1
|
Segars B, Makhoul-Mansour M, Beyrouthy J, Freeman EC. Measuring the Transmembrane Registration of Lipid Domains in Droplet Interface Bilayers through Tensiometry. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2024; 40:11228-11238. [PMID: 38753461 PMCID: PMC11140749 DOI: 10.1021/acs.langmuir.4c00958] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2024] [Revised: 05/08/2024] [Accepted: 05/09/2024] [Indexed: 05/18/2024]
Abstract
Diverse collections of lipids self-assemble into domains within biological membranes, and these domains are typically organized in both the transverse and lateral directions of the membrane. The ability of the membrane to link these domains across the membrane's interior grants cells control over features on the external cellular surface. Numerous hypothesized factors drive the cross-membrane (or transverse) coupling of lipid domains. In this work we seek to isolate these transverse lipid-lipid influences in a simple model system using droplet interface bilayers (DIBs) to better understand the associated mechanics. DIBs enable symmetric and asymmetric combinations of domain-forming lipid mixtures within a model bilayer, and the evolving energetics of the membrane may be tracked using drop-shape analysis. We find that symmetric distributions of domain-forming lipids produce long-lasting, gradual shifts in the DIB membrane energetics that are not observed in asymmetric distributions of the lipids where the domain-forming lipids are only within one leaflet. The approach selected for this work provides experimental measurement of the mismatch penalty associated with antiregistered lipid domains as well as measurements of the influence of rafts on DIB behaviors with suggestions for their future use as a model platform.
Collapse
Affiliation(s)
- Braydon
G. Segars
- School
of Environmental, Civil, Agricultural, and Mechanical Engineering, University of Georgia, 110 Riverbend Road, Athens, Georgia 30605, United States
| | - Michelle Makhoul-Mansour
- School
of Environmental, Civil, Agricultural, and Mechanical Engineering, University of Georgia, 110 Riverbend Road, Athens, Georgia 30605, United States
- Mechanical,
Agricultural, Biomedical, and Environmental Engineering Department,
Tickle College of Engineering, University
of Tennessee Knoxville, 1512 Middle Dr., Knoxville, Tennessee 37916, United States
| | - Joyce Beyrouthy
- School
of Environmental, Civil, Agricultural, and Mechanical Engineering, University of Georgia, 110 Riverbend Road, Athens, Georgia 30605, United States
| | - Eric C. Freeman
- School
of Environmental, Civil, Agricultural, and Mechanical Engineering, University of Georgia, 110 Riverbend Road, Athens, Georgia 30605, United States
| |
Collapse
|
2
|
Direct imaging of liquid domains in membranes by cryo-electron tomography. Proc Natl Acad Sci U S A 2020; 117:19713-19719. [PMID: 32759217 DOI: 10.1073/pnas.2002245117] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Images of micrometer-scale domains in lipid bilayers have provided the gold standard of model-free evidence to understand the domains' shapes, sizes, and distributions. Corresponding techniques to directly and quantitatively assess smaller (nanoscale and submicron) liquid domains have been limited. Researchers commonly seek to correlate activities of membrane proteins with attributes of the domains in which they reside; doing so hinges on identification and characterization of membrane domains. Although some features of membrane domains can be probed by indirect methods, these methods are often constrained by the limitation that data must be analyzed in the context of models that require multiple assumptions or parameters. Here, we address this challenge by developing and testing two methods of identifying submicron domains in biomimetic membranes. Both methods leverage cryo-electron tomograms of ternary membranes under vitrified, hydrated conditions. The first method is optimized for probe-free applications: Domains are directly distinguished from the surrounding membrane by their thickness. This technique quantitatively and accurately measures area fractions of domains, in excellent agreement with known phase diagrams. The second method is optimized for applications in which a single label is deployed for imaging membranes by both high-resolution cryo-electron tomography and diffraction-limited optical microscopy. For this method, we test a panel of probes, find that a trimeric mCherry label performs best, and specify criteria for developing future high-performance, dual-use probes. These developments have led to direct and quantitative imaging of submicron membrane domains in vitrified, hydrated vesicles.
Collapse
|
3
|
Sarmento MJ, Hof M, Šachl R. Interleaflet Coupling of Lipid Nanodomains - Insights From in vitro Systems. Front Cell Dev Biol 2020; 8:284. [PMID: 32411705 PMCID: PMC7198703 DOI: 10.3389/fcell.2020.00284] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2020] [Accepted: 04/02/2020] [Indexed: 01/09/2023] Open
Abstract
The plasma membrane is a complex system, consisting of two layers of lipids and proteins compartmentalized into small structures called nanodomains. Despite the asymmetric composition of both leaflets, coupling between the layers is surprisingly strong. This can be evidenced, for example, by recent experimental studies performed on phospholipid giant unilamellar vesicles showing that nanodomains formed in the outer layer are perfectly registered with those in the inner leaflet. Similarly, microscopic phase separation in one leaflet can induce phase separation in the opposing leaflet that would otherwise be homogeneous. In this review, we summarize the current theoretical and experimental knowledge that led to the current view that domains are – irrespective of their size – commonly registered across the bilayer. Mechanisms inducing registration of nanodomains suggested by theory and calculations are discussed. Furthermore, domain coupling is evidenced by experimental studies based on the sparse number of methods that can resolve registered from independent nanodomains. Finally, implications that those findings using model membrane studies might have for cellular membranes are discussed.
Collapse
Affiliation(s)
- Maria J Sarmento
- J. Heyrovský Institute of Physical Chemistry of the Czech Academy of Sciences, Dolejškova, Prague, Czechia
| | - Martin Hof
- J. Heyrovský Institute of Physical Chemistry of the Czech Academy of Sciences, Dolejškova, Prague, Czechia
| | - Radek Šachl
- J. Heyrovský Institute of Physical Chemistry of the Czech Academy of Sciences, Dolejškova, Prague, Czechia
| |
Collapse
|
4
|
Effects of Passive Phospholipid Flip-Flop and Asymmetric External Fields on Bilayer Phase Equilibria. Biophys J 2018; 115:1956-1965. [PMID: 30393103 DOI: 10.1016/j.bpj.2018.10.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2018] [Revised: 09/21/2018] [Accepted: 10/01/2018] [Indexed: 11/20/2022] Open
Abstract
Compositional asymmetry between the leaflets of bilayer membranes modifies their phase behavior and is thought to influence other important features such as mechanical properties and protein activity. We address here how phase behavior is affected by passive phospholipid flip-flop, such that the compositional asymmetry is not fixed. We predict transitions from "pre-flip-flop" behavior to a restricted set of phase equilibria that can persist in the presence of passive flip-flop. Surprisingly, such states are not necessarily symmetric. We further account for external symmetry breaking, such as a preferential substrate interaction, and show how this can stabilize strongly asymmetric equilibrium states. Our theory explains several experimental observations of flip-flop-mediated changes in phase behavior and shows how domain formation and compositional asymmetry can be controlled in concert, by manipulating passive flip-flop rates and applying external fields.
Collapse
|
5
|
Galimzyanov TR, Kuzmin PI, Pohl P, Akimov SA. Undulations Drive Domain Registration from the Two Membrane Leaflets. Biophys J 2017; 112:339-345. [PMID: 28122219 DOI: 10.1016/j.bpj.2016.12.023] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2016] [Revised: 12/04/2016] [Accepted: 12/12/2016] [Indexed: 02/06/2023] Open
Abstract
Phase separation in biological membranes plays an important role in protein targeting and transmembrane signaling. Its occurrence in both membrane leaflets commonly gives rise to matching liquid or liquid-ordered domains in the opposing monolayers. The underlying mechanism of such co-localization is not fully understood. The decrease of the line tension around the thicker ordered domain constitutes an important driving force. Yet, robust domain coupling requires an additional energy source, which we have now identified as thermal undulations. Our theoretical analysis of elastic deformations in a lipid bilayer shows that stiffer lipid domains tend to distribute into areas with lower fluctuations of monolayer curvature. These areas naturally align in the opposing monolayers. Thus, coupling requires both membrane leafs to display a heterogeneity in splay rigidities. The heterogeneity may either originate from intrinsic lipid properties or be acquired by adsorption of peripheral molecules. Undulations and line tension act synergistically: the gain in energy due a minimized line tension is proportional to domain radius and thus primarily fuels the registration of smaller domains; whereas the energetic contribution of undulations increases with membrane area and thus primarily acts to coalesce larger domains.
Collapse
Affiliation(s)
- Timur R Galimzyanov
- Laboratory of Bioelectrochemistry, A. N. Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, Moscow, Russia; Department of Theoretical Physics and Quantum Technologies, National University of Science and Technology "MISiS", Moscow, Russia
| | - Peter I Kuzmin
- Laboratory of Bioelectrochemistry, A. N. Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, Moscow, Russia
| | - Peter Pohl
- Department of Molecular and Membrane Biophysics, Institute of Biophysics, Johannes Kepler University Linz, Linz, Austria
| | - Sergey A Akimov
- Laboratory of Bioelectrochemistry, A. N. Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, Moscow, Russia; Department of Theoretical Physics and Quantum Technologies, National University of Science and Technology "MISiS", Moscow, Russia.
| |
Collapse
|
6
|
Manna M, Javanainen M, Monne HMS, Gabius HJ, Rog T, Vattulainen I. Long-chain GM1 gangliosides alter transmembrane domain registration through interdigitation. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2017; 1859:870-878. [PMID: 28143757 DOI: 10.1016/j.bbamem.2017.01.033] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2016] [Revised: 01/02/2017] [Accepted: 01/27/2017] [Indexed: 12/25/2022]
Abstract
Extracellular and cytosolic leaflets in cellular membranes are distinctly different in lipid composition, yet they contribute together to signaling across the membranes. Here we consider a mechanism based on long-chain gangliosides for coupling the extracellular and cytosolic membrane leaflets together. Based on atomistic molecular dynamics simulations, we find that long-chain GM1 in the extracellular leaflet exhibits a strong tendency to protrude into the opposing bilayer leaflet. This interdigitation modulates the order in the cytosolic monolayer and thereby strengthens the interaction and coupling across a membrane. Coarse-grained simulations probing longer time scales in large membrane systems indicate that GM1 in the extracellular leaflet modulates the phase behavior in the cytosolic monolayer. While short-chain GM1 maintains phase-symmetric bilayers with a strong membrane registration effect, the situation is altered with long-chain GM1. Here, the significant interdigitation induced by long-chain GM1 modulates the behavior in the cytosolic GM1-free leaflet, weakening and slowing down the membrane registration process. The observed physical interaction mechanism provides a possible means to mediate or foster transmembrane communication associated with signal transduction.
Collapse
Affiliation(s)
- Moutusi Manna
- Department of Physics, Tampere University of Technology, P. O. Box 692, FI- 33101 Tampere, Finland
| | - Matti Javanainen
- Department of Physics, Tampere University of Technology, P. O. Box 692, FI- 33101 Tampere, Finland; Department of Physics, POB 64, FI-00014 University of Helsinki, Finland
| | - Hector Martinez-Seara Monne
- Department of Physics, Tampere University of Technology, P. O. Box 692, FI- 33101 Tampere, Finland; Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, CZ-16610, Prague, Czech Republic
| | - Hans-Joachim Gabius
- Institute of Physiological Chemistry, Faculty of Veterinary Medicine, Ludwig Maximilian University, D-80539 Munchen, Germany
| | - Tomasz Rog
- Department of Physics, Tampere University of Technology, P. O. Box 692, FI- 33101 Tampere, Finland; Department of Physics, POB 64, FI-00014 University of Helsinki, Finland
| | - Ilpo Vattulainen
- Department of Physics, Tampere University of Technology, P. O. Box 692, FI- 33101 Tampere, Finland; Department of Physics, POB 64, FI-00014 University of Helsinki, Finland; MEMPHYS-Center for Biomembrane Physics, University of Southern Denmark, Odense, Denmark.
| |
Collapse
|
7
|
Schmid F. Physical mechanisms of micro- and nanodomain formation in multicomponent lipid membranes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1859:509-528. [PMID: 27823927 DOI: 10.1016/j.bbamem.2016.10.021] [Citation(s) in RCA: 71] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2016] [Revised: 10/19/2016] [Accepted: 10/27/2016] [Indexed: 12/17/2022]
Abstract
This article summarizes a variety of physical mechanisms proposed in the literature, which can generate micro- and nanodomains in multicomponent lipid bilayers and biomembranes. It mainly focusses on lipid-driven mechanisms that do not involve direct protein-protein interactions. Specifically, it considers (i) equilibrium mechanisms based on lipid-lipid phase separation such as critical cluster formation close to critical points, and multiple domain formation in curved geometries, (ii) equilibrium mechanisms that stabilize two-dimensional microemulsions, such as the effect of linactants and the effect of curvature-composition coupling in bilayers and monolayers, and (iii) non-equilibrium mechanisms induced by the interaction of a biomembrane with the cellular environment, such as membrane recycling and the pinning effects of the cytoplasm. Theoretical predictions are discussed together with simulations and experiments. The presentation is guided by the theory of phase transitions and critical phenomena, and the appendix summarizes the mathematical background in a concise way within the framework of the Ginzburg-Landau theory. This article is part of a Special Issue entitled: Lipid order/lipid defects and lipid-control of protein activity edited by Dirk Schneider.
Collapse
Affiliation(s)
- Friederike Schmid
- Institute of Physics, Johannes Gutenberg University, 55099 Mainz, Germany
| |
Collapse
|
8
|
Reigada R. Alteration of interleaflet coupling due to compounds displaying rapid translocation in lipid membranes. Sci Rep 2016; 6:32934. [PMID: 27596355 PMCID: PMC5011781 DOI: 10.1038/srep32934] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2016] [Accepted: 08/17/2016] [Indexed: 12/02/2022] Open
Abstract
The spatial coincidence of lipid domains at both layers of the cell membrane is expected to play an important role in many cellular functions. Competition between the surface interleaflet tension and a line hydrophobic mismatch penalty are conjectured to determine the transversal behavior of laterally heterogeneous lipid membranes. Here, by a combination of molecular dynamics simulations, a continuum field theory and kinetic equations, I demonstrate that the presence of small, rapidly translocating molecules residing in the lipid bilayer may alter its transversal behavior by favoring the spatial coincidence of similar lipid phases.
Collapse
Affiliation(s)
- Ramon Reigada
- Department de Química Física and Institut de Química Teòrica i Computacional (IQTCUB), Universitat de Barcelona, c/ Martí i Franqués 1, Pta 4, 08028 Barcelona Spain
| |
Collapse
|
9
|
Fowler PW, Williamson JJ, Sansom MSP, Olmsted PD. Roles of Interleaflet Coupling and Hydrophobic Mismatch in Lipid Membrane Phase-Separation Kinetics. J Am Chem Soc 2016; 138:11633-42. [PMID: 27574865 PMCID: PMC5025830 DOI: 10.1021/jacs.6b04880] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
![]()
Characterizing
the nanoscale dynamic organization within lipid
bilayer
membranes is central
to our understanding of cell membranes at a molecular level. We investigate
phase separation and communication across leaflets in ternary lipid
bilayers, including saturated lipids with between 12 and 20 carbons
per tail. Coarse-grained molecular dynamics simulations reveal a novel
two-step kinetics due to hydrophobic mismatch, in which the initial
response of the apposed leaflets upon quenching is to increase local
asymmetry (antiregistration), followed by dominance of symmetry (registration)
as the bilayer equilibrates. Antiregistration can become thermodynamically
preferred if domain size is restricted below ∼20 nm, with implications
for the symmetry of rafts and nanoclusters in cell membranes, which
have similar reported sizes. We relate our findings to theory derived
from a semimicroscopic model in which the leaflets experience a “direct”
area-dependent coupling, and an “indirect” coupling
that arises from hydrophobic mismatch and is most important at domain
boundaries. Registered phases differ in composition from antiregistered
phases, consistent with a direct coupling between the leaflets. Increased
hydrophobic mismatch purifies the phases, suggesting that it contributes
to the molecule-level lipid immiscibility. Our results demonstrate
an interplay of competing interleaflet couplings that affect phase
compositions and kinetics, and lead to a length scale that
can influence lateral and transverse bilayer organization within cells.
Collapse
Affiliation(s)
- Philip W Fowler
- Department of Biochemistry, University of Oxford , South Parks Road, Oxford, OX1 3QU, U.K
| | - John J Williamson
- Department of Physics, Institute for Soft Matter Synthesis and Metrology, Georgetown University , 37th and O Streets, N.W., Washington, D.C. 20057, United States
| | - Mark S P Sansom
- Department of Biochemistry, University of Oxford , South Parks Road, Oxford, OX1 3QU, U.K
| | - Peter D Olmsted
- Department of Physics, Institute for Soft Matter Synthesis and Metrology, Georgetown University , 37th and O Streets, N.W., Washington, D.C. 20057, United States
| |
Collapse
|
10
|
Williamson JJ, Olmsted PD. Comment on "Elastic Membrane Deformations Govern Interleaflet Coupling of Lipid-Ordered Domains". PHYSICAL REVIEW LETTERS 2016; 116:079801. [PMID: 26943562 DOI: 10.1103/physrevlett.116.079801] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/14/2015] [Indexed: 06/05/2023]
Affiliation(s)
- J J Williamson
- Department of Physics, Institute for Soft Matter Synthesis and Metrology, Georgetown University, 37th and O Streets N.W., Washington, D.C. 20057, USA
| | - P D Olmsted
- Department of Physics, Institute for Soft Matter Synthesis and Metrology, Georgetown University, 37th and O Streets N.W., Washington, D.C. 20057, USA
| |
Collapse
|
11
|
Williamson JJ, Olmsted PD. Kinetics of symmetry and asymmetry in a phase-separating bilayer membrane. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2015; 92:052721. [PMID: 26651737 DOI: 10.1103/physreve.92.052721] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2015] [Indexed: 06/05/2023]
Abstract
We simulate a phase-separating bilayer in which the leaflets experience a direct coupling favoring local compositional symmetry ("registered" bilayer phases), and an indirect coupling due to hydrophobic mismatch that favors strong local asymmetry ("antiregistered" bilayer phases). For wide ranges of overall leaflet compositions, multiple competing states are possible. For estimated physical parameters, a quenched bilayer may first evolve toward a metastable state more asymmetric than if the leaflets were uncorrelated; subsequently, it must nucleate to reach its equilibrium, more symmetric, state. These phase-transition kinetics exhibit characteristic signatures through which fundamental and opposing interleaflet interactions may be probed. We emphasize how bilayer phase diagrams with a separate axis for each leaflet can account for overall and local symmetry or asymmetry, and capture a range of observations in the experiment and simulation literature.
Collapse
Affiliation(s)
- J J Williamson
- Department of Physics, Institute for Soft Matter Synthesis and Metrology, Georgetown University, 37th and O Streets, N.W., Washington, D.C. 20057, USA
| | - P D Olmsted
- Department of Physics, Institute for Soft Matter Synthesis and Metrology, Georgetown University, 37th and O Streets, N.W., Washington, D.C. 20057, USA
| |
Collapse
|