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：49
页码：E6818-E6824
DOI：10.1073/pnas.1519430112
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：SignificanceG protein-coupled receptors (GPCRs) regulate the activity of virtually all cell types including pancreatic {beta}-cells. {beta}-Cell M3 muscarinic receptors (M3Rs) play an essential role in maintaining proper whole-body glucose homeostasis. Activity of the M3R, like that of other GPCRs, is modulated by phosphorylation by various kinases, including GRKs and casein kinase 2 (CK2). The potential physiological relevance of M3R phosphorylation (or of GPCRs in general) by CK2 remains unknown. We here show that CK2-dependent phosphorylation of {beta}-cell M3Rs significantly impairs M3R-mediated increases in insulin release in vitro and in vivo. Our data demonstrate, for the first time to our knowledge, the physiological relevance of CK2 phosphorylation of a GPCR and suggest the novel concept that kinases acting on {beta}-cell GPCRs may represent therapeutic targets. G protein-coupled receptors (GPCRs) regulate virtually all physiological functions including the release of insulin from pancreatic {beta}-cells. {beta}-Cell M3 muscarinic receptors (M3Rs) are known to play an essential role in facilitating insulin release and maintaining proper whole-body glucose homeostasis. As is the case with other GPCRs, M3R activity is regulated by phosphorylation by various kinases, including GPCR kinases and casein kinase 2 (CK2). At present, it remains unknown which of these various kinases are physiologically relevant for the regulation of {beta}-cell activity. In the present study, we demonstrate that inhibition of CK2 in pancreatic {beta}-cells, knockdown of CK2 expression, or genetic deletion of CK2 in {beta}-cells of mutant mice selectively augmented M3R-stimulated insulin release in vitro and in vivo. In vitro studies showed that this effect was associated with an M3R-mediated increase in intracellular calcium levels. Treatment of mouse pancreatic islets with CX4945, a highly selective CK2 inhibitor, greatly reduced agonist-induced phosphorylation of {beta}-cell M3Rs, indicative of CK2-mediated M3R phosphorylation. We also showed that inhibition of CK2 greatly enhanced M3R-stimulated insulin secretion in human islets. Finally, CX4945 treatment protected mice against diet-induced hyperglycemia and glucose intolerance in an M3R-dependent fashion. Our data demonstrate, for the first time to our knowledge, the physiological relevance of CK2 phosphorylation of a GPCR and suggest the novel concept that kinases acting on {beta}-cell GPCRs may represent novel therapeutic targets.
