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Myelin basic protein component C1 in increasing concentrations can elicit fusion, aggregation, and fragmentation of
S V Mac Millan1, N Ishiyama, G F White
1Department of Molecular Biology and Genetics, University of Guelph, Ontario, Canada.
Abstract:
Myelin basic protein (MBP) is considered to have a primary role in the formation and maintenance of the myelin sheath. Many studies using artificial vesicle systems of simple lipid composition, and generally small size, have shown that MBP can elicit vesicle fusion, aggregation, or even fragmentation under different conditions. Here, we have studied the effects of increasing concentrations of bovine MBP charge isomer C1 (MBP/C1) on large unilamellar vesicles (LUVs) composed of phosphatidylcholine and phosphatidylserine (92:8 molar ratio), or with a lipid composition similar to that of the myelin membrane in vivo (Cyt-LUVs). Using absorbance spectrophotometry, fluorescence resonance energy transfer, dynamic light scattering and transmission electron microscopy, we have shown that vesicle aggregation and some vesicle fusion occurred upon addition of MBP/C1, and as the molar protein-lipid ratio increased. Fragmentation of Cyt-LUVs was observed at very high protein concentrations. These results showed that the phenomena of vesicle fusion, aggregation, and fragmentation can all be observed in one in vitro system, but were dependent on lipid composition and on the relative proportions of protein and lipid.
Insights
Myelin basic protein (MBP) influences large unilamellar vesicles (LUVs) by causing aggregation, fusion, and fragmentation. These effects depend on lipid composition and protein concentration in this in vitro study.
Area of Science:
- Biochemistry
- Neuroscience
- Biophysics
Background:
- Myelin basic protein (MBP) is crucial for myelin sheath formation and maintenance.
- Previous studies show MBP induces vesicle fusion, aggregation, or fragmentation in simple lipid systems.
- The behavior of MBP with complex lipid compositions and larger vesicles remains less understood.
Purpose of the Study:
- To investigate the effects of bovine MBP charge isomer C1 (MBP/C1) on large unilamellar vesicles (LUVs).
- To examine how varying MBP/C1 concentrations impact LUVs with different lipid compositions, including one mimicking the myelin membrane.
- To determine the influence of protein-lipid ratio on MBP-induced vesicle dynamics.
Main Methods:
- Utilized absorbance spectrophotometry and fluorescence resonance energy transfer (FRET).
- Employed dynamic light scattering (DLS) to measure vesicle size changes.
- Conducted transmission electron microscopy (TEM) for direct visualization of vesicle morphology.
Main Results:
- MBP/C1 induced vesicle aggregation and fusion in a concentration-dependent manner.
- Specific lipid compositions (Cyt-LUVs) showed fragmentation at high MBP/C1 concentrations.
- Observed that vesicle fusion, aggregation, and fragmentation are all possible within a single in vitro system.
Conclusions:
- MBP/C1's effects on LUVs are modulated by lipid composition and protein-lipid ratios.
- This study demonstrates a comprehensive range of MBP-induced vesicle behaviors in a controlled in vitro environment.
- Findings provide insights into MBP's role in myelin structure and dynamics.