Name: actin filament breakdown at cell ends
Uploaded: 2023-04-30T09:31:40.000Z
Duration: 1 min 19 s
Channel: JoVE

Actin filament disassembly is guided by proteins like Cofilin&#160; and Gelsolin through distinct mechanisms.
Cofilin, a small protein, binds in a one-on-one ratio with ADP-actin subunits at the F-actin minus-end. As a result, the F-actin twists, reducing the length of each helical turn.
The shrinking F-actin helices generate mechanical stress, increasing the rate of ATP hydrolysis, which makes the filament brittle. This, in turn, eases the release of ADP-actin monomers from the minus-end.
Gelsolin is a&#160; multidomain protein regulated by the calcium ion concentration in the cell. With the binding of calcium ions, Gelsolin undergoes a conformational change that allows it to attach to the sides of F-actin.
Upon binding to the sides of F-actin, the activated Gelsolin-calcium inserts itself between actin subunits in the filament, wedging apart the monomers to form a Gelsolin-actin complex.
As a result, the actin filament breaks into two, where one part has a Gelsolin-Calcium capped plus-end and a minus-end with rapidly dissociating ADP-actins.

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 can bind with ADP-actins in a one-to-one ratio. The actin filament twists when these proteins bind to ADP-actin, generating mechanical stress and making the filament brittle. This stress allows rapid dissociation of the cofilin bound-ADP-G-actins from the filament. The ADF/cofilin proteins are also associated with AIP-1 (actin-interacting protein1), further enhancing the dissociation rate on the minus-end.
Gelsolin is a calcium ion-activated actin-binding protein. Activated gelsolin wedges into a straight actin filament and disrupts the interactions between the actin monomers within the filament, splitting the F-actin into two. One end has a newly formed gelsolin-capped plus-end, while the other filament has a newly formed minus-end with rapidly dissociating ADP-G-actins.
The disassembly of actin filaments can also occur at branched filaments bound to the Arp2/3 complex. GMF binds to the Arp2/3 complex at the branch junction of actin networks. Upon binding, it prevents further nucleation of actin filaments from that site. GMF plays an important role in the lamellipodia formation required for cell movement and migration.

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 ...

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JoVE Core

Cell Biology

Unit 1

The Cytoskeleton I: Actin and Microfilaments

the-cytoskeleton-i-actin-and-microfilaments

KEY TERMS AND CONCEPTS

actin filament breakdown at cell ends

Actin filaments are built from actin subunits, and they can break down from either end. This process is called depolymerization. It happens faster at the minus-end, also called the pointed end, where the subunits are usually in the ADP-actin form.

Several proteins help speed up actin filament breakdown. The actin-depolymerizing factor, or ADF, and cofilin proteins bind to ADP-actin in a one-to-one ratio. When they bind, the filament twists, which creates stress and makes it brittle. That stress helps the cofilin-bound ADP-G-actins leave the filament quickly. ADF and cofilin can also work with AIP-1, or actin-interacting protein 1, which increases the dissociation rate at the minus-end.

Gelsolin is another actin-binding protein that depends on calcium ions for activation. Once activated, it wedges into a straight actin filament and disrupts the links between actin subunits. This splits the F-actin into two pieces. One end becomes a gelsolin-capped plus-end, and the other end becomes a new minus-end where ADP-G-actins dissociate rapidly.

Actin breakdown can also happen in branched filaments linked to the Arp2/3 complex. GMF, or glia maturation factor, binds to the Arp2/3 complex at the branch junction of actin networks. This blocks new actin filament formation from that site. GMF is important for lamellipodia formation, which cells need for movement and migration.

Actin Filament Breakdown at Cell Ends

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Actin filaments are built from actin subunits, and they can break down from either end. This process is called depolymerization. It happens faster at the minus-end, also called the pointed end, where the subunits are usually in the ADP-actin form. Several proteins help speed up actin filament breakdown. The actin-depolymerizing factor, or ADF, and cofilin proteins bind to ADP-actin in a one-to-one ratio. When they bind, the filament twists, which creates stress and makes it brittle. That...

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key terms and concepts

Learn how actin filaments depolymerize from the minus-end and how ADF/cofilin, gelsolin, and GMF help control filament breakdown and cell movement.

Actin Filament Breakdown at Cell Ends | JoVE K12

cell biology

JoVE Core Cell Biology illustrates complex cellular processes in easy-to-understand yet comprehensive animated video lessons. This collection focuses on the essential components and functions of cells, including organelles and membranes, cellular transport, and cell energetics. It is complemented by scientist-in-action videos that demonstrate the application of cell biology in real-world research experiments.

Actin Filament Breakdown at Cell Ends

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