Identification of the Receptors for Prolactin-releasing Peptide (PrRP) and Carassius RFamide Peptide (C-RFa) in Chickens

Prolactin-releasing peptide (PrRP) and its structurally related peptide, Carassius RFamide Peptide (C-RFa), have been reported to play similar roles in regulating food intake and pituitary functions of vertebrates.  However, the identity and functionality of the receptor(s) for PrRP and C-RFa remain largely unknown in non-mammalian vertebrates including birds.  I will present the cloning and characterization of three receptors homologous to mammalian PrRP receptor (PrRPR), named cPrRPR1, cPrRPR2, and cC-RFaR respectively, from chicken brain by RT-PCR. Using a pGL3-NFAT-RE luciferase reporter system, we demonstrated that cPrRPR1 and cPrRPR2 expressed in CHO cells could be activated by chicken PrRP20 and C-RFa20 potently (EC50: <1.0nM), while cC-RFaR could only be activated by C-RFa20 effectively (EC50: 0.11nM), indicating that cPrRPR1 and cPrRPR2 can function as common receptors for PrRP and C-RFa, while cC-RFaR is a receptor highly specific to C-RFa.  Using a pGL3-CRE luciferase reporter system, we further showed that cPrRP20 and cC-RFa20 could activate the intracellular protein kinase A signaling pathway of CHO cells expressing these receptors.  Additionally, the expression of PrRP, C-RFa, and the three receptors in adult chicken tissues was examined by RT-PCR.  C-RFa and the three receptors were detected to be widely expressed in most tissues examined, while the expression of PrRP gene was restricted to several tissues including hypothalamus. These findings, together with evidence showing PrRP and C-RFa are encoded by separate genes in chicken, Xenopus, and zebrafish, strongly suggest that PrRP and C-RFa play distinct roles in non-mammalian vertebrates including chicken.