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Ceramide induces structural defects into phosphatidylcholine bilayers and activates phospholipase A2
H W Huang1, E M Goldberg, R Zidovetzki
1Department of Biology, University of California, Riverside, 92521, USA.
Biochemical and Biophysical Research Communications
|March 27, 1996
Summary
Bovine brain ceramide alters dipalmitoylphosphatidylcholine (DPPC) bilayer structure, inducing phase separation. This structural change correlates with ceramide-activated phospholipase A2 (PL-A2) activity, suggesting pathway cross-talk.
Area of Science:
- Biochemistry
- Biophysics
- Cell Signaling
Background:
- Ceramides are bioactive lipids involved in cell signaling.
- Phospholipase A2 (PL-A2) enzymes hydrolyze phospholipids and play roles in inflammation and signaling.
- Understanding lipid-protein interactions is crucial for elucidating cellular processes.
Purpose of the Study:
- To investigate the structural effects of bovine brain ceramide on dipalmitoylphosphatidylcholine (DPPC) bilayers.
- To determine the impact of ceramide on cobra venom phospholipase A2 (PL-A2) activity.
- To explore potential cross-talk between sphingomyelinase and PL-A2 signaling pathways.
Main Methods:
- 2H Nuclear Magnetic Resonance (NMR) spectroscopy to analyze bilayer structure and order parameters.
- Specific enzymatic assays to quantify PL-A2 activity.
- Varying ceramide concentrations and temperatures (45°C and 60°C) to observe dose- and temperature-dependent effects.
Main Results:
- Ceramide induced lateral phase separation in DPPC bilayers at 45°C, forming distinct gel and liquid crystalline regions.
- Ceramide primarily partitioned into the gel phase at 45°C, with minor effects on liquid crystalline phase order parameters.
- At 60°C, ceramide significantly increased the order parameters of DPPC acyl chains in the liquid crystalline phase.
- Ceramide activated cobra venom PL-A2 in a concentration-dependent manner, with a 3-fold increase at 5 mol% ceramide.
- A correlation was observed between ceramide-induced structural changes in DPPC bilayers and PL-A2 activation.
Conclusions:
- Bovine brain ceramide influences DPPC bilayer organization, leading to phase separation and altered acyl chain dynamics.
- Ceramide directly activates cobra venom PL-A2, indicating a functional link between these molecules.
- These findings suggest a potential cross-talk mechanism between sphingomyelinase and PL-A2 signaling pathways, highlighting a novel aspect of ceramide's biological role.