lamellipodium organization

Definition

Target type: biologicalprocess

A process that is carried out at the cellular level which results in the assembly, arrangement of constituent parts, or disassembly of a lamellipodium. A lamellipodium is a thin sheetlike process extended by the leading edge of a crawling fibroblast; contains a dense meshwork of actin filaments. [GOC:als, PMID:16054028]

Lamellipodium organization is a crucial process in cell motility, particularly in migrating cells such as immune cells, fibroblasts, and epithelial cells. It involves the dynamic assembly and reorganization of the actin cytoskeleton at the leading edge of the cell, forming a sheet-like structure called the lamellipodium. This structure is responsible for generating protrusive force and driving cell movement.

Here's a breakdown of the key steps involved in lamellipodium organization:

1. **Nucleation and Polymerization of Actin Filaments:**
- Actin monomers (G-actin) are added to the barbed ends of existing actin filaments (F-actin) at the leading edge. This process is facilitated by actin-nucleating proteins like Arp2/3 complex, which branches off new filaments from pre-existing ones, creating a dense network.
- Formins are another class of nucleators that promote linear growth of actin filaments.

2. **Formation of Actin Bundles:**
- Actin filaments within the lamellipodium associate with bundling proteins, such as fascin and fimbrin, which organize the filaments into parallel arrays. These bundles provide structural integrity and contribute to the protrusive force.

3. **Regulation by Signaling Pathways:**
- Cell signaling pathways, such as the Rho GTPase pathway, play a crucial role in controlling lamellipodium dynamics.
- Activation of Rac1, a Rho GTPase, promotes lamellipodium formation and extension.
- Cdc42, another Rho GTPase, influences lamellipodium shape and directionality.

4. **Membrane Protrusion and Cell Movement:**
- The polymerization of actin filaments pushes the plasma membrane forward, creating the lamellipodium.
- This protrusion, driven by actin dynamics, allows the cell to move across a surface.

5. **Adhesion and Detachment:**
- As the lamellipodium extends, integrins, transmembrane receptors, bind to extracellular matrix proteins, forming focal adhesions.
- These adhesions provide traction and allow the cell to move forward.
- The rear of the cell detaches from the substrate, facilitating continued movement.

6. **Dynamic Remodeling:**
- Lamellipodium organization is highly dynamic, with constant turnover of actin filaments and reorganization of the network.
- This dynamic nature allows the cell to adapt to changes in its environment and maintain its direction of movement.

Overall, lamellipodium organization is a complex process that relies on a delicate balance of actin dynamics, signaling pathways, and interactions with the extracellular matrix. These processes are essential for cell migration and a wide range of biological functions, including wound healing, immune responses, and development.'
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Proteins (1)

Compounds (6)