GSK3beta: a master switch and a promising target

MicroRNAs as the pivotal regulators of Temozolomide resistance in glioblastoma

Glioblastoma (GBM) is an aggressive nervous system tumor with a poor prognosis. Although, surgery, radiation therapy, and chemotherapy are the current standard protocol for GBM patients, there is still a poor prognosis in these patients. Temozolomide (TMZ) as a first-line therapeutic agent in GBM can easily cross from the blood-brain barrier to inhibit tumor cell proliferation. However, there is a high rate of TMZ resistance in GBM patients. Since, there are limited therapeutic choices for GBM patients who develop TMZ resistance; it is required to clarify the molecular mechanisms of chemo resistance to introduce the novel therapeutic targets. MicroRNAs (miRNAs) regulate chemo resistance through regulation of drug metabolism, absorption, DNA repair, apoptosis, and cell cycle. In the present review we discussed the role of miRNAs in TMZ response of GBM cells. It has been reported that miRNAs mainly induced TMZ sensitivity by regulation of signaling pathways and autophagy in GBM cells. Therefore, miRNAs can be used as the reliable diagnostic/prognostic markers in GBM patients. They can also be used as the therapeutic targets to improve the TMZ response in GBM cells.

Galectin-3 Mediates Tumor Progression in Astrocytoma by Regulating Glycogen Synthase Kinase-3β Activity

Numerous studies have considered galectin-3 or Glycogen synthase kinase 3 beta (GSK3B) as a potential prognosis marker for various cancers. However, the correlation between the protein expression of galectin-3/GSK3B and the clinical parameters of astrocytoma has not been reported. This study aims to validate the correlation between the clinical outcomes and protein expression of galectin-3/GSK3B in astrocytoma. Immunohistochemistry staining was performed to detect galectin-3/GSK3B protein expression in patients with astrocytoma. The Chi-square test, Kaplan-Meier evaluation, and Cox regression analysis were used to determine the correlation between clinical parameters and galectin-3/GSK3B expression. Cell proliferation, invasion, and migration were compared between a non-siRNA group and a galectin-3/GSK3B siRNA group. Protein expression in galectin-3 or GSK3B siRNA-treated cells was evaluated using western blotting. Galectin-3 and GSK3B protein expression were significantly positively correlated with the World Health Organization (WHO) astrocytoma grade and overall survival time. Multivariate analysis revealed that WHO grade, galectin-3 expression, and GSK3B expression were independent prognostic factors for astrocytoma. Galectin-3 or GSK3B downregulation induced apoptosis and decreased cell numbers, migration, and invasion. siRNA-mediated gene silencing of galectin-3 resulted in the downregulation of Ki-67, cyclin D1, VEGF, GSK3B, p-GSK3B Ser9 (p-GSK3B S9), and β-catenin. In contrast, GSK3B knockdown only decreased Ki-67, VEGF, p-GSK3B S9, and β-catenin protein expression but did not affect cyclin D1 and galectin-3 protein expression. The siRNA results indicated that GSK3B is downstream of the galectin-3 gene. These data support that galectin-3 mediated tumor progression by upregulating GSK3B and β-catenin protein expression in glioblastoma. Therefore, galectin-3 and GSK3B are potential prognostic markers, and their genes may be considered to be anticancer targets for astrocytoma therapy.

High-throughput screening of natural compounds and inhibition of a major therapeutic target HsGSK-3β for Alzheimer's disease using computational approaches

BACKGROUND

Alzheimer's disease is a leading neurodegenerative disease worldwide and is the 6th leading cause of death in the USA. AD is a very complex disease and the drugs available in the market cannot fully cure it. The glycogen synthase kinase 3 beta plays a major role in the hyperphosphorylation of tau protein which forms the neurofibrillary tangles which is a major hallmark of AD. In this study, we have used a series of computational approaches to find novel inhibitors against GSK-3β to reduce the TAU hyperphosphorylation.

RESULTS

We have retrieved a set of compounds (n=167,741) and screened against GSK-3β in four sequential steps. The resulting analysis of virtual screening suggested that 404 compounds show good binding affinity and can be employed for pharmacokinetic analysis. From here, we have selected 20 compounds those were good in terms of pharmacokinetic parameters. All these compounds were re-docked by using Autodock Vina followed by Autodock. Four best compounds were employed for MDS and here predicted RMSD, RMSF, Rg, hydrogen bonds, SASA, PCA, and binding-free energy. From all these analyses, we have concluded that out of 167,741 compounds, the ZINC15968620, ZINC15968622, and ZINC70707119 can act as lead compounds against HsGSK-3β to reduce the hyperphosphorylation.

CONCLUSION

The study suggested three compounds (ZINC15968620, ZINC15968622, and ZINC70707119) have great potential to be a drug candidate and can be tested using in vitro and in vivo experiments for further characterization and applications.

Downregulation of GSK-3β Expression via Ultrasound-Targeted Microbubble Destruction Enhances Atherosclerotic Plaque Stability in New Zealand Rabbits

Accumulating evidence suggests that atherosclerosis (AS) is the underlying cause of vascular diseases, including heart disease and stroke. Ultrasound-targeted microbubble destruction (UTMD) technology provides a tolerable, efficient and effective system for drug delivery and gene transfection, which has broad application prospects in the treatment of AS. In addition, glycogen synthase kinase (GSK)-3β has been implicated as a potentially valuable therapeutic agent for AS treatment; however, the specific molecular mechanisms remain unknown. Therefore, this study was conducted to explore the effect of downregulation of GSK-3β expression via UTMD on atherosclerotic plaque stability. We established a THP-1 macrophage-derived foam cell model in vitro and an atherosclerotic plaque model in the right common carotid artery of New Zealand rabbits. We determined levels of the relevant vulnerable plaque stability elements. The results indicate that GSK-3β was upregulated in the foam cells and in atherosclerotic rabbits. Downregulation of GSK-3β expression by UTMD suppressed vulnerable plaque factors and inflammation in vitro and in vivo, changed the cytoskeleton of the foam cells in vitro, increased Young's modulus and decreased the peak intensity of atherosclerotic plaque in vivo. Moreover, GSK-3β inhibition by UTMD did not influence the viability of the foam cells. Collectively, our results indicate that GSK-3β could be a potential target for anti-atherogenic interventions and, in particular, can improve the stability of AS plaques in combination with UTMD.

The Role of Reactive Oxygen Species in the Life Cycle of the Mitochondrion

Currently, it is known that, in living systems, free radicals and other reactive oxygen and nitrogen species play a double role, because they can cause oxidative damage and tissue dysfunction and serve as molecular signals activating stress responses that are beneficial to the organism. It is also known that mitochondria, because of their capacity to produce free radicals, play a major role in tissue oxidative damage and dysfunction and provide protection against excessive tissue dysfunction through several mechanisms, including the stimulation of permeability transition pore opening. This process leads to mitoptosis and mitophagy, two sequential processes that are a universal route of elimination of dysfunctional mitochondria and is essential to protect cells from the harm due to mitochondrial disordered metabolism. To date, there is significant evidence not only that the above processes are induced by enhanced reactive oxygen species (ROS) production, but also that such production is involved in the other phases of the mitochondrial life cycle. Accumulating evidence also suggests that these effects are mediated through the regulation of the expression and the activity of proteins that are engaged in processes such as genesis, fission, fusion, and removal of mitochondria. This review provides an account of the developments of the knowledge on the dynamics of the mitochondrial population, examining the mechanisms governing their genesis, life, and death, and elucidating the role played by free radicals in such processes.

Identification of novel small molecules against GSK3β for Alzheimer's disease using chemoinformatics approach

Alzheimer's disease is a rapidly increasing neurodegenerative disease. It is a multifactorial disease and also a global threat. Several enzymes are implicated in the disease in which Glycogen Synthase Kinase 3 beta is a key enzyme to increase the disease progression by the hyperphosphorylation of the tau protein. We have used an integrative chemoinformatics and pharmacokinetics approach for the identification of novel small molecules. We have retrieved a subset from the ZINC database (n = 5,36,709) and screened against GSK3β in four steps. From here top 298 potent compounds were selected and employed for their pharmacokinetics analysis. We had seen that 29 compounds showed the key characteristics to be a novel drug candidate therefore, all these compounds were employed for redocking studies using Autodock Vina and Autodock. This analysis revealed that four compounds were showing good binding affinity. All these four compounds were employed for MDS analysis of 100 ns From here using a bunch of MD analyses we have found that out of four compounds GSK3β-ZINC21011059 and GSK3β-ZINC21011066 act as a stable protein-ligand complex. Therefore we proposed ZINC21011059 and ZINC21011066 can serve as a novel compounds against GSK3β and predicted scaffold can be used for further optimization towards the improvement of isoform selectivity, and warranting further investigations towards their in vitro and in vivo validation of the bioactivity.

MicroRNA-101 reverses temozolomide resistance by inhibition of GSK3β in glioblastoma

Glioblastoma multiforme (GBM) is a chemotherapy-resistant brain tumor with limited treatment options. Temozolomide (TMZ), an alkylating agent, is a front-line chemotherapeutic drug currently employed in GBM. Although it is currently the most promising chemotherapy for GBM, resistance to TMZ is also common and accounts for many treatment failures. Therefore, understanding the underlying mechanisms that generate resistance is essential to develop more effective chemotherapies. Here, we show that microRNA-101 (miR-101) was significantly downregulated in TMZ-resistant GBM cells and human specimens. Instead, over-expression of miR-101 could sensitize resistant GBM cells to TMZ through downregulation of glycogen synthase kinase 3β (GSK3β). Moreover, we found that GSK3β inhibition could enhance TMZ effect through repression of MGMT via promoter methylation. Importantly, decreased expression of miR-101 is related to poor prognosis in patients with GBM, suggesting its potential role as a new prognostic marker in GBM. In conclusion, our study demonstrates that miR-101 can reverse TMZ resistance by inhibition of GSK3β in GBM, thus offer a novel and powerful strategy for GBM therapy.

Designing of dual inhibitors for GSK-3β and CDK5: Virtual screening and in vitro biological activities study

Alzheimer's disease is a multifactorial neurodegenerative disorder with many drug targets contributing to its etiology. Despite the devastating effects of this disease, therapeutic methods for treating Alzheimer's disease remain limited. The multifactorial nature of Alzheimer's disease strongly supports a multi-target rationale as a drug design strategy. Glycogen synthase kinase-3 beta and cyclin-dependent kinase 5 have been identified as being involved in the pathological hyperphosphorylation of tau proteins, which leads to the formation of neurofibrillary tangles and causes Alzheimer's disease. In this study, using a molecular docking method to screen a virtual library, we discovered molecules that can simultaneously inhibit Glycogen synthase kinase-3 beta and cyclin-dependent kinase 5 as lead compounds for the treatment of Alzheimer's disease. The docking results revealed the key residues in the substrate binding sites of both Glycogen synthase kinase-3 beta and cyclin-dependent kinase 5. A receiver operating characteristic curve indicated that the docking model consistently and selectively scored the majority of active compounds above decoys. The pre-treatment of cells with screened compounds protected them against Aβ_25-35- induced cell death by up to 80%. Collectively, these findings suggest that some compounds have potential to be promising multifunctional agents for Alzheimer's disease treatment.

Piperazine derivatives for therapeutic use: a patent review (2010-present)

INTRODUCTION

Piperazine, a six membered nitrogen containing heterocycle, is of great significance to the rational design of drugs. This moiety can be found in a plethora of well-known drugs with various therapeutic uses, such as antipsychotic, antihistamine, antianginal, antidepressant, anticancer, antiviral, cardio protectors, anti-inflammatory, and imaging agents. Slight modification to the substitution pattern on the piperazine nucleus facilitates a recognizable difference in the medicinal potential of the resultant molecules.

AREAS COVERED

Scifinder was the main source used to search for patents containing piperazine compounds with therapeutic uses. The article describes a variety of molecular designs bearing piperazine entity furnishing CNS agents, anticancer, cardio-protective agents, antiviral, anti-tuberculosis, anti-inflammatory, antidiabetic, and antihistamine profiles, as well as agents relieving pain and useful in imaging applications.

EXPERT OPINION

The great interest gathered to explore piperazine based molecules in relatively few years reflects the broad potential of the entity. Earlier, this scaffold was considered to express CNS activity only. However, a significant increase in research covering studies of several different activities of piperazine ring suggest a successful emergence of the pharmacophore. Certain patents outlined in the present article recommend that piperazines can be a flexible building block to discover drug-like elements and modification of substituents present on the piperazine ring may have a significant impact on the pharmacokinetic and pharmacodynamics factors of the resulting molecules. This article aims to provide insights to piperazine based molecular fragments that would assist drug discoverers to rationally design molecules for various diseases. We anticipate, and highly recommend, further therapeutic investigations on this motif.

Identifying GSK-3β kinase inhibitors of Alzheimer's disease: Virtual screening, enzyme, and cell assays

Glycogen synthase kinase 3β (GSK-3β) is widely known as a critical target protein for treating Alzheimer's disease (AD). We utilized virtual screening to search databases for compounds with the potential to be used in drugs targeting GSK-3β kinase, and kinase as well as cell assays to investigate top-scored, selected compounds. Virtual screening of >1.1 million compounds in the ZINC and in-house databases was conducted using an optimized computational protocol in the docking program GOLD. Of the top-ranked compounds, 16 underwent a luminescent kinase assay and a cell assay using HEK293 cells expressing DsRed-tagged ΔK280 in the repeat domain of tau (tauRD). The compounds VB-003 (a potent GSK-3β inhibitor) and VB-008 (AM404, an anandamide transport inhibitor), with determined IC50 values of 0.25 and 5.4μM, respectively, were identified as reducing tau aggregation. Both compounds increased expression of phospho-GSK-3β (Ser9) and reduced endogenous tau phosphorylation at the sites of Ser202, Thr231, and Ser396. In the ∆K280 tauRD-DsRed SH-SY5Y cells, VB-008, but not VB-003, enhanced HSPB1 and GRP78 expression, increased ∆K280 tauRD-DsRed solubility, and promoted neurite outgrowth. Thus VB-008 performed best to the end of the present study. The identified compound VB-008 may guide the identification and synthesis of potential inhibitors analogous to this compound.

GSK-3β controls autophagy by modulating LKB1-AMPK pathway in prostate cancer cells

BACKGROUND

Glycogen synthase kinase 3β (GSK3B, GSK-3β) is a multi-functional protein kinase involved in various cellular processes and its activity elevates after serum deprivation. We have shown that inhibition of GSK-3β activity triggered a profound autophagic response and subsequent necrotic cell death after serum deprivation in prostate cancer cells. In this study, we dissected the mechanisms involved in GSK-3β inhibition-triggered autophagy.

METHODS

Prostate cancer PC-3 and DU145 cells were used in the study. Multiple GSK-3β specific inhibitors were used including small chemicals TDZD8, Tideglusib, TWS119, and peptide L803-mts. Western blot assay coupled with phospho-specific antibodies were used in detecting signal pathway activation. ATP levels were assessed with ATPLite kit and HPLC methods. Autophagy response was determined by evaluating Microtubule-associated proteins 1A/1B light chain 3B (LC3B) processing and p62 protein stability in Western blot assays. Immunofluorescent microscopy was used to detect LKB1 translocation.

RESULTS

Inhibition of GSK-3β activity resulted in a significant decline of cellular ATP production, leading to a significant increase of AMP/ATP ratio, a strong trigger of AMP-activated protein kinase (AMPK) activation in prostate cancer PC-3 cells. In parallel with increased LC-3B biosynthesis and p62 protein reduction, the classical sign of autophagy induction, AMPK was activated after inhibition of GSK-3β activity. Further analysis revealed that Liver kinase B1 (LKB1) but not Calcium/calmodulin-dependent protein kinase kinase β (CaMKKβ) is involved in AMPK activation and autophagy induction triggered by GSK-3β inhibition. Meanwhile, GSK-3β inhibition promoted LKB1 translocation from nuclear to cytoplasmic compartment and enhanced LKB1 interaction with its regulatory partners Mouse protein-25 (MO25) and STE20-related adaptor (STRAD).

CONCLUSIONS

In conclusion, our data suggest that GSK-3β plays an important role in controlling autophagy induction by modulating the activation of LKB1-AMPK pathway after serum deprivation.

Effect of total glucosides of paeony on rat hepatic injury after cardiopulmonary bypass

AIM: To investigate the effect of total glucosides of paeony (TGP) on rat hepatic injury after cardiopulmonary bypass (CPB) and the underlying mechanism.

METHODS: Two hundred rats were randomly divided into a control group, a sham operation group, low-, medium- and high-dose TGP groups. Except the sham operation group, all other groups received CPB. In the low-, medium- and high-dose TGP treatment groups, 0.6, 1.2 and 1.8 mg/kg TGP was added into the priming solution, respectively. After 2 h of CPB, serum levels of transaminases, total bilirubin, prealbumin, transferrin, C-reactive protein, serum amyloid A, tumor necrosis factor alpha (TNF-α), interleukin-1β (IL-1β), IL-6, growth hormone (GH), growth hormone binding protein (GHBP), insulin-like growth factor-1 (IGF-1) and insulin-like growth factor binding protein-3 (IGFBP-3) were detected. Also, the expression of Na⁺/taurocholate cotransporting polypeptide (NTCP), bile salt export pump (BSEP) and farnesoid X receptor (FXR) in the liver was tested.

RESULTS: Serum levels of glutamic pyruvic transaminase, aspartate transaminase, total bilirubin, prealbumin, transferrin, C-reactive protein, serum amyloid A protein, TNF-α, IL-1β, and IL-6 were significantly higher in the control group after treatment than in the sham operation group (P < 0.05); however, these parameters were significantly lower in the three treatment groups than in the control group (P < 0.05). Serum levels of GH, GHBP, IGF-1 and IGFBP-3 as well as hepatic expression of NTCP, BSEP and FXR were significantly lower in the control group than in the sham operation group (P < 0.05); however, these parameters were significantly higher in the three treatment groups than in the control group (P < 0.05). There were significant differences in all parameters among the three treatment groups (P < 0.05).

CONCLUSION: TGP can protect against liver injury caused by CPB in rats.

Raf kinase inhibitory protein (RKIP): functional pleiotropy in the mammalian brain

In 1984, a cytosolic protein was isolated from bovine brain and coined phosphatidylethanolamine binding protein (PEBP) to describe its phospholipid-binding potential. Its cellular function remained elusive for more than a decade until it was discovered that PEBP had the ability to suppress the Raf1-mitogen activated protein kinase (MAPK) pathway, earning it the new name of Raf1 kinase inhibitory protein (RKIP). This milestone discovery has paved the way for numerous studies that have now extended the reach of RKIP's function to other signaling cascades, within the context of various physiological and pathophysiological systems. This review will summarize our current knowledge of the neurophysiological roles of RKIP in the mammalian brain, including its function in the circadian clock and synaptic plasticity. It will also discuss evidence for an involvement of RKIP and its derived neuropeptide, hippocampal cholinergic neurostimulating peptide (HCNP), in neural development and differentiation. Implications in certain pathologies such as Alzheimer's disease and brain cancer will be highlighted. By chronicling the diverse functions of RKIP in the brain, we hope that this review will serve as a timely resource that ignites future studies on this versatile, multifaceted protein in the nervous system.

Preclinical toxicity of AZD7969: Effects of GSK3β inhibition in adult stem cells

AZD7969 is a potent inhibitor of glycogen synthase kinase 3 (GSK3β), which is a multifunctional serine/threonine kinase that negatively regulates the Wnt/β-catenin signaling pathway. Treatment of rats and dogs with AZD7969 for periods of up to 4 weeks resulted in a number of changes, the most significant of which was a dose-dependent, and treatment-related, increase in proliferation in a number of tissues that was thought to arise from derepression of Wnt/β-catenin signaling in the stem cell compartment. Phenotypically, this resulted in hyperplasia that either maintained normal tissue architecture in the gastrointestinal tract, liver, kidney, and adrenals or effaced normal tissue architecture within the bones, incisor teeth, and femorotibial joint. In addition to these changes, we noted a treatment-related increase in iron loading in the liver and proximal small intestines. This off-target effect was robust, potent, and occurred in both dogs and rats suggesting that AZD7969 might be a useful tool compound to study iron storage disorders in the laboratory.

Identification of glycogen synthase kinase 3α as a therapeutic target in melanoma

Deregulated expression or activity of kinases can lead to melanomas, but often the particular kinase isoform causing the effect is not well established, making identification and validation of different isoforms regulating disease development especially important. To accomplish this objective, an siRNA screen was undertaken that which identified glycogen synthase kinase 3α (GSK3α) as an important melanoma growth regulator. Melanocytes and melanoma cell lines representing various stages of melanoma tumor progression expressed both GSK3α and GSK3β, but analysis of tumors in patients with melanoma showed elevated expression of GSK3α in 72% of samples, which was not observed for GSK3β. Furthermore, 80% of tumors in patients with melanoma expressed elevated levels of catalytically active phosphorylated GSK3α (pGSK3αY279), but not phosphorylated GSK3β (pGSK3βY216). siRNA-mediated reduction in GSK3α protein levels reduced melanoma cell survival and proliferation, sensitized cells to apoptosis-inducing agents and decreased xenografted tumor development by up to 56%. Mechanistically, inhibiting GSK3α expression using siRNA or the pharmacological agent AR-A014418 arrested melanoma cells in the G0/G1 phase of the cell cycle and induced apoptotic death to retard tumorigenesis. Therefore, GSK3α is a key therapeutic target in melanoma.

Design, synthesis and biological evaluation of benzothiazepinones (BTZs) as novel non-ATP competitive inhibitors of glycogen synthase kinase-3β (GSK-3β)

Glycogen synthase kinase-3β (GSK-3β) plays a key role in type II diabetes and Alzheimer's diseases, to which non-ATP competitive inhibitors represent an effectively therapeutical approach due to their good specificity. Herein, a series of small molecules benzothiazepinones (BTZs) as novel non-ATP competitive inhibitors of GSK-3β have been designed and synthesized. The in vitro evaluation performed by luminescent assay showed most BTZ derivatives have inhibitory effects in micromolar scale. Among them compounds 6l, 6t and 6v have the IC50 values of 25.0 μM, 27.8 μM and 23.0 μM, respectively. Moreover 6v is devoid of any inhibitory activity in the assays to other thirteen protein kinases. Besides, SAR is analyzed and a hypothetical enzymatic binding mode is proposed by molecular docking study, which would be useful for new candidates design.

Akt augments the oncogenic potential of the HBx protein of hepatitis B virus by phosphorylation

Hepatitis B virus X protein (HBx) is a putative viral oncoprotein that plays an important role in various cellular processes, including modulation of the phosphatidylinositol 3-kinase/Akt signalling pathway. However, the molecular mechanism of Akt activation remains elusive. Here we show that HBx interacts with Akt1 kinase and is phosphorylated at serine 31 as indicated by mutational analysis of the Akt recognition motif (creating the HBxS31A mutant) or immunoblotting of HBx immunoprecipitates using Akt motif-specific antibody. The Akt-dependent phosphorylation of HBx was abrogated in the presence of the phosphatidylinositol 3-kinase inhibitor LY294002 or Akt1 gene silencing by specific siRNA. Co-immunoprecipitation studies provided evidence for HBx-Akt interaction in a cellular environment. This interaction was also confirmed in hepatoma HepG2.2.15 cells in which HBx was expressed at physiological levels from the integrated hepatitis B viral genome. The HBx-Akt interaction was essential for Akt signalling, and involved displacement of the Akt-bound negative regulator 'C-terminal modulator protein' by HBx. HBx-activated Akt phosphorylated its downstream target glycogen synthase kinase 3β, leading to stabilization of β-catenin, while p65 phosphorylation resulted in enhanced promoter recruitment and expression of target genes encoding cyclin D1 and Bcl-XL. Further, the oncogenic potential of HBx was significantly augmented in the presence of Akt in a soft agar colony formation assay. Together, these results suggest that oncogenic co-operation between HBx and Akt may be important for cell proliferation, abrogation of apoptosis and tumorigenic transformation of cells.

Exploring the binding sites of glycogen synthase kinase 3. Identification and characterization of allosteric modulation cavities

Glycogen synthase kinase 3 (GSK-3) is an important drug target for human severe unmet diseases. Discovery and/or design of allosteric kinase modulators are gaining importance in this field not only for the increased selectivity of this kind of compounds but also for the subtle modulation of the target. This last point is of utmost importance for the GSK-3 inhibition as a therapeutic approach. GSK-3 activity is completely necessary for life, and only the aberrant overactivity found in the pathologies should be inhibited with its inhibitors treatment. We performed here a search for the druggable sites on the enzyme using the fpocket algorithm with the aim to provide allosteric potential binding sites on it and new clues for further drug discoveries. Moreover, our results allowed us to determine the binding sites of different GSK-3 ATP noncompetitive inhibitors, such as manzamine A and the new small molecule VP 0.7, providing evidence for potential allosteric inhibition of GSK-3.

Loss of manganese superoxide dismutase leads to abnormal growth and signal transduction in mouse embryonic fibroblasts

Manganese superoxide dismutase (MnSOD) in the mitochondria plays an important role in cellular defense against oxidative damage. Homozygous MnSOD knockout (Sod2(-/-)) mice are neonatal lethal, indicating the essential role of MnSOD in early development. To investigate the potential cellular abnormalities underlying the aborted development of Sod2(-/-) mice, we examined the growth of isolated mouse embryonic fibroblasts (MEFs) from Sod2(-/-) mice. We found that the proliferation of Sod2(-/-) MEFs was significantly decreased compared with wild-type MEFs despite the absence of morphological differences. The Sod2(-/-) MEFs produced less cellular ATP, had lower O(2) consumption, generated more superoxide, and expressed less Prdx3 protein. Furthermore, the loss of MnSOD dramatically altered several markers involved in cell proliferation and growth, including decreased growth stimulatory function of mTOR signaling and enhanced growth inhibitory function of GSK-3β signaling. Interestingly, the G-protein-coupled receptor-mediated intracellular Ca(2+) signal transduction was also severely suppressed in Sod2(-/-) MEFs. Finally, the ratio of microtubule-associated protein light chain 3 (LC3)-II/LC3-I, an index of autophagic activity, was increased in Sod2(-/-) MEFs, consistent with a reduction in mTOR signal transduction. These data demonstrate that MnSOD deficiency results in alterations in several key signaling pathways, which may contribute to the lethal phenotype of Sod2(-/-) mice.

O-linked beta-N-acetylglucosamine (O-GlcNAc) regulates stress-induced heat shock protein expression in a GSK-3beta-dependent manner

To investigate the mechanisms by which O-linked β-N-acetylglucosamine modification of nucleocytoplasmic proteins (O-GlcNAc) confers stress tolerance to multiple forms of cellular injury, we explored the role(s) of O-GlcNAc in the regulation of heat shock protein (HSP) expression. Using a cell line in which deletion of the O-GlcNAc transferase (OGT; the enzyme that adds O-GlcNAc) can be induced by 4-hydroxytamoxifen, we screened the expression of 84 HSPs using quantitative reverse transcriptase PCR. In OGT null cells the stress-induced expression of 18 molecular chaperones, including HSP72, were reduced. GSK-3β promotes apoptosis through numerous pathways, including phosphorylation of heat shock factor 1 (HSF1) at Ser(303) (Ser(P)(303) HSF1), which inactivates HSF1 and inhibits HSP expression. In OGT null cells we observed increased Ser(P)(303) HSF1; conversely, in cells in which O-GlcNAc levels had been elevated, reduced Ser(P)(303) HSF1 was detected. These data, combined with those showing that inhibition of GSK-3β in OGT null cells recovers HSP72 expression, suggests that O-GlcNAc regulates the activity of GSK-3β. In OGT null cells, stress-induced inactivation of GSK-3β by phosphorylation at Ser(9) was ablated providing a molecular basis for these findings. Together, these data suggest that stress-induced GlcNAcylation increases HSP expression through inhibition of GSK-3β.

Urotensin II induction of adult cardiomyocytes hypertrophy involves the Akt/GSK-3beta signaling pathway

Urotensin II (UII) a potent vasoactive peptide is upregulated in the failing heart and promotes cardiomyocytes hypertrophy, in particular through mitogen-activated protein kinases. However, the regulation by UII of GSK-3beta, a recognized pivotal signaling element of cardiac hypertrophy has not yet been documented. We therefore investigated in adult cardiomyocytes, if UII phosphorylates GSK-3beta and Akt, one of its upstream regulators and stabilizes beta-catenin, a GSK-3beta dependent nuclear transcriptional co-activator. Primary cultures of adult rat cardiomyocytes were stimulated for 48h with UII. Cell size and protein/DNA contents were determined. Phosphorylated and total forms of Akt, GSK-3beta and the total amount of beta-catenin were quantified by western blot. The responses of cardiomyocytes to UII were also evaluated after pretreatment with the chemical phosphatidyl-inositol-3-kinase inhibitor, LY294002, and urantide, a competitive UII receptor antagonist. UII increased cell size and the protein/DNA ratio, consistent with a hypertrophic response. UII also increased phosphorylation of Akt and its downstream target GSK-3beta. beta-Catenin protein levels were increased. All of these effects of UII were prevented by LY294002, and urantide. The UII-induced adult cardiomyocytes hypertrophy involves the Akt/GSK-3beta signaling pathways and is accompanied by the stabilization of the beta-catenin. All these effects are abolished by competitive inhibition of the UII receptor, consistent with new therapeutic perspectives for heart failure treatment.

Molecular imaging of glycogen synthase kinase-3beta and casein kinase-1alpha kinases

Glycogen synthase kinase-3beta (GSK3beta) and casein kinase-1alpha (CK1alpha) are multifunctional kinases that play critical roles in the regulation of a number of cellular processes. In spite of their importance, molecular imaging tools for noninvasive and real-time monitoring of their kinase activities have not been devised. Here we report development of the bioluminescent GSK3beta and CK1alpha reporter (BGCR) based on firefly luciferase complementation. Treatment of SW620 cells stably expressing the reporter with inhibitors of GSK3beta (SB415286 and LiCl) or CK1alpha (CKI-7) resulted in dose- and time-dependent increases in BGCR activity that were validated using Western blotting. No increase in bioluminescence was observed in the case of S37A mutant (GSK3beta inhibitors) or S45A mutant (CKI-7), demonstrating the specificity of the reporter. Imaging of mice tumor xenograft generated with BGCR-expressing SW620 cells following treatment with LiCl showed unique oscillations in GSK3beta activity that were corroborated by phosphorylated GSK3beta immunoblotting. Taken together, the BGCR is a novel molecular imaging tool that reveals unique insight into GSK3beta and CK1alpha kinase activities and may provide a powerful tool in experimental therapeutics for rapid optimization of dose and schedule of targeted therapies and for monitoring therapeutic response.

A kinesin signaling complex mediates the ability of GSK-3beta to affect mood-associated behaviors

Lithium has been the gold standard in the treatment of bipolar disorder (BPD) for 60 y. Like lithium, glycogen synthase kinase 3 (GSK-3) inhibitors display both antimanic-like and antidepressant-like effects in some animal models. However, the molecular mechanisms of both lithium and GSK-3 inhibitors remain unclear. Here we show that the GSK-3 inhibitor AR-A014418 regulated alpha-amino-3-hydroxyl-5-methyl-4-isoxazole-propionate (AMPA)-induced GluR1 and GluR2 internalization via phosphorylation of kinesin light chain 2 (KLC2), the key molecule of the kinesin cargo delivery system. Specifically, AMPA stimulation triggered serine phosphorylation of KLC2 and, subsequently, the dissociation of the GluR1/KLC2 protein complex. This suggests that GSK-3 phosphorylation of KLC2 led to the dissociation of AMPA-containing vesicles from the kinesin cargo system. The peptide TAT-KLCpCDK, a specific inhibitor for KLC2 phosphorylation by GSK-3beta, reduced the formation of long-term depression. Furthermore, the TAT-KLCpCDK peptide showed antimanic-like effects similar to lithium's on amphetamine-induced hyperactivity, a frequently used animal model of mania. It also induced antidepressant-like effects in the tail suspension and forced swim tests, two commonly used animal models of depression. Taken together, the results demonstrated that KLC2 is a cellular target of GSK-3beta capable of regulating synaptic plasticity, particularly AMPA receptor trafficking, as well as mood-associated behaviors in animal models. The kinesin cargo system may provide valuable novel targets for the development of new therapeutics for mood disorders.

GSK3beta: role in therapeutic landscape and development of modulators

Glycogen synthase kinase-3 beta (GSK3beta) is a multifunctional serine/threonine kinase which was originally identified as a regulator of glycogen metabolism. It plays a key role in the regulation of numerous signalling pathways including cellular process such as cell cycle, inflammation and cell proliferation. Over the last few years there is a considerable rise in the number of journals and patents publication by different workers worldwide. Many pharmaceutical companies are focusing on GSK3beta as a therapeutic target for the treatment of disease conditions. The present review is focused on signalling pathways of different disease conditions where GSK3beta is implicated. In this review, we present a comprehensive map of GSK3beta signalling pathways in disease physiologies. Structural analysis of GSK3beta along with molecular modelling reports from numerous workers are reviewed in context of design and development of GSK3beta inhibitors. Patent landscape of the small molecule modulators is profiled. The chemo space for small molecule modulators extracted from public and proprietary Kinase Chembiobase for GSK3beta are discussed. Compounds in different clinical phases of discovery are analysed. The review ends with the overall status of this important therapeutic target and challenges in development of its modulators.

Nrf2:INrf2 (Keap1) signaling in oxidative stress

Nrf2:INrf2 (Keap1) are cellular sensors of chemical- and radiation-induced oxidative and electrophilic stress. Nrf2 is a nuclear transcription factor that controls the expression and coordinated induction of a battery of defensive genes encoding detoxifying enzymes and antioxidant proteins. This is a mechanism of critical importance for cellular protection and cell survival. Nrf2 is retained in the cytoplasm by an inhibitor, INrf2 which functions as an adapter for Cul3/Rbx1-mediated degradation of Nrf2. In response to oxidative/electrophilic stress, Nrf2 is switched on and then off by distinct early and delayed mechanisms. Oxidative/electrophilic modification of INrf2 cysteine 151 and/or protein kinase C phosphorylation of Nrf2 serine 40 results in the escape or release of Nrf2 from INrf2. Nrf2 is stabilized and translocates to the nucleus, forms heterodimers with unknown proteins, and binds the antioxidant response element, which leads to coordinated activation of gene expression. It takes less than 15 min from the time of exposure to switch on nuclear import of Nrf2. This is followed by activation of a delayed mechanism that controls the switching off of Nrf2 activation of gene expression. GSK3beta phosphorylates Fyn at an unknown threonine residue(s), leading to the nuclear localization of Fyn. Fyn phosphorylates Nrf2 tyrosine 568, resulting in the nuclear export of Nrf2, binding with INrf2, and degradation of Nrf2. The switching on and off of Nrf2 protects cells against free radical damage, prevents apoptosis, and promotes cell survival.

Nrf2:INrf2 (Keap1) signaling in oxidative stress

Nrf2:INrf2 (Keap1) are cellular sensors of chemical- and radiation-induced oxidative and electrophilic stress. Nrf2 is a nuclear transcription factor that controls the expression and coordinated induction of a battery of defensive genes encoding detoxifying enzymes and antioxidant proteins. This is a mechanism of critical importance for cellular protection and cell survival. Nrf2 is retained in the cytoplasm by an inhibitor, INrf2 which functions as an adapter for Cul3/Rbx1-mediated degradation of Nrf2. In response to oxidative/electrophilic stress, Nrf2 is switched on and then off by distinct early and delayed mechanisms. Oxidative/electrophilic modification of INrf2 cysteine 151 and/or protein kinase C phosphorylation of Nrf2 serine 40 results in the escape or release of Nrf2 from INrf2. Nrf2 is stabilized and translocates to the nucleus, forms heterodimers with unknown proteins, and binds the antioxidant response element, which leads to coordinated activation of gene expression. It takes less than 15 min from the time of exposure to switch on nuclear import of Nrf2. This is followed by activation of a delayed mechanism that controls the switching off of Nrf2 activation of gene expression. GSK3beta phosphorylates Fyn at an unknown threonine residue(s), leading to the nuclear localization of Fyn. Fyn phosphorylates Nrf2 tyrosine 568, resulting in the nuclear export of Nrf2, binding with INrf2, and degradation of Nrf2. The switching on and off of Nrf2 protects cells against free radical damage, prevents apoptosis, and promotes cell survival.