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

许多药物(如双胍类抗高血糖药、组胺H2受体阻滞剂、铂类 化疗药物等)而毒素(如MPP、百草枯)是亲水性有机阳离子(OCS)，不 通过被动扩散很容易穿过细胞膜。有机阳离子转运体在细胞内起着重要作用。 这些有机碳外源化合物的处置、有效性和毒性。这些转运蛋白也可能参与了 通过吸收内源生物活性胺而产生的各种生理途径。质膜 单胺转运蛋白是首次克隆和鉴定的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的生理底物是含有5-羟色胺(5-羟色胺)的单胺类神经递质。 HT)是最理想的底物。PMAT还运输许多结构不同的阳离子异物 包括神经毒素MPP和治疗药物如二甲双胍。PmAt在 大脑和胃肠道，并与有机阳离子转运体1- 3(OCT1-3)。我们以前的分子和细胞工作有力地支持了pmAt在5-羟色胺信号转导中的作用 包括形成血-脑脊髓的脉络丛在内的屏障组织的通路和OC的转运 体液(脑脊液)屏障。然而，这些研究受到其体外设计和生理功能的限制。 PMAT及其在脑内OC处置中的体内意义尚不清楚。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来评估pmAt基因敲除小鼠的作用和意义 PmAt在体内。利用化学生物学方法，我们还确定了一组有希望的特定小分子 PmAt的分子抑制剂。更令人兴奋的是，pmAt基因缺失的小鼠表现出生理和组织学特征。 结肠异常，可能是与炎症发展相关的早期征兆 肠病。因为5-羟色胺是一种已知参与炎症发病机制的关键胃肠激素 肠道疾病，这些观察表明PMAT可能通过5-羟色胺对结肠炎起保护作用 中介途径。在这个竞争性的续订应用中，我们建议使用我们的新动物模型和 独特的化学工具来研究PMAT的生理、药理和病理功能。在……里面 目的1，我们将进一步鉴定和验证高效和选择性的pmAT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参与调节血-脑脊液屏障的OC外流。最后，在目标3中，我们将研究致病作用 PMAt在肠道炎症反应中的作用。拟议的研究将大大增强 我们对一种新型有机阳离子转运蛋白在体内的作用和意义的理解。这些研究 将为影响OC药物和毒素大脑处置的决定因素提供新的线索。最后，我们的 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.