Multicast tree construction algorithm for dynamic traffic on software defined networks.

Dynamic traffic of multicast communication in the Software Defined Network environment focused less though it is more natural and practical. In multicast communication, the traffic is dynamic due to the dynamic group memberships (i.e.

Glycogen synthase kinase-3β (GSK3β) expression in a mouse model of Alzheimer's disease: a light and electron microscopy study.

Glycogen synthase kinase-3β (GSK3β) activity has been previously linked to Alzheimer's disease (AD) by its phosphorylation of tau and activation by amyloid. GSK3β intracellular distribution is important in regulating its activity by restricting access to compartment-specific substrates. This study investigated regional and intracellular distribution of GSK3β in a mouse model of AD, a bigenic mouse with combined amyloid and tau pathology (BiAT), and controls (FVB).

Dkk1 stabilizes Wnt co-receptor LRP6: implication for Wnt ligand-induced LRP6 down-regulation.

Background: The low density lipoprotein receptor-related protein-6 (LRP6) is an essential co-receptor for canonical Wnt signaling. Dickkopf 1 (Dkk1), a major secreted Wnt signaling antagonist, binds to LRP6 with high affinity and prevents the Frizzled-Wnt-LRP6 complex formation in response to Wnts. Previous studies have demonstrated that Dkk1 promotes LRP6 internalization and degradation when it forms a ternary complex with the cell surface receptor Kremen.

Mitochondrial viability in mouse and human postmortem brain.

Neuronal function in the brain requires energy in the form of ATP, and mitochondria are canonically associated with ATP production in neurons. The electrochemical gradient, which underlies the mitochondrial transmembrane potential (DeltaPsi(mem)), is harnessed for ATP generation. Here we show that DeltaPsi(mem) and ATP-production can be engaged in mitochondria isolated from human brains up to 8.

Light and electron microscopy study of glycogen synthase kinase-3beta in the mouse brain.

Glycogen synthase kinase-3beta (GSK3beta) is highly abundant in the brain. Various biochemical analyses have indicated that GSK3beta is localized to different intracellular compartments within brain cells. However, ultrastructural visualization of this kinase in various brain regions and in different brain cell types has not been reported.

The basal flux of Akt in the mitochondria is mediated by heat shock protein 90.

Akt is a known client protein of heat shock protein 90 (HSP90). We have found that HSP90 is responsible for Akt accumulation in the mitochondria in unstimulated cells. Treatment of SH-SY5Y neuroblastoma cells and human embryonic kidney cells with the HSP90 inhibitors novobiocin and geldanamycin caused substantial decreases in the level of Akt in the mitochondria without affecting the level of Akt in the cytosol.

Unregulated mitochondrial GSK3beta activity results in NADH: ubiquinone oxidoreductase deficiency.

GSK3beta is prominent for its role in apoptosis signaling and has been shown to be involved in Parkinson's disease (PD) pathogenesis. The overall effects of GSK3beta activity on cell fate are well-established, but the effects of mitochondrial GSK3beta activity on mitochondrial function and cell fate are unknown. Here we selectively expressed constitutively active GSK3beta within the mitochondria and found that this enhanced the apoptosis signaling activated by the PD-mimetic NADH:ubiquinone oxidoreductase (complex I) inhibitors 1-methyl-4-phenylpyridinium ion (MPP+) and rotenone.

The protein phosphatase-1/inhibitor-2 complex differentially regulates GSK3 dephosphorylation and increases sarcoplasmic/endoplasmic reticulum calcium ATPase 2 levels.

The ubiquitously expressed protein glycogen synthase kinase-3 (GSK3) is constitutively active, however its activity is markedly diminished following phosphorylation of Ser21 of GSK3alpha and Ser9 of GSK3beta. Although several kinases are known to phosphorylate Ser21/9 of GSK3, for example Akt, relatively much less is known about the mechanisms that cause the dephosphorylation of GSK3 at Ser21/9. In the present study KCl-induced plasma membrane depolarization of SH-SY5Y cells, which increases intracellular calcium concentrations caused a transient decrease in the phosphorylation of Akt at Thr308 and Ser473, and GSK3 at Ser21/9.

Akt1 is dynamically modified with O-GlcNAc following treatments with PUGNAc and insulin-like growth factor-1.

The Ser/Thr kinase Akt1 is activated by growth factors subsequent to its phosphorylation on Thr308 and Ser473. In the present study, Akt1 was found to be constitutively modified with O-GlcNAc. Treatment of SH-SY5Y cells with O(2-acetamido-2-deoxy-D-glucopyranosylidene)amino-N-phenylcarbamate (PUGNAc), which inhibits the enzymatic removal of O-GlcNAc from proteins, increased cytosolic O-GlcNAc-Akt1 levels.

In vivo regulation of GSK3 phosphorylation by cholinergic and NMDA receptors.

Glycogen synthase kinase-3 (GSK3), which is inhibited by serine-phosphorylation, is involved in the neuropathology of Alzheimer's disease (AD). We tested if the two therapeutic strategies used for AD, inhibition of acetylcholinesterase and of N-methyl-D-aspartate (NMDA) receptors, modulate the phosphorylation state of the two isoforms of GSK3 in mouse brain. Large, rapid increases in the levels of phospho-Ser21-GSK3alpha and phospho-Ser9-GSK3beta occurred in mouse hippocampus, cerebral cortex, and striatum after treatment of mice with the muscarinic agonist pilocarpine or the acetylcholinesterase inhibitor physostigmine.

Regulation of FOXO3a by brain-derived neurotrophic factor in differentiated human SH-SY5Y neuroblastoma cells.

FOXO3a is a ubiquitously expressed mammalian forkhead transcription factor with a high expression level in adult brain. The activity of FOXO3a is inhibited by growth factors through activation of phosphatidylinositol 3-kinase (PI3K)/Akt signaling, which phosphorylates FOXO3a and decreases the level of FOXO3a in the nucleus. In the present study, we examined the regulation of FOXO3a by brain-derived neurotrophic factor (BDNF) in retinoic acid (RA)-differentiated human SH-SY5Y neuroblastoma cells.

Rapid accumulation of Akt in mitochondria following phosphatidylinositol 3-kinase activation.

We describe here a new component of the phosphatidylinositol 3-kinase/Akt signaling pathway that directly impacts mitochondria. Akt (protein kinase B) was shown for the first time to be localized in mitochondria, where it was found to reside in the matrix and the inner and outer membranes, and the level of mitochondrial Akt was very dynamically regulated. Stimulation of a variety of cell types with insulin-like growth factor-1, insulin, or stress (induced by heat shock), induced translocation of Akt to the mitochondria within only several minutes of stimulation, causing increases of nearly eight- to 12-fold, and the mitochondrial Akt was in its phosphorylated, active state.

Glycogen synthase kinase-3 beta is highly activated in nuclei and mitochondria.

Glycogen synthase kinase-3 beta (GSK3 beta) is located predominantly in the cytosol, but also is in nuclei and mitochondria. In SH-SY5Y cells, primary cortical neurons, and mouse brain, the portion of active GSK3 beta (not phosphorylated on serine-9) was 5- to 8-fold greater in nuclei and mitochondria than in cytosol. Correspondingly greater GSK3 beta activities were measured in nuclei and mitochondria compared with cytosol.

Glycogen synthase kinase-3beta (GSK3beta) binds to and promotes the actions of p53.

The recent discovery of direct interactions between two important regulators of cell fate, the tumor suppressor p53 and glycogen synthase kinase-3beta (GSK3beta), led us to examine the mechanism and outcomes of this interaction. Two regions of p53 were identified that regulate its binding to GSK3beta. Deletion of the p53 activation domain-1 (AD1), but not mutations that prevent MDM2 binding through the AD1 domain, enhanced GSK3beta binding to p53, indicating that the AD1 domain interferes with p53 binding to GSK3beta.

Glycogen synthase kinase-3beta, mood stabilizers, and neuroprotection.

Glycogen synthase kinase-3beta (GSK-3beta) is a central component in many critical intracellular signaling mechanisms. These include the phosphatidylinositol 3-kinase/Akt cell survival pathway, which inhibits GSK-3beta activity. GSK-3beta itself inhibits the activation of several transcription factors, which are important cell survival factors, such as heat shock factor 1.

Direct, activating interaction between glycogen synthase kinase-3beta and p53 after DNA damage.

Glycogen synthase kinase-3beta (GSK3beta) is a central figure in Wnt signaling, in which its activity is controlled by regulatory binding proteins. Here we show that binding proteins outside the Wnt pathway also control the activity of GSK3beta. DNA damage induced by camptothecin, which activates the tumor suppressor p53, was found to activate GSK3beta.

Mood stabilizers, glycogen synthase kinase-3beta and cell survival.

Glycogen synthase kinase-3beta (GSK3beta) is a central figure in many intracellular signaling systems and is directly regulated by lithium. Substantial evidence now indicates that an important property of the mood stabilizer, lithium, is to influence GSK3beta-linked signaling pathways. This raises the possibility that other mood stabilizers act in a similar manner, which may include modulation of signaling systems leading to GSK3beta, direct regulation of GSK3beta or regulation of signaling intermediates downstream of GSK3beta.

Caspase-3 activation induced by inhibition of mitochondrial complex I is facilitated by glycogen synthase kinase-3beta and attenuated by lithium.

The compound 1-methyl-4-phenylpyridinium (MPP) is a selective inhibitor of mitochondrial complex I, and is widely used in model systems to elicit neurochemical alterations that may be associated with Parkinson's disease. In the present study treatment of human neuroblastoma SH-SY5Y cells with MPP resulted in a time- and concentration-dependent activation of the apoptosis-associated cysteine protease caspase-3, and caused morphological changes characteristic of apoptosis. To test if the activation state of the cell survival-promoting phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway affects MPP-induced caspase-3 activation, PI3K was inhibited with LY294002, or activated with insulin-like growth factor-1.

Proapoptotic stimuli induce nuclear accumulation of glycogen synthase kinase-3 beta.

The goal of this study was to determine whether the intracellular distribution of the proapoptotic enzyme glycogen synthase kinase-3 beta (GSK-3 beta) is dynamically regulated by conditions that activate apoptotic signaling cascades. In untreated human neuroblastoma SH-SY5Y cells, GSK-3 beta was predominantly cytosolic, although a low level was also detected in the nucleus. The nuclear level of GSK-3 beta was rapidly increased after exposure of cells to serum-free media, heat shock, or staurosporine.

Cholinergic- and stress-induced signaling activities in cells overexpressing wild-type and mutant presenilin-1.

This study examined the effects of overexpression of presenilin-1 wild-type (PS1wt) or mutant L286V (PS1m) in human neuroblastoma SH-SY5Y cells on signal transduction systems. Oxotremorine-M-induced activation of AP-1 was 40--53% lower in PS1wt than control cells, and further impaired (63--76%) in PS1m cells. Heat shock (45 degrees C) activated Akt, increased heat shock factor-1 (HSF-1) DNA binding activity, and increased levels of heat shock protein 70, and these responses were not altered by overexpression of PS1wt or PS1m.

Opposing actions of phosphatidylinositol 3-kinase and glycogen synthase kinase-3beta in the regulation of HSF-1 activity.

Elevated temperatures activate the survival promoters Akt and heat shock factor-1 (HSF-1), a transcription factor that induces the expression of heat shock proteins (HSPs), such as HSP-70. Because neuronal mechanisms controlling these responses are not known, these were investigated in human neuroblastoma SH-SY5Y cells. Heat shock (45 degrees C) rapidly activated Akt, extracellular signal-regulated kinases 1 and 2 (ERK1/2), and p38, but only Akt was activated in a phosphatidylinositol 3-kinase (PI-3K)-dependent manner, as the PI-3K inhibitors LY294002 and wortmannin blocked Akt activation, but not ERK1/2 or p38 activation.

Transient oxidative stress in SH-SY5Y human neuroblastoma cells results in caspase dependent and independent cell death and tau proteolysis.

The effects of an oxidative insult on cell survival and tau metabolism were investigated in human neuroblastoma SH-SY5Y cells. In this treatment paradigm cells were exposed to the membrane permeant oxidant tert-butylhydroperoxide (tBHP) for 40 min, returned to fresh media and cell survival/death was monitored during the post-treatment period. Cell viability decreased significantly by 6 hr after tBHP exposure, and by 24 hr lactate dehydrogenase (LDH) release was 40.

Alterations in muscarinic receptor-coupled phosphoinositide hydrolysis and AP-1 activation in Alzheimer's disease cybrid cells.

Alzheimer's disease cybrid cells produced by replacing endogenous mitochondria in human neuroblastoma SH-SY5Y cells with platelet mitochondria from subjects with Alzheimer's disease have higher levels of reactive oxygen species than do cybrid cells with mitochondria from control subjects. These cells were used to test if this chronic mild increase in reactive oxygen species affects muscarinic receptor-coupled signaling activities. Basal and carbachol-stimulated phosphoinositide hydrolysis were higher, and there was less inhibition by glutathione depletion, in Alzheimer's disease than control cybrid cells.

Glycogen synthase kinase-3beta facilitates staurosporine- and heat shock-induced apoptosis. Protection by lithium.

The potential role of glycogen synthase kinase-3beta in modulating apoptosis was examined in human SH-SY5Y neuroblastoma cells. Staurosporine treatment caused time- and concentration-dependent increases in the activities of caspase-3 and caspase-9 but not caspase-1, increased proteolysis of poly(ADP-ribose) polymerase, and induced morphological changes consistent with apoptosis. Overexpression of glycogen synthase kinase-3beta to levels 3.

Rapid activation of heat shock factor-1 DNA binding by H2O2 and modulation by glutathione in human neuroblastoma and Alzheimer's disease cybrid cells.

Because cellular signaling systems are critical mediators of responses to oxidative stress, a condition associated with neurodegenerative disorders, the redox-dependent regulation of heat shock factor-1 (HSF-1) was investigated in human neuroblastoma SH-SY5Y cells. Exposure of cells to 200 microM H2O2 caused a rapid increase in HSF-1 DNA binding that was evident within 10 min, and caused a robust increase that reached levels 8-fold the basal activity. In comparison, the transcription factors, activator protein-1 (AP-1) and early growth response-1 (EGR-1), were activated more slowly and to a lesser extent.