Lactosylceramide: Effect of Acyl Chain Structure on Phase Behavior and Molecular Packing

Abstract

Lactosylceramide (LacCer) is a pivotal intermediate in the metabolism of higher gangliosides, localizes to sphingolipid-sterol "rafts," and has been implicated in cellular signaling. To provide a fundamental characterization of LacCer phase behavior and intermolecular packing, LacCer containing different saturated (16:0, 18:0, 24:0) or monounsaturated (18:1(Delta9), 24:1(Delta15)) acyl chains were synthesized and studied by differential scanning calorimetry and Langmuir film balance approaches. Compared to related sphingoid- and glycerol-based lipids, LacCers containing saturated acyl chains display relatively high thermotropic and pressure-induced transitions. LacCer monolayer films are less elastic in an in-plane sense than sphingomyelin films, but are somewhat more elastic than galactosylceramide films. Together, these findings indicate that the disaccharide headgroup only marginally disrupts gel phase packing and orients more perpendicular than parallel to the interface. This contrasts the reported behavior of digalactosyldiglycerides with saturated acyl chains. Introducing single cis double bonds into the LacCer acyl chains dramatically lowers the high thermotropic and pressure-induced transitions. Greater reductions occur when cis double bonds are located near the middle of the acyl chains. The results are discussed in terms of how an extended disaccharide headgroup can enhance interactions among naturally abundant LacCers with saturated acyl chains.

The many faces (and phases) of ceramide and sphingomyelin II – binary mixtures

“…However, the crosssectional area contribution of these gangliosides does not reach values as small as those observed for the molecular area contribution of GM1, namely about 35 Å 2 (Carrer and Maggio 2001), which is about the minimum possible for two closely packed hydrocarbon chains perpendicular to the interface. This is consistent with previous reports indicating that the extended oligosaccharide chain of gangliosides and other GSLs, oriented perpendicularly to the interface (Maggio et al 1978b(Maggio et al , 1981Li et al 2002;Diociaiuti et al 2004), can largely Bfit^under the area of two closely packed hydrocarbon chains. For the more complex oligosaccharide polar head groups, slightly more spacing is required, especially at low surface pressures (Maggio et al 1981;Carrer and Maggio 2001).…”

Design and Facile Synthesis of Neoglycolipids as Lactosylceramide Mimetics and Their Transformation into Glycoliposomes

“…This transphosphatidylation was performed in a chloroform/aqueous buffer two-phase system with DPPC as a donor and Lac-HD as an acceptor. The mixture was shaken at 25 C for 124 h and fresh enzyme was added twice during the course of the reaction. The resulting product was purified by successive chromatographic steps on Sep-pak Accell QMA, Sephadex LH-20, and Silica gel 60N columns to afford the target product Lac-DPPA in 36% yield on the basis of the amount of acceptor added.…”

“…Such a complex thermotropic behavior has been observed in many glycosphingolipids. 25) For example, in the DSC curve of C16:0-lactosyl-ceramide, endothermic transitions has been observed at 66 C, 69 C, 72 C, and 78 C (corresponding to the chain-melting phase transition temperature). 26) Intermolecular interaction between sugars, such as the lactose of lipid head groups, is one of the main causes of this complicated thermotropic behavior.…”

“…This is probably due to the large steric repulsive interaction between the large-sized head groups (i.e., lactosylphosphoethanol group). 21,25) The ability of glycoliposomes containing Lac-DPPA or Lac-DPPE to trap calcein was analyzed by fluorescence microscopy. In this case, it is notable that a sample containing Lac-DPPE alone self-assembled to form liposomes that possessed the ability to incorporate calcein.…”

Involvement of very long fatty acid-containing lactosylceramide in lactosylceramide-mediated superoxide generation and migration in neutrophils

“…NMR studies of artificial lipid bilayers indicated that C24 fatty acid chains of LacCer interdigitated with fatty acids of the opposing monolayer [54]. Moreover, differential scanning calorimetry and Langmuir film balance experiments indicated that not only C24:0-but also C24:1-LacCer show the condensed and chain-ordered phase behavior [55]. Our data clearly indicate that the C24:0-and C24:1-LacCer but not C16:0-or C22:0-LacCer hydrophobic chains reconstruct the LacCer-mediated Lyn phosphorylation in D-HL-60 cells, which have only trace amounts of C24-LacCers (Fig.…”