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Abstract
Neurotransmitters are stored in small membrane-bound vesicles at synapses; a subset of synaptic vesicles is docked at release sites. Fusion of docked vesicles with the plasma membrane releases neurotransmitters. Membrane fusion at synapses, as well as all trafficking steps of the secretory pathway, is mediated by SNARE proteins. The SNAREs are the minimal fusion machinery. They zipper from N-termini to membrane-anchored C-termini to form a 4-helix bundle that forces the apposed membranes to fuse. At synapses, the SNAREs comprise a single helix from syntaxin and synaptobrevin; SNAP-25 contributes the other two helices to complete the bundle. Unc13 mediates synaptic vesicle docking and converts syntaxin into the permissive "open" configuration. The SM protein, Unc18, is required to initiate and proofread SNARE assembly. The SNAREs are then held in a half-zippered state by synaptotagmin and complexin. Calcium removes the synaptotagmin and complexin block, and the SNAREs drive vesicle fusion. After fusion, NSF and alpha-SNAP unwind the SNAREs and thereby recharge the system for further rounds of fusion. In this chapter, we will describe the discovery of the SNAREs, their relevant structural features, models for their function, and the central role of Unc18. In addition, we will touch upon the regulation of SNARE complex formation by Unc13, complexin, and synaptotagmin.
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Affiliation(s)
- Mark T Palfreyman
- School of Biological Sciences, and Howard Hughes Medical Institute, University of Utah, Salt Lake City, UT, USA
| | - Sam E West
- School of Biological Sciences, and Howard Hughes Medical Institute, University of Utah, Salt Lake City, UT, USA
| | - Erik M Jorgensen
- School of Biological Sciences, and Howard Hughes Medical Institute, University of Utah, Salt Lake City, UT, USA.
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Parra-Rivas LA, Palfreyman MT, Vu TN, Jorgensen EM. Interspecies complementation identifies a pathway to assemble SNAREs. iScience 2022; 25:104506. [PMID: 35754735 PMCID: PMC9213704 DOI: 10.1016/j.isci.2022.104506] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2021] [Revised: 03/23/2022] [Accepted: 05/27/2022] [Indexed: 11/18/2022] Open
Abstract
Unc18 and SNARE proteins form the core of the membrane fusion complex at synapses. To understand the functional interactions within the core machinery, we adopted an "interspecies complementation" approach in Caenorhabditis elegans. Substitutions of individual SNAREs and Unc18 proteins with those from yeast fail to rescue fusion. However, synaptic transmission could be restored in worm-yeast chimeras when two key interfaces were present: an Habc-Unc18 contact site and an Unc18-SNARE motif contact site. A constitutively open form of Unc18 bypasses the requirement for the Habc-Unc18 interface. These data suggest that the Habc domain of syntaxin is required for Unc18 to adopt an open conformation; open Unc18 then templates SNARE complex formation. Finally, we demonstrate that the SNARE and Unc18 machinery in the nematode C. elegans can be replaced by yeast proteins and still carry out synaptic transmission, pointing to the deep evolutionary conservation of these two interfaces.
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Affiliation(s)
- Leonardo A. Parra-Rivas
- Howard Hughes Medical Institute, School of Biological Sciences, University of Utah, Salt Lake City, UT 84112-0840, USA
| | - Mark T. Palfreyman
- Howard Hughes Medical Institute, School of Biological Sciences, University of Utah, Salt Lake City, UT 84112-0840, USA
| | - Thien N. Vu
- Howard Hughes Medical Institute, School of Biological Sciences, University of Utah, Salt Lake City, UT 84112-0840, USA
| | - Erik M. Jorgensen
- Howard Hughes Medical Institute, School of Biological Sciences, University of Utah, Salt Lake City, UT 84112-0840, USA
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Abstract
Mating induces pronounced changes in female reproductive behavior, typically including a dramatic reduction in sexual receptivity. In Drosophila, postmating behavioral changes are triggered by sex peptide (SP), a male seminal fluid peptide that acts via a receptor (SPR) expressed in sensory neurons (SPSNs) of the female reproductive tract. Here, we identify second-order neurons that mediate the behavioral changes induced by SP. These SAG neurons receive synaptic input from SPSNs in the abdominal ganglion and project to the dorsal protocerebrum. Silencing SAG neurons renders virgin females unreceptive, whereas activating them increases the receptivity of females that have already mated. Physiological experiments demonstrate that SP downregulates the excitability of the SPSNs, and hence their input onto SAG neurons. These data thus provide a physiological correlate of mating status in the female central nervous system and a key entry point into the brain circuits that control sexual receptivity.
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Affiliation(s)
- Kai Feng
- Research Institute of Molecular Pathology, Dr. Bohrgasse 7, A-1030 Vienna, Austria
| | - Mark T Palfreyman
- Research Institute of Molecular Pathology, Dr. Bohrgasse 7, A-1030 Vienna, Austria.
| | - Martin Häsemeyer
- Research Institute of Molecular Pathology, Dr. Bohrgasse 7, A-1030 Vienna, Austria
| | - Aaron Talsma
- Research Institute of Molecular Pathology, Dr. Bohrgasse 7, A-1030 Vienna, Austria
| | - Barry J Dickson
- Research Institute of Molecular Pathology, Dr. Bohrgasse 7, A-1030 Vienna, Austria.
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Palfreyman MT. With Happyhour, everyone's under the table. Cell 2009; 137:802-4. [PMID: 19490888 DOI: 10.1016/j.cell.2009.05.016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The molecular and cellular targets that mediate alcohol intoxication are poorly understood. In this issue, Corl et al. (2009) now implicate a new Ste20 family kinase (Happyhour) and the EGFR/ERK signaling pathway it antagonizes in alcohol intoxication in flies.
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Abstract
Synaptic vesicles dock to the plasma membrane at synapses to facilitate rapid exocytosis. Docking was originally proposed to require the soluble N-ethylmaleimide-sensitive fusion attachment protein receptor (SNARE) proteins; however, perturbation studies suggested that docking was independent of the SNARE proteins. We now find that the SNARE protein syntaxin is required for docking of all vesicles at synapses in the nematode Caenorhabditis elegans. The active zone protein UNC-13, which interacts with syntaxin, is also required for docking in the active zone. The docking defects in unc-13 mutants can be fully rescued by overexpressing a constitutively open form of syntaxin, but not by wild-type syntaxin. These experiments support a model for docking in which UNC-13 converts syntaxin from the closed to the open state, and open syntaxin acts directly in docking vesicles to the plasma membrane. These data provide a molecular basis for synaptic vesicle docking.
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Affiliation(s)
- Marc Hammarlund
- Department of Biology, University of Utah, Salt Lake City, Utah, United States of America
- Howard Hughes Medical Institute, University of Utah, Salt Lake City, Utah, United States of America
| | - Mark T Palfreyman
- Department of Biology, University of Utah, Salt Lake City, Utah, United States of America
- Howard Hughes Medical Institute, University of Utah, Salt Lake City, Utah, United States of America
| | - Shigeki Watanabe
- Department of Biology, University of Utah, Salt Lake City, Utah, United States of America
- Howard Hughes Medical Institute, University of Utah, Salt Lake City, Utah, United States of America
| | - Shawn Olsen
- Department of Biology, University of Utah, Salt Lake City, Utah, United States of America
- Howard Hughes Medical Institute, University of Utah, Salt Lake City, Utah, United States of America
| | - Erik M Jorgensen
- Department of Biology, University of Utah, Salt Lake City, Utah, United States of America
- Howard Hughes Medical Institute, University of Utah, Salt Lake City, Utah, United States of America
- * To whom correspondence should be addressed. E-mail:
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Schuske K, Palfreyman MT, Watanabe S, Jorgensen EM. UNC-46 is required for trafficking of the vesicular GABA transporter. Nat Neurosci 2007; 10:846-53. [PMID: 17558401 DOI: 10.1038/nn1920] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [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: 01/11/2007] [Accepted: 05/09/2007] [Indexed: 12/11/2022]
Abstract
Mutations in unc-46 in Caenorhabditis elegans cause defects in all behaviors that are mediated by GABA. Here we show that UNC-46 is a sorting factor that localizes the vesicular GABA transporter to synaptic vesicles. The UNC-46 protein is related to the LAMP (lysosomal associated membrane protein) family of proteins and is localized at synapses. In unc-46 mutants, the vesicular transporter is not found specifically in synaptic vesicles but rather is diffusely spread along the axon. Mislocalization of the transporter severely reduces the frequency of miniature currents, but the remaining currents are normal in amplitude. Because the number of synaptic vesicles is not depleted, it is likely that only a fraction of vesicles harbor the transporter in unc-46 mutants. Our data indicate that the transporter and UNC-46 have mutual roles in sorting. The vesicular GABA transporter recruits UNC-46 to synaptic vesicle precursors in the cell body, and UNC-46 sorts the transporter at the cell body and during endocytosis at the synapse.
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Affiliation(s)
- Kim Schuske
- Howard Hughes Medical Institute and the Department of Biology, University of Utah, 257 South 1400 East, Salt Lake City, Utah 84112-0840, USA
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Abraham C, Hutter H, Palfreyman MT, Spatkowski G, Weimer RM, Windoffer R, Jorgensen EM, Leube RE. Synaptic tetraspan vesicle membrane proteins are conserved but not needed for synaptogenesis and neuronal function in Caenorhabditis elegans. Proc Natl Acad Sci U S A 2006; 103:8227-32. [PMID: 16698939 PMCID: PMC1570102 DOI: 10.1073/pnas.0509400103] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Tetraspan vesicle membrane proteins (TVPs) comprise a major portion of synaptic vesicle proteins, yet their contribution to the synaptic vesicle cycle is poorly understood. TVPs are grouped in three mammalian gene families: physins, gyrins, and secretory carrier-associated membrane proteins (SCAMPs). In Caenorhabditis elegans, only a single member of each of these families exists. These three nematode TVPs colocalize to the same vesicular compartment when expressed in mammalian cells, suggesting that they could serve overlapping functions. To examine their function, C. elegans null mutants were isolated for each gene, and a triple mutant was generated. Surprisingly, these animals develop normally and exhibit normal neuronal architecture and synaptic contacts. In addition, functions of the motor and sensory systems are normal as determined by pharmacological, chemotaxis, and thermotaxis assays. Finally, direct electrophysiological analysis of the neuromuscular junction revealed no phenotype in the TVP mutants. We therefore conclude that TVPs are not needed for the basic neuronal machinery and instead may contribute to subtle higher order functions.
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Affiliation(s)
- Christian Abraham
- *Department of Anatomy and Cell Biology, Johannes Gutenberg University, Becherweg 13, 55128 Mainz, Germany
| | - Harald Hutter
- Max-Planck-Institut für Medizinische Forschung, Jahnstrasse 29, 69120 Heidelberg, Germany
| | - Mark T. Palfreyman
- Department of Biology and Howard Hughes Medical Institute, University of Utah, Salt Lake City, UT 84112-0840; and
| | - Gabriele Spatkowski
- *Department of Anatomy and Cell Biology, Johannes Gutenberg University, Becherweg 13, 55128 Mainz, Germany
| | - Robby M. Weimer
- Department of Biology and Howard Hughes Medical Institute, University of Utah, Salt Lake City, UT 84112-0840; and
- Biologie Cellulaire de la Synapse, Ecole Normale Supérieure, 75005 Paris, France
| | - Reinhard Windoffer
- *Department of Anatomy and Cell Biology, Johannes Gutenberg University, Becherweg 13, 55128 Mainz, Germany
| | - Erik M. Jorgensen
- Department of Biology and Howard Hughes Medical Institute, University of Utah, Salt Lake City, UT 84112-0840; and
| | - Rudolf E. Leube
- *Department of Anatomy and Cell Biology, Johannes Gutenberg University, Becherweg 13, 55128 Mainz, Germany
- **To whom correspondence should be addressed. E-mail:
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Miyabayashi T, Palfreyman MT, Sluder AE, Slack F, Sengupta P. Expression and function of members of a divergent nuclear receptor family in Caenorhabditis elegans. Dev Biol 1999; 215:314-31. [PMID: 10545240 DOI: 10.1006/dbio.1999.9470] [Citation(s) in RCA: 101] [Impact Index Per Article: 4.0] [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] [Indexed: 11/22/2022]
Abstract
Nuclear receptors (NRs) are a large class of ligand-regulated transcriptional modulators that have been shown to play roles in many developmental processes. The Caenorhabditis elegans genome is predicted to encode a large and divergent family of NR proteins. The functions of most of these genes are unknown. As a first step toward defining their roles, we have initiated an expression and functional survey of a subset of these genes. In this study, we demonstrate expression of 21 of 28 NR genes examined, indicating that a large fraction of the predicted genes likely encode functional gene products. We show that five genes are expressed predominantly in neuronal cells, while others are expressed in multiple cell types. Interestingly, we find that eight genes are expressed exclusively in the lateral hypodermal (seam) cells. These eight genes share a high degree of overall homology and cluster in a neighbor-joining tree derived from sequence analysis of the NRs, suggesting that they arose by gene duplication from a common ancestor. We show that overexpression of each of three members of this subfamily results in similar developmental defects, consistent with a redundant role for these genes in the function of the lateral hypodermal cells.
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Affiliation(s)
- T Miyabayashi
- Department of Biology and Volen Center for Complex Systems, Brandeis University, Waltham, Massachusetts 02454, USA
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