NRF2-dependent gene expression promotes ciliogenesis and Hedgehog signaling

Area of Science:

• Cell Biology
• Molecular Biology
• Developmental Biology

Background:

• Nuclear factor erythroid 2-related factor 2 (NRF2) is a key regulator of cellular responses.
• Primary cilia act as cellular antennae, crucial for signaling pathways.
• The interplay between NRF2 and primary cilia is largely unexplored, particularly outside of human embryonic stem cells (hESCs).

Purpose of the Study:

• To investigate the reciprocal regulatory relationship between NRF2 and primary cilia.
• To determine if the Primary Cilia-Autophagy-NRF2 (PAN) axis functions in differentiated cells.
• To elucidate NRF2's role in primary cilia formation, function, and associated signaling pathways.

Main Methods:

• Utilized fibroblasts lacking primary cilia to assess NRF2 activity.
• Employed autophagy-activating mTOR inhibitors to rescue NRF2 activity.
• Analyzed cilia formation, length, and Hedgehog signaling in NRF2-null cells.
• Investigated the expression of ciliogenic and Hedgehog pathway genes, including GLI2 and GLI3.

Main Results:

• Fibroblasts lacking primary cilia exhibit elevated NRF2 activity, which is normalized by mTOR inhibitors, confirming the PAN axis in differentiated cells.
• NRF2 deficiency leads to reduced cilia number and length, and impaired Hedgehog signaling.
• NRF2 promotes the expression of genes essential for cilia formation and Hedgehog pathway function, including GLI2 and GLI3.
• Reduced GLI2 and GLI3 levels in NRF2-null cells are linked to NRF2 binding to their promoter regions.

Conclusions:

• NRF2 and primary cilia engage in a reciprocal regulatory loop.
• The PAN axis is functional in differentiated cells, linking cilia, autophagy, and NRF2.
• NRF2 is essential for proper cilia development and Hedgehog pathway signaling, potentially through regulating GLI transcription factors.
• These findings highlight the significance of NRF2 and ciliary signaling in human health and disease.