Schetz J A, Sibley D R
Experimental Therapeutics Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892, U.S.A.
J Neurochem. 1997 May;68(5):1990-7. doi: 10.1046/j.1471-4159.1997.68051990.x.
Cations of various size and charge were used as atomic scale probes of D1 and D2 dopamine receptors. Those cations that perturbed the binding of D1- and D2-selective dopamine receptor antagonists were identified by screening at 5 mM cation. Pseudo-noble-gas-configuration d-transition metals, such as zinc, exerted a complete inhibition of specific binding, whereas most other cations had little or no effect. The nature of zinc's actions was characterized by measuring the radioligand binding properties of [3H]SCH-23390 and [3H]methylspiperone to cloned D1A and D2L dopamine receptors in either the presence or absence of Zn2+. Zinc exerts a low-affinity, dose-dependent, EDTA-reversible inhibition of the binding of subtype-specific antagonists primarily by decreasing the ligands' affinity for their receptors. The mechanism of zinc inhibition appears to be allosteric modulation of the dopamine receptor proteins because zinc increases the dissociation constant (K(D)) of ligand binding, Schild-type plots of zinc inhibition reach a plateau, and zinc accelerates antagonist dissociation rates. Here we demonstrate the effect of zinc on the binding of D1- and D2-selective antagonists to cloned dopamine receptors and show that the inhibition by zinc is through a dose-dependent, reversible, allosteric, two-state modulation of dopamine receptors.
各种大小和电荷的阳离子被用作D1和D2多巴胺受体的原子尺度探针。通过在5 mM阳离子浓度下进行筛选，确定了那些干扰D1和D2选择性多巴胺受体拮抗剂结合的阳离子。伪惰性气体构型的d过渡金属，如锌，对特异性结合有完全抑制作用，而大多数其他阳离子几乎没有影响或没有影响。通过测量在存在或不存在Zn2+的情况下，[3H]SCH-23390和[3H]甲基螺哌隆与克隆的D1A和D2L多巴胺受体的放射性配体结合特性，来表征锌作用的性质。锌主要通过降低配体对其受体的亲和力，对亚型特异性拮抗剂的结合产生低亲和力且剂量依赖性、EDTA可逆的抑制作用。锌抑制的机制似乎是对多巴胺受体蛋白的变构调节，因为锌增加了配体结合的解离常数（K(D)），锌抑制的Schild型图达到平稳期，并且锌加速了拮抗剂的解离速率。在这里，我们展示了锌对D1和D2选择性拮抗剂与克隆的多巴胺受体结合的影响，并表明锌的抑制作用是通过对多巴胺受体的剂量依赖性、可逆、变构、双态调节实现的。
