Jang Soo Hwa, Byun Jun Kyu, Jeon Won-Il, Choi Seon Young, Park Jin, Lee Bo Hyung, Yang Ji Eun, Park Jin Bong, O'Grady Scott M, Kim Dae-Yong, Ryu Pan Dong, Joo Sang-Woo, Lee So Yeong
From the Laboratories of Veterinary Pharmacology and the Biomedical Research Center, School of Biological Sciences, University of Ulsan, Ulsan 680-749, Korea.
From the Laboratories of Veterinary Pharmacology and.
J Biol Chem. 2015 May 15;290(20):12547-57. doi: 10.1074/jbc.M114.561324. Epub 2015 Mar 31.
It is widely known that ion channels are expressed in the plasma membrane. However, a few studies have suggested that several ion channels including voltage-gated K(+) (Kv) channels also exist in intracellular organelles where they are involved in the biochemical events associated with cell signaling. In the present study, Western blot analysis using fractionated protein clearly indicates that Kv1.3 channels are expressed in the nuclei of MCF7, A549, and SNU-484 cancer cells and human brain tissues. In addition, Kv1.3 is located in the plasma membrane and the nucleus of Jurkat T cells. Nuclear membrane hyperpolarization after treatment with margatoxin (MgTX), a specific blocker of Kv1.3 channels, provides evidence for functional channels at the nuclear membrane of A549 cells. MgTX-induced hyperpolarization is abolished in the nuclei of Kv1.3 silenced cells, and the effects of MgTX are dependent on the magnitude of the K(+) gradient across the nuclear membrane. Selective Kv1.3 blockers induce the phosphorylation of cAMP response element-binding protein (CREB) and c-Fos activation. Moreover, Kv1.3 is shown to form a complex with the upstream binding factor 1 in the nucleus. Chromatin immunoprecipitation assay reveals that Sp1 transcription factor is directly bound to the promoter region of the Kv1.3 gene, and the Sp1 regulates Kv1.3 expression in the nucleus of A549 cells. These results demonstrate that Kv1.3 channels are primarily localized in the nucleus of several types of cancer cells and human brain tissues where they are capable of regulating nuclear membrane potential and activation of transcription factors, such as phosphorylated CREB and c-Fos.
众所周知，离子通道表达于质膜。然而，一些研究表明，包括电压门控钾离子（Kv）通道在内的几种离子通道也存在于细胞内细胞器中，它们参与与细胞信号传导相关的生化事件。在本研究中，使用分级分离蛋白的蛋白质印迹分析清楚地表明，Kv1.3通道在MCF7、A549和SNU - 484癌细胞以及人脑组织的细胞核中表达。此外，Kv1.3位于Jurkat T细胞的质膜和细胞核中。用Kv1.3通道的特异性阻滞剂玛格毒素（MgTX）处理后核膜超极化，为A549细胞核膜上的功能性通道提供了证据。MgTX诱导的超极化在Kv1.3沉默细胞的细胞核中被消除，并且MgTX的作用取决于跨核膜的钾离子梯度大小。选择性Kv1.3阻滞剂诱导环磷酸腺苷反应元件结合蛋白（CREB）的磷酸化和c - Fos激活。此外，Kv1.3在细胞核中与上游结合因子1形成复合物。染色质免疫沉淀分析表明，Sp1转录因子直接结合到Kv1.3基因的启动子区域，并且Sp1调节A549细胞核中Kv1.3的表达。这些结果表明，Kv1.3通道主要定位于几种类型的癌细胞和人脑组织的细胞核中，在那里它们能够调节核膜电位以及转录因子如磷酸化CREB和c - Fos的激活。
