2.3.1 G-Protein-Coupled Receptors (GPCRs)

GPCRs constitute the largest single class of drug targets in current...

GPCRs constitute the largest single class of drug targets in current pharmacopoeia. These seven-transmembrane-domain proteins transduce extracellular signals — hormones, neurotransmitters, sensory stimuli — into intracellular second-messenger cascades via heterotrimeric G-proteins. Drugs acting at GPCRs may be agonists, antagonists, or allosteric modulators; classic examples include beta-blockers acting at adrenoceptors, opioids acting at the mu-opioid receptor, and antihistamines acting at the H1 receptor.