title: Cellular oligomerization of alpha-synuclein is determined by the interaction of oxidized catechols with a C-terminal sequence.
abstract: The mechanisms that govern the formation of alpha-synuclein (alpha-syn) aggregates are not well understood but are considered a central event in the pathogenesis of Parkinson's disease (PD). A critically important modulator of alpha-syn aggregation in vitro is dopamine and other catechols, which can prevent the formation of alpha-syn aggregates in cell-free and cellular model systems. Despite the profound importance of this interaction for the pathogenesis of PD, the processes by which catechols alter alpha-syn aggregation are unclear. Molecular and biochemical approaches were employed to evaluate the mechanism of catechol-alpha-syn interactions and the effect on inclusion formation. The data show that the intracellular inhibition of alpha-syn aggregation requires the oxidation of catechols and the specific noncovalent interaction of the oxidized catechols with residues (125)YEMPS(129) in the C-terminal region of the protein. Cell-free studies using novel near infrared fluorescence methodology for the detection of covalent protein-ortho-quinone adducts showed that although covalent modification of alpha-syn occurs, this does not affect alpha-syn fibril formation. In addition, oxidized catechols are unable to prevent both thermal and acid-induced protein aggregation as well as fibrils formed from a protein that lacks a YEMPS amino acid sequence, suggesting a specific effect for alpha-syn. These results suggest that inappropriate C-terminal cleavage of alpha-syn, which is known to occur in vivo in PD brain or a decline of intracellular catechol levels might affect disease progression, resulting in accelerated alpha-syn inclusion formation and dopaminergic neurodegeneration.
authors.affiliation: Joseph Stokes Jr. Research Institute, Children's Hospital of Philadelphia and University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
authors.forename: Joseph R
authors.initials: JR
authors.lastname: Mazzulli
authors.forename: Maria
authors.initials: M
authors.lastname: Armakola
authors.forename: Michelle
authors.initials: M
authors.lastname: Dumoulin
authors.forename: Ioannis
authors.initials: I
authors.lastname: Parastatidis
authors.forename: Harry
authors.initials: H
authors.lastname: Ischiropoulos
mesh_terms: D000595:Amino Acid Sequence; D002396:Catechols / Q000378:metabolism*; D045744:Cell Line, Tumor; D002474:Cell-Free System; D019084:Fluorescent Antibody Technique, Indirect; D005562:Formazans / Q000378:metabolism; D005822:Genetic Vectors; D006801:Humans; D016086:Lentivirus / Q000235:genetics; D008027:Light; D013058:Mass Spectrometry; D009447:Neuroblastoma / Q000473:pathology; D010084:Oxidation-Reduction; D010957:Plasmids; D011994:Recombinant Proteins / Q000302:isolation & purification / Q000378:metabolism; D012542:Scattering, Radiation; D013050:Spectrometry, Fluorescence; D014161:Transduction, Genetic; D014162:Transfection; D051844:alpha-Synuclein / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*