Role for endocytosis in conjugation in Tetrahymena.

We examined the effect of inhibitors of receptor-mediated endocytosis on cell pair formation during conjugation in Tetrahymena thermophila. Dansylcadaverine (20 microM), methylamine (20 mM), and bacitracin (2 mg/ml) prevented cell pair formation even when added poststarvation, after mixing of cells of opposite mating types (during the preparing interaction). Chloroquine (10 and 25 microM) did not inhibit cell pair formation, leading to the conclusion that inhibition by dansylcadaverine, methylamine, and bacitracin is not due to an alkalinization of the lysosome. These results did not allow us to define the time in the preparing interaction at which inhibition occurs, nor to identify the cellular components involved, but they did support the hypothesis that an endocytotic event(s) plays a role in the cell contact-mediated recognition which occurs during the preparing interaction.