GTP hydrolysis of TC10 promotes neurite outgrowth through exocytic fusion of Rab11- and L1-containing vesicles by releasing exocyst component Exo70

PLoS One. 2013 Nov 4;8(11):e79689. doi: 10.1371/journal.pone.0079689. eCollection 2013.

Abstract

The use of exocytosis for membrane expansion at nerve growth cones is critical for neurite outgrowth. TC10 is a Rho family GTPase that is essential for specific types of vesicular trafficking to the plasma membrane. Recent studies have shown that TC10 and its effector Exo70, a component of the exocyst tethering complex, contribute to neurite outgrowth. However, the molecular mechanisms of the neuritogenesis-promoting functions of TC10 remain to be established. Here, we propose that GTP hydrolysis of vesicular TC10 near the plasma membrane promotes neurite outgrowth by accelerating vesicle fusion by releasing Exo70. Using Förster resonance energy transfer (FRET)-based biosensors, we show that TC10 activity at the plasma membrane decreased at extending growth cones in hippocampal neurons and nerve growth factor (NGF)-treated PC12 cells. In neuronal cells, TC10 activity at vesicles was higher than its activity at the plasma membrane, and TC10-positive vesicles were found to fuse to the plasma membrane in NGF-treated PC12 cells. Therefore, activity of TC10 at vesicles is presumed to be inactivated near the plasma membrane during neuronal exocytosis. Our model is supported by functional evidence that constitutively active TC10 could not rescue decrease in NGF-induced neurite outgrowth induced by TC10 depletion. Furthermore, TC10 knockdown experiments and colocalization analyses confirmed the involvement of Exo70 in TC10-mediated trafficking in neuronal cells. TC10 frequently resided on vesicles containing Rab11, which is a key regulator of recycling pathways and implicated in neurite outgrowth. In growth cones, most of the vesicles containing the cell adhesion molecule L1 had TC10. Exocytosis of Rab11- and L1-positive vesicles may play a central role in TC10-mediated neurite outgrowth. The combination of this study and our previous work on the role of TC10 in EGF-induced exocytosis in HeLa cells suggests that the signaling machinery containing TC10 proposed here may be broadly used for exocytosis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Biological Transport / drug effects
  • Cell Membrane / drug effects
  • Cell Membrane / metabolism
  • Exocytosis* / drug effects
  • Growth Cones / drug effects
  • Growth Cones / metabolism
  • Guanosine Triphosphate / metabolism*
  • HeLa Cells
  • Humans
  • Hydrolysis / drug effects
  • Nerve Growth Factor / pharmacology
  • Neural Cell Adhesion Molecule L1 / metabolism*
  • Neurites / drug effects
  • Neurites / metabolism*
  • PC12 Cells
  • Rats
  • Reactive Oxygen Species / metabolism
  • Vesicular Transport Proteins / metabolism*
  • rab GTP-Binding Proteins / metabolism*
  • rac1 GTP-Binding Protein / metabolism
  • rho GTP-Binding Proteins / metabolism*

Substances

  • Exoc7 protein, rat
  • Neural Cell Adhesion Molecule L1
  • Reactive Oxygen Species
  • Vesicular Transport Proteins
  • Guanosine Triphosphate
  • Nerve Growth Factor
  • RHOQ protein, human
  • rab11 protein
  • rab GTP-Binding Proteins
  • rac1 GTP-Binding Protein
  • rho GTP-Binding Proteins

Grants and funding

This work was supported by Grants-in-Aid for Scientific Research (23300134 and 24657094) from Japan Society for the Promotion of Science (http://www.jsps.go.jp/english/index.html) and the Yamada Science Foundation (http://www.yamadazaidan.jp/english.html) to TN. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.