The role of cyclic nucleotides and cell agglomeration in postaggregative enzyme synthesis in Dictyostelium discoideum.

Accumulation of cell-associated cyclic AMP phosphodiesterase and of two enzymes of carbohydrate metabolism, UDP glucose pyrophosphorylase and glycogen phosphorylase, was examined during development of Dictyostelium discoideum strain V12 M2 on agar and in suspension. In slow-shaken suspension, as well as on agar, phosphodiesterase began to accumulate about 3 hr after the initiation of development and reached a maximum approximately 2 hr later. At this time rapid accumulation of the two other enzymes, referred to as postaggregative enzymes, was initiated. In fast-shaken suspension phosphodiesterase accumulation did not stop, and synthesis of the postaggregative enzymes was greatly reduced. Large agglomerates formed shortly after the initiation of development in the slow-shaken culture, whereas in the fast-shaken culture the cells remained separate for about 5 hr and the agglomerates formed thereafter were much smaller. Addition of cyclic AMP (5 × 10^?4M) to the fast-shaken cells after 6 hr of development arrested further phosphodiesterase accumulation and greatly increased synthesis of the postaggregative enzymes. Cyclic GMP was considerably less effective. In contrast, cyclic AMP and cyclic GMP were equally effective in inducing accumulation of phosphodiesterase when added between 1 and 3 hr of development. We conclude that the synthesis of the two postaggregative enzymes studied here follows immediately upon the phase of phosphodiesterase synthesis and that both phases of synthesis depend in some way upon elevation of intracellular cyclic nucleotide levels.