School of Biological Sciences, The University of Hong Kong, Hong Kong.
Gen Comp Endocrinol. 2012 Nov 1;179(2):305-12. doi: 10.1016/j.ygcen.2012.09.005. Epub 2012 Sep 13.
In mammals, the neuropeptide galanin exerts a variety of physiological roles in the neuroendocrine system through its interactions with three galanin receptor subtypes (GalR1, GalR2 and GalR3). However, little is known about the characteristics of galanin receptors in birds, and it is only recently that avian GalR1 and a novel GalR1-like receptor were first identified in chickens. In this study, we report the cDNA cloning and characterization of the other two chicken galanin receptors, the galanin type II receptor (cGalR2) and a novel GalR2-like receptor (GalR2-L), which share high degrees of similarity in sequence identity, gene structure and signaling properties. cGalR2 and cGalR2-L cDNAs encode two putative receptors of 371 and 370 amino acids, in which they show considerable amino acid sequence identities (65-67%, and 53-55%, respectively) with the mammalian GalR2. RT-PCR assays revealed that cGalR2 and cGalR2-L mRNA were widely expressed in the adult chicken tissues including the whole brain, intestine, lung, ovary, pituitary and different regions of the oviduct. As assayed with different luciferase reporter systems, chicken galanin (cGal 1-29) and human galanin-like peptide (hGALP 1-60) were demonstrated to stimulate the luciferase activities in Chinese hamster ovary cells expressing cGalR2 and cGalR2-L through the activations of cAMP/PKA, Ca(2+)/calcineurin and MAPK/ERK signaling pathways, hence suggesting that both receptors are functionally coupled to the G(s) and G(q) proteins. Furthermore, the previously identified cGalR1 and cGalR1-L were found to be solely coupled to the G(i/o) proteins, and the hGALP (1-60) exhibited only a low potency to cGalR1, cGalR1-L, cGalR2 and cGalR2-L activations.
在哺乳动物中，神经肽甘丙肽通过与三种甘丙肽受体亚型（GalR1、GalR2 和 GalR3）相互作用，在神经内分泌系统中发挥多种生理作用。然而，关于鸟类甘丙肽受体的特性知之甚少，直到最近才在鸡中首次鉴定出禽类 GalR1 和一种新型 GalR1 样受体。在这项研究中，我们报告了另外两种鸡甘丙肽受体，即甘丙肽 II 型受体（cGalR2）和一种新型 GalR2 样受体（GalR2-L）的 cDNA 克隆和特性，它们在序列同一性、基因结构和信号转导特性方面具有高度相似性。cGalR2 和 cGalR2-L cDNA 编码两个假定的受体，分别由 371 和 370 个氨基酸组成，它们与哺乳动物 GalR2 具有相当的氨基酸序列同一性（分别为 65-67%和 53-55%）。RT-PCR 分析显示，cGalR2 和 cGalR2-L mRNA 在成年鸡组织中广泛表达，包括整个大脑、肠、肺、卵巢、垂体和输卵管的不同区域。用不同的荧光素酶报告基因系统检测，鸡甘丙肽（cGal 1-29）和人甘丙肽样肽（hGALP 1-60）被证明通过 cAMP/PKA、Ca(2+)/钙调神经磷酸酶和 MAPK/ERK 信号通路激活，刺激表达 cGalR2 和 cGalR2-L 的中国仓鼠卵巢细胞中的荧光素酶活性，因此表明这两种受体均通过 G(s) 和 G(q) 蛋白功能偶联。此外，先前鉴定的 cGalR1 和 cGalR1-L 被发现仅与 G(i/o) 蛋白偶联，而 hGALP（1-60）对 cGalR1、cGalR1-L、cGalR2 和 cGalR2-L 的激活作用只有低活性。
