title: N-WASP regulates the epithelial junctional actin cytoskeleton through a non-canonical post-nucleation pathway.
abstract: N-WASP is a major cytoskeletal regulator that stimulates Arp2/3-mediated actin nucleation. Here, we identify a nucleation-independent pathway by which N-WASP regulates the cytoskeleton and junctional integrity at the epithelial zonula adherens. N-WASP is a junctional protein whose depletion decreased junctional F-actin content and organization. However, N-WASP (also known as WASL) RNAi did not affect junctional actin nucleation, dominantly mediated by Arp2/3. Furthermore, the junctional effect of N-WASP RNAi was rescued by an N-WASP mutant that cannot directly activate Arp2/3. Instead, N-WASP stabilized newly formed actin filaments and facilitated their incorporation into apical rings at the zonula adherens. A major physiological effect of N-WASP at the zonula adherens thus occurs through a non-canonical pathway that is distinct from its capacity to activate Arp2/3. Indeed, the junctional impact of N-WASP was mediated by the WIP-family protein, WIRE, which binds to the N-WASP WH1 domain. We conclude that N-WASP-WIRE serves as an integrator that couples actin nucleation with the subsequent steps of filament stabilization and organization necessary for zonula adherens integrity.
authors.affiliation: Division of Molecular Cell Biology, Institute for Molecular Bioscience, School of Biomedical Sciences, The University of Queensland, St Lucia, Brisbane, Queensland 4072, Australia.
authors.forename: Eva M
authors.initials: EM
authors.lastname: Kovacs
authors.forename: Suzie
authors.initials: S
authors.lastname: Verma
authors.forename: Radiya G
authors.initials: RG
authors.lastname: Ali
authors.forename: Aparna
authors.initials: A
authors.lastname: Ratheesh
authors.forename: Nicholas A
authors.initials: NA
authors.lastname: Hamilton
authors.forename: Anna
authors.initials: A
authors.lastname: Akhmanova
authors.forename: Alpha S
authors.initials: AS
authors.lastname: Yap
mesh_terms: D051376:Actin-Related Protein 2-3 Complex / Q000378:metabolism; D000199:Actins / Q000378:metabolism*; D022005:Adherens Junctions / Q000378:metabolism*; D018938:Caco-2 Cells; D002352:Carrier Proteins / Q000378:metabolism; D003599:Cytoskeleton / Q000378:metabolism*; D004848:Epithelium / Q000378:metabolism; D006801:Humans; D008840:Microfilament Proteins; D009154:Mutation; D034622:RNA Interference; D051317:Wiskott-Aldrich Syndrome Protein, Neuronal / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*
chemical_list: D051376:Actin-Related Protein 2-3 Complex; D000199:Actins; D002352:Carrier Proteins; D008840:Microfilament Proteins; C495771:WASL protein, human; C465744:WIPF2 protein, human; D051317:Wiskott-Aldrich Syndrome Protein, Neuronal