Actin Retrograde Flow in Permeabilized Cells: Myosin-II Driven Centripetal Movement of Transverse Arcs.

Numerous biological functions such as cytokinesis, changes in cell shape and cell migration require actomyosin-driven cellular contractility. However, the detailed mechanism of how contractile forces drive cellular processes are difficult to decipher due to the complexity of the intracellular environment. In particular, the mesoscopic description of the myosin II-dependent actin retrograde flow in cell lamellum is missing. Here, we describe a methodology for detergent extraction of cell, which preserves integrity of the actin cytoskeleton. This semi-in vitro cell model allows for the observation, using light microscopy, and quantification of changes in the actin cytoskeleton resulting from the activation of cellular contractility upon addition of ATP. This assay also allows for the evaluation of the effects of actin-associated proteins and other related factors in the modulation of the actin contractile activities. Here, we demonstrate the retrograde flow of a well-known actin-based structures- transverse arcs, which are myosin IIA-containing structures that emerge at the boundary between lamellipodium-lamellum and move centripetally in myosin II-dependent fashion.