Mechanism mediating plasma membrane expansion for axon outgrowth (September 12, 2012)

Throughout axon outgrowth, neurons undergo dramatic expansion of the plasma membrane. However, the molecular mechanisms mediating post-Golgi vesicular trafficking for membrane expansion and axon outgrowth remain unclear.

Associate professor Naoyuki Inagaki, D3 student Hitomi Nakazawa in the Laboratory of Neuronal Cell Morphogenesis, Graduate School of Biological Sciences, and coworkers have found that Rab33a participates in axon outgrowth by mediating plasma membrane expansion. The group found that Rab33a was preferentially localized to the Golgi apparatus and post-Golgi vesicles transported along the axonal shaft to the growth cone (axonal tip; Figure). Reduction of Rab33a expression by RNAi inhibited the anterograde transport of the vesicles, leading to their decrease in the growth cones. Furthermore, this treatment reduced membrane fusion of the vesicles at the growth cones and inhibited axon outgrowth. Overexpression of Rab33a, on the other hand, induced excessive accumulation of the vesicles and concurrent formation of surplus axons. These data suggest that Rab33a participates in axon outgrowth by mediating anterograde axonal transport of post-Golgi vesicles and their concomitant fusion at the growth cones.

【Related link】
The paper is published in the Journal below.
http://www.jneurosci.org/content/32/37/12712.abstract

Here is the bibliographic information of the paper.
Hitomi Nakazawa, Tadayuki Sada, Michinori Toriyama, Kenji Tago, Tadao Sugiura, Mitsunori Fukuda, and Naoyuki Inagaki, Rab33a mediates anterograde vesicular transport for membrane exocytosis and axon outgrowth. Journal of Neuroscience 32, 12712-12725, 2012.

An axonal growth cone (axonal tip) of a cultured hippocampal neuron. Rab33a (green) participates in axon outgrowth by mediating anterograde axonal transport of post-Golgi vesicles and their concomitant fusion at the growth cones. Red, actin filaments; blue, microtubules.
An axonal growth cone (axonal tip) of a cultured hippocampal neuron. Rab33a (green) participates in axon outgrowth by mediating anterograde axonal transport of post-Golgi vesicles and their concomitant fusion at the growth cones. Red, actin filaments; blue, microtubules.
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