Biophysical Society Thematic Meeting| Aussois 2019

Biology and Physics Confront Cell-Cell Adhesion

Poster Abstracts

1-POS Board 1 CORTICAL CONTRACTILITY OVERRIDES THE INFLUENCE OF BINDING ENERGY OF TRANS INTERACTIONS DURING ADHERENS JUNCTION FORMATION Aditya Arora 1 ; Ivar Noordstra 2 ; Srikanth Budnar 2 ; Alpha Yap 2 ; Virgile Viasnoff 1 ; 1 National University of Singapore, Mechanobiology Institute, Singapore, Singapore 2 The University of Queensland, Institute for Molecular Bioscience, Brisbane, Australia The role of energetic contribution of trans interactions between cadherins during adherens junction (AJ) formation has been debatable. To elucidate the influence of binding energies of trans interactions on different phases of AJ formation, we engineered E Cadherin constructs whose extracellular domain was replaced by Halo tag to conjugate ssDNA oligonucleotides. Cells with complementary ssDNA initiated trans interactions, followed by AJ formation. Engineered cadherins lacked ability to activate Rac and Rho signalling on trans ligation, but proceeded to form wild type like AJ organization on stimulation with drugs to sequentially downregulate and upregulate tension. The junction formation was temporally divided into two phases; Phase I characterized by overall reduction in cortical tension and initiation of cell-cell contact formation, usually accompanied with a peak in Rac1 activity. Phase II involves activation of RhoA and upregulation of cortical tension, which leads to junctional reorganization and expansion. The contact lengths between a cell pair at the end of the first phase of junction formation was proportional to the binding energies of the oligonucleotides, however, this effect was completely abolished when cortical contractility was exogenously upregulated using Nocodazole or Calyculin A after initial contact formation. Overall, adhesion energy was a determinant of junction size only in early junction formation, however, it seems to have no influence on junction size after re-establishment of cortical contractility/ RhoA activation.

39