Filamin C Modulates Cellular Mechanoresponse Through Focal Adhesion Turnover and Actin Stabilization

The study aimed to elucidate the mechanistic basis of impaired mechanosensitive pathways-YAP/TAZ and β-catenin signaling-in filamin C-deficient cells through investigation of transcriptomic profiles, actin cytoskeleton organization and focal adhesion structure. By using FlncKO-C2C12 cells and testing a number of inhibitors, we identified that mechanosensitive processes depend on filamin C function. We detected that filamin C deficiency leads to increased F/G-actin ratio and expansion of focal adhesion structures along with diminished nuclear accumulation of TAZ and β-catenin and decreased YAP/TAZ activity. Verteporfin-mediated YAP/TAZ inhibition caused adhesion enlargement and slight elevation of F/G-actin ratio in WT-C2C12 but had lower efficiency in FlncKO-C2C12. Of note, actin cytoskeletal stabilization through Jasplakinolide treatment rescued YAP/TAZ signaling specifically in filamin C-deficient cells, whereas inhibition of non-muscle myosin II with (-)Blebbistatin failed to recapitulate the signaling suppression observed in control cells. In addition, ROCK inhibition with Y-27632 demonstrated greater focal adhesion disassembly in FlncKO-C2C12 cells than in WT-C2C12 and produced a genotype-specific response, restoring β-catenin nuclear localization exclusively in FlncKO-C2C12 without affecting WT-C2C12 cells. In summary, we propose that in C2C12 muscle cells filamin C deficiency causes aberrant focal adhesion turnover and impairs actomyosin complex stabilization, which together compromise mechanosensitive pathways-YAP/TAZ and β-catenin-and affect differentiation potential of muscle cells already at the myoblast stage.