Rap1 is rapidly activated upon chemoattractant stimula-tion and plays an important role in cell adhesion and cytoskeletal reorganization during chemotaxis. Here, we de-monstrate that G-protein coupled receptors and G-proteins are essential for chemoattractant-mediated Rap1 activation in Dictyostelium. The rapid Rap1 activation upon cAMP chemoattractant stimulation was absent in cells lacking chemoattractant cAMP receptors cAR1/cAR3 or a subunit of the heterotrimeric G-protein complex Gα2. Loss of guanylyl cyclases GCA/SGC or a cGMP-binding protein GbpC exhibited no effect on Rap1 activation kinetics. These results suggest that Rap1, a key regulator for the regulation of cytoskeletal reorganization during cell move-ment, is activated through the G-protein coupled receptors cAR1/cAR3 and Gα2 proteins in a way independent of the cGMP signaling pathway.

Keywords: chemotaxis, Dictyostelium, GPCR, Rap1, signal transduction