Pilicides inhibit the FGL chaperone/usher assisted biogenesis of the Dr fimbrial polyadhesin from uropathogenic Escherichia coli

Abstract

BackgroundThe global spread of bacterial resistance has given rise to a growing interest in new anti-bacterial agents with a new strategy of action. Pilicides are derivatives of ring-fused 2-pyridones which block the formation of the pili/fimbriae crucial to bacterial pathogenesis. They impair by means of a chaperone-usher pathway conserved in the Gram-negative bacteria of adhesive structures biogenesis. Pili/fimbriae of this type belong to two subfamilies, FGS and FGL, which differ in the details of their assembly mechanism. The data published to date have shown that pilicides inhibit biogenesis of type 1 and P pili of the FGS type which are encoded by uropathogenic E. coli strains.ResultsWe evaluated the anti-bacterial activity of literature pilicides as blockers of the assembly of a model example of FGL-type adhesive structures, – the Dr fimbriae encoded by a dra gene cluster of uropathogenic Escherichia coli strains. In comparison to the strain grown without pilicide, the Dr+ bacteria cultivated in the presence of the 3.5 mM concentration of pilicides resulted in a reduction of 75 to 87% in the adherence properties to CHO cells expressing Dr fimbrial DAF receptor protein. Using quantitative assays, we determined the amount of Dr fimbriae in the bacteria cultivated in the presence of 3.5 mM of pilicides to be reduced by 75 to 81%. The inhibition effect of pilicides is concentration dependent, which is a crucial property for their use as potential anti-bacterial agents. The data presented in this article indicate that pilicides in mM concentration effectively inhibit the adherence of Dr+ bacteria to the host cells, – the crucial, initial step in bacterial pathogenesis.ConclusionsStructural analysis of the DraB chaperone clearly showed it to be a model of the FGL subfamily of chaperones. This permits us to conclude that analyzed pilicides in mM concentration are effective inhibitors of the assembly of adhesins belonging to the Dr family, and more speculatively, of other FGL-type adhesive organelles. The presented data and those published so far permit to speculate that based on the conservation of chaperone-usher pathway in Gram-negative bacteria , the pilicides are potential anti-bacterial agents with activity against numerous pathogens, the virulence of which is dependent on the adhesive structures of the chaperone-usher type.

Urinary tract infections: epidemiology, mechanisms of infection and treatment options

“…16,27–29 — express a large, highly conserved family of adhesive fibres called chaperone–usher pathway (CUP) pili 25,26 . CUP pili are assembled by the chaperone–usher molecular machinery 24,25 and are composed of pilin subunits with incomplete immunoglobulin-like folds that lack the typical carboxy-terminal seventh β-strand 30,31 . Briefly, in a process termed donor-strand complementation, a dedicated periplasmic chaperone ‘donates’ a β-strand to complete the immunoglobulin fold of the subunits, forming a complex with each subunit and ensuring their proper folding and stabilization.…”

“…Targeting CUP pilus function or assembly has therapeutic potential, as it should block UPEC colonization, invasion and biofilm formation, thus preventing disease 30,31,120,121 .…”

“…They have a 2-pyridone scaffold 28,30,31,120 and function by selectively targeting and interfering with crucial chaperone–usher interactions. Further studies have been carried out to investigate their broad spectrum of activity against other CUP pili 122 .…”

“…Thus, the potency of pilicide ec240 is largely due to its ability to induce a phase OFF orientation of the type 1 pilus promoter, rather than any interference with chaperone–usher interactions. Additional work revealed that other pilicides also inhibit the production of Dr pili, another type of UPEC CUP pili that are known to be important in pyelonephritis in mice and humans 30,33 . Furthermore, pilicides have been shown to disrupt CUP pilus biogenesis in K. pneumoniae and also in Haemophilus influenzae (a finding that has important implications for otitis media) 24,29 .…”

Innovative Solutions to Sticky Situations: Antiadhesive Strategies for Treating Bacterial Infections

“…Thus, the potency of pilicide 2 is in part due to the unexpected mechanism of inducing a phase OFF orientation of the type 1 pilus promoter. Additionally, pilicide activity against Dr pili, another type of CUP pili known to play a role in pyelonephritis in mice and humans, has also been confirmed, further expanding the therapeutic potential of these compounds in targeting UTI (154). The exciting ability of these compounds to target multiple CUP pili suggests that these compounds could demonstrate broad therapeutic coverage in the clinic.…”