The dynamics of cytoplasmic streaming, retrograde translocation of externally bound particles and locomotion by Entamoeba invadens were compared. Locomoting amoebae were monopodial, exhibited fountain flow cytoplasmic streaming and translocated externally bound erythrocytes to the rear of cells. The rates of rearward flow of peripheral cytoplasmic vacuoles and of the externally bound particles were equal to the rate of cell forward locomotion. Rhodamine-phalloidin staining revealed a distinct cortical polymerized actin cytoskelton. This was least evident about the periphery of the advancing pseudopod, increased in density toward the rear of the cell and was most concentrated in the uroid. A monoclonal anti-eucaryotic actin antibody, which recognized monomeric Entamoeba actin on immunoblots, stained trophozoites by indirect immunofluorescence throughout the cytoplasm, but not in the cortical regions stained by rhodamine-phalloidin. This and other evidence implied that the antibody recognized only unpolymerized actin in Entamoeba. We propose that locomotion, cytoplasmic streaming and translocation of externally bound particles are driven by a common actin-based mechanism in Entamoeba, possibly involving retrograde cortical actin flow and recycling.

Latex beads and liposomes carrying glycoproteins with carbohydrate sequences recognized by an Entamoeba histolytica galactose-specific binding protein were assessed for their ability to adhere to trophozoites and to stimulate amoeba actin polymerization. Glycoprotein-conjugated beads bound significantly to amoebae but did not stimulate actin polymerization. Glycoprotein-bearing liposomes bound to amoebae and did enhance actin polymerization, as do recognized glycosphingolipid-bearing liposomes (G.