The major objectives of this proposed research are to continue basic investigations into the mechanism of signal-coupling during the initiation of endocytosis in Amoeba proteus and to provide some undergraduate students with a realistic research experience. Endocytosis is a fundamental process which involves the uptake of material external to a cell by surface membrane infolding and vesiculation. Previous work from this laboratory examined the interaction of signal molecules with the cell surface and identified several possible components of the signal pathway associated with the onset of endocytosis. These include a G- protein, cyclic AMP and calcium. A G-protein in the amoeba membrane was identified by ADP-ribosylation of a membrane protein(s) in the presence of cholera and pertussis toxin. Initiation of both phagocytosis and pinocytosis elicit rapid transient oscillations in cytoplasmic cAMP levels and cytoplasmic Ca increases transiently in stimulated cells. This proposal will attempt to further characterizethe components of the signal pathway and try to differentiate between the signal processes occurring during both pinocytosis and phagocytosis. The ameba represents a particularly useful model system in the study of endocytosis and it is expected that this study will increase our insight into the mechanism of endocytosis in this and other systems.
