Membrane tension and membrane fusion

Kozlov, Michael M.; Chernomordik, Leonid V.

doi:10.1016/j.sbi.2015.07.010

Cited by 141 publications

(161 citation statements)

References 50 publications

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“…The sensitivity to its environment is a remarkable physical property of VAMP and it is easy to see how both the pressure and protein concentration can vary at the fusion site and thereby modify TMD dynamics 5 .…”

Section: Resultsmentioning

confidence: 99%

A Central Small Amino Acid in the VAMP2 Transmembrane Domain Regulates the Fusion Pore in Exocytosis

Hastoy

Scotti

Milochau

et al. 2017

Sci Rep

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Exocytosis depends on cytosolic domains of SNARE proteins but the function of the transmembrane domains (TMDs) in membrane fusion remains controversial. The TMD of the SNARE protein synaptobrevin2/VAMP2 contains two highly conserved small amino acids, G100 and C103, in its central portion. Substituting G100 and/or C103 with the β-branched amino acid valine impairs the structural flexibility of the TMD in terms of α-helix/β-sheet transitions in model membranes (measured by infrared reflection-absorption or evanescent wave spectroscopy) during increase in protein/lipid ratios, a parameter expected to be altered by recruitment of SNAREs at fusion sites. This structural change is accompanied by reduced membrane fluidity (measured by infrared ellipsometry). The G100V/C103V mutation nearly abolishes depolarization-evoked exocytosis (measured by membrane capacitance) and hormone secretion (measured biochemically). Single-vesicle optical (by TIRF microscopy) and biophysical measurements of ATP release indicate that G100V/C103V retards initial fusion-pore opening, hinders its expansion and leads to premature closure in most instances. We conclude that the TMD of VAMP2 plays a critical role in membrane fusion and that the structural mobility provided by the central small amino acids is crucial for exocytosis by influencing the molecular re-arrangements of the lipid membrane that are necessary for fusion pore opening and expansion.

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Section: Resultsmentioning

confidence: 99%

A Central Small Amino Acid in the VAMP2 Transmembrane Domain Regulates the Fusion Pore in Exocytosis

Hastoy

Scotti

Milochau

et al. 2017

Sci Rep

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“…As previously demonstrated (44,45,61), liposomes will fuse when three conditions are met: 1) the vesicles have an ion channel (e.g., the nystatin channels) in their membrane, 2) the vesicles adhere or are docked to the bilayer, and 3) there is an osmotic gradient across the bilayer. Under these three conditions, there will be a net entry of water from the trans compartment through the bilayer membrane and into the docked vesicle.…”

Section: Fusion Assaymentioning

confidence: 89%

Drunken Membranes: Short-Chain Alcohols Alter Fusion of Liposomes to Planar Lipid Bilayers

Paxman

Hunt

Hallan

et al. 2017

Biophysical Journal

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Although the effects of ethanol on protein receptors and lipid membranes have been studied extensively, ethanol's effect on vesicles fusing to lipid bilayers is not known. To determine the effect of alcohols on fusion rates, we utilized the nystatin/ergosterol fusion assay to measure fusion of liposomes to a planar lipid bilayer (BLM). The addition of ethanol excited fusion when applied on the cis (vesicle) side, and inhibited fusion on the trans side. Other short-chain alcohols followed a similar pattern. In general, the inhibitory effect of alcohols (trans) occurs at lower doses than the excitatory (cis) effect, with a decrease of 29% in fusion rates at the legal driving limit of 0.08% (w/v) ethanol (IC 50 ¼ 0.2% v/v, 34 mM). Similar inhibitory effects were observed with methanol, propanol, and butanol, with ethanol being the most potent. Significant variability was observed with different alcohols when applied to the cis side. Ethanol and propanol enhanced fusion, butanol also enhanced fusion but was less potent, and low doses of methanol mildly inhibited fusion. The inhibition by trans addition of alcohols implies that they alter the planar membrane structure and thereby increase the activation energy required for fusion, likely through an increase in membrane fluidity. The cis data are likely a combination of the above effect and a proportionally greater lowering of the vesicle lysis tension and hydration repulsive pressure that combine to enhance fusion. Alternate hypotheses are also discussed. The inhibitory effect of ethanol on liposome-membrane fusion is large enough to provide a possible biophysical explanation of compromised neuronal behavior.

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Section: Introductionmentioning

confidence: 99%

“…All membrane fusion reaction results in a fusion pore - a transient, narrow channel (1–2 nm) that connects the two fusing compartments 6, 7, 8 . This dynamic fusion pore may irreversibly widen or close 6, 8 . Small cargoes, like neurotransmitters might be released through the flickering nascent pore 9, 10 , but larger cargoes like hormones and viral genomes requires the dilation of the initial fusion pore 6, 11, 12 .…”

Section: Introductionmentioning

confidence: 99%

Using ApoE Nanolipoprotein Particles To Analyze SNARE-Induced Fusion Pores

et al. 2016

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Here we introduce ApoE-based Nanolipoprotein particles (NLP) – soluble, discoidal bilayer mimetic of ~23 nm in diameter, as fusion partners to study the dynamics of fusion pores induced by SNARE proteins. Using in vitro lipid mixing and content release assays, we report that NLPs reconstituted with synaptic v-SNARE VAMP2 (vNLP) fuse with liposomes containing the cognate t-SNARE (Syntaxin1/SNAP25) partner, with the resulting fusion pore opening directly to the external buffer. Efflux of encapsulated fluorescent dextrans of different size shows that unlike the smaller nanodiscs, these larger NLPs accommodate the expansion of the fusion pore to at least ~ 9 nm and dithionite quenching of fluorescent lipid introduced in vNLP confirms that the NLP fusion pores are short-lived and eventually reseal. The NLPs also have capacity to accommodate larger number of proteins and using vNLPs were defined number of VAMP2 protein, including physiologically relevant copy numbers, we find that 3–4 copies of VAMP2 (minimum 2 per face) are required to keep a nascent fusion pore open and the SNARE proteins act cooperatively to dilate the nascent fusion pore.

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Membrane tension and membrane fusion

Cited by 141 publications

References 50 publications

A Central Small Amino Acid in the VAMP2 Transmembrane Domain Regulates the Fusion Pore in Exocytosis

A Central Small Amino Acid in the VAMP2 Transmembrane Domain Regulates the Fusion Pore in Exocytosis

Drunken Membranes: Short-Chain Alcohols Alter Fusion of Liposomes to Planar Lipid Bilayers

Using ApoE Nanolipoprotein Particles To Analyze SNARE-Induced Fusion Pores

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