Conserved structural features of the synaptic fusion complex: SNARE proteins reclassified as Q-and R-SNAREs (original) (raw)
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SNARE proteins and membrane fusion
El Mednifico Journal, 2013
Diverse proteins catalyze membrane fusion reactions. These mediate recognition of the membranes for fusion and pull the membranes close together to destabilize the lipid/water interface and to initiate mixing of the lipids. In the nervous system, membrane fusion is vital for neuroexocytosis, neuro transmitter release and chemical synaptic transmission. Three neuronal soluble NSF (N-ethyl-maleimide-sensitive fusion protein) attachment receptor (SNARE) proteins exist, namely: (i) vesicle associated membrane protein (VAMP-2), also called synaptobrevin; (ii) 25 kDa synaptosome-associated protein (SNAP-25); and (iii) syntaxin 1A (STX1). The SNAREs are involved in the neuronal membrane fusion process. (El Med J 2:1; 2014)
Self-assembly of SNARE fusion proteins into star-shaped oligomers
Biochemical Journal, 2005
Three evolutionarily conserved proteins known as SNAREs (soluble N-ethylmaleimide-sensitive fusion protein attachment protein receptors) mediate exocytosis from single cell eukaryotes to neurons. Among neuronal SNAREs, syntaxin and SNAP-25 (synaptosome-associated protein of 25 kDa) reside on the plasma membrane, whereas synaptobrevin resides on synaptic vesicles prior to fusion. The SNARE motifs of the three proteins form a helical bundle which probably drives membrane fusion. Since studies in vivo suggested an importance for multiple SNARE complexes in the fusion process, and models appeared in the literature with large numbers of SNARE bundles executing the fusion process, we analysed the quaternary structure of the full-length native SNARE complexes in detail. By employing a preparative immunoaffinity procedure we isolated all of the SNARE complexes from brain, and have shown by size-exclusion chromatography and negative stain electron microscopy that they exist as approx. 30 nm ...
Molecular Cell, 1999
Sacher et al., 1998). Additional general factors acting on SNAREs are NSF (NEM-sensitive factor; Block New York, New York 10021 † Department of Molecular Biophysics et al., 1988) and SNAPs (soluble NSF attachment proteins; Clary et al., 1990), which alter the conformation and Biochemistry Yale University of SNAREs and disassemble v-t SNARE complexes, thereby regenerating separate v-and t-SNAREs for re-New Haven, Connecticut 06520 peated use. Most SNARE proteins possess a single transmembrane domain at their extreme carboxy terminus and Summary are predicted to have a high propensity to form coiledcoil structures. Assembled cytosolic domains of SNARE The topology of a SNARE complex bridging two docked vesicles could act as a mechanical couple to proteins form very stable structures in all cases that have been closely examined (Hayashi et al., 1994; Yang do work on the lipid bilayer resulting in fusion. To test this, we prepared a series of modified SNARE proteins et al., 1999), likely due to their coiled-coil nature. Furthermore, electron microscopic (Hanson et al., 1997b; Hohl and determined their effects on SNARE-dependent membrane fusion. When two helix-breaking proline et al., 1998) and biophysical (Lin and Scheller, 1997; Poirier et al., 1998) analysis of assembled full-length residues are introduced into the juxtamembrane region of VAMP, there is little or no effect on fusion, neuronal SNARE complexes revealed that the transmembrane domains of both the v-SNARE VAMP/synap-and the same change in syntaxin 1A only reduced the extent and rate of fusion by half. The insertion of a tobrevin (Trimble et al., 1988; Baumert et al., 1989; Sü dhof et al., 1989) and the t-SNARE syntaxin 1A (Bennett flexible linker between the transmembrane domain and the conserved coiled-coil domain only moderately et al., 1992, 1993) emerge at the same end of the 7S or 20S particle establishing a parallel orientation of the affected fusion; however, fusion efficiency systematically decreased with increasing length of the linker. assembled SNARE proteins. These characteristics suggested that SNARE proteins are also directly responsible Together, these results rule out a requirement for helical continuity and suggest that distance is a critical for membrane fusion (Hanson et al., 1997a, 1997b; Lin and Scheller, 1997; Hohl et al., 1998), and this has now factor for membrane fusion. been directly demonstrated with artificial liposomes and isolated SNAREs (Weber et al., 1998) and confirmed with Introduction permeabilized cells (Chen et al., 1999). The recently obtained three-dimensional structure of Members of the SNARE (SNAP receptor) protein family the neuronal SNARE complex (Poirier et al., 1998; Sutton (Sö llner et al., 1993a, 1993b) are key components in et al., 1998) has provided additional information to guide the process of transport vesicle docking and fusion. structure-function studies aimed at clarifying the bio-Individual SNARE family members are maintained in disphysical mechanisms involved in fusion. The crystal crete locations throughout the secretory pathway prostructure confirms the previous biophysical predictions viding a roadmap of vesicle flow patterns (Hay and of coiled-coil structure and provides a structural frame-Scheller, 1997; Linial, 1997; Advani et al., 1998; Nichols work to explain the intrinsic stability of the assembled and Pelham, 1998; Steegmaier et al., 1998). The assem-SNARE complex. Another striking feature of the core bly of trans-SNARE complexes (SNAREpins) between SNARE complex structure is its overall similarity to the membranes is likely the underlying principle of lipid biproposed fusogenic cores of a variety of virally encoded layer fusion (Weber et al., 1998; Chen et al., 1999), and fusion proteins (Skehel and Wiley, 1998). This similarity as such, it must be highly regulated in many cell types.
Control of eukaryotic membrane fusion by N-terminal domains of SNARE proteins
… et Biophysica Acta (BBA …, 2003
SNARE proteins function at the center of membrane fusion reactions by forming complexes with each other via their coiled-coil domains. Several SNAREs have N-terminal domains (NTDs) that precede the coiled-coil domain and have critical functions in regulating the fusion cascade. This review will highlight recent findings on NTDs of syntaxins, the longin domain of VAMP proteins and SNAP-23/25 homologues in yeast. Biochemical and genetic experiments as well as the resolution of several NMR and crystal structures of SNARE NTDs shed light on their diverse function. D
Membrane-directed molecular assembly of the neuronal SNARE complex
Journal of Cellular and Molecular Medicine, 2011
Since the discovery and implication of N-ethylmaleimide-sensitive factor (NSF)-attachment protein receptor (SNARE) proteins in membrane fusion almost two decades ago, there have been significant efforts to understand their involvement at the molecular level. In the current study, we report for the first time the molecular interaction between full-length recombinant t-SNAREs and v-SNARE present in opposing liposomes, leading to the assembly of a t-/v-SNARE ring complex. Using high-resolution electron microscopy, the electron density maps and 3D topography of the membrane-directed SNARE ring complex was determined at nanometre resolution. Similar to the t-/v-SNARE ring complex formed when 50 nm v-SNARE liposomes meet a t-SNARE-reconstituted planer membrane, SNARE rings are also formed when 50 nm diameter isolated synaptic vesicles (SVs) meet a t-SNARE-reconstituted planer lipid membrane. Furthermore, the mathematical prediction of the SNARE ring complex size with reasonable accuracy, and the possible mechanism of membrane-directed t-/v-SNARE ring complex assembly, was determined from the study. Therefore in the present study, using both lipososome-reconstituted recombinant t-/v-SNARE proteins, and native v-SNARE present in isolated SV membrane, the membranedirected molecular assembly of the neuronal SNARE complex was determined for the first time and its size mathematically predicted. These results provide a new molecular understanding of the universal machinery and mechanism of membrane fusion in cells, having fundamental implications in human health and disease.
One SNARE complex is sufficient for membrane fusion
Nature Structural & Molecular Biology, 2010
In eukaryotes, most intracellular membrane fusion reactions are mediated by the interaction of SNARE proteins that are present in both fusing membranes. However, the minimal number of SNARE complexes needed for membrane fusion is not known. Here, we show unambiguously that one SNARE complex is sufficient for membrane fusion. We performed controlled in vitro Förster resonance energy transfer (FRET) experiments and found that liposomes bearing only a single SNARE molecule are still capable of fusion with other liposomes, or with purified synaptic vesicles. Furthermore, we demonstrate that multiple SNARE complexes do not act cooperatively, showing that synergy between several SNARE complexes is not needed for membrane fusion. Our findings shed new light on the mechanism of SNARE-mediated membrane fusion and ask for a revision of current views of fusion events such as the fast release of neurotransmitters.