Glycogen Synthetase Kinase 3beta Research Articles

Kororamides, Convolutamines, and Indole Derivatives as Possible Tau and Dual-Specificity Kinase Inhibitors for Alzheimer's Disease: A Computational Study.

Alzheimer’s disease (AD) is becoming one of the most disturbing health and socioeconomic problems nowadays, as it is a neurodegenerative pathology with no treatment, which is expected to grow further due to population ageing. Actual treatments for AD produce only a modest amelioration of symptoms, although there is a constant ongoing research of new therapeutic strategies oriented to improve the amelioration of the symptoms, and even to completely cure the disease. A principal feature of AD is the presence of neurofibrillary tangles (NFT) induced by the aberrant phosphorylation of the microtubule-associated protein tau in the brains of affected individuals. Glycogen synthetase kinase-3 beta (GSK3β), casein kinase 1 delta (CK1δ), dual-specificity tyrosine phosphorylation regulated kinase 1A (DYRK1A) and dual-specificity kinase cdc2-like kinase 1 (CLK1) have been identified as the principal proteins involved in this process. Due to this, the inhibition of these kinases has been proposed as a plausible therapeutic strategy to fight AD. In this study, we tested in silico the inhibitory activity of different marine natural compounds, as well as newly-designed molecules from some of them, over the mentioned protein kinases, finding some new possible inhibitors with potential therapeutic application.

Computer-Aided Drug Design Applied to Marine Drug Discovery: Meridianins as Alzheimer's Disease Therapeutic Agents.

Computer-aided drug discovery/design (CADD) techniques allow the identification of natural products that are capable of modulating protein functions in pathogenesis-related pathways, constituting one of the most promising lines followed in drug discovery. In this paper, we computationally evaluated and reported the inhibitory activity found in meridianins A–G, a group of marine indole alkaloids isolated from the marine tunicate Aplidium, against various protein kinases involved in Alzheimer’s disease (AD), a neurodegenerative pathology characterized by the presence of neurofibrillary tangles (NFT). Balance splitting between tau kinase and phosphate activities caused tau hyperphosphorylation and, thereby, its aggregation and NTF formation. Inhibition of specific kinases involved in its phosphorylation pathway could be one of the key strategies to reverse tau hyperphosphorylation and would represent an approach to develop drugs to palliate AD symptoms. Meridianins bind to the adenosine triphosphate (ATP) binding site of certain protein kinases, acting as ATP competitive inhibitors. These compounds show very promising scaffolds to design new drugs against AD, which could act over tau protein kinases Glycogen synthetase kinase-3 Beta (GSK3β) and Casein kinase 1 delta (CK1δ, CK1D or KC1D), and dual specificity kinases as dual specificity tyrosine phosphorylation regulated kinase 1 (DYRK1A) and cdc2-like kinases (CLK1). This work is aimed to highlight the role of CADD techniques in marine drug discovery and to provide precise information regarding the binding mode and strength of meridianins against several protein kinases that could help in the future development of anti-AD drugs.

Lithium Suppresses Astrogliogenesis by Neural Stem and Progenitor Cells by Inhibiting STAT3 Pathway Independently of Glycogen Synthase Kinase 3 Beta

Transplanted neural stem and progenitor cells (NSCs) produce mostly astrocytes in injured spinal cords. Lithium stimulates neurogenesis by inhibiting GSK3b (glycogen synthetase kinase 3-beta) and increasing WNT/beta catenin. Lithium suppresses astrogliogenesis but the mechanisms were unclear. We cultured NSCs from subventricular zone of neonatal rats and showed that lithium reduced NSC production of astrocytes as well as proliferation of glia restricted progenitor (GRP) cells. Lithium strongly inhibited STAT3 (signal transducer and activator of transcription 3) activation, a messenger system known to promote astrogliogenesis and cancer. Lithium abolished STAT3 activation and astrogliogenesis induced by a STAT3 agonist AICAR (5-aminoimidazole-4-carboxamide 1-beta-D-ribofuranoside), suggesting that lithium suppresses astrogliogenesis by inhibiting STAT3. GSK3β inhibition either by a specific GSK3β inhibitor SB216763 or overexpression of GID5-6 (GSK3β Interaction Domain aa380 to 404) did not suppress astrogliogenesis and GRP proliferation. GSK3β inhibition also did not suppress STAT3 activation. Together, these results indicate that lithium inhibits astrogliogenesis through non-GSK3β-mediated inhibition of STAT. Lithium may increase efficacy of NSC transplants by increasing neurogenesis and reducing astrogliogenesis. Our results also may explain the strong safety record of lithium treatment of manic depression. Millions of people take high-dose (>1 gram/day) lithium carbonate for a lifetime. GSK3b inhibition increases WNT/beta catenin, associated with colon and other cancers. STAT3 inhibition may reduce risk for cancer.

Resistin is expressed in human hepatocytes and induces insulin resistance

Resistin, known as an adipocyte-specific secretory factor (ADSF), is implicated to modulate insulin resistance in rodents. However, the precise role of this factor for human insulin resistance has remained elusive. Here, we investigate the relationship between human resistin and insulin resistance in hepatocytes and the effect of Metformin on resistin. In this study, the expression of resistin in human hepatocytes and hepatic tissues was examined, and the human resistin eukaryotic expression vector was constructed and stably transfected in HepG2 cells. Data showed that resistin is expressed in human hepatocytes and hepatic tissues. Overexpression of human resistin impaired significantly insulin-stimulated glucose uptake and glycogen synthesis in HepG2 cells. It also decreased the expression of insulin receptor substrate 2 (IRS-2) and c-cbl associated protein (CAP), whereas increased the expression of glycogen synthetase kinase 3beta (GSK-3beta). The result suggested that human resistin induced insulin resistance in hepatocytes by blocking the two insulin signal transduction pathways of PI-3K/Akt and of CAP/c-cbl. We also concluded that Metformin reversed the effect of resistin and downregulated the expression of resistin in hepatocytes.

The Role of CDK5/P25 Formation/Inhibition in Neurodegeneration

Cdk5 is an atypical cyclin-dependent kinase localized in the brain, and its activity is dependent upon binding to p35/p39. In addition, while cdk5 has important physiological functions related to brain development, the breakdown of cdk5/p35 into cdk5/p25 increases its kinase activity and neurotoxicity. Interestingly, in recent years increased cdk5/p25 expression has been demonstrated in the brains of patients with Alzheimer's and Parkinson's diseases. Experimental studies performed in neuronal cell cultures indicate that cdk5/p25 plays a prominent role in apoptosis. Moreover, an apoptotic pathway, via an intracellular calcium increase following calpain activation and cdk5/p25 formation, has been postulated. Cdk5/p25 subsequently phosphorylates the nuclear transcription factor myocyte enhancer factor (MEF2), thereby inhibiting its prosurvival activity. However, cdk5/p25 could phosphorylate other substrates such as tau and p53, as well as the retinoblastoma protein pRb. All these data lend credence to the hypothesis that cdk5/p25 acts as a master regulator of neuronal cell death. In addition, cdk5/p25 might also interact with other pathways such as glycogen synthetase kinase 3beta (GSK3beta) and c-JUN kinase. Drugs like roscovitine, flavopiridol, calpain inhibitors, kenpaullone and induribins, which inhibit cdk5/p25 formation, constitute potential drugs for the treatment of neurological disorders. Furthermore, the dual inhibitory effect of some of these drugs on cdk5 and GSK3beta could be beneficial.

Involvement of the Integrin-Linked Kinase Pathway in Hexachlorobenzene-Induced Gender-Specific Rat Hepatocarcinogenesis

Overexpression of the integrin-linked kinase (ILK) pathway disrupts cell-cell interactions, an epigenetic event leading to epithelial cell transformation. Female rats exposed to hexachlorobenzene (HCB) for 5 consecutive days and sampled 45 days later show a decrease in liver gap junctional intercellular communication. We hypothesized that HCB also alters E-cadherin expression and that this alteration is mediated by the ILK pathway. Hepatic ILK levels were markedly increased in HCB-treated female rats. Cytoplasmic/membrane levels of protein kinase B (Akt), a target of ILK, and its phosphorylated active form were decreased in treated female rats. Flow cytometric analysis showed a concomitant increase in nuclear Akt levels. Both ILK and Akt can phosphorylate glycogen synthetase kinase-3beta (GSK3beta), rendering it inactive. Phosphorylated-GSK3beta levels were higher in treated females and resulted in a twofold decrease in the activity of GSK3beta. The inactivation of GSK3beta in HCB-treated female rats resulted in the nuclear translocation of beta-catenin, as demonstrated by both immunocytochemistry and flow cytometric analyses. Western blot analysis showed an 84% decrease in E-cadherin levels in HCB-treated rats as compared to controls, and this decrease was not mediated by Snail activation. Mimicking the activation of ILK with specific GSK3beta inhibitors resulted in downregulation of E-cadherin levels but had no effect on Cx32 expression in the MH(1)C(1) cells. Overall, these results indicate that hepatic E-cadherin is downregulated as a result of an overexpression of the ILK pathway. The concomitant HCB-induced downregulation of intercellular communication does not occur as a result of either E-cadherin downregulation or GSK3beta inactivation.

How Wnt Signaling Affects Bone Repair by Mesenchymal Stem Cells from the Bone Marrow

Human mesenchymal stem cells (hMSCs) from bone marrow are a source of osteoblast progenitors in vivo, and under appropriate conditions they differentiate into osteoblasts ex vivo. The cells provide a convenient cell culture model for the study of osteogenic tissue repair in an experimentally accessible system. Recent advances in the field of skeletal development and osteogenesis have demonstrated that signaling through the canonical wingless (Wnt) pathway is critical for the differentiation of progenitor cell lines into osteoblasts. Inhibition of such signals can predispose hMSCs to cell cycle entry and prevent osteogenesis. Our investigation of the role of Wnt signaling in osteogenesis by hMSCs ex vivo has demonstrated that osteogenesis proceeds in response to bone morphogenic protein 2 stimulation and is sustained by Wnt signaling. In the presence of Dkk-1, an inhibitor of Wnt signaling, the cascade is disrupted, resulting in inhibition of osteogenesis. Peptide mapping studies have provided peptide Dkk-1 agonists and the opportunity for the production of blocking antibodies. Anti-Dkk-1 strategies are clinically relevant since high serum levels of Dkk-1 are thought to contribute to osteolytic lesion formation in multiple myeloma and possibly some forms of osteosarcoma. Specific inhibitors of glycogen synthetase kinase 3beta (GSK3beta), which mimic Wnt signaling, may also have a therapeutic benefit by enhancing in vitro osteogenesis despite the presence of Dkk-1. Antibodies that block Dkk-1 and GSK3beta inhibitors may provide novel opportunities for the enhancement of bone repair in a variety of human diseases such as multiple myeloma and osteosarcoma.

Role of DDC-4/sFRP-4, a secreted frizzled-related protein, at the onset of apoptosis in mammary involution.

Using differential display, we isolated DDC-4, a secreted frizzled-related protein (sFRP), which is induced in the physiological apoptosis of hormonally regulated, reproductive tissues such as mammary gland, prostate, corpus luteum and uterus. The role of this gene in apoptosis was studied in animals overexpressing ectopic DDC-4/sFRP-4. Transgenic mice bearing the DDC-4/sFRP-4 cDNA under the control of the MMTV-LTR promoter showed lactational insufficiency and many apoptotic cells in the alveoli between day 19 of pregnancy and day 4 of lactation as demonstrated by TUNEL reaction and the presence of activated caspase-3. We performed a PKB/Akt kinase assay and studied several of its substrates using phosphorylation-specific antibodies to show reduced phosphorylation in PKB/Akt itself, as well as in glycogen synthetase kinase-3beta (GSK-3beta), BAD, and Forkhead. Taken together, our results show a role for DDC-4/sFRP-4 in abrogating an epithelial cell survival pathway at the onset of mammary gland involution.

Cyclin D1 over-expression correlates with beta-catenin activation, but not with H-ras mutations, and phosphorylation of Akt, GSK3 beta and ERK1/2 in mouse hepatic carcinogenesis.

Mutational activation of beta-catenin and cyclin D1 over-expression are a frequent change in mouse hepatic tumors. Although activated beta-catenin may bind to T cell factor (TCF) family members and transcriptionally activate the cyclin D1 gene, either beta-catenin or cyclin D1 may be activated by various pathways independently of beta-catenin mutations. In this study, we investigated beta-catenin activation and mutations, cyclin D1 expression, H-ras mutations and phosphorylation of extracellular signal regulated protein kinases 1/2 (ERK1/2), Akt and glycogen synthetase kinase 3beta (GSK3 beta) in mouse hepatic carcinogenesis. Nuclear/cytoplasmic staining of beta-catenin, a sign of beta-catenin activation, was frequently observed in association with the high nuclear cyclin D1 labeling index in the hepatic tumors at the late stage of carcinogenesis. The beta-catenin activation was further suggested by the fact that all hepatocellular carcinoma (HCC) cell lines examined showed the nuclear beta-catenin/TCF4 complex together with cyclin D1 over-expression. However, the fact that only 31.8% (7/22) of the lesions with the nuclear/cytoplasmic beta-catenin staining showed beta-catenin mutations indicated that beta-catenin was activated not only by its own mutations but also by other reason(s). On the other hand, there was no correlation between the beta-catenin/cyclin D1 activation and the H-ras mutations or phosphorylation of Akt, GSK3 beta and ERK1/2, although GSK3 beta was frequently over-expressed in the tumors. These results indicate that, although beta-catenin and cyclin D1 activation are well correlated, the Akt/GSK3 beta and ras/ERK1/2 pathways may not play a major role in the beta-catenin/cyclin D1 activation.