Editorial Focus An orphan GPCR finds a home in the heart

G PROTEIN-COUPLED RECEPTORS (GPCRs) are the largest and most successful targets for pharmacotherapy to date, particularly in the area of cardiovascular disease. These receptors are at the forefront of current drug discovery efforts (7). GPCRs also form the largest family of transmembrane receptors, with nearly 800 GPCR loci (12, 18), of which several hundred are categorized as orphan GPCRs. These orphan receptors have no known endogenous ligand. While it is estimated that 300 or so of these genes are olfactory or chemosensory receptors, 100 or more GPCR orphans remain that may have putative hor-monal or neurotransmitter-related functions (3) providing novel targets for disease. Thus, orphans have attracted signif-icant attention in recent years to determine their expression profiles and roles, if any, in physiology and disease. Orphan GPCR research has progressed rapidly in recen