Model membrane systems to reconstitute immune cell signaling

Céspedes, Pablo F.; Beckers, Daniel; Dustin, Michael L.; Sezgin, Erdinç

doi:10.1111/febs.15488

Cited by 32 publications

(36 citation statements)

References 181 publications

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“…In this regard, self-assembling supported lipid bilayers (SLBs) have been well accepted as one of the most suitable model membrane systems, due to their analogous physical and structural properties to those of biomembranes, and their easy preparation and handling methods 1 . Consequently, SLBs have been exploited to investigate membrane architecture and properties such as domain formation 2,3 , lateral diffusion or ion transport 4,5 , and biological processes at the cellular and molecular levels, such as protein-membrane interactions 6 , ligand-receptor interactions, cellular signalling 7,8 or cell adhesion 9,10 .…”

Section: Introductionmentioning

confidence: 99%

Hydration layer of only few molecules controls lipid mobility in biomimetic membranes

Chattopadhyay

Krok

Orlikowska

et al. 2021

Preprint

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Self-assembly of biomembranes results from the intricate interactions between water and the lipids' hydrophilic head groups. Therefore, the lipid-water interplay strongly contributes to modulating membranes architecture, lipid diffusion, and chemical activity. Here, we introduce a new method of obtaining dehydrated, phase-separated, supported lipid bilayers (SLBs) solely by controlling the decrease of their environment's relative humidity. This facilitates the study of the structure and dynamics of SLBs over a wide range of hydration states. We show that the lipid domain structure of phase-separated SLBs is largely insensitive to the presence of the hydration layer. In stark contrast, lipid mobility is drastically affected by dehydration, showing a 6-fold decrease in lateral diffusion. At the same time, the diffusion activation energy increases approximately twofold for the dehydrated membrane. The obtained results, correlated with the hydration structure of a lipid molecule, revealed that about 6-7 water molecules directly hydrating the phosphocholine moiety play a pivotal role in modulating lipid diffusion. These findings could provide deeper insights into the fundamental reactions where local dehydration occurs, for instance during cell-cell fusion, and help us better understand the survivability of anhydrobiotic organisms. Finally, the strong dependence of lipid mobility on the number of hydrating water molecules opens up an application potential for SLBs as very precise, nanoscale hydration sensors.

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Section: Introductionmentioning

confidence: 99%

Hydration layer of only few molecules controls lipid mobility in biomimetic membranes

Chattopadhyay

Krok

Orlikowska

et al. 2021

Preprint

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“…Length differences of ≥5 nm are known to effect the spontaneous segregation of nonbinding molecules from interfaces created by interacting proteins ( 13 – 15 ). Therefore, to reposition the TCR relative to close contacts formed when T cells interacted with supported lipid bilayers (SLBs) used to mimic APC surfaces ( 16 ), we attached Fab fragments of the anti-CD3ε antibody UCHT1 that we extended with the extracellular region of CD45RO [length 21 nm ( 8 )], with and without a polyhistidine (6xHis) tag (giving UFabROH 6 and UFabRO, respectively; Fig. 1 A ).…”

Section: Resultsmentioning

confidence: 99%

Trapping or slowing the diffusion of T cell receptors at close contacts initiates T cell signaling

Chen

Jenkins

Körbel

et al. 2021

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

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T cell activation is initiated by T cell receptor (TCR) phosphorylation. This requires the local depletion of large receptor-type phosphatases from “close contacts” formed when T cells interact with surfaces presenting agonistic TCR ligands, but exactly how the ligands potentiate signaling is unclear. It has been proposed that TCR ligands could enhance receptor phosphorylation and signaling just by holding TCRs in phosphatase-depleted close contacts, but this has not been directly tested. We devised simple methods to move the TCR in and out of close contacts formed by T cells interacting with supported lipid bilayers (SLBs) and to slow the receptor’s diffusion in the contacts, using a series of anti-CD3ε Fab- and ligand-based adducts of the receptor. TCRs engaging a Fab extended with the large extracellular region of CD45 were excluded from contacts and produced no signaling. Conversely, allowing the extended Fab to become tethered to the SLB trapped the TCR in the close contacts, leading to very strong signaling. Importantly, attaching untethered anti-CD3ε Fab or peptide/MHC ligands, each of which were largely inactive in solution but both of which reduced TCR diffusion in close contacts approximately fivefold, also initiated signaling during cell/SLB contact. Our findings indicate that holding TCRs in close contacts or simply slowing their diffusion in phosphatase-depleted regions of the cell surface suffices to initiate signaling, effects we could reproduce in single-particle stochastic simulations. Our study shows that the TCR is preconfigured for signaling in a way that allows it to be triggered by ligands acting simply as receptor “traps.”

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“…Unique interactions between saturated lipids and cholesterol result in the tighter-packed and higher-ordered membrane environment that segregates from relatively less organized and more fluid membrane regions consisting of unsaturated lipids [ 10 , 28 ]. The compositional and topographical complexity of PM makes it challenging to study specific lipid–lipid interactions [ 29 ]. This challenge has facilitated the development of model membrane systems that faithfully control molecular complexity to unravel the biophysical principles of lipid–lipid and protein–lipid interactions [ 30 ], and consequent formation of segregated domains, clusters, and molecular complexes [ 31 ].…”

Section: Phase Separation In Model Membranesmentioning

confidence: 99%

How Does Liquid-Liquid Phase Separation in Model Membranes Reflect Cell Membrane Heterogeneity?

et al. 2021

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Although liquid–liquid phase separation of cytoplasmic or nuclear components in cells has been a major focus in cell biology, it is only recently that the principle of phase separation has been a long-standing concept and extensively studied in biomembranes. Membrane phase separation has been reconstituted in simplified model systems, and its detailed physicochemical principles, including essential phase diagrams, have been extensively explored. These model membrane systems have proven very useful to study the heterogeneity in cellular membranes, however, concerns have been raised about how reliably they can represent native membranes. In this review, we will discuss how phase-separated membrane systems can mimic cellular membranes and where they fail to reflect the native cell membrane heterogeneity. We also include a few humble suggestions on which phase-separated systems should be used for certain applications, and which interpretations should be avoided to prevent unreliable conclusions.

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Model membrane systems to reconstitute immune cell signaling

Cited by 32 publications

References 181 publications

Hydration layer of only few molecules controls lipid mobility in biomimetic membranes

Hydration layer of only few molecules controls lipid mobility in biomimetic membranes

Trapping or slowing the diffusion of T cell receptors at close contacts initiates T cell signaling

How Does Liquid-Liquid Phase Separation in Model Membranes Reflect Cell Membrane Heterogeneity?

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