(The FASEB Journal. 2008;22:lb314)
© 2008 FASEB
Role of ßarrestin in the B2R-mediated ERK activation
May Simaan,
Marie-Yvonne Akoume,
Nadia Houri and
Stephane A Laporte
Medicine, McGill University, Montreal, Canada
ABSTRACT
ßarrestins are multifunctional adaptors that regulate the clathrin-dependent internalization and signalling of G protein-coupled receptors (GPCRs). We have previously reported that the bradykinin B2 receptor (B2R) forms a stable complex with ßarrestin in endosomes and recycles rapidly to the plasma membrane albeit its high avidity to ßarrestin. Several reports indicate that ßarrestins play a role in the ERK activation through G protein-independent mechanisms. The present study aims at determining the role of ßarrestin in the B2R-mediated ERK activation. We first used a B2R mutant which exhibit an increased avidity for ßarrestin and examined the kinetics of ERK activation by western Blot. This mutant showed a higher ERK activation compared to the wild-type receptor. We also tested the effect of the ßarrestin2-381T mutant, which has an increased avidity for B2R, and showed that it increased ERK activation mediated by bradykinin. In mouse embryonic fibroblasts (MEF) from βarrestin knockout mice, activation of the endogenous B2R led to a transient ERK activation. Introduction of ßarrestin to the MEF cells led to a sustained ERK activation. Finally using immunoprecipitaion assay we showed that ERK is recruited to the B2R/ßarrestin complex. These experiments show the involvement of ßarrestin in the activation of the ERKs through the B2R.
