The actin-related protein 2/3 (ARP2/3) complex nucleates branched actin filaments and underlies the formation of lamellipodia — sheet-like protrusions found at the leading edge of migrating cells. By generating a mouse embryonic fibroblast cell line depleted of ARP2/3, Wu et al. show that ARP2/3 and lamellipodia are essential for migration on surfaces coated with extracellular matrix (ECM) proteins (haptotaxis), but they are dispensable for chemotaxis (migration guided by soluble factors). ARP2/3-depleted cells did not form lamellipodia, had altered focal adhesion dynamics and failed to migrate on various ECM gradients. However, ARP2/3-depleted cells formed more filopodial protrusions and, surprisingly, could still respond to a soluble platelet-derived growth factor gradient, albeit more slowly. The requirement for lamellipodia in haptotaxis but not in chemotaxis suggests that cells use distinct mechanisms to respond to these different directional cues.
ORIGINAL RESEARCH PAPER
Wu, C. et al. Arp2/3 is critical for lamellipodia and response to extracellular matrix cues but is dispensable for chemotaxis. Cell 148, 973–987 (2012) Article
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Baumann, K. Chemotaxis without ARP2/3. Nat Rev Mol Cell Biol 13, 211 (2012). https://doi.org/10.1038/nrm3325
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DOI: https://doi.org/10.1038/nrm3325