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Wild Type p53 Regulates Endothelial Barrier Function by mediating Rac1 signaling and inhibiting RhoA activity
Author(s) -
Barabutis Nektarios,
Birmpas Charalampos,
Thangjam Gagan,
Gregory Betsy W,
Clements Mary Ann,
Newton Joseph,
Catravas John D.
Publication year - 2016
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.30.1_supplement.957.11
Subject(s) - rhoa , microbiology and biotechnology , rac1 , phosphorylation , barrier function , gene silencing , signal transduction , small interfering rna , chemistry , biology , transfection , biochemistry , gene
The tumor suppressor and heat shock protein 90 (hsp90) client protein, p53, is a transcription factor which is frequently mutated in human cancers. An emerging body of evidence suggests that p53 also induces strong anti‐inflammatory responses, both in vivo and in vitro . Such activities maintain and preserve vascular barrier function, a key element of lung integrity and defense against endogenous or exogenous insults. We have recently reported that p53 is a major regulator of vascular integrity and endothelial permeability mostly due to its inhibition of the barrier disruptive RhoA signaling. In the present study we further investigated the mechanisms underlying the barrier protective effects of p53. Nutlin‐ or hsp90 inhibitor‐ induced p53 overexpression increased Rac1 activity (GTP‐bound Rac1), a small GTPase with known barrier‐protective effects. Nutlin or hsp90 inhibitor also increased downstream LIMK1/2 phosphorylation/activation as well as cofilin phosphorylation/deactivation thus preventing actin stess fiber formation and promoting cortical actin. When p53 expression was suppressed by siRNA, the opposite effects were observed. Hsp90 inhibitor (AUY‐922)‐induced p53 overexpression also caused an induction of the RhoA negative regulator p190Rho‐GAP that led to inhibition of RhoA activity as well as inhibition of downstream MLC phosphorylation. Real time measurements of endothelial barrier function by continuous monitoring of transendothelial electrical resistance (TER) of human lung microvascular endothelial monolayers revealed a prominent role of p53 in endothelial barrier regulation. Downregulation of p53 by pifithrin attenuated AUY‐922‐induced barrier enhancement, whereas siRNA‐mediated p190Rho‐GAP silencing led to an enhanced LPS‐induced decrease in TER. In conclusion, we propose that p53 regulates vascular barrier function by manipulating the balance of the actin remodeling Rac1 and RhoA pathways. Support or Funding Information This study was supported by National Heart, Lung, and Blood Institute Grants HL101902 and HL93460.