Cdc42 and Actin Control Polarized Expression of TI-VAMP Vesicles to Neuronal Growth Cones and Their Fusion with the Plasma Membrane

Authors:
Alberts P, Rudge R, Eirinopoulou T, Danglot L, Gauthier-Rouviere C and Galli T
In:
Source: Mol Biol Cell
Publication Date: (2006)
Issue: 17(3): 1194-203
Research Area:
Neurobiology
Cells used in publication:
Neuron, hippo/cortical, rat
Species: rat
Tissue Origin: brain
Platform:
Nucleofector® I/II/2b
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.