Alberto Sols Biomedical Research Institute UAM-CSIC and Department of Biochemistry, School of Medicine, Autonomous University of Madrid (UAM), Madrid, Spain.
La Paz University Hospital Research Institute (IdiPAZ), Madrid, Spain.
Sci Rep. 2019 Sep 25;9(1):13896. doi: 10.1038/s41598-019-50356-0.
The transcription factor NRF2 is a master regulator of cellular antioxidant and detoxification responses, but it also regulates other processes such as autophagy and pluripotency. In human embryonic stem cells (hESCs), NRF2 antagonizes neuroectoderm differentiation, which only occurs after NRF2 is repressed via a Primary Cilia-Autophagy-NRF2 (PAN) axis. However, the functional connections between NRF2 and primary cilia, microtubule-based plasma membrane protrusions that function as cellular antennae, remain poorly understood. For instance, nothing is known about whether NRF2 affects cilia, or whether cilia regulation of NRF2 extends beyond hESCs. Here, we show that NRF2 and primary cilia reciprocally regulate each other. First, we demonstrate that fibroblasts lacking primary cilia have higher NRF2 activity, which is rescued by autophagy-activating mTOR inhibitors, indicating that the PAN axis also operates in differentiated cells. Furthermore, NRF2 controls cilia formation and function. NRF2-null cells grow fewer and shorter cilia and display impaired Hedgehog signaling, a cilia-dependent pathway. These defects are not due to increased oxidative stress or ciliophagy, but rather to NRF2 promoting expression of multiple ciliogenic and Hedgehog pathway genes. Among these, we focused on GLI2 and GLI3, the transcription factors controlling Hh pathway output. Both their mRNA and protein levels are reduced in NRF2-null cells, consistent with their gene promoters containing consensus ARE sequences predicted to bind NRF2. Moreover, GLI2 and GLI3 fail to accumulate at the ciliary tip of NRF2-null cells upon Hh pathway activation. Given the importance of NRF2 and ciliary signaling in human disease, our data may have important biomedical implications.
转录因子 NRF2 是细胞抗氧化和解毒反应的主要调节因子，但它也调节其他过程，如自噬和多能性。在人胚胎干细胞 (hESC) 中，NRF2 拮抗神经外胚层分化，只有在 NRF2 通过初级纤毛-自噬-NRF2 (PAN) 轴被抑制后才会发生分化。然而，NRF2 与初级纤毛之间的功能联系，即作为细胞天线的基于微管的质膜突起，仍然知之甚少。例如，目前还不清楚 NRF2 是否影响纤毛，或者纤毛对 NRF2 的调节是否超出 hESC。在这里，我们表明 NRF2 和初级纤毛相互调节。首先，我们证明缺乏初级纤毛的成纤维细胞具有更高的 NRF2 活性，而自噬激活 mTOR 抑制剂可挽救该活性，表明 PAN 轴也在分化细胞中起作用。此外，NRF2 控制纤毛的形成和功能。NRF2 缺失细胞生长的纤毛更少且更短，并显示出 Hedgehog 信号转导受损，这是一种依赖纤毛的途径。这些缺陷不是由于氧化应激增加或纤毛自噬增加，而是由于 NRF2 促进多个纤毛发生和 Hedgehog 途径基因的表达。在这些基因中，我们重点关注 GLI2 和 GLI3，它们是控制 Hh 途径输出的转录因子。在 NRF2 缺失细胞中，它们的 mRNA 和蛋白水平均降低，这与它们的基因启动子包含预测与 NRF2 结合的共识 ARE 序列一致。此外，在 Hh 途径激活时，GLI2 和 GLI3 未能在 NRF2 缺失细胞的纤毛尖端积累。鉴于 NRF2 和纤毛信号在人类疾病中的重要性，我们的数据可能具有重要的生物医学意义。
