Force-dependent structural dynamics of the giant nesprin-2.

The nesprin protein family serves as a critical physical bridge between the cytoskeleton-a fundamental structural scaffold and mechanotransduction hub of the cell, and the nucleus-an intriguing and emerging mechanoresponsive element. Due to the external mechanical cues and the nucleo-cytoskeletal dynamics, the nesprins are physiologically under forces. However, the dynamics of nesprins within physiological forces and loading rates remain largely unexplored. In this study, we employ magnetic-tweezers-based single-molecule manipulation alongside molecular dynamic simulations and AlphaFold structural predictions to comprehensively investigate the dynamics of force-bearing spectrin repeat (SR) domains of the giant nesprin-2 protein. Through direct quantification, we unveil that the numerous SRs undergo mechanical unfolding and refolding dynamics with distinct transition rates within several pN scale. Furthermore, we show that the giant nesprin-2 could act as an effective molecular absorber adeptly maintaining forces on the nucleoskeleton and cytoskeleton linkage within a few pN across displacement spans exceeding one μm. Notably, our findings imply that subtle pN-level mechanical forces intricately modulate nesprin-protein interactions via the dynamics of domain folding and unfolding. Collectively, our study offers a comprehensive understanding of the mechanical characteristics of nesprin-2 giant, shedding light on its pivotal role in nucleoskeleton-cytoskeleton mechanotransduction.