Enterococcal RseP as a target for new diagnostics and antibiotics

Vancomycin-resistant enterococci (VRE) are involved in diverse infections in humans and treatment of these infections has been very challenging in recent years because of their increasing resilience to most antibiotics. We have recently discovered an antimicrobial peptide/bacteriocin called enterocin K1 whicht has a very specific and potent activity against VRE, especially against Enterococcus faecium which accounts for 80-85% of enterococcal infections. The bacteriocin binds specifically to a transmembrane protein called RseP and kills target cells by membrane disruption. Because its mode of killing (membrane disruption) is different from traditional antibiotics, which often are enzyme inhibitors, enterocin K1 readily kills multi-antibiotic resistant VRE. Most importantly, the work with enterocin K1 has revealed RseP to be a novel and excellent drug target. RseP is involved in a stress respons mechanism called regulated intramembrane proteolysis (RIP). This pathway is vital for enterococcal cells to develop virulence and to establish infection. In a rabbit endocarditis model it has been shown that, when the gene encoding RseP is deleted, the affected pathogen is attenuated in the animal host and no virulence developed. Similarly, truncation or frame shift mutations within rseP confer enterococcal cells resistant to enterocin K1 but these cells do not survive in stress conditions (desiccation or higher tempetatures). Thus, enterocin K displays a two-sided attack: membrane-disruption in wt cells or causing inability to develop virulence in RseP mutant cells. In this project proposal, we will study the interaction between enterocin K1 and RseP to explore the potential of enterocin K1 in diagnostics and in therapeutic treatments of VRE infections. Furthermore, we will use the enterocin K1-RseP system to unravel features of ligand binding to RseP so that the knowledge obtained will be used to rationally design molecules with improved properties to inhibit VRE and other RseP containing pathogens such as Staphylococcus aureus, S. haemolyticus.

Vancomycin-resistant enterococci (VRE) are involved in diverse infections in humans and treatment of these infections has been very challenging in recent years because the bacteria have become resilient to most antibiotics. We have recently discovered an antimicrobial peptide/bacteriocin called enterocin K1 that has a very specific and potent activity against VRE, especially against Enterococcus faecium which accounts for 80-85% of enterococcal infections. The bacteriocin binds specifically to a transmembrane protein (called RseP) and kills target cells by membrane disruption. Because its mode of killing (membrane disruption) is different from traditional antibiotics, which often are enzyme inhibitors, enterocin K1 readily kills multi-antibiotic resistant VRE. Most importantly, this work on enterocin K1 has revealed RseP to be a novel and seemingly excellent drug target. RseP is involved in regulated intramembrane proteolysis (RIP) in pathways that are vital for enterococcal cells to develop virulence and establish infection in animal hosts. In a rabbit endocarditis model it has been shown that, when the gene encoding RseP is deleted, the affected pathogen is attenuated in the animal host and no virulence developed. Similarly, truncation or frame shift mutations within rseP confer enterococcal cells resistant to enterocin K1 but these cells do not survive in stress conditions. Thus, binding of enterocin K implies a powerful double-attack (membrane-disruption & causing inability to develop virulence), leaving the pathogen no chance to develop infection. In this project proposal we will study the interaction between enterocin K1 and RseP to assess the potential of enterocin K1 in therapeutic treatments. Furthermore, we will use the enterocin K1-RseP system to unravel features of ligand binding to RseP which could be used to develop or screen for non-bacteriocin-based compounds able to inhibit VRE and other RseP containing pathogens such as Staphylococcus aureus.