Search

Emergence of newer variants of SARS-CoV-2 underscores the need for effective antivirals to complement the vaccination program in managing COVID-19. The multi-functional papain-like protease (PLpro) of SARS-CoV-2 is an essential viral protein that not only regulates the viral replication but also modulates the host immune system, making it a promising therapeutic target. To this end, we developed an in vitro interferon stimulating gene 15 (ISG15)-based Förster resonance energy transfer (FRET) assay and screened the National Cancer Institute (NCI) Diversity Set VI compound library, which comprises 1584 small molecules. Subsequently, we assessed the PLpro enzymatic activity in the presence of screened molecules. We identified three potential PLpro inhibitors, namely, NSC338106, 651084, and 679525, with IC 50 values in the range from 3.3 to 6.0 µM. These molecules demonstrated in vitro inhibition of the enzyme activity and exhibited antiviral activity against SARS-CoV-2, with EC 50 values ranging from 0.4 to 4.6 µM. The molecular docking of all three small molecules to PLpro suggested their specificity towards the enzyme's active site. Overall, our study contributes promising prospects for further developing potential antivirals to combat SARS-CoV-2 infection.

Renal cell carcinoma (RCC) is the deadliest form of urological cancer and is projected to be the fourth most common neoplasm in the USA in males by 2040. In addition to the current poor prognosis with 5-year survival rates hardly reaching 15%, the prevalence of resistance to currently available systemic therapies has also established an urgent need to develop new treatment regimen(s) for advanced RCC. Interferon-stimulated gene 15 (ISG15) is the first identified ubiquitin-like modifier and has been intensively studied for its central role in innate immunity against intracellular pathogens. However, in this study, we identified ISG15 as a novel tumor-associated antigen and prognostic marker in RCC. Further, we therapeutically targeted elevated ISG15 expression by means of a Listeria monocytogenes (Lm)-based vaccine, designated Lm-LLO-ISG15, in both subcutaneous and orthotopic RCC mouse models. Treatment with Lm-LLO-ISG15 resulted in an influx of tumor-infiltrating effector T cells and significant anti-tumor efficacy in both subcutaneous and orthotopic RCC tumor models. Treatment with Lm-LLO-ISG15 also generated a robust interferon-gamma response and attracted a larger pool of polyfunctional T cells into the tumor microenvironment. Importantly, the therapeutic efficacy of Lm-LLO-ISG15 in RCC is comparable to that of anti-PD-1 and sunitinib, the current frontline therapies for RCC patients. Collectively, our work illustrates that targeting ISG15 in RCC with a CTL-based immunotherapy such as Lm-LLO-ISG15 is a promising and potentially translatable therapeutic strategy to enhance survival in RCC patients., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Tuberculosis is a global health problem caused by infection with the Mycobacterium tuberculosis (Mtb) bacteria. Although antibiotic treatment has dramatically reduced the impact of tuberculosis on the population, the existence and spreading of drug resistant strains urgently demands the development of new drugs that target Mtb in a different manner than currently used antibiotics. The prokaryotic ubiquitin-like protein (Pup) proteasome system is an attractive target for new drug development as it is unique to Mtb and related bacterial genera. Using a Pup-based fluorogenic substrate, we screened for inhibitors of Dop, the Mtb depupylating protease, and identified I-OMe-Tyrphostin AG538 (1) and Tyrphostin AG538 (2). The hits were validated and determined to be fast-reversible, non-ATP competitive inhibitors. We synthesized >25 analogs of 1 and 2 and show that several of the synthesized compounds also inhibit the depupylation actions of Dop on native substrate, FabD-Pup. Importantly, the pupylation activity of PafA, the sole Pup ligase in Mtb, was also inhibited by some of these compounds., (© 2021 The Authors. ChemBioChem published by Wiley-VCH GmbH.)

Agents that induce DNA damage can cure some cancers. However, the side effects of chemotherapy are severe because of the indiscriminate action of DNA-damaging agents on both healthy and cancerous cells. DNA repair pathway inhibition provides a less toxic and targeted alternative to chemotherapy. A compelling DNA repair target is the Fanconi anemia (FA) E3 ligase core complex due to its critical-and likely singular-role in the efficient removal of specific DNA lesions. FA pathway inactivation has been demonstrated to specifically kill some types of cancer cells without the addition of exogenous DNA damage, including cells that lack BRCA1, BRCA2, ATM, or functionally related genes. In this perspective, we discuss the genetic and biochemical evidence in support of the FA core complex as a compelling drug target for cancer therapy. In particular, we discuss the genetic, biochemical, and structural data that could rapidly advance our capacity to identify and implement the use of FA core complex inhibitors in the clinic., Competing Interests: Declaration of interests A.J.D. receives sponsored research support from Tessellate Bioscience for projects related to this manuscript., (Copyright © 2021 Elsevier Inc. All rights reserved.)

An urgent medical need to develop novel treatment strategies for patients with pancreatic ductal adenocarcinoma (PDAC) exists. However, despite various efforts in the histopathological and molecular subtyping of PDAC, novel targeted or specific therapies have not been established. Posttranslational modifications (PTMs) with ubiquitin-like proteins, including small ubiquitin-like modifiers (SUMOs), mediate numerous processes that can contribute to the fitness and survival of cancer cells. The contribution of SUMOylation to transcriptional control, DNA repair pathways, mitotic progression, and oncogenic signalling has been described. Here we review functions of the SUMO pathway in PDAC, with a special focus on its connection to an aggressive subtype of the disease characterised by high MYC activity, and discuss SUMOylation inhibitors under development for precise PDAC therapies.

Platelets are small, anucleate cells that play oversized roles in hemostasis, immunity, and inflammation. An important mediator of platelet function is integrin αIIbβ3, which is required for fibrinogen-dependent platelet aggregation during hemostasis. This platelet response is dependent on conformational changes in the integrin induced by "inside-out" biochemical signals that are triggered by platelet agonists. In turn, fibrinogen binding to αIIbβ3 initiates "outside-in" biochemical and mechanical signals that regulate the platelet cytoskeleton and help to promote full platelet aggregation and secretory responses. Without a nucleus, there is a limited range of experimental manipulations that are possible with human platelets to study the molecular basis of integrin signaling in these primary cells. Consequently, many studies of αIIbβ3 function use genetic approaches that rely on heterologous expression systems or platelets from gene-targeted mice, sometimes with uncertain applicability to human platelets. This chapter will detail a method for genetic manipulation of megakaryocytes and platelets derived from human induced pluripotent stem cells for molecular studies of αIIbβ3 signaling and for modeling of human platelet functions potentially relevant to hemostasis, immunity, and inflammation.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent for COVID-19, is a novel human betacoronavirus that is rapidly spreading worldwide. The outbreak currently includes over 3.7 million cases and 260,000 fatalities. As a betacoronavirus, SARS-CoV-2 encodes for a papain-like protease (PLpro) that is likely responsible for cleavage of the coronavirus (CoV) viral polypeptide. The PLpro is also responsible for suppression of host innate immune responses by virtue of its ability to reverse host ubiquitination and ISGylation events. Here, the biochemical activity of SARS-CoV-2 PLpro against ubiquitin (Ub) and interferon-stimulated gene product 15 (ISG15) substrates is evaluated, revealing that the protease has a marked reduction in its ability to process K48 linked Ub substrates compared to its counterpart in SARS-CoV. Additionally, its substrate activity more closely mirrors that of the PLpro from the Middle East respiratory syndrome coronavirus and prefers ISG15s from certain species including humans. Additionally, naphthalene based PLpro inhibitors are shown to be effective at halting SARS-CoV-2 PLpro activity as well as SARS-CoV-2 replication.

Esophageal cancer is one of the leading malignancies worldwide, while around sixty percent of newly diagnosed cases are in China. In recent years, genome-wide sequencing studies and cancer biology studies show that Hippo signaling functions a critical role in esophageal squamous cell carcinoma (ESCC) progression, which could be a promising therapeutic targets in ESCC treatment. However, the detailed mechanisms of Hippo signaling dys-regulation in ESCC remain not clear. Here we identify SHARPIN protein as an endogenous inhibitor for YAP protein. SHARPIN depletion significantly decreases cell migration and invasion capacity in ESCC, which effects could be rescued by further YAP depletion. Depletion SHARPIN increases YAP protein level and YAP/TEAD target genes, such as CTGF and CYR61 in ESCC. Immuno-precipitation assay shows that SHARPIN associates with YAP, promoting YAP degradation possibly via inducing YAP K48-dependent poly-ubiquitination. Our study reveals a novel post-translational mechanism in modulating Hippo signaling in ESCC. Overexpression or activation of SHARPIN could be a promising strategy to target Hippo signaling for ESCC patients., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2019 The Authors. Published by Elsevier Inc. All rights reserved.)

Posttranslational protein modifications are known to be extensively involved in cancer, and a growing number of studies have revealed that the ubiquitin-like modifier FAT10 is directly involved in cancer development. FAT10 was found to be highly upregulated in various cancer types, such as glioma, hepatocellular carcinoma, breast cancer and gastrointestinal cancer. Protein FAT10ylation and interactions with FAT10 lead to the functional change of proteins, including proteasomal degradation, subcellular delocalization and stabilization, eventually having significant effects on cancer cell proliferation, invasion, metastasis and even tumorigenesis. In this review, we summarized the current knowledge on FAT10 and discussed its biological functions in cancer, as well as potential therapeutic strategies based on the FAT10 pathway., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.)

PML/retinoic acid receptor alpha (RARα), as a hallmark of acute promyeloid leukemia (APL), is directly related to the outcome of clinical APL remedy. It is reported that arsenicals can effectively degrade PML/RARα, such as arsenic trioxide and realgar. However, the high toxicity or insolubility have hampered their clinical applications. Realgar transforming solution (RTS) was produced from realgar by bioleaching process in our lab. Previous studies demonstrated that RTS had a significant anti-cancer ability on chronic myeloid leukemia through oncoprotein degradation. The capacity of RTS on treating APL is what is focused on in this study. The results showed that RTS had a noticeable sensitivity in NB4 cell, and RTS remarkably down-regulated PML/RARα expression and induced cell differentiation. Further, RTS could accumulate PML/RARα into the nuclear bodies and then execute degradation, which could be reversed by proteasome inhibitor MG132. The results also exhibited that the reduction of RTS-induced PML/RARα expression accompanied by the elevation of ubiquitin and SUMO-1 protein expression. Finally, PML and SUMO-1 had been demonstrated to be co-localized after RTS treatment by immunofluorescence co-localization assay and immunoprecipitation assay. In conclusion, these results suggested that RTS-induced cell differentiation may attribute to the PML/RARα degradation partially through the ubiquitin-proteasome pathway.

Background: Maternal immune activation (MIA) is an independent risk factor for psychiatric disorders including depression spectrum in the offsprings, but the molecular mechanism is unclear. Recent studies show that interferon-stimulated gene-15 (ISG15) is involved in inflammation and neuronal dendrite development; here we studied the role of ISG15 in MIA-induced depression and the underlying mechanisms., Methods: By vena caudalis injecting polyinosinic: polycytidylic acid (poly I:C) into the pregnant rats to mimic MIA, we used AAV or lentivirus to introduce or silence ISG15 expression. Synaptic plasticity was detected by confocal microscope and Golgi staining. Cognitive performances of the offspring were measured by Open field, Forced swimming and Sucrose preference test., Results: We found that MIA induced depression-like behaviors with dendrite impairments in the offspring with ISG15 level increased in the offsprings' brain. Overexpressing ISG15 in the prefrontal cortex of neonatal cubs (P0) could mimic dendritic pathology and depressive like behaviors, while downregulating ISG15 rescued these abnormalities in the offsprings. Further studies demonstrated that MIA-induced upregulation of inflammatory cytokines promoted ISG15 expression in the offspring' brain which suppressed Rap2A ubiquitination via NEDD4 and thus induced Rap2A accumulation, while upregulating NEDD4 abolished ISG15-induced dendrite impairments., Conclusions: These data reveal that MIA impedes offsprings' dendrite development and causes depressive like behaviors by upregulating ISG15 and suppressing NEDD4/Rap2A signaling. The current findings suggest that inhibiting ISG15 may be a promising intervention of MIA-induced psychiatric disorders in the offsprings., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Manipulation of host protein post-translational modifications (PTMs) is used by various pathogens to interfere with host cell functions. Among these modifications, ubiquitin (UBI) and ubiquitin-like proteins (UBLs) constitute key targets because they are regulators of pathways essential for the host cell. In particular, these PTM modifiers control pathways that have been described as crucial for infection such as pathogen entry, replication, propagation, or detection by the host. Although bacterial pathogens lack eucaryotic-like UBI or UBL systems, many of them produce proteins that specifically interfere with these host PTMs during infection. In this review we discuss the different mechanisms used by bacteria to interfere with host UBI and the two UBLs, SUMO and NEDD8., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Linear ubiquitylation, in which ubiquitin units are covalently linked through N- and C-terminal amino acids, is a unique cellular signaling mechanism. This process is controlled by a single E3 ubiquitin ligase, the linear ubiquitin chain assembly complex (LUBAC), which is composed of three proteins - HOIL-1L, HOIP and SHARPIN. LUBAC is involved in the activation of the canonical NF-κB pathway and has been linked to NF-κB dependent malignancies. In this work, we present HOIP-based stapled alpha-helical peptides designed to inhibit LUBAC through the disruption of the HOIL-1L-HOIP interaction and loss of the functional complex. We find our HOIP peptides to be active LUBAC ubiquitylation inhibitors in vitro, though through interaction with HOIP rather than HOIL. Active peptides were shown to have inhibitory effects on cell viability, reduced NF-κB activity and decreased production of NF-κB related gene products. This work further demonstrates the potential of LUBAC as a therapeutic target and of the use of stapled peptides as inhibitors of protein-protein interactions., (Published by Elsevier Ltd.)

Activating transcription factor 5 (ATF5) is a member of the ATF/cAMP response element-binding protein family of transcription factors. ATF5 regulates stress responses and cell survival, proliferation, and differentiation and also plays a role in viral infections, cancer, diabetes, schizophrenia, and the olfactory system. Moreover, it was found to also have a critical cell cycle-dependent structural function at the centrosome. However, the mechanism that controls the localization of ATF5 at the centrosome is unclear. Here we report that ATF5 is small ubiquitin-like modifier (SUMO) 2/3-modified at a conserved SUMO-targeting consensus site in various types of mammalian cells. We found that SUMOylation of ATF5 is elevated in the G 1 phase of the cell cycle and diminished in the G 2 /M phase. ATF5 SUMOylation disrupted the interaction of ATF5 with several centrosomal proteins and dislodged ATF5 from the centrosome at the end of the M phase. Of note, blockade of ATF5 SUMOylation deregulated the centrosome cycle, impeded ATF5 translocation from the centrosome, and caused genomic instability and G 2 /M arrest in HeLa cells. Our results indicate that ATF5 SUMOylation is an essential mechanism that regulates ATF5 localization and function at the centrosome., (© 2018 by The American Society for Biochemistry and Molecular Biology, Inc.)

Ubiquitination and ubiquitin-like posttranslational modifications (PTM) regulate activity and stability of oncoproteins and tumor suppressors. This implicates PTMs as antineoplastic targets. One way to alter PTMs is to inhibit activity of deubiquitinases (DUB) that remove ubiquitin or ubiquitin-like proteins from substrate proteins. Roles of DUBs in carcinogenesis have been intensively studied, yet few inhibitors exist. Prior work provides a basis for the ubiquitin-specific protease 18 (USP18) as an antineoplastic target. USP18 is the major DUB that removes IFN-stimulated gene 15 (ISG15) from conjugated proteins. Prior work discovered that engineered loss of USP18 increases ISGylation and in contrast to its gain decreases cancer growth by destabilizing growth-regulatory proteins. Loss of USP18 reduced cancer cell growth by triggering apoptosis. Genetic loss of USP18 repressed cancer formation in engineered murine lung cancer models. The translational relevance of USP18 was confirmed by finding its expression was deregulated in malignant versus normal tissues. Notably, the recent elucidation of the USP18 crystal structure offers a framework for developing an inhibitor to this DUB. This review summarizes strong evidence for USP18 as a previously unrecognized pharmacologic target in oncology. Cancer Res; 78(3); 587-92. ©2018 AACR ., (©2018 American Association for Cancer Research.)

Prostate cancer is the most common carcinoma among aged males in western countries and more aggressive and lethal castration resistant prostate cancer often occurs after androgen deprivation therapy. The high expression of androgens and androgen receptor is closely related to prostate cancer. Efficient androgen receptor antagonists, such as enzalutamide and ARN-509, could be employed as potent anti-prostate cancer agents. Nevertheless, recent studies have revealed that F876L mutation in androgen receptor converts the action of enzalutamide and ARN-509 from an antagonist to agonist, so that novel strategies are urgent to address this resistance mechanism. In this review, we focus on the discussion about some novel strategies, which targets androgen receptor mainly through the degrading pathway as potential treatments for prostate cancer., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.)

Small ubiquitin‑related modifier (SUMO) proteins bind to the lysine residue of target proteins to produce functionally mature proteins. The abnormal SUMOylation of certain target proteins is associated with diseases including cancer, heart disease, diabetes, arthritis, degenerative diseases and brain ischemia/stroke. Thus, there has been growing appreciation for the potential importance of the SUMO conjugation pathway as a target for treating these diseases. This review introduces the important steps in the reversible SUMOylation pathway. The SUMO inhibitors disclosed in the patents between 2012 and 2015 are divided into different categories according to their mechanisms of action. Certain compounds disclosed in this review have also been reported in other articles for their inhibition of the SUMOylation pathway following screening in cell lines. Although there are few studies using animal models or clinical trials that have used these compounds, the application of bortezomin, a ubiquitylation inhibitor, for treating cancer indicates that SUMO inhibitors may be clinically successful.

The discovery of ubistatins, small molecules that impair proteasomal degradation of proteins by directly binding to polyubiquitin, makes ubiquitin itself a potential therapeutic target. Although ubistatins have the potential for drug development and clinical applications, the lack of structural details of ubiquitin-ubistatin interactions has impeded their development. Here, we characterized a panel of new ubistatin derivatives using functional and binding assays. The structures of ubiquitin complexes with ubistatin B and hemi-ubistatin revealed direct interactions with ubiquitin's hydrophobic surface patch and the basic/polar residues surrounding it. Ubistatin B binds ubiquitin and diubiquitin tighter than a high-affinity ubiquitin receptor and shows strong preference for K48 linkages over K11 and K63. Furthermore, ubistatin B shields ubiquitin conjugates from disassembly by a range of deubiquitinases and by the 26S proteasome. Finally, ubistatin B penetrates cancer cells and alters the cellular ubiquitin landscape. These findings highlight versatile properties of ubistatins and have implications for their future development and use in targeting ubiquitin-signaling pathways., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Respiratory syncytial virus (RSV) is the most important cause of viral acute respiratory tract infections and hospitalizations in children, for which no vaccine or specific treatments are available. RSV causes airway mucosa inflammation and cellular oxidative damage by triggering production of reactive oxygen species and by inhibiting at the same time expression of antioxidant enzymes, via degradation of the transcription factor NF-E2-related factor 2 (NRF2). RSV infection induces NRF2 deacetylation, ubiquitination, and degradation through a proteasome-dependent pathway. Although degradation via KEAP1 is the most common mechanism, silencing KEAP1 expression did not rescue NRF2 levels during RSV infection. We found that RSV-induced NRF2 degradation occurs in an SUMO-specific E3 ubiquitin ligase - RING finger protein 4 (RNF4)-dependent manner. NRF2 is progressively SUMOylated in RSV infection and either blocking SUMOylation or silencing RNF4 expression rescued both NRF2 nuclear levels and transcriptional activity. RNF4 associates with promyelocytic leukemia - nuclear bodies (PML-NBs). RSV infection induces the expression of PML and PML-NBs formation in an interferon (INF)-dependent manner and also induces NRF2 - PMN-NBs association. Inhibition of PML-NB formation by blocking IFN pathway or silencing PML expression resulted in a significant reduction of RSV-associated NRF2 degradation and increased antioxidant enzyme expression, identifying the RNF4-PML pathway as a key regulator of antioxidant defenses in the course of viral infection., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Because protein-protein interactions underpin most biological processes, developing tools that target them to understand their function or to inform the development of therapeutics is an important task. SUMOylation is the posttranslational covalent attachment of proteins in the SUMO family (SUMO-1, SUMO-2, or SUMO-3), and it regulates numerous cellular pathways. SUMOylated proteins are recognized by proteins with SUMO-interaction motifs (SIMs) that facilitate noncovalent interactions with SUMO. We describe the use of the Affimer system of peptide display for the rapid isolation of synthetic binding proteins that inhibit SUMO-dependent protein-protein interactions mediated by SIMs both in vitro and in cells. Crucially, these synthetic proteins did not prevent SUMO conjugation either in vitro or in cell-based systems, enabling the specific analysis of SUMO-mediated protein-protein interactions. Furthermore, through structural analysis and molecular modeling, we explored the molecular mechanisms that may underlie their specificity in interfering with either SUMO-1-mediated interactions or interactions mediated by either SUMO-2 or SUMO-3. Not only will these reagents enable investigation of the biological roles of SUMOylation, but the Affimer technology used to generate these synthetic binding proteins could also be exploited to design or validate reagents or therapeutics that target other protein-protein interactions., (Copyright © 2017 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.)

Epstein-Barr virus (EBV)-encoded latent membrane protein 1 (LMP1) is an oncoviral protein that plays a pivotal role in EBV-induced oncogenic transformation. The function of LMP1 in EBV-induced oncogenesis has been well studied. However, the molecular mechanisms underlying LMP1 protein stability remain poorly understood. In this study, we found that ribosomal protein s27a (RPS27a) regulates LMP1 stability by a tandem affinity purification analysis. RPS27a interacts directly with LMP1 in vitro and in vivo. Furthermore, overexpression of RPS27a increases the half-life of LMP1 in 293T cells, whereas downregulation of RPS27a using lentiviral shRNA technology accelerates the decrease in LMP1 protein level in EBV-transformed B cells. We show that LMP1 ubiquitination via the proteasome is completely inhibited by overexpression of RPS27a. RPS27a also enhances LMP1-mediated proliferation and invasion, suggesting that RPS27a interacts with LMP1 and stabilizes it by suppressing proteasome-mediated ubiquitination. These results suggest that RSP27a could be a potential target in EBV-infected LMP1-positive cancer cells., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Neddylation is a post-translational protein modification associated with cancer development. MLN4924 is a neddylation inhibitor currently under investigation in multiple phase I studies on various malignancies, and its clincal name is Pevonedistat. It has been documented that MLN4924 blocks Cullins neddylation and inactivates CRLs and, in turn, triggers cell-cycle arrest, apoptosis, senescence and autophagy in many cancer cells. In this study, we investigated the anti-tumor effect of MLN4924 in human clear cell renal carcinoma (ccRCC). Levels of both Nedd8 activating enzyme E1 and Nedd8-conjugating enzyme E2 were higher in ccRCC tissues and RCC cancer cells than in normal. Moreover, MLN4924 treatment led to rapid inhibition of Cullin1 neddylation and notably suppressed growth and survival as well as migration in a dose-and time-dependent manner. Mechanistic studies revealed that MLN4924 induced the accumulation of a number of CRL substrates, including p21, p27 and Wee1 to trigger DNA damage and induce growth arrest at the G2/M phase. MLN4924 also induced anti-migration and anti-invasion by activating E-cadherin and repressing Vimentin. Taken together, this study provides the first evidence that neddylation pathway is overactive in ccRCC and that MLN4924 induces dose-dependent anti-proliferation, anti-migration, anti-invasion in ccRCC cells. The study thus indicates that MLN4924 has potential therapeutic value for the clinical treatment of renal cancer.

Interferon (IFN)-stimulated gene 15 (ISG15) is one of several proteins induced by conceptus-derived Type I or II IFNs in the uterus, and is implicated as an important factor in determining uterine receptivity to embryos in ruminants. But little is known about the role the ISG15 gene or gene product plays during embryo development. In the present study, both the expression profile and function of ISG15 were investigated in early bovine embryos in vitro. ISG15 mRNA was detectable in Day 0, 2, 6 and 8 bovine embryos, but IFN-τ (IFNT) mRNA only appeared from Day 6. This means that embryonic expression of ISG15 on Days 0 and 2 was not induced by embryonic IFNT. However, ISG15 mRNA expression paralleled the expression of IFNT mRNA in Day 6 and 8 embryos. ISG15-lentivirus interference plasmid (ISG15i) was injected into 2-cell embryos to knockdown ISG15 expression. This resulted in decreases in the proportion of hatching blastocysts, the diameter of blastocysts and cell number per diameter of blastocysts compared with control embryos. In addition, ISG15i inhibited IFNT, Ets2 (E26 oncogene homolog 2) mRNA and connexion 43 protein expression in Day 8 blastocysts, whereas exogenous IFNT treatment (100ngmL -1 , from Day 4 to Day 8) improved ISG15 mRNA and connexion 43 protein expression. In conclusion, it appears that ISG15 is involved in early bovine embryo development and that it regulates IFNT expression in the blastocyst.

We report herein the identification of the rhodium(III) complex [Rh(phq) 2 (MOPIP)] + (1) as a potent and selective ATP-competitive neural precursor cell expressed, developmentally down-regulated 8 (NEDD8)-activating enzyme (NAE) inhibitor. Structure-activity relationship analysis indicated that the overall organometallic design of complex 1 was important for anti-inflammatory activity. Complex 1 showed promising anti-inflammatory activity in vivo for the potential treatment of inflammatory bowel disease.

STING (also known as MITA) mediates the innate antiviral signaling and ubiquitination of STING is key to its function. However, the deubiquitination process of STING is unclear. Here we report that USP18 recruits USP20 to deconjugate K48-linked ubiquitination chains from STING and promotes the stability of STING and the expression of type I IFNs and proinflammatory cytokines after DNA virus infection. USP18 deficiency or knockdown of USP20 resulted in enhanced K48-linked ubiquitination and accelerated degradation of STING, and impaired activation of IRF3 and NF-κB as well as induction of downstream genes after infection with DNA virus HSV-1 or transfection of various DNA ligands. In addition, Usp18 -/- mice were more susceptible to HSV-1 infection compared with the wild-type littermates. USP18 did not deubiquitinate STING in vitro but facilitated USP20 to catalyze deubiquitination of STING in a manner independent of the enzymatic activity of USP18. In addition, reconstitution of STING into Usp18 -/- MEFs restored HSV-1-induced expression of downstream genes and cellular antiviral responses. Our findings thus uncover previously uncharacterized roles of USP18 and USP20 in mediating virus-triggered signaling and contribute to the understanding of the complicated regulatory system of the innate antiviral responses.

Inhibitors of apoptosis proteins (IAPs) are antiapoptotic regulators that block cell death, and are frequently overexpressed in several human cancers, where they facilitate evasion of apoptosis and promote cell survival. IAP antagonists are also known as second mitochondria-derived activator of caspase (SMAC)-mimetics, and have recently been considered as novel therapeutic agents for inducing apoptosis, alone and in combination with other anticancer drugs. In this study, we showed that T-3256336, the orally available IAP antagonist has synergistically enhances the antiproliferative effects of the NEDD8-activating enzyme (NAE) inhibitor pevonedistat (TAK-924/MLN4924), and these effects were attenuated by a TNFα-neutralizing antibody. In the present mechanistic analyses, pevonedistat induced TNFα mRNA and triggered IAP antagonist-dependent extrinsic apoptotic cell death in cancer cell lines. Furthermore, synergistic effects of the combination of T-3256336 and pevonedistat were demonstrated in a HL-60 mouse xenograft model. Our findings provide mechanistic evidence of the effects of IAP antagonists in combination with NAE inhibitors, and demonstrate the potential of a new combination therapy for cancer., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Acute lymphoblastic leukemia (ALL) is the leading cause of cancer-related death in children, and cure rates for adults remain dismal. Further, effective treatment strategies for relapsed/refractory ALL remain elusive. We previously uncovered that ALL cells are prone to apoptosis via endoplasmic reticulum (ER) stress/unfolded protein response (UPR)-mediated mechanisms. We investigated the antineoplastic activity of pevonedistat ® , a novel NEDD8-activating enzyme inhibitor that targets E3 cullin-RING ligases (CRLs) dependent proteasomal protein degradation, in ALL. Herein, we report that pevonedistat induces apoptosis in ALL cells by dysregulating the translational machinery leading to induction of proteotoxic/ER stress and UPR-mediated cell death. Mechanistically, pevonedistat led to P-eIF2a dephosphorylation causing atypical proteotoxic/ER stress from failure to halt protein translation via the UPR and upregulation of mTOR/p70S6K. Additional studies revealed that pevonedistat re-balanced the homeostasis of pro- and anti-apoptotic proteins to favor cell death through altered expression and/or activity of Mcl-1, NOXA, and BIM, suggesting that pevonedistat has a "priming" effect on ALL by altering the apoptotic threshold through modulation of Mcl-1 activity. Further, we demonstrated that pevonedistat synergizes with selected anti-leukemic agents in vitro, and prolongs survival of NSG mice engrafted with ALL cells, lending support for the use of pevonedistat as part of a multi-agent approach., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Background: The NEDD8 conjugation pathway modulates the ubiquitination and activity of a wide range of intracellular proteins, and its blockade by pevonedistat is emerging as a promising therapeutic approach in various cancer settings. However, systematic characterization of pevonedistat efficacy in specific tumor types and definition of response predictors are still missing., Methods: We investigated in vitro sensitivity to pevonedistat in 122 colorectal cancer (CRC) cell lines by an ATP-based proliferation assay and evaluated apoptosis and DNA content by flow cytometry. Associations between pevonedistat sensitivity and CRC molecular features were assessed by Student's t test. A 184-gene transcriptional predictor was generated in cell lines and applied to 87 metastatic CRC samples for which patient-derived xenografts (PDXs) were available. In vivo reponse to pevonedistat was assessed in PDX models (≥5 mice per group). All statistical tests were two-sided., Results: Sixteen (13.1%) cell lines displayed a marked response to pevonedistat, featuring DNA re-replication, proliferative block, and increased apoptosis. Pevonedistat sensitivity did not statistically significantly correlate with microsatellite instability or mutations in KRAS or BRAF and was functionally associated with low EGFR pathway activity. While ineffective on predicted resistant PDXs, in vivo administration of pevonedistat statistically significantly impaired growth of five out of six predicted sensitive models (P < .01). In samples from CRC patients, transcriptional prediction of pevonedistat sensitivity was associated with poor prognosis after surgery (hazard ratio [HR] = 2.49, 95% confidence interval [CI] = 1.34 to 4.62, P = .003) and early progression under cetuximab treatment (HR = 3.59, 95% CI = 1.60 to 8.04, P < .001). Histological and immunohistochemical analyses revealed that the pevonedistat sensitivity signature captures transcriptional traits of poor differentiation and high-grade mucinous adenocarcinoma., Conclusions: These results highlight NEDD8-pathway inhibition by pevonedistat as a potentially effective treatment for poorly differentiated, clinically aggressive CRC., (© The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

The preadipocyte-to-adipocyte differentiation (adipogenesis) is a key process in fat mass increase and thus it is regarded as a compelling target for preventing or treating obesity. Of adipogenic hormone receptors, peroxisome proliferator-activated receptor gamma (PPARγ) has crucial roles in adipogenesis and lipid accumulation within adipocytes. Here we demonstrate that the NEDD8 (neuronal precursor cell expressed, developmentally downregulated 8)-based post-translation modification (neddylation) of PPARγ is essential for adipogenesis. During adipogenesis, NEDD8 is robustly induced in preadipocytes and conjugates with PPARγ, leading to PPARγ stabilization. When the neddylation process was blocked by NEDD8-targeting siRNAs (or viral vectors) or an inhibitor MLN4924, adipocyte differentiation and fat tissue development were substantially impaired. We also demonstrate that MLN4924 effectively prevents the high-fat diet-induced obesity and glucose intolerance in mice. This study provides a better understanding of how the PPARγ signaling pathway starts and lasts during adipogenesis and a potential anti-obesity strategy that targets the neddylation of PPARγ.

Metastasis is the main challenge of osteosarcoma treatment. Herein, we first reveal the oncogenic role of FAT10 in metastasis of osteosarcoma. FAT10 was upregulated in osteosarcoma, especially in metastatic osteosarcoma. High level of FAT10 was associated with poorer prognosis of osteosarcoma patients. Moreover, Transwell and Matrigel assays revealed that silencing FAT10 significantly inhibited the invasive and migratory abilities of osteosarcoma cells. Metastasis assay in vivo showed that silencing FAT10 decreased the number of mice with distant metastasis. We also found that FAT10 may act its oncogenic functions through regulating HOXB9. Collectively, the results suggested that FAT10 may be a novel therapeutic target for osteosarcoma patients.

Colorectal cancer is the third most frequently diagnosed cancer and the combination of radiation with capecitabine has been shown to achieve only 15% to 25% of pathologic complete response. This study aimed to investigate the effect of MLN4924, a potent small molecule inhibitor of SKP1-Cullin-F-box proteins E3 ubiquitin ligases, as a novel radiosensitizing agent in colorectal cancer cells. Indeed, we found that MLN4924 effectively sensitized colorectal cancer cells to radiation with a sensitivity-enhancement ratio of 1.61 for HT-29 cells and 1.35 for HCT-116 cells. Mechanistically, MLN4924 significantly enhanced radiation-induced G2/M arrest, apoptosis, and DNA damage response through accumulation of p27. Knockdown of p27 via small interfering RNA partially inhibited MLN4924-induced radiosensitization, indicating a causal role played by p27. Our study suggested that MLN4924 could be further developed as a novel radiosensitizing agent against colorectal cancer., (© The Author(s) 2015.)

MLN4924, also known as pevonedistat, is the first-in-class inhibitor of NEDD8-activating enzyme, which blocks the entire neddylation modification of proteins. Previous preclinical studies and current clinical trials have been exclusively focused on its anticancer property. Unexpectedly, we show here, to our knowledge for the first time, that MLN4924, when applied at nanomolar concentrations, significantly stimulates in vitro tumor sphere formation and in vivo tumorigenesis and differentiation of human cancer cells and mouse embryonic stem cells. These stimulatory effects are attributable to (i) c-MYC accumulation via blocking its degradation and (ii) continued activation of EGFR (epidermal growth factor receptor) and its downstream pathways, including PI3K/AKT/mammalian target of rapamycin and RAS/RAF/MEK/ERK, via inducing EGFR dimerization. Finally, MLN4924 accelerates EGF-mediated skin wound healing in mouse and stimulates cell migration in an in vitro culture setting. Taking these data together, our study reveals that neddylation modification could regulate stem cell proliferation and differentiation and that a low dose of MLN4924 might have a therapeutic value for stem cell therapy and tissue regeneration.

MLN4924 is a recently discovered small molecule inhibitor of NEDD8-Activating Enzyme (NAE). Because cullin RING ligase (CRL), the largest family of E3 ubiquitin ligase, requires cullin neddylation for its activity, MLN4924, therefore, acts as an indirect inhibitor of CRL by blocking cullin neddylation. Given that CRLs components are up-regulated, whereas neddylation modification is over-activated in a number of human cancers, MLN4924 was found to be effective in growth suppression of cancer cells. Whether MLN4924 is effective against gastric cancer cells, however, remains elusive. Here we showed that in gastric cancer cells, MLN4924 rapidly inhibited cullin 1 neddylation and remarkably suppressed growth and survival as well as migration in a dose-and time-dependent manner. Mechanistic studies in combination with siRNA knockdown-based rescue experiments revealed that MLN4924 induced the accumulation of a number of CRL substrates, including CDT1/ORC1, p21/p27, and PHLPP1 to trigger DNA damage response and induce growth arrest at the G2/M phase, to induce senescence, as well as autophagy, respectively. MLN4924 also significantly suppressed migration by transcriptionally activating E-cadherin and repressing MMP-9. Taken together, our study suggest that neddylation modification and CRL E3 ligase are attractive gastric cancer targets, and MLN4924 might be further developed as a potent therapeutic agent for the treatment of gastric cancer.

Neddylation is a posttranslational protein modification that conjugates ubiquitin-like protein neural precursor cell-expressed developmentally downregulated protein 8 (NEDD8) to target proteins and regulates diverse cellular processes. MLN4924, a novel NEDD8 activating enzyme inhibitor, which has emerged as a promising anticancer drug, has a multifaceted function by inhibiting the process of neddylation. However, the potential roles of MLN4924 and neddylation in IFN-β production remain unknown. In this study, we show that MLN4924 inhibits TLR3/4- and retinoic acid-inducible gene-I-induced IFN-β expression in different cells, whereas NEDD8 knockdown had no effects on IFN-β expression. The ability of the MLN4924 to inhibit IFN-β production was confirmed in vivo, as mice treated with MLN4924 exhibited decreased levels of IFN-β upon LPS or polyinosinic-polycytidylic acid stimulation. Furthermore, we show that MLN4924 inhibits IFN regulatory factor 3 (IRF3) transcriptional activation and prevents IRF3 binding to IFN-β promoter. Our findings suggest that MLN4924 inhibits TLR3/4- and retinoic acid-inducible gene-I-induced IFN-β expression by preventing IRF3 binding to the IFN-β promoter, with a neddylation-independent manner. Therefore, our results provide new insight into the mechanism of MLN4924 and may have significant implications for the treatment of MLN4924., (Copyright © 2016 by The American Association of Immunologists, Inc.)

Mammalian target of rapamycin complex 1 (mTORC1) is a master regulator of cellular metabolism, growth, and proliferation. mTORC1 has been implicated in many diseases such as cancer, diabetes, and neurodegeneration, and is a target to prolong lifespan. Here we report a small molecule inhibitor (Cbz-B3A) of mTORC1 signaling. Cbz-B3A inhibits the phosphorylation of eIF4E-binding protein 1 (4EBP1) and blocks 68% of translation. In contrast, rapamycin preferentially inhibits the phosphorylation of p70(S6k) and blocks 35% of translation. Cbz-B3A does not appear to bind directly to mTORC1, but instead binds to ubiquilins 1, 2, and 4. Knockdown of ubiquilin 2, but not ubiquilins 1 and 4, decreases the phosphorylation of 4EBP1, suggesting that ubiquilin 2 activates mTORC1. The knockdown of ubiquilins 2 and 4 decreases the effect of Cbz-B3A on 4EBP1 phosphorylation. Cbz-B3A slows cellular growth of some human leukemia cell lines, but is not cytotoxic. Thus Cbz-B3A exemplifies a novel strategy to inhibit mTORC1 signaling that might be exploited for treating many human diseases. We propose that Cbz-B3A reveals a previously unappreciated regulatory pathway coordinating cytosolic protein quality control and mTORC1 signaling., (© 2016 by The American Society for Biochemistry and Molecular Biology, Inc.)

Mantle cell lymphoma (MCL) is characterized by an aggressive clinical course and inevitable development of refractory disease, stressing the need to develop alternative therapeutic strategies. To this end, we evaluated pevonedistat (MLN4924), a novel potent and selective NEDD8-activating enzyme inhibitor in a panel of MCL cell lines, primary MCL tumor cells, and 2 distinct murine models of human MCL. Pevonedistat exposure resulted in a dose-, time-, and caspase-dependent cell death in the majority of the MCL cell lines and primary tumor cells tested. Of interest, in the MCL cell lines with lower half-maximal inhibitory concentration (0.1-0.5 μM), pevonedistat induced G1-phase cell cycle arrest, downregulation of Bcl-xL levels, decreased nuclear factor (NF)-κB activity, and apoptosis. In addition, pevonedistat exhibited additive/synergistic effects when combined with cytarabine, bendamustine, or rituximab. In vivo, as a single agent, pevonedistat prolonged the survival of 2 MCL-bearing mouse models when compared with controls. Pevonedistat in combination with rituximab led to improved survival compared with rituximab or pevonedistat monotherapy. Our data suggest that pevonedistat has significant activity in MCL preclinical models, possibly related to effects on NF-κB activity, Bcl-xL downregulation, and G1 cell cycle arrest. Our findings support further investigation of pevonedistat with or without rituximab in the treatment of MCL., (© 2016 by The American Society of Hematology.)

FBXW7 is a haploinsufficient tumor suppressor with loss-of-function mutations occurring in human cancers. FBXW7 inactivation causes genomic instability, but the mechanism remains elusive. Here we show that FBXW7 facilitates nonhomologous end-joining (NHEJ) repair and that FBXW7 depletion causes radiosensitization. In response to ionizing radiation, ATM phosphorylates FBXW7 at serine 26 to recruit it to DNA double-strand break (DSB) sites, whereas activated DNA-PKcs phosphorylates XRCC4 at serines 325/326, which promotes binding of XRCC4 to FBXW7. SCF(FBXW7) E3 ligase then promotes polyubiquitylation of XRCC4 at lysine 296 via lysine 63 linkage for enhanced association with the Ku70/80 complex to facilitate NHEJ repair. Consistent with these findings, a small-molecule inhibitor that abrogates XRCC4 polyubiquitylation reduces NHEJ repair. Our study demonstrates one mechanism by which FBXW7 contributes to genome integrity and implies that inactivated FBXW7 in human cancers could be a strategy for increasing the efficacy of radiotherapy., (Copyright © 2016 Elsevier Inc. All rights reserved.)

In terms of infected human individuals, herpesviruses range among the most successful virus families. Subclinical herpesviral infections in healthy individuals contrast with life-threatening syndromes under immunocompromising and immunoimmature conditions. Based on our finding that cytomegaloviruses interact with Cullin Roc ubiquitin ligases (CRLs) in the context of interferon antagonism, we systematically assessed viral dependency on CRLs by utilizing the drug MLN4924. CRL activity is regulated through the conjugation of Cullins with the ubiquitin-like molecule Nedd8. By inhibiting the Nedd8-activating Enzyme (NAE), MLN4924 interferes with Nedd8 conjugation and CRL activity. MLN4924 exhibited pronounced antiviral activity against mouse and human cytomegalovirus, herpes simplex virus (HSV)- 1 (including multi-drug resistant clinical isolates), HSV-2, adeno and influenza viruses. Human cytomegalovirus genome amplification was blocked at nanomolar MLN4924 concentrations. Global proteome analyses revealed that MLN4924 blocks cytomegaloviral replication despite increased IE1 amounts. Expression of dominant negative Cullins assigned this IE regulation to defined Cullin molecules and phenocopied the antiviral effect of MLN4924.

The ubiquitin proteasome system (UPS) plays vital roles in maintaining protein equilibrium mainly through proteolytic degradation of targeted substrates. The archetypical SCF ubiquitin E3 ligase complex contains a substrate recognition subunit F-box protein that recruits substrates to the catalytic ligase core for its polyubiquitylation and subsequent proteasomal degradation. Several well-characterized F-box proteins have been demonstrated that are tightly linked to neoplasia. There is mounting information characterizing F-box protein-substrate interactions with the rationale to develop unique therapeutics for cancer treatment. Here we review that how F-box proteins function in cancer and summarize potential small molecule inhibitors for cancer therapy., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

The ubiquitin-like molecule NEDD8 is essential for viability, growth and development, and is a potential target for therapeutic intervention. We found that the small molecule inhibitor of NEDDylation, MLN4924, alters the morphology and increases the surface size of the nucleolus in human and germline cells of Caenorhabditis elegans in the absence of nucleolar fragmentation. SILAC proteomics and monitoring of rRNA production, processing and ribosome profiling shows that MLN4924 changes the composition of the nucleolar proteome but does not inhibit RNA Pol I transcription. Further analysis demonstrates that MLN4924 activates the p53 tumour suppressor through the RPL11/RPL5-Mdm2 pathway, with characteristics of nucleolar stress. The study identifies the nucleolus as a target of inhibitors of NEDDylation and provides a mechanism for p53 activation upon NEDD8 inhibition. It also indicates that targeting the nucleolar proteome without affecting nucleolar transcription initiates the required signalling events for the control of cell cycle regulators.

SUMOylation is recently found to function as a targeting signal for the degradation of substrates through the ubiquitin-proteasome system. RNF4 is the most studied human SUMO-targeted ubiquitin E3 ligase. However, the relationship between SUMO proteases, SENPs, and RNF4 remains obscure. There are limited examples of the SENP regulation of SUMO2/3-targeted proteolysis mediated by RNF4. The present study investigated the role of SENP3 in the global protein turnover related to SUMO2/3-targeted ubiquitination and focused in particular on the SENP3 regulation of the stability of Sp1. Our data demonstrated that SENP3 impaired the global ubiquitination profile and promoted the accumulation of many proteins. Sp1, a cancer-associated transcription factor, was among these proteins. SENP3 increased the level of Sp1 protein via antagonizing the SUMO2/3-targeted ubiquitination and the consequent proteasome-dependent degradation that was mediated by RNF4. De-conjugation of SUMO2/3 by SENP3 attenuated the interaction of Sp1 with RNF4. In gastric cancer cell lines and specimens derived from patients and nude mice, the level of Sp1 was generally increased in parallel to the level of SENP3. These results provided a new explanation for the enrichment of the Sp1 protein in various cancers, and revealed a regulation of SUMO2/3 conjugated proteins whose levels may be tightly controlled by SENP3 and RNF4.

Purpose: Evaluate the safety, pharmacokinetic profile, pharmacodynamic effects, and antitumor activity of the first-in-class investigational NEDD8-activating enzyme (NAE) inhibitor pevonedistat (TAK-924/MLN4924) in patients with relapsed/refractory lymphoma or multiple myeloma., Experimental Design: Patients with relapsed/refractory myeloma (n = 17) or lymphoma (n = 27) received intravenous pevonedistat 25 to 147 mg/m(2) on days 1, 2, 8, 9 (schedule A; n = 27) or 100 to 261 mg/m(2) on days 1, 4, 8, 11 (schedule B; n = 17) of 21-day cycles., Results: Maximum tolerated doses were 110 mg/m(2) (schedule A) and 196 mg/m(2) (schedule B). Dose-limiting toxicities included febrile neutropenia, transaminase elevations, muscle cramps (schedule A), and thrombocytopenia (schedule B). Common adverse events included fatigue and nausea. Common grade ≥3 events were anemia (19%; schedule A), and neutropenia and pneumonia (12%; schedule B). Clinically significant myelosuppression was uncommon. There were no treatment-related deaths. Pevonedistat pharmacokinetics exhibited a biphasic disposition phase and approximate dose-proportional increases in systemic exposure. Consistent with the short mean elimination half-life of approximately 8.5 hours, little-to-no drug accumulation in plasma was seen after multiple dosing. Pharmacodynamic evidence of NAE inhibition included increased skin levels of CDT-1 and NRF-2 (substrates of NAE-dependent ubiquitin ligases), and increased NRF-2-regulated gene transcript levels in whole blood. Pevonedistat-NEDD8 adduct was detected in bone marrow aspirates, indicating pevonedistat target engagement in the bone marrow compartment. Three lymphoma patients had partial responses; 30 patients achieved stable disease., Conclusions: Pevonedistat demonstrated anticipated pharmacodynamic effects in the clinical setting, a tolerable safety profile, and some preliminary evidence that may be suggestive of the potential for activity in relapsed/refractory lymphoma., (©2015 American Association for Cancer Research.)

Unlabelled: HIV-1 Vpu decreases the exposure of epitopes within the viral envelope glycoprotein (Env) on the surface of infected cells by downregulating both BST2 and CD4. To test the hypothesis that inhibiting Vpu activity would increase the exposure of these epitopes and sensitize infected cells to antibody-dependent cellular cytotoxicity (ADCC), we treated cells with the Nedd8 activation enzyme (NAE) inhibitor MLN4924, which inhibits the cullin1-based ubiquitin ligase complex coopted by Vpu to degrade cellular targets. Treatment of HeLa cells with MLN4924 or expression of a dominant negative mutant of cullin1 inhibited the Vpu-mediated downregulation of CD4 but not the downregulation of BST2. NAE inhibition also increased the surface exposure of CD4-induced epitopes within Env on HEK293 cells containing an inducible HIV genome, on infected CEM T cells, and on infected primary T cells. In contrast, the Vpu-mediated downregulation of BST2 was substantially inhibited by MLN4924 only when T cells were treated with alpha interferon (IFN-α) to induce high levels of BST2 expression. As reported previously, the absence of vpu or nef and even more so the combined absence of these two genes sensitized infected cells to ADCC. However, NAE inhibition affected ADCC minimally. Paradoxically, even in infected, IFN-treated cells in which NAE inhibition substantially rescued the surface level of BST2, the surface level of Env detected with an antibody recognizing a CD4-independent epitope (2G12) was minimally increased. Mutation of the C-terminal Vpu residue W76, which supports the ability of Vpu to stimulate virion release by displacing BST2 from assembly sites on the plasma membrane by a cullin1-independent mechanism, increased the exposure of Env detected by 2G12 on infected T cells. Thus, inhibiting the displacement function of Vpu together with its ability to degrade CD4 and BST2 may be required to sensitize infected cells to ADCC., Importance: Pathogenic viruses encode gene products that enable evasion of host immune surveillance mechanisms. One such mechanism is antibody-dependent cellular cytotoxicity (ADCC), whereby host antibodies bind envelope glycoproteins of the virus that are inserted into the cellular membrane and direct the destruction of infected cells. Targeting pharmacologically the activity of HIV-1 Vpu, which contributes to evasion of ADCC, could potentially sensitize infected cells to this immune surveillance mechanism, an outcome that would have therapeutic implications with respect to the goal of curing HIV-1 infection. The Nedd8 activation enzyme inhibitor MLN4924 blocks the activity of the host ubiquitin ligase that Vpu coopts to direct the degradation of CD4 and BST2. We observed that while MLN4924 partially reverses the activity of Vpu and could become part of a therapeutic approach by virtue of CD4-induced epitope exposure, sufficient Vpu activity as an antagonist of BST2 persists despite this drug to allow escape from ADCC., (Copyright © 2016, American Society for Microbiology. All Rights Reserved.)

Purpose: CKS1B is significantly upregulated in multiple myeloma and associated with poor prognosis. The identification of novel therapies is essential for effective treatment of patients resistant to chemotherapy. The NEDD8 inhibitor MLN4924 selectively targets SCF(Skp2) activation and offers a more specific approach to protein degradation inhibition than total proteasomal inhibition. The goal of this study was to evaluate whether MLN4924 is effective in high CKS1B conditions and identify mechanisms regulating drug potency., Experimental Design: Bortezomib and MLN4924 sensitivity was assessed through proliferation, viability, clonogenic potential, and senescence induction in cells overexpressing CKS1B. The mechanism for MLN4924 sensitivity was elucidated by immunoblot analysis of SCF(skp) substrates and confirmed by shRNA knockdown. The clinical relevance of the NEDD8 pathway was examined in gene expression profiles (GEP) derived from healthy people, patients with monoclonal gammopathy of undetermined significance (MGUS), and multiple myeloma., Results: Cells overexpressing CKS1B were resistant to bortezomib but sensitive to MLN4924. Treatment of CKS1B-overexpressing cells with MLN4924 decreased proliferation, clonogenicity, and induced senescence. MLN4924, but not bortezomib, induced stabilization of p21 and knockdown of p21 resulted in loss of MLN4924 sensitivity. Patients with MGUS and multiple myeloma exhibited increased expression of NEDD8 pathway genes relative to normal plasma cells. Multiple myeloma patients with high NEDD8 expression were linked to bortezomib resistance in clinical trials, and had inferior outcomes., Conclusions: Our data demonstrate that cells with elevated CKS1B expression are resistant to bortezomib but sensitive to MLN4924 and offer a mechanism through the stabilization of p21. These findings provide rationale for targeting the NEDD8 pathway in multiple myeloma patients exhibiting elevated expression of CKS1B. Clin Cancer Res; 21(24); 5532-42. ©2015 AACR., (©2015 American Association for Cancer Research.)

High levels of microRNA-155 (miR-155) are associated with poor outcome in acute myeloid leukemia (AML). In AML, miR-155 is regulated by NF-κB, the activity of which is, in part, controlled by the NEDD8-dependent ubiquitin ligases. We demonstrate that MLN4924, an inhibitor of NEDD8-activating enzyme presently being evaluated in clinical trials, decreases binding of NF-κB to the miR-155 promoter and downregulates miR-155 in AML cells. This results in the upregulation of the miR-155 targets SHIP1, an inhibitor of the PI3K/Akt pathway, and PU.1, a transcription factor important for myeloid differentiation, leading to monocytic differentiation and apoptosis. Consistent with these results, overexpression of miR-155 diminishes MLN4924-induced antileukemic effects. In vivo, MLN4924 reduces miR-155 expression and prolongs the survival of mice engrafted with leukemic cells. Our study demonstrates the potential of miR-155 as a novel therapeutic target in AML via pharmacologic interference with NF-κB-dependent regulatory mechanisms. We show the targeting of this oncogenic microRNA with MLN4924, a compound presently being evaluated in clinical trials in AML. As high miR-155 levels have been consistently associated with aggressive clinical phenotypes, our work opens new avenues for microRNA-targeting therapeutic approaches to leukemia and cancer patients.

Perforin-2 (MPEG1) is an effector of the innate immune system that limits the proliferation and spread of medically relevant Gram-negative, -positive, and acid fast bacteria. We show here that a cullin-RING E3 ubiquitin ligase (CRL) complex containing cullin-1 and βTrCP monoubiquitylates Perforin-2 in response to pathogen associated molecular patterns such as LPS. Ubiquitylation triggers a rapid redistribution of Perforin-2 and is essential for its bactericidal activity. Enteric pathogens such as Yersinia pseudotuberculosis and enteropathogenic Escherichia coli disarm host cells by injecting cell cycle inhibiting factors (Cifs) into mammalian cells to deamidate the ubiquitin-like protein NEDD8. Because CRL activity is dependent upon NEDD8, Cif blocks ubiquitin dependent trafficking of Perforin-2 and thus, its bactericidal activity. Collectively, these studies further underscore the biological significance of Perforin-2 and elucidate critical molecular events that culminate in Perforin-2-dependent killing of both intracellular and extracellular, cell-adherent bacteria.

MLN4924, a small molecule inhibitor of NEDD8 activating enzyme (NAE), has been reported to elicit an anti-tumor effect on various malignancies. In this study, we investigated the anti-tumor effect of MLN4924 in human urothelial carcinoma (UC) in vitro and in vivo by using three human UC cell lines of various grading (T24, NTUB1 and RT4). The impact of MLN4924 on UC cells was determined by measuring viability (MTT), proliferation (BrdU incorporation), cell cycle progression (flow cytometry with propidium iodide staining) and apoptosis (flow cytometry with annexin V-FITC labeling). The cell cycle regulatory molecules, apoptosis-related molecules, and cell stress-related proteins were examined by Western blotting. The influence of tumor cell migration and invasion was analyzed by Transwell and wound healing assays. We also evaluated the effects of MLN4924 on tumor growth by a SCID xenograft mouse model. The data show that MLN4924 induced dose-dependent cytotoxicity, anti-proliferation, anti-migration, anti-invasion and apoptosis in human UC cells, accompanied by activations of Bad, phospho-histone H2A.X, caspase-3, 7 and PARP, decreased level of phospho-Bcl2, and caused cell cycle retardation at the G2M phase. Moreover, MLN4924 activated endoplasmic reticulum stress-related molecules (caspase-4, phospho-eIF2α, ATF-4 and CHOP) and other stress responses (JNK and c-Jun activations). Finally, we confirmed MLN4924 inhibited tumor growth in a UC xenograft mouse model with minimal general toxicity. We concluded that MLN4924 induces apoptosis and cell cycle arrest, as well as activation of cell stress responses in human UC. These findings imply MLN4924 provides a novel strategy for the treatment of UC., (Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.)

The activities of many DNA-repair proteins are controlled through reversible covalent modification by ubiquitin and ubiquitin-like molecules. Nonhomologous end-joining (NHEJ) is the predominant DNA double-strand break (DSB) repair pathway in mammalian cells and is initiated by DSB ends being recognized by the Ku70/Ku80 (Ku) heterodimer. By using MLN4924, an anti-cancer drug in clinical trials that specifically inhibits conjugation of the ubiquitin-like protein, NEDD8, to target proteins, we demonstrate that NEDD8 accumulation at DNA-damage sites is a highly dynamic process. In addition, we show that depleting cells of the NEDD8 E2-conjugating enzyme, UBE2M, yields ionizing radiation hypersensitivity and reduced cell survival following NHEJ. Finally, we demonstrate that neddylation promotes Ku ubiquitylation after DNA damage and release of Ku and Ku-associated proteins from damage sites following repair. These studies provide insights into how the NHEJ core complex dissociates from repair sites and highlight its importance for cell survival following DSB induction., (Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.)

Liver cancer is the second-most frequent cause of cancer death in the world and is highly treatment resistant. We reported previously that inhibition of neddylation pathway with specific NAE inhibitor MLN4924, suppressed the malignant phenotypes of liver cancer. However, during the process, MLN4924 induces pro-survival autophagy as a mechanism of drug resistance. Here, we report that blockage of autophagy with clinically-available autophagy inhibitors (e.g. chloroquine) significantly enhanced the efficacy of MLN4924 on liver cancer cells by triggering apoptosis. Mechanistically, chloroquine enhanced MLN4924-induced up-regulation of pro-apoptotic proteins (e.g. NOXA) and down-regulation of anti-apoptotic proteins. Importantly, the down-regulation of NOXA expression via siRNA silencing substantially attenuated apoptosis of liver cancer cells. Further mechanistic studies revealed that blockage of autophagy augmented MLN4924-induced DNA damage and reactive oxygen species (ROS) generation. The elimination of DNA damage or blockage of ROS production significantly reduced the expression of NOXA, and thereby attenuated apoptosis and reduced growth inhibition of liver cancer cells. Moreover, blockage of autophagy enhanced the efficacy of MLN4924 in an orthotopic model of human liver cancer, with induction of NOXA and apoptosis in tumor tissues. These findings provide important preclinical evidence for clinical investigation of synergistic inhibition of neddylation and autophagy in liver cancer.