Chung F Z, Wu L H, Tian Y, Vartanian M A, Lee H, Bikker J, Humblet C, Pritchard M C, Raphy J, Suman-Chauhan N
Department of Biotechnology, Parke-Davis Pharmaceutical Research Division, Warner-Lambert Company, Ann Arbor, Michigan 48105-1047, USA.
Mol Pharmacol. 1995 Oct;48(4):711-6.
Two classes of structurally different tachykinin neurokinin3 (NK3) antagonists were used to evaluate species difference in antagonist binding between human and rat NK3 receptors. In competition binding experiments with [125I-MePhe7]NKB as radioligand, PD 154740, PD 157672, SR 48968, and SR 142801 displayed lower Ki values for the human NK3 receptor (40 +/- 4, 12 +/- 1,350 +/- 50, and 0.40 +/- 0.05 nM, respectively) than for the rat NK3 receptor (2450 +/- 130, 288 +/- 25, > 10,000, and 11.0 +/- 0.5 nM, respectively). Data from in vitro functional assay showed similar species preference as observed with the competition binding assay. It was shown previously that substitution of only two amino acid residues in the rat receptor to their human counterparts could change the species selectivity of SR 48968, a weak NK3 antagonist. In the double-substituted rat mutant, all three antagonists (PD 154740, PD 157672, and SR 142801) displayed Ki values (76 +/- 8, 16 +/- 2, and 0.50 +/- 0.05 nM, respectively) very similar to the Ki values for the wild-type human NK3 receptor. Thus, in addition to their previously reported effects on SR 48968, these two amino acid residues are responsible for the species selectivity of these three additional NK3 antagonists. Because PD 154740 and PD 157672 are very different structurally from SR 48968 and SR 142801, our results indicate that the two identified residues may be involved in adopting a receptor conformation that favors the binding of NK3 antagonists that display species preference for the human NK3 receptor.
使用两类结构不同的速激肽神经激肽3（NK3）拮抗剂来评估人和大鼠NK3受体之间拮抗剂结合的种属差异。在用[125I-MePhe7]NKB作为放射性配体的竞争结合实验中，PD 154740、PD 157672、SR 48968和SR 142801对人NK3受体的Ki值（分别为40±4、12±1、350±50和0.40±0.05 nM）低于对大鼠NK3受体的Ki值（分别为2450±130、288±25、>10000和11.0±0.5 nM）。体外功能测定的数据显示出与竞争结合测定中观察到的相似的种属偏好。先前已表明，仅将大鼠受体中的两个氨基酸残基替换为人相应的残基，就能改变弱NK3拮抗剂SR 48968的种属选择性。在双取代大鼠突变体中，所有三种拮抗剂（PD 154740、PD 157672和SR 142801）的Ki值（分别为76±8、16±2和0.50±0.05 nM）与野生型人NK3受体的Ki值非常相似。因此，除了它们先前报道的对SR 48968的作用外，这两个氨基酸残基还决定了这三种额外的NK3拮抗剂的种属选择性。由于PD 154740和PD 157672在结构上与SR 48968和SR 142801非常不同，我们的结果表明，所确定的这两个残基可能参与形成一种受体构象，这种构象有利于对人NK3受体显示种属偏好的NK3拮抗剂的结合。
