Michel Goedert

|[alpha]|-Synuclein in Lewy bodies

Lewy bodies, a defining pathological characteristic of Parkinsons disease and dementia with Lewy bodies (DLB), constitute the second most common nerve cell pathology, after the neurofibrillary lesions of Alzheimers disease. Their formation may cause neurodegeneration, but their biochemical composition is unknown. Neurofilaments and ubiquitin are present, but it is unclear whether they are major components of the filamentous material of the Lewy body,. Here we describe strong staining of Lewy bodies from idiopathic Parkinsons disease with antibodies for α-synuclein, a presynaptic protein of unknown function which is mutated in some familial cases of the disease. α-Synuclein may be the main component of the Lewy body in Parkinsons disease. We also show staining for α-synuclein of Lewy bodies from DLB, indicating that the Lewy bodies from these two diseases may have identical compositions.

Multiple isoforms of human microtubule-associated protein tau: sequences and localization in neurofibrillary tangles of Alzheimer's disease

We have determined the sequences of isoforms of human tau protein, which differ from previously reported forms by insertions of 29 or 58 amino acids in the amino-terminal region. Complementary DNA cloning shows that the insertions occur in combination with both three and four tandem repeats. RNAase protection assays indicate that transcripts encoding isoforms with the insertions are expressed in an adult-specific manner. Transcripts encoding four tandem repeats are also expressed in an adult-specific manner, whereas mRNAs encoding three tandem repeats are expressed throughout life, including in fetal brain. The levels of transcripts encoding the 29 or 58 amino acid inserts were not significantly changed in cerebral cortex from patients with Alzheimers disease. Antisera raised against synthetic peptides corresponding to these different human tau isoforms demonstrate that multiple tau protein isoforms are incorporated into the neurofibrillary tangles of Alzheimers disease.

Transmission and spreading of tauopathy in transgenic mouse brain

Hyperphosphorylated tau makes up the filamentous intracellular inclusions of several neurodegenerative diseases, including Alzheimers disease. In the disease process, neuronal tau inclusions first appear in the transentorhinal cortex from where they seem to spread to the hippocampal formation and neocortex. Cognitive impairment becomes manifest when inclusions reach the hippocampus, with abundant neocortical tau inclusions and extracellular β-amyloid deposits being the defining pathological hallmarks of Alzheimers disease. An abundance of tau inclusions, in the absence of β-amyloid deposits, defines Picks disease, progressive supranuclear palsy, corticobasal degeneration and other diseases. Tau mutations cause familial forms of frontotemporal dementia, establishing that tau protein dysfunction is sufficient to cause neurodegeneration and dementia. Thus, transgenic mice expressing mutant (for example, P301S) human tau in nerve cells show the essential features of tauopathies, including neurodegeneration and abundant filaments made of hyperphosphorylated tau protein. By contrast, mouse lines expressing single isoforms of wild-type human tau do not produce tau filaments or show neurodegeneration. Here we have used tau-expressing lines to investigate whether experimental tauopathy can be transmitted. We show that injection of brain extract from mutant P301S tau-expressing mice into the brain of transgenic wild-type tau-expressing animals induces assembly of wild-type human tau into filaments and spreading of pathology from the site of injection to neighbouring brain regions.

Alpha-synuclein and neurodegenerative diseases.

In recent years, two developments have imparted a new direction to research on the aetiology and pathogenesis of Parkinsons disease. First, the discovery that a missense mutation in the α-synuclein gene is a rare genetic cause of Parkinsons disease. Second, the identification of the α-synuclein protein as the main component of Lewy bodies and Lewy neurites, the defining neuropathological characteristics of all cases of Parkinsons and several other diseases. The filamentous inclusions of multiple system atrophy are also made of α-synuclein. These findings have placed α-synuclein dysfunction at the centre of several common neurodegenerative diseases. Here, I review the molecular properties of the synucleins, the different diseases characterized by the accumulation of α-synuclein, and the possible mechanisms by which dysfunction of α-synuclein might lead to neurodegeneration.

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 Alzheimers disease and Downs 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.

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‐Aβ component of Alzheimers 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 α‐synuclein and β‐synuclein, respectively. Both synucleins are expressed predominantly in brain, where they are concentrated in presynaptic nerve terminals.

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 Alzheimers 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.

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 Alzheimers 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.

Filamentous α-synuclein inclusions link multiple system atrophy with Parkinson's disease and dementia with Lewy bodies

α-Synuclein forms the major component of Lewy bodies and Lewy neurites, the defining neuropathological characteristics of Parkinsons disease and dementia with Lewy bodies. Here we show that α-synuclein is also the major component of the filamentous inclusions of multiple system atrophy which comprises several neurodegenerative diseases with a shared filamentous pathology in nerve cells and glial cells. These findings provide an unexpected link between multiple system atrophy and Lewy body disorders and establish that α-synucleinopathies constitute a major class of human neurodegenerative disorder.

GSK3 inhibitors: development and therapeutic potential

Glycogen synthase kinase-3 (GSK3) was initially identified more than two decades ago as an enzyme involved in the control of glycogen metabolism. In recent years it has been shown to have key roles in regulating a diverse range of cellular functions, which have prompted efforts to develop GSK3 inhibitors as therapeutics. Here, we describe the biology of GSK3 relevant to its potential as a target for diabetes and neurodegenerative diseases, and discuss progress in the development of GSK3 inhibitors.