Junctional adhesion molecule A promotes epithelial tight junction assembly to augment lung barrier function.

Area of Science:

• Cell Biology
• Pulmonary Medicine
• Immunology

Background:

• Epithelial barrier integrity is vital for lung health, regulated by tight junction proteins controlling paracellular flux.
• Junctional adhesion molecule A (JAM-A) is an immunoglobulin (Ig) fold transmembrane protein implicated in cell adhesion and barrier function.
• Understanding JAM-A's role in the lung is critical for addressing conditions involving barrier dysfunction.

Purpose of the Study:

• To investigate the function of JAM-A in maintaining lung epithelial barrier integrity.
• To determine the impact of JAM-A depletion on tight junction protein localization and cell structure in alveolar epithelial cells.
• To assess the role of JAM-A in pulmonary edema susceptibility using a mouse model of endotoxemia.

Main Methods:

• Depletion of JAM-A in primary alveolar epithelial cells using short hairpin RNA (shRNA).
• Measurement of transepithelial electrical resistance (TER) and assessment of tight junction protein expression and localization (zonula occludens 1, claudin-18).
• Evaluation of β1 integrin expression, filamentous actin formation, and pulmonary edema in JAM-A knockout (JAM-A(-/-)) mice subjected to lipopolysaccharide (LPS)-induced endotoxemia.

Main Results:

• JAM-A depletion in cultured cells reduced transepithelial resistance by ~30%, decreased zonula occludens 1 expression, and disrupted claudin-18 localization.
• Loss of JAM-A impaired filamentous actin formation and decreased β1 integrin expression, consistent with findings in other organs.
• JAM-A(-/-) mice exhibited increased susceptibility to pulmonary edema following LPS injection, characterized by transient disruption of tight junction proteins (claudin-18, ZO-1, ZO-2) and delayed claudin-4 upregulation.

Conclusions:

• JAM-A plays a critical role in maintaining tight junction homeostasis and lung barrier function.
• JAM-A coordinates interactions between claudins, tight junction scaffolds, and the cytoskeleton to preserve lung barrier integrity.
• Targeting JAM-A may offer therapeutic potential for conditions involving lung barrier dysfunction and edema.