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Epac1 and PDZ-GEF cooperate in Rap1 mediated endothelial junction control

Pannekoek, W. J. and Dijk van, J. and Chan, O. Y. and Huveneers, S. and Linnemann, J. R. and Spanjaard, E. and Brouwer E. M., P. and Meer van der, A. J. and Zwartkruis, F.J. and Rehmann, H. and Rooij de, J. and Bos, J. (2011) Epac1 and PDZ-GEF cooperate in Rap1 mediated endothelial junction control. Cellular Signalling, 23, 2056-64. ISSN 0898-6568.

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Epac1 and its effector Rap1 are important mediators of cAMP induced tightening of endothelial junctions and consequential increased barrier function. We have investigated the involvement of Rap1 signalling in basal, unstimulated, barrier function of a confluent monolayer of HUVEC using real time Electric Cell-substrate Impedance Sensing. Depletion of Rap1, but not Epac1, results in a strong decrease in barrier function. This decrease is also observed when cells are depleted of the cAMP independent Rap exchange factors PDZ-GEF1 and 2, showing that PDZ-GEFs are responsible for Rap1 activity in control of basal barrier function. Monolayers of cells depleted of PDZ-GEF or Rap1 show an irregular, zipper-like organization of VE-cadherin and live imaging of VE-cadherin-GFP reveals enhanced junction motility upon depletion of PDZ-GEF or Rap1. Importantly, activation of Epac1 increases the formation of cortical actin bundles at the cell-cell junctions, inhibits junction motility and restores barrier function of PDZ-GEFs depleted, but not Rap1 depleted cells. We conclude that PDZ-GEF activates Rap1 under resting conditions to stabilize cell-cell junctions and maintain basal integrity. Activation of Rap1 by cAMP/Epac1 induces junctional actin to further tighten cell-cell contacts.

Item Type:Article
Institutes:Hubrecht Instituut
ID Code:12641
Deposited On:19 Sep 2012 09:34
Last Modified:14 Oct 2012 19:06

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