G-protein activation, intracellular Ca2+ mobilization and phosphorylation studies of membrane currents induced by AlF4- in Xenopus oocytes.
We have examined the electrophysiological responses induced by aluminium fluoride (AlF4-) and carbachol in Xenopus oocytes. Application of AlF4- induced Ca(2+)-dependent oscillatory and smooth Cl- currents. Pre-treatment of oocytes with microinjected guanosine 5'-O-(2-thiodiphosphate) diminished the currents, indicating that the effect of AlF4- occurred through G-protein activation. Confocal imaging of intracellular Ca2+ clearly demonstrated that AlF4- could increase the internal Ca2+ concentration in oocytes in the absence of external Ca2+. A protein kinase (PK) activator (4-beta-phorbol 12,13-dibutyrate) decreased the AlF4(-)-induced membrane currents, whereas a PK inhibitor (staurosporine) caused an increase. On the other hand, the protein phosphatase inhibitor (okadaic acid) showed little effect. Although the effects of the phosphorylating/dephosphorylating agents on the carbachol-induced currents were qualitatively similar to the case of AlF4-, some quantitative differences was noted. The results are discussed in terms of the signaling pathways involving muscarinic receptors and G-protein(s) in Xenopus oocytes.
Moon
C
C
Department of Biology, Imperial College of Science, Technology and Medicine, London, United Kingdom.
Fraser
S P
SP
Djamgoz
M B
MB
D017607:Aluminum Compounds / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D002462:Cell Membrane / Q000502:physiology; D004594:Electrophysiology; D005459:Fluorides / Q000494:pharmacology*; D019204:GTP-Binding Proteins / Q000378:metabolism*; D019319:Okadaic Acid / Q000494:pharmacology; D009865:Oocytes / Q000187:drug effects / Q000502:physiology*; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors; D010766:Phosphorylation; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D015398:Signal Transduction; D019311:Staurosporine / Q000494:pharmacology; D014982:Xenopus laevis
D017607:Aluminum Compounds; D019319:Okadaic Acid; D011493:Protein Kinase C; D010749:Phosphoprotein Phosphatases; D019204:GTP-Binding Proteins; D019311:Staurosporine; D005459:Fluorides; D002118:Calcium; C032311:aluminum fluoride