Ligand-independent reduction of cAMP receptors in Dictyostelium discoideum cells over-expressing a mutated ras gene.

Drug-resistance selection in Dictyostelium discoideum transformants resulted in up to eight-times-higher ras protein levels. Over-production of the wild-type ras protein did not lead to an aberrant phenotype. Increased levels of the mutated [G12T]ras protein, however, were correlated with severe deficiencies in aggregation and development. This aberrant phenotype is associated with reduced cAMP binding, due to a lower number of cell-surface receptors. We show that both RNA and cAMP-receptor-protein levels are reduced. These results indicate that ras in Dictyostelium discoideum seems to be involved in regulating cAMP-receptor-gene expression.