VE-cadherin trans-interactions modulate Rac activation and enhancement of lung endothelial barrier by iloprost

J Cell Physiol. 2012 Oct;227(10):3405-16. doi: 10.1002/jcp.24041.


Small GTPase Rac is important regulator of endothelial cell (EC) barrier enhancement by prostacyclin characterized by increased peripheral actin cytoskeleton and increased interactions between VE-cadherin and other adherens junction (AJ) proteins. This study utilized complementary approaches including siRNA knockdown, culturing in Ca(2+) -free medium, and VE-cadherin blocking antibody to alter VE-cadherin extracellular interactions to investigate the role of VE-cadherin outside-in signaling in modulation of Rac activation and EC barrier regulation by prostacyclin analog iloprost. Spatial analysis of Rac activation in pulmonary EC by FRET revealed additional spike in iloprost-induced Rac activity at the sites of newly formed cell-cell junctions. In contrast, disruption of VE-cadherin extracellular trans-interactions suppressed iloprost-activated Rac signaling and attenuated EC barrier enhancement and cytoskeletal remodeling. These inhibitory effects were associated with decreased membrane accumulation and activation of Rac-specific guanine nucleotide exchange factors (GEFs) Tiam1 and Vav2. Conversely, plating of pulmonary EC on surfaces coated with extracellular VE-cadherin domain further promoted iloprost-induced Rac signaling. In the model of thrombin-induced EC barrier recovery, blocking of VE-cadherin trans-interactions attenuated activation of Rac pathway during recovery phase and delayed suppression of Rho signaling and restoration of EC barrier properties. These results suggest that VE-cadherin outside-in signaling controls locally Rac activity stimulated by barrier protective agonists. This control is essential for maximal EC barrier enhancement and accelerated barrier recovery.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adherens Junctions / drug effects
  • Adherens Junctions / metabolism
  • Antibodies / pharmacology
  • Antigens, CD / metabolism*
  • Cadherins / antagonists & inhibitors
  • Cadherins / metabolism*
  • Capillary Permeability / drug effects
  • Cells, Cultured
  • Cytoskeleton / drug effects
  • Cytoskeleton / metabolism
  • Endothelial Cells / cytology
  • Endothelial Cells / drug effects*
  • Endothelial Cells / metabolism*
  • Epoprostenol / pharmacology
  • Guanine Nucleotide Exchange Factors / metabolism
  • Humans
  • Iloprost / pharmacology*
  • Intercellular Junctions / drug effects
  • Intercellular Junctions / metabolism
  • Lung / cytology
  • Lung / drug effects*
  • Lung / metabolism*
  • Proto-Oncogene Proteins c-vav / metabolism
  • Pulmonary Artery / drug effects
  • Pulmonary Artery / metabolism
  • Signal Transduction / drug effects
  • Signal Transduction / genetics
  • T-Lymphoma Invasion and Metastasis-inducing Protein 1
  • rac GTP-Binding Proteins / metabolism*


  • Antibodies
  • Antigens, CD
  • Cadherins
  • Guanine Nucleotide Exchange Factors
  • Proto-Oncogene Proteins c-vav
  • T-Lymphoma Invasion and Metastasis-inducing Protein 1
  • TIAM1 protein, human
  • VAV2 protein, human
  • cadherin 5
  • Epoprostenol
  • rac GTP-Binding Proteins
  • Iloprost