Sensitizing Staphylococcus aureus to antibacterial agents by decoding and blocking the lipid flippase MprF

Abstract

The pandemic of antibiotic resistance represents a major human health threat demanding new antimicrobial strategies. MprF is the synthase and flippase of the phospholipid lysyl-phosphatidylglycerol that increases virulence and resistance of methicillin-resistant Staphylococcus aureus (MRSA) and other pathogens to cationic host defense peptides and antibiotics. With the aim to design MprF inhibitors that could sensitize MRSA to antimicrobial agents and support the clearance of staphylococcal infections with minimal selection pressure, we developed MprF-targeting monoclonal antibodies, which bound and blocked the MprF flippase subunit. Antibody M-C7.1 targeted a specific loop in the flippase domain that proved to be exposed at both sides of the bacterial membrane, thereby enhancing the mechanistic understanding of bacterial lipid translocation. M-C7.1 rendered MRSA susceptible to host antimicrobial peptides and antibiotics such as daptomycin, and it impaired MRSA survival in human phagocytes. Thus, MprF inhibitors are recommended for new anti-virulence approaches against MRSA and other bacterial pathogens.

PplT domain proteins – ubiquitous potential prokaryotic phospholipid translocases

“…PplT proteins may therefore become attractive targets for future anti-fitness drugs to combat major human pathogens. In support of such a strategy, monoclonal antibodies directed against extracellular portions of the PplT domain of the S. aureus MprF have recently been shown by inhibiting the Lys-PG exposure at the outer leaflet of the membrane and therefore sensitize S. aureus to cationic antibiotics [9].…”

“…The two domains function together even if expressed as separate proteins [8]. The flippase domain of MprF consists of eight transmembrane sections [8] and contains a motif that is accessible from both sides of the cytoplasmic membrane [9]. It has been proposed that this part moves during the lipid translocation process or that it is in the center between two larger cavities that form the lipid translocation channel [9].…”

“…The flippase domain of MprF consists of eight transmembrane sections [8] and contains a motif that is accessible from both sides of the cytoplasmic membrane [9]. It has been proposed that this part moves during the lipid translocation process or that it is in the center between two larger cavities that form the lipid translocation channel [9]. The structure of the Rhizobium tropici MprF protein with bound Lys-PG molecules captured in the process of translocation has recently been elucidated by cryo-electron microscopy [7].…”

Insights into the role of lipoteichoic acids and MprF function in Bacillus subtilis

“…Further analysis of LTA synthesis and cell wall composition will help redefine MprF-mediated Dap R mechanism and help appreciate the exact role of MprF in the net cell surface charge and the protection against cationic antimicrobial peptides. Recent research on compounds targeting LTA synthesis (68, 69) and on MprF-targeting monoclonal antibodies (70) suggest these approaches have relevance in combating clinically relevant bacteria.…”

Interference with lipoprotein maturation sensitizes methicillin-resistantStaphylococcus aureusto human group IIA secreted phospholipase A2and daptomycin

“…As a result, S. aureus has evolved resistance strategies against hGIIA-mediated killing, which are geared towards changing the overall charge of the membrane or cell wall. For example, S. aureus increases its surface charge by adding D-alanine residues to teichoic acids through the DltABCD machinery and L-lysine residues to membrane phospholipids through the activities of the enzyme MprF [14, 20]. The two-component regulatory system GraRS controls the expression of both mrpF and dltABCD , thereby controlling S. aureus resistance to cationic antimicrobial peptides and proteins such as hGIIA [21, 22].…”