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Glycosphingolipid-binding specificity of the mannose-binding protein from human sera
M Kyogashima1, H C Krivan, J E Schweinle
1Laboratory of Structural Biology, National Institute of Diabetes, Digestive, and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892.
Archives of Biochemistry and Biophysics
|November 15, 1990
Summary
Mannose-binding protein selectively binds to specific N-acetylglucosamine-terminated glycosphingolipids, Lc3Cer and nLc5Cer. This binding specificity suggests potential in vivo roles and offers a sensitive method for detecting these lipids in tissues.
Area of Science:
- Biochemistry
- Immunology
- Glycobiology
Background:
- Mannose-binding protein (MBP) is a key component of the innate immune system.
- MBP recognizes carbohydrate structures on pathogens.
- The precise binding targets of MBP on host cells are not fully understood.
Purpose of the Study:
- To purify human mannose-binding protein (MBP).
- To investigate the glycosphingolipid-binding specificity of purified MBP.
- To explore potential in vivo functions and diagnostic applications of MBP binding.
Main Methods:
- Affinity chromatography using mannose-Sepharose and underivatized Sepharose for MBP purification.
- Chromatogram overlay and solid-phase assays to determine glycosphingolipid binding.
- Quantification of Lc3Cer and nLc5Cer levels in chronic myeloid leukemia cells.
Main Results:
- MBP was purified to homogeneity from human serum.
- Purified MBP exhibited high-affinity binding to Lc3Cer and nLc5Cer, both terminating in N-acetylglucosamine.
- MBP did not bind to other tested glycosphingolipids lacking terminal N-acetylglucosamine.
- MBP binding assays proved sensitive for detecting low picomole amounts of Lc3Cer and nLc5Cer.
- Chronic myeloid leukemia cells were found to contain both Lc3Cer and nLc5Cer.
Conclusions:
- N-acetylglucosamine-terminated glycosphingolipids, specifically Lc3Cer and nLc5Cer, are high-affinity ligands for human mannose-binding protein.
- These findings suggest that N-acetylglucosamine-terminated glycosphingolipids may function as cell-surface attachment sites for MBP in vivo.
- The specific binding of MBP can be leveraged as a sensitive diagnostic probe for quantifying Lc3Cer and nLc5Cer in biological samples.