The major objectives of the proposed research are to continue basic investigations into the mechanism of phagocytosis using Amoeba proteus as a model cell system, and in the context of an undergraduate institution, to expose undergraduate students to a realistic research experience. Phagocytosis is a fundamental cellular process which involves the uptake of particulate material through surface membrane infolding and vesiculaton. In the initial three years of NSF support for this project it was demonstrated that chemotactic peptides can induce phagocytosis in the amoeba. A more detailed analysis of this process is now proposed. Stimulation of phagocytosis involves calcium movements and possibly components of the arachidonic acid cascade, perhaps in a signal coupling role. The events associated with signal coupling during phagocytosis will now be analyzed. Initial association of the signal with the cell surface will be measured by following the binding of tritiated peptides to the amoeba surface. In order to establish the mechanisms by which surface information is transmitted to the cell interior, the role of G proteins, diacylglycerol, inositol trisphosphate, calcium, and arachidonic acid metabolites in signal transmission will be investigated. The amoeba is a particularly useful model system for the study of endocytosis, and the results of this study should increase our insight into the mechanism of phagocytosis in this and other cells. This study will also contribute to basic understanding of cellular signal transduction mechanisms in general.
