Pressure Perturbation of Actin Suprastructures

Abstract

Parts of the cytoskeleton that are composed of actin are organized into filamentous cross-linked meshworks and bundles, which facilitate numerous cellular processes like cell migration, adhesion or cellular trafficking, to name a few. Actin bundles integrated into the cytoskeleton are key components for force generation and for reinforcing the cell against mechanical stress. From in vivo studies, the filamentous actin structures have been found to be among the most pressure sensitive assemblies. Already in 1966, Ikkai and Ooi reported a strong sensitivity of cellular F-actin towards high hydrostatic pressure (HHP), which depends on the presence of ATP and divalent cations. Details about the thermodynamics and structural changes of the pressure-modulated G to F and F to G transition and HHP effects on actin suprastructures like networks and bundles are largely unknown, however. To shed more light on the stability profile of G-, F- and bundled actin, a variety of spectroscopic, microscopic and calorimetric methods was applied. The designed experiments reveal deeper insights into the structural and thermodynamic properties of these actin species over a wide range of temperatures and pressures. A complete p,T-phase diagram, complemented by species-specific thermodynamic parameters, could be obtained, leading to a deeper molecular-level understanding of G-, filamentous and bundled actin, also at extreme environmental conditions.