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Actin Polymerization

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...

Actin Polymerization and Cell Motility

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 Plug

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...

Actin Treadmilling

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 Filament Depolymerization

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...

Mechanism of Filopodia Formation

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 7, 2026

Live-cell Imaging of Platelet Degranulation and Secretion Under Flow

Live-cell Imaging of Platelet Degranulation and Secretion Under Flow

Published on: July 10, 2017

Actin polymerization and depolymerization in relation to platelet shape change, aggregation and disaggregation.

J R Glenn¹, P Spangenberg, S Heptinstall

¹University Hospital, Queen's Medical Centre, Nottingham, UK.

|November 4, 2010

Summary

This summary is machine-generated.

Platelets contain abundant actin, existing as G-actin and F-actin. Upon activation, platelets increase F-actin production through actin polymerization, altering cell structure.

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Area of Science:

Biochemistry
Cell Biology
Hematology

Background:

Actin is the most abundant protein in platelets, existing in globular (G-actin) and filamentous (F-actin) forms.
F-actin contributes to the platelet's membrane skeleton and cytoskeleton, maintaining cell shape.
In resting platelets, G-actin and F-actin are in equilibrium.

Purpose of the Study:

To describe the role and dynamics of actin in platelet function.
To explain the process of actin polymerization during platelet activation.

Main Methods:

Literature review on platelet actin dynamics.
Analysis of the structural roles of G-actin and F-actin.

Main Results:

Platelet activation shifts the equilibrium from G-actin to F-actin.
This shift, known as actin polymerization, involves increased F-actin production and decreased G-actin.

Conclusions:

Actin polymerization is a key event in platelet activation.
Changes in actin dynamics are crucial for platelet shape and function.