scholarly journals α-Synuclein Senses Lipid Packing Defects and Induces Lateral Expansion of Lipids Leading to Membrane Remodeling

2013 ◽  
Vol 288 (29) ◽  
pp. 20883-20895 ◽  
Author(s):  
Myriam M. Ouberai ◽  
Juan Wang ◽  
Marcus J. Swann ◽  
Celine Galvagnion ◽  
Tim Guilliams ◽  
...  
Keyword(s):  
Lipid Bilayers ◽  
Lipid Membranes ◽  
Binding Mode ◽  
Lateral Expansion ◽  
Optical Biosensing ◽  
Lipid Packing ◽  
Force Microscopy ◽  
Packing Defects ◽  
Lipid Environment ◽  
Dynamic Structures

There is increasing evidence for the involvement of lipid membranes in both the functional and pathological properties of α-synuclein (α-Syn). Despite many investigations to characterize the binding of α-Syn to membranes, there is still a lack of understanding of the binding mode linking the properties of lipid membranes to α-Syn insertion into these dynamic structures. Using a combination of an optical biosensing technique and in situ atomic force microscopy, we show that the binding strength of α-Syn is related to the specificity of the lipid environment (the lipid chemistry and steric properties within a bilayer structure) and to the ability of the membranes to accommodate and remodel upon the interaction of α-Syn with lipid membranes. We show that this interaction results in the insertion of α-Syn into the region of the headgroups, inducing a lateral expansion of lipid molecules that can progress to further bilayer remodeling, such as membrane thinning and expansion of lipids out of the membrane plane. We provide new insights into the affinity of α-Syn for lipid packing defects found in vesicles of high curvature and in planar membranes with cone-shaped lipids and suggest a comprehensive model of the interaction between α-Syn and lipid bilayers. The ability of α-Syn to sense lipid packing defects and to remodel membrane structure supports its proposed role in vesicle trafficking.

scholarly journals AFM nanoindentation reveals decrease of elastic modulus of lipid bilayers near freezing point of water

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Calum Gabbutt ◽  
Wuyi Shen ◽  
Jacob Seifert ◽  
Sonia Contera
Keyword(s):  
Lipid Bilayers ◽  
Lipid Membranes ◽  
Structural Changes ◽  
Freezing Point ◽  
Liquid Environment ◽  
Force Microscopy ◽  
Atomic Force ◽  
Afm Imaging ◽  
Underlying Causes ◽  
Irreversible Injury

AbstractCell lipid membranes are the primary site of irreversible injury during freezing/thawing and cryopreservation of cells, but the underlying causes remain unknown. Here, we probe the effect of cooling from 20 °C to 0 °C on the structure and mechanical properties of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) bilayers using atomic force microscopy (AFM) imaging and AFM-based nanoindentation in a liquid environment. The Young’s modulus of elasticity (E) at each temperature for DPPC was obtained at different ionic strengths. Both at 20 mM and 150 mM NaCl, E of DPPC bilayers increases exponentially –as expected–as the temperature is lowered between 20 °C and 5 °C, but at 0 °C E drops from the values measured at 5 °C. Our results support the hypothesis that mechanical weakening of the bilayer at 0 °C  is produced by  structural changes at the lipid-fluid interface.

Deposition of Lipid Bilayers with Atomic Force Microscopy

2005 ◽  
Vol 11 (S03) ◽  
pp. 44-47 ◽  
Author(s):  
G. D. Tavares ◽  
M. C. de Oliveira ◽  
J. M. C. Vilela ◽  
M. S. Andrade
Keyword(s):  
Lipid Bilayers ◽  
Lipid Membranes ◽  
Force Microscopy ◽  
Langmuir Blodgett ◽  
Flat Substrate ◽  
Atomic Force ◽  
Lipid Mixtures ◽  
A Cell ◽  
Integral Proteins ◽  
Spherical Vesicles

Biological membranes are constituted of lipids organized as a two dimensional bilayer supporting peripheral and integral proteins, providing a barrier between the inside and the outside of a cell [1]. Similar membranes can be prepared from the lipid mixtures forming liposomes. The liposomes are multi or unilamellar spherical vesicles in which an aqueous volume is enclosed and can be used to encapsulate some drugs [2]. In order to better expose the details of their structure, these membranes are generally deposited on the surface of a flat substrate. These supported planar lipid membranes can also provide a model system for investigating the properties and functions of the complex cell membrane and membrane mediated processes such as recognition events and biological signal transduction. Various methods have been used to create artificial lipid membranes supported on a solid surface, being the most used the Langmuir-Blodgett monolayers formation [3], the vesicle fusion or liposome adsorption [4] and the solution spreading [5].

scholarly journals Non-vesicular transfer of membrane proteins from nanoparticles to lipid bilayers

2011 ◽  
Vol 137 (2) ◽  
pp. 217-223 ◽  
Author(s):  
Sourabh Banerjee ◽  
Crina M. Nimigean
Keyword(s):  
Membrane Proteins ◽  
Lipid Bilayer ◽  
Lipid Bilayers ◽  
Single Molecule ◽  
Lipid Membranes ◽  
Single Channel ◽  
Black Lipid Membranes ◽  
Potassium Channel Kcsa ◽  
Lipid Environment ◽  
Biochemical Preparation

Discoidal lipoproteins are a novel class of nanoparticles for studying membrane proteins (MPs) in a soluble, native lipid environment, using assays that have not been traditionally applied to transmembrane proteins. Here, we report the successful delivery of an ion channel from these particles, called nanoscale apolipoprotein-bound bilayers (NABBs), to a distinct, continuous lipid bilayer that will allow both ensemble assays, made possible by the soluble NABB platform, and single-molecule assays, to be performed from the same biochemical preparation. We optimized the incorporation and verified the homogeneity of NABBs containing a prototypical potassium channel, KcsA. We also evaluated the transfer of KcsA from the NABBs to lipid bilayers using single-channel electrophysiology and found that the functional properties of the channel remained intact. NABBs containing KcsA were stable, homogeneous, and able to spontaneously deliver the channel to black lipid membranes without measurably affecting the electrical properties of the bilayer. Our results are the first to demonstrate the transfer of a MP from NABBs to a different lipid bilayer without involving vesicle fusion.

Membrane domain modulation of Aβ1–42 oligomer interactions with supported lipid bilayers: an atomic force microscopy investigation

Nanoscale ◽  
2019 ◽  
Vol 11 (43) ◽  
pp. 20857-20867 ◽  
Author(s):  
Mehdi Azouz ◽  
Christophe Cullin ◽  
Sophie Lecomte ◽  
Michel Lafleur
Keyword(s):  
Lipid Bilayers ◽  
Amyloid Peptide ◽  
Supported Lipid Bilayers ◽  
Membrane Domain ◽  
Force Microscopy ◽  
Atomic Force ◽  
Nucleation Sites ◽  
Microscopy Investigation ◽  
Packing Defects ◽  
As Adsorption

Lipid domains favour membrane perturbations induced by Aβ1–42, an amyloid peptide identified as a trigger of Alzheimer's disease. It is proposed that lipid packing defects at domain interfaces could act as adsorption and nucleation sites.

scholarly journals Fake It ‘Till You Make It—The Pursuit of Suitable Membrane Mimetics for Membrane Protein Biophysics

2020 ◽  
Vol 22 (1) ◽  
pp. 50
Author(s):  
Johannes Thoma ◽  
Björn M. Burmann
Keyword(s):  
Membrane Proteins ◽  
Lipid Bilayers ◽  
Lipid Membranes ◽  
Cubic Phase ◽  
Advantages And Disadvantages ◽  
Membrane Mimetic ◽  
Lipid Environment ◽  
Protein Biophysics ◽  
And Function ◽  
Biological Methods

Membrane proteins evolved to reside in the hydrophobic lipid bilayers of cellular membranes. Therefore, membrane proteins bridge the different aqueous compartments separated by the membrane, and furthermore, dynamically interact with their surrounding lipid environment. The latter not only stabilizes membrane proteins, but directly impacts their folding, structure and function. In order to be characterized with biophysical and structural biological methods, membrane proteins are typically extracted and subsequently purified from their native lipid environment. This approach requires that lipid membranes are replaced by suitable surrogates, which ideally closely mimic the native bilayer, in order to maintain the membrane proteins structural and functional integrity. In this review, we survey the currently available membrane mimetic environments ranging from detergent micelles to bicelles, nanodiscs, lipidic-cubic phase (LCP), liposomes, and polymersomes. We discuss their respective advantages and disadvantages as well as their suitability for downstream biophysical and structural characterization. Finally, we take a look at ongoing methodological developments, which aim for direct in-situ characterization of membrane proteins within native membranes instead of relying on membrane mimetics.

scholarly journals Orientation of Laurdan in Phospholipid Bilayers Influences Its Fluorescence: Quantum Mechanics and Classical Molecular Dynamics Study

Molecules ◽  
2018 ◽  
Vol 23 (7) ◽  
pp. 1707 ◽  
Author(s):  
Mirza Wasif Baig ◽  
Marek Pederzoli ◽  
Piotr Jurkiewicz ◽  
Lukasz Cwiklik ◽  
Jiri Pittner
Keyword(s):  
Molecular Dynamics ◽  
Lipid Bilayers ◽  
Lipid Membranes ◽  
Liquid Crystalline ◽  
Lipid Membrane ◽  
Emission Spectra ◽  
Crystalline Phases ◽  
Classical Molecular Dynamics ◽  
Liquid Crystalline Phases ◽  
Lipid Environment

Fluidity of lipid membranes is known to play an important role in the functioning of living organisms. The fluorescent probe Laurdan embedded in a lipid membrane is typically used to assess the fluidity state of lipid bilayers by utilizing the sensitivity of Laurdan emission to the properties of its lipid environment. In particular, Laurdan fluorescence is sensitive to gel vs liquid–crystalline phases of lipids, which is demonstrated in different emission of the dye in these two phases. Still, the exact mechanism of the environment effects on Laurdan emission is not understood. Herein, we utilize dipalmitoylphosphatidylcholine (DPPC) and dioleoylphosphatidylcholine (DOPC) lipid bilayers, which at room temperature represent gel and liquid–crystalline phases, respectively. We simulate absorption and emission spectra of Laurdan in both DOPC and DPPC bilayers with quantum chemical and classical molecular dynamics methods. We demonstrate that Laurdan is incorporated in heterogeneous fashion in both DOPC and DPPC bilayers, and that its fluorescence depends on the details of this embedding.

scholarly journals Fluorescence Approaches for Characterizing Ion Channels in Synthetic Bilayers

Membranes ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 857
Author(s):  
Md. Sirajul Islam ◽  
James P. Gaston ◽  
Matthew A. B. Baker
Keyword(s):  
Ion Channels ◽  
Membrane Proteins ◽  
Lipid Bilayers ◽  
Lipid Membranes ◽  
Protein Composition ◽  
Cellular Processes ◽  
Model Lipid Membranes ◽  
Wide Range ◽  
Lipid Environment

Ion channels are membrane proteins that play important roles in a wide range of fundamental cellular processes. Studying membrane proteins at a molecular level becomes challenging in complex cellular environments. Instead, many studies focus on the isolation and reconstitution of the membrane proteins into model lipid membranes. Such simpler, in vitro, systems offer the advantage of control over the membrane and protein composition and the lipid environment. Rhodopsin and rhodopsin-like ion channels are widely studied due to their light-interacting properties and are a natural candidate for investigation with fluorescence methods. Here we review techniques for synthesizing liposomes and for reconstituting membrane proteins into lipid bilayers. We then summarize fluorescence assays which can be used to verify the functionality of reconstituted membrane proteins in synthetic liposomes.

scholarly journals Cholesterol is a strong promotor of an α-Synuclein membrane binding mode that accelerates oligomerization

2019 ◽  
Author(s):  
Martin Jakubec ◽  
Espen Bariås ◽  
Samuel Furse ◽  
Morten L. Govasli ◽  
Vinnit George ◽  
...  
Keyword(s):  
Lipid Bilayers ◽  
Molecular Mechanisms ◽  
Neurological Diseases ◽  
Binding Mode ◽  
Model Systems ◽  
Tht Fluorescence ◽  
Fold Reduction ◽  
Membrane Models ◽  
Lag Times ◽  
Lipid Environment

AbstractDysregulation of the biosynthesis of cholesterol and other lipids has been implicated in neurological diseases, including Parkinson's disease, where the misfolding of membraneassociated α-Synuclein is a key molecular event. Recent research also suggests that α-Synuclein aggregation is influenced by the lipid environment. The exact molecular mechanisms responsible for cholesterol’s effect on α-Synuclein binding to lipids and how this binding may affect α-Synuclein oligomerization and fibrillation remain elusive, as does the relative importance of cholesterol versus other lipid factors. We probed the interactions and fibrillation behaviour of α-Synuclein using SMA nanodiscs, containing zwitterionic and anionic lipid model systems with and without cholesterol. SPR and ThT fluorescence assays were then employed to monitor α-Synuclein binding, as well as fibrillation in the absence and presence of membrane models. 1H-15N correlated NMR was used to monitor the fold of α-Synuclein in response to nanodisc binding, and we determined individual residue apparent affinities for the nanodisc-contained bilayers. Cholesterol inhibited α-Synuclein interaction with lipid bilayers. We also find that cholesterol significantly promotes α-Synuclein fibrillation, with a more than 20-fold reduction of lag-times before fibrillation onset. When α-Synuclein-bilayer interactions were analysed for individual residues by solution-state NMR, we observed two different effects of cholesterol. In nanodiscs made of DOPC, cholesterol modulated the NAC part of α-Synuclein, leading to stronger interaction of this region with the lipid bilayer. In contrast, in the nanodiscs comprising DOPC, DOPE and DOPG, the NAC part was mostly unaffected by cholesterol, while the binding of the N-terminal and the C-terminal were both inhibited.

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