Effect of ganoderma spore on mitochondrial autophagy and apoptosis in testicular tissue of diabetic rats / 中国组织工程研究

BACKGROUND:As a common complication of diabetes mellitus,male reproductive disorders have received increasing attention in recent years.Ganoderma spore have hypoglycemic,antioxidant and anti-inflammatory effects,but the regulatory mechanism for diabetic testicular tissue has not been fully elucidated. OBJECTIVE:To investigate the effect of ganoderma spore on the PTEN-induced kinase 1/E3 ubiquitin ligase pathway and cell apoptosis in testicular tissue of diabetic rats. METHODS:Forty male Sprague-Dawley rats were randomly divided into normal group,high fat and high sugar group,diabetic group and ganoderma spore group,with 10 rats in each group.The latter three groups were given high fat/high sugar diet until the end of the experiment.After 1 month of high fat/high sugar diet,the diabetic and ganoderma spore groups were given intraperitoneal injection of streptozotocin(30 mg/kg per day)to establish type 2 diabetic rat models.After successful modeling,the ganoderma spore group was intragastrically given ganoderma spore(300 mg/kg per day),and the other groups were given the same amount of normal saline for continuous 12 weeks.The sperm number and morphology were detected.The histopathological changes of the testicle were observed.Serum testosterone and oxidative stress levels in testicular tissue were measured.The levels of PTEN-induced kinase 1,E3 ubiquitin ligase,and anti-nucleoporin p62 were analyzed by immunohistochemistry and the expression of PTEN-induced kinase 1,E3 ubiquitin ligase,anti-nucleoporin p62,programmed cell death-1,microtubule-associated protein light chain 3 Ⅱ/Ⅰ,caspase 3,cleaved-caspase 3 were detected by western blot assay. RESULTS AND CONCLUSION:Compared with the normal group and the high fat and high sugar group,the diabetic group had decreased sperm number(P＜0.01),increased sperm malformation rate(P＜0.01),and decreased serum testosterone level(P＜0.01).Compared with the diabetic group,ganoderma spore intervention could increase the sperm number(P＜0.05),decrease the malformation rate(P＜0.01),and increase the serum testosterone level(P＜0.01).Compared with the normal group and the high fat and high sugar group,the malondialdehyde level in testis tissue was increased in the diabetic group(P＜0.01),while the levels of glutathione deoxidase and superoxide dismutase decreased(P＜0.01).Compared with the diabetic group,the malondialdehyde level in testis tissue was decreased in the ganoderma spore group(P＜0.01),and the levels of glutathione deoxidase and superoxide dismutase increased(P＜0.01).Immunohistochemical staining showed that compared with the normal group and the high fat and high sugar group,the positive expressions of PTEN-induced kinase 1 and E3 ubiquitin ligase in testicular tissue were decreased in the diabetic group,while the positive expressions of anti-nucleoporin p62 were increased.Compared with the diabetic group,the positive expressions of PTEN-induced kinase 1 and E3 ubiquitin ligase in testicular tissue e were increased in the ganoderma spore group,while the positive expression of anti-nucleoporin p62 was decreased.Western blot assay results indicated that compared to the normal group and the high fat and high sugar group,the expression of PTEN-induced kinase 1 and E3 ubiquitin ligase,programmed cell death-1 and the ratio of microtubule-associated protein light chain 3 Ⅱ/Ⅰ protein were decreased in the diabetic group(P＜0.05 or P＜0.01),while the expressions of anti-nucleoporin p62,caspase3 and cleaved-caspase3 were increased(P＜0.01).Compared with the diabetic group,ganoderma spore intervention could elevate the expression of PTEN-induced kinase 1 and E3 ubiquitin ligase,programmed cell death-1 and the ratio of microtubule-associated protein light chain 3 Ⅱ/Ⅰ protein(P＜0.05 or P＜0.01)as well as reduce the expressions of anti-nucleoporin p62,caspase3 and cleaved-caspase3(P＜0.05 or P＜0.01).Overall,ganoderma spores may activate the PTEN-induced kinase 1/E3 ubiquitin ligase pathway to enhance autophagy in testicular tissue and reduce apoptosis in tissue cells,so as to protect testicular tissue.

Research progress in the role of E3 ubiquitin ligases in viral infection / 中华微生物学和免疫学杂志

Ubiquitination modifications are a kind of post-translational modifications of proteins widely found in eukaryotes and involved in a variety of biological activities. E3 ubiquitin ligases are an important component of the ubiquitin system, with the function of specific recognition of substrate proteins and mediation of different types of ubiquitination modifications. They can regulate the function and life time of substrate proteins. Recent studies have shown that E3 ubiquitin ligases are widely involved in the regulation of the host innate immune response and can directly or indirectly influence viral infection. Moreover, viruses are able to encode or hijack E3 ubiquitin ligases in their long-term evolution, allowing them to play an important role in viral infection and replication cycle. This paper reviewed the progress in the mechanisms of E3 ubiquitin ligases in innate immune responses and viral infection in recent years.

The role of E3 ubiquitin ligases in bone homeostasis and related diseases

The ubiquitin-proteasome system (UPS) dedicates to degrade intracellular proteins to modulate demic homeostasis and functions of organisms. These enzymatic cascades mark and modifies target proteins diversly through covalently binding ubiquitin molecules. In the UPS, E3 ubiquitin ligases are the crucial constituents by the advantage of recognizing and presenting proteins to proteasomes for proteolysis. As the major regulators of protein homeostasis, E3 ligases are indispensable to proper cell manners in diverse systems, and they are well described in physiological bone growth and bone metabolism. Pathologically, classic bone-related diseases such as metabolic bone diseases, arthritis, bone neoplasms and bone metastasis of the tumor, etc., were also depicted in a UPS-dependent manner. Therefore, skeletal system is versatilely regulated by UPS and it is worthy to summarize the underlying mechanism. Furthermore, based on the current status of treatment, normal or pathological osteogenesis and tumorigenesis elaborated in this review highlight the clinical significance of UPS research. As a strategy possibly remedies the limitations of UPS treatment, emerging PROTAC was described comprehensively to illustrate its potential in clinical application. Altogether, the purpose of this review aims to provide more evidence for exploiting novel therapeutic strategies based on UPS for bone associated diseases.

The mechanisms of type 2 diabetic skeletal muscle atrophy and the effects of commonly used hypoglycemic drugs: a review / 药学学报

Type 2 diabetes is a hypermetabolic disease characterized with disorders of glucose/lipid metabolism, absolute or relative lack of insulin, and can induce skeletal muscle atrophy. Hyperglycemia, hyperlipidemia, insulin resistance, and abnormal release of inflammatory factors can lead to abnormal signal transduction in skeletal muscle, thus make protein synthesis and degradation imbalance and eventually causing muscle atrophy. Under normal conditions, insulin-like growth factor 1 (IGF-1)/insulin can activate phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT). AKT not only increases protein synthesis through mammalian target protein of rapamycin (mTOR), but also phosphorylates forkhead box O (FoxO) transcription factor and then inhibits the transcription of several ubiquitin ligases (such as MAFbx/atrogin-1 and MuRF1), or autophagy related genes. The weakened IGF-1/PI3K/AKT pathway in type 2 diabetes is an important factor leading to skeletal muscle atrophy. Studies have shown that the commonly used anti-type 2 diabetic drugs have different effects in regulating the synthesis and degradation of skeletal muscle protein. Studies reported that drugs with effect of anti-diabetic muscle atrophy include thiazolidinediones, glucagon-like peptide analogs, glucose-sodium cotransporter 2 inhibitors, etc.; drugs that are still in controversial or even promote skeletal muscle atrophy include metformin, and some sulfonylurea or non-sulfonylurea insulin secretagogues. This article overviewed and analyzed the currently commonly used drugs for type 2 diabetes and summarized the related mechanisms, with the aim to provide references for the rational applications of drugs for type 2 diabetes.

Effect of Gandou Decoction on Mitophagy in Toxic Milk （TX） Mouse Model of Wilson Disease Based on Pink1/Parkin Pathway / 中国实验方剂学杂志

ObjectiveTo investigate the effects of Gandou decoction （GDD） on the mitophagy of hippocampal neurons in toxic milk （TX） mouse model of Wilson disease and explore the protective mechanism of GDD against neuron injury through the PTEN induced kinase 1 （Pink1） /E3 ubiquitin ligase （Parkin） pathway. MethodSixty mice were randomly divided into a blank group， a model group， a penicillamine group （0.09 g·kg-1）， and low- （5.5 g·kg-1）， medium- （11 g·kg-1）， and high-dose （22 g·kg-1） GDD groups， and treated correspondingly by gavage for 8 weeks. Morris water maze， traction test， and pole test were used for the evaluation of animal behaviors. Hematoxylin-eosin （HE） staining and transmission electron microscopy were used to observe cell apoptosis， ultrastructure， autophagy， and mitochondrial structure. The levels of superoxide dismutase （SOD）， reactive oxygen species （ROS）， and malondialdehyde （MDA） were detected by enzyme-linked immunosorbent assay （ELISA）. Real-time fluorescence-based quantitative polymerase chain reaction （Real-time PCR） was used to detect the mRNA expression of Pink1， Parkin， autophagy-associated protein Beclin-1， microtubule-associated protein 1 light chain 3Ⅱ （LC3Ⅱ）， and p62. Western blot was conducted to detect the protein expression of Pink1， Parkin， Beclin-1， LC3Ⅱ/Ⅰ， and p62. ResultCompared with the blank group， the model group showed prolonged escape latency， decreased times of platform crossing， lower score in the traction test， and longer pole climbing time （P<0.01）. Compared with the model group， the medium- and high-dose GDD groups and the penicillamine group showed shortened escape latencies， increased times of platform crossing， higher scores in the traction test， and shortened pole climbing time （P<0.01）. Compared with the blank group， the model group displayed severely damaged neurons and increased autophagosomes. Compared with the model group， the medium- and high-dose GDD groups and the penicillamine group showed improved neuron damage and reduced autophagosomes. The levels of ROS and MDA were higher and SOD was lower in the model group than those in the blank group （P<0.01）， while the levels of the above indicators were reversed by GDD intervention as compared with the model group （P<0.01）. Compared with the blank group， the model group exhibited up-regulated mRNA and protein expression of Pink1， Parkin， LC3Ⅱ， and Beclin-1 and down-regulated p62 （P<0.05）. Compared with the model group， the medium- and high-dose GDD groups showed reduced mRNA and protein expression of Pink1， Parkin， LC3Ⅱ， and Beclin-1 and increased p62 （P<0.05， P<0.01）. ConclusionGDD can significantly inhibit the excessive mitophagy in neurons of TX mice and protect neurons from damage. The mechanism may be related to the regulation of the Pink1/Parkin pathway.

Signaling pathways involved in inhibition of macrophage phagocytosis by TcpC of uropathogenic Escherichia coli / 中华微生物学和免疫学杂志

Objective:To investigate the signaling pathway of inhibiting macrophage phagocytosis of TIR domain-containing protein encoded by Escherichia coli (TcpC) N-terminal ubiquitin ligase active fragments of uropathogenic Escherichia coli. Methods:Bioinformatics software was used to analyze the amino acid sequences and the function of TcpC N-terminal ubiquitin ligase active fragments as well as the functional sites. PCR was performed to amplify tcpc-330, tcpc-450 and tcpc-510 genes and a prokaryotic expression system was constructed to express the target proteins. The recombinant proteins rTcpC-N110, rTcpC-N150 and rTcpC-N170 were purified by Ni-NTA affinity chromatography. LPS in the recombinant proteins was removed by Detoxi-gel chromatography. The expression of MyD88 at protein and mRNA levels in macrophages incubated with rTcpC-N110, rTcpC-N150, rTcpC-N170 or rTcpC-TIR was detected by Western blot and qRT-PCR. The activation of NF-κB signal pathway and the levels of proinflammatory factors in macrophages incubated with the above TcpC protein fragments were measured by Western blot and ELISA, respectively. Results:Cys12, Trp104 and Trp106 in the N-terminal fragment of TcpC were crucial amino acids in maintaining its ubiquitin ligase activity. The target recombinant proteins rTcpC-N110, rTcpC-N150 and rTcpC-N170 were successfully expressed and purified. After Detoxi-gel chromatography, rTcpC-N110, rTcpC-N150 and rTcpC-N170 extracts were undetectable for LPS. TcpC ubiquitin ligase fragments inhibited the expression of MyD88 at protein level, but not affect its expression at mRNA level in macrophages. LPS-induced phosphorylation of NF-κB signaling pathway-related proteins p50 and p65 was significantly inhibited in macrophages treated with TcpC ubiquitin ligase fragments. Moreover, LPS-induced production of pro-inflammatory factors was also significantly inhibited.Conclusions:The recombinant proteins rTcpC-N110, rTcpC-N150 and rTcpC-N170 could inhibit the expression of MyD88 at protein level and suppress the activation of NF-κB signaling pathway, suggesting that they were closely related to the inhibition of innate immune activity of macrophages.

Recombinant Expression and Purification of F-box and Leucine-rich Repeat Protein 5 (FBXL5) using a Prokaryotic Expression System

Background@#The F-box and Leucine-rich Repeat Protein 5 (FBXL5), a member of the E3 ligases, is considered to be the central iron sensor in mammals. The cryo-EM structure of FBXL5 in complex with IRP2 and SKP1 was reported by Wang et.al. in 2020. Surprisingly, a 2Fe-2S cluster seemed to be responsible for the iron-sensing capability of FBXL5. @*Objectives@#To further explore the mechanism of its regulation, it is important to study the interaction of FBXL5 with other proteins under regulated conditions so we attempted to express FBXL5 in the hopes of studying its interaction with IRPs in vitro. @*Methodology@#Plasmids were constructed to express FBXL5 in Escherichia coli expression hosts. Purification of an MBP-fused FBXL5 and GST-fused FBXL5 were performed using affinity chromatography. Peptide Mass Fingerprinting, Circular Dichroism spectroscopy, and SEC-MALS were employed to analyze the purified MBP-FBXL5. GST-FBXL5 was also used in a pull-down assay with Iron Regulatory Protein 1 (IRP1). @*Results@#We are successful in expressing and partially purifying full-length FBXL5 using E. coli with the aid of a protein tag, the maltose binding protein (MBP) tag. However, cleavage of the protein tag resulted in decreased stability of FBXL5 as shown in SEC-MALS data. CD spectroscopy showed consistent secondary structure of FBXL5. A preliminary pull-down assay of GST-FBXL5 with IRP1 showed that IRP1 displayed interaction with the recombinant GST-FBXL5. @*Conclusion@#FBXL5, a 78-kDa mammalian protein was overexpressed in a prokaryotic expression system made stable by a fusion protein. The interaction of GST-FBXL5 with IRP1 also shows that it is possible to study their interaction in vitro.

The Role of NEDD4-1 in Tumorigenesis of the Digestive System / 中国生物化学与分子生物学报

Neural precursor cell Expressed‚Developmentally Down-regulated protein 4 (NEDD4-1‚ also known as NEDD4 in some papers) is a tumor-related protein that has attracted much attention in recent years. It belongs to the E3 HECT (homologous to E6 associated protein C terminus) ubiquitin ligase‚ which could ubiquitinate various proteins that are subsequently degraded in lysosomes or proteasomes‚ or mediate their nuclear-cytoplasmic translocation‚ or indirectly affect various signaling pathways of different malignant tumors. With the deepening of a large number of tumor-related experiments‚ it has been found that NEDD4-1 can affect the biological behavior of tumors by regulating cell cycle‚ invasion and metastasis of cancer cells‚ antagonize drug resistance and many other pathways. In digestive system tumors‚ NEDD4-1 mainly promotes the proliferation‚ invasion and migration of hepatocellular carcinoma through multiple pathways such as PTEN/ PI3K/ Akt‚ TGF-β‚ Hippo and LDLRAD4. In pancreatic cancer‚ NEDD4-1 acted as an oncogene in the PI3K/ Akt signaling pathway‚ but acted as a tumor suppressor gene in the Myc-Sirt2 signaling circuit. In gastric and colorectal cancer‚ the NEDD4-1-related signaling pathways are different from other digestive system tumors. NEDD4-1 promotes gastric cancer progression and metastasis (via the EGFR signaling pathway) and inhibits colorectal cancer tumor growth (via the Wnt signaling pathway) independently of the PTEN/ PI3K/ Akt pathway. NEDD4-1 has become a hot research direction for therapeutic purposes. In this paper‚ we summarize the functions‚ signaling pathways and potential inhibitors of NEDD4-1 in different digestive system tumors‚ and discuss the relationship between NEDD4-1 and different signaling pathways‚ aiming to provide important reference data for cancer therapy.

ARIH2 Inhibits the Linear Ubiquitination Ligase Activity of LUBAC / 中国生物化学与分子生物学报

Linear ubiquitination plays an important role in tumor and the immune system. Linear ubiq- uitin chain assembly complex ( LUBAC) is the only known ubiquitin ligase that can catalyze the synthesis of linear ubiquitin chains. We found that ubiquitin ligase ariadne homolog 2 ( ARIH2) was a new interacting protein of LUBAC, and ARIH2 inhibited the level of linear ubiquitination of substrates by LUBAC. We further demonstrated that ARIH2 interacted with HOIP by Co-IP experiment, and that HOIP interacted with ARIH2 through the ZF-NZF ( zinc finger-Npl4-Zinc finger) domain by GST pull-down experiments. Moreover, we showed that LUBAC could not modify ARIH2 by linear ubiquitination; On the contrary, ARIH2 inhibited the linear ubiquitination level of LUBAC substrates. The mechanism may be that ARIH2 affects the ubiquitination level of SHANK-associated RH domain interacting protein ( SHARP- IN ), thereby affecting the enzyme activity of LUBAC, which leads to the weakening of the linear ubiquit- ination level of LUBAC to the substrate.

Influence of Circ_HECTD1 on OGD/R-induced hippocampal neuronal damage by regulating the miR-135a-5p/TP53INP1 axis / 中风与神经疾病杂志

@#Objective　To observe the influences of circular RNA HECT domain E3 ubiquitin ligase 1 (Circ_HECTD1) on the proliferation and apoptosis of HT22 cells and its regulatory mechanism on the microRNA-135a-5p (miR-135a-5p)/tumor protein 53-induced nuclear protein 1 (TP53INP1) axis by in vitro oxygen-glucose deprivation/reoxygenation (OGD/R)-induced hippocampal neuron damage.Methods　HT22 cells were routinely cultured,and the cells were separated into Con group,OGD/R group,si-NC group,and si-Circ_HECTD1 group,miR-NC group,miR-135a-5p group,si-Circ_HECTD1+anti-miR-NC group,and si-Circ_HECTD1+anti-miR-135a-5p group.qRT-PCR method was used to detect the expression of Circ_HECTD1,miR-135a-5p and TP53INP1 mRNA;MTT was used to detect cell viability;flow cytometry was used to detect apoptosis;dual-luciferase reporter gene experiment was applied to verify the targeting relationship between Circ_HECTD1 and miR-135a-5p,miR-135a-5p and TP53INP1;Western blot was applied to measure the protein expressions of Bax,Bcl-2 and TP53INP1.Results　After OGD/R induction,the expressions of Circ_HECTD1 and TP53INP1 in HT22 cells were up-regulated,the expression of miR-135a-5p was down-regulated,the cell survival rate and the expression of Bcl-2 protein were remarkably decreased,the apoptosis rate and the expression of Bax protein were remarkably increased (all P<0.05).Silencing the expression of Circ_HECTD1 could remarkably up-regulate the expression of miR-135a-5p in OGD/R-induced HT22 cells,down-regulate the expression of TP53INP1,increase cell survival rate and Bax protein expression,decrease cell apoptosis rate and Bcl-2 protein expression (all P<0.05).There was a targeting relationship between Circ_HECTD1 and miR-135a-5p,between miR-135a-5p and TP53INP1.Overexpression of miR-135a-5p could remarkably down-regulate the expression of TP53INP1,increase cell survival rate and Bcl-2 protein expression,decrease cell apoptosis rate and Bax protein expression (all P<0.05).Inhibition of miR-135a-5p expression could partially reverse the protective effect of silencing Circ_HECTD1 on HT22 cell damage.Conclusion　Silencing Circ_HECTD1 can regulate the miR-135a-5p/TP53INP1 axis and promote cell survival,inhibit cell apoptosis,and protect against OGD/R-induced hippocampal neuron damage.

Speckle type POZ adaptor protein (SPOP) and its role in cancer / La proteína adaptadora Speckle-type POZ (SPOP) y su papel en cáncer

Abstract Proteasomal degradation is an essential regulatory mechanism for cellular homeostasis maintenance. The speckle-type POZ adaptor protein (SPOP) is part of the ubiquitin ligase E3 cullin-3 RING-box1 complex, responsible for the ubiquitination and proteasomal degradation of biomolecules involved in cell cycle control, proliferation, response to DNA damage, epigenetic control, and hormone signaling, among others. Changes in SPOP have been associated with the development of different types of cancer, since it can act as a tumor suppressor mainly in prostate, breast, colorectal, lung cancer and liver cancer, due to point mutations and/or reduced expression, or as an oncogene in kidney cancer by protein overexpression. In endometrial cancer it has a dual role, since it can act as a tumor suppressor or as an oncogene. SPOP is a potential prognostic biomarker and a promising therapeutic target.

Resumen La degradación proteosómica es un mecanismo de regulación esencial para el mantenimiento de la homeostasis celular. La proteína adaptadora Speckle-type POZ (SPOP) hace parte del complejo ubiquitin ligasa E3 cullin-3 RING-box1, encargado de la ubiquitinación y degradación proteosomal de biomoléculas involucradas en el control del ciclo celular, proliferación, respuesta al daño de ADN, control epigenético, señalización hormonal, entre otros. Las alteraciones en SPOP han sido asociadas al desarrollo de diferentes tipos de cáncer, ya que puede actuar como supresor tumoral principalmente en cáncer de próstata, mama, colorrectal y pulmón, debido a mutaciones puntuales y/o expresión reducida o como oncogén en cáncer riñón por sobreexpresión de la proteína. En cáncer endometrial tiene un rol dual, ya que puede actuar como supresor tumoral o como oncogén. SPOP es considerado como un potencial biomarcador pronóstico y un objetivo terapéutico prometedor.

Progress of drugs targeting E3 ubiquitin ligase / 中国药理学通报

The ubiquitin-proteasome pathway is one of the most important pathways of cell protein degradation in eukaryotes, and plays an important role in the regulation of cell proliferation, differentiation, apoptosis, DNA repair and other physiological activities. E3 ubiquitin ligase is the major component of ubiquitinproteasome system, which is responsible for substrate recognition. The abnormal regulation of E3 ubiquitin ligase may cause many diseases such as cancer, Alzheimer's disease and Parkinson's disease. Here, we summarizes the progress of drugs targeting E3 ubiquitin ligase in cancer, Alzheimer's disease, Parkinson's disease, diabetic complications, atherosclerosis, and inflammatory bowel diseases. At present, only a few of small molecule antagonists or agonists targeting E3 ubiquitin ligase are under development. The study of natural products in China is leading the way in the world, and numerous natural products have been identified for pharmacological effects on E3 ubiquitin ligase, which may open up a new avenue for multiple complex diseases.

Emerging Roles of the TRIM Family in Autophagy / 中国生物化学与分子生物学报

Autophagy is a common cellular metabolic process, which is characterized by the formation of double membrane structures named autophagosomes to degrade intracellular components or invading foreign substances to maintain cellular homeostasis. Autophagy is crucial for maintaining cell homeostasis. The dysfunction of autophagy is closely related to the occurrence and development of various diseases, including tumors, neurodegenerative diseases, viral infection, immune diseases and so on. Autophagy may be a potential therapeutic target for these diseases. Therefore, the investigation of autophagy regulation is a hot issue in life science and medical research. The TRIM (tripartite motif-containing proteins) family is a set of proteins with E3 ubiquitin ligase activity and usually contains three conserved domains, a RING zinc finger structure, a B-box structure and a coiled helix domain. Many TRIM family members have been found to play important roles in autophagy regulation, the mechanism of which include modulating autophagy-related signaling pathways, regulating autophagy core molecules and acting as autophagy receptors, etc. TRIMs participate in many biological pathways through regulating autophagy, such as immunity, virus infection and tumors. This review covers the role of TRIM proteins in regulating autophagy, the molecular mechanism and the corresponding biological effects.

Localization of Melanoma-associated Antigen MAGEA1 and Identification of Its Interacting Proteins / 中国生物化学与分子生物学报

Melanoma associated antigen family A1 (MAGEA1) is expressed in germ cells and tumors of various histological origins, but its mechanism is still unclear. In this study, the eukaryotic recombinant MAGEA1 expression plasmids with Flag or GFP tags were constructed and transfected into HeLa and HEK293T cells. Western blotting, immunocytochemistry, co-immunoprecipitation, nuclear protein and cytoplasmic protein separation, and mitochondrial isolation were used to detect the expression and location of MAGEA1 and its interaction with other proteins in cells. The results of immunocytochemistry (ICC) and Western blotting showed that the overexpressed MAGEA1 was mainly localized in the cytoplasm and partially co-localized with mitochondria. Co-immunoprecipitation experiments verified the interactions between MAGEA1 and TRIM31, SNW1, HDAC1, and found that MAGEA1 may mainly interact with HDAC1 in the cytoplasm. The studies above indicate that MAGEA1 may be involved in different cellular biological processes and co-localize with mitochondria. It interacts with TRIM31, SNW1 and HDAC1, while MAGEA1 may mainly interact with HDAC1 in the cytoplasm. We propose that it may be involved in protein ubiquitination and the Notch signaling pathway. The results of this study laid an experimental foundation for the subsequent in-depth study of the mechanism of MAGEA1.

Parkin: an Extremely Versatile E3 Ubiquitin Ligase / 中国生物化学与分子生物学报

Parkin, also known as PARK2, has been closely related to Parkinson's disease (PD) since its discovery. It is considered to be a neuroprotective gene. With the in-depth understanding for its structure, Parkin has been unveiled as an E3 ubiquitin ligase. Parkin is involved in the regulation of cell cycle, mitochondrial homeostasis, energy metabolism and other cellular processes, and is closely related to many diseases. It even plays completely opposite roles in the same pathway, namely cell proliferation and apoptosis, indicating that this must be a gene with an extremely broad and important role. This article summarizes the discovery and structure of Parkin and its self-inhibiting characteristics, focusing on the ubiquitination process that it participates in as E3 ubiquitin ligase and the resulting autophagy, protein degradation, changes in protein subcellular localization and protein interaction. These may all serve as the basis for Parkin to prevent PD and suppress tumors. On this basis, two reasons for Parkin abnormalities leading to PD are summarized: abnormal protein quality control and mitochondrial dysfunction, and extended to cardiovascular and kidney diseases caused by the abnormality of Parkin due to mitochondrial dysfunction. The internal connection between Parkin and cancer is also introduced from the aspects of Parkin as a tumor suppressor, regulating cell cycle, apoptosis and metastasis, oxidative stress and energy metabolism. By maintaining the active state of Parkin or enhancing its expression, it may be possible to improve the condition of PD patients. But the mechanism of Parkin's inhibition of tumor growth remains to be deciphered, and the potential role of Parkin in mediating the relationship between PD and cancer risk should be strengthened. These follow-up in-depth studies and their role in the diagnosis and treatment of related diseases and application of target molecules laid the foundation.

mTOR-targeted cancer therapy: great target but disappointing clinical outcomes, why? / 医学前沿

The mammalian target of rapamycin (mTOR) critically regulates several essential biological functions, such as cell growth, metabolism, survival, and immune response by forming two important complexes, namely, mTOR complex 1 (mTORC1) and complex 2 (mTORC2). mTOR signaling is often dysregulated in cancers and has been considered an attractive cancer therapeutic target. Great efforts have been made to develop efficacious mTOR inhibitors, particularly mTOR kinase inhibitors, which suppress mTORC1 and mTORC2; however, major success has not been achieved. With the strong scientific rationale, the intriguing question is why cancers are insensitive or not responsive to mTOR-targeted cancer therapy in clinics. Beyond early findings on induced activation of PI3K/Akt, MEK/ERK, and Mnk/eIF4E survival signaling pathways that compromise the efficacy of rapalog-based cancer therapy, recent findings on the essential role of GSK3 in mediating cancer cell response to mTOR inhibitors and mTORC1 inhibition-induced upregulation of PD-L1 in cancer cells may provide some explanations. These new findings may also offer us the opportunity to rationally utilize mTOR inhibitors in cancer therapy. Further elucidation of the biology of complicated mTOR networks may bring us the hope to develop effective therapeutic strategies with mTOR inhibitors against cancer.

Degradation of proteins by PROTACs and other strategies

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.

Mechanism of Effect of Ubiquitination Modification Mediated by E3 Ubiquitin Ligase in Inflammatory Bowel Disease / 胃肠病学

Ubiquitination is the important type of post-translational modification of proteins, and its main effects include protein degradation and functional regulation. Studies have shown that abnormal ubiquitination is involved in the development and progress of inflammatory bowel disease (IBD), which makes some ubiquitinases and their antibodies having the potential to be important markers for clinical diagnosis and evaluation of severity of Crohn's disease (CD). This article reviewed the research on mechanism of effect of ubiquitination modification mediated by E3 ubiquitin ligase in IBD.

Effects of electroacupuncture on skeletal muscle and blood glucose in rats with diabetic amyotrophy / 中国针灸

OBJECTIVE@#To explore the effects of electroacupuncture (EA) on skeletal muscle and blood glucose in rats with diabetic amyotrophy.@*METHODS@#Among 40 SD rats, 10 rats were randomly selected into the control group and received no treatment. The remaining 30 rats were treated with intraperitoneal injection of streptozotocin (STZ, 60 mg/kg) to establish diabetes mellitus (DM) model, and then the rats were treated with vascular ligation at right posterior limb to establish amyotrophy model. The rats with diabetic amyotrophy were randomly divided into a model group and an EA group, 10 rats in each group (10 rats were excluded due to unsuccessful model establishment and death). The rats in the EA group was treated with EA at right-side "Yishu (EX-B 3)" "Shenshu (BL 23)" "Zusanli (ST 36)" and "Sanyinjiao (SP 6)", disperse-dense wave, 2 Hz/ 15 Hz, 20 minutes each time, once a day for 3 weeks. Before and after EA treatment, the blood sample was collected from inner canthus and the "glucose oxidase-peroxidase" method was used to detect fasting blood glucose level; ELISA method was used to detect insulin content. At the end of the treatment, HE staining method was used to observe the morphology of ischemic skeletal muscle in the right hindlimb; the real-time PCR method was used to detect the mRNA expression of muscle atrophy F-box (MAFbx), muscle ring finger-1 (MuRF1) and forkhead box O3a (FOXO3a) in the ischemic skeletal muscle tissue of right hindlimb.@*RESULTS@#Before the treatment, the body mass in the model group and EA group was lower than that in the control group (<0.01); after the treatment, the body mass in the control group was increased, while the body mass in the model group and EA group was decreased (<0.01). Compared with the control group, the fasting blood glucose was significantly increased and insulin content was significantly decreased in the model group (<0.01); compared with the model group, the fasting blood glucose was significantly decreased and the insulin content was significantly increased in the EA group after treatment (<0.01). The muscle fibers of the model group were obviously broken, the number of the nuclei decreased, and the nuclei shrinked or even dissolved; the morphology of the muscle tissue of the EA group after intervention was improved compared with the model group. Compared with the control group, the cross-sectional area of ischemic skeletal muscle cells in the right hindlimb in the model group was decreased (<0.01); compared with the model group, the cross-sectional area of ischemic skeletal muscle cells in the right hindlimb was increased in EA group (<0.05). Compared with the control group, the levels of MAFbx, MuRF1 and FOXO3a mRNA in the right hindlimb ischemic skeletal muscle in the model group were increased significantly (<0.01, <0.05); compared with the model group, the levels of MAFbx, MuRF1 and FOXO3a mRNA in the EA group were decreased significantly (<0.05, <0.01).@*CONCLUSION@#EA may play a role in the treatment of diabetic amyotrophy by inducing FOXO3a to reduce the transcription of MAFbx and MuRF1.

A new gene inventory of the ubiquitin and ubiquitin-like conjugation pathways in Giardia intestinalis

BACKGROUND Ubiquitin (Ub) and Ub-like proteins (Ub-L) are critical regulators of complex cellular processes such as the cell cycle, DNA repair, transcription, chromatin remodeling, signal translation, and protein degradation. Giardia intestinalis possesses an experimentally proven Ub-conjugation system; however, a limited number of enzymes involved in this process were identified using basic local alignment search tool (BLAST). This is due to the limitations of BLAST's ability to identify homologous functional regions when similarity between the sequences dips to < 30%. In addition Ub-Ls and their conjugating enzymes have not been fully elucidated in Giardia. OBJETIVE To identify the enzymes involved in the Ub and Ub-Ls conjugation processes using intelligent systems based on the hidden Markov models (HMMs). METHODS We performed an HMM search of functional Pfam domains found in the key enzymes of these pathways in Giardia's proteome. Each open reading frame identified was analysed by sequence homology, domain architecture, and transcription levels. FINDINGS We identified 118 genes, 106 of which corresponded to the ubiquitination process (Ub, E1, E2, E3, and DUB enzymes). The E3 ligase group was the largest group with 82 members; 71 of which harbored a characteristic RING domain. Four Ub-Ls were identified and the conjugation enzymes for NEDD8 and URM1 were described for first time. The 3D model for Ub-Ls displayed the β-grasp fold typical. Furthermore, our sequence analysis for the corresponding activating enzymes detected the essential motifs required for conjugation. MAIN CONCLUSIONS Our findings highlight the complexity of Giardia's Ub-conjugation system, which is drastically different from that previously reported, and provides evidence for the presence of NEDDylation and URMylation enzymes in the genome and transcriptome of G. intestinalis.