cDNA sequence and heterologous expression of the human neurokinin-3 receptor

Functional cDNA clones encoding the human neurokinin-3 receptor were isolated from human brain mRNA. The cloned human neurokinin-3 receptor was expressed in COS cells and Xenopus oocytes, where peptide binding affinity and intracellular effector activation were determined. Neurokinin B is the most potent agonist, followed by eledoisin, substance K and substance P. The binding affinities of these peptides at the human neurokinin-3 receptor differ quantitatively from the rat receptor, implying a functional consequence of the sequence divergence between the two species. Heterologous expression in oocytes revealed that, unlike the neurokinin-1 receptor, the efficacy of ion channel activation mediated by the neurokinin-3 receptor does not approximate the binding affinity. The heterologous expression of the human neurokinin-3 receptor will facilitate further investigation into its biochemical functions.