MOLECULAR CLONING OF THE BOMBESIN RECEPTOR

哺乳动物蛙皮素肽、胃泌素释放肽(GRP)和 神经介素B(NMB)介导正常人体的一系列生物学反应 细胞，包括促进某些人的旁分泌或自分泌生长 小细胞肺癌(SCLC)细胞。最近，我们报道了克隆 以及两种药理上截然不同的啮齿动物和人类的特征 蛙皮素肽受体(胃泌素释放肽受体(GRP-R)) 和神经介素B受体(NMB-R))，具有不同的表达模式 在正常和恶性细胞中。这两种受体都由七个推定的 跨膜结构域由短的细胞内和 与磷脂酶C激活有关的细胞外环， 百日咳的肌醇磷酸代谢与钙动员 毒素不敏感的G蛋白。GRP-R以高亲和力结合GRP，而 NMB-R以高亲和力结合NMB。的构造和表征 GRP-R/NMB-R嵌合受体提示跨膜区5和 第三个细胞内环是高亲和力结合的关键 NMB由NMB-R提供。特定氨基酸的更精确的功能定义 目前正在进行这一领域的重要工作。此外，三分之一的人 哺乳动物蛙毒蛋白受体(BRS-3)是从NCI-N417、NCI-N417和NCI-N417中克隆的。 人小细胞肺癌细胞系。这种受体被蛙皮素肽激活。 配体，但浓度高于GRP-R或NMB-R，表明 BRS-3对GRP和NMB的亲和力较低。BRS-3显示了一个非常 在正常组织中的有限表达模式，仅限于 睾丸的次级精母细胞。相比之下，许多培养的人肺 癌组织表达BRS-3mRNA。独特的药理作用和有限的 BRS 3在正常组织中的分布为研究提供了理论基础 蛙皮素相关化合物，以高亲和力结合BRS-3，它 可能被用来将有毒化合物靶向细胞表面 人类肺癌细胞。

The mammalian bombesin peptides gastrin releasing peptide (GRP) and neuromedin B (NMB) mediate a range of biological responses in normal cells, including promotion of paracrine or autocrine growth in some human small cell lung carcinoma (SCLC) cells. Recently we reported the cloning and characterization of two pharmacologically distinct rodent and human bombesin peptide receptors (gastrin-releasing peptide receptor (GRP-R) and neuromedin-B receptor (NMB-R)), with distinct patterns of expression in normal and malignant cells. Both receptors consist of seven putative membrane-spanning domains separated by short intracellular and extracellular loops, which are coupled to phospholipase C activation, inositol phosphate metabolism, and calcium mobilization through pertussis toxin insensitive G-proteins. GRP-R binds GRP at high affinity, while NMB-R binds NMB at high affinity. Construction and characterization of GRP-R/NMB-R chimeric receptors indicates that transmembrane domain 5 and the third intracellular loop are critical for high affinity binding of NMB by NMB-R. More precise functional definition of specific amino acids of importance in this domain is currently underway. In addition, a third mammalian bombesin receptor (BRS-3) has been cloned from NCI-N417, a human SCLC cell line. This receptor is activated by bombesin peptide ligands, but at higher concentrations than GRP-R or NMB-R, indicating that BRS-3 has lower affinity for GRP and NMB. BRS-3 shows a very limited pattern of expression in normal tissues, restricted to the secondary spermatocytes of testis. In contrast, many cultured human lung carcinoma express BRS-3 mRNA. The unique pharmacology and limited distribution of BRS 3 in normal tissues provide a rationale to search for a bombesin related compound that binds BRS-3 at high-affinity, which could potentially be used to target toxic compounds to the cell surface of human lung carcinoma cells.