Kitayama S, Wang J B, Uhl G R
Molecular Neurobiology Branch, National Institute on Drug Abuse, Baltimore, Maryland 21224.
Synapse. 1993 Sep;15(1):58-62. doi: 10.1002/syn.890150107.
MPP+ (1-methyl-4-phenylpyridinium), a dopaminergic neurotoxin that provides the best available experimental model of Parkinson's disease, is selectively concentrated in dopamine neurons by the dopamine transporter (DAT). DAT also serves as a primary recognition site for cocaine. To help define selective molecular mechanisms by which MPP+ uptake occurs, we have tested dopamine transporters mutated in several residues for their abilities to accumulate dopamine and MPP+, and to bind a cocaine analog. Mutants in DAT 7th and 11th hydrophobic putative transmembrane domains increase MPP+ uptake velocity and affinity (1/KD), respectively. These mutations exert much more modest effects on dopamine uptake and have little impact on cocaine analog binding. These findings provide the first example of mutations that enhance transport and identify specific DAT amino acids selectively involved in neurotoxin uptake. They may also have implications for the feasibility of developing drugs that could specifically block accumulation of Parkinsonism-inducing neurotoxins.
1-甲基-4-苯基吡啶离子（MPP+）是一种多巴胺能神经毒素，它提供了现有最佳的帕金森病实验模型，通过多巴胺转运体（DAT）选择性地富集于多巴胺神经元中。DAT也是可卡因的主要识别位点。为了帮助确定MPP+摄取所涉及的选择性分子机制，我们测试了在几个残基处发生突变的多巴胺转运体积累多巴胺和MPP+以及结合可卡因类似物的能力。DAT第7个和第11个假定的疏水跨膜结构域中的突变分别提高了MPP+的摄取速度和亲和力（1/KD）。这些突变对多巴胺摄取的影响要小得多，对可卡因类似物结合几乎没有影响。这些发现提供了增强转运的突变的首个实例，并确定了选择性参与神经毒素摄取的特定DAT氨基酸。它们可能也对开发能够特异性阻断帕金森病诱导神经毒素积累的药物的可行性具有启示意义。
