Human myelin proteolipid protein structure and lipid bilayer stacking
|Author:||Ruskamo, Salla1; Raasakka, Arne2; Pedersen, Jan Skov3;|
1Faculty of Biochemistry and Molecular Medicine & Biocenter Oulu, University of Oulu, Oulu, Finland
2Department of Biomedicine, University of Bergen, Bergen, Norway
3Department of Chemistry and Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Aarhus, Denmark
4Institut Laue-Langevin (ILL), Grenoble, France
5Central European Institute of Technology, Masaryk University, Brno, Czech Republic
6National Deuteration Facility, The Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee DC, Sydney, NSW, 2232, Australia
|Online Access:||PDF Full Text (PDF, 4.8 MB)|
|Persistent link:|| http://urn.fi/urn:nbn:fi-fe2022122773890
|Publish Date:|| 2022-12-27
The myelin sheath is an essential, multilayered membrane structure that insulates axons, enabling the rapid transmission of nerve impulses. The tetraspan myelin proteolipid protein (PLP) is the most abundant protein of compact myelin in the central nervous system (CNS). The integral membrane protein PLP adheres myelin membranes together and enhances the compaction of myelin, having a fundamental role in myelin stability and axonal support. PLP is linked to severe CNS neuropathies, including inherited Pelizaeus-Merzbacher disease and spastic paraplegia type 2, as well as multiple sclerosis. Nevertheless, the structure, lipid interaction properties, and membrane organization mechanisms of PLP have remained unidentified. We expressed, purified, and structurally characterized human PLP and its shorter isoform DM20. Synchrotron radiation circular dichroism spectroscopy and small-angle X-ray and neutron scattering revealed a dimeric, α-helical conformation for both PLP and DM20 in detergent complexes, and pinpoint structural variations between the isoforms and their influence on protein function. In phosphatidylcholine membranes, reconstituted PLP and DM20 spontaneously induced formation of multilamellar myelin-like membrane assemblies. Cholesterol and sphingomyelin enhanced the membrane organization but were not crucial for membrane stacking. Electron cryomicroscopy, atomic force microscopy, and X-ray diffraction experiments for membrane-embedded PLP/DM20 illustrated effective membrane stacking and ordered organization of membrane assemblies with a repeat distance in line with CNS myelin. Our results shed light on the 3D structure of myelin PLP and DM20, their structure–function differences, as well as fundamental protein–lipid interplay in CNS compact myelin.
Cellular and molecular life sciences
|Type of Publication:||
A1 Journal article – refereed
|Field of Science:||
1182 Biochemistry, cell and molecular biology
Open Access funding provided by University of Oulu including Oulu University Hospital. This work was funded by the Academy of Finland, grant number 275225 and Jane and Aatos Erkko Foundation. Beamtime and user support at EMBL/DESY, SOLEIL, ILL and ISA are gratefully acknowledged. Travel to synchrotrons was supported by the European Union Horizon 2020 programs iNEXT (Grant 653706) and CALIPSOplus (Grant 730872). The National Deuteration Facility at ANSTO is partly funded by The National Collaborative Research Infrastructure Strategy (NCRIS), an Australian Government initiative. We acknowledge the cryo-electron microscopy and tomography core facility CEITEC MU of CIISB, Instruct-CZ Centre supported by MEYS CR (LM2018127).
|EU Grant Number:||
(653706) iNEXT - Infrastructure for NMR, EM and X-rays for translational research
|Academy of Finland Grant Number:||
275225 (Academy of Finland Funding decision)
The small-angle X-ray scattering and diffraction datasets generated during the current study are available in the Zenodo repository, using https://doi.org/10.5281/zenodo.6324818 and the small-angle neutron scattering dataset in the ILL neutron data repository, using https://doi.org/10.5291/ILL-DATA.8-03-1006.
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