101
|
Hikone Y, Hirai G, Mishima M, Inomata K, Ikeya T, Arai S, Shirakawa M, Sodeoka M, Ito Y. A new carbamidemethyl-linked lanthanoid chelating tag for PCS NMR spectroscopy of proteins in living HeLa cells. JOURNAL OF BIOMOLECULAR NMR 2016; 66:99-110. [PMID: 27631409 DOI: 10.1007/s10858-016-0059-4] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2016] [Accepted: 09/02/2016] [Indexed: 05/14/2023]
Abstract
Structural analyses of proteins under macromolecular crowding inside human cultured cells by in-cell NMR spectroscopy are crucial not only for explicit understanding of their cellular functions but also for applications in medical and pharmaceutical sciences. In-cell NMR experiments using human cultured cells however suffer from low sensitivity, thus pseudocontact shifts from protein-tagged paramagnetic lanthanoid ions, analysed using sensitive heteronuclear two-dimensional correlation NMR spectra, offer huge potential advantage in obtaining structural information over conventional NOE-based approaches. We synthesised a new lanthanoid-chelating tag (M8-CAM-I), in which the eight-fold, stereospecifically methylated DOTA (M8) scaffold was retained, while a stable carbamidemethyl (CAM) group was introduced as the functional group connecting to proteins. M8-CAM-I successfully fulfilled the requirements for in-cell NMR: high-affinity to lanthanoid, low cytotoxicity and the stability under reducing condition inside cells. Large PCSs for backbone N-H resonances observed for M8-CAM-tagged human ubiquitin mutant proteins, which were introduced into HeLa cells by electroporation, demonstrated that this approach readily provides the useful information enabling the determination of protein structures, relative orientations of domains and protein complexes within human cultured cells.
Collapse
Affiliation(s)
- Yuya Hikone
- Department of Chemistry, Graduate School of Science and Engineering, Tokyo Metropolitan University, 1-1 Minami-Osawa, Hachioji, Tokyo, 192-0397, Japan
- Synthetic Organic Chemistry Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan
| | - Go Hirai
- Synthetic Organic Chemistry Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan
- AMED-CREST, Japan Agency for Medical Research and Development, 1-7-1 Otemachi, Chiyoda-ku, Tokyo, 100-0004, Japan
| | - Masaki Mishima
- Department of Chemistry, Graduate School of Science and Engineering, Tokyo Metropolitan University, 1-1 Minami-Osawa, Hachioji, Tokyo, 192-0397, Japan
- CREST, Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Saitama, 332-0012, Japan
| | - Kohsuke Inomata
- Quantitative Biology Center, RIKEN, 1-7-22 Suehirocho, Tsurumi-ku, Yokohama, 230-0045, Japan
- PRESTO/Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Saitama, 332-0012, Japan
| | - Teppei Ikeya
- Department of Chemistry, Graduate School of Science and Engineering, Tokyo Metropolitan University, 1-1 Minami-Osawa, Hachioji, Tokyo, 192-0397, Japan
- CREST, Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Saitama, 332-0012, Japan
| | - Souichiro Arai
- Department of Chemistry, Graduate School of Science and Engineering, Tokyo Metropolitan University, 1-1 Minami-Osawa, Hachioji, Tokyo, 192-0397, Japan
| | - Masahiro Shirakawa
- AMED-CREST, Japan Agency for Medical Research and Development, 1-7-1 Otemachi, Chiyoda-ku, Tokyo, 100-0004, Japan
- Department of Molecular Engineering, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto, 615-8510, Japan
| | - Mikiko Sodeoka
- Synthetic Organic Chemistry Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan
- AMED-CREST, Japan Agency for Medical Research and Development, 1-7-1 Otemachi, Chiyoda-ku, Tokyo, 100-0004, Japan
| | - Yutaka Ito
- Department of Chemistry, Graduate School of Science and Engineering, Tokyo Metropolitan University, 1-1 Minami-Osawa, Hachioji, Tokyo, 192-0397, Japan.
- CREST, Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Saitama, 332-0012, Japan.
| |
Collapse
|
102
|
N-terminal domain of complexin independently activates calcium-triggered fusion. Proc Natl Acad Sci U S A 2016; 113:E4698-707. [PMID: 27444020 DOI: 10.1073/pnas.1604348113] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Complexin activates Ca(2+)-triggered neurotransmitter release and regulates spontaneous release in the presynaptic terminal by cooperating with the neuronal soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) and the Ca(2+)-sensor synaptotagmin. The N-terminal domain of complexin is important for activation, but its molecular mechanism is still poorly understood. Here, we observed that a split pair of N-terminal and central domain fragments of complexin is sufficient to activate Ca(2+)-triggered release using a reconstituted single-vesicle fusion assay, suggesting that the N-terminal domain acts as an independent module within the synaptic fusion machinery. The N-terminal domain can also interact independently with membranes, which is enhanced by a cooperative interaction with the neuronal SNARE complex. We show by mutagenesis that membrane binding of the N-terminal domain is essential for activation of Ca(2+)-triggered fusion. Consistent with the membrane-binding property, the N-terminal domain can be substituted by the influenza virus hemagglutinin fusion peptide, and this chimera also activates Ca(2+)-triggered fusion. Membrane binding of the N-terminal domain of complexin therefore cooperates with the other fusogenic elements of the synaptic fusion machinery during Ca(2+)-triggered release.
Collapse
|
103
|
Müntener T, Häussinger D, Selenko P, Theillet FX. In-Cell Protein Structures from 2D NMR Experiments. J Phys Chem Lett 2016; 7:2821-5. [PMID: 27379949 DOI: 10.1021/acs.jpclett.6b01074] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
In-cell NMR spectroscopy provides atomic resolution insights into the structural properties of proteins in cells, but it is rarely used to solve entire protein structures de novo. Here, we introduce a paramagnetic lanthanide-tag to simultaneously measure protein pseudocontact shifts (PCSs) and residual dipolar couplings (RDCs) to be used as input for structure calculation routines within the Rosetta program. We employ this approach to determine the structure of the protein G B1 domain (GB1) in intact Xenopus laevis oocytes from a single set of 2D in-cell NMR experiments. Specifically, we derive well-defined GB1 ensembles from low concentration in-cell NMR samples (∼50 μM) measured at moderate magnetic field strengths (600 MHz), thus offering an easily accessible alternative for determining intracellular protein structures.
Collapse
Affiliation(s)
- Thomas Müntener
- Department of Chemistry, University of Basel , St. Johanns-Ring 19, 4056 Basel, Switzerland
| | - Daniel Häussinger
- Department of Chemistry, University of Basel , St. Johanns-Ring 19, 4056 Basel, Switzerland
| | - Philipp Selenko
- Department of Structural Biology, Leibniz Institute of Molecular Pharmacology (FMP Berlin) , Robert Roessle Straße 10, 13125 Berlin, Germany
| | - Francois-Xavier Theillet
- Department of Structural Biology, Leibniz Institute of Molecular Pharmacology (FMP Berlin) , Robert Roessle Straße 10, 13125 Berlin, Germany
| |
Collapse
|
104
|
Abstract
Intracellular membrane fusion is mediated in most cases by membrane-bridging complexes of soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs). However, the assembly of such complexes in vitro is inefficient, and their uncatalysed disassembly is undetectably slow. Here, we focus on the cellular machinery that orchestrates assembly and disassembly of SNARE complexes, thereby regulating processes ranging from vesicle trafficking to organelle fusion to neurotransmitter release. Rapid progress is being made on many fronts, including the development of more realistic cell-free reconstitutions, the application of single-molecule biophysics, and the elucidation of X-ray and high-resolution electron microscopy structures of the SNARE assembly and disassembly machineries 'in action'.
Collapse
Affiliation(s)
- Richard W Baker
- Department of Molecular Biology, Princeton University, Princeton, New Jersey 08544, USA.,Present address: Department of Cellular and Molecular Medicine, School of Medicine, University of California San Diego, La Jolla, California 92093, USA
| | - Frederick M Hughson
- Department of Molecular Biology, Princeton University, Princeton, New Jersey 08544, USA
| |
Collapse
|
105
|
Zhang H, van Ingen H. Isotope-labeling strategies for solution NMR studies of macromolecular assemblies. Curr Opin Struct Biol 2016; 38:75-82. [PMID: 27295425 DOI: 10.1016/j.sbi.2016.05.008] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2016] [Revised: 05/20/2016] [Accepted: 05/22/2016] [Indexed: 12/21/2022]
Abstract
Proteins come together in macromolecular assemblies, recognizing and binding to each other through their structures, and operating on their substrates through their motions. Detailed characterization of these processes is particularly suited to NMR, a high-resolution technique sensitive to structure, dynamics, and interactions. Advances in isotope-labeling have enabled such studies to an ever-increasing range of systems. Here we highlight recent applications and bring to the fore the range of options to produce labeled proteins and to control the specific placement of isotopes. The increased labeling control and affordability, together with the possibility to combine strategies will further deepen and extend the range of protein assembly investigations.
Collapse
Affiliation(s)
- Heyi Zhang
- Macromolecular Biochemistry, Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, Leiden, The Netherlands
| | - Hugo van Ingen
- Macromolecular Biochemistry, Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, Leiden, The Netherlands.
| |
Collapse
|
106
|
Trimbuch T, Rosenmund C. Should I stop or should I go? The role of complexin in neurotransmitter release. Nat Rev Neurosci 2016; 17:118-25. [PMID: 26806630 DOI: 10.1038/nrn.2015.16] [Citation(s) in RCA: 107] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
When it comes to fusion with the neuronal cell membrane, does a synaptic vesicle have a choice whether to stop or to go? Recent work suggests that complexin, a tiny protein found within the synaptic terminal, contributes to the mechanism through which this choice is made. How complexin plays this consulting part and which synaptic vesicle proteins it interacts with remain open questions. Indeed, studies in mice and flies have led to the proposal of different models of complexin function. We suggest that understanding the modular nature of complexin will help us to unpick its role in synaptic vesicle release.
Collapse
Affiliation(s)
- Thorsten Trimbuch
- Neuroscience Research Center, Charité Universitätsmedizin Berlin, Chariteplatz 1, 10117 Berlin, Germany
| | - Christian Rosenmund
- Neuroscience Research Center, Charité Universitätsmedizin Berlin, Chariteplatz 1, 10117 Berlin, Germany
| |
Collapse
|
107
|
Liu X, Seven AB, Camacho M, Esser V, Xu J, Trimbuch T, Quade B, Su L, Ma C, Rosenmund C, Rizo J. Functional synergy between the Munc13 C-terminal C1 and C2 domains. eLife 2016; 5. [PMID: 27213521 PMCID: PMC4927299 DOI: 10.7554/elife.13696] [Citation(s) in RCA: 82] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2015] [Accepted: 05/22/2016] [Indexed: 11/13/2022] Open
Abstract
Neurotransmitter release requires SNARE complexes to bring membranes together, NSF-SNAPs to recycle the SNAREs, Munc18-1 and Munc13s to orchestrate SNARE complex assembly, and Synaptotagmin-1 to trigger fast Ca2+-dependent membrane fusion. However, it is unclear whether Munc13s function upstream and/or downstream of SNARE complex assembly, and how the actions of their multiple domains are integrated. Reconstitution, liposome-clustering and electrophysiological experiments now reveal a functional synergy between the C1, C2B and C2C domains of Munc13-1, indicating that these domains help bridging the vesicle and plasma membranes to facilitate stimulation of SNARE complex assembly by the Munc13-1 MUN domain. Our reconstitution data also suggest that Munc18-1, Munc13-1, NSF, αSNAP and the SNAREs are critical to form a ‘primed’ state that does not fuse but is ready for fast fusion upon Ca2+ influx. Overall, our results support a model whereby the multiple domains of Munc13s cooperate to coordinate synaptic vesicle docking, priming and fusion. DOI:http://dx.doi.org/10.7554/eLife.13696.001 In the brain, neurons communicate with each other using small molecules called neurotransmitters. Electrical signals in one neuron trigger the release of the neurotransmitters, which then bind to receptor proteins on another neuron nearby. Neurotransmitters are packaged into small compartments called synaptic vesicles and are released from the neuron when these vesicles fuse with the membrane that surrounds the cell. Many proteins are involved in regulating this process to ensure that neurotransmitters are released at the right place and time. A large protein called Munc13 plays an important role in the release of neurotransmitters. It contains many different regions, including a long domain called MUN and three additional domains called C1, C2B and C2C among others. However, it is not clear how all these domains work together to control neurotransmitter release. Here Liu, Seven et al. address this question using purified proteins inserted into membranes as well as experiments in neurons from mice. The experiments show that the C1, C2B and C2C domains all play key roles in neurotransmitter release. Together with the MUN domain, these three domains help to form bridges between synaptic vesicles and the membrane surrounding the neuron. These bridges could help other proteins involved in neurotransmitter release to form a group that induces vesicle fusion. Liu, Seven et al.’s findings also suggest that Munc13 proteins cooperate with other proteins to form a 'primed' state in which a synaptic vesicle is ready to rapidly fuse with a neuron’s membrane when triggered to do so by an electrical signal. A future challenge is to find out how the proteins that form this primed state promote vesicle fusion. DOI:http://dx.doi.org/10.7554/eLife.13696.002
Collapse
Affiliation(s)
- Xiaoxia Liu
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, United States.,Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, United States.,Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, United States
| | - Alpay Burak Seven
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, United States.,Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, United States.,Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, United States
| | - Marcial Camacho
- Department of Neurophysiology, NeuroCure Cluster of Excellence, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Victoria Esser
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, United States.,Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, United States.,Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, United States
| | - Junjie Xu
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, United States.,Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, United States.,Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, United States
| | - Thorsten Trimbuch
- Department of Neurophysiology, NeuroCure Cluster of Excellence, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Bradley Quade
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, United States.,Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, United States.,Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, United States
| | - Lijing Su
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, United States.,Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, United States.,Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, United States
| | - Cong Ma
- Key Laboratory of Molecular Biophysics of the Ministry of Education, Huazhong University of Science and Technology, Wuhan, China.,College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, China
| | - Christian Rosenmund
- Department of Neurophysiology, NeuroCure Cluster of Excellence, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Josep Rizo
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, United States.,Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, United States.,Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, United States
| |
Collapse
|
108
|
Abstract
SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) proteins are a highly conserved set of membrane-associated proteins that mediate intracellular membrane fusion. Cognate SNAREs from two separate membranes zipper to facilitate membrane apposition and fusion. Though the stable post-fusion conformation of SNARE complex has been extensively studied with biochemical and biophysical means, the pathway of SNARE zippering has been elusive. In this review, we describe some recent progress in understanding the pathway of SNARE zippering. We particularly focus on the half-zippered intermediate, which is most likely to serve as the main point of regulation by the auxiliary factors.
Collapse
|
109
|
Phosphorylation of synaptotagmin-1 controls a post-priming step in PKC-dependent presynaptic plasticity. Proc Natl Acad Sci U S A 2016; 113:5095-100. [PMID: 27091977 DOI: 10.1073/pnas.1522927113] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Presynaptic activation of the diacylglycerol (DAG)/protein kinase C (PKC) pathway is a central event in short-term synaptic plasticity. Two substrates, Munc13-1 and Munc18-1, are essential for DAG-induced potentiation of vesicle priming, but the role of most presynaptic PKC substrates is not understood. Here, we show that a mutation in synaptotagmin-1 (Syt1(T112A)), which prevents its PKC-dependent phosphorylation, abolishes DAG-induced potentiation of synaptic transmission in hippocampal neurons. This mutant also reduces potentiation of spontaneous release, but only if alternative Ca(2+) sensors, Doc2A/B proteins, are absent. However, unlike mutations in Munc13-1 or Munc18-1 that prevent DAG-induced potentiation, the synaptotagmin-1 mutation does not affect paired-pulse facilitation. Furthermore, experiments to probe vesicle priming (recovery after train stimulation and dual application of hypertonic solutions) also reveal no abnormalities. Expression of synaptotagmin-2, which lacks a seven amino acid sequence that contains the phosphorylation site in synaptotagmin-1, or a synaptotagmin-1 variant with these seven residues removed (Syt1(Δ109-116)), supports normal DAG-induced potentiation. These data suggest that this seven residue sequence in synaptotagmin-1 situated in the linker between the transmembrane and C2A domains is inhibitory in the unphosphorylated state and becomes permissive of potentiation upon phosphorylation. We conclude that synaptotagmin-1 phosphorylation is an essential step in PKC-dependent potentiation of synaptic transmission, acting downstream of the two other essential DAG/PKC substrates, Munc13-1 and Munc18-1.
Collapse
|
110
|
Wang S, Li Y, Ma C. Synaptotagmin-1 C2B domain interacts simultaneously with SNAREs and membranes to promote membrane fusion. eLife 2016; 5. [PMID: 27083046 PMCID: PMC4878868 DOI: 10.7554/elife.14211] [Citation(s) in RCA: 71] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2016] [Accepted: 04/14/2016] [Indexed: 12/30/2022] Open
Abstract
Synaptotagmin-1 (Syt1) acts as a Ca2+ sensor for neurotransmitter release through its C2 domains. It has been proposed that Syt1 promotes SNARE-dependent fusion mainly through its C2B domain, but the underlying mechanism is poorly understood. In this study, we show that the C2B domain interacts simultaneously with acidic membranes and SNARE complexes via the top Ca2+-binding loops, the side polybasic patch, and the bottom face in response to Ca2+. Disruption of the simultaneous interactions completely abrogates the triggering activity of the C2B domain in liposome fusion. We hypothesize that the simultaneous interactions endow the C2B domain with an ability to deform local membranes, and this membrane-deformation activity might underlie the functional significance of the Syt1 C2B domain in vivo. DOI:http://dx.doi.org/10.7554/eLife.14211.001 Information travels around the nervous system along cells called neurons, which communicate with each other via connections called synapses. When a signal travelling along one neuron reaches a synapse, it triggers the release of molecules known as neurotransmitters. These molecules are then taken up by the next neuron to pass the signal on. Neurotransmitters are stored in compartments called synaptic vesicles and their release from the first neuron depends on the synaptic vesicles fusing with the membrane that surrounds the cell. This “membrane fusion” process is driven by a group of proteins called the SNARE complex. Membrane fusion is triggered by a sudden increase in the amount of calcium ions in the cell, which leads to an increase in the activity of a protein called synaptotagmin-1. A region of this protein known as the C2B domain is able to detect calcium ions, and it can also bind to the cell membrane and SNARE complex proteins. However, it is not clear what roles these interactions play in driving the release of neurotransmitters. Wang, Li et al. have used a variety of biophysical techniques to study these interactions in more detail using purified proteins and other cell components. The experiments show that all three interactions occur at the same time and are all required for synaptotagmin-1 to trigger membrane fusion. Wang, Li et al. propose that these interactions allow synaptotagmin-1 to bend a section of the cell membrane in response to calcium ions. The experiments also show that the C2B domain interacts more strongly with the SNARE complex than previously thought. A future challenge is to observe whether synaptotagmin-1 works in the same way in living cells. DOI:http://dx.doi.org/10.7554/eLife.14211.002
Collapse
Affiliation(s)
- Shen Wang
- Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, China
| | - Yun Li
- Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, China
| | - Cong Ma
- Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, China
| |
Collapse
|
111
|
Lopez-Moya F, Kowbel D, Nueda MJ, Palma-Guerrero J, Glass NL, Lopez-Llorca LV. Neurospora crassa transcriptomics reveals oxidative stress and plasma membrane homeostasis biology genes as key targets in response to chitosan. MOLECULAR BIOSYSTEMS 2016; 12:391-403. [PMID: 26694141 PMCID: PMC4729629 DOI: 10.1039/c5mb00649j] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Chitosan is a natural polymer with antimicrobial activity. Chitosan causes plasma membrane permeabilization and induction of intracellular reactive oxygen species (ROS) in Neurospora crassa. We have determined the transcriptional profile of N. crassa to chitosan and identified the main gene targets involved in the cellular response to this compound. Global network analyses showed membrane, transport and oxidoreductase activity as key nodes affected by chitosan. Activation of oxidative metabolism indicates the importance of ROS and cell energy together with plasma membrane homeostasis in N. crassa response to chitosan. Deletion strain analysis of chitosan susceptibility pointed NCU03639 encoding a class 3 lipase, involved in plasma membrane repair by lipid replacement, and NCU04537 a MFS monosaccharide transporter related to assimilation of simple sugars, as main gene targets of chitosan. NCU10521, a glutathione S-transferase-4 involved in the generation of reducing power for scavenging intracellular ROS is also a determinant chitosan gene target. Ca(2+) increased tolerance to chitosan in N. crassa. Growth of NCU10610 (fig 1 domain) and SYT1 (a synaptotagmin) deletion strains was significantly increased by Ca(2+) in the presence of chitosan. Both genes play a determinant role in N. crassa membrane homeostasis. Our results are of paramount importance for developing chitosan as an antifungal.
Collapse
Affiliation(s)
- Federico Lopez-Moya
- Laboratory of Plant Pathology, Multidisciplinary Institute for Environmental Studies (MIES) Ramon Margalef, Department of Marine Sciences and Applied Biology, University of Alicante, E-03080 Alicante, Spain.
| | - David Kowbel
- Department of Plant and Microbial Biology, University of California, Berkeley CA, 94720-3120 USA.
| | - Maria José Nueda
- Statistics and Operation Research Department, University of Alicante, E-03080 Alicante, Spain.
| | - Javier Palma-Guerrero
- Department of Plant and Microbial Biology, University of California, Berkeley CA, 94720-3120 USA.
| | - N Louise Glass
- Department of Plant and Microbial Biology, University of California, Berkeley CA, 94720-3120 USA.
| | - Luis Vicente Lopez-Llorca
- Laboratory of Plant Pathology, Multidisciplinary Institute for Environmental Studies (MIES) Ramon Margalef, Department of Marine Sciences and Applied Biology, University of Alicante, E-03080 Alicante, Spain.
| |
Collapse
|
112
|
Three steps forward, two steps back: mechanistic insights into the assembly and disassembly of the SNARE complex. Curr Opin Chem Biol 2015; 29:66-71. [PMID: 26498108 DOI: 10.1016/j.cbpa.2015.10.003] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2015] [Accepted: 10/01/2015] [Indexed: 11/20/2022]
Abstract
Membrane fusion is a tightly controlled process in all eukaryotic cell types. The SNARE family of proteins is required for fusion throughout the exocytic and endocytic trafficking pathways. SNAREs on a transport vesicle interact with the cognate SNAREs on the target membrane, forming an incredibly stable SNARE complex that provides energy for the membranes to fuse, although many aspects of the mechanism remain elusive. Recent advances in single-molecule and high-resolution structural methods provide exciting new insights into how SNARE complexes assemble, including measurements of assembly energetics and identification of intermediates in the assembly pathway. These techniques were also key in elucidating mechanistic details into how the SNARE complex is disassembled, including details of the energetics required for ATP-dependent α-SNAP/NSF-mediated SNARE complex disassembly, and the structural changes that accompany ATP hydrolysis by the disassembly machinery. Additionally, SNARE complex formation and disassembly are tightly regulated processes; innovative biochemical and biophysical characterization has deepened our understanding of how these regulators work to control membrane fusion and exocytosis.
Collapse
|
113
|
Bacaj T, Wu D, Burré J, Malenka RC, Liu X, Südhof TC. Synaptotagmin-1 and -7 Are Redundantly Essential for Maintaining the Capacity of the Readily-Releasable Pool of Synaptic Vesicles. PLoS Biol 2015; 13:e1002267. [PMID: 26437117 PMCID: PMC4593569 DOI: 10.1371/journal.pbio.1002267] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2015] [Accepted: 08/27/2015] [Indexed: 12/29/2022] Open
Abstract
In forebrain neurons, Ca(2+) triggers exocytosis of readily releasable vesicles by binding to synaptotagmin-1 and -7, thereby inducing fast and slow vesicle exocytosis, respectively. Loss-of-function of synaptotagmin-1 or -7 selectively impairs the fast and slow phase of release, respectively, but does not change the size of the readily-releasable pool (RRP) of vesicles as measured by stimulation of release with hypertonic sucrose, or alter the rate of vesicle priming into the RRP. Here we show, however, that simultaneous loss-of-function of both synaptotagmin-1 and -7 dramatically decreased the capacity of the RRP, again without altering the rate of vesicle priming into the RRP. Either synaptotagmin-1 or -7 was sufficient to rescue the RRP size in neurons lacking both synaptotagmin-1 and -7. Although maintenance of RRP size was Ca(2+)-independent, mutations in Ca(2+)-binding sequences of synaptotagmin-1 or synaptotagmin-7--which are contained in flexible top-loop sequences of their C2 domains--blocked the ability of these synaptotagmins to maintain the RRP size. Both synaptotagmins bound to SNARE complexes; SNARE complex binding was reduced by the top-loop mutations that impaired RRP maintenance. Thus, synaptotagmin-1 and -7 perform redundant functions in maintaining the capacity of the RRP in addition to nonredundant functions in the Ca(2+) triggering of different phases of release.
Collapse
Affiliation(s)
- Taulant Bacaj
- Department of Molecular and Cellular Physiology and Howard Hughes Medical Institute, Stanford University, Stanford, California, United States of America
| | - Dick Wu
- Department of Molecular and Cellular Physiology and Howard Hughes Medical Institute, Stanford University, Stanford, California, United States of America
- Nancy Pritzker Laboratory, Department of Psychiatry and Behavioral Sciences, Stanford University Medical School, Stanford, California, United States of America
| | - Jacqueline Burré
- Department of Molecular and Cellular Physiology and Howard Hughes Medical Institute, Stanford University, Stanford, California, United States of America
| | - Robert C. Malenka
- Nancy Pritzker Laboratory, Department of Psychiatry and Behavioral Sciences, Stanford University Medical School, Stanford, California, United States of America
| | - Xinran Liu
- Department of Cell Biology, Yale University School of Medicine, New Haven, Connecticut, United States of America
| | - Thomas C. Südhof
- Department of Molecular and Cellular Physiology and Howard Hughes Medical Institute, Stanford University, Stanford, California, United States of America
- * E-mail:
| |
Collapse
|
114
|
Affiliation(s)
- Mary Munson
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts, USA
| |
Collapse
|
115
|
Synaptotagmin-1 binds to PIP(2)-containing membrane but not to SNAREs at physiological ionic strength. Nat Struct Mol Biol 2015; 22:815-23. [PMID: 26389740 PMCID: PMC4596797 DOI: 10.1038/nsmb.3097] [Citation(s) in RCA: 86] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2015] [Accepted: 08/26/2015] [Indexed: 12/19/2022]
Abstract
The Ca(2+) sensor synaptotagmin-1 is thought to trigger membrane fusion by binding to acidic membrane lipids and SNARE proteins. Previous work has shown that binding is mediated by electrostatic interactions that are sensitive to the ionic environment. However, the influence of divalent or polyvalent ions, at physiological concentrations, on synaptotagmin's binding to membranes or SNAREs has not been explored. Here we show that binding of rat synaptotagmin-1 to membranes containing phosphatidylinositol 4,5-bisphosphate (PIP2) is regulated by charge shielding caused by the presence of divalent cations. Surprisingly, polyvalent ions such as ATP and Mg(2+) completely abrogate synaptotagmin-1 binding to SNAREs regardless of the presence of Ca(2+). Altogether, our data indicate that at physiological ion concentrations Ca(2+)-dependent synaptotagmin-1 binding is confined to PIP2-containing membrane patches in the plasma membrane, suggesting that membrane interaction of synaptotagmin-1 rather than SNARE binding triggers exocytosis of vesicles.
Collapse
|
116
|
Zhou Q, Lai Y, Bacaj T, Zhao M, Lyubimov AY, Uervirojnangkoorn M, Zeldin OB, Brewster AS, Sauter NK, Cohen AE, Soltis SM, Alonso-Mori R, Chollet M, Lemke HT, Pfuetzner RA, Choi UB, Weis WI, Diao J, Südhof TC, Brunger AT. Architecture of the synaptotagmin-SNARE machinery for neuronal exocytosis. Nature 2015; 525:62-7. [PMID: 26280336 PMCID: PMC4607316 DOI: 10.1038/nature14975] [Citation(s) in RCA: 224] [Impact Index Per Article: 24.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2015] [Accepted: 07/27/2015] [Indexed: 02/07/2023]
Abstract
Synaptotagmin-1 and neuronal SNARE proteins have central roles in evoked synchronous neurotransmitter release; however, it is unknown how they cooperate to trigger synaptic vesicle fusion. Here we report atomic-resolution crystal structures of Ca(2+)- and Mg(2+)-bound complexes between synaptotagmin-1 and the neuronal SNARE complex, one of which was determined with diffraction data from an X-ray free-electron laser, leading to an atomic-resolution structure with accurate rotamer assignments for many side chains. The structures reveal several interfaces, including a large, specific, Ca(2+)-independent and conserved interface. Tests of this interface by mutagenesis suggest that it is essential for Ca(2+)-triggered neurotransmitter release in mouse hippocampal neuronal synapses and for Ca(2+)-triggered vesicle fusion in a reconstituted system. We propose that this interface forms before Ca(2+) triggering, moves en bloc as Ca(2+) influx promotes the interactions between synaptotagmin-1 and the plasma membrane, and consequently remodels the membrane to promote fusion, possibly in conjunction with other interfaces.
Collapse
Affiliation(s)
- Qiangjun Zhou
- Department of Molecular and Cellular Physiology, Howard Hughes Medical Institute, Stanford University, Stanford, California 94305, USA
- Departments of Neurology and Neurological Sciences, Photon Science, and Structural Biology, Stanford University, Stanford, California 94305, USA
| | - Ying Lai
- Department of Molecular and Cellular Physiology, Howard Hughes Medical Institute, Stanford University, Stanford, California 94305, USA
- Departments of Neurology and Neurological Sciences, Photon Science, and Structural Biology, Stanford University, Stanford, California 94305, USA
| | - Taulant Bacaj
- Department of Molecular and Cellular Physiology, Howard Hughes Medical Institute, Stanford University, Stanford, California 94305, USA
| | - Minglei Zhao
- Department of Molecular and Cellular Physiology, Howard Hughes Medical Institute, Stanford University, Stanford, California 94305, USA
- Departments of Neurology and Neurological Sciences, Photon Science, and Structural Biology, Stanford University, Stanford, California 94305, USA
| | - Artem Y Lyubimov
- Department of Molecular and Cellular Physiology, Howard Hughes Medical Institute, Stanford University, Stanford, California 94305, USA
- Departments of Neurology and Neurological Sciences, Photon Science, and Structural Biology, Stanford University, Stanford, California 94305, USA
| | - Monarin Uervirojnangkoorn
- Department of Molecular and Cellular Physiology, Howard Hughes Medical Institute, Stanford University, Stanford, California 94305, USA
- Departments of Neurology and Neurological Sciences, Photon Science, and Structural Biology, Stanford University, Stanford, California 94305, USA
| | - Oliver B Zeldin
- Department of Molecular and Cellular Physiology, Howard Hughes Medical Institute, Stanford University, Stanford, California 94305, USA
- Departments of Neurology and Neurological Sciences, Photon Science, and Structural Biology, Stanford University, Stanford, California 94305, USA
| | - Aaron S Brewster
- Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Nicholas K Sauter
- Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Aina E Cohen
- SLAC National Accelerator Laboratory, Stanford, California 94305, USA
| | - S Michael Soltis
- SLAC National Accelerator Laboratory, Stanford, California 94305, USA
| | | | - Matthieu Chollet
- SLAC National Accelerator Laboratory, Stanford, California 94305, USA
| | - Henrik T Lemke
- SLAC National Accelerator Laboratory, Stanford, California 94305, USA
| | - Richard A Pfuetzner
- Department of Molecular and Cellular Physiology, Howard Hughes Medical Institute, Stanford University, Stanford, California 94305, USA
- Departments of Neurology and Neurological Sciences, Photon Science, and Structural Biology, Stanford University, Stanford, California 94305, USA
| | - Ucheor B Choi
- Department of Molecular and Cellular Physiology, Howard Hughes Medical Institute, Stanford University, Stanford, California 94305, USA
- Departments of Neurology and Neurological Sciences, Photon Science, and Structural Biology, Stanford University, Stanford, California 94305, USA
| | - William I Weis
- Departments of Structural Biology, Molecular and Cellular Physiology, and Photon Science, Stanford University, Stanford, California 94305, USA
| | - Jiajie Diao
- Department of Molecular and Cellular Physiology, Howard Hughes Medical Institute, Stanford University, Stanford, California 94305, USA
- Departments of Neurology and Neurological Sciences, Photon Science, and Structural Biology, Stanford University, Stanford, California 94305, USA
| | - Thomas C Südhof
- Department of Molecular and Cellular Physiology, Howard Hughes Medical Institute, Stanford University, Stanford, California 94305, USA
| | - Axel T Brunger
- Department of Molecular and Cellular Physiology, Howard Hughes Medical Institute, Stanford University, Stanford, California 94305, USA
- Departments of Neurology and Neurological Sciences, Photon Science, and Structural Biology, Stanford University, Stanford, California 94305, USA
| |
Collapse
|