Molecular Basis of Cell Membrane Adaptation in Daptomycin-ResistantEnterococcus faecalis

Abstract

Daptomycin is a last-resort lipopeptide antibiotic that disrupts cell membrane (CM) and peptidoglycan homeostasis. Enterococcus faecalis has developed a sophisticated mechanism to avoid daptomycin killing by re-distributing CM anionic phospholipids away from the septum. The CM changes are orchestrated by a three-component regulatory system, designated LiaFSR, with a possible contribution of cardiolipin synthase (Cls). However, the mechanism by which LiaFSR controls the CM response and the role of Cls are unknown. Here, we show that cardiolipin synthase activity is essential for anionic phospholipid redistribution and daptomycin resistance since deletion of the two genes (cls1andcls2) encoding Cls abolished CM remodeling. We identified LiaY, a transmembrane protein regulated by LiaFSR, as an important mediator of CM remodeling required for re-distribution of anionic phospholipid microdomains via interactions with Cls1. Together, our insights provide a mechanistic framework on the enterococcal response to cell envelope antibiotics that could be exploited therapeutically.

LiaR-dependent gene expression contributes to antimicrobial responses in group AStreptococcus

“…In Enterococcus faecalis , reduced daptomycin susceptibility was associated with redistribution of cardiolipin-rich membrane microdomains away from the bacterial division septa in a manner dependent on LiaF mutation (Tran et al 2013). Recent research further suggests that LiaFSR-dependent regulation of cardiolipin synthase expression is the mechanism responsible for this daptomycin resistance phenotype (Nguyen et al 2023). Given the known association of the ExPortal with peptidoglycan synthesis (Vega, Port, and Caparon 2013), it is possible that anionic lipid redistribution associated with constitutive LiaR phosphorylation reduced AMP killing by disrupting interaction of the tested AMPs with their targets of action (e.g., bacitracin and hNP-1 interaction with lipid II).…”

“…Such LiaR-regulated factors include additional LiaR operon genes (e.g. LiaIGH) (Jordan et al 2006), secreted signaling peptides (LiaXYZ) (Axell-House et al 2024), ABC transporters (Fritsch et al 2011; Chilambi et al 2020), and factors involved in lipid membrane remodeling (Chilambi et al 2020; Nguyen et al 2023). Our studies further demonstrate that the LiaFSR systems of Gram-positive pathogens, while highly conserved, act via clearly distinct mechanisms likely reflective of the unique environmental niche each species occupies.…”