title: Positively selected FimH residues enhance virulence during urinary tract infection by altering FimH conformation.
abstract: Chaperone-usher pathway pili are a widespread family of extracellular, Gram-negative bacterial fibers with important roles in bacterial pathogenesis. Type 1 pili are important virulence factors in uropathogenic Escherichia coli (UPEC), which cause the majority of urinary tract infections (UTI). FimH, the type 1 adhesin, binds mannosylated glycoproteins on the surface of human and murine bladder cells, facilitating bacterial colonization, invasion, and formation of biofilm-like intracellular bacterial communities. The mannose-binding pocket of FimH is invariant among UPEC. We discovered that pathoadaptive alleles of FimH with variant residues outside the binding pocket affect FimH-mediated acute and chronic pathogenesis of two commonly studied UPEC strains, UTI89 and CFT073. In vitro binding studies revealed that, whereas all pathoadaptive variants tested displayed the same high affinity for mannose when bound by the chaperone FimC, affinities varied when FimH was incorporated into pilus tip-like, FimCGH complexes. Structural studies have shown that FimH adopts an elongated conformation when complexed with FimC, but, when incorporated into the pilus tip, FimH can adopt a compact conformation. We hypothesize that the propensity of FimH to adopt the elongated conformation in the tip corresponds to its mannose binding affinity. Interestingly, FimH variants, which maintain a high-affinity conformation in the FimCGH tip-like structure, were attenuated during chronic bladder infection, implying that FimH's ability to switch between conformations is important in pathogenesis. Our studies argue that positively selected residues modulate fitness during UTI by affecting FimH conformation and function, providing an example of evolutionary tuning of structural dynamics impacting in vivo survival.
authors.affiliation: Center for Women's Infectious Disease Research, Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, MO 63110.
authors.forename: Drew J
authors.initials: DJ
authors.lastname: Schwartz
authors.forename: Vasilios
authors.initials: V
authors.lastname: Kalas
authors.forename: Jerome S
authors.initials: JS
authors.lastname: Pinkner
authors.forename: Swaine L
authors.initials: SL
authors.lastname: Chen
authors.forename: Caitlin N
authors.initials: CN
authors.lastname: Spaulding
authors.forename: Karen W
authors.initials: KW
authors.lastname: Dodson
authors.forename: Scott J
authors.initials: SJ
authors.lastname: Hultgren
mesh_terms: D018830:Adhesins, Escherichia coli / Q000737:chemistry / Q000378:metabolism*; D000483:Alleles; D000595:Amino Acid Sequence; D000596:Amino Acids / Q000378:metabolism*; D000818:Animals; D002908:Chronic Disease; D060085:Coinfection / Q000382:microbiology / Q000473:pathology; D003556:Cystitis / Q000382:microbiology / Q000473:pathology; D004926:Escherichia coli / Q000378:metabolism* / Q000472:pathogenicity*; D036781:Fimbriae Proteins / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D008358:Mannose / Q000378:metabolism; D051379:Mice; D008954:Models, Biological; D046912:Multiprotein Complexes / Q000378:metabolism; D011485:Protein Binding; D017433:Protein Structure, Secondary; D013329:Structure-Activity Relationship; D014551:Urinary Tract / Q000382:microbiology / Q000473:pathology; D014552:Urinary Tract Infections / Q000382:microbiology* / Q000473:pathology; D014774:Virulence
chemical_list: D018830:Adhesins, Escherichia coli; D000596:Amino Acids; D046912:Multiprotein Complexes; C058769:fimH protein, E coli; D036781:Fimbriae Proteins; D008358:Mannose
keywords: chronic cystitis; microbial pathogenesis; protein conformations; protein dynamics