| 10794729 |
Bandyopadhyay A, Shin DW, Kim DH: Regulation of ATP-induced calcium release in COS-7 cells by calcineurin. . Biochem J. 2000 May 15;348 Pt 1:173-81.
Experiments were conducted to examine the role of calcineurin in regulating Ca (2+) fluxes in mammalian cells. In COS-7 cells, increasing concentrations (1-10 microM) of ATP triggered intracellular Ca (2+) release in a dose-dependent manner. Treatment of the cells with calcineurin inhibitors such as cyclosporin A (CsA), deltamethrin and FK506 resulted in an enhancement of ATP-induced intracellular Ca (2+) release. Measurement of calcineurin-specific phosphatase activity in vitro demonstrated a high level of endogenous calcineurin activities in COS-7 cells, which was effectively inhibited by the addition of deltamethrin or CsA. The expression of constitutively active calcineurin (CnADeltaCaMAI) inhibited the ATP-induced increase in intracellular Ca (2+) concentration ([Ca (2+)](i)), in both the presence and the absence of extracellular Ca (2+). These results suggest that the constitutively active calcineurin prevented Ca (2+) release from the intracellular stores. In the calcineurin-transfected cells, treatment with CsA restored the calcineurin-mediated inhibition of intracellular Ca (2+) release. Protein kinase C-mediated phosphorylation of Ins (1,4,5) P (3) receptor [Ins (1,4,5) P (3) R] was partly inhibited by the extracts prepared from the vector-transfected cells and completely inhibited by those from cells co-transfected with CnADeltaCaMAI and calcineurin B. On the addition of 10 microM CsA, the inhibited phosphorylation of Ins (1,4,5) P (3) R was restored in both the vector-transfected cells and the calcineurin-transfected cells. These results show direct evidence that Ca (2+) release through Ins (1, 4,5) P (3) R in COS-7 cells is regulated by calcineurin-mediated dephosphorylation. |
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