Lamellipodium

Lamellipodium is a highly dynamic, sheet-like cell membrane extension found at the leading edge of cells during the process of cell migration. Lamellipodia are characterized by their broad, flat projections and are essential for various cellular processes, including wound healing, embryonic development, and cancer cell invasion. They play a crucial role in the actin cytoskeleton reorganization, which is vital for cell movement.

Structure and Function

Lamellipodia are composed of a dense network of actin filaments that continuously polymerize at the leading edge, pushing the cell membrane forward. This actin polymerization is regulated by a family of proteins known as nucleation-promoting factors (NPFs), which includes the Wiskott-Aldrich syndrome protein (WASP) and the WASP-family verprolin-homologous protein (WAVE) complex. The dynamic rearrangement of the actin cytoskeleton in lamellipodia is also influenced by Rho GTPases, particularly Rac1, which is a key regulator of lamellipodium extension.

Lamellipodia serve several functions in the cell, primarily facilitating cell movement by adhering to the extracellular matrix (ECM) and pulling the cell forward. This process involves the coordination of actin polymerization, membrane protrusion, and the formation of new focal adhesions at the leading edge, followed by the disassembly of adhesions at the rear end of the cell, allowing for cell translocation.

Role in Disease

Aberrant regulation of lamellipodia formation and function can contribute to disease progression, particularly in cancer. Cancer cells often exhibit increased lamellipodium activity, which enhances their migratory and invasive capabilities, aiding in metastasis. Targeting the molecular pathways that regulate lamellipodium dynamics is a potential therapeutic strategy for limiting cancer cell dissemination.

Research and Techniques

The study of lamellipodia has been greatly advanced by the development of live-cell imaging techniques, such as fluorescence microscopy, which allows for the visualization of actin dynamics and lamellipodium formation in real-time. Additionally, molecular biology techniques, including gene knockdown and overexpression studies, have been instrumental in identifying the key regulators of lamellipodium dynamics.

See Also

• Filopodium
• Cell migration
• Cytoskeleton
• Extracellular matrix