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Uropathogenic Escherichia coli modulates immune responses and its curli fimbriae interact with the antimicrobial peptide LL-37.

Kai-Larsen Y, Lüthje P, Chromek M, Peters V, Wang X, Holm A, Kádas L, Hedlund KO, Johansson J, Chapman MR, Jacobson SH, Römling U, Agerberth B, Brauner A - PLoS Pathog. (2010)

Bottom Line: Our results suggest that curli and cellulose exhibit differential and complementary functions.Cellulose production, on the other hand, reduced immune induction and hence delayed bacterial elimination from the kidneys.Thus, even relatively low concentrations of LL-37 inhibited curli-mediated biofilm formation in vitro.

View Article: PubMed Central - PubMed

Affiliation: Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden.

ABSTRACT
Bacterial growth in multicellular communities, or biofilms, offers many potential advantages over single-cell growth, including resistance to antimicrobial factors. Here we describe the interaction between the biofilm-promoting components curli fimbriae and cellulose of uropathogenic E. coli and the endogenous antimicrobial defense in the urinary tract. We also demonstrate the impact of this interplay on the pathogenesis of urinary tract infections. Our results suggest that curli and cellulose exhibit differential and complementary functions. Both of these biofilm components were expressed by a high proportion of clinical E. coli isolates. Curli promoted adherence to epithelial cells and resistance against the human antimicrobial peptide LL-37, but also increased the induction of the proinflammatory cytokine IL-8. Cellulose production, on the other hand, reduced immune induction and hence delayed bacterial elimination from the kidneys. Interestingly, LL-37 inhibited curli formation by preventing the polymerization of the major curli subunit, CsgA. Thus, even relatively low concentrations of LL-37 inhibited curli-mediated biofilm formation in vitro. Taken together, our data demonstrate that biofilm components are involved in the pathogenesis of urinary tract infections by E. coli and can be a target of local immune defense mechanisms.

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Related in: MedlinePlus

LL-37 binds to recombinant polymerized CsgA and isolated wild-type curli.(A) Western blot analysis of supernatants after precipitation of LL-37 with curli. By adding polymeric CsgA (pol CsgA) or wild-type curli (wt curli) to a solution of 0.1 µM LL-37, the levels of LL-37 decreased in the supernatants after centrifugation. (B) Surface plasmon resonance. LL-37 exhibits a stronger association and lower dissociation rates to both polymeric (upper panel) and monomeric CsgA (lower panel) compared to the control peptides sLL-37 and VIP.
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ppat-1001010-g005: LL-37 binds to recombinant polymerized CsgA and isolated wild-type curli.(A) Western blot analysis of supernatants after precipitation of LL-37 with curli. By adding polymeric CsgA (pol CsgA) or wild-type curli (wt curli) to a solution of 0.1 µM LL-37, the levels of LL-37 decreased in the supernatants after centrifugation. (B) Surface plasmon resonance. LL-37 exhibits a stronger association and lower dissociation rates to both polymeric (upper panel) and monomeric CsgA (lower panel) compared to the control peptides sLL-37 and VIP.

Mentions: In order to elucidate one possible mechanism that could influence the increased resistance of curliated bacteria against LL-37, the binding of LL-37 to wild-type curli and recombinant CsgA was assessed. A precipitation assay showed a pronounced decrease of LL-37 in supernatants from samples containing wild-type curli or polymerized CsgA (Figure 5A). Further, LL-37 binding to both monomeric and polymeric CsgA was demonstrated by surface plasmon resonance (Figure 5B). By comparing the response during loading of the peptide in a time frame of 0–180 s, the sensogram of LL-37 demonstrated a higher association with CsgA than the control peptides, i.e. scrambled LL-37 (sLL-37) and the vasoactive intestinal peptide (VIP) [27]. Furthermore, the binding curves reveal that the control peptides had faster dissociation rates than LL-37, indicating a weaker binding to CsgA. This was especially pronounced for the binding to polymeric CsgA. Determination of binding constants was precluded, since LL-37 and in particular CsgA forms oligomers and polymers, respectively, and thus generate several different assemblies.


Uropathogenic Escherichia coli modulates immune responses and its curli fimbriae interact with the antimicrobial peptide LL-37.

Kai-Larsen Y, Lüthje P, Chromek M, Peters V, Wang X, Holm A, Kádas L, Hedlund KO, Johansson J, Chapman MR, Jacobson SH, Römling U, Agerberth B, Brauner A - PLoS Pathog. (2010)

LL-37 binds to recombinant polymerized CsgA and isolated wild-type curli.(A) Western blot analysis of supernatants after precipitation of LL-37 with curli. By adding polymeric CsgA (pol CsgA) or wild-type curli (wt curli) to a solution of 0.1 µM LL-37, the levels of LL-37 decreased in the supernatants after centrifugation. (B) Surface plasmon resonance. LL-37 exhibits a stronger association and lower dissociation rates to both polymeric (upper panel) and monomeric CsgA (lower panel) compared to the control peptides sLL-37 and VIP.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2908543&req=5

ppat-1001010-g005: LL-37 binds to recombinant polymerized CsgA and isolated wild-type curli.(A) Western blot analysis of supernatants after precipitation of LL-37 with curli. By adding polymeric CsgA (pol CsgA) or wild-type curli (wt curli) to a solution of 0.1 µM LL-37, the levels of LL-37 decreased in the supernatants after centrifugation. (B) Surface plasmon resonance. LL-37 exhibits a stronger association and lower dissociation rates to both polymeric (upper panel) and monomeric CsgA (lower panel) compared to the control peptides sLL-37 and VIP.
Mentions: In order to elucidate one possible mechanism that could influence the increased resistance of curliated bacteria against LL-37, the binding of LL-37 to wild-type curli and recombinant CsgA was assessed. A precipitation assay showed a pronounced decrease of LL-37 in supernatants from samples containing wild-type curli or polymerized CsgA (Figure 5A). Further, LL-37 binding to both monomeric and polymeric CsgA was demonstrated by surface plasmon resonance (Figure 5B). By comparing the response during loading of the peptide in a time frame of 0–180 s, the sensogram of LL-37 demonstrated a higher association with CsgA than the control peptides, i.e. scrambled LL-37 (sLL-37) and the vasoactive intestinal peptide (VIP) [27]. Furthermore, the binding curves reveal that the control peptides had faster dissociation rates than LL-37, indicating a weaker binding to CsgA. This was especially pronounced for the binding to polymeric CsgA. Determination of binding constants was precluded, since LL-37 and in particular CsgA forms oligomers and polymers, respectively, and thus generate several different assemblies.

Bottom Line: Our results suggest that curli and cellulose exhibit differential and complementary functions.Cellulose production, on the other hand, reduced immune induction and hence delayed bacterial elimination from the kidneys.Thus, even relatively low concentrations of LL-37 inhibited curli-mediated biofilm formation in vitro.

View Article: PubMed Central - PubMed

Affiliation: Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden.

ABSTRACT
Bacterial growth in multicellular communities, or biofilms, offers many potential advantages over single-cell growth, including resistance to antimicrobial factors. Here we describe the interaction between the biofilm-promoting components curli fimbriae and cellulose of uropathogenic E. coli and the endogenous antimicrobial defense in the urinary tract. We also demonstrate the impact of this interplay on the pathogenesis of urinary tract infections. Our results suggest that curli and cellulose exhibit differential and complementary functions. Both of these biofilm components were expressed by a high proportion of clinical E. coli isolates. Curli promoted adherence to epithelial cells and resistance against the human antimicrobial peptide LL-37, but also increased the induction of the proinflammatory cytokine IL-8. Cellulose production, on the other hand, reduced immune induction and hence delayed bacterial elimination from the kidneys. Interestingly, LL-37 inhibited curli formation by preventing the polymerization of the major curli subunit, CsgA. Thus, even relatively low concentrations of LL-37 inhibited curli-mediated biofilm formation in vitro. Taken together, our data demonstrate that biofilm components are involved in the pathogenesis of urinary tract infections by E. coli and can be a target of local immune defense mechanisms.

Show MeSH
Related in: MedlinePlus