A Novel KCNJ2 Nonsense Mutation, S369X, Impedes Trafficking and Causes a Limited Form of Andersen-Tawil Syndrome
A Novel KCNJ2 Nonsense Mutation, S369X, Impedes Trafficking and Causes a Limited Form of Andersen-Tawil Syndrome
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DOI：
10.1161/circgenetics.110.958157
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发表时间：
2011-06-01
影响因子：
--
通讯作者：
Horie, Minoru
中科院分区：
文献类型：
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作者：
Doi, Takahiro;Makiyama, Takeru;Horie, Minoru
背景：编码向内整流K（+）通道Kir2.1的基因KCNJ2突变与安德森-塔维尔综合征（ATS）有关，其特征为：(1)室性心动过速伴QT间期延长，(2)周期性麻痹，(3)畸形特征。方法和结果-我们在一名13岁男孩中发现了一种新的KCNJ2突变S369X，该男孩患有明显的q -间期延长和轻度周期性瘫痪。突变导致细胞质c端区域中间的截断，消除了内质网（ER）到高尔基体输出信号。与KCNJ2野生型（WT）相比，转染KCNJ2- s369x的中国仓鼠卵巢细胞的电流记录显示，K（+）电流明显更小（-84 +/- 14 vs -542 +/- 46皮安/皮帕[pA/pF]； -140 mV; P < 0.0001）。WT和S369X亚基的共表达没有表现出显性负抑制作用，但产生的电流比WT + S369X更大（-724 +/- 98 pA/pF> -[84 + 42] pA/pF；各1 μ g； -140 mV）。共聚焦显微镜分析显示，单独表达时，荧光蛋白标记的S369X亚基主要保留在内质网中；然而，当与WT共表达时，S369X亚基在质膜上的表达部分恢复。荧光共振能量转移分析表明，在细胞内区室中，WT和S369X亚基之间存在直接的蛋白-蛋白相互作用。结论：S369X突变导致内质网输出基序缺失。然而，通过直接与WT蛋白组装可以部分弥补运输缺陷，从而导致质膜定位和通道功能的有限恢复。这种缓解可以解释为什么我们的患者表现出相对轻微的ATS表型。（中国心血管病杂志，2011;4:253-260）
Background-Mutations in KCNJ2, a gene encoding the inward rectifier K(+) channel Kir2.1, are associated with Andersen-Tawil syndrome (ATS), which is characterized by (1) ventricular tachyarrhythmias associated with QT (QU)-interval prolongation, (2) periodic paralysis, and (3) dysmorphic features.Methods and Results-We identified a novel KCNJ2 mutation, S369X, in a 13-year-old boy with prominent QU-interval prolongation and mild periodic paralysis. The mutation results in the truncation at the middle of the cytoplasmic C-terminal domain that eliminates the endoplasmic reticulum (ER)-to-Golgi export signal. Current recordings from Chinese hamster ovary cells transfected with KCNJ2-S369X exhibited significantly smaller K(+) currents compared with KCNJ2 wild type (WT) (1 mu g each) (-84 +/- 14 versus -542 +/- 46 picoamperes per picofarad [pA/pF]; -140 mV; P < 0.0001). Coexpression of the WT and S369X subunits did not show a dominant-negative suppression effect but yielded larger currents than those of WT + S369X (-724 +/- 98 pA/pF> -[84 + 42] pA/pF; 1 mu g each; -140 mV). Confocal microscopy analysis showed that the fluorescent protein-tagged S369X subunits were predominantly retained in the ER when expressed alone; however, the expression of S369X subunits to the plasma membrane was partially restored when coexpressed with WT. Fluorescence resonance energy transfer analysis demonstrated direct protein-protein interactions between WT and S369X subunits in the intracellular compartment.Conclusions-The S369X mutation causes a loss of the ER export motif. However, the trafficking deficiency can be partially rescued by directly assembling with the WT protein, resulting in a limited restoration of plasma membrane localization and channel function. This alleviation may explain why our patient presented with a relatively mild ATS phenotype. (Circ Cardiovasc Genet. 2011; 4: 253-260.)