Microtubule Depolymerization Suppresses α-Synuclein Accumulation in a Mouse Model of Multiple System Atrophy

Abstract

Multiple system atrophy (MSA) is a neurodegenerative disease caused by an accumulation of ␣-synuclein (␣-syn) in oligodendrocytes. Little is known about the cellular mechanisms by which ␣-syn accumulation causes neuronal degeneration in MSA. Our previous research, however, revealed that in a mouse model of MSA, oligodendrocytic inclusions of ␣-syn induced neuronal accumulation of ␣-syn, as well as progressive neuronal degeneration. Here we identify the mechanisms that underlie neuronal accumulation of ␣-syn in a mouse MSA model. We found that the ␣-syn protein binds to ␤-III tubulin in microtubules to form an insoluble complex. The insoluble ␣-syn complex progressively accumulates in neurons and leads to neuronal dysfunction. Furthermore, we demonstrated that the neuronal accumulation of insoluble ␣-syn is suppressed by treatment with a microtubule depolymerizing agent. The underlying pathological process appeared to also be inhibited by this treatment , providing promise for future therapeutic approaches.

β-III Tubulin Fragments Inhibit α-Synuclein Accumulation in Models of Multiple System Atrophy

“…The exogenous ␣-syn in oligodendrocytes was of human origin, and the endogenous ␣-syn in neurons was of mouse origin in the mouse CNS. These Tg mice not only recapitulated many features of MSA neuropathology but also provided evidence that formation of GCIs triggers neuronal accumulation of insoluble ␣-syn, leading to neuronal dysfunction and degeneration in the mouse CNS (10,12,13). This is consistent with the neuronal pathology in the human pathology of MSA (14).…”

“…resulted in the formation of an insoluble protein complex that progressively accumulated in the neurites of Tg neurons, leading to neuronal dysfunction (12). Furthermore, we demonstrated that accumulation of insoluble ␣-syn was suppressed by a microtubule-depolymerizing agent, indicating that free ␤-III tubulin-␣-syn molecules are less prone to inclusion formation (12,16).…”

“…Furthermore, we demonstrated that accumulation of insoluble ␣-syn was suppressed by a microtubule-depolymerizing agent, indicating that free ␤-III tubulin-␣-syn molecules are less prone to inclusion formation (12,16). Although the binding of neuronal ␣-syn to ␤-III tubulin is a key pathogenic process in the MSA mouse model, it is still unclear whether and how ␣-syn binds to ␤-III tubulin in patients with MSA.…”

“…Anti-␣-synuclein Antibodies-syn4469 is a polyclonal antibody raised against mouse ␣-syn that selectively recognizes a mouse ␣-syn epitope between amino acid (aa) residues 115 and 125 (12). To generate an antibody specific to human ␣-syn, a synthetic peptide corresponding to the human wild-type ␣-syn aa 100 -110 (LGKNEEGAPQE) was conjugated with keyhole limpet hemocyanin and used to immunize rabbits.…”

“…Primary cultures of neurons and glial cells were prepared as described previously (12,15). Briefly, cerebral cortices were dissected from P0 to P1 Tg mice and dissociated.…”