Department of Pediatrics, University of Wisconsin, Madison, Wisconsin, United States of America ; Department of Ophthalmology and Visual Sciences, University of Wisconsin, Madison, Wisconsin, United States of America ; McPherson Eye Research Institute, University of Wisconsin, Madison, Wisconsin, United States of America.
PLoS One. 2013 Aug 19;8(8):e71744. doi: 10.1371/journal.pone.0071744. eCollection 2013.
Snowflake Vitreoretinal Degeneration (SVD) is associated with the R162W mutation of the Kir7.1 inwardly-rectifying potassium channel. Kir7.1 is found at the apical membrane of Retinal Pigment Epithelial (RPE) cells, adjacent to the photoreceptor neurons. The SVD phenotype ranges from RPE degeneration to an abnormal b-wave to a liquid vitreous. We sought to determine how this mutation alters the structure and function of the human Kir7.1 channel. In this study, we expressed a Kir7.1 construct with the R162W mutation in CHO cells to evaluate function of the ion channel. Compared to the wild-type protein, the mutant protein exhibited a non-functional Kir channel that resulted in depolarization of the resting membrane potential. Upon co-expression with wild-type Kir7.1, R162W mutant showed a reduction of IKir7.1 and positive shift in '0' current potential. Homology modeling based on the structure of a bacterial Kir channel protein suggested that the effect of R162W mutation is a result of loss of hydrogen bonding by the regulatory lipid binding domain of the cytoplasmic structure.
雪flake 型玻璃体视网膜变性 (SVD) 与 Kir7.1 内向整流钾通道的 R162W 突变有关。Kir7.1 存在于视网膜色素上皮 (RPE) 细胞的顶膜上，与光感受器神经元相邻。SVD 表型范围从 RPE 变性到异常 b 波再到液体玻璃体。我们试图确定这种突变如何改变人类 Kir7.1 通道的结构和功能。在这项研究中，我们在 CHO 细胞中表达了带有 R162W 突变的 Kir7.1 构建体，以评估离子通道的功能。与野生型蛋白相比，突变蛋白表现出非功能性 Kir 通道，导致静息膜电位去极化。与野生型 Kir7.1 共表达时，R162W 突变体表现出 IKir7.1 的减少和“0”电流电位的正移。基于细菌 Kir 通道蛋白结构的同源建模表明，R162W 突变的影响是细胞质结构的调节脂质结合域失去氢键的结果。
