Human myelin proteolipid protein structure and lipid bilayer stacking

Area of Science:

• Neuroscience
• Structural Biology
• Biochemistry

Background:

• Myelin sheath insulation is vital for nerve impulse transmission.
• Myelin proteolipid protein (PLP) is the most abundant protein in CNS myelin, essential for its stability and compaction.
• PLP is implicated in severe neurological disorders like Pelizaeus-Merzbacher disease and multiple sclerosis.

Purpose of the Study:

• To elucidate the 3D structure, lipid interactions, and membrane organization mechanisms of human PLP and its isoform DM20.
• To understand the structure-function relationships of PLP and DM20.
• To investigate the role of protein-lipid interplay in CNS compact myelin formation.

Main Methods:

• Expression and purification of human PLP and DM20.
• Synchrotron radiation circular dichroism spectroscopy, small-angle X-ray and neutron scattering for structural analysis.
• Reconstitution into lipid membranes and analysis using electron cryomicroscopy, atomic force microscopy, and X-ray diffraction.

Main Results:

• PLP and DM20 adopt a dimeric, α-helical conformation in detergent complexes.
• Reconstituted PLP and DM20 spontaneously form multilamellar myelin-like membrane assemblies.
• Specific lipids like cholesterol and sphingomyelin enhance membrane organization, while PLP/DM20 drives effective membrane stacking and ordered organization.

Conclusions:

• The study reveals the 3D structure of PLP and DM20, highlighting structural variations and their functional impact.
• PLP and DM20 play a fundamental role in organizing CNS compact myelin through protein-lipid interactions.
• Understanding PLP structure and function offers insights into myelin-related neuropathies.