title: Dequalinium-induced protofibril formation of alpha-synuclein.
abstract: alpha-Synuclein is the major constituent of Lewy bodies, a pathological signature of Parkinson disease, found in the degenerating dopaminergic neurons of the substantia nigra pars compacta. Amyloidosis generating the insoluble fibrillar protein deposition has been considered to be responsible for the cell death observed in the neurodegenerative disorder. In order to develop a controlling strategy toward the amyloid formation, 1,1'-(1,10-decanediyl)-bis-[4-a-mino-2-methylquinolinium] (dequalinium), was selected and examined in terms of its specific molecular interaction with alpha-synuclein. The protein was self-oligomerized by dequalinium, which gave rise to the ladder formation on N-[2-hydroxy-1,1-bis(hydroxymethyl)ethyl]glycine/SDS-PAGE in the presence of a coupling reagent of N-(ethoxycarbonyl)-2-ethoxy-1,2-dihydroquinoline. The double-headed structure of dequalinium with the two cationic 4-aminoquinaldinium rings was demonstrated to be critical for the protein self-oligomerization. The dequalinium-binding site was located on the acidic C-terminal region of the protein with an approximate dissociation constant of 5.5 mum. The protein self-oligomerization induced by the compound has resulted in the protofibril formation of alpha-synuclein before it has developed into amyloids. The protofibrils were demonstrated to affect the membrane intactness of liposomes, and they have also been shown to influence cell viability of human neuroblastoma cells. In addition, dequalinium treatment of the alpha-synuclein-overexpressing cells exerted a significant cell death. Therefore, it is pertinent to consider that dequalinium could be used as a molecular probe to assess toxic mechanisms related to the amyloid formation of alpha-synuclein. Ultimately, the compound could be employed to develop therapeutic and preventive strategies toward alpha-synucleinopathies including Parkinson disease.
authors.affiliation: School of Chemical and Biological Engineering, College of Engineering, Seoul National University, San 56-1, Shillim-Dong, Kwanak-Ku, Seoul 151-744, Korea.
authors.forename: Choong-Hwan
authors.initials: CH
authors.lastname: Lee
authors.forename: Hyun Jin
authors.initials: HJ
authors.lastname: Kim
authors.forename: Jung-Ho
authors.initials: JH
authors.lastname: Lee
authors.forename: Hyun-Ju
authors.initials: HJ
authors.lastname: Cho
authors.forename: Jongsun
authors.initials: J
authors.lastname: Kim
authors.forename: Kwang Chul
authors.initials: KC
authors.lastname: Chung
authors.forename: Seunho
authors.initials: S
authors.lastname: Jung
authors.forename: Seung R
authors.initials: SR
authors.lastname: Paik
mesh_terms: D000682:Amyloid / Q000737:chemistry; D000891:Anti-Infective Agents, Local / Q000494:pharmacology*; D001665:Binding Sites; D002412:Cations; D016923:Cell Death; D045744:Cell Line, Tumor; D002470:Cell Survival; D002942:Circular Dichroism; D003650:Decamethonium Compounds / Q000494:pharmacology; D003868:Dequalinium / Q000494:pharmacology*; D004591:Electrophoresis, Polyacrylamide Gel; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D008081:Liposomes / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D018625:Microscopy, Atomic Force; D008956:Models, Chemical; D015233:Models, Statistical; D010300:Parkinson Disease / Q000473:pathology; D011485:Protein Binding; D011487:Protein Conformation; D011798:Quinaldines / Q000494:pharmacology; D011804:Quinolines / Q000494:pharmacology; D051844:alpha-Synuclein / Q000737:chemistry*
chemical_list: D000682:Amyloid; D000891:Anti-Infective Agents, Local; D002412:Cations; D003650:Decamethonium Compounds; D004791:Enzyme Inhibitors; D008081:Liposomes; D011798:Quinaldines; D011804:Quinolines; D051844:alpha-Synuclein; C033019:decamethonium; C037073:2-methylquinoline; D003868:Dequalinium