Signaling Pathway from G-Protein Families

G-aS-coupled receptors stimulate adenylyl cyclase (AC), which synthesizes cAMP from ATP. In contrast Gai-coupled receptors inhibit AC and so reduce cAMP formation. The bg subunits from Gai and other G proteins are able to activate the MAP kinase pathways and PLCb. GPCRs coupled to the Gaq family of G proteins stimulate PLCb, which cleaves membrane phospholipids to produce IP3, which mobilizes intracellular calcium, and DAG, which activates PKC. Second messenger pathways then activate a range of effector systems to change cell behaviour; in many cases this includes the regulation of gene transcription. Dotted line shows a more indirect pathway.

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REFERENCES: Stephen J Hill, Jillian G Baker, and Stephen Rees. Reporter-gene systems for the study of G-protein-coupled receptors. Current Opinion in Pharmacology 2001, 1, 526-32.