Spreading of a mycobacterial cell surface lipid into host epithelial membranes promotes infectivity

Abstract

<jats:title>ABSTRACT</jats:title><jats:p>Several virulence lipids populate the outer cell wall of pathogenic mycobacteria (Jackson, 2014). Phthiocerol dimycocerosate (PDIM), one of the most abundant outer membrane lipids (Anderson, 1929), plays important roles in both defending against host antimicrobial programs (Camacho et al., 2001; Cox et al., 1999; Murry et al., 2009) and in evading these programs altogether (Cambier et al., 2014a; Rousseau et al., 2004). Immediately following infection, mycobacteria rely on PDIM to evade toll-like receptor (TLR)-dependent recruitment of bactericidal monocytes which can clear infection (Cambier et al., 2014b). To circumvent the limitations in using genetics to understand virulence lipid function, we developed a chemical approach to introduce a clickable, semi-synthetic PDIM onto the cell wall of <jats:italic>Mycobacterium marinum</jats:italic>. Upon infection of zebrafish, we found that PDIM rapidly spreads into host epithelial membranes, and that this spreading inhibits TLR activation. PDIM’s ability to spread into epithelial membranes correlated with its enhanced fluidity afforded by its methyl-branched mycocerosic acids. Additionally, PDIM’s affinity for cholesterol promoted its occupation of epithelial membranes; treatment of zebrafish with statins, cholesterol synthesis inhibitors, decreased spreading and provided protection from infection. This work establishes that interactions between host and pathogen lipids influence mycobacterial infectivity and suggests the use of statins as tuberculosis preventive therapy by inhibiting PDIM spread.</jats:p>

Mycobacterium marinum phthiocerol dimycocerosates enhance macrophage phagosomal permeabilization and membrane damage

“…Supporting this hypothesis, multiple groups have observed that loss of PDIM reduces phagosomal permeabilization in M. tuberculosis [23][24][25][26]. As the study of M. marinum has provided new insights into PDIM's role in pathogenesis [4,7], we set out to determine if this PDIM-ESX-1 interaction was conserved in M. marinum. In this paper, we confirm that as in M. tuberculosis, proper PDIM localization is required for M. marinum to effectively permeabilize macrophage phagosomes.…”

“…PDIM-deficient mutants in M. marinum and M. tuberculosis are attenuated in animal models of infection [2][3][4] and membrane permeability [5,6]. Contact between mycobacteria and host environment results in the transfer of surface PDIM into host membranes, suppressing toll-like receptor signaling (TLR) and preventing the recruitment of microbicidal monocytes during infection [4,7,8]. Consequently, PDIM mutants are rapidly phagocytosed and killed by microbicidal monocytes [4].…”

Host Cell Targets of Released Lipid and Secreted Protein Effectors of Mycobacterium tuberculosis

“…PDIM, another major virulence lipid of Mtb, was found in macrophages membranes during infection (Augenstreich et al, 2019). Preliminary results on Mm coating with fluorescent modified PDIM indicated a transfer and a diffusion of these lipids upon contact with macrophages (Cambier et al, 2020). These results also support a passive transfer of PDIM upon contact of the bacteria with host cells.…”

Mycobacterium marinumphthiocerol dimycocerosates enhance macrophage phagosomal permeabilization and membrane damage

“…Supporting this hypothesis, multiple groups have observed that loss of PDIM reduces phagosomal permeabilization in M. tuberculosis [23–26]. As the study of M. marinum has provided new insights into PDIM’s role in pathogenesis[4,7], we set out to determine if this PDIM-ESX-1 interaction was conserved in M. marinum . In this paper, we confirm that as in M. tuberculosis , proper PDIM localization is required for M. marinum to effectively permeabilize macrophage phagosomes.…”

“…PDIM-deficient mutants in M. marinum and M. tuberculosis are attenuated in animal models of infection[2–4] and membrane permeability[5,6]. Contact between mycobacteria and host environment results in the transfer of surface PDIM into host membranes, suppressing toll-like receptor signaling (TLR) and preventing the recruitment of microbicidal monocytes during infection[4,7,8]. Consequently, PDIM mutants are rapidly phagocytosed and killed by microbicidal monocytes[4].…”