Mechanisms by which NMDA receptor antibodies mediate a novel autoimmune disease

描述（由申请人提供）：当对肿瘤的免疫反应与神经系统中的蛋白质交叉反应，导致神经元功能改变时，出现神经副肿瘤综合征。最近，我们的实验室与Josep Dalmau博士（宾夕法尼亚大学医院神经病学系）的实验室合作，帮助描述了一种新的副肿瘤综合征，抗N-甲基-D-天冬氨酸受体（a-NMDAR）脑炎。这种综合征发生在表达NMDAR的畸胎瘤患者中，这些患者随后出现各种神经问题，包括健忘症、精神病和自主神经窘迫。我们在3年内发现了40多名患者，表明这种疾病经常未被诊断和治疗，可能导致自主神经不稳定死亡。患者通过血浆置换恢复，表明抗体参与。虽然我们以前已经表明，这些患者产生α-NMDA受体抗体，但尚不清楚这些抗体如何介导这种表型。NMDAR功能减退以前曾被认为与精神分裂症的发病机制有关;基于临床现象的相似性， α-NMDAR脑炎可能是一种自身免疫性疾病， 精神分裂症的变化。我建议研究NMDAR抗体触发这些神经问题的机制，这可能会为精神分裂症的一般机制提供更广泛的见解。为此，我将使用全细胞膜片钳和Ca 2+成像来确定这些抗体是否对通道功能有直接影响。这些抗体也可以改变细胞表面通道的数量或这些通道的位置，可能是通过破坏与锚定蛋白的相互作用。我将用细胞表面标记技术，主要是生物素化来检验这种可能性。最后，我将绘制受体的主要免疫原，方法是用缺失受体部分的突变型NMDAR亚基以及嵌合受体检测HEK 293细胞。找到抗原决定基有助于开发免疫诊断测试，防止不必要的死亡。公共卫生相关性：精神分裂症病因的主要理论之一是NMDA受体功能减退。因此，抗NMDAR脑炎，其中个体产生针对NMDAR的抗体，然后引起类似于精神分裂症的心理症状，为研究这种受体的具体贡献提供了独特的机会。然而，除了这种可能与精神分裂症的机械联系之外，这种疾病只是最近才发现的，似乎经常未被诊断，因此未得到治疗。为这种情况开发一种更好的测试方法，这项研究可以帮助解决这个问题。

DESCRIPTION (provided by applicant): Neural paraneoplastic syndromes arise when an immune response to a tumor cross reacts with a protein in the nervous system, causing alterations of neuronal function. Recently, our laboratory in collaboration with the laboratory of Dr. Josep Dalmau (Department of Neurology, Hospital of the University of Pennsylvania) has helped characterize a new paraneoplastic syndrome, anti-N-methyl-D-aspartate receptor (a-NMDAR) encephalitis. This syndrome develops in patients with teratomas that express NMDARs, who then present with a variety of neurological problems including amnesia, psychosis, and autonomic distress. We have found over 40 patients in 3 years, indicating that this disorder frequently goes undiagnosed and untreated, probably resulting in death from autonomic instability. Patients recover with plasmapheresis, indicating antibody involvement. While we have previously shown that these patients make a-NMDA receptor antibodies, it is unclear how these antibodies mediate this phenotype. NMDAR hypofunction has previously been implicated in the pathogenesis of schizophrenia; based on the similarities of the clinical phenomena, it is possible that a-NMDAR encephalitis represents an autoimmune disorder that mimics the neurological changes occurring in schizophrenia. I propose to investigate the mechanisms by which NMDAR antibodies trigger these neurological problems, which may provide broader insights into the general mechanisms of schizophrenia. To do so, I will use whole-cell patch clamp and Ca2+ imaging to determine if these antibodies have a direct effect on channel function. These antibodies could also change in the number of channels on the cell surface or the location of those channels, possibly by disrupting an interaction with an anchoring protein. I will examine this possibility with cell-surface labeling techniques, primarily biotinylations. Finally, I will map the main immunogen of the receptor by transfecting HEK293 cells with mutant NMDAR subunits that are missing portions of the receptor, as well as chimeric receptors. Finding the epitope could help develop an immunodiagnostic test, preventing unnecessary deaths. PUBLIC HEALTH RELEVANCE: One of the major theories of the cause of schizophrenia is hypofunction of the NMDA receptor. Anti-NMDAR encephalitis, therefore, in which individuals make antibodies to the NMDAR that then cause psychological symptoms similar to schizophrenia, presents a unique opportunity for studying the specific contribution of this receptor. In addition to this possible mechanistic connection to schizophrenia, however, this disease was only recently discovered and seems to frequently go undiagnosed and therefore untreated. Developing a better test for this condition, which this research could help do, would help solve this problem.