title: CK2 acts as a potent negative regulator of receptor-mediated insulin release in vitro and in vivo.
abstract: G protein-coupled receptors (GPCRs) regulate virtually all physiological functions including the release of insulin from pancreatic β-cells. β-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 β-cell activity. In the present study, we demonstrate that inhibition of CK2 in pancreatic β-cells, knockdown of CK2α expression, or genetic deletion of CK2α in β-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 β-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 β-cell GPCRs may represent novel therapeutic targets.
authors.affiliation: Molecular Signaling Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892;
authors.forename: Mario
authors.initials: M
authors.lastname: Rossi
authors.affiliation: Molecular Signaling Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892;
authors.forename: Inigo
authors.initials: I
authors.lastname: Ruiz de Azua
authors.affiliation: Molecular Signaling Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892;
authors.forename: Luiz F
authors.initials: LF
authors.lastname: Barella
authors.affiliation: Molecular Signaling Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892;
authors.forename: Wataru
authors.initials: W
authors.lastname: Sakamoto
authors.affiliation: Molecular Signaling Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892;
authors.forename: Lu
authors.initials: L
authors.lastname: Zhu
authors.affiliation: Molecular Signaling Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892;
authors.forename: Yinghong
authors.initials: Y
authors.lastname: Cui
authors.affiliation: Mouse Transgenic Core Facility, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892;
authors.forename: Huiyan
authors.initials: H
authors.lastname: Lu
authors.affiliation: Sophie Davis School of Biomedical Education, The City College of New York, New York, NY 10031;
authors.forename: Heike
authors.initials: H
authors.lastname: Rebholz
authors.affiliation: Department of Biochemistry and Biophysics, University of Pennsylvania School of Medicine, Philadelphia, PA 19104;
authors.forename: Franz M
authors.initials: FM
authors.lastname: Matschinsky
authors.affiliation: Department of Biochemistry and Biophysics, University of Pennsylvania School of Medicine, Philadelphia, PA 19104;
authors.forename: Nicolai M
authors.initials: NM
authors.lastname: Doliba
authors.affiliation: Medical Research Council Toxicology Unit, University of Leicester, Leicester LE1 9HN, United Kingdom.
authors.forename: Adrian J
authors.initials: AJ
authors.lastname: Butcher
authors.affiliation: Medical Research Council Toxicology Unit, University of Leicester, Leicester LE1 9HN, United Kingdom.
authors.forename: Andrew B
authors.initials: AB
authors.lastname: Tobin
authors.affiliation: Molecular Signaling Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892; jurgenw@helix.nih.gov.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Wess
mesh_terms: D000818:Animals; D019556:COS Cells; D047390:Casein Kinase II / Q000502:physiology*; D002522:Chlorocebus aethiops; D005260:Female; D057809:HEK293 Cells; D006801:Humans; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009287:Naphthyridines / Q000494:pharmacology; D010619:Phenazines; D043587:Receptor, Muscarinic M3 / Q000502:physiology*
chemical_list: D007328:Insulin; D009287:Naphthyridines; D010619:Phenazines; D043587:Receptor, Muscarinic M3; C555142:silmitasertib; D047390:Casein Kinase II
keywords: G protein-coupled receptors; GPCR regulation; glucose homeostasis; mouse models; β-cell function