Exploiting thioether reactivity to label mycobacterial glycans

Area of Science:

• Microbiology
• Glycobiology
• Chemical Biology

Background:

• Mycobacterium tuberculosis (Mtb) poses a significant global health threat, with its cell envelope glycans acting as crucial virulence factors.
• Studying Mtb glycans is challenging due to the lack of methods for site-selective modification and labeling.
• Mannose-capped lipoarabinomannan (ManLAM) is a key Mtb glycolipid involved in immune evasion.

Purpose of the Study:

• To develop a novel bioconjugation strategy for site-selective labeling of Mtb glycans.
• To exploit the unique thioether in methylthioxylofuranose (MTX) for selective glycan modification.
• To visualize ManLAM localization and dynamics during infection.

Main Methods:

• Utilized an oxaziridine probe to target the thioether in MTX-containing glycans.
• Performed selective labeling of MTX-glycans in vitro and in live Mtb cells.
• Visualized ManLAM localization in live cells and a macrophage infection model.

Main Results:

• Demonstrated selective labeling of MTX-glycans, even in the presence of protein methionine.
• Successfully visualized ManLAM localization in live cells and during macrophage infection.
• Showcased the stability of the label and Mtb cell envelope in an infection model.

Conclusions:

• Developed a novel and efficient method for site-selective glycan labeling in Mtb.
• The MTX thioether serves as a valuable handle for glycan bioconjugation.
• This approach enables dynamic studies of Mtb cell envelope components during infection.