Drug Transport at the CNS Barriers

描述（由申请人提供）：有机阳离子（OC）转运体在体内许多内源性和外源性OC的处置和清除中起重要作用。与肾脏和肝脏相比，人们对大脑中OC的消除机制知之甚少。这是相当不幸的，因为许多中枢神经系统活性化合物，包括单胺类神经递质（如多巴胺、血清素）、中枢神经系统药物（如金刚烷胺、尼古丁）和神经毒素（如1-甲基-4-苯基吡啶（MPP+））是依赖转运体调节其脑水平的小亲水性OCs。质膜单胺转运蛋白（PMAT）是本实验室首次克隆的一种新型脑OC转运蛋白。虽然在结构上与平衡核苷转运蛋白家族（SLC29）相关，但PMAT具有独特且令人惊讶的多样化底物特异性，可转运结构异质的OCs，如生物胺、临床使用的药物和神经毒素。在人类和啮齿类动物中，PMAT在大脑中表达最丰富，在血脑脊液（CSF）屏障（即BCSFB或脉络膜丛）中高度集中。我们假设PMAT是BCSFB的主要OC转运体，负责从大脑中清除各种内源性和外源性OC。提出了三个具体目标（SAs）。SA1的重点是阐明控制转运体-底物相互作用的分子机制，以解释PMAT独特和通用的底物特异性。SA2的重点是阐明PMAT的转运机制，并建立BCSFB OC通量的细胞模型。最后，在SA3中，我们将构建并验证转基因动物模型，这将允许各种机制研究来揭示PMAT的体内作用。我们将运用分子生化技术、计算生物学、电生理学、免疫组织化学和转基因等实验方法，阐明PMAT在清除脑内神经递质、药物和毒素方面的结构、功能和生物学意义。所提出的研究对我们理解大脑的正常和病理生理功能具有广泛的意义。对中枢神经系统屏障OC转运体的详细了解也有助于解释和预测中枢神经系统隔室中OC药物和毒素的药代动力学和药效学，并有助于开发针对大脑的药物靶向新策略。

DESCRIPTION (provided by applicant): Organic cation (OC) transporters play important roles in the disposition and clearance of many endogenous and foreign OCs in the body. In contrast to the kidney and liver, little is known about OC elimination mechanisms in the brain. This is rather unfortunate because many CNS active compounds, including monoamine neurotransmitters (e.g. dopamine, serotonin), CNS drugs (e.g. amantadine, nicotine) and neurotoxins (e.g. 1-methyl-4-phenylpyridinium (MPP+)) are small hydrophilic OCs that rely on transporters to regulate their brain levels. This proposal focuses on plasma membrane monoamine transporter (PMAT), a novel brain OC transporter first cloned in our laboratory. While structurally related to the equilibrative nucleoside transporter family (SLC29), PMAT possesses a unique and surprisingly diverse substrate specificity, transporting structurally heterogeneous OCs such as biogenic amines, clinically used drugs and neurotoxins. In humans and rodents, PMAT is most abundantly expressed in the brain and highly concentrated in the blood-cerebrospinal fluid (CSF) barrier (i.e. BCSFB or choroid plexus). We hypothesized that PMAT is the principal OC transporter at the BCSFB and is responsible for removing a variety of endogenous and xenobiotic OCs from the brain. Three Specific Aims (SAs) have been proposed. SA1 is focused on elucidating the molecular mechanisms governing transporter-substrate interactions to explain the unique and versatile substrate specificity of PMAT. SA2 is focused on elucidating the transport mechanism of PMAT and developing a cellular model for OC flux at the BCSFB. Lastly, in SA3, we will construct and validate a transgenic animal model, which will allow a variety of mechanistic studies to reveal the in vivo action of PMAT. We will apply several experimental methods, ranging from molecular biochemical techniques, computational biology, electrophysiology, immunohistochemistry to transgenic approach, to elucidate the structure, function and biological significance of PMAT in clearing neurotransmitters, drugs and toxins in the brain. The proposed studies have broad implications in our understanding of normal and pathophysiological functions of the brain. Detailed knowledge of OC transporters at the CNS barriers can also help to explain and predict the pharmacokinetics and pharmacodynamics of OC drugs and toxins in the CNS compartment and aid in the development of new strategies for drug targeting to the brain.