cAMP-independent oscillations of adenylate cyclase in Dictyostelium discoideum

In starved Dictyostelium discoideum amoebae, extracellular cAMP appears to regulate adenylate cyclase activity such that synthesis of cAMP is rhythmic. Here we report that periodic modulation of adenylate cyclase also occurs via a cAMP-independent mechanism. This was demonstrated using cells which have high levels of adenylate cyclase activity, as measured in cell extracts, but which do not express this enzymic potential when intact. Such cells still rhythmically modify their adenylate cyclase activity and both the periodicity and the amplitude of the oscillations are similar to those seen in cells actively synthesizing cAMP. The phenomenon is observed using both wild-type cells and certain aggregation-minus mutants. The results implicate a mechanism which is cAMP independent in the regulation of adenylate cyclase as well as in the synchrony of the cell population.