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Vol. 17, Issue 3, 1194-1203, March 2006
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* Membrane Traffic in Neuronal and Epithelial Morphogenesis, Institut National de la Santé et de la Recherche Médicale Avenir Team, 75005 Paris, France;
Institut Jacque Monod, Unité Mixte de Recherche 7592 Centre National de la Recherche Scientifique, Universities Paris 6 and 7, 75005 Paris, France;
Institut National de la Santé et de la Recherche Médicale U536, Institut du Fer-à-Moulin, 75005 Paris, France; and
|| "Rho GTPases, Adhesion and Skeletal Muscle," Centre de Recherches de Biochimie Macromoléculaire-Centre National de la Recherche Scientifique Formation de Recherche en Evolution 2593, 34293 Montpellier, France
Submitted July 18, 2005;
Revised December 5, 2005;
Accepted December 20, 2005
Monitoring Editor: Jennifer Lippincott-Schwartz
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.
The online version of this article contains supplemental material at MBC Online (http://www.molbiolcell.org).
Present address: Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06520.
Address correspondence to: Thierry Galli (thierry{at}tgalli.net).
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