title: Arp2/3 complex interactions and actin network turnover in lamellipodia.
abstract: 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.
authors.affiliation: Cytoskeleton Dynamics Group, Helmholtz Centre for Infection Research, Braunschweig, Germany.
authors.forename: Frank P L
authors.initials: FP
authors.lastname: Lai
authors.forename: Malgorzata
authors.initials: M
authors.lastname: Szczodrak
authors.forename: Jennifer
authors.initials: J
authors.lastname: Block
authors.forename: Jan
authors.initials: J
authors.lastname: Faix
authors.forename: Dennis
authors.initials: D
authors.lastname: Breitsprecher
authors.forename: Hans G
authors.initials: HG
authors.lastname: Mannherz
authors.forename: Theresia E B
authors.initials: TE
authors.lastname: Stradal
authors.forename: Graham A
authors.initials: GA
authors.lastname: Dunn
authors.forename: J Victor
authors.initials: JV
authors.lastname: Small
authors.forename: Klemens
authors.initials: K
authors.lastname: Rottner
mesh_terms: D051344:Actin Capping Proteins / Q000378:metabolism; D051339:Actin Depolymerizing Factors / Q000378:metabolism; D051376:Actin-Related Protein 2-3 Complex / Q000378:metabolism*; D000199:Actins / Q000378:metabolism*; D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism; D000818:Animals; D045744:Cell Line, Tumor; D051356:Cortactin / Q000378:metabolism; D036681:Fluorescence Recovery After Photobleaching; D051379:Mice; D008954:Models, Biological; D011485:Protein Binding; D011554:Pseudopodia / Q000378:metabolism*; D011817:Rabbits; D051300:Wiskott-Aldrich Syndrome Protein Family / Q000378:metabolism
chemical_list: D051344:Actin Capping Proteins; D051339:Actin Depolymerizing Factors; D051376:Actin-Related Protein 2-3 Complex; D000199:Actins; D048868:Adaptor Proteins, Signal Transducing; D051356:Cortactin; D051300:Wiskott-Aldrich Syndrome Protein Family