Mechanical regulation of vinculin conformations and interactions.

Abstract

Vinculin, as an essential mechanosensitive protein, transmits intracellular tension initiated from the cell-cell and the cell-matrix interfaces, to modulate cellular and tissue functions. However, the tension-dependent conformations and interactions of vinculin are largely unknown. Vinculin provides the mechanical linkages between talin and actin at Focal adhesions, or alpha-catenin and actin at Adherens junctions. In drosophila, vinculin also functions at the muscle attachment sites with Cbl-associated proteins (CAPs) to regulate the cytoskeletal organization and membrane morphology. In this work, we combined single-molecule manipulation, AlphaFold2-based structural prediction, molecular dynamic (MD) simulation and theoretical modelling to understand the tension-dependent conformational changes of drosophila vinculin domains and its interaction with drosophila CAP isoform E (dCAP-E). We reveal that vinculin domains unfold in discrete steps, within 5-15 pN at a physiologically relevant tension loading rate. Based on the structural conformations predicted by AlphaFold2 and confirmed by MD simulation, a theoretical model is developed which predicts a tension-dependent binding affinity between the drosophila vinculin linker and dCAP-E within the physiologically relevant tension range. Together, the results suggest two roles of vinculin, as a tension buffering structure via tension-dependent unfolding and refolding of domains and as a mechanosensor via tension-dependent binding with its binding partners.