Accumulation of phosphorylated alpha-synuclein in the brain and peripheral ganglia of patients with multiple system atrophy.

We immunohistochemically examined the brain and peripheral sympathetic ganglia from eight patients with multiple system atrophy (MSA), using an antibody specific for phosphorylated alpha-synuclein (anti-PSer129). Phosphorylated alpha-synuclein was deposited in five cellular locations: oligodendroglial cytoplasm and nucleus, and neuronal cytoplasm, processes and nucleus. Many neuronal cytoplasmic inclusions (NCIs) were found in the pontine and inferior olivary nuclei and, to a lesser extent, in the substantia nigra, locus ceruleus, and neocortical and hippocampal neurons. NCIs were also found in the sympathetic ganglia in two out of the eight cases. Moreover, anti-PSer129 immunohistochemistry revealed extensive neuropil pathology; swollen neurites were abundant in the pontine nucleus, delicate neurites were observed in the deeper layers of the cerebral cortex and thalamus, and neuropil threads and dot-like structures were distributed in the basal ganglia and brainstem. Diffuse neuronal cytoplasmic staining (pre-NCI) was frequently found in the pontine and inferior olivary nuclei. Thus, the widespread accumulation of phosphorylated alpha-synuclein in both glial and neuronal cells is a pathological feature in patients suffering from MSA.

Alpha-synuclein accumulates in Purkinje cells in Lewy body disease but not in multiple system atrophy.

Alpha-synuclein has an important role in the pathogenesis of Parkinson disease (PD), dementia with Lewy bodies (DLB), and multiple system atrophy (MSA), comprising a new disease concept, that of alpha-synucleinopathies. Cerebellar degeneration with Purkinje cell depletion is present in the majority of MSA cases. By contrast, cerebellar pathology has not been demonstrated unequivocally in either PD or DLB. Recent immunohistochemical studies using anti-alpha-synuclein antibodies have shown that LB-type degeneration in PD and DLB is more widespread than previously recognized. To determine whether cerebellar Purkinje cells might be involved in alpha-synuclein pathology, we carried out immunohistochemical examinations of the cerebella of patients with PD (n = 10), DLB (n = 7), MSA (n = 10), Alzheimer disease and other tauopathies (n = 9), and age-matched control subjects (n = 10), using antibodies specific for alpha-synuclein. Although no abnormal accumulation of alpha-synuclein was noted in the Purkinje cell somata, numerous alpha-synuclein-positive, round inclusions were found in the cerebellar white matter in all the patients with PD and DLB. Immunohistochemical and ultrastructural examinations revealed that the majority of these inclusions was located in the Purkinje cell axons and consisted of granulo-filamentous structures. No such inclusions were observed in MSA, tauopathies, or controls. These findings indicate that Purkinje cells are also the victims of a-synuclein pathology in PD and DLB, but not in MSA.

Accumulation of phosphorylated alpha-synuclein in aging human brain.

Alpha-synuclein in Lewy bodies (LBs) is phosphorylated at Ser129. We raised monoclonal and polyclonal antibodies to this phosphorylation site (psyn) and examined 157 serial autopsy brains from a geriatric hospital. Anti-psyn immunoreactivity was observed in 40 of these cases (25.5%). Immunohistochemistry revealed 4 novel types of pathology: diffuse neuronal cytoplasmic staining (pre-LB); neuropil thread-like structures (Lewy threads); dot-like structures similar to argyrophilic grains (Lewy dots); and axons in the white matter (Lewy axons). This novel pathology was abundantly present around LBs and also involved the limbic subcortical white matter, the cerebral cortical molecular layer, and the spongiform changes of the medial temporal lobe associated with cases of dementia with LBs (DLB). The phosphorylated alpha-synuclein was limited to the temporal lobe in cases of Parkinson disease, spread from the temporal lobe to the frontal lobe in cases of DLB transitional form and further spread to the parietal and occipital lobes in DLB neocortical form. Our findings suggest that LB-related pathology initially involves the neuronal perikarya, dendrites, and axons, causes impairment of axonal transport and synaptic transmission, and later leads to the formation of LBs, a hallmark of functional disturbance long before neuronal cell death.

Phosphorylation of alpha-synuclein characteristic of synucleinopathy lesions is recapitulated in alpha-synuclein transgenic Drosophila.

alpha-Synuclein is a major component of Lewy bodies in the brains of patients with Parkinson's disease (PD) as well as of neuronal/glial inclusions in a subset of neurodegenerative disorders collectively termed synucleinopathies. Here we studied by immunohistochemistry the accumulation of alpha-synuclein in transgenic (TG) Drosophila overexpressing wild-type (WT) or familial PD-linked mutant (i.e. A30P and A53T) alpha-synuclein in neurons, with special reference to the phosphorylation at Ser129, that is characteristic of human synucleinopathy lesions. Progressive accumulation of human alpha-synuclein was widely observed in the cell bodies and neurites of major neuronal nuclei in TG Drosophila brains, and phosphorylation of alpha-synuclein at Ser129 was detected in a limited subset of neurons approximately 1 week after alpha-synuclein immunoreactivity was first detected. Phosphorylated alpha-synuclein was most abundant in A53T mutant, followed by A30P and WT Drosophila. These results suggest that accumulation and phosphorylation of alpha-synuclein is recapitulated in neurons of alpha-synuclein transgenic Drosophila, that underscores the relevance of this model to human synucleinopatheis.

Misfolded proteinase K-resistant hyperphosphorylated alpha-synuclein in aged transgenic mice with locomotor deterioration and in human alpha-synucleinopathies.

The pathological modifications of alpha-synuclein (alphaS) in Parkinson disease and related diseases are poorly understood. We have detected misfolded alphaS in situ based on the proteinase K resistance (PK resistance) of alphaS fibrils, and using specific antibodies against S129-phosphorylated alphaS as well as oxidized alphaS. Unexpectedly massive neuritic pathology was found in affected human brain regions, in addition to classical alphaS pathology. PK resistance and abnormal phosphorylation of alphaS developed with increasing age in (Thy1)-h[A30P] alphaS transgenic mice, concomitant with formation of argyrophilic, thioflavin S-positive, and electron-dense inclusions that were occasionally ubiquitinated. alphaS pathology in the transgenic mice was predominantly in the brainstem and spinal cord. Astrogliosis was found in these heavily affected tissues. Homozygous mice showed the same pathology approximately one year earlier. The transgenic mice showed a progressive deterioration of locomotor function. Thus, misfolding and hyperphosphorylation of alphaS may cause dysfunction of affected brain regions.

Phosphorylated alpha-synuclein is ubiquitinated in alpha-synucleinopathy lesions.

alpha-Synuclein is one of the major components of intracellular fibrillary aggregates in the brains of a subset of neurodegenerative disorders, including Parkinson's disease, dementia with Lewy bodies, multiple system atrophy, and Hallervorden-Spatz disease, which are referred to as alpha-synucleinopathies. We have shown previously (Fujiwara, H., Hasegawa, M., Dohmae, N., Kawashima, A., Masliah, E., Goldberg, M. S., Shen, J., Takio, K., and Iwatsubo, T. (2002) Nat. Cell Biol. 4, 160-164) that alpha-synuclein deposited in synucleinopathy brains is extensively phosphorylated at Ser-129 and migrates at 15 kDa. Here we examined the biochemical characteristics of the additional, higher molecular mass species of phosphorylated alpha-synuclein-positive polypeptides that also are recovered in the Sarkosyl-insoluble fraction of synucleinopathy and migrate at about 22 and 29 kDa. These 22 and 29 kDa bands were positive for three different anti-ubiquitin antibodies and comigrated perfectly with in vitro ubiquitinated alpha-synuclein that may correspond to mono- and diubiquitinated alpha-synuclein, respectively. Furthermore, cyanogen bromide cleavage of the 22 and 29 kDa polypeptides shifted the mobility to 19 and 26 kDa, respectively, and they retained immunoreactivity for both ubiquitin and alpha-synuclein. Finally, protein sequence analysis showed that the 19 kDa band contained two amino-terminal sequences of alpha-synuclein and ubiquitin. These results strongly suggest that phosphorylated alpha-synuclein is targeted to mono- and diubiquitination in synucleinopathy brains, which may have implications for mechanisms of these diseases.

Hyperphosphorylation and insolubility of alpha-synuclein in transgenic mouse oligodendrocytes.

(Oligodendro)glial cytoplasmic inclusions composed of alpha-synuclein (alpha SYN) characterize multiple system atrophy (MSA). Mature oligodendrocytes (OLs) do not normally express alpha SYN, so MSA pathology may arise from aberrant expression of alpha SYN in OLs. To study pathological deposition of alpha SYN in OLs, transgenic mice were generated in which human wild-type alpha SYN was driven by a proteolipid protein promoter. Transgenic alpha SYN was detected in OLs but no other brain cell type. At the light microscopic level, the transgenic alpha SYN profiles resembled glial cytoplasmic inclusions. Strikingly, the diagnostic hyperphosphorylation at S129 of alpha SYN was reproduced in the transgenic mice. A significant proportion of the transgenic alpha SYN was detergent insoluble, as in MSA patients. The histological and biochemical abnormalities were specific for the disease-relevant alpha SYN because control green fluorescent protein was fully soluble and evenly distributed throughout OL cell bodies and processes. Thus, ectopic expression alpha SYN in OLs might initiate salient features of MSA pathology.

alpha-Synuclein is phosphorylated in synucleinopathy lesions.

The deposition of the abundant presynaptic brain protein alpha-synuclein as fibrillary aggregates in neurons or glial cells is a hallmark lesion in a subset of neurodegenerative disorders. These disorders include Parkinson's disease (PD), dementia with Lewy bodies (DLB) and multiple system atrophy, collectively referred to as synucleinopathies. Importantly, the identification of missense mutations in the alpha-synuclein gene in some pedigrees of familial PD has strongly implicated alpha-synuclein in the pathogenesis of PD and other synucleinopathies. However, specific post-translational modifications that underlie the aggregation of alpha-synuclein in affected brains have not, as yet, been identified. Here, we show by mass spectrometry analysis and studies with an antibody that specifically recognizes phospho-Ser 129 of alpha-synuclein, that this residue is selectively and extensively phosphorylated in synucleinopathy lesions. Furthermore, phosphorylation of alpha-synuclein at Ser 129 promoted fibril formation in vitro. These results highlight the importance of phosphorylation of filamentous proteins in the pathogenesis of neurodegenerative disorders.