Cell-cell contact and cAMP are critical regulators of Dictyostelium discoideum development. Dr. Fontana has shown that cell-cell contact evokes cAMP secretion and alters amoebal responsiveness to subsequent applications of cAMP. These observations provide a biochemical, quantitatable assay for a contact-mediated event and suggest that, in some instances, cell-cell contact may regulate development by altering cAMP levels. Her first objective involves the elucidation of the mechanism through which cell-cell contact elicits these responses. The following will be examined to determine their involvement in the transduction of the contact stimulus: the adenylate cyclase, a GTP- binding protein, the ras protein, a cytoplasmic component, and IP3. The contact receptor and ligand will be identified using biochemical and immunological methods. The second objective is the implication of these contact-mediated responses in the regulation of development. Mutant analysis will be employed. The third objectiv is the characterization of Dictyostelium in vivo cyclic nucleotide metabolism. A technique involving 18O labeling will be utilized. Understanding the mechanisms by which chemical signals and cell-cell contact regulate development in this primitive eukaryotic organism may lead to a greater understanding of the mechanisms by which these regulate development in humans.
