Mechanistic Studies of α-Synuclein Prion-Like Transmission in Disease Models

University Of Florida, Gainesville FL

Investigators

Abstract

Project Summary/Abstract: α-synuclein (αS) is an abundantly expressed neuronal protein which forms pathological inclusions in a spectrum of neurodegenerative diseases. Although αS inclusions are a commonality in Parkinson’s disease (PD), Lewy body Dementias (DLB), and Multiple System Atrophy (MSA), the cellular and regional distribution of pathological inclusions varies widely between diseases. Importantly, the progression of these diseases corresponds with the spread of αS pathology through the CNS. The progression of αS pathology requires the aggregation and propagation of αS inclusions, although the origins and mechanisms of this process are not well understood. Biochemical and ultrastructural studies of aggregates from human disease brains and prion-type αS propagation models have revealed distinct properties of αS in various disease contexts, lending to the hypothesis of disease strains. In this strain hypothesis, it is thought that the cell types and regions in which αS inclusions form imbue conformational distinctions to aggregates, leading to distinct pathological courses. Post-translational modifications (PTMs) can imbue distinct biochemical characteristics and represent a mechanism for generating disease strains. Of these PTMs, extensive cleavage of the acidic, carboxy (C)-terminal residues is a common modification to αS found in pathological inclusions and one that leads to increased aggregation of αS in vitro. In mouse models seeded with human disease brain extracts, the abundance of αS pathology and specific C-terminally cleaved αS rich pathology reveals differences in disease strains. Our lab has generated a large panel of αS antibodies, including those to C-terminally cleaved αS, which show the heterogeneous nature of αS pathology in both LBD and MSA. Most notably, we have found populations of neuronal pathology in the pons of MSA brains which is distinct from the predominant oligodendrocytic pathology that defines MSA. αS in the CNS is primarily expressed in neurons, and therefore newfound neuronal pathology represents a point of origin for the broader oligodendrocytic pathology in MSA. The connection between affected cell types, patterns of C-terminal cleavage, and the potency of tissue-derived seeds is not understood. For this reason, the present study will leverage the seeding properties of human brain-derived and recombinant αS aggregates to study seeding dynamics in mouse lines that express human αS and which have a known disease phenotype. Aim 1 will compare seeding using brain extracts from the pons or cerebellum from MSA cases, distinguishing their seeding activity immunohistochemically with a panel of novel, truncation-specific antibodies. Aim 2 will investigate the differential seeding properties of synthetic αS fibrils comprised of specific disease- relevant C-terminally truncated forms of αS compared to that of full-length αS. These studies will provide insight into the pathogenesis of αS related diseases, differentiating regional pathology, and exploring C-terminal truncation of αS as a disease mechanism.