Epithelial Protein Lost In Neoplasm (EPLIN) Interacts with α-Catenin and Actin Filaments in Endothelial Cells and Stabilizes Vascular Capillary Network in Vitro

Adeline Chervin-Pétinot,Marie Courçon,Sébastien Almagro,Alice Nicolas,Alexei Grichine,Didier Grunwald,Marie-Hélène Prandini,Philippe Huber,Danielle Gulino-Debrac

doi:10.1074/jbc.m111.328682

Abstract

Adherens junctions are required for vascular endothelium integrity. These structures are formed by the clustering of the homophilic adhesive protein VE-cadherin, which recruits intracellular partners, such as β- and α-catenins, vinculin, and actin filaments. The dogma according to which α-catenin bridges cadherin·β-catenin complexes to the actin cytoskeleton has been challenged during the past few years, and the link between the VE-cadherin·catenin complex and the actin cytoskeleton remains unclear. Recently, epithelial protein lost in neoplasm (EPLIN) has been proposed as a possible bond between the E-cadherin·catenin complex and actin in epithelial cells. Herein, we show that EPLIN is expressed at similar levels in endothelial and epithelial cells and is located at interendothelial junctions in confluent cells. Co-immunoprecipitation and GST pulldown experiments provided evidence that EPLIN interacts directly with α-catenin and tethers the VE-cadherin·catenin complex to the actin cytoskeleton. In the absence of EPLIN, vinculin was delocalized from the junctions. Furthermore, suppression of actomyosin tension using blebbistatin triggered a similar vinculin delocalization from the junctions. In a Matrigel assay, EPLIN-depleted endothelial cells exhibited a reduced capacity to form pseudocapillary networks because of numerous breakage events. In conclusion, we propose a model in which EPLIN establishes a link between the cadherin·catenin complex and actin that is independent of actomyosin tension. This link acts as a mechanotransmitter, allowing vinculin binding to α-catenin and formation of a secondary molecular bond between the adherens complex and the cytoskeleton through vinculin. In addition, we provide evidence that the EPLIN clutch is necessary for stabilization of capillary structures in an angiogenesis model.

Highlights

Cohesion of interendothelial junctions is maintained by the connections existing between the VE-cadherin1⁄7catenin complex and the actin cytoskeleton
epithelial protein lost in neoplasm (EPLIN) Is Expressed in Endothelial Cells at Intercellular Junctions—In epithelial cells, EPLIN was recently shown to link actin filaments to ␣-catenin when bound to the E-cadherin1⁄7␤catenin complex [18]
To test whether EPLIN is able to promote interaction between the endothelial catenin1⁄7cadherin complex and F-actin as it does in epithelial cells, its subcellular localization was explored in human umbilical vascular endothelial cells (HUVECs)

Summary

Background

Cohesion of interendothelial junctions is maintained by the connections existing between the VE-cadherin1⁄7catenin complex and the actin cytoskeleton. Adherens junctions are required for vascular endothelium integrity These structures are formed by the clustering of the homophilic adhesive protein VE-cadherin, which recruits intracellular partners, such as ␤- and ␣-catenins, vinculin, and actin filaments. We propose a model in which EPLIN establishes a link between the cadherin1⁄7catenin complex and actin that is independent of actomyosin tension. This link acts as a mechanotransmitter, allowing vinculin binding to ␣-catenin and formation of a secondary molecular bond between the adherens complex and the cytoskeleton through vinculin. VE-cad recruits intracellular partners that establish specific links with the actin cytoskeleton and stabilize the interendothelial junctions [5]. It is still accepted that the lack of catenin association to F-actin destabilizes cadherin-mediated cell adhesion

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EXPERIMENTAL PROCEDURES

RESULTS

DISCUSSION