A critical role for VE-cadherin in regulating actin dynamics during endothelial maturation and non-inflammatory activation via a tension-sensitive intermediate state

Epithelial and endothelial monolayers maintain homeostasis by adapting to physiological stimuli and injury through conversion processes that remain incompletely understood. Using endothelial cell cultures (HUVEC), we investigate how monolayer maturation and non-inflammatory remodeling are molecularly regulated. Maturation involves reduced cell perimeter causing increased junctional VE-cadherin, which recruits junctional actin and integrins, establishing a quiescent, stable monolayer. Remarkably, we identify a previously unrecognized, rapid and reversible intermediate-state , marked by VE-cadherin linearization and actomyosin relaxation via MLC-dephosphorylation, that emerges during non-inflammatory activation triggered by onset or increase in shear stress. This novel intermediate-state enhances junctional actin and integrin recruitment, strengthening barrier-function while protecting endothelial cells from overstimulation and mechanical damage. Re-phosphorylation of MLC dissolves junctional actin and induces formation of junction-associated-intermittent-lamellipodia (JAIL), enabling cell shape change and arterial phenotype conversion. Overall, loss of actomyosin tension and junctional VE-cadherin-concentration defines actin recruitment and reveals a tension-sensitive, cell-protective intermediate state that primes endothelial remodeling, offering an expanded model for mechano-transduction and shear stress adaptation.