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Ceramide stimulates a cytosolic protein phosphatase
1Department of Medicine, Duke University Medical Center, Durham, North Carolina 27710.
The Journal of Biological Chemistry
|March 15, 1992
Summary
Ceramides activate a specific cytosolic protein phosphatase, revealing a new signaling pathway. This pathway influences cell proliferation and differentiation, offering insights into cellular regulation.
Area of Science:
- Cellular Biology
- Biochemistry
- Molecular Signaling
Background:
- A sphingomyelin cycle generates ceramide, a known modulator of cell proliferation and differentiation.
- Extracellular agents can trigger sphingomyelin hydrolysis, producing ceramide.
Purpose of the Study:
- To investigate the molecular targets of ceramide action.
- To identify novel intracellular signaling pathways regulated by ceramide.
Main Methods:
- Assaying cytosolic serine/threonine protein phosphatase activity in response to various ceramides.
- Using okadaic acid to inhibit phosphatase activity and determine IC50 values.
- Employing sequential anion exchange chromatography for enzyme purification.
Main Results:
- C2-ceramide, C6-ceramide, and natural ceramides dose-dependently activated a cytosolic serine/threonine protein phosphatase.
- Activation occurred at low micromolar concentrations (0.1-10 microM), while sphingosine and sphingomyelin were inactive.
- The ceramide-stimulated phosphatase was inhibited by okadaic acid (IC50 0.1-1 nM) and insensitive to Mg2+/Mn2+.
- Purified enzyme showed a 3.5-fold stimulation by ceramide.
Conclusions:
- A novel intracellular signaling pathway is identified, with a specific phosphatase acting as a molecular target for ceramide.
- This pathway has potential roles in regulating cell proliferation and differentiation.