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Targeted protein degradation (TPD) techniques eliminate pathogenic proteins by hijacking the intracellular proteolysis machinery which includes the ubiquitin-proteasome system (UPS) and the lysosomal degradation pathway, holding promise to overcome the limitations of traditional inhibitors and further broaden the target space including many “undruggable” targets, and provide new targeted treatments for drug discovery. In this review, recent advances in a variety of promising TPD strategies were summarized, such as proteolysis targeting chimera (PROTAC), molecular glue, lysosome-targeting chimaera (LYTAC), autophagosome-tethering compound (ATTEC), autophagy-targeting chimera AUTAC and AUTOTAC, particularly. The representative case studies, potential applications and challenges were analyzed.
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Chronic hepatitis B virus (HBV) infection is one of the leading causes of hepatocellular carcinoma (HCC). Ubiquitin-proteasome system (UPS) mediates the post-translational modification and degradation of protein in eukaryotic cells. Recent studies have revealed that UPS plays an important role in HBV infection and hepatocarcinogenesis. Targeting HBx to intervene in the progression of HBV infection or HBV-related HCC has become a research hotspot both domestically and internationally in recent years. This article reviewed the progress in HBx promoting HBV infection and hepatocarcinogenesis through UPS.
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Objective:To investigate the relationship between serum fibroblast growth factor 21 (FGF21) and sarcopenia in hemodialysis (HD) patients, and to explore the relationship between FGF21 and signal pathways related to skeletal muscle metabolism in uremic state at the cellular level.Methods:The data of the HD patients from the blood purification center of the Third Affiliated Hospital of Soochow University were collected in this prospective observational study between January 2018 and December 2019. Serum FGF21 concentration was detected by enzyme-linked immunosorbent assay (ELISA). Meanwhile, the skeletal muscle indexes (SMI) at the fourth thoracic vertebra (T4) and the first lumbar vertebra (L1) were assessed by chest CT. According to the T4 SMI and L1 SMI, the patients were divided into sarcopenia group and non-sarcopenia group. The relationship between serum FGF21 and sarcopenia was analyzed. The C2C12 mouse myoblasts were cultured in vitro, which were intervened with healthy human serum, healthy human serum+different concentrations of FGF21, uremic serum, uremic serum+different concentrations of FGF21. The expressions of muscle ring finger protein-1 (MURF1), muscle atrophy F-box (Atrogin-1), myogenic differentiation (MyoD) and myogenin (MyoG) were detected by Western blotting. Results:A total of 118 HD patients with age of (52.64±15.29) years were enrolled in the study, including 64 males (54.2%) and 54 females (45.8%). The images at T4 and L1 level assessed by chest CT could be acquired from 118 patients and 82 patients, respectively. According to the lowest sex-specific quartile ( P25) of T4 SMI (male < 59.92 cm 2/m 2, female < 46.75 cm 2/m 2) and the lowest sex-specific quartile ( P25) of L1 SMI (male < 29.02 cm 2/m 2, female < 24.50 cm 2/m 2), patients were divided into sarcopenia group and non-sarcopenia group, and there were 29(24.58%) and 20(24.39%) patients in the sarcopenia group, respectively. When the patients were divided into two groups according to the sex-specific lowest quartile of T4 SMI, although the serum FGF21 level in the sarcopenia group was higher than that in the non-sarcopenia group, there was no statistical significance between the two groups [448.52(183.96, 1 684.08) ng/L vs. 273.65 (152.83, 535.54) ng/L, Z=-1.741, P=0.082]. When the patients were divided into two groups according to the sex-specific lowest quartile of L1 SMI, the serum FGF21 level in the sarcopenia group was significantly higher than that in the non-sarcopenia group [460.95(188.91, 1 276.38) ng/L vs. 239.10(133.25, 466.36) ng/L, Z=-2.170, P=0.030]. Binary logistic regression analysis showed that higher serum FGF21 was an independent influencing factor for sarcopenia in HD patients regardless of whether the patients were divided into two groups according to the sex-specific lowest quartile of T4 SMI or the sex-specific lowest quartile of L1 SMI (T4 SMI grouping: OR=4.085, 95% CI 1.778-9.388, P=0.001; L1 SMI grouping: OR=7.327, 95% CI 1.841-29.160, P=0.005). At T4 and L1 levels, the area under the receiver operating characteristic curve of FGF21 in predicting sarcopenia in HD patients was 0.636(95% CI 0.494-0.779, P=0.036) and 0.684(95% CI 0.535-0.833, P=0.018), respectively. Cell experiment showed that compared with the uremic serum group, the expressions of MURF1 and Atrogin-1 in myotube cells were increased, while the expressions of MyoD and MyoG were significantly decreased in uremic serum+FGF21 group (both P < 0.05). Conclusions:Higher serum FGF21 is associated with an increased risk of sarcopenia in HD patients. FGF21 may increase the expression of ubiquitin proteasome system, reduce the synthesis and differentiation of skeletal muscle protein, and promote the occurrence of muscle atrophy in uremic patients
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This study aims to investigate the effect and mechanism of hydnocarpin(HC) in treating triple negative breast cancer(TNBC). Cell counting kit-8(CCK-8), xCELLigence real-time cellular analysis(RTCA), and colony formation assay were employed to determine the effects of HC on the proliferation of two TNBC cell lines: MDA-MB-231 and MDA-MB-436. The effects of HC on the migration and invasion of TNBC cells were detected by high-content analysis, wound-healing assay, and Transwell assay. The changes in the epithelial-mesenchymal transition(EMT) and the expression of invasion-and migration-associated proteins [E-cadherin, vimentin, Snail, matrix metalloproteinase-2(MMP-2), and MMP-9] were detected by Western blot. Western blot and RT-qPCR were employed to determine the protein and mRNA levels of Yes-associated protein(YAP) and downstream targets(CTGF and Cyr61). TNBC cells were transfected with Flag-YAP for the overexpression of YAP, and the role of YAP as a key target for HC to inhibit TNBC malignant progression was examined by CCK-8 assay, Transwell assay, and wound-healing assay. The pathway of HC-induced YAP degradation was detected by the co-treatment of proteasome inhibitor with HC and ubiquitination assay. The binding of HC to YAP and the E3 ubiquitin ligase Ccr4-not transcription complex subunit 4(CNOT4) was detected by microscale thermophoresis(MST) assay and drug affinity responsive target stability(DARTS) assay. The results showed that HC significantly inhibited the proliferation, colony formation, invasion, and EMT of TNBC cells. HC down-regulated the protein and mRNA levels of CTGF and Cyr61. HC down-regulated the total protein level of YAP, while it had no effect on the mRNA level of YAP. The overexpression of YAP antagonized the inhibitory effects of HC on the proliferation, migration, and invasion of TNBC cells. HC promoted the degradation of YAP through the proteasome pathway and up-regulated the ubiquitination level of YAP. The results of MST and DARTS demonstrated direct binding between HC, YAP, and CNOT4. The above results indicated that HC inhibited the malignant progression of TNBC via CNOT4-mediated degradation and ubiquitination of YAP.
Subject(s)
Humans , Triple Negative Breast Neoplasms/metabolism , Matrix Metalloproteinase 2/metabolism , Cell Line, Tumor , Cell Proliferation , Cell Movement , Ubiquitination , RNA, Messenger/metabolism , Epithelial-Mesenchymal Transition , Transcription Factors/metabolismABSTRACT
Immunoproteasome is a variant of proteasome with structural differences in 20S subunits optimizing them for the production of antigenic peptides with higher binding affinity to major histocompatibility complex (MHC)-I molecules. Apart from this primary function in antigen presentation, immunoproteasome is also responsible for the degradation of proteins, both unfolded proteins for the maintenance of protein homeostasis and tumor suppressor proteins contributing to tumor progression. The altered expression of immunoproteasome is frequently observed in cancers; however, its expression levels and effects vary among different cancer types exhibiting antagonistic roles in tumor development. This review focuses on the dichotomous role of immunoproteasome in different cancer types, as well as summarizes the current progression in immunoproteasome activators and inhibitors. Specifically targeting immunoproteasome may be a beneficial therapeutic intervention in cancer treatment and understanding the role of immunoproteasome in cancers will provide a significant therapeutic insight for the prevention and treatment of cancers.
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Objective:To investigate the effect of interfering S-phase kinase associated protein 1 (SKP1) gene on apoptosis in Parkinson's disease(PD) cell model induced by 1-methyl-4-phenyl-pyridine ion (MPP+ ) and the mechanism of ubiquitin proteasome system degradation of α-synuclein (α-syn) influence.Methods:SH-SY5Y cells were divided into control group, MPP+ group, SKP1 interference group, and SKP1 interference+ MG132(UPS inhibitor) group.The cells in the control group were cultured normally. The cells in the latter three groups were incubated with MPP+ (0.5 mmol/L) for 24 h as PD model cells.The cells in SKP1 interference group were transfected with lentivirus SKP1-siRNA, and the cells in SKP1 interference+ MG132 group were transfected with lentivirus SKP1 siRNA and added with MG132 (0.5 μmol/L) for 24 h. The protein levels and mRNA levels of SKP1, microtubule-associated protein light chain 3 (LC3), lysosome-associated membrane protein (LAMP), α-syn, ubiquitin activating enzyme E1 (UBE1), parkin, and p27 in cells were detected by Western blot and RT-PCR.Flow cytometry was used to detect cell apoptosis and cycle level, and CCK-8 method was used to detect cell proliferation level.Co-immunoprecipitation method was used to explore the interaction between SKP1 and p27. SPSS 23.0 software was used for statistical analysis. One-way ANOVA was used for comparison among groups, and LSD test was used for further pairwise comparison.Results:RT-PCR and Western blot results showed that the mRNA levels and protein levels of autophagy related proteins and ubiquitin related proteins LC3, LAMP2, α-syn, UBE1, parkin and p27 in the four groups were statistically significant(mRNA: F=99.155, 43.028, 138.464, 28.200, 22.009, 28.147, all P<0.05; F=245.517, 157.634, 315.920, 2 336.472, 477.429, 2 350.201, all P<0.05). The mRNA and protein levels of LC3, Lamp2, α-syn and p27 in SKP1 interference group were lower than those in MPP+ group (all P<0.05), while the mRNA and protein levels of UBE1 and parkin were higher than those in MPP+ group (all P<0.05). The mRNA and protein levels of LC3, α-syn and p27 in SKP1 interference+ MG132 group were higher than those in SKP1 interference group (all P<0.05), and the mRNA and protein levels of UBE1 and parkin were lower than those in SKP1 interference group (all P<0.05). The results of flow cytometry and CCK-8 method showed that the apoptosis rate and cell inhibition rate among the four groups were significantly different( F=2 749.420, 171.508, both P<0.05). The apoptosis rate of SKP1 interference group was lower than that of MPP+ group ((8.22±0.25)%, (15.30±0.21)%, P<0.05), while the cell inhibition rate of SKP1 interference group was lower than that of MPP+ group((26.31±3.73)%, (55.05±3.84)%, P<0.05). The apoptosis rate of SKP1 interference+ MG132 group ((9.49±0.07)%) was higher than that of SKP1 interference group, and the cell inhibition rate ((36.06±2.85)%) was higher than that of SKP1 interference group (both P<0.05). The results of immunoprecipitation method showed that P27 decreased after SKP1 immunoprecipitation. Conclusion:After SKP1 gene was interfered, the autophagy function of PD cells decreased, which may be related to parkin promoting α-syn ubiquitination, activating UBE1/ Parkin-mediated UPS pathway to degrade α-syn, and mediating P27 to inhibit apoptosis.
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Ubiquitin-proteasome system (UPS) plays an important role in neurodegenerative diseases, such as Alzheimer's disease (AD), Parkinson's disease (PD), and Huntington's disease (HD). The discovery of UPS activators for anti-neurodegenerative diseases is becoming increasingly important. In this study, we aimed to identify potential UPS activators using the high-throughput screening method with the high-content fluorescence imaging system and validate the neuroprotective effect in the cell models of AD. At first, stable YFP-CL1 HT22 cells were successfully constructed by transfecting the YFP-CL1 plasmid into HT22 cells, together with G418 screening. The degradation activity of the test compounds via UPS was monitored by detecting the YFP fluorescence intensity reflected by the ubiquitin-proteasome degradation signal CL1. By employing the high-content fluorescence imaging system, together with stable YFP-CL1 HT22 cells, the UPS activators were successfully screened from our established TCM library. The representative images were captured and analyzed, and quantification of the YFP fluorescence intensity was performed by flow cytometry. Then, the neuroprotective effect of the UPS activators was investigated in pEGFP-N1-APP (APP), pRK5-EGFP-Tau P301L (Tau P301L), or pRK5-EGFP-Tau (Tau) transiently transfected HT22 cells using fluorescence imaging, flow cytometry, and Western blot. In conclusion, our study established a high-content fluorescence imaging system coupled with stable YFP-CL1 HT22 cells for the high-throughput screening of the UPS activators. Three compounds, namely salvianolic acid A (SAA), salvianolic acid B (SAB), and ellagic acid (EA), were identified to significantly decrease YFP fluorescence intensity, which suggested that these three compounds are UPS activators. The identified UPS activators were demonstrated to clear AD-related proteins, including APP, Tau, and Tau P301L. Therefore, these findings provide a novel insight into the discovery and development of anti-AD drugs.
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Humans , Alzheimer Disease/drug therapy , Neuroprotective Agents , Optical Imaging , Proteasome Endopeptidase Complex , UbiquitinABSTRACT
【Objective】 To explore the potential biomarkers and related enrichment pathways of dilated cardiomyopathy （DCM） by bioinformatics methods. 【Methods】 The data sets related to DCM in GEO database were searched， and microarray data sets GSE42955 and GSE1869 of human cardiomyocytes were extracted. Then， the differentially expressed genes （DEGS） were analyzed using R language， and the protein-protein interaction network was analyzed to identify the core genes and core modules of differential expression. The gene ontology database （GO） enrichment and Kyoto Gene and Genome Encyclopedia （KEGG） pathway analyses were performed. The data sets related to DCM in ArrayExpress database were searched， and the human cardiomyocytes microarray data set E-TABM-480 was extracted to verify the expressions of core genes and modules. 【Results】 We identified 10 DEGS， namely， DZIP3， FBXO32， BTBD6， FBXL5， ASB8， COMMD1， LTN1， FBXO21， RCHY1 and ARIH2， and the core DEG was DZIP3. After GO and KEGG analyses， the GO and KEGG of the above DEGS were mainly related to the ubiquitin-proteasome system. 【Conclusion】 Bioinformatics analysis shows that the ubiquitin-proteasome system plays an important role in the pathogenesis of DCM， and the mechanism remains to be further studied.
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Targeted protein degradation (TPD) technology facilitates specific and efficient degradation of disease-related proteins through hijacking the two major protein degradation systems in mammalian cells: ubiquitin-proteasome system and lysosome pathway. Compared with traditional small molecule-inhibitors, TPD-based drugs exhibit the characteristics of a broader target spectrum. Compared with techniques interfere with protein expression on the gene and mRNA level, TPD-based drugs are target-specific, efficaciously rapid, and not constrained by post-translational modification of proteins. In the past 20 years, various TPD-based technologies have been developed. Most excitingly, two TPD-based therapeutic drugs have been approved by FDA for phase Ⅰ clinical trials in 2019. Despite of the early stage characteristics and various obstructions of the TPD technology, it could serve as a powerful tool for the development of novel drugs. This review summarizes the advances of different degradation systems based on TPD technologies and their applications in disease therapy. Moreover, the advantages and challenges of various technologies were discussed systematically, with the aim to provide theoretical guidance for further application of TPD technologies in scientific research and drug development.
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Animals , Proteasome Endopeptidase Complex/metabolism , Protein Processing, Post-Translational , Proteins/metabolism , Proteolysis , TechnologyABSTRACT
Pluripotent stem cells (PSCs) can immortally self-renew in culture with a high proliferation rate, and they possess unique metabolic characteristics that facilitate pluripotency regulation. Here, we review recent progress in understanding the mechanisms that link cellular metabolism and homeostasis to pluripotency regulation, with particular emphasis on pathways involving amino acid metabolism, lipid metabolism, the ubiquitin-proteasome system and autophagy. Metabolism of amino acids and lipids is tightly coupled to epigenetic modification, organelle remodeling and cell signaling pathways for pluripotency regulation. PSCs harness enhanced proteasome and autophagy activity to meet the material and energy requirements for cellular homeostasis. These regulatory events reflect a fine balance between the intrinsic cellular requirements and the extrinsic environment. A more complete understanding of this balance will pave new ways to manipulate PSC fate.
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Pluripotent stem cells (PSCs) can immortally self-renew in culture with a high proliferation rate, and they possess unique metabolic characteristics that facilitate pluripotency regulation. Here, we review recent progress in understanding the mechanisms that link cellular metabolism and homeostasis to pluripotency regulation, with particular emphasis on pathways involving amino acid metabolism, lipid metabolism, the ubiquitin-proteasome system and autophagy. Metabolism of amino acids and lipids is tightly coupled to epigenetic modification, organelle remodeling and cell signaling pathways for pluripotency regulation. PSCs harness enhanced proteasome and autophagy activity to meet the material and energy requirements for cellular homeostasis. These regulatory events reflect a fine balance between the intrinsic cellular requirements and the extrinsic environment. A more complete understanding of this balance will pave new ways to manipulate PSC fate.
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Pluripotent stem cells (PSCs) can immortally self-renew in culture with a high proliferation rate, and they possess unique metabolic characteristics that facilitate pluripotency regulation. Here, we review recent progress in understanding the mechanisms that link cellular metabolism and homeostasis to pluripotency regulation, with particular emphasis on pathways involving amino acid metabolism, lipid metabolism, the ubiquitin-proteasome system and autophagy. Metabolism of amino acids and lipids is tightly coupled to epigenetic modification, organelle remodeling and cell signaling pathways for pluripotency regulation. PSCs harness enhanced proteasome and autophagy activity to meet the material and energy requirements for cellular homeostasis. These regulatory events reflect a fine balance between the intrinsic cellular requirements and the extrinsic environment. A more complete understanding of this balance will pave new ways to manipulate PSC fate.
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Blocking the biological functions of scaffold proteins and aggregated proteins is a challenging goal. PROTAC proteolysis-targeting chimaera (PROTAC) technology may be the solution, considering its ability to selectively degrade target proteins. Recent progress in the PROTAC strategy include identification of the structure of the first ternary eutectic complex, extra-terminal domain-4-PROTAC-Von-Hippel-Lindau (BRD4-PROTAC-VHL), and PROTAC ARV-110 has entered clinical trials for the treatment of prostate cancer in 2019. These discoveries strongly proved the value of the PROTAC strategy. In this perspective, we summarized recent meaningful research of PROTAC, including the types of degradation proteins, preliminary biological data in vitro and in vivo, and new E3 ubiquitin ligases. Importantly, the molecular design, optimization strategy and clinical application of candidate molecules are highlighted in detail. Future perspectives for development of advanced PROTAC in medical fields have also been discussed systematically.
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OBJECTIVE: To explore the effects of human A30P mutant α-synuclein (α-syn) on autophagy lysosome pathway and ubiquitin proteasome system. METHODS: Constructing stable cell lines expressing human A30P mutant α-syn in PC12 cells, and detecting the levels of autophagy related proteins LC3-II and p62 as well as ubiquitinated proteins. Furthermore, the influence of A30P mutant α-syn on cell viability upon normal and stress conditions was conducted by MTT assay. RESULTS: Expressing A30P mutant α-syn could significantly reduce autophagy related protein LC3-II level and increase level of autophagy substrate p62, as well as promote aggregation of ubiquitinated proteins. Otherwise, expressing A30P mutant α-syn did not reduce cell viability under normal conditions. However, cell viability was significantly reduced under treatment with neurotoxin rotenone or serum free condition in A30P mutant α-syn groups compared with empty vector group. CONCLUSION: Over expression of human A30P mutant α-syn could impair the protein degradation system and increase the sensitivity of cells to toxic insults.
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OBJECTIVE: Ubiquitin-specific peptidase 46 gene (USP46) polymorphisms is part of ubiquitin-proteasome system, which is responsible for dynamic cellular processes such as the regulation of cell cycle. USP46 has been reported to be associated with major depressive disorder. The objective of the present study was to investigate the association of USP46 polymorphisms with affective temperamental traits in healthy subjects. METHODS: A total of 557 Korean healthy volunteers were recruited, and 545 subjects (328 male, 217 female) were included in the final analysis. The DNA of the subjects was isolated from saliva samples. Two single-nucleotide polymorphisms (SNPs) rs346005, rs2244291 in USP46 were genotyped. Affective temperaments were assessed using the Korean version of Temperament Evaluation of the Memphis, Pisa, Paris, and San Diego Autoquestionnaire (TEMPS-A). RESULTS: A significant association was found between rs346005 genotypes and TEMPS-A only in male subjects. In particular, subjects with the CC genotype of rs346005 showed a more depressive temperament than subjects with AA or CA genotypes in males. For rs2244291, there were no associations between the rs2244291 genotypes and TEMPS-A scores. CONCLUSION: Some affective temperaments may serve as a genetic predisposing factors for affective disorders, such as depressive disorder, via vulnerability genes related to the ubiquitin-proteasome system.
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Humans , Male , Causality , Cell Cycle , Depressive Disorder , Depressive Disorder, Major , DNA , Genetic Association Studies , Genotype , Healthy Volunteers , Mood Disorders , Saliva , Temperament , VolunteersABSTRACT
Ubiquitin-proteasome system (UPS) is the important protein degradation system in eukaryotic cells, participates in cell cycle, gene transcription, antigen-presenting, cell proliferation and differentiation, signal transduction and many other physiological processes.UPS dysfunction relates to pathogenic mechanisms in a variety of diseases such as cancer, neurodegenerative diseases and cardiovascular disease.In recent years, more and more researches confirmed that UPS exists in the retina, some retinal damage appeared in patients with neurodegenerative conditions.UPS is involved in the pathogenesis of diabetic retinopathy, age-related macular degeneration, macular pigment degeneration and other retinal diseases by regulating retinal oxidative stress, inflammation, angiogenesis, nerve damage, signal transduction and so on.Some signaling pathways, such as nuclear factor κB (NF-κB), transforming growth factor-β (TGF-β) and reactive oxygen species (ROS) play an important role.Their proteins degradation and synthesis of imbalances have a significant impact on the pathophysiological process of retinal diseases.Proteasome inhibitors can reduce inflammation pathological changes in retinal lesions.This review focused on the research progress of UPS in the development of retinopathy.
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Ubiquitin-proteasome system ( UPS ) is the important protein degradation system in eukaryotic cells,participates in cell cycle, gene transcription, antigen-presenting, cell proliferation and differentiation, signal transduction and many other physiological processes. UPS dysfunction relates to pathogenic mechanisms in a variety of diseases such as cancer, neurodegenerative diseases and cardiovascular disease. In recent years, more and more researches confirmed that UPS exists in the retina,some retinal damage appeared in patients with neurodegenerative conditions. UPS is involved in the pathogenesis of diabetic retinopathy, age-related macular degeneration, macular pigment degeneration and other retinal diseases by regulating retinal oxidative stress,inflammation,angiogenesis,nerve damage,signal transduction and so on. Some signaling pathways,such as nuclear factor κB (NF-κB),transforming growth factor-β ( TGF-β) and reactive oxygen species ( ROS) play an important role. Their proteins degradation and synthesis of imbalances have a significant impact on the pathophysiological process of retinal diseases. Proteasome inhibitors can reduce inflammation pathological changes in retinal lesions. This review focused on the research progress of UPS in the development of retinopathy.
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@#[Abstract] Objective: To investigate the impact of FBXW7 gene mutation on cell proliferation, apoptosis, migration, and invasion processes of colorectal cancer HCT-116 cell line. Methods: Recombinant plasmids carrying wild-type and mutant-type FBXW7 SNP were constructed and transfected into HCT-116 cell line; the FBXW7 protein expression level in HCT-116 strains after transfection was detected by Western blotting. Subsequently, cell proliferation capacity was tested by CCK-8 assay; tumor cell colony formation ability was tested by HTCA; cell apoptosis function was tested by FCM; cell migration and invasion were tested by scratch assay and Transwell assay, respectively. Results: Higher HBXW7 protein expression level was detected in HCT-116 strain transfected with wild-type HBXW7 in comparison to the control group (strains transfected with mutant-type HBXW7), negative-control (strains transfected with empty plasmids), and blank-control (strains untransfected) (all P<0.05). Compared with the other groups, strains transfected with wildtype HBXW7 exhibited significantly reduced proliferation, colony formation, migration and invasion ability (all P<0.05), but obviously increased apoptosis rate (P<0.05). Conclusion： ：FBXW7 gene mutation can down-regulate its protein expression, and further promote the proliferation, migration and invasion as well as inhibit the apoptosis of HCT-116 cells.
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Objective: To investigate the mechanisms of nuclear export signal of androgen receptor (NESAR) in the regulation of androgen receptor (AR) protein expression and stability in prostate cancer.Methods: The green fluorescent protein fusion protein expression vectors pEGFP-AR(1-918aa), pEGFP-NESAR (743-817aa), pEGFP-NAR (1-665aa) and pEGFP-NAR-NESAR, and lysine mutants of NESAR pEGFP-NESAR K776R, pEGFP-NESAR K807R and pEGFP-NESAR K776R/K807R, were transiently transfec-ted into prostate cancer cell line PC3.Fluorescence microscopy, Western blot and immunoprecipitation were used to detect NESAR regulation of androgen receptor stability.Results: Under the fluorescence microscope, NESAR-containing fusion proteins were cytoplasmic localization, and their fluorescence intensities were much weaker than those without NESAR.The expression levels of NESAR-containing fusion proteins were significantly lower than those without NESAR.The half-lives of GFP-NESAR and GFP-NAR-NESAR were less than 6 h, while the expression of GFP and GFP-NAR was relatively stable and the half-life was more than 24 h in the presence of cycloheximide.The expression levels of GFP-NESAR were significantly increased by proteasome inhibitor MG132 treatment in a dose-dependent manner;in contrast, MG132 did not show any significant effect on the protein levels of GFP.When new protein synthesis was blocked, MG132 could also prevent the degradation of GFP-NESAR in the transfected cells in the presence of cycloheximide, while it had no significant effect on GFP protein stability in the parallel experiment.GFP immunoprecipitation showed that the ubiquitination level of GFP-NESAR fusion protein was significantly higher than that of the GFP control.The mutations of lysine sites K776 and K807 in NESAR significantly reduced the level of ubiquitination, and showed increased protein stability, indicating that they were the key amino acid residues of NESAR ubiquitination.Conclusion: NESAR was unstable and decreased the stability of its fusion proteins.NESAR was the target of polyubiquitination and mediated the degradation of its fusion proteins through the ubiquitin-proteasome pathway in prostate cancer cells.Our research provides a new way to regulate the level and/or activity of AR proteins, thus helping us understand the molecular mechanisms of AR degradation and strict control of AR in the progression to castration-resistance.
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Objective Nrf2 is an important neuroprotective factor and the ubiquitin proteasome system ( UPS) , as a highly specific intracellular protein degradation pathway, plays an important role in maintaining gene and protein functions.This paper pres-ents a preliminary study on the relationship between Nrf2 and the ubiquitin proteasome system in the mouse model of traumatic brain in-jury ( TBI) . Methods Forty-two healthy male ICR mice were randomly divided into three groups: control, TBI +sulforaphane ( SFN) and TBI+vehicle, and 12 Nrf2-knockout mice were included in the TBI+Nrf2 -/-group.The animals of the TBI+SFN group were treated with SFN while those of the TBI+vehicle group with the same volume of 10%corn oil at 5 minutes after TBI.At 24 hours after TBI, brain samples were collected from the mice for determining the Nrf2 expression and ubiquitinated protein content by Western blot and the changes in the Nrf2 and ubiquitinated proteins were observed by immunohistochemistry and electron microscopy. Results Compared with the controls, the mice in the TBI+vehicle group showed significantly increased expressions of Nrf2 ( 0.09 ± 0.02 vs 0.66 ±0.09, P<0.05) and ubiquitinated proteins (3.27 ± 0.21 vs 10.58 ±0.75, P<0.05).In comparison with animals in the TBI+vehicle group, those in the TBI+SFN group exhibited a signifi-cant increase in the Nrf2 protein level (0.66 ±0.09 vs 1.22 ±0.14, P<0.05) but a decrease in the ubiquitinated protein level (10.58 ±0.75 vs 6.97 ±0.86, P<0.05), and those in the TBI+Nrf2 -/-group showed a markedly decreased expression of the Nrf2 protein (0.66 ±0.09 vs 0.17 ±0.02, P<0.05) but increased expression of the ubiquitinated protein (10.58 ±0.75 vs 14.35 ± 0.65, P<0.05).Similar results were observed by immunohistochemistry and electron microscopy. Conclusion Nrf2 played a neu-roprotective role in the mouse model of traumatic brain injury by regulating the ubiquitin proteasome system.