An α-catenin actin-binding domain unfolding mutant designed to lower force-dependent actin-binding promotes epithelial strength but interferes with cell-cell coordination

Abstract

ABSTRACTα-catenin (α-cat) displays force-dependent binding to actin filaments, but the features of adherens junction structure and function most vulnerable to loss of this allosteric mechanism remain to be generalized across epithelial cell-types. By reconstituting an α-cat F-actin-binding domain unfolding mutant known to exhibit enhanced binding to actin (α-cat-H0-FABD+) into α-cat knock-out Madin Darby Canine Kidney (MDCK) cells, we show that partial loss of the α-cat catch bond mechanism (via an altered H0 α-helix) leads to stronger epithelial sheet integrity with greater co-localization between the α-cat-H0-FABD+mutant and actin. α-cat-H0-FABD+- expressing cells are less efficient at closing scratch-wounds or uniformly packing, suggesting reduced capacity for more dynamic cell-cell coordination. Evidence α-cat-H0-FABD+is equally accessible to the conformationally sensitive α18 antibody epitope as WT α-cat suggests this mutant favors binding to lower tension cortical actin networks. These data suggest signals that reduce the force-sensitivity of the α-cat-cortical actin interaction might improve epithelial monolayer strength through enhanced coupling to lower tension cortical actin networks, but that such association would render α-cat less selective of higher-tension actin networks, extracting a cost for dynamic processes.