Science · 1981 · 403 citations · 21 references
A novel isotope‑dilution fluorography was used, where endogenous cAMP competed with 3H‑cAMP for high‑affinity protein‑kinase sites on a Millipore filter to map its distribution in aggregating Dictyostelium monolayers. cAMP appeared in spiral or concentric waves centered on aggregation foci, with peak concentrations near 10⁻⁶ M and widths of 0.3–1 mm, correlating with cell elongation toward high‑cAMP zones and supporting a periodic relay model of aggregation.
The distribution of adenosine 3′,5′-monophosphate (cyclic AMP) in fields of aggregating amoebae of Dictyostelium discoideum was examined by a novel isotope dilution-fluorographic technique. Cellular cyclic AMP was visualized by its competition with exogenous 3 H-labeled cyclic AMP for high-affinity binding sites on protein kinase immobilized on a Millipore filter used to blot the monolayer. The cyclic AMP was distributed in spiral or concentric circular wave patterns which centered on the foci of the aggregations. These patterns were correlated with those of cell shape change that propagate through the monolayers: cells in regions of high concentrations of cyclic AMP were elongated (presumably moving up a cyclic AMP gradient), whereas those in regions of low cyclic AMP concentrations were randomly directed. The highest cyclic AMP concentrations were about 10 -6 M . The widths of the regions of elevated cyclic AMP were about 0.3 to 1 millimeter which, assuming a wave velocity of 300 micrometers per minute, suggests that a cell signals for about 1 to 3 minutes. These observations support the hypothesis that the aggregation process in Dictyostelium is mediated by the periodic relay of cyclic AMP signals and suggest a simple scheme for the dynamics of the aggregation process.
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