Disturbed Neuronal ER-Golgi Sorting of Unassembled Glycine Receptors Suggests Altered Subcellular Processing Is a Cause of Human Hyperekplexia
Disturbed Neuronal ER-Golgi Sorting of Unassembled Glycine Receptors Suggests Altered Subcellular Processing Is a Cause of Human Hyperekplexia
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DOI：
10.1523/jneurosci.1509-14.2015
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发表时间：
2015-01-07
影响因子：
5.3
通讯作者：
Villmann, Carmen
中科院分区：
文献类型：
--
作者：
Schaefer, Natascha;Kluck, Christoph J.;Villmann, Carmen
最近对隐性神经亢进发病机制的研究表明甘氨酸受体 (GlyR) α 1 生物合成受到干扰。在这里，我们利用转染细胞系和原代神经元中的表达，检查了在人类神经亢进患者中鉴定出的一系列新型甘氨酸受体突变体的特性。尽管糖基化亚群向前运输至 ER-高尔基体中间区室和顺式高尔基体区室，但定位于 GlyR α 1 大胞外结构域的所有新型突变体均降低了细胞表面表达，并且高比例的受体保留在 ER 中。 CD光谱显示突变型受体具有与野生型受体相似的二级结构元件比例。环 B 中的两个突变体（G160R、T162M）具有功能，但环 D/β 2-3 中的突变体均无功能。一种非功能性截短突变体 (R316X) 可以通过与缺少 C 末端结构域的共表达来挽救。我们得出的结论是，一部分 GlyR α 1 突变体可以转运到质膜，但不一定形成功能性离子通道。我们认为环 D/β 2-3 是 GlyR 运输和功能的重要决定因素，而环 B 的改变会改变激动剂效力，表明此处的残基是配体结合的关键元素。
Recent studies on the pathogenic mechanisms of recessive hyperekplexia indicate disturbances in glycine receptor (GlyR) alpha 1 biogenesis. Here, we examine the properties of a range of novel glycine receptor mutants identified in human hyperekplexia patients using expression in transfected cell lines and primary neurons. All of the novel mutants localized in the large extracellular domain of the GlyR alpha 1 have reduced cell surface expression with a high proportion of receptors being retained in the ER, although there is forward trafficking of glycosylated subpopulations into the ER-Golgi intermediate compartment and cis-Golgi compartment. CD spectroscopy revealed that the mutant receptors have proportions of secondary structural elements similar to wild-type receptors. Two mutants in loop B (G160R, T162M) were functional, but none of those in loop D/beta 2-3 were. One nonfunctional truncated mutant (R316X) could be rescued by coexpression with the lacking C-terminal domain. We conclude that a proportion of GlyR alpha 1 mutants can be transported to the plasma membrane but do not necessarily form functional ion channels. We suggest that loop D/beta 2-3 is an important determinant for GlyR trafficking and functionality, whereas alterations to loop B alter agonist potencies, indicating that residues here are critical elements in ligand binding.