Research progress on linear ubiquitin chain assembly complex and OTU deubiquitinase with linear linkage specificity in tumor / 药学实践杂志

Linear ubiquitination is an important post-translational modification that has been discovered in recent years. The linear ubiquitin chain is formed by the linkage of glycine residue of one ubiquitin protein to the methionine residue of another ubiquitin. This process is regulated by the linear ubiquitin chain assembly complex (LUBAC) and the OTU deubiquitinase with linear linkage specificity (OTULIN). Linear ubiquitination is involved in various biological processes, including immune response, inflammation, and cell apoptosis. Recent studies have shown that linear ubiquitination is closely related to the occurrence, development, and drug resistance of tumors by affecting signaling pathways such as NF-κB and Wnt/β-catenin. The research progress on the function of LUBAC and OTULIN in tumors was reviewed in this paper.

Activation of insulin-like growth factor-1 receptor (IGF-1R) promotes growth of colorectal cancer through triggering the MEX3A-mediated degradation of RIG-I

Insulin-like growth factor-1 receptor (IGF-1R) has been made an attractive anticancer target due to its overexpression in cancers. However, targeting it has often produced the disappointing results as the role played by cross talk with numerous downstream signalings. Here, we report a disobliging IGF-1R signaling which promotes growth of cancer through triggering the E3 ubiquitin ligase MEX3A-mediated degradation of RIG-I. The active β-arrestin-2 scaffolds this disobliging signaling to talk with MEX3A. In response to ligands, IGF-1Rβ activated the basal βarr2 into its active state by phosphorylating the interdomain domain on Tyr64 and Tyr250, opening the middle loop (Leu130‒Cys141) to the RING domain of MEX3A through the conformational changes of βarr2. The models of βarr2/IGF-1Rβ and βarr2/MEX3A could interpret the mechanism of the activated-IGF-1R in triggering degradation of RIG-I. The assay of the mutants βarr2Y64A and βarr2Y250A further confirmed the role of these two Tyr residues of the interlobe in mediating the talk between IGF-1Rβ and the RING domain of MEX3A. The truncated-βarr2 and the peptide ATQAIRIF, which mimicked the RING domain of MEX3A could prevent the formation of βarr2/IGF-1Rβ and βarr2/MEX3A complexes, thus blocking the IGF-1R-triggered RIG-I degradation. Degradation of RIG-I resulted in the suppression of the IFN-I-associated immune cells in the TME due to the blockade of the RIG-I-MAVS-IFN-I pathway. Poly(I:C) could reverse anti-PD-L1 insensitivity by recovery of RIG-I. In summary, we revealed a disobliging IGF-1R signaling by which IGF-1Rβ promoted cancer growth through triggering the MEX3A-mediated degradation of RIG-I.

TRIB3 promotes pulmonary fibrosis through inhibiting SLUG degradation by physically interacting with MDM2

Pulmonary fibrosis (PF) is the pathological structure of incurable fibroproliferative lung diseases that are attributed to the repeated lung injury-caused failure of lung alveolar regeneration (LAR). Here, we report that repetitive lung damage results in a progressive accumulation of the transcriptional repressor SLUG in alveolar epithelial type II cells (AEC2s). The abnormal increased SLUG inhibits AEC2s from self-renewal and differentiation into alveolar epithelial type I cells (AEC1s). We found that the elevated SLUG represses the expression of the phosphate transporter SLC34A2 in AEC2s, which reduces intracellular phosphate and represses the phosphorylation of JNK and P38 MAPK, two critical kinases supporting LAR, leading to LAR failure. TRIB3, a stress sensor, interacts with the E3 ligase MDM2 to suppress SLUG degradation in AEC2s by impeding MDM2-catalyzed SLUG ubiquitination. Targeting SLUG degradation by disturbing the TRIB3/MDM2 interaction using a new synthetic staple peptide restores LAR capacity and exhibits potent therapeutic efficacy against experimental PF. Our study reveals a mechanism of the TRIB3-MDM2-SLUG-SLC34A2 axis causing the LAR failure in PF, which confers a potential strategy for treating patients with fibroproliferative lung diseases.

The E3 ubiquitin ligase NEDD4-1 protects against acetaminophen-induced liver injury by targeting VDAC1 for degradation

Acetaminophen (APAP) overdose is a major cause of liver injury. Neural precursor cell expressed developmentally downregulated 4-1 (NEDD4-1) is an E3 ubiquitin ligase that has been implicated in the pathogenesis of numerous liver diseases; however, its role in APAP-induced liver injury (AILI) is unclear. Thus, this study aimed to investigate the role of NEDD4-1 in the pathogenesis of AILI. We found that NEDD4-1 was dramatically downregulated in response to APAP treatment in mouse livers and isolated mouse hepatocytes. Hepatocyte-specific NEDD4-1 knockout exacerbated APAP-induced mitochondrial damage and the resultant hepatocyte necrosis and liver injury, while hepatocyte-specific NEDD4-1 overexpression mitigated these pathological events both in vivo and in vitro. Additionally, hepatocyte NEDD4-1 deficiency led to marked accumulation of voltage-dependent anion channel 1 (VDAC1) and increased VDAC1 oligomerization. Furthermore, VDAC1 knockdown alleviated AILI and weakened the exacerbation of AILI caused by hepatocyte NEDD4-1 deficiency. Mechanistically, NEDD4-1 was found to interact with the PPTY motif of VDAC1 through its WW domain and regulate K48-linked ubiquitination and degradation of VDAC1. Our present study indicates that NEDD4-1 is a suppressor of AILI and functions by regulating the degradation of VDAC1.

Discovery of a first-in-class ANXA3 degrader for the treatment of triple-negative breast cancer

Triple-negative breast cancer (TNBC) is a nasty disease with extremely high malignancy and poor prognosis. Annexin A3 (ANXA3) is a potential prognosis biomarker, displaying an excellent correlation of ANXA3 overexpression with patients' poor prognosis. Silencing the expression of ANXA3 effectively inhibits the proliferation and metastasis of TNBC, suggesting that ANXA3 can be a promising therapeutic target to treat TNBC. Herein, we report a first-in-class ANXA3-targeted small molecule (R)-SL18, which demonstrated excellent anti-proliferative and anti-invasive activities to TNBC cells. (R)-SL18 directly bound to ANXA3 and increased its ubiquitination, thereby inducing ANXA3 degradation with moderate family selectivity. Importantly, (R)-SL18 showed a safe and effective therapeutic potency in a high ANXA3-expressing TNBC patient-derived xenograft model. Furthermore, (R)-SL18 could reduce the β-catenin level, and accordingly inhibit the Wnt/β-catenin signaling pathway in TNBC cells. Collectively, our data suggested that targeting degradation of ANXA3 by (R)-SL18 possesses the potential to treat TNBC.

Construction of TRAF6 ubiquitin site 331 mutant colorectal cancer cell stable line and its effect on biological behavior of colorectal cancer cells / 中华肿瘤杂志

Objective: To investigate the effect of ubiquitin mutation at position 331 of tumor necrosis factor receptor related factor 6 (TRAF6) on the biological characteristics of colorectal cancer cells and its mechanism. Methods: lentivirus wild type (pCDH-3×FLAG-TRAF6) and mutation (pCDH-3×FLAG-TRAF6-331mut) of TRAF6 gene expression plasmid with green fluorescent protein tag were used to infect colorectal cancer cells SW480 and HCT116, respectively. The infection was observed by fluorescence microscope, and the expressions of TRAF6 and TRAF6-331mut in cells was detected by western blot. Cell counting kit-8 (CCK-8) and plate cloning test were used to detect the proliferation ability of colorectal cancer cells in TRAF6 group and TRAF6-331mut group, cell scratch test to detect cell migration, Transwell chamber test to detect cell migration and invasion, immunoprecipitation to detect the ubiquitination of TRAF6 and TRAF6-331mut with ubiquitinof lysine binding sites K48 and K63. Western blot was used to detect the effects of TRAF6 and TRAF6-331mut over expression on the nuclear factor kappa-B (NF-κB) and mitogen activated protein kinase mitogen-activated protein kinase (MAPK)/activating protein-1(AP-1) signal pathway. Results: The successful infection of colorectal cancer cells was observed under fluorescence microscope. Western blot detection showed that TRAF6 and TRAF6-331mut were successfully expressed in colorectal cancer cells. The results of CCK-8 assay showed that on the fourth day, the absorbance values of HCT116 and SW480 cells in TRAF6-331mut group were 1.89±0.39 and 1.88±0.24 respectively, which were lower than those in TRAF6 group (2.09±0.12 and 2.17±0.45, P=0.036 and P=0.011, respectively). The results of plate colony formation assay showed that the number of clones of HCT116 and SW480 cells in TRAF6-331mut group was 120±14 and 85±14 respectively, which was lower than those in TRAF6 group (190±21 and 125±13, P=0.001 and P=0.002, respectively). The results of cell scratch test showed that after 48 hours, the percentage of wound healing distance of HCT116 and SW480 cells in TRAF6-331mut group was (31±12)% and (33±14)%, respectively, which was lower than those in TRAF6 group [(43±13)% and (43±7)%, P=0.005 and 0.009, respectively]. The results of Transwell migration assay showed that the migration numbers of HCT116 and SW480 cells in TRAF6-331mut group were significantly lower than those in TRAF6 group (P<0.001 and P<0.002, respectively). The results of Transwell invasion assay showed that the number of membrane penetration of HCT116 and SW480 cells in TRAF6-331mut group was significantly lower than those in TRAF6 group (P=0.008 and P=0.009, respectively). The results of immunoprecipitation detection showed that the ubiquitin protein of K48 chain pulled by TRAF6-331mut was lower than that of wild type TRAF6 in 293T cells co-transfected with K48 (0.57±0.19), and the ubiquitin protein of K63 chain pulled down by TRAF6-331mut in 293T cells co-transfected with K63 was lower than that of wild type TRAF6 (0.89±0.08, P<0.001). Western blot assay showed that the protein expression levels of NF-κB, p-NF-κB and p-AP-1 in TRAF6-331mut-HCT116 cells were 0.63±0.08, 0.42±0.08 and 0.60±0.07 respectively, which were lower than those in TRAF6-HCT116 cells (P=0.002, P<0.001 and P<0.001, respectively). The expression level of AP-1 protein in TRAF6-HCT116 cells was 0.89±0.06, compared with that in TRAF6-HCT116 cells. The difference was not statistically significant (P>0.05). The protein expression levels of NF-κB, p-NF-κB and p-AP-1 in TRAF6-331mut-SW480 cells were 0.50±0.06, 0.51±0.04, 0.48±0.02, respectively, which were lower than those in TRAF6-SW480 cells (all P<0.001). There was no significant difference in AP-1 protein expression between TRAF6-331mut-SW480 cells and TRAF6-SW480 cells. Conclusion: The ubiquitin site mutation of TRAF6 gene at 331 may prevent the binding of TRAF6 and ubiquitin lysine sites K48 and K63, and then affect the expressions of proteins related to downstream NF-κB and MAPK/AP-1 signal pathways, and inhibit the proliferation, migration and invasion of colorectal cancer cells.

Effects of herbal cake separated moxibustion on Tim-4 and ubiquitination of PD-1 in rabbits with immunosuppression / 中国针灸

OBJECTIVE@#To observe the effects of herbal cake separated moxibustion on macrophage effector molecule T-cell immunoglobulin and mucin-domain containing-4 (Tim-4) and ubiquitination of programmed cell death protein 1 (PD-1) in rabbits with immunosuppression, and to explore the possible mechanism on herbal cake separated moxibustion in improving immunosuppression.@*METHODS@#Thirty-two big-ear white rabbits were randomly divided into a normal group, a model group, a moxa stick moxibustion group and a herbal cake separated moxibustion group, 8 rabbits in each group. Except the normal group, the immunosuppression model was established by intraperitoneal injection of cyclophosphamide of60 mg/kg in the other 3 groups. "Shenque" (CV 8), "Shenshu" (BL 23), "Zusanli" (ST 36), etc. were selected in both the moxa stick moxibustion group and the herbal cake separated moxibustion group. Moxa stick moxibustion was applied in the moxa stick moxibustion group, one cone at each acupoint; herbal cake separated moxibustion was applied in the herbal cake separated moxibustion group, 5 cones at each acupoint. The intervention was given once every other day for 10 times in both groups. Leukocyte content in peripheral blood was detected by blood cell analyzer; the positive expression of PD-1 in CD+4 T lymphocytes, CD+8T lymphocytes and CD+68 macrophages in peripheral blood was measured by flow cytometry, the serum levels of interleukin 2 (IL-2), CD8, CD68 and Tim-4 were detected by ELISA, and the expression of Tim-4 and F-box only protein 38 (FBXO38) in the liver and spleen tissues was measured by immunohistochemistry.@*RESULTS@#Compared with the normal group, in the model group, white blood cell count (WBC) and percentage of neutrophils (NEU%) were decreased while percentage of lymphocyte (LYM%) was increased (P<0.01) in peripheral blood; the positive expression rates of PD-1 in CD+4 T lymphocytes, CD+8T lymphocytes and CD+68 macrophages in peripheral blood were increased (P<0.01); the serum levels of IL-2, CD68 and Tim-4 were increased (P<0.01), the serum level of CD8 was decreased (P<0.01); the average optical density (AOD) of Tim-4 in the liver tissue and FBXO38 in the liver and spleen tissues was increased (P<0.01). Compared with the model group, in the moxa stick moxibustion group and the herbal cake separated moxibustion group, WBC and NEU% were increased (P<0.01); the positive expression rates of PD-1 in CD+4 T lymphocytes, CD+8T lymphocytes and CD+68 macrophages in peripheral blood were decreased (P<0.01); the serum levels of IL-2, CD68 and Tim-4 were decreased (P<0.01), the serum levels of CD8 were increased (P<0.01); the AOD of Tim-4 and FBXO38 in the liver tissue and FBXO38 in the spleen tissue was decreased (P<0.01, P<0.05). Compared with the moxa stick moxibustion group, in the herbal cake separated moxibustion group, the positive expression rate of PD-1 in CD+68 macrophages in peripheral blood was increased (P<0.05); serum level of Tim-4 was increased (P<0.01); AOD of Tim-4 in the liver tissue was decreased (P<0.05).@*CONCLUSION@#Herbal cake separated moxibustion can improve immunosuppression by regulating the expression of macrophage effector molecule Tim-4 and the FBXO38 mediated ubiquitination of PD-1, Tim-4 may be one of the specific indexes of immunomodulation involving with herbal cake separated moxibustion.

Effect of icariin on ubiquitination of amyloid precur-sor protein in Alzheimer's disease mice / 中国药理学与毒理学杂志

OBJECTIVE To investigate the effect of icariin(ICA)on the ubiquitination modification of β-amy-loid precursor protein(APP)in Alzheimer's disease mice.METHODS In vitro,① HEK 293 cells stably overex-pressing human APP695(OE-hAPP)were treated with different concentrations of ICA(10-100 μmol·L-1)for 24 h and the cell viability was detected by MTT assay.②CHX(50 mg·L-1)was used to block protein synthesis and MG132(20 μmol·L-1)inhibits proteasome activity,then the level of APP in different time(0,0.5,1,2,3 and 4 h)and the ubiquitination were tested by Western blotting.③ E3 ubiquitin ligases HMG-CoA reductase degradation pro-tein 1(HRD1)protein expression in OE-hAPP was tested by Western blotting,as well as the level and ubiquitination of APP were tested under HRD1 silent condition by Co-IP and Western blotting.In vivo,① male APP/PS1 mice and wild type(WT)mice were randomly divided into 5 groups:WT,WT+ICA,APP/PS1,APP/PS1+ICA,and APP/PS1+donepezil(DPZ)groups.ICA(60 mg·kg-1·d-1)and DPZ(1 mg·kg-1·d-1)were treated for 3 months by gavage from 6 months of age,and WT mice were given equal volume of distilled water.②Morris water maze and Y-maze experiments were used to detect the alteration of spatial learning memory function.③ After then,the brain tissues were collected,total proteins were extracted,APP antibodies were subjected to Co-IP,and total ubiqui-tination(Ub),K48-linked polyubiquitination(UbK48)and K63-linked polyubiquitination of APP level,APP and HRD1 proteins were detected by Western blotting.RESULTS In vitro results showed that ICA significantly enhanced APP degradation(vs control,P＜0.01),up-reg-ulated HRD1 expression(vs control,P＜0.05;vs OE-hAPP,P＜0.05),elevated the level Ub and UbK48 of APP,as well as increased APP degradation.Moreover,silenced HRD1 gene abolished abovementioned effects of ICA(vs control-siRNA,P＜0.05;vs HRD1-siRNA,P＜0.05).In vivo results showed that ICA improved the spa-tial learning and memory function APP/PS1 mice by Mor-ris water maze and Y-maze tests,increased HRD1 expres-sion(vs APP/PS1 + vehicle,P＜0.05),enhanced APP ubiquitination and reduced APP protein level(vs APP/PS1 + vehicle,P＜0.01).CONCLUSION ICA promotes the ubiquitination and proteasome-dependent degrada-tion of APP by up-regulating HRD1,thereby improving the spatial learning and memory function of Alzheimer disease mice.

The deubiquitinating enzyme 13 retards non-alcoholic steatohepatitis via blocking inactive rhomboid protein 2-dependent pathway

Nowadays potential preclinical drugs for the treatment of nonalcoholic steatohepatitis (NASH) have failed to achieve expected therapeutic efficacy because the pathogenic mechanisms are underestimated. Inactive rhomboid protein 2 (IRHOM2), a promising target for treatment of inflammation-related diseases, contributes to deregulated hepatocyte metabolism-associated nonalcoholic steatohepatitis (NASH) progression. However, the molecular mechanism underlying Irhom2 regulation is still not completely understood. In this work, we identify the ubiquitin-specific protease 13 (USP13) as a critical and novel endogenous blocker of IRHOM2, and we also indicate that USP13 is an IRHOM2-interacting protein that catalyzes deubiquitination of Irhom2 in hepatocytes. Hepatocyte-specific loss of the Usp13 disrupts liver metabolic homeostasis, followed by glycometabolic disorder, lipid deposition, increased inflammation, and markedly promotes NASH development. Conversely, transgenic mice with Usp13 overexpression, lentivirus (LV)- or adeno-associated virus (AAV)-driven Usp13 gene therapeutics mitigates NASH in 3 models of rodent. Mechanistically, in response to metabolic stresses, USP13 directly interacts with IRHOM2 and removes its K63-linked ubiquitination induced by ubiquitin-conjugating enzyme E2N (UBC13), a ubiquitin E2 conjugating enzyme, and thus prevents its activation of downstream cascade pathway. USP13 is a potential treatment target for NASH therapy by targeting the Irhom2 signaling pathway.

Expression of monoubiquitination histone H2B in esophageal carcinoma and its clinical significance / 肿瘤研究与临床

Objective:To investigate the expression of monoubiquitination histone H2B (H2Bub) in esophageal cancer tissues and its correlation with the prognosis of patients.Methods:A total of 75 patients who underwent thoracic esophagectomy in Shanxi Province Cancer Hospital from May 2010 to December 2015 were selected. The expression of H2Bub protein in esophageal carcinoma and para-carcinoma tissues was detected by using immunohistochemical method. The relationship between H2Bub expression level and the clinicopathological characteristics was analyzed, Kaplan-Meier method was used to analyze the relationship H2Bub expression level and the survival.Results:H2Bub was positively expressed in esophageal carcinoma and para-carcinoma tissues, and weakly positive expressed H2Bub was found in para-carcinoma tissues, while not found in esophageal carcinoma tissues. The strongly positive expression rate of H2Bub in esophageal carcinoma tissues was higher than that in para-carcinoma tissues [84.0% (63/75) vs. 22.7% (17/75), χ2 = 34.68, P < 0.001]. Compared with para-carcinoma tissues, 64.0% (48/75) of H2Bub expression level in carcinoma tissues was up-regulated, and 2.7% (2/75) of H2Bub expression level was down-regulated. The up-regulated expression of H2Bub in esophageal carcinoma tissues compared with para-carcinoma tissues was not related with the gender, age, tumor diameter, lymph node metastasis and T staging (all P > 0.05). The proportion of patients with up-regulated expression of H2Bub in poorly differentiated carcinoma tissues was lower than that in moderately and highly differentiated carcinoma tissues [43.8% (7/16) vs. 66.7% (34/51), 87.5% (7/8), P = 0.037]. The median overall survival time was 70 months (95% CI 45-95 months) and 68 months (95% CI 54-82 months), respectively in 12 esophageal carcinoma patients with moderately positive expressed H2Bub and 63 esophageal carcinoma patients with strongly positive expressed H2Bub, and the difference was statistically significant ( P = 0.606). Among 48 patients with up-regulated expression of H2Bub in esophageal carcinoma tissues compared with para-carcinoma tissues, the median overall survival time of poorly differentiated esophageal carcinoma group (7 cases) was shorter than that of highly differentiated (7 cases) and moderately differentiated (34 cases) esophageal carcinoma group [36 months (95% CI 24-37 months) vs. 68 months (95% CI 38-98 months), 68 months (95% CI 44-91 months)], and the differences were statistically significant (all P < 0.05). Conclusions:The expression level of H2Bub in esophageal carcinoma tissues is up-regulated compared with that in para-carcinoma tissues. The up-regulated H2Bub expression level of patients with poorly differentiated esophageal carcinoma with poor prognosis is obvious.

Juglone induces proliferation inhibition and apoptosis of cervical cancer cells via promoting c-Myc ubiquitination / 南方医科大学学报

OBJECTIVE@#To observe the expression of c-Myc protein in cervical cancer HeLa cells and explore the effect of juglone on the proliferation and apoptosis of HeLa cells by affecting c-Myc ubiquitination.@*METHODS@#HeLa cells treated with different concentrations (0, 10, 20, or 50 μmol/L) of juglone or with 20 μmol/L juglone for different time lengths were examined for expression of c-Myc protein with Western blotting. The half-life of c-Myc protein was determined using cycloheximide (CHX) and c-Myc protein degradation was detected using coimmunoprecipitation. We also assessed the effects of 20 μmol/L juglone combined with 0, 1.0 or 2.0 μmol/L MG132 (a proteasome inhibitor) on c-Myc expression. The effects of 20 μmol/L juglone on the proliferation and apoptosis of HeLa cells with RNA interference-mediated knockdown of c-Myc were evaluated with MTT assay and flow cytometry.@*RESULTS@#Treatment with juglone significantly lowered c-Myc protein expression in HeLa cells in a concentration-and time-dependent manner (P < 0.05). Juglone obviously shortened the half-life of c-Myc protein, and the addition of MG132 significantly up-regulated the expression level of c-Myc protein (P < 0.05). Juglone treatment also promoted ubiquitination of c-Myc protein in HeLa cells. Compared with the cells transfected with a negative control construct, the cells transfected with si-c-Myc showed significantly decreased proliferation inhibition and a lowered cell rate with early apoptosis after juglone treatment (P < 0.05).@*CONCLUSION@#Juglone inhibits proliferation and promotes apoptosis of HeLa cells by affecting the ubiquitination of c-Myc protein.

Chidamide inhibits the NOTCH1-MYC signaling axis in T-cell acute lymphoblastic leukemia / 医学前沿

T-cell acute lymphoblastic leukemia (T-ALL) is one of the most dangerous hematological malignancies, with high tumor heterogeneity and poor prognosis. More than 60% of T-ALL patients carry NOTCH1 gene mutations, leading to abnormal expression of downstream target genes and aberrant activation of various signaling pathways. We found that chidamide, an HDAC inhibitor, exerts an antitumor effect on T-ALL cell lines and primary cells including an anti-NOTCH1 activity. In particular, chidamide inhibits the NOTCH1-MYC signaling axis by down-regulating the level of the intracellular form of NOTCH1 (NICD1) as well as MYC, partly through their ubiquitination and degradation by the proteasome pathway. We also report here the preliminary results of our clinical trial supporting that a treatment by chidamide reduces minimal residual disease (MRD) in patients and is well tolerated. Our results highlight the effectiveness and safety of chidamide in the treatment of T-ALL patients, including those with NOTCH1 mutations and open the way to a new therapeutic strategy for these patients.

Research progress on ubiquitin-specific proteases in regulation of bone remodeling / 口腔疾病防治

@#Maintaining bone homeostasis relies on the balance between bone remodeling involving bone resorption by osteoclasts and bone formation by osteoblasts under physiological conditions. An increasing number of studies have shown that the ubiquitin-proteasome system plays an important role in bone remodeling. The ubiquitination process is reversible through the action of deubiquitinase (DUB), and ubiquitin-specific proteases (USPs) are the largest of the DUB families. This article summarizes the mechanisms by which USPs regulate bone homeostasis, including USP4 and USP7, by affecting bone formation through signaling pathways such as Wnt/β-catenin and cylindromatosis (CYLD) and regulating bone resorption through signaling pathways such as nuclear factor-kappa B (NF-κB). In addition to affecting bone resorption and bone formation during bone reconstruction, the effect of USPs on bone is also reflected in the osteogenic differentiation of human periodontal membrane stem cells and implant bone binding. Future research should determine whether USPs have a greater regulatory effect on bone reconstruction and the specific mechanism of their regulatory effect to provide more approaches for the treatment of bone diseases.

Effect of key enzymes ubiquitination sites on the biosynthesis of naringenin / 生物工程学报

Flavonoids have a variety of biological activities and have important applications in food, medicine, cosmetics, and many other fields. Naringenin is a platform chemical for the biosynthesis of many important flavonoids. Ubiquitination plays a pivotal role in the post-translational modification of proteins and participates in the regulation of cellular activities. Ubiquitinated proteins can be degraded by the ubiquitin-protease system, which is important for maintaining the physiological activities of cells, and may also exert a significant impact on the expression of exogenous proteins. In this study, a real-time in-situ detection system for ubiquitination modification has been established in Saccharomyces cerevisiae by using a fluorescence bimolecular complementation approach. The ubiquitination level of protein was characterized by fluorescence intensity. By using the approach, the potential ubiquitination sites of proteins involved in the naringenin biosynthesis pathway have been obtained. The lysine residues of the relevant ubiquitination sites were mutated to arginine to reduce the ubiquitination level. The mutants of tyrosine ammonia-lyase (FjTAL) and chalcone synthase (SjCHS, SmCHS) showed decreased fluorescence, suggested that a decreased ubiquitination level. After fermentation verification, the S. cerevisiae expressing tyrosine ammonia-lyase FjTAL mutant FjTAL-K487R accumulated 74.2 mg/L p-coumaric acid at 72 h, which was 32.3% higher than that of the original FjTAL. The strains expressing chalcone synthase mutants showed no significant change in the titer of naringenin. The results showed that mutation of the potential ubiquitination sites of proteins involved in the naringenin biosynthesis pathway could increase the titer of p-coumaric acid and have positive effect on naringenin biosynthesis.

MFN1 ubiquitination mediates lipopolysaccharide-induced mitochondrial dysfunction and pyroptosis in Raw264.7 mouse macrophages / 中华微生物学和免疫学杂志

Objective:To investigate the regulatory effects of mitofusin 1 (MFN1) on lipopolysaccharide (LPS)-induced Raw264.7 mouse macrophages pyroptosis and to provide reference for further study on the prevention of inflammation and fibrosis caused by macrophage dysfunction.Methods:Raw264.7 mouse macrophages were cultured in vitro and used to construct a model of LPS-induced pyroptosis. CCK-8 staining, PI staining, LDH release assay and Western blot were used to verify the Raw264.7 pyroptosis induced by LPS. MFN1 expression was detected by Western blot. DCFH-DA probe was used to detect the synthesis of total reactive oxygen species (ROS); Mito-SOX was used to detect mitochondrial ROS; JC-1 mitochondrial membrane potential was detected by fluorescence probe to reflect mitochondrial damage. Based on Ubibrowser database, it was predicted that MFN1 could bind to a variety of E3 ubiquitin ligases. Then, immunofluorescence and co-immunoprecipitation (CO-IP) were used to analyze MFN1 ubiquitination. An overexpression plasmid for MFN1 was constructed and transfected into Raw264.7 cells to detect the changes in pyroptosis and mitochondrial function. Results:LPS could induce the pyroptosis of Raw264.7 cells and mitochondrial dysfunction. MFN1 expression was decreased after LPS stimulation. Ubiquitinated MFN1 was detected by CO-IP. Ubiquitination inhibitor MG-132 inhibited LPS-induced expression of pyroptosis-related proteins including NLRP3, Pro-caspase-1, Caspase-1, IL-1β and IL-18 and improved mitochondrial function. MFN1 overexpression relieved the mitochondrial dysfunction and pyroptosis of Raw264.7 cells induced by LPS.Conclusions:The ubiquitination of MFN1 induced by LPS was involved in mitochondrial dysfunction and macrophage pyroptosis, suggesting that MFN1 was a potential target for the treatment of macrophage-induced inflammation and related diseases.

TRIM21 suppresses invasion of hepatocellular carcinoma cells by promoting β-catenin ubiquitylation and degradation / 南方医科大学学报

OBJECTIVE@#To explore the role of TRIM21 in modulating the invasive phenotype of hepatocellular carcinoma (HCC) cells and its mechanism of action.@*METHODS@#RNA interference technique was used to knock down the expression of TRIM21 and β-catenin, alone or in combination, in HCC cell lines 97H and LM3, and the interfering efficiency and the activity of closely related pathways were determined using Western blotting. The two cells with TRIM21 knockdown (siTRIM21 97H and siTRIM21 LM3 cells) were assessed for their invasion ability in vitro using Transwell invasion assay, and the lung metastasis capacity of siTRIM21 LM3 cells following tail vein injection was evaluated in nude mice. The binding of TRIM21 with β-catenin and the ubiquitylation level of β-catenin in TRIM21-overexpressing HEK293 cells were determined with Western blotting and co-immunoprecipitation assay. We also compared the overall survival of patients with CTNNB1highTRIM21high and CTNNB1highTRIM21low HCC subtypes using Kaplan-Meier method based on filtrated and grouped HCC clinical data from TCGA database.@*RESULTS@#TRIM21 knockdown significantly enhanced the invasion ability of 97H and LM3 cells in vitro (P < 0.01 or 0.05) and the lung metastasis ability of LM3 cells in nude mice (P < 0.01), and simultaneous knockdown of β -catenin obviously suppressed the in vitro invasiveness of the cells (P < 0.0001 or 0.05). Co-immunoprecipitation assay showed that TRIM21 was capable of directly binding with β-catenin protein to accelerate the ubiquitination and degradation of the latter, leading to inhibition of nuclear translocation of β-catenin and hence reduced invasiveness of HCC cells. Bioinformatic analysis showed that compared patients with CTNNB1highTRIM21low HCC subtype where Wnt pathway was activated, the patients with CTNNB1highTRIM21high HCC subtype had a significantly better survival outcomes (P < 0.05).@*CONCLUSION@#A high expression of TRIM21 suppresses the invasion of HCC cells by promoting β-catenin ubiquitylation and degradation, which possibly explains the poor prognosis of CTNNB1highTRIM21low HCC patients.

Clinical value of deubiquitination modification in evaluating the prognosis of patients with diffuse large B-cell lymphoma / 中国医师进修杂志

Objective:To observe the expression levels of small ubiquitinated protein specific protease (SENP) 1 and small ubiquitin-related modifier protein (SUMO) 1 in patients with diffuse large B-cell lymphoma (DLBCL), and analyze the clinical value of evaluating prognosis.Methods:The clinical data of 66 patients with DLBCL (DLBCL group) in Inner Mongolia People′s Hospital from February 2017 to October 2020 were retrospectively analyzed, and 60 cases of healthy people in the same period were selected as the healthy control group. The expression levels of SENP1 and SUMO1 were detected by enzyme linked immunosorbent assay (ELISA). The correlation between the expression levels of SENP1, SUMO1 and clinical characteristics was analyzed. The independent risk factors affecting the prognosis were analyzed by Cox multivariate analysis.Results:The SENP1 in DLBCL group was significantly higher than that in healthy control group (50.39 ± 6.86 vs. 7.47 ± 1.32), the SUMO1 in DLBCL group was significantly lower than that in healthy control group (8.84 ± 2.13 vs. 31.49 ± 5.89), and there were statistical differences ( t = 47.640 and 29.210, P<0.01). There were statistical differences in SENP1 and SUMO1 among patients with different clinical stages ( P<0.01). The expression levels of SENP1 and SUMO1 were correlated with clinical stage and international prognostic index (IPI) ( P<0.05), and were not correlated with age, gender, disease site and clinical symptoms ( P>0.05). The 3-year survival rate in patients with high SENP1 expression (30 cases) was significantly lower than that in patients with low SENP1 expression (36 cases), the 3-year survival rate in patients with high SUMO1 expression (38 cases) was significantly higher than that in patients with low SUMO1 expression (28 cases), and there were statistical differences (26.67% vs. 75.00% and 73.68% vs. 39.29%, P<0.05). Cox multivariate regression analysis result showed that clinical stage, IPI, SENP1 and SUMO1 were independent risk factors affecting the prognosis in patients with DLBCL ( HR = 1.352, 1.487, 2.048 and 3.295; 95% CI 1.180 to 1.691, 1.187 to 1.602, 2.536 to 4.023 and 2.752 to 5.325; P<0.05 or <0.01). Conclusions:In patients with DLBCL, SENP1 is highly expressed and SUMO1 is lowly expressed. The expression levels of SENP1 and SUMO1 are closely related to clinical stage and IPI in patients with DLBCL, and they are independent risk factors of the prognosis.

Research progress of ubiquitin-specific peptidases in tumorigenesis and development / 国际外科学杂志

Protein ubiquitination is one of the important mechanisms regulating protein stability and activity under physiological condition. Among them, E1/E2/E3 ligases and deubiquitination enzyme play an important regulatory role in the process of protein ubiquitination, while deubiquitination may induce the occurrence of tumors, asthma and other diseases. Ubiquitin-specific peptidases, as the main members of the deubiquitination enzyme family, have been proved to be closely related to the occurrence and development of tumors, among which some ubiquitin-specific peptidases have been used as new targets for anti-tumor therapy. Therefore, this study aims to briefly review the regulatory mechanisms of ubiquitin-specific peptidases in the process of tumor genesis and development, which will provide more research directions for tumor therapy.

Effect of the regulator of G-protein signaling 2 on the proliferation and invasion of oral squamous cell carcinoma cells and its molecular mechanism / 华西口腔医学杂志

OBJECTIVES@#This study aims to investigate the effect of the regulator of G-protein signaling 2 (RGS2) on the proliferation and invasion of oral squamous cell carcinoma (OSCC) cells and its potential molecular mechanism. Metho⁃ds The expression status and clinical significance of RGS2 in head and neck squamous cell carcinomas and matched adjacent normal tissues were evaluated using TCGA database. Three OSCC cell lines (i.e., SCC-9, Cal27, and Fadu) were overexpressed with RGS2, and the effect of RGS2 on cell proliferation and invasion was determined using the Transwell, clone formation, and cell counting kit (CCK)-8 assays. Moreover, the yeast two-hybrid scree-ning and co-immunoprecipitation (Co-IP) assays were conducted to detect the correlation of RGS2, four and a half LIM domains protein 1 (FHL1), and damage DNA-binding protein 1 (DDB1).@*RESULTS@#The expression level of RGS2 in OSCC was significantly lower than that in matched adjacent normal tissues (@*CONCLUSIONS@#RGS2 plays an important role in the inhibition of OSCC proliferation and invasion. The structure stability of RGS2 is competitively regulated by FHL1 and DDB1.

TRIB3‒GSK-3

Pulmonary fibrosis (PF) is a chronic, progressive, fatal interstitial lung disease with limited available therapeutic strategies. We recently reported that the protein kinase glycogen synthase kinase-3