Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden.
Neuropharmacology. 2011 Oct-Nov;61(5-6):937-49. doi: 10.1016/j.neuropharm.2011.06.022. Epub 2011 Jul 5.
Voltage sensitivity has been demonstrated for some GPCRs. At the dopamine D(2S) receptor, this voltage sensitivity is agonist-specific; some agonists, including dopamine, exhibit decreased potency at depolarized potentials, whereas others are not significantly affected. In the present study, we examined some of the receptor-agonist interactions contributing to these differences, and investigated how dopamine D(2S) receptor voltage sensitivity affects clinically used dopamine agonists. GIRK channel activation in voltage-clamped Xenopus oocytes was used as readout of receptor activation. Structurally distinct agonists and complementary site-directed mutagenesis of the receptor's binding site were used to investigate the role of agonist-receptor interactions. We also confirmed that the depolarization-induced decrease of dopamine potency in GIRK activation is correlated by decreased binding of radiolabeled dopamine, and by decreased potency in G protein activation. In the mutagenesis experiments, a conserved serine residue as well as the conserved aspartate in the receptor's binding site were found to be important for voltage sensitive potency of dopamine. Furthermore, the voltage sensitivity of the receptor had distinct effects on different therapeutic D(2) agonists. Depolarization decreased the potency of several compounds, whereas for others, efficacy was reduced. For some agonists, both potency and efficacy were diminished, whereas for others still, neither parameter was significantly altered. The present work identifies some of the ligand-receptor interactions which determine agonist-specific effects of voltage at the dopamine D(2S) receptor. The observed differences between therapeutic agonists might be clinically relevant, and make them potential tools for investigating the roles of dopamine D(2) receptor voltage sensitivity in native tissue.
已经证明了一些 GPCR 具有电压敏感性。在多巴胺 D(2S)受体中，这种电压敏感性是激动剂特异性的；一些激动剂，包括多巴胺，在去极化电位下表现出降低的效力，而其他激动剂则没有受到明显影响。在本研究中，我们检查了导致这些差异的一些受体-激动剂相互作用，并研究了多巴胺 D(2S)受体电压敏感性如何影响临床使用的多巴胺激动剂。在电压钳制的非洲爪蟾卵母细胞中，GIRK 通道的激活被用作受体激活的读数。使用结构上不同的激动剂和受体结合位点的互补定点突变来研究激动剂-受体相互作用的作用。我们还证实，GIRK 激活中去极化诱导的多巴胺效力降低与放射性标记多巴胺的结合减少以及 G 蛋白激活的效力降低相关。在突变实验中，发现受体结合位点中的保守丝氨酸残基和保守天冬氨酸残基对于多巴胺的电压敏感效力很重要。此外，受体的电压敏感性对不同的治疗性 D(2)激动剂有明显的影响。去极化降低了几种化合物的效力，而对于其他化合物，效力降低。对于一些激动剂，效力和功效都降低了，而对于其他激动剂，这两个参数都没有明显改变。本工作确定了一些决定多巴胺 D(2S)受体上激动剂特异性电压作用的配体-受体相互作用。治疗性激动剂之间观察到的差异可能具有临床相关性，并使它们成为研究多巴胺 D(2)受体电压敏感性在天然组织中的作用的潜在工具。
