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)

The role of microtubule-associated proteins in the assembly of tubulin to microtubules in vitro has been studied. 1. It has been confirmed that pure tubulin obtained by phosphocellulose column chromatography does not significantly assemble in vitro in the absence of minor components which co-polymerize with tubulin. Although tubulin aggregates in a morpholino-ethanesulfonate buffer containing high Mg2+ concentrations, this process was neither inhibited by Ca2+ or colchicine, nor reversed by cold exposure. 2. Microtubule-associated proteins were prepared, either by phosphocellulose column chromatography or by a direct method based on boiling reassembled microtubules in the presence of 2 mM dithiothreitol and 0.75 M NaCl. From each of these preparations two protein fractions were purified, either by Ultrogel ACA34 chromatography or by sucrose gradient ultracentrifugation. The first one, with a high molecular weight, did not promote tubulin assembly; ageing of this material did not induce any activity. On the other hand, the second fraction, with an apparent molecular weight of 70 000 (tau protein), when almost completely purified, was active in promoting assembly. Thus a single specific protein is able to promote assembly of pure tubulin.
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PMID:Microtubule assembly in vitro. Purification of assembly-promoting factors. 91 95

The present study examined the distribution of the high molecular weight (HMW) tau protein isoform in the nervous system by immunoblotting and immunohistochemistry. Some of the biochemical properties of this 110 kDa tau protein were explored, including its heat stability, phosphorylation and partitioning with cold/Ca2+ stable vs. soluble microtubules. Qualitative western blot analysis revealed that HMW tau is preferentially expressed in neurons with peripherally projecting axons. For example, this isotype was present in sciatic nerve, ventral and dorsal roots, trigeminal nerve, vagus nerve, dorsal root ganglia (DRG) and spinal cord, but was present in only trace amounts in CNS regions. Another tau isoform of slightly smaller size (90-100 kDa), termed mid-molecular weight (MMW) tau, was present in abundant quantity in optic nerve samples and detectable in several other CNS regions, including hippocampus and cerebellum. The 110 kDa HMW tau as well as MMW tau and the other tau isoforms were found to be heat stable proteins. The HMW and MMW tau isoforms preferentially partitioned with the cold and Ca+2 insoluble tubulin fraction, but the association of HMW tau with stable microtubules was very susceptible to proteolysis. Dephosphorylation of fresh tissue with alkaline phosphatase produced no apparent shift in the mobility of HMW tau on SDS-PAGE but did alter the mobility of other brain tau isoforms, including MMW tau. Immunocytochemical staining with tau-1 antibody in the DRG, which contains HMW tau but no other tau isotypes, showed localization to mainly small neurons and was not altered by dephosphorylation of the histological sections.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Regional distribution and biochemical characteristics of high molecular weight tau in the nervous system. 145 89

Three isoforms of human tau protein were compared for their abilities to induce microtubule assembly. The three isoforms, tau 3 (tau containing three microtubule-binding domains), tau 4 (tau containing four microtubule-binding domains) and tau 4L (tau containing four microtubule binding domains plus a 58-amino-acid insert near the N-terminus) were expressed in E. coli and purified using ammonium sulfate precipitation, ion exchange, and size exclusion chromatography. All three isoforms induced microtubule assembly at micromolar concentrations and showed similar critical concentrations for assembly of 0.4-0.45 microM. However, tau 4 induced microtubule formation at a rate five- to tenfold faster than either tau 3 or tau 4L. The rate of microtubule elongation seen with tau 4 was twofold greater than with tau 3 or tau 4L, suggesting that the faster rate of microtubule assembly seen with tau 4 was due, at least in part, to faster elongation. Tau 4 induced a greater number of microtubules to form at steady state than did tau 3 or tau 4L. The microtubules generated with each tau isoform had similar steady-state length distributions and were equally susceptible to cold-induced disassembly. These results indicate that the additional microtubule-binding domain in tau 4 enhances microtubule assembly, while the 58-amino-acid insert negates the stimulatory effect of the fourth microtubule-binding domain.
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PMID:Differences in the abilities of human tau isoforms to promote microtubule assembly. 179 99

The protein domain responsible for the interaction of tau with tubulin has been identified. Biophysical studies indicated that the synthetic peptide Val187-Gly204 (VRSKIG-STENLKHQPGGG) from the repetitive sequence on tau binds to two sites on the tubulin heterodimer and to one site on each of the microtubule-associated protein-interacting C-terminal tubulin peptides alpha(430-441) and beta(422-434). The binding data showed a relatively stronger interaction of Val187-Gly204 with beta(422-434) as compared to that with alpha(430-441). The interaction of this tau peptide with either alpha or beta tubulin peptides appears to be associated with conformational changes in both the tau and the tubulin peptides. The beta tubulin peptide also appears to induce a structural change of tau fragment Val218-Gly235. Interestingly, tau peptides Val187-Gly204 and Val218-Gly235 induced tubulin self-assembly in a cold-reversible fashion, and incorporated into the assembled polymers. The specificity of the interaction of the tau peptide was supported by the competition of tau protein for the interaction with the tubulin polymer. In addition, the tau peptide appears to contain the principal antigenic determinant(s) recognized by anti-idiotypic antibodies that react with the tubulin binding domains on microtubule-associated proteins. The present findings together with the demonstration of the presence of multiple sites for the binding of the alpha(430-441) and beta(422-434) tubulin fragments to tau, and the existence of repetitive sequences on tau, strongly support the hypothesis that the region of tau defined by the repetitive sequences is involved in its interaction with tubulin.
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PMID:A discrete repeated sequence defines a tubulin binding domain on microtubule-associated protein tau. 251 58

Microtubule-associated protein (MAP)-2 is a multi-domain cytoskeletal protein that copurifies with brain microtubules (MTs) through repeated cycles of warm polymerization and cold disassembly. Recent equilibrium binding studies of high molecular weight MAP-2ab to taxol-stabilized MTs suggest that the interactions are highly cooperative, as indicated by sigmoidal binding curves, non-linear Scatchard plots, and an apparent all-or-none response in MAP binding in titration experiments (Wallis, K. T., Azhar, S., Rho, M. B., Lewis, S. A., Cowan, N. J., and Murphy, D. B. (1993) J. Biol. Chem. 268, 15158-15167). To learn more about the mechanism of MAP-2 binding to MTs, we investigated the binding properties of bacterially expressed MT-binding region (MTBR) of bovine brain MAP-2. Scatchard plots of the binding data showed no evidence of cooperativity, as reflected by the linear plots of v/[MTBR]free versus v. The stoichiometry was 1-1.1 mol of MTBR/mol of tubulin dimer, and the dissociation constant for the MTBR was 1.1 microM. Bovine brain tau protein competitively inhibited MAP-2 binding, as evidenced by an increased Kd value for MTBR binding to MTs. Although the second repeat peptide m2 (VTSK-CGSLKNIRHRPGGG) is thought to play a dominant role in MAP-2 binding to MTs, a MTBR mutant (with m2 replaced by the third octadecapeptide repeat m3) displays an Kd of 2.8 +/- 0.1 microM and stoichiometry of 0.9 +/- 0.05 mol of MTBR/mol of tubulin dimer. Another mutant with additional copies of the second repeat, designated by us as MTBR[m12m2m32], displayed noncooperative binding with a Kd of 0.53 +/- 0.05 microM and a stoichiometry of 2.2 +/- 0.2 mol of mutant MTBR/tubulin dimer. Equilibrium sedimentation experiments demonstrated that the wild-type MTBR is monomeric, whereas MTBR[m12m2m32] self-associates to a stable dimer over the concentration range used in our MT binding studies. This finding indicates that only one of the two MT-binding sites on the dimer is probably linked to a microtubule at any given time.
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PMID:Non-cooperative binding of the MAP-2 microtubule-binding region to microtubules. 783 56

During brain development, the microtubule-associated protein tau presents a transient state of high phosphorylation. We have investigated the developmental distribution of the phosphorylated fetal-type tau in the developing rat cortex and in cultures of embryonic cortical neurons, using antibodies which react with tau in a phosphorylation-dependent manner. The phosphorylated fetal-type tau was present in the developing cortex at 20 days but not at 18 days of embryonic life and was not detected before four to five days in neuronal culture. The cyclin-dependent kinase p34cdc2 was expressed only in germinal layers in the embryonic brain and was not co-localized with phosphorylated tau. After 10 days of postnatal life, the phosphorylated tau progressively disappeared from cortical neurons, disappearing first from the deepest cortical layers where neurons are ontogenetically the oldest. Phosphorylated tau was found in axons and dendrites of cortical neurons at all developmental stages whereas unphosphorylated tau tended to disappear from dendrites during development. The timing of appearance of phosphorylated tau in the cortex, by comparison with the expression of other developmental markers, indicates that phosphorylated tau is present at a high level only during the period of intense neuritic outgrowth and that it disappears during the period of neurite stabilization and synaptogenesis, concomitantly to the expression of adult tau isoforms. In control cultures and in cultures treated with colchicine, the phosphorylated tau was not associated to cold-stable and to colchicine-resistant microtubules. These in vivo results suggest that the high expression of phosphorylated tau species is correlated with the presence of a dynamic microtubule network during a period of high plasticity in the developing brain.
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PMID:Distribution of the phosphorylated microtubule-associated protein tau in developing cortical neurons. 789 84

The neuronal microtubule-associated protein tau has been implicated in the development of axonal morphology including the organization of microtubules into a uniformly oriented array of microtubules commonly referred to as "bundle." Determination of the functional organization of tau has revealed that regions of tau protein which flank the microtubule-binding domain affect the bundling of microtubules in vitro with a microtubule-binding fragment of tau being most effective [Brandt and Lee, 1993: J. Biol. Chem. 268:3414-3419]. In order to study the relation of microtubule bundles that form in vitro to those observed in the axon, we determined the orientation of individual microtubules in bundles and the effects of bundling on microtubule assembly and stability in cell-free assembly reactions. Here we report that bundles induced by a microtubule-binding fragment of tau contain randomly oriented microtubules as determined by using the difference in growth rates at microtubule plus and minus ends. We demonstrate that in vitro bundling increases microtubule growth (about 30%), stabilizes microtubules against dilution- and cold-induced disassembly, and allows microtubule nucleation despite the absence of a tau region which has previously been shown to be required for tau-dependent microtubule nucleation. We conclude that conditions that stabilize microtubules can lead to bundle formation and allow microtubule assembly by a mechanism different from that employed by microtubule-associated proteins. The data also support the view that additional mechanisms besides the action of tau and tubulin exist in order to organize microtubules in the axon.
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PMID:Orientation, assembly, and stability of microtubule bundles induced by a fragment of tau protein. 808 73

Quantitative blot immunolabeling techniques were used to compare the effect of cold water stress (CWS) on the phosphorylation of brain tau protein in two strains of C57BL/6J mice: ob/ob and ob/+. CWS induced immediate, significant (4-6 fold) and continuous accumulation of Alzheimer's like forms of tau phosphorylated at Ser 202. The effect was considerably (150-200%) higher in ob/ob mice compared to ob/+ mice. By contrast, the unphosphorylated tau immunoreactivity decreased after the CWS, whereas no changes were detected in the abundance of several other antigens. The level of anti Erk 1 + 2 immunoreactivity corresponding to 36-37 kDa polypeptide was 2-3 fold higher in ob/ob than in ob/+ mice. No strain differences were detected in the abundance of several other protein kinases. Obtained results support the hypothesis that Erk 1 or 2 like protein kinase may be involved in the restructuring of neuronal cytoskeleton in response to environmental stress.
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PMID:Stress-induced tau phosphorylation in mouse strains with different brain Erk 1 + 2 immunoreactivity. 982 Nov 59

We previously showed that starvation causes reversible hyperphosphorylation of tau in the mouse brain. To explore possible involvement of stress in tau hyperphosphorylation quantitative analysis of phosphorylated tau in four brain regions of mice subjected to cold water stress (CWS) was made by immunoblot analyses using phosphorylation-dependent antibodies directed to eight sites on tau known to be hyperphosphorylated in the brain of Alzheimer's disease (AD) patients. Ser199, Ser202/Thr205, Thr231/Ser235 were hyperphosphorylated 20 and 40 min after CWS. The response was pronounced in the hippocampus and cerebral hemisphere, but weak in the cerebellum in parallel with the regional vulnerability in AD. Among the regulatory phosphorylation of protein kinases studied, a transient phosphorylation of tau protein kinase I/glycogen synthase kinase 3beta at Ser9 was most conspicuous.
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PMID:Stress-induced hyperphosphorylation of tau in the mouse brain. 1256 Jan 1

The abnormal hyperphosphorylation of tau protein in brain is attributed to a number of neurodegenerative diseases such as Alzheimer disease. It has been reported that cold water stress (CWS) could cause rapid reversible tau phosphorylation in brain. To explore the possible long-tem effects of CWS on tau phosphorylation, we employed the immunoblot and immunohistochemical methods to analyze the phosphorylation of tau in the hippocampus of mice subjected to CWS. Results showed that CWS stimulation caused not only an early phase reversible tau phosphorylation, but also a later phase tau phosphorylation after 6h. The distribution pattern of phosphorylated tau (P-tau) in the later phase was different to that of early phase. At 1h after CWS, defined as early phase, P-tau was strikingly located in the mossy fibers and nerve terminals at the molecular layer of dentate gray (DG), whereas at 12h, defined as later phase, P-tau was dominantly located in the somatodendritic compartments of neurons in DG and CA3/CA1 regions, but obviously decreased in the mossy fibers and nerve terminals of molecular layer. These findings demonstrate that CWS leads to prominent changes of tau phosphorylation and P-tau localization in the hippocampus in a time dependent manner.
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PMID:Dynamic changes of phosphorylated tau in mouse hippocampus after cold water stress. 1600 67


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