title: Reversible inhibition of alpha-synuclein fibrillization by dopaminochrome-mediated conformational alterations.
abstract: Previous studies demonstrated that alpha-synuclein (alpha-syn) fibrillization is inhibited by dopamine, and studies to understand the molecular basis of this process were conducted (Conway, K. A., Rochet, J. C., Bieganski, R. M., and Lansbury, P. T., Jr. (2001) Science 294, 1346-1349). Dopamine inhibition of alpha-syn fibrillization generated exclusively spherical oligomers that depended on dopamine autoxidation but not alpha-syn oxidation, because mutagenesis of Met, His, and Tyr residues in alpha-syn did not abrogate this inhibition. However, truncation of alpha-syn at residue 125 restored the ability of alpha-syn to fibrillize in the presence of dopamine. Mutagenesis and competition studies with specific synthetic peptides identified alpha-syn residues 125-129 (i.e. YEMPS) as an important region in the dopamine-induced inhibition of alpha-syn fibrillization. Significantly, the dopamine oxidation product dopaminochrome was identified as a specific inhibitor of alpha-syn fibrillization. Dopaminochrome promotes the formation of spherical oligomers by inducing conformational changes, as these oligomers regained the ability to fibrillize by simple denaturation/renaturation. Taken together, these data indicate that dopamine inhibits alpha-syn fibrillization by inducing structural changes in alpha-syn that can occur through the interaction of dopaminochrome with the 125YEMPS129 motif of alpha-syn. These results suggest that the dopamine autoxidation can prevent alpha-syn fibrillization in dopaminergic neurons through a novel mechanism. Thus, decreased dopamine levels in substantia nigra neurons might promote alpha-syn aggregation in Parkinson's disease.
authors.affiliation: Center for Neurodegenerative Disease Research, Department of Pathology and Laboratory Medicine, Institute on Aging, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
authors.forename: Erin H
authors.initials: EH
authors.lastname: Norris
authors.forename: Benoit I
authors.initials: BI
authors.lastname: Giasson
authors.forename: Roberto
authors.initials: R
authors.lastname: Hodara
authors.forename: Shaohua
authors.initials: S
authors.lastname: Xu
authors.forename: John Q
authors.initials: JQ
authors.lastname: Trojanowski
authors.forename: Harry
authors.initials: H
authors.lastname: Ischiropoulos
authors.forename: Virginia M-Y
authors.initials: VM
authors.lastname: Lee
mesh_terms: D020816:Amino Acid Motifs; D002942:Circular Dichroism; D018076:DNA, Complementary / Q000378:metabolism; D004298:Dopamine / Q000737:chemistry / Q000378:metabolism; D006639:Histidine / Q000737:chemistry; D006801:Humans; D045563:Indolequinones / Q000737:chemistry*; D008715:Methionine / Q000737:chemistry; D018625:Microscopy, Atomic Force; D008854:Microscopy, Electron; D016296:Mutagenesis; D009154:Mutation; D009419:Nerve Tissue Proteins / Q000037:antagonists & inhibitors*; D018384:Oxidative Stress; D010100:Oxygen / Q000378:metabolism; D010300:Parkinson Disease / Q000378:metabolism; D010455:Peptides / Q000737:chemistry; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000737:chemistry; D017550:Spectroscopy, Fourier Transform Infrared; D051843:Synucleins; D013997:Time Factors; D014443:Tyrosine / Q000737:chemistry; D051844:alpha-Synuclein
chemical_list: D018076:DNA, Complementary; D045563:Indolequinones; D009419:Nerve Tissue Proteins; D010455:Peptides; D011994:Recombinant Proteins; C497604:SNCA protein, human; D051843:Synucleins; D051844:alpha-Synuclein; C091584:aminochrome 1; D014443:Tyrosine; D006639:Histidine; D008715:Methionine; D010100:Oxygen; D004298:Dopamine