p120-Catenin Regulates Clathrin-dependent Endocytosis of VE-Cadherin

Abstract

VE-cadherin is an adhesion molecule critical to vascular barrier function and angiogenesis. VE-cadherin expression levels are regulated by p120 catenin, which prevents lysosomal degradation of cadherins by unknown mechanisms. To test whether the VE-cadherin cytoplasmic domain mediates endocytosis, and to elucidate the nature of the endocytic machinery involved, the VE-cadherin tail was fused to the interleukin (IL)-2 receptor (IL-2R) extracellular domain. Internalization assays demonstrated that the VE-cadherin tail dramatically increased endocytosis of the IL-2R in a clathrin-dependent manner. Interestingly, p120 inhibited VE-cadherin endocytosis via a mechanism that required direct interactions between p120 and the VE-cadherin cytoplasmic tail. However, p120 did not inhibit transferrin internalization, demonstrating that p120 selectively regulates cadherin internalization rather than globally inhibiting clathrin-dependent endocytosis. Finally, cell surface labeling experiments in cells expressing green fluorescent protein-tagged p120 indicated that the VE-cadherin-p120 complex dissociates upon internalization. These results support a model in which the VE-cadherin tail mediates interactions with clathrin-dependent endocytic machinery, and this endocytic processing is inhibited by p120 binding to the cadherin tail. These findings suggest a novel mechanism by which a cytoplasmic binding partner for a transmembrane receptor can serve as a selective plasma membrane retention signal, thereby modulating the availability of the protein for endo-lysosomal processing.

Endothelial basement membrane laminin 511 is essential for shear stress response

“…In particular, integrin α3β1 together with one or more other β1 integrins appears to play a central role; however, conclusive identification of α3β1 integrin in vivo is not possible at present, due to the absence of appropriate tools for use in mouse tissues. Our data suggest that the higher strength of adhesion provided by laminin 511 acts to stabilize VE‐cadherin at cell–cell junctions by inhibiting its endocytosis, reflected in the enhanced association with p120 catenin (Xiao et al , 2005; Chiasson et al , 2009). This enhanced junctional localization of VE‐cadherin induced by laminin 511 correlated with increased cell–cell adhesion strength as shown in the dual pipette‐pulling assays and, in vivo , by the enhanced junctional phospho‐myosin II staining in Lama4 −/− mice, which show an aberrant ubiquitous laminin α5 expression (van Nieuw Amerongen et al , 2007; Abraham et al , 2009).…”

Integrin β1 controls VE-cadherin localization and blood vessel stability

“…The interaction between VE-cadherin and p120 d-catenin prevents clathrin-dependent endocytosis of the cadherin and is essential for endothelial barrier function [26][27][28][29] . In control retinal vessels, anti-p120 immunosignal was visible at endothelial cell-cell contacts and overlapped with anti-VE-cadherin staining (Fig.…”

The importance of E-cadherin binding partners to evaluate the pathogenicity of E-cadherin missense mutations associated to HDGC

“…23 The p120-catenin is the best known inhibitor of cadherin endocytosis, as its binding to the E-cadherin juxtamembrane domain is required for maintenance and stability of E-cadherin molecules at the PM and, simultaneously, it physically blocks the interaction with proteins from the endocytic machinery, such as clathrin adaptor proteins and Hakai. [29][30][31][32][33] Importantly, Hakai binds directly to E-cadherin and, being an E3 ubiquitin ligase, it ubiquitinates and induces E-cadherin endocytosis. 33 Taking into account the present knowledge about E-cadherin regulation, we tested whether and how the E-cadherin cytoplasmic mutations interfere with key trafficking-related partners, leading to abnormal E-cadherin expression, localization and function, supporting their pathogenic relevance.…”

“…27,28 At the PM, p120-catenin binds to the cadherin juxtamembrane domain, stabilizing and preventing the entry of E-cadherin into degradative endocytic pathways. [29][30][31][32] E-cadherin deprived of p120 is prone to interact with other proteins, such as clathrin adapter proteins and Hakai, promoting E-cadherin internalization. 32,33 After internalization, E-cadherin can be recycled back to the PM or targeted for degradation.…”

“…[29][30][31][32] E-cadherin deprived of p120 is prone to interact with other proteins, such as clathrin adapter proteins and Hakai, promoting E-cadherin internalization. 32,33 After internalization, E-cadherin can be recycled back to the PM or targeted for degradation. 23 In the present work, we aim to determine whether E-cadherin cytoplasmic mutations associated to HDGC interfere with the binding of key partners for E-cadherin trafficking and, as consequence, lead to E-cadherin deregulation and loss of function.…”