title: PKC-mediated inhibitory feedback of the cholecystokinin 1 receptor controls the shape of oscillatory Ca²⁺ signals.
abstract: Translation of extracellular hormonal input into cellular responses is often mediated by repetitive increases in cytosolic free Ca(2+) concentration ([Ca(2+) ]c ). Amplitude, duration and frequency of these so-called [Ca(2+) ]c oscillations then carry information about the nature and concentration of the extracellular signalling molecule. At present, there are different hypotheses concerning the induction and control of these oscillations. Here, we investigated the role of agonist-induced receptor phosphorylation in this process using Chinese hamster ovary cells stably expressing a variant of the cholecystokinin 1 receptor (CCK1R) lacking the four consensus sites for protein kinase C (PKC) phosphorylation and deficient in CCK-induced receptor phosphorylation (CCK1R-mt cells). In the presence of cholecystokinin-(26-33)-peptide amide (CCK-8), these cells displayed Ca(2+) oscillations with a much more pronounced bursting dynamics rather than the dominant spiking dynamics observed in Chinese hamster ovary cells stably expressing the wild-type CCK1R. The bursting behaviour returned to predominantly spiking behaviour following removal of extracellular Ca(2+) , suggesting that CCK-8-induced, PKC-mediated CCK1R phosphorylation inhibits Ca(2+) influx across the plasma membrane. To gain mechanistic insight into the underlying mechanism we developed a mathematical model able to reproduce the experimental observations. From the model we conclude that binding of CCK-8 to the CCK1R leads to activation of PKC which subsequently phosphorylates the receptor to inhibit the receptor-mediated influx of Ca(2+) across the plasma membrane. Receptor-specific differences in this feedback mechanism may, at least in part, explain the observation that different agonists evoke [Ca(2+) ]c oscillations with different kinetics in the same cell type.
authors.affiliation: Department of Biochemistry, Radboud Institute for Molecular Life Sciences and Centre for Systems Biology and Bioenergetics, Radboud University Medical Center, Nijmegen, The Netherlands.
authors.forename: Peter H G M
authors.initials: PH
authors.lastname: Willems
authors.affiliation: BIOMS, BioQuant, Heidelberg University, Germany.|School of Computer Science, Manchester Institute of Biotechnology, University of Manchester, UK.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Pahle
authors.affiliation: Department of Biochemistry, Radboud Institute for Molecular Life Sciences and Centre for Systems Biology and Bioenergetics, Radboud University Medical Center, Nijmegen, The Netherlands.
authors.forename: Xenia L
authors.initials: XL
authors.lastname: Stalpers
authors.affiliation: Department of Modelling of Biological Processes, COS Heidelberg/BioQuant, Heidelberg University, Germany.
authors.forename: Douaa
authors.initials: D
authors.lastname: Mugahid
authors.affiliation: Department of Modelling of Biological Processes, COS Heidelberg/BioQuant, Heidelberg University, Germany.
authors.forename: Alexander
authors.initials: A
authors.lastname: Nikolaew
authors.affiliation: Department of Biochemistry, Radboud Institute for Molecular Life Sciences and Centre for Systems Biology and Bioenergetics, Radboud University Medical Center, Nijmegen, The Netherlands.
authors.forename: Werner J H
authors.initials: WJ
authors.lastname: Koopman
authors.affiliation: Department of Modelling of Biological Processes, COS Heidelberg/BioQuant, Heidelberg University, Germany.
authors.forename: Ursula
authors.initials: U
authors.lastname: Kummer
mesh_terms: D000818:Animals; D016466:CHO Cells; D020013:Calcium Signaling; D003198:Computer Simulation; D006224:Cricetinae; D003412:Cricetulus; D025461:Feedback, Physiological; D008954:Models, Biological; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D043886:Receptor, Cholecystokinin A / Q000378:metabolism*
chemical_list: D043886:Receptor, Cholecystokinin A; D011493:Protein Kinase C
keywords: Ca2+ models; Ca2+ oscillations; bursting; spiking