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Related Concept Videos

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

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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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Mechanism of Lamellipodia Formation01:31

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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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Actin Filament Depolymerization01:19

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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).
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Actin Polymerization and Cell Motility01:13

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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....
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Formation of Higher-order Actin Filaments01:11

Formation of Higher-order Actin Filaments

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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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Related Experiment Video

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Directly Measuring Forces Within Reconstituted Active Microtubule Bundles
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Molecular Relay Stations in Membrane Nanotubes: IRSp53 Involved in Actin-Based Force Generation.

Tamás Madarász1, Brigitta Brunner2, Henriett Halász1

  • 1Department of Biophysics, Medical School, University of Pécs, H-7624 Pécs, Hungary.

International Journal of Molecular Sciences
|September 9, 2023
PubMed
Summary

Membrane nanotubes grow via actin polymerization, but long-distance force generation is unclear. IRSp53 protein acts as molecular relay stations, enabling sustained actin polymerization for nanotube elongation.

Keywords:
IRSp53actinfluorescence microscopymembrane nanotubeprotein–protein interactions

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Related Experiment Videos

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Area of Science:

  • Cell Biology
  • Biophysics

Background:

  • Membrane nanotubes are crucial cell protrusions connecting cells over micrometers.
  • Actin filament polymerization drives nanotube formation and growth, but the mechanisms for long-distance force generation remain unclear.
  • Actin bundles may be involved, but require regeneration over extended lengths.

Purpose of the Study:

  • To investigate the role of IRSp53 protein and its I-BAR domain in the formation and elongation of membrane nanotubes.
  • To explore the potential of IRSp53 in establishing molecular relay stations for actin polymerization along nanotubes.

Main Methods:

  • Studied the interactions between actin filaments and full-length IRSp53 protein.
  • Analyzed the function of the N-terminal I-BAR domain of IRSp53.

Main Results:

  • The I-BAR domain is implicated in the initial phase of cell projection formation.
  • Full-length IRSp53 is essential for the elongation of these protrusions.
  • IRSp53 binds to the nanotube membrane and nucleates actin polymerization.

Conclusions:

  • IRSp53 establishes periodic molecular relay stations along membrane nanotubes.
  • These relay stations support continuous actin polymerization, generating the force necessary for nanotube growth.