Role of different cytoskeleton filaments in the mechanical property of the cytoplasm of a live cell

The cytoplasm is the major component of live cells by volume, and its mechanical property plays a critical role in cell bioactivity, including mitosis, migration, and cargo transport. There is a constant interest in understanding the cytoplasm of a live cell from a mechanical perspective. It is known that the cytoskeleton network dominates the mechanical property of the cytoplasm. And an essential feature of the cell cytoskeleton is that the cytoskeleton is a composite of different filaments, including actin, intermediate filament, and microtubules. In this study, we combine magnetic tweezer with live cell imaging techniques to directly visualize the deformation of the cytoskeleton networks under load. And we study each filament's role during the cytoskeleton's deformation. We find the intermediate filament plays a supportive yet critical role in cytoskeleton stiffness. And the rigid microtubules and F-actin both significantly contribute to the cytoskeleton stiffness.