Filopodium

Filopodium is a slender cytoplasmic projection that extends beyond the leading edge of lamellipodia in migrating cells. It is a type of pseudopodium that contains parallel bundles of actin filaments and is involved in cell motility, cell-to-cell interactions, and cell-to-matrix interactions.

Structure and Function

Filopodia are thin, rod-like projections from the cell surface. They are composed of parallel bundles of actin filaments, cross-linked by actin-bundling proteins such as fascin and fimbrin. The actin filaments in filopodia are oriented with their barbed (plus) ends towards the cell membrane, which is the direction of actin polymerization.

Filopodia are involved in a variety of cellular processes. They play a crucial role in cell motility by probing the cell's environment and helping to direct the movement of the cell. They are also involved in cell-to-cell interactions, such as the formation of synapses between neurons, and in cell-to-matrix interactions, which are important for cell adhesion and migration.

Formation of Filopodia

The formation of filopodia is initiated by the polymerization of actin filaments, which pushes the cell membrane outward. This process is regulated by a variety of proteins, including the Rho family of GTPases, which control actin dynamics, and the Ena/VASP proteins, which promote actin polymerization.

The tips of filopodia are often capped by proteins such as mDia2 and IRSp53, which can bind to the barbed ends of actin filaments and promote further polymerization. Other proteins, such as myosin X, are involved in the transport of these capping proteins to the tips of filopodia.

Role in Disease

Abnormalities in the formation or function of filopodia can contribute to a variety of diseases. For example, mutations in the genes encoding the proteins that regulate filopodia formation can lead to developmental disorders and cancer. In addition, filopodia play a role in the invasion of host cells by certain pathogens, such as bacteria and viruses.

See Also

• Lamellipodium
• Pseudopodium
• Actin filament
• Cell motility
• Cell adhesion

Filopodium Resources
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