Molecular order and dynamics of phosphatidylcholine bilayer membranes in the presence of cholesterol, ergosterol and lanosterol: a comparative study using 2H-, 13C- and 31P-NMR spectroscopy

Abstract

We report the results of a comparative study of the molecular order and dynamics of phosphatidylcholine (PC) bilayer membranes in the absence and presence of cholesterol, ergosterol and lanosterol, using deuterium (2H) nuclear magnetic resonance (NMR) of deuterated phospholipid molecules, in addition to solid state 13C and 31P-NMR. Using dimyristoylphosphatidylcholines (DMPCs) specifically labeled at positions 2', 3', 4', 6', 8', 10' and 12' of the sn-2 chain together with the perdeuterated 2-[2H27]DMPC derivative, the order profile for 9 of the 13 methylene groups of the sn-2 chain was established at 25 degrees C for DMPC, DMPC/cholesterol, DMPC/ergosterol and DMPC/lanosterol membranes, at a fixed sterol/phospholipid mol ratio of 30%, and in the presence of excess water. The overall ordering effects were found to be ergosterol > cholesterol >> lanosterol. Transverse relaxation (T2e) studies of these systems indicated that while for DMPC, DMPC/cholesterol and DMPC/ergosterol the relative relaxation rates were in qualitative agreement with models which assume cooperative motions of the bilayer molecules as the main relaxation mechanism, those in DMPC/lanosterol were anomalously high, suggesting alterations of lipid packing. Using dipalmitoylphosphatidylcholine (DPPC) deuterated at the trimethylammonium group of the choline moiety, we found that the differential ordering and motional effects induced by the sterols in the acyl chains were also reflected in the headgroup, both in the gel (L beta) and liquid-crystalline phases. 13C and 1H spin dynamics studies of these systems, including cross-polarization, rotating frame longitudinal relaxation and dipolar echo relaxation rates showed that the mobility of the different regions of the phospholipid molecules in the binary lipid systems were inversely correlated with the ordering effects induced by the sterols. A novel combination of C-D bond order parameters (obtained by 2H-NMR) and 13C-1H cross polarization rates confirmed these results. The effects of the same sterols at the same molar proportion on the unsaturated lipid 1-[2H31]palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylcholine (2H31-POPC) at 25 and 35 degrees C were different from those observed on DMPC and showed ordering effects which are largest for cholesterol, while ergosterol and lanosterol produced significantly smaller effects. Transverse relaxation studies indicate that while cholesterol does not perturb cooperative motions in POPC, both ergosterol and lanosterol do. Again, high-resolution solid state 13C-NMR studies support the conclusions of the 2H-NMR experiments.(ABSTRACT TRUNCATED AT 400 WORDS)

Yeast Lipids Can Phase-separate into Micrometer-scale Membrane Domains

“…(i) In the presence of SM, replacement of cholesterol by ergosterol results in a membrane order that is as high as the order of membranes of the well characterized raft mixture SM/PC/cholesterol. This result confirms previous reports showing the property of ergosterol to have a condensing effect on glycerophospholipids (43)(44)(45)(46). (ii) Yeast PI increases the order of membranes containing IPC, irrespective of whether cholesterol or ergosterol is used as the sterol in these mixtures.…”

“…Ergosterol differs from cholesterol in additional double bonds in the B ring and the hydrocarbon side chain and an additional methylation at C24, the latter two making the side chain stiffer and bulkier, respectively (59). These structural attributes were proposed to restrict the motions of acyl chains more efficiently and thus lead to stronger ordering by ergosterol as compared with cholesterol (43)(44)(45)(46). As judged from the higher order of IPC/ergosterol membranes, this effect is more pronounced for IPC, whereas the sterol structure does not seem to be critical for the ordering of C18-SM-containing bilayers (Fig.…”

“…First, the preferential interaction of IPC with ergosterol via hydrogen bonds and van der Waals interactions between the very long saturated fatty acid and the rigid sterol ring backbone could be important. IPC might be preferred over yeast PI because the most abundant yeast PI species comprise an unsaturated fatty acid, which is probably unfavorable for an interaction with ergosterol (28,46). Second, the very long chain fatty acid of IPC might lead to a hydrophobic mismatch between the IPC-rich Lo-like domain and the adjacent Ld-like domain (61).…”

The effects of cholesterol and β-sitosterol on the structure of saturated diacylphosphatidylcholine bilayers

“…The increase of the thickness of DPPC or DMPC bilayers at t [ t m as an effect of cholesterol can be explained by the known ability of cholesterol to suppress trans-gauche isomerisation of saturated phosphatidylcholine chains in their fluid state (Korstanje et al 1990;Kusumi et al 1986;Marsh and Smith 1973;Miao et al 2002;Mouritsen and Zuckermann 2004;Schreier-Muccillo et al 1973;Urbina et al 1995;Vist and Davis 1990). Huang and Feigenson (1999) proposed the ''umbrella model'' as an explanation of this phenomenon.…”

Cholesterol Packing around Lipids with Saturated and Unsaturated Chains: A Simulation Study

“…They concluded that POPC and cholesterol exist at this concentration in an ordered lattice arrangement. Evidence that POPC and DPPC or DMPC interact differently with cholesterol and other sterols is also contained in studies of Urbina et al 12 They utilize NMR spectroscopy to comparatively study POPC, DPPC, and DMPC bilayers containing, separately, cholesterol, ergosterol, and lanosterol at sterol concentrations between 10% and 50%. They conclude that the sterols have a less marked effect on POPC than they have on DPPC.…”