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M Goedert

Publications and source records attributed to M Goedert.

At least 127 records · Page 7Linked to original sources
PubMed1994

Monoclonal antibody PHF-1 recognizes tau protein phosphorylated at serine residues 396 and 404.

The microtubule-associated protein tau is hyperphosphorylated in the paired helical filaments (PHFs) of Alzheimer's disease. Immunological and direct chemical studies have identified Ser396 and Ser404 as two of the phosphorylated sites. Previously, we have demonstrated, using synthetic tau peptides containing phosphorylated Ser396, that this site is recognized by the monoclonal antibody PHF-1. The present study extends this observation by showing that PHF-1 recognizes tau peptides containing either individually phosphorylated Ser396 or Ser404, but that there is a > 10-fold increase in the sensitivity of detection of tau peptides by PHF-1 when both serines are phosphorylated. The recognition of singly or doubly phosphorylated Ser396 and Ser404 in tau by PHF-1 can also be demonstrated in Chinese hamster ovary cells transfected with full-length wild-type tau constructs or mutant constructs with Ala substituted for Ser396 or Ser404. We conclude that the PHF-1 epitope contains both phosphorylated Ser396 and Ser404.

Alzheimer Disease↗
PubMed1994

Isoform-specific interactions of apolipoprotein E with the microtubule-associated protein MAP2c: implications for Alzheimer's disease.

The apolipoprotein E type 4 allele is a susceptibility gene for late-onset Alzheimer's disease. Apolipoprotein E is found in neurons, some of which contain paired helical filaments made of the microtubule-associated protein tau. Previous studies have demonstrated that the apoE3 isoform, but not the apoE4 isoform, binds tau with high avidity. Because the microtubule-associated protein MAP2c also effects microtubule assembly and stability, we examined interactions between apoE isoforms and MAP2c. Similar to the tau-binding results, apoE3, but not apoE4, bound MAP2c. Binding was detectable down to 10(-9) M MAP2c and 10(-8) M apoE3. Isoform-specific interactions of apoE with the microtubule-associated proteins MAP2c and tau might affect intracellular maintenance of microtubules and could contribute to a time-dependent pathogenesis of Alzheimer's disease.

Alzheimer Disease↗
PubMed1994

Isoform-specific interactions of apolipoprotein E with microtubule-associated protein tau: implications for Alzheimer disease.

The apolipoprotein E (apoE) type 4 allele (APOE4) is a susceptibility gene for late-onset familial and sporadic Alzheimer disease. ApoE is found in some neurofibrillary tangle-bearing neurons, one of the major pathologic hallmarks of the disease. Neurofibrillary tangles contain paired helical filaments formed from hyperphosphorylated microtubule-associated protein tau. In vitro, tau binds avidly to apoE3, but not to apoE4, forming a bimolecular complex. Tau phosphorylated with a brain extract does not bind either isoform. ApoE3 binds to the microtubule-binding repeat region of tau, which is also the region that is thought to cause self-assembly into the paired helical filament. Binding studies with fragments of ApoE demonstrate that the tau-binding region of apoE3 corresponds to its receptor-binding domain and is distinct from the region that binds lipoprotein particles or beta/A4 peptide. Isoform-specific interactions of apoE with tau may regulate intraneuronal tau metabolism in Alzheimer disease and alter the rate of formation of paired helical filaments and neurofibrillary tangles.

Alzheimer Disease↗
PubMed1994

Epitope mapping of monoclonal antibodies to the paired helical filaments of Alzheimer's disease: identification of phosphorylation sites in tau protein.

Tau is a neuronal phosphoprotein the expression of which is developmentally regulated. A single tau isoform is expressed in fetal human brain but six isoforms are expressed in adult human brain, with the fetal isoform corresponding to the shortest adult isoform. Phosphorylation is also developmentally regulated, as fetal tau is phosphorylated at more sites than adult tau. In Alzheimer's disease, the six adult tau isoforms become hyperphosphorylated and form the paired helical filament (PHF), the major fibrous component of the neurofibrillary lesions. One way to identify phosphorylated sites in tau is to use antibodies that recognize phosphorylated residues within a specific amino acid sequence. We here characterize the two novel phosphorylation-dependent anti-tau antibodies AT270 and AT180 and identify their epitopes as containing phosphorylated Thr-181 and Thr-231 respectively. With these antibodies we show that these two threonine residues are partially phosphorylated in fetal and adult tau and almost fully phosphorylated in PHF tau. This result contrasts with previous studies of Ser-202 and Ser-396 which are partially phosphorylated in fetal tau, unphosphorylated in adult tau but almost fully phosphorylated in PHF tau.

Alzheimer Disease↗
PubMed1994

Identification of two distinct synucleins from human brain.

Two abundant proteins of 140 and 134 amino acids were purified and sequenced from human brain. They were identified through their reactivity on immunoblots with a partially characterised monoclonal antibody that recognises tau protein in a phosphorylation-dependent manner. The 140 amino acid protein is identical with the precursor of the non-A beta component of Alzheimer's disease amyloid which in turn is highly homologous to synuclein from Torpedo electroplaques and rat brain. The 134 amino acid protein is the human homologue of bovine phosphoneuroprotein 14; it is 61% identical in sequence to the 140 amino acid protein. The previously unrecognised homology between these two proteins defines a family of human brain synucleins. We refer to the 140 and 134 amino acid proteins as alpha-synuclein and beta-synuclein, respectively. Both synucleins are expressed predominantly in brain, where they are concentrated in presynaptic nerve terminals.

Alzheimer Disease↗
PubMed1994

Assembly of Alzheimer-like filaments from full-length tau protein.

The principal fibrous component of neurofibrillary pathology in Alzheimer's disease, the paired helical filament, is formed from hyperphosphorylated microtubule-associated protein tau. Here we show that recombinant tau protein either in a non-phosphorylated state or following phosphorylation with brain extract can be assembled in vitro into filaments resembling those seen in Alzheimer's disease.

Alzheimer Disease↗
PubMed1994

Hypothesis: microtubule instability and paired helical filament formation in the Alzheimer disease brain are related to apolipoprotein E genotype.

A genetic classification of Alzheimer disease(s) (AD) is presented. We describe a potential metabolic process in individuals who inherit apolipoprotein E-epsilon 4 (APOE4, gene; apoE4, protein) alleles, leading to increased risk and earlier age of onset of late-onset Alzheimer disease. Apolipoprotein E-epsilon 3 (apoE3) binds to tau protein, possibly slowing the initial rate of tau phosphorylation and self-assembly into paired helical filaments (PHFs); apoE4 does not bind tau. Tau promotes microtubule assembly and stabilizes microtubules; hyperphosphorylated tau does not bind, thereby destabilizing microtubules. Hyperphosphorylated tau may self-assemble into PHFs. Over time a bias toward destabilization of microtubules and the formation of neurofibrillary tangles may occur in individuals who inherit APOE4 alleles, leading to a shorter functional neuronal life span. This hypothesis focuses attention on two important aspects of AD research design: (1) Although the inheritance of APOE4 is associated with increased risk and decreased age of onset, apoE4 does not directly cause the disease. Our data point to the absence of an important function of apoE3 or apoE2 in individuals who do not inherit these alleles as the genetically relevant metabolic factor. This has important implications for design of experiments directed toward understanding the relevant neuronal metabolism. (2) Should this hypothesis be proven and confirmed, targets for pharmaceutical therapy designed to mimic the metabolic function of apoE3 or apoE2 become a realistic preventive strategy.

Alzheimer Disease↗
PubMed1994

Regenerating sciatic nerve axons contain the adult rather than the embryonic pattern of microtubule associated proteins.

Microtubule associated proteins play a central role in the control of axon growth. We have used immunohistochemical techniques to establish which microtubule-associated proteins are present in the rat hindlimb spinal cord, dorsal root ganglia and peripheral nerves during axonal growth during embryogenesis, in adulthood, and during regeneration of crushed sciatic nerves. During embryogenesis microtubule-associated protein-1b and tau are present in all neurons and axons, microtubule-associated protein-2 is present in neurons but not in axons, and there is no microtubule-associated protein-1a. In adults, microtubule-associated protein-1a and microtubule-associated protein-1b are present in all sciatic nerve axons and in motor and dorsal root ganglion neurons. Tau, in its adult form, is present in many fine probably sensory axons, but not in most larger axons, and in motor and sensory neurons. Microtubule-associated protein-2 is present only in neurons. During regeneration the pattern of microtubule-associated protein expression retains the adult pattern. All regenerating axons contain microtubule-associated protein-1a and microtubule-associated protein-1b, none contain microtubule-associated protein-2, and a subset of fine axons contain tau. There is no detectable change in microtubule-associated protein expression by motoneurons. While axons are clearly able to regenerate without either microtubule-associated protein-2 or tau, tau containing axons appear to regenerate faster than those which lack it. It is possible that the failure of neurons to recapitulate the embryonic pattern of microtubule-associated protein expression during regeneration could be a reason why regenerative axon growth is slower and less vigorous than axon growth in embryos.

Animals↗
PubMed1993

The abnormal phosphorylation of tau protein at Ser-202 in Alzheimer disease recapitulates phosphorylation during development.

Tau is a neuronal phosphoprotein whose expression is developmentally regulated. A single tau isoform is expressed in fetal human brain but six isoforms are expressed in adult brain, with the fetal isoform corresponding to the shortest of the adult isoforms. Phosphorylation of tau is also developmentally regulated, as fetal tau is phosphorylated at more sites than adult tau. In Alzheimer disease, the six adult tau isoforms become abnormally phosphorylated and form the paired helical filament, the major fibrous component of the characteristic neurofibrillary lesions. We show here that Ser-202 (in the numbering of the longest human brain tau isoform) is a phosphorylation site that distinguishes fetal from adult tau and we identify it as one of the abnormal phosphorylation sites in Alzheimer disease. The abnormal phosphorylation of tau at Ser-202 in Alzheimer disease thus recapitulates normal phosphorylation during development.

Adult↗
PubMed1993

Tau proteins are abnormally expressed in olfactory epithelium of Alzheimer patients and developmentally regulated in human fetal spinal cord.

In pathological conditions, the microtubule-associated tau proteins may accumulate in neuronal perikarya or be expressed de novo in certain populations of neurons. For example, olfactory epithelium (OE) neurons in Alzheimer's disease (AD) patients express tau in their axons when these axons become dystrophic. In this study, we examined human postmortem olfactory tissue with a panel of tau antibodies that bind to epitopes located in subdomains spanning nearly the entire length of all six known isoforms of human CNS tau. In addition, the developing human spinal cord was probed with a similar panel of tau antibodies to determine whether or not fetal tau epitopes were reexpressed in the dystrophic OE neurites of AD patients. Electron microscopy was performed to examine the ultrastructure of the filaments present in these dystrophic OE neurites. We show here that all the tau epitopes examined are expressed in dystrophic OE neurites of AD patients, but that certain tau epitopes are preferentially expressed in the dystrophic neurites of AD. We also demonstrate that many of the epitopes present in the dystrophic neurites of AD are expressed early in the developing spinal cord and are later extinguished, including adult tau epitopes present in the brain. Finally, our EM studies reveal the presence within dystrophic OE neurites of approximately 10 to 15-nm-diameter filaments. These results suggest that the entire extent of multiple tau molecules is present in dystrophic OE neurites, with certain modifications of tau occurring preferentially in the dystrophic neurites of AD patients.

Aged↗
PubMed1993

Tau protein and the neurofibrillary pathology of Alzheimer's disease.

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 an abnormally phosphorylated state. PHF-tau is hyperphosphorylated on all six adult brain 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 involved in the abnormal phosphorylation of tau.

Alzheimer Disease↗
PubMed1993

Human tau isoforms confer distinct morphological and functional properties to stably transfected fibroblasts.

Tau protein is a neuronal microtubule-associated protein that promotes the assembly and stability of microtubules. To evaluate the biological significance of tau isoform diversity, NIH-3T3 cells were stably transfected with cDNAs encoding each of the six isoforms present in human brain. Cells expressing different isoforms developed distinct morphologies. Cell lines expressing 3-repeat tau isoforms developed large flat cell bodies while cells expressing 4-repeat isoforms had small, round cell bodies. All transfected cell lines, except those expressing the shortest tau isoform, displayed very long thin neurite-like processes. Tau colocalized with microtubules in both the cell body and the long processes in all of the tau-transfected cells. Tau also displayed a diffuse amorphous staining pattern that was concentrated around the cell nucleus. Microtubule bundling was not enhanced in any of the transfected cells as compared to untransfected controls. The transfected cells showed increased resistance to colchicine treatment. Thus, different tau isoforms can confer unique cellular morphologies to 3T3 cells and can alter the susceptibility of these cells to a microtubule depolymerizing agent.

3T3 Cells↗
PubMed1993

Abnormal tau phosphorylation at Ser396 in Alzheimer's disease recapitulates development and contributes to reduced microtubule binding.

Abnormally phosphorylated tau proteins (A68) are the building blocks of Alzheimer's disease (AD) paired helical filaments. The biological consequences of the conversion of normal adult tau to A68 remain unknown. Here we demonstrate that native A68 does not bind to microtubules (MTs), yet dephosphorylated A68 regains the ability to bind to MTs. Ser396 is phosphorylated in A68, but not in normal adult tau, whereas fetal tau is phosphorylated transiently at this site. Phosphorylation of tau at Ser396 by protein kinases in CHO cells and rat brain produces an electrophoretic mobility similar to that of A68. Using CHO cells transfected with an Ala396 mutant, we show that the phosphorylation of tau at Ser396 reduces its affinity for MTs and its ability to stabilize MTs against nocodazole-induced depolymerization. Our results demonstrate that the abnormal phosphorylation of tau in AD involves Ser396, and we suggest that this may be mediated by the inappropriate activation of fetal kinases or the reduced activity of tau protein phosphatases. Thus, phosphorylation of Ser396 may destabilize MTs in AD, resulting in the degeneration of affected cells.

Adult↗
PubMed1992

p42 MAP kinase phosphorylation sites in microtubule-associated protein tau are dephosphorylated by protein phosphatase 2A1. Implications for Alzheimer's disease [corrected].

The paired helical filament (PHF), which comprises the major fibrous element of the neurofibrillary tangle of Alzheimer's disease, is composed of abnormally phosphorylated microtubule-associated protein tau. Here we show that p42 MAP kinase phosphorylates recombinant tau and converts it to a form which is similar to PHF tau. Of the major serine/threonine protein phosphatases found in mammalian tissues only protein phosphatase 2A (PP2A) could dephosphorylate tau phosphorylated in this manner, with PP2A1 being the most effective form of the enzyme.

Brain↗
PubMed1992

The microtubule binding repeats of tau protein assemble into filaments like those found in Alzheimer's disease.

The paired helical filament, which comprises the major fibrous element of the neurofibrillary tangle in Alzheimer's disease, contains abnormally phosphorylated microtubule-associated protein tau as its principal constituent. The repeat region of tau protein, which represents the microtubule binding domain, forms the core of the filament. Here we show that an expressed fragment of tau protein spanning the repeat region can assemble in vitro into filaments like those found in Alzheimer's disease.

Alzheimer Disease↗
PubMed1992

The Alzheimer-like phosphorylation of tau protein reduces microtubule binding and involves Ser-Pro and Thr-Pro motifs.

Tau protein can be transformed into an Alzheimer-like state by phosphorylation with a kinase activity from brain [Biernat et al. (1992) EMBO J. 11, 1593-1597]. Here we show that the phosphorylation at Ser-Pro motifs strongly decreases tau's affinity for microtubules. The major reduction occurs during the first of the three main stages of phosphorylation. The data explain the lower stability of microtubules resulting from the pathological tau phosphorylation.

Alzheimer Disease↗
PubMed1992

Cloning of a big tau microtubule-associated protein characteristic of the peripheral nervous system.

Microtubule-associated protein tau consists in brain of a series of isoforms of 48- to 67-kDa apparent molecular mass that are encoded by mRNAs of approximately 6 kilobases (kb) and that are generated from a single gene by alternative splicing. Previously, a tau-like protein of 110-kDa apparent molecular mass was described in peripheral ganglia and in peripheral neuronlike cell lines. We now report the cloning and sequencing of a rat cDNA encoding this big tau. The corresponding protein contains sequence identical to the longest of the previously cloned small tau isoforms but with an additional 254 amino acid insert in the amino-terminal half. Big tau is produced from an 8-kb mRNA generated by alternative splicing from the same gene that encodes small tau. Production of big tau from the cloned sequence gives a protein of 110-kDa apparent molecular mass that aligns on SDS/PAGE with big tau protein extracted from peripheral ganglia. RNA blots show that in peripheral ganglia from adult rats only the 8-kb mRNA band corresponding to big tau is found, whereas in ganglia from newborn rats both 6- and 8-kb tau mRNA bands are found. In tissues from the central nervous system only the 6-kb mRNA band can be detected. Big tau protein is therefore produced specifically in the peripheral nervous system, and it will be interesting to see whether further molecular differences between the two major divisions of the vertebrate nervous system will be discovered.

Amino Acid Sequence↗