PHAGOCYTOSIS IN ACANTHAMOEBA .2. SOLUBLE AND INSOLUBLE MANNOSE-RICH LIGANDS STIMULATE PHOSPHOINOSITIDE METABOLISM

The generation of second messengers during phagocytosis of yeast by Acanthamoeba castellanii was examined. The kinetics of binding and internalization of yeast by Acanthamoeba were measured and this was compared with the generation of known second messengers. We observed stimulated degradation of PI-4, 5-P2 to 1,4,5 IP3 with kinetics similar to that observed for the binding of yeast to amoeba. Similar production of IP3 could be induced upon treatment with a soluble mannosylated glycoprotein. We propose that the Acanthamoeba mannose receptor stimulates the degradation of PI-4, 5-P2 to 1,4,5 IP3 as an initial event in phagocytosis.