Biophysical Society Thematic Meeting| Aussois 2019

Biology and Physics Confront Cell-Cell Adhesion

Tuesday Speaker Abstracts

INSIDE-OUT REGULATION OF CADHERIN ADHESION Ramesh Koirala 1,2 ; Andrew Priest 1,2 ; Martijn Gloerich 3 ; Soichiro Yamada 1 ; Sanjeevi Sivasankar 1 ; 1 University of California at Davis, Biomedical Engineering, Davis, CA, USA 2 Iowa State University, Physics and Astronomy, Ames, IA, USA 3 University Medical Center, Center for Molecular Medicine, Utrecht, The Netherlands During morphogenesis and wound healing, cellular migration and rearrangements rely on tightly regulated changes in cadherin adhesion. However, the molecular mechanisms by which cadherin adhesion is regulated remains poorly understood. To addresses this critical gap, we integrated biophysical measurements of cadherin structure-function with cell biological manipulations of cadherin-cytoskeleton interactions. Our data demonstrates, for the first time, that changes in E- cadherin (Ecad) ectodomain structure and adhesion are regulated from the inside-out by Ecad linkage to the actin cytoskeleton. Ecad ectodomains bind in two load bearing adhesive conformations: strand-swap dimers and X-dimers. We have previously used ultrasensitive, single molecule Atomic Force Microscopy (AFM) to show that X-dimers and strand-swap dimers have different adhesive properties [1-3]. Here we use high resolution, live cell AFM to correlate the structure and adhesion of Ecad ectodomains to their cytoskeletal linked states in parental, α- catenin knockout, and vinculin knockout MDCK cells. We demonstrate that in MDCK cells, only a third of non-junctional Ecad robustly bind to the actin cytoskeleton; the remaining Ecad only transiently associate with cortical actin. Robust linkage of Ecad to the cytoskeleton requires both α-catenin and vinculin. Strikingly, we show that while the ectodomains of cytoskeleton bound Ecads adopt an strand- swap dimer conformation, Ecad in the α-catenin and vinculin knockout cells only form X- dimers. Finally, we show that collective migration of epithelial cells is disrupted when α-catenin or vinculin are knocked-out. Our data directly demonstrates ‘inside-out’ regulation of cadherin ectodomain conformation by cytoplasmic proteins and connects these structural changes to collective cell migration.1. Rakshit et al., Proc. Natl. Acad. Sci. U.S.A., 2012,109 (46) : p. 18815-188202. Manibog et al., Nat. Commun., 2014, 5 (3941)3. Manibog et al., Proc. Natl. Acad. Sci. U.S.A., 2016, 113 (39): p. E5711-E5720

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