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Munc18

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https://www.readbyqxmd.com/read/28827281/munc18a-clusters-snare-bearing-liposomes-prior-to-trans-snare-zippering
#1
Matthew Grant Arnold, Pratikshya Adhikari, Baobin Kang, Hao Xu
Sec1-Munc18 (SM) proteins cooperate with SNAREs {SNAP [soluble NSF (N-ethylmaleimide-sensitive factor) attachment protein] receptors} to mediate membrane fusion in eukaryotic cells. Studies of Munc18a/Munc18-1/Stxbp1 in neurotransmission suggest that SM proteins accelerate fusion kinetics primarily by activating the partially zippered trans-SNARE complex. However, accumulating evidence has argued for additional roles for SM proteins in earlier steps in the fusion cascade. Here we investigate the function of Munc18a in reconstituted exocytic reactions mediated by neuronal and non-neuronal SNAREs...
August 21, 2017: Biochemical Journal
https://www.readbyqxmd.com/read/28821673/unc-18-and-tomosyn-antagonistically-control-synaptic-vesicle-priming-downstream-of-unc-13-in-c-elegans
#2
Seungmee Park, Na-Ryum Bin, Bin Yu, Raymond Wong, Ewa Sitarska, Kyoko Sugita, Ke Ma, Junjie Xu, Chi-Wei Tien, Arash Algouneh, Ekaterina Turlova, Siyan Wang, Pranay Siriya, Waleed Shahid, Lorraine Kalia, Zhong-Ping Feng, Philippe P Monnier, Hong-Shuo Sun, Mei Zhen, Shangbang Gao, Josep Rizo, Shuzo Sugita
Munc18-1/UNC-18 is believed to prime SNARE-mediated membrane fusion, yet the underlying mechanisms remain enigmatic. Here, we examined how potential gain-of-function mutations of Munc18-1/UNC-18 affect locomotory behavior and synaptic transmission, and how Munc18-1-mediated priming is related to Munc13-1/UNC-13 and Tomosyn/TOM-1, positive and negative SNARE regulators, respectively. We show that a Munc18-1(P335A)/UNC-18(P334A) mutation leads to significantly increased locomotory activity and acetylcholine release in C...
August 8, 2017: Journal of Neuroscience: the Official Journal of the Society for Neuroscience
https://www.readbyqxmd.com/read/28776026/reconstitution-of-calcium-mediated-exocytosis-of-dense-core-vesicles
#3
Alex J B Kreutzberger, Volker Kiessling, Binyong Liang, Patrick Seelheim, Shrutee Jakhanwal, Reinhard Jahn, J David Castle, Lukas K Tamm
Regulated exocytosis is a process by which neurotransmitters, hormones, and secretory proteins are released from the cell in response to elevated levels of calcium. In cells, secretory vesicles are targeted to the plasma membrane, where they dock, undergo priming, and then fuse with the plasma membrane in response to calcium. The specific roles of essential proteins and how calcium regulates progression through these sequential steps are currently incompletely resolved. We have used purified neuroendocrine dense-core vesicles and artificial membranes to reconstruct in vitro the serial events that mimic SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor)-dependent membrane docking and fusion during exocytosis...
July 2017: Science Advances
https://www.readbyqxmd.com/read/28772123/molecular-mechanisms-of-synaptic-vesicle-priming-by-munc13-and-munc18
#4
Ying Lai, Ucheor B Choi, Jeremy Leitz, Hong Jun Rhee, Choongku Lee, Bekir Altas, Minglei Zhao, Richard A Pfuetzner, Austin L Wang, Nils Brose, JeongSeop Rhee, Axel T Brunger
Munc13 catalyzes the transit of syntaxin from a closed complex with Munc18 into the ternary SNARE complex. Here we report a new function of Munc13, independent of Munc18: it promotes the proper syntaxin/synaptobrevin subconfiguration during assembly of the ternary SNARE complex. In cooperation with Munc18, Munc13 additionally ensures the proper syntaxin/SNAP-25 subconfiguration. In a reconstituted fusion assay with SNAREs, complexin, and synaptotagmin, inclusion of both Munc13 and Munc18 quadruples the Ca(2+)-triggered amplitude and achieves Ca(2+) sensitivity at near-physiological concentrations...
August 2, 2017: Neuron
https://www.readbyqxmd.com/read/28724787/disrupted-apical-exocytosis-of-cargo-vesicles-causes-enteropathy-in-fhl5-patients-with-munc18-2-mutations
#5
Georg F Vogel, Jorik M van Rijn, Iris M Krainer, Andreas R Janecke, Carsten Posovzsky, Marta Cohen, Claire Searle, Prevost Jantchou, Johanna C Escher, Natalie Patey, Ernest Cutz, Thomas Müller, Sabine Middendorp, Michael W Hess, Lukas A Huber
Familial hemophagocytic lymphohistiocytosis 5 (FHL5) is an autosomal recessive disease caused by mutations in STXBP2, coding for Munc18-2, which is required for SNARE-mediated membrane fusion. FHL5 causes hematologic and gastrointestinal symptoms characterized by chronic enteropathy that is reminiscent of microvillus inclusion disease (MVID). However, the molecular pathophysiology of FHL5-associated diarrhea is poorly understood. Five FHL5 patients, including four previously unreported patients, were studied...
July 20, 2017: JCI Insight
https://www.readbyqxmd.com/read/28635948/munc13-1-and-munc18-1-together-prevent-nsf-dependent-de-priming-of-synaptic-vesicles
#6
Enqi He, Keimpe Wierda, Rhode van Westen, Jurjen H Broeke, Ruud F Toonen, L Niels Cornelisse, Matthijs Verhage
Synaptic transmission requires a stable pool of release-ready (primed) vesicles. Here we show that two molecules involved in SNARE-complex assembly, Munc13-1 and Munc18-1, together stabilize release-ready vesicles by preventing de-priming. Replacing neuronal Munc18-1 by a non-neuronal isoform Munc18-2 (Munc18-1/2SWAP) supports activity-dependent priming, but primed vesicles fall back into a non-releasable state (de-prime) within seconds. Munc13-1 deficiency produces a similar defect. Inhibitors of N-ethylmaleimide sensitive factor (NSF), N-ethylmaleimide (NEM) or interfering peptides, prevent de-priming in munc18-1/2SWAP or munc13-1 null synapses, but not in CAPS-1/2 null, another priming-deficient mutant...
June 21, 2017: Nature Communications
https://www.readbyqxmd.com/read/28520937/atypical-endocannabinoid-signaling-initiates-a-new-form-of-memory-related-plasticity-at-a-cortical-input-to-hippocampus
#7
Weisheng Wang, Yousheng Jia, Danielle T Pham, Linda C Palmer, Kwang-Mook Jung, Conor D Cox, Gavin Rumbaugh, Daniele Piomelli, Christine M Gall, Gary Lynch
Endocannabinoids (ECBs) depress transmitter release at sites throughout the brain. Here, we describe another form of ECB signaling that triggers a novel form of long-term potentiation (LTP) localized to the lateral perforant path (LPP) which conveys semantic information from cortex to hippocampus. Two cannabinoid CB1 receptor (CB1R) signaling cascades were identified in hippocampus. The first is pregnenolone sensitive, targets vesicular protein Munc18-1 and depresses transmitter release; this cascade is engaged by CB1Rs in Schaffer-Commissural afferents to CA1 but not in the LPP, and it does not contribute to LTP...
May 17, 2017: Cerebral Cortex
https://www.readbyqxmd.com/read/28504692/mint3-mediated-l1cam-expression-in-fibroblasts-promotes-cancer-cell-proliferation-via-integrin-%C3%AE-5%C3%AE-1-and-tumour-growth
#8
H J Nakaoka, Z Tanei, T Hara, J S Weng, A Kanamori, T Hayashi, H Sato, A Orimo, K Otsuji, K Tada, T Morikawa, T Sasaki, M Fukayama, M Seiki, Y Murakami, T Sakamoto
Fibroblasts are some of the major cells in tumour tissues that influence tumour progression and drug resistance. However, our understanding on fibroblast-mediated tumour malignancy remains incomplete. Munc18-1-interacting protein 3 (Mint3) is known as an activator of hypoxia-inducible factor-1 (HIF-1) even during normoxia in cancer cells, macrophages and fibroblasts. Although Mint3 promotes ATP production via glycolysis by activating HIF-1 in cancer cells and macrophages, the biological role of Mint3-mediated HIF-1 activation in fibroblasts remains unclear...
May 15, 2017: Oncogenesis
https://www.readbyqxmd.com/read/28483813/an-activated-q-snare-sm-protein-complex-as-a-possible-intermediate-in-snare-assembly
#9
Shrutee Jakhanwal, Chung-Tien Lee, Henning Urlaub, Reinhard Jahn
Assembly of the SNARE proteins syntaxin1, SNAP25, and synaptobrevin into a SNARE complex is essential for exocytosis in neurons. For efficient assembly, SNAREs interact with additional proteins but neither the nature of the intermediates nor the sequence of protein assembly is known. Here, we have characterized a ternary complex between syntaxin1, SNAP25, and the SM protein Munc18-1 as a possible acceptor complex for the R-SNARE synaptobrevin. The ternary complex binds synaptobrevin with fast kinetics, resulting in the rapid formation of a fully zippered SNARE complex to which Munc18-1 remains tethered by the N-terminal domain of syntaxin1...
June 14, 2017: EMBO Journal
https://www.readbyqxmd.com/read/28477408/autoinhibition-of-munc18-1-modulates-synaptobrevin-binding-and-helps-to-enable-munc13-dependent-regulation-of-membrane-fusion
#10
Ewa Sitarska, Junjie Xu, Seungmee Park, Xiaoxia Liu, Bradley Quade, Karolina Stepien, Kyoko Sugita, Chad A Brautigam, Shuzo Sugita, Josep Rizo
Munc18-1 orchestrates SNARE complex assembly together with Munc13-1 to mediate neurotransmitter release. Munc18-1 binds to synaptobrevin, but the relevance of this interaction and its relation to Munc13 function are unclear. NMR experiments now show that Munc18-1 binds specifically and non-specifically to synaptobrevin. Specific binding is inhibited by a L348R mutation in Munc18-1 and enhanced by a D326K mutation designed to disrupt the 'furled conformation' of a Munc18-1 loop. Correspondingly, the activity of Munc18-1 in reconstitution assays that require Munc18-1 and Munc13-1 for membrane fusion is stimulated by the D326K mutation and inhibited by the L348R mutation...
May 6, 2017: ELife
https://www.readbyqxmd.com/read/28471021/syntaxin-4-mediates-endosome-recycling-for-lytic-granule-exocytosis-in-cytotoxic-t-lymphocytes
#11
Waldo A Spessott, Maria L Sanmillan, Vineet V Kulkarni, Margaret E McCormick, Claudio G Giraudo
Adaptive and innate immunity utilize the perforin-killing pathway to eliminate virus-infected or cancer cells. Cytotoxic T-lymphocytes (CTLs) and natural killer cells mediate this process by releasing toxic proteins at the contact area with target cells known as immunological synapse (IS). Formation of a stable IS and exocytosis of toxic proteins requires persistent fusion of Rab11a recycling endosomes with the plasma membrane (PM) that may assure the delivery of key effector proteins. Despite the importance of the recycling endosomal compartment, the membrane fusion proteins that control this process at the IS remain elusive...
July 2017: Traffic
https://www.readbyqxmd.com/read/28468610/a-case-report-of-novel-mutation-in-prf1-gene-which-causes-familial-autosomal-recessive-hemophagocytic-lymphohistiocytosis
#12
Mohammad Reza Bordbar, Farzaneh Modarresi, Mohammad Ali Farazi Fard, Hassan Dastsooz, Nader Shakib Azad, Mohammad Ali Faghihi
BACKGROUND: Hemophagocytic Lymphohistiocytosis (HLH) is a life-threatening immunodeficiency and multi-organ disease that affects people of all ages and ethnic groups. Common symptoms and signs of this disease are high fever, hepatosplenomegaly, and cytopenias. Familial form of HLH disease, which is an autosomal recessive hematological disorder is due to disease-causing mutations in several genes essential for NK and T-cell granule-mediated cytotoxic function. For an effective cytotoxic response from cytotoxic T lymphocyte or NK cell encountering an infected cell or tumor cell, different processes are required, including trafficking, docking, priming, membrane fusion, and entry of cytotoxic granules into the target cell leading to apoptosis...
May 3, 2017: BMC Medical Genetics
https://www.readbyqxmd.com/read/28356294/exocytosis-proteins-as-novel-targets-for-diabetes-prevention-and-or-remediation
#13
REVIEW
Arianne Aslamy, Debbie C Thurmond
Diabetes remains one of the leading causes of morbidity and mortality worldwide, affecting an estimated 422 million adults. In the US, it is predicted that one in every three children born as of 2000 will suffer from diabetes in their lifetime. Type 2 diabetes results from combinatorial defects in pancreatic β-cell glucose-stimulated insulin secretion and in peripheral glucose uptake. Both processes, insulin secretion and glucose uptake, are mediated by exocytosis proteins, SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) complexes, Sec1/Munc18 (SM), and double C2-domain protein B (DOC2B)...
May 1, 2017: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
https://www.readbyqxmd.com/read/28348137/early-golgi-abnormalities-and-neurodegeneration-upon-loss-of-presynaptic-proteins-munc18-1-syntaxin-1-or-snap-25
#14
Tatiana C Santos, Keimpe Wierda, Jurjen H Broeke, Ruud F Toonen, Matthijs Verhage
The loss of presynaptic proteins Munc18-1, syntaxin-1, or SNAP-25 is known to produce cell death, but the underlying features have not been compared experimentally. Here, we investigated these features in cultured mouse CNS and DRG neurons. Side-by-side comparisons confirmed massive cell death, before synaptogenesis, within 1-4 DIV upon loss of t-SNAREs (syntaxin-1, SNAP-25) or Munc18-1, but not v-SNAREs (synaptobrevins/VAMP1/2/3 using tetanus neurotoxin (TeNT), also in TI-VAMP/VAMP7 knock-out (KO) neurons)...
April 26, 2017: Journal of Neuroscience: the Official Journal of the Society for Neuroscience
https://www.readbyqxmd.com/read/28292915/a-cascade-of-multiple-proteins-and-lipids-catalyzes-membrane-fusion
#15
William Wickner, Josep Rizo
Recent studies suggest revisions to the SNARE paradigm of membrane fusion. Membrane tethers and/or SNAREs recruit proteins of the Sec 1/Munc18 family to catalyze SNARE assembly into trans-complexes. SNARE-domain zippering draws the bilayers into immediate apposition and provides a platform to position fusion triggers such as Sec 17/α-SNAP and/or synaptotagmin, which insert their apolar "wedge" domains into the bilayers, initiating the lipid rearrangements of fusion.
March 15, 2017: Molecular Biology of the Cell
https://www.readbyqxmd.com/read/28267240/integrated-functions-of-membrane-type-1-matrix-metalloproteinase-in-regulating-cancer-malignancy-beyond-a-proteinase
#16
REVIEW
Takeharu Sakamoto, Motoharu Seiki
Membrane-type 1 matrix metalloproteinase (MT1-MMP) is expressed in different types of invasive and proliferative cells, including cancer cells and stromal cells. MT1-MMP cleaves extracellular matrix proteins, membrane proteins and other pericellular proteins, thereby changing the cellular microenvironment and regulating signal activation. Critical roles of protease activity in cancer cell proliferation, invasion and metastasis have been demonstrated by many groups. MT1-MMP also has a non-protease activity in that it inhibits the oxygen-dependent suppression of hypoxia-inducible factors (HIFs) via Munc18-1-interacting protein 3 (Mint3) and thereby enhances the expression of HIF target genes...
June 2017: Cancer Science
https://www.readbyqxmd.com/read/28265073/sm-protein-munc18-2-facilitates-transition-of-syntaxin-11-mediated-lipid-mixing-to-complete-fusion-for-t-lymphocyte-cytotoxicity
#17
Waldo A Spessott, Maria L Sanmillan, Margaret E McCormick, Vineet V Kulkarni, Claudio G Giraudo
The atypical lipid-anchored Syntaxin 11 (STX11) and its binding partner, the Sec/Munc (SM) protein Munc18-2, facilitate cytolytic granule release by cytotoxic T lymphocytes (CTLs) and natural killer (NK) cells. Patients carrying mutations in these genes develop familial hemophagocytic lymphohistiocytosis, a primary immunodeficiency characterized by impaired lytic granule exocytosis. However, whether a SNARE such as STX11, which lacks a transmembrane domain, can support membrane fusion in vivo is uncertain, as is the precise role of Munc18-2 during lytic granule exocytosis...
March 14, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28137749/conformational-change-of-syntaxin-linker-region-induced-by-munc13s-initiates-snare-complex-formation-in-synaptic-exocytosis
#18
Shen Wang, Ucheor B Choi, Jihong Gong, Xiaoyu Yang, Yun Li, Austin L Wang, Xiaofei Yang, Axel T Brunger, Cong Ma
The soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) protein syntaxin-1 adopts a closed conformation when bound to Munc18-1, preventing binding to synaptobrevin-2 and SNAP-25 to form the ternary SNARE complex. Although it is known that the MUN domain of Munc13-1 catalyzes the transition from the Munc18-1/syntaxin-1 complex to the SNARE complex, the molecular mechanism is unclear. Here, we identified two conserved residues (R151, I155) in the syntaxin-1 linker region as key sites for the MUN domain interaction...
March 15, 2017: EMBO Journal
https://www.readbyqxmd.com/read/28118494/strain-dependent-effects-of-acute-alcohol-on-synaptic-vesicle-recycling-and-post-tetanic-potentiation-in-medial-glutamate-inputs-to-the-mouse-basolateral-amygdala
#19
Dominic A Gioia, Brian McCool
BACKGROUND: Inbred mouse strains are differentially sensitive to the acute effects of ethanol (EtOH) and are useful tools for examining how unique genomes differentially affect alcohol-related behaviors and physiology. DBA/2J mice have been shown to be sensitive to the acute anxiolytic effects of alcohol as well as the anxiogenic effects of withdrawal from chronic alcohol exposure, while B6 mice are resistant to both. Considering that the basolateral amygdala (BLA) is an important brain region for the acute and chronic effects of EtOH on fear and anxiety related behaviors, we hypothesized that there would be strain-dependent differences in the acute effects of EtOH in BLA slices...
April 2017: Alcoholism, Clinical and Experimental Research
https://www.readbyqxmd.com/read/28116546/cortical-synaptic-transmission-and-plasticity-in-acute-liver-failure-are-decreased-by-presynaptic-events
#20
Mariusz Popek, Bartosz Bobula, Joanna Sowa, Grzegorz Hess, Rafał Polowy, Robert Kuba Filipkowski, Małgorzata Frontczak-Baniewicz, Barbara Zabłocka, Jan Albrecht, Magdalena Zielińska
Neurological symptoms of acute liver failure (ALF) reflect decreased excitatory transmission, but the status of ALF-affected excitatory synapse has not been characterized in detail. We studied the effects of ALF in mouse on synaptic transmission and plasticity ex vivo and its relation to distribution of (i) synaptic vesicles (sv) and (ii) functional synaptic proteins within the synapse. ALF-competent neurological and biochemical changes were induced in mice with azoxymethane (AOM). Electrophysiological characteristics (long-term potentiation, whole-cell recording) as well as synapse ultrastructure were evaluated in the cerebral cortex...
January 23, 2017: Molecular Neurobiology
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