Role of ABC efflux transporters in ALS

描述（由申请人提供）：有限的药物渗透是治疗CNS疾病时经常遇到的障碍。可能导致这种现象的一种机制是ATP结合盒（ABC）药物外排转运蛋白（即P-糖蛋白或P-gp、多药耐药蛋白或MRP、乳腺癌耐药蛋白或BCRP，又称为ABCG 2）在血脑屏障（BBB）和血脑脊液（BCSF）屏障上的作用。ABC转运蛋白也在较低程度上定位于CNS实质细胞，在那里它们充当物质神经渗透的次级屏障。外排转运蛋白还排出毒素和毒素，以防止它们在细胞中的有害积累，构成细胞适应疾病介导的和环境应激的主要机制。肌萎缩侧索硬化症（ALS）是一种神经系统退行性疾病，其ABC转运蛋白的定位和调控机制尚不清楚。我们的初步数据显示，增加P-gp表达的脊髓星形胶质细胞的SOD 1-G93 A小鼠模型的ALS，以及在脊髓标本匀浆的散发性和家族性ALS患者。从治疗的角度来看，这表明药物在CNS中渗透的障碍因疾病而增加，必须克服以开发有效的ALS药物疗法。鉴于其多特异性，外排转运蛋白作为中枢神经系统疾病的关键参与者的认识是毫无疑问的，尽管重要的问题仍然没有答案。例如：ALS如何影响外排转运蛋白的定位和功能？哪些ALS特异性信号通路负责P-gp的上调？ALS介导的P-gp和/或其他ABC转运蛋白的上调是否会改变我们治疗该疾病的小鼠模型以及最终ALS患者的方式？为了填补这一知识空白，我们提出：（1）研究ALS中P-gp和其他相关ABC药物转运蛋白的活性、表达和分布概况;（2）研究ALS体外和体内模型中非神经元细胞中的外排转运蛋白活性是否有助于运动神经元变性;（3）研究消除ABC转运蛋白功能对ALS治疗的影响。 公共卫生相关性：肌萎缩侧索硬化症（ALS）是最具破坏性和致命性的进行性神经肌肉疾病之一，影响脊髓和运动皮层中的运动神经元。在美国，超过30，000人患有这种疾病，今年将有大约5，000名美国人被诊断患有ALS。多药外排ABC转运蛋白限制大量药物进入大脑和脊髓，导致有希望的候选药物的成功率很低，并调节多种物质的排出，包括可能对细胞有害的catabolic和潜在的毒性分子。因此，调节这些转运蛋白的活性和表达模式可以改善药物递送到大脑和脊髓中，并影响整体细胞内稳态。在本申请中，我们建议研究这些ABC转运蛋白在ALS中的调节和作用。我们的最终目标是了解ALS的致病机制，以提高药物治疗这种疾病的成功机会。

DESCRIPTION (provided by applicant): Limited drug penetration is an obstacle that is often encountered in the treatment of CNS diseases. One mechanism that may contribute to this phenomenon is the expression of ATP-binding cassette (ABC) drug efflux transporters (i.e. P-glycoprotein or P-gp, Multi-drug resistance proteins or MRPs, breast cancer resistance protein or BCRP, a.k.a. ABCG2) at the blood brain barrier (BBB) and blood cerebrospinal fluid (BCSF) barrier. ABC transporters also localize to a lesser extent at the CNS parenchyma cells where they act as secondary barrier to neural penetration of substances. Efflux transporters also extrude catabolites and toxins to prevent their harmful accumulation in the cell, constituting the major mechanism of cell adaptation to disease-mediated and environmental stress. Little is known on ABC transporters localization and regulation in amyotrophic lateral sclerosis (ALS), a neurodegenerative disease of the motor system. Our preliminary data show increased P-gp expression in spinal cord astrocytes of the SOD1-G93A mouse model of ALS as well as in spinal cord specimen homogenates of sporadic and familial ALS patients. From a therapeutic perspective, this suggests that the obstacle to drug penetration in the CNS is increased by the disease and must be overcome to develop effective pharmacotherapies for ALS. Given their multi-specificity, the recognition of efflux transporters as critical players in CNS diseases is unquestioned although important questions remain unanswered. For example: How does ALS affect efflux transporters localization and function? Which ALS-specific signaling pathways are responsible for up-regulation in P-gp? Will ALS-mediated up-regulation in P-gp and/or other ABC transporters change how we therapeutically treat the mouse model of the disease, and ultimately ALS patients? To fill this gap in knowledge, we propose: (1) To investigate activity, expression and distribution profile of P- gp and other relevant ABC drug transporters in ALS; (2) To study whether efflux transporter activity in non- neuronal cells contributes to motor neuron degeneration in in-vitro and in-vivo models of ALS; (3) To investigate the impact of eliminating ABC transporter function on ALS therapeutics. PUBLIC HEALTH RELEVANCE: Amyotrophic lateral sclerosis (ALS) is one of the most devastating and lethal progressive neuromuscular disorders, affecting motor neurons in the spinal cord and motor cortex. Over 30,000 people are living with this disease in the United States and approximately 5,000 Americans will be diagnosed with ALS this year. Multidrug efflux ABC transporters limit the entry into the brain and spinal cord of a large number of drugs, contributing to the poor success rate of promising drug candidates, and regulate the extrusion of a variety of substances, including catabolites and potential toxic molecules that could be harmful to cells. Modulating the activity and expression pattern of these transporters could therefore improve drug delivery into the brain and spinal cord and affect the overall cellular homeostasis. In this application we propose to study the regulation and role of these ABC transporters in ALS. Our ultimate goal is to understand the pathogenic mechanisms of ALS to improve the chances of success of pharmacotherapy for this disease.