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First published online June 3, 2009
doi: 10.1242/10.1242/jcs.042325

Journal of Cell Science 122, 2108-2118 (2009)
Published by The Company of Biologists 2009
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Research Article

EFA6A encodes two isoforms with distinct biological activities in neuronal cells

Cristina Sironi1, Tambet Teesalu2, Anna Muggia1, Gabriele Fontana1, Fortunata Marino1, Sara Savaresi3 and Daniela Talarico1,*

1 Division of Genetics and Cell Biology, San Raffaele Scientific Institute, Milan, Italy
2 Vascular Mapping Center, Burnham Institute for Medical Research at University of California Santa Barbara, Santa Barbara, CA 93106, USA
3 Department of Biochemistry, University of Zürich, Winterthurer Strasse 190, 8057 Zürich, CH, Switzerland

* Author for correspondence (e-mail: talarico.daniela{at}hsr.it)

Accepted 3 March 2009

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.

Key words: EFA6A, ARF6 GEF, Cytoskeletal remodeling, Neurons, Neurite extension, Dendrite branching, Rho-GTPases


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