REORGANIZATION OF MICROTUBULE SYSTEM IN PULMONARY ENDOTHELIAL CELLS IN RESPONSE TO
THROMBIN TREATMENT
K. M. Smurova,1, 2 A, A. Birukova,2 J. G. Garcia,2
I. A. Vorobjev,1
I. B. Alieva,1 A. D. Verin 2
1 Belozersky Institute of Physico-Chemical Biology, Moscow State University, Russia and
2 Division of Pulmonary and Critical Care Medicine, Johns Hopkins University School of Medicine, USA;
1 e-mail: smurova@belozersky.msu.ru
Thrombin induces rapid and reversible increase of endothelial (EC) barrier permeability associated with actin cytoskeleton
remodeling and contraction. The role of microtubules (Mts) in EC barrier regulation compared with actin systems is poorly understood.
In this work we studied pathways of Mt and actin regulation in response to thrombin treatment in cultured EC, and the involvement of trimeric
G-proteins and in this process. Cells were treated with thrombin, and further analysed using immunofluorescent staining of actin and Mts,
digital microscopy and morphometric analysis. In normal cells actin network consists of thin bundles basically located in the cell periphery,
Mt density decreases from the cell center to the cell edge. Thrombin (25 nM) induced endothelial dysfunction associated with a rapid
(within 5 min) decrease of peripheral Mt network and a slower actin stress fiber formation in the cytoplasm. Pretreatment with Pertussis
toxin, which is Gi protein inhibitor, attenuated thrombin-induced stress fiber formation and Mt disassembly. Overexpression of activated
G12, G13, Gi and Gq proteins, which are involved in thrombin receptor-mediated signaling, resulted in increasing stress fibers thickness
and density and complete Mt disassembly. From the results obtained we suggest that thrombin regulates actin cytoskeleton of EC using
local Mt depolymerization at the cell edge.
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