Coupling Mechanism of a GPCR and a Heterotrimeric G Protein During Chemoattractant Gradient Sensing in Dictyostelium

摘要: The coupling of heterotrimeric guanine nucleotide-binding protein (G protein)-coupled receptors (GPCRs) with G proteins is fundamental for GPCR signaling; however, the mechanism still debated. Moreover, how proposed mechanisms affect dynamics downstream signaling remains unclear. Here, through experiments involving fluorescence recovery after photobleaching and single-molecule imaging, we directly measured mobilities cyclic adenosine monophosphate (cAMP) receptor 1 (cAR1), a chemoattractant receptor, βγ subunit in live cells. We found that cAR1 diffused more slowly plasma membrane than did Gβγ. Upon binding ligand to mobility was unchanged, whereas speed fraction faster-moving Gβγ subunits decreased. Our measurements showed relatively immobile freely, suggesting chemoattractant-bound transiently interacted proteins. Using models possible mechanisms, computed temporal kinetics activation. resonance energy transfer imaging data fully activated induced sustained dissociation α subunits, which indicated ligand-bound continuously. Finally, simulations high-affinity essential translate extracellular gradient signals into directional cellular responses. suggest use ligand-induced rather precoupled control activation during chemotaxis.