Allosteric interactions between the antagonist prazosin and amiloride analogs at the human alpha(1A)-adrenergic receptor.
Allosteric interactions between the antagonist prazosin and amiloride analogs at the human alpha(1A)-adrenergic receptor.
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DOI：
10.1124/mol.57.3.436
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发表时间：
2000-03
影响因子：
3.6
通讯作者：
R. Leppik;A. Mynett;S. Lazareno;N. Birdsall
中科院分区：
文献类型：
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作者：
R. Leppik;A. Mynett;S. Lazareno;N. Birdsall
先前已经证明，阿米洛利可与人α（2A）-肾上腺素能受体上明确定义的变构位点相互作用。在这项研究中，探讨了人类α（1A）-肾上腺素能受体是否也具有等效的变构位点的问题。所检测的6种阿米洛利以浓度依赖性方式强烈增加拮抗剂[（3）H]哌唑嗪与α（1A）-肾上腺素能受体的解离速率。与母体阿米洛利，解离数据拟合良好的方程来自三元复合物变构模型，兼容阿米洛利在一个定义的变构网站上的α（1A）-肾上腺素能受体。与此相反，[（3）H]哌唑嗪在阿米洛利类似物存在下的解离数据与从单变构位点模型导出的方程不相容，但可以通过从双变构位点模型导出的方程很好地拟合。然而，某些个别参数无法解析。所观察到的解离速率常数急剧增加，增加阿米洛利类似物的浓度，在某些情况下，数据可以用逻辑方程拟合。从这样的拟合计算的斜率因子为1.2至2.1。可以得出结论，在α（1A）-和α（2A）-肾上腺素能受体的阿米洛利的结构结合关系是不同的。五种阿米洛利类似物（而非母体阿米洛利）与α（1A）-肾上腺素能受体的相互作用与两个（而非一个）变构位点的存在相容，因此比α（2A）-肾上腺素能受体的相互作用更复杂。
It has been demonstrated previously that amilorides can interact with a well defined allosteric site on the human alpha(2A)-adrenergic receptor. In this study, the question was explored as to whether the human alpha(1A)-adrenergic receptor also possesses an equivalent allosteric site. The six amilorides examined strongly increased the dissociation rate of the antagonist [(3)H]prazosin from the alpha(1A)-adrenergic receptor in a concentration-dependent manner. With the parent amiloride, the dissociation data were well fitted by an equation derived from the ternary complex allosteric model, compatible with amiloride acting at a defined allosteric site on the alpha(1A)-adrenergic receptor. In contrast, the dissociation data for [(3)H]prazosin in the presence of the amiloride analogs were not compatible with the equation derived from a one-allosteric-site model, but could be fitted well by an equation derived from a two-allosteric-site model. However, certain individual parameters could not be resolved. The observed dissociation rate constants increased steeply with increasing amiloride analog concentration, and in some cases the data could be fitted with a logistic equation. The slope factors calculated from such fits were 1.2 to 2.1. It is concluded that the structure-binding relationships of the amilorides at the alpha(1A)- and alpha(2A)-adrenergic receptors are different. The interactions of the five amiloride analogs, but not the parent amiloride, with the alpha(1A)-adrenergic receptor are compatible with the presence of two (but not one) allosteric sites, and is thus more complex than that found for the alpha(2A)-adrenergic receptor.