title: CIP4 coordinates with phospholipids and actin-associated proteins to localize to the protruding edge and produce actin ribs and veils.
abstract: Cdc42-interacting protein 4 (CIP4), a member of the F-BAR family of proteins, plays important roles in a variety of cellular events by regulating both membrane and actin dynamics. In many cell types, CIP4 functions in vesicle formation, endocytosis and membrane tubulation. However, recent data indicate that CIP4 is also involved in protrusion in some cell types, including cancer cells (lamellipodia and invadopodia) and neurons (ribbed lamellipodia and veils). In neurons, CIP4 localizes specifically to extending protrusions and functions to limit neurite outgrowth early in development. The mechanism by which CIP4 localizes to the protruding edge membrane and induces lamellipodial/veil protrusion and actin rib formation is not known. Here, we show that CIP4 localization to the protruding edge of neurons is dependent on both the phospholipid content of the plasma membrane and the underlying organization of actin filaments. Inhibiting phosphatidylinositol (3,4,5)-trisphosphate (PIP3) production decreases CIP4 at the membrane. CIP4 localization to the protruding edge is also dependent on Rac1/WAVE1, rather than Cdc42/N-WASP. Capping actin filaments with low concentrations of cytochalasin D or by overexpressing capping protein dramatically decreases CIP4 at the protruding edge, whereas inactivating Arp2/3 drives CIP4 to the protruding edge. We also demonstrate that CIP4 dynamically colocalizes with Ena/VASP and DAAM1, two proteins known to induce unbranched actin filament arrays and play important roles in neuronal development. Together, this is the first study to show that the localization of an F-BAR protein depends on both actin filament architecture and phospholipids at the protruding edge of developing neurons.
authors.affiliation: University of Wisconsin-Madison, Department of Neuroscience, Madison, WI 53706, USA.
authors.forename: Witchuda
authors.initials: W
authors.lastname: Saengsawang
authors.forename: Kendra L
authors.initials: KL
authors.lastname: Taylor
authors.forename: Derek C
authors.initials: DC
authors.lastname: Lumbard
authors.forename: Kelly
authors.initials: K
authors.lastname: Mitok
authors.forename: Amanda
authors.initials: A
authors.lastname: Price
authors.forename: Lauren
authors.initials: L
authors.lastname: Pietila
authors.forename: Timothy M
authors.initials: TM
authors.lastname: Gomez
authors.forename: Erik W
authors.initials: EW
authors.lastname: Dent
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism*; D051376:Actin-Related Protein 2-3 Complex / Q000378:metabolism; D000818:Animals; D015815:Cell Adhesion Molecules / Q000235:genetics / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism*; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008840:Microfilament Proteins / Q000235:genetics / Q000378:metabolism; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D015778:Minor Histocompatibility Antigens; D016501:Neurites / Q000378:metabolism*; D009479:Neuropeptides / Q000378:metabolism; D010743:Phospholipids / Q000378:metabolism; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism; D021381:Protein Transport / Q000502:physiology; D051300:Wiskott-Aldrich Syndrome Protein Family / Q000378:metabolism; D051317:Wiskott-Aldrich Syndrome Protein, Neuronal / Q000378:metabolism; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism; D020830:rac1 GTP-Binding Protein / Q000378:metabolism; D020741:rho GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism; D000098662:Vasodilator-Stimulated Phosphoprotein
chemical_list: D051376:Actin-Related Protein 2-3 Complex; D015815:Cell Adhesion Molecules; D004268:DNA-Binding Proteins; C092744:ENA-VASP proteins; D008840:Microfilament Proteins; D008869:Microtubule-Associated Proteins; D015778:Minor Histocompatibility Antigens; D009479:Neuropeptides; D010743:Phospholipids; D010750:Phosphoproteins; C484602:Rac1 protein, mouse; C485787:Trip10 protein, mouse; C495772:Wasl protein, mouse; D051300:Wiskott-Aldrich Syndrome Protein Family; D051317:Wiskott-Aldrich Syndrome Protein, Neuronal; D000098662:Vasodilator-Stimulated Phosphoprotein; C500365:Daam1 protein, mouse; D020764:cdc42 GTP-Binding Protein; D020830:rac1 GTP-Binding Protein; D020741:rho GTP-Binding Proteins
keywords: Actin polymerization; CIP4; F-BAR; Lamellipodia