INVIVO RECEPTOR-MEDIATED PHOSPHORYLATION OF A G-PROTEIN IN DICTYOSTELIUM

Extracellular adenosine 3′,5′-monophosphate (cAMP) serves multiple roles in Dictyostelium development, acting as a chemoattractant, a cell-cell signaling molecule, and an inducer of differentiation. The Dictyostelium G-protein α subunit Gα2 appears to be the major transducer linking the surface cAMP receptor to these intracellular responses. On stimulation of cells with cAMP, Gα2 is phosphorylated on one or more serine residues, resulting in an alteration of its electrophoretic mobility. Phosphorylation of Gα2 is triggered by increased occupancy of the surface cAMP receptor and is rapid and transient, coinciding with the time course of activation of physiological responses.