Differential allosteric modulation by amiloride analogues of agonist and antagonist binding at A1 and A3 adenosine receptors
Differential allosteric modulation by amiloride analogues of agonist and antagonist binding at A1 and A3 adenosine receptors
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DOI：
10.1016/s0006-2952(02)01556-3
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发表时间：
2003-02-15
影响因子：
5.8
通讯作者：
Jacobson, KA
中科院分区：
文献类型：
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作者：
Gao, ZG;Melman, N;Jacobson, KA
先前发现利尿剂阿米洛利及其类似物是与 A(2A) 腺苷受体结合的拮抗剂的变构调节剂。在这项研究中，阿米洛利类似物对 A(1) 和 A(3) 受体拮抗剂结合以及 A(1) 激动剂结合进行变构调节的可能性。对 A(2A) 和 A(3) 受体进行了探索。阿米洛利类似物增加了两种拮抗剂放射性配体[H-3]8-环戊基-1,3-二丙黄嘌呤([H-3]DPCPX)和[H-3]8-乙基-4-甲基-2-苯基-(8R)-4,5,7,8-四氢-1H-咪唑并[2, 1-i]嘌呤-5-酮的解离率([H-3]PSB-11)，分别来自A(1)和A(3)受体。阿米洛利和 5-(N,N-二甲基)阿米洛利 (DMA) 对 A(1) 受体比对 A(3) 受体更有效，而 5-(N.N-六亚甲基)阿米洛利 (HMA) 对 A(3) 受体更有效。因此，阿米洛利类似物是 A(1)、A(2A) 和 A(3) 腺苷受体亚型拮抗剂结合的变构抑制剂。与对拮抗剂占据受体的作用相反，阿米洛利类似物不影响 A(1) 激动剂 [H-3]N-6-[(R)-苯丙丙基]腺苷 ([H-3]R-PIA) 从 A(1) 受体或 A(2A) 激动剂的解离速率来自 A(2A) 受体的 [H-3]2-[对-(2-羧乙基)苯基-乙基氨基]-5'-N-乙基羧酰胺腺苷 ([H-3]CGS21680)。阿米洛利类似物显着降低了 A(3) 激动剂放射性配体 [I-125]N-6-(4-氨基-3-碘苄基)腺苷-5'-N-甲基脲酰胺 ([I-125]-AB-MECA) 从 A(3) 受体的解离率。阿米洛利类似物在激动剂占据和拮抗剂占据受体上的结合模式显着不同，这在本研究测试的所有三种腺苷受体亚型中得到了证明。在表达人 A(3) 受体的完整 CHO 细胞中使用环 AMP 功能测定进一步探讨阿米洛利类似物对 A(3) 受体激动剂作用的影响。结合和功能测定均支持阿米洛利类似物与 A(3) 受体的变构相互作用，(C) 2002 Elsevier Science Inc. 保留所有权利。
The diuretic drug amiloride and its analogues were found previously to be allosteric modulators of antagonist binding to A(2A) adenosine receptors. In this study, the possibility of the allosteric modulation by amiloride analogues of antagonist binding at A(1) and A(3) receptors, as well as agonist binding at A(1). A(2A), and A(3) receptors, was explored. Amiloride analogues increased the dissociation rates of two antagonist radioligands, [H-3]8-cyclopentyl-1,3-diproplxanthine ([H-3]DPCPX) and [H-3]8-ethyl-4-methyl-2-phenyl-(8R)-4,5,7,8-tetrahydro-1H-imidazo[2, 1-i]purin-5-one ([H-3]PSB-11), from A(1) and A(3) receptors, respectively. Amiloride and 5-(N,N-dimethyl)amiloride (DMA) were more potent at A(1) receptors than at A(3) receptors, while 5-(N.N-hexamethylene)amiloride (HMA) was more potent at A(3) receptors. Thus, amiloride analogues are allosteric inhibitors of antagonist binding at A(1), A(2A), and A(3) adenosine receptor subtypes. In contrast to their effects on antagonist-occupied receptors, amiloride analogues did not affect the dissociation rates of the A(1) agonist [H-3]N-6-[(R)-phenyhsopropyl]adenosine ([H-3]R-PIA) from A(1) receptors or the A(2A) agonist [H-3]2-[p-(2-carboxvethyl)phenyl-ethylamino]-5'-N-ethylearboxamidoadenosine ([H-3]CGS21680) from A(2A) receptors. The dissociation rate of the A(3) agonist radioligand [I-125]N-6-(4-amino-3-iodobenzyl)adenosine-5'-N-methyluronamide ([I-125]-AB-MECA) from A(3) receptors was decreased significantly by amiloride analogues. The binding modes of amiloride analogues at agonist-occupied and antagonist-occupied receptors differed markedly, which was demonstrated in all three subtypes of adenosine receptors tested in this study. The effects of the amiloride analogues on the action of the A(3) receptor agonist were explored further using a cyclic AMP functional assay in intact CHO cells expressing the human A(3) receptor. Both binding and functional assays support the allosteric interactions of amiloride analogues with A(3) receptors, (C) 2002 Elsevier Science Inc. All rights reserved.