Cell communication by periodic cyclic-AMP pulses

Abstract

At the surface of aggregating cells of the slime mould, Dictyostelium discoideum, two different sites interacting with extracellular cAMP are detectable: binding sites and cyclic-nucleotide phosphodiesterase. Both sites are developmentally regulated. An adequate stimulus for the chemoreceptor system in D. discoideum is the change of cAMP concentration in time, rather than concentration per se: long-term binding of cAMP causes only a short-term response. The system is, consequently, adapted to the recognition of pulses rather than to steady-state concentrations of cAMP. The cells are, nevertheless, able to sense stationary spatial gradients and to respond to them by chemotactic orientation. The possibility is discussed that they do so by transforming spatial concentration changes into temporal ones, using extending pseudopods as sensors.