Expression of the extraneuronal monoamine transporter in RPE and neural retina
Expression of the extraneuronal monoamine transporter in RPE and neural retina
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DOI：
10.1076/0271-3683(200003)20:3;1-9;ft195
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发表时间：
2000-01-01
影响因子：
2
通讯作者：
Smith, SB
中科院分区：
文献类型：
--
作者：
Rajan, PD;Kekuda, R;Smith, SB
目的.多巴胺在视网膜中具有几种重要功能，包括在控制感光盘脱落到RPE中的可能作用。虽然一些细胞表达多巴胺的转运蛋白，但RPE细胞不表达，这使我们想知道新描述的儿茶酚胺转运系统，神经元单胺转运蛋白（摄取（2））（也称为有机阳离子转运蛋白3（OCT 3））是否存在于RPE中，并可能作为多巴胺的转运蛋白发挥作用。OCT 3也接受组胺作为转运底物，因此我们研究了这种视网膜神经递质与OCT 3的相互作用。通过原位杂交、北方印迹分析和RT-PCR分析小鼠眼内OCT 3的表达。在培养的人ARPE-19细胞中通过监测1-甲基-4-苯基吡啶鎓（MPP+）的摄取来分析OCT 3的功能，MPP+是一种神经毒素，其是OCT 3的已知底物。原位杂交分析表明，OCT 3在小鼠RPE和神经视网膜的几种细胞类型中表达，包括感光细胞、神经节细胞、无长突细胞和水平细胞。通过北方印迹分析和RT-PCR证实OCT 3在RPE中的表达。培养的ARPE-19细胞中MPP+摄取的特征包括碱性pH刺激转运、高亲和力（K-t = 28 +/-4 μ M）、与几种阳离子药物和单胺神经递质竞争以及对类固醇敏感。此外，多巴胺和组胺可抑制RPE细胞对MPP+的摄取，IC50值（50%抑制所需浓度）分别为637 +/-84 μ M和150 +/-20 μ M。这项研究提供了关于有机阳离子转运蛋白OCT3在眼睛特别是RPE中的表达和功能的第一份报告。这些数据具有生理学和药理学相关性，因为OCT 3可能参与多巴胺和组胺从视网膜下腔的清除，并且还可能在视网膜神经毒素MPP+的处置中发挥关键作用。
Purpose. Dopamine has several important functions in the retina including a possible role in controlling photoreceptor disk shedding to the RPE. While some cells express a transporter for dopamine, the RPE cell does not, leading us to ask whether the newly described catecholamine transport system, the extraneuronal monoamine transporter (uptake(2)) (also known as organic cation transporter 3 (OCT3), is present in RPE and might function as a transporter for dopamine. OCT3 also accepts histamine as a transportable substrate and so we investigated the interaction of this retinal neurotransmitter with OCT3.Methods. OCT3 expression in the mouse eye was analyzed by in situ hybridization, Northern blot analysis and RT-PCR. OCT3 function was analyzed in cultured human ARPE-19 cells by monitoring the uptake of 1-methyl-4-phenyl pyridinium (MPP+), a neurotoxin, which is a known substrate for OCT3.Results. In situ hybridization analysis showed that OCT3 is expressed in mouse RPE and in several cell types of the neural retina, including photoreceptor, ganglion, amacrine, and horizontal cells. The expression of OCT3 in RPE was confirmed by Northern blot analysis and RT-PCR. The characteristics of MPP+ uptake in cultured ARPE-19 cells included the stimulation of transport by alkaline pH, high affinity (K-t = 28 +/- 4 mu M), competition with several cationic drugs and monoamine neurotransmitters and sensitivity to steroids. In addition, the uptake of MPP+ in RPE cells was inhibited by dopamine and histamine with IC50 values (concentration needed for 50% inhibition) of 637 +/- 84 mu M and 150 +/- 20 mu M, respectively.Conclusions. This study provides the first report on the expression and function of an organic cation transporter, OCT3, in the eye and in particular the RPE. The data have physiological and pharmacological relevance as it is likely that OCT3 participates in the clearance of dopamine and histamine from the subretinal space and may also play a key role in the disposition of the retinal neurotoxin MPP+.