lamellipodia

Cells utilize actin filaments to produce protrusive and contractile arrays that cooperate to drive cell motility.

The generation of the two arrays and the coupling between them result from the unique properties of the lamellipodium, a protrusive leaflet of cytoplasm at the cell edge.

From the lamellipodium into the lamella behind, there is a transition from a fast retrograde flow of actin polymer driven by polymerization to a slow flow driven by the interaction of anti-parallel arrays of actin with myosin.

In addition to driving protrusion, the lamellipodium appears to play a role in supplying filaments to the lamella for the assembly of the contractile network required for traction.

The protrusion of the cell membrane is fundamental to cell shape change and locomotion. Actin polymerization plays a critical role in this process. The leading edge of motile cells is dominated by thin actin-rich structures called lamellipodia, which exhibit highly dynamic behavior characterized by rapid extension and retraction.

Lamellipodia, filopodia and membrane ruffles are essential for cell motility, the organization of membrane domains, phagocytosis and the development of substrate adhesions.

Many aspects of the mechanism of lamellipodial protrusion are echoed in the intracellular motility of certain bacterial and viral pathogens, such as the bacterium Listeria monocytogenes.

Their formation relies on the regulated recruitment of molecular scaffolds to their tips (to harness and localize actin polymerization), coupled to the coordinated organization of actin filaments into lamella networks and bundled arrays.

Their turnover requires further molecular complexes for the disassembly and recycling of lamellipodium components.

See also

 WASP
 Arp2/3

References

 Mogilner A. On the edge: modeling protrusion. Curr Opin Cell Biol. 2006 Feb;18(1):32-9. PMID: 16318917

 Small JV, Resch GP. The comings and goings of actin: coupling protrusion and retraction in cell motility. Curr Opin Cell Biol. 2005 Oct;17(5):517-23. PMID: 16099152

 Vartiainen MK, Machesky LM. The WASP-Arp2/3 pathway: genetic insights. Curr Opin Cell Biol. 2004 Apr;16(2):174-81. PMID: 15196561

 Wehrle-Haller B, Imhof B. The inner lives of focal adhesions. Trends Cell Biol. 2002 Aug;12(8):382-9. PMID: 12191915

 Small JV, Stradal T, Vignal E, Rottner K. The lamellipodium: where motility begins. Trends Cell Biol. 2002 Mar;12(3):112-20. PMID: 11859023