title: Cdc42 and actin control polarized expression of TI-VAMP vesicles to neuronal growth cones and their fusion with the plasma membrane.
abstract: Tetanus neurotoxin-insensitive vesicle-associated membrane protein (TI-VAMP)-mediated fusion of intracellular vesicles with the plasma membrane is crucial for neurite outgrowth, a pathway not requiring synaptobrevin-dependent exocytosis. Yet, it is not known how the TI-VAMP membrane trafficking pathway is regulated or how it is coordinated with cytoskeletal dynamics within the growth cone that guide neurite outgrowth. Here, we demonstrate that TI-VAMP, but not synaptobrevin 2, concentrates in the peripheral, F-actin-rich region of the growth cones of hippocampal neurons in primary culture. Its accumulation correlates with and depends upon the presence of F-actin. Moreover, acute stimulation of actin remodeling by homophilic activation of the adhesion molecule L1 induces a site-directed, actin-dependent recruitment of the TI-VAMP compartment. Expression of a dominant-positive mutant of Cdc42, a key regulator of cell polarity, stimulates formation of F-actin- and TI-VAMP-rich filopodia outside the growth cone. Furthermore, we report that Cdc42 activates exocytosis of pHLuorin tagged TI-VAMP in an actin-dependent manner. Collectively, our data suggest that Cdc42 and regulated assembly of the F-actin network control the accumulation and exocytosis of TI-VAMP-containing membrane vesicles in growth cones to coordinate membrane trafficking and actin remodeling during neurite outgrowth.
authors.affiliation: Membrane Traffic in Neuronal and Epithelial Morphogenesis, Institut National de la Santé et de la Recherche Médicale Avenir Team, 75005 Paris, France.
authors.forename: Philipp
authors.initials: P
authors.lastname: Alberts
authors.forename: Rachel
authors.initials: R
authors.lastname: Rudge
authors.forename: Theano
authors.initials: T
authors.lastname: Irinopoulou
authors.forename: Lydia
authors.initials: L
authors.lastname: Danglot
authors.forename: Cécile
authors.initials: C
authors.lastname: Gauthier-Rouvière
authors.forename: Thierry
authors.initials: T
authors.lastname: Galli
mesh_terms: D000199:Actins / Q000378:metabolism*; D000818:Animals; D001369:Axons / Q000378:metabolism; D019556:COS Cells; D002448:Cell Adhesion; D002462:Cell Membrane / Q000378:metabolism*; D016764:Cell Polarity; D002478:Cells, Cultured; D002522:Chlorocebus aethiops; D005089:Exocytosis; D020439:Growth Cones / Q000378:metabolism*; D008561:Membrane Fusion; D008666:Metalloendopeptidases / Q000378:metabolism; D021381:Protein Transport; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D050600:SNARE Proteins / Q000378:metabolism*; D013744:Tetanus Toxin / Q000378:metabolism; D022161:Transport Vesicles / Q000378:metabolism*; D050988:Vesicle-Associated Membrane Protein 2 / Q000378:metabolism; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism*
chemical_list: D000199:Actins; D011993:Recombinant Fusion Proteins; D050600:SNARE Proteins; D013744:Tetanus Toxin; C494706:Vamp2 protein, rat; D050988:Vesicle-Associated Membrane Protein 2; C035979:tetanospasmin; D008666:Metalloendopeptidases; D020764:cdc42 GTP-Binding Protein