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      The synaptic pathology of α-synuclein aggregation in dementia with Lewy bodies, Parkinson’s disease and Parkinson’s disease dementia

      review-article
      Acta Neuropathologica
      Springer-Verlag
      α-Synuclein, Protein aggregates, Synapse, Neurodegeneration, Dendritic spines

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          Abstract

          Parkinson’s disease (PD) and dementia with Lewy bodies (DLB) are usually associated with loss of dopaminergic neurons. Loss of substantia nigra neurons and presence of Lewy body inclusions in some of the remaining neurons are the hallmark pathology seen in the final stages of the disease. Attempts to correlate Lewy body pathology to either cell death or severity of clinical symptoms, however, have not been successful. While the pathophysiology of the neurodegenerative process can hardly be explained by Lewy bodies, the clinical symptoms do indicate a degenerative process located at the presynapse resulting in a neurotransmitter deficiency. Recently it was shown that 90% or even more of α-synuclein aggregates in DLB cases were located at the presynapses in the form of very small deposits. In parallel, dendritic spines are retracted, whereas the presynapses are relatively preserved, suggesting a neurotransmitter deprivation. The same α-synuclein pathology can be demonstrated for PD. These findings give rise to the notion that not cell death but rather α-synuclein aggregate-related synaptic dysfunction causes the neurodegeneration. This opens new perspectives for understanding PD and DLB. If presynaptic α-synuclein aggregation, not neuronal loss, is the key issue of the neurodegenerative process, then PD and DLB may eventually be treatable in the future. The disease may progress via trans-synaptical spread, suggesting that stem cell transplants are of limited use. Future therapies may focus on the regeneration of synapses.

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          Most cited references106

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          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.
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            Inherent toxicity of aggregates implies a common mechanism for protein misfolding diseases.

            A range of human degenerative conditions, including Alzheimer's disease, light-chain amyloidosis and the spongiform encephalopathies, is associated with the deposition in tissue of proteinaceous aggregates known as amyloid fibrils or plaques. It has been shown previously that fibrillar aggregates that are closely similar to those associated with clinical amyloidoses can be formed in vitro from proteins not connected with these diseases, including the SH3 domain from bovine phosphatidyl-inositol-3'-kinase and the amino-terminal domain of the Escherichia coli HypF protein. Here we show that species formed early in the aggregation of these non-disease-associated proteins can be inherently highly cytotoxic. This finding provides added evidence that avoidance of protein aggregation is crucial for the preservation of biological function and suggests common features in the origins of this family of protein deposition diseases.
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              Aggregation of alpha-synuclein in Lewy bodies of sporadic Parkinson's disease and dementia with Lewy bodies.

              Lewy bodies (LBs) are hallmark lesions of degenerating neurons in the brains of patients with Parkinson's disease (PD) and dementia with Lewy bodies (DLB). Recently, a point mutation in the gene encoding the presynaptic alpha-synuclein protein was identified in some autosomal-dominantly inherited familial PD pedigrees, and light microscopic studies demonstrated alpha-synuclein immunoreactivity in LBs of sporadic PD and DLB. To characterize alpha-synuclein in LBs, we raised monoclonal antibodies (MAbs) to LBs purified from DLB brains and obtained a MAb specific for alpha-synuclein that intensely labeled LBs. Light and electron microscopic immunocytochemical studies performed with this MAb as well as other antibodies to alpha-and beta-synuclein showed that alpha-synuclein, but not beta-synuclein, is a component of LBs in sporadic PD and DLB. Western blot analyses of highly purified LBs from DLB brains showed that full-length as well as partially truncated and insoluble aggregates of alpha-synuclein are deposited in LBs. Thus, these data strongly implicate alpha-synuclein in the formation of LBs and the selective degeneration of neurons in sporadic PD and DLB.
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                Author and article information

                Contributors
                wjschulz@med.uni-goettingen.de , http://www.prionresearch.de
                Journal
                Acta Neuropathol
                Acta Neuropathologica
                Springer-Verlag (Berlin/Heidelberg )
                0001-6322
                1432-0533
                20 June 2010
                20 June 2010
                August 2010
                : 120
                : 2
                : 131-143
                Affiliations
                Prion and Dementia Research Unit, Department of Neuropathology, University Medical Center Göttingen, Robert-Koch-Str. 40, 37075 Göttingen, Germany
                Article
                711
                10.1007/s00401-010-0711-0
                2892607
                20563819
                632bf7de-e106-44d2-856d-9b4a0758b591
                © The Author(s) 2010
                History
                : 28 February 2010
                : 31 May 2010
                : 11 June 2010
                Categories
                Review
                Custom metadata
                © Springer-Verlag 2010

                Neurology
                α-synuclein,dendritic spines,protein aggregates,synapse,neurodegeneration
                Neurology
                α-synuclein, dendritic spines, protein aggregates, synapse, neurodegeneration

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