The plasma membrane monoamine transporter (PMAT): expression and role in mIBG disposition in neuroblastoma

许多药物（如双胍类降糖药、组胺H2受体阻滞剂、铂类 化学治疗等）和毒素（如MPP+、百草枯）是亲水性有机阳离子（OC）， 容易通过被动扩散穿过细胞膜。有机阳离子转运蛋白在生物学中发挥着重要作用 这些OC异生物质的处置、功效和毒性。这些运输者也可能参与 各种生理途径，通过其吸收内源性生物活性胺。质膜 单胺转运蛋白（PMAT）是一种新的多特异性有机阳离子转运蛋白 在我们的实验室里。PMAT的生理底物是具有5-羟色胺（5-HT）的单胺神经递质。 HT）是最优选的底物。PMAT还转运许多结构多样的阳离子异生物质 包括神经毒素MPP+和治疗药物如二甲双胍。PMAT在大脑中高度表达 脑和胃肠道，并与有机阳离子转运蛋白1- 3（OCT 1 -3）。我们先前的分子和细胞工作强烈支持PMAT在5-HT信号传导中的作用 通道和OC运输在屏障组织，包括脉络丛，形成血液-脑脊液 液体（CSF）屏障。然而，这些研究受限于它们的体外设计，以及它们的生理功能。 PMAT及其在脑OC处置中的体内意义仍不明确。我们最近创作了一部小说 PMAT基因敲除小鼠模型，它提供了一个独特的资源，以评估的作用和意义， 体内PMAT。使用化学生物学方法，我们还确定了一组有前途的特定小分子。 PMAT的分子抑制剂。更令人兴奋的是，PMAT敲除小鼠表现出生理和组织学上的差异， 结肠异常，可能代表与炎症发展相关的早期体征 肠道疾病。因为5-HT是一种关键的肠道激素，已知参与炎症的发病机制， 肠道疾病，这些观察结果表明PMAT对结肠炎的保护作用可能通过5-HT 介导的途径。在这个竞争性的更新应用中，我们建议使用我们的新型动物模型， 独特的化学工具来研究PMAT的生理、药理和病理功能。在 目标1，我们将进一步表征和验证PMAT的高效和选择性小分子抑制剂。 在目标2中，我们将使用我们的基因敲除动物模型和特定的化学抑制剂来研究 PMAT介导血-CSF屏障处的OC流出。最后，在目标3中，我们将研究 PMAT在肠道炎症反应中的作用。拟议的研究将大大提高 我们的理解在体内的作用和意义的一种新的有机阳离子转运蛋白。这些研究 将揭示影响OC药物和毒素大脑处置的决定因素。最后我们 研究将阐明PMAT在肠道中的病理生理作用，并为遗传因素提供新的见解 影响宿主对炎症性肠病的易感性。

Many drugs (e.g. biguanide antihyperglycemics, histamine H2 receptor blockers, platinum-based chemotherapeutics etc.) and toxins (e.g. MPP+, paraquat) are hydrophilic organic cations (OCs) that do not readily cross cell membranes by passive diffusion. Organic cation transporters play important roles in the disposition, efficacy and toxicity of these OC xenobiotics. These transporters are also likely to be involved in various physiological pathways through their uptake of endogenous bioactive amines. The plasma membrane monoamine transporter (PMAT) is a new polyspecific organic cation transporter first cloned and characterized in our laboratory. The physiologic substrates of PMAT are the monoamine neurotransmitters with serotonin (5- HT) being the most preferred substrate. PMAT also transports many structurally diverse cationic xenobiotics including the neurotoxin MPP+ and therapeutic drugs such as metformin. PMAT is highly expressed in the brain and the gastrointestinal tract, and has overlapping substrate specificity with organic cation transporters 1- 3 (OCT1-3). Our previous molecular and cellular work strongly supports a role of PMAT in 5-HT signaling pathways and in OC transport at barrier tissues including choroid plexus that forms the blood- cerebrospinal fluid (CSF) barrier. However, these studies are limited by their in vitro design, and the physiological function of PMAT and its in vivo significance in brain OC disposition remain undefined. We have recently created a novel PMAT knockout mouse model, which provides a unique resource to evaluate the roles and significance of PMAT in vivo. Using a chemical biology approach, we also identified a set of promising specific small molecule inhibitors for PMAT. More excitingly, the PMAT null mice exhibited physiological and histological abnormalities in the colon which could represent early signs associated with the development of inflammatory bowel disease. Because 5-HT is a key gut hormone known to be involved in the pathogenesis of inflammatory bowel disease, these observations suggest a protective role of PMAT against colitis likely through 5-HT mediated pathway. In this competing renewal application, we propose to use our novel animal model and unique chemical tools to investigate the physiological, pharmacological and pathological function of PMAT. In Aim 1, we will further characterize and validate highly potent and selective small molecule inhibitors for PMAT. In Aim 2, we will use our knockout animal model and specific chemical inhibitors to investigate the role of PMAT in mediating OC efflux at the blood-CSF barrier. Lastly, in Aim 3, we will investigate the pathogenic role of PMAT in the development of inflammatory response in the gut. The proposed studies will greatly enhance our understandings of the in vivo roles and significance of a novel organic cation transporter. These studies will shed new light on the determinants influencing brain disposition of OC drugs and toxins. Finally, our studies will elucidate the pathophysiologic role of PMAT in the gut and offer new insights into genetic factors influencing host susceptibility to inflammatory bowel disease.