Cereblon negatively regulates TLR4 signaling through the attenuation of ubiquitination of TRAF6

The Relationship Between the Expression of CRBN in Peripheral Blood and the Severity and Prognosis of Adult Sepsis

Objective

To investigate the correlation between the expression of cereblon (CRBN) protein in peripheral blood and the severity and prognosis of sepsis.

Methods

A total of 130 patients with sepsis admitted to our hospital were selected as the observation subjects (sepsis group). The patients were divided into mild group, moderate group and severe group according to their conditions. The patients were divided into survival group and death group according to their living conditions within 28 days after admission. 130 health individuals were selected as the control group. The levels of CRBN mRNA, CRP and PCT in peripheral blood were detected.

Results

The levels of serum CRBN mRNA, CRP, and PCT in patients with sepsis were higher than those in the control group (P<0.05); As the condition worsens, the levels of CRBN mRNA, CRP, and PCT gradually increase, and there are statistically significant differences among patients with mild, moderate, and severe sepsis; Correlation analysis showed that the expression of CRBN mRNA in sepsis patients was positively correlated with CRP, PCT levels, APACHE II score and SOFA score (P<0.05); the 28-day cumulative survival rate of patients with high CRBN mRNA expression was significantly lower than that of patients with low CRBN mRNA expression (P<0.05); compared with the survival group, the levels of serum CRBN mRNA, CRP and PCT in the death group were significantly higher (P<0.05); the AUC of death in sepsis patients diagnosed by CRBN mRNA, CRP and PCT was 0.961, the combined diagnostic efficacy was higher than that of single detection (P<0.05).

Conclusion

The expression level of CRBN in the peripheral blood of patients with sepsis is increased, which is related to the severity and prognosis of the patients. The combination of CRP and PCT has certain diagnostic value for the death of sepsis patients.

β-arrestin 2 negatively regulates lung cancer progression by inhibiting the TRAF6 signaling axis for NF-κB activation and autophagy induced by TLR3 and TLR4

β-arrestin 2 (ARRB2) is functionally implicated in cancer progression via various signaling pathways. However, its role in lung cancer remains unclear. To obtain clinical insight on its function in lung cancer, microarray data from lung tumor tissues (LTTs) and matched lung normal tissues (mLNTs) of primary non-small cell lung cancer (NSCLC) patients (n = 37) were utilized. ARRB2 expression levels were markedly decreased in all 37 LTTs compared to those in matched LNTs of NSCLC patients. They were significantly co-related to enrichment gene sets associated with oncogenic and cancer genes. Importantly, Gene Set Enrichment Analysis (GSEA) between three LTTs with highly down-regulated ARRB2 and three LTTs with lowly down-regulated ARRB2 revealed significant enrichments related to toll-like receptor (TLR) signaling and autophagy genes in three LTTs with highly down-regulated ARRB2, suggesting that ARRB2 was negatively involved in TLR-mediated signals for autophagy induction in lung cancer. Biochemical studies for elucidating the molecular mechanism revealed that ARRB2 interacted with TNF receptor-associated factor 6 (TRAF6) and Beclin 1 (BECN1), thereby inhibiting the ubiquitination of TRAF6-TAB2 to activate NF-κB and TRAF6-BECN1 for autophagy stimulated by TLR3 and TLR4, suggesting that ARRB2 could inhibit the TRAF6-TAB2 signaling axis for NF-κB activation and TRAF6-BECN1 signaling axis for autophagy in response to TLR3 and TLR4. Notably, ARRB2-knockout (ARRB2KO) lung cancer cells exhibited marked enhancements of cancer migration, invasion, colony formation, and proliferation in response to TLR3 and TLR4 stimulation. Altogether, our current data suggest that ARRB2 can negatively regulate lung cancer progression by inhibiting TLR3- and TLR4-induced autophagy.

FFAR2 antagonizes TLR2- and TLR3-induced lung cancer progression via the inhibition of AMPK-TAK1 signaling axis for the activation of NF-κB

BACKGROUND

Free fatty acid receptors (FFARs) and toll-like receptors (TLRs) recognize microbial metabolites and conserved microbial products, respectively, and are functionally implicated in inflammation and cancer. However, whether the crosstalk between FFARs and TLRs affects lung cancer progression has never been addressed.

METHODS

We analyzed the association between FFARs and TLRs using The Cancer Genome Atlas (TCGA) lung cancer data and our cohort of non-small cell lung cancer (NSCLC) patient data (n = 42), and gene set enrichment analysis (GSEA) was performed. For the functional analysis, we generated FFAR2-knockout (FFAR2KO) A549 and FFAR2KO H1299 human lung cancer cells and performed biochemical mechanistic studies and cancer progression assays, including migration, invasion, and colony-formation assays, in response to TLR stimulation.

RESULTS

The clinical TCGA data showed a significant down-regulation of FFAR2, but not FFAR1, FFAR3, and FFAR4, in lung cancer, and a negative correlation with TLR2 and TLR3. Notably, GSEA showed significant enrichment in gene sets related to the cancer module, the innate signaling pathway, and the cytokine-chemokine signaling pathway in FFAR2^DownTLR2^UpTLR3^Up lung tumor tissues (LTTs) vs. FFAR2^upTLR2^DownTLR3^Down LTTs. Functionally, treatment with propionate (an agonist of FFAR2) significantly inhibited human A549 or H1299 lung cancer migration, invasion, and colony formation induced by TLR2 or TLR3 through the attenuation of the cAMP-AMPK-TAK1 signaling axis for the activation of NF-κB. Moreover, FFAR2KO A549 and FFAR2KO H1299 human lung cancer cells showed marked increases in cell migration, invasion, and colony formation in response to TLR2 or TLR3 stimulation, accompanied by elevations in NF-κB activation, cAMP levels, and the production of C-C motif chemokine ligand (CCL)2, interleukin (IL)-6, and matrix metalloproteinase (MMP) 2 cytokines.

CONCLUSION

Our results suggest that FFAR2 signaling antagonized TLR2- and TLR3-induced lung cancer progression via the suppression of the cAMP-AMPK-TAK1 signaling axis for the activation of NF-κB, and its agonist might be a potential therapeutic agent for the treatment of lung cancer.

A New Generation of IMiDs as Treatments for Neuroinflammatory and Neurodegenerative Disorders

The immunomodulatory imide drug (IMiD) class, which includes the founding drug member thalidomide and later generation drugs, lenalidomide and pomalidomide, has dramatically improved the clinical treatment of specific cancers, such as multiple myeloma, and it combines potent anticancer and anti-inflammatory actions. These actions, in large part, are mediated by IMiD binding to the human protein cereblon that forms a critical component of the E3 ubiquitin ligase complex. This complex ubiquitinates and thereby regulates the levels of multiple endogenous proteins. However, IMiD-cereblon binding modifies cereblon's normal targeted protein degradation towards a new set of neosubstrates that underlies the favorable pharmacological action of classical IMiDs, but also their adverse actions-in particular, their teratogenicity. The ability of classical IMiDs to reduce the synthesis of key proinflammatory cytokines, especially TNF-α levels, makes them potentially valuable to reposition as drugs to mitigate inflammatory-associated conditions and, particularly, neurological disorders driven by an excessive neuroinflammatory element, as occurs in traumatic brain injury, Alzheimer's and Parkinson's diseases, and ischemic stroke. The teratogenic and anticancer actions of classical IMiDs are substantial liabilities for effective drugs in these disorders and can theoretically be dialed out of the drug class. We review a select series of novel IMiDs designed to avoid binding with human cereblon and/or evade degradation of downstream neosubstrates considered to underpin the adverse actions of thalidomide-like drugs. These novel non-classical IMiDs hold potential as new medications for erythema nodosum leprosum (ENL), a painful inflammatory skin condition associated with Hansen's disease for which thalidomide remains widely used, and, in particular, as a new treatment strategy for neurodegenerative disorders in which neuroinflammation is a key component.

Novel, thalidomide-like, non-cereblon binding drug tetrafluorobornylphthalimide mitigates inflammation and brain injury

BACKGROUND

Quelling microglial-induced excessive neuroinflammation is a potential treatment strategy across neurological disorders, including traumatic brain injury (TBI), and can be achieved by thalidomide-like drugs albeit this approved drug class is compromised by potential teratogenicity. Tetrafluorobornylphthalimide (TFBP) and tetrafluoronorbornylphthalimide (TFNBP) were generated to retain the core phthalimide structure of thalidomide immunomodulatory imide drug (IMiD) class. However, the classical glutarimide ring was replaced by a bridged ring structure. TFBP/TFNBP were hence designed to retain beneficial anti-inflammatory properties of IMiDs but, importantly, hinder cereblon binding that underlies the adverse action of thalidomide-like drugs.

METHODS

TFBP/TFNBP were synthesized and evaluated for cereblon binding and anti-inflammatory actions in human and rodent cell cultures. Teratogenic potential was assessed in chicken embryos, and in vivo anti-inflammatory actions in rodents challenged with either lipopolysaccharide (LPS) or controlled cortical impact (CCI) moderate traumatic brain injury (TBI). Molecular modeling was performed to provide insight into drug/cereblon binding interactions.

RESULTS

TFBP/TFNBP reduced markers of inflammation in mouse macrophage-like RAW264.7 cell cultures and in rodents challenged with LPS, lowering proinflammatory cytokines. Binding studies demonstrated minimal interaction with cereblon, with no resulting degradation of teratogenicity-associated transcription factor SALL4 or of teratogenicity in chicken embryo assays. To evaluate the biological relevance of its anti-inflammatory actions, two doses of TFBP were administered to mice at 1 and 24 h post-injury following CCI TBI. Compared to vehicle treatment, TFBP reduced TBI lesion size together with TBI-induction of an activated microglial phenotype, as evaluated by immunohistochemistry 2-weeks post-injury. Behavioral evaluations at 1- and 2-weeks post-injury demonstrated TFBP provided more rapid recovery of TBI-induced motor coordination and balance impairments, versus vehicle treated mice.

CONCLUSION

TFBP and TFNBP represent a new class of thalidomide-like IMiDs that lower proinflammatory cytokine generation but lack binding to cereblon, the main teratogenicity-associated mechanism. This aspect makes TFBP and TFNBP potentially safer than classic IMiDs for clinical use. TFBP provides a strategy to mitigate excessive neuroinflammation associated with moderate severity TBI to, thereby, improve behavioral outcome measures and warrants further investigation in neurological disorders involving a neuroinflammatory component.

Thalidomide Attenuates Mast Cell Activation by Upregulating SHP-1 Signaling and Interfering with the Action of CRBN

Allergy is a chronic inflammatory disease, and its incidence has increased worldwide in recent years. Thalidomide, which was initially used as an anti-emetic drug but was withdrawn due to its teratogenic effects, is now used to treat blood cancers. Although the anti-inflammatory and immunomodulatory properties of thalidomide have been reported, little is known about its influence on the mast cell-mediated allergic reaction. In the present study, we aimed to evaluate the anti-allergic activity of thalidomide and the underlying mechanism using mouse bone marrow-derived mast cells (BMMCs) and passive cutaneous anaphylaxis (PCA) mouse models. Thalidomide markedly decreased the degranulation and release of lipid mediators and cytokines in IgE/Ag-stimulated BMMCs, with concurrent inhibition of FcεRI-mediated positive signaling pathways including Syk and activation of negative signaling pathways including AMP-activated protein kinase (AMPK) and SH2 tyrosine phosphatase-1 (SHP-1). The knockdown of AMPK or SHP-1 with specific siRNA diminished the inhibitory effects of thalidomide on BMMC activation. By contrast, the knockdown of cereblon (CRBN), which is the primary target protein of thalidomide, augmented the effects of thalidomide. Thalidomide reduced the interactions of CRBN with Syk and AMPK promoted by FcεRI crosslinking, thereby relieving the suppression of AMPK signaling and suppressing Syk signaling. Furthermore, oral thalidomide treatment suppressed the PCA reaction in mice. In conclusion, thalidomide suppresses FcεRI-mediated mast cell activation by activating the AMPK and SHP-1 pathways and antagonizing the action of CRBN, indicating that it is a potential anti-allergic agent.

Activity of a Novel Anti-Inflammatory Agent F-3,6'-dithiopomalidomide as a Treatment for Traumatic Brain Injury

Traumatic brain injury (TBI) is a major risk factor for several neurodegenerative disorders, including Parkinson's disease (PD) and Alzheimer's disease (AD). Neuroinflammation is a cause of later secondary cell death following TBI, has the potential to aggravate the initial impact, and provides a therapeutic target, albeit that has failed to translate into clinical trial success. Thalidomide-like compounds have neuroinflammation reduction properties across cellular and animal models of TBI and neurodegenerative disorders. They lower the generation of proinflammatory cytokines, particularly TNF-α which is pivotal in microglial cell activation. Unfortunately, thalidomide-like drugs possess adverse effects in humans before achieving anti-inflammatory drug levels. We developed F-3,6'-dithiopomalidomide (F-3,6'-DP) as a novel thalidomide-like compound to ameliorate inflammation. F-3,6'-DP binds to cereblon but does not efficiently trigger the degradation of the transcription factors (SALL4, Ikaros, and Aiolos) associated with the teratogenic and anti-proliferative responses of thalidomide-like drugs. We utilized a phenotypic drug discovery approach that employed cellular and animal models in the selection and development of F-3,6'-DP. F-3,6'-DP significantly mitigated LPS-induced inflammatory markers in RAW 264.7 cells, and lowered proinflammatory cytokine/chemokine levels in the plasma and brain of rats challenged with systemic LPS. We subsequently examined immunohistochemical, biochemical, and behavioral measures following controlled cortical impact (CCI) in mice, a model of moderate TBI known to induce inflammation. F-3,6'-DP decreased CCI-induced neuroinflammation, neuronal loss, and behavioral deficits when administered after TBI. F-3,6'-DP represents a novel class of thalidomide-like drugs that do not lower classical cereblon-associated transcription factors but retain anti-inflammatory actions and possess efficacy in the treatment of TBI and potentially longer-term neurodegenerative disorders.

USP15 negatively regulates lung cancer progression through the TRAF6-BECN1 signaling axis for autophagy induction

TNF receptor-associated factor 6 (TRAF6)-BECN1 signaling axis plays a pivotal role in autophagy induction through ubiquitination of BECN1, thereby inducing lung cancer migration and invasion in response to toll-like receptor 4 (TLR4) stimulation. Herein, we provide novel molecular and cellular mechanisms involved in the negative effect of ubiquitin-specific peptidase 15 (USP15) on lung cancer progression. Clinical data of the TCGA and primary non-small cell lung cancer (NSCLC) patients (n = 41) revealed that the expression of USP15 was significantly downregulated in lung cancer patients. Importantly, USP15-knockout (USP15KO) A549 and USP15KO H1299 lung cancer cells generated with CRISPR-Cas9 gene-editing technology showed increases in cancer migration and invasion with enhanced autophagy induction in response to TLR4 stimulation. In addition, biochemical studies revealed that USP15 interacted with BECN1, but not with TRAF6, and induced deubiquitination of BECN1, thereby attenuating autophagy induction. Notably, in primary NSCLC patients (n = 4) with low expression of USP15, 10 genes (CCNE1, MMP9, SFN, UBE2C, CCR2, FAM83A, ETV4, MYO7A, MMP11, and GSDMB) known to promote lung cancer progression were significantly upregulated, whereas 10 tumor suppressor genes (FMO2, ZBTB16, FCN3, TCF21, SFTPA1B, HPGD, SOSTDC1, TMEM100, GDF10, and WIF1) were downregulated, providing clinical relevance of the functional role of USP15 in lung cancer progression. Taken together, our data demonstrate that USP15 can negatively regulate the TRAF6-BECN1 signaling axis for autophagy induction. Thus, USP15 is implicated in lung cancer progression.

Caspase-8: Friend or Foe in Bortezomib/Lenalidomide-Based Therapy for Myeloma

Antiproliferation and proapoptosis are two major molecular mechanisms of action of drugs used for the treatment of multiple myeloma. Proteasome inhibitors, such as bortezomib (PS-341), and immunomodulatory drugs (IMiDs), such as lenalidomide, are the two drug types approved for the treatment of myeloma. Bortezomib and lenalidomide activate caspase-8 and promote the apoptosis of myeloma cells. However, caspase-8 inhibition potentiated the antiproliferative effect of lenalidomide and bortezomib in myeloma cells, suggesting that caspase-8 could regulate proliferation and apoptosis in the opposite pathway. In this mini-review, I summarized recent advances in determining the molecular mechanisms of caspase-8 in bortezomib–lenalidomide-based therapy for myeloma and explored the possible functions of caspase-8 in the proliferation and apoptosis of myeloma cells. Furthermore, future directions of caspase-8-based therapy for myeloma have been discussed.

Cereblon contributes to cardiac dysfunction by degrading Cav1.2α

AIMS

Cereblon (CRBN) is a substrate receptor of the E3 ubiquitin ligase complex that was reported to target ion channel proteins. L-type voltage-dependent Ca2+ channel (LTCC) density and dysfunction is a critical player in heart failure with reduced ejection fraction (HFrEF). However, the underlying cellular mechanisms by which CRBN regulates LTCC subtype Cav1.2α during cardiac dysfunction remain unclear. Here, we explored the role of CRBN in HFrEF by investigating the direct regulatory role of CRBN in Cav1.2α activity and examining how it can serve as a target to address myocardial dysfunction.

METHODS AND RESULTS

Cardiac tissues from HFrEF patients exhibited increased levels of CRBN compared with controls. In vivo and ex vivo studies demonstrated that whole-body CRBN knockout (CRBN-/-) and cardiac-specific knockout mice (Crbnfl/fl/Myh6Cre+) exhibited enhanced cardiac contractility with increased LTCC current (ICaL) compared with their respective controls, which was modulated by the direct interaction of CRBN with Cav1.2α. Mechanistically, the Lon domain of CRBN directly interacted with the N-terminal of Cav1.2α. Increasing CRBN levels enhanced the ubiquitination and proteasomal degradation of Cav1.2α and decreased ICaL. In contrast, genetic or pharmacological depletion of CRBN via TD-165, a novel PROTAC-based CRBN degrader, increased surface expression of Cav1.2α and enhanced ICaL. Low CRBN levels protected the heart against cardiomyopathy in vivo.

CONCLUSION

Cereblon selectively degrades Cav1.2α, which in turn facilitates cardiac dysfunction. A targeted approach or an efficient method of reducing CRBN levels could serve as a promising strategy for HFrEF therapeutics.

KEY QUESTION

KEY FINDING

TAKE-HOME MESSAGE

Cereblon modulates cardiac function by altering Cav1.2α current density and CRBN-targeting therapy could serve as a novel strategy for future HFrEF therapeutics.

The ubiquitination-dependent and -independent functions of cereblon in cancer and neurological diseases

Cereblon (CRBN) mediates the teratogenic effect of thalidomide in zebrafish, chicken, and humans. It additionally modulates the anti-myeloma effect of the immunomodulatory drugs (IMiDs) thalidomide, lenalidomide, and pomalidomide. IMiDs bind to CRBN and recruit neo-substrates for their ubiquitination and proteasome-mediated degradation, which significantly expands the application of proteolysis-targeting chimeras (PROTACs) for targeted drug discovery. However, the underlying molecular mechanisms by which CRBN mediates the teratogenicity and anti-myeloma effect of IMiDs are not fully elucidated. Furthermore, the normal physiological functions of endogenous CRBN have not been extensively studied, which precludes the thorough assessment of side effects of the CRBN ligand-based PROTACs in the treatment of cancer and neurological diseases. To advance our understanding of the diverse functions of CRBN, in this review, we will survey the ubiquitination-dependent and -independent functions of CRBN, summarize recent advances in the discovery of constitutive and neo-substrates of CRBN, and explore the molecular functions of CRBN in cancer treatment and in the development of neurological diseases. We will also discuss the potential future directions towards the identification of CRBN substrates and interacting proteins, and CRBN-ligand-based drug discovery in the treatment of cancer and neurological diseases.

Molecular Mechanisms of Cereblon-Interacting Small Molecules in Multiple Myeloma Therapy

Thalidomide analogues (or immunomodulatory imide drugs, IMiDs) are cornerstones in the treatment of multiple myeloma (MM). These drugs bind Cereblon (CRBN), a receptor for the Cullin-ring 4 ubiquitin-ligase (CRL4) complex, to modify its substrate specificity. IMiDs mediate CRBN-dependent engagement and proteasomal degradation of ‘neosubstrates’, Ikaros (IKZF1) and Aiolos (IKZF3), conveying concurrent antimyeloma activity and T-cell costimulation. There is now a greater understanding of physiological CRBN functions, including endogenous substrates and chaperone activity. CRISPR Cas9-based genome-wide screening has further elucidated the complex cellular machinery implicated in IMiD sensitivity, including IKZF1/3-independent mechanisms. New-generation IMiD derivatives with more potent anti-cancer properties—the CELMoDs (Cereblon E3 ligase modulators)—are now being evaluated. Rational drug design also allows ‘hijacking’ of CRL4^CRBN utilising proteolysis targeting chimeras (PROTACs) to convey entirely distinct substrate repertoires. As all these chemotypes—thalidomide, IMiDs, CELMoDs and PROTACs—engage CRBN and modify its functions, we describe them here in aggregate as ‘CRBN-interacting small molecules’ (CISMs). In this review, we provide a contemporary summary of the biological consequences of CRBN modulation by CISMs. Detailed molecular insight into CRBN–CISM interactions now provides an opportunity to more effectively target previously elusive cancer dependencies, representing a new and powerful tool for the implementation of precision medicine.

Neurodevelopmental Disorders (NDD) Caused by Genomic Alterations of the Ubiquitin-Proteasome System (UPS): the Possible Contribution of Immune Dysregulation to Disease Pathogenesis

Over thirty years have passed since the first description of ubiquitin-positive structures in the brain of patients suffering from Alzheimer’s disease. Meanwhile, the intracellular accumulation of ubiquitin-modified insoluble protein aggregates has become an indisputable hallmark of neurodegeneration. However, the role of ubiquitin and a fortiori the ubiquitin-proteasome system (UPS) in the pathogenesis of neurodevelopmental disorders (NDD) is much less described. In this article, we review all reported monogenic forms of NDD caused by lesions in genes coding for any component of the UPS including ubiquitin-activating (E1), -conjugating (E2) enzymes, ubiquitin ligases (E3), ubiquitin hydrolases, and ubiquitin-like modifiers as well as proteasome subunits. Strikingly, our analysis revealed that a vast majority of these proteins have a described function in the negative regulation of the innate immune response. In this work, we hypothesize a possible involvement of autoinflammation in NDD pathogenesis. Herein, we discuss the parallels between immune dysregulation and neurodevelopment with the aim at improving our understanding the biology of NDD and providing knowledge required for the design of novel therapeutic strategies.

Cereblon: promise and challenges for combating human diseases

Cereblon (CRBN) is a substrate recognition protein in the E3-ligase ubiquitin complex. The binding target of CRBN varies according to tissues and cells, and the protein regulates various biological functions by regulating tissue-specific targets. As new endogenous targets of CRBN have been identified over the past decade, the physiological and pathological functions of CRBN and its potential as a therapeutic target in various diseases have greatly expanded. For this purpose, in this review article, we introduce the basic principle of the ubiquitin-proteasome system, the regulation of physiological/pathological functions related to the endogenous substrate of CRBN, and the discovery of immunomodulatory imide drug-mediated neo-substrates of CRBN. In addition, the development of CRBN-based proteolysis-targeting chimeras, which has been actively researched recently, and strategies for developing therapeutic agents using them are introduced. These recent updates on CRBN will be useful in the establishment of strategies for disease treatment and utilization of CRBNs in biomedical engineering and clinical medicine.

Cereblon regulates NK cell cytotoxicity and migration via Rac1 activation

Rearrangement of the actin cytoskeleton is critical for cytotoxic and immunoregulatory functions as well as migration of natural killer (NK) cells. However, dynamic reorganization of actin is a complex process, which remains largely unknown. Here, we investigated the role of the protein Cereblon (CRBN), an E3 ubiquitin ligase complex co‐receptor and the primary target of the immunomodulatory drugs, in NK cells. We observed that CRBN partially colocalizes with F‐actin in chemokine‐treated NK cells and is recruited to the immunological synapse, thus suggesting a role for this protein in cytoskeleton reorganization. Accordingly, silencing of CRBN in NK cells results in a reduced cytotoxicity that correlates with a defect in conjugate and lytic synapse formation. Moreover, CRBN depletion significantly impairs the ability of NK cells to migrate and reduces the enhancing effect of lenalidomide on NK cell migration. Finally, we provided evidence that CRBN is required for activation of the small GTPase Rac1, a critical mediator of cytoskeleton dynamics. Indeed, in CRBN‐depleted NK cells, chemokine‐mediated or target cell–mediated Rac1 activation is significantly reduced. Altogether our data identify a critical role for CRBN in regulating NK cell functions and suggest that this protein may mediate the stimulatory effect of lenalidomide on NK cells.

Circ_0114428 Regulates Sepsis-Induced Kidney Injury by Targeting the miR-495-3p/CRBN Axis

Septic acute kidney injury (AKI) is considered as a severe and common complication of sepsis, with complex pathogenesis. Recently, Circular RNA (circRNA) is considered to be implicated in this disease. This study was intended to elucidate the role of circ_0114428 and the potential mechanism of action in sepsis-induced kidney injury. Sepsis-induced kidney injury cell model was established in human kidney 2 (HK2) cells by the treatment of lipopolysaccharide (LPS). The expression of circ_0114428, CRBN mRNA, and miR-495-3p was detected by quantitative real-time polymerase chain reaction (qRT-PCR). Cell viability was assessed by cell counting kit-8 (CCK-8) assay. The inflammatory response was monitored according to the release of proinflammatory factors by enzyme-linked immunosorbent assay (ELISA). Cell apoptosis was evaluated by flow cytometry assay. The activities of oxidative indicators were examined using the corresponding kits. Endoplasmic reticulum (ER) stress-related proteins and CRBN protein were quantified by western blot. RNA immunoprecipitation (RIP) assay was performed to ensure whether circ_0114428 could interact with Argonaute 2 (Ago2) protein. The potential miRNAs targeted by circ_0114428 were predicted by the bioinformatics tool and screened by RNA pull-down assay. The interaction between miR-495-3p and circ_0114428 or CRBN was validated by dual-luciferase reporter assay. The results showed that circ_0114428 and CRBN were upregulated in septic AKI serum specimens and LPS-induced HK2 cells. Circ_0114428 knockdown attenuated LPS-induced apoptosis, inflammation, oxidative stress, and ER stress, which were rescued by CRBN overexpression. Further analysis revealed that miR-495-3p was targeted by circ_0114428 and directly bound to CRBN, and circ_0114428 regulated CRBN expression by sponging miR-495-3p. Besides, miR-495-3p inhibition also reversed the effects of circ_0114428 knockdown. In conclusion, circ_00114428 knockdown attenuated LPS-induced HK2 cell injury by regulating CRBN expression via targeting miR-495-3p.

AMPKα1 Regulates Lung and Breast Cancer Progression by Regulating TLR4-Mediated TRAF6-BECN1 Signaling Axis

Simple Summary

TRAF6-BECN1 signaling axis in TLR4 signal plays an essential role for the autophagy induction, thereby it regulates cancer migration and invasion. Here we show that AMPKα1, one of the isoforms of AMPK, is functionally involved in autophagy induction by regulating the TRAF6-BECN1 signaling axis. In this context, AMPKα1-knockout lung or breast cancer cells exhibited the attenuation of cancer cell migration and invasion induced by TLR4 simulation. Additionally, we could find that the expression of AMPKα1 is positively associated with gene expressions related to autophagy, migration, and metastasis of cancer cells in primary non-small cell lung cancers (NSCLCs). These findings demonstrate that AMPKα1 plays a pivotal role in cancer progression by regulating the TRAF6-BECN1 signaling axis for autophagy induction.

Abstract

TRAF6-BECN1 signaling axis is critical for autophagy induction and functionally implicated in cancer progression. Here, we report that AMP-activated protein kinase alpha 1 (AMPKα1, PRKAA1) is positively involved in autophagy induction and cancer progression by regulating TRAF6-BECN1 signaling axis. Mechanistically, AMPKα1 interacted with TRAF6 and BECN1. It also enhanced ubiquitination of BECN1 and autophagy induction. AMPKα1-knockout (AMPKα1KO) HEK293T or AMPKα1-knockdown (AMPKα1KD) THP-1 cells showed impaired autophagy induced by serum starvation or TLR4 (Toll-like receptor 4) stimulation. Additionally, AMPKα1KD THP-1 cells showed decreases of autophagy-related and autophagosome-related genes induced by TLR4. AMPKα1KO A549 cells exhibited attenuation of cancer migration and invasion induced by TLR4. Moreover, primary non-small cell lung cancers (NSCLCs, n = 6) with low AMPKαl levels showed markedly decreased expression of genes related to autophagy, cell migration and adhesion/metastasis, inflammation, and TLRs whereas these genes were significantly upregulated in NSCLCs (n = 5) with high AMPKαl levels. Consistently, attenuation of cancer migration and invasion could be observed in AMPKα1KO MDA-MB-231 and AMPKα1KO MCF-7 human breast cancer cells. These results suggest that AMPKα1 plays a pivotal role in cancer progression by regulating the TRAF6-BECN1 signaling axis for autophagy induction.

p62 is Negatively Implicated in the TRAF6-BECN1 Signaling Axis for Autophagy Activation and Cancer Progression by Toll-Like Receptor 4 (TLR4)

Toll-like receptors (TLRs) induce the activation of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and autophagy through the TNF (Tumor necrosis factor) receptor-associated factor 6 (TRAF6)-evolutionarily conserved signaling intermediate in Toll pathways (ECSIT) and TRAF6-BECN1 signaling axes, respectively. Having shown that p62 negatively regulates Toll-like receptor 4 (TLR4)-mediated signaling via TRAF6-ECSIT signaling axis, we herein investigated whether p62 is functionally implicated in the TRAF6-BECN1 signaling axis, thereby regulating cancer cell migration and invasion. p62 interacted with TRAF6 and BECN1, to interrupt the functional associations required for TRAF6-BECN1 complex formation, leading to inhibitions of BECN1 ubiquitination and autophagy activation. Importantly, p62-deficient cancer cells, such as p62-knockdown (p62^KD) SK-HEP-1, p62^KD MDA-MB-231, and p62-knockout (p62^KO) A549 cells, showed increased activation of autophagy induced by TLR4 stimulation, suggesting that p62 negatively regulates autophagy activation. Moreover, these p62-deficient cancer cells exhibited marked increases in cell migration and invasion in response to TLR4 stimulation. Collectively, these results suggest that p62 is negatively implicated in the TRAF6-BECN1 signaling axis, thereby inhibiting cancer cell migration and invasion regulated by autophagy activation in response to TLR4 stimulation.

Neuroinflammation as a Factor of Neurodegenerative Disease: Thalidomide Analogs as Treatments

Neuroinflammation is initiated when glial cells, mainly microglia, are activated by threats to the neural environment, such as pathogen infiltration or neuronal injury. Although neuroinflammation serves to combat these threats and reinstate brain homeostasis, chronic inflammation can result in excessive cytokine production and cell death if the cause of inflammation remains. Overexpression of tumor necrosis factor-α (TNF-α), a proinflammatory cytokine with a central role in microglial activation, has been associated with neuronal excitotoxicity, synapse loss, and propagation of the inflammatory state. Thalidomide and its derivatives, termed immunomodulatory imide drugs (IMiDs), are a class of drugs that target the 3'-untranslated region (3'-UTR) of TNF-α mRNA, inhibiting TNF-α production. Due to their multi-potent effects, several IMiDs, including thalidomide, lenalidomide, and pomalidomide, have been repurposed as drug treatments for diseases such as multiple myeloma and psoriatic arthritis. Preclinical studies of currently marketed IMiDs, as well as novel IMiDs such as 3,6'-dithiothalidomide and adamantyl thalidomide derivatives, support the development of IMiDs as therapeutics for neurological disease. IMiDs have a competitive edge compared to similar anti-inflammatory drugs due to their blood-brain barrier permeability and high bioavailability, with the potential to alleviate symptoms of neurodegenerative disease and slow disease progression. In this review, we evaluate the role of neuroinflammation in neurodegenerative diseases, focusing specifically on the role of TNF-α in neuroinflammation, as well as appraise current research on the potential of IMiDs as treatments for neurological disorders.

CRBN Is a Negative Regulator of Bactericidal Activity and Autophagy Activation Through Inhibiting the Ubiquitination of ECSIT and BECN1

Cereblon (CRBN) as a multifunctional protein has been extensively studied. Here, we show that CRBN is a negative regulator of bactericidal activity and autophagy activation. Mitochondrial localization of CRBN was significantly increased in response to Toll-like receptor 4 (TLR4) stimulation. CRBN interrupted the association of evolutionarily conserved signaling intermediate in Toll pathways (ECSIT)-TNF-receptor associated factor 6 (TRAF6) complex, thereby inhibiting the ubiquitination of ECSIT, which plays a pivotal role for the production of mitochondrial reactive oxygen species (mROS). Subsequently, mROS levels were markedly elevated in CRBN-knockdown (CRBN^KD) THP-1 cells, and that led to resistance against S. typhimurium infection, indicating CRBN is a negative regulator of bactericidal activity through the regulation of mROS. Additionally, CRBN inhibited TRAF6-induced ubiquitination of BECN1 (Beclin 1), and that induced autophagy activation in CRBN^KD THP-1, CRBN-knockout (CRBN^KO) H1299, and CRBN^KO MCF7 cancer cells in response to TLR4 stimulation. Notably, we found that the ability of cancer migration and invasion was significantly enhanced in CRBN^KO H1299 and CRBN^KO MCF7 cancer cells, as compared with those of control cancer cells. Collectively, these results suggest that CRBN is a negative regulator of bactericidal activity and autophagy activation through inhibiting the TRAF6-induced ubiquitination of ECSIT and BECN1, respectively.

Sonic Hedgehog signaling limits atopic dermatitis via Gli2-driven immune regulation

Hedgehog (Hh) proteins regulate development and tissue homeostasis, but their role in atopic dermatitis (AD) remains unknown. We found that on induction of mouse AD, Sonic Hedgehog (Shh) expression in skin and Hh pathway action in skin T cells were increased. Shh signaling reduced AD pathology and the levels of Shh expression determined disease severity. Hh-mediated transcription in skin T cells in AD-induced mice increased Treg populations and their suppressive function through increased active transforming growth factor–β (TGF-β) in Treg signaling to skin T effector populations to reduce disease progression and pathology. RNA sequencing of skin CD4⁺ T cells from AD-induced mice demonstrated that Hh signaling increased expression of immunoregulatory genes and reduced expression of inflammatory and chemokine genes. Addition of recombinant Shh to cultures of naive human CD4⁺ T cells in iTreg culture conditions increased FOXP3 expression. Our findings establish an important role for Shh upregulation in preventing AD, by increased Gli-driven, Treg cell–mediated immune suppression, paving the way for a potential new therapeutic strategy.

p62 Negatively Regulates TLR4 Signaling via Functional Regulation of the TRAF6-ECSIT Complex

Sequestosome 1 (SQSTM1, p62), a ubiquitin binding protein, plays a role in cell signaling, oxidative stress, and autophagy. However, its functional role in inflammatory signaling is controversial. Recent studies have shown that p62 is negatively implicated in inflammatory responses. But, the precise molecular mechanisms by which p62 regulates inflammatory responses remain unclear. In this study, we report on a new regulatory role for p62 in TLR4-mediated signaling. p62 overexpression led to the suppression of NF-κB activation and the production of pro-inflammatory cytokines, TNF-α, IL-6, and IL-1β in response to TLR4 stimulation. In contrast, p62^−/− mouse embryonic fibroblast (MEF) cells exhibited marked enhancement of NF-κB activation and production of pro-inflammatory cytokines by TLR4 stimulation, compared to p62^+/+ MEF cells. Additionally, the TLR4-induced activation of signal transduction was significantly augmented in p62^−/− MEF cells, indicating that p62 was negatively implicated in TLR4-mediated signaling. Biochemical studies revealed that p62 interacted with the internal domain of evolutionarily conserved signaling intermediate in Toll pathways (ECSIT), which is critical for associating with the TNF receptor associated factor 6 (TRAF6)-ECSIT complex to activate NF-κB in TLR4 signaling. Interestingly, p62-ECSIT interaction inhibited the interaction between TRAF6 and ECSIT and attenuated the ubiquitination of ECSIT. Furthermore, upon LPS challenge, the mortality of p62^−/− (p62-knockout) mice was markedly enhanced compared to p62^+/+ (p62 wild-type) mice. Taken together, our data demonstrate that p62 negatively regulated TLR4 signaling via functional regulation of the TRAF6-ECSIT complex.

Cereblon attenuates DNA damage-induced apoptosis by regulating the transcription-independent function of p53

Cereblon (CRBN) is the substrate receptor of the cullin 4-RING E3 ligase complex and has been employed for targeted protein degradation in the treatment of cancers. However, its normal physiological functions and molecular mechanism in the regulation of DNA damage response are largely unknown. Here we find that CRBN plays a protective role against DNA damage-induced apoptosis in cell lines and primary cells. Mechanistic studies demonstrate that although CRBN does not affect the ubiquitination and degradation of the tumor suppressor p53, it directly interacts with p53 and therefore, suppresses the interaction between p53 and anti-apoptotic regulators Bcl-2 and Bcl-X_L. CRBN depletion enhances the interaction between p53 and Bcl-2/Bcl-X_L, reduces mitochondrial membrane potential, increases the cleavage of caspase-3 and poly(ADP-ribose) polymerase 1, and thus promotes DNA damage-induced apoptosis in cell lines and primary cells upon etoposide treatment. Moreover, Crbn knockout mice exhibit increased mortality upon etoposide challenge. Taken together, our data elucidate a novel molecular mechanism by which CRBN inhibits DNA damage response in vitro and in vivo. This work extends our understanding of the broad spectrum of physiological roles for CRBN and may suggest its potential application in the treatment of DNA damage-associated diseases.

Treatment of Lymphoid and Myeloid Malignancies by Immunomodulatory Drugs

Thalidomide and its derivatives (lenalidomide, pomalidomide, avadomide, iberdomide hydrochoride, CC-885 and CC-90009) form the family of immunomodulatory drugs (IMiDs). Lenalidomide (CC5013, Revlimid®) was approved by the US FDA and the EMA for the treatment of multiple myeloma (MM) patients, low or intermediate-1 risk transfusion-dependent myelodysplastic syndrome (MDS) with chromosome 5q deletion [del(5q)] and relapsed and/or refractory mantle cell lymphoma following bortezomib. Lenalidomide has also been studied in clinical trials and has shown promising activity in chronic lymphocytic leukemia (CLL) and non-Hodgkin lymphoma (NHL). Lenalidomide has anti-inflammatory effects and inhibits angiogenesis. Pomalidomide (CC4047, Imnovid® [EU], Pomalyst® [USA]) was approved for advanced MM insensitive to bortezomib and lenalidomide. Other IMiDs are in phases 1 and 2 of clinical trials. Cereblon (CRBN) seems to have an important role in IMiDs action in both lymphoid and myeloid hematological malignancies. Cereblon acts as the substrate receptor of a cullin-4 really interesting new gene (RING) E3 ubiquitin ligase CRL4CRBN. This E3 ubiquitin ligase in the absence of lenalidomide ubiquitinates CRBN itself and the other components of CRL4CRBN complex. Presence of lenalidomide changes specificity of CRL4CRBN which ubiquitinates two transcription factors, IKZF1 (Ikaros) and IKZF3 (Aiolos), and casein kinase 1α (CK1α) and marks them for degradation in proteasomes. Both these transcription factors (IKZF1 and IKZF3) stimulate proliferation of MM cells and inhibit T cells. Low CRBN level was connected with insensitivity of MM cells to lenalidomide. Lenalidomide decreases expression of protein argonaute-2, which binds to cereblon. Argonaute-2 seems to be an important drug target against IMiDs resistance in MM cells. Lenalidomide decreases also basigin and monocarboxylate transporter 1 in MM cells. MM cells with low expression of Ikaros, Aiolos and basigin are more sensitive to lenalidomide treatment. The CK1α gene (CSNK1A1) is located on 5q32 in commonly deleted region (CDR) in del(5q) MDS. Inhibition of CK1α sensitizes del(5q) MDS cells to lenalidomide. CK1α mediates also survival of malignant plasma cells in MM. Though, inhibition of CK1α is a potential novel therapy not only in del(5q) MDS but also in MM. High level of full length CRBN mRNA in mononuclear cells of bone marrow and of peripheral blood seems to be necessary for successful therapy of del(5q) MDS with lenalidomide. While transfusion independence (TI) after lenalidomide treatment is more than 60% in MDS patients with del(5q), only 25% TI and substantially shorter duration of response with occurrence of neutropenia and thrombocytopenia were achieved in lower risk MDS patients with normal karyotype treated with lenalidomide. Shortage of the biomarkers for lenalidomide response in these MDS patients is the main problem up to now.

Inhibition of TRAF6 ubiquitin-ligase activity by PRDX1 leads to inhibition of NFKB activation and autophagy activation

TRAF6 (TNF receptor associated factor 6) plays a pivotal role in NFKB activation and macroautphagy/autophagy activation induced by TLR4 (toll like receptor 4) signaling. The objective of this study was to determine the functional role of PRDX1 (peroxiredoxin 1) in NFKB activation and autophagy activation. PRDX1 interacted with the ring finger domain of TRAF6 and inhibited its ubiquitin-ligase activity. The inhibition on TRAF6 ubiquitin-ligase activity by PRDX1 induced the suppression of ubiquitination of an evolutionarily conserved signaling intermediate in Toll pathways (ECSIT) essential for NFKB activation and BECN1 (beclin 1) required for autophagy activation. An inhibitory effect of PRDX1 on TRAF6 was clearly evidenced in PRDX1-knockdown (PRDX1KD) THP-1, PRDX1KD MDA-MB-231, and PRDX1KD SK-HEP-1 cells. PRDX1KD THP-1 cells showed increases of NFKB activation, pro-inflammatory cytokine production, NFKB-dependent gene expression induced by TLR4 stimulation, and resistance against Salmonella typhimurium infection. Additionally, migration and invasion abilities of PRDX1KD MDA-MB-231 and PRDX1KD SK-HEP-1 cancer cells were significantly enhanced compared to those of control cancer cells. Taken together, these results suggest that PRDX1 negatively regulates TLR4 signaling for NFKB activation and autophagy functions such as bactericidal activity, cancer cell migration, and cancer cell invasion by inhibiting TRAF6 ubiquitin-ligase activity.

ABBREVIATIONS

3-MA: 3-methyladenine; BECN1: beclin 1; CHUK/IKKA: conserved helix-loop-helix ubiquitous kinase; ECSIT: ECSIT signalling integrator; ELISA: enzyme-linked immunosorbent assay; NFKB: nuclear factor kappa-light-chain-enhancer of activated B cells; IB: immunoblotting; IKBKB/IKKB: inhibitor of nuclear factor kappa B kinase subunit beta; IL1B: interleukin 1 beta; IL6: interleukin 6; IP: immunoprecipitation; LPS: lipopolysaccharide; MAP1LC3/LC3: microtuble associated protein 1 light chain 3; MAP3K7/TAK1: mitogen-activated protein kinase kinase kinase 7; MAPK14/p38: mitogen-activated protein kinase 14; mROS: mitochondrial reactive oxygen species; PRDX1: peroxiredoxin 1; PRDX6: peroxiredoxin 6; RELA/p65: RELA proto-oncogene, NF-kB subunit; TRAF6 TNF: receptor associated factor 6.

Cereblon suppresses the lipopolysaccharide-induced inflammatory response by promoting the ubiquitination and degradation of c-Jun

Chronic inflammation is associated with multiple human disorders, such as rheumatoid arthritis, metabolic diseases, and neurodegenerative diseases. Therefore, alleviation of inflammation induced by environmental stimuli is important for disease prevention or treatment. Cereblon (CRBN) functions as a substrate receptor of the cullin-4 RING E3 ligase to mediate protein ubiquitination and degradation. Although it has been reported that CRBN reduces the inflammatory response through its nonenzymatic function, its role as a substrate receptor of the E3 ligase is not explored in mediating this process. Here we used a quantitative proteomics approach to find that the major component of the activator protein 1 (AP-1) complex, c-Jun, is significantly down-regulated upon CRBN expression. Biochemical approaches further discover that CRBN interacts and partially colocalizes with c-Jun and promotes the formation of Lys⁴⁸-linked polyubiquitin chains on c-Jun, enhancing c-Jun degradation. We further reveal that CRBN attenuates the transcriptional activity of the AP-1 complex and reduces the mRNA expression and protein level of several pro-inflammatory cytokines. Moreover, flow cytometry analyses show that CRBN attenuates lipopolysaccharide-induced apoptosis in differentiated THP-1 cells. Through genetic manipulation and pharmacological inhibition, we uncover a new molecular mechanism by which CRBN regulates the inflammatory response and apoptosis induced by lipopolysaccharide. Our work and previous studies demonstrate that CRBN suppresses the inflammatory response by promoting or inhibiting the ubiquitination of two key molecules at different levels of the inflammatory cascade through its enzymatic function as a substrate receptor and its nonenzymatic function as a protein binding partner.

Toll-Like Receptor 2 Signaling and Current Approaches for Therapeutic Modulation in Synucleinopathies

The innate immune response in the central nervous system (CNS) is implicated as both beneficial and detrimental to health. Integral to this process are microglia, the resident immune cells of the CNS. Microglia express a wide variety of pattern-recognition receptors, such as Toll-like receptors, that detect changes in the neural environment. The activation of microglia and the subsequent proinflammatory response has become increasingly relevant to synucleinopathies, including Parkinson's disease the second most prevalent neurodegenerative disease. Within these diseases there is evidence of the accumulation of endogenous α-synuclein that stimulates an inflammatory response from microglia via the Toll-like receptors. There have been recent developments in both new and old pharmacological agents designed to target microglia and curtail the inflammatory environment. This review will aim to delineate the process of microglia-mediated inflammation and new therapeutic avenues to manage the response.

Down-regulation of miR-146b-5p by long noncoding RNA MALAT1 in hepatocellular carcinoma promotes cancer growth and metastasis

MicroRNAs play an important role in liver cancer genesis and progression. In this study, we identified down-regulation of miR-146b-5p associated with tumor growth, metastasis and poor survival in hepatocellular carcinoma (HCC) patients. miR-146b-5p could suppress proliferation, migration, and invasion and induced apoptosis in vitro and in vivo. Remarkably, TNF receptor associated factor 6 (TRAF6) was confirmed as a direct target of miR-146b-5p in HCC and miR-146b-5p exerted the tumor suppression roles through inhibiting the phosphorylation of Akt mediated by TRAF6. Furthermore, we identified long non-coding RNA MALAT1 as a molecular sponge of miR-146b-5p to down-regulate its expression in HCC. In general, our results indicate that miR-146b-5p inhibits tumor growth and metastasis of HCC by targeting TRAF6 mediated Akt phosphorylation.

Ligand-mediated protein degradation reveals functional conservation among sequence variants of the CUL4-type E3 ligase substrate receptor cereblon

Upon binding to thalidomide and other immunomodulatory drugs, the E3 ligase substrate receptor cereblon (CRBN) promotes proteosomal destruction by engaging the DDB1-CUL4A-Roc1-RBX1 E3 ubiquitin ligase in human cells but not in mouse cells, suggesting that sequence variations in CRBN may cause its inactivation. Therapeutically, CRBN engagers have the potential for broad applications in cancer and immune therapy by specifically reducing protein expression through targeted ubiquitin-mediated degradation. To examine the effects of defined sequence changes on CRBN's activity, we performed a comprehensive study using complementary theoretical, biophysical, and biological assays aimed at understanding CRBN's nonprimate sequence variations. With a series of recombinant thalidomide-binding domain (TBD) proteins, we show that CRBN sequence variants retain their drug-binding properties to both classical immunomodulatory drugs and dBET1, a chemical compound and targeting ligand designed to degrade bromodomain-containing 4 (BRD4) via a CRBN-dependent mechanism. We further show that dBET1 stimulates CRBN's E3 ubiquitin-conjugating function and degrades BRD4 in both mouse and human cells. This insight paves the way for studies of CRBN-dependent proteasome-targeting molecules in nonprimate models and provides a new understanding of CRBN's substrate-recruiting function.

Ubiquitin-Specific Protease 14 Negatively Regulates Toll-Like Receptor 4-Mediated Signaling and Autophagy Induction by Inhibiting Ubiquitination of TAK1-Binding Protein 2 and Beclin 1

Ubiquitin-specific protease 14 (USP14), one of three proteasome-associated deubiquitinating enzymes, has multifunctional roles in cellular context. Here, we report a novel molecular mechanism and function of USP14 in regulating autophagy induction and nuclear factor-kappa B (NF-κB) activation induced by toll-like receptor (TLR) 4 (TLR4). USP14 interacted with tumor necrosis factor (TNF) receptor-associated factor 6 (TRAF6) and interrupted the association of Beclin 1 with TRAF6, leading to inhibition of TRAF6-mediated ubiquitination of Beclin 1. Reduced expression of USP14 in USP14-knockdown (USP14^KD) THP-1 cells enhanced autophagy induction upon TLR4 stimulation as shown by the increased conversion of cytosolic LC3-I to membrane-bound LC3-II. Moreover, USP14^KD human breast carcinoma MDA-MB-231 cells and USP14^KD human hepatic adenocarcinoma SK-HEP-1 cells showed increased cell migration and invasion, indicating that USP14 is negatively implicated in the cancer progression by the inhibition of autophagy induction. Furthermore, we found that USP14 interacted with TAK1-binding protein (TAB) 2 protein and induced deubiquitination of TAB 2, a key factor in the activation of NF-κB. Functionally, overexpression of USP14 suppressed TLR4-induced activation of NF-κB. In contrast, USP14^KD THP-1 cells showed enhanced activation of NF-κB, NF-κB-dependent gene expression, and production of pro-inflammatory cytokines such as IL-6, IL-1β, and tumor necrosis factor-α. Taken together, our data demonstrate that USP14 can negatively regulate autophagy induction by inhibiting Beclin 1 ubiquitination, interrupting association between TRAF6 and Beclin 1, and affecting TLR4-induced activation of NF-κB through deubiquitination of TAB 2 protein.

Cereblon deficiency confers resistance against polymicrobial sepsis by the activation of AMP activated protein kinase and heme-oxygenase-1

Cereblon (CRBN) has a pleiotropic role in important cellular processes and is a potential therapeutic target in several diseases, including mental retardation, cancer, and metabolic disorders. The role of CRBN in polymicrobial sepsis induced by cecal ligation and puncture (CLP) was investigated using CRBN-deficient (KO) mice. Survival following CLP was significantly higher in KO mice compared to wild-type (WT) controls (50% vs 0% at day 6 after CLP). The improved survival of KO mice was accompanied by reduced peripheral blood bacterial load and lung injury. Serum tumor necrosis factor (TNF)-α and high mobility group box 1 (HMGB1) concentrations were significantly lower in KO mice than in WT mice. Peritoneal macrophages from KO mice with CLP-induced septic mouse had higher levels of activation of AMPK and heme oxygenase-1 (HO-1). Forced expression of CRBN in macrophage of KO mice suppressed activation of 5' adenosine monophosphate-activated protein kinase (AMPK) and HO-1 and augmented expression of TNF-α and HMGB1 as inhibition of AMPK by compound C. These studies demonstrate the contribution of CRBN expression to the pathogenesis of CLP-induced sepsis and peritoneal macrophage responses and suggest a novel therapeutic modality for polymicrobial sepsis.

Intracerebroventricular injection of miR-146a relieves seizures in an immature rat model of lithium-pilocarpine induced status epilepticus

OBJECTIVE

Status epilepticus (SE) is a common, life-threatening neurological emergency that confers a high degree of morbidity and mortality. Increasing evidence indicates that neuroinflammation plays a critical role in the pathogenesis of SE. MicroRNA-146a (miR-146a) has been reported to be an important posttranscriptional inflammation-associated microRNA. The aim of this study was to investigate the effect of miR-146a in SE and the mechanism by which it operates.

METHODS

To study the effect of miR-146a in SE, we chose intracerebroventricular injection for rat at 21-28days old, and made a lithium-pilocarpine-induced SE rat model. We assessed latency time and Lado grade by behavior observation. We performed qPCR, ELISA and western blot tests on rat hippocampus to measure the expression levels of miR-146a, IL-1β, TNF-α, TLR4 and NF-κB.

RESULTS

In the miR-146a antagomir injection group, the latency to generalized convulsions was shorter, the duration and degree of seizures were more severe, the expression level of miR-146a was clearly decreased, and IL-1β, TNF-α, TLR4 and NF-κB were all significantly up-regulated. The opposite was true for rats treated with miR-146a agomir.

CONCLUSION

Our findings elucidate the role of inflammation in the pathogenesis of SE in immature rats, and show that regulating the expression level of miR-146a may provide a novel insights into the pathogenesis of SE.

Cereblon: A Protein Crucial to the Multiple Functions of Immunomodulatory Drugs as well as Cell Metabolism and Disease Generation

It is well known that cereblon is a key protein in autosomal recessive nonsyndromic mental retardation. Studies have reported that it has an intermediary role in helping immunomodulatory drugs perform their immunomodulatory and tumoricidal effects. In addition, cereblon also regulates the expression, assembly, and activities of other special proteins related to cell proliferation and metabolism, resulting in the occurrence and development of metabolic diseases. This review details the multiple functions of cereblon and the underlying mechanisms. We also put forward some unsolved problems, including the intrinsic mechanism of cereblon function and the possible regulatory mechanisms of its expression.

A Brighter Side to Thalidomide: Its Potential Use in Immunological Disorders

Thalidomide and its derivatives are immunomodulatory drugs (IMiDs) known for their sedative, teratogenic, anti-angiogenic, and anti-inflammatory properties. Commonly used in the treatment of cancers such as multiple myeloma and myelodysplastic syndrome (MDS), IMiDs have also been used in the treatment of an inflammatory skin pathology associated with Hansen's disease/leprosy. They have also shown promise in the treatment of autoimmune disorders including systemic lupus erythmatosus (SLE) and inflammatory bowel disease (IBD). Recent structural and experimental observations have revolutionized our understanding of these properties by revealing the fundamental molecular events underpinning IMiD activity. We review these findings, their relevance to IMiD therapy in immunological disorders, and discuss how further research might unlock the vast clinical potential of these compounds.