Inhibition of bradykinin-induced calcium increase by phosphatase inhibitors in neuroblastoma x glioma hybrid NG108-15 cells.
Prior treatment of NG108-15 cells with phosphatase inhibitors including okadaic acid and calyculin A inhibited the elevation of cytosolic Ca2+ concentration ([Ca2+]i) induced by bradykinin by approximately 63%. This inhibition was dependent on the concentration of okadaic acid with an IC50 of 0.15 nM. Okadaic acid treatment only lowered the maximal response of [Ca2+]i increase and had no effect on the EC50 value for bradykinin regardless of the presence of extracellular Ca2+. Neither the capacity of 45Ca2+ accumulation within intracellular nonmitochondrial Ca2+ stores nor the magnitude of [Ca2+]i increase induced by thapsigargin was reduced by the treatment of okadaic acid. In contrast, the same phosphatase inhibitor treatment inhibited the bradykinin-evoked inositol 1,4,5-trisphosphate (IP3) generation, the Mn2+ influx, and the capacity of mitochondrial Ca2+ accumulation. Furthermore, the sensitivity of IP3 in the Ca2+ release was suppressed by okadaic acid pretreatment. Our results suggest that the reduction of bradykinin-induced [Ca2+]i rise by the promotion of protein phosphorylation was attributed to the reduced activity of phospholipase C, the decreased sensitivity to IP3, and the slowed rate of Ca2+ influx. Thus, phosphorylation plays a role in bradykinin-sensitive Ca2+ signaling cascade in NG108-15 cells.
Hu
S Y
SY
Department of Biochemistry, National Defense Medical Center, Taipei, Taiwan, Republic of China.
Song
S L
SL
Ho
M Y
MY
Chueh
S H
SH
D000818:Animals; D001920:Bradykinin / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005910:Glioma; D006822:Hybrid Cells / Q000187:drug effects / Q000201:enzymology; D008387:Marine Toxins; D051379:Mice; D009447:Neuroblastoma; D019319:Okadaic Acid / Q000494:pharmacology; D010080:Oxazoles / Q000494:pharmacology; D010744:Phosphoric Monoester Hydrolases / Q000037:antagonists & inhibitors*; D010766:Phosphorylation; D015398:Signal Transduction / Q000502:physiology; D019284:Thapsigargin / Q000494:pharmacology; D010738:Type C Phospholipases / Q000378:metabolism
D004791:Enzyme Inhibitors; D008387:Marine Toxins; D010080:Oxazoles; D019319:Okadaic Acid; D019284:Thapsigargin; C059041:calyculin A; D010744:Phosphoric Monoester Hydrolases; D010738:Type C Phospholipases; D001920:Bradykinin; D002118:Calcium