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Robinson CM, Duggan A, Forrester A. ER exit in physiology and disease. Front Mol Biosci 2024; 11:1352970. [PMID: 38314136 PMCID: PMC10835805 DOI: 10.3389/fmolb.2024.1352970] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2023] [Accepted: 01/05/2024] [Indexed: 02/06/2024] Open
Abstract
The biosynthetic secretory pathway is comprised of multiple steps, modifications and interactions that form a highly precise pathway of protein trafficking and secretion, that is essential for eukaryotic life. The general outline of this pathway is understood, however the specific mechanisms are still unclear. In the last 15 years there have been vast advancements in technology that enable us to advance our understanding of this complex and subtle pathway. Therefore, based on the strong foundation of work performed over the last 40 years, we can now build another level of understanding, using the new technologies available. The biosynthetic secretory pathway is a high precision process, that involves a number of tightly regulated steps: Protein folding and quality control, cargo selection for Endoplasmic Reticulum (ER) exit, Golgi trafficking, sorting and secretion. When deregulated it causes severe diseases that here we categorise into three main groups of aberrant secretion: decreased, excess and altered secretion. Each of these categories disrupts organ homeostasis differently, effecting extracellular matrix composition, changing signalling events, or damaging the secretory cells due to aberrant intracellular accumulation of secretory proteins. Diseases of aberrant secretion are very common, but despite this, there are few effective therapies. Here we describe ER exit sites (ERES) as key hubs for regulation of the secretory pathway, protein quality control and an integratory hub for signalling within the cell. This review also describes the challenges that will be faced in developing effective therapies, due to the specificity required of potential drug candidates and the crucial need to respect the fine equilibrium of the pathway. The development of novel tools is moving forward, and we can also use these tools to build our understanding of the acute regulation of ERES and protein trafficking. Here we review ERES regulation in context as a therapeutic strategy.
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Affiliation(s)
- Claire M Robinson
- School of Medicine, Health Sciences Centre, University College Dublin, Dublin, Ireland
- Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Dublin, Ireland
| | - Aislinn Duggan
- School of Medicine, Health Sciences Centre, University College Dublin, Dublin, Ireland
- Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Dublin, Ireland
| | - Alison Forrester
- Research Unit of Cell Biology (URBC), Namur Research Institute for Life Sciences (NARILIS), University of Namur, Namur, Belgium
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2
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Xu J, Ma H, Shi L, Zhou H, Cheng Y, Tong J, Meng B, Xu X, He K, Ding S, Zhang J, Yue L, Xiang G. Inflammatory Cell-Derived MYDGF Attenuates Endothelial LDL Transcytosis to Protect Against Atherogenesis. Arterioscler Thromb Vasc Biol 2023; 43:e443-e467. [PMID: 37767706 DOI: 10.1161/atvbaha.123.319905] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2023] [Accepted: 09/12/2023] [Indexed: 09/29/2023]
Abstract
BACKGROUND Inflammation contributes to the pathogenesis of atherosclerosis. But little is known about the potential benefits of inflammatory cells to atherosclerosis. The aim of this study was to investigate the function of inflammatory cells/endothelium axis and determine whether and how inflammatory cell-derived MYDGF (myeloid-derived growth factor) inhibited endothelial LDL (low-density lipoprotein) transcytosis. METHODS In in vivo experiments, both loss- and gain-of-function strategies were used to evaluate the effect of inflammatory cell-derived MYDGF on LDL transcytosis. We generated monocyte/macrophage-targeted MYDGF-null mice on an Ldlr (LDL receptor)-/- background in the loss-of-function strategy and restored the inflammatory cell-derived MYDGF by bone marrow transplantation and inflammatory cell-specific overexpression of MYDGF mice model in the gain-of-function strategy. In in vitro experiments, coculture experiments between primary mouse aortic endothelial cells and macrophages and mouse aortic endothelial cells supplemented with or without recombinant MYDGF were conducted. RESULTS Inflammatory cell-derived MYDGF deficiency aggravated endothelial LDL transcytosis, drove LDL uptake by artery wall, and thus exacerbated atherosclerosis in vivo. Inflammatory cell-derived MYDGF restoration by bone marrow transplantation and inflammatory cell MYDGF overexpression alleviated LDL transport across the endothelium, prevented LDL accumulation in the subendothelial space, and subsequently ameliorated atherosclerosis in vivo. Furthermore, in the in vitro study, macrophages isolated from MYDGF+/+ mice and recombinant MYDGF attenuated LDL transcytosis and uptake in mouse aortic endothelial cells. Mechanistically, MYDGF inhibited MAP4K4 (mitogen-activated protein kinase kinase kinase kinase isoform 4) phosphorylation, enhanced activation of Akt (protein kinase B)-1, and diminished the FoxO (forkhead box O) 3a signaling cascade to exert protective effects of MYDGF on LDL transcytosis and atherosclerosis. CONCLUSIONS The findings support a role for inflammatory cell-derived MYDGF served as a cross talk factor between inflammatory cells and endothelial cells that inhibits LDL transcytosis across endothelium. MYDGF may become a novel therapeutic drug for atherosclerosis, and the beneficial effects of inflammatory cell in atherosclerosis deserve further attention.
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Affiliation(s)
- Jinling Xu
- Department of Endocrinology, General Hospital of Central Theater Command, Wuhan, China (J.X., L.S., Y.C., J.T., B.M., X.X., J.Z., L.Y., G.X.)
- The First School of Clinical Medicine, Southern Medical University, Guangdong, China (J.X., L.S., Y.C., J.T., K.H., S.D., G.X.)
| | - Huaxing Ma
- Department of Hepatobiliary Surgery, The Affiliated Hospital of Guizhou Medical University, China (H.M.)
| | - Lingfeng Shi
- Department of Endocrinology, General Hospital of Central Theater Command, Wuhan, China (J.X., L.S., Y.C., J.T., B.M., X.X., J.Z., L.Y., G.X.)
- The First School of Clinical Medicine, Southern Medical University, Guangdong, China (J.X., L.S., Y.C., J.T., K.H., S.D., G.X.)
| | - Hui Zhou
- Department of General Surgery, The Third Xiangya Hospital, Central South University, Hunan, China (H.Z.)
| | - Yangyang Cheng
- Department of Endocrinology, General Hospital of Central Theater Command, Wuhan, China (J.X., L.S., Y.C., J.T., B.M., X.X., J.Z., L.Y., G.X.)
- Department of Hepatobiliary Surgery, The Affiliated Hospital of Guizhou Medical University, China (H.M.)
| | - Jiayue Tong
- Department of Endocrinology, General Hospital of Central Theater Command, Wuhan, China (J.X., L.S., Y.C., J.T., B.M., X.X., J.Z., L.Y., G.X.)
- The First School of Clinical Medicine, Southern Medical University, Guangdong, China (J.X., L.S., Y.C., J.T., K.H., S.D., G.X.)
| | - Biying Meng
- Department of Endocrinology, General Hospital of Central Theater Command, Wuhan, China (J.X., L.S., Y.C., J.T., B.M., X.X., J.Z., L.Y., G.X.)
| | - Xiaoli Xu
- Department of Endocrinology, General Hospital of Central Theater Command, Wuhan, China (J.X., L.S., Y.C., J.T., B.M., X.X., J.Z., L.Y., G.X.)
| | - Kaiyue He
- The First School of Clinical Medicine, Southern Medical University, Guangdong, China (J.X., L.S., Y.C., J.T., K.H., S.D., G.X.)
| | - Sheng Ding
- The First School of Clinical Medicine, Southern Medical University, Guangdong, China (J.X., L.S., Y.C., J.T., K.H., S.D., G.X.)
| | - Jiajia Zhang
- Department of Endocrinology, General Hospital of Central Theater Command, Wuhan, China (J.X., L.S., Y.C., J.T., B.M., X.X., J.Z., L.Y., G.X.)
| | - Ling Yue
- Department of Endocrinology, General Hospital of Central Theater Command, Wuhan, China (J.X., L.S., Y.C., J.T., B.M., X.X., J.Z., L.Y., G.X.)
| | - Guangda Xiang
- Department of Endocrinology, General Hospital of Central Theater Command, Wuhan, China (J.X., L.S., Y.C., J.T., B.M., X.X., J.Z., L.Y., G.X.)
- The First School of Clinical Medicine, Southern Medical University, Guangdong, China (J.X., L.S., Y.C., J.T., K.H., S.D., G.X.)
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3
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Palfreyman MT, West SE, Jorgensen EM. SNARE Proteins in Synaptic Vesicle Fusion. ADVANCES IN NEUROBIOLOGY 2023; 33:63-118. [PMID: 37615864 DOI: 10.1007/978-3-031-34229-5_4] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/25/2023]
Abstract
Neurotransmitters are stored in small membrane-bound vesicles at synapses; a subset of synaptic vesicles is docked at release sites. Fusion of docked vesicles with the plasma membrane releases neurotransmitters. Membrane fusion at synapses, as well as all trafficking steps of the secretory pathway, is mediated by SNARE proteins. The SNAREs are the minimal fusion machinery. They zipper from N-termini to membrane-anchored C-termini to form a 4-helix bundle that forces the apposed membranes to fuse. At synapses, the SNAREs comprise a single helix from syntaxin and synaptobrevin; SNAP-25 contributes the other two helices to complete the bundle. Unc13 mediates synaptic vesicle docking and converts syntaxin into the permissive "open" configuration. The SM protein, Unc18, is required to initiate and proofread SNARE assembly. The SNAREs are then held in a half-zippered state by synaptotagmin and complexin. Calcium removes the synaptotagmin and complexin block, and the SNAREs drive vesicle fusion. After fusion, NSF and alpha-SNAP unwind the SNAREs and thereby recharge the system for further rounds of fusion. In this chapter, we will describe the discovery of the SNAREs, their relevant structural features, models for their function, and the central role of Unc18. In addition, we will touch upon the regulation of SNARE complex formation by Unc13, complexin, and synaptotagmin.
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Affiliation(s)
- Mark T Palfreyman
- School of Biological Sciences, and Howard Hughes Medical Institute, University of Utah, Salt Lake City, UT, USA
| | - Sam E West
- School of Biological Sciences, and Howard Hughes Medical Institute, University of Utah, Salt Lake City, UT, USA
| | - Erik M Jorgensen
- School of Biological Sciences, and Howard Hughes Medical Institute, University of Utah, Salt Lake City, UT, USA.
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4
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Morimoto K, Yanase K, Kajimoto T, Kita Y. Metal-Free Synthesis of Acyl Glycosides and Application to Oligosaccharide Synthesis. Org Lett 2022; 24:9028-9032. [DOI: 10.1021/acs.orglett.2c03661] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Affiliation(s)
- Koji Morimoto
- College of Pharmaceutical Sciences, Ritsumeikan University, 1-1-1 Nojihigashi, Kusatsu, Shiga 525-8577, Japan
- Research Organization of Science and Technology, Ritsumeikan University, 1-1-1 Nojihigashi, Kusatsu, Shiga 525-8577, Japan
| | - Kana Yanase
- College of Pharmaceutical Sciences, Ritsumeikan University, 1-1-1 Nojihigashi, Kusatsu, Shiga 525-8577, Japan
| | - Tetsuya Kajimoto
- College of Pharmaceutical Sciences, Ritsumeikan University, 1-1-1 Nojihigashi, Kusatsu, Shiga 525-8577, Japan
- Research Organization of Science and Technology, Ritsumeikan University, 1-1-1 Nojihigashi, Kusatsu, Shiga 525-8577, Japan
| | - Yasuyuki Kita
- Research Organization of Science and Technology, Ritsumeikan University, 1-1-1 Nojihigashi, Kusatsu, Shiga 525-8577, Japan
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5
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Yamakawa T, Yuslimatin Mujizah E, Matsuno K. Notch Signalling Under Maternal-to-Zygotic Transition. Fly (Austin) 2022; 16:347-359. [PMID: 36346359 PMCID: PMC9645253 DOI: 10.1080/19336934.2022.2139981] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
The development of all animal embryos is initially directed by the gene products supplied by their mothers. With the progression of embryogenesis, the embryo's genome is activated to command subsequent developments. This transition, which has been studied in many model animals, is referred to as the Maternal-to-Zygotic Transition (MZT). In many organisms, including flies, nematodes, and sea urchins, genes involved in Notch signaling are extensively influenced by the MZT. This signaling pathway is highly conserved across metazoans; moreover, it regulates various developmental processes. Notch signaling defects are commonly associated with various human diseases. The maternal contribution of its factors was first discovered in flies. Subsequently, several genes were identified from mutant embryos with a phenotype similar to Notch mutants only upon the removal of the maternal contributions. Studies on these maternal genes have revealed various novel steps in the cascade of Notch signal transduction. Among these genes, pecanex and almondex have been functionally characterized in recent studies. Therefore, in this review, we will focus on the roles of these two maternal genes in Notch signaling and discuss future research directions on its maternal function.
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Affiliation(s)
- Tomoko Yamakawa
- Department of Biological Sciences, Graduate School of Science, Osaka University, Osaka, Japan,CONTACT Tomoko Yamakawa Department of Biological Sciences, Graduate School of Science, Osaka University, Osaka, Japan
| | | | - Kenji Matsuno
- Department of Biological Sciences, Graduate School of Science, Osaka University, Osaka, Japan
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6
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Cui L, Li H, Xi Y, Hu Q, Liu H, Fan J, Xiang Y, Zhang X, Shui W, Lai Y. Vesicle trafficking and vesicle fusion: mechanisms, biological functions, and their implications for potential disease therapy. MOLECULAR BIOMEDICINE 2022; 3:29. [PMID: 36129576 PMCID: PMC9492833 DOI: 10.1186/s43556-022-00090-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2022] [Accepted: 07/12/2022] [Indexed: 11/10/2022] Open
Abstract
Intracellular vesicle trafficking is the fundamental process to maintain the homeostasis of membrane-enclosed organelles in eukaryotic cells. These organelles transport cargo from the donor membrane to the target membrane through the cargo containing vesicles. Vesicle trafficking pathway includes vesicle formation from the donor membrane, vesicle transport, and vesicle fusion with the target membrane. Coat protein mediated vesicle formation is a delicate membrane budding process for cargo molecules selection and package into vesicle carriers. Vesicle transport is a dynamic and specific process for the cargo containing vesicles translocation from the donor membrane to the target membrane. This process requires a group of conserved proteins such as Rab GTPases, motor adaptors, and motor proteins to ensure vesicle transport along cytoskeletal track. Soluble N-ethyl-maleimide-sensitive factor (NSF) attachment protein receptors (SNARE)-mediated vesicle fusion is the final process for vesicle unloading the cargo molecules at the target membrane. To ensure vesicle fusion occurring at a defined position and time pattern in eukaryotic cell, multiple fusogenic proteins, such as synaptotagmin (Syt), complexin (Cpx), Munc13, Munc18 and other tethering factors, cooperate together to precisely regulate the process of vesicle fusion. Dysfunctions of the fusogenic proteins in SNARE-mediated vesicle fusion are closely related to many diseases. Recent studies have suggested that stimulated membrane fusion can be manipulated pharmacologically via disruption the interface between the SNARE complex and Ca2+ sensor protein. Here, we summarize recent insights into the molecular mechanisms of vesicle trafficking, and implications for the development of new therapeutics based on the manipulation of vesicle fusion.
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7
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Cullinan MM, Klipp RC, Bankston JR. Regulation of acid-sensing ion channels by protein binding partners. Channels (Austin) 2021; 15:635-647. [PMID: 34704535 PMCID: PMC8555555 DOI: 10.1080/19336950.2021.1976946] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
Abstract
Acid-sensing ion channels (ASICs) are a family of proton-gated cation channels that contribute to a diverse array of functions including pain sensation, cell death during ischemia, and more broadly to neurotransmission in the central nervous system. There is an increasing interest in understanding the physiological regulatory mechanisms of this family of channels. ASICs have relatively short N- and C-termini, yet a number of proteins have been shown to interact with these domains both in vitro and in vivo. These proteins can impact ASIC gating, localization, cell-surface expression, and regulation. Like all ion channels, it is important to understand the cellular context under which ASICs function in neurons and other cells. Here we will review what is known about a number of these potentially important regulatory molecules.
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Affiliation(s)
- Megan M Cullinan
- Department of Physiology and Biophysics, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
| | - Robert C Klipp
- Department of Physiology and Biophysics, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
| | - John R Bankston
- Department of Physiology and Biophysics, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
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8
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Sauvola CW, Littleton JT. SNARE Regulatory Proteins in Synaptic Vesicle Fusion and Recycling. Front Mol Neurosci 2021; 14:733138. [PMID: 34421538 PMCID: PMC8377282 DOI: 10.3389/fnmol.2021.733138] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Accepted: 07/20/2021] [Indexed: 01/01/2023] Open
Abstract
Membrane fusion is a universal feature of eukaryotic protein trafficking and is mediated by the soluble N-ethylmaleimide sensitive factor attachment protein receptor (SNARE) family. SNARE proteins embedded in opposing membranes spontaneously assemble to drive membrane fusion and cargo exchange in vitro. Evolution has generated a diverse complement of SNARE regulatory proteins (SRPs) that ensure membrane fusion occurs at the right time and place in vivo. While a core set of SNAREs and SRPs are common to all eukaryotic cells, a specialized set of SRPs within neurons confer additional regulation to synaptic vesicle (SV) fusion. Neuronal communication is characterized by precise spatial and temporal control of SNARE dynamics within presynaptic subdomains specialized for neurotransmitter release. Action potential-elicited Ca2+ influx at these release sites triggers zippering of SNAREs embedded in the SV and plasma membrane to drive bilayer fusion and release of neurotransmitters that activate downstream targets. Here we discuss current models for how SRPs regulate SNARE dynamics and presynaptic output, emphasizing invertebrate genetic findings that advanced our understanding of SRP regulation of SV cycling.
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Affiliation(s)
- Chad W Sauvola
- The Picower Institute for Learning and Memory, Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA, United States
| | - J Troy Littleton
- The Picower Institute for Learning and Memory, Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA, United States.,Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, United States
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10
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Woo DH, Hur YN, Jang MW, Justin Lee C, Park M. Inhibitors of synaptic vesicle exocytosis reduce surface expression of postsynaptic glutamate receptors. Anim Cells Syst (Seoul) 2020; 24:341-348. [PMID: 33456718 PMCID: PMC7781898 DOI: 10.1080/19768354.2020.1838607] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Bafilomycin A1, a vacuolar H+-ATPase inhibitor, and botulinum toxin B and tetanus toxin, both vesicle fusion inhibitors, are widely known exocytosis blockers that have been used to inhibit the presynaptic release of neurotransmitters. However, protein trafficking mechanisms, such as the insertion of postsynaptic receptors and astrocytic glutamate-releasing channels into the plasma membrane, also require exocytosis. In our previous study, exocytosis inhibitors reduced the surface expression of astrocytic glutamate-releasing channels. Here, we further investigated whether exocytosis inhibitors influence the surface expression of postsynaptic receptors. Using pH-sensitive superecliptic pHluorin (SEP)-tagged postsynaptic glutamate receptors, including GluA1, GluA2, GluN1, and GluN2A, we found that bafilomycin A1, botulinum toxin B, and/or tetanus toxin reduce the SEP fluorescence of SEP-GluA1, SEP-GluA2, SEP-GluN1, and SEP-GluN2A. These findings indicate that presynaptic vesicle exocytosis inhibitors also affect the postsynaptic trafficking machinery for surface expression. Finally, this study provides profound insights assembling presynaptic, postsynaptic and astrocytic viewpoints into the interpretation of the data obtained using these synaptic vesicle exocytosis inhibitors.
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Affiliation(s)
- Dong Ho Woo
- Drug Abuse Research Group, Research Center of Convergence Toxicology, Korea Institute of Toxicology, Daejeon, South Korea
| | - Young-Na Hur
- Brain Science Institute, Korea Institute of Science and Technology, Seoul, South Korea
| | - Minwoo Wendy Jang
- KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul, South Korea.,Center for Cognition and Sociality, Cognitive Glioscience Group, Institute for Basic Science, Daejeon, Korea
| | - C Justin Lee
- Center for Cognition and Sociality, Cognitive Glioscience Group, Institute for Basic Science, Daejeon, Korea
| | - Mikyoung Park
- Brain Science Institute, Korea Institute of Science and Technology, Seoul, South Korea.,Department of Neuroscience, Korea University of Science and Technology, Daejeon, South Korea
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11
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Nishiwaki Y, Masai I. β-SNAP activity in the outer segment growth period is critical for preventing BNip1-dependent apoptosis in zebrafish photoreceptors. Sci Rep 2020; 10:17379. [PMID: 33060680 PMCID: PMC7567113 DOI: 10.1038/s41598-020-74360-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2020] [Accepted: 09/28/2020] [Indexed: 12/03/2022] Open
Abstract
BNip1, which functions as a t-SNARE component of the syntaxin18 complex, is localized on the ER membrane and regulates retrograde transport from Golgi to the ER. BNip1 also has a BH3 domain, which generally releases pro-apoptotic proteins from Bcl2-mediated inhibition. Previously we reported that retinal photoreceptors undergo BNip1-dependent apoptosis in zebrafish β-snap1 mutants. Here, we investigated physiological roles of BNip1-dependent photoreceptor apoptosis. First, we examined the spatio-temporal profile of photoreceptor apoptosis in β-snap1 mutants, and found that apoptosis occurs only during a small developmental window, 2–4 days-post-fertilization (dpf), in which an apical photoreceptive membrane structure, called the outer segment (OS), grows rapidly. Transient expression of β-SNAP1 during this OS growing period prevents photoreceptor apoptosis in β-snap1 mutants, enabling cone to survive until at least 21 dpf. These observations suggest that BNip1-mediated apoptosis is linked to excessive activation of vesicular transport associated with rapid growth of the OS. Consistently, knockdown of Ift88 and Kif3b, which inhibits protein transport to the OS, rescued photoreceptor apoptosis in β-snap1 mutants. Treatment with rapamycin, which inhibits protein synthesis via the mTOR pathway, also rescued photoreceptor apoptosis in β-snap1 mutants. These data suggest that BNip1 performs risk assessment to detect excessive vesicular transport in photoreceptors.
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Affiliation(s)
- Yuko Nishiwaki
- Developmental Neurobiology Unit, Okinawa Institute of Science and Technology Graduate University, 1919-1 Tancha, Onna, Okinawa, 904-0495, Japan
| | - Ichiro Masai
- Developmental Neurobiology Unit, Okinawa Institute of Science and Technology Graduate University, 1919-1 Tancha, Onna, Okinawa, 904-0495, Japan.
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12
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Jang E, Robert J, Rohrer L, von Eckardstein A, Lee WL. Transendothelial transport of lipoproteins. Atherosclerosis 2020; 315:111-125. [PMID: 33032832 DOI: 10.1016/j.atherosclerosis.2020.09.020] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/14/2020] [Revised: 09/15/2020] [Accepted: 09/18/2020] [Indexed: 02/06/2023]
Abstract
The accumulation of low-density lipoproteins (LDL) in the arterial wall plays a pivotal role in the initiation and pathogenesis of atherosclerosis. Conversely, the removal of cholesterol from the intima by cholesterol efflux to high density lipoproteins (HDL) and subsequent reverse cholesterol transport shall confer protection against atherosclerosis. To reach the subendothelial space, both LDL and HDL must cross the intact endothelium. Traditionally, this transit is explained by passive filtration. This dogma has been challenged by the identification of several rate-limiting factors namely scavenger receptor SR-BI, activin like kinase 1, and caveolin-1 for LDL as well as SR-BI, ATP binding cassette transporter G1, and endothelial lipase for HDL. In addition, estradiol, vascular endothelial growth factor, interleukins 6 and 17, purinergic signals, and sphingosine-1-phosphate were found to regulate transendothelial transport of either LDL or HDL. Thorough understanding of transendothelial lipoprotein transport is expected to elucidate new therapeutic targets for the treatment or prevention of atherosclerotic cardiovascular disease and the development of strategies for the local delivery of drugs or diagnostic tracers into diseased tissues including atherosclerotic lesions.
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Affiliation(s)
- Erika Jang
- Keenan Centre for Biomedical Research, St. Michael's Hospital, Toronto, Canada; Department of Laboratory Medicine and Pathobiology, University of Toronto, Canada
| | - Jerome Robert
- Institute of Clinical Chemistry, University of Zurich and University Hospital of Zurich, Switzerland
| | - Lucia Rohrer
- Institute of Clinical Chemistry, University of Zurich and University Hospital of Zurich, Switzerland
| | - Arnold von Eckardstein
- Institute of Clinical Chemistry, University of Zurich and University Hospital of Zurich, Switzerland.
| | - Warren L Lee
- Keenan Centre for Biomedical Research, St. Michael's Hospital, Toronto, Canada; Department of Laboratory Medicine and Pathobiology, University of Toronto, Canada; Interdepartmental Division of Critical Care, Department of Medicine, University of Toronto, Canada; Department of Biochemistry, University of Toronto, Canada; Institute of Medical Science, University of Toronto, Canada.
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13
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SNAP-25 Puts SNAREs at Center Stage in Metabolic Disease. Neuroscience 2019; 420:86-96. [DOI: 10.1016/j.neuroscience.2018.07.035] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2018] [Revised: 07/12/2018] [Accepted: 07/19/2018] [Indexed: 12/20/2022]
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14
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Sparks RP, Arango AS, Starr ML, Aboff ZL, Hurst LR, Rivera-Kohr DA, Zhang C, Harnden KA, Jenkins JL, Guida WC, Tajkhorshid E, Fratti RA. A small-molecule competitive inhibitor of phosphatidic acid binding by the AAA+ protein NSF/Sec18 blocks the SNARE-priming stage of vacuole fusion. J Biol Chem 2019; 294:17168-17185. [PMID: 31515268 DOI: 10.1074/jbc.ra119.008865] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2019] [Revised: 09/04/2019] [Indexed: 12/13/2022] Open
Abstract
The homeostasis of most organelles requires membrane fusion mediated by soluble N -ethylmaleimide-sensitive factor (NSF) attachment protein receptors (SNAREs). SNAREs undergo cycles of activation and deactivation as membranes move through the fusion cycle. At the top of the cycle, inactive cis-SNARE complexes on a single membrane are activated, or primed, by the hexameric ATPase associated with the diverse cellular activities (AAA+) protein, N-ethylmaleimide-sensitive factor (NSF/Sec18), and its co-chaperone α-SNAP/Sec17. Sec18-mediated ATP hydrolysis drives the mechanical disassembly of SNAREs into individual coils, permitting a new cycle of fusion. Previously, we found that Sec18 monomers are sequestered away from SNAREs by binding phosphatidic acid (PA). Sec18 is released from the membrane when PA is hydrolyzed to diacylglycerol by the PA phosphatase Pah1. Although PA can inhibit SNARE priming, it binds other proteins and thus cannot be used as a specific tool to further probe Sec18 activity. Here, we report the discovery of a small-molecule compound, we call IPA (inhibitor of priming activity), that binds Sec18 with high affinity and blocks SNARE activation. We observed that IPA blocks SNARE priming and competes for PA binding to Sec18. Molecular dynamics simulations revealed that IPA induces a more rigid NSF/Sec18 conformation, which potentially disables the flexibility required for Sec18 to bind to PA or to activate SNAREs. We also show that IPA more potently and specifically inhibits NSF/Sec18 activity than does N-ethylmaleimide, requiring the administration of only low micromolar concentrations of IPA, demonstrating that this compound could help to further elucidate SNARE-priming dynamics.
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Affiliation(s)
- Robert P Sparks
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801
| | - Andres S Arango
- Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801
| | - Matthew L Starr
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801
| | - Zachary L Aboff
- Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801
| | - Logan R Hurst
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801
| | - David A Rivera-Kohr
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801
| | - Chi Zhang
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801
| | - Kevin A Harnden
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801
| | - Jermaine L Jenkins
- Structural Biology and Biophysics Facility, University of Rochester Medical Center, Rochester, New York 14642
| | - Wayne C Guida
- Department of Chemistry, University of South Florida, Tampa, Florida 336204
| | - Emad Tajkhorshid
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801.,Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801.,Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801
| | - Rutilio A Fratti
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 .,Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801
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15
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Zhang C, Liu P. The New Face of the Lipid Droplet: Lipid Droplet Proteins. Proteomics 2018; 19:e1700223. [DOI: 10.1002/pmic.201700223] [Citation(s) in RCA: 49] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2018] [Revised: 08/13/2018] [Indexed: 12/20/2022]
Affiliation(s)
- Congyan Zhang
- National Laboratory of BiomacromoleculesCAS Center for Excellence in BiomacromoleculesInstitute of BiophysicsChinese Academy of Sciences Beijing 100101 China
- University of Chinese Academy of Sciences Beijing 100049 China
| | - Pingsheng Liu
- National Laboratory of BiomacromoleculesCAS Center for Excellence in BiomacromoleculesInstitute of BiophysicsChinese Academy of Sciences Beijing 100101 China
- University of Chinese Academy of Sciences Beijing 100049 China
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16
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Barkovich KJ, Moore MK, Hu Q, Shokat KM. Chemical genetic inhibition of DEAD-box proteins using covalent complementarity. Nucleic Acids Res 2018; 46:8689-8699. [PMID: 30102385 PMCID: PMC6158709 DOI: 10.1093/nar/gky706] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2018] [Revised: 07/07/2018] [Accepted: 08/06/2018] [Indexed: 12/17/2022] Open
Abstract
DEAD-box proteins are an essential class of enzymes involved in all stages of RNA metabolism. The study of DEAD-box proteins is challenging in a native setting since they are structurally similar, often essential and display dosage sensitivity. Pharmacological inhibition would be an ideal tool to probe the function of these enzymes. In this work, we describe a chemical genetic strategy for the specific inactivation of individual DEAD-box proteins with small molecule inhibitors using covalent complementarity. We identify a residue of low conservation within the P-loop of the nucleotide-binding site of DEAD-box proteins and show that it can be mutated to cysteine without a substantial loss of enzyme function to generate electrophile-sensitive mutants. We then present a series of small molecules that rapidly and specifically bind and inhibit electrophile-sensitive DEAD-box proteins with high selectivity over the wild-type enzyme. Thus, this approach can be used to systematically generate small molecule-sensitive alleles of DEAD-box proteins, allowing for pharmacological inhibition and functional characterization of members of this enzyme family.
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Affiliation(s)
- Krister J Barkovich
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, CA 94158, USA
| | - Megan K Moore
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, CA 94158, USA
| | - Qi Hu
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, CA 94158, USA
| | - Kevan M Shokat
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, CA 94158, USA
- Howard Hughes Medical Institute, University of California, San Francisco, CA 94158, USA
- Department of Chemistry, University of California, Berkeley, CA 94720, USA
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17
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Insight into Notch Signaling Steps That Involve pecanex from Dominant-Modifier Screens in Drosophila. Genetics 2018; 209:1099-1119. [PMID: 29853475 DOI: 10.1534/genetics.118.300935] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2018] [Accepted: 05/22/2018] [Indexed: 12/14/2022] Open
Abstract
Notch signaling plays crucial roles in intercellular communications. In Drosophila, the pecanex (pcx) gene, which encodes an evolutionarily conserved multi-pass transmembrane protein, appears to be required to activate Notch signaling in some contexts, especially during neuroblast segregation in the neuroectoderm. Although Pcx has been suggested to contribute to endoplasmic reticulum homeostasis, its functions remain unknown. Here, to elucidate these roles, we performed genetic modifier screens of pcx We found that pcx heterozygotes lacking its maternal contribution exhibit cold-sensitive lethality, which is attributed to a reduction in Notch signaling at decreased temperatures. Using sets of deletions that uncover most of the second and third chromosomes, we identified four enhancers and two suppressors of the pcx cold-sensitive lethality. Among these, five genes encode known Notch-signaling components: big brain, Delta (Dl), neuralized (neur), Brother of Bearded A (BobA), a member of the Bearded (Brd) family, and N-ethylmaleimide-sensitive factor 2 (Nsf2). We showed that BobA suppresses Dl endocytosis during neuroblast segregation in the neuroectoderm, as Brd family genes reportedly do in the mesoderm for mesectoderm specification. Analyses of Nsf2, a key regulator of vesicular fusion, suggested a novel role in neuroblast segregation, which is distinct from Nsf2's previously reported role in imaginal tissues. Finally, jim lovell, which encodes a potential transcription factor, may play a role in Notch signaling during neuroblast segregation. These results reveal new research avenues for Pcx functions and Notch signaling.
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18
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Ryu JK, Jahn R, Yoon TY. Review: Progresses in understanding N-ethylmaleimide sensitive factor (NSF) mediated disassembly of SNARE complexes. Biopolymers 2017; 105:518-31. [PMID: 27062050 DOI: 10.1002/bip.22854] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2016] [Revised: 03/19/2016] [Accepted: 04/06/2016] [Indexed: 11/09/2022]
Abstract
N-ethylmaleimide sensitive factor (NSF) is a key protein of intracellular membrane traffic. NSF is a highly conserved protein belonging to the ATPases associated with other activities (AAA+ proteins). AAA+ share common domains and all transduce ATP hydrolysis into major conformational movements that are used to carry out conformational work on client proteins. Together with its cofactor SNAP, NSF is specialized on disassembling highly stable SNARE complexes that form after each membrane fusion event. Although essential for all eukaryotic cells, however, the details of this reaction have long been enigmatic. Recently, major progress has been made in both elucidating the structure of NSF/SNARE complexes and in understanding the reaction mechanism. Advances in both cryo EM and single molecule measurements suggest that NSF, together with its cofactor SNAP, imposes a tight grip on the SNARE complex. After ATP hydrolysis and phosphate release, it then builds up mechanical tension that is ultimately used to rip apart the SNAREs in a single burst. Because the AAA domains are extremely well-conserved, the molecular mechanism elucidated for NSF is presumably shared by many other AAA+ ATPases. © 2016 Wiley Periodicals, Inc. Biopolymers 105: 518-531, 2016.
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Affiliation(s)
- Je-Kyung Ryu
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Delft, CJ, 2628, the Netherlands
| | - Reinhard Jahn
- Department of Neurobiology, Max-Planck-Institute for Biophysical Chemistry, Göttingen, 37077, Germany
| | - Tae-Young Yoon
- Center for Nanomedicine, Institute for Basic Science (IBS) and Y-IBS Institute, Yonsei University, Seoul, 03722, South Korea
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19
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Hasegawa Y, Futamata H, Tashiro Y. Complexities of cell-to-cell communication through membrane vesicles: implications for selective interaction of membrane vesicles with microbial cells. Front Microbiol 2015; 6:633. [PMID: 26191043 PMCID: PMC4490254 DOI: 10.3389/fmicb.2015.00633] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2015] [Accepted: 06/11/2015] [Indexed: 12/15/2022] Open
Affiliation(s)
- Yusuke Hasegawa
- Department of Applied Chemistry and Biochemical Engineering, Graduate School of Engineering, Shizuoka University Hamamatsu, Japan
| | - Hiroyuki Futamata
- Department of Applied Chemistry and Biochemical Engineering, Graduate School of Engineering, Shizuoka University Hamamatsu, Japan
| | - Yosuke Tashiro
- Department of Applied Chemistry and Biochemical Engineering, Graduate School of Engineering, Shizuoka University Hamamatsu, Japan
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20
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Schekman R. [The genes and proteins which control the process of secretion]. Biol Aujourdhui 2015; 209:35-61. [PMID: 26115712 DOI: 10.1051/jbio/2015011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
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21
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22
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Ryu JK, Min D, Rah SH, Kim SJ, Park Y, Kim H, Hyeon C, Kim HM, Jahn R, Yoon TY. Spring-loaded unraveling of a single SNARE complex by NSF in one round of ATP turnover. Science 2015; 347:1485-9. [PMID: 25814585 DOI: 10.1126/science.aaa5267] [Citation(s) in RCA: 68] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
During intracellular membrane trafficking, N-ethylmaleimide-sensitive factor (NSF) and alpha-soluble NSF attachment protein (α-SNAP) disassemble the soluble NSF attachment protein receptor (SNARE) complex for recycling of the SNARE proteins. The molecular mechanism by which NSF disassembles the SNARE complex is largely unknown. Using single-molecule fluorescence spectroscopy and magnetic tweezers, we found that NSF disassembled a single SNARE complex in only one round of adenosine triphosphate (ATP) turnover. Upon ATP cleavage, the NSF hexamer developed internal tension with dissociation of phosphate ions. After latent time measuring tens of seconds, NSF released the built-up tension in a burst within 20 milliseconds, resulting in disassembly followed by immediate release of the SNARE proteins. Thus, NSF appears to use a "spring-loaded" mechanism to couple ATP hydrolysis and unfolding of substrate proteins.
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Affiliation(s)
- Je-Kyung Ryu
- National Creative Research Initiative Center for Single-Molecule Systems Biology, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 305-701, South Korea. Department of Physics, KAIST, Daejeon 305-701, South Korea
| | - Duyoung Min
- National Creative Research Initiative Center for Single-Molecule Systems Biology, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 305-701, South Korea. Department of Physics, KAIST, Daejeon 305-701, South Korea
| | - Sang-Hyun Rah
- National Creative Research Initiative Center for Single-Molecule Systems Biology, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 305-701, South Korea. Department of Physics, KAIST, Daejeon 305-701, South Korea
| | - Soo Jin Kim
- Graduate School of Medical Science and Engineering, KAIST, Daejeon 305-701, South Korea
| | - Yongsoo Park
- Department of Neurobiology, Max-Planck-Institute for Biophysical Chemistry, 37077 Göttingen, Germany
| | - Haesoo Kim
- Graduate School of Medical Science and Engineering, KAIST, Daejeon 305-701, South Korea
| | - Changbong Hyeon
- Korea Institute for Advanced Study, Seoul 130-722, South Korea
| | - Ho Min Kim
- Graduate School of Medical Science and Engineering, KAIST, Daejeon 305-701, South Korea
| | - Reinhard Jahn
- Department of Neurobiology, Max-Planck-Institute for Biophysical Chemistry, 37077 Göttingen, Germany.
| | - Tae-Young Yoon
- National Creative Research Initiative Center for Single-Molecule Systems Biology, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 305-701, South Korea. Department of Physics, KAIST, Daejeon 305-701, South Korea.
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23
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Zhao M, Wu S, Zhou Q, Vivona S, Cipriano DJ, Cheng Y, Brunger AT. Mechanistic insights into the recycling machine of the SNARE complex. Nature 2015; 518:61-7. [PMID: 25581794 PMCID: PMC4320033 DOI: 10.1038/nature14148] [Citation(s) in RCA: 190] [Impact Index Per Article: 21.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2014] [Accepted: 12/10/2014] [Indexed: 12/11/2022]
Abstract
Evolutionarily conserved SNARE (soluble N-ethylmaleimide sensitive factor attachment protein receptors) proteins form a complex that drives membrane fusion in eukaryotes. The ATPase NSF (N-ethylmaleimide sensitive factor), together with SNAPs (soluble NSF attachment protein), disassembles the SNARE complex into its protein components, making individual SNAREs available for subsequent rounds of fusion. Here we report structures of ATP- and ADP-bound NSF, and the NSF/SNAP/SNARE (20S) supercomplex determined by single-particle electron cryomicroscopy at near-atomic to sub-nanometre resolution without imposing symmetry. Large, potentially force-generating, conformational differences exist between ATP- and ADP-bound NSF. The 20S supercomplex exhibits broken symmetry, transitioning from six-fold symmetry of the NSF ATPase domains to pseudo four-fold symmetry of the SNARE complex. SNAPs interact with the SNARE complex with an opposite structural twist, suggesting an unwinding mechanism. The interfaces between NSF, SNAPs, and SNAREs exhibit characteristic electrostatic patterns, suggesting how one NSF/SNAP species can act on many different SNARE complexes.
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Affiliation(s)
- Minglei Zhao
- Department of Molecular and Cellular Physiology, Howard Hughes Medical Institute, Stanford University, Stanford, California 94305, USA
| | - Shenping Wu
- Keck Advanced Microscopy Laboratory, Department of Biochemistry and Biophysics, University of California, San Francisco, California 94158, USA
| | - Qiangjun Zhou
- Department of Molecular and Cellular Physiology, Howard Hughes Medical Institute, Stanford University, Stanford, California 94305, USA
| | - Sandro Vivona
- Department of Molecular and Cellular Physiology, Howard Hughes Medical Institute, Stanford University, Stanford, California 94305, USA
| | - Daniel J Cipriano
- Department of Molecular and Cellular Physiology, Howard Hughes Medical Institute, Stanford University, Stanford, California 94305, USA
| | - Yifan Cheng
- Keck Advanced Microscopy Laboratory, Department of Biochemistry and Biophysics, University of California, San Francisco, California 94158, USA
| | - Axel T Brunger
- 1] Department of Molecular and Cellular Physiology, Howard Hughes Medical Institute, Stanford University, Stanford, California 94305, USA [2] Department of Neurology and Neurological Sciences, Department of Structural Biology, Department of Photon Science, Stanford University, Stanford, California 94305, USA
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24
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Südhof TC. Der molekulare Mechanismus der Neurotransmitterfreisetzung und Nervenzell-Synapsen (Nobel-Aufsatz). Angew Chem Int Ed Engl 2014. [DOI: 10.1002/ange.201406359] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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25
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Südhof TC. The molecular machinery of neurotransmitter release (Nobel lecture). Angew Chem Int Ed Engl 2014; 53:12696-717. [PMID: 25339369 DOI: 10.1002/anie.201406359] [Citation(s) in RCA: 118] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2014] [Indexed: 12/18/2022]
Abstract
The most important property of synaptic transmission is its speed, which is crucial for the overall workings of the brain. In his Nobel Lecture, T. C. Südhof explains how the synaptic vesicle and the plasma membrane undergo rapid fusion during neurotransmitter release and how this process is spatially organized, such that opening of Ca(2+) -channels allows rapid translation of the entering Ca(2+) signal into a fusion event.
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Affiliation(s)
- Thomas C Südhof
- Department of Molecular and Cellular Physiology and Howard Hughes Medical Institute, Lorry Lokey SIM1 Building 07-535 Room G1021, 265 Campus Drive, Stanford University School of Medicine, CA 94305 (USA)
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26
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Abstract
Targeting membrane proteins for degradation requires the sequential action of ESCRT sub-complexes ESCRT-0 to ESCRT-III. Although this machinery is generally conserved among kingdoms, plants lack the essential ESCRT-0 components. A new report closes this gap by identifying a novel protein family that substitutes for ESCRT-0 function in plants.
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Affiliation(s)
- Michael Sauer
- Centro Nacional de Biotecnología, CSIC, 28049 Madrid, Spain.
| | - Jiří Friml
- Institute of Science and Technology Austria, 3400 Klosterneuburg, Austria; Mendel Centre for Plant Genomics and Proteomics, Masaryk University, CEITEC MU, CZ-625 00 Brno, Czech Republic.
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27
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28
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Rothman JE. The principle of membrane fusion in the cell (Nobel lecture). Angew Chem Int Ed Engl 2014; 53:12676-94. [PMID: 25087728 DOI: 10.1002/anie.201402380] [Citation(s) in RCA: 100] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2014] [Indexed: 01/06/2023]
Abstract
Cells contain small membrane-enclosed vesicles which transport many kinds of cargo between the compartments of the cell. The result is a choreographed program of secretory, biosynthetic, and endocytic protein traffic that serves the cell's internal physiologic needs.
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Affiliation(s)
- James Edward Rothman
- Department of Cell Biology, Yale University, 333 Cedar Street, CT 06520 New Haven (USA)
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29
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Abstract
The 2013 Nobel Prize in Physiology or Medicine has been awarded to James Rothman, Randy Schekman, and Thomas Südhof "for their discoveries of machinery regulating vesicle traffic, a major transport system in our cells". I present a personal view of the membrane trafficking field, highlighting the contributions of these three Nobel laureates in a historical context.
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Affiliation(s)
- Suzanne R Pfeffer
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA 94305-5307, USA.
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30
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Sun J. A legend of the SNARE complex and synaptotagmin-the insight into synaptic transmission. SCIENCE CHINA. LIFE SCIENCES 2013; 56:1150-1153. [PMID: 24222513 DOI: 10.1007/s11427-013-4572-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/03/2013] [Accepted: 11/04/2013] [Indexed: 06/02/2023]
Affiliation(s)
- JianYuan Sun
- Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China,
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31
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Galli T, Kuster A, Tareste D. Une récompense pour la découverte des acteurs et des mécanismes moléculaires fondamentaux du trafic vésiculaire intracellulaire. Med Sci (Paris) 2013; 29:1055-8. [DOI: 10.1051/medsci/20112713024] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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32
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Ikawa K, Satou A, Fukuhara M, Matsumura S, Sugiyama N, Goto H, Fukuda M, Inagaki M, Ishihama Y, Toyoshima F. Inhibition of endocytic vesicle fusion by Plk1-mediated phosphorylation of vimentin during mitosis. Cell Cycle 2013; 13:126-37. [PMID: 24196446 PMCID: PMC3925722 DOI: 10.4161/cc.26866] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2013] [Revised: 10/18/2013] [Accepted: 10/18/2013] [Indexed: 11/19/2022] Open
Abstract
Endocytic vesicle fusion is inhibited during mitosis, but the molecular pathways that mediate the inhibition remain unclear. Here we uncovered an essential role of Polo-like kinase 1 (Plk1) in this mechanism. Phosphoproteomic analysis revealed that Plk1 phosphorylates the intermediate filament protein vimentin on Ser459, which is dispensable for its filament formation but is necessary for the inhibition of endocytic vesicle fusion in mitosis. Furthermore, this mechanism is required for integrin trafficking toward the cleavage furrow during cytokinesis. Our results thus identify a novel mechanism for fusion inhibition in mitosis and implicate its role in vesicle trafficking after anaphase onset.
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Affiliation(s)
- Keisuke Ikawa
- Department of Cell Biology; Institute for Virus Research; Kyoto University; Sakyo-ku, Kyoto, Japan
- Department of Mammalian Regulatory Network; Graduate School of Biostudies; Kyoto University; Sakyo-ku, Kyoto, Japan
| | - Ayaka Satou
- Department of Molecular & Cellular BioAnalysis; Graduate School of Pharmaceutical Sciences; Kyoto University; Sakyo-ku, Kyoto, Japan
| | - Mitsuko Fukuhara
- Department of Cell Biology; Institute for Virus Research; Kyoto University; Sakyo-ku, Kyoto, Japan
- Department of Mammalian Regulatory Network; Graduate School of Biostudies; Kyoto University; Sakyo-ku, Kyoto, Japan
| | - Shigeru Matsumura
- Department of Cell Biology; Institute for Virus Research; Kyoto University; Sakyo-ku, Kyoto, Japan
- Department of Mammalian Regulatory Network; Graduate School of Biostudies; Kyoto University; Sakyo-ku, Kyoto, Japan
| | - Naoyuki Sugiyama
- Department of Molecular & Cellular BioAnalysis; Graduate School of Pharmaceutical Sciences; Kyoto University; Sakyo-ku, Kyoto, Japan
| | - Hidemasa Goto
- Division of Biochemistry; Aichi Cancer Center Research Institute; Chikusa-ku, Nagoya, Japan
| | - Mitsunori Fukuda
- Department of Developmental Biology and Neurosciences; Graduate School of Life Sciences; Tohoku University; Sendai, Miyagi, Japan
| | - Masaki Inagaki
- Division of Biochemistry; Aichi Cancer Center Research Institute; Chikusa-ku, Nagoya, Japan
| | - Yasushi Ishihama
- Department of Molecular & Cellular BioAnalysis; Graduate School of Pharmaceutical Sciences; Kyoto University; Sakyo-ku, Kyoto, Japan
| | - Fumiko Toyoshima
- Department of Cell Biology; Institute for Virus Research; Kyoto University; Sakyo-ku, Kyoto, Japan
- Department of Mammalian Regulatory Network; Graduate School of Biostudies; Kyoto University; Sakyo-ku, Kyoto, Japan
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33
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Nishiwaki Y, Yoshizawa A, Kojima Y, Oguri E, Nakamura S, Suzuki S, Yuasa-Kawada J, Kinoshita-Kawada M, Mochizuki T, Masai I. The BH3-only SNARE BNip1 mediates photoreceptor apoptosis in response to vesicular fusion defects. Dev Cell 2013; 25:374-87. [PMID: 23725763 DOI: 10.1016/j.devcel.2013.04.015] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2012] [Revised: 03/15/2013] [Accepted: 04/27/2013] [Indexed: 11/25/2022]
Abstract
Intracellular vesicular transport is important for photoreceptor function and maintenance. However, the mechanism underlying photoreceptor degeneration in response to vesicular transport defects is unknown. Here, we report that photoreceptors undergo apoptosis in a zebrafish β-soluble N-ethylmaleimide-sensitive factor attachment protein (β-SNAP) mutant. β-SNAP cooperates with N-ethylmaleimide-sensitive factor to recycle the SNAP receptor (SNARE), a key component of the membrane fusion machinery, by disassembling the cis-SNARE complex generated in the vesicular fusion process. We found that photoreceptor apoptosis in the β-SNAP mutant was dependent on the BH3-only protein BNip1. BNip1 functions as a component of the syntaxin-18 SNARE complex and regulates retrograde transport from the Golgi to the endoplasmic reticulum. Failure to disassemble the syntaxin-18 cis-SNARE complex caused BNip1-dependent apoptosis. These data suggest that the syntaxin-18 cis-SNARE complex functions as an alarm factor that monitors vesicular fusion competence and that BNip1 transforms vesicular fusion defects into photoreceptor apoptosis.
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Affiliation(s)
- Yuko Nishiwaki
- Developmental Neurobiology Unit, Okinawa Institute of Science and Technology Graduate University, 1919-1 Tancha, Onna, Okinawa 904-0412, Japan
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Sztul E. Nobel Prize for Cellular Logistics! CELLULAR LOGISTICS 2013; 3:e27194. [PMID: 25054086 PMCID: PMC4091106 DOI: 10.4161/cl.27194] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/08/2013] [Accepted: 11/08/2013] [Indexed: 11/29/2022]
Affiliation(s)
- Elizabeth Sztul
- Department of Cell, Developmental and Integrative Biology; University of Alabama at Birmingham; Birmingham, AL USA
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35
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Mongin AA, Dohare P, Jourd'heuil D. Selective vulnerability of synaptic signaling and metabolism to nitrosative stress. Antioxid Redox Signal 2012; 17:992-1012. [PMID: 22339371 PMCID: PMC3411350 DOI: 10.1089/ars.2012.4559] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
SIGNIFICANCE Nitric oxide (NO) plays diverse physiological roles in the central nervous system, where it modulates neuronal communication, regulates blood flow, and contributes to the innate immune responses. In a number of brain pathologies, the excessive production of NO also leads to the formation of reactive and toxic intermediates generically termed reactive nitrogen species (RNS). RNS cause irreversible or poorly reversible damage to brain cells. RECENT ADVANCES Recent work in the field focused on the ability of NO and RNS to yield protein modifications, including the S-nitrosation of cysteine residues, which, in many instances, impact cellular functions and viability. CRITICAL ISSUES The vast majority of neuropathological studies focus on the loss of cell viability, but nitrosative stress may also strongly impair the functions of neuronal processes: axonal projections and dendritic trees. The functional integrity of axons and dendrites critically depends on local metabolism and effective delivery of metabolic enzymes and organelles. Here, we summarize the existing literature describing the effects of nitrosative stress on the major pathways of energetic metabolism: glycolysis, tricarboxylic acid cycle, and mitochondrial respiration, with the emphasis on modifications of protein thiols. FUTURE DIRECTIONS We propose that axons and dendrites are highly vulnerable to nitrosative stress because of their low glycolytic capacity and high dependence on timely delivery of metabolic enzymes and organelles from the cell body. Thus, supplementation with the end products of glycolysis, pyruvate or lactate, may help preserve metabolism in distal neuronal processes and protect or restore synaptic function in the ailing brain.
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Affiliation(s)
- Alexander A Mongin
- Center for Neuropharmacology and Neuroscience, Albany Medical College, New York 12208, USA.
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36
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Saloheimo M, Pakula TM. The cargo and the transport system: secreted proteins and protein secretion in Trichoderma reesei (Hypocrea jecorina). Microbiology (Reading) 2012; 158:46-57. [DOI: 10.1099/mic.0.053132-0] [Citation(s) in RCA: 98] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Affiliation(s)
- Markku Saloheimo
- VTT Technical Research Centre of Finland, PO Box 1000, FIN-02044 VTT, Finland
| | - Tiina M. Pakula
- VTT Technical Research Centre of Finland, PO Box 1000, FIN-02044 VTT, Finland
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Armstrong SM, Khajoee V, Wang C, Wang T, Tigdi J, Yin J, Kuebler WM, Gillrie M, Davis SP, Ho M, Lee WL. Co-regulation of transcellular and paracellular leak across microvascular endothelium by dynamin and Rac. THE AMERICAN JOURNAL OF PATHOLOGY 2011; 180:1308-1323. [PMID: 22203054 DOI: 10.1016/j.ajpath.2011.12.002] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Received: 05/20/2011] [Revised: 11/23/2011] [Accepted: 12/02/2011] [Indexed: 12/23/2022]
Abstract
Increased permeability of the microvascular endothelium to fluids and proteins is the hallmark of inflammatory conditions such as sepsis. Leakage can occur between (paracellular) or through (transcytosis) endothelial cells, yet little is known about whether these pathways are linked. Understanding the regulation of microvascular permeability is essential for the identification of novel therapies to combat inflammation. We investigated whether transcytosis and paracellular leakage are co-regulated. Using molecular and pharmacologic approaches, we inhibited transcytosis of albumin in primary human microvascular endothelium and measured paracellular permeability. Blockade of transcytosis induced a rapid increase in paracellular leakage that was not explained by decreases in caveolin-1 or increases in activity of nitric oxide synthase. The effect required caveolin-1 but was observed in cells depleted of clathrin, indicating that it was not due to the general inhibition of endocytosis. Inhibiting transcytosis by dynamin blockade increased paracellular leakage concomitantly with the loss of cortical actin from the plasma membrane and the displacement of active Rac from the plasmalemma. Importantly, inhibition of paracellular leakage by sphingosine-1-phosphate, which activates Rac and induces cortical actin, caused a significant increase in transcytosis of albumin in vitro and in an ex vivo whole-lung model. In addition, dominant-negative Rac significantly diminished albumin uptake by endothelia. Our findings indicate that transcytosis and paracellular permeability are co-regulated through a signaling pathway linking dynamin, Rac, and actin.
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Affiliation(s)
- Susan M Armstrong
- Institute of Medical Science, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Vahid Khajoee
- Keenan Research Centre of the Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, Ontario, Canada
| | - Changsen Wang
- Keenan Research Centre of the Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, Ontario, Canada
| | - Tieling Wang
- Keenan Research Centre of the Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, Ontario, Canada
| | - Jayesh Tigdi
- Keenan Research Centre of the Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, Ontario, Canada
| | - Jun Yin
- Keenan Research Centre of the Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, Ontario, Canada
| | - Wolfgang M Kuebler
- Keenan Research Centre of the Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, Ontario, Canada
| | - Mark Gillrie
- Departments of Microbiology and Infectious Diseases and Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Shevaun P Davis
- Departments of Microbiology and Infectious Diseases and Medicine, University of Calgary, Calgary, Alberta, Canada
| | - May Ho
- Departments of Microbiology and Infectious Diseases and Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Warren L Lee
- Institute of Medical Science, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada; Keenan Research Centre of the Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, Ontario, Canada; Division of Respirology and Interdepartmental Division of Critical Care Medicine, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada.
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Abstract
Presynaptic nerve terminals release neurotransmitters by synaptic vesicle exocytosis. Membrane fusion mediating synaptic exocytosis and other intracellular membrane traffic is affected by a universal machinery that includes SNARE (for "soluble NSF-attachment protein receptor") and SM (for "Sec1/Munc18-like") proteins. During fusion, vesicular and target SNARE proteins assemble into an α-helical trans-SNARE complex that forces the two membranes tightly together, and SM proteins likely wrap around assembling trans-SNARE complexes to catalyze membrane fusion. After fusion, SNARE complexes are dissociated by the ATPase NSF (for "N-ethylmaleimide sensitive factor"). Fusion-competent conformations of SNARE proteins are maintained by chaperone complexes composed of CSPα, Hsc70, and SGT, and by nonenzymatically acting synuclein chaperones; dysfunction of these chaperones results in neurodegeneration. The synaptic membrane-fusion machinery is controlled by synaptotagmin, and additionally regulated by a presynaptic protein matrix (the "active zone") that includes Munc13 and RIM proteins as central components.
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Affiliation(s)
- Thomas C Südhof
- Department of Molecular and Cellular Physiology, and Howard Hughes Medical Institute, Stanford University Medical School, Stanford, California 94305, USA.
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Requirements for the catalytic cycle of the N-ethylmaleimide-Sensitive Factor (NSF). BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2011; 1823:159-71. [PMID: 21689688 DOI: 10.1016/j.bbamcr.2011.06.003] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/23/2011] [Revised: 05/23/2011] [Accepted: 06/06/2011] [Indexed: 12/23/2022]
Abstract
The N-ethylmaleimide-Sensitive Factor (NSF) was one of the initial members of the ATPases Associated with various cellular Activities Plus (AAA(+)) family. In this review, we discuss what is known about the mechanism of NSF action and how that relates to the mechanisms of other AAA(+) proteins. Like other family members, NSF binds to a protein complex (i.e., SNAP-SNARE complex) and utilizes ATP hydrolysis to affect the conformations of that complex. SNAP-SNARE complex disassembly is essential for SNARE recycling and sustained membrane trafficking. NSF is a homo-hexamer; each protomer is composed of an N-terminal domain, NSF-N, and two adjacent AAA-domains, NSF-D1 and NSF-D2. Mutagenesis analysis has established specific roles for many of the structural elements of NSF-D1, the catalytic ATPase domain, and NSF-N, the SNAP-SNARE binding domain. Hydrodynamic analysis of NSF, labeled with (Ni(2+)-NTA)(2)-Cy3, detected conformational differences in NSF, in which the ATP-bound conformation appears more compact than the ADP-bound form. This indicates that NSF undergoes significant conformational changes as it progresses through its ATP-hydrolysis cycle. Incorporating these data, we propose a sequential mechanism by which NSF uses NSF-N and NSF-D1 to disassemble SNAP-SNARE complexes. We also illustrate how analytical centrifugation might be used to study other AAA(+) proteins.
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Gadella BM, Evans JP. Membrane Fusions During Mammalian Fertilization. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2011; 713:65-80. [DOI: 10.1007/978-94-007-0763-4_5] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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Abstract
Exocytosis is a highly conserved and essential process. Although numerous proteins are involved throughout the exocytotic process, the defining membrane fusion step appears to occur through a lipid-dominated mechanism. Here we review and integrate the current literature on protein and lipid roles in exocytosis, with emphasis on the multiple roles of cholesterol in exocytosis and membrane fusion, in an effort to promote a more molecular systems-level view of the as yet poorly understood process of Ca2+-triggered membrane mergers.
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Kim OJ. A single mutation at lysine 241 alters expression and trafficking of the D2 dopamine receptor. J Recept Signal Transduct Res 2009; 28:453-64. [PMID: 18946766 DOI: 10.1080/10799890802379410] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Ubiquitination of G protein-coupled receptors has been identified to regulate receptor signal transduction including agonist-induced internalization and sorting of internalized receptor for degradation or for recycling. Using co-immunoprecipitation and immunoblot analysis, I found that the membrane-associated D(2) dopamine receptor (DAR) is mono-ubiquitinated in the absence of an agonist following heterologous expression in human embryonic kidney cells (HEK293). By using site-directed mutagenesis, this report shows that the loss of lysine-241, K241A D(2) DAR reduced the amount of membrane-associated D(2) DAR. It is of interest that the K241A D(2) DAR also had a distinctly different ubiquitination pattern than the wild-type D(2) DAR. It is important to note that the ubiquitinated mutant D(2) DAR was degraded through ubiquitin-proteasome pathway. These data provide the factual evidence that a loss of lysine-241 of the D(2) DAR affects receptor ubiquitination and renders the protein susceptible to the proteasomal degradation.
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Affiliation(s)
- Ok-Jin Kim
- Department of Pharmacology and Toxicology, School of Pharmacy, University of Kansas, Lawrence, Kansas 66045-7582, USA.
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Buckley CE, Goldsmith P, Franklin RJM. Zebrafish myelination: a transparent model for remyelination? Dis Model Mech 2009; 1:221-8. [PMID: 19093028 DOI: 10.1242/dmm.001248] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
There is currently an unmet need for a therapy that promotes the regenerative process of remyelination in central nervous system diseases, notably multiple sclerosis (MS). A high-throughput model is, therefore, required to screen potential therapeutic drugs and to refine genomic and proteomic data from MS lesions. Here, we review the value of the zebrafish (Danio rerio) larva as a model of the developmental process of myelination, describing the powerful applications of zebrafish for genetic manipulation and genetic screens, as well as some of the exciting imaging capabilities of this model. Finally, we discuss how a model of zebrafish myelination can be used as a high-throughput screening model to predict the effect of compounds on remyelination. We conclude that zebrafish provide a highly versatile myelination model. As more complex transgenic zebrafish lines are developed, it might soon be possible to visualise myelination, or even remyelination, in real time. However, experimental outputs must be designed carefully for such visual and temporal techniques.
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Affiliation(s)
- Clare E Buckley
- Department of Veterinary Medicine, University of Cambridge, Cambridge, CB3 0ES, UK
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Abstract
The two universally required components of the intracellular membrane fusion machinery, SNARE and SM (Sec1/Munc18-like) proteins, play complementary roles in fusion. Vesicular and target membrane-localized SNARE proteins zipper up into an alpha-helical bundle that pulls the two membranes tightly together to exert the force required for fusion. SM proteins, shaped like clasps, bind to trans-SNARE complexes to direct their fusogenic action. Individual fusion reactions are executed by distinct combinations of SNARE and SM proteins to ensure specificity, and are controlled by regulators that embed the SM-SNARE fusion machinery into a physiological context. This regulation is spectacularly apparent in the exquisite speed and precision of synaptic exocytosis, where synaptotagmin (the calcium-ion sensor for fusion) cooperates with complexin (the clamp activator) to control the precisely timed release of neurotransmitters that initiates synaptic transmission and underlies brain function.
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Affiliation(s)
- Thomas C. Südhof
- Department of Cellular and Molecular Physiology, Stanford University, Palo Alto, CA 94304-5543 USADepartment of Cell Biology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520 USA
| | - James E. Rothman
- Department of Cellular and Molecular Physiology, Stanford University, Palo Alto, CA 94304-5543 USADepartment of Cell Biology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520 USA
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Jeon S, Kim YJ, Kim ST, Moon W, Chae Y, Kang M, Chung MY, Lee H, Hong MS, Chung JH, Joh TH, Lee H, Park HJ. Proteomic analysis of the neuroprotective mechanisms of acupuncture treatment in a Parkinson's disease mouse model. Proteomics 2008; 8:4822-32. [DOI: 10.1002/pmic.200700955] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
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Abstract
BACKGROUND In patients with insulinoma, biochemical proof of inappropriately elevated insulin secretion during hypoglycemia is required prior to surgery. Because circulating insulin levels usually vary widely, we have used the combined OGTT-fasting test to define new normative criteria for a retrospective systematic analysis. METHODS We retrospectively analyzed insulin concentrations from OGTT-fasting tests of 64 patients with surgically removed insulinomas. In addition, the response to intravenous somatostatin infusions was estimated. Normative criteria were defined to obtain comparable estimates of insulin concentrations: basal, glucose-stimulated maximum, postglucose plateau, and secretory bursts. RESULTS Three types of insulin secretion patterns were identified: (1) the autonomous secretion pattern (type 1, N=17) with basal and post-OGTT plateau insulin concentrations of approximately 50 mU/L, suppression after OGTT by 41%, virtual absence of distinctive secretory bursts, and resistance to somatostatin-mediated suppression (25 %); (2) the inadequate suppression pattern (type 2, N=28) with moderately elevated basal and post-OGTT insulin concentrations of approximately 20 mU/L, suppression after OGTT by 73%, absence of secretory bursts, and incomplete somatostatin-induced suppression (56 %); (3) the late-burst secretion pattern (type 3, N=19) with similar basal and post-OGTT insulin concentrations of 17 mU/L, suppression after OGTT by 76%, true insulin bursts of Delta 13+/-11 mU/L (184%), and nearly complete somatostatin-induced suppression by 64%. CONCLUSIONS By means of a new normative analysis of the combined OGTT-fasting test, three different patterns of insulin secretion can be described in patients with insulinoma: the autonomous secretion type, the inadequate suppression type, and the late-burst secretion type.
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Affiliation(s)
- Christiane Saddig
- Department of Oncology and Hematology, Kliniken Essen-Mitte, Henricistrasse 92, 45136 Essen, Germany
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Nonvesicular phospholipid transfer between peroxisomes and the endoplasmic reticulum. Proc Natl Acad Sci U S A 2008; 105:15785-90. [PMID: 18836080 DOI: 10.1073/pnas.0808321105] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
The endoplasmic reticulum (ER) plays an important role in peroxisome biogenesis; some peroxisomal membrane proteins are inserted into the ER and trafficked to peroxisomes in vesicles. These vesicles could also provide the phospholipids required for the growth of peroxisomal membranes, because peroxisomes lack phospholipid biosynthesis enzymes. To test this, we established a novel assay to monitor phospholipid transfer between the ER and peroxisomes and found that phospholipids are rapidly trafficked between these compartments. This transport is not blocked in mutants with conditional defects in Sec proteins required for vesicular trafficking from the ER or in Pex3p, a protein required for peroxisome membrane biogenesis. ER to peroxisome lipid transport was reconstituted in vitro and does not require cytosolic factors or ATP. Our findings indicate that lipids are directly transferred from the ER to peroxisomes by a nonvesicular pathway and suggest that ER to peroxisome vesicular transport is not required to provide lipids for peroxisomal growth.
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Abstract
Subcellular compartmentalization, cell growth, hormone secretion and neurotransmission require rapid, targeted, and regulated membrane fusion. Fusion entails extensive lipid rearrangements by two apposed (docked) membrane vesicles, joining their membrane proteins and lipids and mixing their luminal contents without lysis. Fusion of membranes in the secretory pathway involves Rab GTPases; their bound ‘effector’ proteins, which mediate downstream steps; SNARE proteins, which can ‘snare’ each other, in cis (bound to one membrane) or in trans (anchored to apposed membranes); and SNARE-associated proteins (SM proteins; NSF or Sec18p; SNAP or Sec17p; and others) cooperating with specific lipids to catalyze fusion. In contrast, mitochondrial and cell-cell fusion events are regulated by and use distinct catalysts.
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50
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Bitto E, Bingman CA, Kondrashov DA, McCoy JG, Bannen RM, Wesenberg GE, Phillips GN. Structure and dynamics of gamma-SNAP: insight into flexibility of proteins from the SNAP family. Proteins 2008; 70:93-104. [PMID: 17634982 DOI: 10.1002/prot.21468] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Soluble N-ethylmaleimide-sensitive factor attachment protein gamma (gamma-SNAP) is a member of an eukaryotic protein family involved in intracellular membrane trafficking. The X-ray structure of Brachydanio rerio gamma-SNAP was determined to 2.6 A and revealed an all-helical protein comprised of an extended twisted-sheet of helical hairpins with a helical-bundle domain on its carboxy-terminal end. Structural and conformational differences between multiple observed gamma-SNAP molecules and Sec17, a SNAP family protein from yeast, are analyzed. Conformational variation in gamma-SNAP molecules is matched with great precision by the two lowest frequency normal modes of the structure. Comparison of the lowest-frequency modes from gamma-SNAP and Sec17 indicated that the structures share preferred directions of flexibility, corresponding to bending and twisting of the twisted sheet motif. We discuss possible consequences related to the flexibility of the SNAP proteins for the mechanism of the 20S complex disassembly during the SNAP receptors recycling.
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Affiliation(s)
- Eduard Bitto
- Center for Eukaryotic Structural Genomics, University of Wisconsin-Madison, Madison, Wisconsin 53706-1544, USA
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