Analysis of the P/Q-type calcium channel in autopsied patients with paraneoplastic cerebellar degeneration (PCD) and Lambert-Eaton myasthenic syndrome (LEMS)

本研究的目的是阐明小脑对P/Q型电压门控钙通道(VGCC)的自身免疫是否与Lambert-Eaton肌无力综合征(LEMS)的副肿瘤性小脑变性(PCD)的发病有关。我们使用从三个患有LEMS的PCD患者和包括一名LEMS患者在内的其他六个疾病患者的尸检中获得的人类小脑组织作为对照。我们比较了这些患者的小脑P/Q型VGCC和对照的自身抗体-通道复合体的数量和比率，用Scatchard分析和Ann_&lt；125&gt；I-w-conooxin MVIIC结合分析，并用放射自显影分析它们的分布。SCATCHARD分析显示低分子肝硬化症患者小脑P/Q型VGCC数量(63.0±7.0fmol/mg，n=3)明显低于正常对照组(297.8±38.9fmol/mg，n=6)。免疫沉淀法测定PCD-LEMS患者自身抗体-VGCC复合体与总P/Q型VGCC的比值升高。我们用与P/Q型VGCC特异结合的I-ω-芋螺毒素MVIIC分析了小脑标本的放射自显影图像。在PCD-LEMS小脑中，P/Q型VGCC的毒素结合部位明显减少，尤其是在正常小脑中P/Q型VGCC最丰富的分子层。提示小脑分子层P/Q型VGCC是PCD合并LEMS的免疫学靶点。

The aim of this study was to clarify whether autoimmunity against P/Q-type voltage-gated calcium channels (VGCC) in the cerebellum was associated with the pathogenesis of paraneoplastic cerebellar degeneration (PCD) with Lambert-Eaton myasthenic syndrome (LEMS). We used human cerebellar tissues obtained at autopsy from three PCD with LEMS patients and six other disease patients including one with LEMS as the controls. We compared cerebellar P/Q-type VGCC in these patients and controls for the amount and ratio of autoantibody-channel complex using an _<125>I-w-conotoxin MVIIC binding assay with Scatchard analysis, and their distribution using autoradiography. The quantity of cerebellar P/Q-type VGCC measured by Scatchard analysis were reduced in PCD with LEMS patients (63.0±7.0 fmol/mg, n=3), compared with the controls (297.8±38.9 fmol/mg, n=6). The ratio of autoantibody-VGCC complexes to total P/Q-type VGCC measured by immunoprecipitation assay were increased in PCD-LEMS patients. We analysed the autoradiographic image of cerebellar specimens using ^<125>I-ω-conotoxin MVIIC, which specifically binds to P/Q-type VGCC. In PCD-LEMS cerebellum, the toxin binding sites of P/Q-type VGCC were markedly reduced compared to control specimens, especially in the molecular layer which is the richest area of P/Q-type VGCC in the normal cerebellum. These results suggest that P/Q-type VGCC of the cerebellar molecular layer is the immunological target in developing PCD with LEMS.