%0 Journal Article
%T ERK5 Activation by Gq-Coupled Muscarinic Receptors Is Independent of Receptor Internalization and ¦Â-Arrestin Recruitment
%A Guzm¨¢n S¨¢nchez-Fern¨¢ndez
%A Sof¨ªa Cabezudo
%A Carlota Garc¨ªa-Hoz
%A Andrew B. Tobin
%A Federico Mayor Jr
%A Catalina Ribas
%J PLOS ONE
%D 2013
%I Public Library of Science (PLoS)
%R 10.1371/journal.pone.0084174
%X G-protein-coupled receptors (GPCRs) are known to activate both G protein- and ¦Â-arrestin-dependent signalling cascades. The initiation of mitogen-activated protein kinase (MAPK) pathways is a key downstream event in the control of cellular functions including proliferation, differentiation, migration and apoptosis. Both G proteins and ¦Â-arrestins have been reported to mediate context-specific activation of ERK1/2, p38 and JNK MAPKs. Recently, the activation of ERK5 MAPK by Gq-coupled receptors has been described to involve a direct interaction between G¦Áq and two novel effectors, PKC¦Æ and MEK5. However, the possible contribution of ¦Â-arrestin towards this pathway has not yet been addressed. In the present work we sought to investigate the role of receptor internalization processes and ¦Â-arrestin recruitment in the activation of ERK5 by Gq-coupled GPCRs. Our results show that ERK5 activation is independent of M1 or M3 muscarinic receptor internalization. Furthermore, we demonstrate that phosphorylation-deficient muscarinic M1 and M3 receptors are still able to fully activate the ERK5 pathway, despite their reported inability to recruit ¦Â-arrestins. Indeed, the overexpression of G¦Áq, but not that of ¦Â-arrestin1 or ¦Â-arrestin2, was found to potently enhance ERK5 activation by GPCRs, whereas silencing of ¦Â-arrestin2 expression did not affect the activation of this pathway. Finally, we show that a ¦Â-arrestin-biased mutant form of angiotensin II (SII; Sar1-Ile4-Ile8 AngII) failed to promote ERK5 phosphorylation in primary cardiac fibroblasts, as compared to the natural ligand. Overall, this study shows that the activation of ERK5 MAPK by model Gq-coupled GPCRs does not depend on receptor internalization, ¦Â-arrestin recruitment or receptor phosphorylation but rather is dependent on G¦Áq-signalling.
%U http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0084174