The mechanisms by which the microtubule cytoskeleton regulates the permeability of endothelial barrier are not well understood. Here, we demonstrate that microtubule-associated end-binding protein 3 (EB3), a core component of the microtubule plus-end protein complex, binds to inositol 1,4,5-trisphosphate receptors (IP 3Rs) through an S/TxIP EB-binding motif. In endothelial cells, α-thrombin, a pro-inflammatory mediator that stimulates phospholipase Cβ, increases the cytosolic Ca 2+ concentration and elicits clustering of IP 3R3s. These responses, and the resulting Ca 2+-dependent phosphorylation of myosin light chain, are prevented by depletion of either EB3 or mutation of the TxIP motif of IP 3R3 responsible for mediating its binding to EB3. We also show that selective EB3 gene deletion in endothelial cells of mice abrogates α-thrombin-induced increase in endothelial permeability. We conclude that the EB3-mediated interaction of IP 3Rs with microtubules controls the assembly of IP 3Rs into effective Ca 2+ signaling clusters, which thereby regulate microtubule-dependent endothelial permeability.
IP 3 receptors (IP 3Rs) bind to microtubule end-binding protein EB3
EB3, in turn, promotes IP 3R clustering and Ca 2+ signals in endothelial cells
IP 3R-EB3 interaction thereby contributes to endothelial barrier disruption
In vivo EB3 deletion in endothelial cells protects from vascular hyperpermeability
End binding proteins (EBs) mediate interactions between growing microtubules and intracellular structures. Geyer et al. demonstrate that interactions between EB3 and IP 3 receptors control clustering of IP 3 receptors in endothelial cells and Ca 2+ signaling, and thus permeability of endothelial barrier in inflammatory diseases.