期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2015
卷号：112
期号：37
页码：E5160-E5168
DOI：10.1073/pnas.1508836112
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：SignificanceERK1/2 are important G protein-coupled receptor (GPCR) signaling effectors, but their role as possible GPCR regulators remains largely uncharted. We report that ERK1/2 activation leads to the phosphorylation of {beta}-arrestin-2 on Ser14 and Thr276, promoting the intracellular sequestration of unliganded GPCRs. This subcellular redistribution results in the dampening of cell responsiveness to GPCRs' ligand-mediated activation, positioning ERK1/2 as both a downstream effector and a negative regulator of GPCRs. Because ERK1/2 also is stimulated by receptor tyrosine kinases and is deregulated in many diseases, and because GPCRs respond to a large number of hormones and neurotransmitters, this newly uncovered regulatory process is poised to play a central role in controlling cell responsiveness in health and disease. MAPKs are activated in response to G protein-coupled receptor (GPCR) stimulation and play essential roles in regulating cellular processes downstream of these receptors. However, very little is known about the reciprocal effect of MAPK activation on GPCRs. To investigate possible crosstalk between the MAPK and GPCRs, we assessed the effect of ERK1/2 on the activity of several GPCR family members. We found that ERK1/2 activation leads to a reduction in the steady-state cell-surface expression of many GPCRs because of their intracellular sequestration. This subcellular redistribution resulted in a global dampening of cell responsiveness, as illustrated by reduced ligand-mediated G-protein activation and second-messenger generation as well as blunted GPCR kinases and {beta}-arrestin recruitment. This ERK1/2-mediated regulatory process was observed for GPCRs that can interact with {beta}-arrestins, such as type-2 vasopressin, type-1 angiotensin, and CXC type-4 chemokine receptors, but not for the prostaglandin F receptor that cannot interact with {beta}-arrestin, implicating this scaffolding protein in the receptor's subcellular redistribution. Complementation experiments in mouse embryonic fibroblasts lacking {beta}-arrestins combined with in vitro kinase assays revealed that {beta}-arrestin-2 phosphorylation on Ser14 and Thr276 is essential for the ERK1/2-promoted GPCR sequestration. This previously unidentified regulatory mechanism was observed after constitutive activation as well as after receptor tyrosine kinase- or GPCR-mediated activation of ERK1/2, suggesting that it is a central node in the tonic regulation of cell responsiveness to GPCR stimulation, acting both as an effector and a negative regulator.
