Glycogen synthase kinase-3 is involved in the regulation of the cell cycle in cerebellar granule cells

Glycogen synthase kinase-3β mediates toll-like receptors 4/nuclear factor kappa-B-activated cerebral ischemia-reperfusion injury through regulation of fat mass and obesity-associated protein

BACKGROUND

Glycogen synthase kinase-3β (GSK3β), fat mass and obesity-associated protein (FTO), and toll-like receptors 4 (TLR4) take on critical significance in different biological processes, whereas their interactions remain unclear. The objective was the investigation of the interaction effect in cerebral ischemia-reperfusion (I/R) injury.

METHODS

The function of the cerebral cortex in the mouse middle cerebral artery occlusion (MCAO) model (each group n = 6) and P12 cells oxygen-glucose deprivation/reoxygenation (OGD/R) model was analyzed using short hairpin GSK3β lentivirus and overexpression of FTO lentivirus (in vitro), TLR4 inhibitor (TAK242), and LiCl to regulate GSK3β, FTO, TLR4 expression, and GSK3β activity, respectively.

RESULTS

After GSK3β knockdown in the OGD/R model of PC12 cells, the levels of TLR4 and p-p65 were lower than in the control, and the level of FTO was higher than in the control. Knockdown GSK3β reversed the OGD/R-induced nuclear factor kappa-B transfer to the intranuclear nuclei. As indicated by the result, TLR4 expression was down-regulated by overexpressed FTO, and TLR4 expression was up-regulated notably after inhibition of FTO with the use of R-2HG. After the inhibition of the activity of GSK3β in vivo, the reduction of FTO in mice suffering from MCAO was reversed.

CONCLUSIONS

Our research shows that GSK3β/FTO/TLR4 pathway contributes to cerebral I/R injury.

GSK3 as a Regulator of Cytoskeleton Architecture: Consequences for Health and Disease

Glycogen synthase kinase 3 (GSK3) was initially isolated as a critical protein in energy metabolism. However, subsequent studies indicate that GSK-3 is a multi-tasking kinase that links numerous signaling pathways in a cell and plays a vital role in the regulation of many aspects of cellular physiology. As a regulator of actin and tubulin cytoskeleton, GSK3 influences processes of cell polarization, interaction with the extracellular matrix, and directional migration of cells and their organelles during the growth and development of an animal organism. In this review, the roles of GSK3–cytoskeleton interactions in brain development and pathology, migration of healthy and cancer cells, and in cellular trafficking of mitochondria will be discussed.

When Good Kinases Go Rogue: GSK3, p38 MAPK and CDKs as Therapeutic Targets for Alzheimer's and Huntington's Disease

Alzheimer's disease (AD) is a mostly sporadic brain disorder characterized by cognitive decline resulting from selective neurodegeneration in the hippocampus and cerebral cortex whereas Huntington's disease (HD) is a monogenic inherited disorder characterized by motor abnormalities and psychiatric disturbances resulting from selective neurodegeneration in the striatum. Although there have been numerous clinical trials for these diseases, they have been unsuccessful. Research conducted over the past three decades by a large number of laboratories has demonstrated that abnormal actions of common kinases play a key role in the pathogenesis of both AD and HD as well as several other neurodegenerative diseases. Prominent among these kinases are glycogen synthase kinase (GSK3), p38 mitogen-activated protein kinase (MAPK) and some of the cyclin-dependent kinases (CDKs). After a brief summary of the molecular and cell biology of AD and HD this review covers what is known about the role of these three groups of kinases in the brain and in the pathogenesis of the two neurodegenerative disorders. The potential of targeting GSK3, p38 MAPK and CDKS as effective therapeutics is also discussed as is a brief discussion on the utilization of recently developed drugs that simultaneously target two or all three of these groups of kinases. Multi-kinase inhibitors either by themselves or in combination with strategies currently being used such as immunotherapy or secretase inhibitors for AD and knockdown for HD could represent a more effective therapeutic approach for these fatal neurodegenerative diseases.

Histone deacetylase-3: Friend and foe of the brain

IMPACT STATEMENT

Brain development and degeneration are highly complex processes that are regulated by a large number of molecules and signaling pathways the identities of which are being unraveled. Accumulating evidence points to histone deacetylases and epigenetic mechanisms as being important regulators of these processes. In this review, we describe that histone deacetylase-3 (HDAC3) is a particularly crucial regulator of both neurodevelopment and neurodegeneration. In addition, HDAC3 regulates memory formation, synaptic plasticity, and the cognitive impairment associated with normal aging. Understanding how HDAC3 functions contributes to the normal development and functioning of the brain while also promoting neurodegeneration could lead to the development of therapeutic approaches for neurodevelopmental, neuropsychiatric, and neurodegenerative disorders.

GSK-3 modulates SHH-driven proliferation in postnatal cerebellar neurogenesis and medulloblastoma

Cerebellar development requires regulated proliferation of cerebellar granule neuron progenitors (CGNPs). Inadequate CGNP proliferation causes cerebellar hypoplasia whereas excessive CGNP proliferation can cause medulloblastoma, the most common malignant pediatric brain tumor. Although sonic hedgehog (SHH) signaling is known to activate CGNP proliferation, the mechanisms downregulating proliferation are less defined. We investigated CGNP regulation by GSK-3, which downregulates proliferation in the forebrain, gut and breast by suppressing mitogenic WNT signaling in mouse. In striking contrast to these systems, we found that co-deleting Gsk3a and Gsk3b blocked CGNP proliferation, causing severe cerebellar hypoplasia. The GSK-3 inhibitor CHIR-98014 similarly downregulated SHH-driven proliferation. Transcriptomic analysis showed activated WNT signaling and upregulated Cdkn1a in Gsk3a/b -deleted CGNPs. Ctnnb co-deletion increased CGNP proliferation and rescued cerebellar hypoproliferation in Gsk3a/b mutants, demonstrating physiological control of CGNPs by GSK-3, mediated through WNT. SHH-driven medulloblastomas similarly required GSK-3, as co-deleting Gsk3a/b blocked tumor growth in medulloblastoma-prone SmoM2 mice. These data show that a GSK-3/WNT axis modulates the developmental proliferation of CGNPs and the pathological growth of SHH-driven medulloblastoma. The requirement for GSK-3 in SHH-driven proliferation suggests that GSK-3 may be targeted for SHH-driven medulloblastoma therapy.

Reelin, tau phosphorylation and psychiatric complications in patients with hippocampal sclerosis and structural abnormalities in temporal lobe epilepsy

INTRODUCTION

Temporal lobe epilepsy (TLE) is the most common adult epileptic syndrome. About 30-70% of those cases have neuropsychiatric complications. More than 10% of patients have TLE because of focal cortical dysplasia (FCD) type IIIa.

OBJECTIVES

The objective of this study was to review the evidence of reelin (RELN) deficiency and tau phosphorylation role in the histopathological, neuropsychiatric, and hyperexcitability features in TLE because of dysplasia type IIIa.

METHODS

The current literature was reviewed using Cochrane, EMBASE, PROSPERO, MEDLINE, and PubMed from 1995 to July 2018. Articles of interest were reviewed by one investigator (RAM).

RESULTS

Reelin deficit is related to an abnormal migration of neurons in dentate gyrus, and its deficit causes dentate gyrus abnormalities, which in turn has been associated with memory deficits in patients with TLE. A decreased in the expression of RELN ribonucleic acid (RNA) was found in patients with TLE and dysplasia type IIIa compared with patients with TLE and isolated hippocampal sclerosis (HS). Reelin might affect the distribution and dynamic instability of microtubules within neurons in the cerebral cortex and their phosphorylation. Amyloid pathology, tauopathy, or phosphorylated tau (p-tau) overexpression has been reported in epileptic human brain and in animal models of epilepsy.

CONCLUSION

Reelin deficit may determine an abnormal cortical lamination and dentate gyrus dispersion and might be associated with an abnormal tau phosphorylation. These processes can be associated with an abnormal hyperexcitability, neuropsychiatric complications, and a myriad of typical histopathological features seen in patients with TLE because of dysplasia type IIIa.

Gsk3 Signalling and Redox Status in Bipolar Disorder: Evidence from Lithium Efficacy

Objective. To discuss the link between glycogen synthase kinase-3 (GSK3) and the main biological alterations demonstrated in bipolar disorder (BD), with special attention to the redox status and the evidence supporting the efficacy of lithium (a GSK3 inhibitor) in the treatment of BD. Methods. A literature research on the discussed topics, using Pubmed and Google Scholar, has been conducted. Moreover, a manual selection of interesting references from the identified articles has been performed. Results. The main biological alterations of BD, pertaining to inflammation, oxidative stress, membrane ion channels, and circadian system, seem to be intertwined. The dysfunction of the GSK3 signalling pathway is involved in all the aforementioned "biological causes" of BD. In a complex scenario, it can be seen as the common denominator linking them all. Lithium inhibition of GSK3 could, at least in part, explain its positive effect on these biological dysfunctions and its superiority in terms of clinical efficacy. Conclusions. Deepening the knowledge on the molecular bases of BD is fundamental to identifying the biochemical pathways that must be targeted in order to provide patients with increasingly effective therapeutic tools against an invalidating disorder such as BD.

Sunitinib produces neuroprotective effect via inhibiting nitric oxide overproduction

BACKGROUND

Sunitinib is an inhibitor of the multiple receptor tyrosine kinases (RTKs) for cancer therapy. Some sunitinib analogues could prevent neuronal death induced by various neurotoxins. However, the neuroprotective effects of sunitinib have not been reported.

METHODS

Cerebellar granule neurons (CGNs) and SH-SY5Y cells were exposed to low-potassium and MPP(+) challenges, respectively. MTT assay, FDA/PI staining, Hoechst staining, DAF-FM, colorimetric nitric oxide synthase (NOS) activity assay, and Western blotting were applied to detect cell viability, NO production, NOS activity, and neuronal NOS (nNOS) expression. Short hairpin RNA was used to decrease nNOS expression. In vitro NOS enzyme activity assay was used to determine the direct inhibition of nNOS by sunitinib.

RESULTS

Sunitinib prevented low-potassium-induced neuronal apoptosis in CGNs and MPP(+) -induced neuronal death in SH-SY5Y cells. However, PTK787, another RTK inhibitor, failed to decrease neurotoxicity in the same models. Sunitinib reversed the increase in NO levels, NOS activity, and nNOS expression induced by low potassium or MPP(+) . Knockdown of nNOS expression partially abolished the neuroprotective effects of sunitinib. Moreover, sunitinib directly inhibited nNOS enzyme activity.

CONCLUSIONS

Sunitinib exerts its neuroprotective effects by inhibiting NO overproduction, possibly via the inhibition of nNOS activity and the decrease in nNOS expression.

Glycogen Synthase Kinase 3β Inhibitor (2'Z,3'E)-6-Bromo-indirubin- 3'-Oxime Enhances Drug Resistance to 5-Fluorouracil Chemotherapy in Colon Cancer Cells

OBJECTIVE

To explore the effects and mechanism of glycogen synthase kinase 3β (GSK-3β) inhibitor (2'Z,3'E)-6-bromo-indirubin-3'-oxime (BIO) on drug resistance in colon cancer cells.

METHODS

The colon cancer SW480 and SW620 cells were treated with BIO, 5-fluorouracil (5-FU) and BIO/5-FU, separately. Cell cycle distribution, apoptosis level and efflux ability of rhodamine 123 (Rh123) were detected by flow cytometry. The protein expressions of P-glycoprotein (P-gp), multidrug resistance protein 2 (MRP2), thymidylate synthase (TS), β-catenin, E2F-1 and Bcl-2 were detected by Western blot. β-catenin and P-gp were stained with double immunofluorescence and observed under a confocal microscope.

RESULTS

BIO up-regulated β-catenin, P-gp, MRP2 and TS, enhanced the efflux ability of Rh123, decreased Bcl-2 protein and gave the opposite effect to E2F-1 protein in SW480 and SW620 cells. Furthermore, BIO significantly inhibited cell apoptosis, increased S and G(2)/M phase cells, and reduced the cell apoptosis induced by 5-FU in SW480 cells, whereas the effects were slight or not obvious in SW620 cells.

CONCLUSION

GSK-3β was involved in drug resistance regulation, and activation of β-catenin and inhibition of E2F-1 may be the most responsible for the enhancement of 5-FU chemotherapy resistance induced by GSK-3β inhibitor BIO in colon cancer.

The role of GSK3beta in the development of the central nervous system

Glycogen synthase kinase 3β (GSK3β) is a multifunctional serine/threonine kinase. It is particularly abundant in the developing central nervous system (CNS). Since GSK3β has diverse substrates ranging from metabolic/signaling proteins and structural proteins to transcription factors, it is involved in many developmental events in the immature brain, such as neurogenesis, neuronal migration, differentiation and survival. The activity of GSK3β is developmentally regulated and is affected by various environmental/cellular insults, such as deprivation of nutrients/trophic factors, oxidative stress and endoplasmic reticulum stress. Abnormalities in GSK3β activity may disrupt CNS development. Therefore, GSK3β is a critical signaling protein that regulates brain development. It may also determine neuronal susceptibility to damages caused by various environmental insults.

Deptor knockdown enhances mTOR Activity and protein synthesis in myocytes and ameliorates disuse muscle atrophy

Deptor is an mTOR binding protein that affects cell metabolism. We hypothesized that knockdown (KD) of Deptor in C2C12 myocytes will increase protein synthesis via stimulating mTOR-S6K1 signaling. Deptor KD was achieved using lentiviral particles containing short hairpin (sh)RNA targeting the mouse Deptor mRNA sequence, and control cells were transfected with a scrambled control shRNA. KD reduced Deptor mRNA and protein content by 90%, which increased phosphorylation of mTOR kinase substrates, 4E-BP1 and S6K1, and concomitantly increased protein synthesis. Deptor KD myoblasts were both larger in diameter and exhibited an increased mean cell volume. Deptor KD increased the percentage of cells in the S phase, coincident with an increased phosphorylation (S807/S811) of retinoblastoma protein (pRb) that is critical for the G(1) to S phase transition. Deptor KD did not appear to alter basal apoptosis or autophagy, as evidenced by the lack of change for cleaved caspase-3 and light chain (LC)3B, respectively. Deptor KD increased proliferation rate and enhanced myotube formation. Finally, in vivo Deptor KD (~50% reduction) by electroporation into gastrocnemius of C57/BL6 mice did not alter weight or protein synthesis in control muscle. However, Deptor KD prevented atrophy produced by 3 d of hindlimb immobilization, at least in part by increasing protein synthesis. Thus, our data support the hypothesis that Deptor is an important regulator of protein metabolism in myocytes and demonstrate that decreasing Deptor expression in vivo is sufficient to ameliorate muscle atrophy.

Activation of ataxia telangiectasia muted under experimental models and human Parkinson's disease

In the present study we demonstrated that neurotoxin MPP(+)-induced DNA damage is followed by ataxia telangiectasia muted (ATM) activation either in cerebellar granule cells (CGC) or in B65 cell line. In CGC, the selective ATM inhibitor KU-55933 showed neuroprotective effects against MPP(+)-induced neuronal cell loss and apoptosis, lending support to the key role of ATM in experimental models of Parkinson's disease. Likewise, we showed that knockdown of ATM levels in neuroblastoma B65 cells using an ATM-specific siRNA attenuates the phosphorylation of retinoblastoma protein without affecting other cell-cycle proteins involved in the G(0)/G(1) cell-cycle phase. Moreover, we demonstrated DNA damage, in human brain samples of PD patients. These findings support a model in which MPP(+) leads to ATM activation with a subsequent DNA damage response and activation of pRb. Therefore, this study demonstrates a new link between DNA damage by MPP(+) and cell-cycle re-entry through retinoblastoma protein phosphorylation.

Potential mechanisms involved in the prevention of neurodegenerative diseases by lithium

Lithium is a monovalent cation that was introduced in 1949 by John Cade for the treatment of bipolar disorder. Clinical reports and subsequent studies confirmed this application and the beneficial effects of this compound. However, over the last 15 years, various authors have also demonstrated the neuroprotective effects of lithium against several neurotoxic paradigms. Thus, experimental studies in neuronal cell cultures and animal models of Alzheimer disease and others pathologies have provided strong evidence for the potential benefits of lithium. The main mechanism underlying its neuroprotective effects is thought to be inhibition of glycogen synthase kinase-3 (GSK-3), although other biochemical pathways in the brain could also be affected. In this review, the main mechanisms of lithium action are summarized, including the modulation of glutamate receptors, effects on arachidonic acid metabolism, its role with respect to AKT, and other potential mechanisms. In addition, its effects on neuroprotective proteins such as Bcl-2 and p53 are also discussed. Although the cellular and molecular biological effects of lithium may constitute an effective therapeutic strategy for Alzheimer disease, further clinical and experimental studies with this drug and specific GSK-3 inhibitors are necessary to confirm the use of lithium in therapeutic approaches to neurodegenerative diseases.

Anti-aging properties of melatonin in an in vitro murine senescence model: involvement of the sirtuin 1 pathway

Sirtuin 1 is a member of the sirtuin family of protein deacetylases, which have attracted considerable attention as mediators of lifespan extension in several model organisms. Induction of sirtuin 1 expression also attenuates neuronal degeneration and death in animal models of Alzheimer's disease and Huntington's disease. In this study, an in vitro model of neuronal aging was used to test in several ways whether melatonin acts as a sirtuin 1 inducer and if this effect could be neuroprotective. It is shown that melatonin is able to increase the level of this deacetylase in young primary neurons, as well as in aged neurons. We also observed an increase in the deacetylation of several substrates of sirtuin 1, such as p53, PGC-1alpha, FoxO1, ADAM10 and NFkappaB. In addition, there was a reduction in its nuclear translocation and, subsequently, an improvement in transcriptional activity. Sirtinol, a sirtuin 1 inhibitor, was used to correlate these effects with sirtuin. It is shown that sirtinol reduces sirtuin 1 expression and impairs the beneficial action of melatonin on cell viability and apoptosis prevention. Moreover, some of the sirtuin 1 substrates studied also reversed the melatonin effect when sirtinol is added to the cells, mainly p53. Globally, these results add weight to the findings of previous reports, indicating a new role for melatonin in improving cell function gated to an increased neuroprotective role for the sirtuin 1 pathway.

GSK3beta in ethanol neurotoxicity

Alcohol consumption during pregnancy is a significant public health problem and may result in a wide range of adverse outcomes for the child. The developing central nervous system (CNS) is particularly susceptible to ethanol toxicity. Children with fetal alcohol spectrum disorders (FASD) have a variety of cognitive, behavioral, and neurological impairments. FASD currently represents the leading cause of mental retardation in North America ahead of Down syndrome and cerebral palsy. Ethanol exposure during development causes multiple abnormalities in the brain such as permanent loss of neurons, ectopic neurons, and alterations in synaptogenesis and myelinogenesis. These alcohol-induced structural alterations in the developing brain underlie many of the behavioral deficits observed in FASD. The cellular and molecular mechanisms of ethanol neurotoxicity, however, remain unclear. Ethanol elicits cellular stresses, including oxidative stress and endoplasmic reticulum stress. Glycogen synthase kinase 3beta (GSK3beta), a multifunctional serine/threonine kinase, responds to various cellular stresses. GSK3beta is particularly abundant in the developing CNS, and regulates diverse developmental events in the immature brain, such as neurogenesis and neuronal differentiation, migration, and survival. Available evidence indicates that the activity of GSK3beta in the CNS is affected by ethanol. GSK3beta inhibition provides protection against ethanol neurotoxicity, whereas high GSK3beta activity/expression sensitizes neuronal cells to ethanol-induced damages. It appears that GSK3beta is a converging signaling point that mediates some of ethanol's neurotoxic effects.

Activation of Akt by lithium: pro-survival pathways in aging

The effects of lithium on senescence were investigated using the senescence-accelerated mouse prone 8 (SAMP8) mice and cultures of aging cerebellar granule cells. Our in vitro findings, using cerebellar granule neurons, demonstrate that lithium (1-10mM) exerts neuroprotective effects in young cultures (7-8 days) against LY294002-induced Akt inhibition. Furthermore, lithium (10mM) inhibits GSK-3beta activity by upregulating p-GSK-3beta (ser-9) and increases p-FOXO1 (Ser256) suggesting an effective anti-apoptotic effect. Our data also showed that lithium in aged cultures exerts anti-apoptotic effects via Akt activation and consequent inhibition of downstream targets regulated by this enzyme. Finally, the administration of lithium to senescence-accelerated mice (SAMP8) and senescence-accelerated resistant mice (SAMR1) at 3 months of age also caused increased Akt activity and p-FoxO-1. These results demonstrate the effectiveness of lithium in preventing age-related neural loss and the potential therapeutic applications of lithium in treatment/prevention of neurological disease.

The p38(MAPK) signaling pathway regulates neuronal apoptosis through the phosphorylation of the retinoblastoma protein

We investigated the role of SB202190, a selective p38 mitogen-activated protein kinase (MAPK) inhibitor in cerebellar granule neurons (CGC) in response to serum potassium deprivation (S/K deprivation), an apoptotic stimulus. CGC apoptosis after S/K deprivation was shown to be mediated through cell cycle re-entry and the induction of transcription factor E2F-1. We found that SB 202190 (10muM) inhibits retinoblastoma protein (pRb) phosphorylation, in response to S/K deprivation. Moreover, the expression of cyclin E and E2F-1 were also significantly decreased. Interestingly, SB202190 did not affect or modulate the increase in the protein expression levels of cyclin D1. Similarly, p-Akt and p-GSK3 protein levels, measured after 12h S/K deprivation, did not appear to be regulated by SB 202190 (10muM). These data indicate that the neuroprotective effects of the p38 inhibitor were not mediated via Akt activation. In conclusion, these results suggest that p38MAPK converged with the cell cycle in S/K deprivation-induced apoptosis through pRb phosphorylation.

Swedish amyloid precursor protein mutation increases cell cycle-related proteins in vitro and in vivo

Reactivation of the cell cycle, including DNA replication, might play a major role in Alzheimer's disease. In this study, we report that the expressions of Swedish double mutation of amyloid precursor protein (Swe-APP) or of the APP intracellular domain (AICD) into nerve growth factor (NGF)-differentiated PC12 cells or rat primary cortical neurons increased mRNA and protein levels of cyclin D1 and cyclin B1. Treatment with lithium chloride (a glycogen synthase kinase-3beta inhibitor) down-regulated cyclin B1 induced by Swe-APP expression but up-regulated cyclin D1 expression induced by Swe-APP, suggesting that glycogen synthase kinase-3beta activity is involved in these expression changes of cyclins D1 and B1. Swe-APP, which is a prevailing cause of familial Alzheimer's disease, is well known to increase amyloid beta peptide production both in vitro and in vivo, but the underlying molecular means whereby it leads to the pathogenesis of AD remains unknown. The finding that cyclin D1 and B1 expressions were up-regulated by Swe-APP in in vitro cultured cells was substantiated in the brain tissues of Tg2576 mice, which harbor the Swe-APP mutation. These results suggest that some disturbances in cell cycle regulation may be involved in Swe-APP or AICD-induced neurodegeneration and that these contribute to the pathogenesis of AD.

Cell cycle activation in striatal neurons from Huntington's disease patients and rats treated with 3-nitropropionic acid

This study was undertaken to investigate the potential role of cell cycle re-entry in an experimental model of Huntington's disease and in human brain samples. We found that after treatment of rats with the mitochondrial neurotoxin 3-nitropropionic acid, the expression of cell cycle markers of G1 phase measured by immunohistochemistry was induced in the striatal brain region. Furthermore, we detected an increase in the nuclear and also cytoplasmatic E2F-1 expression, suggesting that this protein could activate the apoptotic cascade in rat brain. Western blot analysis of post-mortem brain samples from patients also showed an increase in the expression of E2F-1 and cyclin D1 in comparison with control samples. These results indicate that cell cycle re-entry is activated in Huntington's disease and may contribute to the neurodegenerative process.

A molecular study of pathways involved in the inhibition of cell proliferation in neuroblastoma B65 cells by the GSK-3 inhibitors lithium and SB-415286

Pharmacological GSK-3 inhibitors are potential drugs for the treatment of neurodegenerative diseases, cancer and diabetes. We examined the antiproliferative effects of two GSK-3 inhibitors, lithium and SB-415286, on B65 neuroblastoma cell line. Treatment of B65 cells with either drug administered separately caused a decrease in cell proliferation that was associated with G₂/M cell cycle arrest. Cell-cycle proteins such as cyclins D, E, A, cdk4 and cdk2 were up-regulated. Since lithium and SB-415286-induced G₂/M arrest we studied changes in the expression of proteins involved in this phase, specifically cyclin B, cdc2 and the phosphorylated form of this protein (tyr15-cdc2). Both drugs increased the expression of tyr15-cdc2, thus inhibiting mitosis. On the other hand, SB-415286 increased the expression of SIRT2, involved in the regulation of proliferation. Moreover, cell-cycle arrest mediated by SB-415286 was accompanied by apoptosis that was not prevented by 100 μM of zVAD-fmk (benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone), a pan-caspase inhibitor. Likewise, GSK-3 inhibitors did not affect the mitochondrial release of apoptosis inducing factor (AIF). We conclude that inhibitors of GSK-3 induced cell-cycle arrest, mediated by the phosphorylation of cdc2 and, in the case of SB-415286, SIRT2 expression, which induced apoptosis in a caspase-independent manner.

Novel aryl and heteroaryl substituted N-[3-(4-phenylpiperazin-1-yl)propyl]-1,2,4-oxadiazole-5-carboxamides as selective GSK-3 inhibitors

Synthesis, biological evaluation, and SAR dependencies for a series of novel aryl and heteroaryl substituted N-[3-(4-phenylpiperazin-1-yl)propyl]-1,2,4-oxadiazole-5-carboxamide inhibitors of GSK-3beta kinase are described. The inhibitory activity of the synthesized compounds is highly dependent on the character of substituents in the phenyl ring and the nature of terminal heterocyclic fragment of the core molecular scaffold. The most potent compounds from this series contain 3,4-di-methyl or 2-methoxy substituents within the phenyl ring and 3-pyridine fragment connected to the 1,2,4-oxadiazole heterocycle. These compounds selectively inhibit GSK-3beta kinase with IC(50) value of 0.35 and 0.41 microM, respectively.