Wang Ling, Reinach Peter, Lu Luo
Division of Molecular Medicine, Harbor-UCLA Medical Center, David Geffen School of Medicine, University of California Los Angeles, 1124 W. Carson Street, C-2, Torrance, CA 90502, USA.
Exp Cell Res. 2005 Nov 15;311(1):39-48. doi: 10.1016/j.yexcr.2005.08.020. Epub 2005 Oct 10.
Tumor necrosis factor (TNF-alpha) in various cell types induces either cell death or mitogenesis through different signaling pathways. In the present study, we determined in human corneal epithelial cells how TNF-alpha also promotes cell survival. Human corneal epithelial (HCE) cells were cultured in DMEM/F-12 medium containing 10% FBS. TNF-alpha stimulation induced activation of a voltage-gated K+ channel detected by measuring single channel activity using patch clamp techniques. The effect of TNF-alpha on downstream events included NFkappaB nuclear translocation and increases in DNA binding activities, but did not elicit ERK, JNK, or p38 limb signaling activation. TNF-alpha induced increases in p21 expression resulting in partial cell cycle attenuation in the G1 phase. Cell cycle progression was also mapped by flow cytometer analysis. Blockade of TNF-alpha-induced K+ channel activity effectively prevented NFkappaB nuclear translocation and binding to DNA, diminishing the cell-survival protective effect of TNF-alpha. In conclusion, TNF-alpha promotes survival of HCE cells through sequential stimulation of K+ channel and NFkappaB activities. This response to TNF-alpha is dependent on stimulating K+ channel activity because following suppression of K+ channel activity TNF-alpha failed to activate NFkappaB nuclear translocation and binding to nuclear DNA.
肿瘤坏死因子（TNF-α）在不同细胞类型中通过不同信号通路诱导细胞死亡或有丝分裂。在本研究中，我们确定了在人角膜上皮细胞中TNF-α如何促进细胞存活。人角膜上皮（HCE）细胞在含有10%胎牛血清的DMEM/F-12培养基中培养。通过膜片钳技术测量单通道活性检测到TNF-α刺激诱导电压门控钾通道的激活。TNF-α对下游事件的影响包括NFκB核转位和DNA结合活性增加，但未引发ERK、JNK或p38丝裂原活化蛋白激酶信号激活。TNF-α诱导p21表达增加，导致G1期细胞周期部分衰减。细胞周期进程也通过流式细胞仪分析进行绘制。阻断TNF-α诱导的钾通道活性有效地阻止了NFκB核转位和与DNA的结合，削弱了TNF-α的细胞存活保护作用。总之，TNF-α通过依次刺激钾通道和NFκB活性促进HCE细胞存活。对TNF-α的这种反应依赖于刺激钾通道活性，因为在抑制钾通道活性后，TNF-α未能激活NFκB核转位和与核DNA的结合。
