The role of LIM kinase 1 in cytoskeleton dynamics and endothelial barrier function

Homeostatic barrier function of the endothelium is achieved by the dynamic regulation of the endothelial cell shape change, endothelial cell-to-cell adherence, and endothelial cell-to-matrix adherence. Microtubule and actin cytoskeleton function not only as rigid structural elements, but also as highly dynamic polymers, which dynamically regulate cell motility, inflammatory responses, wound healing and metastasis.; We sought to identify and describe the role of LIMK1 in the coordination of microtubule and actin cytoskeleton dynamics, and endothelial barrier function.; First study showed for the first time that LIMK1 was co-localized and formed complex with tubulin via its PDZ domain in human umbilical vein endothelial cells. We determined that thrombin induced not only actin polymerization in endothelial cells, but also microtubule destabilization, which was accompanied by the LIMK1 redistribution to sites with increased actin dynamics. The affinity of LIMK1 for the complex formation with tubulin or actin appeared to be dependent on the activation state of LIMK1. Finally, we showed that LIMK1 kinase activity was required for the thrombin-induced modulation of microtubule destabilization and actin polymerization. These dada indicate that LIMK1 may coordinate microtubule and actin cytoskeleton dynamics in endothelial cells.; Second study described the novel role of LIMK1 in endothelial barrier regulation. We showed that removal of LIMK1 significantly improved endothelial barrier function via decreasing permeability as was revealed by in-vivo lung perfusion studies of LIMK1 knockout mice as well as transmission electron microscopy. Measurements of trans-endothelial electrical resistance as well as confocal microscopy provided us with the evidence that kinase activity of LIMK1 was important for the gap formation and modulation of endothelial barrier function. We determined that impaired cofilin phosphorylation in LIMK1 knockout mice at least partially accounted for the observed improvement of the endothelial barrier function. Finally, we showed that removal of LIMK1 significantly decreased lung edema formation in the endotoxin-induced sepsis model as well as it increased the survival rate. Our findings suggest that removal of LIMK1 leads to less permeable blood vessels, and favor the possibility that inhibition of LIMK1 function may improve conditions of acute lung injury during sepsis.