title: Mechanisms of protein oligomerization: inhibitor of functional amyloids templates α-synuclein fibrillation.
abstract: Small organic molecules that inhibit functional bacterial amyloid fibers, curli, are promising new antibiotics. Here we investigated the mechanism by which the ring-fused 2-pyridone FN075 inhibits fibrillation of the curli protein CsgA. Using a variety of biophysical techniques, we found that FN075 promotes CsgA to form off-pathway, non-amyloidogenic oligomeric species. In light of the generic properties of amyloids, we tested whether FN075 would also affect the fibrillation reaction of human α-synuclein, an amyloid-forming protein involved in Parkinson's disease. Surprisingly, FN075 stimulates α-synuclein amyloid fiber formation as measured by thioflavin T emission, electron microscopy (EM), and atomic force microscopy (AFM). NMR data on (15)N-labeled α-synuclein show that upon FN075 addition, α-synuclein oligomers with 7 nm radius form in which the C-terminal 40 residues remain disordered and solvent exposed. The polypeptides in these oligomers contain β-like secondary structure, and the oligomers are detectable by AFM, EM, and size-exclusion chromatography (SEC). Taken together, FN075 triggers oligomer formation of both proteins: in the case of CsgA, the oligomers do not proceed to fibers, whereas for α-synuclein, the oligomers are poised to rapidly form fibers. We conclude that there is a fine balance between small-molecule inhibition and templation that depends on protein chemistry.
authors.affiliation: Department of Chemistry, Chemical Biological Center, Umeå University, 901 87 Umeå, Sweden.
authors.forename: Istvan
authors.initials: I
authors.lastname: Horvath
authors.forename: Christoph F
authors.initials: CF
authors.lastname: Weise
authors.forename: Emma K
authors.initials: EK
authors.lastname: Andersson
authors.forename: Erik
authors.initials: E
authors.lastname: Chorell
authors.forename: Magnus
authors.initials: M
authors.lastname: Sellstedt
authors.forename: Christoffer
authors.initials: C
authors.lastname: Bengtsson
authors.forename: Anders
authors.initials: A
authors.lastname: Olofsson
authors.forename: Scott J
authors.initials: SJ
authors.lastname: Hultgren
authors.forename: Matthew
authors.initials: M
authors.lastname: Chapman
authors.forename: Magnus
authors.initials: M
authors.lastname: Wolf-Watz
authors.forename: Fredrik
authors.initials: F
authors.lastname: Almqvist
authors.forename: Pernilla
authors.initials: P
authors.lastname: Wittung-Stafshede
mesh_terms: D000682:Amyloid / Q000037:antagonists & inhibitors* / Q000378:metabolism; D000900:Anti-Bacterial Agents / Q000737:chemistry* / Q000494:pharmacology*; D004926:Escherichia coli / Q000187:drug effects / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000378:metabolism*; D006801:Humans; D010300:Parkinson Disease / Q000378:metabolism; D011728:Pyridones / Q000737:chemistry* / Q000494:pharmacology*; D051844:alpha-Synuclein / Q000378:metabolism*
chemical_list: D000682:Amyloid; D000900:Anti-Bacterial Agents; D029968:Escherichia coli Proteins; D011728:Pyridones; D051844:alpha-Synuclein; C489688:csgA protein, E coli; C017679:2-hydroxypyridine