Opposite effects of adenosine on two types of cAMP-induced gene expression in Dictyostelium indicate the involvement of at least two different intracellular pathways for the transduction of cAMP signals.

Adenosine promotes the cAMP-induced increase of mRNAs, probed with the cDNAs D11 and D14, which are preferentially expressed in prestalk cells, while it inhibits cAMP-induced prespore gene expression. Half-maximal inhibition of prespore gene expression occurs at about 300 muM, while prestalk stimulation by adenosine occurs at about 100-fold lower concentrations and requires the presence of cAMP. These results indicate that adenosine interferes with the transduction to cAMP to gene expression and suggest the involvement of two different adenosine target sites. Our data furthermore indicate that the transduction of extracellular cAMP to prespore gene or prestalk gene expression occurs via divergent pathways.