Molecular Modulators of Bacterial Functional Amyloid Assembly.

[摘要] Amyloid formation is historically associated with protein misfolding and is the hallmark of many neurodegenerative conditions. A new class of ;;functional amyloids” has recently emerged that has transformed that amyloid field. Functional amyloids, unlike disease-associated amyloids, assemble through dedicated and highly controlled pathways. Escherichia coli produce an extracellular functional amyloid called curli. Curli are the major structural component of E. coli biofilms and mediate colonization and invasion during infection. E. coli must control the assembly of curli to avoid amyloid-related cytotoxicity as the amyloid fold is inherently toxic to biological membranes.The overarching goal of this dissertation was to understand the mechanisms E. coli possess to control the secretion and assembly of curli fibers. I first demonstrated that general molecular chaperones inhibited curli amyloid assembly in vitro. The cytoplasmic chaperones, DnaK and Hsp33, and the periplasmic chaperone Spy inhibited CsgA amyloid polymerization in vitro. Next, I report the discovery that csgC encodes an extraordinarily efficient and selective inhibitor of amyloid assembly. CsgC functioned at molar ratios as low as 1:500 (CsgC:CsgA) to inhibit CsgA polymerization. CsgC inhibited polymerization of closely related amyloid-forming client proteins but not the unrelated Alzheimer’s disease-associated protein Amyloid Beta. Remarkably, CsgC inhibited amyloid formation by alpha-synuclein, the amyloid-forming protein associated with Parkinson’s disease. Alpha-synuclein shares only an 8-9 amino acid motif with CsgA. When the shared motif was mutated in Alpha-synuclein CsgC was no long able to inhibit amyloid assembly. Together these findings suggest a unique mechanism of inhibition. Finally, I report new molecular insights into the function of the curli secretion protein CsgE. Collectively, I present evidence of a multitude of efficient and dedicated amyloid modulators that contribute to the controlled assembly of curli amyloid assembly.

[发布机构] University of Michigan

[效力级别] Curli

[关键词] Molecular Modulators of Bacterial FunctionalAmyloid Assembly;Curli;CsgA;CsgC;Amyloid-Beta;Alpha-synuclein;Molecular;Cellular and Developmental Biology;Science;Molecular, Cellular and Developmental Biology