Cloning of a cDNA encoding a non-isopeptide-selective subtype of the endothelin receptor

ENDOTHELIN-1 was initially identified as a 21-residue potent vasoconstrictor peptide produced by vascular endothelial cells, but was subsequently found to have many effects on both vascular and non-vascular tissues^1,2. The discovery of three isopeptides of the endothelin family³, ET-1, ET-2 and ET-3, each possessing a diverse set of pharmacological activities of different potency, suggested the existence of several different endothelin receptor subtypes^3-7. Endothelins may elicit biological responses by various signal-transduction mechanisms, including the G protein-coupled activation of phospholipase C and the activation of voltage-dependent Ca²⁺ channels^8-10. Thus, different subtypes of the endothelin receptor may use different signal-transduction mechanisms. Here we report the cloning of a complementary DNA encoding one subtype belonging to the superf amily of G protein-coupled receptors. COS-7 cells transfected with the cDNA express specific and high-affinity binding sites for endothelins, responding to binding by the production of inositol phosphates and a transient increase in the concentration of intracellular free Ca²⁺. The three endothelin isopeptides are roughly equipotent in displacing ¹²⁵I-labelled ET-1 binding and causing Ca²⁺ mobilization. A messenger RNA corresponding to the cDNA is detected in many rat tissues including the brain, kidney and lung but not in vascular smooth muscle cells. These results indicate that this cDNA encodes a 'nonselective' subtype of the receptor which is different from the vascular smooth muscle receptor.