End Binding protein 3 regulates calcium signaling and permeability of the endothelial barrier

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End binding (EBs) proteins bind growing microtubule (MT) plus ends and promote MT growth. We have recently shown that Vascular Endothelial (VE)‐cadherin outside‐in signaling regulates phosphorylation of EB3 to suppress MT persistent growth and thus allowing for the assembly of adherens junctions (AJs). Depletion of EB3 has no effect on either MT dynamics or formation of (AJs) in confluent endothelial monolayers. However, depletion of EB3 significantly attenuates cell shape change and permeability increase in cells subjected to pro‐inflammatory mediator thrombin. EB3 interacts with inositol 1,4,5‐thriphosphate receptor type 3 (IP3R3) and facilitates agonist‐induced clustering of IP3R3 and IP3‐dependent release of calcium from intracellular stores. Cell permeant variant of IP3R3‐derivative peptide containing EB3 consensus motif reduces the interaction between EB3 and IP3R3 and mitigates increased endothelial permeability response. Furthermore, infusion of this peptide in ex vivo murine lung preparation attenuates increase in lung vascular liquid permeability (Kf,c) in response to activation of the Protease‐Activated Receptor‐1 (PAR‐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.This work was supported by NIH grants R01 HL103922 and Giles F. Filley Memorial Award to Y. K.; R01 HL 45638 to A.B. M.; T32 HL07829–17 support to M. G.