actin-based cell projection

Definition

Target type: cellularcomponent

A cell projection supported by an assembly of actin filaments, and which lacks microtubules. [PMID:15661519]

Actin-based cell projections are dynamic structures that extend from the cell surface, enabling a variety of cellular processes such as motility, adhesion, and signal transduction. These projections can be classified into several distinct types, each with unique structural and functional characteristics. They are all characterized by the presence of an actin cytoskeleton, which provides the structural support and driving force for their formation and movement.

The core of an actin-based cell projection consists of a bundle of actin filaments. These filaments are assembled from monomeric actin subunits, which are added to the plus end of the filament, while disassembly occurs at the minus end. The polymerization of actin filaments is regulated by a complex network of proteins, including capping proteins, nucleating factors, and cross-linking proteins. Capping proteins bind to the plus ends of actin filaments, preventing further elongation. Nucleating factors promote the formation of new actin filaments. Cross-linking proteins connect actin filaments together, providing structural integrity to the projection.

The specific composition and arrangement of actin filaments within a projection vary depending on the type of projection. For example, filopodia are thin, finger-like projections that are rich in long, parallel bundles of actin filaments. Lamellipodia are broad, sheet-like projections that contain a network of branched actin filaments. Microvilli are short, finger-like projections that are covered by a plasma membrane and contain a core of tightly packed actin filaments.

In addition to actin, a variety of other proteins are involved in the formation and function of actin-based cell projections. These proteins include:

* **Myosin:** Myosin is a motor protein that uses ATP to move along actin filaments. Myosin plays a role in the contraction of actin filaments, which is important for the movement of cell projections.
* **Adhesion proteins:** Adhesion proteins link the actin cytoskeleton to the extracellular matrix, providing a stable anchor for the projection. These proteins include integrins, cadherins, and selectins.
* **Signaling molecules:** Signaling molecules, such as Rho GTPases, regulate the assembly and disassembly of actin filaments. These molecules are activated by a variety of stimuli, including growth factors, cytokines, and extracellular matrix components.

Actin-based cell projections are highly dynamic structures that constantly remodel in response to environmental cues. Their formation and movement are tightly regulated by a complex interplay of signaling pathways, protein-protein interactions, and cytoskeletal dynamics. This dynamic nature allows cells to adapt to their surroundings, migrate, and respond to external stimuli.
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Proteins (1)

Compounds (1)