Pathomechanisms of autoantibody-induced autoimmunity to AMPA receptors

最近，在边缘脑炎患者中发现了几种潜在的致病抗体(AB)。这些AB是否直接导致疾病的发病机制，以及它们如何导致典型的疾病症状，例如认知缺陷、记忆受损、癫痫发作或人格变化，迄今尚未得到证实。在这里，我们将研究各种纯化的带有AB的患者IgG制剂对AMPA受体在突触传递中的影响。AMPA受体功能相关的GluR2亚基已被确定为人AUTO-AB的特异性靶位。利用超分辨dSTORM显微镜，我们的目标是研究突触表达的变化和AMPA受体亚单位的定位。我们将使用膜片钳记录在刺激单个突触连接后分离的神经元来研究AB在突触传递中的作用。这些膜片钳记录将与各自受体区域的dSTORM分析相关联。对突触传递的量子参数以及对短期和长期可塑性的影响将在急性海马片中进行测试。在小鼠脑内立体定向应用患者免疫球蛋白组分后，将研究AB诱导的学习和记忆变化。组织学方面，我们将评估受体密度和突触结构的变化。这些实验旨在阐明AB抗AMPA受体的边缘脑炎的潜在病理生理机制。在基础科学方面，该项目可能为自身免疫介导的AMPA受体GluR2亚单位功能障碍提供新的见解。从临床上看，AB介导的病理生理学证据可以作为这种谱系障碍的主要例子的证据，并将直接影响边缘脑炎患者的治疗策略。

Recently, several potentially pathogenic antibodies (AB) against neuronal ionotropic receptors (e.g. AMPA and NMDA receptors) have been described in patients with limbic encephalitis. If these AB contribute directly to disease pathogenesis and how they might induce typical disease symptoms, e.g. cognitive deficits, impaired memory, seizures, or changes in personality has not been demonstrated to date. Here, we will investigate the impact of various purified patient IgG preparations with AB to the AMPA receptor on synaptic transmission. The functional relevant GluR2 subunit of the AMPA-receptor has been identified to be the specific target epitope of the human auto-AB. Using super-resolution dSTORM microscopy we aim to investigate changes in synaptic expression and localisation of AMPA-receptor subunits. We will use patch-clamp recordings of dissociated neurons after stimulation of individual synaptic boutons to investigate AB-mediated effects on synaptic transmission. These patch-clamp recordings will be correlated with dSTORM analysis of the respective receptor fields. Effects on quantal parameters of synaptic transmission and on short- and long-term plasticity will be tested in acute hippocampal slices. AB-induced alterations of learning and memory will be investigated after stereotactic intracerebral application of patient-IgG fractions in mice. Histologically, we will evaluate receptor density and changes in synaptic architecture. These experiments aim to elucidate the underlying pathophysiology of limbic encephalitis with AB against AMPA-receptors. In terms of basic science, this project might provide new insights into autoimmune-mediated dysfunctions of the AMPA receptor GluR2 subunit. From the clinical view, evidence of AB-mediated pathophysiology could serve as a proof of principle example in this spectrum disorder and would have direct implications on the therapeutic strategy treating patients suffering from limbic encephalitis.