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

Isabelle Lajoie-Mazenc,Daniel Tovar,Marie Penary,Barbara Lortal,Sophie Allart,Cyril Favard,Meryem Brihoum,Anne Pradines,Gilles Favre

doi:10.1074/jbc.m709639200

Abstract

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.

Highlights

With its close relatives RhoA and RhoC, plays a negative role in oncogenesis and may act as a tumor suppressor [3]
RhoBv14⌬4 was fused to a Gal4 DNA-binding domain (Gal4-BD) and used as a bait to screen a human brain cDNA library fused to a Gal4activating domain
A computer BLAST search in the human GenBankTM data base revealed that this cDNA sequence encoded the 241 C-terminal amino acids of microtubule-associated protein 1A (MAP1A), and corresponded to its associated light chain (LC2)

Summary

Introduction

With its close relatives RhoA and RhoC, plays a negative role in oncogenesis and may act as a tumor suppressor [3]. Active RhoB prevents intracellular trafficking of the EGF receptor between endocytic compartments [20, 34, 35] in a process that may involve PRK1 [36], the exchange factor Vav2 [33], and Dia, which controls the movement of endosomes along the actin cytoskeleton [37]. RhoB has been implicated in the intracellular trafficking of AKT [38] and in controlling the outward movement of Src to the plasma membrane [39]. Taken together, these findings highlight the important. The ability of MAP1A/LC2 to interact with RhoB provides new insights into the involvement of RhoB and the microtubule cytoskeleton in the mechanisms underlying the controlled subcellular targeting of signaling molecules

Methods

Results

Conclusion