Mitochondrial dysfunction represses HIF-1α protein synthesis through AMPK activation in human hepatoma HepG2 cells
Mitochondrial dysfunction represses HIF-1α protein synthesis through AMPK activation in human hepatoma HepG2 cells
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DOI：
10.1016/j.bbagen.2013.06.004
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发表时间：
2013-10-01
影响因子：
3
通讯作者：
Lee, Hsin-Chen
中科院分区：
文献类型：
--
作者：
Hsu, Chia-Chi;Wang, Chun-Hui;Lee, Hsin-Chen
背景资料：缺氧诱导因子-1 α（HIF-1 α）是一种重要的转录因子，调节细胞对缺氧的反应，并且在癌症进展中也起关键作用。近年来，在肝细胞癌（HCC）中检测到线粒体DNA（mtDNA）的体细胞突变和拷贝数减少。这些突变被证明有可能导致线粒体功能障碍。然而，线粒体功能障碍对HIF-1 α功能的影响和机制尚未完全了解。本研究旨在探讨线粒体功能障碍调控HIF-1 α表达的潜在机制。方法：分别用不同线粒体呼吸抑制剂和解偶联剂处理人肝癌HepG 2细胞，测定HIF-1 α mRNA和蛋白表达以及转录激活活性。结果：线粒体抑制剂和解偶联剂分别降低了常氧和缺氧条件下HepG 2细胞中HIF-1 α的蛋白水平和转录激活活性。线粒体功能障碍抑制的HIF-1 α蛋白合成与p70（S6 K）和4 E-BP-1磷酸化降低相关。此外，线粒体功能障碍降低细胞内ATP含量，提高AMPK的磷酸化。用AMPK抑制剂化合物C和AMPK敲低治疗部分挽救了线粒体功能障碍抑制的HIF-1 α表达。结论：线粒体功能障碍导致HepG 2细胞中通过AMPK依赖的方式减少HIF-1 α蛋白合成。线粒体功能对于癌症进展中HIF-1 α的表达很重要。(c)2013爱思唯尔有限公司版权所有。
Background: Hypoxia-inducible factor-1 alpha (HIF-1 alpha) is an important transcription factor that modulates cellular responses to hypoxia and also plays critical roles in cancer progression. Recently, somatic mutations and decreased copy number of mitochondrial DNA (mtDNA) were detected in hepatocellular carcinoma (HCC). These mutations were shown to have the potential to cause mitochondrial dysfunction. However, the effects and mechanisms of mitochondrial dysfunction on HIF-1 alpha function are not fully understood. This study aims to explore the underlying mechanism by which mitochondrial dysfunction regulates HIF-1 alpha expression.Methods: Human hepatoma HepG2 cells were treated with various mitochondrial respiration inhibitors and an uncoupler, respectively, and the mRNA and protein expressions as well as transactivation activity of HIF-1 alpha were determined. The role of AMP-activated protein kinase (AMPK) was further analyzed by compound C and AMPK knock-down.Results: Treatments of mitochondrial inhibitors and an uncoupler respectively reduced both the protein level and transactivation activity of HIF-1 alpha in HepG2 cells under normoxia or hypoxia. The mitochondrial dysfunction-repressed HIF-1 alpha protein synthesis was associated with decreased phosphorylations of p70(S6K) and 4E-BP-1. Moreover, mitochondrial dysfunction decreased intracellular ATP content and elevated the phosphorylation of AMPK. Treatments with compound C, an AMPK inhibitor, and knock-down of AMPK partially rescued the mitochondrial dysfunction-repressed HIF-1 alpha expression.Conclusions: Mitochondrial dysfunctions resulted in reduced HIF-1 alpha protein synthesis through AMPK-dependent manner in HepG2 cells.General significance: Our results provided a mechanism for communication from mitochondria to the nucleus through AMPK-HIF-1 alpha. Mitochondrial function is important for HIF-1 alpha expression in cancer progression. (c) 2013 Elsevier B.V. All rights reserved.