title: ARNO and ARF6 regulate axonal elongation and branching through downstream activation of phosphatidylinositol 4-phosphate 5-kinase alpha.
abstract: In the developing nervous system, controlled neurite extension and branching are critical for the establishment of connections between neurons and their targets. Although much is known about the regulation of axonal development, many of the molecular events that regulate axonal extension remain unknown. ADP-ribosylation factor nucleotide-binding site opener (ARNO) and ADP-ribosylation factor (ARF)6 have important roles in the regulation of the cytoskeleton as well as membrane trafficking. To investigate the role of these molecules in axonogenesis, we expressed ARNO and ARF6 in cultured rat hippocampal neurons. Expression of catalytically inactive ARNO or dominant negative ARF6 resulted in enhanced axonal extension and branching and this effect was abrogated by coexpression of constitutively active ARF6. We sought to identify the downstream effectors of ARF6 during neurite extension by coexpressing phosphatidyl-inositol-4-phosphate 5-Kinase alpha [PI(4)P 5-Kinase alpha] with catalytically inactive ARNO and dominant negative ARF6. We found that PI(4)P 5-Kinase alpha plays a role in neurite extension and branching downstream of ARF6. Also, expression of inactive ARNO/ARF6 depleted the actin binding protein mammalian ena (Mena) from the growth cone leading edge, indicating that these effects on axonogenesis may be mediated by changes in cytoskeletal dynamics. These results suggest that ARNO and ARF6, through PI(4)P 5-Kinase alpha, regulate axonal elongation and branching during neuronal development.
authors.affiliation: Department of Cell Biology and Anatomy, College of Medicine, University of Arizona, Tucson, Arizona 85724, USA.
authors.forename: Delia J
authors.initials: DJ
authors.lastname: Hernández-Deviez
authors.forename: Michael G
authors.initials: MG
authors.lastname: Roth
authors.forename: James E
authors.initials: JE
authors.lastname: Casanova
authors.forename: Jean M
authors.initials: JM
authors.lastname: Wilson
mesh_terms: D000089982:ADP-Ribosylation Factor 6; D020727:ADP-Ribosylation Factors / Q000378:metabolism*; D000818:Animals; D001369:Axons / Q000378:metabolism; D002478:Cells, Cultured; D003001:Cloning, Molecular; D003599:Cytoskeleton / Q000378:metabolism*; D004622:Embryo, Mammalian / Q000378:metabolism; D005260:Female; D020690:GTPase-Activating Proteins / Q000378:metabolism*; D049452:Green Fluorescent Proteins; D006624:Hippocampus / Q000196:embryology / Q000378:metabolism*; D008164:Luminescent Proteins; D008856:Microscopy, Fluorescence; D016501:Neurites / Q000378:metabolism; D009474:Neurons / Q000378:metabolism*; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction; D020830:rac1 GTP-Binding Protein / Q000378:metabolism
chemical_list: D000089982:ADP-Ribosylation Factor 6; D020690:GTPase-Activating Proteins; D008164:Luminescent Proteins; C102474:cytohesin-2; D049452:Green Fluorescent Proteins; D017853:Phosphotransferases (Alcohol Group Acceptor); C020077:1-phosphatidylinositol-4-phosphate 5-kinase; D020727:ADP-Ribosylation Factors; C000715349:Arf6 protein, rat; D020830:rac1 GTP-Binding Protein