Understanding Of Actin Dynamics Research Articles

A functional family of fluorescent nucleotide analogues to investigate actin dynamics and energetics

Actin polymerization provides force for vital processes of the eukaryotic cell, but our understanding of actin dynamics and energetics remains limited due to the lack of high-quality probes. Most current probes affect dynamics of actin or its interactions with actin-binding proteins (ABPs), and cannot track the bound nucleotide. Here, we identify a family of highly sensitive fluorescent nucleotide analogues structurally compatible with actin. We demonstrate that these fluorescent nucleotides bind to actin, maintain functional interactions with a number of essential ABPs, are hydrolyzed within actin filaments, and provide energy to power actin-based processes. These probes also enable monitoring actin assembly and nucleotide exchange with single-molecule microscopy and fluorescence anisotropy kinetics, therefore providing robust and highly versatile tools to study actin dynamics and functions of ABPs.

Structural Dynamics of the Actin-Binding Domains in Dystrophin and Utrophin

twisting of the filaments. In many mechanical cellular activities, such as cell movements, division, and controls of cell shape, modulation of filament stretching and twisting dynamics has been linked to regulatory actin-binding protein function. For example, mechanical stretching under tension causes structural changes in twist because of the mechanical characteristic of double helical filaments, that might prevent cofilin from binding to the actin filament. Therefore, it is important to quantitatively evaluate the stretching-twisting coupling behaviors of actin filaments for better understanding of actin dynamics. This study investigates the stretching-twisting coupling behaviors using molecular dynamics simulations. A model for the actin filament consisting of fourteen actin subunits in an ionic solvent was constructed as a minimal functional unit. To evaluate the stretching-twisting coupling behaviors, longitudinal and twisting Brownian motions of the filament were analyzed. The result demonstrated that the longitudinal and twisting motions of the filament exhibit a strong correlation, which indicate that the double-helix structure was untwisted under tensile force. The results obtained from this study contribute to the understanding of mechanochemical interactions concerning actin dynamics, showing that increased tensile force in the filament prevents actin regulatory proteins from binding to the filament.

Molecular Dynamics Analysis of Coupling Behaviors Between Extension and Torsion of Actin Filaments

Actin filaments are semi-flexible polymers that display mechanical stretching, twisting and bending motions, and have a double helical structure consisting of globular actin molecules, that induces coupling motions between stretching and twisting of the filaments. In many mechanical cellular activities, such as cell movements, division, and controls of cell shape, modulation of filament stretching and twisting dynamics has been linked to regulatory actin-binding protein function. For example, mechanical stretching under tension causes structural changes in twist because of the mechanical characteristic of double helical filaments, that might prevent cofilin from binding to the actin filament. Therefore, it is important to quantitatively evaluate the stretching-twisting coupling behaviors of actin filaments for better understanding of actin dynamics. This study investigates the stretching-twisting coupling behaviors using molecular dynamics simulations. A model for the actin filament consisting of fourteen actin subunits in an ionic solvent was constructed as a minimal functional unit. To evaluate the stretching-twisting coupling behaviors, longitudinal and twisting Brownian motions of the filament were analyzed. The result demonstrated that the longitudinal and twisting motions of the filament exhibit a strong correlation, which indicate that the double-helix structure was untwisted under tensile force. The results obtained from this study contribute to the understanding of mechanochemical interactions concerning actin dynamics, showing that increased tensile force in the filament prevents actin regulatory proteins from binding to the filament.

Signalling to actin assembly via the WASP (Wiskott-Aldrich syndrome protein)-family proteins and the Arp2/3 complex.

The assembly of a branched network of actin filaments provides the mechanical propulsion that drives a range of dynamic cellular processes, including cell motility. The Arp2/3 complex is a crucial component of such filament networks. Arp2/3 nucleates new actin filaments while bound to existing filaments, thus creating a branched network. In recent years, a number of proteins that activate the filament nucleation activity of Arp2/3 have been identified, most notably the WASP (Wiskott-Aldrich syndrome protein) family. WASP-family proteins activate the Arp2/3 complex, and consequently stimulate actin assembly, in response to extracellular signals. Structural studies have provided a significant refinement in our understanding of the molecular detail of how the Arp2/3 complex nucleates actin filaments. There has also been much progress towards an understanding of the complicated signalling processes that regulate WASP-family proteins. In addition, the use of gene disruption in a number of organisms has led to new insights into the specific functions of individual WASP-family members. The present review will discuss the Arp2/3 complex and its regulators, in particular the WASP-family proteins. Emphasis will be placed on recent developments in the field that have furthered our understanding of actin dynamics and cell motility.