Institute for Integrative Physiology, Center for Systems Biology of O2 Sensing, Biological Sciences Division, The University of Chicago, Chicago, Illinois, United States of America.
PLoS One. 2019 Apr 24;14(4):e0215905. doi: 10.1371/journal.pone.0215905. eCollection 2019.
The alpha subunit of the voltage gated human ether-a-go-go-related (hERG) potassium channel regulates cell excitability in a broad range of cell lines. HERG channels are also expressed in a variety of cancer cells and control cell proliferation and apoptosis. Hypoxia, a common feature of tumors, alters gating properties of hERG currents in SH-SY5Y neuroblastoma cells. In the present study, we examined the molecular mechanisms and physiological significance underlying hypoxia-altered hERG currents in SH-SY5Y neuroblastoma cells. Hypoxia reduced the surface expression of 150kDa form and increased 125kDa form of hERG protein expression in the endoplasmic reticulum (ER). The changes in protein expression were associated with ~50% decrease in hERG potassium conductance. ER retention of hERG 125kDa form by CH was due to defective trafficking and was rescued by exposing cells to hypoxia at low temperatures or treatment with E-4031, a hERG channel blocker. Prolonged association of hERG with molecular chaperone Hsp90 resulting in complex oligomeric insoluble aggregates contributed to ER accumulation and trafficking defect. Hypoxia increased reactive oxygen species (ROS) levels and manganese (111) tetrakis (1methyl-4-pyridyl) porphyrin pentachloride, a membrane-permeable antioxidant prevented hypoxia-induced degradation of 150kDa and accumulation of 125kDa forms. Impaired trafficking of hERG by hypoxia was associated with reduced cell proliferation and this effect was prevented by antioxidant treatment. These results demonstrate that hypoxia through increased oxidative stress impairs hERG trafficking, leading to decreased K+ currents resulting in cell cycle arrest in SH-SY5Y cells.
电压门控人 ether-a-go-go 相关（hERG）钾通道的α亚基调节广泛的细胞系中的细胞兴奋性。HERG 通道也在各种癌细胞中表达，并控制细胞增殖和凋亡。缺氧是肿瘤的常见特征，改变了 SH-SY5Y 神经母细胞瘤细胞中 hERG 电流的门控特性。在本研究中，我们研究了缺氧改变 SH-SY5Y 神经母细胞瘤细胞中 hERG 电流的分子机制和生理意义。缺氧降低了 hERG 蛋白在 150kDa 形式和内质网（ER）中增加 125kDa 形式的表面表达。蛋白表达的变化与 hERG 钾电导约减少 50%有关。CH 导致 hERG 125kDa 形式在 ER 中的滞留是由于转运缺陷引起的，并通过在低温下将细胞暴露于缺氧或用 hERG 通道阻滞剂 E-4031 处理来挽救。hERG 与分子伴侣 Hsp90 的长时间关联导致复杂的寡聚不溶性聚集体的形成，导致 ER 积累和转运缺陷。缺氧增加了活性氧（ROS）水平和锰（111）四（1-甲基-4-吡啶基）卟啉五氯，一种膜通透抗氧化剂可防止缺氧诱导的 150kDa 降解和 125kDa 形式的积累。缺氧对 hERG 的转运损伤与细胞增殖减少有关，这种效应可通过抗氧化剂治疗来预防。这些结果表明，缺氧通过增加氧化应激损害 hERG 转运，导致 K+电流减少，从而导致 SH-SY5Y 细胞周期停滞。
