Walker Valerie E, Atanasiu Roxana, Lam Hung, Shrier Alvin
Department of Physiology, McGill University, Montreal, Quebec H3G 1Y6, Canada.
J Biol Chem. 2007 Aug 10;282(32):23509-16. doi: 10.1074/jbc.M701006200. Epub 2007 Jun 14.
The Long QT Syndrome is a cardiac disorder associated with ventricular arrhythmias that can lead to syncope and sudden death. One prominent form of the Long QT syndrome has been linked to mutations in the HERG gene (KCNH2) that encodes the voltage-dependent delayed rectifier potassium channel (I(Kr)). In order to search for HERG-interacting proteins important for HERG maturation and trafficking, we conducted a proteomics screen using myc-tagged HERG transfected into cardiac (HL-1) and non-cardiac (human embryonic kidney 293) cell lines. A partial list of putative HERG-interacting proteins includes several known components of the cytosolic chaperone system, including Hsc70 (70-kDa heat shock cognate protein), Hsp90 (90-kDa heat shock protein), Hdj-2, Hop (Hsp-organizing protein), and Bag-2 (BCL-associated athanogene 2). In addition, two membrane-integrated proteins were identified, calnexin and FKBP38 (38-kDa FK506-binding protein, FKBP8). We show that FKBP38 immunoprecipitates and co-localizes with HERG in our cellular system. Importantly, small interfering RNA knock down of FKBP38 causes a reduction of HERG trafficking, and overexpression of FKBP38 is able to partially rescue the LQT2 trafficking mutant F805C. We propose that FKBP38 is a co-chaperone of HERG and contributes via the Hsc70/Hsp90 chaperone system to the trafficking of wild type and mutant HERG potassium channels.
长QT综合征是一种与室性心律失常相关的心脏疾病，可导致晕厥和猝死。长QT综合征的一种主要形式与编码电压依赖性延迟整流钾通道（I(Kr)）的HERG基因（KCNH2）突变有关。为了寻找对HERG成熟和运输重要的HERG相互作用蛋白，我们使用转染到心脏（HL-1）和非心脏（人胚肾293）细胞系中的myc标签HERG进行了蛋白质组学筛选。推定的HERG相互作用蛋白的部分列表包括胞质伴侣系统的几个已知成分，包括Hsc70（70 kDa热休克同源蛋白）、Hsp90（90 kDa热休克蛋白）、Hdj-2、Hop（Hsp组织蛋白）和Bag-2（BCL相关抗凋亡基因2）。此外，还鉴定出两种膜整合蛋白，钙连接蛋白和FKBP38（38 kDa FK506结合蛋白，FKBP8）。我们发现在我们的细胞系统中FKBP38与HERG免疫共沉淀并共定位。重要的是，FKBP38的小干扰RNA敲低导致HERG运输减少，FKBP38的过表达能够部分挽救LQT2运输突变体F805C。我们提出FKBP38是HERG的共伴侣，并通过Hsc70/Hsp90伴侣系统促进野生型和突变型HERG钾通道的运输。
