JAM-A Acts via C/EBP-α to Promote Claudin-5 Expression and Enhance Endothelial Barrier Function

Area of Science:

• Endothelial biology
• Molecular mechanisms of barrier function
• Tight junction regulation

Background:

• Intercellular tight junctions are vital for endothelial barrier integrity.
• Dysfunction of tight junctions is implicated in pathological conditions like inflammation and cancer.
• Junctional adhesion molecule A (JAM-A) is a key tight junction component, but its precise role in barrier regulation is unclear.

Purpose of the Study:

• To elucidate the molecular mechanisms by which JAM-A influences tight junction organization and endothelial permeability.
• To investigate the role of JAM-A in regulating vascular barrier function under physiological and pathological conditions.

Main Methods:

• Genetic deletion of JAM-A in mice to assess vascular permeability.
• Analysis of claudin-5 expression in various tissues.
• Investigated the role of CCAAT/enhancer-binding protein-α (C/EBP-α) as a downstream regulator.
• Utilized gain-of-function and loss-of-function studies for C/EBP-α.
• Examined the molecular interactions involving JAM-A, β-catenin, EPAC, and C/EBP-α.
• Analyzed patient tissue biopsies from glioblastoma and ovarian cancer.

Main Results:

• JAM-A deletion increased vascular permeability and decreased claudin-5 expression.
• C/EBP-α acts as a transcription factor for claudin-5, enhancing vascular barrier function.
• JAM-A promotes C/EBP-α expression by suppressing β-catenin and activating EPAC.
• C/EBP-α directly binds the claudin-5 promoter.
• JAM-A-C/EBP-α-claudin-5 pathway was impaired in cancer patient tissues.

Conclusions:

• JAM-A positively modulates the transcription factor C/EBP-α, which up-regulates claudin-5 expression to decrease endothelial permeability.
• This study reveals a novel molecular pathway regulating vascular permeability through tight junctions.
• The findings offer insights into potential therapeutic strategies for diseases characterized by endothelial barrier dysfunction.