Bee venom phospholipase A2 is recognized by the macrophage mannose receptor

A high affinity and a specific binding site for bee venom PLA2 was found on the surface of J774E macrophages. The binding sites for bee venom PLA2 are entirely different from the binding sites for pancreatic and snake venom PLA2 as revealed by competition experiments. Binding and uptake of bee venom PLA2 by 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 PLA2 is probably mediated by macrophage mannose receptor. An affinity labeling experiment revealed that the bee venom PLA2 specifically binds to a single polypeptide with a mass of approximately 180 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 PLA2 bind to the same site on macrophages. These observations were further supported by the binding of bee venom PLA2 to cells which are known to express the mannose receptor and by specific binding of bee venom PLA2 to the purified mannose receptor. These data confirm that bee venom PLA2 binding to macrophages is mediated through the mannose receptor.