Dunah A W, Wang Y, Yasuda R P, Kameyama K, Huganir R L, Wolfe B B, Standaert D G
Department of Neurology, Massachusetts General Hospital, Boston, Massachusetts, USA.
Mol Pharmacol. 2000 Feb;57(2):342-52.
Recent evidence has linked striatal N-methyl-D-aspartate (NMDA) receptor function to the adverse effects of long-term dopaminergic treatment in Parkinson's disease. We have studied the abundance, composition, and phosphorylation of NMDA receptor subunits (NRs) in the rat 6-hydroxydopamine lesion model of parkinsonism. In lesioned striatum, the abundance of NR1 and NR2B in striatal membranes was decreased to 68 +/- 3.2 and 62 +/- 4.4%, respectively, relative to the unlesioned striata, whereas the abundance of NR2A was unchanged. Coimmunoprecipitation of NMDA receptors under nondenaturing conditions revealed that these changes reflected a selective depletion of receptors composed of NR1/NR2B, without alteration in receptors composed of NR1/NR2A. However, the abundance and composition of striatal NMDA receptors in extracts containing both cytoplasmic and membrane proteins were not altered in lesioned rats, suggesting that the changes in the membrane fraction resulted from intracellular redistribution of receptors. The phosphorylation of NR1 protein at serine 890 and serine 896, but not at serine 897, and the tyrosine phosphorylation of NR2B but not NR2A were decreased in the membrane fraction of the lesioned striatum. Chronic treatment of lesioned rats with L-dopa normalized the alterations in the abundance and subunit composition of the NMDA receptors in striatal membranes, and produced striking hyperphosphorylation, both of NR1 at serine residues, and NR2A and NR2B at tyrosine residues. These findings suggest that the adverse motor effects of chronic L-dopa therapy may result from alterations in regulatory phosphorylation sites on NMDA receptors.
最近有证据表明，纹状体N-甲基-D-天冬氨酸（NMDA）受体功能与帕金森病长期多巴胺能治疗的不良反应有关。我们在大鼠帕金森病6-羟基多巴胺损伤模型中研究了NMDA受体亚基（NRs）的丰度、组成和磷酸化情况。在损伤的纹状体中，相对于未损伤的纹状体，纹状体膜中NR1和NR2B的丰度分别降至68±3.2%和62±4.4%，而NR2A的丰度未改变。在非变性条件下对NMDA受体进行免疫共沉淀显示，这些变化反映了由NR1/NR2B组成的受体的选择性耗竭，而由NR1/NR2A组成的受体没有改变。然而，在含有细胞质和膜蛋白的提取物中，损伤大鼠纹状体NMDA受体的丰度和组成没有改变，这表明膜部分的变化是由受体内在再分布引起的。在损伤纹状体的膜部分，NR1蛋白在丝氨酸890和丝氨酸896处的磷酸化，但在丝氨酸897处没有，以及NR2B的酪氨酸磷酸化但不是NR2A的酪氨酸磷酸化减少。用左旋多巴长期治疗损伤大鼠可使纹状体膜中NMDA受体的丰度和亚基组成的改变恢复正常，并使NR1在丝氨酸残基、NR2A和NR2B在酪氨酸残基处产生显著的过度磷酸化。这些发现表明，长期左旋多巴治疗的不良运动效应可能是由NMDA受体调节磷酸化位点的改变引起的。
