RESUMEN
The REGγ-20S proteasome is an ubiquitin- and ATP-independent degradation system, targeting selective substrates, possibly helping to regulate aging. The studies we report here demonstrate that aging-associated REGγ decline predisposes to decreasing tau turnover, as in a tauopathy. The REGγ proteasome promotes degradation of human and mouse tau, notably phosphorylated tau and toxic tau oligomers that shuttle between the cytoplasm and nuclei. REGγ-mediated proteasomal degradation of tau was validated in 3- to 12-month-old REGγ KO mice, REGγ KO;PS19 mice, and PS19 mice with forebrain conditional neuron-specific overexpression of REGγ (REGγ OE) and behavioral abnormalities. Coupled with tau accumulation, we found with REGγ-deficiency, neuron loss, dendrite reduction, tau filament accumulation, and microglial activation are much more prominent in the REGγ KO;PS19 than the PS19 model. Moreover, we observed that the degenerative neuronal lesions and aberrant behaviors were alleviated in REGγ OE;PS19 mice. Memory and other behavior analysis substantiate the role of REGγ in prevention of tauopathy-like symptoms. In addition, we investigated the potential mechanism underlying aging-related REGγ decline. This study provides valuable insights into the novel regulatory mechanisms and potential therapeutic targets for tau-related neurodegenerative diseases.
Asunto(s)
Complejo de la Endopetidasa Proteasomal , Tauopatías , Humanos , Animales , Ratones , Lactante , Complejo de la Endopetidasa Proteasomal/genética , Complejo de la Endopetidasa Proteasomal/metabolismo , Tauopatías/genética , Autoantígenos/metabolismo , Citoplasma/metabolismo , Envejecimiento/genéticaRESUMEN
Epithelial-mesenchymal transition (EMT) inducing transcription factor TWIST1 plays a vital role in cancer metastasis. How the tumor-suppressive E3 ligase, speckle-type POZ protein (SPOP), regulates TWIST1 in breast cancer remains unknown. In this study, we report that SPOP physically interacts with, ubiquitinates, and destabilizes TWIST1. SPOP promotes K63-and K48-linked ubiquitination of TWIST1, predominantly at K73, thereby suppressing cancer cell migration and invasion. Silencing SPOP significantly enhances EMT, which accelerates breast cancer cell migration and invasiveness in vitro and lung metastasis in vivo. Clinically, SPOP is negatively correlated with the levels of TWIST1 in highly invasive breast carcinomas. Reduced SPOP expression, along with elevated TWIST1 levels, is associated with poor prognosis in advanced breast cancer patients, particularly those with metastatic triple-negative breast cancer (TNBC). Taken together, we have disclosed a new mechanism linking SPOP to TWIST1 degradation. Thus SPOP may serve as a prognostic marker and a potential therapeutic target for advanced TNBC patients.
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Diabetic vascular endothelial impairment is one of the main causes of death in patients with diabetes lacking adequately defined mechanisms or effective treatments. REGγ, the 11S proteasome activator known to promote the degradation of cellular proteins in a ubiquitin- and ATP-independent manner, emerges as a new regulator in the cardiovascular system. Here, we found that REGγ was upregulated in streptozocin (STZ)-induced diabetic mouse aortic endothelium in vivo and high glucose (HG)-treated vascular endothelial cells (ECs) in vitro. REGγ deficiency ameliorated endothelial impairment in STZ-induced diabetic mice by protecting against a decline in cellular glucose uptake and associated vascular ECs dysfunction by suppressing high mobility group AT-hook 2 (HMGA2) decay. Mechanically, REGγ interacted with and degraded the transcription factor HMGA2 directly, leading to decreased HMGA2 transcriptional activity, subsequently lowered expression of glucose transporter type 1 (GLUT1), and reduced cellular glucose uptake, vascular endothelial dysfunction, and impaired diabetic endothelium. Ablation of endogenous GLUT1 or HMGA2 or overexpressing exogenous HMGA2 in vascular ECs significantly blocked or reestablished the REGγ-dependent action on cellular glucose uptake and vascular endothelial functions of HG stimulation in vitro. Furthermore, exogenously introducing HMGA2 improved diabetic mice endothelial impairment features caused by REGγ in vivo, thereby substantiating a REGγ-HMGA2-GLUT1 pathway in diabetic endothelial impairment. Our findings indicate that modulating REGγ-proteasome activity may be a potential therapeutic approach for diabetic disorders with endothelial impairment.
Asunto(s)
Diabetes Mellitus Experimental , Complejo de la Endopetidasa Proteasomal , Animales , Autoantígenos , Células Endoteliales/metabolismo , Endotelio/metabolismo , Glucosa , Transportador de Glucosa de Tipo 1/genética , Humanos , Ratones , Complejo de la Endopetidasa Proteasomal/metabolismoRESUMEN
Leucine-rich repeat containing G protein-coupled receptor 5 (Lgr5), a marker of intestinal stem cells (ISCs), is considered to play key roles in tissue homoeostasis and regeneration after acute radiation injury. However, the activation of Lgr5 by integrated signaling pathways upon radiation remains poorly understood. Here, we show that irradiation of mice with whole-body depletion or conditional ablation of REGγ in Lgr5+ stem cell impairs proliferation of intestinal crypts, delaying regeneration of intestine epithelial cells. Mechanistically, REGγ enhances transcriptional activation of Lgr5 via the potentiation of both Wnt and Hippo signal pathways. TEAD4 alone or cooperates with TCF4, a transcription factor mediating Wnt signaling, to enhance the expression of Lgr5. Silencing TEAD4 drastically attenuated ß-catenin/TCF4 dependent expression of Lgr5. Together, our study reveals how REGγ controls Lgr5 expression and expansion of Lgr5+ stem cells in the regeneration of intestinal epithelial cells. Thus, REGγ proteasome appears to be a potential therapeutic target for radiation-induced gastrointestinal disorders.
Asunto(s)
Intestinos , Complejo de la Endopetidasa Proteasomal , Animales , Autoantígenos/metabolismo , Mucosa Intestinal/metabolismo , Ratones , Complejo de la Endopetidasa Proteasomal/metabolismo , Receptores Acoplados a Proteínas G/genética , Receptores Acoplados a Proteínas G/metabolismo , Células Madre , Vía de Señalización WntRESUMEN
SMAD4 is mutated in human lung cancer, but the underlying mechanism by which Smad4 loss-of-function (LOF) accelerates lung cancer metastasis is yet to be elucidated. Here, we generate a highly aggressive lung cancer mouse model bearing conditional KrasG12D, p53fl/fl LOF and Smad4fl/fl LOF mutations (SPK), showing a much higher incidence of tumor metastases than the KrasG12D, p53fl/fl (PK) mice. Molecularly, PAK3 is identified as a downstream effector of Smad4, mediating metastatic signal transduction via the PAK3-JNK-Jun pathway. Upregulation of PAK3 by Smad4 LOF in SPK mice is achieved by attenuating Smad4-dependent transcription of miR-495 and miR-543. These microRNAs (miRNAs) directly bind to the PAK3 3'UTR for blockade of PAK3 production, ultimately regulating lung cancer metastasis. An inverse correlation between Smad4 and PAK3 pathway components is observed in human lung cancer. Our study highlights the Smad4-PAK3 regulation as a point of potential therapy in metastatic lung cancer.
Asunto(s)
Neoplasias Pulmonares/patología , MicroARNs/genética , Proteína Smad4/metabolismo , Quinasas p21 Activadas/metabolismo , Regiones no Traducidas 3' , Animales , Movimiento Celular , Regulación Neoplásica de la Expresión Génica , Humanos , Proteínas Quinasas JNK Activadas por Mitógenos/metabolismo , Mutación con Pérdida de Función , Neoplasias Pulmonares/genética , Neoplasias Pulmonares/metabolismo , Ratones , MicroARNs/metabolismo , Metástasis de la Neoplasia , Proteínas Proto-Oncogénicas c-jun/metabolismo , Transducción de Señal , Proteína Smad4/genética , Activación Transcripcional , Quinasas p21 Activadas/genéticaRESUMEN
Aims: Intact intestinal epithelium is essential to maintain normal intestinal physiological function. Irradiation-induced gastrointestinal syndrome or inflammatory bowel disease occurred when epithelial integrity was impaired. This study aims at exploring the mechanism of procyanidin B2 (PB2) administration to promote intestinal injury repair in mice. Results: PB2 treatment reduces reactive oxygen species (ROS) accumulation and protects the intestine damage from irradiation. Mechanistic studies reveal that PB2 could effectively slow down the degradation of nuclear factor-erythroid 2-related factor 2 (Nrf2) and it significantly triggers Nrf2 into the nucleus, which leads to subsequent antioxidant enzyme expression. However, knockdown of Nrf2 attenuates PB2-induced protection in the intestine. More importantly, PB2 also promotes leucine-rich repeat-containing G protein-coupled receptor 5 (Lgr5)-positive intestinal stem cells (Lgr5+ ISCs) driven regeneration via enhancing Wnt/ß-catenin signaling, which depends on, at least in part, activation of the Nrf2 signal. Evidence from an injury model of intestinal organoids is similar with in vivo results. Correspondingly, results from flow cytometric analysis and luciferase reporter assay reveal that PB2 also inhibits the level of ROS and promotes Lgr5 expression in vitro. Finally, PB2 alleviates the severity of experimental colitis and colitis-associated cancer in a long-term inflammatory model via inhibiting nuclear localization of p65. Innovation: This study, for the first time, reveals a role of PB2 for intestinal regeneration and repair after radiation or dextran sulfate sodium-induced injury in mice. Conclusion: Our results indicate that PB2 can repress oxidative stress via Nrf2/ARE signaling and then promote intestinal injury repair.
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Biflavonoides/administración & dosificación , Catequina/administración & dosificación , Neoplasias Asociadas a Colitis/tratamiento farmacológico , Intestinos/fisiología , Factor 2 Relacionado con NF-E2/metabolismo , Proantocianidinas/administración & dosificación , Especies Reactivas de Oxígeno/metabolismo , Animales , Biflavonoides/farmacología , Catequina/farmacología , Línea Celular , Núcleo Celular/metabolismo , Neoplasias Asociadas a Colitis/inducido químicamente , Neoplasias Asociadas a Colitis/metabolismo , Regulación Neoplásica de la Expresión Génica/efectos de los fármacos , Células HCT116 , Humanos , Intestinos/citología , Intestinos/efectos de los fármacos , Intestinos/metabolismo , Masculino , Ratones , Estrés Oxidativo/efectos de los fármacos , Proantocianidinas/farmacología , Transporte de Proteínas/efectos de los fármacos , Proteolisis/efectos de los fármacos , Receptores Acoplados a Proteínas G/metabolismo , Células Madre/citología , Células Madre/efectos de los fármacos , Células Madre/metabolismo , Vía de Señalización Wnt/efectos de los fármacos , Cicatrización de Heridas , Ensayos Antitumor por Modelo de XenoinjertoRESUMEN
Despite significant progression in the study of hepatocellular carcinoma (HCC), the role of the proteasome in regulating cross talk between mTOR signaling and glycolysis in liver cancer progression is not fully understood. Here, we demonstrate that deficiency of REGγ, a proteasome activator, in mice significantly attenuates DEN-induced liver tumor formation. Ablation of REGγ increases the stability of PP2Ac (protein phosphatase 2 catalytic subunit) in vitro and in vivo, which dephosphorylates PRAS40 (AKT1 substrate 1) and stabilizes the interaction between PRAS40 and Raptor to inactive mTORC1-mediated hyper-glycolytic metabolism. In the DEN-induced animal model and clinical hepato-carcinoma samples, high levels of REGγ in HCC tumor regions contribute to reduced expression of PP2Ac, leading to accumulation of phosphorylated PRAS40 and mTORC1-mediated activation of HIF1α. Interestingly, mTORC1 enhances REGγ activity in HCC, forming a positive feedback regulatory loop. In conclusion, our study identifies REGγ-PP2Ac-PRAS40 axis as a new layer in regulating mTORC1 activity and downstream glycolytic alterations during HCC development, highlighting the REGγ-proteasome as a potential target for personalized HCC therapy.
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Autoantígenos/metabolismo , Carcinoma Hepatocelular/metabolismo , Glucólisis , Neoplasias Hepáticas/metabolismo , Diana Mecanicista del Complejo 1 de la Rapamicina/metabolismo , Proteínas de Neoplasias/metabolismo , Complejo de la Endopetidasa Proteasomal/metabolismo , Animales , Autoantígenos/genética , Carcinoma Hepatocelular/genética , Carcinoma Hepatocelular/patología , Células Hep G2 , Humanos , Neoplasias Hepáticas/genética , Neoplasias Hepáticas/patología , Diana Mecanicista del Complejo 1 de la Rapamicina/genética , Ratones , Ratones Noqueados , Proteínas de Neoplasias/genética , Complejo de la Endopetidasa Proteasomal/genéticaRESUMEN
An amendment to this paper has been published and can be accessed via a link at the top of the paper.
RESUMEN
A major challenge in chemotherapy is chemotherapy resistance in cells lacking p53. Here we demonstrate that NIP30, an inhibitor of the oncogenic REGγ-proteasome, attenuates cancer cell growth and sensitizes p53-compromised cells to chemotherapeutic agents. NIP30 acts by binding to REGγ via an evolutionarily-conserved serine-rich domain with 4-serine phosphorylation. We find the cyclin-dependent phosphatase CDC25A is a key regulator for NIP30 phosphorylation and modulation of REGγ activity during the cell cycle or after DNA damage. We validate CDC25A-NIP30-REGγ mediated regulation of the REGγ target protein p21 in vivo using p53-/- and p53/REGγ double-deficient mice. Moreover, Phosphor-NIP30 mimetics significantly increase the growth inhibitory effect of chemotherapeutic agents in vitro and in vivo. Given that NIP30 is frequently mutated in the TCGA cancer database, our results provide insight into the regulatory pathway controlling the REGγ-proteasome in carcinogenesis and offer a novel approach to drug-resistant cancer therapy.
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Autoantígenos/metabolismo , Péptidos y Proteínas de Señalización Intracelular/metabolismo , Proteínas Nucleares/metabolismo , Complejo de la Endopetidasa Proteasomal/metabolismo , Inhibidores de Proteasoma/metabolismo , Proteína p53 Supresora de Tumor/deficiencia , Animales , Autoantígenos/genética , Ciclo Celular , Línea Celular Tumoral , Inhibidor p21 de las Quinasas Dependientes de la Ciclina/metabolismo , Resistencia a Antineoplásicos , Células HEK293 , Xenoinjertos , Humanos , Péptidos y Proteínas de Señalización Intracelular/genética , Ratones , Ratones Noqueados , Proteínas Nucleares/genética , Fosforilación , Complejo de la Endopetidasa Proteasomal/deficiencia , Complejo de la Endopetidasa Proteasomal/genética , Proteína p53 Supresora de Tumor/genética , Fosfatasas cdc25/metabolismoRESUMEN
Pathological cardiac hypertrophy eventually leads to heart failure without adequate treatment. REGγ is emerging as 11S proteasome activator of 20S proteasome to promote the degradation of cellular proteins in a ubiquitin- and ATP-independent manner. Here, we found that REGγ was significantly upregulated in the transverse aortic constriction (TAC)-induced hypertrophic hearts and angiotensin II (Ang II)-treated cardiomyocytes. REGγ deficiency ameliorated pressure overload-induced cardiac hypertrophy were associated with inhibition of cardiac reactive oxygen species (ROS) accumulation and suppression of protein phosphatase 2A catalytic subunit α (PP2Acα) decay. Mechanistically, REGγ interacted with and targeted PP2Acα for degradation directly, thereby leading to increase of phosphorylation levels and nuclear export of Forkhead box protein O (FoxO) 3a and subsequent of SOD2 decline, ROS accumulation, and cardiac hypertrophy. Introducing exogenous PP2Acα or SOD2 to human cardiomyocytes significantly rescued the REGγ-mediated ROS accumulation of Ang II stimulation in vitro. Furthermore, treatment with superoxide dismutase mimetic, MnTBAP prevented cardiac ROS production and hypertrophy features that REGγ caused in vivo, thereby establishing a REGγ-PP2Acα-FoxO3a-SOD2 pathway in cardiac oxidative stress and hypertrophy, indicates modulating the REGγ-proteasome activity may be a potential therapeutic approach in cardiac hypertrophy-associated disorders.
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Autoantígenos/fisiología , Cardiomegalia/metabolismo , Complejo de la Endopetidasa Proteasomal/fisiología , Especies Reactivas de Oxígeno/metabolismo , Animales , Animales Recién Nacidos , Células HEK293 , Humanos , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Miocitos Cardíacos , Estrés Oxidativo , Cultivo Primario de Células , Ratas , Ratas Sprague-DawleyRESUMEN
Lung cancer is one of the cancers with highest morbidity and mortality rates and the metastasis of lung cancer is a leading cause of death. Mechanisms of lung cancer metastasis are yet to be fully understood. Herein, we demonstrate that mice deficient for REGγ, a proteasome activator, exhibited a significant reduction in tumor size, numbers, and metastatic rate with prolonged survival in a conditional Kras/p53 mutant lung cancer model. REGγ enhanced the TGFß-Smad signaling pathway by ubiquitin-ATP-independent degradation of Smad7, an inhibitor of the TGFß pathway. Activated TGFß signaling in REGγ-positive lung cancer cells led to diminished expression of E-cadherin, a biomarker of epithelial-mesenchymal transitions (EMT), and elevated mesenchymal markers compared with REGγ-deficient lung cancer cells. REGγ overexpression was found in lung cancer patients with metastasis, correlating with the reduction of E-Cadherin/Smad7 and a poor prognosis. Overall, our study indicates that REGγ promotes lung cancer metastasis by activating TGF-ß signaling via degradation of Smad7. Thus, REGγ may serve as a novel therapeutic target for lung cancers with poor prognosis.
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Antígenos CD/metabolismo , Cadherinas/metabolismo , Neoplasias Pulmonares/metabolismo , Proteínas Asociadas a Pancreatitis/metabolismo , Proteína smad7/metabolismo , Células A549 , Animales , Transición Epitelial-Mesenquimal , Humanos , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Factor de Crecimiento Transformador beta/antagonistas & inhibidoresRESUMEN
Anaplastic thyroid cancer (ATC) is the most aggressive human thyroid malignancy, characterized by dedifferentiation and resistance to radioiodine therapy. The underlying mechanisms regulating ATC dedifferentiation are largely unknown. Here, we show that REGγ, a noncanonical proteasome activator highly expressed in ATC, is an important regulator of differentiation in ATC cells. Ablation of REGγ significantly restored expression of thyroid-specific genes, enhanced iodine uptake, and improved the efficacy of 131I therapy in ATC xenograft models. Mechanistically, REGγ directly binds to the TGF-ß signaling antagonist Smad7 and promotes its degradation, leading to the activation of the TGF-ß signal pathway. With gain- and loss-of-function studies, we demonstrate that Smad7 is an important mediator for the REGγ function in ATC cell dedifferentiation, which is supported by expression profiles in human ATC tissues. It seems that REGγ impinges on repression of thyroid-specific genes and promotion of tumor malignancy in ATC cells by activating the TGF-ß signal pathway via degradation of Smad7. Thus, REGγ may serve as a novel therapeutic target for allowing radioiodine therapy in anaplastic thyroid cancer patients with poor prognosis.
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Autoantígenos/metabolismo , Complejo de la Endopetidasa Proteasomal/metabolismo , Proteína smad7/metabolismo , Carcinoma Anaplásico de Tiroides/metabolismo , Neoplasias de la Tiroides/metabolismo , Factor de Crecimiento Transformador beta/metabolismo , Diferenciación Celular , Línea Celular , Humanos , Transducción de Señal , Carcinoma Anaplásico de Tiroides/patología , Carcinoma Anaplásico de Tiroides/radioterapia , Neoplasias de la Tiroides/patología , Neoplasias de la Tiroides/radioterapiaRESUMEN
For quite a long time, the 11S proteasome activator REGÉ and REGß, but not REGγ, are known to control immunoproteasome and promote antigen processing. Here, we demonstrate that REGγ functions as an inhibitor for immunoproteasome and autoimmune disease. Depletion of REGγ promotes MHC class I-restricted presentation to prime CD8+ T cells in vitro and in vivo. Mice deficient for REGγ have elevation of CD8+ T cells and DCs, and develop age-related spontaneous autoimmune symptoms. Mechanistically, REGγ specifically interacts with phosphorylated STAT3 and promotes its degradation in vitro and in cells. Inhibition of STAT3 dramatically attenuates levels of LMP2/LMP7 and antigen presentation in cells lacking REGγ. Importantly, treatment with STAT3 or LMP2/7 inhibitor prevented accumulation of immune complex in REGγ-/- kidney. Moreover, REGγ-/- mice also expedites Pristane-induced lupus. Bioinformatics and immunohistological analyses of clinical samples have correlated lower expression of REGγ with enhanced expression of phosphorylated STAT3, LMP2 and LMP7 in human Lupus Nephritis. Collectively, our results support the concept that REGγ is a new regulator of immunoproteasome to balance autoimmunity.
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Envejecimiento/inmunología , Autoantígenos/metabolismo , Enfermedades Autoinmunes/inmunología , Linfocitos T CD8-positivos/inmunología , Células Dendríticas/inmunología , Complejo de la Endopetidasa Proteasomal/metabolismo , Inhibidores de Proteasoma/metabolismo , Envejecimiento/genética , Animales , Presentación de Antígeno , Autoantígenos/genética , Enfermedades Autoinmunes/genética , Células Cultivadas , Cisteína Endopeptidasas/metabolismo , Antígenos de Histocompatibilidad Clase I/metabolismo , Ratones , Ratones Noqueados , Complejo de la Endopetidasa Proteasomal/genética , Factor de Transcripción STAT3/metabolismoRESUMEN
Purpose: Colorectal cancer is one of the most commonly diagnosed cancers closely associated with inflammation and hyperactive growth. We previously demonstrated a regulatory circuit between the proteasome activator REGγ and NF-kappaB (NF-κB) during colon inflammation, known to be important in the development of colitis-associated cancer as well as sporadic colorectal cancer. How the inflammatory microenvironment affects the Hippo pathway during colorectal cancer development is largely unknown.Experimental Design: Here, we used REGγ-deficient colon cancer cell lines, REGγ knockout mice, and human colorectal cancer samples to identify the novel molecular mechanism by which REGγ functions as an oncoprotein in the development of colorectal cancer.Results: REGγ can directly interact with Lats1 and promote its degradation, which facilitates Yes-associated protein (YAP) activation in colon cancer cells. REGγ deficiency significantly attenuated colon cancer growth, associated with decreased YAP activity. Suppression of tumor growth due to REGγ depletion was overcome by constitutively active YAP. Surprisingly, reciprocal activation of the YAP and NF-κB pathways was observed in human colon cancer cells. REGγ overexpression was found in over 60% of 172 colorectal cancer specimens, highly correlating with the elevation of YAP and p65. Postoperative follow-up revealed a significantly lower survival rate in patients with concomitantly high expression of REGγ, YAP, and p-p65.Conclusions: REGγ could be a master regulator during colorectal cancer development to promote YAP signaling and reinforce cross-talks between inflammation and growth pathways, and REGγ might be a new marker for prognosis of colorectal cancer patients. Clin Cancer Res; 24(8); 2015-25. ©2018 AACR.
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Autoantígenos/metabolismo , Proteínas de Ciclo Celular/metabolismo , Neoplasias del Colon/metabolismo , FN-kappa B/metabolismo , Complejo de la Endopetidasa Proteasomal/metabolismo , Proteínas Serina-Treonina Quinasas/metabolismo , Transducción de Señal , Factores de Transcripción/metabolismo , Animales , Línea Celular Tumoral , Movimiento Celular , Proliferación Celular , Transformación Celular Neoplásica/genética , Transformación Celular Neoplásica/metabolismo , Neoplasias del Colon/genética , Neoplasias del Colon/mortalidad , Neoplasias del Colon/patología , Modelos Animales de Enfermedad , Xenoinjertos , Vía de Señalización Hippo , Humanos , Ratones , Pronóstico , Unión Proteica , Proteolisis , Análisis de SupervivenciaRESUMEN
Increasing incidence of inflammatory bowel disorders demands a better understanding of the molecular mechanisms underlying its multifactorial aetiology. Here we demonstrate that mice deficient for REGγ, a proteasome activator, show significantly attenuated intestinal inflammation and colitis-associated cancer in dextran sodium sulfate model. Bone marrow transplantation experiments suggest that REGγ's function in non-haematopoietic cells primarily contributes to the phenotype. Elevated expression of REGγ exacerbates local inflammation and promotes a reciprocal regulatory loop with NFκB involving ubiquitin-independent degradation of IκBÉ. Additional deletion of IκBÉ restored colitis phenotypes and inflammatory gene expression in REGγ-deficient mice. In sum, this study identifies REGγ-mediated control of IκBÉ as a molecular mechanism that contributes to NFκB activation and promotes bowel inflammation and associated tumour formation in response to chronic injury.
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Autoantígenos/metabolismo , Colitis/enzimología , Quinasa I-kappa B/metabolismo , FN-kappa B/metabolismo , Complejo de la Endopetidasa Proteasomal/metabolismo , Animales , Colitis/inducido químicamente , Colitis/complicaciones , Neoplasias del Colon/etiología , Sulfato de Dextran , Células HCT116 , Células HEK293 , Humanos , Mucosa Intestinal/metabolismo , Ratones Endogámicos C57BL , Ratones NoqueadosRESUMEN
GSK3ß regulates some functions of the brain, but the mechanisms involved in the maintenance of GSK3ß protein stability remain ambiguous. REGγ, an important proteasome activator for ubiquitin-independent protein degradation, has been shown to degrade certain intact proteins and is involved in the regulation of important biological processes. Here we demonstrate that REGγ promotes the degradation of GSK3ß protein in vitro and in vivo. With increased GSK3ß activity, REGγ knockout (REGγ-/-) mice exhibit late-onset sensorimotor gating and cognitive deficiencies including decreased working memory, hyperlocomotion, increased stereotype, defective prepulse inhibition (PPI), and disability in nest building, at the age of 8 months or older. Inhibition of GSK3ß rescued the compromised PPI phenotypes and working memory deficiency in the knockout mice. Also, we found an age-dependent decrease in the trypsin-like proteasomal activity in REGγ-/- mice brains, which may be reflective of a lack of degradation of GSK3ß. Collectively, our findings reveal a novel regulatory pathway in which the REGγ-proteasome controls the steady-state level of GSK3ß protein. Dysfunction in this non-canonical proteasome degradation pathway may contribute to the sensorimotor gating deficiency and cognitive disorders in aging mice.
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Autoantígenos/metabolismo , Glucógeno Sintasa Quinasa 3 beta/metabolismo , Memoria a Corto Plazo/fisiología , Comportamiento de Nidificación/fisiología , Inhibición Prepulso/fisiología , Complejo de la Endopetidasa Proteasomal/metabolismo , Animales , Autoantígenos/genética , Encefalopatías/metabolismo , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Actividad Motora , Complejo de la Endopetidasa Proteasomal/genética , Proteolisis , Regulación hacia ArribaRESUMEN
Here we report that mice deficient for the proteasome activator, REGγ, exhibit a marked resistance to TPA (12-O-tetradecanoyl-phorbol-13-acetate)-induced keratinocyte proliferation, epidermal hyperplasia and onset of papillomas compared with wild-type counterparts. Interestingly, a massive increase of REGγ in skin tissues or cells resulting from TPA induces activation of p38 mitogen-activated protein kinase (MAPK/p38). Blocking p38 MAPK activation prevents REGγ elevation in HaCaT cells with TPA treatment. AP-1, the downstream effector of MAPK/p38, directly binds to the REGγ promoter and activates its transcription in response to TPA stimulation. Furthermore, we find that REGγ activates Wnt/ß-catenin signalling by degrading GSK-3ß in vitro and in cells, increasing levels of CyclinD1 and c-Myc, the downstream targets of ß-catenin. Conversely, MAPK/p38 inactivation or REGγ deletion prevents the increase of cyclinD1 and c-Myc by TPA. This study demonstrates that REGγ acts in skin tumorigenesis mediating MAPK/p38 activation of the Wnt/ß-catenin pathway.
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Autoantígenos/genética , Carcinogénesis/genética , Queratinocitos/metabolismo , Complejo de la Endopetidasa Proteasomal/genética , Neoplasias Cutáneas/genética , Vía de Señalización Wnt , Animales , Autoantígenos/metabolismo , Carcinógenos/farmacología , Línea Celular , Proliferación Celular/genética , Ciclina D1/metabolismo , Técnicas de Silenciamiento del Gen , Glucógeno Sintasa Quinasa 3/metabolismo , Glucógeno Sintasa Quinasa 3 beta , Humanos , Queratinocitos/citología , Queratinocitos/efectos de los fármacos , Ratones , Ratones Noqueados , Complejo de la Endopetidasa Proteasomal/metabolismo , Proteínas Proto-Oncogénicas c-myc/metabolismo , Neoplasias Cutáneas/inducido químicamente , Neoplasias Cutáneas/metabolismo , Acetato de Tetradecanoilforbol/farmacología , Factor de Transcripción AP-1/metabolismo , Proteínas Quinasas p38 Activadas por Mitógenos/antagonistas & inhibidoresRESUMEN
Steroid receptor coactivator 1 (SRC-1) drives diverse gene expression programs necessary for the dynamic regulation of cancer metastasis, inflammation and gluconeogenesis, pointing to its overlapping roles as an oncoprotein and integrator of cell metabolic programs. Nutrient utilization has been intensely studied with regard to cellular adaptation in both cancer and noncancerous cells. Nonproliferating cells consume glucose through the citric acid cycle to generate NADH to fuel ATP generation via mitochondrial oxidative phosphorylation. In contrast, cancer cells undergo metabolic reprogramming to support rapid proliferation. To generate lipids, nucleotides, and proteins necessary for cell division, most tumors switch from oxidative phosphorylation to glycolysis, a phenomenon known as the Warburg Effect. Because SRC-1 is a key coactivator responsible for driving a hepatic gluconeogenic program under fasting conditions, we asked whether SRC-1 responds to alterations in nutrient availability to allow for adaptive metabolism. Here we show SRC-1 is stabilized by the 26S proteasome in the absence of glucose. RNA profiling was used to examine the effects of SRC-1 perturbation on gene expression in the absence or presence of glucose, revealing that SRC-1 affects the expression of complex I of the mitochondrial electron transport chain, a set of enzymes responsible for the conversion of NADH to NAD(+). NAD(+) and NADH were subsequently identified as metabolites that underlie SRC-1's response to glucose deprivation. Knockdown of SRC-1 in glycolytic cancer cells abrogated their ability to grow in the absence of glucose consistent with SRC-1's role in promoting cellular adaptation to reduced glucose availability.
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Glucosa/metabolismo , Homeostasis , NAD/metabolismo , Coactivador 1 de Receptor Nuclear/fisiología , Línea Celular Tumoral , Supervivencia Celular , Complejo I de Transporte de Electrón/metabolismo , Metabolismo Energético , Expresión Génica , Humanos , Complejo de la Endopetidasa Proteasomal/metabolismo , Estabilidad Proteica , ProteolisisRESUMEN
Biallelic mutations in BLM cause Bloom syndrome (BS), a genome instability disorder characterized by growth retardation, sun sensitivity and a predisposition to cancer. As evidence of decreased genome stability, BS cells demonstrate not only elevated levels of spontaneous sister chromatid exchanges (SCEs), but also exhibit chromosomal radial formation. The molecular nature and mechanism of radial formation is not known, but radials have been thought to be DNA recombination intermediates between homologs that failed to resolve. However, we find that radials in BS cells occur over 95% between non-homologous chromosomes, and occur non-randomly throughout the genome. BLM must be phosphorylated at T99 and T122 for certain cell cycle checkpoints, but it is not known whether these modifications are necessary to suppress radial formation. We find that exogenous BLM constructs preventing phosphorylation at T99 and T122 are not able to suppress radial formation in BS cells, but are able to inhibit SCE formation. These findings indicate that BLM functions in 2 distinct pathways requiring different modifications. In one pathway, for which the phosphorylation marks appear dispensable, BLM functions to suppress SCE formation. In a second pathway, T99 and T122 phosphorylations are essential for suppression of chromosomal radial formation, both those formed spontaneously and those formed following interstrand crosslink damage.