Surface Receptor Mediated Activation and Adaptation of Adenylate Cyclase in Dictyostelium discoideum

Abstract

The cellular slime mold Dictyostelium discoideum offers an attractive model system for studying a variety of physiological processes such as Chemotaxis, inter- and intra-cellular communication, gene expression, pattern formation and morphogenesis. Early in the developmental phase of the organisms’ life cycle up to 106 identical unicellular amoebae are induced to migrate chemotactically towards a central region. This aggregation process occurs in response to cyclic AMP secreted by one or more centrally situated cells. Cyclic AMP acts not only as a chemotactic signal but also induces the synthesis and secretion of cAMP from the responding cells. The net result is a concomitant inward migration of cells and outward propagation of cAMP waves throughout the population. The rate of cAMP-induced cAMP synthesis is not constant but oscillates with a frequency of 5–10 minutes. This occurs because cAMP-stimulated adenylate cyclase activity adapts or becomes desensitized in the presence of cAMP.