K2P2.1 shapes morphology and function of brain endothelial cells via actin network remodeling

K2P2.1 (gene: Kcnk2), a two-pore domain potassium channel, is an important regulator of leukocyte transmigration across the blood-brain barrier. However, the underlying molecular mechanisms remain poorly characterized. We here show that Kcnk2-/- mouse brain microvascular endothelial cells (MBMECs) show an altered surface morphology with increased formation of membrane protrusions. Those protrusions express clusters of cell adhesion molecules facilitating leukocyte adhesion and migration in vitro and in vivo. Kcnk2-/- MBMECs further display enhanced cortical stiffness and stress fiber formation, indicating altered cellular actin dynamics. Accordingly, we observe K2P2.1 redistribution to intracellular actin fibers and activation of actin modulating proteins (Cofilin1, Arp2/3). Pharmacological inhibition of phosphatidylinositol-(4,5)-bisphosphate (PI(4,5)P2), an essential regulator of those proteins, reverse the Kcnk2-/- phenotype. In the mechanosensitive conformation, K2P2.1 shields PI(4,5)P2 from interaction with other actin regulatory proteins. Actin rearrangements are induced by stimulus-related K2P2.1 internalization. Thus, K2P2.1-mediated regulatory processes are essential for actin dynamics, fast, reversible, and pharmacologically targetable.