Neuropeptide W: an anorectic peptide regulated by leptin and metabolic state.

Neuropeptide W (NPW) is an anorectic peptide produced in the brain. Here, we showed that NPW was present in several hypothalamic nuclei, including the paraventricular hypothalamic nucleus, ventromedial hypothalamic nucleus, lateral hypothalamus, and hypothalamic arcuate nucleus. NPW expression was significantly up-regulated in leptin-deficient ob/ob and leptin receptor-deficient db/db mice. The increase in NPW expression in ob/ob mice was abrogated to control levels after leptin replacement. Leptin induced suppressors of cytokine signaling-3 after phosphorylation of signal transducer and activator of transcription-3 in NPW-expressing neurons. In addition, we demonstrated that NPW reduces feeding via the melanocortin-4-receptor signaling pathway. We also showed that NPW activates proopiomelanocortin and inhibits neuropeptide Y neurons using loose-patch extracellular recording of these neurons identified by promoter-driven green fluorescent protein expression. This study indicates that NPW may play an important role in the regulation of feeding and energy metabolism under the conditions of leptin insufficiency.

Identification of urotensin II-related peptide as the urotensin II-immunoreactive molecule in the rat brain.

Urotensin II (UII) has been reported as the most potent known vasoconstrictor. While rat and mouse orthologs of UII precursor protein have been reported, only the tentative structures of UII peptides of these animals have been demonstrated, since prepro-UII proteins lack typical processing sites for their mature peptides. In the present study, we isolated a novel peptide, UII-related peptide (URP), from the extract of the rat brain as the sole immunoreactive substance to anti-UII antibody; the amino acid sequence of the peptide was determined as ACFWKYCV. cDNAs encoding rat, mouse, and human precursor proteins for URP were cloned and revealed that the sequences of mouse and human URP peptides are the same as that for rat URP. Prepro-URP gene is expressed in several rat tissues such as those of the thymus, spleen, testis, and spinal cord, although with lower levels than the prepro-UII gene. In the human, the prepro-URP gene is expressed comparably to prepro-UII in several tissues except the spinal cord. URP was found to bind and activate the human or rat UII receptors (GPR14) and showed a hypotensive effect when administered to anesthetized rats. These results suggest that URP is the endogenous and functional ligand for UII receptor in the rat and mouse, and possibly in the human. We also describe the preparation of specific monoclonal antibodies raised against UII peptide and the establishment of a highly sensitive enzyme immunoassay system for UII peptides.

Identification of neuropeptide W as the endogenous ligand for orphan G-protein-coupled receptors GPR7 and GPR8.

The structurally related orphan G-protein-coupled receptors GPR7 and GPR8 are expressed in the central nervous system, and their ligands have not been identified. Here, we report the identification of the endogenous ligand for both of these receptors. We purified the peptide ligand from porcine hypothalamus using stable Chinese hamster ovary cell lines expressing human GPR8 and cloned the cDNA encoding its precursor protein. The cDNA encodes two forms of the peptide ligand with lengths of 23 and 30 amino acid residues as mature peptides. We designated the two ligands neuropeptide W-23 (NPW23) and neuropeptide W-30 (NPW30). The amino acid sequence of NPW23 is completely identical to that of the N-terminal 23 residues of NPW30. Synthetic NPW23 and NPW30 activated and bound to both GPR7 and GPR8 at similar effective doses. Intracerebroventricular administration of NPW23 in rats increased food intake and stimulated prolactin release. These findings indicate that neuropeptide W is the endogenous ligand for both GPR7 and GPR8 and acts as a mediator of the central control of feeding and the neuroendocrine system.