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| Open AccessSYPL1 defines a vesicular pathway essential for sperm cytoplasmic droplet formation and male fertility
The cytoplasmic droplet is an elusive structure of mammalian sperm. Here, the authors uncover a key gene that defines a vesicular pathway essential for cytoplasmic droplet formation and male fertility.
- Jiali Liu
- , Louis Hermo
- & Chen Chen
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| Open AccessTetraspanin-8 sequesters syntaxin-2 to control biphasic release propensity of mucin granules
The mechanisms regulating granule secretion are not fully understood. Here the authors show that tetraspanin-8 sequesters syntaxin-2 at the cell surface, limiting the syntaxin available for fusion and the quantities of mucin secreted. This mechanism may also apply to insulin release
- José Wojnacki
- , Agustin Leonardo Lujan
- & Vivek Malhotra
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| Open AccessPlasma membrane flipping of Syntaxin-2 regulates its inhibitory action on insulin granule exocytosis
Kang and colleagues find that plasma membrane flipping of Syntaxin-2 from inside (inhibitory) to outside (relief of inhibition) of pancreatic β-cells helps fine-tune insulin secretion. Increasing this flipping efficiency can alleviate the impaired insulin secretion in diabetes.
- Fei Kang
- , Li Xie
- & Herbert Y. Gaisano
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| Open AccessmTOR-mediated phosphorylation of VAMP8 and SCFD1 regulates autophagosome maturation
Autophagy relies on coordinated fusion of organelle membranes, although the interplay between the regulatory machinery is not well studied. Here, the authors show that SNARE complex formation is inhibited by mTORC1 phosphorylation of VAMP8, which prevents autophagosome-lysosome fusion.
- Hong Huang
- , Qinqin Ouyang
- & Rong Liu
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| Open AccessSTX17 dynamically regulated by Fis1 induces mitophagy via hierarchical macroautophagic mechanism
Mitophagy plays a critical role in cellular homeostasis, and PINK1/Parkin-mediated mitophagy is the most thoroughly characterized. Here, Xian et al. show that STX17 induces mitophagy via a macroautophagy pathway regulated by Fis1, by a PINK1/Parkin-independent route.
- Hongxu Xian
- , Qiaoyun Yang
- & Yih-Cherng Liou
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| Open AccessSNAREs define targeting specificity of trafficking vesicles by combinatorial interaction with tethering factors
Intracellular vesicle targeting is mediated by Rab GTPases that cooperate with phosphatidylinositides and SNARE proteins, which then facilitate membrane fusion. Here, the authors microinject artificial vesicles into HeLa cells and find that SNAREs play a more prominent role in targeting specificity of trafficking vesicles than previously known.
- Seiichi Koike
- & Reinhard Jahn
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| Open AccessMunc18 and Munc13 serve as a functional template to orchestrate neuronal SNARE complex assembly
Synaptic exocytosis depends on formation of the SNARE complex but its assembly mechanism is still under debate. Here, the authors identify an interaction between Munc13-1 and synaptobrevin-2 that is critical for the transition of the Munc18-1/syntaxin-1 complex to the SNARE complex.
- Shen Wang
- , Yun Li
- & Cong Ma
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| Open AccessIdentification and characterization of a novel botulinum neurotoxin
There are seven well-established types of Botulinum neurotoxins (BoNTs). Here the authors report the identification and characterization of a new type of BoNT—BoNT/X—which cleaves a different site on canonical BoNTs substrates and targets SNARE family members not cleaved by known BoNTs.
- Sicai Zhang
- , Geoffrey Masuyer
- & Pål Stenmark
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The trans-SNARE-regulating function of Munc18-1 is essential to synaptic exocytosis
Munc18-1 binds trans-SNARE complexes and promotes membrane fusion in vitro. Here the authors provide genetic evidence that this trans-SNARE-regulating function plays an essential role in synaptic releases in neurons, and show that this function is disrupted by a disease-causing Munc18-1 mutation.
- Chong Shen
- , Shailendra S. Rathore
- & Jingshi Shen
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| Open AccessTwo-photon fluorescence lifetime imaging of primed SNARE complexes in presynaptic terminals and β cells
Synaptic vesicles are held in a fusion-competent state prior to their rapid release, which is thought to depend upon formation of trans-SNARE complexes. Takahashi et al. directly image this primed state using FLIM/FRET, and demonstrate differences in basal SNARE organization between neurons and β cells.
- Noriko Takahashi
- , Wakako Sawada
- & Haruo Kasai
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| Open AccessDirect quantitative detection of Doc2b-induced hemifusion in optically trapped membranes
Membrane fusion in cells is triggered by an increase in Ca2+ and involves SNARE complexes and calcium-sensing proteins, but the mechanism underlying the Ca2+-sensors’ role in fusion remains unclear. Here the authors show in vitro that the Ca2+-sensor Doc2b acts directly on membranes and induces a hemifusion intermediate in the presence of calcium.
- Ineke Brouwer
- , Asiya Giniatullina
- & Alexander J. Groffen
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| Open AccessHydrophobic mismatch sorts SNARE proteins into distinct membrane domains
Clustering of proteins in the plasma membrane plays an important role in the regulation of both cellular signalling and membrane remodelling. Milovanovic et al.demonstrate that mismatch between transmembrane domain length and the lipid bilayer thickness is sufficient to drive clustering of SNARE proteins.
- Dragomir Milovanovic
- , Alf Honigmann
- & Reinhard Jahn
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SNARE-fusion mediated insertion of membrane proteins into native and artificial membranes
The study of cell membrane proteins can be simplified by incorporating them into lipid bilayers, but doing this for multiple proteins can be challenging. Here, the authors present a technique to achieve this, and show reconstitution of a bacterial respiratory chain from individual components.
- Gustav Nordlund
- , Peter Brzezinski
- & Christoph von Ballmoos
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Caesium accumulation in yeast and plants is selectively repressed by loss of the SNARE Sec22p/SEC22
The active uptake of radiocaesium by plants via potassium transport systems results in contamination of food supplies. Here, the authors show that loss of the v-SNARE protein Sec22p/SEC22 specifically reduces the accumulation of Cs+in yeast and plants by repressing its deposition to vacuoles.
- Stephan Dräxl
- , Johannes Müller
- & Anton R. Schäffner
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Dynamin−SNARE interactions control trans-SNARE formation in intracellular membrane fusion
Dynamin promotes membrane fission by constricting the neck of invaginating membranes; however, it was recently shown that dynamin also regulates membrane fusion. Here the authors show that this fusogenic activity is mediated by interaction with the Qa SNARE, thereby promoting trans-SNARE formation.
- Kannan Alpadi
- , Aditya Kulkarni
- & Christopher Peters
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| Open AccessMechanical unzipping and rezipping of a single SNARE complex reveals hysteresis as a force-generating mechanism
Interactions between (SNARE) proteins on vesicle and target membranes provide the force necessary to drive membrane fusion. By applying piconewton forces to single SNARE complexes, the authors identify a partially assembled intermediate state that reveals how force is generated in a consistent direction.
- Duyoung Min
- , Kipom Kim
- & Tae-Young Yoon
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COG complexes form spatial landmarks for distinct SNARE complexes
COG complexes are thought to be involved in tethering of intra-Golgi vesicles. Here the authors show that individual COG complex subunits direct the assembly of distinct vesicle-tethering platforms, suggesting that COG subunits have a role in the specificity of vesicular sorting.
- Rose Willett
- , Tetyana Kudlyk
- & Vladimir Lupashin
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Cytotoxicity of botulinum neurotoxins reveals a direct role of syntaxin 1 and SNAP-25 in neuron survival
Botulinum toxins can cause substantial neurodegeneration. Peng et al. study cultured rat hippocampal neurons and find that botulinum toxin-induced cytotoxicity occurs only when there is effective cleavage of the SNARE proteins, syntaxin 1 or SNAP-25, by type C and type E botulinum toxins.
- Lisheng Peng
- , Huisheng Liu
- & Min Dong
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Synaptobrevin2 is the v-SNARE required for cytotoxic T-lymphocyte lytic granule fusion
Cytotoxic T lymphocytes kill target cells through the fusion of lytic granules at the immunological synapse. Using high-resolution microscopy techniques Matti et al.identify synaptobrevin2 as the vesicular SNARE protein required for this fusion reaction.
- Ulf Matti
- , Varsha Pattu
- & Jens Rettig
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A single-vesicle content mixing assay for SNARE-mediated membrane fusion
SNARE protein-mediated vesicle fusion is usually monitored by indirect lipid mixing. Diaoet al. have developed a FRET-based single-vesicle content mixing assay, which elucidates fusion pore formation, and shows that the yeast SNARE complex mediates pore expansion in the absence of accessory proteins.
- Jiajie Diao
- , Zengliu Su
- & Taekjip Ha