Yamamoto Ichiro, Kaiya Hiroyuki, Tsutsui Chihiro, Sakai Takafumi, Tsukada Akira, Miyazato Mikiya, Tanaka Minoru
High-Tech Research Center, Nippon Veterinary and Life Science University, Musashino, Tokyo 180-8602, Japan.
Gen Comp Endocrinol. 2008 May 1;156(3):509-14. doi: 10.1016/j.ygcen.2008.03.007. Epub 2008 Mar 19.
Motilin is a peptide hormone involved in gastrointestinal motility. GPR38, initially cloned as an orphan receptor, is now considered a specific receptor for motilin. Previously, molecular characterization of the motilin receptor had only been performed in mammalian and fish species. In this study, we cloned cDNA for chicken motilin receptor from the duodenum and characterized its primary structure, tissue distribution, and biological activity. The cDNA encoded 349 amino acids showing significant overall sequence identity to mammalian motilin receptors. Chicken motilin increased intracellular Ca2+ concentration in human embryonic kidney (HEK) 293 cells transiently expressing the recombinant chicken motilin receptor. Comparison of the cDNA sequence with the genomic sequence of chicken motilin receptor revealed that the chicken motilin receptor gene consists of two exons separated by an intron. Real-time PCR analysis showed that chicken motilin receptor mRNA is expressed in a wide range of tissues in 21-day-old chickens, with markedly high levels in the proventriculus, duodenum, and oviduct. The expression levels of the mRNA in the proventriculus and duodenum were highest just before hatching and rapidly decreased during post-hatch development. These results suggest that chicken motilin receptor is largely involved in gastrointestinal functions at pre- and post-hatch periods through an intracellular signaling pathway accompanied by an increase in Ca2+ levels.
胃动素是一种参与胃肠动力的肽类激素。GPR38最初作为孤儿受体被克隆，现在被认为是胃动素的特异性受体。此前，胃动素受体的分子特征仅在哺乳动物和鱼类中进行过研究。在本研究中，我们从十二指肠克隆了鸡胃动素受体的cDNA，并对其一级结构、组织分布和生物学活性进行了表征。该cDNA编码349个氨基酸，与哺乳动物胃动素受体的整体序列具有显著的同源性。鸡胃动素可增加瞬时表达重组鸡胃动素受体的人胚肾（HEK）293细胞内的Ca2+浓度。将该cDNA序列与鸡胃动素受体的基因组序列进行比较，发现鸡胃动素受体基因由两个外显子组成，中间被一个内含子隔开。实时PCR分析表明，鸡胃动素受体mRNA在21日龄鸡的多种组织中均有表达，在前胃、十二指肠和输卵管中表达水平明显较高。前胃和十二指肠中mRNA的表达水平在孵化前最高，在孵化后发育过程中迅速下降。这些结果表明，鸡胃动素受体在孵化前后通过伴随Ca2+水平升高的细胞内信号通路在很大程度上参与胃肠功能。
