Arp2/3 complex interactions and actin network turnover in lamellipodia

• Frank PL Lai ^[1] ; Malgorzata Szczodrak ^[1] ; Jennifer Block ^[1] ; Jan Faix ^[2] ; Dennis Breitsprecher ^[2] ; Hans G Mannherz ^[5] ; Theresia EB Stradal ^[1] ; Graham A Dunn ^[3] ; J Victor Small ^[4] ; Klemens Rottner ^[1]
  1. [1] Helmholtz Centre for Infection Research

     Helmholtz Centre for Infection Research

     Kreisfreie Stadt Braunschweig, Alemania

     
  2. [2] Hannover Medical School

     Hannover Medical School

     Region Hannover, Alemania

     
  3. [3] King's College London

     King's College London

     Reino Unido

     
  4. [4] Institute of Molecular Biotechnology

     Institute of Molecular Biotechnology

     Innere Stadt, Austria

     
  5. [5] Department of Anatomy and Embryology, Ruhr University, Bochum, Germany

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• Localización: EMBO journal: European Molecular Biology Organization, ISSN 0261-4189, Vol. 27, Nº. 7, 2008, págs. 982-992
• Idioma: inglés
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  • Cell migration is initiated by lamellipodia—membrane-enclosed sheets of cytoplasm containing densely packed actin filament networks. Although the molecular details of network turnover remain obscure, recent work points towards key roles in filament nucleation for Arp2/3 complex and its activator WAVE complex. Here, we combine fluorescence recovery after photobleaching (FRAP) of different lamellipodial components with a new method of data analysis to shed light on the dynamics of actin assembly/disassembly. We show that Arp2/3 complex is incorporated into the network exclusively at the lamellipodium tip, like actin, at sites coincident with WAVE complex accumulation. Capping protein likewise showed a turnover similar to actin and Arp2/3 complex, but was confined to the tip. In contrast, cortactin—another prominent Arp2/3 complex regulator—and ADF/cofilin—previously implicated in driving both filament nucleation and disassembly—were rapidly exchanged throughout the lamellipodium. These results suggest that Arp2/3- and WAVE complex-driven actin filament nucleation at the lamellipodium tip is uncoupled from the activities of both cortactin and cofilin. Network turnover is additionally regulated by the spatially segregated activities of capping protein at the tip and cofilin throughout the mesh.