Selective induction of gene expression and second-messenger accumulation in Dictyostelium discoideum by the partial chemotactic antagonist 8-p-chlorophenylthioadenosine 3',5'-cyclic monophosphate

During development of the cellular slime mold Dictyostelium discoideum, cAMP induces chemotaxis and expression of different classes of genes by means of interaction with surface cAMP receptors. We describe a cAMP derivative, 8-p-chlorophenylthioadenosine 3',5'-cyclic monophosphate (8-CPT-cAMP), which inhibits cAMP-induced chemotaxis at low concentrations but induces chemotaxis at supersaturating concentrations. This compound, moreover, selectively activates expression of aggregative genes but not of postaggregative genes. 8-CPT-cAMP induces normal cGMP and cAMP accumulation but in contrast to cAMP, which increases inositol 1,4,5-trisphosphate levels, 8-CPT-cAMP decreases inositol 1,4,5-trisphosphate levels. The derivative induces reduced activation of guanine nucleotide regulatory proteins, which may cause its defective activation of inositol 1,4,5-trisphosphate production. Our data suggest that disruption of inositolphospholipid signaling impairs chemotaxis and expression of a subclass of cAMP-regulated genes.