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)

Abundant neurofibrillary tangles, neuropil threads and plaque neurites constitute the neurofibrillary pathology of Alzheimer's disease. They form in the nerve cells that undergo degeneration in the disease where their regional distribution correlates with the degree of dementia. Each lesion contains the paired helical filament (PHF) as its major fibrous component. Recent work has shown that PHFs are composed of the microtubule-associated protein tau in a hyperphosphorylated state. PHF-tau is hyperphosphorylated on six adult brain tau isoforms. As a consequence, tau is unable to bind to microtubules and is believed to self-assemble into the PHF. Current evidence suggests that protein kinases or protein phosphatases with a specificity for serine/threonine-proline residues play an important role in the hyperphosphorylation of tau. Candidate protein kinases include mitogen-activated protein kinase, glycogen synthase kinase-3 and cyclin-dependent kinase 5, whereas the trimeric form of protein phosphatase 2A is a candidate phosphatase.
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PMID:Molecular dissection of the paired helical filament. 756 42

Neurofibrillary lesions found in Alzheimer disease (AD) are known to react with antibodies raised against different molecules. At least 20 components have been detected in neurofibrillary tangles. These components can be roughly categorized into five groups, which include structural proteins, kinases and other cytosolic enzymes, stress-related molecules, amyloid and amyloid binding proteins, and others. Among them, an abnormal form of microtubule associated protein tau, PHF-tau, is a major component of Alzheimer NFT. Kinases associated with NFT, especially those belonging to the family of proline-directed Ser/Thr kinases, are considered to be important for PHF-tau hyperphosphorylation. A potentially significant kinase is a Cdc2-related kinase, which is associated tightly with paired helical filaments, has a molecular weight of 33kDa and is different from other known Cdc2-related kinases. The possibility that some of the NFT-associated elements may play an active role in the pathogenesis of Alzheimer's disease was supported by recent studies, in which advanced glycated products and markers of oxidant stress were located in NFT. In addition, PHF-tau was found to be glycated, and in vitro glycated tau was capable of inducing oxidant stress. Further characterization of different components of NFT by biochemical and other approaches will be important for understanding the mechanisms involved in the supramolecular aggregation of PHF within NFT.
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PMID:Alzheimer neurofibrillary lesions: molecular nature and potential roles of different components. 756 47

The paired helical filament (PHF), which makes up the major fibrous component of the neurofibrillary lesions of Alzheimer's disease, is composed of hyperphosphorylated and abnormally phosphorylated microtubule-associated protein tau. Previous studies have identified serine and threonine residues phosphorylated in PHF-tau and have shown that tau can be phosphorylated at several of these sites by proline-directed protein kinases and cyclic AMP-dependent protein kinase. Here we have investigated which protein phosphatase activities can dephosphorylate recombinant tau phosphorylated with mitogen-activated protein kinase, glycogen synthase kinase-3 beta, neuronal cdc2-like kinase, or cyclic AMP-dependent protein kinase. We show that protein phosphatase 2A is by far the major protein phosphatase activity in brain that dephosphorylates tau phosphorylated in this manner.
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PMID:Protein phosphatase 2A is the major enzyme in brain that dephosphorylates tau protein phosphorylated by proline-directed protein kinases or cyclic AMP-dependent protein kinase. 759 82

Hyperphosphorylated microtubule-associated protein tau is the major component of the paired helical filament of Alzheimer's disease. Phosphorylation-dependent anti-tau antibodies are being used to identify specific amino acids that are phosphorylated in tau from normal brain and Alzheimer's disease brain. As such, monoclonal antibody AT8 is widely used. By a combination of site-directed mutagenesis of recombinant tau and in vitro phosphorylation, we show that AT8 requires tau protein to be phosphorylated at both serine 202 and threonine 205 (using the numbering of the longest human brain tau isoform.
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PMID:Monoclonal antibody AT8 recognises tau protein phosphorylated at both serine 202 and threonine 205. 762 36

This paper summarizes our recent studies on microtubule-associated protein tau and its pathological state resembling that of the paired helical filaments of Alzheimer's disease. The Alzheimer-like state of tau protein can be identified and analyzed in terms of certain phosphorylation sites and phosphorylation-dependent antibody epitopes. It can be induced by protein kinases which tend to phosphorylate serine or threonine residues followed by a proline; this includes mitogen-activated protein kinase (MAPK) and glycogen-synthase kinase 3 (GSK-3). Both of these are tightly associated with microtubules as well as with paired helical filaments. Structurally, tau appears as a rod-like molecule; it tends to self-associate into dimers whose monomers are antiparallel. Constructs of truncated tau made up of antiparallel dimers of the microtubule binding domain can be assembled into paired helical filaments in vitro.
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PMID:Microtubule-associated protein tau, paired helical filaments, and phosphorylation. 769 33

Abundant neurofibrillary tangles, neuropil threads and senile plaque neurites constitute the neurofibrillary pathology of Alzheimer's disease. They form in the nerve cells that undergo degeneration in the disease, in which their regional distribution correlates with the degree of dementia. Each lesion contains the paired helical filament (PHF) as its major fibrous component. Recent work has shown that PHFs are composed of the microtubule-associated protein tau in a hyperphosphorylated state. PHF-tau is hyperphosphorylated on six adult brain tau isoforms. As a consequence, tau is unable to bind to microtubules and is believed to self-assemble into the PHF. Current evidence suggests that protein kinases or protein phosphatases with a specificity for serine/threonine-proline residues are instrumental in the hyperphosphorylation of tau. Candidate protein kinases include mitogen-activated protein kinase, glycogen synthase kinase 3 and cyclin-dependent kinase 5, whereas the trimeric form of protein phosphatase 2A is a candidate phosphatase.
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PMID:Molecular dissection of the neurofibrillary lesions of Alzheimer's disease. 776 34

MAP kinases (MAPK) are a family of serine/threonine (Ser/Thr) kinases that link cell surface signals to changes in enzyme activity and gene expression. They are the products of the newly described gene family referred to as extracellular signal regulated kinases (ERKs). Moreover, MAPKs phosphorylate tau in vitro at Ser/Thr Proline sites, generating a multiply phosphorylated tau protein that is similar to the hyperphosphorylated tau found in Alzheimer neurofibrillary tangles (NFTs). We studied MAPK immunoreactivity and in situ hybridization patterns of the two major genes that comprise MAPK activity, ERK1 and ERK2, in the human hippocampal formation. Our goal was to determine whether the pattern of ERK expression is consistent with the hypothesis that MAPKs contribute to NFT formation. ERK1 mRNA is present in small amounts and confined primarily to dentate gyrus granule cells. ERK2 mRNA, by contrast, gives a much stronger hybridization signal and is present in dentate gyrus granule cells and pyramidal cells throughout all hippocampal subfields and adjacent temporal neocortex. Quantitative measures of ERK2 mRNA reveal that NFT-bearing neurons contain approximately 15% less ERK2 mRNA than nearest neighbors that do not contain NFT. NFT-bearing neurons contain approximately 25% less polyA mRNA, suggesting a relative preservation of ERK2 mRNA even in metabolically compromised cells. MAPK immunoreactivity (which represents both ERK1 and ERK2) is seen in neuronal soma, dendrites, axons, and in reactive astrocytes. In Alzheimer's disease, neurons that contain NFTs are also MAPK immunoreactive, but neurons that contain the highest amounts of MAPK immunoreactivity are not necessarily vulnerable for NFT. MAPK immunoreactivity is present in the same neurons as NFT and in the same subcellular compartments as tau, supporting a role for MAPKs in tau phosphorylation in Alzheimer's disease. However, the presence of ERK immunoreactivity is not sufficient to predispose neurons to NFT formation.
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PMID:Extracellular signal regulated kinases. Localization of protein and mRNA in the human hippocampal formation in Alzheimer's disease. 812 42

Brain proline-directed protein kinase (BPDK), which contains a catalytic subunit homologous to and displaying site-specific phosphorylation similar to p34cdc2 kinase (Lew, J., Winkfein, R. J., Paudel, H. K., and Wang, J. H. (1992) J. Biol. Chem. 267, 25922-25926), has been examined for possible involvement in tau phosphorylation. Immunoblot analyses using peptide antibodies specific for BPDK have revealed the presence of the kinase in bovine brain microtubules purified extensively by repeated polymerization and depolymerization cycles. When the microtubule proteins are separated into the tubulin and microtubule-associated protein fractions, BPDK is found exclusively in the latter fraction. BPDK phosphorylates both tau and MAP2, the former protein being phosphorylated to a stoichiometry of 3.8 mol of phosphate/mol of tau. Analysis of the phosphopeptides isolated from the tryptic digest of the phosphorylated bovine tau has revealed seven phosphorylation sites. Based on the sequence alignment between bovine and human tau proteins, these sites correspond to Ser-195, Ser-202, Thr-205, Thr-231, Ser-235, Ser-396, and Ser-404 of human tau. Mass spectrometric analysis of the tau protein isolated from Alzheimer's paired helical filaments (PHFs) has determined three abnormal phosphorylation sites and two phosphopeptides containing a total of five abnormal phosphates (Hasegawa, M., Morishima-Kawashima, M., Takio, K., Suzuki, M., Titani, K., and Ihara, Y. (1992) J. Biol. Chem. 267, 17047-17054). Two of the sites in tau phosphorylated by BPDK, Thr-231 and Ser-235, are among the abnormal phosphorylation sites, and the other sites phosphorylated by BPDK are within phosphopeptides from PHF-tau. These results suggest that BPDK may be one of the kinases responsible for the abnormal phosphorylation-associated PHF-tau.
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PMID:Brain proline-directed protein kinase phosphorylates tau on sites that are abnormally phosphorylated in tau associated with Alzheimer's paired helical filaments. 822 79

The product of the Saccharomyces cerevisiae MCK1 gene is a protein kinase that phosphorylates poly (Glu,Tyr) in vitro and is itself phosphorylated at both tyrosine and serine in vivo. To characterize the substrate specificity of Mck1, the enzyme was purified to apparent homogeneity from the soluble fraction of yeast cell extracts by ammonium sulfate precipitation, followed by ion exchange chromatography (Q- and S-Sepharose), dye-ligand affinity chromatography (Orange A-agarose), adsorption chromatography (hydroxylapatite), and ion exchange fast protein liquid chromatography (Mono-S). In the absence of an exogenous substrate, purified Mck1 was able to autophosphorylate on tyrosine and serine. A catalytically inactive mutant (K68R in conserved kinase domain II) expressed in an mck1 delta strain did not contain detectable phosphotyrosine, confirming that the tyrosine phosphorylation observed in vivo is due to autophosphorylation, but did contain phosphoserine, suggesting that Mck1 is a target for other cellular protein kinases. Purified Mck1 phosphorylated a variety of proteins in heat-inactivated yeast extracts, primarily on serine (and threonine). The purified enzyme also used a number of mammalian proteins as phosphoacceptors, including myelin basic protein (MBP), microtubule-associated protein 2 (MAP-2), and tau protein. All of these substrates were phosphorylated on either serine or threonine (or both). Mck1 isolated from yeast extracts by immunoprecipitation with an anti-Mck1 antibody directed against its C terminus also phosphorylated MBP at serine. In the same immune complex kinase assay, the K68R mutant did not detectably phosphorylate MBP, indicating that the serine-specific phosphotransferase activity of Mck1 is intrinsic and not due to contamination by an associated kinase. These findings demonstrate that Mck1 is a member of a novel class of protein kinases that displays the ability to phosphorylate all three hydroxyamino acids in proteins.
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PMID:Yeast MCK1 protein kinase autophosphorylates at tyrosine and serine but phosphorylates exogenous substrates at serine and threonine. 840 52

Modified forms of tau proteins are major components of the paired helical filaments (PHFs) present in Alzheimer brains. In this study, tau from cytosolic samples obtained from normal and Alzheimer disease brains were fractionated by iron-chelated affinity chromatography (ICAC) to discriminate between isoforms phosphorylated to different extents using an stepwise pH gradient. Immunoblot analysis of the different fractions using antibody Tau-1 (recognizing an unphosphorylated epitope in tau and in PHF-tau after dephosphorylation) and antibody SMI 31 (recognizing a phosphorylated epitope in PHF-tau) have been carried out. Phosphorylated tau species (Tau 1-nonreactive and SMI 31-reactive) are only isolated from the Alzheimer samples at pH = 8.5. These tau species although having other Ser/Thr-Pro motifs susceptible of phosphorylation by proline-directed protein kinases are not further phosphorylated in vitro by MAP2 kinase whereas the fraction isolated at pH 7.0, which contains underphosphorylated tau species, is phosphorylated. Thus, soluble tau species phosphorylated both at the sites constituting the Tau-1 and the SMI 31 epitopes are present in Alzheimer but not in normal brain cytosol and can be isolated by ICAC. These modifications may be a prerequisite for PHF formation.
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PMID:Isolation of a phosphorylated soluble tau fraction from Alzheimer's disease brain. 854


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