Department of Pharmacology, Graduate School of Pharmaceutical Sciences, Kyoto University, Sakyo-ku, Kyoto, Japan
Department of Neurology, Graduate School of Medicine, Kyoto University, Shogoin, Sakyo-ku, Kyoto, Japan
Department of Cellular Pharmacology, Graduate School of Pharmaceutical Sciences, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Japan
Correspondence to: Toshiaki Kume, Ph.D., Department of Pharmacology, Graduate School of Pharmaceutical
Sciences, Kyoto University, 46-29 Yoshida-shimoadachi-cho, Sakyo-ku, Kyoto 606-8501, Japan. Tel.: +81 75 753
4576, Fax: +81 75 753 4579; E-mail: [email protected].
Abstract: Background: The formation of intracellular aggregates containing α-synuclein (α-syn) is a main pathological feature of Parkinson disease. The propagation of α-syn aggregation via cell-to-cell transmission has been implicated in the progression of Parkinson disease. Objective: Our aim is to clarify the molecular mechanisms underlying the formation of intracellular aggregation by extracellular α-syn. Methods: We investigated the effects of exogenous α-syn aggregates on intracellular α-syn immunoreactivity in α-syn-overexpressing SH-SY5Y cells using two antibodies to distinct epitopes of α-syn. To obtain α-syn aggregates, α-syn solution was aged with continuous agitation. Results: Immunoreactivity against the acidic C-terminal domain of the intracellular α-syn was reduced by exposure to agedα-syn, whereas that against the hydrophobic non-amyloid component region was not changed. The reduction in immunoreactivity was not suppressed by protease inhibitors but was mimicked by neutralization of the negative charges on the C-terminal of the intracellular α-syn induced by spermine or extracellular acidification. Conclusions: These results suggest that the reduction in immunoreactivity is attributed not to proteolytic cleavage but to a conformational change at the C-terminus of the intracellular α-syn. The conformational change at the C-terminus of the intracellular α-syn might be involved in an initial step of fibril formation by exogenous α-syn aggregates.