Phosphatidylcholine-cholesterol interactions: bilayers of heteroacid lipids containing linoleate lose calorimetric transitions at low cholesterol concentration

Keough, K. M. W.; Giffin, Bruce F.; Matthews, P.L.J.

doi:10.1016/0005-2736(89)90379-9

Cited by 39 publications

(20 citation statements)

References 20 publications

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“…5) [39], in agreement with reported observations [40,45]. By plotting excitation or emission GP values vs. temperature, the abrupt change observed in the absence of cholesterol and indicative of the phospholipid phase transition is progressively smoothed in samples with increasing cholesterol concentration.…”

Section: The Homogenizing Effect Of Cholesterolsupporting

confidence: 90%

“…Several spectroscopic studies reported a strong modification of phase properties of phospholipids due to the presence of cholesterol [40][41][42][43][44][45][46][47][48][49][50][51]. Depending on their relative concentration and on temperature, the phase properties of vesicles composed of binary mixtures of cholesterol and phospholipids have been described by the solid-ordered, liquid-disordered and liquid-ordered phases [52,53].…”

Section: The Homogenizing Effect Of Cholesterolmentioning

confidence: 99%

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Membrane lipid domains and dynamics as detected by Laurdan fluorescence

1995

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(Laurdan) is a membrane probe of recent characterization, which shows high sensitivity to the polarity of its environment. Steady-state Laurdan excitation and emission spectra have different maxima and shape in the two phospholipid phases, due to differences in the polarity and in the amount of dipolar relaxation, ha bilayers composed of a mixture of gel and liquid-crystalline phases, the properties of Laurdan excitation and emission spectra are intermediate between those obtained in the pure phases. These spectral properties are analyzed using the generalized polarization (GP). The GP value can be used for the quantitation of each phase. The wavelength dependence of the GP value is used to ascertain the coexistence of different phase domains in the bilayer. Moreover, by following the evolution of Laurdan emission vs. time after excitation, the kinetics of phase fluctuation in phospholipid vesicles composed of coexisting gel and liquid-crystalline phases was determined. GP measurements performed in several cell lines did not give indications of coexistence of phase domains in their membranes. In natural membranes, Laurdan parameters indicate a homogeneously fluid environment, with restricted molecular motion in comparison with the phospholipid liquid-crystalline phase. The influence of cholesterol on the phase properties of the two phospholipid phases is proposed to be the cause of the phase behavior observed in na~u'al membranes. In bilayers composed of different phospholipids and various cholesterol concentrations, Laurdan response is very similar to that arising from cell membranes. In the absence of cholesterol, from the steady-state and time-resolved measurements of Laurdan in phospholipid vesicles, the condition for the occurrence of separate coexisting domains in the bilayer has been determined: the molecular ratio between the two phases must be in the range between 30% and 70%. Below and above this range, a single homogeneous phase is observed, with the properties of the more concentrated phase, slightly modified by the presence of the other. Moreover, in this concentration range, the calculated dimension of the domains is very small, between 20 and 50 A.

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Section: The Homogenizing Effect Of Cholesterolsupporting

confidence: 90%

Section: The Homogenizing Effect Of Cholesterolmentioning

confidence: 99%

Membrane lipid domains and dynamics as detected by Laurdan fluorescence

1995

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“…Monounsaturated PCs have been reported to form phases with l o characteristics when combined with physiological proportions of cholesterol (Thewalt and Bloom, 1992;Mateo et al, 1995). Evidence has also been reported that in bilayers cholesterol can discriminate significantly among different phospholipids based on differences in headgroup as well as acyl chain structure (van Dijck et al, 1976;van Dijck, 1979;Demel et al, 1977;Lange et al, 1979;Nakagawa et al, 1979;Wattenberg and Silbert, 1983;Yeagle and Young, 1986;Keough et al, 1989;Vilcheze et al, 1996;McMullen and McElhaney, 1997;Epand et al, 2000;McMullen et al, 2000). Such findings raise the possibility that segregated l o and l d domains could form in mixtures combining cytoplasmic-leaflet phospholipids with cholesterol, as Keller et al (1998) have reported under some conditions in monolayer systems at the air-water interface.…”

Section: Introductionmentioning

confidence: 79%

“…The conclusions noted above have significant implications for understanding the organization of lipids at the cytoplasmic face of a lipid raft in the plasma or other membranes of animal cells. Although differences in the interactions of inner-leaflet phospholipids with one another and with cholesterol may be significant (Demel et al, 1977;Yeagle and Young, 1986;Keough et al, 1989;Kariel et al, 1991;Huster et al, 1998;Mitchell and Litman, 1998), they seem by themselves to be insufficient to drive the spontaneous segregation of l o -domains within the cytoplasmic leaflet of the membrane. If the cytoplasmic leaflet of lipid rafts indeed exists in a l o state distinct from that of the surrounding lipids, it seems that this organization can be explained only by invoking factors extrinsic to the innermonolayer lipids themselves.…”

Section: Discussionmentioning

confidence: 99%

Cholesterol Does Not Induce Segregation of Liquid-Ordered Domains in Bilayers Modeling the Inner Leaflet of the Plasma Membrane

Wang

Silvius

2001

Biophysical Journal

141

111

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A fluorescence-quenching method has been used to assess the potential formation of segregated liquid-ordered domains in lipid bilayers combining cholesterol with mixtures of amino and choline phospholipids like those found in the cytoplasmic leaflet of the mammalian cell plasma membrane. When present in proportions >20-30 mol %, different saturated phospholipids show a strong proclivity to form segregated domains when combined with unsaturated phospholipids and cholesterol, in a manner that is only weakly affected by the nature of the phospholipid headgroups. By contrast, mixtures containing purely unsaturated phospholipids and cholesterol do not exhibit detectable segregation of domains, even in systems whose components differ in headgroup structure, mono- versus polyunsaturation and/or acyl chain heterogeneity. These results indicate that mixtures of phospholipids resembling those found in the inner leaflet of the plasma membrane do not spontaneously form segregated liquid-ordered domains. Instead, our findings suggest that factors extrinsic to the inner-monolayer lipids themselves (e.g., transbilayer penetration of long sphingolipid acyl chains) would be essential to confer a distinctive, more highly ordered organization to the cytoplasmic leaflet of "lipid raft" structures in animal cell membranes.

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“…The behaviour vs. wavelength is qualitatively similar to that observed in the liquid-crystalline phase and quite different from that observed in the presence of coexisting domains of the two phases. Several recent articles reported on the progressive removal of phospholipid phase transition by cholesterol addition [32][33][34]. Many groups are concerned with the occurrence of phospholipid domains containing different cholesterol concentrations in model systems [21][22][23][24]35,36].…”

Section: Discussionmentioning

confidence: 99%