Another ligand fishing for G protein-coupled receptor 14. Discovery of urotensin II-related peptide in the rat brain

Urotensin II (UII), which was originally isolated from the teleost urophysis, was identified as an endogenous ligand for orphan G protein-coupled receptor 14 (GPR14). The structure of mammalian UII was confirmed by isolation from spinal cord in porcine, or was easily predicted from the sequence of prepro-UII in human. For rat and mouse, however, only the tentative sequences of UII peptides have been demonstrated because the typical processing sites are absent from the amino-terminal region of the mature peptides. Isolation of UII-like immunoreactivity in rat brain revealed the presence of a novel peptide, designated urotensin II-related peptide (URP). URP binds and activates the human and rat urotensin II receptors (GPR14) and has a hypotensive effect when administrated to anesthetized rats. Based on the DNA sequences of the cloned prepro-URP gene, the amino acid sequences of mature URP for mouse and human are identical to that for rat URP. These results suggest that URP is the endogenous and functional ligand for urotensin II receptor in the rat and mouse, and possibly in the human.