Related Experiment Videos
Ceramide activates heterotrimeric protein phosphatase 2A
R T Dobrowsky1, C Kamibayashi, M C Mumby
1Department of Medicine, Duke University Medical Center, Durham, North Carolina 27710.
The Journal of Biological Chemistry
|July 25, 1993
Summary
Ceramide acts as a lipid second messenger, specifically activating heterotrimeric protein phosphatase 2A (PP2A) in rat brain cells. This activation requires the B subunit and is dependent on the ceramide
Area of Science:
- Biochemistry
- Cell Biology
- Neuroscience
Background:
- Ceramides are bioactive lipids implicated in various cellular processes.
- Cytosolic protein phosphatases play crucial roles in signal transduction.
- Protein Phosphatase 2A (PP2A) is a key enzyme involved in dephosphorylation.
Purpose of the Study:
- To investigate the interaction between ceramide and cytosolic protein phosphatases.
- To determine if ceramide directly activates Protein Phosphatase 2A (PP2A).
- To characterize the specific forms of PP2A and ceramide involved in this activation.
Main Methods:
- Isolation of PP2A in various subunit compositions (heterotrimer, heterodimer, free subunit) from rat T9 glioma cells and rat brain.
- Assessing the catalytic activity of isolated PP2A in the presence of varying concentrations and types of C2-ceramide.
- Investigating the role of the B subunit in ceramide-mediated activation using trypsinization and heparin treatment.
- Evaluating the specificity of ceramide activation using related sphingolipids and stereoisomers.
Main Results:
- Ceramide specifically activated heterotrimeric PP2A (AB'C, ABαC) but not heterodimeric (AC) or free C subunits.
- Activation was dependent on the acyl chain length of ceramide, with hexanoyl, decanoyl, and myristoyl chains being effective.
- The B subunit of PP2A was essential for ceramide-mediated activation, as its removal abolished the effect.
- Specific stereoisomers of C2-ceramide differentially activated different heterotrimeric forms of PP2A.
- Ceramide-activated protein phosphatase (CAPP) activity exhibited two peaks, with the second peak showing significant ceramide stimulation.
Conclusions:
- Ceramide acts as a specific lipid second messenger that modulates the activity of heterotrimeric PP2A.
- The findings support the hypothesis that ceramide directly activates PP2A, influencing cellular signaling pathways.
- Understanding this interaction provides insights into the role of ceramide in cellular regulation and disease.