Tracing the Endocytosis of Claudin-5 in Brain Endothelial Cells

Claudin-5 is a transmembrane tight junction protein highly expressed in brain endothelial cells, the site of the blood–brain barrier. The properties of the brain endothelial tight junction complex are considered to be dependent on claudin-5 cell–cell interaction, putting this protein in a position to play a major role in the maintenance of brain endothelial barrier integrity. Thus, alterations in claudin-5 function can lead to “opening” of the paracellular route and increased brain endothelial barrier permeability. Recent work from the authors’s laboratory has established that caveolae-dependent internalization/recycling of claudin-5 is a mechanism underlying transient increases in brain endothelial paracellular permeability in the presence of pro-inflammatory mediators. The biochemical and microscopic techniques presented here were used to investigate trafficking of claudin-5 during those changes in paracellular permeability.