Lange Philipp S, Er Fikret, Gassanov Natig, Hoppe Uta C
Department of Internal Medicine III, University of Cologne, Joseph-Stelzmann-Strasse 9, 50924 Cologne, Germany.
Cardiovasc Res. 2003 Aug 1;59(2):321-7. doi: 10.1016/s0008-6363(03)00434-6.
The Andersen's syndrome is a hereditary disease, which is characterized by cardiac arrhythmias, periodic paralysis and dysmorphic features. Recently, mutations of the KCNJ2 gene, which encodes the inward rectifying potassium channel subunit Kir2.1, have been identified in affected individuals. However, the functional effects of these mutations have not yet been fully elucidated.
To clarify this situation we generated known Andersen disease mutants of KCNJ2 which did not yield any measurable K(+) currents in CHO cells indicating that the Andersen mutants failed to form functional homomultimeric complexes. EGFP-tagged KCNJ2 wild-type and mutant channels distributed in a similar homogeneous pattern in the cell membrane suggesting that protein trafficking was not altered by the Andersen mutations but rather implicating that the mutations rendered the KCNJ2 channel non-functional. In heterologous coexpression experiments the Andersen mutants exerted a dominant-negative effect on wild-type KCNJ2. However, the extent of suppression varied between the different KCNJ2 mutants. Given our results in CHO cells, we expressed the disease mutant KCNJ2-S136F in neonate rat cardiomyocytes using adenoviral gene transfer to test the effect of Andersen mutants on native I(K1). I(K1) density was indeed significantly reduced in KCNJ2-S136F-infected cells (n=9) compared to control cells (n=9) over a voltage range from -70 to -150 mV (P<0.05).
These results support that Kir2.x channels are a critical component of native I(K1) in neonate rat cardiomyocytes and that a dominant-negative suppression of I(K1) in native cells is the pathophysiological correlate of the Andersen's syndrome.
安德森综合征是一种遗传性疾病，其特征为心律失常、周期性麻痹和畸形特征。最近，在受影响个体中已鉴定出编码内向整流钾通道亚基Kir2.1的KCNJ2基因突变。然而，这些突变的功能影响尚未完全阐明。
为阐明这种情况，我们构建了已知的KCNJ2安德森病突变体，这些突变体在CHO细胞中未产生任何可测量的钾电流，表明安德森突变体未能形成功能性同多聚体复合物。带有增强型绿色荧光蛋白（EGFP）标签的KCNJ2野生型和突变型通道在细胞膜中以相似的均匀模式分布，这表明蛋白质转运未因安德森突变而改变，而是意味着这些突变使KCNJ2通道失去功能。在异源共表达实验中，安德森突变体对野生型KCNJ2发挥显性负效应。然而，不同KCNJ2突变体的抑制程度有所不同。鉴于我们在CHO细胞中的结果，我们使用腺病毒基因转移在新生大鼠心肌细胞中表达疾病突变体KCNJ2-S136F，以测试安德森突变体对天然内向整流钾电流（I(K1)）的影响。在-70至-150 mV的电压范围内，与对照细胞（n = 9）相比，KCNJ2-S136F感染的细胞（n = 9）中的I(K1)密度确实显著降低（P<0.05）。
这些结果支持Kir2.x通道是新生大鼠心肌细胞中天然I(K1)的关键组成部分，并且天然细胞中I(K1)的显性负抑制是安德森综合征的病理生理相关因素。
