Inhibition of Bradykinin-Induced Calcium Increase by Phosphatase Inhibitors in Neuroblastoma × Glioma Hybrid NG108-15 Cells |
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Authors: | Shei-Ying Hu Shu-Ling Song Mei-Ying Ho Sheau-Huei Chueh |
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Institution: | Department of Biochemistry and; Graduate Institute of Life Sciences, National Defense Medical Center, Taipei, Taiwan, Republic of China |
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Abstract: | Abstract: 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 ~63%. This inhibition was dependent on the concentration of okadaic acid with an IC50 of 0.15 n M . 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. |
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Keywords: | Bradykinin NG108-15 cells Phosphatase inhibitor Cytosolic Ca2+ concentration |
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