Exploiting thioether reactivity to label mycobacterial glycans
Year: 2025
Type: article
Abstract: Mycobacterium tuberculosis ( Mtb ) is a leading cause of death worldwide. Mtb cell envelope glycans are potent virulence factors that play key roles in mediating infection of host tissues and modulating the host immune response. However, there are few ways to site-selectively modify and label these or any glycans to study their functions in disease. This gap arises because glycans generally lack functional groups amenable to bioconjugation strategies. Methylthioxylofuranose (MTX), a rare monosaccharide in select pathogenic mycobacteria, is an exception. MTX is appended to mannose-capped lipoarabinomannan (ManLAM), an antigenic glycolipid in the Mtb cell envelope implicated in downregulating the host immune system during infection. MTX is unique not only in its prevalence but also in its functionality—it contains a thioether not present in other glycans. We envisioned exploiting the MTX thioether to selectively label ManLAM with an oxaziridine probe. Here, we show that MTX-containing glycans can be labeled selectively in the test tube and live cells, highlighting the reactivity and accessibility of this motif. Our approach labels ManLAM efficiently despite the presence of protein methionine residues and can distinguish between different mycobacterial species. Using an oxaziridine equipped with a reporter, we could visualize ManLAM localization in live cells and a macrophage infection model, highlighting the stability of the label and the cell envelope in this environment. These studies will enable investigations of dynamic changes in a critical Mtb cell envelope component during infection. Moreover, the selective reactivity of thioethers can be leveraged to expand the repertoire of glycan bioconjugation strategies.
Language: English
Subfield: Organic Chemistry
Field: Chemistry
Domain: Physical Sciences
Open Access status: hybrid
Funders: National Science Foundation, Harvard University, Harvard University Center for AIDS Research, Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, National Institutes of Health, Center for AIDS Research, University of Washington, National Cancer Institute, National Institute of Allergy and Infectious Diseases, National Institute of Arthritis and Musculoskeletal and Skin Diseases, Division of Graduate Education
Awards: G1203476693, G1456240154, G1575283533, G1646638647, G1722716446, G2417641742, G345173699, G4581281568, Graduate Research Fellowship Program (GRFP), IL-26 in host defense against infection by intracellular bacteria in skin, G6675063934, Graduate Research Fellowship Program (GRFP), G7287189751, G7590741913, G7785852513, G8198795195, G8683364977, Metabolic determinants of Mtb virulence, vulnerability and variation, Cancer Center Support (Core) Grant, Chemical Biological Discovery of Lipid Virulence Factors in the Major Bacterial Pathogens, Chemical Probes of Mycobacteria, Harvard University Center for AIDS Research
OpenAlex ID: W4410085809