Pharmacological correction of long QT-linked mutations in KCNH2 (hERG) increases the trafficking of Kv11.1 channels stored in the transitional endoplasmic reticulum.
Pharmacological correction of long QT-linked mutations in KCNH2 (hERG) increases the trafficking of Kv11.1 channels stored in the transitional endoplasmic reticulum.
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DOI：
10.1152/ajpcell.00406.2012
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发表时间：
2013-11
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通讯作者：
Jennifer L. Smith;Allison R. Reloj;Parvathi Nataraj;Daniel C Bartos;E. Schroder;A. Moss;S. Ohno;M. Horie;C. Anderson;C. January;B. Delisle
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作者：
Jennifer L. Smith;Allison R. Reloj;Parvathi Nataraj;Daniel C Bartos;E. Schroder;A. Moss;S. Ohno;M. Horie;C. Anderson;C. January;B. Delisle
KCNH2编码Kv11.1，是心脏快速激活延迟整流器K（+）电流（IKr）的基础。功能缺失的KCNH2突变可导致2型长QT综合征（LQT2），并且大多数LQT2相关的错义突变抑制Kv11.1通道的转运。结合Kv11.1并阻断IKr的药物（如E-4031）可作为药理学伴侣，增加大多数LQT2通道的转运和功能表达（药理学校正）。我们之前的研究表明，LQT2通道选择性地存储在内质网（ER）内的微管依赖性室中。我们检验了药物纠正促进储存在这个隔室的LQT2通道的运输的假设。对表达运输缺陷LQT2通道G601S的细胞进行共聚焦分析表明，微管依赖性内质网室是过渡性内质网。E-4031和蛋白质合成抑制剂环己亚胺的实验表明，药理学校正促进了储存在该隔室中的G601S的转运。用E-4031或雷诺嗪（一种阻断IKr且半衰期短的药物）治疗细胞30分钟足以引起药理学纠正。此外，G601S功能表达的增加在药物洗脱后持续4-5小时。Rab11B是一种调节Kv11.1转运的小GTPase，其显性阴性形式的共表达研究阻止了过渡ER对G601S转运的药理学纠正。这些数据表明，通过rab11b依赖性途径，药物纠正迅速增加了储存在过渡内质网中的LQT2通道的运输，我们得出结论，雷诺嗪等药物的药物伴侣活性可能具有治疗潜力。
KCNH2 encodes Kv11.1 and underlies the rapidly activating delayed rectifier K(+) current (IKr) in the heart. Loss-of-function KCNH2 mutations cause the type 2 long QT syndrome (LQT2), and most LQT2-linked missense mutations inhibit the trafficking of Kv11.1 channels. Drugs that bind to Kv11.1 and block IKr (e.g., E-4031) can act as pharmacological chaperones to increase the trafficking and functional expression for most LQT2 channels (pharmacological correction). We previously showed that LQT2 channels are selectively stored in a microtubule-dependent compartment within the endoplasmic reticulum (ER). We tested the hypothesis that pharmacological correction promotes the trafficking of LQT2 channels stored in this compartment. Confocal analyses of cells expressing the trafficking-deficient LQT2 channel G601S showed that the microtubule-dependent ER compartment is the transitional ER. Experiments with E-4031 and the protein synthesis inhibitor cycloheximide suggested that pharmacological correction promotes the trafficking of G601S stored in this compartment. Treating cells in E-4031 or ranolazine (a drug that blocks IKr and has a short half-life) for 30 min was sufficient to cause pharmacological correction. Moreover, the increased functional expression of G601S persisted 4-5 h after drug washout. Coexpression studies with a dominant-negative form of Rab11B, a small GTPase that regulates Kv11.1 trafficking, prevented the pharmacological correction of G601S trafficking from the transitional ER. These data suggest that pharmacological correction quickly increases the trafficking of LQT2 channels stored in the transitional ER via a Rab11B-dependent pathway, and we conclude that the pharmacological chaperone activity of drugs like ranolazine might have therapeutic potential.