title: Cortactin localization to sites of actin assembly in lamellipodia requires interactions with F-actin and the Arp2/3 complex.
abstract: Cortactin is an actin-binding protein that is enriched within the lamellipodia of motile cells and in neuronal growth cones. Here, we report that cortactin is localized with the actin-related protein (Arp) 2/3 complex at sites of actin polymerization within the lamellipodia. Two distinct sequence motifs of cortactin contribute to its interaction with the cortical actin network: the fourth of six tandem repeats and the amino-terminal acidic region (NTA). Cortactin variants lacking either the fourth tandem repeat or the NTA failed to localize at the cell periphery. Tandem repeat four was necessary for cortactin to stably bind F-actin in vitro. The NTA region interacts directly with the Arp2/3 complex based on affinity chromatography, immunoprecipitation assays, and binding assays using purified components. Cortactin variants containing the NTA region were inefficient at promoting Arp2/3 actin nucleation activity. These data provide strong evidence that cortactin is specifically localized to sites of dynamic cortical actin assembly via simultaneous interaction with F-actin and the Arp2/3 complex. Cortactin interacts via its Src homology 3 (SH3) domain with ZO-1 and the SHANK family of postsynaptic density 95/dlg/ZO-1 homology (PDZ) domain-containing proteins, suggesting that cortactin contributes to the spatial organization of sites of actin polymerization coupled to selected cell surface transmembrane receptor complexes.
authors.affiliation: Department of Microbiology and Cancer Center, University of Virginia Health Sciences Center, Charlottesville, Virginia 22908, USA.
authors.forename: S A
authors.initials: SA
authors.lastname: Weed
authors.forename: A V
authors.initials: AV
authors.lastname: Karginov
authors.forename: D A
authors.initials: DA
authors.lastname: Schafer
authors.forename: A M
authors.initials: AM
authors.lastname: Weaver
authors.forename: A W
authors.initials: AW
authors.lastname: Kinley
authors.forename: J A
authors.initials: JA
authors.lastname: Cooper
authors.forename: J T
authors.initials: JT
authors.lastname: Parsons
mesh_terms: D051377:Actin-Related Protein 2; D051378:Actin-Related Protein 3; D000199:Actins / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D001692:Biological Transport; D002478:Cells, Cultured; D051356:Cortactin; D003598:Cytoskeletal Proteins; D051379:Mice; D008840:Microfilament Proteins / Q000378:metabolism*; D008969:Molecular Sequence Data; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011554:Pseudopodia; D020449:Repetitive Sequences, Amino Acid; D017386:Sequence Homology, Amino Acid; D020744:rac GTP-Binding Proteins / Q000378:metabolism
chemical_list: D051377:Actin-Related Protein 2; D051378:Actin-Related Protein 3; D000199:Actins; C495927:Actr2 protein, mouse; C495929:Actr3 protein, mouse; D051356:Cortactin; C495869:Cttn protein, mouse; D003598:Cytoskeletal Proteins; D008840:Microfilament Proteins; D020744:rac GTP-Binding Proteins