Class A G protein-coupled receptor (Class A GPCR)

Class A G protein-coupled receptors (rhodopsin-like GPCRs) are the largest and most diverse subfamily of GPCRs in humans, responsible for transducing a broad spectrum of extracellular signals—including small molecules, peptides, proteins, and sensory stimuli—via seven-transmembrane domains to activate intracellular G proteins and downstream signaling pathways[3][7][9]. They play critical roles in nearly all physiological systems (including sensory perception, neurotransmission, endocrine, immune, and cardiovascular function) and represent the most prevalent class of therapeutic targets, with more than 500 FDA-approved drugs and hundreds in clinical development. Over 80% of all human GPCRs belong to this class, and they are subdivided into aminergic, peptidergic, nucleotide, lipid, protein, sensory, and orphan receptor subgroups. Their structural flexibility, liganding diversity, and tissue-specific expression profiles make them both powerful targets and challenging molecules for drug design and pharmacotherapy[3][9][7].

Other names

Rhodopsin-like receptorRhodopsin family7TM receptor (for "seven-transmembrane")Heptahelical receptor

Agonism (activation of GPCR to mimic endogenous ligand); Antagonism (blockade of ligand binding or receptor activation); Inverse agonism (decrease constitutive receptor activity); Allosteric modulation (enhance or reduce function at distinct sites); Partial agonism/antagonism