Exibir código-fonte para JEAN-LOUIS MARTIEL AND ALBERT GOLDBETER

'''abstract'''

ABSTRACT We analyze a model based on receptor modification for the cAMP signaling system that controls
aggregation of the slime mold Dictyostelium discoideum after starvation. The model takes into account both the
desensitization of the cAMP receptor by reversible phosphorylation and the activation of adenylate cyclase that follows
binding of extracellular cAMP to the unmodified receptor. The dynamics of the signaling system is studied in terms of
three variables, namely, intracellular and extracellular cAMP, and the fraction of receptor in active state. Using
parameter values collected from experimental studies on cAMP signaling and receptor phosphorylation, we show that
the model accounts qualitatively and, in a large measure, quantitatively for the various modes of dynamic behavior
observed in the experiments: (a) autonomous oscillations of cAMP, (b) relay of suprathreshold cAMP pulses, i.e.,
excitability, characterized by both an absolute and a relative refractory period, and (c) adaptation to constant cAMP
stimuli. A two-variable version of the model is used to demonstrate the link between excitability and oscillations by
phase plane analysis. The response of the model to repetitive stimulation allows comprehension, in terms of receptor
desensitization, of the role of periodic signaling in Dictyostelium and, more generally, the function of pulsatile patterns

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