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Lipid Vesicle-mediated Affinity Chromatography using Magnetic Activated Cell Sorting (LIMACS): a Novel Method to Analyze Protein-lipid Interaction
Published on: April 26, 2011
Mammalian ORMDL proteins mediate the feedback response in ceramide biosynthesis.
Deanna L Siow1, Binks W Wattenberg
1James Graham Brown Cancer Center, Louisville, KY 40202, USA.
The Journal of Biological Chemistry
|October 16, 2012
Summary
Mammalian ORMDL proteins (ORMDL1-3) are key regulators of ceramide biosynthesis, mediating feedback inhibition. Their depletion eliminates this regulation, highlighting their essential role in controlling ceramide levels.
Area of Science:
- Cellular lipid metabolism
- Sphingolipid biochemistry
Background:
- Yeast Orm1/2 proteins regulate ceramide biosynthesis.
- Ceramide is a critical sphingolipid in mammalian cells, acting as a signaling molecule and precursor.
Purpose of the Study:
- To investigate the role of mammalian ORMDL proteins (ORMDL1-3) in regulating ceramide biosynthesis.
- To determine if ORMDL proteins mediate the feedback inhibition of ceramide synthesis.
Main Methods:
- Knockdown of ORMDL1-3 in HeLa cells.
- Treatment of cells with short-chain ceramide (C6) and sphingosine.
- Assay of ceramide biosynthesis rates.
- Inhibition studies using permeabilized cells and C6-ceramide.
Main Results:
- Depletion of ORMDL1-3 proteins eliminated the negative feedback of exogenous ceramide on ceramide biosynthesis.
- ORMDL proteins are functionally redundant, requiring simultaneous knockdown of all three isoforms to abolish feedback inhibition.
- C6-ceramide inhibited serine palmitoyltransferase, the rate-limiting enzyme, in a manner dependent on membrane-bound elements.
Conclusions:
- ORMDL proteins are the primary regulators of ceramide biosynthesis in mammalian cells.
- Understanding ORMDL function is crucial for therapeutically manipulating ceramide levels.
- SMSr does not appear to regulate ceramide biosynthesis but may be involved in downstream metabolism.
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