“…Actin networks must dynamically change their configurations to generate the forces needed within cells for many of their essential biological processes 1 , 3 – 5 , 7 , 10 – 16 . The ability of proteins to bend individual or groups of linear actin filaments is emerging as an important contributor to the dynamic regulation of higher-order actin assemblies required for cellular processes such as the formation of an actin ring, cell migration, and endocytosis 48 , 72 , 73 , 112 , 113 . Bending actin filaments directly regulates actin network geometries, provides directional actin branching for ABP binding (i.e., Arp2/3 prefers binding to the convex side of actin filaments 38 ), provides regions for more efficient severing 54 , and can be used to generate force by unbending.…”
In many cellular contexts, intracellular actomyosin networks must generate directional forces to carry out cellular tasks such as migration and endocytosis, which play important roles during normal developmental processes. A number of different actin binding proteins have been identified that form linear or branched actin, and that regulate these filaments through activities such as bundling, crosslinking, and depolymerization to create a wide variety of functional actin assemblies. The helical nature of actin filaments allows them to better accommodate tensile stresses by untwisting, as well as to bend to great curvatures without breaking. Interestingly, this latter property, the bending of actin filaments, is emerging as an exciting new feature for determining dynamic actin configurations and functions. Indeed, recent studies using
in vitro
assays have found that proteins including IQGAP, Cofilin, Septins, Anillin, α-Actinin, Fascin, and Myosins—alone or in combination—can influence the bending or curvature of actin filaments. This bending increases the number and types of dynamic assemblies that can be generated, as well as the spectrum of their functions. Intriguingly, in some cases, actin bending creates directionality within a cell, resulting in a chiral cell shape. This actin-dependent cell chirality is highly conserved in vertebrates and invertebrates and is essential for cell migration and breaking L-R symmetry of tissues/organs. Here, we review how different types of actin binding protein can bend actin filaments, induce curved filament geometries, and how they impact on cellular functions.
“…Actin networks must dynamically change their configurations to generate the forces needed within cells for many of their essential biological processes 1 , 3 – 5 , 7 , 10 – 16 . The ability of proteins to bend individual or groups of linear actin filaments is emerging as an important contributor to the dynamic regulation of higher-order actin assemblies required for cellular processes such as the formation of an actin ring, cell migration, and endocytosis 48 , 72 , 73 , 112 , 113 . Bending actin filaments directly regulates actin network geometries, provides directional actin branching for ABP binding (i.e., Arp2/3 prefers binding to the convex side of actin filaments 38 ), provides regions for more efficient severing 54 , and can be used to generate force by unbending.…”
In many cellular contexts, intracellular actomyosin networks must generate directional forces to carry out cellular tasks such as migration and endocytosis, which play important roles during normal developmental processes. A number of different actin binding proteins have been identified that form linear or branched actin, and that regulate these filaments through activities such as bundling, crosslinking, and depolymerization to create a wide variety of functional actin assemblies. The helical nature of actin filaments allows them to better accommodate tensile stresses by untwisting, as well as to bend to great curvatures without breaking. Interestingly, this latter property, the bending of actin filaments, is emerging as an exciting new feature for determining dynamic actin configurations and functions. Indeed, recent studies using
in vitro
assays have found that proteins including IQGAP, Cofilin, Septins, Anillin, α-Actinin, Fascin, and Myosins—alone or in combination—can influence the bending or curvature of actin filaments. This bending increases the number and types of dynamic assemblies that can be generated, as well as the spectrum of their functions. Intriguingly, in some cases, actin bending creates directionality within a cell, resulting in a chiral cell shape. This actin-dependent cell chirality is highly conserved in vertebrates and invertebrates and is essential for cell migration and breaking L-R symmetry of tissues/organs. Here, we review how different types of actin binding protein can bend actin filaments, induce curved filament geometries, and how they impact on cellular functions.
“…Our prediction is supported by the high-resolution experimental images showing that filaments in migrating lamellipodia branch in several successive generations 7 , 11 , 36 . Because the Arp2/3 complex prefers to bind on bent filaments 34 , 52 and thus the branched actin network can regulate its successive branches to adapt for cell migration, the low number of successive branching generations in experiment 13 might be observed from cells that were not in an active migration state. Fig.…”
Branched actin network supports cell migration through extracellular microenvironments. However, it is unknown how intracellular proteins adapt the elastic properties of the network to the highly varying extracellular resistance. Here we develop a three-dimensional assembling model to simulate the realistic self-assembling process of the network by encompassing intracellular proteins and their dynamic interactions. Combining this multiscale model with finite element method, we reveal that the network can not only sense the variation of extracellular resistance but also self-adapt its elastic properties through remodeling with intracellular proteins. Such resistance-adaptive elastic behaviours are versatile and essential in supporting cell migration through varying extracellular microenvironments. The bending deformation mechanism and anisotropic Poisson’s ratios determine why lamellipodia persistently evolve into sheet-like structures. Our predictions are confirmed by published experiments. The revealed self-adaptive elastic properties of the networks are also applicable to the endocytosis, phagocytosis, vesicle trafficking, intracellular pathogen transport and dendritic spine formation.
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