Mechanics of membrane fusion/pore formation

Fuhrmans, Marc; Marelli, Giovanni; Smirnova, Yuliya G.; Müller, Marcus

doi:10.1016/j.chemphyslip.2014.07.010

Cited by 57 publications

(45 citation statements)

References 127 publications

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“…The fusion of lipid vesicles and membranes has been simulated using both coarse-grain and atomistic models (for a recent review see ref. 22). Atomic-resolution simulations of vesicle fusion indicate that the process is triggered by the translocation of a few lipid tails from the fusing vesicles into the hydrophilic region3.…”

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confidence: 99%

Fusing simulation and experiment: The effect of mutations on the structure and activity of the influenza fusion peptide

Lousa

Pinto

Victor

et al. 2016

Sci Rep

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During the infection process, the influenza fusion peptide (FP) inserts into the host membrane, playing a crucial role in the fusion process between the viral and host membranes. In this work we used a combination of simulation and experimental techniques to analyse the molecular details of this process, which are largely unknown. Although the FP structure has been obtained by NMR in detergent micelles, there is no atomic structure information in membranes. To answer this question, we performed bias-exchange metadynamics (BE-META) simulations, which showed that the lowest energy states of the membrane-inserted FP correspond to helical-hairpin conformations similar to that observed in micelles. BE-META simulations of the G1V, W14A, G12A/G13A and G4A/G8A/G16A/G20A mutants revealed that all the mutations affect the peptide’s free energy landscape. A FRET-based analysis showed that all the mutants had a reduced fusogenic activity relative to the WT, in particular the mutants G12A/G13A and G4A/G8A/G16A/G20A. According to our results, one of the major causes of the lower activity of these mutants is their lower membrane affinity, which results in a lower concentration of peptide in the bilayer. These findings contribute to a better understanding of the influenza fusion process and open new routes for future studies.

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mentioning

confidence: 99%

Fusing simulation and experiment: The effect of mutations on the structure and activity of the influenza fusion peptide

Lousa

Pinto

Victor

et al. 2016

Sci Rep

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“…The initiating step for bilayer–bilayer fusion is physical interaction and adhesion, which is enhanced by complementary membrane surface charge and curvature strain [31,42]. To evaluate the effect of membrane surface charge on GUV–SUV fusion (Step 3 in Fig.…”

Section: Resultsmentioning

confidence: 99%

“…Membrane bilayer fusion is a process that proceeds through proximity, physical contact, and an energetic barrier transition that is facilitated by headgroup composition and bilayer strain curvature [42]. We maximized GUV–SUV fusion and SERCA activity by optimizing lipid composition and solution conditions; in particular, (i) 15% EDOPC was used as a helper lipid to facilitate GUV–SUV fusion, (ii) an SUV prep with small diameter was used to enhance fusogenicity, and (iii) 200 µM Triton X-100 was used for transient permeabilization of GUV-SERCA to allow addition of physiological salts and substrates required for assay of Ca 2+ transport V max .…”

Section: Discussionmentioning

confidence: 99%

Direct detection of SERCA calcium transport and small-molecule inhibition in giant unilamellar vesicles

Bian

Autry

Casemore

et al. 2016

Biochemical and Biophysical Research Communications

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We have developed a charge-mediated fusion method to reconstitute the sarco/endoplasmic reticulum Ca2+-ATPase (SERCA) in giant unilamellar vesicles (GUV). Intracellular Ca2+ transport by SERCA controls key processes in human cells, such as proliferation, signaling, and contraction. Small-molecule effectors of SERCA are urgently needed as therapeutics for Ca2+ dysregulation in human diseases including cancer, diabetes, and heart failure. Here we report the development of a method for efficiently reconstituting SERCA in GUV, and we describe a streamlined protocol based on optimized parameters (e.g., lipid components, SERCA preparation, and activity assay requirements). ATP-dependent Ca2+ transport by SERCA in single GUV was detected directly using confocal fluorescence microscopy with the Ca2+ indicator Fluo-5F. The GUV reconstitution system was validated for functional screening of Ca2+ transport using thapsigargin (TG), a small-molecule inhibitor of SERCA currently in clinical trials as a prostate cancer prodrug. The GUV system overcomes the problem of inhibitory Ca2+ accumulation for SERCA in native and reconstituted small unilamellar vesicles (SUV). We propose that charge-mediated fusion provides a widely-applicable method for GUV reconstitution of clinically-important membrane transport proteins. We conclude that GUV reconstitution is a technological advancement for evaluating small-molecule effectors of SERCA.

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“…Given the intimacy between G E and the overall geometry of a structure, this may further imply that the overall geometry of stalk is also universal among monolayers of various compositions. Indeed, experimental and computational studies have shown that the overall geometry of stalk is highly conserved among monolayers of diverse compositions 6 , as well as among various coarse-grained models used in the computational studies 9 . Given the energetic/geometric invariability of stalk and the variation in G E,planar upon changing C 0 , we argue that the fusion promotion by making C 0 more negative is effected mainly via a rise in G E,planar , rather than a drop in G E,stalk .…”

Section: Discussionmentioning

confidence: 99%

Revisit the Correlation between the Elastic Mechanics and Fusion of Lipid Membranes

Fan

Tsang

Chen

et al. 2017

Biophysical Journal

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Membrane fusion is a vital process in key cellular events. The fusion capability of a membrane depends on its elastic properties and varies with its lipid composition. It is believed that as the composition varies, the consequent change in C 0 (monolayer spontaneous curvature) is the major factor dictating fusion, owing to the associated variation in G E s (elastic energies) of the fusion intermediates (e.g. stalk). By exploring the correlations among fusion, C 0 and K cp (monolayer bending modulus), we revisit this long-held belief and re-examine the fusogenic contributions of some relevant factors. We observe that not only C 0 but also K cp variations affect fusion, with depression in K cp leading to suppression in fusion. Variations in G E s and inter-membrane interactions cannot account for the K cp -fusion correlation; fusion is suppressed even as the G E s decrease with K cp , indicating the presence of factor(s) with fusogenic importance overtaking that of G E . Furthermore, analyses find that the C 0 influence on fusion is effected via modulating G E of the pre-fusion planar membrane, rather than stalk. The results support a recent proposition calling for a paradigm shift from the conventional view of fusion and may reshape our understanding to the roles of fusogenic proteins in regulating cellular fusion machineries.Membrane fusion is vital for living organisms. Many cellular events, such as the release of neurotransmitters, the invasion of enveloped viruses, the intracellular trafficking of proteins and the conception for sexual reproduction, involve membrane fusion 1,2 . Complete of the fusion process sees two membrane-bound entities merge into a single one, with the initially discrete membranes and the enclosed contents mixed together. Cellular implementation of fusion requires the concerted action of an intricate machinery consisting of lipids, fusogenic proteins and fusion-triggering stimulants (e.g., Ca 2+ ) 3,4 . While the wide diversity of the lipids, proteins and other biomolecules involved in cellular fusion often complicates the attempts to explore the inner working shared by various fusion machineries, protein-free model membranes with defined lipid compositions [e.g., liposome, also known as unilamellar vesicle (ULV), a hollow spherical structure bound with a single lipid bilayer] have been proven an indispensable tool in uncovering the universal mechanism for all sorts of fusion 3,5 . It is known from model membrane studies that initiating and advancing the fusion process demand the overcoming of several energy barriers; recognizing these barriers has provided insight on how proteins regulate cellular fusion machineries 3,5 . The first energy barrier arises from the need to bring two fusion-destined membranes into close proximity to initiate fusion 6,7 . The barrier, an inter-membrane interaction known as hydration repulsion, results from the resistance to removing inter-membrane water needed for shortening the inter-membrane distance 8 . Once fusion is initiated, the next energy barriers ...

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Mechanics of membrane fusion/pore formation

Cited by 57 publications

References 127 publications

Fusing simulation and experiment: The effect of mutations on the structure and activity of the influenza fusion peptide

Fusing simulation and experiment: The effect of mutations on the structure and activity of the influenza fusion peptide

Direct detection of SERCA calcium transport and small-molecule inhibition in giant unilamellar vesicles

Revisit the Correlation between the Elastic Mechanics and Fusion of Lipid Membranes

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