Actin Network Architecture Can Determine Myosin Motor Activity

Abstract

The organization of actin filaments into higher-ordered structures governs eukaryotic cell shape and movement. Global actin network size and architecture is maintained in a dynamic steady-state through regulated assembly and disassembly. Here, we used experimentally defined actin structures in vitro to investigate how the activity of myosin motors depends on network architecture. Direct visualization of filaments revealed myosin-induced actin network deformation. During this reorganization myosins selectively contracted and disassembled anti-parallel actin structures while parallel actin bundles remained unaffected. The local distribution of nucleation sites and the resulting orientation of actin filaments appeared to regulate the scalability of the contraction process. This “orientation selection” mechanism for selective contraction and disassembly suggests how the dynamics of the cellular actin cytoskeleton can be spatially controlled by actomyosin contractility.

Coronin 1B supports RhoA signaling at cell-cell junctions through Myosin II

“…While the stability of NMII can be regulated by various factors, including its activation via RhoA kinases or the phosphorylation of its heavy-chain, 2,29 actin architecture can also play an important role in determining NMII organization and cellular contractility. 21,30 In support of this, we identify a necessary role for the actin regulator, Coronin 1B, which strengthens NMIIA localization at ZA through the organization of junctional F-actin networks into bundles. As a result, this apically stabilized NMIIA provides a cortical landmark for a feedback network that confers robustness for RhoA signaling.…”

“…7 In addition to activation by RhoA-ROCK signaling 2,19 , the junctional localization of NMIIA can also be influenced by the F-actin networks with which it associates. 20,21 Actin regulators comprise actin polymerization factors as well as regulators of F-actin architecture. Both these groups of proteins can modulate NMII localization and cortical stability by either altering cellular F-actin content or through reorganization of filament networks to facilitate the incorporation of NMII.…”

Cytoskeletal control of B cell responses to antigens

“…If myosin slides actin filaments that are structurally incompatible with contraction, the filaments buckle and break 26 . Therefore, myosin not only contracts, but also remodels the cortex 27,28 . In addition, myosin can induce flows of free actin filaments into aster-like formations 29,30 , and potentially transport proteins via co-assembly with the cargo-binding protein MYO18A 31 .…”

Separation of distinct adhesion complexes and associated cytoskeleton by a micro-stencil-printing method

“…25 The key feature is just to ink the stampcil with a specific protein of the extracellular matrix and to match the cell type so that the expected contacts can be formed. This could also work for studying adherens junctions by inking cadherins on the stampcils: it would allow us to study the interplay between focal contacts and cell-cell contacts on planar surfaces.…”