Lectin-like characteristics of recombinant human interleukin-1β recognizing glycans of the glycosylphosphatidylinositol anchor

Abstract

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-lβ 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-lβ was found to bind specifically to the apical membranes with a K(a) value of 4.6 x 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-lβ can directly interact with the mannose 6-phosphate diester component of the intact glycan of GPI anchors on plasma membranes.