A Human Orphan Calcitonin Receptor-like Structure

Abstract

A novel calcitonin receptor-like protein of 461 amino acids with seven putative transmembrane domains has been identified through molecular cloning in a cDNA library of the human cerebellum. 91% and 56% of the amino acids are identical in a rat orphan calcitonin receptor-like sequence and the human calcitonin receptor, respectively. 5.2 kb mRNA is predominantly expressed in the lung, heart and kidney. Specific binding of 125I -labeled salmon calcitonin and human calcitonin gene-related peptide-I to COS-7 cells transiently transfected with the receptor cDNA was less then 0.5%. Cellular cAMP accumulation was indistinguishable in cDNA transfected and non-transfected control COS-7 and renal tubular cells from the American opossum stimulated with human and salmon calcitonin, human calcitonin gene-related peptide-I and -II, human amylin, human adrenomedullin, lizard helodermin, salmon stanniocalcin and chicken parathyroid hormone-related protein. The receptor-like protein whose ligand remains to be discovered belongs to the family of receptors of calcitonin, parathyroid hormone, secretin, vasointestinal peptide and pituitary adenylate cyclase-activating polypeptide.