A recent publication in the journal eLife describes a multidisciplinary study evaluating how the mechanical properties of actin filaments regulate the binding of associated proteins. Specifically, the researchers used the C-Trap® to demonstrate how applied forces on actin filaments enhance binding of cell–cell adhesion protein α-catenin, but not its homolog vinculin.
The findings reveal previously unknown mechanisms by which mechanical cues trigger signaling pathways related to intercellular adhesion, causing several chronic conditions when aberrant.
Mei et al. investigated force-dependent interactions between actin filaments and the actin-binding domains of α-catenin and vinculin through an optical tweezers strategy. In essence, they captured actin filaments between two optically trapped beads, stretched the filament at different forces, and assessed the association of fluorescently tagged actin-binding domains in response to the mechanical manipulation. The latter measurements could be performed by recording the interactions with the correlated confocal microscopy function.
The researchers found that tension on the actin filaments enhances the binding of α-catenin, suggesting that the protein can sense myosin-induced contraction of the actin filaments. By contrast, they did not find the same contraction-dependent binding properties in the vinculin protein. Further validation through cryo-electron microscopy and protein truncation assays revealed that α-catenin’s force-detection on actin fibers resided from its distinct C-terminal extension.
Thus, measuring forces on actin filaments – which are associated with filament polymerization and architecture – paved the way to identify characteristic features of closely related actin-binding proteins.
“We propose this force-activated [fibrous] F actin binding could play an important role in the formation and reinforcement of cell-cell adhesion complexes, facilitating mechanically regulated interactions between α-catenin and actomyosin cables tuned for high sensitivity to motor-generated forces,” the authors concluded.
“Defects in mechanotransduction are associated with numerous diseases, including muscular dystrophies, cardiomyopathies, and metastatic cancer, yet therapeutics which specifically target these pathways are largely absent due to our ignorance of the mechanisms that transduce mechanical signals through the cytoskeleton,”
Congratulations to Lin Mei and all the other authors involved in this study for this exciting publication!
For more information, read the full article published in the journal eLife titled “Molecular mechanism for direct actin force-sensing by α-catenin“.