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Related Concept Videos

Formation of Higher-order Actin Filaments01:11

Formation of Higher-order Actin Filaments

2.9K
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...
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Generation of Straight or Branched Actin Filaments01:14

Generation of Straight or Branched Actin Filaments

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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...
2.9K
Mechanism of Filopodia Formation01:39

Mechanism of Filopodia Formation

2.3K
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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Actin Polymerization01:42

Actin Polymerization

6.3K
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...
6.3K
Actin Polymerization and Cell Motility01:13

Actin Polymerization and Cell Motility

5.1K
Actin is a family of globular proteins that are highly abundant in eukaryotic cells. It makes up approximately 1-5% of total cell protein concentration. Actin monomers polymerize to form a complex network of polarized filaments, the actin cytoskeleton, that plays a crucial role in many cellular processes, including cell motility, division, endocytosis, and metastasis of cancer cells.
Actin cytoskeleton dynamics can produce pushing, pulling, and resistance forces that help the cell to migrate....
5.1K
Actin Filament Depolymerization01:19

Actin Filament Depolymerization

3.0K
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...
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Updated: Jun 1, 2025

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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Fascin structural plasticity mediates flexible actin bundle construction.

Rui Gong1, Matthew J Reynolds2, Keith R Carney3,4

  • 1Laboratory of Structural Biophysics and Mechanobiology, The Rockefeller University, New York, NY, USA. rgong@rockefeller.edu.

Nature Structural & Molecular Biology
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Fascin protein forms actin filament bundles essential for cell structures. Inhibitors targeting fascin show promise for cancer therapy by blocking its F-actin cross-linking mechanism.

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Area of Science:

  • Biochemistry
  • Structural Biology
  • Cell Biology

Background:

  • Fascin is a key actin-binding protein that cross-links actin filaments (F-actin) into bundles.
  • These bundles are crucial for cellular structures like filopodia and stereocilia.
  • Dysregulation of fascin contributes to cancer metastasis, making it a therapeutic target.

Purpose of the Study:

  • To elucidate the F-actin cross-linking mechanisms of human fascin-1 at various scales.
  • To understand how fascin-1 builds and regulates actin bundles.
  • To investigate the structural basis for fascin inhibitor activity.

Main Methods:

  • Cryo-electron microscopy (cryo-EM) and cryo-electron tomography (cryo-ET).
  • Custom denoising algorithms and computational modeling.
  • Structural analysis of fascin-actin cross-bridges and filament bundles.

Main Results:

  • Determined the asymmetric F-actin binding conformation of fascin.
  • Identified that the inhibitor G2 allosterically blocks this binding site.
  • Revealed fascin's structural plasticity enables adaptation to varied F-actin orientations in bundles.
  • Uncovered geometric rules governing fascin binding patterns and bundle size limitation.

Conclusions:

  • Fascin utilizes nanoscale structural dynamics to construct and control micron-scale actin bundles.
  • Understanding fascin's mechanism provides insights into its role in cell migration and metastasis.
  • The structural findings support the development of fascin-based cancer therapeutics.