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Ceramide activates heterotrimeric protein phosphatase 2A
Ceramide activates a cytosolic protein phosphatase present in rat T9 glioma cells and rat brain. Ceramide-activated protein phosphatase (CAPP) was found to share several properties with protein phosphatase 2A (PP2A) leading to the hypothesis that ceramide may directly activate PP2A. PP2A was isolate...
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Published in: | The Journal of biological chemistry 1993-07, Vol.268 (21), p.15523-15530 |
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Main Authors: | , , , |
Format: | Article |
Language: | English |
Subjects: | |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Get full text |
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Summary: | Ceramide activates a cytosolic protein phosphatase present in rat T9 glioma cells and rat brain. Ceramide-activated protein
phosphatase (CAPP) was found to share several properties with protein phosphatase 2A (PP2A) leading to the hypothesis that
ceramide may directly activate PP2A. PP2A was isolated as a heterotrimer (AB'C, AB alpha C), heterodimer (AC), or free C subunit,
and the effect of ceramide on the catalytic activity was assessed. C2-ceramide, 5-20 microM, activated heterotrimeric PP2A
up to 3.5-fold but had no effect on the activity of AC or C. Ceramides possessing hexanoyl, decanoyl, and myristoyl but not
stearoyl acyl chains also activated heterotrimeric PP2A. Ceramide activation of heterotrimeric PP2A required the presence
of a B subunit since trypsinization or heparin treatment abolished ceramide activation. Activation of heterotrimeric PP2A
was specific for ceramide because related sphingolipids had no effect. Moreover, dihydro-C2-ceramide, which lacks the trans
double bond in the sphingoid base, inhibited AB'C activity by > 90% at 10 microM. The specificity of activation of AB'C and
AB alpha C by stereoisomers of C2-ceramide was found to differ. Whereas activation of AB'C by either DL-erythro- or threo-C2-ceramide
was similar, AB alpha C was activated by either D- or L-erythro-C2-ceramide but not by the threo isomers. CAPP isolated from
T9 cells was most effectively activated by D-erythro-C2-ceramide. CAPP was found to possess two peaks of ceramide activated
phosphatase activity. The initial peak of activity was coincident with the elution of AB'C and was stimulated 1.8-fold by
20 microM C2-ceramide. A second peak of phosphatase activity was negligible in the absence of ceramide but was stimulated
5.5-fold by 20 microM C2-ceramide. These results support the hypothesis that ceramide is a specific lipid second messenger
modulating heterotrimeric PP2A activity. |
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ISSN: | 0021-9258 1083-351X |
DOI: | 10.1016/S0021-9258(18)82288-8 |