title: E. coli chaperones DnaK, Hsp33 and Spy inhibit bacterial functional amyloid assembly.
abstract: Amyloid formation is an ordered aggregation process, where β-sheet rich polymers are assembled from unstructured or partially folded monomers. We examined how two Escherichia coli cytosolic chaperones, DnaK and Hsp33, and a more recently characterized periplasmic chaperone, Spy, modulate the aggregation of a functional amyloid protein, CsgA. We found that DnaK, the Hsp70 homologue in E. coli, and Hsp33, a redox-regulated holdase, potently inhibited CsgA amyloidogenesis. The Hsp33 anti-amyloidogenesis activity was oxidation dependent, as oxidized Hsp33 was significantly more efficient than reduced Hsp33 at preventing CsgA aggregation. When soluble CsgA was seeded with preformed amyloid fibers, neither Hsp33 nor DnaK were able to efficiently prevent soluble CsgA from adopting the amyloid conformation. Moreover, both DnaK and Hsp33 increased the time that CsgA was reactive with the amyloid oligomer conformation-specific A11 antibody. Since CsgA must also pass through the periplasm during secretion, we assessed the ability of the periplasmic chaperone Spy to inhibit CsgA polymerization. Like DnaK and Hsp33, Spy also inhibited CsgA polymerization in vitro. Overexpression of Spy resulted in increased chaperone activity in periplasmic extracts and in reduced curli biogenesis in vivo. We propose that DnaK, Hsp33 and Spy exert their effects during the nucleation stages of CsgA fibrillation. Thus, both housekeeping and stress induced cytosolic and periplasmic chaperones may be involved in discouraging premature CsgA interactions during curli biogenesis.
authors.affiliation: Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, MI, USA.
authors.forename: Margery L
authors.initials: ML
authors.lastname: Evans
authors.forename: Jens C
authors.initials: JC
authors.lastname: Schmidt
authors.forename: Marianne
authors.initials: M
authors.lastname: Ilbert
authors.forename: Shannon M
authors.initials: SM
authors.lastname: Doyle
authors.forename: Shu
authors.initials: S
authors.lastname: Quan
authors.forename: James C A
authors.initials: JC
authors.lastname: Bardwell
authors.forename: Ursula
authors.initials: U
authors.lastname: Jakob
authors.forename: Sue
authors.initials: S
authors.lastname: Wickner
authors.forename: Matthew R
authors.initials: MR
authors.lastname: Chapman
mesh_terms: D000682:Amyloid / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D001426:Bacterial Proteins / Q000378:metabolism; D004926:Escherichia coli / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000378:metabolism*; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism*; D006360:Heat-Shock Proteins / Q000378:metabolism*; D033903:Periplasmic Proteins / Q000378:metabolism*; D013050:Spectrometry, Fluorescence
chemical_list: D000682:Amyloid; D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; C492165:HSP33 protein, E coli; D018840:HSP70 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D033903:Periplasmic Proteins; C104888:Spy protein, E coli; C489688:csgA protein, E coli; C077481:Crl protein, Bacteria; C063842:dnaK protein, E coli