Sphingosine and Phorbol Ester Modulate Protein Kinase C Activity and Modify ATP-Evoked Calcium Mobilization in Glioma C6 Cells

The effect of sphingosine and 12-O-tetradecanoyl-phorbol-13-acetate (TPA) on ATP-evoked Ca2+ mobilization in glioma C6 cells was studied with the Fura-2 video-imaging technique. Treatment of the cells with TPA, an activator of protein kinase C, reduced the ATP-evoked release of Ca2+ from the intrace...

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Bibliographic Details
Published in:Biochemical and biophysical research communications 1999-07, Vol.260 (3), p.614-618
Main Authors: Czajkowski, Rafał, Barańska, Jolanta
Format: Article
Language:English
Subjects:
Adenosine Triphosphate - antagonists & inhibitors
Adenosine Triphosphate - pharmacology
Animals
Calcium - metabolism
Calcium Signaling - drug effects
Endoplasmic Reticulum - drug effects
Endoplasmic Reticulum - enzymology
Endoplasmic Reticulum - metabolism
Enzyme Activation - drug effects
Glioma - enzymology
Glioma - metabolism
Glioma - pathology
Indoles - pharmacology
Maleimides - pharmacology
Protein Kinase C - antagonists & inhibitors
Protein Kinase C - metabolism
Rats
sphingosine
Sphingosine - antagonists & inhibitors
Sphingosine - pharmacology
Tetradecanoylphorbol Acetate - antagonists & inhibitors
Tetradecanoylphorbol Acetate - pharmacology
Thapsigargin - pharmacology
Time Factors
Tumor Cells, Cultured
Type C Phospholipases - metabolism
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Summary:The effect of sphingosine and 12-O-tetradecanoyl-phorbol-13-acetate (TPA) on ATP-evoked Ca2+ mobilization in glioma C6 cells was studied with the Fura-2 video-imaging technique. Treatment of the cells with TPA, an activator of protein kinase C, reduced the ATP-evoked release of Ca2+ from the intracellular stores, whereas sphingosine, known from in vitro studies as a protein kinase C inhibitor, potentiated Ca2+ release synergistically with ATP. ATP-induced Ca2+ mobilization was also enhanced by a specific protein kinase C inhibitor, GF 109203X. Pretreatment of the cells with GF 109203X prevented TPA action, whereas TPA diminished the stimulatory effect of sphingosine. However, this sphingosine effect was only observed after a short (1 min) treatment, whereas a longer treatment (5 min) reduced ATP-evoked Ca2+ release. It is therefore concluded that sphingosine has two apparent actions: it inhibits protein kinase C providing a positive feedback regulation of receptor signals and it releases Ca2+ from intracellular stores by an unknown mechanism, possibly independent of protein kinase C.
ISSN:0006-291X
1090-2104
DOI:10.1006/bbrc.1999.0946