Gao Jie, Wu Dan, Guo Taylor B, Ruan Qin, Li Tie, Lu Zhenyu, Xu Ming, Dai Wei, Lu Luo
Department of Medical Genetics, Shanghai Second Medical University, PR China.
Exp Cell Res. 2004 Jul 15;297(2):461-71. doi: 10.1016/j.yexcr.2004.03.047.
Upon exposure to ultraviolet (UV) radiation, osmotic changes or the presence of reactive oxygen species (ROS) c-Jun N-terminal kinases (JNKs) are rapidly activated. Extensive studies have elucidated molecular components that mediate the activation of JNKs. However, it remains unclear whether activation of JNKs by various stress signals involves different pathways. Here we show that K(+) channel activity is involved in mediating apoptosis induced by UV but not by H(2)O(2) in myelocytic leukemic ML-1 cells. Specifically, JNKs were rapidly phosphorylated upon treatment of ML-1 cells with UV and H(2)O(2). UV-induced, but not H(2)O(2)-induced, JNK-1 phosphorylation was inhibited by pretreatment with 4-aminopyridine (4-AP), a K(+) channel blocker. 4-AP also blocked UV-induced increase in JNK activity as well as p38 phosphorylation. Immunofluorescent microscopy revealed that phosphorylated JNKs were concentrated at centrosomes in ML-1 cells and that these proteins underwent rapid subcellular translocation upon UV treatment. Consistently, the subcellular translocation of JNKs induced by UV was largely blocked by 4-AP. Furthermore, UV-induced JNK activation was blocked by NEM, a sulfhydryl alkylating agent also affecting K(+) current. Both UV- and H(2)O(2)-induced JNK activities were inhibited by glutathione, suggesting that the redox status does play an important role in the activation of JNKs. Taken together, our findings suggest that JNK activation by UV and H(2)O(2) is mediated by distinct yet overlapping pathways and that K(+) channel activity and redox status are differentially required for UV- and H(2)O(2)-induced activation of JNKs.
暴露于紫外线（UV）辐射、渗透变化或活性氧（ROS）时，c-Jun氨基末端激酶（JNKs）会迅速被激活。广泛的研究已经阐明了介导JNKs激活的分子成分。然而，尚不清楚各种应激信号对JNKs的激活是否涉及不同的途径。在这里，我们表明钾离子（K⁺）通道活性参与介导髓系白血病ML-1细胞中紫外线诱导的凋亡，但不参与过氧化氢（H₂O₂）诱导的凋亡。具体而言，用紫外线和H₂O₂处理ML-1细胞后，JNKs会迅速磷酸化。钾离子通道阻滞剂4-氨基吡啶（4-AP）预处理可抑制紫外线诱导的JNK-1磷酸化，但不能抑制H₂O₂诱导的JNK-1磷酸化。4-AP还可阻断紫外线诱导的JNK活性增加以及p38磷酸化。免疫荧光显微镜检查显示，磷酸化的JNKs集中在ML-1细胞的中心体，并且这些蛋白质在紫外线处理后会迅速发生亚细胞易位。一致地，4-AP在很大程度上阻断了紫外线诱导的JNKs亚细胞易位。此外，紫外线诱导的JNK激活被N-乙基马来酰亚胺（NEM）阻断，NEM是一种也影响钾离子电流的巯基烷基化剂。谷胱甘肽抑制了紫外线和H₂O₂诱导的JNK活性，这表明氧化还原状态在JNKs的激活中确实起着重要作用。综上所述，我们的研究结果表明，紫外线和H₂O₂对JNKs的激活是由不同但重叠的途径介导的，并且钾离子通道活性和氧化还原状态在紫外线和H₂O₂诱导的JNKs激活中具有不同的需求。
