Osmoprotective transcription factor NFAT5/TonEBP modulates nuclear factor-kappaB activity

Area of Science:

• Cellular Biology
• Molecular Biology
• Physiology

Background:

• Tonicity-responsive binding-protein (TonEBP/NFAT5) is a transcription factor regulating osmoprotection.
• Its activity is modulated by extracellular tonicity, crucial for counteracting cell shrinkage.

Purpose of the Study:

• To investigate the role of TonEBP in cellular responses to hypertonicity beyond classical osmoprotection.
• To elucidate the mechanisms by which TonEBP influences nuclear factor-κB (NF-κB) signaling under hypertonic conditions.

Main Methods:

• Analysis of NF-κB activation under hypertonic stress.
• Investigation of signal transduction pathways involving p38 kinase and Akt.
• Identification of protein-protein interactions between TonEBP and NF-κB components.
• Functional studies in renal collecting duct epithelial cells and macrophages.

Main Results:

• Hypertonicity enhances NF-κB stimulation, partly mediated by TonEBP.
• Activation of p38 kinase and Akt are critical for TonEBP activity and NF-κB pathway components.
• TonEBP interacts with p65 (a subunit of NF-κB) in a tonicity-dependent manner.
• NF-κB-TonEBP complexes enhance gene expression from NF-κB-responsive elements.

Conclusions:

• TonEBP plays a novel role in augmenting NF-κB activity during hypertonic stress.
• The TonEBP-NF-κB interaction is a key mechanism for cellular adaptation to hypertonicity.
• TonEBP and Akt signaling are crucial for NF-κB activation in response to osmotic challenges, impacting renal and immune cells.