Real time observation of chaperone-modulated talin mechanics with single molecule resolution

Abstract

AbstractRecent single-molecule studies have recognized talin as a mechanosensitive hub in focal adhesion, where its function is strongly regulated by mechanical force. For instance, at low force (below 5 pN), folded talin binds RIAM for integrin activation; whereas at high force (above 5 pN), it unfolds to activate vinculin binding for focal adhesion stabilization. Being a cytoplasmic protein, talin might interact with several cytosolic chaperones: however, the role of chaperones in talin mechanics is unknown.To address this question, we investigated the force response of a mechanically stable talin domain with a set of well-known holdase (DnaJ, DnaK, Hsp70, and Hsp40) and foldase (DnaKJE, DsbA) chaperones, using single-molecule magnetic tweezers. Our findings demonstrate that chaperone could affect adhesion proteins stability by changing their folding mechanics; while holdase chaperones reduce their unfolding force to ∼6 pN, foldase chaperones shift it up to ∼15 pN. Since talin is mechanically synced within 2 pN force ranges, these changes are significant in cellular condition. Furthermore, we determined the fundamental mechanism of this altered mechanical stability, where chaperones directly reshape their energy landscape: unfoldase chaperone (DnaK) decreases the unfolding barrier height from 26.8 to 21.7 kBT, while foldase chaperone (DsbA) increases it to 33.5 kBT. We reconciled our observations with eukaryotic Hsp70 and Hsp40 chaperones and observed their similar function of decreasing the talin unfolding barrier to 23.1 kBT. The quantitative mapping of this chaperone-induced talin folding landscape directly illustrates that chaperones perturb the adhesion protein stability under physiological force, thereby influencing their force-dependent interactions and adhesion dynamics.