The ARF-GEF ARNO and ARF6 regulate dendritic and axonal development in cultured rat hippocampal neurons

Abstract

The unique morphology of nerve cells is a key feature of the complex organization of the nervous system. Neurite extension and branching are dynamic processes that take place throughout the life of a neuron. The development of dendritic and axonal processes requires the coordination of membrane-cytoskeletal rearrangements to ensure the establishment of proper neural connections. These events are thought to be largely regulated by signaling pathways involving the Rho-family of small guanine triphosphatases (GTPases). Another family of small GTP-binding proteins, the ARF (ADP-ribosylation factor) family, has been implicated in the regulation of membrane transport and actin filament reorganization in non-neuronal cells. However, it is unknown what role ARF family members play in the modulation of these events during neurite extension and branching. Therefore, we have analyzed the role of the ARF-guanine exchange factor (GEF) ARNO (ARF-nucleotide binding site opener) in dendritic arbor development and axonal elongation and branching by overexpressing wild-type and mutant forms of ARNO and ARF6 in cultured rat hippocampal neurons. The overexpression of catalytically inactive ARNO and dominant-negative ARF6 result in increased dendritic branching as well as enhanced axonal extension and branching. Expression of inactive ARNO caused a redistribution of a subset of endosomes to the axonal plasma membrane and displacement of the profilin-binding protein Mena from the growth cone plasma membrane. These results suggest that ARNO through ARF6 negatively regulates dendritic branching and axonal elongation and branching during neural development.