51
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Affiliation(s)
- James E Rothman
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA
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52
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Michalski N, Goutman JD, Auclair SM, Boutet de Monvel J, Tertrais M, Emptoz A, Parrin A, Nouaille S, Guillon M, Sachse M, Ciric D, Bahloul A, Hardelin JP, Sutton RB, Avan P, Krishnakumar SS, Rothman JE, Dulon D, Safieddine S, Petit C. Otoferlin acts as a Ca 2+ sensor for vesicle fusion and vesicle pool replenishment at auditory hair cell ribbon synapses. eLife 2017; 6:e31013. [PMID: 29111973 PMCID: PMC5700815 DOI: 10.7554/elife.31013] [Citation(s) in RCA: 73] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2017] [Accepted: 11/06/2017] [Indexed: 01/01/2023] Open
Abstract
Hearing relies on rapid, temporally precise, and sustained neurotransmitter release at the ribbon synapses of sensory cells, the inner hair cells (IHCs). This process requires otoferlin, a six C2-domain, Ca2+-binding transmembrane protein of synaptic vesicles. To decipher the role of otoferlin in the synaptic vesicle cycle, we produced knock-in mice (OtofAla515,Ala517/Ala515,Ala517) with lower Ca2+-binding affinity of the C2C domain. The IHC ribbon synapse structure, synaptic Ca2+ currents, and otoferlin distribution were unaffected in these mutant mice, but auditory brainstem response wave-I amplitude was reduced. Lower Ca2+ sensitivity and delay of the fast and sustained components of synaptic exocytosis were revealed by membrane capacitance measurement upon modulations of intracellular Ca2+ concentration, by varying Ca2+ influx through voltage-gated Ca2+-channels or Ca2+ uncaging. Otoferlin thus functions as a Ca2+ sensor, setting the rates of primed vesicle fusion with the presynaptic plasma membrane and synaptic vesicle pool replenishment in the IHC active zone.
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Affiliation(s)
- Nicolas Michalski
- Unité de Génétique et Physiologie de l’AuditionInstitut PasteurParisFrance
- UMRS 1120, Institut National de la Santé et de la Recherche MédicaleParisFrance
- Sorbonne Universités, UPMC Université Paris 06, Complexité du VivantParisFrance
| | - Juan D Goutman
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, Consejo Nacional de Investigaciones Científicas y TécnicasBuenos AiresArgentina
| | - Sarah Marie Auclair
- Department of Cell BiologyYale University School of MedicineNew HavenUnited States
| | - Jacques Boutet de Monvel
- Unité de Génétique et Physiologie de l’AuditionInstitut PasteurParisFrance
- UMRS 1120, Institut National de la Santé et de la Recherche MédicaleParisFrance
- Sorbonne Universités, UPMC Université Paris 06, Complexité du VivantParisFrance
| | - Margot Tertrais
- UMRS 1120, Institut National de la Santé et de la Recherche MédicaleParisFrance
- Laboratoire de Neurophysiologie de la Synapse Auditive, Bordeaux NeurocampusUniversité de BordeauxBordeauxFrance
| | - Alice Emptoz
- Unité de Génétique et Physiologie de l’AuditionInstitut PasteurParisFrance
- UMRS 1120, Institut National de la Santé et de la Recherche MédicaleParisFrance
- Sorbonne Universités, UPMC Université Paris 06, Complexité du VivantParisFrance
| | - Alexandre Parrin
- Unité de Génétique et Physiologie de l’AuditionInstitut PasteurParisFrance
- UMRS 1120, Institut National de la Santé et de la Recherche MédicaleParisFrance
- Sorbonne Universités, UPMC Université Paris 06, Complexité du VivantParisFrance
| | - Sylvie Nouaille
- Unité de Génétique et Physiologie de l’AuditionInstitut PasteurParisFrance
- UMRS 1120, Institut National de la Santé et de la Recherche MédicaleParisFrance
- Sorbonne Universités, UPMC Université Paris 06, Complexité du VivantParisFrance
| | - Marc Guillon
- Wave Front Engineering Microscopy Group, Neurophotonics Laboratory, Centre National de la Recherche Scientifique, UMR 8250University Paris Descartes, Sorbonne Paris CitéParisFrance
| | - Martin Sachse
- Center for Innovation & Technological ResearchUltrapole, Institut PasteurParisFrance
| | - Danica Ciric
- Unité de Génétique et Physiologie de l’AuditionInstitut PasteurParisFrance
- UMRS 1120, Institut National de la Santé et de la Recherche MédicaleParisFrance
- Sorbonne Universités, UPMC Université Paris 06, Complexité du VivantParisFrance
| | - Amel Bahloul
- Unité de Génétique et Physiologie de l’AuditionInstitut PasteurParisFrance
- UMRS 1120, Institut National de la Santé et de la Recherche MédicaleParisFrance
- Sorbonne Universités, UPMC Université Paris 06, Complexité du VivantParisFrance
- Centre National de la Recherche ScientifiqueFrance
| | - Jean-Pierre Hardelin
- Unité de Génétique et Physiologie de l’AuditionInstitut PasteurParisFrance
- UMRS 1120, Institut National de la Santé et de la Recherche MédicaleParisFrance
- Sorbonne Universités, UPMC Université Paris 06, Complexité du VivantParisFrance
| | - Roger Bryan Sutton
- Department of Cell Physiology and Molecular BiophysicsTexas Tech University Health Sciences CenterLubbockUnited States
- Center for Membrane Protein ResearchTexas Tech University Health Sciences CenterLubbockUnited States
| | - Paul Avan
- Laboratoire de Biophysique SensorielleUniversité Clermont AuvergneClermont-FerrandFrance
- UMR 1107, Institut National de la Santé et de la Recherche MédicaleClermont-FerrandFrance
- Centre Jean PerrinClermont-FerrandFrance
| | - Shyam S Krishnakumar
- Department of Cell BiologyYale University School of MedicineNew HavenUnited States
- Department of Clinical and Experimental EpilepsyInstitute of Neurology, University College LondonLondonUnited Kingdom
| | - James E Rothman
- Department of Cell BiologyYale University School of MedicineNew HavenUnited States
- Department of Clinical and Experimental EpilepsyInstitute of Neurology, University College LondonLondonUnited Kingdom
| | - Didier Dulon
- UMRS 1120, Institut National de la Santé et de la Recherche MédicaleParisFrance
- Laboratoire de Neurophysiologie de la Synapse Auditive, Bordeaux NeurocampusUniversité de BordeauxBordeauxFrance
| | - Saaid Safieddine
- Unité de Génétique et Physiologie de l’AuditionInstitut PasteurParisFrance
- UMRS 1120, Institut National de la Santé et de la Recherche MédicaleParisFrance
- Sorbonne Universités, UPMC Université Paris 06, Complexité du VivantParisFrance
- Centre National de la Recherche ScientifiqueFrance
| | - Christine Petit
- Unité de Génétique et Physiologie de l’AuditionInstitut PasteurParisFrance
- UMRS 1120, Institut National de la Santé et de la Recherche MédicaleParisFrance
- Sorbonne Universités, UPMC Université Paris 06, Complexité du VivantParisFrance
- Syndrome de Usher et Autres Atteintes Rétino-CochléairesInstitut de la VisionParisFrance
- Collège de FranceParisFrance
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53
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Rothman JE, Krishnakumar SS, Grushin K, Pincet F. Hypothesis - buttressed rings assemble, clamp, and release SNAREpins for synaptic transmission. FEBS Lett 2017; 591:3459-3480. [PMID: 28983915 PMCID: PMC5698743 DOI: 10.1002/1873-3468.12874] [Citation(s) in RCA: 60] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2017] [Revised: 10/02/2017] [Accepted: 10/02/2017] [Indexed: 11/21/2022]
Abstract
Neural networks are optimized to detect temporal coincidence on the millisecond timescale. Here, we offer a synthetic hypothesis based on recent structural insights into SNAREs and the C2 domain proteins to explain how synaptic transmission can keep this pace. We suggest that an outer ring of up to six curved Munc13 ‘MUN’ domains transiently anchored to the plasma membrane via its flanking domains surrounds a stable inner ring comprised of synaptotagmin C2 domains to serve as a work‐bench on which SNAREpins are templated. This ‘buttressed‐ring hypothesis’ affords straightforward answers to many principal and long‐standing questions concerning how SNAREpins can be assembled, clamped, and then released synchronously with an action potential.
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Affiliation(s)
- James E Rothman
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA
| | - Shyam S Krishnakumar
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA
| | - Kirill Grushin
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA
| | - Frederic Pincet
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA.,Laboratoire de Physique Statistique, Ecole Normale Supérieure, PSL Research University, Université Paris Diderot Sorbonne Paris Cité, Sorbonne Universités UPMC Univ, CNRS, Paris, France
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54
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Praschberger R, Lowe SA, Malintan NT, Giachello CNG, Patel N, Houlden H, Kullmann DM, Baines RA, Usowicz MM, Krishnakumar SS, Hodge JJL, Rothman JE, Jepson JEC. Mutations in Membrin/GOSR2 Reveal Stringent Secretory Pathway Demands of Dendritic Growth and Synaptic Integrity. Cell Rep 2017; 21:97-109. [PMID: 28978487 PMCID: PMC5640804 DOI: 10.1016/j.celrep.2017.09.004] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2017] [Revised: 08/17/2017] [Accepted: 09/01/2017] [Indexed: 11/16/2022] Open
Abstract
Mutations in the Golgi SNARE (SNAP [soluble NSF attachment protein] receptor) protein Membrin (encoded by the GOSR2 gene) cause progressive myoclonus epilepsy (PME). Membrin is a ubiquitous and essential protein mediating ER-to-Golgi membrane fusion. Thus, it is unclear how mutations in Membrin result in a disorder restricted to the nervous system. Here, we use a multi-layered strategy to elucidate the consequences of Membrin mutations from protein to neuron. We show that the pathogenic mutations cause partial reductions in SNARE-mediated membrane fusion. Importantly, these alterations were sufficient to profoundly impair dendritic growth in Drosophila models of GOSR2-PME. Furthermore, we show that Membrin mutations cause fragmentation of the presynaptic cytoskeleton coupled with transsynaptic instability and hyperactive neurotransmission. Our study highlights how dendritic growth is vulnerable even to subtle secretory pathway deficits, uncovers a role for Membrin in synaptic function, and provides a comprehensive explanatory basis for genotype-phenotype relationships in GOSR2-PME.
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Affiliation(s)
- Roman Praschberger
- Department of Clinical and Experimental Epilepsy, UCL Institute of Neurology, London, UK
| | - Simon A Lowe
- School of Physiology, Pharmacology, and Neuroscience, University of Bristol, Bristol, UK
| | - Nancy T Malintan
- Department of Clinical and Experimental Epilepsy, UCL Institute of Neurology, London, UK
| | - Carlo N G Giachello
- Faculty of Biology, Medicine, and Health, Division of Neuroscience & Experimental Psychology, Manchester Academic Health Science Centre, University of Manchester, Manchester, UK
| | - Nian Patel
- Department of Clinical and Experimental Epilepsy, UCL Institute of Neurology, London, UK
| | - Henry Houlden
- Department of Molecular Neuroscience, UCL Institute of Neurology, London, UK
| | - Dimitri M Kullmann
- Department of Clinical and Experimental Epilepsy, UCL Institute of Neurology, London, UK
| | - Richard A Baines
- Faculty of Biology, Medicine, and Health, Division of Neuroscience & Experimental Psychology, Manchester Academic Health Science Centre, University of Manchester, Manchester, UK
| | - Maria M Usowicz
- School of Physiology, Pharmacology, and Neuroscience, University of Bristol, Bristol, UK
| | - Shyam S Krishnakumar
- Department of Clinical and Experimental Epilepsy, UCL Institute of Neurology, London, UK; Department of Cell Biology, Yale School of Medicine, New Haven, CT, USA
| | - James J L Hodge
- School of Physiology, Pharmacology, and Neuroscience, University of Bristol, Bristol, UK
| | - James E Rothman
- Department of Clinical and Experimental Epilepsy, UCL Institute of Neurology, London, UK; Department of Cell Biology, Yale School of Medicine, New Haven, CT, USA
| | - James E C Jepson
- Department of Clinical and Experimental Epilepsy, UCL Institute of Neurology, London, UK.
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55
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Krishnakumar SS, Li F, Coleman J, Schauder CM, Kümmel D, Pincet F, Rothman JE, Reinisch KM. Correction: Re-visiting the trans insertion model for complexin clamping. eLife 2017; 6. [PMID: 28880147 PMCID: PMC5589411 DOI: 10.7554/elife.31512] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2017] [Accepted: 08/24/2017] [Indexed: 11/13/2022] Open
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56
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Wang J, Li F, Bello OD, Sindelar CV, Pincet F, Krishnakumar SS, Rothman JE. Circular oligomerization is an intrinsic property of synaptotagmin. eLife 2017; 6. [PMID: 28850328 PMCID: PMC5576491 DOI: 10.7554/elife.27441] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2017] [Accepted: 08/11/2017] [Indexed: 11/13/2022] Open
Abstract
Previously, we showed that synaptotagmin1 (Syt1) forms Ca2+-sensitive ring-like oligomers on membranes containing acidic lipids and proposed a potential role in regulating neurotransmitter release (Zanetti et al., 2016). Here, we report that Syt1 assembles into similar ring-like oligomers in solution when triggered by naturally occurring polyphosphates (PIP2 and ATP) and magnesium ions (Mg2+). These soluble Syt1 rings were observed by electron microscopy and independently demonstrated and quantified using fluorescence correlation spectroscopy. Oligomerization is triggered when polyphosphates bind to the polylysine patch in C2B domain and is stabilized by Mg2+, which neutralizes the Ca2+-binding aspartic acids that likely contribute to the C2B interface in the oligomer. Overall, our data show that ring-like polymerization is an intrinsic property of Syt1 with reasonable affinity that can be triggered by the vesicle docking C2B-PIP2 interaction and raise the possibility that Syt1 rings could pre-form on the synaptic vesicle to facilitate docking.
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Affiliation(s)
- Jing Wang
- Departments of Cell Biology, Yale University School of Medicine, New Haven, United States
| | - Feng Li
- Departments of Cell Biology, Yale University School of Medicine, New Haven, United States
| | - Oscar D Bello
- Departments of Cell Biology, Yale University School of Medicine, New Haven, United States.,Department of Clinical and Experimental Epilepsy, Institute of Neurology, University College London, London, United Kingdom
| | - Charles Vaughn Sindelar
- Departments of Molecular Biophysics and Biochemistry, Yale University School of Medicine, New Haven, United States
| | - Frédéric Pincet
- Departments of Cell Biology, Yale University School of Medicine, New Haven, United States.,Laboratoire de Physique Statistique, UMR CNRS 8550 Associée aux Universités Paris 6 et Paris 7, Paris, France
| | - Shyam S Krishnakumar
- Departments of Cell Biology, Yale University School of Medicine, New Haven, United States.,Department of Clinical and Experimental Epilepsy, Institute of Neurology, University College London, London, United Kingdom
| | - James E Rothman
- Departments of Cell Biology, Yale University School of Medicine, New Haven, United States.,Department of Clinical and Experimental Epilepsy, Institute of Neurology, University College London, London, United Kingdom
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57
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Yue X, Bao M, Christiano R, Li S, Mei J, Zhu L, Mao F, Yue Q, Zhang P, Jing S, Rothman JE, Qian Y, Lee I. ACBD3 functions as a scaffold to organize the Golgi stacking proteins and a Rab33b-GAP. FEBS Lett 2017; 591:2793-2802. [PMID: 28777890 DOI: 10.1002/1873-3468.12780] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2017] [Revised: 07/19/2017] [Accepted: 07/22/2017] [Indexed: 01/24/2023]
Abstract
Golgin45 plays important roles in Golgi stack assembly and is known to bind both the Golgi stacking protein GRASP55 and Rab2 in the medial-Golgi cisternae. In this study, we sought to further characterize the cisternal adhesion complex using a proteomics approach. We report here that Acyl-CoA binding domain containing 3 (ACBD3) is likely to be a novel binding partner of Golgin45. ACBD3 interacts with Golgin45 via its GOLD domain, while its co-expression significantly increases Golgin45 targeting to the Golgi. Furthermore, ACBD3 recruits TBC1D22, a Rab33b GTPase activating protein (GAP), to a large multi-protein complex containing Golgin45 and GRASP55. These results suggest that ACBD3 may provide a scaffolding to organize the Golgi stacking proteins and a Rab33b-GAP at the medial-Golgi.
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Affiliation(s)
- Xihua Yue
- Shanghai Institute for Advanced Immunochemical Studies, ShanghaiTech University, China
| | - Mengjing Bao
- Shanghai Institute for Advanced Immunochemical Studies, ShanghaiTech University, China
| | - Romain Christiano
- Department of Genetics and Complex Diseases, School of Public Health, Harvard medical school, Boston, MA, USA
| | - Siyang Li
- Shanghai Institute for Advanced Immunochemical Studies, ShanghaiTech University, China.,Institute of Biochemistry and Cell Biology, Shanghai, China.,University of Chinese Academy of Sciences, Shanghai, China
| | - Jia Mei
- Shanghai Institute for Advanced Immunochemical Studies, ShanghaiTech University, China
| | - Lianhui Zhu
- Shanghai Institute for Advanced Immunochemical Studies, ShanghaiTech University, China
| | - Feifei Mao
- Shanghai Institute for Advanced Immunochemical Studies, ShanghaiTech University, China
| | - Qiang Yue
- Shanghai Institute for Advanced Immunochemical Studies, ShanghaiTech University, China.,Institute of Biochemistry and Cell Biology, Shanghai, China.,University of Chinese Academy of Sciences, Shanghai, China
| | - Panpan Zhang
- Shanghai Institute for Advanced Immunochemical Studies, ShanghaiTech University, China.,Institute of Biochemistry and Cell Biology, Shanghai, China.,University of Chinese Academy of Sciences, Shanghai, China
| | - Shuaiyang Jing
- Shanghai Institute for Advanced Immunochemical Studies, ShanghaiTech University, China.,Institute of Biochemistry and Cell Biology, Shanghai, China.,University of Chinese Academy of Sciences, Shanghai, China
| | - James E Rothman
- Shanghai Institute for Advanced Immunochemical Studies, ShanghaiTech University, China.,Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA
| | - Yi Qian
- Shanghai Institute for Advanced Immunochemical Studies, ShanghaiTech University, China
| | - Intaek Lee
- Shanghai Institute for Advanced Immunochemical Studies, ShanghaiTech University, China
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58
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Bottanelli F, Kilian N, Ernst AM, Rivera-Molina F, Schroeder LK, Kromann EB, Lessard MD, Erdmann RS, Schepartz A, Baddeley D, Bewersdorf J, Toomre D, Rothman JE. A novel physiological role for ARF1 in the formation of bidirectional tubules from the Golgi. Mol Biol Cell 2017; 28:1676-1687. [PMID: 28428254 PMCID: PMC5469610 DOI: 10.1091/mbc.e16-12-0863] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2017] [Revised: 04/11/2017] [Accepted: 04/14/2017] [Indexed: 11/11/2022] Open
Abstract
Capitalizing on CRISPR/Cas9 gene-editing techniques and super-resolution nanoscopy, we explore the role of the small GTPase ARF1 in mediating transport steps at the Golgi. Besides its well-established role in generating COPI vesicles, we find that ARF1 is also involved in the formation of long (∼3 µm), thin (∼110 nm diameter) tubular carriers. The anterograde and retrograde tubular carriers are both largely free of the classical Golgi coat proteins coatomer (COPI) and clathrin. Instead, they contain ARF1 along their entire length at a density estimated to be in the range of close packing. Experiments using a mutant form of ARF1 affecting GTP hydrolysis suggest that ARF1[GTP] is functionally required for the tubules to form. Dynamic confocal and stimulated emission depletion imaging shows that ARF1-rich tubular compartments fall into two distinct classes containing 1) anterograde cargoes and clathrin clusters or 2) retrograde cargoes and coatomer clusters.
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Affiliation(s)
- Francesca Bottanelli
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06520
| | - Nicole Kilian
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06520
| | - Andreas M Ernst
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06520
| | - Felix Rivera-Molina
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06520
| | - Lena K Schroeder
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06520
| | - Emil B Kromann
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06520.,Department of Biomedical Engineering, Yale University, New Haven, CT 06520
| | - Mark D Lessard
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06520
| | - Roman S Erdmann
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06520.,Department of Chemistry, Yale University, New Haven, CT 06520
| | - Alanna Schepartz
- Department of Chemistry, Yale University, New Haven, CT 06520.,Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, CT 06520
| | - David Baddeley
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06520.,Nanobiology Institute, Yale University, West Haven, CT 06516
| | - Joerg Bewersdorf
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06520.,Department of Biomedical Engineering, Yale University, New Haven, CT 06520.,Nanobiology Institute, Yale University, West Haven, CT 06516
| | - Derek Toomre
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06520.,Nanobiology Institute, Yale University, West Haven, CT 06516
| | - James E Rothman
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06520 .,Nanobiology Institute, Yale University, West Haven, CT 06516
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59
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Chelban V, Patel N, Vandrovcova J, Zanetti MN, Lynch DS, Ryten M, Botía JA, Bello O, Tribollet E, Efthymiou S, Davagnanam I, Bashiri FA, Wood NW, Rothman JE, Alkuraya FS, Houlden H, Houlden H. Mutations in NKX6-2 Cause Progressive Spastic Ataxia and Hypomyelination. Am J Hum Genet 2017; 100:969-977. [PMID: 28575651 PMCID: PMC5473715 DOI: 10.1016/j.ajhg.2017.05.009] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2017] [Accepted: 05/08/2017] [Indexed: 11/29/2022] Open
Abstract
Progressive limb spasticity and cerebellar ataxia are frequently found together in clinical practice and form a heterogeneous group of degenerative disorders that are classified either as pure spastic ataxia or as complex spastic ataxia with additional neurological signs. Inheritance is either autosomal dominant or autosomal recessive. Hypomyelinating features on MRI are sometimes seen with spastic ataxia, but this is usually mild in adults and severe and life limiting in children. We report seven individuals with an early-onset spastic-ataxia phenotype. The individuals come from three families of different ethnic backgrounds. Affected members of two families had childhood onset disease with very slow progression. They are still alive in their 30s and 40s and show predominant ataxia and cerebellar atrophy features on imaging. Affected members of the third family had a similar but earlier-onset presentation associated with brain hypomyelination. Using a combination of homozygozity mapping and exome sequencing, we mapped this phenotype to deleterious nonsense or homeobox domain missense mutations in NKX6-2. NKX6-2 encodes a transcriptional repressor with early high general and late focused CNS expression. Deficiency of its mouse ortholog results in widespread hypomyelination in the brain and optic nerve, as well as in poor motor coordination in a pattern consistent with the observed human phenotype. In-silico analysis of human brain expression and network data provides evidence that NKX6-2 is involved in oligodendrocyte maturation and might act within the same pathways of genes already associated with central hypomyelination. Our results support a non-redundant developmental role of NKX6-2 in humans and imply that NKX6-2 mutations should be considered in the differential diagnosis of spastic ataxia and hypomyelination.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | - Henry Houlden
- Department of Molecular Neuroscience, University College London, London WC1N 3BG, UK; Neurogenetics Laboratory, The National Hospital for Neurology and Neurosurgery, London WC1N 3BG, UK
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60
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Salpietro V, Lin W, Vedove AD, Storbeck M, Liu Y, Efthymiou S, Manole A, Wiethoff S, Ye Q, Saggar A, McElreavey K, Krishnakumar SS, Pitt M, Bello OD, Rothman JE, Basel‐Vanagaite L, Hubshman MW, Aharoni S, Manzur AY, Wirth B, Houlden H. Homozygous mutations in VAMP1 cause a presynaptic congenital myasthenic syndrome. Ann Neurol 2017; 81:597-603. [PMID: 28253535 PMCID: PMC5413866 DOI: 10.1002/ana.24905] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2016] [Revised: 02/24/2017] [Accepted: 02/24/2017] [Indexed: 11/07/2022]
Abstract
We report 2 families with undiagnosed recessive presynaptic congenital myasthenic syndrome (CMS). Whole exome or genome sequencing identified segregating homozygous variants in VAMP1: c.51_64delAGGTGGGGGTCCCC in a Kuwaiti family and c.146G>C in an Israeli family. VAMP1 is crucial for vesicle fusion at presynaptic neuromuscular junction (NMJ). Electrodiagnostic examination showed severely low compound muscle action potentials and presynaptic impairment. We assessed the effect of the nonsense mutation on mRNA levels and evaluated the NMJ transmission in VAMP1lew/lew mice, observing neurophysiological features of presynaptic impairment, similar to the patients. Taken together, our findings highlight VAMP1 homozygous mutations as a cause of presynaptic CMS. Ann Neurol 2017;81:597–603
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Affiliation(s)
- Vincenzo Salpietro
- Department of Molecular Neuroscience, Institute of NeurologyUniversity College London Institute of NeurologyLondonUnited Kingdom
| | - Weichun Lin
- Department of NeuroscienceUniversity of Texas Southwestern Medical CenterDallasTX
| | - Andrea Delle Vedove
- Institute of Human Genetics, Center for Molecular Medicine CologneCologneGermany
- Institute for GeneticsUniversity of CologneCologneGermany
| | - Markus Storbeck
- Institute of Human Genetics, Center for Molecular Medicine CologneCologneGermany
- Institute for GeneticsUniversity of CologneCologneGermany
| | - Yun Liu
- Department of NeuroscienceUniversity of Texas Southwestern Medical CenterDallasTX
| | - Stephanie Efthymiou
- Department of Molecular Neuroscience, Institute of NeurologyUniversity College London Institute of NeurologyLondonUnited Kingdom
| | - Andreea Manole
- Department of Molecular Neuroscience, Institute of NeurologyUniversity College London Institute of NeurologyLondonUnited Kingdom
| | - Sarah Wiethoff
- Department of Molecular Neuroscience, Institute of NeurologyUniversity College London Institute of NeurologyLondonUnited Kingdom
| | - Qiaohong Ye
- Department of NeuroscienceUniversity of Texas Southwestern Medical CenterDallasTX
| | - Anand Saggar
- St George's Hospital, National Health Service Foundation TrustLondonUnited Kingdom
| | | | - Shyam S. Krishnakumar
- Department of Cell BiologyYale School of MedicineNew HavenCT
- Department of Clinical and Experimental EpilepsyUniversity College London Institute of NeurologyLondonUnited Kingdom
| | | | - Matthew Pitt
- Department of Clinical NeurophysiologyGreat Ormond Street Hospital for Children, National Health Service Foundation TrustLondonUnited Kingdom
| | - Oscar D. Bello
- Department of Cell BiologyYale School of MedicineNew HavenCT
- Department of Clinical and Experimental EpilepsyUniversity College London Institute of NeurologyLondonUnited Kingdom
| | - James E. Rothman
- Department of Cell BiologyYale School of MedicineNew HavenCT
- Department of Clinical and Experimental EpilepsyUniversity College London Institute of NeurologyLondonUnited Kingdom
| | - Lina Basel‐Vanagaite
- Pediatric Genetics Unit, Schneider Children's Medical Center of IsraelPetach TikvaIsrael
- Raphael Recanati Genetic Institute, Rabin Medical CenterPetach TikvaIsrael
- Sackler Faculty of MedicineTel Aviv UniversityTel AvivIsrael
| | - Monika Weisz Hubshman
- Pediatric Genetics Unit, Schneider Children's Medical Center of IsraelPetach TikvaIsrael
- Raphael Recanati Genetic Institute, Rabin Medical CenterPetach TikvaIsrael
- Sackler Faculty of MedicineTel Aviv UniversityTel AvivIsrael
| | - Sharon Aharoni
- Sackler Faculty of MedicineTel Aviv UniversityTel AvivIsrael
- Institute of Child Neurology, Schneider Children's Medical Center of IsraelPetach TikvaIsrael
| | - Adnan Y. Manzur
- Department of Pediatric NeurologyDubowitz Neuromuscular Centre, Great Ormond Street Hospital for Children National Health Service Foundation TrustLondonUnited Kingdom
| | - Brunhilde Wirth
- Institute of Human Genetics, Center for Molecular Medicine CologneCologneGermany
| | - Henry Houlden
- Department of Molecular Neuroscience, Institute of NeurologyUniversity College London Institute of NeurologyLondonUnited Kingdom
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61
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Gruget C, Coleman J, Krishankumar S, Rothman JE, Pincet F, Donaldson S. Synaptotagmin Interactions with Membranes: Measuring the Force of Calcium Triggering of Neurotransmission. Biophys J 2017. [DOI: 10.1016/j.bpj.2016.11.220] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
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62
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Huang F, Sirinakis G, Allgeyer ES, Schroeder LK, Duim WC, Kromann EB, Phan T, Rivera-Molina FE, Myers JR, Irnov I, Lessard M, Zhang Y, Handel MA, Jacobs-Wagner C, Lusk CP, Rothman JE, Toomre D, Booth MJ, Bewersdorf J. Ultra-High Resolution 3D Imaging of Whole Cells. Cell 2016; 166:1028-1040. [PMID: 27397506 PMCID: PMC5005454 DOI: 10.1016/j.cell.2016.06.016] [Citation(s) in RCA: 177] [Impact Index Per Article: 22.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2016] [Revised: 05/02/2016] [Accepted: 06/03/2016] [Indexed: 12/23/2022]
Abstract
Fluorescence nanoscopy, or super-resolution microscopy, has become an important tool in cell biological research. However, because of its usually inferior resolution in the depth direction (50-80 nm) and rapidly deteriorating resolution in thick samples, its practical biological application has been effectively limited to two dimensions and thin samples. Here, we present the development of whole-cell 4Pi single-molecule switching nanoscopy (W-4PiSMSN), an optical nanoscope that allows imaging of three-dimensional (3D) structures at 10- to 20-nm resolution throughout entire mammalian cells. We demonstrate the wide applicability of W-4PiSMSN across diverse research fields by imaging complex molecular architectures ranging from bacteriophages to nuclear pores, cilia, and synaptonemal complexes in large 3D cellular volumes.
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Affiliation(s)
- Fang Huang
- Department of Cell Biology, School of Medicine, Yale University, New Haven, CT 06520, USA; Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN 47907, USA
| | - George Sirinakis
- Department of Cell Biology, School of Medicine, Yale University, New Haven, CT 06520, USA; The Gurdon Institute, University of Cambridge, Cambridge CB2 1QN, UK
| | - Edward S Allgeyer
- Department of Cell Biology, School of Medicine, Yale University, New Haven, CT 06520, USA; The Gurdon Institute, University of Cambridge, Cambridge CB2 1QN, UK
| | - Lena K Schroeder
- Department of Cell Biology, School of Medicine, Yale University, New Haven, CT 06520, USA
| | - Whitney C Duim
- Department of Cell Biology, School of Medicine, Yale University, New Haven, CT 06520, USA; Department of Chemistry, Harvey Mudd College, Claremont, CA 91711, USA
| | - Emil B Kromann
- Department of Cell Biology, School of Medicine, Yale University, New Haven, CT 06520, USA; Department of Biomedical Engineering, Yale University, CT 06520, USA
| | - Thomy Phan
- Department of Cell Biology, School of Medicine, Yale University, New Haven, CT 06520, USA
| | - Felix E Rivera-Molina
- Department of Cell Biology, School of Medicine, Yale University, New Haven, CT 06520, USA
| | - Jordan R Myers
- Department of Cell Biology, School of Medicine, Yale University, New Haven, CT 06520, USA
| | - Irnov Irnov
- Microbial Sciences Institute, Yale University, West Haven, CT 06516, USA; Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT 06520, USA
| | - Mark Lessard
- The Jackson Laboratory, Bar Harbor, ME 04609, USA
| | - Yongdeng Zhang
- Department of Cell Biology, School of Medicine, Yale University, New Haven, CT 06520, USA
| | | | - Christine Jacobs-Wagner
- Microbial Sciences Institute, Yale University, West Haven, CT 06516, USA; Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT 06520, USA; Howard Hughes Medical Institute, Yale University, New Haven, CT 06520, USA; Department of Microbial Pathogenesis, Yale School of Medicine, New Haven, CT 06520, USA
| | - C Patrick Lusk
- Department of Cell Biology, School of Medicine, Yale University, New Haven, CT 06520, USA
| | - James E Rothman
- Department of Cell Biology, School of Medicine, Yale University, New Haven, CT 06520, USA; Nanobiology Institute, Yale University, West Haven, CT 06516, USA
| | - Derek Toomre
- Department of Cell Biology, School of Medicine, Yale University, New Haven, CT 06520, USA; Nanobiology Institute, Yale University, West Haven, CT 06516, USA
| | - Martin J Booth
- Department of Engineering Science, University of Oxford, Oxford OX1 3PJ, UK; Centre for Neural Circuits and Behaviour, University of Oxford, Oxford OX1 3SR, UK
| | - Joerg Bewersdorf
- Department of Cell Biology, School of Medicine, Yale University, New Haven, CT 06520, USA; Department of Biomedical Engineering, Yale University, CT 06520, USA; Nanobiology Institute, Yale University, West Haven, CT 06516, USA.
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63
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Zanetti MN, Bello OD, Wang J, Coleman J, Cai Y, Sindelar CV, Rothman JE, Krishnakumar SS. Ring-like oligomers of Synaptotagmins and related C2 domain proteins. eLife 2016; 5. [PMID: 27434670 PMCID: PMC4977156 DOI: 10.7554/elife.17262] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2016] [Accepted: 07/18/2016] [Indexed: 01/25/2023] Open
Abstract
We recently reported that the C2AB portion of Synaptotagmin 1 (Syt1) could self-assemble into Ca(2+)-sensitive ring-like oligomers on membranes, which could potentially regulate neurotransmitter release. Here we report that analogous ring-like oligomers assemble from the C2AB domains of other Syt isoforms (Syt2, Syt7, Syt9) as well as related C2 domain containing protein, Doc2B and extended Synaptotagmins (E-Syts). Evidently, circular oligomerization is a general and conserved structural aspect of many C2 domain proteins, including Synaptotagmins. Further, using electron microscopy combined with targeted mutations, we show that under physiologically relevant conditions, both the Syt1 ring assembly and its rapid disruption by Ca(2+) involve the well-established functional surfaces on the C2B domain that are important for synaptic transmission. Our data suggests that ring formation may be triggered at an early step in synaptic vesicle docking and positions Syt1 to synchronize neurotransmitter release to Ca(2+) influx.
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Affiliation(s)
- Maria N Zanetti
- Department of Cell Biology, Yale School of Medicine, New Haven, United States
| | - Oscar D Bello
- Department of Cell Biology, Yale School of Medicine, New Haven, United States
| | - Jing Wang
- Department of Cell Biology, Yale School of Medicine, New Haven, United States
| | - Jeff Coleman
- Department of Cell Biology, Yale School of Medicine, New Haven, United States
| | - Yiying Cai
- Department of Cell Biology, Yale School of Medicine, New Haven, United States
| | - Charles V Sindelar
- Department of Molecular Biophysics and Biochemistry, Yale School of Medicine, New Haven, United States
| | - James E Rothman
- Department of Cell Biology, Yale School of Medicine, New Haven, United States
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64
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Dancourt J, Zheng H, Bottanelli F, Allgeyer ES, Bewersdorf J, Graham M, Liu X, Rothman JE, Lavieu G. Small cargoes pass through synthetically glued Golgi stacks. FEBS Lett 2016; 590:1675-86. [PMID: 27174538 PMCID: PMC4925213 DOI: 10.1002/1873-3468.12210] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2016] [Revised: 05/02/2016] [Accepted: 05/09/2016] [Indexed: 11/07/2022]
Abstract
How are proteins transported across the stacked cisternae of the Golgi apparatus? Do they stay within the cisterna while the latter matures and progresses in an anterograde manner, or do they navigate between the cisternae via vesicles? Using synthetic biology, we engineered new tools designed to stabilize intercisternal adhesion such that Golgi cisternae are literally glued together, thus preventing any possible cisternal progression. Using bulk secretory assays and single-cell live imaging, we observed that small cargoes (but not large aggregated cargoes including collagen) still transited through glued Golgi, although the rate of transport was moderately reduced. ARF1, whose membrane recruitment is required for budding COPI vesicles, continues to cycle on and off glued Golgi. Numerous COPI-size vesicles were intercalated among the glued Golgi cisternae. These results suggest that cisternal progression is not required for anterograde transport, but do not address the possibility of cisternal maturation in situ.
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Affiliation(s)
- Julia Dancourt
- Department of Cell Biology, School of Medicine, Yale University, New Haven, CT, USA
| | - Hong Zheng
- Department of Cell Biology, School of Medicine, Yale University, New Haven, CT, USA
| | - Francesca Bottanelli
- Department of Cell Biology, School of Medicine, Yale University, New Haven, CT, USA
| | - Edward S Allgeyer
- Department of Cell Biology, School of Medicine, Yale University, New Haven, CT, USA
| | - Joerg Bewersdorf
- Department of Cell Biology, School of Medicine, Yale University, New Haven, CT, USA
| | - Morven Graham
- Department of Cell Biology, School of Medicine, Yale University, New Haven, CT, USA
| | - Xinran Liu
- Department of Cell Biology, School of Medicine, Yale University, New Haven, CT, USA
| | - James E Rothman
- Department of Cell Biology, School of Medicine, Yale University, New Haven, CT, USA
| | - Grégory Lavieu
- Department of Cell Biology, School of Medicine, Yale University, New Haven, CT, USA
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65
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Abstract
Here we introduce ApoE-based nanolipoprotein particle (NLP)-a soluble, discoidal bilayer mimetic of ∼23 nm in diameter, as fusion partners to study the dynamics of fusion pores induced by SNARE proteins. Using in vitro lipid mixing and content release assays, we report that NLPs reconstituted with synaptic v-SNARE VAMP2 (vNLP) fuse with liposomes containing the cognate t-SNARE (Syntaxin1/SNAP25) partner, with the resulting fusion pore opening directly to the external buffer. Efflux of encapsulated fluorescent dextrans of different sizes show that unlike the smaller nanodiscs, these larger NLPs accommodate the expansion of the fusion pore to at least ∼9 nm, and dithionite quenching of fluorescent lipid introduced in vNLP confirms that the NLP fusion pores are short-lived and eventually reseal. The NLPs also have capacity to accommodate larger number of proteins and using vNLPs with defined number of VAMP2 protein, including physiologically relevant copy numbers, we find that 3-4 copies of VAMP2 (minimum 2 per face) are required to keep a nascent fusion pore open, and the SNARE proteins act cooperatively to dilate the nascent fusion pore.
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66
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Xu W, Nathwani B, Lin C, Wang J, Karatekin E, Pincet F, Shih W, Rothman JE. A Programmable DNA Origami Platform to Organize SNAREs for Membrane Fusion. J Am Chem Soc 2016; 138:4439-47. [PMID: 26938705 DOI: 10.1021/jacs.5b13107] [Citation(s) in RCA: 67] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complexes are the core molecular machinery of membrane fusion, a fundamental process that drives inter- and intracellular communication and trafficking. One of the questions that remains controversial has been whether and how SNAREs cooperate. Here we show the use of self-assembled DNA-nanostructure rings to template uniform-sized small unilamellar vesicles containing predetermined maximal number of externally facing SNAREs to study the membrane-fusion process. We also incorporated lipid-conjugated complementary ssDNA as tethers into vesicle and target membranes, which enabled bypass of the rate-limiting docking step of fusion reactions and allowed direct observation of individual membrane-fusion events at SNARE densities as low as one pair per vesicle. With this platform, we confirmed at the single event level that, after docking of the templated-SUVs to supported lipid bilayers (SBL), one to two pairs of SNAREs are sufficient to drive fast lipid mixing. Modularity and programmability of this platform makes it readily amenable to studying more complicated systems where auxiliary proteins are involved.
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Affiliation(s)
| | - Bhavik Nathwani
- Wyss Institute for Biologically Inspired Engineering and Biological Chemistry and Molecular Pharmacology, Harvard Medical School, and Department of Cancer Biology, Dana Farber Cancer Institute , Boston, Massachusetts 02115, United States
| | - Chenxiang Lin
- Wyss Institute for Biologically Inspired Engineering and Biological Chemistry and Molecular Pharmacology, Harvard Medical School, and Department of Cancer Biology, Dana Farber Cancer Institute , Boston, Massachusetts 02115, United States
| | | | - Erdem Karatekin
- Laboratoire de Neurophotonique, Université Paris Descartes, Faculté des Sciences Fondamentales et Biomédicales, Centre National de la Recherche Scientifique (CNRS) UMR8250, 45, rue des Saints Pères, 75270 Cedex 06 Paris, France
| | - Frederic Pincet
- Laboratoire de Physique Statistique, Ecole Normale Supérieure de Paris, Université Pierre et Marie Curie, Université Paris Diderot, Centre National de la Recherche Scientifique, UMR 8550, 24 rue Lhomond, 75005 Paris, France
| | - William Shih
- Wyss Institute for Biologically Inspired Engineering and Biological Chemistry and Molecular Pharmacology, Harvard Medical School, and Department of Cancer Biology, Dana Farber Cancer Institute , Boston, Massachusetts 02115, United States
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67
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François-Martin C, Rothman JE, Pincet F. Experimental Measurement of the Activation Energy of Phospholipid Membrane Fusion. Biophys J 2016. [DOI: 10.1016/j.bpj.2015.11.2778] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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68
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69
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Xu W, Wang J, Rothman JE, Pincet F. Accelerating SNARE-Mediated Membrane Fusion by DNA-Lipid Tethers. Angew Chem Int Ed Engl 2015; 54:14388-92. [PMID: 26439984 DOI: 10.1002/anie.201506844] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2015] [Indexed: 11/08/2022]
Abstract
SNARE proteins are the core machinery to drive fusion of a vesicle with its target membrane. Inspired by the tethering proteins that bridge the membranes and thus prepare SNAREs for docking and fusion, we developed a lipid-conjugated ssDNA mimic that is capable of regulating SNARE function, in situ. The DNA-lipid tethers consist of a 21 base pairs binding segment at the membrane distal end that can bridge two liposomes via specific base-pair hybridization. A linker at the membrane proximal end is used to control the separation distance between the liposomes. In the presence of these artificial tethers, SNARE-mediated lipid mixing is significantly accelerated, and the maximum fusion rate is obtained with the linker shorter than 40 nucleotides. As a programmable tool orthogonal to any native proteins, the DNA-lipid tethers can be further applied to regulate other biological processes where capturing and bridging of two membranes are the prerequisites for the subsequent protein function.
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Affiliation(s)
- Weiming Xu
- Nanobiology Institute, Yale University, West Haven, CT 06516 (USA).,Yale University, Department of Cell Biology, School of Medicine, New Haven, CT 06511 (USA)
| | - Jing Wang
- Nanobiology Institute, Yale University, West Haven, CT 06516 (USA).,Yale University, Department of Cell Biology, School of Medicine, New Haven, CT 06511 (USA)
| | - James E Rothman
- Nanobiology Institute, Yale University, West Haven, CT 06516 (USA). .,Yale University, Department of Cell Biology, School of Medicine, New Haven, CT 06511 (USA).
| | - Frédéric Pincet
- Nanobiology Institute, Yale University, West Haven, CT 06516 (USA). .,Yale University, Department of Cell Biology, School of Medicine, New Haven, CT 06511 (USA). .,Laboratoire de Physique Statistique, Ecole Normale Supérieure de Paris, Université Pierre et Marie Curie, Université Paris Diderot, Centre National de la Recherche Scientifique, Paris, 75005 (France).
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70
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Motta I, Gohlke A, Adrien V, Li F, Gardavot H, Rothman JE, Pincet F. Correction to Formation of Giant Unilamellar Proteo-Liposomes by Osmotic Shock. Langmuir 2015; 31:9521. [PMID: 26293386 DOI: 10.1021/acs.langmuir.5b02955] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
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71
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Abstract
Giant unilamellar vesicles (GUVs), composed of a phospholipid bilayer, are often used as a model system for cell membranes. However, the study of proteo-membrane interactions in this system is limited as the incorporation of integral and lipid-anchored proteins into GUVs remains challenging. Here, we present a simple generic method to incorporate proteins into GUVs. The basic principle is to break proteo-liposomes with an osmotic shock. They subsequently reseal into larger vesicles which, if necessary, can endure the same to obtain even larger proteo-GUVs. This process does not require specific lipids or reagents, works under physiological conditions with high concentrations of protein, the proteins remains functional after incorporation. The resulting proteo-GUVs can be micromanipulated. Moreover, our protocol is valid for a wide range of protein substrates. We have successfully reconstituted three structurally different proteins, two trans-membrane proteins (TolC and the neuronal t-SNARE), and one lipid-anchored peripheral protein (GABARAP-Like 1 (GL1)). In each case, we verified that the protein remains active after incorporation and in its correctly folded state. We also measured their mobility by performing diffusion measurements via fluorescence recovery after photobleaching (FRAP) experiments on micromanipulated single GUVs. The diffusion coefficients are in agreement with previous data.
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Affiliation(s)
- Isabelle Motta
- Laboratoire de Physique Statistique, Ecole Normale Supérieure de Paris, Université Pierre et Marie Curie, Université Paris Diderot, Centre National de la Recherche Scientifique, UMR 8550, 24 rue Lhomond, 75005 Paris, France
| | - Andrea Gohlke
- Laboratoire de Physique Statistique, Ecole Normale Supérieure de Paris, Université Pierre et Marie Curie, Université Paris Diderot, Centre National de la Recherche Scientifique, UMR 8550, 24 rue Lhomond, 75005 Paris, France
- Department of Cell Biology, Nanobiology Institute, School of Medicine, Yale University, 333 Cedar Street, New Haven, CT 06520, USA
| | - Vladimir Adrien
- Laboratoire de Physique Statistique, Ecole Normale Supérieure de Paris, Université Pierre et Marie Curie, Université Paris Diderot, Centre National de la Recherche Scientifique, UMR 8550, 24 rue Lhomond, 75005 Paris, France
- Laboratoire de Cristallographie et RMN Biologiques, Université Paris Descartes, CNRS, UMR 8015, Paris, France
| | - Feng Li
- Department of Cell Biology, Nanobiology Institute, School of Medicine, Yale University, 333 Cedar Street, New Haven, CT 06520, USA
| | - Hélène Gardavot
- Laboratoire de Physique Statistique, Ecole Normale Supérieure de Paris, Université Pierre et Marie Curie, Université Paris Diderot, Centre National de la Recherche Scientifique, UMR 8550, 24 rue Lhomond, 75005 Paris, France
| | - James E. Rothman
- Department of Cell Biology, Nanobiology Institute, School of Medicine, Yale University, 333 Cedar Street, New Haven, CT 06520, USA
| | - Frederic Pincet
- Laboratoire de Physique Statistique, Ecole Normale Supérieure de Paris, Université Pierre et Marie Curie, Université Paris Diderot, Centre National de la Recherche Scientifique, UMR 8550, 24 rue Lhomond, 75005 Paris, France
- Department of Cell Biology, Nanobiology Institute, School of Medicine, Yale University, 333 Cedar Street, New Haven, CT 06520, USA
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72
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Krishnakumar SS, Li F, Coleman J, Schauder CM, Kümmel D, Pincet F, Rothman JE, Reinisch KM. Re-visiting the trans insertion model for complexin clamping. eLife 2015; 4. [PMID: 25831964 PMCID: PMC4384536 DOI: 10.7554/elife.04463] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2014] [Accepted: 03/02/2015] [Indexed: 12/03/2022] Open
Abstract
We have previously proposed that complexin cross-links multiple pre-fusion SNARE complexes via a trans interaction to function as a clamp on SNARE-mediated neurotransmitter release. A recent NMR study was unable to detect the trans clamping interaction of complexin and therefore questioned the previous interpretation of the fluorescence resonance energy transfer and isothermal titration calorimetry data on which the trans clamping model was originally based. Here we present new biochemical data that underscore the validity of our previous interpretation and the continued relevancy of the trans insertion model for complexin clamping. DOI:http://dx.doi.org/10.7554/eLife.04463.001 Molecules called neurotransmitters are used to carry signals between neurons. The neurotransmitters in the first neuron are stored in small bubble-like structures called synaptic vesicles. When this neuron is ready to send a signal to a second neuron, the membrane that encloses the synaptic vesicle fuses with the cell membrane that surrounds the neuron. This involves SNARE proteins in the vesicle membrane interacting with similar proteins in the cell membrane to form a SNARE complex, which then proceeds to ‘zip’ the two membranes together. Other proteins are involved in the fusion process and the release of the neurotransmitters. For example, complexins bind to SNARE proteins during the formation of the SNARE complex in order to temporarily halt the fusion process. This ‘clamping’ interaction ensures that the neurotransmitters are released at the appropriate time. Researchers have proposed two different models of the clamping interaction. In the trans clamping model a region in the complexins called the accessory helix extends forward and clamps SNARE proteins that are present on the two membranes. An alternative model explains clamping in terms of electrostatic interactions between the accessory helix and the two membranes. These interactions are repulsive because the accessory helix and the membranes are all negatively charged. Now Krishnakumar, Li et al.—including some of the researchers who first proposed the trans clamping model—have used a variety of biochemical techniques to re-examine the clamping interaction. These experiments support the idea that the accessory helix binds to and clamps a SNARE protein, as suggested by the trans clamping model. The results of recent in vivo experiments on fruit flies have also provided support for the trans clamping model, although further work is need to compare the models in both in vitro and in vivo systems. DOI:http://dx.doi.org/10.7554/eLife.04463.002
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Affiliation(s)
- Shyam S Krishnakumar
- Department of Cell Biology, Yale University School of Medicine, New Haven, United States
| | - Feng Li
- Department of Cell Biology, Yale University School of Medicine, New Haven, United States
| | - Jeff Coleman
- Department of Cell Biology, Yale University School of Medicine, New Haven, United States
| | - Curtis M Schauder
- Department of Cell Biology, Yale University School of Medicine, New Haven, United States
| | - Daniel Kümmel
- Department of Cell Biology, Yale University School of Medicine, New Haven, United States.,School of Biology/Chemistry, Univeristät Osnabrück, Osnabrück, Germany
| | - Frederic Pincet
- Department of Cell Biology, Yale University School of Medicine, New Haven, United States.,Laboratoire de Physique Statistique, UMR CNRS 8550 Associée aux Unive, Ecole Normale Supérieure, Paris, France
| | - James E Rothman
- Department of Cell Biology, Yale University School of Medicine, New Haven, United States
| | - Karin M Reinisch
- Department of Cell Biology, Yale University School of Medicine, New Haven, United States
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73
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Zhu J, Rothman JE. Mechanical Model for Self-Assembly of Synaptotagmin on a Lipid Membrane. Biophys J 2015. [DOI: 10.1016/j.bpj.2014.11.2243] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022] Open
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74
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Krishnakumar SS, Kümmel D, Jones SJ, Radoff DT, Reinisch KM, Rothman JE. Conformational dynamics of calcium-triggered activation of fusion by synaptotagmin. Biophys J 2014; 105:2507-16. [PMID: 24314081 DOI: 10.1016/j.bpj.2013.10.029] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2013] [Revised: 10/11/2013] [Accepted: 10/23/2013] [Indexed: 01/03/2023] Open
Abstract
Synaptotagmin triggers rapid exocytosis of neurotransmitters from synaptic vesicles in response to Calcium (Ca(2+)) ions. Here, we use a novel Nanodisc-based system, designed to be a soluble mimetic of the clamped synaptic vesicle-bilayer junction, combined with fluorescence resonance energy transfer (FRET) spectroscopy to monitor the structural relationships among SNAREs (soluble N-ethylmaleimide-sensitive factor attachment protein receptor), Synaptotagmin C2 domains, and the lipid bilayer in real time during the Ca(2+)-activation process. We report that Synaptotagmin remains rigidly fixed on the partially assembled SNARE complex with no detectable internal rearrangement of its C2 domains, even as it rapidly inserts into the bilayer. We hypothesize that this straightforward, one-step physical mechanism could explain how this Ca(2+)- sensor rapidly activates neurotransmitter release from the clamped state.
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Affiliation(s)
- Shyam S Krishnakumar
- Department of Cell Biology, Yale University School of Medicine, New Haven, Connecticut.
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75
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Zorman S, Rebane AA, Ma L, Yang G, Molski MA, Coleman J, Pincet F, Rothman JE, Zhang Y. Common intermediates and kinetics, but different energetics, in the assembly of SNARE proteins. eLife 2014; 3:e03348. [PMID: 25180101 PMCID: PMC4166003 DOI: 10.7554/elife.03348] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2014] [Accepted: 08/29/2014] [Indexed: 01/10/2023] Open
Abstract
Soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) are evolutionarily conserved machines that couple their folding/assembly to membrane fusion. However, it is unclear how these processes are regulated and function. To determine these mechanisms, we characterized the folding energy and kinetics of four representative SNARE complexes at a single-molecule level using high-resolution optical tweezers. We found that all SNARE complexes assemble by the same step-wise zippering mechanism: slow N-terminal domain (NTD) association, a pause in a force-dependent half-zippered intermediate, and fast C-terminal domain (CTD) zippering. The energy release from CTD zippering differs for yeast (13 kBT) and neuronal SNARE complexes (27 kBT), and is concentrated at the C-terminal part of CTD zippering. Thus, SNARE complexes share a conserved zippering pathway and polarized energy release to efficiently drive membrane fusion, but generate different amounts of zippering energy to regulate fusion kinetics. DOI:http://dx.doi.org/10.7554/eLife.03348.001 Many processes in living things need molecules to be transported within, or between, cells. For example, damaged or waste molecules are transported within a cell to structures that can break the molecules down, while nerve impulses are transmitted from one neuron to the next via the release of signaling molecules. Cells—and the compartments within cells—are surrounded by membranes that act as barriers to certain molecules. Vesicles are small, membrane-enclosed packages that are used to transport molecules between different membranes; and in order to release its cargo, a vesicle must fuse with its target membrane. To fuse like this, the forces that act to push membranes away from one another need to be overcome. Proteins called SNARES, which are embedded in both membranes, are the molecular engines that power the fusion process. Once the SNARE proteins from the vesicle and the target membrane bind, they assemble into a more compact complex that pulls the two membranes close together and allows fusion to take place. The final shape of an assembled SNARE complex is essentially the same for all SNARE complexes; however, it is not known whether all of these complexes fold using the same method. Now Zorman et al. have used optical tweezers—an instrument that uses a highly focused laser beam to hold and manipulate microscopic objects—to observe the folding and unfolding of four different types of SNARE complex. All four SNARE complexes followed the same step-by-step process: the leading ends of the SNARE proteins slowly bound to each other; the process paused; then the rest of the proteins rapidly ‘zippered’ together. Zorman et al. revealed that, although the steps in the processes were the same, the energy released in the last step was different when different complexes assembled. This suggests that the energy released by the ‘zippering’ of different SNARE proteins is optimized to match the required speed of different membrane fusion events. Furthermore, Zorman et al. propose that the reason why the majority of energy is released in the later stages of complex assembly is because this is when the repulsion between the two membranes is strongest. The discoveries of Zorman et al. will now aid future efforts aimed at understanding better how the numerous other proteins that interact with SNARE proteins regulate the process of membrane fusion. DOI:http://dx.doi.org/10.7554/eLife.03348.002
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Affiliation(s)
- Sylvain Zorman
- Department of Cell Biology, Yale University School of Medicine, New Haven, United States
| | | | - Lu Ma
- Department of Cell Biology, Yale University School of Medicine, New Haven, United States
| | - Guangcan Yang
- Department of Cell Biology, Yale University School of Medicine, New Haven, United States
| | - Matthew A Molski
- Department of Cell Biology, Yale University School of Medicine, New Haven, United States
| | - Jeff Coleman
- Department of Cell Biology, Yale University School of Medicine, New Haven, United States
| | - Frederic Pincet
- Department of Cell Biology, Yale University School of Medicine, New Haven, United States
| | - James E Rothman
- Department of Cell Biology, Yale University School of Medicine, New Haven, United States
| | - Yongli Zhang
- Department of Cell Biology, Yale University School of Medicine, New Haven, United States
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76
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Abstract
Breaking down the ribbon of mammalian cells strongly inhibits intra-Golgi transport of large cargoes without altering the rate of transport of smaller cargoes. These results imply that the ribbon structure is an essential requirement for transport of large cargoes in mammalian cells. In mammalian cells, individual Golgi stacks fuse laterally to form the characteristic perinuclear ribbon structure. Yet the purpose of this remarkable structure has been an enigma. We report that breaking down the ribbon of mammalian cells strongly inhibits intra-Golgi transport of large cargoes without altering the rate of transport of smaller cargoes. In addition, insect cells that naturally harbor dispersed Golgi stacks have limited capacity to transport artificial oversized cargoes. These results imply that the ribbon structure is an essential requirement for transport of large cargoes in mammalian cells, and we suggest that this is because it enables the dilated rims of cisternae (containing the aggregates) to move across the stack as they transfer among adjacent stacks within the ribbon structure.
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Affiliation(s)
- Gregory Lavieu
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06520
| | - Myun Hwa Dunlop
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06520
| | - Alexander Lerich
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06520
| | - Hong Zheng
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06520
| | - Francesca Bottanelli
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06520
| | - James E Rothman
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06520
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77
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Li F, Kümmel D, Coleman J, Reinisch KM, Rothman JE, Pincet F. A half-zippered SNARE complex represents a functional intermediate in membrane fusion. J Am Chem Soc 2014; 136:3456-64. [PMID: 24533674 PMCID: PMC3985920 DOI: 10.1021/ja410690m] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
![]()
SNARE
(soluble N-ethylmaleimide-sensitive factor
attachment protein receptor) proteins mediate fusion by pulling biological
membranes together via a zippering mechanism. Recent biophysical studies
have shown that t- and v-SNAREs can assemble in multiple stages from
the N-termini toward the C-termini. Here we show that functionally,
membrane fusion requires a sequential, two-step folding pathway and
assign specific and distinct functions for each step. First, the N-terminal
domain (NTD) of the v-SNARE docks to the t-SNARE, which leads to a
conformational rearrangement into an activated half-zippered SNARE
complex. This partially assembled SNARE complex locks the C-terminal
(CTD) portion of the t-SNARE into the same structure as in the postfusion
4-helix bundle, thereby creating the binding site for the CTD of the
v-SNARE and enabling fusion. Then zippering of the remaining CTD,
the membrane-proximal linker (LD), and transmembrane (TMD) domains
is required and sufficient to trigger fusion. This intrinsic property
of the SNAREs fits well with the action of physiologically vital regulators
such as complexin. We also report that NTD assembly is the rate-limiting
step. Our findings provide a refined framework for delineating the
molecular mechanism of SNARE-mediated membrane fusion and action of
regulatory proteins.
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Affiliation(s)
- Feng Li
- Department of Cell Biology, School of Medicine, Yale University , 333 Cedar Street, New Haven, Connecticut 06520, United States
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78
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Pellett PA, Dietrich F, Bewersdorf J, Rothman JE, Lavieu G. Inter-Golgi transport mediated by COPI-containing vesicles carrying small cargoes. eLife 2013; 2:e01296. [PMID: 24137546 PMCID: PMC3787390 DOI: 10.7554/elife.01296] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2013] [Accepted: 08/21/2013] [Indexed: 01/15/2023] Open
Abstract
A core prediction of the vesicular transport model is that COPI vesicles are responsible for trafficking anterograde cargoes forward. In this study, we test this prediction by examining the properties and requirements of inter-Golgi transport within fused cells, which requires mobile carriers in order for exchange of constituents to occur. We report that both small soluble and membrane-bound secretory cargo and exogenous Golgi resident glycosyl-transferases are exchanged between separated Golgi. Large soluble aggregates, which traverse individual stacks, do not transfer between Golgi, implying that small cargoes (which can fit in a typical transport vesicle) are transported by a different mechanism. Super-resolution microscopy reveals that the carriers of both anterograde and retrograde cargoes are the size of COPI vesicles, contain coatomer, and functionally require ARF1 and coatomer for transport. The data suggest that COPI vesicles traffic both small secretory cargo and steady-state Golgi resident enzymes among stacked cisternae that are stationary. DOI:http://dx.doi.org/10.7554/eLife.01296.001 All eukaryotic cells contain an organelle called the Golgi apparatus, which consists of a series of four to six flattened structures called cisternae. Proteins that are intended for secretion from the cell, or proteins that go on to become part of the cell membrane, must pass through the Golgi, where they undergo modifications that ensure they are targeted to the correct place. There are two main models for how proteins are transported from the entry side of the Golgi, known as the cis face, to the exit side (trans face), through a process known as anterograde transport. One possibility is that the cargo protein matures within a single cisterna, which gradually moves from the cis to the trans face without the protein ever leaving it. Alternatively, the cisternae may remain fixed in position, while individual proteins are carried between them by specialized transport vesicles called COPI vesicles. Now, Pellett et al. have used modern molecular biology techniques to revisit this question, more than 25 years after members of the same group first obtained evidence suggesting the involvement of COPI vesicles. To do this, they labelled the proteins that reside within the Golgi of one cell green, and those within the Golgi of another cell, red. They then fused the two cells together, and traced the movement of labelled proteins between the two organelles. Proteins that are known to undergo anterograde transport were also transported between the two Golgi, whereas large protein aggregates were not. Super-resolution microscopy revealed that the transported proteins were carried in vesicles the size of COPI vesicles and surrounded by a coat protein that resembles COPI. Moreover, transport involved the adaptor protein ARF, which helps to load cargo into COPI vesicles. By providing evidence that Golgi resident proteins and proteins that normally undergo anterograde transport can be carried by COPI vesicles between two physically separate Golgi, Pellett et al. increase the weight of evidence that COPI vesicles may also be responsible for both retrograde and anterograde transport within the Golgi itself. DOI:http://dx.doi.org/10.7554/eLife.01296.002
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Affiliation(s)
- Patrina A Pellett
- Department of Cell Biology , Yale University School of Medicine , New Haven , United States ; Department of Chemistry , Yale University , New Haven , United States
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79
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Abstract
We have designed a membrane ‘staple’, which consists of membrane-anchored repeats of the trans-aggregating FM domain that face the lumen of the secretory pathway. In the presence of the disaggregating drug these proteins transit the secretory pathway. When the drug is removed these proteins form electron-dense plaques which we term staples. Unexpectedly, when initially positioned within the cis-Golgi, staples remained at the cis face of the Golgi even after many hours. By contrast, soluble FM-aggregates transited the Golgi. Staples and soluble aggregates placed in cis-Golgi cisternae therefore have different fates. Whereas the membrane staples are located in the flattened, stacked central regions of the cisternae, the soluble aggregates are in the dilated rims. This suggests that while the cisternae are static on the time scale of protein traffic, the dilated rims are mobile and progress in the cis → trans direction via a mechanism that we term ‘Rim Progression’. DOI:http://dx.doi.org/10.7554/eLife.00558.001 Most plant and animal cells contain an organelle known as the Golgi apparatus, which consists of a series of four to six stacked cisternae. Almost all the proteins that are secreted from the cell, or targeted to its plasma membrane, transit through the Golgi. This process takes roughly 5–20 min. Although transport of proteins through the Golgi was first observed more than 50 years ago, it is still unclear exactly how this process occurs. One possibility is that proteins to be packaged move through the cisternae enclosed in vesicles, as if on a conveyor belt. Alternatively, the proteins themselves may remain stationary while the Golgi cisternae move over them. Now, Lavieu et al. provide evidence that the Golgi shows both mobile and static behaviour depending on the type and size of the cargo being processed. To distinguish between these two mechanisms, they created a new type of protein cargo—which they called a ‘staple’—that became fixed to the walls on each side of the cisternae and could not, therefore, move freely through the Golgi. They compared the processing of this protein to that of a more typical soluble protein cargo, which could move freely through the Golgi stack. Surprisingly, the Golgi processed these two types of cargo in very different ways. The staples remained embedded in the walls in the center of the cisternae, whereas the conventional soluble cargo was transported past the staples and collected at the edges of the cisternae, which are known as rims. These are wider than the center of the cisternae, and the staples are too narrow to span them. Lavieu et al. suggest that the Golgi cisternae can be divided into two functionally distinct domains: the centers of cisternae, which remain stationary, and the edges or rims, which can move. In addition to increasing our understanding of how proteins are prepared for transport inside cells, this new mechanism reconciles seemingly conflicting data by revealing that the Golgi can be both mobile and static. DOI:http://dx.doi.org/10.7554/eLife.00558.002
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Affiliation(s)
- Gregory Lavieu
- Department of Cell Biology , Yale University School of Medicine , New Haven , United States
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80
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Gao Y, Zorman S, Gundersen G, Xi Z, Ma L, Sirinakis G, Rothman JE, Zhang Y. Single Neuronal Snare Complexes Zipper in Three Distinct Stages. Biophys J 2013. [DOI: 10.1016/j.bpj.2012.11.531] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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81
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Gao Y, Zorman S, Gundersen G, Xi Z, Ma L, Sirinakis G, Rothman JE, Zhang Y. Single reconstituted neuronal SNARE complexes zipper in three distinct stages. Science 2012; 337:1340-3. [PMID: 22903523 DOI: 10.1126/science.1224492] [Citation(s) in RCA: 298] [Impact Index Per Article: 24.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins drive membrane fusion by assembling into a four-helix bundle in a zippering process. Here, we used optical tweezers to observe in a cell-free reconstitution experiment in real time a long-sought SNARE assembly intermediate in which only the membrane-distal amino-terminal half of the bundle is assembled. Our findings support the zippering hypothesis, but suggest that zippering proceeds through three sequential binary switches, not continuously, in the amino- and carboxyl-terminal halves of the bundle and the linker domain. The half-zippered intermediate was stabilized by externally applied force that mimicked the repulsion between apposed membranes being forced to fuse. This intermediate then rapidly and forcefully zippered, delivering free energy of 36 k(B)T (where k(B) is Boltzmann's constant and T is temperature) to mediate fusion.
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Affiliation(s)
- Ying Gao
- Department of Cell Biology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA
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82
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Abstract
Neurotransmitters are released through nascent fusion pores, which ordinarily dilate after bilayer fusion, preventing consistent biochemical studies. We used lipid bilayer nanodiscs as fusion partners; their rigid protein framework prevents dilation and reveals properties of the fusion pore induced by SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor). We found that although only one SNARE per nanodisc is required for maximum rates of bilayer fusion, efficient release of content on the physiologically relevant time scale of synaptic transmission apparently requires three or more SNARE complexes (SNAREpins) and the native transmembrane domain of vesicle-associated membrane protein 2 (VAMP2). We suggest that several SNAREpins simultaneously zippering their SNARE transmembrane helices within the freshly fused bilayers provide a radial force that prevents the nascent pore from resealing during synchronous neurotransmitter release.
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Affiliation(s)
- Lei Shi
- Department of Cell Biology, School of Medicine, Yale University, 333 Cedar Street, New Haven, CT 06520, USA
| | - Qing-Tao Shen
- Department of Molecular Biophysics and Biochemistry, Yale University, 333 Cedar Street, New Haven, CT 06520, USA
| | - Alexander Kiel
- Department of Cell Biology, School of Medicine, Yale University, 333 Cedar Street, New Haven, CT 06520, USA
| | - Jing Wang
- Department of Cell Biology, School of Medicine, Yale University, 333 Cedar Street, New Haven, CT 06520, USA
| | - Hong-Wei Wang
- Department of Molecular Biophysics and Biochemistry, Yale University, 333 Cedar Street, New Haven, CT 06520, USA
| | - Thomas J. Melia
- Department of Cell Biology, School of Medicine, Yale University, 333 Cedar Street, New Haven, CT 06520, USA
| | - James E. Rothman
- Department of Cell Biology, School of Medicine, Yale University, 333 Cedar Street, New Haven, CT 06520, USA
| | - Frédéric Pincet
- Department of Cell Biology, School of Medicine, Yale University, 333 Cedar Street, New Haven, CT 06520, USA
- Laboratoire de Physique Statistique, UMR CNRS 8550 associée aux Universités Paris 6 et Paris 7, Ecole Normale Supérieure, 24 rue Lhomond, 75005 Paris, France
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83
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Cremona ML, Matthies HJG, Pau K, Bowton E, Speed N, Lute BJ, Anderson M, Sen N, Robertson SD, Vaughan RA, Rothman JE, Galli A, Javitch JA, Yamamoto A. Erratum: Corrigendum: Flotillin-1 is essential for PKC-triggered endocytosis and membrane microdomain localization of DAT. Nat Neurosci 2011. [DOI: 10.1038/nn1211-1617a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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84
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Abstract
F.-Ulrich Hartl and Arthur Horwich will share this year's Lasker Basic Medical Science Award for the discovery of the cell's protein-folding machinery, exemplified by cage-like structures that convert newly synthesized proteins into their biologically active forms. Their fundamental findings reveal mechanisms that operate in normal physiologic processes and help to explain the problems that arise in diseases of protein folding.
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Affiliation(s)
- James E Rothman
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06520-8002, USA.
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85
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Pellett PA, Sun X, Gould TJ, Rothman JE, Xu MQ, Corrêa IR, Bewersdorf J. Two-color STED microscopy in living cells. Biomed Opt Express 2011; 2:2364-71. [PMID: 21833373 PMCID: PMC3149534 DOI: 10.1364/boe.2.002364] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2011] [Revised: 07/21/2011] [Accepted: 07/21/2011] [Indexed: 05/15/2023]
Abstract
Diffraction-unlimited resolution provided by Stimulated Emission Depletion (STED) microscopy allows for imaging cellular processes in living cells that are not visible by conventional microscopy. However, it has so far not been possible to study dynamic nanoscale interactions because multicolor live cell STED microscopy has yet to be demonstrated and suitable labeling technologies and protocols are lacking. Here we report the first realization of two-color STED imaging in living cells. Using improved SNAP(f) and CLIP(f) technologies to label epidermal growth factor (EGF) and EGF receptor (EGFR), we report resolutions of 78 nm and 82 nm for 22 sequential two-color scans in living cells.
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Affiliation(s)
- Patrina A. Pellett
- Department of Cell Biology, Yale School of Medicine, 333 Cedar Street, New Haven, Connecticut 06510, USA
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06510, USA
| | - Xiaoli Sun
- New England Biolabs, 240 County Road, Ipswich, Massachusetts 01938, USA
| | - Travis J. Gould
- Department of Cell Biology, Yale School of Medicine, 333 Cedar Street, New Haven, Connecticut 06510, USA
| | - James E. Rothman
- Department of Cell Biology, Yale School of Medicine, 333 Cedar Street, New Haven, Connecticut 06510, USA
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06510, USA
| | - Ming-Qun Xu
- New England Biolabs, 240 County Road, Ipswich, Massachusetts 01938, USA
| | - Ivan R. Corrêa
- New England Biolabs, 240 County Road, Ipswich, Massachusetts 01938, USA
| | - Joerg Bewersdorf
- Department of Cell Biology, Yale School of Medicine, 333 Cedar Street, New Haven, Connecticut 06510, USA
- Department of Biomedical Engineering, Yale University, 333 Cedar Street, New Haven, Connecticut 06510, USA
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86
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Krishnakumar SS, Radoff DT, Kümmel D, Giraudo CG, Li F, Khandan L, Baguley SW, Coleman J, Reinisch KM, Pincet F, Rothman JE. A conformational switch in complexin is required for synaptotagmin to trigger synaptic fusion. Nat Struct Mol Biol 2011; 18:934-40. [PMID: 21785412 DOI: 10.1038/nsmb.2103] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2011] [Accepted: 05/19/2011] [Indexed: 11/09/2022]
Abstract
The crystal structure of complexin bound to a prefusion SNAREpin mimetic shows that the accessory helix extends away from the SNAREpin in an 'open' conformation, binding another SNAREpin and inhibiting its assembly, to clamp fusion. In contrast, the accessory helix in the postfusion complex parallels the SNARE complex in a 'closed' conformation. Here we use targeted mutations, FRET spectroscopy and a functional assay that reconstitutes Ca(2+)-triggered exocytosis to show that the conformational switch from open to closed in complexin is needed for synaptotagmin-Ca(2+) to trigger fusion. Triggering fusion requires the zippering of three crucial aspartate residues in the switch region (residues 64-68) of v-SNARE. Conformational switching in complexin is integral to clamp release and is probably triggered when its accessory helix is released from its trans-binding to the neighboring SNAREpin, allowing the v-SNARE to complete zippering and open a fusion pore.
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Affiliation(s)
- Shyam S Krishnakumar
- Department of Cell Biology, Yale University School of Medicine, New Haven, Connecticut, USA
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87
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Abstract
This essay looks backward on the past three decades of research toward understanding the mechanism of macromolecular traffic through and within the Golgi apparatus with an eye to the future. I also explain why I feel the Golgi should continue to hold the attention of molecular cell biologists.
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Affiliation(s)
- James E Rothman
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06510, USA.
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88
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Karatekin E, Gohlke A, Smith M, Vavylonis D, Rothman JE. Visualizing Release of Single Fluorophores at Membrane Fusion Sites. Biophys J 2011. [DOI: 10.1016/j.bpj.2010.12.1230] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
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89
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Ji H, Coleman J, Yang R, Melia TJ, Rothman JE, Tareste D. Protein determinants of SNARE-mediated lipid mixing. Biophys J 2010; 99:553-60. [PMID: 20643074 DOI: 10.1016/j.bpj.2010.04.060] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2010] [Revised: 04/19/2010] [Accepted: 04/26/2010] [Indexed: 01/14/2023] Open
Abstract
Soluble N-ethylmaleimide sensitive factor attachment protein receptor (SNARE)-mediated lipid mixing can be efficiently recapitulated in vitro by the incorporation of purified vesicle membrane (-v) SNARE and target membrane (t-) SNARE proteins into separate liposome populations. Despite the strong correlation between the observed activities in this system and the known SNARE physiology, some recent works have suggested that SNARE-mediated lipid mixing may be limited to circumstances where membrane defects arise from artifactual reconstitution conditions (such as nonphysiological high-protein concentrations or unrealistically small liposome populations). Here, we show that the previously published strategies used to reconstitute SNAREs into liposomes do not significantly affect either the physical parameters of the proteoliposomes or the ability of SNAREs to drive lipid mixing in vitro. The surface density of SNARE proteins turns out to be the most critical parameter, which controls both the rate and the extent of SNARE-mediated liposome fusion. In addition, the specific activity of the t-SNARE complex is significantly influenced by expression and reconstitution protocols, such that we only observe optimal lipid mixing when the t-SNARE proteins are coexpressed before purification.
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Affiliation(s)
- Hong Ji
- Department of Cell Biology, School of Medicine, Yale University, New Haven, Connecticut, USA
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90
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Shen J, Rathore SS, Khandan L, Rothman JE. SNARE bundle and syntaxin N-peptide constitute a minimal complement for Munc18-1 activation of membrane fusion. ACTA ACUST UNITED AC 2010; 190:55-63. [PMID: 20603329 PMCID: PMC2911676 DOI: 10.1083/jcb.201003148] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Whittling away SNARE complex components reveals essential domains for Munc18-1–mediated membrane fusion. Sec1/Munc18 (SM) proteins activate intracellular membrane fusion through binding to cognate SNAP receptor (SNARE) complexes. The synaptic target membrane SNARE syntaxin 1 contains a highly conserved Habc domain, which connects an N-peptide motif to the SNARE core domain and is thought to participate in the binding of Munc18-1 (the neuronal SM protein) to the SNARE complex. Unexpectedly, we found that mutation or complete removal of the Habc domain had no effect on Munc18-1 stimulation of fusion. The central cavity region of Munc18-1 is required to stimulate fusion but not through its binding to the syntaxin Habc domain. SNAP-25, another synaptic SNARE subunit, contains a flexible linker and exhibits an atypical conjoined Qbc configuration. We found that neither the linker nor the Qbc configuration is necessary for Munc18-1 promotion of fusion. As a result, Munc18-1 activates a SNARE complex with the typical configuration, in which each of the SNARE core domains is individually rooted in the membrane bilayer. Thus, the SNARE four-helix bundle and syntaxin N-peptide constitute a minimal complement for Munc18-1 activation of fusion.
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Affiliation(s)
- Jingshi Shen
- Department of Molecular, University of Colorado at Boulder, Boulder, CO 80309, USA.
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91
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92
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Karatekin E, Di Giovanni J, Iborra C, Coleman J, O'Shaughnessy B, Seagar M, Rothman JE. A Fast, Single-Vesicle Fusion Assay Mimics Physiological SNARE Requirements. Biophys J 2010. [DOI: 10.1016/j.bpj.2009.12.3362] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022] Open
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93
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Emr S, Glick BS, Linstedt AD, Lippincott-Schwartz J, Luini A, Malhotra V, Marsh BJ, Nakano A, Pfeffer SR, Rabouille C, Rothman JE, Warren G, Wieland FT. Journeys through the Golgi--taking stock in a new era. ACTA ACUST UNITED AC 2009; 187:449-53. [PMID: 19948493 PMCID: PMC2779233 DOI: 10.1083/jcb.200909011] [Citation(s) in RCA: 133] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The Golgi apparatus is essential for protein sorting and transport. Many researchers have long been fascinated with the form and function of this organelle. Yet, despite decades of scrutiny, the mechanisms by which proteins are transported across the Golgi remain controversial. At a recent meeting, many prominent Golgi researchers assembled to critically evaluate the core issues in the field. This report presents the outcome of their discussions and highlights the key open questions that will help guide the field into a new era.
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Affiliation(s)
- Scott Emr
- Department of Cell and Developmental Biology, CRG-Centre de Regulació Genòmica, Institutcio Catalana de Recerca I Estudis Avancats, 88 08003 Barcelona, Spain
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94
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Paumet F, Wesolowski J, Garcia-Diaz A, Delevoye C, Aulner N, Shuman HA, Subtil A, Rothman JE. Intracellular bacteria encode inhibitory SNARE-like proteins. PLoS One 2009; 4:e7375. [PMID: 19823575 PMCID: PMC2756591 DOI: 10.1371/journal.pone.0007375] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2009] [Accepted: 09/15/2009] [Indexed: 11/24/2022] Open
Abstract
Pathogens use diverse molecular machines to penetrate host cells and manipulate intracellular vesicular trafficking. Viruses employ glycoproteins, functionally and structurally similar to the SNARE proteins, to induce eukaryotic membrane fusion. Intracellular pathogens, on the other hand, need to block fusion of their infectious phagosomes with various endocytic compartments to escape from the degradative pathway. The molecular details concerning the mechanisms underlying this process are lacking. Using both an in vitro liposome fusion assay and a cellular assay, we showed that SNARE-like bacterial proteins block membrane fusion in eukaryotic cells by directly inhibiting SNARE-mediated membrane fusion. More specifically, we showed that IncA and IcmG/DotF, two SNARE-like proteins respectively expressed by Chlamydia and Legionella, inhibit the endocytic SNARE machinery. Furthermore, we identified that the SNARE-like motif present in these bacterial proteins encodes the inhibitory function. This finding suggests that SNARE-like motifs are capable of specifically manipulating membrane fusion in a wide variety of biological environments. Ultimately, this motif may have been selected during evolution because it is an efficient structural motif for modifying eukaryotic membrane fusion and thus contribute to pathogen survival.
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Affiliation(s)
- Fabienne Paumet
- Thomas Jefferson University, Department of Microbiology and Immunology, Philadelphia, Pennsylvania, United States of America.
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95
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Giraudo CG, Garcia-Diaz A, Eng WS, Chen Y, Hendrickson WA, Melia TJ, Rothman JE. Alternative zippering as an on-off switch for SNARE-mediated fusion. Science 2009; 323:512-6. [PMID: 19164750 DOI: 10.1126/science.1166500] [Citation(s) in RCA: 131] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Membrane fusion between vesicles and target membranes involves the zippering of a four-helix bundle generated by constituent helices derived from target- and vesicle-soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs). In neurons, the protein complexin clamps otherwise spontaneous fusion by SNARE proteins, allowing neurotransmitters and other mediators to be secreted when and where they are needed as this clamp is released. The membrane-proximal accessory helix of complexin is necessary for clamping, but its mechanism of action is unknown. Here, we present experiments using a reconstituted fusion system that suggest a simple model in which the complexin accessory helix forms an alternative four-helix bundle with the target-SNARE near the membrane, preventing the vesicle-SNARE from completing its zippering.
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Affiliation(s)
- Claudio G Giraudo
- Department of Physiology and Cellular Biophysics, Columbia University, College of Physicians and Surgeons, 1150 Saint Nicholas Avenue, Russ Berrie Building, Room 520, New York, NY 10032, USA.
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96
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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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97
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Giraudo CG, Garcia-Diaz A, Eng WS, Yamamoto A, Melia TJ, Rothman JE. Distinct domains of complexins bind SNARE complexes and clamp fusion in vitro. J Biol Chem 2008; 283:21211-9. [PMID: 18499660 PMCID: PMC2475712 DOI: 10.1074/jbc.m803478200] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2008] [Indexed: 12/29/2022] Open
Abstract
In regulated exocytosis, the core membrane fusion machinery proteins, the SNARE proteins, are assisted by a group of regulatory factors in order to couple membrane fusion to an increase of intracellular calcium ion (Ca(2+)) concentration. Complexin-I and synaptotagmin-I have been shown to be key elements for this tightly regulated process. Many studies suggest that complexin-I can arrest the fusion reaction and that synaptotagmin-I can release the complexin-I blockage in a calcium-dependent manner. Although the actual molecular mechanism by which they exert their function is still unknown, recent in vivo experiments postulate that domains of complexin-I produce different effects on neurotransmitter release. Herein, by using an in vitro flipped SNARE cell fusion assay, we have identified and characterized the minimal functional domains of complexin-I necessary to couple calcium and synaptotagmin-I to membrane fusion. Moreover, we provide evidence that other isoforms of complexin, complexin-II, -III, and -IV, can also be functionally coupled to synaptotagmin-I and calcium. These correspond closely to results from in vivo experiments, providing further validation of the physiological relevance of the flipped SNARE system.
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Affiliation(s)
- Claudio G. Giraudo
- Department of Physiology and
Cellular Biophysics, Columbia University, College of Physicians and Surgeons,
New York, New York 10032 and the
Department of Neurology, Columbia
University, New York, New York 10032
| | - Alejandro Garcia-Diaz
- Department of Physiology and
Cellular Biophysics, Columbia University, College of Physicians and Surgeons,
New York, New York 10032 and the
Department of Neurology, Columbia
University, New York, New York 10032
| | - William S. Eng
- Department of Physiology and
Cellular Biophysics, Columbia University, College of Physicians and Surgeons,
New York, New York 10032 and the
Department of Neurology, Columbia
University, New York, New York 10032
| | - Ai Yamamoto
- Department of Physiology and
Cellular Biophysics, Columbia University, College of Physicians and Surgeons,
New York, New York 10032 and the
Department of Neurology, Columbia
University, New York, New York 10032
| | - Thomas J. Melia
- Department of Physiology and
Cellular Biophysics, Columbia University, College of Physicians and Surgeons,
New York, New York 10032 and the
Department of Neurology, Columbia
University, New York, New York 10032
| | - James E. Rothman
- Department of Physiology and
Cellular Biophysics, Columbia University, College of Physicians and Surgeons,
New York, New York 10032 and the
Department of Neurology, Columbia
University, New York, New York 10032
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98
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Abstract
The Golgi apparatus seems to consist of distinct cis and trans compartments that are proposed to act sequentially to refine the protein export of the endoplasmic reticulum by removing escaped endoplasmic reticulum proteins. Refinement may be a multi-stage process that employs a principle akin to fractional distillation; the stack of cisternae comprising the cis Golgi may be the plates in this distillation tower. The trans Golgi, consisting of the last one or two cisternae, may be the receiver that collects from the cis Golgi only its most refined fraction for later distribution to specific locations throughout the cell.
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99
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Li F, Pincet F, Perez E, Eng WS, Melia TJ, Rothman JE, Tareste D. Energetics and dynamics of SNAREpin folding across lipid bilayers. Nat Struct Mol Biol 2007; 14:890-6. [PMID: 17906638 DOI: 10.1038/nsmb1310] [Citation(s) in RCA: 201] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2007] [Accepted: 09/05/2007] [Indexed: 11/09/2022]
Abstract
Membrane fusion occurs when SNAREpins fold up between lipid bilayers. How much energy is generated during SNAREpin folding and how this energy is coupled to the fusion of apposing membranes is unknown. We have used a surface forces apparatus to determine the energetics and dynamics of SNAREpin formation and characterize the different intermediate structures sampled by cognate SNAREs in the course of their assembly. The interaction energy-versus-distance profiles of assembling SNAREpins reveal that SNARE motifs begin to interact when the membranes are 8 nm apart. Even after very close approach of the bilayers (approximately 2-4 nm), the SNAREpins remain partly unstructured in their membrane-proximal region. The energy stabilizing a single SNAREpin in this configuration (35 k(B)T) corresponds closely with the energy needed to fuse outer but not inner leaflets (hemifusion) of pure lipid bilayers (40-50 k(B)T).
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Affiliation(s)
- Feng Li
- Laboratoire de Physique Statistique, Unité Mixte de Recherche 8550, Centre National de la Recherche Scientifique associée aux Universités Paris VI et Paris VII, Ecole Normale Supérieure, 24 rue Lhomond, 75005 Paris, France
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100
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Shen J, Tareste DC, Paumet F, Rothman JE, Melia TJ. Selective Activation of Cognate SNAREpins by Sec1/Munc18 Proteins. Cell 2007; 128:183-95. [PMID: 17218264 DOI: 10.1016/j.cell.2006.12.016] [Citation(s) in RCA: 379] [Impact Index Per Article: 22.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2006] [Revised: 10/31/2006] [Accepted: 12/05/2006] [Indexed: 01/11/2023]
Abstract
Sec1/Munc18 (SM) proteins are required for every step of intracellular membrane fusion, but their molecular mechanism of action has been unclear. In this work, we demonstrate a fundamental role of the SM protein: to act as a stimulatory subunit of its cognate SNARE fusion machinery. In a reconstituted system, mammalian SNARE pairs assemble between bilayers to drive a basal fusion reaction. Munc18-1/nSec1, a synaptic SM protein required for neurotransmitter release, strongly accelerates this reaction through direct contact with both t- and v-SNAREs. Munc18-1 accelerates fusion only for the cognate SNAREs for exocytosis, therefore enhancing fusion specificity.
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Affiliation(s)
- Jingshi Shen
- Department of Physiology and Cellular Biophysics, Columbia University, New York, NY 10032, USA
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