title: Regulation of cell shape by Cdc42 is mediated by the synergic actin-bundling activity of the Eps8-IRSp53 complex.
abstract: Actin-crosslinking proteins organize actin into highly dynamic and architecturally diverse subcellular scaffolds that orchestrate a variety of mechanical processes, including lamellipodial and filopodial protrusions in motile cells. How signalling pathways control and coordinate the activity of these crosslinkers is poorly defined. IRSp53, a multi-domain protein that can associate with the Rho-GTPases Rac and Cdc42, participates in these processes mainly through its amino-terminal IMD (IRSp53 and MIM domain). The isolated IMD has actin-bundling activity in vitro and is sufficient to induce filopodia in vivo. However, the manner of regulation of this activity in the full-length protein remains largely unknown. Eps8 is involved in actin dynamics through its actin barbed-ends capping activity and its ability to modulate Rac activity. Moreover, Eps8 binds to IRSp53. Here, we describe a novel actin crosslinking activity of Eps8. Additionally, Eps8 activates and synergizes with IRSp53 in mediating actin bundling in vitro, enhancing IRSp53-dependent membrane extensions in vivo. Cdc42 binds to and controls the cellular distribution of the IRSp53-Eps8 complex, supporting the existence of a Cdc42-IRSp53-Eps8 signalling pathway. Consistently, Cdc42-induced filopodia are inhibited following individual removal of either IRSp53 or Eps8. Collectively, these results support a model whereby the synergic bundling activity of the IRSp53-Eps8 complex, regulated by Cdc42, contributes to the generation of actin bundles, thus promoting filopodial protrusions.
authors.affiliation: Istituto FIRC di Oncologia Molecolare (IFOM), Via Adamello 16, 20139, Milan, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Disanza
authors.forename: Sara
authors.initials: S
authors.lastname: Mantoani
authors.forename: Maud
authors.initials: M
authors.lastname: Hertzog
authors.forename: Silke
authors.initials: S
authors.lastname: Gerboth
authors.forename: Emanuela
authors.initials: E
authors.lastname: Frittoli
authors.forename: Anika
authors.initials: A
authors.lastname: Steffen
authors.forename: Kerstin
authors.initials: K
authors.lastname: Berhoerster
authors.forename: Hans-Juergen
authors.initials: HJ
authors.lastname: Kreienkamp
authors.forename: Francesca
authors.initials: F
authors.lastname: Milanesi
authors.forename: Pier Paolo
authors.initials: PP
authors.lastname: Di Fiore
authors.forename: Andrea
authors.initials: A
authors.lastname: Ciliberto
authors.forename: Theresia E B
authors.initials: TE
authors.lastname: Stradal
authors.forename: Giorgio
authors.initials: G
authors.lastname: Scita
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism*; D000199:Actins / Q000378:metabolism*; D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D019556:COS Cells; D048430:Cell Shape; D002522:Chlorocebus aethiops; D006367:HeLa Cells; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D011485:Protein Binding; D021381:Protein Transport; D011554:Pseudopodia / Q000378:metabolism; D051300:Wiskott-Aldrich Syndrome Protein Family / Q000378:metabolism; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism*
chemical_list: D000199:Actins; D048868:Adaptor Proteins, Signal Transducing; C119539:BAIAP2 protein, human; C489989:EPS8 protein, human; D047908:Intracellular Signaling Peptides and Proteins; D009419:Nerve Tissue Proteins; D051300:Wiskott-Aldrich Syndrome Protein Family; D020764:cdc42 GTP-Binding Protein