Differentiation of Crohn’s Disease-Associated Isolates from Other Pathogenic Escherichia coli by Fimbrial Adhesion under Shear Force

Abstract

Shear force exerted on uropathogenic Escherichia coli adhering to surfaces makes type-1 fimbriae stretch out like springs to catch on to mannosidic receptors. This mechanism is initiated by a disruption of the quaternary interactions between the lectin and the pilin of the two-domain FimH adhesin and transduces allosterically to the mannose-binding pocket of FimH to increase its affinity. Mannose-specific adhesion of 14 E. coli pathovars was measured under flow, using surface plasmon resonance detection on functionalized graphene-coated gold interfaces. Increasing the shear had important differential consequences on bacterial adhesion. Adherent-invasive E. coli, isolated from the feces and biopsies of Crohn’s disease patients, consistently changed their adhesion behavior less under shear and displayed lower SPR signals, compared to E. coli opportunistically infecting the urinary tract, intestines or loci of knee and hip prostheses. We exemplified this further with the extreme behaviors of the reference strains UTI89 and LF82. Whereas their FimA major pilins have identical sequences, FimH of LF82 E. coli is marked by the Thr158Pro mutation. Positioned in the inter-domain region known to carry hot spots of mutations in E. coli pathotypes, residue 158 is indicated to play a structural role in the allosteric regulation of type-1 fimbriae-mediated bacterial adhesion.

Targeting Dynamical Binding Processes in the Design of Non-Antibiotic Anti-Adhesives by Molecular Simulation—The Example of FimH

“…SPR experiments with natural variants of FimH (e.g., aa. 158; Table 1 ) found in different E. coli strains corroborate the importance of the linker loop in the shear-dependent conformational change [ 22 , 46 , 47 ]. The analysis of sMD simulations combined with experimental data highlighted that below a force of about 60 pN, the unbinding of the mannose is mainly observed from the LA state (with a rate of 6 s −1 [ 61 ].…”

“…Independent of the used sMD approach the interdomain linker loop extended under the applied force. In line with the observed importance of the linker, SPR experiments highlight that natural variants of FimH with different amino acids in the position 158 (located in the linker loop region, see Figure 1 A) show different responses to stress [ 22 , 46 , 47 ]: the adhesion strength of the uropathogenic UTI89 E. coli strain with a threonine at position 158 of FimH shows an optimum at higher shear, whereas in strains (AIEC7082 and LF82) carrying an alanine or a proline respectively at aa. position 158, bacterial binding is less or not enhanced with increasing fluid shear.…”

Sites for Dynamic Protein-Carbohydrate Interactions of O- and C-Linked Mannosides on the E. coli FimH Adhesin

“…Binding of anti-adhesives at the clamp loop holding Ile13 where large shear-force induced conformational changes occur, with the interplay of aglycon stacking with either the Ile13 or the Tyr48 side chain, is a mechanism as yet little explored in drug discovery of FimH antagonists of E. coli adhesion [ 42 ]. These novel structural insights, namely that ortho -biphenyl substituents on mannose can sample a binding interface on the FimH adhesin, notably one that is directly involved in the regulation of FimH affinity of pathogenic E coli under shear force, opens new perspectives for non-antibiotic therapies and anti-adhesive design [ 39 , 40 , 43 ].…”

Selection for non-specific adhesion is a driver of FimH evolution increasing Escherichia coli biofilm capacity

“…These variants are often single point, non-synonymous amino acid substitutions found in the lectin domain but not affecting the mannose-binding pocket directly. While adaptive mutations identified in our study were also found in the lectin domain of the protein, only position 87 (G87C) has been previously described in pathoadaptive variants 28,44,45,48 and described as a mutational hotspot with amino acid changes to arginine, alanine, serine and cysteine 28 . The G87S and G87C variants are the only mutants that display moderate increases in mannose-binding, but still display catch-bond properties under flow conditions 28 .…”