Stimulation of Ca(2+)-dependent membrane currents in Xenopus oocytes by microinjection of pyrimidine nucleotide-glucose conjugates.
Microinjection, but not extracellular application, of cytidine-5'-diphosphate-D-glucose (CDPG) has been shown to elicit Ca(2+)-dependent currents in Xenopus laevis oocytes. These responses were comparable to those of inositol-1,4,5-trisphosphate (InsP3) in being both rapid and dose dependent. For example, maximal amplitudes of CDPG-induced current were similar (approximately 365 +/- 75 nA at 1 microM CDPG) to those of InsP3. The CDPG currents were insensitive to removal of extracellular Ca2+, indicating the dependence on Ca2+ release from intracellular Ca2+ stores but not on Ca2+ entry through plasma membrane. CDPG-induced currents were reduced or abolished by pretreatment with thapsigargin, by injection of the Ca2+ chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid, or by extracellular perfusion of the Cl- channel blocker niflumic acid but were insensitive to injection of the InsP3 antagonist heparin. These results suggest that CDPG induces Ca2+ discharge from intracellular Ca2+ stores via a mechanism distinct from that of InsP3 in Xenopus oocytes. Another pyrimidine nucleotide-glucose derivative, uridine-5'-diphosphate-alpha-D-glucose, also induced Ca(2+)-dependent currents, but the activity was lower than that of CDPG (maximal amplitude, 272 +/- 62 nA). Other nucleotide-glucose compounds (adenosine-5'-diphosphate-D-glucose, guanosine-5'-diphosphate-D-glucose, and thymidine-5'-diphosphate-D-glucose) had no current responses when injected into oocytes. After injection of CDPG, CDPG-induced Ca2+ release appeared to couple to a Ca2+ entry pathway similar to that coupled to InsP3. These results indicate that pyrimidine nucleotide-glucose conjugates may provide novel pharmacological tools for the study of Ca2+ signaling in oocytes.
Kim
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Department of Biological Chemistry, School of Medicine, University of California, Davis 95616-8635, USA.
Thomas
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Hanley
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D000245:Adenosine Diphosphate Glucose / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology*; D002614:Chelating Agents / Q000494:pharmacology; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D005260:Female; D005947:Glucose / Q000031:analogs & derivatives / Q000494:pharmacology; D005998:Glycine / Q000031:analogs & derivatives / Q000494:pharmacology; D006156:Guanosine Diphosphate Sugars / Q000494:pharmacology; D015544:Inositol 1,4,5-Trisphosphate / Q000008:administration & dosage / Q000494:pharmacology*; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects; D008845:Microinjections; D009702:Nucleoside Diphosphate Sugars / Q000494:pharmacology*; D009865:Oocytes / Q000187:drug effects / Q000502:physiology*; D013440:Sulfides; D013876:Thiophenes; D014532:Uridine Diphosphate Glucose / Q000494:pharmacology; D014981:Xenopus
D002614:Chelating Agents; D006156:Guanosine Diphosphate Sugars; D009702:Nucleoside Diphosphate Sugars; D013440:Sulfides; D013876:Thiophenes; C073881:cytidine diphosphate-glucose; C035227:stepronin; D000245:Adenosine Diphosphate Glucose; D004533:Egtazic Acid; C100085:guanosine diphosphate glucose; D015544:Inositol 1,4,5-Trisphosphate; D005947:Glucose; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; D002118:Calcium; D005998:Glycine; D014532:Uridine Diphosphate Glucose