Valproic acid-inducible Arl4D and cytohesin-2/ARNO, acting through the downstream Arf6, regulate neurite outgrowth in N1E-115 cells.

Abstract

The mood-stabilizing agent valproic acid (VPA) potently promotes neuronal differentiation. As yet, however, little is known about the underlying molecular mechanism. Here, we show that VPA upregulates cytohesin-2 and mediates neurite outgrowth in N1E-115 neuroblastoma cells. Cytohesin-2 is the guanine-nucleotide exchange factor (GEF) for small GTPases of the Arf family; it regulates many aspects of cellular functions including morphological changes. Treatment with the specific cytohesin family inhibitor SecinH3 or knockdown of cytohesin-2 with its siRNA results in blunted induction of neurite outgrowth in N1E-115 cells. The outgrowth is specifically inhibited by siRNA knockdown of Arf6, but not by that of Arf1. Furthermore, VPA upregulates Arl4D, an Arf-like small GTPase that has recently been identified as the regulator that binds to cytohesin-2. Arl4D knockdown displays an inhibitory effect on neurite outgrowth resulting from VPA, while expression of constitutively active Arl4D induces outgrowth. We also demonstrate that the addition of cell-permeable peptide, coupling the cytohesin-2-binding region of Arl4D into cells, reduces the effect of VPA. Thus, Arl4D is a previously unknown regulator of neurite formation through cytohesin-2 and Arf6, providing another example that the functional interaction of two different small GTPases controls an important cellular function.

• Authors: Junji Yamauchi, Yuki Miyamoto, Tomohiro Torii, Reiko Mizutani, Kazuaki Nakamura, Atsushi Sanbe, Hiroshi Koide, Shinji Kusakawa, Akito Tanoue
• Journal: Experimental cell research (Exp Cell Res) Vol. 315 Issue 12 Pg. 2043-52 (Jul 15 2009) ISSN: 1090-2422 [Electronic] United States
• PMID: 19327349 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• ADP-Ribosylation Factor 6
• Anticonvulsants
• GTPase-Activating Proteins
• SecinH3
• Triazoles
• cytohesin-2
• Valproic Acid
• ADP-Ribosylation Factors
• Arf6 protein, mouse
• Arl5a protein, mouse

Topics

• ADP-Ribosylation Factor 6
• ADP-Ribosylation Factors (biosynthesis, physiology)
• Animals
• Anticonvulsants (pharmacology)
• Cell Line
• Cell Line, Tumor
• GTPase-Activating Proteins (physiology)
• Mice
• Neurites (drug effects, physiology)
• Neurogenesis
• Triazoles (pharmacology)
• Up-Regulation
• Valproic Acid (pharmacology)