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Updated: May 13, 2026
08:02
Using Microfluidics and Fluorescence Microscopy to Study the Assembly Dynamics of Single Actin Filaments and Bundles
Published on: May 5, 2022
Electrostatics control actin filament nucleation and elongation kinetics
Alvaro H Crevenna1, Nikolaus Naredi-Rainer, André Schönichen
1AG Cellular Dynamics and Cell Patterning, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany. alvaro.crevenna@cup.uni-muenchen.de
The Journal of Biological Chemistry
|March 15, 2013
Summary
This study reveals that acidic pH enhances actin polymerization, crucial for cell movement and division. Understanding pH effects on actin dynamics is vital for cellular processes.
Area of Science:
- Biochemistry
- Cell Biology
- Biophysics
Background:
- The actin cytoskeleton is essential for cellular morphogenesis, migration, and division.
- Intracellular pH is known to regulate actin-binding proteins, but its direct effect on actin dynamics remains unclear.
Purpose of the Study:
- To comprehensively characterize the impact of pH on actin polymerization dynamics.
- To elucidate the mechanisms underlying pH-dependent actin behavior.
Main Methods:
- Utilized bulk assays, total internal reflection fluorescence microscopy, and fluorescence fluctuation spectroscopy.
- Employed theoretical modeling to analyze protein-protein interactions and electrostatics.
Main Results:
- Actin nucleation and elongation are significantly enhanced at acidic pH, peaking near actin's isoelectric point (pI).
- pH affects monomer association rates similarly at both filament ends but differentially impacts dissociation rates.
- Electrostatic interactions, driven by charge repulsion, explain the observed pH sensitivity.
Conclusions:
- Actin polymerization dynamics are sensitive to pH, with acidic conditions promoting polymerization.
- Electrostatics play a key role in modulating actin dynamics, influencing filament asymmetry.
- Cellular pH regulation is a significant factor influencing actin dynamics in vivo, as supported by Listeria propulsion studies.
Related Concept Videos
01:14Generation of Straight or Branched Actin Filaments
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...
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...
01:42Actin 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...
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...
01:19Actin 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...
In F-actin, the ADF/cofilin proteins...
01:39Mechanism 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...
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...
01:11Formation 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...
The high-order actin networks...
01:26Introduction 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.