Site of action of β-ligands at the human β1-adrenoceptor
Site of action of β-ligands at the human β1-adrenoceptor
复制标题
DOI：
10.1124/jpet.104.082875
复制
发表时间：
2005-06-01
影响因子：
3.5
通讯作者：
Baker, JG
中科院分区：
文献类型：
--
作者：
Baker, JG
传统上，拮抗剂亲和力测量被认为对于定义细胞或组织内存在的受体或受体亚型很重要。该值的任何变化通常都被视为第二个受体存在的证据。然而，高效配体会诱导 β2-肾上腺素受体发生时间和磷酸化依赖性变化，导致对拮抗剂的亲和力降低 10 倍。此外，β1-肾上腺素受体现在被认为以两种不同的活性构象存在，这两种构象的区别在于它们的药理学特性。在本研究中，使用在中国仓鼠卵巢细胞中稳定表达的具有环AMP反应元件报告基因的人β1-肾上腺素受体，确定了一系列β-激动剂和β-拮抗剂的作用位点。肾上腺素和去甲肾上腺素被证实通过儿茶酚胺位点具有激动剂作用，而所有拮抗剂对儿茶酚胺而不是第二位点具有更高的亲和力。然而，这两个站点的亲和力排名顺序不同，表明它们确实是独立的实体。然而，发现儿茶酚胺位点拮抗剂亲和力的测量取决于存在的激动剂。例如，沙莫特罗、西马特罗、特布他林和福莫特罗激动剂反应比儿茶酚胺反应本身更容易被 CGP 20712A[2-羟基-5-(2-[{羟基-3-(4-[1-甲基-4-三氟甲基-2-咪唑基]苯氧基)丙基}氨基]乙氧基)苯甲酰胺]拮抗。然而，这与之前报道的人类 β2-肾上腺素受体激动剂功效无关。因此，某些激动剂（例如西马特罗）可能纯粹激活儿茶酚胺位点，而另一些激动剂则纯粹激活次级位点（例如，CGP 12177 [(-)-4-(3-叔丁基氨基-2-羟基丙氧基)-苯并咪唑-2-酮]），而其他激动剂（例如儿茶酚胺）则不同程度地激活这两个位点。
Antagonist affinity measurements have traditionally been considered important in defining the receptor or receptor subtypes present within cells or tissues. Any change in this value has normally been taken as evidence for the presence of a second receptor. However, highly efficacious ligands induce a time and phosphorylation-dependent change in the beta 2-adrenoceptor resulting in 10-fold lower affinity for antagonists. Also the beta 1-adrenoceptor is now considered to exist in two different active conformations which are distinguished by their pharmacological properties. In this study, the site of action of a range of beta-agonists and beta-antagonists was determined using the human beta 1-adrenoceptor stably expressed in Chinese hamster ovary cells with cyclic AMP response element reporter genes. Adrenaline and noradrenaline were confirmed as having agonist actions via the catecholamine site, whereas all antagonists had higher affinity for the catecholamine rather than secondary site. However, the rank order of affinity for the two sites was different suggesting that they are indeed separate entities. The measurements of antagonist affinity at the catecholamine site, however, were found to depend upon the agonist present. For example, xamoterol, cimaterol, terbutaline, and formoterol agonist responses were more readily antagonized by CGP 20712A[2-hydroxy-5-(2-[{hydroxy-3-(4-[1-methyl-4-trifluoromethyl-2- imidazolyl] phenoxy)propyl}amino]ethoxy)benzamide] than the catecholamine responses themselves. This, however, was not related to agonist efficacy as has previously been reported for the human beta 2-adrenoceptor. Therefore, it may be that some agonists (e.g., cimaterol) purely activate the catecholamine site and others purely activate the secondary site (e.g., CGP 12177 [(-)-4-(3-tert-butylamino-2-hydroxypropoxy)-benzimidazol-2-one]), whereas the others (e.g., catecholamines) activate both sites to differing degrees.