Regulation of dendritic development by the ARF exchange factor ARNO.

Here we analyzed the role of ARF6, a member of the ADP-ribosylation factor (ARF) family of small GTPases, in dendritic arbor development in rat hippocampal neurons in culture. Overexpression of the inactive form of the GTP exchange factor ARNO (ARF nucleotide binding site opener) or inactive ARF6 enhanced dendritic branching, whereas coexpression of either Rac1 (a member of the Rho family of small GTPases known to control dendritic dynamics and growth) or active ARF6 with inactive ARNO eliminated the enhanced branching effect. These results indicate that the ARF family of small GTPases contributes to the regulation of dendritic branching, and that ARF6 activation turns on two independent pathways that suppress dendritic branching in vivo: one through Rac1 and the other through ARF6.