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Selectivity of lipid-protein interaction with myelin proteolipids PLP and DM-20. A fluorescence anisotropy study
D Houbre1, P Schindler, E Trifilieff
1Centre de Recherches Pharmaceutiques, URA 491 du CNRS, Université Louis Pasteur, Illkirch, France.
Abstract:
The two main myelin proteolipids, PLP (30 kDa) and DM-20 (25 kDa), differ by an internal deletion in DM-20. The deleted fragment, of 35 amino acids (116-150), corresponds to the major hydrophilic domain of PLP. Fluorescence anisotropy experiments using diphenylhexatriene as a fluorescent probe were performed to detect the phase separation induced by these two proteolipids in multilamellar vesicles of binary composition. We found that in vesicles composed of 30% L-alpha-PS and 70% DPPC, the PLP boundary layer contained about 18 motionally restricted phospholipids, almost exclusively L-alpha-PS. On the contrary, the DM-20 boundary layer contained only 14 to 15 phospholipids, with a composition no different from that of the bulk vesicle. In mixtures of DMPG and DPPC, the selectivity of PLP for the acidic phospholipid DMPG was maintained, but was lower than that observed for L-alpha-PS. We assume that this selectivity of PLP stems mainly from electrostatic interactions between the charged residues of the 116-150 fragment, deleted in DM-20, and the acidic phospholipids. These results suggest that fragment 116-150 may play a specific role in the interaction of PLP with the lipid bilayer of the myelin membrane.
Insights
Myelin proteolipid protein (PLP) and its shorter form DM-20 interact differently with lipid bilayers. The PLP hydrophilic domain influences phospholipid interactions, suggesting a role in myelin membrane structure.
Area of Science:
- Biochemistry
- Neuroscience
- Molecular Biology
Background:
- Myelin proteolipids, including PLP and DM-20, are crucial for CNS myelin structure.
- PLP and DM-20 differ by a 35-amino acid deletion (116-150) in DM-20, which forms a major hydrophilic domain in PLP.
- Understanding their lipid interactions is key to myelin function.
Purpose of the Study:
- To investigate the differential effects of PLP and DM-20 on lipid bilayer phase separation.
- To determine the role of the deleted fragment (116-150) in PLP's interaction with phospholipids.
Main Methods:
- Fluorescence anisotropy experiments using diphenylhexatriene.
- Analysis of proteolipid-induced phase separation in binary lipid vesicles (L-alpha-PS/DPPC and DMPG/DPPC).
Main Results:
- PLP induced greater phospholipid restriction in L-alpha-PS/DPPC vesicles compared to DM-20.
- PLP showed selectivity for acidic phospholipids (L-alpha-PS and DMPG), though less pronounced for DMPG.
- DM-20 boundary layers had a composition similar to the bulk vesicle.
Conclusions:
- The 116-150 fragment of PLP is critical for its selective interaction with acidic phospholipids.
- Electrostatic interactions involving charged residues in the 116-150 fragment likely drive PLP's lipid binding.
- This fragment may play a specific role in anchoring PLP to the myelin membrane lipid bilayer.