Underlying mechanisms of glucocorticoid-induced β-cell death and dysfunction: a new role for glycogen synthase kinase 3.
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ABSTRACT:
SUBMITTER: Delangre E
PROVIDER: S-EPMC8651641 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Glucocorticoids (GCs) bind to the glucocorticoid receptor (GR) to regulate diverse biological functions from cell growth to apoptosis. Drugs that mimic their action are the most commonly prescribed therapeutic agents in the world and are currently used for the treatment of many diseases including asthma, autoimmune disorders, and some cancers. However, the mechanisms by which one hormone, via one receptor, modulates such diverse biological functions remain unclear. We hypothesized that epigenetic alteration to the GR may contribute to its signaling diversity, and here we demonstrate that Glycogen Synthase Kinase-3-beta phosphorylates GR on Serine 404 in a glucocorticoid-dependent manner. U-2 OS cells expressing a mutant GR that is incapable of Ser404 phosphorylation have enhanced global transcriptional responses, stronger NF-kappaB transrepression, and enhanced cell death in response to dexamethasone. Conversely, presence of Ser404 phosphorylation on the GR inhibits glucocorticoid-dependent NF-kappaB transrepression and cell death of these osteoblasts. Collectively, our results describe a novel convergence point of the GSK-3-beta pathway with the GR resulting in altered glucocorticoid regulated signaling. Our results also provide a mechanism by which the phosphorylation status of Ser404 in GR can dictate how cells will ultimately respond to GCs. Keywords: Glucocorticoid Receptor; GSK-3-beta; NF-kappaB Transrepression; Phosphorylation
2008-11-24 | GSE11205 | GEO
Project description:Glucocorticoids are the only therapy that has been demonstrated to alter the progress of Duchenne muscular dystrophy (DMD), the most common muscular dystrophy in children. However, glucocorticoids disturb skeletal muscle metabolism and hamper myogenesis and muscle regeneration. The mechanisms involved in the glucocorticoid-mediated suppression of myogenic differentiation are not fully understood. Glycogen synthase kinase-3β (GSK-3β) is considered to play a central role as a negative regulator in myogenic differentiation. Here, we showed that glucocorticoid treatment during the first 48 h in differentiation medium decreased the level of phosphorylated Ser9-GSK-3β, an inactive form of GSK-3β, suggesting that glucocorticoids affect GSK-3β activity. We then investigated whether GSK-3β inhibition could regulate glucocorticoid-mediated suppression of myogenic differentiation in vitro. Two methods were employed to inhibit GSK-3β: pharmacological inhibition with LiCl and GSK-3β gene knockdown. We found that both methods resulted in enhanced myotube formation and increased levels of muscle regulatory factors and muscle-specific protein expression. Importantly, GSK-3β inhibition attenuated glucocorticoid-induced suppression of myogenic differentiation. Collectively, these data suggest the involvement of GSK-3β in the glucocorticoid-mediated impairment of myogenic differentiation. Therefore, the inhibition of GSK-3β may be a strategy for preventing glucocorticoid-induced muscle degeneration.
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Project description:The human pathogen Helicobacter pylori influences cell adhesion, proliferation, and apoptosis and is involved in gastric adenocarcinoma formation. In our study we analyzed the impact of H. pylori infection on the regulation of beta-catenin, which plays a central role in both cell adhesion and tumorigenesis. Infection of Madin-Darby canine kidney cells with H. pylori led to suppression of Ser/Thr phosphorylation and ubiquitin-dependent degradation of beta-catenin and to up-regulation of lymphoid enhancer-binding factor/T cell factor (LEF/TCF)-dependent transcription. The impaired Ser/Thr phosphorylation of beta-catenin was accompanied by an increase of glycogen synthase kinase 3beta phosphorylation. Inhibition of Akt kinase, an up-stream regulator of glycogen synthase kinase 3, by a specific inhibitor Akti-1/2 or depletion of Akt with siRNA restored Ser/Thr phosphorylation of beta-catenin. We conclude that glycogen synthase kinase 3beta activity exerts an important role in beta-catenin regulation and LEF/TCF transactivation in H. pylori-infected Madin-Darby canine kidney cells.
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Project description:Neuroinflammation is a crucial mechanism related to many neurological diseases. Extensive studies in recent years have indicated that dysregulation of Glycogen Synthase Kinase 3 Beta (GSK3β) contributes to the development and progression of these disorders through regulating the neuroinflammation processes. Inhibitors of GSK3β have been shown to be beneficial in many neuroinflammatory disease models including Alzheimer's disease, multiple sclerosis and AIDS dem entia complex. Glial activation and elevated pro-inflammation cytokines (signs of neuroinflammation) in the spinal cord have been widely recognized as a pivotal mechanism underlying the development and maintenance of many types of pathological pain. The role of GSK3β in the pathogenesis of pain has recently emerged. In this review, we will first review the GSK3β structure, regulation, and mechanisms by which GSK3βregulates inflammation. We will then describe neuroinflammationin general and in specific types of neurological diseases and the potential beneficial effects induced by inhibiting GSK3β. Finally, we will provide new evidence linking aberrant levels of GSK3β in the development of pathological pain.
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Project description:Mixed lineage kinase 3 (MLK3) is a mitogen-activated protein kinase kinase kinase member that activates the c-Jun N-terminal kinase (JNK) pathway. Aberrant activation of MLK3 has been implicated in neurodegenerative diseases. Similarly, glycogen synthase kinase (GSK)-3beta has also been shown to activate JNK and contribute to neuronal apoptosis. Here, we show a functional interaction between MLK3 and GSK-3beta during nerve growth factor (NGF) withdrawal-induced cell death in PC-12 cells. The protein kinase activities of GSK-3beta, MLK3, and JNK were increased upon NGF withdrawal, which paralleled increased cell death in NGF-deprived PC-12 cells. NGF withdrawal-induced cell death and MLK3 activation were blocked by a GSK-3beta-selective inhibitor, kenpaullone. However, the MLK family inhibitor, CEP-11004, although preventing PC-12 cell death, failed to inhibit GSK-3beta activation, indicating that induction of GSK-3beta lies upstream of MLK3. In GSK-3beta-deficient murine embryonic fibroblasts, ultraviolet light was unable to activate MLK3 kinase activity, a defect that was restored upon ectopic expression of GSK-3beta. The activation of MLK3 by GSK-3beta occurred via phosphorylation of MLK3 on two amino acid residues, Ser(789) and Ser(793), that are located within the C-terminal regulatory domain of MLK3. Furthermore, the cell death induced by GSK-3beta was mediated by MLK3 in a manner dependent on its phosphorylation of the specific residues within the C-terminal domain by GSK-3beta. Taken together, our data provide a direct link between GSK-3beta and MLK3 activation in a neuronal cell death pathway and identify MLK3 as a direct downstream target of GSK-3beta. Inhibition of GSK-3 is thus a potential therapeutic strategy for neurodegenerative diseases caused by trophic factor deprivation.
| S-EPMC5323256 | biostudies-literature
Project description:Aberrant glycogen synthase kinase 3beta (GSK-3beta) activity is associated with the progression of several pathological conditions such as diabetes, Alzheimer's, and cancer. GSK-3beta regulates cellular processes by directly phosphorylating metabolic enzymes and transcription factors. Here, we discovered a new target for GSK-3beta phosphorylation: the human glucocorticoid receptor (GR). Glucocorticoid signaling is essential for life and regulates diverse biological functions from cell growth to metabolism to apoptosis. Specifically, we found hormone-dependent GR phosphorylation on serine 404 by GSK-3beta. Cells expressing a GR that is incapable of GSK-3beta phosphorylation had a redirection of the global transcriptional response to hormone, including the activation of additional signaling pathways, in part due to the altered ability of unphosphorylatable GR to recruit transcriptional cofactors CBP/p300 and the p65 (RelA) subunit of NF-kappaB. Furthermore, GSK-3beta-mediated GR phosphorylation inhibited glucocorticoid-dependent NF-kappaB transrepression and attenuated the glucocorticoid-dependent cell death of osteoblasts. Collectively, our results describe a novel convergence point of the GSK-3beta and the GR pathways, resulting in altered hormone-regulated signaling. Our results also provide a mechanism by which GSK-3beta activity can dictate how cells will ultimately respond to glucocorticoids.
| S-EPMC2593428 | biostudies-literature
Project description:Constitutive nuclear factor kappaB (NF-kappaB) activation is among the many deregulated signaling pathways that are proposed to drive pancreatic cancer cell growth and survival. Recent reports suggest that glycogen synthase kinase-3beta (GSK-3beta) plays a key role in maintaining basal NF-kappaB target gene expression and cell survival in pancreatic cancer cell lines. However, the mechanism by which GSK-3beta facilitates constitutive NF-kappaB signaling in pancreatic cancer remains unclear. In this report, we analyze the contributions of both GSK-3 isoforms (GSK-3alpha and GSK-3beta) in regulating NF-kappaB activation and cell proliferation in pancreatic cancer cell lines (Panc-1 and MiaPaCa-2). We show that GSK-3 isoforms are differentially required to maintain basal NF-kappaB DNA binding activity, transcriptional activity, and cell proliferation in Panc-1 and MiaPaCa-2 cells. Our data also indicate that IkappaB kinase (IKK) subunits are not equally required to regulate pancreatic cancer-associated NF-kappaB activity and cell growth. Importantly, we provide the first evidence that GSK-3 maintains constitutive NF-kappaB signaling in pancreatic cancer by regulating IKK activity. These data provide new insight into GSK-3-dependent NF-kappaB regulation and further establish GSK-3 and IKK as potential therapeutic targets for pancreatic cancer.
| S-EPMC2647811 | biostudies-literature
Project description:BACKGROUND:Arrhythmogenic cardiomyopathy/arrhythmogenic right ventricular cardiomyopathy (ARVC) is an inherited cardiac disease characterized by fibrofatty replacement of the myocardium, resulting in heart failure and sudden cardiac death. The most aggressive arrhythmogenic cardiomyopathy/ARVC subtype is ARVC type 5 (ARVC5), caused by a p.S358L mutation in TMEM43 (transmembrane protein 43). The function and localization of TMEM43 are unknown, as is the mechanism by which the p.S358L mutation causes the disease. Here, we report the characterization of the first transgenic mouse model of ARVC5. METHODS:We generated transgenic mice overexpressing TMEM43 in either its wild-type or p.S358L mutant (TMEM43-S358L) form in postnatal cardiomyocytes under the control of the α-myosin heavy chain promoter. RESULTS:We found that mice expressing TMEM43-S358L recapitulate the human disease and die at a young age. Mutant TMEM43 causes cardiomyocyte death and severe fibrofatty replacement. We also demonstrate that TMEM43 localizes at the nuclear membrane and interacts with emerin and β-actin. TMEM43-S358L shows partial delocalization to the cytoplasm, reduced interaction with emerin and β-actin, and activation of glycogen synthase kinase-3β (GSK3β). Furthermore, we show that targeting cardiac fibrosis has no beneficial effect, whereas overexpression of the calcineurin splice variant calcineurin Aβ1 results in GSK3β inhibition and improved cardiac function and survival. Similarly, treatment of TMEM43 mutant mice with a GSK3β inhibitor improves cardiac function. Finally, human induced pluripotent stem cells bearing the p.S358L mutation also showed contractile dysfunction that was partially restored after GSK3β inhibition. CONCLUSIONS:Our data provide evidence that TMEM43-S358L leads to sustained cardiomyocyte death and fibrofatty replacement. Overexpression of calcineurin Aβ1 in TMEM43 mutant mice or chemical GSK3β inhibition improves cardiac function and increases mice life span. Our results pave the way toward new therapeutic approaches for ARVC5.
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Project description:Myocardial infarction-induced remodeling includes chamber dilatation, contractile dysfunction, and fibrosis. Of these, fibrosis is the least understood. After myocardial infarction, activated cardiac fibroblasts deposit extracellular matrix. Current therapies to prevent fibrosis are inadequate, and new molecular targets are needed.Herein we report that glycogen synthase kinase-3? (GSK-3?) is phosphorylated (inhibited) in fibrotic tissues from ischemic human and mouse heart. Using 2 fibroblast-specific GSK-3? knockout mouse models, we show that deletion of GSK-3? in cardiac fibroblasts leads to fibrogenesis, left ventricular dysfunction, and excessive scarring in the ischemic heart. Deletion of GSK-3? induces a profibrotic myofibroblast phenotype in isolated cardiac fibroblasts, in post-myocardial infarction hearts, and in mouse embryonic fibroblasts deleted for GSK-3?. Mechanistically, GSK-3? inhibits profibrotic transforming growth factor-?1/SMAD-3 signaling via interactions with SMAD-3. Moreover, deletion of GSK-3? resulted in the significant increase of SMAD-3 transcriptional activity. This pathway is central to the pathology because a small-molecule inhibitor of SMAD-3 largely prevented fibrosis and limited left ventricular remodeling.These studies support targeting GSK-3? in myocardial fibrotic disorders and establish critical roles of cardiac fibroblasts in remodeling and ventricular dysfunction.
| S-EPMC4153405 | biostudies-literature
Project description:PURPOSE:GSK3? is a protein kinase that can suppress a number of key oncoproteins. We have previously shown in preclinical models of pancreatic ductal adenocarcinoma (PDAC) that inhibition of GSK3? causes stabilization and nuclear translocation of ?-catenin, poor differentiation, proliferation, and resistance to radiation. The objective of this study was to determine its utility as a biomarker of clinical outcomes. EXPERIMENTAL DESIGN:Automated Quantitative Immunofluorescence Analysis (AQUA) of GSK3? was performed on a tissue microarray with samples from 163 patients treated on RTOG 9704. On the basis of findings in an exploratory cohort, GSK3? was analyzed as a categorical variable using its upper quartile (>Q3) as a cut point. Overall survival (OS) and disease-free survival (DFS) were estimated with the Kaplan-Meier method, and GSK3? groupings were compared using the log-rank test. Univariable and multivariable Cox proportional hazards models were used to determine associations between GSK3? and OS/DFS. RESULTS:The 3-year OS rates for GSK3??Q3 versus GSK3? >Q3 were 16% (95% confidence intervals; CI, 10%-23%) and 30% (95% CI, 17%-44%), respectively, P = 0.0082. The 3-year DFS rates were 9% (95% CI, 5%-15%) and 20% (95% CI, 9%-33%) respectively, P value = 0.0081. On multivariable analysis, GSK3? was a significant predictor of OS. Patients with GSK3? >Q3 had a 46% reduced risk of dying of pancreatic cancer (HR, 0.54; 95% CI, 0.31-0.96, P value = 0.034). The HR for DFS was 0.65 (95% CI, 0.39-1.07; P value = 0.092). CONCLUSIONS:GSK3? expression is a strong prognosticator in PDAC, independent of other known factors such as tumor (T) stage, nodal status, surgical margins and CA19-9. Clin Cancer Res; 21(24); 5612-8. ©2015 AACR.
| S-EPMC4681598 | biostudies-literature