PKA regulatory subunits mediate synergy among conserved G-protein-coupled receptor cascades.
G-protein-coupled receptors sense extracellular chemical or physical stimuli and transmit these signals to distinct trimeric G-proteins. Activated Gα-proteins route signals to interconnected effector cascades, thus regulating thresholds, amplitudes and durations of signalling. Gαs- or Gαi-coupled receptor cascades are mechanistically conserved and mediate many sensory processes, including synaptic transmission, cell proliferation and chemotaxis. Here we show that a central, conserved component of Gαs-coupled receptor cascades, the regulatory subunit type-II (RII) of protein kinase A undergoes adenosine 3'-5'-cyclic monophosphate (cAMP)-dependent binding to Gαi. Stimulation of a mammalian Gαi-coupled receptor and concomitant cAMP-RII binding to Gαi, augments the sensitivity, amplitude and duration of Gαi:βγ activity and downstream mitogen-activated protein kinase signalling, independent of protein kinase A kinase activity. The mechanism is conserved in budding yeast, causing nutrient-dependent modulation of a pheromone response. These findings suggest a direct mechanism by which coincident activation of Gαs-coupled receptors controls the precision of adaptive responses of activated Gαi-coupled receptor cascades.
Pubmed ID: 22186894 RIS Download
Adaptation, Physiological | Cloning, Molecular | Cyclic AMP | Cyclic AMP-Dependent Protein Kinase Type II | Escherichia coli | GTP-Binding Protein alpha Subunits | Gene Expression Regulation, Fungal | Mitogen-Activated Protein Kinase 1 | Mutation | Phosphorylation | Plasmids | Protein Binding | Protein Subunits | Receptors, G-Protein-Coupled | Recombinant Fusion Proteins | Saccharomyces cerevisiae | Saccharomyces cerevisiae Proteins | Signal Transduction | Transformation, Bacterial