Pinto A, Gillard S, Moss F, Whyte K, Brust P, Williams M, Stauderman K, Harpold M, Lang B, Newsom-Davis J, Bleakman D, Lodge D, Boot J
Neurosciences Group, Institute of Molecular Medicine, University of Oxford, The John Radcliffe Hospital, Oxford, OX3 9DS, United Kingdom.
Proc Natl Acad Sci U S A. 1998 Jul 7;95(14):8328-33. doi: 10.1073/pnas.95.14.8328.
The pharmacological properties of voltage-dependent calcium channel (VDCC) subtypes appear mainly to be determined by the alpha1 pore-forming subunit but, whether P-and Q-type VDCCs are encoded by the same alpha1 gene presently is unresolved. To investigate this, we used IgG antibodies to presynaptic VDCCs at motor nerve terminals that underlie muscle weakness in the autoimmune Lambert-Eaton myasthenic syndrome (LEMS). We first studied their action on changes in intracellular free Ca2+ concentration [Ca2+]i in human embryonic kidney (HEK293) cell lines expressing different combinations of human recombinant VDCC subunits. Incubation for 18 h with LEMS IgG (2 mg/ml) caused a significant dose-dependent reduction in the K+-stimulated [Ca2+]i increase in the alpha1A cell line but not in the alpha1B, alpha1C, alpha1D, and alpha1E cell lines, establishing the alpha1A subunit as the target for these autoantibodies. Exploiting this specificity, we incubated cultured rat cerebellar neurones with LEMS IgG and observed a reduction in P-type current in Purkinje cells and both P- and Q-type currents in granule cells. These data are consistent with the hypothesis that the alpha1A gene encodes for the pore-forming subunit of both P-type and Q-type VDCCs.
电压依赖性钙通道（VDCC）亚型的药理学特性似乎主要由α1孔形成亚基决定，但P型和Q型VDCC是否由同一α1基因编码目前尚无定论。为了研究这一问题，我们使用针对运动神经末梢突触前VDCC的IgG抗体，这些神经末梢是自身免疫性兰伯特-伊顿肌无力综合征（LEMS）中肌肉无力的基础。我们首先研究了它们对表达不同组合的人类重组VDCC亚基的人胚肾（HEK293）细胞系中细胞内游离Ca2+浓度[Ca2+]i变化的作用。用LEMS IgG（2 mg/ml）孵育18小时导致α1A细胞系中K+刺激的[Ca2+]i增加出现显著的剂量依赖性降低，但在α1B、α1C、α1D和α1E细胞系中未出现这种情况，从而确定α1A亚基是这些自身抗体的靶点。利用这种特异性，我们用LEMS IgG孵育培养的大鼠小脑神经元，观察到浦肯野细胞中P型电流以及颗粒细胞中P型和Q型电流均降低。这些数据与α1A基因编码P型和Q型VDCC的孔形成亚基这一假设一致。
