Cytoskeleton Dynamics

What are lamellipodia and lamella?

The lamellipodia and lamella are plate-like extensions of the cell that play crucial roles in both cell motility and migration, and mechanosensing. These structures form and function over distinct steps.

Lamellipodia are thin, sheet-like membrane protrusions found at the leading edge (front) of motile cells such as endothelial cells, neurons, immune cells and epithelial cells. These structures are generally devoid of major organelles and are instead composed of a dense and dynamic network of actin filaments. The forces generated by actin filament assembly at the leading edge induce membrane protrusion and subsequent lamellipodial growth. This has been extensively reviewed in [1][2][3][4][5].

The lamellum or lamella (LM; plural lamellae) localizes behind the lamellipodium and is usually the broadest structure in motile cells (typically 10-15 µm wide). Consisting primarily of condensed linear actin bundles, the actin filament network of the lamella is more stable and less dynamic than that of lamellipodia [6] and may also resist compression. Lamellae feature stronger and more mature adhesion sites (reviewed in [7]) and also contain myosin II, a motor protein that is essential in cell motility.

References

1. Theriot JA, and Mitchison TJ. Actin microfilament dynamics in locomoting cells. Nature 1991; 352(6331):126-31. [PMID: 2067574]
2. Mitchison TJ, and Cramer LP. Actin-based cell motility and cell locomotion. Cell 1996; 84(3):371-9. [PMID: 8608590]
3. Carlier M, Le Clainche C, Wiesner S, and Pantaloni D. Actin-based motility: from molecules to movement. Bioessays 2003; 25(4):336-45. [PMID: 12655641]
4. Pollard TD, and Borisy GG. Cellular motility driven by assembly and disassembly of actin filaments. Cell 2003; 112(4):453-65. [PMID: 12600310]
5. Le Clainche C, and Carlier M. Regulation of actin assembly associated with protrusion and adhesion in cell migration. Physiol. Rev. 2008; 88(2):489-513. [PMID: 18391171]
6. Ponti A, Machacek M, Gupton SL, Waterman-Storer CM, and Danuser G. Two distinct actin networks drive the protrusion of migrating cells. Science 2004; 305(5691):1782-6. [PMID: 15375270]
7. Geiger B, Spatz JP, and Bershadsky AD. Environmental sensing through focal adhesions. Nat. Rev. Mol. Cell Biol. 2009; 10(1):21-33. [PMID: 19197329]