What is the primary second messenger associated with GPCR activation?

The primary second messenger associated with G protein-coupled receptor (GPCR) activation is cyclic adenosine monophosphate (cAMP). When a ligand binds to a GPCR, it activates the associated G protein, which often stimulates the enzyme adenylate cyclase. This enzyme converts ATP to cAMP, which then serves as a second messenger inside the cell. cAMP plays a critical role in various signaling pathways, influencing numerous physiological processes such as metabolism, gene transcription, and the regulation of ion channels and enzymes.

In contrast, while inositol trisphosphate (IP3) and diacylglycerol (DAG) are other important second messengers, they are primarily associated with different signaling pathways initiated by certain GPCRs that activate phospholipase C. cGMP is typically involved in signaling pathways related to nitric oxide and the natriuretic peptides rather than broad GPCR activation. Therefore, cAMP is the most commonly recognized and studied second messenger in the context of GPCR signaling.