lamellipodium assembly

Definition

Target type: biologicalprocess

Formation of a lamellipodium, a thin sheetlike extension of the surface of a migrating cell. [GOC:mah, ISBN:0815316194]

Lamellipodia are dynamic, sheet-like protrusions of the plasma membrane found in migrating cells. They are essential for cell motility, allowing cells to explore their environment, respond to stimuli, and move towards specific targets. The assembly of lamellipodia is a complex and highly regulated process involving the coordinated action of numerous proteins, including actin, myosin, and various signaling molecules.

**Initiation:** The formation of a lamellipodium typically begins with the activation of a signaling pathway, often triggered by chemoattractants or other extracellular cues. These signals activate Rho GTPases, particularly Rac and Cdc42, which in turn regulate the activity of downstream effector proteins.

**Actin Polymerization:** One of the key steps in lamellipodium assembly is the polymerization of actin filaments. Rac activates the Arp2/3 complex, a protein complex that nucleates the formation of new actin filaments. The Arp2/3 complex binds to the sides of existing filaments, creating branched networks that provide the structural basis for the lamellipodium.

**Lamellipodium Extension:** The polymerization of actin filaments at the leading edge of the cell pushes the plasma membrane forward, creating the lamellipodium. This process is aided by the activity of myosin II, which generates contractile forces that help to shape and stabilize the lamellipodium.

**Membrane Recycling:** The extension of the lamellipodium requires the delivery of new membrane components to the leading edge. This is achieved through the recycling of endocytic vesicles, which fuse with the plasma membrane, adding new lipids and proteins.

**Adhesion and Traction:** As the lamellipodium extends, it encounters the extracellular matrix (ECM). Cell adhesion molecules, such as integrins, bind to ECM components, providing a foothold for the cell. This adhesion generates traction forces that pull the cell forward.

**Retraction:** The lamellipodium is a dynamic structure that constantly undergoes cycles of extension and retraction. Retraction occurs when the actin filaments are depolymerized, and the membrane is recycled.

**Regulation:** The assembly and disassembly of lamellipodia are tightly regulated by a variety of signaling pathways and feedback mechanisms. These mechanisms ensure that lamellipodia are formed in response to appropriate stimuli and that their size and shape are appropriate for the cell's needs.

The assembly of lamellipodia is a complex and dynamic process that is essential for cell migration. Understanding this process is crucial for elucidating the mechanisms of development, wound healing, and immune responses.'
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Proteins (6)

Compounds (218)