title: Membrane-bound α-synuclein interacts with glucocerebrosidase and inhibits enzyme activity.
abstract: Mutations in GBA, the gene encoding glucocerebrosidase, the lysosomal enzyme deficient in Gaucher disease increase the risk for developing Parkinson disease. Recent research suggests a relationship between glucocerebrosidase and the Parkinson disease-related amyloid-forming protein, α-synuclein; however, the specific molecular mechanisms responsible for association remain elusive. Previously, we showed that α-synuclein and glucocerebrosidase interact selectively under lysosomal conditions, and proposed that this newly identified interaction might influence cellular levels of α-synuclein by either promoting protein degradation and/or preventing aggregation. Here, we demonstrate that membrane-bound α-synuclein interacts with glucocerebrosidase, and that this complex formation inhibits enzyme function. Using site-specific fluorescence and Förster energy transfer probes, we mapped the protein-enzyme interacting regions on unilamellar vesicles. Our data suggest that on the membrane surface, the glucocerebrosidase-α-synuclein interaction involves a larger α-synuclein region compared to that found in solution. In addition, α-synuclein acts as a mixed inhibitor with an apparent IC(50) in the submicromolar range. Importantly, the membrane-bound, α-helical form of α-synuclein is necessary for inhibition. This glucocerebrosidase interaction and inhibition likely contribute to the mechanism underlying GBA-associated parkinsonism.
authors.affiliation: Laboratory of Molecular Biophysics, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Thai Leong
authors.initials: TL
authors.lastname: Yap
authors.forename: Arash
authors.initials: A
authors.lastname: Velayati
authors.forename: Ellen
authors.initials: E
authors.lastname: Sidransky
authors.forename: Jennifer C
authors.initials: JC
authors.lastname: Lee
mesh_terms: D000595:Amino Acid Sequence; D002462:Cell Membrane / Q000378:metabolism; D002942:Circular Dichroism; D031541:Fluorescence Resonance Energy Transfer; D005456:Fluorescent Dyes; D005962:Glucosylceramidase / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017386:Sequence Homology, Amino Acid; D013050:Spectrometry, Fluorescence; D051844:alpha-Synuclein / Q000378:metabolism*
chemical_list: D005456:Fluorescent Dyes; D051844:alpha-Synuclein; D005962:Glucosylceramidase