Cloning and characterization of an endothelin-3 specific receptor (ET sub(C) receptor) from Xenopus laevis dermal melanophores

We report here the presence of a receptor specific for endothelin-3 (termed ET sub(C) receptor or ET sub(C)R) on Xenopus laevis dermal melanophores. Activation of ET sub(C)R causes the dispersion of the pigment granules within the melanophores. The EC sub(50) for ET-3 to induce the pigment dispersion is 24 plus or minus 7 nM, compared to greater than 10 mu M for both ET-1 and -2. This effect desensitizes in a manner that is dependent on both time and the concentration of ET-3 used to stimulate the cells. A cDNA encoding for ET sub(C)R was isolated by a polymerase chain reaction-mediated DNA amplification strategy using degenerate oligonucleotides prepared based on conserved regions of other known G-protein-coupled receptor sequences and by the subsequent screening of a frog melanophore cDNA library. The cloned cDNA consists of 2,240 nucleotides, with an open reading frame coding for 444 amino acids containing an initial 20-amino acid signal sequence. The predicted mature peptide consists of 424 amino acids with a heptahelical structure common to the G-protein-coupled receptor surperfamily.