title: EFA6A encodes two isoforms with distinct biological activities in neuronal cells.
abstract: The processes of neurite extension and remodeling require a close coordination between the cytoskeleton and the cell membranes. The small GTPase ARF6 (ADP-ribosylation factor 6) has a central role in regulating membrane traffic and actin dynamics, and its activity has been demonstrated to be involved in neurite elaboration. EFA6A has been shown to act as a guanine nucleotide exchange factor (GEF) for ARF6. Here, we report that two distinct isoforms of the EFA6A gene are expressed in murine neural tissue: a long isoform of 1025 amino acids (EFA6A), and a short isoform of 393 amino acids (EFA6As). EFA6A encompasses proline-rich regions, a Sec7 domain (mediating GEF activity on ARF6), a PH domain, and a C-terminal region with coiled-coil motifs. EFA6As lacks the Sec7 domain, and it comprises the PH domain and the C-terminal region. The transcript encoding EFA6As is the result of alternative promoter usage. EFA6A and EFA6As have distinct biological activities: upon overexpression in HeLa cells, EFA6A induces membrane ruffles, whereas EFA6As gives rise to cell elongation; in primary cortical neurons EFA6A promotes neurite extension, whereas EFA6As induces dendrite branching. Our findings suggest that EFA6A could participate in neuronal morphogenesis through the regulated expression of two functionally distinct isoforms.
authors.affiliation: Division of Genetics and Cell Biology, San Raffaele Scientific Institute, Milan, Italy.
authors.forename: Cristina
authors.initials: C
authors.lastname: Sironi
authors.forename: Tambet
authors.initials: T
authors.lastname: Teesalu
authors.forename: Anna
authors.initials: A
authors.lastname: Muggia
authors.forename: Gabriele
authors.initials: G
authors.lastname: Fontana
authors.forename: Fortunata
authors.initials: F
authors.lastname: Marino
authors.forename: Sara
authors.initials: S
authors.lastname: Savaresi
authors.forename: Daniela
authors.initials: D
authors.lastname: Talarico
mesh_terms: D000089982:ADP-Ribosylation Factor 6; D000818:Animals; D001921:Brain / Q000196:embryology / Q000378:metabolism; D002478:Cells, Cultured; D003001:Cloning, Molecular; D003599:Cytoskeleton / Q000235:genetics / Q000378:metabolism; D004622:Embryo, Mammalian; D018507:Gene Expression Regulation, Developmental; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics* / Q000378:metabolism / Q000502:physiology*; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D016501:Neurites / Q000378:metabolism / Q000502:physiology; D009474:Neurons / Q000378:metabolism / Q000502:physiology*; D016716:PC12 Cells; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D051381:Rats
chemical_list: D000089982:ADP-Ribosylation Factor 6; D020662:Guanine Nucleotide Exchange Factors; D020033:Protein Isoforms; C504475:Psd protein, rat; C000715348:ARF6 protein, human; C000715727:Arf6 protein, mouse; C000715349:Arf6 protein, rat