Lactosylceramide: lateral interactions with cholesterol.
Lactosylceramide (LacCer) is a key intermediate in glycosphingolipid metabolism and is highly enriched in detergent-resistant biomembrane fractions associated with microdomains, i.e., rafts and caveolae. Here, the lateral interactions of cholesterol with LacCers containing various homogeneous saturated (8:0, 16:0, 18:0, 24:0) or monounsaturated acyl chains (18:1, 24:1) have been characterized using a Langmuir-type film balance. Cholesterol-induced changes in lateral packing were assessed by measuring changes in average molecular area, i.e., area condensations, and in lateral elasticity, i.e., surface compressional moduli (C S(-1)) with emphasis on high surface pressures (> or = 30 mN/m) that mimic biomembrane conditions. Cholesterol most dramatically affected the lateral packing elasticity of LacCers with long saturated acyl chains at sterol mole fractions > or = 0.3, consistent with liquid-ordered (LO) phase formation. The lateral elasticity within the LacCer-cholesterol LO-phase was much lower than that observed within pure LacCer condensed, i.e., gel, phase. The magnitude of the cholesterol-induced reduction in lateral elasticity was strongly mitigated by cis monounsaturation in the LacCer acyl chain. At identical high sterol mole fractions, higher lateral elasticity was observed within LacCer-cholesterol mixtures compared with galactosylceramide-cholesterol and sphingomyelin-cholesterol mixtures. The results show how changes to sphingolipid headgroup and acyl chain structure contribute to the modulation of lateral packing elasticity in sphingolipid-cholesterol LO-phases.
Zhai
Xiuhong
X
University of Minnesota, Hormel Institute, Austin, Minnesota, USA.
Li
Xin-Min
XM
Momsen
Maureen M
MM
Brockman
Howard L
HL
Brown
Rhoderick E
RE
D015703:Antigens, CD / Q000737:chemistry*; D002784:Cholesterol / Q000737:chemistry*; D004548:Elasticity; D007790:Lactosylceramides / Q000737:chemistry*; D008051:Lipid Bilayers / Q000737:chemistry; D044367:Phase Transition; D013109:Sphingomyelins / Q000737:chemistry
D015703:Antigens, CD; D007790:Lactosylceramides; D008051:Lipid Bilayers; D013109:Sphingomyelins; C009744:CDw17 antigen; D002784:Cholesterol