NEW APPROACHES TO THE MECHANISM AND THERAPY FOR MYASTHENIA GRAVIS

描述（由申请人提供）：重症肌无力是一种神经系统疾病，其特征是骨骼肌无力和易疲劳。针对神经肌肉接头（NMJ）处的烟碱乙酰胆碱受体（AChR）的自身免疫抗体已知是该疾病的主要原因。AChR是一种配体门控离子通道，介导电信号从运动神经到肌肉的传递。约三分之二的重症肌无力患者血清中的自身免疫抗体与主要免疫原性区（MIR）结合，MIR是位于AChR α亚基胞外结构域上的表位。抗体交联肌肉细胞膜上的乙酰胆碱受体，导致受体内化/降解速率增加，神经肌肉传递受损。目前治疗重症肌无力只能暂时缓解症状。它们通常是非特异性的，不能改变疾病的原因。我们研究的长期目标是确定新的药物，可以更有效地与更少的副作用重症肌无力。在这项R21授权申请中，将在酵母表达系统中产生大量的人肌肉AChR α亚基的N-末端胞外结构域。受体片段将与mAb 35（一种可引起实验性重症肌无力的参比单克隆抗体）复合结晶。蛋白质复合物的三维结构将通过X射线衍射测定。结构信息将是合理设计药物的关键，可以防止自身免疫抗体与AChR结合。公共卫生相关性这项研究应该为烟碱乙酰胆碱受体和导致重症肌无力（一种相对常见的神经系统疾病）的自身免疫抗体之间形成的复合物的分子结构提供新的见解。蛋白质晶体结构的坐标将大大有助于更有效和更具体的药物的合理设计，以及了解特定的生化过程在重症肌无力的发展中的作用。如果成功的话，这项R21补助金申请中概述的探索性研究可能会为未来的药物发现开辟一条新的途径，旨在有效控制患者的疾病。

DESCRIPTION (provided by applicant): Myasthenia gravis is a neurological disorder characterized by weakness and fatigability of the skeletal muscles. Autoimmune antibodies against the nicotinic acetylcholine receptor (AChR) at the neuromuscular junction (NMJ) are known to be the main cause of the disease. The AChR is a ligand-gated ion channel that mediates the transmission of electric signals from motor nerve to muscle. About two-thirds of autoimmune antibodies from sera of patients with myasthenia gravis bind to the Main Immunogenic Region (MIR), an epitope located on the extracellular domain of the alpha subunit of AChR. The antibodies cross-link the AChRs on muscle cell membrane, resulting in an increased rate of internalization/degradation of the receptor and impaired neuromuscular transmission. Current treatments for myasthenia gravis can only temporarily relieve symptoms. They are usually non-specific and cannot change the cause of the disease. The long-term goal of our research is to identify new drugs that can act more effectively with fewer side-effects for myasthenia gravis. In this R21 grant application, large quantities of the N-terminal, extracellular domain of alpha subunit of human muscle AChR will be generated in a yeast expression system. The receptor fragment will be crystallized in complex with mAb35, a reference monoclonal antibody that can cause experimental myasthenia gravis. The three-dimensional structure of the protein complex will be determined by x-ray diffraction. The structural information will be key to rational design of drugs that can prevent binding of autoimmune antibodies to AChR. PUBLIC HEALTH RELEVANCE This study should provide new insight into the molecular structure of a complex formed between the nicotinic acetylcholine receptor and autoimmune antibodies that causes myasthenia gravis, a relatively common neurological disease. The coordinates of the protein crystal structure will aid greatly the rational design of more potent and specific drugs as well as for understanding the role of a particular biochemical process in the development of myasthenia gravis. If successful, the exploratory study outlined in this R21 grant application may open a new avenue for future drug discovery aimed at effective control of the disease in patients.