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https://www.readbyqxmd.com/read/29040524/potentiation-of-excitatory-synaptic-transmission-ameliorates-aggression-in-mice-with-stxbp1-haploinsufficiency
#1
Hiroyuki Miyamoto, Atsushi Shimohata, Manabu Abe, Teruo Abe, Emi Mazaki, Kenji Amano, Toshimitsu Suzuki, Tetsuya Tatsukawa, Shigeyoshi Itohara, Kenji Sakimura, Kazuhiro Yamakawa
Genetic studies point to a major role of de novo mutations in neurodevelopmental disorders of intellectual disability, autism spectrum disorders, and epileptic encephalopathy. The STXBP1 gene encodes the syntaxin-binding protein 1 (Munc18-1) that critically controls synaptic vesicle exocytosis and synaptic transmission. This gene harbors a high frequency of de novo mutations, which may play roles in these neurodevelopmental disorders. However, the system and behavioral-level pathophysiological changes caused by these genetic defects remain poorly understood...
October 11, 2017: Human Molecular Genetics
https://www.readbyqxmd.com/read/29029784/regulation-of-insulin-exocytosis-by-calcium-dependent-protein-kinase-c-in-beta-cells
#2
REVIEW
Adam J Trexler, Justin W Taraska
The control of insulin release from pancreatic beta cells helps ensure proper blood glucose level, which is critical for human health. Protein kinase C has been shown to be one key control mechanism for this process. After glucose stimulation, calcium influx into beta cells triggers exocytosis of insulin-containing dense-core granules and activates protein kinase C via calcium-dependent phospholipase C-mediated generation of diacylglycerol. Activated protein kinase C potentiates insulin release by enhancing the calcium sensitivity of exocytosis, likely by affecting two main pathways that could be linked: (1) the reorganization of the cortical actin network, and (2) the direct phosphorylation of critical exocytotic proteins such as munc18, SNAP25, and synaptotagmin...
November 2017: Cell Calcium
https://www.readbyqxmd.com/read/28887593/v-snare-function-in-chromaffin-cells
#3
REVIEW
Madhurima Dhara, Ralf Mohrmann, Dieter Bruns
Vesicle fusion is elementary for intracellular trafficking and release of signal molecules, thus providing the basis for diverse forms of intercellular communication like hormonal regulation or synaptic transmission. A detailed characterization of the mechanisms underlying exocytosis is key to understand how the nervous system integrates information and generates appropriate responses to stimuli. The machinery for vesicular release employs common molecular players in different model systems including neuronal and neuroendocrine cells, in particular members of the SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptors) protein family, Sec1/Munc18-like proteins, and other accessory factors...
September 8, 2017: Pflügers Archiv: European Journal of Physiology
https://www.readbyqxmd.com/read/28880475/recent-new-insights-into-the-role-of-snare-and-associated-proteins-in-insulin-granule-exocytosis
#4
REVIEW
Herbert Y Gaisano
Initial work on the exocytotic machinery of predocked insulin secretory granules (SGs) in pancreatic β-cells mimicked the SNARE hypothesis work in neurons, which includes SM/SNARE complex and associated priming proteins, fusion clamps and Ca(2+) sensors. However, β-cell SGs, unlike neuronal synaptic vesicles, exhibit a biphasic secretory response that requires additional distinct features in exocytosis including newcomer SGs that undergo minimal docking time at the plasma membrane (PM) before fusion and multi-SG (compound) fusion...
September 2017: Diabetes, Obesity & Metabolism
https://www.readbyqxmd.com/read/28860966/a-stimulation-function-of-synaptotagmin-1-in-ternary-snare-complex-formation-dependent-on-munc18-and-munc13
#5
Yun Li, Shen Wang, Tianzhi Li, Le Zhu, Yuanyuan Xu, Cong Ma
The Ca(2+) sensor synaptotagmin-1 (Syt1) plays an essential function in synaptic exocytosis. Recently, Syt1 has been implicated in synaptic vesicle priming, a maturation step prior to Ca(2+)-triggered membrane fusion that is believed to involve formation of the ternary SNARE complex and require priming proteins Munc18-1 and Munc13-1. However, the mechanisms of Syt1 in synaptic vesicle priming are still unclear. In this study, we found that Syt1 stimulates the transition from the Munc18-1/syntaxin-1 complex to the ternary SNARE complex catalyzed by Munc13-1...
2017: Frontiers in Molecular Neuroscience
https://www.readbyqxmd.com/read/28858288/simultaneous-lipid-and-content-mixing-assays-for-in-vitro-reconstitution-studies-of-synaptic-vesicle-fusion
#6
Xiaoxia Liu, Alpay Burak Seven, Junjie Xu, Victoria Esser, Lijing Su, Cong Ma, Josep Rizo
This protocol describes reconstitution assays to study how the neurotransmitter release machinery triggers Ca(2+)-dependent synaptic vesicle fusion. The assays monitor fusion between proteoliposomes containing the synaptic vesicle SNARE synaptobrevin (with or without the Ca(2+) sensor synaptotagmin-1) and proteoliposomes initially containing the plasma membrane SNAREs syntaxin-1 and soluble NSF attachment protein (SNAP)-25. Lipid mixing (from fluorescence de-quenching of Marina-Blue-labeled lipids) and content mixing (from development of fluorescence resonance energy transfer (FRET) between phycoerythrin-biotin (PhycoE-Biotin) and Cy5-streptavidin trapped in the two proteoliposome populations) are measured simultaneously to ensure that true, nonleaky membrane fusion is monitored...
September 2017: Nature Protocols
https://www.readbyqxmd.com/read/28852855/how-does-the-stimulus-define-exocytosis-in-adrenal-chromaffin-cells
#7
REVIEW
Fernando D Marengo, Ana M Cárdenas
The extent and type of hormones and active peptides secreted by the chromaffin cells of the adrenal medulla have to be adjusted to physiological requirements. The chromaffin cell secretory activity is controlled by the splanchnic nerve firing frequency, which goes from approximately 0.5 Hz in basal conditions to more than 15 Hz in stress. Thus, these neuroendocrine cells maintain a tonic release of catecholamines under resting conditions, massively discharge intravesicular transmitters in response to stress, or adequately respond to moderate stimuli...
August 29, 2017: Pflügers Archiv: European Journal of Physiology
https://www.readbyqxmd.com/read/28827281/munc18a-clusters-snare-bearing-liposomes-prior-to-trans-snare-zippering
#8
Matthew Grant Arnold, Pratikshya Adhikari, Baobin Kang, Hao Xu 徐昊
Sec1-Munc18 (SM) proteins co-operate 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...
September 24, 2017: Biochemical Journal
https://www.readbyqxmd.com/read/28821673/unc-18-and-tomosyn-antagonistically-control-synaptic-vesicle-priming-downstream-of-unc-13-in-caenorhabditis-elegans
#9
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 examine 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 Caenorhabditis elegans, as well as enhanced synaptic neurotransmission in cultured mammalian neurons...
September 6, 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
#10
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
#11
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
#12
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
#13
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
#14
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
#15
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
#16
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
#17
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
#18
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
#19
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
#20
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
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