Prevalence of Submandibular Gland Synucleinopathy in Parkinson's Disease, Dementia with Lewy Bodies and other Lewy Body Disorders

How strong is the evidence that Parkinson's disease is a prion disorder?

PURPOSE OF REVIEW

We describe evidence supporting the hypothesis that α-synuclein has a prion-like role in Parkinson's disease and related α-synucleinopathies, and discuss how this novel thinking impacts the development of diagnostics and disease-modifying therapies.

RECENT FINDINGS

Observations that immature dopamine neurons grafted to Parkinson's disease patients can develop Lewy bodies triggered a surge of interest in the putative prion-like properties of α-synuclein. We recount results from experiments which confirm that misfolded α-synuclein can exhibit disease-propagating properties, and describe how they relate to the spreading of α-synuclein aggregates in α-synucleinopathies. We share insights into the underlying molecular mechanisms and their relevance to novel therapeutic targets. Finally, we discuss what the initial triggers of α-synuclein misfolding might be, where in the body the misfolding events might take place, and how this can instruct development of novel diagnostic tools. We speculate that differences in anatomical trigger sites and variability in α-synuclein fibril structure can contribute to clinical differences between α-synucleinopathies.

SUMMARY

The realization that α-synuclein pathology can propagate between brain regions in neurodegenerative diseases has deepened and expanded our understanding of potential pathogenic processes which can lead to the development of novel diagnostic tools as well as the identification of new therapeutic targets.

Parkinson's Disease: Assay of Phosphorylated α-Synuclein in Skin Biopsy for Early Diagnosis and Association with Melanoma

Parkinson's disease (PD) is a degenerative disorder of the central nervous system, in which a small naturally unfolded protein α-synuclein plays an essential role. α-Synuclein belongs to a synuclein family comprising three members: α, β, and γ-synucleins associated with neurodegenerative and neoplastic diseases and involved in development. Several studies revealed that α-synuclein is present not only in the brain, but also in the skin and other peripheral tissues. This finding open a new approach to PD diagnosis based on the assay of α-synuclein from a biological sample of a living patient. Furthermore, PD is associated with an increased risk of skin melanoma. An important posttranslational modification of α-synuclein is phosphorylation at serine-129, which may convert the protein into pathological species both in PD and melanoma. Thus, analysis of phosphorylated α-synuclein might be an important diagnostic test for both diseases providing additional information about the mechanism of pathology.