Adhesion between Cerebroside Bilayers

Abstract

The structure, hydration properties, and adhesion energy of the membrane glycolipid galactosylceramide (GalCer) were studied by osmotic stress/X-ray diffraction analysis.(1) Fully hydrated GalCer gave a repeat period of 67 A, which decreased less than 2 A with application of applied osmotic pressures as large as 1.6 x 10(9) dyn/cm(2). These results, along with the invariance of GalCer structure obtained by a Fourier analysis of the X-ray data, indicated that there was an extremely narrow fluid space (less than the diameter of a single water molecule) between fully hydrated cerebroside bilayers. Electron density profiles showed that the hydrocarbon chains from apposing GalCer monolayers partially interdigitated in the center of the bilayer. To obtain information on the adhesive properties of GalCer bilayers, we incorporated into the bilayer various mole ratios of the negatively charged lipid dipalmitoylphosphatidylglycerol (DPPG) to provide known electrostatic repulsion between the bilayers. Although 17 and 20 mol % DPPG swelled (disjoined) the GalCer bilayers by an amount predictable from electrostatic double-layer theory, 5, 10, 13, and 15 mol % DPPG did not disjoin the bilayers. By calculating the magnitude of the electrostatic pressure necessary to disjoin the bilayers, we estimated the adhesion energy for GalCer bilayers to be about -1.5 erg/cm(2), a much larger value than that previously measured for phosphatidylcholine bilayers. The observed discontinuous disjoining with increased electrostatic pressure and this relatively large value for adhesion energy indicated the presence of an attractive interaction, in addition to van der Waals attraction, between cerebroside bilayers. Possible attractive interactions are hydrogen bond formation and hydrophobic interactions between the galactose headgroups of apposing GalCer bilayers.

Loss of electrostatic cell-surface repulsion mediates myelin membrane adhesion and compaction in the central nervous system

“…Whereas oligodendrocyte precursor cells synthesize gangliosides with negatively charged and branched sugar residues attached to their head groups, differentiated oligodendrocytes produce galactosylceramide as their major glycolipid (40,41). Interestingly, studies on artificial bilayers reveal relatively strong adhesive forces between galactosylceramides, even a much stronger value than measured for phosphatidylcholine (42). Our study provides evidence that the shift in the synthesis of specific glycolipid species is functionally relevant for the adhesiveness of the oligodendrocyte plasma membrane.…”

Lipid metabolism in myelinating glial cells: lessons from human inherited disorders and mouse models

“…They pack tightly and have the remarkable property that their fl uid/solid phase transition temperature is above body temperature, so that glycolipids have a solid 'gel' phase at body temperature (118)(119)(120). Accordingly, CGT knockout mice, which lack glycosphingolipids, have increased myelin membrane fl uidity and therefore increased ion permeability, which may disrupt saltatory conduction ( 121 ).…”

Bilayer structure of ganglioside/cholesterol mixed system in the presence of Ca2+

“…8. The attractive interaction between sugar headgroups of apposing bilayers has been demonstrated for the galactosylceramide-containing bilayers by the osmotic stress/X-ray diffraction analysis (Kulkarni et al, 1999), and sugar-sugar interdigitation between the lactosylceramide-containing bilayers was indicated by the surface force measurement (Yu et al, 1998). It is known that a large amount of water molecules bound to the headgroup of G M1 (Bach et al, 1982;Arnulphi et al, 1997;Hirai & Takizawa, 1998;Hayakawa & Hirai, 2002).…”