Reorganization of Lipid Diffusion by Myelin Basic Protein as Revealed by STED Nanoscopy.
Myelin is a multilayered membrane that ensheathes axonal fibers in the vertebrate nervous system, allowing fast propagation of nerve action potentials. It contains densely packed lipids, lacks an actin-based cytocortex, and requires myelin basic protein (MBP) as its major structural component. This protein is the basic constituent of the proteinaceous meshwork that is localized between adjacent cytoplasmic membranes of the myelin sheath. Yet, it is not clear how MBP influences the organization and dynamics of the lipid constituents of myelin. Here, we used optical stimulated emission depletion super-resolution microscopy in combination with fluorescence correlation spectroscopy to assess the characteristics of diffusion of different fluorescent lipid analogs in myelin membrane sheets of cultured oligodendrocytes and in micrometer-sized domains that were induced by MBP in live epithelial PtK2 cells. Lipid diffusion was significantly faster and less anomalous both in oligodendrocytes and inside the MBP-rich domains of PtK2 cells compared with undisturbed live PtK2 cells. Our data show that MBP reorganizes lipid diffusion, possibly by preventing the buildup of an actin-based cytocortex and by preventing most membrane proteins from entering the myelin sheath region. Yet, in contrast to myelin sheets in oligodendrocytes, the MBP-induced domains in epithelial PtK2 cells demonstrate no change in lipid order, indicating that segregation of long-chain lipids into myelin sheets is a process specific to oligodendrocytes.
Cellular Neuroscience, Max Planck Institute of Experimental Medicine, Göttingen, Germany.
Olena
O
Steshenko
Department of Nanobiophotonics, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany; Centre for Neural Circuits and Behaviour, University of Oxford, Oxford, United Kingdom.
Débora M
DM
Andrade
Department of Nanobiophotonics, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany; Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany.
Alf
A
Honigmann
Department of Nanobiophotonics, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany.
Veronika
V
Mueller
MRC Human Immunology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, United Kingdom.
Falk
F
Schneider
MRC Human Immunology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, United Kingdom.
Erdinc
E
Sezgin
Department of Nanobiophotonics, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany.
Stefan W
SW
Hell
Cellular Neuroscience, Max Planck Institute of Experimental Medicine, Göttingen, Germany; Institute of Neuronal Cell Biology, Technical University Munich, Munich, Germany. Electronic address: simons@em.mpg.de.
Mikael
M
Simons
Department of Nanobiophotonics, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany; MRC Human Immunology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, United Kingdom. Electronic address: christian.eggeling@rdm.ox.ac.uk.
Christian
C
Eggeling
D008841:Actin Cytoskeleton / Q000378:metabolism; D000818:Animals; D001921:Brain / Q000378:metabolism; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism*; D004058:Diffusion; D004847:Epithelial Cells / Q000378:metabolism; D004983:Ethanolamines / Q000378:metabolism*; D005456:Fluorescent Dyes; D005699:Galactosylceramides / Q000378:metabolism*; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D008297:Male; D051379:Mice; D008853:Microscopy / Q000379:methods; D004676:Myelin Basic Protein / Q000378:metabolism*; D009836:Oligodendroglia / Q000378:metabolism; D048328:Potoroidae; D013050:Spectrometry, Fluorescence; D013109:Sphingomyelins / Q000378:metabolism*
D004983:Ethanolamines; D005456:Fluorescent Dyes; D005699:Galactosylceramides; D008164:Luminescent Proteins; D004676:Myelin Basic Protein; D013109:Sphingomyelins; C005448:phosphorylethanolamine