Energetics and dynamics of SNAREpin folding across lipid bilayers

Li, Feng; Pincet, Frédéric; Perez, Éric; Eng, William; Melia, Thomas J.; Rothman, James E.; Tareste, David

doi:10.1038/nsmb1310

Cited by 246 publications

(293 citation statements)

References 60 publications

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“…This intermediate may be transient in vivo, formed after trans-SNARE complex assembly and close to the point of fusion. Although detailed electrophysiological experiments will be needed to determine the precise role of SNARE complex dimers in membrane fusion events, one can speculate from their solution structure how they might contribute toward formation of an oligomeric complex around a fusion pore, consistent with the energies required to bring about membrane fusion (Li et al, 2007). It is interesting to note that the syb2(W89A,W90A) mutant does not seem to be defective in mediating liposomal fusion events (Siddiqui et al, 2007), whereas it profoundly inhibits Ca 2ϩ -dependent secretion.…”

Section: Discussionmentioning

confidence: 99%

A Role for Soluble N-Ethylmaleimide-sensitive Factor Attachment Protein Receptor Complex Dimerization during Neurosecretion

Fdez

Jowitt

Wang

et al. 2008

MBoC

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The interactions underlying the cooperativity of soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complexes during neurotransmission are not known. Here, we provide a molecular characterization of a dimer formed between the cytoplasmic portions of neuronal SNARE complexes. Dimerization generates a two-winged structure in which the C termini of cytosolic SNARE complexes are in apposition, and it involves residues from the vesicleassociated SNARE synaptobrevin 2 that lie close to the cytosol-membrane interface within the full-length protein.Mutation of these residues reduces stability of dimers formed between SNARE complexes, without affecting the stability of each individual SNARE complex. These mutations also cause a corresponding decrease in the ability of botulinum toxin-resistant synaptobrevin 2 to rescue regulated exocytosis in toxin-treated neuroendocrine cells. Moreover, such synaptobrevin 2 mutants give rise to a dominant-negative inhibition of exocytosis. These data are consistent with an important role for SNARE complex dimers in neurosecretion.

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Section: Discussionmentioning

confidence: 99%

A Role for Soluble N-Ethylmaleimide-sensitive Factor Attachment Protein Receptor Complex Dimerization during Neurosecretion

Fdez

Jowitt

Wang

et al. 2008

MBoC

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“…13, are interpreted as the total free energy required to induce stalk formation [e.g. (64)(65)(66)]. However, this value only includes bending and tilt deformations with respect to a flat monolayer of the same area.…”

Section: Discussionmentioning

confidence: 99%

Energetics of stalk intermediates in membrane fusion are controlled by lipid composition

Aeffner

Reusch²,

Weinhausen³

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

164

246

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We have used X-ray diffraction on the rhombohedral phospholipid phase to reconstruct stalk structures in different pure lipids and lipid mixtures with unprecedented resolution, enabling a quantitative analysis of geometry, as well as curvature and hydration energies. Electron density isosurfaces are used to study shape and curvature properties of the bent lipid monolayers. We observe that the stalk structure is highly universal in different lipid systems. The associated curvatures change in a subtle, but systematic fashion upon changes in lipid composition. In addition, we have studied the hydration interaction prior to the transition from the lamellar to the stalk phase. The results indicate that facilitating dehydration is the key to promote stalk formation, which becomes favorable at an approximately constant interbilayer separation of 9.0 AE 0.5 Å for the investigated lipid compositions.curvature energy | hydration force | lipid bilayer | E xocytosis, intracellular transport, neurotransmission, fertilization, or viral entry, require that two membranes merge into one. This event, membrane fusion, involves a complex interplay of different membrane lipids, proteins, and water molecules on length scales of few nm. Following the "lipidic pore hypothesis", it is now well accepted that membrane fusion involves a sequence of lipidic nonbilayer intermediates, whose formation is catalyzed and guided by a specialized protein machinery (1, 2). A stage termed "hemifusion" in which the lipids of the outer leaflets of two membrane-enclosed compartments about to fuse can mix, whereas the inner leaflets and the enclosed content remain unaltered (3), has been confirmed by a variety of methods including conical electron tomography (4) and, more indirectly; e.g., by electron spin resonance (5) and fluorescence recovery after photobleaching (6). Studying the fusion of protein-free bilayers of well defined lipid composition can contribute useful insights into the physical principles governing the merger of their more complex biological counterparts and clarify the effect of individual lipid species.The first connection between two lipid bilayers is the so-called stalk sketched in Fig. 1A (7). The proximal lipid monolayers have merged into one strongly curved monolayer, whereas the distal ones are still separated and intact. A persistent problem in membrane biophysics is to determine the precise structure of stalks and the free energy barrier for stalk formation. In a long series of papers (8-16), this determination has been attempted within the framework of the continuum theory of membrane elasticity (17, 18). More recently, with the advent of sufficient computational power, simulations including molecular details have become feasible [e.g. (19, 20) and references therein]. While stalk formation between lipid bilayers in close contact is generally accepted as the initial step in possibly all membrane fusion reactions (7), the subsequent stages from stalk to complete fusion are still debated and different pathways may exist (21)....

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“…In vitro studies have demonstrated the sufficiency of SNAREs to mediate fusion when reconstituted into a number of model systems, including freestanding lipid vesicles (4-7), supported lipid bilayers (8)(9)(10), and tethered vesicles (11). Generally these studies suggest that SNAREs are able to bring two membranes into close apposition by forming a trans complex in a docking reaction which is highly energetically favorable (12). This is illustrated in Fig.…”

mentioning

confidence: 92%

Effects of linker sequences on vesicle fusion mediated by lipid-anchored DNA oligonucleotides

Chan

Lengerich

Boxer

2009

Proc. Natl. Acad. Sci. U.S.A.

277

287

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Synthetic lipid-oligonucleotide conjugates inserted into lipid vesicles mediate fusion when one population of vesicles displays the 5 -coupled conjugate and the other the 3 -coupled conjugate, so that anti-parallel hybridization allows the membrane surfaces to come into close proximity. Improved assays show that lipid mixing proceeds more quickly and to a much greater extent than content mixing, suggesting the latter is rate limiting. To test the effect of membrane-membrane spacing on fusion, a series of conjugates was constructed by adding 2-24 noncomplementary bases at the membrane-proximal ends of two complementary sequences. Increasing linker lengths generally resulted in progressively reduced rates and extents of lipid and content mixing, in contrast to higher vesicle docking rates. The relatively flexible, single-stranded DNA linker facilitates docking but allows greater spacing between the vesicles after docking, thus making the transition into fusion less probable, but not preventing it altogether. These experiments demonstrate the utility of DNA as a model system for fusion proteins, where sequence can easily be modified to systematically probe the effect of distance between bilayers in the fusion reaction.DNA machine ͉ synthetic biology F usion of lipid membranes plays a central role in many biological processes. For example, in the case of synaptic transmission, the reaction is tightly regulated by a number of proteins of which the SNAREs [soluble N-ethylmaleimide sensitive factor (NSF) attachment protein receptors] have been shown to play a crucial role (1-3). In vitro studies have demonstrated the sufficiency of SNAREs to mediate fusion when reconstituted into a number of model systems, including freestanding lipid vesicles (4-7), supported lipid bilayers (8-10), and tethered vesicles (11). Generally these studies suggest that SNAREs are able to bring two membranes into close apposition by forming a trans complex in a docking reaction which is highly energetically favorable (12). This is illustrated in Fig. 1A, which is based on the x-ray structures of the soluble domains of SNARE proteins in complex (13). Several steps along the mechanism to achieve membrane fusion following this basic docking step have been proposed, and some of these are illustrated in Fig. 2, which also serves to illustrate assays commonly used to assess their role. In this step-wise mechanism, the bilayers first dock, then adopt an intermediate, hemifused state in which the outer leaflets have merged, but the inner leaflets and contents remain distinct. A transition into full fusion then involves mixing of both leaflets and content exchange.Despite substantial research on the role of SNARE proteins in the fusion process, many questions remain regarding the physical mechanism. Studies using simpler model systems can provide insight into the fundamental mechanisms of the rearrangement of bilayers and lead to a better understanding of the biological process (14, 15). We have prepared a series of DNA-lipid conjugates in which DNA o...

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Energetics and dynamics of SNAREpin folding across lipid bilayers

Cited by 246 publications

References 60 publications

A Role for Soluble N-Ethylmaleimide-sensitive Factor Attachment Protein Receptor Complex Dimerization during Neurosecretion

A Role for Soluble N-Ethylmaleimide-sensitive Factor Attachment Protein Receptor Complex Dimerization during Neurosecretion

Energetics of stalk intermediates in membrane fusion are controlled by lipid composition

Effects of linker sequences on vesicle fusion mediated by lipid-anchored DNA oligonucleotides

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