Rozengurt E, Fabregat I, Coffer A, Gil J, Sinnett-Smith J
Imperial Cancer Research Fund, Lincoln's Inn Fields, London, UK.
J Cell Sci Suppl. 1990;13:43-56. doi: 10.1242/jcs.1990.supplement_13.6.
Bombesin and structurally related peptides including gastrin releasing peptide (GRP) are potent mitogens for Swiss 3T3 cells. The early cellular and molecular responses elicited by bombesin and structurally related peptides have been elucidated in detail. Further understanding of the molecular basis of the potent mitogenic response initiated by bombesin is required in order to elucidate the mechanism by which the occupied receptor communicates with effector molecules in the cell. Transmembrane signalling mechanisms involving either a tyrosine kinase or a guanine nucleotide-binding regulatory protein (G protein) have been proposed. Here we summarize our experimental evidence indicating that a G protein(s) is involved in the coupling of the bombesin receptor to the generation of intracellular signals related to mitogenesis. Evidence for the role of G proteins in bombesin signal transduction pathways has been obtained by assessing the effects of guanine nucleotide analogues on both receptor-mediated responses in permeabilized cells and ligand binding in membrane preparations. We found that [125I]GRP-receptor complexes were solubilized from Swiss 3T3 cell membranes by using the detergents taurodeoxycholate or deoxycholate. Addition of guanosine 5-[gamma-thio]triphosphate (GTP gamma S) to ligand-receptor complexes isolated by gel filtration enhanced the rate of ligand dissociation in a concentration-dependent and nucleotide-specific manner. These results demonstrate the successful solubilization of [125I]GRP-receptor complexes from Swiss 3T3 cell membranes and provide evidence for the physical association between the ligand-receptor complex and a guanine nucleotide binding protein(s).
蛙皮素以及包括胃泌素释放肽（GRP）在内的结构相关肽是瑞士3T3细胞的强效促有丝分裂原。蛙皮素和结构相关肽引发的早期细胞和分子反应已得到详细阐明。为了阐明被占据的受体与细胞内效应分子通信的机制，需要进一步了解蛙皮素引发的强效促有丝分裂反应的分子基础。有人提出了涉及酪氨酸激酶或鸟嘌呤核苷酸结合调节蛋白（G蛋白）的跨膜信号传导机制。在这里，我们总结了我们的实验证据，表明一种或多种G蛋白参与了蛙皮素受体与与有丝分裂相关的细胞内信号产生的偶联。通过评估鸟嘌呤核苷酸类似物对通透细胞中受体介导的反应和膜制剂中配体结合的影响，已获得G蛋白在蛙皮素信号转导途径中作用的证据。我们发现，使用牛磺脱氧胆酸盐或脱氧胆酸盐可从瑞士3T3细胞膜中溶解[125I]GRP受体复合物。向通过凝胶过滤分离的配体-受体复合物中添加鸟苷5-[γ-硫代]三磷酸（GTPγS）以浓度依赖性和核苷酸特异性方式提高了配体解离速率。这些结果证明了从瑞士3T3细胞膜中成功溶解[125I]GRP受体复合物，并为配体-受体复合物与一种或多种鸟嘌呤核苷酸结合蛋白之间的物理关联提供了证据。
