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M Goedert

Publications and source records attributed to M Goedert.

At least 145 records · Page 8Linked to original sources
PubMed1992

The switch of tau protein to an Alzheimer-like state includes the phosphorylation of two serine-proline motifs upstream of the microtubule binding region.

The paired helical filaments (PHFs) of Alzheimer's disease consist mainly of the microtubule-associated protein tau. PHF tau differs from normal human brain tau in that it has a higher Mr and a special state of phosphorylation. However, the protein kinase(s) involved, the phosphorylation sites on tau and the resulting conformational changes are only poorly understood. Here we show that a new monoclonal antibody, AT8, records the PHF-like state of tau in vitro, and we describe a kinase activity that turns normal tau into a PHF-like state. The epitope of AT8 is around residue 200, outside the region of internal repeats and requires the phosphorylation of serines 199 and/or 202. Both of these are followed by a proline, suggesting that the kinase activity belongs to the family of proline-directed kinases. The epitope of AT8 is nearly coincident with that of another phosphorylation-dependent antibody, TAU1 [Binder, L.I., Frankfurter, A. and Rebhun, L. (1985) J. Cell Biol., 101, 1371-1378], but the two are complementary since TAU1 requires a dephosphorylated epitope.

Alzheimer Disease↗
PubMed1992

Tau proteins of Alzheimer paired helical filaments: abnormal phosphorylation of all six brain isoforms.

Preparations of dispersed paired helical filaments (PHFs) from the brains of Alzheimer's disease and Down's syndrome patients display on gels three principal bands corresponding to abnormally modified forms of the microtubule-associated protein tau. Interpretation of the pattern is difficult because there are six tau isoforms in normal brain and phosphorylation changes their mobility. By enzymatic dephosphorylation at high temperature, we have shifted the three abnormal bands obtained from dispersed PHFs to align with the six nonphosphorylated tau isoforms. By using antibodies specific for some of the inserts that distinguish the various isoforms and label PHFs, we have established a correspondence between PHFs, abnormal bands, and isoforms. This identification of isoforms is a necessary step in unravelling the molecular pathogenesis of PHFs.

Aged↗
PubMed1992

Construction and characterization of a yeast artificial chromosome library containing 1.5 equivalents of human chromosome 21.

A library of yeast artificial chromosomes (YACs) was constructed from a human/hamster somatic cell hybrid containing human chromosome 21 (q11-qter). Cells were embedded in agarose, and the DNA was partially digested with EcoRI, released into solution by agarase treatment of the agarose plugs, ligated into pYAC4, and transferred into yeast. Double screening of the yeast transformants with human and hamster genomic DNA allowed the selection of clones hybridizing only with human DNA. The library consists of 321 clones, amounting to 1.5 equivalents (61 Mb) of chromosome 21. The mean YAC size calculated from 178 clones is 190 +/- 100 kb. Screening of the library with eight sequence-tagged sites gave six positives. Among 21 YACs tested by in situ hybridization, 17 mapped to chromosome 21.

Animals↗
PubMed1991

Use of a heat-stable microtubule-associated protein class-specific antibody to investigate the mechanism of microtubule binding.

Members of the heat-stable family of microtubule-associated proteins (MAPs), MAP 2, tau, and MAP 4, contain three or four tandem imperfect repeated sequences close to their carboxyl termini. These sequences lie within the microtubule-binding domains of the MAPs; they have been proposed to be responsible for microtubule binding and the ability of these MAPs to lower the critical concentration for microtubule assembly. Their spacing may reflect that of the regularly arrayed tubulin subunits on the microtubule surface. We here characterize the 32- and 34-kDa chymotryptic microtubule-binding fragments of MAP 2 identified in earlier work. We identify the primary chymotryptic cleavage site in high molecular weight MAP 2 as between Phe1525 and Lys1526, within 13 amino acids of the known MAP 2 splice junction. We have raised a monoclonal antibody to the 32- and 34-kDa fragments and find that it reacts with all members of the heat-stable MAPs class. To determine where it reacts, we sequenced immunoreactive subfragments of the 32- and 34-kDa fragments, selected several cDNA clones with the antibody, and tested for antibody reactivity against a series of synthetic MAP 2 and tau peptides. We identify the epitope sequence as HHVPGGG (His-His-Val-Pro-Gly-Gly-Gly). The antibody also recognized several other MAP 2 and tau repeats. Despite reacting with this highly conserved element, we find that the antibody does not block microtubule binding, but binds to the MAPs and co-sediments with microtubules. These results suggest that there are other regions besides the repeated elements which are essential for microtubule binding.

Amino Acid Sequence↗
PubMed1991

Localization of the Alz-50 epitope in recombinant human microtubule-associated protein tau.

Alz-50 is a monoclonal antibody that stains the neurofibrillary pathology of Alzheimer's disease, as well as apparently normal nerve cells that are at risk of developing neurofibrillary tangles. On immunoblots it recognizes microtubule-associated protein tau and proteins of 60-68 kDa that are associated with Alzheimer's disease. We have used recombinant tau proteins expressed in E. coli to map the Alz-50 epitope to amino-terminal residues 2-10, a region common to all known human tau isoforms. A direct correspondence between immunoblots and histological staining was established by the abolition of Alz-50 staining following adsorption with recombinant tau proteins retaining amino-terminal sequences. This suggests that tau pathology represents an early event in the development of the neurofibrillary pathology of Alzheimer's disease.

Aged↗
PubMed1991

Molecular characterization of microtubule-associated proteins tau and MAP2.

Tau and MAP2 are two of the major microtubule-associated proteins in the vertebrate nervous system. They promote microtubule assembly and stability, and might be involved in the establishment and maintenance of neuronal polarity. In nerve cells immunohistochemistry shows complementary distributions, with tau being concentrated in axons and high molecular mass MAP2 being confined to dendrites. Each protein consists of multiple isoforms that contain three or four homologous tandem repeats near the carboxy-terminus, which constitute microtubule-binding domains. In humans, tau consists of at least six isoforms of related amino acid sequences that are produced from a single gene by alternative mRNA splicing and that are expressed in a stage- and cell type-specific manner. Tau is also a component of the paired helical filaments associated with Alzheimer's disease and other disorders of the CNS. Rat MAP2 consists of at least three isoforms produced from a single gene: high molecular mass MAP2a and MAP2b, and low molecular mass MAP2c. MAP2c is expressed only during early development and has so far been seen only in axons; MAP2a appears to replace MAP2c, whereas MAP2b is expressed throughout life. Messenger RNAs for MAP2 of high molecular mass are expressed both in cell bodies and in dendrites, consistent with the dendritic localization of the corresponding protein isoforms.

Amino Acid Sequence↗
PubMed1991

Neurofibrillary tangles and beta-amyloid deposits in Alzheimer's disease.

Alzheimer's disease is characterized by the presence of abundant neurofibrillary tangles and beta-amyloid deposits in neocortex, hippocampus and amygdala. The major protein components of tangles and plaques have recently been identified. These findings, briefly reviewed here, will allow researchers to design investigations that will lead to an understanding of the pathogenesis of the disease and to the development of new therapeutic approaches that may result in an effective treatment.

Alzheimer Disease↗
PubMed1991

Tau proteins and neurofibrillary degeneration.

The paired helical filament is the major fibrous component of neurofibrillary pathology in Alzheimer's disease. Over the last three years evidence has accumulated that the microtubule-associated protein tau forms an important, if not the sole, constituent of the paired helical filament. Tau protein in normal brain is bound to axonal microtubules by a tandem repeat region. In Alzheimer's disease a proportion of tau protein becomes abnormally phosphorylated and is no longer associated with axonal microtubules but instead accumulates in paired helical filaments throughout affected nerve cells. The tandem repeat region contributes substantially to the structural core of the paired helical filament, around which the amino-terminal half of the molecule forms a disordered coat.

Alzheimer Disease↗
PubMed1990

Molecular structure of microtubule-associated protein 2b and 2c from rat brain.

Full length cDNA clones encoding microtubule-associated proteins (MAP) 2b and 2c from rat brain have been isolated and sequenced. The cDNA fragments spanning the coding regions for both MAP2b and MAP2c were assembled and expressed in Escherichia coli. The mobility of these bacterial expressed proteins in sodium dodecyl sulfate gels is identical to that of MAP2b and MAP2c from rat brain. The protein sequence of rat MAP2b has been compared to the full length sequence from mouse and the partial sequence from human high molecular weight MAP2. This comparison has revealed that MAP2b is composed of several highly conserved domains flanked by domains with extensive sequence divergence. Two of the conserved domains, found either at the NH2 or COOH terminus, overlap with the binding domain for the regulatory subunit of the cAMP-dependent protein kinase II and the microtubule-binding domain, respectively. A third homologous domain of unknown function lies in a central region of MAP2b. Secondary structure prediction suggests that the portion of MAP2b which extends from the microtubule surface is composed of an extensive number of alpha-helices separated by small turns which may account for the extended yet flexible structure of MAP2. Interestingly, the 4000-base pair deletion from the middle of MAP2b which generates MAP2c not only removes these helices, but also this third highly conserved MAP2b domain.

Amino Acid Sequence↗
PubMed1990

The mas oncogene as a neural peptide receptor: expression, regulation and mechanism of action.

The human mas oncogene, which renders transfected NIH/3T3 cells tumorigenic, was identified as a subtype of angiotensin receptor by transient expression in Xenopus oocytes and stable expression in the mammalian neuronal cell line, NG115-401L. The mas receptor preferentially recognizes angiotensin III, and is expressed at high levels in brain. The mas/angiotensin receptor functions through the breakdown of inositol lipids and can drive DNA synthesis, unlike another inositol-linked peptide receptor, that for bradykinin. Comparative analysis of several early biochemical events elicited by either angiotensin or bradykinin stimulation of mas-transfected cells has not indicated a specific difference correlated with mitogenic activity. In particular, the inositol lipid kinase, phosphatidylinositol-3-kinase, thought to be involved in the mitogenic mechanism of platelet-derived growth factor receptors, is unaffected by activation of mas. These results have shown that a proto-oncogene encodes a neural peptide receptor, indicating that peptide receptors may be involved in differentiation and proliferation processes, as are other identified proto-oncogenes.

Amino Acid Sequence↗
PubMed1990

Phosphorylation of microtubule-associated protein tau: identification of the site for Ca2(+)-calmodulin dependent kinase and relationship with tau phosphorylation in Alzheimer tangles.

The microtubule array in neuronal cells undergoes extensive growth, dynamics and rearrangements during neurite outgrowth. While little is known about how these changes are regulated, microtubule-associated proteins (MAPs) including tau protein are likely to perform an important role. Tau is one of the MAPs in mammalian brain. When isolated it is usually a mixture of several isoforms containing between 341 and 441 residues that arise from alternative splicing. Tau can be phosphorylated by several protein kinases. Phosphorylation at certain sites results in major structural and functional changes, as seen by changes in electrophoretic mobility, interaction with microtubules, molecular length and elasticity. Here we show that the sites of phosphorylation by four kinases (PKA, PKC, CK and CaMK) all lie in the C-terminal microtubule-binding half of tau, but only the phosphorylation by CaM kinase shows the pronounced shift in electrophoretic mobility characteristic for tau from Alzheimer neurofibrillary tangles. By using a combination of limited proteolysis, protein sequencing and protein engineering we show that a single phosphorylation site is responsible for this shift, located at Ser 405 in the C-terminal tail of the protein outside the region of internal repeats. Phosphorylation at this site not only reduces the electrophoretic mobility of tau, it also makes the protein long and stiff, as shown earlier. The site is likely to be phosphorylated in tau from Alzheimer neurofibrillary tangles.

Alzheimer Disease↗
PubMed1990

Expression of separate isoforms of human tau protein: correlation with the tau pattern in brain and effects on tubulin polymerization.

We have expressed six previously cloned isoforms of human microtubule-associated tau protein in Escherichia coli and purified them to homogeneity in a biologically active form. They range from 352 to 441 amino acids in length and differ from each other by the presence of three or four tandem repeats in the carboxy-terminal half and by the presence or absence of 29 or 58 amino acid inserts in the amino-terminus. When mixed together they gave a set of six bands on SDS-PAGE gels with apparent molecular weights of 48-67 kd and with a characteristic pattern of spacings. Four of these bands aligned with the major tau bands found in adult human cerebral cortex following perchloric acid extraction and alkaline phosphatase treatment. They consisted of isoforms with three repeats and no insertions, four repeats and no amino-terminal insertions and three- and four-repeat containing isoforms with the 29 amino acid insertion. In fetal human brain extracts treated with alkaline phosphatase one of the two major tau bands aligned with the three-repeat containing isoform with no insertions, whereas the molecular nature of the second major tau band remains to be established. The recombinant tau isoforms were biologically active at micromolar concentrations, as assessed by their ability to promote microtubule assembly. The rates of assembly were 2.5-3.0 times faster for isoforms containing four repeats when compared with three-repeat containing isoforms, with no significant contribution by the amino-terminal insertions.

Aged↗
PubMed1990

Molecular neuropathology of Alzheimer's disease: in situ hybridization studies.

1. Abundant senile plaques and neurofibrillary tangles in certain brain regions constitute the major neuropathological characteristics of Alzheimer's disease. Recent work has established that the amyloid beta protein, which is derived from a large precursor, constitutes the major constituent of plaque amyloid, whereas the microtubule-associated protein tau is a component of the paired helical filament, the major constituent of neurofibrillary tangles. 2. Multiple isoforms of amyloid beta protein precursor and tau protein are produced from a single gene through alternative RNA splicing. By Northern blotting amyloid beta protein precursor transcripts are found throughout central and peripheral tissues, whereas tau protein transcripts are only found in the nervous system. 3. In the central nervous system the cellular localization of amyloid beta protein precursor and tau protein transcripts is neuronal. The cells affected in Alzheimer's disease patients produce both types of transcripts; however, the various transcripts are also found in cells not affected in the course of the disease. At present, there exists no evidence to suggest that an overproduction of amyloid beta protein precursor or tau protein is the reason for plaque and tangle formation. The formation of the latter probably results from posttranslational events.

Alzheimer Disease↗
PubMed1990

Different configurational states of beta-amyloid and their distributions relative to plaques and tangles in Alzheimer disease.

Antibodies have been raised against synthetic peptides corresponding to different parts of the beta-amyloid sequence. These antibodies stain different kinds of amyloid distributions in the hippocampal formation in Alzheimer disease, suggesting the existence of different states of aggregation and/or folding of beta-amyloid molecules. An antibody directed against the middle region of beta-amyloid stained mostly amyloid plaques without cores, whereas an antibody directed against the carboxyl-terminal region of beta-amyloid stained only amyloid plaques with cores. An antiserum directed against the amino terminus of beta-amyloid stained numerous tangle-bearing cells and bodies, as well as the neuritic component of plaques and neuropil threads. These antibodies, in conjunction with anti-tau antibodies, were used to demonstrate a close spatial relationship between amyloid deposits and neurofibrillary tangles.

Alzheimer Disease↗
PubMed1990

Topographical relationship between beta-amyloid and tau protein epitopes in tangle-bearing cells in Alzheimer disease.

Double-labeling immunohistochemistry was used to investigate the topographical relationship between beta-amyloid and tau protein epitopes present in cells bearing neurofibrillary tangles found in the hippocampal formation of patients with Alzheimer disease. An antiserum raised against the amino terminus of beta-amyloid stained numerous tangle-bearing cells and other bodies ("extracellular tangles"), but double labeling showed that the beta-amyloid staining is invariably peripheral to that of the tau-positive tangle proper. This and other results suggest that the extracellular amyloid plaques and the intracellular neurofibrillary tangles are biochemically distinct but may result from related pathological events that originate at the level of the nerve cell and lead to its degeneration.

Alzheimer Disease↗
PubMed1989

Distribution of beta-nerve growth factor receptors in the human basal forebrain.

The distribution of neurons expressing the receptor for beta-nerve growth factor has been examined immunohistochemically in serial coronal sections of basal forebrain from aged normal human subjects. Neurons expressing the receptor were observed in the nucleus of the diagonal band of Broca and in the anterior, the intermediate, and the posterior portions of the nucleus basalis of Meynert. Neurons could also be seen in the medial septal nucleus and embedded in myelinated fibre tracts such as those of the external capsule, cingulum, medullary laminae of the globus pallidus, ansa penduncularis, ansa lenticularis, and anterior commissure. In situ hybridization with a 35S cDNA probe to the human beta-nerve growth factor receptor confirms a neuronal location as the site of synthesis of beta-nerve growth factor receptors in the nucleus basalis of Meynert in a fifth brain. A high percentage of Nissl-stained hyperchromic magnocellular neurons expressed the receptor for beta-nerve growth factor, suggesting that most neurons in the human cholinergic magnocellular basal forebrain system express these receptors. Recent data suggest that beta-nerve growth factor functions as a neurotrophic factor in basal forebrain cholinergic neurons. In Alzheimer's disease there is known to be a reduction in cholinergic function and an apparent loss of neurons in the cholinergic nucleus basalis of Meynert. For this reason we have examined the distribution of receptors for beta-nerve growth factor in the normal human basal forebrain in order to form a basis for comparison to those with Alzheimer's disease.

Aged↗
PubMed1989

Cloning and sequencing of the cDNA encoding an isoform of microtubule-associated protein tau containing four tandem repeats: differential expression of tau protein mRNAs in human brain.

We have isolated cDNA clones encoding a 383-amino acid isoform of the human microtubule-associated protein tau. It differs from previously determined tau sequences by the presence of an additional repeat of 31 amino acids, giving four, rather than three, tandem repeats in its carboxy-terminal half. The extra repeat is encoded by a separate exon. Probes derived from cDNA clones encoding the three (type I) and four repeat (type II) tau protein isoforms detected mRNAs for both forms in all adult human brain areas examined. However, in foetal brain only type I mRNA was found. Type I and type II mRNAs were present in pyramidal cells in cerebral cortex. In the hippocampal formation, type I mRNA was found in pyramidal and granule cells; type II mRNA was detected in most, though not all, pyramidal cells but not in granule cells. These observations indicate that tau protein mRNAs are expressed in a stage- and cell-specific manner. Tau protein is found in the protease-resistant core of the paired helical filament, the major constituent of the neurofibrillary tangle in Alzheimer's disease. Taken in conjunction with previous findings, the present results indicate that both the three and four repeat-containing tau protein isoforms are present in the core of the paired helical filament.

Amino Acid Sequence↗