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Sequential activation of RhoA and FAK/paxillin leads to ATP release and actin reorganization in human endothelium
Author(s) -
Hirakawa Masakazu,
Oike Masahiro,
Karashima Yuji,
Ito Yushi
Publication year - 2004
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.2004.065334
Subject(s) - rhoa , microbiology and biotechnology , paxillin , focal adhesion , lysophosphatidic acid , stress fiber , tyrosine phosphorylation , actin cytoskeleton , rho associated protein kinase , actin , mdia1 , phosphorylation , ptk2 , clostridium difficile toxin b , mechanosensitive channels , cytoskeleton , chemistry , biology , protein kinase c , signal transduction , biochemistry , mitogen activated protein kinase kinase , clostridium difficile toxin a , receptor , ion channel , cell , antibiotics , clostridium difficile
We have investigated the cellular mechanisms of mechanical stress‐induced immediate responses in human umbilical vein endothelial cells (HUVECs). Hypotonic stress (HTS) induced ATP release, which evoked a Ca 2+ transient, followed by actin reorganization within a few minutes, in HUVECs. Disruption of the actin cytoskeleton did not suppress HTS‐induced ATP release, and inhibition of the ATP‐mediated Ca 2+ response did not affect actin reorganization, thereby indicating that these two responses are not interrelated. ATP release and actin reorganization were also induced by lysophosphatidic acid (LPA). HTS and LPA induced membrane translocation of RhoA, which occurs when RhoA is activated, and tyrosine phosphorylation of focal adhesion kinase (FAK) and paxillin. Tyrosine kinase inhibitors (herbimycin A or tyrphostin 46) inhibited both HTS‐ and LPA‐induced ATP release and actin reorganization, but did not affect RhoA activation. In contrast, Rho‐kinase inhibitor (Y27632) inhibited all of the HTS‐ and LPA‐induced responses. These results indicate that the activation of the RhoA/Rho‐kinase pathway followed by tyrosine phosphorylation of FAK and paxillin leads to ATP release and actin reorganization in HUVECs. Furthermore, the fact that HTS and LPA evoke exactly the same intracellular signals and responses suggests that even these immediate mechanosensitive responses are in fact not mechanical stress‐specific.