Contraction speed of the actomyosin cytoskeleton in the absence of the cell membrane

Abstract

The contraction of the actomyosin cytoskeleton, which is produced by the sliding of myosin II along actin filaments, drives important cellular activities such as cytokinesis and cell migration. To explain the contraction velocities observed in such physiological processes, we have studied the contraction of intact cytoskeletons of Dictyostelium discoideum cells after removing the plasma membrane using Triton X-100. The technique developed in this work allows for the quantitative measurement of contraction rates of individual cytoskeletons. The relationship of the contraction rates with forces was analyzed using three different myosins with different in vitro sliding velocities. The cytoskeletons containing these myosins were always contractile and the contraction rate was correlated with the sliding velocity of the myosins. However, the values of the contraction rate were two to three orders of magnitude slower than expected from the in vitro sliding velocities of the myosins, presumably due to internal and external resistive forces. The contraction process also depended on actin cross-linking proteins. The lack of a-actinin increased the contraction rate 2-fold and reduced the capacity of the cytoskeleton to retain internal materials, while the lack of filamin resulted in the ATP-dependent disruption of the cytoskeleton. Interestingly, the myosin-dependent contraction rate of intact contractile rings is also reportedly much slower than the in vitro sliding velocity of myosin, and is similar to the contraction rates of cytoskeletons (different by only 2-3 fold), suggesting that the contraction of intact cells and cytoskeletons is limited by common mechanisms.

Advances in Micropipette Aspiration: Applications in Cell Biomechanics, Models, and Extended Studies

“…A simple approach, suitable for some suspended cells and taking into account the actomyosin cortex contractility, is to consider the cell mechanically equivalent to a liquid drop, its shape being determined by the cortical tension T c (38,50) produced by the actomyosin cortex (51). The equilibrium shape corresponds to spherical surfaces inside and outside the microcapillary, respectively, with radii R in and R out , and the Laplace equation is used:…”

Simple measurement of the apparent viscosity of a cell from only one picture: Application to cardiac stem cells

“…The mechanical role played by different components in the cells has been identified by studying the mechanical properties of cells subjected to different ambient conditions or after inhibiting or enhancing the activity of different proteins [15,21,22] or studying separately the internal components, in particular, the cytoskeleton [23]. Furthermore, the crucial role of mechanical cues and mechanical properties of cells in diseases has been identified in some particular cases, such as stiffening of red blood cells by malaria parasite or mechanistic influences in cancer cells [24].…”

Study of the influence of actin-binding proteins using linear analyses of cell deformability

“…Table 1 Experimental results obtained by micropipette aspiration in the present work, and by studying the contraction of cytoskeletons in the previous work by the authors, 38 and the proposed related molecular mechanisms, as explained in the discussion section…”