Characterization of the Ternary Mixture of Sphingomyelin, POPC, and Cholesterol: Support for an Inhomogeneous Lipid Distribution at High Temperatures

Bunge, Andreas; Müller, Peter; Stöckl, Martin; Herrmann, Andreas; Huster, Daniel

doi:10.1529/biophysj.107.112904

Cited by 131 publications

(162 citation statements)

References 65 publications

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“…Thus, no PCer-rich gel is present at this temperature. At this temperature, there is no formation of the l o phase (44), confirming that the dissolution of Cer gel in Chol-rich membranes is independent of l o phase formation. The samples were then slowly cooled back to 24°C, and the long lifetime component of t-PnA fluorescence decay was recovered.…”

Section: Cer-rich Gel Dissolution By Chol Is Independent Of Raft Formmentioning

confidence: 54%

Cholesterol-rich Fluid Membranes Solubilize Ceramide Domains

Castro¹,

Silva²,

Fedorov³

et al. 2009

Journal of Biological Chemistry

130

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A uniquely sensitive method for ceramide domain detection allowed us to study in detail cholesterol-ceramide interactions in lipid bilayers with low (physiological) ceramide concentrations, ranging from low or no cholesterol (a situation similar to intracellular membranes, such as endoplasmic reticulum) to high cholesterol (similar to mammalian plasma membrane). Diverse fluorescence spectroscopy and microscopy experiments were conducted showing that for low cholesterol amounts ceramide segregates into gel domains that disappear upon increasing cholesterol levels. This was observed in different raft (sphingomyelin/cholesterol-containing) and non-raft (sphingomyelin-absent) membranes, i.e. mimicking different types of cell membranes. Cholesterol-ceramide interactions have been described mainly as raft sphingomyelin-dependent. Here sphingomyelin independence is demonstrated. In addition, ceramide-rich domains re-appear when either cholesterol is converted by cholesterol oxidase to cholestenone or the temperature is decreased. Ceramide is more soluble in cholesterol-rich fluid membranes than in cholesterol-poor ones, thereby increasing the chemical potential of cholesterol. Ceramide solubility depends on the average gel-fluid transition temperature of the remaining membrane lipids. The inability of cholestenone-rich membranes to dissolve ceramide gel domains shows that the cholesterol ordering and packing properties are fundamental to the mixing process. We also show that the solubility of cholesterol in ceramide domains is low. The results are rationalized by a ternary phospholipid/ceramide/cholesterol phase diagram, providing the framework for the better understanding of biochemical phenomena modulated by cholesterol-ceramide interactions such as cholesterol oxidase activity, lipoprotein metabolism, and lipid targeting in cancer therapy. It also suggests that the lipid compositions of different organelles are such that ceramide gel domains are not formed unless a stress or pathological situation occurs.Cholesterol (Chol) 3 is the most abundant sterol in mammalian plasma membrane and has unique biophysical properties (1, 2). Chol interacts with the high melting temperature (T m ) sphingolipids (SL) in the membrane, leading to the formation of SL/Chol-enriched microdomains (so-called lipid rafts). These domains are in a more ordered state (usually referred to as liquid-ordered (l o ) phase) than the bulk membrane (liquid-disordered phase (l d )) (3, 4). Ceramide (Cer) is an SL formed in stress situations either from sphingomyelin (SM) in rafts or synthesized de novo by serine palmitoyltransferase and ceramide synthase. Both of these processes can be induced by diverse stimuli (5). Cer-induced membrane alterations (e.g. raft fusion into large signaling platforms (6)) were proposed to be the mechanism by which this lipid mediates diverse cellular processes, namely apoptosis (7-10). Cer presents an unusually small polar headgroup and in general very high gel-fluid T m (e.g. for palmitoyl-Cer (PCer) it is ϳ90°C) (11)....

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Section: Cer-rich Gel Dissolution By Chol Is Independent Of Raft Formmentioning

confidence: 54%

Cholesterol-rich Fluid Membranes Solubilize Ceramide Domains

Castro¹,

Silva²,

Fedorov³

et al. 2009

Journal of Biological Chemistry

130

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“…For these sterols, a preferential interaction with the saturated sn-1 chain of POPC (over the unsaturated sn-2 chain) was detected. Importantly, this preferential association with saturated lipid chains, previously suggested as a possible driving force for the formation of cholesterol-induced membrane domains such as lipid rafts, 5,8,83,84 is attenuated for both shorter-and longerchained sterols.…”

Section: Discussionmentioning

confidence: 80%

Influence of the sterol aliphatic side chain on membrane properties: a molecular dynamics study

Robalo

Ramalho

Huster

et al. 2015

Phys. Chem. Chem. Phys.

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Following a recent experimental investigation of the effect of the length of the alkyl side chain in a series of cholesterol analogues (Angew. Chem., Int. Ed., 2013, 52, 12848-12851), we report here an atomistic molecular dynamics characterization of the behaviour of methyl-branched side chain sterols (iso series) in POPC bilayers. The studied sterols included androstenol (i-C0-sterol) and cholesterol (i-C8-sterol), as well as four other derivatives (i-C5, i-C10, i-C12 and i-C14-sterol). For each sterol, both subtle local effects and more substantial differential alterations of membrane properties along the iso series were investigated. The location and orientation of the tetracyclic ring system is almost identical in all compounds. Among all the studied sterols, cholesterol is the sterol that presents the best matching with the hydrophobic length of POPC acyl chains, whereas longer-chained sterols interdigitate into the opposing membrane leaflet. In accordance with the experimental observations, a maximal ordering effect is observed for intermediate sterol chain length (i-C5, cholesterol, i-C10). Only for these sterols a preferential interaction with the saturated sn-1 chain of POPC (compared to the unsaturated sn-2 chain) was observed, but not for either shorter or longer-chained derivatives. This work highlights the importance of the sterol alkyl chain in the modulation of membrane properties and lateral organization in biological membranes.

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“…We then used the average intersect point of these curves to provide an estimate of the transition temperature. This method gave a result of 311.9±2.8 K which is in good agreement of the experimental range of 311 K-314.5 K (most experiments give the exact value as 314.5 K) [101,44,102,103,104]. While the system setup here involved over five times as many lipids as what was used to determine the transition temperatures of PCs, this method shows that at reasonable accurate estimate of the transition temperature can be obtained using only 25 ns simulations as opposed to 100 ns simulations used in simulations of PCs [130].…”

Section: Discussionsupporting

confidence: 82%

“…For example palmitoyl is predominantly found in erythrocytes [43], while stearoyl is more common in nervous tissue [44,45]. With regard to the lateral distribution of sphingomyelin experimental anal- [44], whereas the transition temperature for PSM is between 311 K-314.5 K (38°C-41.5°C) [101,44,102,103,104]. Experimentally cholesterol is observed to preferentially co-localise with sphingomyelins over phosphatidylcholines [105].…”

Section: Introductionmentioning

confidence: 99%

Signals in motion: Determining how signal transduction is mechanically coupled through type-I cytokine receptors

Corbett¹

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The ability of a cell to recognise and respond to external stimuli is essential for cell survival and growth. Type-I cytokine receptors regulate many inflammatory, homeostatic, and growth and development signalling pathways. For example, the erythropoietin receptor is the main driver of red blood cell production from stem cells. All type-I cytokine receptors consist of an extracellular ligandbinding domain, a single helical transmembrane domain and an intracellular domain that associates with kinase/transcription factor signalling pathway, for example the JAK2/STAT5 pathway. Despite being extensively studied and structures of the extracellular domains of many of these receptors being known, the precise mechanism by which these receptors couple the event of ligand-binding to intracellular activation is not known. Indeed, multiple mechanisms have been proposed from experimental and crystallographic data for different receptors. For example, the activation of the growth hormone receptor is proposed to involve a relative rotation of two receptor chains, while in the case of the erythropoietin receptor the chains were suggested to separate in a scissor-like mechanism. In part, this is due to the limits of resolution achievable by experimental approaches as well as a lack of appreciation for the dynamical properties of the receptor proteins and the membrane environment.This thesis focuses on the use of fully atomistic molecular dynamics simulations to investigate the mechanism of activation for the type-I cytokine receptors. In particular MD simulations are used to probe whether conformations of the receptors observed crystallographically are representative of physiological conformations. Further to this, the quality of the X-ray crystal structures is tested by recreation of the crystal lattice in MD simulations. The effect of membrane composition is investigated by comparing the behaviour of the transmembrane domain in bulk and cholesterol-enriched raft-like bilayers. Finally, receptor dimers are examined for active and inactive conformations in raft-like bilayers containing sphingomyelin. Force field parameters for the lipid sphingomyelin that were used to build raft-like bilayers were also generated and validated. The work draws into question several of the mechanistic models proposed for the type-I cytokine receptors and demonstrates the difficulty in proposing a detailed mechanism of action based on limited sets of structural data. In particular, they highlight the limitations of the use of structural data in proposing a model when only a part of the receptor is considered. Results from the simulations also suggest that the lipid composition can influence the structure and behaviour of the receptors. Taken together the work shows the importance of considering not only the ligand-binding domain of the receptor but also the restrictions imposed by the transmembrane domain and structural influences caused by the membrane when proposing a mechanism of activation for this important class of cell surface recept...

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Characterization of the Ternary Mixture of Sphingomyelin, POPC, and Cholesterol: Support for an Inhomogeneous Lipid Distribution at High Temperatures

Cited by 131 publications

References 65 publications

Cholesterol-rich Fluid Membranes Solubilize Ceramide Domains

Cholesterol-rich Fluid Membranes Solubilize Ceramide Domains

Influence of the sterol aliphatic side chain on membrane properties: a molecular dynamics study

Signals in motion: Determining how signal transduction is mechanically coupled through type-I cytokine receptors

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