Langosch D, Laube B, Rundström N, Schmieden V, Bormann J, Betz H
Max-Planck-Institut für Hirnforschung, Frankfurt, Germany.
EMBO J. 1994 Sep 15;13(18):4223-8. doi: 10.1002/j.1460-2075.1994.tb06742.x.
Hereditary hyperekplexia is a dominant neurological disorder associated with point mutations at the channel-forming segment M2 of the glycine receptor alpha 1 subunit. Voltage-clamp recordings from the heterologously expressed mutants (alpha 1R271L or alpha 1R271Q) revealed 146- to 183-fold decreased potencies of glycine to activate the chloride channel, and significantly reduced maximal whole-cell currents as compared with wild-type receptors. In contrast, the ability of the competitive antagonist strychnine to block glycine-induced currents was similar in all cases. Radioligand binding assays showed a 90- to 1365-fold reduction in the ability of glycine to displace [3H]strychnine from its binding site on the mutant receptors. Paralleling the reductions in whole-cell current, the elementary main-state conductances of the mutants (alpha 1R271L, 64 pS; alpha 1R271Q, 14 pS) were lower than that of the wild-type receptor (86 pS). The decreased agonist affinities and chloride conductances of the mutants are likely to cause neural hyperexcitability of affected patients by impairing glycinergic inhibition. In addition, our data reveal that structural modifications of the ion-channel region can affect agonist binding to the glycine receptor.
遗传性惊吓症是一种显性神经疾病，与甘氨酸受体α1亚基的通道形成片段M2处的点突变有关。对异源表达突变体（α1R271L或α1R271Q）进行电压钳记录显示，与野生型受体相比，甘氨酸激活氯离子通道的效力降低了146至183倍，且最大全细胞电流显著减小。相比之下，竞争性拮抗剂士的宁阻断甘氨酸诱导电流的能力在所有情况下都相似。放射性配体结合试验表明，甘氨酸从突变体受体上的结合位点置换[3H]士的宁的能力降低了90至1365倍。与全细胞电流的降低情况相似，突变体（α1R271L，64 pS；α1R271Q，14 pS）的基本主态电导低于野生型受体（86 pS）。突变体激动剂亲和力和氯离子电导的降低可能通过损害甘氨酸能抑制作用导致受影响患者的神经兴奋性过高。此外，我们的数据表明，离子通道区域的结构修饰会影响激动剂与甘氨酸受体的结合。
