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Lectin-like Characteristics of Recombinant Human Interleukin-1β Recognizing Glycans of the Glycosylphosphatidylinositol Anchor*

We found that 35S-labeled recombinant human interleukin-1β (rhIL-1β) binds phosphatidylinositol-specific phospholipase C-treated human placental alkaline phosphatase, phosphatidylinositol-specific phospholipase C-treated trypanosome surface variant glycoproteins, and urinary uromodulin immobilized on plates or immobilized on CNBr-activated Sepharose 4B. The interaction between rhIL-1β and these glycoproteins was lectin-like, since it was inhibited in the presence of specific saccharides, i.e. mannose 6-phosphate or synthetic Ac-NH·CH2·CH2·PO4 −→6Manα1→(±2Manα1→±6Manα1→)propyl at about 1 μm. On the other hand, a wide variety of compounds including biantennary sugar chains derived from these glycoproteins as well as ethanolamine phosphate, inositol phosphate, mannose 6-sulfate, mannose 1-phosphate, glucose 6-phosphate, and mannitol 6-phosphate did not show any inhibitory effect at concentrations up to 1 mm. These results indicate that rhIL-1β interacts with these glycoproteins via the mannose 6-phosphate diester of glycans on the glycosylphosphatidylinositol (GPI) anchor. Furthermore, when monolayers of polarized Madin-Darby canine kidney cells on polycarbonate filter membranes were incubated with 35S-rhIL-1β in either the apical or basolateral chamber, 35S-interleukin-1β was found to bind specifically to the apical membranes with a K a value of 4.6 × 107 m −1, and the specific interaction was inhibited by 1 μm mannose 6-phosphate. Since the mannose 6-phosphate diester moiety exists only in the GPI glycans on plasma membranes, it was evident that interleukin-1β can directly interact with the mannose 6-phosphate diester component of the intact glycan of GPI anchors on plasma membranes.