Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P10636 (tau protein)
 5,110 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Hyperphosphorylation of the microtubule-associated protein tau is a characteristic feature of neurodegenerative tauopathies including Alzheimer disease. Over-activation of proline-directed kinases, such as cyclin-dependent kinase 5 (Cdk5) and glycogen synthase kinase 3 (GSK3), has been implicated in the aberrant phosphorylation of tau at proline-directed sites. In this study we tested the roles of Cdk5 and GSK3 in tau hyperphosphorylation in vivo using transgenic mice with p25-induced Cdk5 over-activation. We found that over-activation of Cdk5 in young transgenic animals does not induce tau hyperphosphorylation at sites recognized by the antibodies AT8, AT100, PHF-1, and TG3. In fact, we observed that Cdk5 over-activation leads to inhibition of GSK3. However, in old transgenic animals the inhibition of GSK3 is lost and results in increased GSK3 activity, which coincides with tau hyperphosphorylation at the AT8 and PHF-1 sites. Pharmacological inhibition of GSK3 in old transgenic mice by chronic treatment with lithium leads to a reduction of the age-dependent increase in tau hyperphosphorylation. Furthermore, we found that Cdk5, GSK3, and PP2A co-immunoprecipitate, suggesting a functional association of these molecules. Together, these results reveal the role of GSK3 as a key mediator of tau hyperphosphorylation, whereas Cdk5 acts as a modulator of tau hyperphosphorylation via the inhibitory regulation of GSK3. Furthermore, these findings suggest that disruption of regulation of GSK3 activity underlies tau hyperphosphorylation in neurodegenerative tauopathies. Hence, GSK3 may be a prime target for therapeutic intervention in tauopathies including Alzheimer disease.
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PMID:The roles of cyclin-dependent kinase 5 and glycogen synthase kinase 3 in tau hyperphosphorylation. 1680 97

Acute treatment with kainate 30 mg/kg (KA) produced behavioral alterations and reactive gliosis. However, it did not produce major death of mouse hippocampal neurons, indicating that concentrations were not cytotoxic. KA caused rapid and temporal Erk phosphorylation (at 6h) and Akt dephosphorylation (1-3 days). Concomitantly, the activation of GSK3beta was increased 1-3 days after KA. After 7 days, a reduction in GSK3beta activation was observed. Caspase-3 activity increased, but to a lesser extent than calpain activation (measured by fluorimetry and calpain-cleaved alpha-spectrin). As calpain is involved in cdk5 activation, and cdk5 is related to GSK3beta, the cdk5/p25 pathway was examined. Results showed that the p25/p35 ratio in KA-injected mice for 3 days was 73.6% higher than control levels. However, no changes in cdk5 expression were detected. Both Western blot and immunohistochemistry against p-Tau(Thr(231)) indicated an increase at this phosphorylated site of tau protein. Indeed an increase in p-Tau(Ser(199)) and p-Tau(Ser(396)) was observed by Western blot. Our results demonstrate that tau hyperphosphorylation, induced by KA, is due to an increase in GSK3beta/cdk5 activity in combination with an inactivation of Akt. This indicates that the calpain/cdk5 pathway for tau phosphorylation has a potential role in delayed apoptotic death evoked by excitotoxicity. Moreover, the subsequent activation of caspase and calpain proteases leads to dephosphorylation of tau, thus increasing microtubular destructuration. Taken together, our results provide new insights in the activation of several kinase-pathways implicated in cytoskeletal alterations that are a common feature of neurodegenerative diseases.
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PMID:Kainate induces AKT, ERK and cdk5/GSK3beta pathway deregulation, phosphorylates tau protein in mouse hippocampus. 1711 46

This study is to explore the effect of ginsenoside Rb1 on the process of beta-amyloid peptide(25-35) (Abeta(25-35)) -induced hyperphosphorylation of tau protein, and on the level of cyclin-dependent kinase 5 activator, p25/p35. Western blotting and/or immunocytochemical staining were used to detect the levels of phosphorylation of tau protein at the sites of Thr205, Ser396, Ser404 in hippocampal neurons, cdk5 and p25/p35. After exposure to Abeta(25-35) (20 micromol x L(-1)) for 12 h, the levels of tau protein phosphorylation at the sites of Thr205, Ser396, Ser404 were enhanced, the level of p25 was increased, but the level of protein cdk5 was not changed markedly. Pretreatment with ginsenoside Rb1 reduced Abeta(25-35) -induced hyperphosphorylation of tau protein and decreased the lever of p25, but had no effect on cdk5. Ginsenoside Rb1 can attenuate Abeta(25-35) -induced hyperphosphorylation of tau protein through CDK5 signal pathway.
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PMID:[Ginsenoside Rb1 attenuates beta-amyloid peptide(25-35) -induced hyperphosphorylation of tau protein through CDK5 signal pathway]. 1794 29

Tau hyperphosphorylation, amyloid plaques, and neuronal death are major neuropathological features of Alzheimer's disease (AD) and Prion-related encephalopathies (PRE). Cyclin-dependent kinase 5 (Cdk5) is a serine/threonine kinase, active in post-mitotic neurons, where it regulates survival and death pathways. Overactivation of Cdk5 is conferred by p25, a truncated fragment of the p35 activator formed upon calpain activation. Cdk5 deregulation causes abnormal phosphorylation of microtubule-associated protein tau, leading to neurodegeneration. In this work we investigated the involvement of Cdk5 in the neurodegeneration triggered by amyloid-beta (Abeta) and prion (PrP) peptides, the culprit agents of AD and PRE. As a work model, we used cultured rat cortical neurons treated with Abeta 1-40 and PrP 106-126 synthetic peptides. The obtained data show that apoptotic neuronal death caused by both the peptides was in part due to Cdk5 deregulation. After peptide treatment, p25 levels were significantly enhanced in a pattern consistent with the augment in calpain activity. Moreover, Abeta 1-40 and PrP 106-126 increased the levels of tau protein phosphorylated at Ser202/Thr205. Cdk5 (roscovitine) and calpain (MDL28170) inhibitors reverted tau hyperphosphorylation and prevented neuronal death caused by Abeta 1-40 and PrP 106-126. This study demonstrates, for the first time, that Cdk5 is involved in PrP-neurotoxicity. Altogether, our data suggests that Cdk5 plays an active role in the pathogenesis of AD and PRE.
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PMID:Role of cyclin-dependent kinase 5 in the neurodegenerative process triggered by amyloid-Beta and prion peptides: implications for Alzheimer's disease and prion-related encephalopathies. 1796 32

Within the histopathology of Alzheimer's disease (AD) certain hallmarks are beeing observed. The occurance of protein deposits belong to such characteristic features. Such deposits can be found extracellular as beta-amyloid (Abeta) plaques and intracellular as neurofibrillary tangles (NFTs). In the search for novel AD therapeutics it became of great interest to investigate the formation of NFTs and their contribution to the AD symptomatic. NFTs consist of hyperphosphorylated tau protein. Within the phosphorylation process of tau protein two kinases are of great importance: cyclin dependent kinase 5 (cdk5) and its truncated regulatory subunit p25 and glycogen synthase kinase 3beta (GSK-3beta). The role of both kinases within the NFT formation process is still under debate. To better understand the pathophysiological process highly selective inhibitors of both kinases are of value. Known inhibitors lack the necessary selectivity. We developed novel 1-aza-9-oxafluo-renes as selective GSK-3beta inhibitors. Structure-activity relationships of a series of 4-phenyl substituted derivatives are discussed. Variation of the 3-side chain led to selective carbonyl amide derivatives with selectivity factors of more than 100 at the tested ATP competitor concentrations. Such selectivities permit specific investigation of the role of GSK-3beta within the NFT formation processes.
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PMID:Probing novel 1-aza-9-oxafluorenes as selective GSK-3beta inhibitors. 1800 Sep 38

The deposition of highly phosphorylated microtubule-associated tau protein has been observed in ALS with cognitive impairment (ALSci). In these studies, we have examined whether the expression of two candidate protein kinases for mediating tau hyperphosphorylation (GSK3beta or CDK5) are also altered. The expression of GSK, CDK and p25/p35 was assayed in human frontal, hippocampal, cerebellar, cervical (dorsal and ventral) and lumbar (dorsal and ventral) tissue from neurologically intact control (5), ALS (5) or ALSci (5) patients using RT-PCR, Western blot or immunohistochemistry. To assess GSK-3beta activity, we examined GSK3beta, phospho-GSK3beta and phospho-beta-catenin expression. Expression levels relative to that of beta-actin were compared by ANOVA. The expression of GSK, GSK3beta and phospho-GSK3beta was increased in both ALS and ALSci compared to that of the control. This was accompanied by an increased expression of phospho-beta-catenin. No significant difference between control, ALS or ALSci was observed with respect to the expression of CDK5 or p25/p35. Both GSK3beta and phospho-GSK3beta immunoreactive neurons were mainly located in layer II and layer III in the frontal cortex and in layer II in the hippocampus. This was consistent with the previously described distribution of hyperphosphorylated tau bearing neurons in ALS and ALSci. These data suggest that GSK3beta expression is upregulated in ALS and ALSci and that GSK3beta activation is associated with the intraneuronal deposition of hyperphosphorylated tau protein. This supports the potential role for GSK3beta as a therapeutic target in ALS.
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PMID:Upregulation of GSK3beta expression in frontal and temporal cortex in ALS with cognitive impairment (ALSci). 1822 34

3,4-Methylenedioxymethamphetamine (MDMA) ("Ecstasy") produces neurotoxic effects, which result into an impairment of learning and memory and other neurological dysfunctions. We examined whether MDMA induces increases in tau protein phosphorylation, which are typically associated with Alzheimer's disease and other chronic neurodegenerative disorders. We injected mice with MDMA at cumulative doses of 10-50 mg/kg intraperitoneally, which are approximately equivalent to doses generally consumed by humans. MDMA enhanced the formation of reactive oxygen species and induced reactive gliosis in the hippocampus, without histological evidence of neuronal loss. An acute or 6 d treatment with MDMA increased tau protein phosphorylation in the hippocampus, revealed by both anti-phospho(Ser(404))-tau and paired helical filament-1 antibodies. This increase was restricted to the CA2/CA3 subfields and lasted 1 and 7 d after acute and repeated MDMA treatment, respectively. Tau protein was phosphorylated as a result of two nonredundant mechanisms: (1) inhibition of the canonical Wnt (wingless-type MMTV integration site family) pathway, with ensuing activation of glycogen synthase kinase-3beta; and (2) activation of type-5 cyclin-dependent kinase (Cdk5). MDMA induced the expression of the Wnt antagonist, Dickkopf-1, and the expression of the Cdk5-activating protein, p25. In addition, the increase in tau phosphorylation was attenuated by strategies that rescued the Wnt pathway or inhibited Cdk5. Finally, an impairment in hippocampus-dependent spatial learning was induced by doses of MDMA that increased tau phosphorylation, although the impairment outlasted this biochemical event. We conclude that tau hyperphosphorylation in the hippocampus may contribute to the impairment of learning and memory associated with MDMA abuse.
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PMID:Enhanced tau phosphorylation in the hippocampus of mice treated with 3,4-methylenedioxymethamphetamine ("Ecstasy"). 1835 27

Tau-tubulin kinase-1 (TTBK1) is involved in phosphorylation of tau protein at specific Serine/Threonine residues found in paired helical filaments, suggesting its role in tauopathy pathogenesis. We found that TTBK1 levels were upregulated in brains of human Alzheimer' disease (AD) patients compared with age-matched non-AD controls. To understand the effects of TTBK1 activation in vivo, we developed transgenic mice harboring human full-length TTBK1 genomic DNA (TTBK1-Tg). Transgenic TTBK1 is highly expressed in subiculum and cortical pyramidal layers, and induces phosphorylated neurofilament aggregation. TTBK1-Tg mice show significant age-dependent memory impairment as determined by radial arm water maze test, which is associated with enhancement of tau and neurofilament phosphorylation, increased levels of p25 and p35, both activators of cyclin-dependent protein kinase 5 (CDK5), enhanced calpain I activity, and reduced levels of hippocampal NMDA receptor types 2B (NR2B) and D. Enhanced CDK5/p35 complex formation is strongly correlated with dissociation of F-actin from p35, suggesting the inhibitory mechanism of CDK5/p35 complex formation by F-actin. Expression of recombinant TTBK1 in primary mouse cortical neurons significantly downregulated NR2B in a CDK5- and calpain-dependent manner. These data suggest that TTBK1 in AD brain may be one of the underlying mechanisms inducing CDK5 and calpain activation, NR2B downregulation, and subsequent memory dysfunction.
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PMID:Spatial learning impairment, enhanced CDK5/p35 activity, and downregulation of NMDA receptor expression in transgenic mice expressing tau-tubulin kinase 1. 1911 86

Increasing evidence is demonstrating that drugs affecting dopamine levels in the brain induce cytoskeletal modifications. These evolving changes may impact neuronal synaptic plasticity as cytoskeletal constituents are involved in the maintenance of dendritic processes, and any alterations in their stability could influence major cellular compartments of neurons, such as dendrites, spines and synapses. Here, we describe a molecular chain of events that links dopamine D1 receptor activation to hyperphosphorylation of the microtubule-associated protein tau, which is normally involved in microtubules stabilization. We show, in SK-N-MC cells and rat striatal sections, that phosphorylation of tau at serines 199-202 and 214 appears to be mediated through activation of calcium-dependent intracellular mechanism, subsequent to D1 receptor-induced cAMP-dependent protein kinase A (PKA). We demonstrate, using pharmacological tools, that PKA activation causes increase of calcium levels, leading to cyclin-dependent kinase 5 activation by calpain proteolysis of p35 to p25 and glycogen synthase kinase 3beta activation by its phosphorylation at tyrosine 216. The D2 receptor agonism or lowering cAMP levels has no effect in our experimental settings. Moreover, we do not observe any association between phosphorylated tau and cellular damage. These data unravel novel mechanisms of tau hyperphosphorylation during G-protein-coupled receptor activation and are the first to show that stimulation of D1 receptors could have a profound influence on the neuronal cytoskeletal constituent tau.
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PMID:Dopamine D1 receptor activation induces tau phosphorylation via cdk5 and GSK3 signaling pathways. 1959 49

Tau-tubulin kinase-1 (TTBK1) phosphorylates microtubule-associated protein tau at specific serine/threonine residues found in paired helical filaments (PHFs), and its expression is up-regulated in the brain in Alzheimer disease, suggesting its role in tauopathy pathogenesis. To understand the effects of TTBK1 on tauopathy in vivo, we have developed bigenic mice overexpressing full-length TTBK1 and the P301L tau mutant. The bigenic mice show enhanced tau phosphorylation at multiple sites (AT8, 12E8, PHF-1, and pS422), tauC3-immunoreactive tau fragmentation, and accumulation of tau aggregates in cortical and hippocampal neurons at 12-13 mo of age. However, the phosphorylated tau aggregates were predominantly sarkosyl soluble and migrated in the light sucrose density fraction after discontinuous sucrose gradient ultracentrifugation, which suggests that they form small oligomers. The bigenic mice show significant locomotor dysfunction as determined by both rotorod and grip strength tests, as well as enhanced loss of motor neurons in the L4-L5 spinal cord. This neuronal dysfunction and degeneration was associated with increased levels of tau oligomers, cyclin-dependent protein kinase 5 activators p35 and p25, and pY216 phosphorylated glycogen synthase kinase 3-beta. These data suggest that TTBK1 up-regulation enhances tau phosphorylation and oligomerization, whose toxicity results in enhanced neurodegeneration and locomotor dysfunction in a tauopathy animal model.
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PMID:Tau-tubulin kinase 1 enhances prefibrillar tau aggregation and motor neuron degeneration in P301L FTDP-17 tau-mutant mice. 2035 35


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