Small molecule deoxynyboquinone triggers alkylation and ubiquitination of Keap1 at Cys489 on Kelch domain for Nrf2 activation and inflammatory therapy

Activation of nuclear factor erythroid 2-related factor 2(Nrf2)by Kelch-like ECH-associated protein 1(Keap1)alkylation plays a central role in anti-inflammatory therapy.However,activators of Nrf2 through alkylation of Keap1-Kelch domain have not been identified.Deoxynyboquinone(DNQ)is a natural small molecule discovered from marine actinomycetes.The current study was designed to investigate the anti-inflammatory effects and molecular mechanisms of DNQ via alkylation of Keap1.DNQ exhibited significant anti-inflammatory properties both in vitro and in vivo.The pharmacophore responsible for the anti-inflammatory properties of DNQ was determined to be theα,β-unsaturated amides moieties by a chemical reaction between DNQ and N-acetylcysteine.DNQ exerted anti-inflammatory effects through activation of Nrf2/ARE pathway.Keap1 was demonstrated to be the direct target of DNQ and bound with DNQ through conjugate addition reaction involving alkylation.The specific alkylation site of DNQ on Keap1 for Nrf2 activation was elucidated with a synthesized probe in conjunction with liquid chromatography-tandem mass spectrometry.DNQ triggered the ubiquitination and subsequent degradation of Keap1 by alkylation of the cysteine residue 489(Cys489)on Keap1-Kelch domain,ultimately enabling the activation of Nrf2.Our findings revealed that DNQ exhibited potent anti-inflammatory capacity throughα,β-unsaturated amides moieties active group which specifically activated Nrf2 signal pathway via alkylation/ubiquitination of Keap1-Kelch domain,suggesting the potential values of targeting Cys489 on Keap1-Kelch domain by DNQ-like small molecules in inflammatory therapies.

Hydralazine represses Fpn ubiquitination to rescue injured neurons via competitive binding to UBA52

A major impedance to neuronal regeneration after peripheral nerve injury (PNI) is the activation of various programmed cell death mechanisms in the dorsal root ganglion. Ferroptosis is a form of programmed cell death distinguished by imbalance in iron and thiol metabolism, leading to lethal lipid peroxidation. However, the molecular mechanisms of ferroptosis in the context of PNI and nerve regeneration remain unclear. Ferroportin (Fpn), the only known mammalian nonheme iron export protein, plays a pivotal part in inhibiting ferroptosis by maintaining intracellular iron homeostasis. Here, we explored in vitro and in vivo the involvement of Fpn in neuronal ferroptosis. We first delineated that reactive oxygen species at the injury site induces neuronal ferroptosis by increasing intracellular iron via accelerated UBA52-driven ubiquitination and degradation of Fpn, and stimulation of lipid peroxidation. Early administration of the potent arterial vasodilator, hydralazine (HYD), decreases the ubiquitination of Fpn after PNI by binding to UBA52, leading to suppression of neuronal cell death and significant acceleration of axon regeneration and motor function recovery. HYD targeting of ferroptosis is a promising strategy for clinical management of PNI.

DI-3-n-butylphthalide exerts neuroprotective effects by modulating hypoxia-inducible factor 1-alpha ubiquitination to attenuate oxidative stress-induced apoptosis

DI-3-n-butylphthalide is used to treat mild and moderate acute ischemic stroke.However,the precise underlying mechanism requires further investigation.In this study,we investigated the molecular mechanism of DI-3-n-butylphthalide action by various means.We used hydrogen peroxide to induce injury to PC12cells and RAW264.7 cells to mimic neuronal oxidative stress injury in stroke in vitro and examined the effects of DI-3-n-butylphthalide.We found that DI-3-nbutylphthalide pretreatment markedly inhibited the reduction in viability and reactive oxygen species production in PC12 cells caused by hydrogen peroxide and inhibited cell apoptosis.Furthermore,DI-3-n-butylphthalide pretreatment inhibited the expression of the pro-apoptotic genes Bax and Bnip3.DI-3-nbutylphthalide also promoted ubiquitination and degradation of hypoxia inducible factor 1α,the key transcription factor that regulates Bax and Bnip3 genes.These findings suggest that DI-3-n-butylphthalide exhibits a neuroprotective effect on stroke by promoting hypoxia inducible factor-1α ubiquitination and degradation and inhibiting cell apoptosis.

Calcyclin-binding protein contributes to cholangiocarcinoma progression by inhibiting ubiquitination of MCM2

Background:Cholangiocarcinoma(CCA)represents the epithelial cell cancer with high aggressiveness whose five-year survival rate is poor with standard treatment.Calcyclin-binding protein(CACYBP)shows aberrant expression within several malignant tumors,but the role of CACYBP in CCA remains unknown.Methods:Immunohistochemical(IHC)analysis was used to identify CACYBP overexpression in clinical samples of CCA patients.Moreover,its correlation with clinical outcome was revealed.Furthermore,CACYBP’s effect on CCA cell growth and invasion was investigated in vitro and in vivo using loss-of-function experiments.Results:CACYBP showed up-regulation in CCA,which predicts the dismal prognostic outcome.CACYBP had an important effect on in-vitro and in-vivo cancer cell proliferation and migration.Additionally,knockdown of CACYBP weakened protein stability by promoting ubiquitination of MCM2.Accordingly,MCM2 up-regulation partly reversed CACYBP deficiency’s inhibition against cancer cell viability and invasion.Thus,MCM2 might drive CCA development by Wnt/β-catenin pathway.Conclusions:CACYBP exerted a tumor-promoting role in CCA by suppressing ubiquitination of MCM2 and activating Wnt/β-catenin pathway,hence revealing that it may be the possible therapeutic target for CCA treatment.

Fanconi Anemia and Ubiquitination

Fanconi anemia （FA） is a rare recessive hereditary disease characterized clinically by congenital defects, progressive bone-marrow failure, and cancer predisposition. Cells from FA patients exhibit hypersensitivity to DNA cross-linking agents, such as mitomycin C （MMC）. To date, at least 12 FA genes have been found deleted or mutated in FA cells, and 10 FA gene products form a core complex involved in FA/BRCA2 DNA repair pathway-FA pathway. The ubiquitin E3 ligase FANCL, an important factor of FA core complex, co-functions with a new ubiquitin conjugating enzyme UBE2T to catalyze the monoubiquitination of FANCD2. FANCD2-Ub binds BRCA2 to form a new complex located in chromatin foci and then take part in DNA repair process. The deubiquitylating enzyme USP1 removes the mono-ubiquitin from FANCD2-Ub following completion of the repair process, then restores the blocked cell cycle to normal order by shutting off the FA pathway. In a word, the FANCD2 activity adjusted exquisitely by ubiquitination and/or deubiquitination in vivo may co-regulate the FA pathway involving in variant DNA repair pathway.

Feedback regulation of cholesterol synthesis： sterol-accelerated ubiquitination and degradation of HMG CoA reductase

3-Hydroxy-3-methylglutaryl coenzyme A （HMG CoA） reductase produces mevalonate, an important intermediate in the synthesis of cholesterol and essential nonsterol isoprenoids. The reductase is subject to an exorbitant amount of feedback control through multiple mechanisms that are mediated by sterol and nonsterol end-products of mevalonate metabolism. Here, I will discuss recent advances that shed light on one mechanism for control of reductase, which involves rapid degradation of the enzyme. Accumulation of certain sterols triggers binding of reductase to endoplasmic reticulum （ER） membrane proteins called Insig-1 and Insig-2. Reductase-Insig binding results in recruitment of a membrane-associated ubiquitin ligase called gp78, which initiates ubiquitination of reductase. This ubiquitination is an obligatory reaction for recognition and degradation of reductase from ER membranes by cytosolic 26S proteasomes. Thus, sterol-accelerated degradation of reductase represents an example of how a general cellular process （ER-associated degradation） is used to control an important metabolic pathway （cholesterol synthesis）.

Ubiquitination-mediated protein degradation and modification:an emerging theme in plant-microbe interactions

Post-translational modification is central to protein stability and to the modulation of protein activity. Various types of protein modification, such as phosphorylation, methylation, acetylation, myristoylation, glycosylation, and ubiquitination, have been reported. Among them, ubiquitination distinguishes itself from others in that most of the ubiquitinated proteins are targeted to the 26S proteasome for degradation. The ubiquitin/26S proteasome system constitutes the major protein degradation pathway in the cell. In recent years, the importance of the ubiquitination machinery in the control of numerous eukaryotic cellular functions has been increasingly appreciated. Increasing number of E3 ubiquitin ligases and their substrates, including a variety of essential cellular regulators have been identified. Studies in the past several years have revealed that the ubiquitination system is important for a broad range of plant developmental processes and responses to abiotic and biotic stresses. This review discusses recent advances in the functional analysis of ubiquitination-associated proteins from plants and pathogens that play important roles in plant-microbe interactions.

Wwp2 mediates Oct4 ubiquitination and its own auto-ubiquitination in a dosage-dependent manner

Transcription factor Oct4 plays critical roles in maintaining pluripotency and controlling lineage commitment of embryonic stem cells （ESCs）. Our previous study indicates that Wwp2, a mouse HECT-type E3 ubiquitin ligase, ubiquitinates Oct4 and promotes its degradation in a heterologous system. However, roles of Wwp2 in regulating en- dogenous Oct4 protein levels as well as molecular characteristics of the function of Wwp2 have not been determined. Here, we report that Wwp2 plays an important role in Oct4 ubiquitination and degradation during differentiation of embryonal carcinoma cells （ECCs）, although it does not appear to affect Oct4 protein levels in the undifferentiated ECCs and ESCs. Importantly, inhibition of Wwp2 expression by specific RNA interference elevates the Oct4 protein level, leading to attenuation in retinoid acid-induced activation of differentiation-related marker genes. Mechanisti- cally, Wwp2 catalyzes Oct4 poly-ubiquitination via the lysine 63 linkage in a dosage-dependent manner. Interest- ingly, Wwp2 also regulates its own ligase activity in a similar manner. Moreover, auto-ubiquitination of Wwp2 occurs through an intra-molecular mechanism. Taken together, these results demonstrate a crucial role of Wwp2 in con- trolling endogenous Oct4 protein levels during differentiation processes of ECCs and suggest an interesting dosage- dependent mechanism for regulating the catalytic activity of the E3 ubiquitin ligase, Wwp2.

NLRC3 alleviates hypoxia/reoxygenation induced inflammation in RAW264.7 cells by inhibiting K63-linked ubiquitination of TRAF6

Background:NOD-like receptor family CARD domain containing 3(NLRC3)plays an important role in both innate and adaptive immunity.This study was to explore the function and related mechanisms of NLRC3 in a hypoxia/reoxygenation(H/R)-induced inflammatory response in RAW264.7 cells.Methods:Liver ischemia-reperfusion(I/R)model in mice and H/R model in RAW264.7 cells were constructed.Western blotting was used to determine the protein expression level of NLRC3 in liver tissue and NLRC3,TRAF6,p–p65,p65,IκB–α,and the K63-linked ubiquitination level of TRAF6 in cells.The immunofluorescence assay was performed to evaluate the nuclear level of the NF–κB(p65).ELISA was conducted to measure the content of IL–1βin serum and cell supernatant.The interaction between NLRC3 and TRAF6 in cells was analyzed by the Co-IP assay.Results:The NLRC3 protein level in liver tissue was decreased with the prolongation of reperfusion time(P<0.05).The expression of NLRC3 and IκB–αprotein in RAW264.7 was decreased gradually,while the expression of p–p65 and TRAF6 proteins and K63-linked ubiquitination of TRAF6 were increased gradually with the prolongation of reoxgenation time(P<0.05).The Co-IP assay revealed that NLRC3 and TRAF6 can bind to each other directly.However,NLRC3 had no effect on the expression of TRAF6 protein.The ubiquitination test results showed that the K63-linked ubiquitination level of TRAF6 in H/R+Lv–NLRC3 group was significantly lower than that in the H/R+negative control(NC)group(P<0.05).Moreover,the activation of NF–κB in H/R+Lv–NLRC3 group was inhibited compared with that in the H/R+NC group,and the level of the inflammatory factor IL–1βin the cell culture supernatant was also decreased accordingly(P<0.05).Conclusions:NLRC3 might alleviate H/R-induced inflammation in RAW264.7 cells by inhibiting K63-linked ubiquitination of TRAF6.

NUMB maintains bone mass by promoting degradation of PTEN and GLI1 via ubiquitination in osteoblasts

The adaptor protein NUMB is involved in asymmetric division and cell fate determination and recognized as an antagonist of Notch.Previous studies have proved that Notch activation in osteoblasts contributes to a high bone mass. In this study, however, an osteopenic phenotype was found in 9-week-old mice using osteoblastic specific Col1a1–2.3-Cre to ablate both Numb and its homologue Numbl. The trabecular bone mass decreased dramatically while the cortical bone mass was unaffected. Here, the Notch signal was not activated,while the tensin homologue deleted on human chromosome 10(PTEN), which dephosphorylates phosphatidylinositide 3-kinases, was elevated, attenuating protein kinase B(Akt). The ubiquitination assay revealed that NUMB may physiologically promote PTEN ubiquitination in the presence of neural precursor cell-expressed developmentally downregulated protein 4–1. In addition, the deficiency of Numb/Numbl also activated the Hedgehog pathway through GLI1. This process was found to improve the ratio of the receptor activator of nuclear factor-k B ligand to osteoprotegerin, which enhanced the differentiation of osteoclasts and bone resorption. In conclusion, this study provides an insight into new functons of NUMB and NUMBL on bone homeostasis.

API2-MALT1 oncoprotein promotes lymphomagenesis via unique program of substrate ubiquitination and proteolysis

Lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma) is the most common extranodal B cell tumor and accounts for 8% of non-Hodgkin&#x02019;s lymphomas. Gastric MALT lymphoma is the best-studied example and is a prototypical neoplasm that occurs in the setting of chronic inflammation brought on by persistent infection or autoimmune disease. Cytogenetic abnormalities are commonly acquired during the course of disease and the most common is chromosomal translocation t(11;18)(q21;q21), which creates the API2-MALT1 fusion oncoprotein. t(11;18)-positive lymphomas can be clinically aggressive and have a higher rate of dissemination than t(11;18)-negative tumors. Many cancers, including MALT lymphomas, characteristically exhibit deregulated over-activation of cellular survival pathways, such as the nuclear factor-&#x003ba;B (NF-&#x003ba;B) pathway. Molecular characterization of API2-MALT1 has revealed it to be a potent activator of NF-&#x003ba;B, which is required for API2-MALT1-induced cellular transformation, however the mechanisms by which API2-MALT1 exerts these effects are only recently becoming apparent. The API2 moiety of the fusion binds tumor necrosis factor (TNF) receptor associated factor (TRAF) 2 and receptor interacting protein 1 (RIP1), two proteins essential for TNF receptor-induced NF-&#x003ba;B activation. By effectively mimicking ligand-bound TNF receptor, API2-MALT1 promotes TRAF2-dependent ubiquitination of RIP1, which then acts as a scaffold for nucleating and activating the canonical NF-&#x003ba;B machinery. Activation occurs, in part, through MALT1 moiety-dependent recruitment of TRAF6, which can directly modify NF-&#x003ba;B essential modulator, the principal downstream regulator of NF-&#x003ba;B. While the intrinsic MALT1 protease catalytic activity is dispensable for this canonical NF-&#x003ba;B signaling, it is critical for non-canonical NF-&#x003ba;B activation. In this regard, API2-MALT1 recognizes NF-&#x003ba;B inducing kinase (NIK), the essential upstream regulator of non-canonical NF-&#x003ba;B, and cleaves it to generate a stable, constitutively active fragment. Thus, API2-MALT1 harnesses multiple unique pathways to achieve deregulated NF-&#x003ba;B activation. Emerging data from our group and others have also detailed additional gain-of-function activities of API2-MALT1 that extend beyond NF-&#x003ba;B activation. Specifically, API2-MALT1 recruits and subverts multiple other signaling factors, including LIM domain and actin-binding protein 1 (LIMA1) and Smac/DIABLO. Like NIK, LIMA1 represents a unique substrate for API2-MALT1 protease activity, but unlike NIK, its cleavage sets in motion a major NF-&#x003ba;B-independent pathway for promoting oncogenesis. In this review, we highlight the most recent results characterizing these unique and diverse gain-of-function activities of API2-MALT1 and how they contribute to lymphomagenesis.

BTB-BACK-TAZ domain protein MdBT2-mediated MdMYB73 ubiquitination negatively regulates malate accumulation and vacuolar acidification in apple

As an important primary metabolite,malate plays a key role in regulating osmotic pressure,pH homeostasis,stress tolerance,and fruit quality of apple.The R2R3-MYB transcription factor(TF)MdMYB73 was identified as a protein that plays a critical role in determining malate accumulation and vacuolar acidification by directly regulating the transcription of aluminum-activated malate transporter 9(MdALMT9),vacuolar ATPase subunit A(MdVHA-A),and vacuolar pyrophosphatase 1(MdVHP1)in apple.In addition,the bHLH TF MdCIbHLH1 interacts with MdMYB73 and enhances the transcriptional activity of MdMYB73.Our previous studies demonstrated that the BTB-BACK-TAZ domain protein MdBT2 can degrade MdCIbHLH1 to influence malate accumulation and vacuolar acidification.However,the potential upstream regulators of MdMYB73 are currently unknown.In this study,we found that MdBT2 directly interacts with and degrades MdMYB73 through the ubiquitin/26S proteasome pathway to regulate malate accumulation and vacuolar acidification.A series of functional assays with apple calli and fruit showed that MdBT2 controls malate accumulation and vacuolar acidification in an MdMYB73-dependent manner.Overall,our findings shed light on the mechanism by which the BTB-BACK-TAZ domain protein MdBT2 regulates malate accumulation and vacuolar acidification by targeting MdMYB73 and MdCIbHLH1 for ubiquitination in apple.This information may help guide traditional breeding programs and fruit tree molecular breeding,and lead to improvements in fruit quality and stress tolerance.

FBW7-mediated ubiquitination and degradation of KLF5

Krüppel-like factor(KLF) family proteins are transcription factors that regulate numerous cellular functions, such as cell proliferation, differentiation, and cell death. Posttranslational modification of KLF proteins is important for their transcriptional activities and biological functions. One KLF family member with important roles in cell proliferation and tumorigenesis is KLF5. The function of KLF5 is tightly controlled by post-translational modifications, including SUMOylation, phosphorylation, and ubiquitination. Recent studies from our lab and others' have demonstrated that the tumor suppressor FBW7 is an essential E3 ubiquitin ligase that targets KLF5 for ubiquitination and degradation. KLF5 contains functional Cdc4 phospho-degrons(CPDs), which are required for its interaction with FBW7. Mutation of CPDs in KLF5 blocks the ubiquitination and degradation of KLF5 by FBW7. The protein kinase Glycogen synthase kinase 3β is involved in the phosphorylation of KLF5 CPDs. In both cancer cell lines and mousemodels, it has been shown that FBW7 regulates the expression of KLF5 target genes through the modulation of KLF5 stability. In this review, we summarize the current progress on delineating FBW7-mediated KLF5 ubiquitination and degradation.

SERPINE2 promotes liver cancer metastasis by inhibiting c-Cbl-mediated EGFR ubiquitination and degradation

Background:Liver cancer is a malignancy with high morbidity and mortality rates.Serpin family E member 2(SERPINE2)has been reported to play a key role in the metastasis of many tumors.In this study,we aimed to investigate the potential mechanism of SERPINE2 in liver cancer metastasis.Methods:The Cancer Genome Atlas database(TCGA),including DNA methy-lation and transcriptome sequencing data,was utilized to identify the crucial oncogene associated with DNA methylation and cancer progression in liver can-cer.Data from the TCGA and RNA sequencing for 94 pairs of liver cancer tissues were used to explore the correlation between SERPINE2 expression and clin-ical parameters of patients.DNA methylation sequencing was used to detect the DNA methylation levels in liver cancer tissues and cells.RNA sequencing,cytokine assays,immunoprecipitation(IP)and mass spectrometry(MS)assays,protein stability assays,and ubiquitination assays were performed to explore the regulatory mechanism of SERPINE2 in liver cancer metastasis.Patient-derived xenografts and tumor organoid models were established to determine the role of SERPINE2 in the treatment of liver cancer using sorafenib.Results:Based on the public database screening,SERPINE2 was identified as a tumor promoter regulated by DNA methylation.SERPINE2 expression was significantly higher in liver cancer tissues and was associated with the dismal prognosis in patients with liver cancer.SERPINE2 promoted liver cancer metas-tasis by enhancing cell pseudopodia formation,cell adhesion,cancer-associated fibroblast activation,extracellular matrix remodeling,and angiogenesis.IP/MS assays confirmed that SERPINE2 activated epidermal growth factor receptor(EGFR)and its downstream signaling pathways by interacting with EGFR.Mechanistically,SERPINE2 inhibited EGFR ubiquitination and maintained its protein stability by competing with the E3 ubiquitin ligase,c-Cbl.Additionally,EGFR was activated in liver cancer cells after sorafenib treatment,and SER-PINE2 knockdown-induced EGFR downregulation significantly enhanced the therapeutic efficacy of sorafenib against liver cancer.Furthermore,we found that SERPINE2 knockdown also had a sensitizing effect on lenvatinib treatment.Conclusions:SERPINE2 promoted liver cancer metastasis by preventing EGFR degradation via c-Cbl-mediated ubiquitination,suggesting that inhibition of the SERPINE2-EGFR axis may be a potential target for liver cancer treatment.

RNF187 governs the maintenance of mouse GC-2 cell development by facilitating histone H3 ubiquitination at K57/80

RING finger 187(RNF187),a ubiquitin-ligating(E3)enzyme,plays a crucial role in the proliferation of cancer cells.However,it remains unclear whether RNF187 exhibits comparable functionality in the development of germline cells.To investigate thepotential involvement of RNF187 in germ cell development,we conducted interference and overexpression assays using GC-2 cells,a mouse spermatocyte-derived cell line.Our findings reveal that the interaction between RNF187 and histone H3 increases theviability,proliferation,and migratory capacity of GC-2 cells.Moreover,we provide evidence demonstrating that RNF187 interactswith H3 and mediates the ubiquitination of H3 at lysine 57(K57)or lysine 80(K80),directly or indirectly resulting in increasedcellular transcription.This is a study to report the role of RNF187 in maintaining the development of GC-2 cells by mediatinghistone H3 ubiquitination,thus highlighting the involvement of the K57 and K80 residues of H3 in the epistatic regulation of genetranscription.These discoveries provide a new theoretical foundation for further comprehensive investigations into the functionof RNF187 in the reproductive system.

TBBPA rather than its main derivatives enhanced growth of endometrial cancer via p53 ubiquitination

Tetrabromobisphenol A(TBBPA)and its derivatives widely exist in various environments and biota.Although the available data indicate that TBBPA exposure is highly associated with the increased incidence of endometrial cancer(EC),the effects of TBBPA and its main derivatives on EC proliferation and the involved crucial mechanism remain unclear.The present study aimed to investigate the effects of TBBPA and its derivatives under environmental concentrations on the proliferation of EC,and the crucial mechanism on the progression of EC caused by bromine fame retardants exposure.In this research,TBBPA and two of the most common TBBPA derivatives including TBBPA bis(2-hydroxyethyl ether)(TBBPABHEE)and TBBPA bis(dibromopropyl ether)(TBBPA-BDBPE)were screened for their capacities in induced EC proliferation and explored the related mechanism by in vitro cell culture model and in vivo mice model.Under environmental concentrations,TBBPA promoted the proliferation of EC,the main derivatives of TBBPA(TBBPA-BHEE and TBBPA-BDBPE)did not present the similar facilitation effects.The ubiquitination degradation of p53 was crucial in TBBPA induced EC proliferation,which resulted in the increase of downstream cell cycle and decrease of apoptosis.The further molecular docking result suggested the high affinity between TBBPA and ubiquitinated proteasome.This finding revealed the effects of TBBPA and its derivatives on EC proliferation,thus providing novel insights into the underlying mechanisms of TBBPA-caused EC.

RNF6 promotes chronic myelogenous leukemia cell proliferation and migration by stabilizing vimentin via multiple atypical ubiquitinations

Chronic myelogenous leukemia(CML)is a malignancy from bone marrow myeloid stem cells mainly driven by the fusion gene BCR-ABL.In addition to BCR-ABL,other genes including RNF6 are also dysregulated in CML cells.1 RNF6,a ubiquitin ligase of the RING family,promotes various cancer cell proliferation,chemoresistance,and tumor growth in vivo by targeting various proteins for ubiquitination and degradation,including SHP1,TLE3,FOXA1,and MAD1.^(2) However,its specific mechanism in CML is not known.

Cand2 inhibits CRL-mediated ubiquitination and suppresses autophagy to facilitate pathogenicity of phytopathogenic fungi

The ubiquitin–proteasome system and the autophagy system are the two primary mechanisms used by eukaryotes to maintain protein homeostasis,and both are closely related to the pathogenicity of the rice blast fungus.In this research,we identified MoCand2 as an inhibitor of ubiquitination in Magnaporthe oryzae.Through this role,MoCand2 participates in the regulation of autophagy and pathogenicity.Spe-cifically,we found that deletion of MoCand2 increased the ubiquitination level in M.oryzae,whereas overexpression of MoCand2 inhibited the accumulation of ubiquitinated proteins.Interaction analyses showed that MoCand2 is a subunit of Cullin-RING ligases(CRLs).It suppresses ubiquitination by blocking the assembly of CRLs and downregulating the expression of key CRL subunits.Further research indi-cated that MoCand2 regulates autophagy through ubiquitination.MoCand2 knockout led to over-ubiquitination and over-degradation of MoTor,and we confirmed that MoTor content was negatively correlated with autophagy level.In addition,MoCand2 knockout accelerated the K63 ubiquitination of MoAtg6 and strengthened the assembly and activity of the phosphatidylinositol-3-kinase class 3 complex,thus enhancing autophagy.Abnormal ubiquitination and autophagy in DMocand2 resulted in defects in growth,conidiation,stress resistance,and pathogenicity.Finally,sequence alignment and functional an-alyses in other phytopathogenic fungi confirmed the high conservation of fungal Cand2s.Our research thus reveals a novel mechanism by which ubiquitination regulates autophagy and pathogenicity in phyto-pathogenic fungi.

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.

Cytosolic TGM2 promotes malignant progression in gastric cancer by suppressing the TRIM21-mediated ubiquitination/degradation of STAT1 in a GTP binding-dependent modality

Background:Previous studies have revealed the critical role of transglutaminase 2(TGM2)as a potential therapeutic target in cancers,but the oncogenic roles and underlying mechanisms of TGM2 in gastric cancer(GC)are not fully understood.In this study,we examined the role and potential mechanism of TGM2 in GC.Methods:Western blotting,immunohistochemistry,CCK8,colony formation and transwell assays were used to measure TGM2 expression in the GC cells and tissues and to examine the in vitro role of TGM2 in GC.Xenograft and in vivo metastasis experiments were performed to examine the in vivo role of TGM2 in GC.Gene set enrichment analysis,quantitative PCR and western blotting were conducted to screen for potential TGM2 targets involved in GC.Gain/loss-offunction and rescue experiments were conducted to detect the biological roles of STAT1 in GC cells in the context of TGM2.Co-immunoprecipitation,mass spectrometry,quantitative PCR and western blotting were conducted to identify STAT1-interacting proteins and elucidate their regulatory mechanisms.Mutations in TGM2 and two molecules(ZM39923 and A23187)were used to identify the enzymatic activity of TGM2 involved in the malignant progression of GC and elucidate the underlying mechanism.Results:In this study,we demonstrated elevated TGM2 expression in the GC tissues,which closely related to pathological grade,and predicted poor survival in patients with GC.TGM2 overexpression or knockdown promoted(and inhibited)cell proliferation,migration,and invasion,which were reversed by STAT1 knockdown or overexpression.Further studies showed that TGM2 promoted GC progression by inhibiting STAT1 ubiquitination/degradation.Then,tripartite motif-containing protein 21(TRIM21)was identified as a ubiquitin E3 ligase of STAT1 in GC.TGM2 maintained STAT1 stability by facilitating the dissociation of TRIM21 and STAT1 with GTP-binding enzymatic activity.A23187 abolished the role of TGM2 in STAT1 and reversed the pro-tumor role of TGM2 in vitro and in vivo.Conclusions:This study revealed a critical role and regulatory mechanism of TGM2 on STAT1 in GC and highlighted the potential of TGM2 as a therapeutic target,which elucidates the development of medicine or strategies by regulating the GTP-binding activity of TGM2 in GC.