Chicken neuropeptide Y-family receptor Y4: a receptor with equal affinity for pancreatic polypeptide, neuropeptide Y and peptide YY I Lundell, T Boswell 1 and D Larhammar Department of Neuroscience, Unit of Pharmacology, Uppsala University, Box 593, S-751 24 Uppsala, Sweden 1 Roslin Institute, Roslin, Midlothian EH25 9PS, UK (Requests for offprints should be addressed to I Lundell; Email: Ingrid.Lundell@Neuro.UU.SE) Abstract Within the neuropeptide Y (NPY) family of peptides, pancreatic polypeptide is the most divergent across species. It differs in 20 of 36 positions between human and chicken. In mammals, it binds primarily to the Y4 receptor, to which NPY and peptide YY (PYY) bind with lower affinities. Because of these large sequence differences in pancreatic polypeptide, we decided to characterise the chicken Y4 receptor. We report here that Y4 displays the least sequence conservation among the Y-family receptors, with only 57–60% overall amino acid identity between chicken and mammals, compared with 64–83% for the Y1, Y2 and Y5 receptors. After expression of the chicken Y4 receptor in COS-7 cells, 125 I-labelled porcine (p) PYY bound with a K d of 20 pM. In competition with 125 I-pPYY, chicken pancreatic polypeptide bound with high affinity at 140 pM. Interestingly, chicken PYY bound with even greater affinity at 68 pM. The affinity of NPY, 160 pM, was similar to that of pancreatic polypeptide. Chicken Y4 is less sensitive than is mammalian Y4 to truncation of the amino terminus of the NPY molecule. RT-PCR revealed expression in several peripheral organs, including adipose tissue and oviduct. In brain, Y4 mRNA was detected in the brainstem, cerebellum and hippocampus. In situ hybridisation to brain sections showed expression in the dorsal motor nucleus of the vagus in the brainstem. Thus the chicken Y4 receptor is less selective and anatomically more widespread than that in mammals, probably reflecting the original properties of the Y4 receptor. Journal of Molecular Endocrinology (2002) 28, 225–235 Introduction The neuropeptide Y (NPY) family of peptides consists, in chicken and mammals, of pancreatic polypeptide, peptide YY (PYY) and NPY itself, all of which are 36–37 amino acids long. NPY is extremely well conserved and has only one amino acid replacement between human and chicken, and four replacements between human and zebrafish (Blomqvist et al. 1992, Larhammar 1996, Cerda- Reverter & Larhammar 2000, Söderberg et al. 2000). PYY is more divergent, and pancreatic polypeptide differs greatly between species, with only 16 of 36 positions identical between human and chicken (Kimmel et al. 1975, Larhammar 1996, Cerda-Reverter & Larhammar 2000). Chicken pancreatic polypeptide (chPP) was the first NPY-family peptide to be isolated (Kimmel et al. 1975). The physiological effects, particularly on metabolism and digestive physiology, have been a focus of intense investigation for all three peptides (Hazelwood 1993, Kalra et al. 1999). NPY has been implicated in the control of food intake, metab- olism, blood pressure, circadian rhythms and reproduction (Kalra et al. 1999). NPY has also been found to stimulate feeding in birds (Kuenzel et al. 1987, Richardson et al. 1995), a reptile (Morris & Crews 1990) and fish (Lopez-Patino et al. 1999, Narnaware et al. 2000, de Pedro et al. 2000). Moreover, in chicken (Boswell et al. 1999) and fish (Silverstein et al. 1998, Narnaware & Peter 2001) NPY gene expression in the hypothalamus is 225 Journal of Molecular Endocrinology (2002) 28, 225–235 0952–5041/02/028–225 © 2002 Society for Endocrinology Printed in Great Britain Online version via http://www.endocrinology.org Downloaded from Bioscientifica.com at 06/02/2024 04:05:45PM via free access