Krüppel-like factor 4 (Human Protein: KLF4; Human Gene: Klf4; Murine Protein: KLF4; Murine Gene: Klf4) is a zinc finger-containing transcription factor with diverse regulatory functions. Mouse embryonic fibroblasts (MEFs) lacking Klf4 exhibit genomic instability, increased reactive oxygen species (ROS), and decreased autophagy. Elevated ROS is linked to impairments in mitochondrial damage recovery responses and is often tied to disruption in mitochondrial-targeted autophagy known as mitophagy. In this study, we sought to identify a mechanistic connection between KLF4 and mitophagy. Using flow cytometry, we found that Klf4-null MEFs have diminished ability to recover mitochondrial health and regulate ROS levels after mitochondrial damage. Confocal microscopy indicated decreased localization of autophagy protein LC3 to mitochondria following mitochondrial damage in Klf4-null cells, suggesting decreased mitophagy. Western blotting and RT-PCR revealed decreased mRNA and protein expression of the mitophagy-associated protein Bnip3 and antioxidant protein GSTα4 in Klf4-null cells, providing a rationale for their impaired mitophagy and ROS accumulation. Inducing Bnip3 expression in these cells recovered mitophagy but did not decrease ROS accumulation. Our findings suggest that in Klf4-null cells, decreased Bnip3 expression impairs mitophagy and is associated with increased mitochondrial ROS production after mitochondrial damage, providing a rationale for their genomic instability and supports a tumor suppressive role for KLF4 in certain tumors as previously observed.

中文翻译：

---

缺乏Krüppel样因子4的细胞表现出线粒体功能障碍和线粒体受损。

克虏伯样因子4（人类蛋白：KLF4；人类基因：Klf4；鼠蛋白：KLF4；鼠基因：Klf4）是一种含锌指的转录因子，具有多种调控功能。缺少Klf4的小鼠胚胎成纤维细胞（MEF）表现出基因组不稳定性，活性氧（ROS）增加和自噬减少。ROS升高与线粒体损伤恢复反应的损伤有关，并且通常与针对线粒体的自噬（称为线粒体吞噬）的破坏有关。在这项研究中，我们试图确定KLF4和线粒体之间的机械连接。使用流式细胞仪，我们发现空Klf4的MEFs降低了恢复线粒体健康并调节线粒体损伤后ROS水平的能力。共聚焦显微镜检查表明，自噬蛋白LC3在线粒体损伤后在Klf4空细胞中的定位降低，从而降低了线粒体的吞噬能力。Western印迹和RT-PCR显示，Klf4缺失细胞中与线粒体相关的蛋白Bnip3和抗氧化蛋白GSTα4的mRNA和蛋白表达降低，这为线粒体受损和ROS积累提供了理论依据。在这些细胞中诱导Bnip3表达可以恢复线粒体，但不会减少ROS的积累。我们的发现表明，在Klf4无效细胞中，Bnip3表达的降低会损害线粒体，并与线粒体损伤后线粒体ROS的产生相关，为它们的基因组不稳定性提供了理论依据，并支持KLF4在某些肿瘤中的抑癌作用，如先前观察到的。