Article
- The EMBO Journal (2004) 23, 749 - 759
- doi:10.1038/sj.emboj.7600084
Published online: 5 February 2004
Subject Categories:
Sra-1 and Nap1 link Rac to actin assembly driving lamellipodia formation
Anika Steffen1, Klemens Rottner1, Julia Ehinger1, Metello Innocenti2, Giorgio Scita2, Jürgen Wehland1 and Theresia EB Stradal1
- German Research Centre for Biotechnology, Department of Cell Biology, Braunschweig, Germany
- European Institute of Oncology, Department of Experimental Oncology, Milano, Italy
Correspondence to:
Theresia EB Stradal, German Research Centre for Biotechnology (GBF), Department of Cell Biology, Mascheroder Weg 1, D-38124 Braunschweig, Germany. Tel.: +49 531 6181 442; Fax: +49 531 6181 444; E-mail: ths@gbf.de
Received 15 September 2003; Accepted 18 December 2003
Abstract
The Rho-GTPase Rac1 stimulates actin remodelling at the cell periphery by relaying signals to Scar/WAVE proteins leading to activation of Arp2/3-mediated actin polymerization. Scar/WAVE proteins do not interact with Rac1 directly, but instead assemble into multiprotein complexes, which was shown to regulate their activity in vitro. However, little information is available on how these complexes function in vivo. Here we show that the specifically Rac1-associated protein-1 (Sra-1) and Nck-associated protein 1 (Nap1) interact with WAVE2 and Abi-1 (e3B1) in resting cells or upon Rac activation. Consistently, Sra-1, Nap1, WAVE2 and Abi-1 translocated to the tips of membrane protrusions after microinjection of constitutively active Rac. Moreover, removal of Sra-1 or Nap1 by RNA interference abrogated the formation of Rac-dependent lamellipodia induced by growth factor stimulation or aluminium fluoride treatment. Finally, microinjection of an activated Rac failed to restore lamellipodia protrusion in cells lacking either protein. Thus, Sra-1 and Nap1 are constitutive and essential components of a WAVE2- and Abi-1-containing complex linking Rac to site-directed actin assembly.
Keywords:
- Abi,
- lamellipodium,
- Rac,
- WAVE
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