TNIK: A redox sensor in endothelial cell permeability.

Area of Science:

• Molecular Biology
• Cell Biology
• Physiology

Background:

• Endothelial barrier integrity is crucial for preventing vascular leak and edema.
• Tumor Necrosis Factor-alpha (TNF-α) regulates endothelial permeability via Ezrin-Radixin-Moesin (ERM) proteins during inflammation.

Purpose of the Study:

• To identify kinases regulating ERM proteins in TNF-α-mediated endothelial permeability.
• To elucidate the role of TNIK in endothelial barrier function and inflammatory edema.
• To investigate the redox regulation of TNIK activity.

Main Methods:

• Identification of TNIK as an ERM-phosphorylating kinase in human endothelial cells.
• In vitro studies on TNF-α-induced cellular stiffness and gap formation.
• In vivo assessment of TNIK's role in inflammatory edema.
• Investigation of hydrogen peroxide (H₂O₂) effects on TNIK activity and structure.

Main Results:

• TNIK directly phosphorylates and activates ERM proteins at the endothelial plasma membrane.
• TNIK mediates TNF-α-induced endothelial cell stiffening, gap formation, and in vivo edema.
• Hydrogen peroxide (H₂O₂) reversibly inhibits TNIK via oxidation of C202, forming disulfide bonds and reducing kinase activity.
• Inhibition of reactive oxygen species enhances TNIK activity, leading to ERM phosphorylation and endothelial cell contraction.

Conclusions:

• TNIK is a key regulator of TNF-α-induced endothelial permeability and inflammatory edema.
• Redox signaling, specifically H₂O₂-mediated oxidation of TNIK, provides a reversible inhibitory mechanism for kinase activity.
• The interplay between TNIK, ERM phosphorylation, and redox balance is critical for maintaining endothelial barrier integrity.