Mechanisms by which NMDA receptor antibodies mediate a novel autoimmune disease

描述(申请人提供)：当对肿瘤的免疫反应与神经系统中的蛋白质发生交叉反应，导致神经功能改变时，就会出现神经副肿瘤综合征。最近，我们的实验室与宾夕法尼亚大学医院神经科Josep Dalmau博士的实验室合作，帮助确定了一种新的副肿瘤综合征-抗N-甲基-D-天冬氨酸受体(a-NMDAR)脑炎的特征。这种综合征发生在表达NMDAR的畸胎瘤患者身上，然后他们会出现各种神经问题，包括健忘症、精神病和自主神经障碍。我们在3年内发现了40多名患者，表明这种疾病经常得不到诊断和治疗，可能会导致自主神经不稳定而死亡。患者通过血浆置换恢复，表明抗体参与。虽然我们之前已经证明这些患者会产生a-NMDA受体抗体，但这些抗体是如何调节这种表型的还不清楚。NMDAR功能低下以前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，它 A-NMDAR脑炎可能是一种自身免疫性疾病，类似于神经性 精神分裂症中发生的变化。我建议调查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钙成像来确定这些抗体是否对通道功能有直接影响。这些抗体还可以改变细胞表面的通道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来研究这种可能性，主要是生物素化。最后，我将通过将缺失受体部分的突变NMDAR亚单位以及嵌合受体导入HEK293细胞来绘制受体的主要免疫原。找到表位可能有助于开发一种免疫诊断测试，防止不必要的死亡。与公共健康相关：精神分裂症病因的主要理论之一是NMDA受体功能低下。因此，抗NMDAR脑炎为研究这种受体的具体作用提供了一个独特的机会。在这种脑炎中，个体产生针对NMDAR的抗体，然后导致类似精神分裂症的心理症状。然而，除了这种可能的机制与精神分裂症的联系外，这种疾病是最近才发现的，似乎经常没有得到诊断，因此也没有得到治疗。为这种情况开发一种更好的测试，这项研究可以帮助做，将有助于解决这个问题。

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.