APOPTOTIC CELL-DEATH INDUCED BY PHYSARUMIN (HEMAGGLUTININ FROM MYXOMYCETE, PHYSARUM-POLYCEPHALUM)

Physarumin, a carbohydrate-binding protein (hemagglutinin or lectin), was isolated front the plasmodium of Physarum polycephalum. Physarumin agglutinated not only several species of erythrocytes but also tumor cells such as AH109A ascites hepatoma cells, sarcoma 180 ascites cells and mouse leukemia P388 cell lines. Physarumin had tumor cell growth- inhibitory activity, and induced the apoptosis of P388 cell lines. Phy sarumin-induced apoptosis required binding to a 68 kDa counter-recepto r on the P388 cell surface. Since the agglutinating and antiproliferat ive activities of physarumin were inhibited by asialofetuin and thyrog lobulin, respectively, it is suggested that physarumin reacts with the galactose moiety of carbohydrate chains of physarumin receptor.