Fibronectin "receptor" in Entamoeba histolytica: purification and association with the cytoskeleton.

Preferential binding of E. histolytica trophozoites to fibronectin (FN) is mediated by a 37 kDa peptide (1). We report now the further purification of this "putative" FN receptor (FN-R) and its characterization as an external membrane component also associated to the cortical cytoskeleton. The FN-R was solubilized from Triton-cytoskeletons and separated by chromatography in FN-Sepharose. The FN-R, labeled when live trophozoites were iodinated with 125I, remained associated to the cytoskeleton together with the FN bound to it, but was removed from the surface by trypsinization. The association of the FN-R to the cytoskeleton was inhibited by cytochalasin D, which also interferes with the adhesion of trophozoites to FN substrates and the organization of actin adhesion plates.