Nag Kakon, Sultana Naznin, Kato Akira, Hirose Shigehisa
Department of Biological Sciences, Tokyo Institute of Technology, 4259-B19 Nagatsuta-cho, Midori-ku, Yokohama 226-8501, Japan.
Biochem Biophys Res Commun. 2007 Nov 3;362(4):1037-43. doi: 10.1016/j.bbrc.2007.08.107. Epub 2007 Aug 29.
Calcitonin receptor (CTR) is a member of class B G protein-coupled receptor (GPCR) superfamily. We have recently identified the CTR gene and its two transcriptional isoforms, mfCTR and mfCTRDeltaN, in mefugu (mf) (Takifugu obscurus). Here we characterized the mfCTRDeltaN that lacks hormone-binding extracellular N-terminal domain. Strong expression in the liver and weak but broad tissue distribution of its mRNA, revealed by Northern analysis, suggested physiological significance of this headless splice variant. Biochemical and immunocytochemical analyses revealed that it acts as a naturally occurring dominant negative isoform by forming a heterodimer with normal CTR. The headless mfCTRDeltaN characterized here is the first case of N-terminally truncated dominant negative form of GPCR, and immunocytochemistry used for detecting the heterodimer formation may be useful as a novel method for analyzing membrane protein interaction in a living cell.
降钙素受体（CTR）是B类G蛋白偶联受体（GPCR）超家族的成员。我们最近在暗纹东方鲀（mf）（Takifugu obscurus）中鉴定出了CTR基因及其两种转录异构体mfCTR和mfCTRDeltaN。在此，我们对缺乏激素结合细胞外N端结构域的mfCTRDeltaN进行了表征。Northern分析显示，其mRNA在肝脏中强烈表达，在其他组织中表达较弱但分布广泛，这表明这种无头剪接变体具有生理意义。生化和免疫细胞化学分析表明，它通过与正常CTR形成异源二聚体，作为一种天然存在的显性负性异构体发挥作用。这里表征的无头mfCTRDeltaN是GPCR N端截短显性负性形式的首例，用于检测异源二聚体形成的免疫细胞化学可能作为一种分析活细胞中膜蛋白相互作用的新方法。
