Adaptation of Dictyostelium Discoideum Cells to Chemotactic Signals
The cellular slime mold Dictyostelium discoideum lives in the soil where it feeds on bacteria. Exhaustion of the food supply induces cell aggregation. Subsequently, cells differentiate to two cell types; spores embedded in a slime droplet on top of a tubular stalk of vacuolized cells. Cell aggregation is mediated by Chemotaxis. Upon starvation some cells start to secrete a chemoattractant which has been identified as cAMP (1). Extracellular cAMP induces two responses, which are both mediated by cell surface receptors. First, cAMP activates adenylate cyclase; the produced cAMP is secreted and may trigger other cells, thus relaying the signal. Second, cAMP induces a chemotactic response by which cells move in the direction of the cAMP source. The combined effects of cAMP relay and Chemotaxis may lead to the accumulation of as many as 100,000 cells in a central collecting point derived from an area of about 1 cm2 (see 2,3 for recent reviews).
KeywordsAdenylate Cyclase Guanylate Cyclase Pertussis Toxin cAMP Concentration Dictyostelium Discoideum
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