Microtubule‐associated protein EB3 regulates calcium signaling and facilitates increase in endothelial permeability

Abstract

End binding proteins (EBs) are highly conserved microtubule plus‐end tracking accessory factors that bind to growing microtubule ends and suppress microtubule catastrophe events. We investigated the roles of EB1 and EB3 in regulating endothelial cytoskeletal dynamics and cell shape change, the primary determinants of the permeability of endothelial barrier. Protein depletion experiments showed that EB3, but not EB1, facilitates thrombin‐induced release of calcium from endoplasmic reticulum (ER), and thereby activates calcium entry from extracellular stores. We observed that EB3 interacts with inositol 1,4,5‐thriphosphate receptor type 3 (IP3R3) in lung microvasculature. Cell permeant variant of IP3R3 derivative peptide containing EB3 consensus motif reduced the interaction between EB3 and IP3R3 and mitigated increased endothelial permeability response associated with the cell shape changes. Furthermore, infusion of IP3R3 derivative peptide in ex vivo murine lung preparation attenuates the increase in lung vascular liquid permeability (Kf,c) in response to activation of the Protease‐Activated Receptor ‐1. Intravenous injection of this peptide prevents lung injury and reduces the lethality of polymicrobial sepsis in mice. These data indicate that EB3 regulates calcium signaling in endothelium and facilitates pulmonary vascular leak in disease states.