Abstract: 

Mechanical cross-talk between talin-centered adhesions to the extracellular matrix plays a crucial role in cell migration and polarity. On the cytoplasmic side, the talin-dependent interactome network coordinates between the actin network and intermediate filament, controlling the adhesion maturation. However, these adhesion processes are dependent on alternating states of talin protein: autoinhibited and active extended form. While autoinhibited talin mostly exhibits domain-domain interactions, their active extended form interacts with different binding proteins while transducing the force. Additionally, due to actomyosin contractility, these complexes are continuously under mechanical stress and are critical determinants of adhesion turnover. It is well-established that talin domains exhibit different mechanical responses that also reflect into their force-dependent interactions with other focal adhesion (FA) partners. However, less studies have been performed on how these interactions affect their folding mechanics, mechanical stability, and conformational stiffness. Although few studies have reported talin interactions with vinculin and KANK1 under the physiological force range; however, interactions with other adhesion stimuli including ionic strength and adhesion-targeting drugs have not been studied much. This is due to the technological limitations which could monitor multiple molecular properties during protein interactions in real-time.

Here, we have developed microfluidic magnetic tweezers that allow us to quantify these fundamental properties and their dynamic changes in varying chemical environments on a single protein specimen. Using this methodology, we monitored the conformational changes and the folding dynamics of the talin protein under varying salt conditions. The folding dynamics of the talin protein is strongly force-dependent and thus, its mechanical stability is a critical factor for the adhesion assembly. Additionally, Hsp70 and Hsp40 as linchpin FA-resident proteins, have been observed to shift the talin folding mechanics towards the lower force range and thus, mechanically destabilizing the protein. Interestingly, we have shown that talin possesses a unique bi-modal unfolding distribution under mechanical force: a well-characterized low force population at ~9 pN and a high force population at ~30 pN. With different drugs, a specific variation has been observed in this force distribution: tamoxifen exhibits a strong biphasic effect on talin mechanical stability, while cyanidin-3-O-glucoside promotes its steady increase with the concentration. However, another drug letrozole has been found to exhibit a much weaker biphasic effect than tamoxifen. To explain this drug-modulated talin mechanical stability, we have performed computational studies and observed that Cyanidin 3-O-glucoside forms highest intermolecular H bonds, followed by that through letrozole and tamoxifen binding. Overall, these single-molecule insights will provide an unprecedented mechanical behaviour of talin that will present a novel perspective for its diverse force-dependent interactions to control the adhesion dynamics.

About the speaker: 

Soham has been a Ph.D. scholar at Ashoka University since 2019. He obtained his B.Sc and M.Sc. in Microbiology from the University of Calcutta. His research interest lies in studying the force-dependent interactions of talin protein and how it regulates their folding mechanics and associated physical properties.