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Related Concept Videos

Actin Filament Depolymerization01:19

Actin Filament Depolymerization

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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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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...
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Mechanism of Filopodia Formation01:39

Mechanism of Filopodia Formation

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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

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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...
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Disassembly of Intermediate Filaments01:35

Disassembly of Intermediate Filaments

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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...
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Mechanism of Lamellipodia Formation01:31

Mechanism of Lamellipodia Formation

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Cells migrating in response to external stimuli form lamellipodia, which are thin membrane protrusions supported by a mesh of linked, branched, or unbranched actin filaments. These actin filaments interact with myosin motor proteins, creating the dynamic actomyosin complex within the cytoskeleton. Contractility, or the ability to generate contractile stress, is inherent to the actomyosin complex. It helps cells detect the stiffness of the surrounding ECM and exert contractile force for...
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Related Experiment Video

Updated: May 30, 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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The actin filament pointed-end depolymerase Srv2/CAP depolymerizes barbed ends, displaces capping protein, and

Ekram M Towsif1, Shashank Shekhar1

  • 1Departments of Physics, Cell Biology and Biochemistry, Emory University, Atlanta, GA 30322.

Proceedings of the National Academy of Sciences of the United States of America
|January 28, 2025
PubMed
Summary
This summary is machine-generated.

Cyclase-associated protein (CAP) unexpectedly depolymerizes actin filaments at barbed ends, not just pointed ends. This discovery reveals CAP as a crucial regulator of cellular actin dynamics, impacting filament assembly and disassembly.

Keywords:
actincapping proteincyclase-associated proteindepolymerizationformin

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Area of Science:

  • Cell Biology
  • Biochemistry
  • Biophysics

Background:

  • Cellular actin networks are essential for cell structure and function.
  • Actin filament dynamics are regulated by polymerization at barbed ends and depolymerization at pointed ends.
  • The role of proteins in barbed-end depolymerization has been less understood.

Purpose of the Study:

  • To investigate the mechanisms of actin filament depolymerization at barbed ends.
  • To determine the role of cyclase-associated protein (CAP) in barbed-end dynamics.
  • To elucidate how CAP interacts with other actin-binding proteins like formin and capping protein.

Main Methods:

  • Microfluidics-assisted three-color single-molecule imaging.
  • Quantitative analysis of actin filament dynamics.
  • In vitro reconstitution assays with purified proteins.

Main Results:

  • Cyclase-associated protein (CAP) functions as a processive depolymerase at actin filament barbed ends.
  • CAP tracks barbed ends, inducing rapid depolymerization (up to 60 subunits/sec).
  • CAP modulates barbed-end dynamics even under assembly-promoting conditions and interacts with formin and capping protein.

Conclusions:

  • Cyclase-associated protein (CAP) is a novel barbed-end depolymerase, expanding its known functions beyond pointed-end regulation.
  • CAP's dual role in filament dynamics (pointed-end and barbed-end) establishes it as a central regulator of cellular actin networks.
  • CAP's interactions with formin and capping protein highlight its complex integration into actin regulatory pathways.