title: Role of ßarrestins in bradykinin B2 receptor-mediated signalling.
abstract: G protein-coupled receptors (GPCRs) can engage multiple pathways to activate ERK1/2 via both G proteins and/or ßarrestin. Receptor recruitment of ßarrestin is also important for GPCR desensitization, internalization and resensitization. Modulation of the receptor/ßarrestin interaction through modification of either component would presumably alter the output generated by receptor activation. Here we examined how ßarrestins regulate bradykinin (BK) B2 receptor (B2R) signalling and desensitization by either truncating ßarrestin1 or ßarrestin2 or by alanine substitution of a serine/threonine cluster in the C-terminal tail of B2R (B2R-4A), conditions which all affect the avidity of the B2R/ßarrestin complex. We first demonstrate that BK-mediated ERK1/2 activation is biphasic containing an early peak (between 2-5min) followed by sustained activation for at least 60min. The early but not the sustained phase was predictably affected by inhibition of either Gαq/11 or Gαi/o, whereas loss of ßarrestin2 but not ßarrestin1 resulted in diminished prolonged ERK1/2 activation. ßarrestin2's role was further examined using a truncation mutant with augmented avidity for the agonist-occupied receptor, revealing an increase in both immediate and extended ERK1/2 signalling. We also show that ERK1/2 is recruited to the B2R/ßarrestin complex on endosomes as well as the plasma membrane. Moreover, we investigated ßarrestin's role using the B2R-4A, which is deficient in ßarrestin binding and does not internalize. We show that ERK1/2 signalling downstream of the receptor is entirely G protein-dependent and receptor-mediated intracellular calcium mobilization studies revealed a lack of desensitization. Functionally, the lack of desensitization resulted in increased cell growth and migration compared to the wild-type receptor, which was sensitive to MEK inhibition. These results highlight ßarrestin's crucial role in the maintenance of proper B2R signalling.
authors.affiliation: McGill University Health Center Research Institute, Department of Medicine, Royal Victoria Hospital, 687 Pine Avenue West, Montreal, Quebec, Canada.
authors.forename: Brandon
authors.initials: B
authors.lastname: Zimmerman
authors.forename: May
authors.initials: M
authors.lastname: Simaan
authors.forename: Marie-Yvonne
authors.initials: MY
authors.lastname: Akoume
authors.forename: Nadia
authors.initials: N
authors.lastname: Houri
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Chevallier
authors.forename: Philippe
authors.initials: P
authors.lastname: Séguéla
authors.forename: Stéphane A
authors.initials: SA
authors.lastname: Laporte
mesh_terms: D019390:Arrestins / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D002465:Cell Movement; D049109:Cell Proliferation; D011992:Endosomes / Q000378:metabolism; D004789:Enzyme Activation; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D019950:Mitogen-Activated Protein Kinase 1 / Q000737:chemistry / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D050505:Mutant Proteins / Q000378:metabolism; D010766:Phosphorylation; D043782:Receptor, Bradykinin B2 / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D000071557:beta-Arrestins
chemical_list: D019390:Arrestins; D050505:Mutant Proteins; D043782:Receptor, Bradykinin B2; D011993:Recombinant Fusion Proteins; D000071557:beta-Arrestins; D049452:Green Fluorescent Proteins; C535150:MAPK1 protein, human; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3