Cloning and expression of cDNA encoding a rat adrenomedullin receptor

Adrenomedullin is a potent vasodilator peptide that exerts major effects on cardiovascular function. Its actions are mediated through an abundant class of specific binding sites that activate adenylyl cyclase through a G protein-coupled mechanism. We report here the identification of a cDNA clone for the adrenomedullin receptor that was originally isolated as an orphan receptor from rat lung. The cDNA encodes a polypeptide of 395 residues that contains seven transmembrane domains and has a general structural resemblance to other members of the G protein-linked receptor superfamily. When expressed in COS-7 cells, this receptor mediates a cAMP response to adrenomedullin with an EC50 of 7 x 10(-9) M, and binds 125I-adrenomedullin with a KD of 8.2 x 10(-9) M, properties that are consistent with those observed in cardiovascular and other target tissues. The receptor gene is expressed as several mRNA species of which the most prominent is a 1.8-kilobase transcript found in the lung, adrenal, heart, spleen, cerebellum, and other sites. Identification of this receptor cDNA should facilitate further investigation of the cellular actions of adrenomedullin and its regulatory effects in normal and disordered states of cardiovascular function.