article published Stefan Koestler author Anika Steffen author Maria Nemethova author 34E27F1C-F248-11E8-B48F-1D18A9856A87 Moritz Winterhoff author Ningning Luo author J. Holleboom author Jessica Krupp author Sonja Jacob author Marlene Vinzenz author Florian Schur author 48AD8942-F248-11E8-B48F-1D18A9856A870000-0003-4790-8078 Kai Schlüter author Peter Gunning author Christoph Winkler author Christian Schmeiser author Jan Faix author Theresia Stradal author John Small author Klemens Rottner author Lamellipodia are sheet-like protrusions formed during migration or phagocytosis and comprise a network of actin filaments. Filament formation in this network is initiated by nucleation/branching through the actin-related protein 2/3 (Arp2/3) complex downstream of its activator, suppressor of cAMP receptor/WASP-family verprolin homologous (Scar/WAVE), but the relative relevance of Arp2/3-mediated branching versus actin filament elongation is unknown. Here we use instantaneous interference with Arp2/3 complex function in live fibroblasts with established lamellipodia. This allows direct examination of both the fate of elongating filaments upon instantaneous suppression of Arp2/3 complex activity and the consequences of this treatment on the dynamics of other lamellipodial regulators. We show that Arp2/3 complex is an essential organizer of treadmilling actin filament arrays but has little effect on the net rate of actin filament turnover at the cell periphery. In addition, Arp2/3 complex serves as key upstream factor for the recruitment of modulators of lamellipodia formation such as capping protein or cofilin. Arp2/3 complex is thus decisive for filament organization and geometry within the network not only by generating branches and novel filament ends, but also by directing capping or severing activities to the lamellipodium. Arp2/3 complex is also crucial to lamellipodia-based migration of keratocytes. American Society for Biology2013 10.1091/mbc.E12-12-0857 24182861 - 2875 yes S. Koestler <i>et al.</i>, “Arp2/3 complex is essential for actin network treadmilling as well as for targeting of capping protein and cofilin,” <i>Molecular Biology of the Cell</i>, vol. 24, no. 18. American Society for Biology, pp. 2861–2875, 2013. Koestler S, Steffen A, Nemethova M, Winterhoff M, Luo N, Holleboom J, Krupp J, Jacob S, Vinzenz M, Schur FK, Schlüter K, Gunning P, Winkler C, Schmeiser C, Faix J, Stradal T, Small J, Rottner K. 2013. Arp2/3 complex is essential for actin network treadmilling as well as for targeting of capping protein and cofilin. Molecular Biology of the Cell. 24(18), 2861–2875. Koestler, Stefan, Anika Steffen, Maria Nemethova, Moritz Winterhoff, Ningning Luo, J. Holleboom, Jessica Krupp, et al. “Arp2/3 Complex Is Essential for Actin Network Treadmilling as Well as for Targeting of Capping Protein and Cofilin.” <i>Molecular Biology of the Cell</i>. American Society for Biology, 2013. <a href="https://doi.org/10.1091/mbc.E12-12-0857">https://doi.org/10.1091/mbc.E12-12-0857</a>. Koestler S, Steffen A, Nemethova M, et al. Arp2/3 complex is essential for actin network treadmilling as well as for targeting of capping protein and cofilin. <i>Molecular Biology of the Cell</i>. 2013;24(18):2861-2875. doi:<a href="https://doi.org/10.1091/mbc.E12-12-0857">10.1091/mbc.E12-12-0857</a> Koestler, Stefan, et al. “Arp2/3 Complex Is Essential for Actin Network Treadmilling as Well as for Targeting of Capping Protein and Cofilin.” <i>Molecular Biology of the Cell</i>, vol. 24, no. 18, American Society for Biology, 2013, pp. 2861–75, doi:<a href="https://doi.org/10.1091/mbc.E12-12-0857">10.1091/mbc.E12-12-0857</a>. S. Koestler, A. Steffen, M. Nemethova, M. Winterhoff, N. Luo, J. Holleboom, J. Krupp, S. Jacob, M. Vinzenz, F.K. Schur, K. Schlüter, P. Gunning, C. Winkler, C. Schmeiser, J. Faix, T. Stradal, J. Small, K. Rottner, Molecular Biology of the Cell 24 (2013) 2861–2875. Koestler, S., Steffen, A., Nemethova, M., Winterhoff, M., Luo, N., Holleboom, J., … Rottner, K. (2013). Arp2/3 complex is essential for actin network treadmilling as well as for targeting of capping protein and cofilin. <i>Molecular Biology of the Cell</i>. American Society for Biology. <a href="https://doi.org/10.1091/mbc.E12-12-0857">https://doi.org/10.1091/mbc.E12-12-0857</a> 8122018-12-11T11:48:38Z2021-01-12T08:17:00Z