Development of a Peptide Antagonist against fsr Quorum Sensing of Enterococcus faecalis
ABSTRACT The Enterococcus faecalis fsr quorum sensing (QS) involves an 11-residue cyclic peptide named gelatinase biosynthesis-activating pheromone (GBAP) that autoinduces two pathogenicity-related extracellular proteases in a cell density-dependent fashion. To identify anti-pathogenic agents that target fsr QS signaling, peptide antagonists of GBAP were created by our unique drug design approach based on reverse alanine scanning. First of all, a receptor-binding scaffold (RBS), [Ala(4,5,6,8,9,11)]Z-GBAP, was created, in which all amino acids within the ring region of GBAP, except for two essential aromatic residues were substituted to alanine. Next, the substituted alanine residues were changed back to the original amino acid one by one, permitting selection of those peptide combinations exhibiting increased antagonist activity. After three cycles of this reverse alanine scan, [Ala(5,9,11)]Z-GBAP was obtained as a maximally reverted peptide (MRP) holding the strongest antagonist activity. Then, the 5th residue in MRP, which is one of critical residues to determine agonist-antagonist activity, was further modified by substituting with different types of amino acids including unnatural amino acids. As a result, [Tyr(Bzl)(5), Ala(9,11)]Z-GBAP, named ZBzl-YAA5911, showed the strongest antagonist activity [IC(50) = 26.2 nM and Kd against GBAP receptor (FsrC) = 39.4 nM]. In vivo efficacy of this peptide was assessed with an aphakic rabbit endophthalmitis model. ZBzl-YAA5911 suppressed the translocation of E. faecalis from the aqueous humor into the vitreous cavity by more than one order of magnitude and significantly reduced retinal damage. We propose that ZBzl-YAA5911 or its derivatives would be useful as anti-infective agents to attenuate virulence expression in this opportunistic pathogen.
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ABSTRACT: Seven β-aryl substituted γ-alkylidene-γ-lactones analogues of rubrolides were synthesized from mucobromic acid and converted through a lactamization with isobutylamine into their corresponding γ-hydroxy-γ-lactams (76-85%). These lactams were converted into (Z)- and (E)-γ-alkylidene-γ-lactams (23-45%). All compounds were fully characterized by IR, NMR ((1)H and (13)C), COSY and HETCOR bidimensional experiments, and NOE difference spectroscopy experiments when necessary. Evaluation of these three different classes of compounds against Enterococcus faecalis biofilm formation showed that all classes are active and the highest biofilm inhibition activity was caused by lactam 13f (IC50 = 0.76 μg/mL). Moreover, in almost all cases at least one of the lactams is more active than its correspondent γ-alkylidene-γ-lactone. The use of rubrolides as a lead structure has proven successful for the identification of new compounds displaying novel antibacterial activities, namely biofilm inhibition, which have the potential for the development of antimicrobial drugs targeted to inhibition of the initial stages of bacterial infections, rather than bacterial viability. Such drugs are less prompt to induce bacterial resistance, being therefore a more cost-effective investment for pharmaceutical research.European Journal of Medicinal Chemistry 05/2014; 82C:127-138. DOI:10.1016/j.ejmech.2014.05.035 · 3.43 Impact Factor
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ABSTRACT: Almost a century on from the discovery of penicillin, the war against bacterial infection still rages compounded by the emergence of strains resistant to virtually every clinically approved antibiotic and the dearth of new antibacterial agents entering the clinic. Consequently there is renewed interest in drugs which attenuate virulence rather than bacterial growth. Since the metaphors of warfare are often used to describe the battle between pathogen and host, we will describe in such a context, the molecular communication (quorum sensing) mechanisms used by bacteria to co-ordinate virulence at the population level. Recent progress in exploiting this information through the design of anti-virulence deception strategies that disrupt quorum sensing through signal molecule inactivation, inhibition of signal molecule biosynthesis or the blockade of signal transduction and their advantages and disadvantages are considered.Bioorganic Chemistry 04/2014; 55. DOI:10.1016/j.bioorg.2014.04.005 · 2.14 Impact Factor