Scientific Glossary

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cAMP is produced when Gs-coupled GPCRs activate adenylyl cyclase, converting ATP to cAMP. It then activates protein kinase A (PKA), which phosphorylates numerous target proteins. cAMP signaling mediates effects of glucagon, TSH, FSH, LH, CRH, and many other hormones. GLP-1 receptor activation produces cAMP as its primary second messenger, which drives glucose-dependent insulin secretion. cAMP-PDE inhibitors (like theophylline) amplify cAMP signals by preventing its degradation.

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GPCRs are transmembrane receptors that couple to intracellular G proteins upon ligand binding. The G protein then activates secondary messengers (cAMP, IP3, DAG) to produce cellular responses. The GLP-1 receptor, ghrelin receptor (GHSR), melanocortin receptors (MC1R-MC5R), GnRH receptor, and KISS1R are all GPCRs. Over 30% of approved drugs target GPCRs, highlighting their pharmaceutical importance. GPCR activation and desensitization mechanisms are critical for understanding peptide pharmacology.