Extracellular vesicles contain filamentous alpha-synuclein and facilitate the propagation of Parkinson's pathology

Parkinson's disease (PD) is characterized by the pathological deposition of a-synuclein (a-syn) inclusions, known as Lewy bodies/neurites. Emerging evidence suggests that extracellular vesicles (EVs) play a role in facilitating the spreading of Lewy pathology between the peripheral nervous system and the central nervous system. We analyzed serum EVs obtained from patients with PD (n = 142), multiple system atrophy (MSA) (n = 18), progressive supranuclear palsy (PSP) (n = 28), rapid eye movement sleep behavior disorder (n = 31), and controls (n = 105). While we observed a significant reduction in the number of EVs in PD compared to controls (p = 0.006), we also noted a substantial increase in filamentous α-synuclein within EVs in PD compared to controls (p < 0.0001), MSA (0.012), and PSP (p = 0.03). Further analysis unveiled the role of EVs in facilitating the transmission of filamentous α-synuclein between neurons and from peripheral blood to the CNS. These findings highlight the potential utility of serum α-synuclein filaments within EVs as diagnostic markers for synucleinopathies and underscore the significance of EVs in promoting the dissemination of filamentous α-synuclein throughout the entire body.

Analysis of α-Synuclein in Exosomes

Alpha synuclein (α-Syn), a presynaptic protein with unknown function, is accumulated in Lewy bodies/neurites that are one of the hallmark pathologies of Parkinson's disease (PD). Missense or multiplication mutations in SNCA, which codes α-Syn, result in a genetic form of PD, further indicating the involvement of α-Syn in PD pathogenesis. Recent pathological and experimental studies suggest that α-Syn possesses a secretory feature, as it is detected in the culture media, in the cerebrospinal fluid, and even in the blood. Secreted α-Syn can spread throughout the body and invade the CNS, disseminating the α-Syn associated pathology. Exosomes are small extracellular vesicles that carry many proteins, lipids, or miRNA. We and others have discovered α-Syn in exosomes and revealed that exosomes may regulate intracellular α-Syn levels by transporting outside the cells. In this chapter, we describe a protocol to measure α-Syn levels in exosomes.