A new model for chemotactic signal transduction in Dictyostelium discoideum.

Dictyostelium discoideum amoebae were employed to study the refractoriness and adaptation of the rapid (5sec) accumulation of actin in their Triton-insoluble cytoskeletons following stimulation with specific chemoattractants. Amoebae became refractory within 10sec for this response but no adaptation occurred during this period. Amoebae desensitized for one attractant were not desensitized for another and responses to stimulation with a mixture of attractants were approximately additive. The characteristics of these processes are compared to published studies of adaptation in other chemoattractant-induced responses and a new model for the chemotactic signal transduction pathway is formulated. We conclude that intracellular cGMP accumulation may be on a separate branch of the pathway from the actin response.