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Filamin A, the Arp2/3 complex, and the morphology and function of cortical actin filaments in human melanoma cells

L A Flanagan1, J Chou, H Falet

  • 1Hematology Division, Brigham and Women's Hospital, Department of Medicine, Harvard Medical School, Boston, MA 02115, USA.

The Journal of Cell Biology
|November 14, 2001
PubMed

Insights

Filamin A (FLNa) is essential for cell crawling by stabilizing orthogonal actin networks. Actin branching by the Arp2/3 complex alone is insufficient for cell locomotion or leading-edge stability.

Area of Science:

  • Cell Biology
  • Biochemistry
  • Biophysics

Background:

  • Actin filaments form the cell's cytoskeleton, crucial for cell shape, movement, and mechanical stability.
  • The Arp2/3 complex and filamin A (FLNa) are key actin-binding proteins involved in regulating actin architecture.
  • Understanding the distinct roles of these proteins is vital for deciphering cellular locomotion mechanisms.

Purpose of the Study:

  • To investigate the specific roles of filamin A (FLNa) and the Arp2/3 complex in establishing cellular actin architecture.
  • To determine the contribution of FLNa to cell morphology and locomotion.
  • To clarify the necessity of FLNa-mediated actin organization for cell migration.

Main Methods:

  • Comparative morphological analysis of FLNa-deficient melanoma cells and FLNa-expressing derivatives.
  • Immunolocalization studies using antibodies specific to FLNa and the Arp2/3 complex.
  • Assessment of cell protrusion dynamics and cell crawling behavior upon serum stimulation.

Main Results:

  • FLNa-deficient cells exhibited transient flat protrusions that converted to blebs, hindering cell crawling.
  • Lamellae of FLNa-deficient cells contained dense, long actin filaments, unlike the orthogonal networks in motile FLNa-expressing cells.
  • FLNa localized at orthogonal actin filament junctions, while Arp2/3 complex staining was more diffuse.

Conclusions:

  • Filamin A is essential for stabilizing the orthogonal actin networks required for cellular locomotion.
  • Arp2/3 complex-mediated actin branching alone is insufficient for creating orthogonal actin organization or maintaining leading-edge stability.
  • FLNa plays a critical role in enabling cell migration by organizing the actin cytoskeleton.

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