Cells "walk" through a fascinating process of controlled movement. It is not exactly walking in the way we think of it, but more like crawling.
The Cell Crawling Mechanism
The key to cell movement is a dynamic process involving these main elements:
- Actin Polymerization: The cell's leading edge extends forward due to the rapid assembly (polymerization) of actin filaments, which form a dense network.
- Cell Adhesions: This actin network interacts with the surface (substrate) through specialized cell adhesion points, allowing the cell to grip the surface.
- Force Generation: The cell applies force at its rear, which causes the rear of the cell membrane to detach from the surface, while the front pulls forward. The actin network density decreases towards the rear of the cell.
- Actin Remnants: The rear actin network remnants then undergo crashing due to this force application by the cell membrane.
Step-by-Step Cell Movement
| Step | Description |
|---|---|
| 1 | Protrusion: The cell extends its leading edge by rapidly assembling actin filaments. |
| 2 | Adhesion: The cell's extended edge attaches to the surface through adhesion points. |
| 3 | Contraction: The cell generates force at its rear, causing the cell body to be pulled towards the front. |
| 4 | Rear Detachment: The rear of the cell detaches from the surface, and the actin network remnants at the rear are broken down. |
This cycle of protrusion, adhesion, contraction, and detachment allows the cell to move across a surface.
Key Elements
- Actin Network: A meshwork of protein filaments that is critical for cell shape and movement.
- Cell Adhesions: Specialized protein complexes that anchor the cell to the substrate.
- Cell Membrane: The outer layer of the cell, which is critical for movement.
- Polymerization: The process of assembling small subunits (actin monomers) into long chains.
Summary: According to the provided reference, crawling proceeds through the protrusion of the cell's leading edge, this protrusion is driven by the polymerization of the actin network. The actin network interacts with the substrate via cell adhesions. The actin network density lessens towards the cell's rear, where the network remnants are then crushed by the cell membrane through the application of force.
