G protein-coupled receptors

G protein-coupled receptors (GPCRs), also known as seven-(pass)-transmembrane domain receptors, 7TM receptors, heptahelical receptors, serpentine receptor, and G protein-linked receptors (GPLR), constitute a large protein family of receptors that detect molecules outside the cell and activate internal signal transduction pathways and, ultimately, cellular responses. They are called seven-transmembrane receptors because they pass through the cell membrane seven times.

Structure

GPCRs are integral membrane proteins that possess seven membrane-spanning domains or transmembrane helices. The extracellular parts of the receptor can be glycosylated. These extracellular loops also contain two highly conserved cysteine residues which build disulfide bonds to stabilize the receptor structure.

Function

GPCRs are involved in a wide variety of physiological processes. Some examples of their physiological roles include:

• The visual sense: The opsins use a photoisomerization reaction to translate electromagnetic radiation into cellular signals. Rhodopsin, for example, uses the conversion of 11-cis-retinal to all-trans-retinal for this purpose.
• The gustatory sense (taste): GPCRs in taste cells mediate release of gustducin in response to bitter-, umami- and sweet-tasting substances.
• The sense of smell: Receptors of the olfactory epithelium bind odorants (olfactory receptors) and pheromones (vomeronasal receptors)

Signaling

GPCRs are involved in a wide variety of signaling processes, including but not limited to:

• Cell density sensing
• In yeast, GPCRs are involved in mating
• In humans, GPCRs are involved in sensing cell density differences.

Pharmacology

GPCRs are targeted by various drugs, with over 30% of all modern medicinal drugs, including beta blockers, antihistamines and various kinds of psychiatric medications working through GPCRs.

See also

• Adrenergic receptor
• Dopamine receptor
• Histamine receptor
• Serotonin receptor
• Opioid receptor

External links

• GPCRDB: Information system for G protein-coupled receptors (GPCRs)
• IUPHAR GPCR Database
• GPCR-HetNet