The lateral membrane organization and dynamics of myelin proteins PLP and MBP are dictated by distinct galactolipids and the extracellular matrix

PLoS One. 2014 Jul 8;9(7):e101834. doi: 10.1371/journal.pone.0101834. eCollection 2014.

Abstract

In the central nervous system, lipid-protein interactions are pivotal for myelin maintenance, as these interactions regulate protein transport to the myelin membrane as well as the molecular organization within the sheath. To improve our understanding of the fundamental properties of myelin, we focused here on the lateral membrane organization and dynamics of peripheral membrane protein 18.5-kDa myelin basic protein (MBP) and transmembrane protein proteolipid protein (PLP) as a function of the typical myelin lipids galactosylceramide (GalC), and sulfatide, and exogenous factors such as the extracellular matrix proteins laminin-2 and fibronectin, employing an oligodendrocyte cell line, selectively expressing the desired galactolipids. The dynamics of MBP were monitored by z-scan point fluorescence correlation spectroscopy (FCS) and raster image correlation spectroscopy (RICS), while PLP dynamics in living cells were investigated by circular scanning FCS. The data revealed that on an inert substrate the diffusion rate of 18.5-kDa MBP increased in GalC-expressing cells, while the diffusion coefficient of PLP was decreased in sulfatide-containing cells. Similarly, when cells were grown on myelination-promoting laminin-2, the lateral diffusion coefficient of PLP was decreased in sulfatide-containing cells. In contrast, PLP's diffusion rate increased substantially when these cells were grown on myelination-inhibiting fibronectin. Additional biochemical analyses revealed that the observed differences in lateral diffusion coefficients of both proteins can be explained by differences in their biophysical, i.e., galactolipid environment, specifically with regard to their association with lipid rafts. Given the persistence of pathological fibronectin aggregates in multiple sclerosis lesions, this fundamental insight into the nature and dynamics of lipid-protein interactions will be instrumental in developing myelin regenerative strategies.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Line
  • Extracellular Matrix / metabolism*
  • Fibronectins / physiology
  • Galactolipids / metabolism*
  • Laminin / physiology
  • Membrane Microdomains / metabolism*
  • Myelin Basic Protein / metabolism*
  • Myelin Proteolipid Protein / metabolism*
  • Protein Transport
  • Rats

Substances

  • Fibronectins
  • Galactolipids
  • Laminin
  • Mbp protein, rat
  • Myelin Basic Protein
  • Myelin Proteolipid Protein
  • Plp1 protein, rat

Grant support

This work was supported by grants from the Netherlands Organization of Scientific Research (NWO, www.nwo.nl, WB, 016.096.329), the Dutch MS Research Foundation (‘Stichting MS Research’, www.msresearch.nl, WB, DH), the Research Foundation Flanders (www.fwo.be, JH), and the Deutsche Forschungsgemeinschaft (DFG, DCL) through the collaborative research grant SFB1032 and the Excellence Initiative Nanosystems Initiative Munich (NIM) and Ludwig-Maximilians-Universität Munich via the LMU Innovative BioImaging Network and the Center for NanoScience. The research visit to Dr. Don C. Lamb's laboratory was supported by an EMBO Short Term Fellowship (www.EMBO.org, ASTF 463-2012/EMBO, HO). Part of the work has been performed at the UMCG Microscopy and Imaging Center (UMIC), which is sponsored by NWO grant 175-010-2009-023. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.