Hallmarks of Reversible Phase Separation in Living, Unperturbed Cell Membranes

Rayermann, Scott; Rayermann, Glennis E.; Merz, Alex; Keller, Sarah L.

doi:10.1016/j.bpj.2016.11.2823

Cited by 4 publications

(3 citation statements)

References 113 publications

(165 reference statements)

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“…Despite this simple definition and much supporting evidence [10][11][12][13][14][15][16][17] , there remains significant controversy about the existence and functionality of raft domains in living cells 3 . In large part, the controversies persist because raft domains have not been directly, microscopically observed in living cell PMs, although liquid lipid-driven domains have been imaged directly in yeast vacuoles 17,18 . PM nanodomains may be difficult to image due to the limits on spatial and temporal resolution of currently available technologies.…”

Section: Introductionmentioning

confidence: 99%

Myelin-Associated MAL and PLP Are Unusual among Multipass Transmembrane Proteins in Preferring Ordered Membrane Domains

et al. 2020

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Eukaryotic membranes can be partitioned into lipid-driven membrane microdomains called lipid rafts, which function to sort lipids and proteins in the plane of the membrane. As protein selectivity underlies all functions of lipid rafts, there has been significant interest in understanding the structural and molecular determinants of raft affinity. Such determinants have been described for lipids and single-spanning transmembrane proteins; however, how multi-pass transmembrane proteins (TMPs) partition between ordered and disordered phases has not been widely explored.Here we used cell-derived Giant Plasma Membrane Vesicles (GPMVs) to systematically measure multi-pass TMP partitioning to ordered membrane domains. Across a set of 24 structurally and functionally diverse multi-pass TMPs, the large majority (92%) had minimal raft affinity. The only exceptions were two myelin-associated four pass TMPs, Myelin and Lymphocyte protein (MAL) and ProteoLipid Protein (PLP). We characterized the potential mechanisms for their exceptional raft affinity and observed that PLP requires cholesterol and sphingolipids for optimal association with ordered membrane domains and that PLP and MAL appear to compete for cholesterolmediated raft affinity. These observations suggest broad conclusions about the composition of ordered membrane domains in cells and point to previously unrecognized drivers of raft affinity for multi-pass transmembrane proteins.

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Section: Introductionmentioning

confidence: 99%

Myelin-Associated MAL and PLP Are Unusual among Multipass Transmembrane Proteins in Preferring Ordered Membrane Domains

et al. 2020

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“…The studies of lateral phase separation in the plane of the lipid monolayers and bilayers in terms of mobility of membrane-anchored motifs and lipid conformations have come a long way since the early original work carried out 30–50years ago. − Several recent experimental and computational studies have shown stark evidence of lateral phase separation in vitro model ternary − and quaternary lipid mixtures − and in vivo cell membranes. − The model ternary in vitro systems generally consist of a saturated lipid, unsaturated lipid, and cholesterol. Depending on the cholesterol content, ternary systems show two-phase coexistence as “liquid-ordered” L o and “liquid-disordered” L d phases at higher cholesterol concentrations and “liquid-ordered gel” L β and “liquid-disordered” L d phases at lower cholesterol concentrations.…”

Section: Introductionmentioning

confidence: 99%

Interpretation of Phase Boundary Fluctuation Spectra in Biological Membranes with Nanoscale Organization

Iyer

Negi

Srivastava

2020

J. Chem. Theory Comput.

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In this work, we use support vector machine algorithm to detect simple and complex interfaces in atomistic and coarse-grained molecular simulation trajectories of phase-separating lipid bilayer systems. We show that the power spectral density of the interfacial height fluctuations and, in turn, the line tension of the lipid bilayer systems depends on the order parameter used to identify the intrinsic interface. To highlight the effect of artificial smoothing of the interface on the fluctuation spectra and the ensuing line tension calculations, we perform a convolution of the boundaries identified at molecular resolution with a 2D Gaussian function of variance ε2 equal to the resolution limit, (1/2πε2)exp( – |r|2/2ε2). The convolution function is given by h ⊗ g where h is the instantaneous height fluctuation, and g is the Gaussian function. This is similar to the effect of point spread functions in experiments. We find that the region of fluctuation spectra that scales according to capillary wave theory formalism depends on the complexity of the interfacial geometry, which may not always be detected at experimental resolutions. We propose that the different k regimes in the fluctuation spectra can be used to characterize mode-dependent interfacial tensions to understand the interfaces beyond the linear line tension calculations.

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“…The study of lateral phase separation in the plane of the lipid monolayers and bilayer in terms of mobility of membrane anchored motifs and lipid conformations have come a long way since the early original work carried out 30-50 years ago [1][2][3][4][5][6][7][8][9][10]. Several recent experimental and computational studies have shown stark evidence of lateral phase separation in in-vitro model ternary [11][12][13][14][15] and quaternary lipid mixtures [16][17][18] and in in-vivo cell membranes [19][20][21][22][23]. The model ternary in-vitro systems generally consists of a saturated lipid, unsaturated lipid and cholesterol.…”

Section: Introductionmentioning

confidence: 99%

Interpretation of Phase Boundary Fluctuation Spectra in Biological Membranes with Nanoscale Organization

Iyer

Negi

Srivastava

2019

Preprint

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In this work, we use Support Vector Machine algorithm to detect simple and complex interfaces in atomistic and coarse-grained molecular simulation trajectories of phase separating lipid bilayer systems. We show that the power spectral density of the interfacial height fluctuations and in turn the line tension of the lipid bilayer systems depend on the order parameter used to identify the intrinsic interface. To highlight the effect of artificial smoothing of the interface on the fluctuation spectra and the ensuing line tension calculations, we perform a convolution of the boundaries identified at molecular resolution with a 2D Gaussian function of variance ε 2 equal to the resolution limit, (1/2πε 2 )exp(−|r| 2 /2ε 2 ).The convolution function is given by h⊗g, where h is the instantaneous height fluctuation and g is the Gaussian function. This is similar to the effect of point spread functions in experiments. We find that the region of fluctuation spectra that scales according to capillary wave theory formalism depends on the complexity of the interfacial geometry, which may not always be detected at experimental resolutions. We propose that the different q-regimes in the fluctuation spectra can be used to characterize mode dependent interfacial tensions to understand the interfaces beyond the linear line tension calculations.This could also be useful in interpretation of fluctuating boundaries in out-of-equilibrium in-vivo membrane systems that carry information about the nature of non-thermal (active) fluctuations in these systems.

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Hallmarks of Reversible Phase Separation in Living, Unperturbed Cell Membranes

Abstract: Hallmarks of Reversible Phase Separation in Living, Unperturbed Cell Membranes

Cited by 4 publications

References 113 publications

Myelin-Associated MAL and PLP Are Unusual among Multipass Transmembrane Proteins in Preferring Ordered Membrane Domains

Myelin-Associated MAL and PLP Are Unusual among Multipass Transmembrane Proteins in Preferring Ordered Membrane Domains

Interpretation of Phase Boundary Fluctuation Spectra in Biological Membranes with Nanoscale Organization

Interpretation of Phase Boundary Fluctuation Spectra in Biological Membranes with Nanoscale Organization

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