QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

Vol. 18, Issue 8, 3131-3143, August 2007

This Article Full Text Full Text (PDF) Supplemental Materials All Versions of this Article: E06-12-1101v1 18/8/3131    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Dequidt, C. Articles by Thoumine, O. Search for Related Content PubMed PubMed Citation Articles by Dequidt, C. Articles by Thoumine, O.

Fast Turnover of L1 Adhesions in Neuronal Growth Cones Involving Both Surface Diffusion and Exo/Endocytosis of L1 Molecules

Caroline Dequidt^*, Lydia Danglot, Philipp Alberts, Thierry Galli, Daniel Choquet^*, and Olivier Thoumine^*

*Unité Mixte de Recherche Centre National de la Recherche Scientifique 5091, Institut François Magendie, Université Bordeaux 2, 33077 Bordeaux, France; and Membrane Traffic in Epithelial and Neuronal Morphogenesis, Equipe Avenir Inserm, Institut Jacques Monod, Unité Mixte de Recherche Centre National de la Recherche Scientifique 7592, Universités Paris 6 et 7, 75251 Paris, France

Submitted December 13, 2006; Revised May 7, 2007; Accepted May 18, 2007
Monitoring Editor: Paul Forscher

We investigated the interplay between surface trafficking and binding dynamics of the immunoglobulin cell adhesion molecule L1 at neuronal growth cones. Primary neurons were transfected with L1 constructs bearing thrombin-cleavable green fluorescent protein (GFP), allowing visualization of newly exocytosed L1 or labeling of membrane L1 molecules by Quantum dots. Intracellular L1–GFP vesicles showed preferential centrifugal motion, whereas surface L1–GFP diffused randomly, revealing two pathways to address L1 to adhesive sites. We triggered L1 adhesions using microspheres coated with L1–Fc protein or anti-L1 antibodies, manipulated by optical tweezers. Microspheres coupled to the actin retrograde flow at the growth cone periphery while recruiting L1–GFP molecules, of which 50% relied on exocytosis. Fluorescence recovery after photobleaching experiments revealed a rapid recycling of L1–GFP molecules at L1–Fc (but not anti-L1) bead contacts, attributed to a high lability of L1–L1 bonds at equilibrium. L1–GFP molecules truncated in the intracellular tail as well as neuronal cell adhesion molecules (NrCAMs) missing the clathrin adaptor binding sequence showed both little internalization and reduced turnover rates, indicating a role of endocytosis in the recycling of mature L1 contacts at the base of the growth cone. Thus, unlike for other molecules such as NrCAM or N-cadherin, diffusion/trapping and exo/endocytosis events cooperate to allow the fast renewal of L1 adhesions.

The online version of this article contains supplemental material at MBC Online (http://www.molbiolcell.org).

Address correspondence to: Olivier Thoumine (olivier.thoumine{at}pcs.u-bordeaux2.fr).

Abbreviations used: DIV, days in vitro; DRG, dorsal root ganglion; L1–Fc, L1 extracellular domain fused to human Fc; L1–GFP, L1 fused to GFP; MSD, mean squared displacement; QD, quantum dot.

This article has been cited by other articles:

				L. Bard, C. Boscher, M. Lambert, R.-M. Mege, D. Choquet, and O. Thoumine A Molecular Clutch between the Actin Flow and N-Cadherin Adhesions Drives Growth Cone Migration J. Neurosci., June 4, 2008; 28(23): 5879 - 5890. [Abstract] [Full Text] [PDF]