作者:Mia Engström、Jussi Tomperi、Kamel El-Darwish、Mikaela Åhman、Juha-Matti Savola、Siegfried Wurster
DOI:10.1124/jpet.104.075531
日期:2005.1
We have discovered a novel compound, J-2156 [(1′ S , 2 S )-4-amino- N -(1′-carbamoyl-2′-phenylethyl)-2-(4″-methyl-1″-naphthalenesulfonylamino)butanamide], that belongs to a new class of somatostatin receptor ligands. J-2156 binds with nanomolar affinity to the human somatostatin receptor subtype 4 and is over 400-fold subtype-selective against the other somatostatin receptors. When evaluated in a [35S]guanosine-5′- O -(3-thio) triphosphate binding assay, J-2156 elicited a response 2 to 3 times as large as that of somatostatin-28 and somatostatin-14. That somatostatin-14 is clearly not a maximally efficacious agonist could be verified by demonstrating that it displays the typical behavior of a partial agonist when tested against J-2156. Increasing concentrations of somatostatin-14 cause a concentration-dependent rightward shift of the dose-response curves for J-2156, without affecting its maximal response. This lack of reduction of the maximal response and the fact that the superior efficacy of J-2156 is detected in membranes argue against desensitization and internalization as possible explanations for the superior efficacy of J-2156. More likely is that somatostatin-14 and J-2156 stabilize distinct receptor conformations that differ in their ability to interact with G-proteins. In a cyclic AMP assay, J-2156, somatostatin-28, and somatostatin-14 all act as full agonists. However, this outcome is most likely due to the presence of a receptor reserve in the cyclic AMP assay since there is a large gain of apparent potency in the cyclic AMP assay and the gain is larger for J-2156 than for somatostatin. We conclude that the endogenous ligands somatostatin-14 and somatostatin-28 do not define maximal agonism on the human somatostatin receptor subtype 4 and that J-2156 represents a so-called superagonist.
我们发现了一种新型化合物 J-2156[(1′S , 2 S )-4- 氨基-N-(1′-氨基甲酰基-2′-苯基乙基)-2-(4″-甲基-1″-萘磺酰氨基)丁酰胺],它属于一类新的体生长抑素受体配体。J-2156 与人类体生长抑素受体亚型 4 的结合亲和力为纳摩尔级,对其他体生长抑素受体的亚型选择性超过 400 倍。在[35S]鸟苷-5′-O-(3-硫代)三磷酸结合试验中进行评估时,J-2156 所引起的反应是索马他汀-28 和索马他汀-14 的 2 至 3 倍。在与 J-2156 的测试中,体生长抑素-14 表现出部分激动剂的典型行为,这证明体生长抑素-14 显然不是一种最大效力的激动剂。增加体节素-14 的浓度会导致 J-2156 的剂量-反应曲线随浓度变化而右移,但不会影响其最大反应。由于最大反应没有减弱,而且在膜中检测到 J-2156 的卓越功效,因此不能用脱敏和内化来解释 J-2156 的卓越功效。更有可能的是,体生长抑素-14 和 J-2156 稳定了不同的受体构象,它们与 G 蛋白相互作用的能力也不同。在环磷酸腺苷检测中,J-2156、体生长抑素-28 和体生长抑素-14 都是完全激动剂。然而,这种结果很可能是由于在环 AMP 试验中存在受体储备,因为在环 AMP 试验中存在明显的效力增益,而且 J-2156 的增益大于索马他汀。我们的结论是,内源性配体索马司他汀-14 和索马司他汀-28 对人类索马司他汀受体亚型 4 没有最大激动作用,J-2156 是一种所谓的超级拮抗剂。