VE-cadherin-induced Cdc42 Signaling Regulates Formation of Membrane Protrusions in Endothelial Cells

Panos Kouklis,Maria Konstantoulaki,Asrar B Malik

doi:10.1074/jbc.m212591200

Panos Kouklis, Maria Konstantoulaki + Show 1 more

Open Access

https://doi.org/10.1074/jbc.m212591200

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Abstract

The cytoplasmic domain of cadherins and the associated catenins link the cytoskeleton with signal transduction pathways. To study the signaling function of non-junctional VE-cadherin, which can form during the loss VE-cadherin homotypic adhesion, wild type VE-cadherin or VE-cadherin cytoplasmic domain (DeltaEXD) was expressed in sub-confluent endothelial cells. We observed that Cdc42 was activated in transfected cells and that these cells also developed Cdc42-dependent >70-microm-long plasma membrane protrusions. The formation of these structures required actin polymerization, and they developed specifically in endothelial cells as compared with epithelial cells. Expression of the VE-cadherin cytoplasmic domain lacking the beta-catenin binding site also induced Cdc42 activation; thus, its activation cannot be ascribed to beta-catenin binding. However, these cells were not able to form the protrusions. These results suggest that the cytoplasmic domain of non-junctional VE-cadherin can serve as a scaffold involved in Cdc42 activation at the endothelial plasma membrane. beta-Catenin and the associated alpha-catenin may serve as support sites for actin polymerization, leading to formation of long plasma membrane protrusions. Thus, non-junctional VE-cadherin actively participates in inside-out signaling at the plasma membrane, leading to the development of endothelial membrane protrusions.

Highlights

Tk;2Endothelium forms a semi-permeable barrier that regulates the flux of liquid and solutes [11, 12] as well as leukocyte transmigration from the microvasculature to sites of injury and infection [13,14,15]
These cells were not able to form the protrusions. These results suggest that the cytoplasmic domain of non-junctional VE-cadherin can serve as a scaffold involved in Cdc42 activation at the endothelial plasma membrane. ␤-Catenin and the associated ␣-catenin may serve as support sites for actin polymerization, leading to formation of long plasma membrane protrusions
These results suggest a novel role of VE-cadherin cytoplasmic domain in the formation of membrane protrusions, which may be involved in the restoration of endothelial junctional barrier function after the loss of homotypic VE-cadherin adhesion

Summary

Introduction

Tk;2Endothelium forms a semi-permeable barrier that regulates the flux of liquid and solutes [11, 12] as well as leukocyte transmigration from the microvasculature to sites of injury and infection [13,14,15]. We observed that non-junctional VEcadherin induced through its cytoplasmic domain the activation of Cdc42 and the formation of Ͼ70-␮m-long plasma membrane protrusions. Membrane Protrusions in Endothelial Cells Expressing VEcadherin Cytoplasmic Domain Require Cdc42—In HMEC cotransfected with dominant-negative mutant N17Cdc42 and ⌬EXD mutant we observed that co-expression of N17Cdc42 inhibited the formation of protrusions (Fig. 4).

Results

Conclusion