The Tumor Suppressor pVHL Down-regulates Never-in-Mitosis A-related Kinase 8 via Hypoxia-inducible Factors to Maintain Cilia in Human Renal Cancer Cells
The Tumor Suppressor pVHL Down-regulates Never-in-Mitosis A-related Kinase 8 via Hypoxia-inducible Factors to Maintain Cilia in Human Renal Cancer Cells
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DOI：
10.1074/jbc.m114.589226
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发表时间：
2015-01-16
影响因子：
4.8
通讯作者：
Chen, Guang
中科院分区：
文献类型：
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作者：
Ding, Xiao-Fei;Zhou, Jun;Chen, Guang
NEK8(NIMA相关的有丝分裂基因8)参与细胞骨架、纤毛和DNA损伤反应/修复。NEK8的异常表达和/或功能障碍与肿瘤的发生发展有关。然而，调控NEK8的机制并没有得到很好的宣传。我们在这里证明了pVHL可能参与了对NEK8的调节。我们发现野生型VHL的CAK-I细胞表达NEK8的水平低于VHL缺失的细胞，如786-O、769-P和A-498细胞。此外，pVHL过表达下调了786-O细胞中NEK8蛋白的表达，而pVHL下调则上调了CAK-I细胞中NEK8蛋白的表达。此外，我们还发现，阳性低氧反应元件(HREs)位于NEK8序列的启动子上，低氧可以诱导不同类型细胞中NEK8的表达。与此一致的是，异构体特异性siRNA下调低氧诱导因子α(HIF-1α或HIF-2α)降低了低氧诱导NEK8表达的能力。在体内，NEK8和HIF-1α在实验性缺氧缺血再灌注大鼠肾脏中的表达增加。此外，NEK8 siRNA通过抑制pVHL下调的NEK8表达，显著阻断pVHL下调诱导的纤毛解体。这些结果支持NEK8可能是一个新的低氧诱导基因。综上所述，我们的研究结果表明，NEK8可能是一个新的HIF靶基因，pVHL可以通过HIF下调NEK8的表达，从而维持人肾癌细胞的原发纤毛结构。
NEK8 (never in mitosis gene A (NIMA)-related kinase 8) is involved in cytoskeleton, cilia, and DNA damage response/repair. Abnormal expression and/or dysfunction of NEK8 are related to cancer development and progression. However, the mechanisms that regulate NEK8 are not well declared. We demonstrated here that pVHL may be involved in regulating NEK8. We found that CAK-I cells with wild-type vhl expressed a lower level of NEK8 than the cells loss of vhl, such as 786-O, 769-P, and A-498 cells. Moreover, pVHL overexpression down-regulated the NEK8 protein in 786-O cells, whereas pVHL knockdown up-regulated NEK8 in CAK-I cells. In addition, we found that the positive hypoxia response elements (HREs) are located in the promoter of the nek8 sequence and hypoxia could induce nek8 expression in different cell types. Consistent with this, down-regulation of hypoxia-inducible factors alpha (HIF-1 alpha or HIF-2 alpha) by isoform-specific siRNA reduced the ability of hypoxia inducing nek8 expression. In vivo, NEK8 and HIF-1 alpha expression were increased in kidneys of rats subjected to an experimental hypoxia model of ischemia and reperfusion. Furthermore, NEK8 siRNA transfection significantly blocked pVHL-knockdown-induced cilia disassembling, through impairing the pVHL-knockdown-up-regulated NEK8 expression. These results support that nek8 may be a novel hypoxia-inducible gene. In conclusion, our findings show that nek8 may be a new HIF target gene and pVHL can down-regulate NEK8 via HIFs to maintain the primary cilia structure in human renal cancer cells.