title: Mechanisms of arginine-vasopressin-induced Ca2+ oscillations in beta-cells (HIT-T15): a role for oscillating protein kinase C.
abstract: We examined the role of protein kinase C (PKC) for the generation of arginine-vasopressin (AVP)-linked Ca2+ oscillations in beta-cells (HIT-T15). Activation of PKC by phorbol-12,13-dibutyrate (PDBu) reduced the frequency and finally abolished AVP-induced Ca2+ oscillations. The PKC inhibitors Gö 6976, Ro-32-0432, or chelerythrine converted Ca2+ oscillations to a plateau-like rise in cytosolic free Ca2+, and PKC down-regulation reduced the percentage of cells exhibiting AVP-induced Ca2+ oscillations. Several mechanisms were identified by which PKC could exert feedback on the AVP-linked Ca2+ oscillator. PDBu, but not the PKC inhibitors, inhibited AVP-stimulated inositol 1,4,5-trisphosphate production and mobilization of internal Ca2+. Ca2+ influx through voltage-sensitive Ca2+ channels was attenuated by PDBu and PKC inhibitors, indicating complex PKC-dependent regulation of voltage-sensitive Ca2+ channels involving stimulatory as well as inhibitory components. Furthermore, AVP caused oscillatory translocation of yellow fluorescent protein (YFP)-tagged PKCalpha and PKCbetaIota to the plasma membrane, which paralleled the Ca2+ oscillations in single cells. Repetitive translocation of YFP-PKCalpha and -PKCbetaIota could also be elicited by repetitive release of caged Ca2+. By contrast, AVP-stimulated translocation of YFP-PKCepsilon was monophasic, not synchronized with Ca2+ oscillations, and could not be mimicked by release of caged Ca2+. In conclusion, undisturbed activation of PKCs is a necessary intermediate to generate or maintain AVP-induced Ca2+ oscillations in pancreatic beta-cells. The data further suggest that classical PKCs, predominantly by inhibition of inositol 1,4,5-trisphosphate production, provide the negative feedback required for AVP-induced Ca2+ oscillations to occur that is mediated by their repetitive activation by oscillating Ca2+ concentrations.
authors.affiliation: Institut für Pharmakologie, Charité-Universitätsmedizin Berlin, 14195 Berlin, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Schaefer
authors.forename: Harald
authors.initials: H
authors.lastname: Mischak
authors.forename: Susanne
authors.initials: S
authors.lastname: Schnell
authors.forename: Anne
authors.initials: A
authors.lastname: Griese
authors.forename: Roman
authors.initials: R
authors.lastname: Iakubov
authors.forename: Gabriele
authors.initials: G
authors.lastname: Riepenhausen
authors.forename: Christof
authors.initials: C
authors.lastname: Schöfl
mesh_terms: D000818:Animals; D001127:Arginine Vasopressin / Q000502:physiology*; D001692:Biological Transport / Q000502:physiology; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism; D002460:Cell Line; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015544:Inositol 1,4,5-Trisphosphate / Q000037:antagonists & inhibitors; D007515:Islets of Langerhans / Q000378:metabolism*; D007527:Isoenzymes / Q000378:metabolism; D009991:Oscillometry; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
chemical_list: D015220:Calcium Channels; D004791:Enzyme Inhibitors; D007527:Isoenzymes; D001127:Arginine Vasopressin; D015240:Phorbol 12,13-Dibutyrate; D015544:Inositol 1,4,5-Trisphosphate; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium