School of Biological Sciences, The University of Hong Kong, Hong Kong, PR China.
Gen Comp Endocrinol. 2011 Jan 15;170(2):391-400. doi: 10.1016/j.ygcen.2010.10.011. Epub 2010 Oct 25.
Galanin is a multi-functional neuropeptide that is widely distributed in the mammalian central nervous system and peripheral tissues. It exerts multiple physiological functions through interaction with 3 known G protein-coupled receptors (GPCR), namely, galanin type I, II and III (GalR1, 2 and 3) receptors, which have only been identified in mammals. In this study, we reported the cloning and characterization of chicken galanin type I receptor (GalR1) and a novel galanin receptor with considerable homology to chicken GalR1, which herein is designated as galanin type I-like receptor (GalR1-L). Chicken GalR1 and GalR1-L full-length cDNAs were cloned from chicken brain and small intestine tissue, respectively. The former encodes a protein of 357 amino acids that shares 84-86% amino acid sequence identities with its mammalian counterparts, whereas the latter encodes a 363-amino acid protein with comparatively lower identities (55-56%) to the mammalian GalR1. Using reverse transcription (RT)-PCR assays, we examined the expression of both receptors in adult chicken tissues. Both receptors were found to be widely distributed in the tissues examined, including brain, small intestine, kidney, ovary, pancreas, pituitary and spleen. Interestingly, cGalR1 expression was detected in different regions of chicken oviduct, while cGalR1-L expression was restricted to the vagina. Using a pGL3-CRE luciferase reporter system, chicken galanin peptide (1-29) was demonstrated to inhibit both basal and forskolin-stimulated luciferase activities, in dose-dependent manners, through the cAMP-mediated signaling pathway in Chinese hamster ovary (CHO) cells expressing either cGalR1 or cGalR1-L, thus suggesting the functional couplings of both receptors to G(i) proteins. Together, the characterization of chicken GalR1 and GalR1-L provides a better understanding of the physiological roles of galanin in avian species.
甘丙肽是一种多功能神经肽，广泛分布于哺乳动物中枢神经系统和外周组织中。它通过与 3 种已知的 G 蛋白偶联受体（GPCR），即甘丙肽 I、II 和 III（GalR1、2 和 3）受体相互作用，发挥多种生理功能，而这些受体仅在哺乳动物中被发现。在这项研究中，我们报道了鸡甘丙肽 I 型受体（GalR1）和一种与鸡 GalR1 具有高度同源性的新型甘丙肽受体的克隆和特征，将其命名为甘丙肽 I 型样受体（GalR1-L）。我们分别从鸡脑组织和小肠组织中克隆了鸡 GalR1 和 GalR1-L 的全长 cDNA。前者编码一个由 357 个氨基酸组成的蛋白质，与哺乳动物的同源物具有 84-86%的氨基酸序列同一性，而后者编码一个 363 个氨基酸的蛋白质，与哺乳动物 GalR1 的同一性相对较低（55-56%）。通过逆转录（RT）-PCR 检测，我们研究了这两种受体在成年鸡组织中的表达。发现这两种受体在检测的组织中广泛分布，包括脑、小肠、肾、卵巢、胰腺、垂体和脾。有趣的是，cGalR1 在鸡输卵管的不同区域被检测到表达，而 cGalR1-L 仅在阴道中被检测到表达。使用 pGL3-CRE 荧光素酶报告基因系统，鸡甘丙肽肽（1-29）被证明通过 cAMP 介导的信号通路，以剂量依赖的方式抑制中国仓鼠卵巢（CHO）细胞中表达的 cGalR1 或 cGalR1-L 的基础和福司可林刺激的荧光素酶活性，从而表明这两种受体与 G(i) 蛋白的功能偶联。总之，鸡 GalR1 和 GalR1-L 的特征为了解甘丙肽在禽类中的生理作用提供了更好的认识。
