Filipodium

Filipodium
Details
Function	Cell motility and sensing
Identifiers
TA98
TH	{{#property:P1694}}
TE	{{#property:P1693}}
FMA	{{#property:P1402}}
Anatomical terminology

Filipodium (plural: filipodia) are slender cytoplasmic projections that extend from the leading edge of migrating cells. They are composed primarily of actin filaments and are involved in sensing the environment, cell signaling, and cell motility. Filipodia are critical for various cellular processes, including embryonic development, wound healing, and cancer metastasis.

Structure

Filipodia are thin, spike-like protrusions that can extend several micrometers from the cell surface. They are primarily composed of parallel bundles of actin filaments, which are cross-linked by actin-binding proteins such as fascin and fimbrin. The actin filaments in filipodia are oriented with their barbed ends pointing towards the plasma membrane, facilitating rapid polymerization and extension.

Function

Filipodia serve several important functions in cells:

• Sensing the Environment: Filipodia act as sensory organelles that probe the extracellular environment. They can detect chemical gradients, mechanical cues, and other signals that guide cell movement and behavior.

• Cell Motility: By extending and retracting, filipodia help cells to move. They can anchor to the extracellular matrix or other cells, pulling the cell body forward in a process known as "filopodial crawling."

• Cell Signaling: Filipodia are involved in cell signaling pathways. They can interact with other cells and transmit signals that influence cell fate, differentiation, and proliferation.

Formation

The formation of filipodia is a complex process that involves the coordinated action of several proteins:

• Actin Polymerization: The polymerization of actin filaments is driven by proteins such as formins and the Arp2/3 complex.

• Actin-Binding Proteins: Proteins like fascin and fimbrin cross-link actin filaments into tight bundles, stabilizing the structure of filipodia.

• Regulatory Proteins: Small GTPases such as Cdc42 play a crucial role in the initiation and regulation of filipodia formation.

Clinical Significance

Filipodia are implicated in various pathological conditions:

• Cancer Metastasis: Cancer cells often exhibit increased filipodia formation, which aids in their migration and invasion into surrounding tissues.

• Developmental Disorders: Abnormal filipodia function can lead to developmental defects, as they are essential for processes like neural crest cell migration.

• Wound Healing: Filipodia are involved in the re-epithelialization of wounds, facilitating the closure of the wound by migrating epithelial cells.

Research Techniques

Several techniques are used to study filipodia:

• Live Cell Imaging: Fluorescent markers and time-lapse microscopy are used to visualize filipodia dynamics in living cells.

• Electron Microscopy: Provides detailed images of the ultrastructure of filipodia.

• Molecular Biology Techniques: Gene knockdown or overexpression studies help elucidate the roles of specific proteins in filipodia formation and function.

Also see

• Lamellipodium
• Pseudopodia
• Cell migration
• Actin cytoskeleton

Cell biology

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