Concanavalin A-induced redistribution of surface receptors in Acanthamoeba castellanii at different growth phases.

Concanavalin A (ConA)-induced redistribution of surface receptors has been studied in Acanthamoeba castellanii at different growth phases utilizing double fluorescent techniques and transmission electron microscopy. When the amoebae were incubated with 2 micrograms and 10 micrograms tetramethylrhodamine isothiocyanate (TRITC)-ConA/ml for 4 min and 15 min at 28 degrees C the staining pattern was characterized by various numbers of scattered aggregates of fluorescent ConA. Double labeling of the amoebae showed that the fluorescent aggregates represented internalized label, and the internalization was not preceded by any aggregation of ConA receptors on the cell surface as visualized by incubating with anti-ConA serum followed by fluorescein isothiocyanate-conjugated anti-IgG. Following exposure of the amoebae to 10 micrograms TRITC-ConA/ml for 4 min and 15 min at 28 degrees C intracellular accumulation of some of the fluorescent aggregates in cap-like structures occurred at the logarithmic and postlogarithmic growth phases but not at the early stationary growth phase. Electron microscopic observation of amoebae labeled with ferritin-conjugated ConA at 28 degrees C revealed a uniform surface labeling and an intracellular accumulation of the label in vesicular and tubular structures, and occasionally in cap-like structures. Surface capping of ConA receptors in Acanthamoeba was induced by treating the amoebae with ConA and anti-ConA serum at 0 degrees C followed by incubation at 28 degrees C. The formation of surface caps in Acanthamoeba showed growth-phase dependency, too. The visualization of the surface caps at the electron microscopic level was performed by indirect staining utilizing protein A-colloidal gold.(ABSTRACT TRUNCATED AT 250 WORDS)