scholarly journals Multiple features within Sed5p mediate it’s COPI-independent trafficking and Golgi localization

2019 ◽  
Author(s):  
Guanbin Gao ◽  
David K. Banfield
Keyword(s):  
Membrane Fusion ◽  
Transmembrane Domain ◽  
Yeast Cells ◽  
Multiple Features ◽  
Protein Retention ◽  
Golgi Retention ◽  
Sensitive Factor ◽  
Protein Receptors ◽  
Snare Motif ◽  
Sm Protein

ABSTRACTProtein retention and the transport of proteins and lipids into and out of the Golgi is intimately linked to the biogenesis and homeostasis of this sorting hub of eukaryotic cells. Of particular importance are membrane proteins that mediate membrane fusion events with and within the Golgi – the Soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs). In the Golgi of budding yeast cells a single syntaxin - the SNARE Sed5p - oversees membrane fusion within the Golgi. Determining how Sed5p is localized to and trafficked within the Golgi is critical to informing our understanding of the mechanism(s) of biogenesis and homeostasis of this organelle. Here we establish that the Golgi retention and trafficking of Sed5p between the Golgi and the ER is independent of COPI function, the composition of the transmembrane domain, and binding of the Sec1-Munc18 (SM) protein Sly1p. Rather, the steady state localization of Sed5p to the Golgi appears to be primarily conformation-based relying on intra-molecular associations between the Habc domain and SNARE-motif.

scholarly journals Double-transmembrane domain reduces fusion rate by increasing lipid-protein mismatch

2020 ◽  
Author(s):  
B. Bu ◽  
Z. Tian ◽  
D. Li ◽  
K. Zhang ◽  
B. Ji ◽  
...  
Keyword(s):  
Membrane Fusion ◽  
Transmembrane Domain ◽  
Fusion Rate ◽  
Protein Receptor ◽  
In Vitro Reconstitution ◽  
Sensitive Factor ◽  
Protein Receptors ◽  
Pass Energy ◽  
Autophagosome Maturation

ABSTRACTMembrane fusion mediated by Soluble N-ethylmaleimide-sensitive factor activating protein receptor (SNARE) proteins is an important cellular process. For neuronal SNAREs, the single transmembrane domain has been proposed to pass zippering energy to membranes for inducing fast fusion. In contrast, the SNARE protein, syntaxin 17, for membrane fusion involved in autophagosome maturation contains an unusual V-shape double-transmembrane domain that may influence its capability to pass energy. Here, we showed that this double-transmembrane domain significantly reduces fusion with an in vitro reconstitution system. Through theoretic modelling, we found that this V-shape double-transmembrane domain increases lipid-protein mismatch, which reduces the energy transduction for fusion. Moreover, our model also revealed the involvement of 2-3 SNAREs in a general fusion process.SIGNIFICANT STATEMENTSoluble N-ethylmaleimide-sensitive factor activating protein receptors (SNAREs) serve as the molecular machine to mediate membrane fusion. The zipper formation of core structure extending to membranes by two single transmembrena domains (TMDs) is the main driving force of membrane fusion. The role of TMD in fusion is unclear. By adding an extra TMD, we found that the hydrophobic mismatch effect between the thickness of the membrane and the length of TMDs plays an important role in regulating fusion.

Roles of the cytoplasmic and transmembrane domains of syntaxins in intracellular localization and trafficking

2001 ◽  
Vol 114 (17) ◽  
pp. 3115-3124 ◽  
Author(s):  
Kazuo Kasai ◽  
Kimio Akagawa
Keyword(s):  
Plasma Membrane ◽  
Transmembrane Domain ◽  
Intracellular Localization ◽  
Transmembrane Domains ◽  
Cytoplasmic Domains ◽  
Immunofluorescence Analysis ◽  
Attachment Protein ◽  
Transport Pathways ◽  
Sensitive Factor ◽  
Protein Receptors

Syntaxins are target-soluble N-ethylmaleimide-sensitive factor-attachment protein receptors (t-SNAREs) involved in docking and fusion of vesicles in exocytosis and endocytosis. Many syntaxin isoforms have been isolated, and each one displays a distinct intracellular localization pattern. However, the signals that drive the specific intracellular localization of syntaxins are poorly understood. In this study, we used indirect immunofluorescence analysis to examine the localization of syntaxin chimeras, each containing a syntaxin transmembrane domain fused to a cytoplasmic domain derived from a different syntaxin. We show that the cytoplasmic domains of syntaxins 5, 6, 7 and 8 have important effects on intracellular localization. We also demonstrate that the transmembrane domain of syntaxin 5 is sufficient to localize the chimera to the compartment expected for wild-type syntaxin 5. Additionally, we find that syntaxins 6, 7 and 8, but not syntaxin 5, are present at the plasma membrane, and that these syntaxins cycle through the plasma membrane by virtue of their cytoplasmic domains. Finally, we find that di-leucine-based motifs in the cytoplasmic domains of syntaxins 7 and 8 are necessary for their intracellular localization and trafficking via distinct transport pathways. Combined, these results suggest that both the cytoplasmic and the transmembrane domains play important roles in intracellular localization and trafficking of syntaxins.

scholarly journals Syntaxin 7 and VAMP-7 are SolubleN-Ethylmaleimide–sensitive Factor Attachment Protein Receptors Required for Late Endosome–Lysosome and Homotypic Lysosome Fusion in Alveolar Macrophages

2000 ◽  
Vol 11 (7) ◽  
pp. 2327-2333 ◽  
Author(s):  
Diane McVey Ward ◽  
Jonathan Pevsner ◽  
Matthew A. Scullion ◽  
Michael Vaughn ◽  
Jerry Kaplan
Keyword(s):  
Alveolar Macrophages ◽  
Transmembrane Domain ◽  
Late Endosome ◽  
Endocytic Pathway ◽  
Attachment Protein ◽  
Protein Receptor ◽  
Early Endosomes ◽  
Sensitive Factor ◽  
Protein Receptors

Endocytosis in alveolar macrophages can be reversibly inhibited, permitting the isolation of endocytic vesicles at defined stages of maturation. Using an in vitro fusion assay, we determined that each isolated endosome population was capable of homotypic fusion. All vesicle populations were also capable of heterotypic fusion in a temporally specific manner; early endosomes, isolated 4 min after internalization, could fuse with endosomes isolated 8 min after internalization but not with 12-min endosomes or lysosomes. Lysosomes fuse with 12-min endosomes but not with earlier endosomes. Using homogenous populations of endosomes, we have identified Syntaxin 7 as a soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) required for late endosome–lysosome and homotypic lysosome fusion in vitro. A bacterially expressed human Syntaxin 7 lacking the transmembrane domain inhibited homotypic late endosome and lysosome fusion as well as heterotypic late endosome–lysosome fusion. Affinity-purified antibodies directed against Syntaxin 7 also inhibited lysosome fusion in vitro but had no affect on homotypic early endosome fusion. Previous work suggested that human VAMP-7 (vesicle-associated membrane protein-7) was a SNARE required for late endosome–lysosome fusion. A bacterially expressed human VAMP-7 lacking the transmembrane domain inhibited both late endosome–lysosome fusion and homotypic lysosome fusion in vitro. These studies indicate that: 1) fusion along the endocytic pathway is a highly regulated process, and 2) two SNARE molecules, Syntaxin 7 and human VAMP-7, are involved in fusion of vesicles in the late endocytic pathway in alveolar macrophages.

Sec22b-dependent assembly of endoplasmic reticulum Q-SNARE proteins

2008 ◽  
Vol 410 (1) ◽  
pp. 93-100 ◽  
Author(s):  
Takehiro Aoki ◽  
Masaki Kojima ◽  
Katsuko Tani ◽  
Mitsuo Tagaya
Keyword(s):  
Endoplasmic Reticulum ◽  
Membrane Fusion ◽  
Transmembrane Domain ◽  
Cd Spectroscopy ◽  
Snare Proteins ◽  
Peripheral Membrane Proteins ◽  
Protein Receptor ◽  
Snare Motif ◽  
Α Helix ◽  
Protein Attachment

SNARE (soluble N-ethylmaleimide-sensitive fusion protein-attachment protein receptor) proteins involved in membrane fusion usually contain a conserved α-helix (SNARE motif) that is flanked by a C-terminal transmembrane domain. They can be classified into Q-SNARE and R-SNARE based on the structural property of their motifs. Assembly of four SNARE motifs (Qa, b, c and R) is supposed to trigger membrane fusion. We have previously shown that ER (endoplasmic reticulum)-localized syntaxin 18 (Qa) forms a complex with BNIP1 (Qb), p31/Use1 (Qc), Sec22b (R) and several peripheral membrane proteins. In the present study, we examined the interaction of syntaxin 18 with other SNAREs using pulldown assays and CD spectroscopy. We found that the association of syntaxin 18 with Sec22b induces an increase in α-helicity of their SNARE motifs, which results in the formation of high-affinity binding sites for BNIP1 and p31. This R-SNARE-dependent Q-SNARE assembly is quite different from the assembly mechanisms of SNAREs localized in organelles other than the ER. The implication of the mechanism of ER SNARE assembly is discussed in the context of the physiological roles of the syntaxin 18 complex.

scholarly journals Regulation of exocytosis by the exocyst subunit Sec6 and the SM protein Sec1

2012 ◽  
Vol 23 (2) ◽  
pp. 337-346 ◽  
Author(s):  
Francesca Morgera ◽  
Margaret R. Sallah ◽  
Michelle L. Dubuke ◽  
Pallavi Gandhi ◽  
Daniel N. Brewer ◽  
...  
Keyword(s):  
Membrane Fusion ◽  
Secretory Pathway ◽  
Secretory Vesicle ◽  
Snare Complex ◽  
Attachment Protein ◽  
Protein Receptor ◽  
Sensitive Factor ◽  
Membrane Bound ◽  
Sm Protein ◽  
Snare Complex Formation

Trafficking of protein and lipid cargo through the secretory pathway in eukaryotic cells is mediated by membrane-bound vesicles. Secretory vesicle targeting and fusion require a conserved multisubunit protein complex termed the exocyst, which has been implicated in specific tethering of vesicles to sites of polarized exocytosis. The exocyst is directly involved in regulating soluble N-ethylmaleimide–sensitive factor (NSF) attachment protein receptor (SNARE) complexes and membrane fusion through interactions between the Sec6 subunit and the plasma membrane SNARE protein Sec9. Here we show another facet of Sec6 function—it directly binds Sec1, another SNARE regulator, but of the Sec1/Munc18 family. The Sec6–Sec1 interaction is exclusive of Sec6–Sec9 but compatible with Sec6–exocyst assembly. In contrast, the Sec6–exocyst interaction is incompatible with Sec6–Sec9. Therefore, upon vesicle arrival, Sec6 is proposed to release Sec9 in favor of Sec6–exocyst assembly and to simultaneously recruit Sec1 to sites of secretion for coordinated SNARE complex formation and membrane fusion.

scholarly journals A Novel Site of Action for α-SNAP in the SNARE Conformational Cycle Controlling Membrane Fusion

2008 ◽  
Vol 19 (3) ◽  
pp. 776-784 ◽  
Author(s):  
Marcin Barszczewski ◽  
John J. Chua ◽  
Alexander Stein ◽  
Ulrike Winter ◽  
Rainer Heintzmann ◽  
...  
Keyword(s):  
Membrane Fusion ◽  
Plasma Membranes ◽  
Secretory Granules ◽  
Neuroendocrine Cells ◽  
Snare Complex ◽  
Protein Receptor ◽  
Sensitive Factor ◽  
Site Of Action ◽  
Snare Motif ◽  
Liposome Fusion

Regulated exocytosis in neurons and neuroendocrine cells requires the formation of a stable soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complex consisting of synaptobrevin-2/vesicle-associated membrane protein 2, synaptosome-associated protein of 25 kDa (SNAP-25), and syntaxin 1. This complex is subsequently disassembled by the concerted action of α-SNAP and the ATPases associated with different cellular activities-ATPase N-ethylmaleimide-sensitive factor (NSF). We report that NSF inhibition causes accumulation of α-SNAP in clusters on plasma membranes. Clustering is mediated by the binding of α-SNAP to uncomplexed syntaxin, because cleavage of syntaxin with botulinum neurotoxin C1 or competition by using antibodies against syntaxin SNARE motif abolishes clustering. Binding of α-SNAP potently inhibits Ca2+-dependent exocytosis of secretory granules and SNARE-mediated liposome fusion. Membrane clustering and inhibition of both exocytosis and liposome fusion are counteracted by NSF but not when an α-SNAP mutant defective in NSF activation is used. We conclude that α-SNAP inhibits exocytosis by binding to the syntaxin SNARE motif and in turn prevents SNARE assembly, revealing an unexpected site of action for α-SNAP in the SNARE cycle that drives exocytotic membrane fusion.

scholarly journals Topological arrangement of the intracellular membrane fusion machinery

2011 ◽  
Vol 22 (14) ◽  
pp. 2612-2619 ◽  
Author(s):  
Shailendra S. Rathore ◽  
Nilanjan Ghosh ◽  
Yan Ouyang ◽  
Jingshi Shen
Keyword(s):  
Membrane Fusion ◽  
Fusion Reaction ◽  
Coiled Coil ◽  
Intracellular Membrane ◽  
Sm Proteins ◽  
Protein Receptors ◽  
Reconstituted System ◽  
Sm Protein ◽  
First Time ◽  
Intracellular Membrane Fusion

Soluble N-ethylmaleimide–sensitive factor attachment protein receptors (SNAREs) form a four-helix coiled-coil bundle that juxtaposes two bilayers and drives a basal level of membrane fusion. The Sec1/Munc18 (SM) protein binds to its cognate SNARE bundle and accelerates the basal fusion reaction. The question of how the topological arrangement of the SNARE helices affects the reactivity of the fusion proteins remains unanswered. Here we address the problem for the first time in a reconstituted system containing both SNAREs and SM proteins. We find that to be fusogenic a SNARE topology must support both basal fusion and SM stimulation. Certain topological combinations of exocytic SNAREs result in basal fusion but cannot support SM stimulation, whereas other topologies support SM stimulation without inducing basal fusion. It is striking that of all the possible topological combinations of exocytic SNARE helices, only one induces efficient fusion. Our results suggest that the intracellular membrane fusion complex is designed to fuse bilayers according to one genetically programmed topology.

scholarly journals SNARE zippering requires activation by SNARE-like peptides in Sec1/Munc18 proteins

2018 ◽  
Vol 115 (36) ◽  
pp. E8421-E8429 ◽  
Author(s):  
Haijia Yu ◽  
Chong Shen ◽  
Yinghui Liu ◽  
Bridget L. Menasche ◽  
Yan Ouyang ◽  
...  
Keyword(s):  
Membrane Fusion ◽  
Lipid Bilayers ◽  
Fusion Reaction ◽  
Coiled Coil ◽  
Fusion Reactions ◽  
Sm Proteins ◽  
Close Proximity ◽  
Protein Receptors ◽  
Sm Protein

Soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) catalyze membrane fusion by forming coiled-coil bundles between membrane bilayers. The SNARE bundle zippers progressively toward the membranes, pulling the lipid bilayers into close proximity to fuse. In this work, we found that the +1 and +2 layers in the C-terminal domains (CTDs) of SNAREs are dispensable for reconstituted SNARE-mediated fusion reactions. By contrast, all CTD layers are required for fusion reactions activated by the cognate Sec1/Munc18 (SM) protein or a synthetic Vc peptide derived from the vesicular (v-) SNARE, correlating with strong acceleration of fusion kinetics. These results suggest a similar mechanism underlying the stimulatory functions of SM proteins and Vc peptide in SNARE-dependent membrane fusion. Unexpectedly, we identified a conserved SNARE-like peptide (SLP) in SM proteins that structurally and functionally resembles Vc peptide. Like Vc peptide, SLP binds and activates target (t-) SNAREs, accelerating the fusion reaction. Disruption of the t-SNARE–SLP interaction inhibits exocytosis in vivo. Our findings demonstrated that a t-SNARE–SLP intermediate must form before SNAREs can drive efficient vesicle fusion.

scholarly journals Comparative study of commercially available and homemade anti-VAMP7 antibodies using CRISPR/Cas9-depleted HeLa cells and VAMP7 knockout mice

F1000Research ◽  
2018 ◽  
Vol 7 ◽  
pp. 1649
Author(s):  
Agathe Verraes ◽  
Beatrice Cholley ◽  
Thierry Galli ◽  
Sebastien Nola
Keyword(s):  
Membrane Protein ◽  
Membrane Fusion ◽  
Hela Cells ◽  
Intracellular Membrane ◽  
Wild Type ◽  
Attachment Protein ◽  
Sensitive Factor ◽  
Protein Receptors ◽  
Brain Extracts ◽  
Intracellular Membrane Fusion

VAMP7 (vesicle-associated membrane protein) belongs to the intracellular membrane fusion SNARE (Soluble N-ethylmaleimide-sensitive factor attachment protein receptors) protein family. In this study, we used CRISPR/Cas9 genome editing technology to generate VAMP7 knockout (KO) human HeLa cells and mouse KO brain extracts in order to test the specificity and the background of a set of commercially available and homemade anti-VAMP7 antibodies. We propose a simple profiling method to analyze western blotting and immunocytochemistry staining profiles and determine the extent of the antibodies’ specificity. Using this method, we were able to rank the performance of a set of available antibodies and further showed an optimized procedure for VAMP7 immunoprecipitation, which we validated using wild-type and KO mouse brain extracts.

scholarly journals Low energy cost for optimal speed and control of membrane fusion

2017 ◽  
Vol 114 (6) ◽  
pp. 1238-1241 ◽  
Author(s):  
Claire François-Martin ◽  
James E. Rothman ◽  
Frederic Pincet
Keyword(s):  
Activation Energy ◽  
Membrane Fusion ◽  
Fusion Proteins ◽  
Lipid Vesicles ◽  
Attachment Protein ◽  
Sensitive Factor ◽  
Protein Receptors ◽  
Energy Consuming ◽  
And Control ◽  
To Receive

Membrane fusion is the cell’s delivery process, enabling its many compartments to receive cargo and machinery for cell growth and intercellular communication. The overall activation energy of the process must be large enough to prevent frequent and nonspecific spontaneous fusion events, yet must be low enough to allow it to be overcome upon demand by specific fusion proteins [such as soluble N-ethylmaleimide–sensitive factor attachment protein receptors (SNAREs)]. Remarkably, to the best of our knowledge, the activation energy for spontaneous bilayer fusion has never been measured. Multiple models have been developed and refined to estimate the overall activation energy and its component parts, and they span a very broad range from 20 kBT to 150 kBT, depending on the assumptions. In this study, using a bulk lipid-mixing assay at various temperatures, we report that the activation energy of complete membrane fusion is at the lowest range of these theoretical values. Typical lipid vesicles were found to slowly and spontaneously fully fuse with activation energies of ∼30 kBT. Our data demonstrate that the merging of membranes is not nearly as energy consuming as anticipated by many models and is ideally positioned to minimize spontaneous fusion while enabling rapid, SNARE-dependent fusion upon demand.

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