Neural-precursor-cell-expressed Developmentally Down-regulated 8 Research Articles

Differential expression of NEDD8 in different pathological types of chronic rhinosinusitis with nasal polyps

Objective:To analyze the differential expression of neural precursor cell-expressed developmentally downregulated 8（NEDD8） protein in nasal polyp tissues of patients with different pathological types of chronic rhinorhinosinusitis with nasal polyps（CRSwNP）. Methods:All specimens were obtained from the specimen library of Beijing Tongren Hospital, and were all patients who underwent nasal endoscopic surgery for chronic rhinosinusitis in Beijing Tongren Hospital. Hematoxylin-eosin staining（HE） was used to detect the number of eosinophils in nasal polyps, and CRSwNP patients were grouped according to the number of eosinophils in nasal polyps, immunohistochemistry was used to detect and analyze the expression level of NEDD8 protein in nasal polyps. Results:The expression level of NEDD8 protein in nasal polyps of patients with eosinophilic chronic rhinorhinosinusitis with nasal polyps was significantly higher than that of patients with non-eosinophilic chronic rhinosinusitis and nasal polyps（P<0.05）. In addition, there was a significant positive correlation between the expression level of NEDD8 protein and the number of eosinophils in nasal polyp tissue（r=0.79, P=0.02）. Conclusion:There are differences in the expression of NEDD8 protein in patients with chronic rhinosinusitis and nasal polyps of different pathological types.

Targeting neddylation as a novel approach to lung cancer treatment (Review).

As a protein that resembles ubiquitin, neural precursor cell expressed developmentally downregulated 8 (NEDD8) takes part in neddylation, which modifies substrates in a manner similar to ubiquitination and alters the activity of target proteins. Neddylation may affect the activity of multiple signaling pathways, have a regulatory role in tumor formation, progression and metastasis, and influence the prognosis of cancer treatment. The present review summarizes the regulatory roles of NEDD8 in the MDM2‑p53, NF‑κB, PI3K/AKT/mTOR, hypoxia‑inducible factor, Hippo and receptor tyrosine kinase signaling pathways, as well as in the development and progression of lung cancer.

Neddylation Regulates Class IIa and III Histone Deacetylases to Mediate Myoblast Differentiation.

As the largest tissue in the body, skeletal muscle has multiple functions in movement and energy metabolism. Skeletal myogenesis is controlled by a transcriptional cascade including a set of muscle regulatory factors (MRFs) that includes Myogenic Differentiation 1 (MYOD1), Myocyte Enhancer Factor 2 (MEF2), and Myogenin (MYOG), which direct the fusion of myogenic myoblasts into multinucleated myotubes. Neddylation is a posttranslational modification that covalently conjugates ubiquitin-like NEDD8 (neural precursor cell expressed, developmentally downregulated 8) to protein targets. Inhibition of neddylation impairs muscle differentiation; however, the underlying molecular mechanisms remain less explored. Here, we report that neddylation is temporally regulated during myoblast differentiation. Inhibition of neddylation through pharmacological blockade using MLN4924 (Pevonedistat) or genetic deletion of NEDD8 Activating Enzyme E1 Subunit 1 (NAE1), a subunit of the E1 neddylation-activating enzyme, blocks terminal myoblast differentiation partially through repressing MYOG expression. Mechanistically, we found that neddylation deficiency enhances the mRNA and protein expressions of class IIa histone deacetylases 4 and 5 (HDAC4 and 5) and prevents the downregulation and nuclear export of class III HDAC (NAD-Dependent Protein Deacetylase Sirtuin-1, SIRT1), all of which have been shown to repress MYOD1-mediated MYOG transcriptional activation. Together, our findings for the first time identify the crucial role of neddylation in mediating class IIa and III HDAC co-repressors to control myogenic program and provide new insights into the mechanisms of muscle disease and regeneration.

Overexpressed NEDD8 as a potential therapeutic target in esophageal squamous cell carcinoma.

Objective:The hyperactivated neddylation pathway plays an important role in tumorigenesis and is emerging as a promising anticancer target. We aimed to study whether NEDD8 (neural precursor cell expressed, developmentally down-regulated 8) might serve as a therapeutic target in esophageal squamous cell carcinoma (ESCC).Methods:The clinical relevance of NEDD8 expression was evaluated by using The Cancer Genome Atlas (TCGA) database and tissue arrays. NEDD8-knockdown ESCC cells generated with the CRISPR/Cas9 system were used to explore the anticancer effects and mechanisms. Quantitative proteomic analysis was used to examine the variations in NEDD8 knockdown-induced biological pathways. The cell cycle and apoptosis were assessed with fluorescence activated cell sorting. A subcutaneous-transplantation mouse tumor model was established to investigate the anticancer potential of NEDD8 silencing in vivo.Results:NEDD8 was upregulated at both the mRNA and protein expression levels in ESCC, and NEDD8 overexpression was associated with poorer overall patient survival (mRNA level: P = 0.028, protein level: P = 0.026, log-rank test). Downregulation of NEDD8 significantly suppressed tumor growth both in vitro and in vivo. Quantitative proteomic analysis revealed that downregulation of NEDD8 induced cell cycle arrest, DNA damage, and apoptosis in ESCC cells. Mechanistic studies demonstrated that NEDD8 knockdown led to the accumulation of cullin-RING E3 ubiquitin ligases (CRLs) substrates through inactivation of CRLs, thus suppressing the malignant phenotype by inducing cell cycle arrest and apoptosis in ESCC. Rescue experiments demonstrated that the induction of apoptosis after NEDD8 silencing was attenuated by DR5 knockdown.Conclusions:Our study elucidated the anti-ESCC effects and underlying mechanisms of NEDD8 knockdown, and validated NEDD8 as a potential target for ESCC therapy.

Neddylation, an Emerging Mechanism Regulating Cardiac Development and Function.

Defects in protein quality control have been increasingly recognized as pathogenic factors in the development of heart failure, a persistent devastating disease lacking efficacious therapies. Ubiquitin and ubiquitin-like proteins, a family of post-translational modifying polypeptides, play important roles in controlling protein quality by maintaining the stability and functional diversity of the proteome. NEDD8 (neural precursor cell expressed, developmentally downregulated 8), a small ubiquitin-like protein, was discovered two decades ago but until recently the biological significance of NEDD8 modifications (neddylation) in the heart has not been appreciated. In this review, we summarize the current knowledge of the biology of neddylation, highlighting several mechanisms by which neddylation regulates the function of its downstream targets, and discuss the expanding roles for neddylation in cardiac physiology and disease, with an emphasis on cardiac protein quality control. Finally, we outline challenges linked to the study of neddylation in health and disease.

The Impact of Cand1 in Prostate Cancer.

Evidence has accumulated asserting the importance of cullin-RING (really interesting new gene) ubiquitin ligases (CRLs) and their regulator Cullin-associated neural-precursor-cell-expressed developmentally down-regulated 8 (NEDD8) dissociated protein 1 (Cand1) in various cancer entities. However, the role of Cand1 in prostate cancer (PCa) has not been intensively investigated so far. Thus, in the present study, we aimed to assess the relevance of Cand1 in the clinical and preclinical setting. Immunohistochemical analyses of radical prostatectomy specimens of PCa patients showed that Cand1 protein levels are elevated in PCa compared to benign areas. In addition, high Cand1 levels were associated with higher Gleason Scores, as well as higher tumor recurrence and decreased overall survival. In line with clinical findings, in vitro experiments in different PCa cell lines revealed that knockdown of Cand1 reduced cell viability and proliferation and increased apoptosis, therefore underlining its role in tumor progression. We also found that the cyclin-dependent kinase inhibitor p21 is significantly upregulated upon downregulation of Cand1. Using bioinformatic tools, we detected genes encoding for proteins linked to mRNA turnover, protein polyubiquitination, and proteasomal degradation to be significantly upregulated in Cand1high tumors. Next generation sequencing of PCa cell lines resistant to the anti-androgen enzalutamide revealed that Cand1 is mutated in enzalutamide-resistant cells, however, with little functional and clinically relevant impact in the process of resistance development. To summarize the present study, we found that high Cand1 levels correlate with PCa aggressiveness.

Pharmaceutical Inhibition of Neddylation as Promising Treatments for Various Cancers.

Neddylation is an important post-translational modification of proteins, in which a NEDD8 (neural-precursor-cell-expressed developmentally down-regulated 8) is covalently introduced onto the substrate proteins to regulate their functions and homeostasis. As neddylation is frequently up-regulated in various cancers, its interference was proposed as a promising therapy of related diseases. The recent advances in developing neddylation interfering agents were summarized to provide an overview of current achievements and perspectives for future development. Reports on neddylation interfering agents were acquired from Pubmed as well as the EPO and clinicaltrials.gov websites, which were subsequently analyzed and summarized according to targets, chemical structures and biological activities. Neddylation as a sophisticated procedure comprises proteolytic processing of NEDD8 precursor, deploying conjugating enzymes E1 (NAE), E2 (UBE2M and UBE2F) and various E3, as well as translocating NEDD8 along these conjugating enzymes sequentially and finally to substrate proteins. Among these nodes, NAE, UBE2M and the interaction between UBE2M-DCN1 have been targeted by small molecules, metal complexes, peptides and RNAi. A NAE inhibitor pevonedistat (MLN4924) is currently under evaluation in clinical trials for the treatment of various cancers. With multiple inhibitory approaches of neddylation being introduced, the development of neddylation interference as a novel cancer therapy is significantly boosted recently, although its efficacy and the best way to achieve that are still to be demonstrated in clinical trials.

NEDD8-conjugated Cullin4 positive regulates antimicrobial peptides expression in Eriocheir sinensis

The ubiquitin-proteasome system is involved in numerous cellular processes, such as signal transduction, autophagy, cell cycle control, embryogenesis, and regulation of immune response. Neural precursor cell expressed developmentally downregulated 8 (NEDD8) is a ubiquitin-like protein that activates Cullin-RING ligases and modifies substrates via neddylation. However, there is limited information on how neddylation regulates innate immunity in crustaceans. In the present study, we identified the evolutionarily conserved NEDD8 with the ubiquitin homologue domain in the Chinese mitten crab (Eriocheir sinensis), named it EsNEDD8. Then, we analyzed the expression patterns and cellular location of its substrate, EsCullin4. qRT-PCR showed that both EsNEDD8 and EsCullin4 were widely expressed in all the selected tissues, and EsCullin4 was significantly upregulated in hemocytes after bacterial stimulation. Moreover, silencing of EsCullin4 significantly suppressed the expression of antimicrobial peptides (AMPs) in the hemocytes after bacterial stimulation, and inhibition of EsCullin4 neddylation by treatment with the NEDD8-activating enzyme inhibitor MLN4924 significantly inhibited the expression of the AMPs. Thus, the results show that EsNEDD8-modified EsCullin4 could control antimicrobial activities via regulation of AMPs expression in the Chinese mitten crab.

Interplay between SUMOylation and NEDDylation regulates RPL11 localization and function.

The ribosomal protein L11 (RPL11) integrates different types of stress into a p53-mediated response. Here, we analyzed the impact of the ubiquitin-like protein SUMO on the RPL11-mouse double-minute 2 homolog-p53 signaling. We show that small ubiquitin-related modifier (SUMO)1 and SUMO2 covalently modify RPL11. We find that SUMO negatively modulates the conjugation of the ubiquitin-like protein neural precursor cell-expressed developmentally downregulated 8 (NEDD8) to RPL11 and promotes the translocation of the RP outside of the nucleoli. Moreover, the SUMO-conjugating enzyme, Ubc9, is required for RPL11-mediated activation of p53. SUMOylation of RPL11 is triggered by ribosomal stress, as well as by alternate reading frame protein upregulation. Collectively, our data identify SUMO protein conjugation to RPL11 as a new regulator of the p53-mediated cellular response to different types of stress and reveal a previously unknown SUMO-NEDD8 interplay.-El Motiam, A., Vidal, S., de la Cruz-Herrera, C. F., Da Silva-Álvarez, S., Baz-Martínez, M., Seoane, R., Vidal, A., Rodríguez, M. S., Xirodimas, D. P., Carvalho, A. S., Beck, H. C., Matthiesen, R., Collado, M., Rivas, C. Interplay between SUMOylation and NEDDylation regulates RPL11 localization and function.

Neddylation, a novel paradigm in liver cancer

Liver cancer is the sixth most prevailing cancer worldwide. Hepatocellular carcinoma (HCC), the most common form of primary liver cancer, has a rather heterogeneous pathogenesis making it highly refractive to current therapeutic approaches. Hence, HCC patients have a poor and gloomy prognosis making liver cancer the second leading cause of global cancer-related deaths. On this basis, a more global mechanism, such as post-translational modifications (PTMs) of proteins, may provide a valuable therapeutic approach for HCC clinical management by simultaneously regulating multiple disrupted signaling pathways. In the last years, the ubiquitin-like molecule NEDD8 (Neural precursor cell-expressed developmentally downregulated-8) conjugation pathway, neddylation, was shown to be aberrant in HCC patients with a significant positive correlation found among global levels of neddylation and poorer prognosis. Even though the best-established role for NEDD8 is the activation of ubiquitin E3 ligase family of cullin-RING ligases, the putative role for other NEDD8 substrates has been explored in recent years leading to the identification of novel neddylation targets in HCC. Importantly, treatment with the small pharmacological inhibitor Pevonedistat (MLN4924) (Millennium Pharmaceuticals, Takeda Pharmaceutical), currently in clinical trials for the treatment of some types of leukemias and other advanced solid tumors, was shown to suppress the outgrowth of hepatoma cells and liver cancer in pre-clinical mouse models. Overall, considering that the neddylation inhibitor Pevonedistat was well-tolerated and displayed a significant antitumor effect in pre-clinical models, combinatory pharmacological treatment based on Pevonedistat are highly recommended to enter clinical trials targeting advanced HCC.

FBXW8-dependent degradation of MRFAP1 in anaphase controls mitotic cell death.

Mof4 family associated protein 1 (MRFAP1) is a 14 kDa nuclear protein, which involves in maintaining normal histone modification levels by negatively regulating recruitment of the NuA4 (nucleosome acetyltransferase of H4) histone acetyltransferase complex to chromatin. MRFAP1 has been identified as one of the most up-regulated proteins after NEDD8 (neural precursor cell expressed developmentally down-regulated 8) inhibition in multiple human cell lines. However, the biological function of MRFAP1 and the E3 ligase that targets MRFAP1 for destruction remain mysterious. Here we show, by using an immunoprecipitation-based proteomics screen, that MRFAP1 is an interactor of the F-box protein FBXW8. MRFAP1 is degraded by means of the ubiquitin ligase Cul7/FBXW8 during mitotic anaphase-telophase transition and accumulated in mitotic metaphase. Overexpression of FBXW8 increased the polyubiquitination and decreased the stability of MRFAP1, whereas knockdown of FBXW8 prolonged the half-life of MRFAP1. Moreover, forced expression of MRFAP1 in HeLa cells caused growth retardation and genomic instability, leading to severe mitotic cell death. Thus, Cul7/FBXW8-mediated destruction of MRFAP1 is a regulatory component monitoring the anaphase-telophase transition and preventing genomic instability.

NEDDylation antagonizes ubiquitination of proliferating cell nuclear antigen and regulates the recruitment of polymerase \u03b7 in response to oxidative DNA damage

ABSTRACTNEDDylation has been shown to participate in the DNA damage pathway, but the substrates of neural precursor cell expressed developmentally downregulated 8 (NEDD8) and the roles of NEDDylation involved in the DNA damage response (DDR) are largely unknown. Translesion synthesis (TLS) is a damage-tolerance mechanism, in which RAD18/RAD6-mediated monoubiquitinated proliferating cell nuclear antigen (PCNA) promotes recruitment of polymerase η (polη) to bypass lesions. Here we identify PCNA as a substrate of NEDD8, and show that E3 ligase RAD18-catalyzed PCNA NEDDylation antagonizes its ubiquitination. In addition, NEDP1 acts as the deNEDDylase of PCNA, and NEDP1 deletion enhances PCNA NEDDylation but reduces its ubiquitination. In response to H2O2 stimulation, NEDP1 disassociates from PCNA and RAD18-dependent PCNA NEDDylation increases markedly after its ubiquitination. Impairment of NEDDylation by Ubc12 knockout enhances PCNA ubiquitination and promotes PCNA-polη interaction, while up-regulation of NEDDylation by NEDD8 overexpression or NEDP1 deletion reduces the excessive accumulation of ubiquitinated PCNA, thus inhibits PCNA-polη interaction and blocks polη foci formation. Moreover, Ubc12 knockout decreases cell sensitivity to H2O2-induced oxidative stress, but NEDP1 deletion aggravates this sensitivity. Collectively, our study elucidates the important role of NEDDylation in the DDR as a modulator of PCNA monoubiquitination and polη recruitment.

Effects of inhibition of neural precursor cell-expressed developmentally down regulated 8 gene on biological behavior, and androgen receptor of human prostate cancer cells

Objective To explore the effect of lentivirus-mediated short hairpin RNA (shRNA) silencing neural precursor cell-expressed developmentally down regulated 8 (NEDD8) gene on androgen receptor (AR), prostate specific antigen (PSA), proliferation, apoptosis and invasion of human prostate cancer LNCap and VCaP cells. Methods LNCap and VCaP cells were transfected with lentivirus-mediated NEDD8-shRNA. The mRNA and protein expression of NEDD8, AR and PSA was detected by real-time fluorescent quantitative polymerase chain reaction (FQ-PCR) and Western blotting, respectively. The proliferation, apoptosis and invasion abilities were evaluated by cell counting kit-8 (CCK-8) assay, flow cytometry and Transwell TM assay, respectively. Results After transfection with NEDD8-shRNA, NEDD8 mRNA expression in LnCaP and VCaP was (0.11±0.03) fold and (0.16±0.04) fold, respectively, as compared to the blank control group; AR mRNA expression was (0.52±0.04) fold and (0.42±0.05) fold; PSA mRNA expression was (0.49±0.04) fold and (0.59±0.06) fold. NEDD8, AR and PSA protein expression in LnCaP and VCaP was (11.26±2.65)% and (6.26±2.04)%, (30.36±4.35)% and (15.36±3.37)%, and (13.37±2.70)% and (11.36±2.67)%, respectively. As compared with the control groups, the mRNA and protein expression levels of NEDD8, AR and PSA were significantly inhibited after transfection with NEDD8-shRNA (P=0.000). As compared with the control groups, the proliferation of LnCaP and VCaP was significantly inhibited after transfection with NEDD8-shRNA. The apoptosis rate of LNCap and VCaP cells was (15.08±1.23)% and (20.37±1.76)% respectively, which was significantly enhanced as compared with the control groups (P=0.001, P=0.000). After transfection, the number of LnCaP and VCaP cells invading the Matrigel was (55.5±12.5) and (60.8±11.3) respectively, which was significantly reduced as compared with the control groups (P=0.000, P=0.004). Conclusion NEDD8 may downregulate AR at the transcriptional level. The lentivirus-mediated shRNA silencing NEDD8 gene could inhibit the proliferation and invasion, and promote apoptosis of LNCap and VCaP cells. Key words: Prostate cancer; Neural precursor cell-expressed developmentally down regulated factor 8; Androgen receptor; RNA interference

Mechanisms of Deubiquitinase Specificity and Regulation.

Protein ubiquitination is one of the most powerful posttranslational modifications of proteins, as it regulates a plethora of cellular processes in distinct manners. Simple monoubiquitination events coexist with more complex forms of polyubiquitination, the latter featuring many different chain architectures. Ubiquitin can be subjected to further posttranslational modifications (e.g., phosphorylation and acetylation) and can also be part of mixed polymers with ubiquitin-like modifiers such as SUMO (small ubiquitin-related modifier) or NEDD8 (neural precursor cell expressed, developmentally downregulated 8). Together, cellular ubiquitination events form a sophisticated and versatile ubiquitin code. Deubiquitinases (DUBs) reverse ubiquitin signals with equally high sophistication. In this review, we conceptualize the many layers of specificity that DUBs encompass to control the ubiquitin code and discuss examples in which DUB specificity has been understood at the molecular level. We further discuss the many mechanisms of DUB regulation with a focus on those that modulate catalytic activity. Our review provides a framework to tackle lingering questions in DUB biology.

Inhibition of atherogenesis by the COP9 signalosome subunit 5 in vivo

Constitutive photomorphogenesis 9 (COP9) signalosome 5 (CSN5), an isopeptidase that removes neural precursor cell-expressed, developmentally down-regulated 8 (NEDD8) moieties from cullins (thus termed "deNEDDylase") and a subunit of the cullin-RING E3 ligase-regulating COP9 signalosome complex, attenuates proinflammatory NF-κB signaling. We previously showed that CSN5 is up-regulated in human atherosclerotic arteries. Here, we investigated the role of CSN5 in atherogenesis in vivo by using mice with myeloid-specific Csn5 deletion. Genetic deletion of Csn5 in Apoe-/- mice markedly exacerbated atherosclerotic lesion formation. This was broadly observed in aortic root, arch, and total aorta of male mice, whereas the effect was less pronounced and site-specific in females. Mechanistically, Csn5 KO potentiated NF-κB signaling and proinflammatory cytokine expression in macrophages, whereas HIF-1α levels were reduced. Inversely, inhibition of NEDDylation by MLN4924 blocked proinflammatory gene expression and NF-κB activation while enhancing HIF-1α levels and the expression of M2 marker Arginase 1 in inflammatory-elicited macrophages. MLN4924 further attenuated the expression of chemokines and adhesion molecules in endothelial cells and reduced NF-κB activation and monocyte arrest on activated endothelium in vitro. In vivo, MLN4924 reduced LPS-induced inflammation, favored an antiinflammatory macrophage phenotype, and decreased the progression of early atherosclerotic lesions in mice. On the contrary, MLN4924 treatment increased neutrophil and monocyte counts in blood and had no net effect on the progression of more advanced lesions. Our data show that CSN5 is atheroprotective. We conclude that MLN4924 may be useful in preventing early atherogenesis, whereas selectively promoting CSN5-mediated deNEDDylation may be beneficial in all stages of atherosclerosis.

Neural precursor cell expressed, developmentally downregulated 8‑activating enzyme inhibitor MLN4924 sensitizes colorectal cancer cells to oxaliplatin by inducing DNA damage, G2 cell cycle arrest and apoptosis.

Oxaliplatin-based chemotherapy is a primary treatment for patients with metastatic colorectal cancer (CRC); however, its efficacy is limited. Therefore, novel therapeutic agents are urgently required. MLN4924 is a first‑in‑class inhibitor of neural precursor cell expressed, developmentally downregulated8 (NEDD8)‑activating enzyme E1, and has entered various phase‑I/II clinical trials for cancer therapy due to its significant anticancer efficacy. The aim of the present study was to examine the synergistic effect and underlying mechanisms of MLN4924 and oxaliplatin combined treatment for CRC. It was demonstrated that MLN4924 treatment induced the DNA damage response (DDR) by inactivating cullin‑ring ubiquitin ligases, subsequently leading to cell cycle disturbance and apoptosis in CRC cells. MLN4924 treatment increased the oxaliplatin‑induced DDR, G2 cell cycle arrest and apoptosis. Protein expression levels of phosphorylated checkpoint kinase2 (p‑CHK2), p21 and p53, which are well‑known functional proteins involved in G2 cell cycle arrest, were assessed. p‑CHK2 protein expression levels were increased following combined treatment with MLN4924 and oxaliplatin, whereas p21/p53 protein expression levels were not. In conclusion, MLN4924 treatment may sensitize CRC cells to oxaliplatin treatment by inducing the DDR and increasing protein expression levels of p‑CHK2, leading to G2 cell cycle arrest and apoptosis. Therefore, combined MLN4924 and oxaliplatin‑based chemotherapy may be a potential therapeutic strategy for the treatment of CRC.

Effects of insulin and the glucagon‐like peptide 1 receptor agonist liraglutide on the kidney proteome in db/db mice

Diabetes mellitus (DM) is a worldwide disease that affects 9% of the adult world population and type 2 DM accounts for 90% of those. A common consequence of DM is kidney complications, which could lead to kidney failure. We studied the potential effects of treatment with insulin and the glucagon‐like peptide 1 receptor (GLP‐1R) agonist liraglutide on the diabetic kidney proteome through the use of the db/db mouse model system and mass spectrometry (MS). Multivariate analyses revealed distinct effects of insulin and liraglutide on the db/db kidney proteome, which was seen on the protein levels of, for example, pterin‐4 α‐carbinolamine dehydratase/dimerization cofactor of hepatocyte nuclear factor‐1α (PCBD1), neural precursor cell expressed developmentally down‐regulated‐8 (NEDD8), transcription elongation factor‐B polypeptide‐1 (ELOC) and hepcidin (HEPC). Furthermore, the separation of the insulin, liraglutide and vehicle db/db mouse groups in multivariate analyses was not mainly related to the albumin excretion rate (AER) or the level of glycated hemoglobin A1c (HbA1c%) in the mice. In summary, we show that insulin and liraglutide give rise to separate protein profiles in the db/db mouse kidney.

MLN4924 therapy as a novel approach in cancer treatment modalities

MLN4924 is an investigational and a newly discovered small molecule that is a potent and selective inhibitor of the NEDD8 (Neural precursor cell-Expressed Developmentally down-regulated 8) Activating Enzyme (NAE), a pivotal regulator of the Cullin Ring Ligases E3 (CRL), which has been implicated recently in DNA damage. MLN4924 effectively inhibits tumour cell growth by inducing all three common types of death, namely apoptosis, autophagy and senescence and it was also reported that the formation of capillary vessels was significantly suppressed by MLN4924.In this review, we are going to highlight the molecular mechanism of MLN4924 in cancer therapy and its pros and cons in cancer therapy.

The COP9 SIGNALOSOME Is Required for Postembryonic Meristem Maintenance in Arabidopsis thaliana

Cullin-RING E3 ligases (CRLs) regulate different aspects of plant development and are activated by modification of their cullin subunit with the ubiquitin-like protein NEDD8 (NEural precursor cell expressed Developmentally Down-regulated 8) (neddylation) and deactivated by NEDD8 removal (deneddylation). The CONSTITUTIVELY PHOTOMORPHOGENIC9 (COP9) signalosome (CSN) acts as a molecular switch of CRLs activity by reverting their neddylation status, but its contribution to embryonic and early seedling development remains poorly characterized. Here, we analyzed the phenotypic defects of csn mutants and monitored the cullin deneddylation/neddylation ratio during embryonic and early seedling development. We show that while csn mutants can complete embryogenesis (albeit at a slower pace than wild-type) and are able to germinate (albeit at a reduced rate), they progressively lose meristem activity upon germination until they become unable to sustain growth. We also show that the majority of cullin proteins are progressively neddylated during the late stages of seed maturation and become deneddylated upon seed germination. This developmentally regulated shift in the cullin neddylation status is absent in csn mutants. We conclude that the CSN and its cullin deneddylation activity are required to sustain postembryonic meristem function in Arabidopsis.

A lysine-to-arginine mutation on NEDD8 markedly reduces the activity of cullin RING E3 ligase through the impairment of neddylation cascades

Neural-precursor-cell-expressed developmentally down-regulated 8 (NEDD8) is a ubiquitin-like modifier, which forms covalent conjugates on lysines of its substrates. This post-translational modification, neddylation, plays important roles in tumor cell proliferation and viability. Ubiquitin can form diverse polyubiquitin chains, on its seven lysines, which play important functions in various biological processes. However, the roles of lysines in NEDD8 have not been explored. Here, we generated nine NEDD8 point mutants, each with one lysine replaced by an arginine, to study the putative function of lysines in NEDD8. Our experiments discover that Lys27 in NEDD8 is a critical residue for protein neddylation. Replacement of this residue with arginine almost completely eliminates the conjugation of NEDD8 to its substrates. Furthermore, we find that the K27R mutant impairs NEDD8 conjugation to the E2 enzyme, which normally forms thioester bonds for further transferring NEDD8 to its ligases and substrates. Therefore, this mutation completely inhibits global protein neddylation, including neddylation of cullin family proteins, resulting in decreased activity of cullin-RING E3 ligases. This work sheds new light on the roles of NEDD8 lysines on neddylation cascades and provides a dominant negative mutant for the study of neddylation and its biological functions.