd3, Scn5a and Kcnn3. Mechanistically, mmu_circ_0005019 exerted biological functions by acting as a miR-499-5p sponge to regulate the expression of its target gene Kcnn3. Conclusions Our findings highlight mmu_circ_0005019 played a protective role in AF development and might serve as an attractive candidate target for AF treatment.

scholarly journals Anti-NLRP3 Inflammasome Natural Compounds: An Update

Biomedicines ◽  
2021 ◽  
Vol 9 (2) ◽  
pp. 136
Author(s):  
Baolong Liu ◽  
Jiujiu Yu
Keyword(s):  
Nlrp3 Inflammasome ◽  
Protein Complex ◽  
Molecular Mechanisms ◽  
Inflammatory Responses ◽  
Natural Compounds ◽  
Pyrin Domain ◽  
Inflammatory Protein ◽  
Wide Range ◽  
Activation Mechanisms ◽  
Stress Signals

The nucleotide-binding domain and leucine-rich repeat related (NLR) family, pyrin domain containing 3 (NLRP3) inflammasome is a multimeric protein complex that recognizes various danger or stress signals from pathogens, the host, and the environment, leading to activation of caspase-1 and inducing inflammatory responses. This pro-inflammatory protein complex plays critical roles in pathogenesis of a wide range of diseases including neurodegenerative diseases, autoinflammatory diseases, and metabolic disorders. Therefore, intensive efforts have been devoted to understanding its activation mechanisms and to searching for its specific inhibitors. Approximately forty natural compounds with anti-NLRP3 inflammasome properties have been identified. Here, we provide an update about new natural compounds that have been identified within the last three years to inhibit the NLRP3 inflammasome and offer an overview of the underlying molecular mechanisms of their anti-NLRP3 inflammasome activities.

scholarly journals Aggregated Tau-PHF6 (VQIVYK) Potentiates NLRP3 Inflammasome Expression and Autophagy in Human Microglial Cells

Cells ◽  
2021 ◽  
Vol 10 (7) ◽  
pp. 1652
Author(s):  
Chinmaya Panda ◽  
Clara Voelz ◽  
Pardes Habib ◽  
Christian Mevissen ◽  
Thomas Pufe ◽  
...  
Keyword(s):  
Tau Protein ◽  
Nlrp3 Inflammasome ◽  
Time Dependent ◽  
Microglial Cells ◽  
Inflammasome Activation ◽  
Dependent Manner ◽  
Progressive Dementia ◽  
Microglial Polarization ◽  
Protein Levels ◽  
Pyrin Domain

Intra-neuronal misfolding of monomeric tau protein to toxic β-sheet rich neurofibrillary tangles is a hallmark of Alzheimer’s disease (AD). Tau pathology correlates not only with progressive dementia but also with microglia-mediated inflammation in AD. Amyloid-beta (Aβ), another pathogenic peptide involved in AD, has been shown to activate NLRP3 inflammasome (NOD-like receptor family, pyrin domain containing 3), triggering the secretion of proinflammatory interleukin-1β (IL1β) and interleukin-18 (IL18). However, the effect of tau protein on microglia concerning inflammasome activation, microglial polarization, and autophagy is poorly understood. In this study, human microglial cells (HMC3) were stimulated with the unaggregated and aggregated forms of the tau-derived PHF6 peptide (VQIVYK). Modulation of NLRP3 inflammasome was examined by qRT-PCR, immunocytochemistry, and Western blot. We demonstrate that fibrillar aggregates of VQIVYK upregulated the NLRP3 expression at both mRNA and protein levels in a dose- and time-dependent manner, leading to increased expression of IL1β and IL18 in HMC3 cells. Aggregated PHF6-peptide also activated other related inflammation and microglial polarization markers. Furthermore, we also report a time-dependent effect of the aggregated PHF6 on BECN1 (Beclin-1) expression and autophagy. Overall, the PHF6 model system-based study may help to better understand the complex interconnections between Alzheimer’s PHF6 peptide aggregation and microglial inflammation, polarization, and autophagy.

scholarly journals Long noncoding RNA SNHG25 promotes the malignancy of endometrial cancer by sponging microRNA-497-5p and increasing FASN expression

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Yuhua He ◽  
Shuifang Xu ◽  
Yi Qi ◽  
Jinfang Tian ◽  
Fengying Xu
Keyword(s):  
Endometrial Cancer ◽  
Long Noncoding Rna ◽  
Noncoding Rna ◽  
Fatty Acid Synthase ◽  
Molecular Mechanisms ◽  
Luciferase Reporter ◽  
Migration And Invasion ◽  
Study Cohort ◽  
Loss Of Function ◽  
Ec Cells

Abstract Background Small nucleolar RNA host gene 25 (SNHG25), a long noncoding RNA, has been well-studied in epithelial ovarian cancer. However, the specific functions of SNHG25 in endometrial cancer (EC) have not been studied yet. In this study, we aimed to elucidate the clinical significance of SNHG25 in EC and determine the regulatory activity of SNHG25 on the tumor-associated EC phenotype. We also thoroughly explored the molecular mechanisms underlying SNHG25 function in EC. Methods Gene expression was measured using quantitative real-time polymerase chain reaction. The detailed functions of SNHG25 in EC were examined by performing loss-of-function experiments. Moreover, the regulatory mechanisms involving SNHG25, microRNA-497-5p, and fatty acid synthase (FASN) were unveiled using the luciferase reporter assay and RNA immunoprecipitation. Results We observed a high level of SNHG25 in EC using the TCGA dataset and our study cohort. Patients with a high SNHG25 level had shorter overall survival than those with a low SNHG25 level. SNHG25 deficiency resulted in tumor-repressing activities in EC cells by decreasing cell proliferation, migration, and invasion and promoting cell apoptosis. Furthermore, the function of SNHG25 depletion in impairing tumor growth in vivo was confirmed. SNHG25 sequestered miR-497-5p as a competing endogenous RNA in EC and consequently positively regulated FASN expression. Thus, the decrease in miR-497-5p or increase in FASN could neutralize the modulatory actions of SNHG25 knockdown in EC cells. Conclusions The depletion of SNHG25 impedes the oncogenicity of EC by targeting the miR-497-5p/FASN axis. The newly elucidated SNHG25/miR-497-5p/FASN pathway may be a promising target for the molecular-targeted management of EC.

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