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Updated: Jun 28, 2026
08:02
Using Microfluidics and Fluorescence Microscopy to Study the Assembly Dynamics of Single Actin Filaments and Bundles
Published on: May 5, 2022
Formin differentially utilizes profilin isoforms to rapidly assemble actin filaments
Erin M Neidt1, Bonnie J Scott1, David R Kovar2
1Departments of Molecular Genetics and Cell Biology and Biochemistry and Molecular Biology, The University of Chicago, Chicago, Illinois 60637.
The Journal of Biological Chemistry
|November 4, 2008
Summary
Specific formin and profilin protein pairs are crucial for efficient actin polymerization. Researchers found that formin domains (FH1 and FH2) dictate which profilin isoforms are best utilized for cellular processes.
Area of Science:
- Cell biology
- Biochemistry
- Molecular dynamics
Background:
- Cells utilize formin proteins to assemble actin filaments, a process essential for various cellular functions.
- The presence of multiple formin and profilin isoforms suggests potential specificity in their interactions to regulate actin polymerization.
Purpose of the Study:
- To investigate the specific interactions between different profilin isoforms and formin proteins involved in cytokinesis.
- To determine how formin domains contribute to the selective utilization of profilin-actin.
Main Methods:
- Bulk actin polymerization assays.
- Single-filament total internal reflection fluorescence microscopy.
- Analysis of formin-profilin chimera and profilin point mutants.
Main Results:
- Fission yeast formin Cdc12p specifically utilizes the SpPRF profilin isoform.
- Nematode worm formin CYK-1 preferentially uses the essential CePFN-1 profilin isoform over non-essential ones.
- Both FH1 and FH2 domains of formins are critical for profilin isoform specificity, with FH1 domains showing preferential selection of profilin-actin.
Conclusions:
- Actin polymerization efficiency is dependent on specific formin-profilin isoform pairings.
- Formin FH1 and FH2 domains are tailored to optimally interact with specific profilin-actin complexes, ensuring precise regulation of cellular processes.
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...
01:11Formation 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...
01:19Actin 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...
01:42Actin 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...
01:39Mechanism 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...
01:26Introduction 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.