p120-Catenin Inhibits VE-Cadherin Internalization through a Rho-independent Mechanism

Abstract

Monitoring Editor: M. Bishr Omary p120-catenin is a cytoplasmic binding partner of cadherins and functions as a set point for cadherin expression by preventing cadherin endocytosis, and degradation. p120 is known to regulate cell motility and invasiveness by inhibiting RhoA activity. However, the relationship between these functions of p120 is not understood. Here, we provide evidence that p120 functions as part of a plasma membrane retention mechanism for VE-cadherin by preventing the recruitment of VE-cadherin into membrane domains enriched in components of the endocytic machinery, including clathrin and the adaptor complex AP-2. The mechanism by which p120 regulates VE-cadherin entry into endocytic compartments is dependent on p120's interaction with the cadherin juxtamembrane domain, but occurs independently of p120's prevention of Rho GTPase activity. These findings clarify the mechanism for p120's function in stabilizing VE-cadherin at the plasma membrane and demonstrate a novel role for p120 in modulating the availability of cadherins for entry into a clathrin-dependent endocytic pathway. INTRODUCTIONVE-cadherin is a central component of endothelial adherens junctions and mediates homophilic interactions between neighboring endothelial cells. Adhesion and signaling events mediated by VE-cadherin play key roles in vascular barrier function and angiogenesis (Vestweber, 2008;Wallez and Huber, 2008). Likewise, several endothelial signaling pathways are known to regulate endothelial cell-cell interactions through regulation of VE-cadherin or other adherens junction molecules (Gavard and Gutkind, 2006;Lampugnani et al., 2006). The cytoplasmic domain of VE-cadherin interacts with members of the armadillo family of proteins, including ␤-catenin and p120-catenin (p120). These interactions regulate association of cadherins with the actin cytoskeleton and are important for strong cell-cell adhesion (Pokutta and Weis, 2007;Hartsock and Nelson, 2008). Furthermore, gene ablation studies have revealed key roles for VE-cadherin, ␤-catenin, and p120 in vascular development, underscoring the importance of adherens junction components in vascular biology and vertebrate development (Carmeliet et al., 1999;Gory-Faure et al., 1999;Cattelino et al., 2003; Xiao, Oas, and Kowalczyk, unpublished observations).An important aspect of the ability of cells to dynamically modulate their adhesive state is the regulation of cadherin availability at the cell surface. One cellular mechanism that is commonly used to rapidly alter the expression of cell surface receptors is membrane trafficking. Cells utilize several endocytic pathways to retrieve receptors from the cell surface. The most common of these is clathrin-dependent, in which transmembrane cargos are sorted into clathrincoated pits at the plasma membrane. Endocytic adaptor proteins, including the tetrameric adaptor complex AP-2, play a fundamental role in the recruitment and formation of clathrin-coated vesicles at the plasma membrane through the ability to bind to lipids, cargo, c...

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.…”

“…Although the binding of p120 inhibits VE-cadherin internalization, d-catenin is also a negative regulator of the Rho/Rho-kinase pathway and myosin light chain (MLC) phosphorylation in ECs 26,28 . VE-cadherin promotes Rho-kinase activity, MLC phosphorylation and actomyosin contractility, which, in turn, enhances VE-cadherin accumulation at cell junctions and thereby vessel stability 33,34 .…”

Dynamics between actin and the VE-cadherin/catenin complex

“…[65][66][67] Many of these functions were also demonstrated for regulation of the VE-cadherin in endothelium. [68][69][70][71][72][73][74][75][76] Importantly, recent data indicates the involvement of p120 ctn in controlling ARP2/3 complex-mediated actin polymerization at endothelial junctions, by binding to the nuclear-promoting factors Wiskott-Aldrich Syndrome Protein (N-WASP) 21 and to cortactin. 77,78 Both the ARP2/3 complex 11,21 and cortactin [79][80][81][82][83][84][85] control endothelial integrity, and particularly, N-WASP control ARP2/3 complex-mediated formation of new VE-cadherin adhesion sites, which drive the VE-cadherin dynamics.…”