International Union of Pharmacology.  XXXI.  Recommendations for the nomenclature of multimeric G protein-coupled receptors. 
A receptor is defined by the International Union of Pharmacology Committee on Receptor Nomenclature and Drug Classification (NC-IUPHAR) as a protein, or a complex of proteins, which recognizes physiologically relevant ligands that can regulate the protein to mediate cellular events (Ruffolo et al.,  2000).  This definition does not include associated proteins, which are not required for agonist recognition and/or receptor assembly.  Thus, G proteins are not included in the nomenclature of G protein-coupled receptors (GPCRs).  Similarly, proteins which modify receptor disposition, such as proteins with a PDZ domain (Sheng and Sala, 2001), and which associate with the cytosolic portion of the receptor are not included.  The question arises, however, as to the way to name multimeric receptors where subunits influence receptor assembly and agonist recognition.  The essential issue is whether to name the individual proteins or the association of proteins?  NC-IUPHAR recommends that, where possible, the functional receptor complex be given a different name from that of the subunits.