title: A role for phosphorylation of inositol 1,4,5-trisphosphate receptors in defining calcium signals induced by Peptide agonists in pancreatic acinar cells.
abstract: Stimulation of pancreatic acinar cells with acetylcholine (ACh) and cholecystokinin (CCK) results in an elevation of cytosolic calcium ([Ca(2+)](c)) through activation of inositol 1,4,5-trisphosphate receptors (InsP(3)R). The global temporal pattern of the [Ca(2+)](c) changes produced by ACh or CCK stimulation differs significantly. The hypothesis was tested that CCK stimulation results in a protein kinase A (PKA)-mediated phosphorylation of InsP(3)R and this event contributes to the generation of agonist-specific [Ca(2+)](c) signals. Physiological concentrations of CCK evoked phosphorylation of the type III InsP(3)R, which was blocked by pharmacological inhibition of PKA. Imaging of fura-2-loaded acinar cells revealed that the rate of [Ca(2+)](c) rise during CCK-evoked oscillations slows with each subsequent oscillation, consistent with a developing modulation of release, whereas the kinetics of ACh-evoked oscillations remain constant. Stimulation of cells with ACh following activation of PKA resulted in a slowing of the ACh-evoked [Ca(2+)](c) rise, which now resembled a time-matched CCK response. PKA activation also resulted in a slowing of [Ca(2+)](c) increases elicited by photolysis of caged InsP(3). Targeted, PKA-mediated phosphorylation of type III InsP(3)R is involved in a physiological CCK response, as disruption of the targeting of PKA with the peptide HT31 resulted in marked changes in the CCK-evoked [Ca(2+)](c) signal but had no effect on ACh-evoked responses. Stimulation of cells with bombesin, which evokes [Ca(2+)](c) oscillations indistinguishable from those produced by CCK, also results in PKA-mediated phosphorylation of type III InsP(3)R. Thus, we conclude that PKA-mediated phosphorylation of type III InsP(3)R is a general mechanism by which the patterns of [Ca(2+)](c) oscillations are shaped in pancreatic acinar cells.
authors.affiliation: Department of Pharmacology and Physiology, University of Rochester, Rochester, New York 14642, USA.
authors.forename: Stephen V
authors.initials: SV
authors.lastname: Straub
authors.forename: David R
authors.initials: DR
authors.lastname: Giovannucci
authors.forename: Jason I E
authors.initials: JI
authors.lastname: Bruce
authors.forename: David I
authors.initials: DI
authors.lastname: Yule
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology*; D000818:Animals; D003994:Bucladesine / Q000494:pharmacology; D015220:Calcium Channels / Q000187:drug effects / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D002478:Cells, Cultured; D002766:Cholecystokinin / Q000494:pharmacology*; D005576:Colforsin / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D003600:Cytosol / Q000502:physiology; D066298:In Vitro Techniques; D053496:Inositol 1,4,5-Trisphosphate Receptors; D007700:Kinetics; D008297:Male; D051379:Mice; D009991:Oscillometry; D010179:Pancreas / Q000187:drug effects / Q000502:physiology*; D018408:Patch-Clamp Techniques; D010766:Phosphorylation; D018160:Receptors, Cytoplasmic and Nuclear / Q000187:drug effects / Q000378:metabolism*
chemical_list: D015220:Calcium Channels; D053496:Inositol 1,4,5-Trisphosphate Receptors; D018160:Receptors, Cytoplasmic and Nuclear; D005576:Colforsin; D003994:Bucladesine; D002766:Cholecystokinin; D017868:Cyclic AMP-Dependent Protein Kinases; D000109:Acetylcholine