Laemmle Baerbel, Schindler Marcus, Beilmann Mario, Hamilton Bradford S, Doods Henri N, Wieland Heike A
Department of Cardiovascular Research, Boehringer Ingelheim Pharma KG, 88397 Biberach, Germany.
Regul Pept. 2003 Mar 28;111(1-3):21-9. doi: 10.1016/s0167-0115(02)00220-3.
Recently, an orphan G protein coupled receptor (GPCR) termed NPGPR was described. A shorter variant of this receptor lacking exon 1 was shown to have subnanomolar affinity for neuropeptide FF (NPFF), a pain modulatory peptide, and therefore was named NPFF(2) receptor. Here, we characterize the full-length cloned NPGPR and identify a novel short form lacking exon 2 with a differential pattern of mRNA abundance in several tissues and organs. The NPGPR is most similar to the recently cloned neuropeptide FF (NPFF) receptor which lacks exon 1, but also shows high homology to the orexin and neuropeptide Y (NPY) receptor families, two neuropeptides involved in food intake regulation. Therefore, we used binding studies to examine the interaction of NPFF, orexin and NPY with the NPGPR. [125I] NPFF was displaced by NPFF with an IC(50) of 14.7 +/- 8.8 nM, whereas [125I] Orexin B was displaced by Orexin B with an IC(50) of 415 +/- 195 nM. We conclude that orexins interact with the NPGPR and that the affinity of NPFF for NPGPR is approximately 100-fold lower than for the NPFF2 receptor. We postulate that NPGPR is a splice variant of the family of NPFF receptors and displays a binding profile different from the other members of the NPFF receptor family due to the presence of exon 1. In order to evaluate whether NPGPR levels are affected by the feeding status, we examined the mRNA level using real-time PCR in two feeding models, i.e. before and after diet-induced body weight increase as well as after chronic food restriction in rats. However, hypothalamic NPGPR mRNA was unchanged in both models. Therefore, our evidence does not support the hypothesis that NPGPR is involved in feeding regulation.
最近，一种名为NPGPR的孤儿G蛋白偶联受体（GPCR）被报道。该受体缺少外显子1的较短变体对疼痛调节肽神经肽FF（NPFF）具有亚纳摩尔亲和力，因此被命名为NPFF(2)受体。在此，我们对全长克隆的NPGPR进行了表征，并鉴定出一种缺少外显子2的新型短形式，其在多个组织和器官中的mRNA丰度模式不同。NPGPR与最近克隆的缺少外显子1的神经肽FF（NPFF）受体最为相似，但也与食欲素和神经肽Y（NPY）受体家族高度同源，这两种神经肽参与食物摄入调节。因此，我们通过结合研究来检测NPFF、食欲素和NPY与NPGPR的相互作用。[125I]NPFF被NPFF以14.7±8.8 nM的IC(50)置换，而[125I]食欲素B被食欲素B以415±195 nM的IC(50)置换。我们得出结论，食欲素与NPGPR相互作用，且NPFF对NPGPR的亲和力比对NPFF2受体的亲和力低约100倍。我们推测NPGPR是NPFF受体家族的一种剪接变体，由于外显子1的存在，其结合特征与NPFF受体家族的其他成员不同。为了评估NPGPR水平是否受进食状态影响，我们在两种进食模型中使用实时PCR检测了mRNA水平，即在饮食诱导体重增加前后以及大鼠长期食物限制后。然而，在两种模型中下丘脑NPGPR mRNA均未改变。因此，我们的证据不支持NPGPR参与进食调节的假说。
