Extracellular Matrix Stiffness Controls Actin Cytoskeletal Tension

Mechanical properties of the extracellular matrix (ECM) regulate cell behavior and strongly impact the cytoskeleton, yet direct measurements of actin tension across different ECM stiffnesses are lacking. Using a genetically encoded FRET-based actin tension sensor, we show that cells cultured on stiffer substrates exhibit increased spreading, reduced multicellular aggregation, and higher molecular tension within filamentous actin. Complementary measurements using an -actinin tension sensor support increased cytoskeletal mechanical loading. These results provide direct evidence that ECM stiffness modulates intracellular actin tension during mechanotransduction.