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Related Concept Videos

Actin Filament Depolymerization01:19

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...
Adaptability of Cytoskeletal Filaments01:12

Adaptability of Cytoskeletal Filaments

The cytoskeleton is a complex dynamic structure performing varied functions based on cellular requirements. The adaptability of the individual filaments in the cytoskeleton determines their ability to perform various functions within the cell. It can undergo rapid reorganization during processes like cell division or remain stable for several hours as in the interphase. The adaptability of these filaments depends on stringent regulatory mechanisms. The microfilament and microtubules of the...
Actin Treadmilling01:18

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 Polymerization01:42

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...
Generation of Straight or Branched Actin Filaments01:14

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...
Mechanism of Filopodia Formation01:39

Mechanism of Filopodia Formation

Filopodia are thin, actin-rich cellular protrusions that play an important role in many fundamental cellular functions. They vary in their occurrence, length, and positioning in different cell types, suggesting their diverse roles.
Their main function is to guide migrating cells during normal tissue morphogenesis or cancer metastasis by recognizing and making initial contacts with the extracellular matrix. However, they can also act as stationary cell anchors or help to establish communication...

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Related Experiment Video

Updated: Jun 28, 2026

Tuning the Contractility and Deformation Modes of Active Actin-Based Assemblies In Vitro: From Two-Dimensional Active Networks to Liquid Crystal Drops
06:48

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

Published on: July 11, 2025

Dynamic stabilization of actin filaments.

Hao Yuan Kueh1, William M Brieher, Timothy J Mitchison

  • 1Department of Systems Biology, Harvard Medical School, 200 Longwood Avenue, Boston, MA 02115, USA.

Proceedings of the National Academy of Sciences of the United States of America
|October 22, 2008
PubMed
Summary

Actin filaments exhibit two distinct shrinkage rates: rapid for new filaments and slow for aged ones. Cofilin treatment accelerates shrinkage, suggesting structural plasticity regulates actin dynamics.

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Using Microfluidics and Fluorescence Microscopy to Study the Assembly Dynamics of Single Actin Filaments and Bundles
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Using Microfluidics and Fluorescence Microscopy to Study the Assembly Dynamics of Single Actin Filaments and Bundles

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Reconstitution of Actin-Based Motility with Commercially Available Proteins
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Reconstitution of Actin-Based Motility with Commercially Available Proteins

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Related Experiment Videos

Last Updated: Jun 28, 2026

Tuning the Contractility and Deformation Modes of Active Actin-Based Assemblies In Vitro: From Two-Dimensional Active Networks to Liquid Crystal Drops
06:48

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

Published on: July 11, 2025

Using Microfluidics and Fluorescence Microscopy to Study the Assembly Dynamics of Single Actin Filaments and Bundles
08:02

Using Microfluidics and Fluorescence Microscopy to Study the Assembly Dynamics of Single Actin Filaments and Bundles

Published on: May 5, 2022

Reconstitution of Actin-Based Motility with Commercially Available Proteins
08:40

Reconstitution of Actin-Based Motility with Commercially Available Proteins

Published on: October 28, 2022

Area of Science:

  • Biochemistry
  • Cell Biology
  • Biophysics

Background:

  • Actin filaments are crucial cytoskeletal components.
  • Their dynamics are tightly regulated for cellular functions.
  • Aging actin filaments were predicted to become less stable.

Purpose of the Study:

  • To investigate the aging process of actin filaments in vitro.
  • To characterize the distinct shrinkage dynamics of actin filament populations.
  • To explore the role of structural rearrangements in actin filament stability.

Main Methods:

  • In vitro polymerization and depolymerization assays.
  • Measurement of filament shrinkage rates.
  • Treatment with cofilin to assess its effect on filament stability.

Main Results:

  • Two actin filament populations were identified with significantly different shrinkage rates: rapid (1.8/s) for newly polymerized and slow (0.1/s) for aged filaments.
  • Aged filaments, contrary to predictions, showed increased stability.
  • Cofilin treatment induced rapid shrinkage (5.9/s) from both filament ends, reverting aged filaments to a dynamic state.

Conclusions:

  • Actin filament stabilization with age is attributed to structural rearrangement from a disordered to a canonical Holmes helix structure.
  • Cofilin binding reverses this stabilization by disrupting the ordered structure.
  • Internal structural plasticity of actin filaments is fundamental for regulating actin dynamics and assembly turnover rates.