Glycogen Synthase Kinase-3 Activity Research Articles

Ethanol-induced damage to the developing spinal cord: The involvement of CCR2 signaling

Ethanol exposure during development causes fetal alcohol spectrum disorders (FASD). A large body of evidence shows that ethanol produces multiple abnormalities in the developing central nervous system (CNS), such as smaller brain size, reduced volume of cerebral white matter, permanent loss of neurons, and alterations in synaptogenesis and myelinogenesis. The effects of ethanol on the developing spinal cord, however, receive little attention and remain unclear. We used a third trimester equivalent mouse model to investigate the effect of ethanol on the developing spinal cord. Ethanol caused apoptosis and neurodegeneration in the dorsal horn neurons of mice of early postnatal days, which was accompanied by glial activation, macrophage infiltration, and increased expression of CCR2, a receptor for monocyte chemoattractant protein 1 (MCP-1). Ethanol-induced neuronal death during development resulted in permanent loss of spinal cord neurons in adult mice. Ethanol stimulated endoplasmic reticulum (ER) stress and oxidative stress, and activated glycogen synthase kinase 3β (GSK3β) and c-Jun N-terminal kinase (JNK) pathways. Knocking out MCP-1 or CCR2 made mice resistant to ethanol-induced apoptosis, ER stress, glial activation, and activation of GSK3β and JNK. CCR2 knock out offered much better protection against ethanol-induced damage to the spinal cord. Thus, developmental ethanol exposure caused permanent loss of spinal cord neurons and CCR2 signaling played an important role in ethanol neurotoxicity.

Proteomic characterisation reveals active Wnt-signalling by human multipotent stromal cells as a key regulator of beta cell survival and proliferation.

Novel strategies to stimulate the expansion of beta cell mass in situ are warranted for diabetes therapy. The aim of this study was to elucidate the secretome of human bone marrow (BM)-derived multipotent stromal cells (MSCs) with documented islet regenerative paracrine function. We hypothesised that regenerative MSCs will secrete a unique combination of protein factors that augment islet regeneration. Human BM-derived MSCs were examined for glucose-lowering capacity after transplantation into streptozotocin-treated NOD/severe combined immunodeficiency (SCID) mice and segregated into samples with regenerative (MSCR) vs nonregenerative (MSCNR) capacity. Secreted proteins associated with islet regenerative function were identified using stable isotope labelling with amino acids in cell culture (SILAC)-based quantitative proteomics. To functionally validate the importance of active Wnt signalling, we stimulated the Wnt-signalling pathway in MSCNR samples during ex vivo expansion using glycogen synthase kinase 3 (GSK3) inhibition (CHIR99201), and the conditioned culture media (CM) generated was tested for the capacity to support cultured human islet cell survival and proliferation in vitro. MSCR showed increased secretion of proteins associated with cell growth, matrix remodelling, immunosuppressive and proangiogenic properties. In contrast, MSCNR uniquely secreted proteins known to promote inflammation and negatively regulate angiogenesis. Most notably, MSCR maintained Wnt signalling via Wnt5A/B (~2.5-fold increase) autocrine activity during ex vivo culture, while MSCNR repressed Wnt signalling via Dickkopf-related protein (DKK)1 (~2.5-fold increase) and DKK3 secretion. Inhibition of GSK3 activity in MSCNR samples increased the accumulation of nuclear β-catenin and generated CM that augmented beta cell survival (13% increases) and proliferation when exposed to cultured human islets. Maintenance of active Wnt signalling within human MSCs promotes the secretion of matricellular and proangiogenic proteins that formulate a niche for islet regeneration.

Silencing of long non-coding RNA CCAT2 depressed malignancy of oral squamous cell carcinoma via Wnt/β-catenin pathway

Oral squamous cell carcinoma is a common and lethal malignancy affecting the head and neck region. CCAT2 (colon cancer-associated transcript 2) gene is affiliated with long non-coding RNAs, which are often found to have important regulatory roles in cancers. This study aims to assess the expression and clinical significance of CCAT2 gene, identify its malignant biological behaviors, and explore the possible mechanisms in oral squamous cell carcinoma. CCAT2 expression was detected by quantitative real-time polymerase chain reaction, and its relationship with clinical factors was assayed using the Kaplan-Meier survival curve. The biological behaviors of CCAT2 and its potential mechanisms in oral squamous cell carcinoma were explored by the combined use of CCAT2 knockdown technology and the Wnt/β-catenin pathway agonist lithium chloride (LiCl). Our results showed that CCAT2 functioning as a potential oncogene was upregulated in oral squamous cell carcinoma. CCAT2 with high expression level was correlated with poor differentiation, higher T stage, and clinical stage, which made CCAT2 to be a prognostic biomarker in oral squamous cell carcinoma. LiCl-activated Wnt/β-catenin signaling pathway could partly restore the CCAT2-mediated malignant biological behaviors of oral squamous cell carcinoma cells by suppressing β-catenin, CCND1, and MYC and activating glycogen synthase kinase 3 beta expression. These findings might assist in the discovery of novel potential diagnostic and therapeutic target for oral squamous cell carcinoma, thereby improve the effects of clinical treatment in patients.

Osteoblastic heparan sulfate glycosaminoglycans control bone remodeling by regulating Wnt signaling and the crosstalk between bone surface and marrow cells

Stimulating bone formation is an important challenge for bone anabolism in osteoporotic patients or to repair bone defects. The osteogenic properties of matrix glycosaminoglycans (GAGs) have been explored; however, the functions of GAGs at the surface of bone-forming cells are less documented. Syndecan-2 is a membrane heparan sulfate proteoglycan that is associated with osteoblastic differentiation. We used a transgenic mouse model with high syndecan-2 expression in osteoblasts to enrich the bone surface with cellular GAGs. Bone mass was increased in these transgenic mice. Syndecan-2 overexpression reduced the expression of receptor activator of NF-kB ligand (RANKL) in bone marrow cells and strongly inhibited bone resorption. Osteoblast activity was not modified in the transgenic mice, but bone formation was decreased in 4-month-old transgenic mice because of reduced osteoblast number. Increased proteoglycan expression at the bone surface resulted in decreased osteoblastic and osteoclastic precursors in bone marrow. Indeed, syndecan-2 overexpression increased apoptosis of mesenchymal precursors within the bone marrow. However, syndecan-2 specifically promoted the vasculature characterized by high expression of CD31 and Endomucin in 6-week-old transgenic mice, but this was reduced in 12-week-old transgenic mice. Finally, syndecan-2 functions as an inhibitor of Wnt-β-catenin–T-cell factor signaling pathway, activating glycogen synthase kinase 3 and then decreasing the Wnt-dependent production of Wnt ligands and R-spondin. In conclusion, our results show that GAG supply may improve osteogenesis, but also interfere with the crosstalk between the bone surface and marrow cells, altering the supporting function of osteoblasts.

Wnt and GSK3 Signaling Pathways in Bipolar Disorder: Clinical and Therapeutic Implications.

The neurobiology of bipolar disorder, a chronic and systemic ailment is not completely understood. The bipolar phenotype manifests in myriad ways, and psychopharmacological agents like lithium have long term beneficial effects. The enzyme glycogen synthase kinase 3 (GSK3) has come into focus, as lithium and several other mood stabilizing medications inhibit its activity. This kinase and its key upstream modulator, Wnt are dysregulated in mood disorders and there is a growing impetus to delineate the chief substrates involved in the development of these illnesses. In May 2016, a comprehensive literature search was undertaken which revealed that there is over activity of GSK3 in bipolar disorder with deleterious downstream effects like proinflammatory status, increased oxidative stress, and circadian dysregulation leading to declining neurotrophic support and enhanced apoptosis of neural elements. By developing specific GSK3 inhibitors the progressive worsening in bipolar disorder can be forestalled with improved prospects for the sufferers.

Anti-tumor effects of differentiation-inducing factor-1 in malignant melanoma: GSK-3-mediated inhibition of cell proliferation and GSK-3-independent suppression of cell migration and invasion

Differentiation-inducing factor-1 (DIF-1) isolated from Dictyostelium discoideum strongly inhibits the proliferation of various mammalian cells through the activation of glycogen synthase kinase-3 (GSK-3). To evaluate DIF-1 as a novel anti-cancer agent for malignant melanoma, we examined whether DIF-1 has anti-proliferative, anti-migratory, and anti-invasive effects on melanoma cells using in vitro and in vivo systems. DIF-1 reduced the expression levels of cyclin D1 and c-Myc by facilitating their degradation via GSK-3 in mouse (B16BL6) and human (A2058) malignant melanoma cells, and thereby strongly inhibited their proliferation. DIF-1 suppressed the canonical Wnt signaling pathway by lowering the expression levels of transcription factor 7-like 2 and β-catenin, key transcription factors in this pathway. DIF-1 also inhibited cell migration and invasion, reducing the expression of matrix metalloproteinase-2; however, this effect was not dependent on GSK-3 activity. In a mouse lung tumor formation model, repeated oral administrations of DIF-1 markedly reduced melanoma colony formation in the lung. These results suggest that DIF-1 inhibits cell proliferation by a GSK-3-dependent mechanism and suppresses cell migration and invasion by a GSK-3-independent mechanism. Therefore, DIF-1 may have a potential as a novel anti-cancer agent for the treatment of malignant melanoma.

Transfection of tumor metastasis suppressor gene nm23-H1 up-regulates the activity of glycogen synthase kinase -3β in lung cancer cell line L9981

Objective To investigate the influence of tumor metastasis suppressor gene nm23-H1 on the activity of glycogen synthase kinase -3β (GSK-3β) in lung cancer cell line L9981. Methods The levels of GSK-3β expression in cytoplasm and nucleus were determined with anti-GSK-3β antibody in lung cancer cell line control group (cell line with nm23-H1 gene deletion), nm23-H1 transfection group (cell line with nm23-H1 transfected) and blank transfection group (cell line with vector transfected) by Western blotting. The activity of GSK-3β among those three groups was detected by immunoprecipitation and analyzed by a radioactive isotope scintillation counter before and after treatment with 20 mmol/L LiCl. Results (1) The expression indensity of GSK-3β in cytoplasm and nucleus was (6 639±503) and (4 481±446) A in nm23-H1 transfection group, (645±352) and (726±68) A in blank transfection group, and (763±267) and (683±49) A in control group, respectively. There was very significance in GSK-3β expressive indensity of both cytoplasm and nucleus among nm23-H1 transfection group, blank transfection group and control group (P=0.025). There was significant difference between nm23-H1 transfection group and blank transfection group or control group (P=0.017), but no significant difference was observed between blank transfection group and control group (P=0.094). (2) The GSK-3β activity in cytoplasm and nucleus was (29 371±2 492) and (9 647±859) counts per minute in nm23-H1 transfection group, (11 241±1 495) and (1 492±176) counts per minute in blank transfection group, and (14 271±1 137) and (1 853±113) counts per minute in control group, respectively. There was very significant difference in GSK-3β activity of both cytoplasm and nucleus among nm23-H1 transfection group, blank transfection group and control group (P=0.032). The GSK-3β activity in nm23-H1 transfection group was significantly higher than that in blank transfection group and control group (P=0.027), but no significant difference was observed between the blank transfection group and control group (P=0.131). (3) After treatment with 20 mmol/L LiCl, the expression indensity of GSK-3β in cytoplasm and nucleus was (5 037±427) and (823±350) A in nm23-H1 transfection group, (2 174±126) and (248±12) A in blank transfection group, and (2 273±128) and (253±14) A in control group. No significant difference in GSK-3β expression indensity existed before and after treatment with LiCl in nm23-H1 transfection group (P=0.168). However, the GSK-3β expression indensity in cytoplasm and nucleus before treatment was remarkably higher than that after treatment in both blank transfection group and control group (P=0.012, 0.015). (4) After treatment with 20 mmol/L LiCl, the GSK-3β activity in cytoplasm and nucleus was (12 837±1 042) and (748±215) counts per minute in nm23-H1 transfection group, (4 739±401) and (947±126) counts per minute in control group, and (4 638±401) and (1 162±127) counts per minute in blank transfection group, respectively. The GSK-3β activity in cytoplasm and nucleus after treatment with LiCl was remarkably lower than that before treatment in nm23-H1 transfection group, blank transfection group and control group (P=0.006, 0.029, 0.010). Conclusion Transfection of nm23-H1 gene can significantly up-regulate the expression level and activity of GSK-3β in lung cancer cell line. The inhibitory effects of nm23-H1 gene on the signal transduction of Wnt pathway might be carried out through up regulating GSK-3β expression and activity in lung cancer cell line. Key words: Lung cancer cell lines; nm23-H1 gene; Wnt signal pathway; Glycogen synthase kinase -3β

GSK-3 as a novel prognostic indicator in leukemia.

While leukemias represent a diverse set of diseases with malignant cells derived from myeloid or lymphoid origin, a common feature is the dysregulation of signal transduction pathways that influence leukemogeneisis, promote drug resistance, and favor leukemia stem cells. Mutations in PI3K, PTEN, RAS, or other upstream regulators can activate the AKT kinase which has central roles in supporting cell proliferation and survival. A major target of AKT is Glycogen Synthase Kinase 3 (GSK3). GSK3 has two isoforms (alpha and beta) that were studied as regulators of metabolism but emerged as central players in cancer in the early 1990s. GSK3 is unique in that the isoforms are constitutively active. Active GSK3 promotes destruction of oncogenic proteins such as beta Catenin, c-MYC, and MCL-1 and thus has tumor suppressor properties. In AML, inactivation of GSK3 is associated with poor overall survival. Interestingly in some leukemias GSK3 targets a tumor suppressor and thus the kinases can act as tumor promoters in those instances. An example is GSK3 targeting p27Kip1 in AML with MLL translocation. This review will cover the role of GSK3 in various leukemias both as tumor suppressor and tumor promoter. We will also briefly cover current state of GSK3 inhibitors for leukemia therapy.

GSK-3 protein and the heart: friend or foe?

Metabolic syndrome manifesting as obesity, insulin resistance and type 2 diabetes mellitus is currently pandemic. Each of these, in its own right, is strongly related to the development of cardiovascular disease. The cardiomyopathy associated with these disorders is characterised by curtailed glucose uptake and utilisation, elevated risk of damage after ischaemia and contractile dysfunction. Current research have indicated that the serine/threonine kinase, glycogen synthase kinase 3 (GSK-3), may play a central role in the development of all these dysfunctions. The development of new generations of inhibitors of this kinase, has renewed interest in its utilisation as therapeutic target. This review has therefore focused on the role of GSK-3 in the development of the obesity-related cardiomyopathy and has highlighted and discussed the detrimental as well as beneficial effects of the GSK-3 inhibitors that are currently available. We have discussed the different roleplayers such as the insulin signalling pathway, modulation of apoptosis and mitochondrial function, SERCA2 expression and regulation of the development of hypertrophy in the context of GSK-3 activity.

Flavones with inhibitory effects on glycogen synthase kinase 3β

Because glycogen synthase kinase-3 (GSK-3) activity is linked to various human diseases, it has been targeted in new drug development. Flavonoids, including luteolin, apigenin, and quercetin, inhibit GSK-3β; however, the relationships between their structural properties and inhibitory effects are unclear. We measured the inhibitory effects of 34 flavonoid derivatives on GSK-3β and calculated hologram quantitative structure–activity relationships to provide information on pharmacophores for designing novel compounds with better activities. The in vitro binding effect of flavonoids was confirmed using Western blotting for myricetin, which showed the best inhibitory activity, and the binding mode between myricetin and GSK-3β was elucidated using in silico docking.

Glycogen synthase kinase 3 regulates photic signaling in the suprachiasmatic nucleus.

Glycogen synthase kinase 3 (GSK3) is a serine-threonine kinase that regulates mammalian circadian rhythms at the behavioral, molecular and neurophysiological levels. In the central circadian pacemaker, the suprachiasmatic nucleus (SCN), inhibitory phosphorylation of GSK3 exhibits a rhythm across the 24h day. We have recently shown that GSK3 is capable of influencing both the molecular clock and SCN neuronal activity rhythms. However, it is not known whether GSK3 regulates the response to environmental cues such as light. The goal of this study was to test the hypothesis that GSK3 activation mediates light-induced SCN excitability and photic entrainment. Immunofluorescence staining in the SCN of mice showed that late-night light exposure significantly increased GSK3 activity (decreased pGSK3β levels) 30-60min after the light-pulse. In addition, pharmacological inhibition of GSK3 blocked the expected light-induced excitability in SCN neurons; however, this effect was not associated with changes in resting membrane potential or input resistance. Behaviorally, mice with constitutively active GSK3 (GSK3-KI) re-entrained to a 6-h phase advance in the light-dark cycle in significantly fewer days than WT control animals. Furthermore, the behavioral and SCN neuronal activity of GSK3-KI mice was phase-advanced compared to WT, in both normal and light-exposed conditions. Finally, GSK3-KI mice exhibited normal negative-masking behavior and electroretinographic responses to light, suggesting that the enhanced photic entrainment is not due to an overall increased sensitivity to light in these animals. Taken together, these results provide strong evidence that GSK3 activation contributes to light-induced phase-resetting at both the neurophysiological and behavioral levels.

Anti-helminthic niclosamide inhibits Ras-driven oncogenic transformation via activation of GSK-3.

Despite the importance of Ras oncogenes as a therapeutic target in human cancer, their ‘undruggable’ tertiary structures limit the effectiveness of anti-Ras drugs. Canonical Wnt signaling contributes to Ras activity by glycogen synthase kinase 3 (GSK-3)-dependent phosphorylation at the C-terminus and subsequent degradation. In the accompanying report, we show that the anti-helminthic niclosamide directly binds to GSK-3 and inhibits Axin functions in colon cancer cells, with reversion of Snail-mediated epithelial-mesenchymal transition. In this study, we report that niclosamide effectively suppresses Ras and nuclear NFAT activities regardless of the mutational status of Ras at nM levels. Mechanistically, niclosamide increased endogenous GSK-3 activity, shortening the half-life of mutant Ras. Further, niclosamide activates Raf-1 kinase inhibitory protein, a downstream target of Snail repressor. Niclosamide treatment attenuates Ras-induced oncogenic potential in vitro and in vivo. These findings provide a clinically available repositioned Ras inhibitor as well as a novel strategy for inhibiting the Ras via GSK-3.

Dynamic Akt/mTOR Signaling in Children with Autism Spectrum Disorder.

Autism spectrum disorder (ASD) is a behaviorally defined disorder affecting 1 in 68 children. Currently, there is no known cause for the majority of ASD cases nor are there physiological diagnostic tools or biomarkers to aid behavioral diagnosis. Whole-genome linkage studies, genome-wide association studies, copy number variation screening, and SNP analyses have identified several ASD candidate genes, but which vary greatly among individuals and family clusters, suggesting that a variety of genetic mutations may result in a common pathology or alter a common mechanistic pathway. The Akt/mammalian target of rapamycin (mTOR) pathway is involved in many cellular processes including synaptic plasticity and immune function that can alter neurodevelopment. In this study, we examined the activity of the Akt/mTOR pathway in cells isolated from children with ASD and typically developing controls. We observed higher activity of mTOR, extracellular receptor kinase, and p70S6 kinase and lower activity of glycogen synthase kinase 3 (GSK3)α and tuberin (TSC2) in cells from children with ASD. These data suggest a phosphorylation pattern indicative of higher activity in the Akt/mTOR pathway in children with general/idiopathic ASD and may suggest a common pathological pathway of interest for ASD.

Activation of Ras-ERK Signaling and GSK-3 by Amyloid Precursor Protein and Amyloid Beta Facilitates Neurodegeneration in Alzheimer's Disease.

It is widely accepted that amyloid β (Aβ) generated from amyloid precursor protein (APP) oligomerizes and fibrillizes to form neuritic plaques in Alzheimer’s disease (AD), yet little is known about the contribution of APP to intracellular signaling events preceding AD pathogenesis. The data presented here demonstrate that APP expression and neuronal exposure to oligomeric Aβ42 enhance Ras/ERK signaling cascade and glycogen synthase kinase 3 (GSK-3) activation. We find that RNA interference (RNAi)-directed knockdown of APP in B103 rat neuroblastoma cells expressing APP inhibits Ras-ERK signaling and GSK-3 activation, indicating that APP acts upstream of these signal transduction events. Both ERK and GSK-3 are known to induce hyperphosphorylation of tau and APP at Thr668, and our findings suggest that aberrant signaling by APP facilitates these events. Supporting this notion, analysis of human AD brain samples showed increased expression of Ras, activation of GSK-3, and phosphorylation of APP and tau, which correlated with Aβ levels in the AD brains. Furthermore, treatment of primary rat neurons with Aβ recapitulated these events and showed enhanced Ras-ERK signaling, GSK-3 activation, upregulation of cyclin D1, and phosphorylation of APP and tau. The finding that Aβ induces Thr668 phosphorylation on APP, which enhances APP proteolysis and Aβ generation, denotes a vicious feedforward mechanism by which APP and Aβ promote tau hyperphosphorylation and neurodegeneration in AD. Based on these results, we hypothesize that aberrant proliferative signaling by APP plays a fundamental role in AD neurodegeneration and that inhibition of this would impede cell cycle deregulation and neurodegeneration observed in AD.

Antiepileptic Drug-Induced Apoptosis Was Prevented by L-Type Calcium Channel Activator in Cultured Rat Cortical Cells

Experimental data have shown that antiepileptic drugs cause neurodegeneration in developing rats. Valproate (VPA) is the drug of choice in primary generalized epilepsies, and carbamazepine (CBZ) is one of the most prescribed drugs in partial seizures. These drugs block sodium channels, thereby reducing sustained repetitive neuronal firing. The intracellular mechanisms whereby AEDs induce neuronal cell death are unclear. We examined whether AEDs induce apoptotic cell death in cultured cortical cells and whether calcium ions are involved in the AED-induced cell death. VPA and CBZ increased apoptotic cell death and induced morphological changes that were characterized by cell shrinkage and nuclear condensation or fragmentation. Incubation of cortical cultures with VPA or CBZ decreased phospho-Akt levels. CBZ decreased the intracellular calcium levels. On the other hand, FPL64176, an L-type calcium channel activator, increased the intracellular calcium levels and prevented the AED-induced apoptosis. Glycogen synthase kinase-3 inhibitors, such as alsterpaullone and azakenpaullone, prevented the AED-induced apoptosis. These results suggest that intracellular calcium level changes are associated with AEDs and apoptosis and that the activation of glycogen synthase kinase-3 is involved in the death of rat cortical neurons.

The role of glycogen synthase kinase 3 beta in brain injury induced by myocardial ischemia/reperfusion injury in a rat model of diabetes mellitus.

Myocardial ischemia/reperfusion injury can lead to severe brain injury. Glycogen synthase kinase 3 beta is known to be involved in myo-cardial ischemia/reperfusion injury and diabetes mellitus. However, the precise role of glycogen synthase kinase 3 beta in myocardial ischemia/reperfusion injury-induced brain injury is unclear. In this study, we observed the effects of glycogen synthase kinase 3 beta on brain injury induced by myocardial ischemia/reperfusion injury in diabetic rats. Rat models of diabetes mellitus were generated via intraperitoneal injection of streptozotocin. Models of myocardial ischemia/reperfusion injury were generated by occluding the anterior descending branch of the left coronary artery. Post-conditioning comprised three cycles of ischemia/reperfusion. Immunohistochemical staining and western blot assays demonstrated that after 48 hours of reperfusion, the structure of the brain was seriously damaged in the experimental rats compared with normal controls. Expression of Bax, interleukin-6, interleukin-8, terminal deoxynucleotidyl transferase dUTP nick end labeling, and cleaved caspase-3 in the brain was significantly increased, while expression of Bcl-2, interleukin-10, and phospho-glycogen synthase kinase 3 beta was decreased. Diabetes mellitus can aggravate inflammatory reactions and apoptosis. Ischemic post-conditioning with glycogen synthase kinase 3 beta inhibitor lithium chloride can effectively reverse these changes. Our results showed that myocardial ischemic post-conditioning attenuated myocardial ischemia/reperfusion injury-induced brain injury by activating glyco-gen synthase kinase 3 beta. According to these results, glycogen synthase kinase 3 beta appears to be an important factor in brain injury induced by myocardial ischemia/reperfusion injury.

Insensitivity of PI3K/Akt/GSK3 signaling in peripheral blood mononuclear cells of age-related macular degeneration patients.

Our recent studies with cultured retinal pigment epithelium cells suggested that overexpression of interleukin 17 receptor C (IL-17RC), a phenomenon observed in peripheral blood and chorioretinal tissues with age-related macular degeneration (AMD), was associated with altered activation of phosphatidylinositide 3-kinase (PI3K), Akt, and glycogen synthase kinase 3 (GSK3). We wondered whether or not altered PI3K, Akt, and GSK3 activities could be detected in peripheral blood mononuclear cells (PBMC) obtained from AMD patients. In the patients' PBMC, absent or reduced serine-phosphorylation of GSK3α or GSK3β was observed, which was accompanied with increased phosphorylation of GSK3 substrates (e.g. CCAAT enhancer binding protein α, insulin receptor substrate 1, and TAU), indicative of enhanced GSK3 activation. In addition, decreased protein mass of PI3K85α and tyrosine-phosphorylation of PI3K50α was present in PBMC of the AMD patients, suggesting impaired PI3K activation. Moreover, abnormally lowered molecular weight forms of Akt and GSK3 were detected in PBMC of the AMD patients. These data demonstrate that despite the presence of high levels of IL-17RC, Wnt-3a and vascular endothelial growth factor, the PI3K/Akt/GSK3 signaling pathway is insensitive to these stimuli in PBMC of the AMD patients. Thus, measurement of PI3K/Akt/GSK3 expression and activity in PBMC may serve as a surrogate biomarker for AMD.

Glycogen Synthase Kinase-3β (GSK-3β) and Nuclear Factor Kappa-B (NFKB) in Childhood Acute Lymphoblastic Leukemia

Acute lymphocytic leukemia (ALL) is the most common hematologic malignancy in early childhood. In children with acute lymphoblastic leukemia (ALL), the activity of glycogen synthase kinase (GSK-3β) has been associated with changes in the transcriptional activity and expression of nuclear factor kappa beta (NFKB) in the mononuclear cells of bone marrow. The aim of the study was to determine the possible role of glycogen synthase kinase 3beta (GSK-3β) and nuclear factor kappa beta (NFKB) as prognostic variables in pediatric patients with ALL. This was a descriptive, transversal, and observational study. Bone marrow and blood samples were obtained from 30 children with newly-diagnosed ALL, who were seen at the Hematology-Oncology Service, Hospital para el Niño (HPN), Toluca, Mexico, from 2014‒2015. Anthropometric variables, clinical lab results, immunophenotype and cytogenetic abnormalities were registered. GSK-3β was evaluated through immunohistochemistry, and NFKB messenger RNA (mRNA) with real-time polymerase chain reaction (qPCR). The cases of ALL were classified into two groups of risk: high and habitual. Thirty patients were included in this study, with a mean age of 7.1 years (range 2‒13 years). Twenty-one were male and 9 female. Employing the morphological classification, 26 patients had type L1 ALL and the remaining 4 patients had type L2 ALL. Abnormal genes were found in 7 (23.33%) patients, ETV-RUNX1 in 3, followed by TCF3-PBX1 (two), STL1-TAL1 (one), and BCR-ABL1 (one). NFKB relative expression levels, in comparison to the GSK-3β immunohistochemistry results of the bone marrow samples, showed significant differences between positive and negative cases (p = 0.001) and between weak-positive and negative cases (p = 0.002). These results suggest that GSK-3β may be a prognostic biomarker in childhood ALL.

Ubiquitin ligase E6AP mediates nonproteolytic polyubiquitylation of β-catenin independent of the E6 oncoprotein

Recently, we showed that the ubiquitin ligase E6AP stabilizes β-catenin and activates its transcriptional activity. These activities were enhanced by the human papillomavirus (HPV) E6 protein. In the present study, we explored the function of E6AP, which increases β-catenin stabilization and transcriptional activation. Here, we report that E6AP interacts with β-catenin and mediates its nonproteolytic ubiquitylation, as evidenced in transiently transfected cell-based and in vitro reconstitution ubiquitylation assays. Overexpression of E6AP increased β-catenin polyubiquitylation and, consistent with that, knockdown or knock-out of E6AP expression reduced β-catenin polyubiquitylation. The ubiquitylation of β-catenin by E6AP was dependent on its E3 ubiquitin ligase activity, but it was proteasome-independent and did not require HPV-E6, phosphorylation of β-catenin by glycogen synthase kinase 3β (GSK3β) or activity of the β-catenin 'destruction complex'. We also show that transcriptional activation of β-catenin by E6AP is coupled with β-catenin protein stabilization, but not its ubiquitylation. In contrast to β-catenin ubiquitylation, β-catenin protein stability and its transcriptional activity were absolutely dependent on the activity of the destruction complex and phosphorylation by GSK3β. Collectively, our data uncover a dual role for E6AP in the regulation of β-catenin ubiquitylation, stability and transcriptional activity, with HPV-E6 enhancing only part of E6AP activities.

Role and regulation of Glycogen synthase kinase-3 beta in bovine spermatozoa.

The serine/threonine kinase Glycogen synthase kinase 3 (GSK-3) is a master switch that regulates a multitude of cellular pathways, including the acrosome reaction in sperm. In epididymal sperm cells, for example, GSK-3 activity correlates with inhibition of motility-yet no direct pathways connecting GSK-3 activation with loss of motility have been described. Indeed, the details of how GSK-3 is regulated during sperm capacitation and the acrosome reaction remains obscure. To this end, we addressed the involvement of the GSK-3 beta isoform in several known pathways that contribute to motility and the acrosome reaction. We established that Protein kinase A (PKA) is the main regulator of GSK-3β in sperm, as pre-treatment of cells with a GSK-3 inhibitor prior to addition of H89, an inhibitor of PKA, attenuated the motility loss induced by blocking PKA activity. Both induced and spontaneous acrosome reactions also occurred less frequently in sperm treated with GSK-3 inhibitors. Finally, we observed a slow decline in phosphorylation of GSK-3β on Ser 9, which represents an inhibited state, during sperm capacitation; this phenotype is reversed during the induced acrosome reaction, in parallel to activation of Protein phosphatase 1. These results suggest that maintenance of sperm motility and acrosome reaction timing are mediated by PKA through the regulation of GSK-3 beta activity. Mol. Reprod. Dev. 84: 8-18, 2017. © 2016 Wiley Periodicals, Inc.