Virulence Mechanisms of Mycobacterial Lipids

Mycobacterial pathogens deploy a specialised array of cell envelope lipids to undermine host defences and promote persistent infection. Chief among these are phthiocerol dimycocerosates (PDIM) and phenolic glycolipids (PGL), which together shape the outcome of tuberculosis and related diseases. PDIM integrate into phagosomal membranes, perturbing lipid organisation to facilitate escape into the cytosol, where bacilli exploit a protected niche and trigger necrotic cell death. PGL interact with host receptors to dampen inflammatory signalling, limit nitric oxide production and subvert toll-like receptor pathways, thereby creating an immune-silent environment. Biosynthetic gene clusters and transcriptional repressors coordinate the synthesis and export of these lipids in response to environmental cues. Biophysical studies have revealed that the methyl-branched chains of PDIM and the aromatic sugar moieties of PGL not only alter membrane fluidity and receptor clustering but also drive lateral spreading into host membranes. By modulating phagosomal integrity, autophagic recognition and cytokine production, mycobacterial lipids are central to immune evasion, dissemination and long-term survival, making the enzymes of their biosynthesis promising targets for novel therapies.

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Virulence Mechanisms of Mycobacterial Lipids publication trend

The graph below shows the total number of articles in virulence mechanisms of mycobacterial lipids across all publications each year (not limited to Nature Index journals).

Technical terms

Phthiocerol dimycocerosates (PDIM): Long-chain, methyl-branched lipids in the mycobacterial envelope that disrupt phagosomal membranes and facilitate cytosolic access.

Phenolic glycolipids (PGL): Aromatic sugar-containing lipids that modulate host immune receptors to suppress inflammatory and antimicrobial responses.

Phagosome: A membrane-bound compartment in phagocytic cells that sequesters engulfed pathogens for degradation.

Xenophagy: A specialised form of autophagy targeting intracellular pathogens for lysosomal destruction.

Bioorthogonal labelling: A chemical strategy to tag biomolecules in living systems without interfering with native biochemical processes.

References

1. Bioorthogonal Metabolic Labeling of the Virulence Factor Phenolic Glycolipid in Mycobacteria. ACS Chemical Biology (2024).
2. The Cell Wall Lipid PDIM Contributes to Phagosomal Escape and Host Cell Exit of Mycobacterium tuberculosis. mBio (2017).
3. Spreading of a mycobacterial cell surface lipid into host epithelial membranes promotes infectivity. eLife (2020).
4. Mycobacterial Phenolic Glycolipids Selectively Disable TRIF-Dependent TLR4 Signaling in Macrophages. Frontiers in Immunology (2018).
5. Playing hide-and-seek with host macrophages through the use of mycobacterial cell envelope phthiocerol dimycocerosates and phenolic glycolipids. Frontiers in Cellular and Infection Microbiology (2014).
6. Underestimated Manipulative Roles of Mycobacterium tuberculosis Cell Envelope Glycolipids During Infection. Frontiers in Immunology (2019).