Group II Activators of G-protein Signaling: Monitoring the Interaction of Gα with the G-protein Regulatory Motif in the Intact Cell

The G-protein regulatory (GPR) motif serves as a docking site for G alpha i-GDP free of G beta gamma. The GPR-G alpha complex may function at the cell cortex and/or at intracellular sites. GPR proteins include the Group II Activators of G-protein signaling identified in a functional screen for receptor-independent activators of G-protein signaling (GPSM1-3, RGS12) each of which contain 1-4 GPR motifs. GPR motifs are also found in PCP2/L7(GPSM4), Rap1-Gap1 Transcript Variant 1, and RGS14. While the biochemistry of the interaction of GPR proteins with purified G alpha is generally understood, the dynamics of this signaling complex and its regulation within the cell remains undefined. Major questions in the field revolve around the factors that regulate the subcellular location of GPR proteins and their interaction with G alpha i and other binding partners in the cell. As an initial approach to this question, we established a platform to monitor the GPR-G alpha i complex in intact cells using bioluminescence resonance energy transfer.