Biophysical Society Thematic Meeting| Aussois 2019

Biology and Physics Confront Cell-Cell Adhesion

Tuesday Speaker Abstracts

A GEOMETRY-BASED MODEL DESCRIBES LUMEN STABILITY IN EPITHELIAL CELLS Alex Dunn Stanford University, Stanford, California USA No Abstract

VE-CADHERIN ENDOCYTOSIS REGULATES CELL POLARITY, COLLECTIVE CELL MIGRATION AND ANGIOGENESIS Cynthia Grimsley-Myers 1 ; Chantel Cadwell 1 ; Robin Isaacson 1 ; Jazmin Campos 1 ; William Giang 1 ; Andrew Kowalczyk ; 1 Emory University, Cell Biology, Atlanta, GA, USA Vascular morphogenesis is thought to require fine tuning of endothelial cell-cell adhesion, but the cellular mechanisms that govern the plasticity of adhesion are poorly understood. We hypothesized that endocytosis of vascular endothelial cadherin (VE-cad) is a key modulator of adherens junction plasticity, and that unbalancing this regulation would alter both angiogenesis and vascular permeability. VE-cad endocytosis is mediated by an internalization motif (DEE) within the p120-catenin binding domain of the VE-cad cytoplasmic tail. We used CRISPR/CAS9 to generate a series of mouse mutants with VE-cad point mutations that specifically disrupt endocytosis (VE-cadDEE) and/or p120 binding (VE-cadGGG). We found that mutating conserved GGG residues to uncouple p120 from VE-cad caused decreased VE-cad levels, microvascular hemorrhaging, and impaired postnatal survival. Thus, p120-binding is essential for VE-cad stability and vascular integrity in vivo. By contrast, mice lacking the DEE endocytic residues had normal vascular permeability. Furthermore, the VE-cadDEE mutation rescued the lethality observed in mice lacking endothelial p120, demonstrating that p120 is dispensable if cadherin is stabilized. However, VE- cadDEE animals displayed striking defects in microvascular patterning in the embryonic yolk sac, postnatal retina, and in ex vivo aortic ring explants. These defects included decreased microvascular density and reduced branching. In vitro, we found that VE-cad endocytosis is required for establishment of polarity during collective cell migration. These migration defects in the DEE mutant cells were alleviated by additional mutations in VE-cad that abrogated actin associations, suggesting that DEE-mediated endocytosis coordinates cell polarity and migration by regulating the dynamics of the actin cytoskeleton. These findings indicate that that p120 binding to VE-cad is essential for normal vascular integrity, while VE-cad endocytosis is required for endothelial cells to polarize and undergo directed collective cell migration during neovascularization.

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