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Related Concept Videos

Introduction to Actin01:26

Introduction to Actin

Actin is a highly conserved cytoskeletal protein found abundantly in eukaryotic cells. It constitutes 10% weight of the total cellular protein in muscle cells, while in non-muscle cells, it is lower and makes up around 1–5 percent of the total cell protein. Actin found in the unicellular amoebae and complex multicellular animals is around 80% similar, demonstrating their conservation over a billion years of evolution.  Actin coding genes are conserved within species and across different species.
Formation of Higher-order Actin Filaments01:11

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...
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...
Structure and Function of Platelets01:18

Structure and Function of Platelets

The cell fragments known as platelets are disc-shaped, with an average diameter of about 3 μm and a thickness of roughly 1 μm. They play a crucial role in the body's vascular clotting system, which also involves plasma proteins, blood cells, and blood vessel tissues.
Platelets are continually replenished, circulating in the bloodstream for 9-12 days before being removed by phagocytes, primarily in the spleen. A microliter of circulating blood contains between 150,000 and 450,000 platelets, with...
Actin Polymerization and Cell Motility01:13

Actin Polymerization and Cell Motility

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.
Formation of the Platelet Plug01:22

Formation of the Platelet Plug

The platelet phase, the second stage of hemostasis, commences around 15-20 seconds after an injury. It follows and overlaps with the vascular phase, during which blood vessels constrict to minimize blood loss.
As the injured blood vessel contracts, endothelial cells undergo contraction, revealing collagen fibers in the basement membrane and underlying connective tissue. Furthermore, the plasma membrane of endothelial cells becomes adhesive, preparing the site for platelet adhesion. Platelets...

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Related Experiment Video

Updated: Jul 10, 2026

A Uniform Shear Assay for Human Platelet and Cell Surface Receptors via Cone-plate Viscometry
04:32

A Uniform Shear Assay for Human Platelet and Cell Surface Receptors via Cone-plate Viscometry

Published on: June 5, 2019

Studies on the actin-binding protein HS1 in platelets.

Steven G Thomas1, Simon D J Calaminus, Jocelyn M Auger

  • 1School of Biosciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK. s.thomas@bham.ac.uk

BMC Cell Biology
|November 13, 2007
PubMed
Summary

Hematopoietic stem cell protein HS1 is not essential for platelet function, including activation, shape change, and aggregation. Studies using HS1 knockout mice show normal platelet spreading and clot retraction, suggesting no major role in hemostasis.

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Actin Co-Sedimentation Assay; for the Analysis of Protein Binding to F-Actin
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An In Vitro Assay to Study Platelet Migration Using RGD-Functionalized Avidin-Biotin Tethers
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An In Vitro Assay to Study Platelet Migration Using RGD-Functionalized Avidin-Biotin Tethers

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Related Experiment Videos

Last Updated: Jul 10, 2026

A Uniform Shear Assay for Human Platelet and Cell Surface Receptors via Cone-plate Viscometry
04:32

A Uniform Shear Assay for Human Platelet and Cell Surface Receptors via Cone-plate Viscometry

Published on: June 5, 2019

Actin Co-Sedimentation Assay; for the Analysis of Protein Binding to F-Actin
07:53

Actin Co-Sedimentation Assay; for the Analysis of Protein Binding to F-Actin

Published on: March 28, 2008

An In Vitro Assay to Study Platelet Migration Using RGD-Functionalized Avidin-Biotin Tethers
05:43

An In Vitro Assay to Study Platelet Migration Using RGD-Functionalized Avidin-Biotin Tethers

Published on: November 8, 2024

Area of Science:

  • Hematology
  • Cell Biology
  • Biochemistry

Background:

  • Platelet cytoskeleton dynamics are crucial for thrombus formation and shape change upon activation.
  • The Arp2/3 complex is vital for lamellipodia formation, driven by actin polymerization.
  • Hematopoietic-specific protein HS1 and cortactin are key regulators of the Arp2/3 complex.

Purpose of the Study:

  • To investigate the role of hematopoietic-specific protein HS1 (HS1) in platelet function.
  • To utilize HS1 knockout (HS1-/-) mice to assess platelet behavior in the absence of HS1.

Main Methods:

  • Analysis of platelet activation, shape change, and aggregation in HS1-/- mice.
  • Assessment of platelet spreading on adhesion proteins.
  • Evaluation of F-actin and Arp2/3 complex distribution within platelets.
  • Measurement of clot retraction and tail bleeding times.

Main Results:

  • HS1 is not required for platelet activation, shape change, or aggregation.
  • Platelets from HS1-/- mice exhibit normal spreading, F-actin, and Arp2/3 complex distribution.
  • Clot retraction, platelet secretion, and bleeding times are unaffected in HS1-/- mice.

Conclusions:

  • HS1 does not appear to play a major role in platelet function.
  • The function of HS1 in platelets may be redundant or masked by the presence of cortactin.