Dual roles of the Arabidopsis PEAT complex in histone H2A deubiquitination and H4K5 acetylation

Histone H2A monoubiquitination is associated with transcriptional repression and needs to be removed by deubiquitinases to facilitate gene transcription in eukaryotes.However,the deubiquitinase responsible for genome-wide H2A deubiquitination in plants has yet to be identified.In this study,we found that the previously identified PWWP-EPCR-ARID-TRB(PEAT)complex components interact with both the ubiquitin-specific protease UBP5 and the redundant histone acetyltransferases HAM1 and HAM2(HAM1/2)to form a larger version of PEAT complex in Arabidopsis thaliana.UBP5 functions as an H2A deubiquitinase in a nucleosome substrate-dependent manner in vitro and mediates H2A deubiquitination at the whole-genome level in vivo.HAM1/2 are shared subunits of the PEAT complex and the conserved NuA4 histone acetyltransferase com-plex,and are responsible for histone H4K5 acetylation.Within the PEAT complex,the PWWP components(PWWP1,PWWP2,and PWWP3)directly interact with UBP5 and are necessary for UBP5-mediated H2A deu-biquitination,while the EPCR components(EPCR1 and EPCR2)directly interact with HAM1/2 and are required for HAM1/2-mediated H4K5acetylation.Collectively,our study not onlyidentifies dual roles of thePEAT com-plex in H2A deubiquitination and H4K5 acetylation but also illustrates how these processes collaborate at the whole-genome level to regulate the transcription and development in plants.

Deubiquitination complex platform:A plausible mechanism for regulating the substrate specificity of deubiquitinating enzymes

Deubiquitinating enzymes(DUBs) or deubiquitinases facilitate the escape of multiple proteins from ubiquitin-proteasome degradation and are critical for regulating protein expression levels in vivo.Therefore,dissecting the underlying mechanism of DUB recognition is needed to advance the development of drugs related to DUB signaling pathways.To data,extensive studies on the ubiquitin chain specificity of DUBs have been reported,but substrate protein recognition is still not clearly understood.As a breakthrough,the scaffolding role may be significant to substrate protein selectivity.From this perspective,we systematically characterized the scaffolding proteins and complexes contributing to DUB substrate selectivity.Furthermore,we proposed a deubiquitination complex platform(DCP) as a potentially generic mechanism for DUB substrate recognition based on known examples,which might fill the gaps in the understanding of DUB substrate specificity.

Emerging role of ubiquitination/deubiquitination modification of PD-1/PD-L1 in cancer immunotherapy

As members of the immune checkpoint family, PD-1 and its ligand PD-L1 play critical roles in maintaining the balance between autoimmunity and tolerance. The interaction of PD-1/PD-L1 is also involved in tumor evasion inside the tumor microenvironment, caused by reduced T cell activation, proliferation, cytotoxic secretion, and survival. Previous research has shown that the expression level of PD-1/PD-L1 may be regulated by ubiquitin-mediated proteasome degradation, which is an important mode of post-translational modification (PTM). PD-1/PD-L1 ubiquitin modification research in tumor immunotherapy is the subject of the present review, which aims to assess the most recent developments in this area. We offer a short explanation of PD-1/PD-L1 as well as some basic background information on the UPS system and discuss many routes that target E3s and DUBs, respectively, in the regulation of PD-1/PD-L1 in tumor immunotherapy. In addition, we offer numerous innovative prospective research areas for the future, as well as novel immunotherapy concepts and ideas. Taken together, the information compiled herein should serve as a comprehensive repository of information about tumor immunotherapy that is currently available, and it should be useful in the design of future studies, as well as the development of potential targets and strategies for future tumor immunotherapy.

Hexyl-pentynoic acid serves as a novel radiosensitizer for breast cancer by inhibiting UCHL3-dependent Rad51 deubiquitination

Objective:To investigate the effects and underlying mechanism of 2-hexyl-4-pentynoic acid(HPTA),a derivative of valproic acid(VPA),on radiotherapy in breast cancer.Methods:MCF7 cells and 7,12-dimethylbenz-[α]-anthracene(DMBA)-induced transformed human normal breast cells(MCF10A–DMBA cells)were irradiated with 8 Gy X-rays.For both cells there were four groups:control,valproic acid(VPA)/HPTA,IR,and VPA/HPTA+IR groups.MTT and clonogenic survival assays were performed to assess cell proliferation,and comet assay was performed to evaluate DNA damage.Protein expression ofγH2AX,53BP1,Rad51,and BRCA1 was examined via immunofluorescence and immunoblotting.Cycloheximide chase and ubiquitination experiments were conducted to determine Rad51 ubiquitination.In vivo experiments involved a rat model of DMBA-induced breast cancer,with four fractionated doses of 2 Gy.Tumor tissue pathological changes andγH2AX,Rad51,and UCHL3 expression levels were measured by hematoxylin-eosin staining,immunohistochemistry,and immunoblotting.Results:Compared with the IR group,15μmol/L HPTA reduced the cell proliferation ability of irradiated MCF7 cells(t=2.16,P<0.05).The VPA/HPTA+IR group exhibited significantly increased DNA double-strand breaks relative to those in the IR group(VPA+IR vs.IR,t=13.37,P<0.05;HPTA+IR vs.IR,t=8.48,P<0.05).Immunofluorescence and immunoblotting experiments demonstrated that the VPA/HPTA+IR group displayed signifi-cantly increased cell foci formation,γH2AX and 53BP1 protein expression levels compared to the IR group[(γH2AX:VPA+IR vs.IR,t=8.88,P<0.05;HPTA+IR vs.IR,t=8.90,P<0.05),(53BP1,VPA+IR vs.IR,t=5.73,P<0.05;HPTA+IR vs.IR,t=6.40,P<0.05)].Further,Rad51 expression was downregulated(VPA+IR vs.IR,t=3.12,P<0.05;HPTA+IR vs.IR,t=2.70,P<0.05),and Rad51 inhibition effectively counteracted HPTA-induced radiosensitization.Ubiquitination detection further verified that HPTA inhibits Rad51 expression via UCHL3-dependent Rad51 deubiquitination.In vivo study results showed that 20 mg/kg HPTA significantly enhanced the radiosensitivity of breast tumors in rats by inhibiting Rad51 expression.Conclusions:HPTA is a highly effective radiosensitizer that enhances the radiotherapeutic efficacy of breast cancer treatment through UCHL3-dependent deubiquitination of Rad51.

;he regulation of TGF-β/SMAD signaling by protein deubiquitination

Transforming growth factor-β （TGF-β） members are key cytokines that control embryogenesis and tissue homeostasis via transmembrane TGF-β type II （TβR II） and type I （TβRI） and serine/threonine kinases receptors. Aberrant activation of TGF-β signaling leads to diseases, including cancer. In advanced cancer, the TGF-β/SMAD pathway can act as an oncogenic factor driving tumor cell invasion and metastasis, and thus is considered to be a therapeutic target. The activity of TGF-β/SMAD pathway is known to be regulated by ubiquitination at multiple levels. As ubiquitination is reversible, emerging studies have uncovered key roles for ubiquitin-removals on TGF-β signaling components by deubiquitinating enzymes （DUBs）. In this paper, we summarize the latest findings on the DUBs that control the activity of the TGF-β signaling pathway. The regula- tory roles of these DUBs as a driving force for cancer progression as well as their underlying working mech- anisms are also discussed.

The role of ubiquitination and deubiquitination in the regulation of cell junctions

Maintenance of cell junctions plays a crucial role in the regulation of cellular functions including cell proliferation, permeability, and cell death. Disruption of cell junctions is implicated in a variety of human disorders, such as inflammatory diseases and cancers. Understanding molecular regulation of cell junctions is important for development of therapeutic strategies for intervention of human diseases. Ubiquitination is an important type of post-translational modification that primarily regulates endogenous protein stability, recep- tor internalization, enzyme activity, and protein-protein interactions. Ubiquitination is tightly regulated by ubiq- uitin E3 ligases and can be reversed by deubiquitinating enzymes. Recent studies have been focusing on inves- tigating the effect of protein stability in the regulation of cell-cell junctions. Ubiquitination and degradation of cadherins, claudins, and their interacting proteins are implicated in epithelial and endothelial barrier disruption. Recent studies have revealed that ubiquitination is involved in regulation of Rho GTPases＇ biological activities. Taken together these studies, ubiquitination plays a critical role in modulating cell junctions and motility. In this review, we will discuss the effects of ubiquitination and deubiquitination on protein stability and expression of key proteins in the cell-cell junctions, including junction proteins, their interacting proteins, and small Rho GTPases. We provide an overview of protein stability in modulation of epithelial and endothelial barrier integrity and introduce potential future search directions to better understand the effects of ubiquitination on human disorders caused by dysfunction of cell junctions.

Deubiquitination of BES1 by UBP12/UBP13 promotes brassinosteroid signaling and plant growth

As a key transcription factor in the brassinosteroid (BR) signaling pathway, the activity and expression ofBES1 (BRI1-EMS-SUPPRESSOR 1) are stringently regulated. BES1 degradation is mediated by ubiquitinrelated 26S proteasomal and autophagy pathways, which attenuate and terminate BR signaling;however,the opposing deubiquitinases (DUBs) are still unknown. Here, we showed that the ubp12-2w/13-3 doublemutant phenocopies the BR-deficient dwarf mutant, suggesting that the two DUBs UBP12/UBP13 antagonize ubiquitin-mediated degradation to stabilize BES1. These two DUBs can trim tetraubiquitin with K46 and K63 linkages in vitro. UBP12/BES1 and UBP13/BES1 complexes are localized in bothcytosol and nuclei. UBP12/13 can deubiquitinate polyubiquitinated BES1 in vitro and in planta, andUBP12 interacts with and deubiquitinates both inactive, phosphorylated BES1 and active, dephosphorylated BES1 in vivo. UBP12 overexpression in BES1OE plants significantly enhances cell elongation in hypocotyls and petioles and increases the ratio of leaf length to width compared with BES1OE or UBP12OE plants.Hypocotyl elongation and etiolation result from elevated BES1 levels because BES1 degradation is retardedby UBP12 in darkness or in light with BR. Protein degradation inhibitor experiments show that the majorityof BES1 can be degraded by either the proteasomal or the autophagy pathway, but a minor BES1 fractionremains pathway specific. In conclusion, UBP12/UBP13 deubiquitinate BES1 to stabilize the latter as a positive regulator for BR responses.

Deubiquitination in prostate cancer progression:role of USP22

Prostate cancer(PCa)is the leading cause of cancer death in men.With more therapeutic modalities available,the overall survival in PCa has increased significantly in recent years.Patients with relapses after advanced secondgeneration anti-androgen therapy however,often show poor disease prognosis.This group of patients often die from cancer-related complicacies.Multiple approaches have been taken to understand disease recurrence and to correlate the gene expression profile.In one such study,an 11-gene signature was identified to be associated with PCa recurrence and poor survival.Amongst them,a specific deubiquitinase called ubiquitin-specific peptidase 22(USP22)was selectively and progressively overexpressed with PCa progression.Subsequently,it was shown to regulate androgen receptors and Myc,the two most important regulators of PCa progression.Furthermore,USP22 has been shown to be associated with the development of therapy resistant PCa.Inhibiting USP22 was also found to be therapeutically advantageous,especially in clinically challenging and advanced PCa.This review provides an update of USP22 related functions and challenges associated with PCa research and explains why targeting this axis is beneficial for PCa relapse cases.

Novel mutations in ubiquitin-specific protease 26 gene might cause spermatogenesis impairment and male infertility

Aim： To study the incidence of single nucleotide polymorphisms in ubiquitin-specific protease 26 （USP26） gene and its involvement in idiopathic male infertility in China. Methods： Routine semen analysis was performed. Infertility factors such as immunological, infectious and biochemical disorders were examined to select patients with idiopathic infertility. DNA was isolated from peripheral blood of the selected patients and control population, which were examined for mutations using polymerase chain reaction-single strand conformation polymorphism analysis. Furthermore, nucleotide sequences were sequenced in some patients and controls. Results： Of 41 infertile men, 9 （22.0%, P = 0.01） had changes in USP26 gene on the X chromosome. A compound mutation （364insACA; 460G→A） was detected in 8 patients （19.5%, P = 0.01） and a 1044T→A substitution was found in 1 patient （2.4%, P 〉 0.05）. All three variations led to changes in the coding amino acids. Two substitutions predict some changes： 460G→ A changes a valine into an isoleucine, and 1044T → A substitutes a leucine for a phenylalanine. Another insertion of three nucleotides ACA causes an insertion of threonine. No other changes were found in the remaining patients and fertile controls. Conclusion： The USP26 gene might be of importance in male reproduction. Mutations in this gene might be associated with male infertility, and might negatively affect testicular function. Further research on this issue is in progress.

The expression of Usp26 gene in mouse testis and brain

Deubiquitinating enzymes （DUBs） play an important role in ubiquitin-dependent processes as negative regulators of protein ubiquitination. Ubiquitin-specific protease 26 （USP26） is a member of this family. The expression of Usp26 in mammalian testis and in other tissues has yet to be fully elucidated. To study the expression of Usp26 mRNA and protein in various murine tissues, reverse transcription （RT）-PCR and immunohistochemistry analyses were carried out. The RT-PCR analysis showed that the Usp26 transcript was expressed in all of the tested tissues. USP26 protein localization was examined by immunohistochemistry, and it was shown that USP26 was not detectable at 20 days postpartum, with the expression restricted to the cytoplasm of condensing spermatids （steps 9-16）, Leydig cells and nerve fibers in the brain. In addition, the USP26 protein was detected at moderate levels in myocardial ceils, the corpus of epidydimis, epithelium of the renal tubules and the seminal gland of postnatal day 35 mice. Its spatial and temporal expression pattern suggests that Usp26 may play an important role in development or function of the testis and brain. Further research into these possibilities is in progress.

Deubiquitinating enzyme regulation of the p53 pathway: A lesson from Otub1

Deubiquitination has emerged as an important mechanism of p53 regulation. A number of deubiquitinating enzymes(DUBs) from the ubiquitin-specific protease family have been shown to regulate the p53-MDM2-MDMX networks. We recently reported that Otub1, a DUB from the OTU-domain containing protease family, is a novel p53 regulator. Interestingly, Otub1 abrogates p53 ubiquitination and stabilizes and activates p53 in cells independently of its deubiquitinating enzyme activity. Instead, it does so by inhibiting the MDM2 cognate ubiquitin-conjugating enzyme(E2) UbcH5. Otub1 also regulates other biological signaling through this non-canonical mechanism, suppression of E2, including the inhibition of DNA-damage-induced chromatin ubiquitination. Thus, Otub1 evolves as a unique DUB that mainly suppresses E2 to regulate substrates. Here we review the current progress made towards the understanding of the complex regulation of the p53 tumor suppressor pathway by DUBs, the biological function of Otub1 including its positive regulation of p53, and the mechanistic insights into how Otub1 suppresses E2.

The Role of CYLD in Blocking Oncogenic Cell Signaling in Melanoma

Dysregulation of components of the ubiqutin system has been linked to many diseases including melanoma. This is vital since the post-translational modification of different proteins via direct ubiquitin attachment is an important process for various cellular processes. CYLD is a tumor suppressor gene and deubiquitinating enzyme, which can remove polyubiquitin chains from their specific substrate and interfere with different signaling pathways. CYLD is frequently downregulated or even lost in melanoma cell lines or tissues compared to melanocytes. Down-regulation of CYLD leads to sustained oncogenic signaling that promotes melanoma progression and metastasis. In this review, we summarize the recent insights into the mechanisms which are responsible for the down-regulation of CYLD levels in melanoma and the signaling interactions of the CYLD gene product in melanoma. We argue that these recent insights into CYLD function invite the development of novel molecular strategies for melanoma prevention and treatment.

METTL5 stabilizes c-Myc by facilitating USP5 translation to reprogram glucose metabolism and promote hepatocellular carcinoma progression

Background:Hepatocellular carcinoma(HCC)is one of the most prevalent cancers in the world,with a high likelihood of metastasis and a dismal prognosis.The reprogramming of glucosemetabolism is critical in the development ofHCC.TheWarburg effect has recently been confirmed to occur in a variety of cancers,including HCC.However,little is known about the molecular biological mechanisms underlying the Warburg effect in HCC cells.In this study,we sought to better understand how methyltransferase 5,N6-adenosine(METTL5)controls the development of HCC and theWarburg effect.Methods:In the current study,quantitative real-time polymerase chain reaction and Western blotting were used to detect the expression of METTL5 in HCC tissues and cell lines.Several different cell models and animal models were established to determine the role of METTL5 in glucose metabolism reprogramming and the underlying molecularmechanism of HCC.Glutathione-S-transferase pulldown,coimmunoprecipitation,RNA sequencing,non-targeted metabolomics,polysome profiling,and luciferase reporter assays were performed to investigate the molecular mechanisms of METTL5 in HCC cells.Results:We discovered that METTL5 drove glucose metabolic reprogramming to promote the proliferation and metastasis of HCC.Mechanistically,upregulation of METTL5 promoted c-Myc stability and thus activated its downstream glycolytic genes lactate dehydrogenase A(LDHA),enolase 1(ENO1),triosephosphate isomerase 1(TPI1),solute carrier family 2 member 1(SLC2A1),and pyruvate kinase M2(PKM2).The c-Box and ubiquitin binding domain(UBA)regions of ubiquitin specific peptidase 5(USP5)binded to c-Myc protein and inhibited K48-linked polyubiquitination of c-Myc.Further study revealed that METTL5 controled the USP5 translation process,which in turn regulated the ubiquitination of c-Myc.Furthermore,we identified cAMP responsive element binding protein 1(CREB1)/P300 as a critical transcriptional regulator ofMETTL5 that promoted the transcription of METTL5 in HCC.In patient-derived tumor xenograft(PDX)models,adenovirus-mediated knockout of METTL5 had a good antitumor effect and prolonged the survival of PDX-bearing mice.Conclusions:These findings point to a novel mechanism by which CREB1/P300-METTL5-USP5-c-Myc controls abnormal glucose metabolism and promotes tumor growth,suggesting that METTL5 is a potential therapeutic target and prognostic biomarker for HCC.

Semi-synthesis of biotin-bearing activity-based ubiquitin probes through sequential enzymatic ligation,N-S acyl transfer and aminolysis reaction

Activity-based Ubiquitin probes(Ub-ABPs)carrying a reporter group have emerged as effective tools for the investigation of deubiquitinating enzymes(DUBs),such as studying the molecular mechanism of DUBs,profiling new DUBs.But so far,the synthesis of commonly used biotin-bearing Ub-ABPs is a technical challenge.Here,we report a one-pot semi-synthetic strategy for the acquiring of Ub-ABPs carrying a biotin tag through sequential enzymatic ligation,N-S acyl transfer and aminolysis reaction without any purification steps.These probes enable to capture the different family of DUBs for enrichment and immunoblotting using the attached biotin tag.

Mechanism of inhibiting type I interferon induction by hepatitis B virus X protein

Hepatitis B virus(HBV)is regarded as a stealth virus,invading and replicating efficiently in human liver undetected by host innate antiviral immunity.Here,we show that type I interferon(IFN)induction but not its downstream signaling is blocked by HBV replication in HepG2.2.15 cells.This effect may be partially due to HBV X protein(HBx),which impairs IFNβpromoter activation by both Sendai virus(SeV)and components implicated in signaling by viral sensors.As a deubiquitinating enzyme(DUB),HBx cleaves Lys63-linked polyubiquitin chains from many proteins except TANK-binding kinase 1(TBK1).It binds and deconjugates retinoic acid-inducible gene I(RIG I)and TNF receptor-associated factor 3(TRAF3),causing their dissociation from the downstream adaptor CARDIF or TBK1 kinase.In addition to RIG I and TRAF3,HBx also interacts with CARDIF,TRIF,NEMO,TBK1,inhibitor of kappa light polypeptide gene enhancer in B-cells,kinase epsilon(IKKi)and interferon regulatory factor 3(IRF3).Our data indicate that multiple points of signaling pathways can be targeted by HBx to negatively regulate production of type I IFN.

OTUD5 promotes innate antiviral and antitumor immunity through deubiquitinating and stabilizing STING

Stimulator of interferon genes(STING)is an adaptor protein that is critical for effective innate antiviral and antitumor immunity.The activity of STING is heavily regulated by protein ubiquitination,which is fine-tuned by both E3 ubiquitin ligases and deubiquitinases.Here,we report that the deubiquitinase OTUD5 interacts with STING,cleaves its K48-linked polyubiquitin chains,and promotes its stability.Consistently,knockout of OTUD5 resulted in faster turnover of STING and subsequently impaired type I IFN signaling following cytosolic DNA stimulation.More importantly,Lyz2-Cre Otud5^(fl/Y) mice and CD11-Cre Otud5^(fl/Y) mice showed more susceptibility to herpes simplex virus type 1(HSV-1)infection and faster development of melanomas than their corresponding control littermates,indicating that OTUD5 is indispensable for STING-mediated antiviral and antitumor immunity.Our data suggest that OTUD5 is a novel checkpoint in the cGAS-STING cytosolic DNA sensing pathway.

Biochemical properties of K_(11,48)-branched ubiquitin chains

As one of the most widely existing post-translational modification models, ubiquitination regulates diverse cellular activities. In eukaryotes, K-branched ubiquitin chains play key roles in cell cycle and protein quality control. However, the structural and biochemical properties of K-branched ubiquitin chains have not been well examined. Here we employed the synthetic linkage-and length-defined K-branched ubiquitin chains to examine their binding and hydrolysis properties in vitro. Quantitatively affinity determination of ubiquitin chains to the proteasome ubiquitin receptor S5 a indicated that the S5 a exhibited preference binding to K-branched chains over K-linked chains, but not K-conjugated chains. In addition, deubiquitination experiments were carried out and the results showed that K-branched chains were preferably hydrolyzed by proteasome-associated deubiquitinase Rpnll than homotypic Kor K-linked chains.

Deubiquitinase ubiquitin-specific protease 3 (USP3) inhibits HIV-1 replication via promoting APOBEC3G (A3G) expression in both enzyme activity-dependent and -independent manners

Background: Ubiquitination plays an essential role in many biological processes, including viral infection, and can be reversed by deubiquitinating enzymes (DUBs). Although some studies discovered that DUBs inhibit or enhance viral infection by various mechanisms, there is lack of information on the role of DUBs in virus regulation, which needs to be further investigated.Methods: Immunoblotting, real-time polymerase chain reaction,in vivo/in vitro deubiquitination, protein immunoprecipitation, immunofluorescence, and co-localization biological techniques were employed to examine the effect of ubiquitin-specific protease 3 (USP3) on APOBEC3G (A3G) stability and human immunodeficiency virus (HIV) replication. To analyse the relationship between USP3 and HIV disease progression, we recruited 20 HIV-infected patients to detect the levels of USP3 and A3G in peripheral blood and analysed their correlation with CD4^(+) T-cell counts. Correlation was estimated by Pearson correlation coefficients (for parametric data).Results: The results demonstrated that USP3 specifically inhibits HIV-1 replication in an A3G-dependent manner. Further investigation found that USP3 stabilized 90% to 95% of A3G expression by deubiquitinating Vif-mediated polyubiquitination and blocking its degradation in an enzyme-dependent manner. It also enhances the A3G messenger RNA (mRNA) level by binding to A3G mRNA and stabilizing it in an enzyme-independent manner. Moreover, USP3 expression was positively correlated with A3G expression (r= 0.5110) and CD4^(+) T-cell counts (r= 0.5083) in HIV-1-infected patients.Conclusions: USP3 restricts HIV-1 viral infections by increasing the expression of the antiviral factor A3G. Therefore, USP3 may be an important target for drug development and serve as a novel therapeutic strategy against viral infections.

Conservation and divergence of the histone H2B monoubiquitination pathway from yeast to humans and plants

Histone ubiquitination plays a critical role in the regulation of transcription,and histone H2B monoubiquitination(H2Bub1)is mainly associated with transcriptional activation.Recent studies in yeast,humans,and Arabidopsis have revealed the conservation of chromatin modification via H2Bub1 during evolution.Rad6-Bre1 and their homologs are responsible for H2B monoubiquitination in diverse eukaryotic organisms,and the PAF complex is required for H2Bub1 to proceed.H2Bub1 is involved in many developmental processes in yeast,humans,and Arabidopsis,and it activates gene transcription by regulating the H3K4 methylation state.Notably,the level of H3K4 methylation is entirely dependent on H2Bub1 in yeast and humans,whereas the H3K4 methylation level of only a small number of genes in Arabidopsis is dependent on H2Bub1.In this review,we summarize the enzymes involved in H2B monoubiquitination and deubiquitination,and discuss the biologic functions of H2Bub1 in different organisms.In addition,we focus on recent advances in our understanding of the molecular mechanisms that enable H2Bub1 to perform its function.

USP19 suppresses inflammation and promotes M2-like macrophage polarization by manipulating NLRP3 function via autophagy

Macrophage polarization to proinflammatory M1-like or anti-inflammatory M2-like cells is critical to mount a host defense or repair tissue.The exact molecular mechanisms controlling this process are still elusive.Here,we report that ubiquitin-specific protease 19(USP19)acts as an anti-inflammatory switch that inhibits inflammatory responses and promotes M2-like macrophage polarization.USP19 inhibited NLRP3 inflammasome activation by increasing autophagy flux and decreasing the generation of mitochondrial reactive oxygen species.In addition,USP19 inhibited the proteasomal degradation of inflammasome-independent NLRP3 by cleaving its polyubiquitin chains.USP19-stabilized NLRP3 promoted M2-like macrophage polarization by direct association with interferon regulatory factor 4,thereby preventing its p62-mediated selective autophagic degradation.Consistent with these observations,compared to wild-type mice,Usp19−/−mice had decreased M2-like macrophage polarization and increased interleukin-1βsecretion,in response to alum and chitin injections.Thus,we have uncovered an unexpected mechanism by which USP19 switches the proinflammatory function of NLRP3 into an anti-inflammatory function,and suggest that USP19 is a potential therapeutic target for inflammatory interventions.