title: Trimeric form of intracellular ATP synthase subunit β of Aggregatibacter actinomycetemcomitans binds human interleukin-1β.
abstract: Bacterial biofilms resist host defenses and antibiotics partly because of their decreased metabolism. Some bacteria use proinflammatory cytokines, such as interleukin (IL)-1β, as cues to promote biofilm formation and to alter virulence. Although one potential bacterial IL-1β receptor has been identified, current knowledge of the bacterial IL-1β sensing mechanism is limited. In chronic biofilm infection, periodontitis, Aggregatibacter actinomycetemcomitans requires tight adherence (tad)-locus to form biofilms, and tissue destroying active lesions contain more IL-1β than inactive ones. The effect of IL-1β on the metabolic activity of A. actinomycetemcomitans biofilm was tested using alamarBlue™. The binding of IL-1β to A. actinomycetemcomitans cells was investigated using transmission electron microscopy and flow cytometry. To identify the proteins which interacted with IL-1β, different protein fractions from A. actinomycetemcomitans were run in native-PAGE and blotted using biotinylated IL-1β and avidin-HRP, and identified using mass spectroscopy. We show that although IL-1β slightly increases the biofilm formation of A. actinomycetemcomitans, it reduces the metabolic activity of the biofilm. A similar reduction was observed with all tad-locus mutants except the secretin mutant, although all tested mutant strains as well as wild type strains bound IL-1β. Our results suggest that IL-1β might be transported into the A. actinomycetemcomitans cells, and the trimeric form of intracellular ATP synthase subunit β interacted with IL-1β, possibly explaining the decreased metabolic activity. Because ATP synthase is highly conserved, it might universally enhance biofilm resistance to host defense by binding IL-1β during inflammation.
authors.affiliation: Department of Biochemistry and Food Chemistry, University of Turku, Turku, Finland.
authors.forename: Annamari
authors.initials: A
authors.lastname: Paino
authors.forename: Heidi
authors.initials: H
authors.lastname: Tuominen
authors.forename: Mari
authors.initials: M
authors.lastname: Jääskeläinen
authors.forename: Jonna
authors.initials: J
authors.lastname: Alanko
authors.forename: Jari
authors.initials: J
authors.lastname: Nuutila
authors.forename: Sirkka E
authors.initials: SE
authors.lastname: Asikainen
authors.forename: Lauri J
authors.initials: LJ
authors.lastname: Pelliniemi
authors.forename: Marja T
authors.initials: MT
authors.lastname: Pöllänen
authors.forename: Casey
authors.initials: C
authors.lastname: Chen
authors.forename: Riikka
authors.initials: R
authors.lastname: Ihalin
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D018441:Biofilms; D001704:Biopolymers / Q000378:metabolism*; D005434:Flow Cytometry; D006801:Humans; D053583:Interleukin-1beta / Q000378:metabolism*; D046529:Microscopy, Electron, Transmission; D015661:Pasteurellaceae / Q000201:enzymology*; D011485:Protein Binding
chemical_list: D001426:Bacterial Proteins; D001704:Biopolymers; D053583:Interleukin-1beta