Bee venom phospholipase A₂Is recognized by the macrophage mannose receptor

Abstract

A high affinity and a specific binding site for bee venom PLA₂was found on the surface of J774E macrophages. The binding sites for bee venom PLA₂are entirely different from the binding sites for pancreatic and snake venom PLA₂as revealed by competition experiments. Binding and uptake of bee venom PLA₂by J774E macrophages was shown to be competed by mannose-BSA, glucose-BSA,N-acetylglucosamine-BSA, but not by galactose-BSA, indicating that the binding of bee venom PLA₂is probably mediated by macrophage mannose receptor. An affinity labeling experiment revealed that the bee venom PLA₂specifically binds to a single polypeptide with a mass of 𕐟80 kDa. Moreover, the affinity labeled protein component, i.e., the binding site, was not detected in the presence of excess mannose-BSA, suggesting that mannose-BSA and the bee venom PLA₂bind to the same site on macrophages. These observations were further supported by the binding of bee venom PLA₂to cells which are known to express the mannose receptor and by specific binding of bee venom PLA₂to the purified mannose receptor. These data confirm that bee venom PLA₂binding to macrophages is mediated through the mannose receptor.