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Actin Filament Depolymerization

Actin Filament Depolymerization

Actin filaments (F-actin) are composed of actin subunits. The dissociation of actin monomers can occur from either end of F-actin. The rate of dissociation is faster from the minus-end or the pointed end, where the actin subunits exist with a bound ADP, together known as ADP-actin. The depolymerization of F-actin is aided by proteins, including the actin-depolymerizing factor (ADF) and cofilin family of proteins, gelsolin, and glia maturation factor (GMF).
In F-actin, the ADF/cofilin proteins...

Actin Treadmilling

Actin Treadmilling

Actin filaments undergo polymerization and depolymerization from either end. The polymerization and depolymerization rates depend on the cytosolic concentration of free G-actins. The polymerization rate is generally higher at the plus or barbed end, while the depolymerization rate is higher at the minus or pointed end. At a steady state, critical concentration describes the concentration of free G-actin monomers at which the polymerization rate at the plus end is equal to that of the...

Actin Polymerization

Actin Polymerization

Actin polymerization occurs through the head-to-tail association of binding sites on monomeric actin or G-actin to form filamentous or F-actin. The polymerization can be divided into three phases ̶ nucleation, elongation, and steady-state phase.
The nucleation phase involves forming a stable nucleus consisting of three actin monomers to form a new actin filament. Actin-binding proteins such as formins and Arp2/3 complex help filament growth post-nucleation. The Formins form straight actin...

Formation of Higher-order Actin Filaments

Formation of Higher-order Actin Filaments

The polymerization of G-actin monomers into filamentous F-actin is a multi-step process. Once the F-actins are formed, they can bundle together in different arrangements to form higher-order networks and regulate cellular functions. Common examples include the formation of lamellipodia and filopodia at the cell's leading edge by actin reorganization in a migrating cell. The microvilli on the brush border epithelial cells are also formed through the F-actin network.
The high-order actin networks...

Disassembly of Intermediate Filaments

Disassembly of Intermediate Filaments

Intermediate filaments (IFs) do not undergo spontaneous disassembly. Enzymes, kinases, and phosphatases add and remove phosphates from specific sites to regulate their disassembly. The IF concentration in the cytoplasm also regulates the disassembly. If the concentration crosses a threshold, it activates the protein kinases in the vicinity, allowing the phosphorylation of IFs.
Keratin proteins, found at the cell periphery near cell junctions, undergo a cycle of assembly and disassembly. In Type...

Generation of Straight or Branched Actin Filaments

Generation of Straight or Branched Actin Filaments

The straight or branched structure formation of actin filaments is controlled by nucleating proteins such as the formins and Arp2/3 complex. Formin-mediated assembly results in straight filaments, whereas Arp2/3 protein complex-mediated assembly results in branched actin filaments.
Arp2/3 Complex
Arp2/3 complex is a seven-subunit complex consisting of two proteins similar to actin- Arp2 and Arp3, and five other subunits that help keep Arp2 and Arp3 inactive. When required, the complex is...

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Related Experiment Video

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Tuning the Contractility and Deformation Modes of Active Actin-Based Assemblies In Vitro: From Two-Dimensional Active Networks to Liquid Crystal Drops

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Slow down of actin depolymerization by cross-linking molecules.

Kurt M Schmoller¹, Christine Semmrich, Andreas R Bausch

¹Lehrstuhl für Biophysik E27, Technische Universität München, Garching, Germany.

Journal of Structural Biology

|September 14, 2010

Summary

This summary is machine-generated.

Actin cross-linking proteins stabilize cellular cytoskeleton filaments, preventing rapid depolymerization. Even depolymerizing factors like cofilin are insufficient without molecular motors for highly cross-linked networks.

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Monitoring Actin Disassembly with Time-lapse Microscopy

Monitoring Actin Disassembly with Time-lapse Microscopy

Published on: November 8, 2006

Area of Science:

Cell Biology
Biophysics

Background:

Actin filaments are crucial for cellular structure and dynamics.
Mechanisms ensuring cytoskeletal filament stability are less understood than polymerization/depolymerization.
Cross-linking proteins are implicated in stabilizing actin networks.

Purpose of the Study:

To investigate the role of cross-linking and bundling proteins in actin filament stability.
To elucidate the mechanisms governing the disintegration of cross-linked actin networks.

Main Methods:

Utilized multiple depolymerization methods to study actin filament dynamics.
Investigated the effect of varying concentrations of cross-linking and bundling proteins.
Examined the combined effects of depolymerizing factors and molecular motors on actin networks.

Main Results:

Cross-linking and bundling proteins significantly suppress actin depolymerization in a concentration-dependent manner.
The actin depolymerizing factor cofilin alone cannot rapidly disintegrate highly cross-linked actin networks.
Simultaneous use of molecular motors is required for fast disintegration of highly cross-linked actin networks.

Conclusions:

Cross-linking molecules play a critical role in stabilizing actin filaments against depolymerization.
The kinetic stability of actin networks is significantly influenced by cross-linking proteins.
Understanding these interactions is vital for comprehending cytoskeleton organization and function.