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J. Biol. Chem., Vol. 283, Issue 7, 4155-4164, February 15, 2008

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MAP1A Light Chain-2 Interacts with GTP-RhoB to Control Epidermal Growth Factor (EGF)-dependent EGF Receptor Signaling^*

Isabelle Lajoie-Mazenc^¶1, Daniel Tovar^¶, Marie Penary^¶, Barbara Lortal^¶, Sophie Allart^||, Cyril Favard^**, Meryem Brihoum, Anne Pradines^¶, and Gilles Favre^¶

From the INSERM U563, Département Oncogénèse, Signalisation et Innovation Thérapeutique, Toulouse F-31059, Université Paul Sabatier, Faculté des Sciences Pharmaceutiques, Toulouse F-31059, ^¶Institut Claudius Regaud, Toulouse F-31052, ^||INSERM IFR30, Plateau Technique d'Imagerie Cellulaire, BP3028 Toulouse F-31024, and ^**CNRS UMR5089, IPBS, Toulouse F-31077, France

Rho GTPases have been implicated in the control of several cellular functions, including regulation of the actin cytoskeleton, cell proliferation, and oncogenesis. Unlike RhoA and RhoC, RhoB localizes in part to endosomes and controls endocytic trafficking. Using a yeast two-hybrid screen and a glutathione S-transferase pulldown assay, we identified LC2, the light chain of the microtubule-associated protein MAP1A, as a novel binding partner for RhoB. GTP binding and the 18-amino acid C-terminal hypervariable domain of RhoB are critical for its binding to MAP1A/LC2. Coimmunoprecipitation and immunofluorescence experiments showed that this interaction occurs in U87 cells. Down-regulation of MAP1A/LC2 expression decreased epidermal growth factor (EGF) receptor expression and modified the signaling response to EGF treatment. We concluded that MAP1A/LC2 is critical for RhoB function in EGF-induced EGF receptor regulation. Because MAP1A/LC2 is thought to function as an adaptor between microtubules and other molecules, we postulate that the RhoB and MAP1A/LC2 interactions facilitate endocytic vesicle trafficking and regulate the trafficking of signaling molecules.

Received for publication, November 27, 2007

^* This work was supported by institutional funding from INSERM, Université Paul Sabatier, Ligue Contre le Cancer, Association pour la Recherche sur le Cancer, and Groupe de Recherche de l'Institut Claudius Regaud. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

¹ To whom correspondence should be addressed: INSERM U563, Institut Claudius Regaud, F-31052 Toulouse Cedex, France. Tel.: 33-5-61-42-42-20; Fax: 33-5-61-42-46-31; E-mail: lajoie.isabelle{at}claudiusregaud.fr.

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