Limited cholesterol depletion causes aggregation of plasma membrane lipid rafts inducing T cell activation

Mahammad, Saleemulla; Dinić, Jelena; Adler, Jeremy; Parmryd, Ingela

doi:10.1016/j.bbalip.2010.02.003

Cited by 58 publications

(55 citation statements)

References 64 publications

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“…We reconstituted the fluorescent FITC-LW21 at 3 mol% into C24∶1 PC GUVs and infused cholesterol by a recently developed MBCD-Chol exchange protocol. This allowed careful loading of membranes below saturation levels (23). Using confocal microscopy we observed the segregation of FITC-LW21 into microscaled, line-shaped domains within a fluid bilayer.…”

Section: Discussionmentioning

confidence: 97%

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Lateral sorting in model membranes by cholesterol-mediated hydrophobic matching

Kaiser

Orłowski

Róg

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

148

115

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Theoretical studies predict hydrophobic matching between transmembrane domains of proteins and bilayer lipids to be a physical mechanism by which membranes laterally self-organize. We now experimentally study the direct consequences of mismatching of transmembrane peptides of different length with bilayers of different thicknesses at the molecular level. In both model membranes and simulations we show that cholesterol critically constrains structural adaptations at the peptide-lipid interface under mismatch. These constraints translate into a sorting potential and lead to selective lateral segregation of peptides and lipids according to their hydrophobic length.H ydrophobicity is the key criterion for lipids and proteins to integrate into membranes (1). This self-assembly is driven by the minimization of hydrophobic surface area exposed to the aqueous phase (2). Next to sterols, eukaryotic membranes contain a variety of phospholipids with different chain length (3) and proteins with a variety of transmembrane (TM) domain lengths (4). Why cell membranes contain so many lipids is still enigmatic. But one reason could be membrane sorting due to grouping of TM proteins and lipids with similar hydrophobic length.The "mattress model" predicts that the embedding of a rigid, helical TM protein into a fluid bilayer causes the lipids to adapt locally to a mismatch (5). In this way exposure of hydrophobic surface area is minimized. The adaptive flexing and straightening of the lipids can also be accompanied by a tilting of the protein (6). Because of these strain-causing adaptations of the bilayer, selective association of matching lipids with TM proteins as well as macroscopic sorting processes according to hydrophobic length have been predicted by theory and simulation (7,8). Membrane properties such as elasticity-modulated by cholesterolwere also predicted as crucial parameters (9). Such mismatchdependent, cholesterol-induced sorting has indeed been proposed as a retention mechanism for the Golgi-resident proteins in the secretory pathway (10).Due to the complexity of cell membranes, model membranes have proven a valuable system to investigate hydrophobic matching (11-13). Hydrophobic peptides of the poly-leucine type have been used as generic TM proteins because of the ease of their organic solvent-based reconstitution (14,15). From these experiments, it has become clear that TM proteins indeed tolerate moderate mismatch with the bilayer (13,14,16). However, large mismatch as well as cholesterol have been found to reduce efficiency of TM peptide incorporation into bilayers, suggesting that there are energetic limitations to mismatch buffering (12).Despite indication for selective protein-lipid interactions and hydrophobic matching (17, 18), actual sorting of TM proteins and accompanying lipid cosorting has not been reconstituted in vitro. Therefore, it remains unclear whether hydrophobic mismatch is a significant parameter in the organization of proteinacious membranes.Using TM peptides and lipids of defined acyl chain...

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Section: Discussionmentioning

confidence: 97%

“…We always maintained 10 mol% of C18∶1 PC to keep the bilayer fluid and more stable (see SI Text). Then we carefully infused 3.8 μM cholesterol as a methyl-β-cyclodextrin complex (MBCD-Chol) (23). This induced a substantial clustering of FITC-LW21 in the C24∶1 PC membrane into line-shaped domains within minutes ( Fig.…”

Section: Resultsmentioning

confidence: 99%

Lateral sorting in model membranes by cholesterol-mediated hydrophobic matching

Kaiser

Orłowski

Róg

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

148

115

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“…Once a cell is dead, it is hardly surprising that a cellular process ceases to function and it is incorrect to ascribe this failure to the importance of cholesterol and/or lipid rafts. This was the case in the T cell signalling field [22] and care must be taken to make sure that cells remain viable. …”

Section: Introductionmentioning

confidence: 99%

Cholesterol Depletion Using Methyl-β-cyclodextrin

Mahammad

Parmryd

2014

Methods in Molecular Biology

Self Cite

226

166

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Cholesterol is an essential component of mammalian cells. It is the major lipid constituent of the plasma membrane and is also abundant in most other organelle membranes. In the plasma membrane cholesterol plays critical physical roles in the maintenance of membrane fluidity and membrane permeability. It is also important for membrane trafficking, cell signalling and lipid as well as protein sorting. Cholesterol is essential for the formation of liquid ordered domains in model membranes, which in cells are known as lipid nanodomains or lipid rafts. Cholesterol depletion is widely used to study the role of cholesterol in cellular processes and can be performed over days using inhibitors of its synthesis or acutely over minutes using chemical reagents. Acute cholesterol depletion by methyl-β-cyclodextrin (MBCD) is the most widely used method and here we describe how it should be performed to avoid the common side-effect cell death.

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“…The objective of this work is therefore to understand the composition and more importantly, the initiation process of the formation of lipid rafts in cellular membranes. Prior studies have suggested the existence of interactions between cholesterol and sphingolipids (9). As cholesterol binds in-between two sphingomyelin molecules the assembly is rigid and more resistant to solvation, hence an increase in sphingolipids and a minimum amount of cholesterol may lead to lipid raft formation.…”

Section: Resultsmentioning

confidence: 99%

The Stability of Lipid Rafts-Like Micro-Domains Is Dependent on the Available Amount of Cholesterol

Nguyen¹,

Chintamsetti²,

Chennuru³

2016

JBPC

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Lipid rafts are sterol and sphingolipid rich membrane domains that possibly may play roles in multiple cellular processes. These domains are still the matter of debate and it is still unknown by which mechanism if any and organisms promote their formation. This study centers on the ease of in vitro formation of lipid rafts-like structures as it relates to the relative availability of sphingolipids, phospholipids, cholesterol, and membrane proteins. Following a 12 h incubation period, isolation and extraction of the lipid rafts-like assemblies, the composition of the structures was evaluated using HPLC. Cholesterol and sphingomyelin were detected at 206 nm and phosphatidylcholine was detected at 254 nm. Identification of lactose permease, a typical membrane protein, was done using FTIR. The thermal stability of the produced structures was also determined. Results show that the addition of cholesterol significantly increased both the amount of insoluble lipid rafts-like structures and their stability, and that the availability of a minimum amount of sphingolipid was necessary to produce larger amounts of more stable structures. However, the addition of phospholipids hindered the formation of lipid rafts-like assemblies and those formed were generally less stable.

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Limited cholesterol depletion causes aggregation of plasma membrane lipid rafts inducing T cell activation

Cited by 58 publications

References 64 publications

Lateral sorting in model membranes by cholesterol-mediated hydrophobic matching

Lateral sorting in model membranes by cholesterol-mediated hydrophobic matching

Cholesterol Depletion Using Methyl-β-cyclodextrin

The Stability of Lipid Rafts-Like Micro-Domains Is Dependent on the Available Amount of Cholesterol

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