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First published online September 18, 2007
doi: 10.1242/10.1242/jcs.007948
Research Article |
1 Unité de Trafic Membranaire et Pathogenèse, Institut Pasteur, 75724, Paris CEDEX 15, France
2 UMR 6212 CNRS/Université Aix Marseille II, IBDML, case 907, Faculté des Sciences de Luminy, 13288, Marseille CEDEX 09, France
3 Membrane Traffic in Neuronal and Epithelial Morphogenesis, INSERM Avenir Team, 75005, Paris, France
4 Institut Jacque Monod, CNRS UMR7592, Universities Paris 6&7, 75005, Paris, France
5 Dipartimento di Biologia e Patologia Cellulare e Molecolare, Università degli Studi di Napoli Federico II, 80131 Napoli, Italy
* Author for correspondence (e-mail: zurzolo{at}pasteur.fr)
Accepted 6 July 2007
SNARE [soluble N-ethylmaleimide-sensitive factor (NSF) attachment protein (SNAP) receptor] proteins control the membrane-fusion events of eukaryotic membrane-trafficking pathways. Specific vesicular and target SNAREs operate in specific trafficking routes, but the degree of specificity of SNARE functions is still elusive. Apical fusion requires the polarized distribution at the apical surface of the t-SNARE syntaxin 3, and several v-SNAREs including TI-VAMP and VAMP8 operate at the apical plasma membrane in polarized epithelial cells. It is not known, however, whether specific v-SNAREs are involved in direct and indirect routes to the apical surface. Here, we used RNAi to assess the role of two tetanus-neurotoxin-insensitive v-SNAREs, TI-VAMP/VAMP7 and VAMP8, in the sorting of raft- and non-raft-associated apical markers that follow either a direct or a transcytotic delivery, respectively, in FRT or Caco2 cells. We show that TI-VAMP mediates the direct apical delivery of both raft- and non-raft-associated proteins. By contrast, sorting by means of the transcytotic pathway is not affected by TI-VAMP knockdown but does appear to be regulated by VAMP8. Together with the specific role of VAMP3 in basolateral transport, our results demonstrate a high degree of specificity in v-SNARE function in polarized cells.
Key words: SNAREs, TI-VAMP, VAMP8, Epithelial cells, Polarized sorting, Transcytosis
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