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Correa E, Mialon M, Cizeron M, Bessereau JL, Pinan-Lucarre B, Kratsios P. UNC-30/PITX coordinates neurotransmitter identity with postsynaptic GABA receptor clustering. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.02.14.580278. [PMID: 38405977 PMCID: PMC10888783 DOI: 10.1101/2024.02.14.580278] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/27/2024]
Abstract
Terminal selectors are transcription factors that control neuronal identity by regulating the expression of key effector molecules, such as neurotransmitter (NT) biosynthesis proteins, ion channels and neuropeptides. Whether and how terminal selectors control neuronal connectivity is poorly understood. Here, we report that UNC-30 (PITX2/3), the terminal selector of GABA motor neuron identity in C. elegans , is required for NT receptor clustering, a hallmark of postsynaptic differentiation. Animals lacking unc-30 or madd-4B, the short isoform of the MN-secreted synapse organizer madd-4 ( Punctin/ADAMTSL ), display severe GABA receptor type A (GABA A R) clustering defects in postsynaptic muscle cells. Mechanistically, UNC-30 acts directly to induce and maintain transcription of madd-4B and GABA biosynthesis genes (e.g., unc-25/GAD , unc-47/VGAT ). Hence, UNC-30 controls GABA A R clustering on postsynaptic muscle cells and GABA biosynthesis in presynaptic cells, transcriptionally coordinating two critical processes for GABA neurotransmission. Further, we uncover multiple target genes and a dual role for UNC-30 both as an activator and repressor of gene transcription. Our findings on UNC-30 function may contribute to our molecular understanding of human conditions, such as Axenfeld-Rieger syndrome, caused by PITX2 and PITX3 gene mutations.
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Florin F, Bonneau B, Briseño-Roa L, Bessereau JL, Jospin M. Calcineurin-Dependent Homeostatic Response of C. elegans Muscle Cells upon Prolonged Activation of Acetylcholine Receptors. Cells 2023; 12:2201. [PMID: 37681933 PMCID: PMC10486475 DOI: 10.3390/cells12172201] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2023] [Revised: 08/29/2023] [Accepted: 08/30/2023] [Indexed: 09/09/2023] Open
Abstract
Pharmacological adaptation is a common phenomenon observed during prolonged drug exposure and often leads to drug resistance. Understanding the cellular events involved in adaptation could provide new strategies to circumvent this resistance issue. We used the nematode Caenorhabditis elegans to analyze the adaptation to levamisole, an ionotropic acetylcholine receptor agonist, used for decades to treat nematode parasitic infections. Genetic screens in C. elegans identified "adapting mutants" that initially paralyze upon exposure to levamisole as the wild type (WT), but recover locomotion after a few hours whereas WT remain paralyzed. Here, we show that levamisole induces a sustained increase in cytosolic calcium concentration in the muscle cells of adapting mutants, lasting several hours and preceding a decrease in levamisole-sensitive acetylcholine receptors (L-AChR) at the muscle plasma membrane. This decrease correlated with a drop in calcium concentration, a relaxation of the animal's body and a resumption of locomotion. The decrease in calcium and L-AChR content depends on calcineurin activation in muscle cells. We also showed that levamisole adaptation triggers homeostatic mechanisms in muscle cells including mitochondria remodeling, lysosomal tubulation and an increase in autophagic activity. Levamisole adaptation thus provides a new experimental paradigm for studying how cells cope with calcium stress.
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Affiliation(s)
- Franklin Florin
- Institut NeuroMyoGène, CNRS UMR-5284, INSERM U-1314, MeLiS, Université Lyon, Université Claude Bernard Lyon 1, F-69008 Lyon, France (B.B.); (J.-L.B.)
| | - Benjamin Bonneau
- Institut NeuroMyoGène, CNRS UMR-5284, INSERM U-1314, MeLiS, Université Lyon, Université Claude Bernard Lyon 1, F-69008 Lyon, France (B.B.); (J.-L.B.)
- Institut Curie, CNRS UMR3347, INSERM U1021, Université Paris-Saclay, F-91405 Orsay, France
| | - Luis Briseño-Roa
- Institut NeuroMyoGène, CNRS UMR-5284, INSERM U-1314, MeLiS, Université Lyon, Université Claude Bernard Lyon 1, F-69008 Lyon, France (B.B.); (J.-L.B.)
- Medetia Pharmaceuticals, Institut Imagine, F-75015 Paris, France
| | - Jean-Louis Bessereau
- Institut NeuroMyoGène, CNRS UMR-5284, INSERM U-1314, MeLiS, Université Lyon, Université Claude Bernard Lyon 1, F-69008 Lyon, France (B.B.); (J.-L.B.)
| | - Maëlle Jospin
- Institut NeuroMyoGène, CNRS UMR-5284, INSERM U-1314, MeLiS, Université Lyon, Université Claude Bernard Lyon 1, F-69008 Lyon, France (B.B.); (J.-L.B.)
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Nakayama M, Nishimura O, Nishimura Y, Kitaichi M, Kuraku S, Sone M, Hama C. Control of Synaptic Levels of Nicotinic Acetylcholine Receptor by the Sequestering Subunit Dα5 and Secreted Scaffold Protein Hig. J Neurosci 2023; 43:3989-4004. [PMID: 37117011 PMCID: PMC10255049 DOI: 10.1523/jneurosci.2243-21.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2021] [Revised: 04/05/2023] [Accepted: 04/10/2023] [Indexed: 04/30/2023] Open
Abstract
The presentation of nicotinic acetylcholine receptors (nAChRs) on synaptic membranes is crucial for generating cholinergic circuits, some of which are associated with memory function and neurodegenerative disorders. Although the physiology and structure of nAChR, a cation channel comprising five subunits, have been extensively studied, little is known about how the receptor levels in interneuronal synapses are determined and which nAChR subunits participate in the regulatory process in cooperation with synaptic cleft matrices and intracellular proteins. By a genetic screen of Drosophila, we identified mutations in the nAChR subunit Dα5 gene as suppressors that restored the mutant phenotypes of hig, which encodes a secretory matrix protein localized to cholinergic synaptic clefts in the brain. Only the loss of function of Dα5 among the 10 nAChR subunits suppressed hig mutant phenotypes in both male and female flies. Dα5 behaved as a lethal factor when Hig was defective; loss of Dα5 in hig mutants rescued lethality, upregulating Dα6 synaptic levels. By contrast, levels of Dα5, Dα6, and Dα7 subunits were all reduced in hig mutants. These three subunits have distinct properties for interaction with Hig or trafficking, as confirmed by chimeric subunit experiments. Notably, the chimeric Dα5 protein, which has the extracellular sequences that display no positive interaction with Hig, exhibited abnormal distribution and lethality even in the presence of Hig. We propose that the sequestering subunit Dα5 functions by reducing synaptic levels of nAChR through internalization, and this process is blocked by Hig, which tethers Dα5 to the synaptic cleft matrix.SIGNIFICANCE STATEMENT Because the cholinergic synapse is one of the major synapses that generate various brain functions, numerous studies have sought to reveal the physiology and structure of the nicotinic acetylcholine receptor (nAChR). However, little is known about how synaptic levels of nAChR are controlled and which nAChR subunits participate in the regulatory process in cooperation with synaptic cleft matrices. By a genetic screen of Drosophila, we identified mutations in the nAChR subunit Dα5 gene as suppressors that restored the mutant phenotypes of hig, which encodes a secretory matrix protein localized to cholinergic synaptic clefts. Our data indicate that Dα5 functions in reducing synaptic levels of nAChR, and this process is blocked by Hig, which tethers Dα5 to the synaptic cleft matrix.
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Affiliation(s)
- Minoru Nakayama
- Faculty of Life Sciences, Kyoto Sangyo University, Kyoto 603-8555, Japan
- Faculty of Science, Toho University, Funabashi 274-8510, Japan
| | - Osamu Nishimura
- Laboratory for Phyloinformatics, RIKEN Center for Biosystems Dynamics Research, RIKEN, Kobe 650-0047, Japan
| | - Yuhi Nishimura
- Faculty of Life Sciences, Kyoto Sangyo University, Kyoto 603-8555, Japan
| | - Miwa Kitaichi
- Faculty of Life Sciences, Kyoto Sangyo University, Kyoto 603-8555, Japan
| | - Shigehiro Kuraku
- Laboratory for Phyloinformatics, RIKEN Center for Biosystems Dynamics Research, RIKEN, Kobe 650-0047, Japan
| | - Masaki Sone
- Faculty of Science, Toho University, Funabashi 274-8510, Japan
| | - Chihiro Hama
- Faculty of Life Sciences, Kyoto Sangyo University, Kyoto 603-8555, Japan
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4
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Mizumoto K, Jin Y, Bessereau JL. Synaptogenesis: unmasking molecular mechanisms using Caenorhabditis elegans. Genetics 2023; 223:iyac176. [PMID: 36630525 PMCID: PMC9910414 DOI: 10.1093/genetics/iyac176] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2022] [Accepted: 10/22/2022] [Indexed: 01/13/2023] Open
Abstract
The nematode Caenorhabditis elegans is a research model organism particularly suited to the mechanistic understanding of synapse genesis in the nervous system. Armed with powerful genetics, knowledge of complete connectomics, and modern genomics, studies using C. elegans have unveiled multiple key regulators in the formation of a functional synapse. Importantly, many signaling networks display remarkable conservation throughout animals, underscoring the contributions of C. elegans research to advance the understanding of our brain. In this chapter, we will review up-to-date information of the contribution of C. elegans to the understanding of chemical synapses, from structure to molecules and to synaptic remodeling.
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Affiliation(s)
- Kota Mizumoto
- Department of Zoology, University of British Columbia, Vancouver V6T 1Z3, Canada
| | - Yishi Jin
- Department of Neurobiology, University of California San Diego, La Jolla, CA 92093, USA
| | - Jean-Louis Bessereau
- Univ Lyon, University Claude Bernard Lyon 1, CNRS UMR 5284, INSERM U 1314, Melis, 69008 Lyon, France
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5
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Izquierdo PG, Charvet CL, Neveu C, Green AC, Tattersall JEH, Holden-Dye L, O'Connor V. Modelling organophosphate intoxication in C. elegans highlights nicotinic acetylcholine receptor determinants that mitigate poisoning. PLoS One 2023; 18:e0284786. [PMID: 37083685 PMCID: PMC10121051 DOI: 10.1371/journal.pone.0284786] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2022] [Accepted: 04/06/2023] [Indexed: 04/22/2023] Open
Abstract
Organophosphate intoxication via acetylcholinesterase inhibition executes neurotoxicity via hyper stimulation of acetylcholine receptors. Here, we use the organophosphate paraoxon-ethyl to treat C. elegans and use its impact on pharyngeal pumping as a bio-assay to model poisoning through these neurotoxins. This assay provides a tractable measure of acetylcholine receptor mediated contraction of body wall muscle. Investigation of the time dependence of organophosphate treatment and the genetic determinants of the drug-induced inhibition of pumping highlight mitigating modulation of the effects of paraoxon-ethyl. We identified mutants that reduce acetylcholine receptor function protect against the consequence of intoxication by organophosphates. Data suggests that reorganization of cholinergic signalling is associated with organophosphate poisoning. This reinforces the under investigated potential of using therapeutic approaches which target a modulation of nicotinic acetylcholine receptor function to treat the poisoning effects of this important class of neurotoxins.
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Affiliation(s)
- Patricia G Izquierdo
- Biological Sciences, Institute for Life Sciences, University of Southampton, Southampton, United Kingdom
| | - Claude L Charvet
- French National Institute for Agricultural Research (INRA), Infectiologie Animale et Santé Publique, Nouzilly, France
| | - Cedric Neveu
- French National Institute for Agricultural Research (INRA), Infectiologie Animale et Santé Publique, Nouzilly, France
| | - A Christopher Green
- Dstl, Defence Science and Technology Laboratory, Porton Down, Salisbury, Wiltshire, United Kingdom
| | - John E H Tattersall
- Dstl, Defence Science and Technology Laboratory, Porton Down, Salisbury, Wiltshire, United Kingdom
| | - Lindy Holden-Dye
- Dstl, Defence Science and Technology Laboratory, Porton Down, Salisbury, Wiltshire, United Kingdom
| | - Vincent O'Connor
- Biological Sciences, Institute for Life Sciences, University of Southampton, Southampton, United Kingdom
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6
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An extracellular scaffolding complex confers unusual rectification upon an ionotropic acetylcholine receptor in C. elegans. Proc Natl Acad Sci U S A 2022; 119:e2113545119. [PMID: 35858330 PMCID: PMC9304021 DOI: 10.1073/pnas.2113545119] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Biophysical properties of ligand-gated receptors can be profoundly modified by auxiliary subunits or by the lipid microenvironment of the membrane. Hence, it is sometimes challenging to relate the properties of receptors reconstituted in heterologous expression systems to those of their native counterparts. Here we show that the properties of Caenorhabditis elegans levamisole-sensitive acetylcholine receptors (L-AChRs), the ionotropic acetylcholine receptors targeted by the cholinergic anthelmintic levamisole at neuromuscular junctions, can be profoundly modified by their clustering machinery. We uncovered that L-AChRs exhibit a strong outward rectification in vivo, which was not previously described in heterologous systems. This unusual feature for an ionotropic AChR is abolished by disrupting the interaction of the receptors with the extracellular complex required for their synaptic clustering. When recorded at -60 mV, levamisole-induced currents are similar in the wild type and in L-AChR-clustering-defective mutants, while they are halved in these mutants at more depolarized physiological membrane potentials. Consequently, levamisole causes a strong muscle depolarization in the wild type, which leads to complete inactivation of the voltage-gated calcium channels and to an irreversible flaccid paralysis. In mutants defective for L-AChR clustering, the levamisole-induced depolarization is weaker, allowing voltage-gated calcium channels to remain partially active, which eventually leads to adaptation and survival of the worms. This explains why historical screens for C. elegans mutants resistant to levamisole identified the components of the L-AChR clustering machinery, in addition to proteins required for receptor biosynthesis or efficacy. This work further emphasizes the importance of pursuing ligand-gated channel characterization in their native environment.
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7
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Davis AN, Tanis JE. Measuring Caenorhabditis elegans Sensitivity to the Acetylcholine Receptor Agonist Levamisole. J Vis Exp 2022:10.3791/64056. [PMID: 35758705 PMCID: PMC10016203 DOI: 10.3791/64056] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
At the neuromuscular junction (NMJ), the binding of the excitatory neurotransmitter acetylcholine (ACh) to postsynaptic receptors leads to muscle contraction. As in vertebrate skeletal muscle, cholinergic signaling in the body wall muscles of the model organism Caenorhabditis elegans is required for locomotion. Exposure to levamisole, a pharmacological agonist of one class of ACh receptors on the body wall muscles, causes time-dependent paralysis of wild-type animals. Altered sensitivity to levamisole suggests defects in signaling at the NMJ or muscle function. Here, a protocol for a liquid levamisole assay performed on C. elegans grown in 24-well plates is presented. Vigorous swimming of the animals in liquid allows for the assessment and quantitation of levamisole-induced paralysis in hundreds of worms over a one-hour time period without requiring physical manipulation. This procedure can be used with both wild-type and mutants that have altered sensitivity to levamisole to demonstrate the functional consequences of altered signaling at the NMJ.
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8
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The signaling pathway of levamisole-sensitive-acetylcholine receptors involved in short-term forgetting of Caenorhabditis elegans. Mol Genet Genomics 2022; 297:1027-1038. [PMID: 35585325 DOI: 10.1007/s00438-022-01901-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2022] [Accepted: 04/16/2022] [Indexed: 10/18/2022]
Abstract
In contrast to the popular opinion that forgetting is only the opposite of learning and memory, active forgetting explains the intrinsic instability of a labile memory that lasts for hours and has its own signal transduction pathways. However, the detailed mechanisms underlying forgetting are still lacking, though the investigations available in this field offer the first insights into their regulation. To identify the alternative signaling pathways that control the process of forgetting, we used the short-term forgetting model of Caenorhabditis elegans and discovered the involvement of lev-10, a scaffolded transmembrane protein of L-AChR, by screening the candidate genes that potentially functioned in synaptic plasticity. The LEV-9/LEV-10/L-AChR functional complex was confirmed to participate in forgetting occurrence. Furthermore, EGL-9 functioned upstream of LEV-10 and negatively regulated the latter during forgetting. Meanwhile, EGL-9 was also the target of miR-51, and hence the mutation of miR-51 similarly affected the function of L-AChR and delayed the short-term forgetting. Our findings have identified an integrated signaling pathway responsible for active forgetting, which provides the new experimental evidence on the cholinergic forgetting signal.
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9
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González-Calvo I, Cizeron M, Bessereau JL, Selimi F. Synapse Formation and Function Across Species: Ancient Roles for CCP, CUB, and TSP-1 Structural Domains. Front Neurosci 2022; 16:866444. [PMID: 35546877 PMCID: PMC9083331 DOI: 10.3389/fnins.2022.866444] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Accepted: 03/28/2022] [Indexed: 11/17/2022] Open
Abstract
The appearance of synapses was a crucial step in the creation of the variety of nervous systems that are found in the animal kingdom. With increased complexity of the organisms came a greater number of synaptic proteins. In this review we describe synaptic proteins that contain the structural domains CUB, CCP, or TSP-1. These domains are found in invertebrates and vertebrates, and CUB and CCP domains were initially described in proteins belonging to the complement system of innate immunity. Interestingly, they are found in synapses of the nematode C. elegans, which does not have a complement system, suggesting an ancient function. Comparison of the roles of CUB-, CCP-, and TSP-1 containing synaptic proteins in various species shows that in more complex nervous systems, these structural domains are combined with other domains and that there is partial conservation of their function. These three domains are thus basic building blocks of the synaptic architecture. Further studies of structural domains characteristic of synaptic proteins in invertebrates such as C. elegans and comparison of their role in mammals will help identify other conserved synaptic molecular building blocks. Furthermore, this type of functional comparison across species will also identify structural domains added during evolution in correlation with increased complexity, shedding light on mechanisms underlying cognition and brain diseases.
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Affiliation(s)
- Inés González-Calvo
- Center for Interdisciplinary Research in Biology (CIRB), Collège de France, CNRS, INSERM, PSL Research University, Paris, France
| | - Mélissa Cizeron
- Univ Lyon, Université Claude Bernard Lyon 1, CNRS UMR-5284, INSERM U-1314, MeLiS, Institut NeuroMyoGène, Lyon, France
| | - Jean-Louis Bessereau
- Univ Lyon, Université Claude Bernard Lyon 1, CNRS UMR-5284, INSERM U-1314, MeLiS, Institut NeuroMyoGène, Lyon, France
| | - Fekrije Selimi
- Center for Interdisciplinary Research in Biology (CIRB), Collège de France, CNRS, INSERM, PSL Research University, Paris, France
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10
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Izquierdo PG, Calahorro F, Thisainathan T, Atkins JH, Haszczyn J, Lewis CJ, Tattersall JEH, Green AC, Holden-Dye L, O'Connor V. Cholinergic signaling at the body wall neuromuscular junction distally inhibits feeding behavior in Caenorhabditis elegans. J Biol Chem 2021; 298:101466. [PMID: 34864060 PMCID: PMC8801469 DOI: 10.1016/j.jbc.2021.101466] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2021] [Revised: 11/13/2021] [Accepted: 11/30/2021] [Indexed: 12/27/2022] Open
Abstract
Complex biological functions within organisms are frequently orchestrated by systemic communication between tissues. In the model organism Caenorhabditis elegans, the pharyngeal and body wall neuromuscular junctions are two discrete structures that control feeding and locomotion, respectively. Separate, the well-defined neuromuscular circuits control these distinct tissues. Nonetheless, the emergent behaviors, feeding and locomotion, are coordinated to guarantee the efficiency of food intake. Here, we show that pharmacological hyperactivation of cholinergic transmission at the body wall muscle reduces the rate of pumping behavior. This was evidenced by a systematic screening of the effect of the cholinesterase inhibitor aldicarb on the rate of pharyngeal pumping on food in mutant worms. The screening revealed that the key determinants of the inhibitory effect of aldicarb on pharyngeal pumping are located at the body wall neuromuscular junction. In fact, the selective stimulation of the body wall muscle receptors with the agonist levamisole inhibited pumping in a lev-1-dependent fashion. Interestingly, this response was independent of unc-38, an alpha subunit of the nicotinic receptor classically expressed with lev-1 at the body wall muscle. This implies an uncharacterized lev-1-containing receptor underpins this effect. Overall, our results reveal that body wall cholinergic transmission not only controls locomotion but simultaneously inhibits feeding behavior.
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Affiliation(s)
- Patricia G Izquierdo
- School of Biological Sciences, Faculty of Environmental and Life Sciences, University of Southampton, Southampton, United Kingdom.
| | - Fernando Calahorro
- School of Biological Sciences, Faculty of Environmental and Life Sciences, University of Southampton, Southampton, United Kingdom
| | - Thibana Thisainathan
- School of Biological Sciences, Faculty of Environmental and Life Sciences, University of Southampton, Southampton, United Kingdom
| | - James H Atkins
- School of Biological Sciences, Faculty of Environmental and Life Sciences, University of Southampton, Southampton, United Kingdom
| | - Johanna Haszczyn
- School of Biological Sciences, Faculty of Environmental and Life Sciences, University of Southampton, Southampton, United Kingdom
| | - Christian J Lewis
- School of Biological Sciences, Faculty of Environmental and Life Sciences, University of Southampton, Southampton, United Kingdom
| | - John E H Tattersall
- Dstl, Defence Science and Technology Laboratory, Porton Down, Salisbury, Wiltshire, United Kingdom
| | - A Christopher Green
- Dstl, Defence Science and Technology Laboratory, Porton Down, Salisbury, Wiltshire, United Kingdom
| | - Lindy Holden-Dye
- School of Biological Sciences, Faculty of Environmental and Life Sciences, University of Southampton, Southampton, United Kingdom
| | - Vincent O'Connor
- School of Biological Sciences, Faculty of Environmental and Life Sciences, University of Southampton, Southampton, United Kingdom
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11
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Zhou X, Vachon C, Cizeron M, Romatif O, Bülow HE, Jospin M, Bessereau JL. The HSPG syndecan is a core organizer of cholinergic synapses. J Cell Biol 2021; 220:212450. [PMID: 34213535 PMCID: PMC8258370 DOI: 10.1083/jcb.202011144] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2020] [Revised: 04/13/2021] [Accepted: 05/26/2021] [Indexed: 12/15/2022] Open
Abstract
The extracellular matrix has emerged as an active component of chemical synapses regulating synaptic formation, maintenance, and homeostasis. The heparan sulfate proteoglycan (HSPG) syndecans are known to regulate cellular and axonal migration in the brain. They are also enriched at synapses, but their synaptic functions remain more elusive. Here, we show that SDN-1, the sole orthologue of syndecan in C. elegans, is absolutely required for the synaptic clustering of homomeric α7-like acetylcholine receptors (AChRs) and regulates the synaptic content of heteromeric AChRs. SDN-1 is concentrated at neuromuscular junctions (NMJs) by the neurally secreted synaptic organizer Ce-Punctin/MADD-4, which also activates the transmembrane netrin receptor DCC. Those cooperatively recruit the FARP and CASK orthologues that localize α7-like-AChRs at cholinergic NMJs through physical interactions. Therefore, SDN-1 stands at the core of the cholinergic synapse organization by bridging the extracellular synaptic determinants to the intracellular synaptic scaffold that controls the postsynaptic receptor content.
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Affiliation(s)
- Xin Zhou
- Université de Lyon, Université Claude Bernard Lyon 1, Centre National de la Recherche Scientifique Unite Mixte de Recherche 5310, Institut National de la Santé et de la Recherche Médicale U1217, Institut NeuroMyoGène, Lyon, France
| | - Camille Vachon
- Université de Lyon, Université Claude Bernard Lyon 1, Centre National de la Recherche Scientifique Unite Mixte de Recherche 5310, Institut National de la Santé et de la Recherche Médicale U1217, Institut NeuroMyoGène, Lyon, France
| | - Mélissa Cizeron
- Université de Lyon, Université Claude Bernard Lyon 1, Centre National de la Recherche Scientifique Unite Mixte de Recherche 5310, Institut National de la Santé et de la Recherche Médicale U1217, Institut NeuroMyoGène, Lyon, France
| | - Océane Romatif
- Université de Lyon, Université Claude Bernard Lyon 1, Centre National de la Recherche Scientifique Unite Mixte de Recherche 5310, Institut National de la Santé et de la Recherche Médicale U1217, Institut NeuroMyoGène, Lyon, France
| | - Hannes E Bülow
- Department of Genetics and Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY
| | - Maëlle Jospin
- Université de Lyon, Université Claude Bernard Lyon 1, Centre National de la Recherche Scientifique Unite Mixte de Recherche 5310, Institut National de la Santé et de la Recherche Médicale U1217, Institut NeuroMyoGène, Lyon, France
| | - Jean-Louis Bessereau
- Université de Lyon, Université Claude Bernard Lyon 1, Centre National de la Recherche Scientifique Unite Mixte de Recherche 5310, Institut National de la Santé et de la Recherche Médicale U1217, Institut NeuroMyoGène, Lyon, France
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12
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Cizeron M, Granger L, Bülow HE, Bessereau JL. Specific heparan sulfate modifications stabilize the synaptic organizer MADD-4/Punctin at C. elegans neuromuscular junctions. Genetics 2021; 218:6275221. [PMID: 33983408 DOI: 10.1093/genetics/iyab073] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2021] [Accepted: 04/16/2021] [Indexed: 01/01/2023] Open
Abstract
Heparan sulfate proteoglycans contribute to the structural organization of various neurochemical synapses. Depending on the system, their role involves either the core protein or the glycosaminoglycan chains. These linear sugar chains are extensively modified by heparan sulfate modification enzymes, resulting in highly diverse molecules. Specific modifications of glycosaminoglycan chains may thus contribute to a sugar code involved in synapse specificity. Caenorhabditis elegans is particularly useful to address this question because of the low level of genomic redundancy of these enzymes, as opposed to mammals. Here, we systematically mutated the genes encoding heparan sulfate modification enzymes in C. elegans and analyzed their impact on excitatory and inhibitory neuromuscular junctions. Using single chain antibodies that recognize different heparan sulfate modification patterns, we show in vivo that these two heparan sulfate epitopes are carried by the SDN-1 core protein, the unique C. elegans syndecan orthologue, at neuromuscular junctions. Intriguingly, these antibodies differentially bind to excitatory and inhibitory synapses, implying unique heparan sulfate modification patterns at different neuromuscular junctions. Moreover, while most enzymes are individually dispensable for proper organization of neuromuscular junctions, we show that 3-O-sulfation of SDN-1 is required to maintain wild-type levels of the extracellular matrix protein MADD-4/Punctin, a central synaptic organizer that defines the identity of excitatory and inhibitory synaptic domains at the plasma membrane of muscle cells.
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Affiliation(s)
- Mélissa Cizeron
- Univ Lyon, Université Claude Bernard Lyon 1, CNRS UMR 5310, INSERM U 1217, Institut NeuroMyoGène, 69008 Lyon, France
| | - Laure Granger
- Univ Lyon, Université Claude Bernard Lyon 1, CNRS UMR 5310, INSERM U 1217, Institut NeuroMyoGène, 69008 Lyon, France
| | - Hannes E Bülow
- Department of Genetics & Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461, United States
| | - Jean-Louis Bessereau
- Univ Lyon, Université Claude Bernard Lyon 1, CNRS UMR 5310, INSERM U 1217, Institut NeuroMyoGène, 69008 Lyon, France
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13
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Chaya T, Patel S, Smith EM, Lam A, Miller EN, Clupper M, Kervin K, Tanis JE. A C. elegans genome-wide RNAi screen for altered levamisole sensitivity identifies genes required for muscle function. G3-GENES GENOMES GENETICS 2021; 11:6169532. [PMID: 33713125 PMCID: PMC8049432 DOI: 10.1093/g3journal/jkab047] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/11/2020] [Accepted: 02/09/2021] [Indexed: 01/17/2023]
Abstract
At the neuromuscular junction (NMJ), postsynaptic ionotropic acetylcholine receptors (AChRs) transduce a chemical signal released from a cholinergic motor neuron into an electrical signal to induce muscle contraction. To identify regulators of postsynaptic function, we conducted a genome-wide RNAi screen for genes required for proper response to levamisole, a pharmacological agonist of ionotropic L-AChRs at the Caenorhabditis elegans NMJ. A total of 117 gene knockdowns were found to cause levamisole hypersensitivity, while 18 resulted in levamisole resistance. Our screen identified conserved genes important for muscle function including some that are mutated in congenital myasthenic syndrome, congenital muscular dystrophy, congenital myopathy, myotonic dystrophy, and mitochondrial myopathy. Of the genes found in the screen, we further investigated those predicted to play a role in endocytosis of cell surface receptors. Loss of the Epsin homolog epn-1 caused levamisole hypersensitivity and had opposing effects on the levels of postsynaptic L-AChRs and GABAA receptors, resulting in increased and decreased abundance, respectively. We also examined other genes that resulted in a levamisole-hypersensitive phenotype when knocked down including gas-1, which functions in Complex I of the mitochondrial electron transport chain. Consistent with altered ATP synthesis impacting levamisole response, treatment of wild-type animals with levamisole resulted in L-AChR–dependent depletion of ATP levels. These results suggest that the paralytic effects of levamisole ultimately lead to metabolic exhaustion.
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Affiliation(s)
- Timothy Chaya
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Shrey Patel
- Department of Biological Sciences, University of Delaware, Newark, DE 19716, USA
| | - Erin M Smith
- Department of Biological Sciences, University of Delaware, Newark, DE 19716, USA
| | - Andy Lam
- Department of Biological Sciences, University of Delaware, Newark, DE 19716, USA
| | - Elaine N Miller
- Department of Biological Sciences, University of Delaware, Newark, DE 19716, USA
| | - Michael Clupper
- Department of Biological Sciences, University of Delaware, Newark, DE 19716, USA
| | - Kirsten Kervin
- Department of Biological Sciences, University of Delaware, Newark, DE 19716, USA
| | - Jessica E Tanis
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.,Department of Biological Sciences, University of Delaware, Newark, DE 19716, USA
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14
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Treinin M, Jin Y. Cholinergic transmission in C. elegans: Functions, diversity, and maturation of ACh-activated ion channels. J Neurochem 2020; 158:1274-1291. [PMID: 32869293 DOI: 10.1111/jnc.15164] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2020] [Revised: 08/13/2020] [Accepted: 08/21/2020] [Indexed: 02/06/2023]
Abstract
Acetylcholine is an abundant neurotransmitter in all animals. Effects of acetylcholine are excitatory, inhibitory, or modulatory depending on the receptor and cell type. Research using the nematode C. elegans has made ground-breaking contributions to the mechanistic understanding of cholinergic transmission. Powerful genetic screens for behavioral mutants or for responses to pharmacological reagents identified the core cellular machinery for synaptic transmission. Pharmacological reagents that perturb acetylcholine-mediated processes led to the discovery and also uncovered the composition and regulators of acetylcholine-activated channels and receptors. From a combination of electrophysiological and molecular cellular studies, we have gained a profound understanding of cholinergic signaling at the levels of synapses, neural circuits, and animal behaviors. This review will begin with a historical overview, then cover in-depth current knowledge on acetylcholine-activated ionotropic receptors, mechanisms regulating their functional expression and their functions in regulating locomotion.
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Affiliation(s)
- Millet Treinin
- Department of Medical Neurobiology, Hadassah Medical school - Hebrew University, Jerusalem, Israel
| | - Yishi Jin
- Section of Neurobiology, Division of Biological Sciences, University of California San Diego, La Jolla, CA, USA
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15
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Sengupta S, Crowe LB, You S, Roberts MA, Jackson FR. A Secreted Ig-Domain Protein Required in Both Astrocytes and Neurons for Regulation of Drosophila Night Sleep. Curr Biol 2019; 29:2547-2554.e2. [PMID: 31353186 DOI: 10.1016/j.cub.2019.06.055] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2019] [Revised: 05/20/2019] [Accepted: 06/19/2019] [Indexed: 12/29/2022]
Abstract
Endogenous rhythmic behaviors are evolutionarily conserved and essential for life. In mammalian and invertebrate models, well-characterized neuronal circuits and evolutionarily conserved mechanisms regulate circadian behavior and sleep [1-4]. In Drosophila, neuronal populations located in multiple brain regions mediate arousal, sleep drive, and homeostasis (reviewed in [3, 5-7]). Similar to mammals [8], there is also evidence that fly glial cells modulate the neuronal circuits controlling rhythmic behaviors, including sleep [1]. Here, we describe a novel gene (CG14141; aka Nkt) that is required for normal sleep. NKT is a 162-amino-acid protein with a single IgC2 immunoglobulin (Ig) domain and a high-quality signal peptide [9], and we show evidence that it is secreted, similar to its C. elegans ortholog (OIG-4) [10]. We demonstrate that Nkt-null flies or those with selective knockdown in either neurons or glia have decreased and fragmented night sleep, indicative of a non-redundant requirement in both cell types. We show that Nkt is required in fly astrocytes and in a specific set of wake-promoting neurons-the mushroom body (MB) α'β' cells that link sleep to memory consolidation [11]. Importantly, Nkt gene expression is required in the adult nervous system for normal sleep, consistent with a physiological rather than developmental function for the Ig-domain protein.
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Affiliation(s)
- Sukanya Sengupta
- Department of Neuroscience, Sackler School of Biomedical Sciences, Tufts University School of Medicine, Boston, MA 02111, USA
| | - Lauren B Crowe
- Department of Neuroscience, Sackler School of Biomedical Sciences, Tufts University School of Medicine, Boston, MA 02111, USA
| | - Samantha You
- Department of Neuroscience, Sackler School of Biomedical Sciences, Tufts University School of Medicine, Boston, MA 02111, USA
| | - Mary A Roberts
- Department of Neuroscience, Sackler School of Biomedical Sciences, Tufts University School of Medicine, Boston, MA 02111, USA
| | - F Rob Jackson
- Department of Neuroscience, Sackler School of Biomedical Sciences, Tufts University School of Medicine, Boston, MA 02111, USA.
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16
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Hendi A, Kurashina M, Mizumoto K. Intrinsic and extrinsic mechanisms of synapse formation and specificity in C. elegans. Cell Mol Life Sci 2019; 76:2719-2738. [PMID: 31037336 PMCID: PMC11105629 DOI: 10.1007/s00018-019-03109-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2019] [Revised: 04/11/2019] [Accepted: 04/15/2019] [Indexed: 12/18/2022]
Abstract
Precise neuronal wiring is critical for the function of the nervous system and is ultimately determined at the level of individual synapses. Neurons integrate various intrinsic and extrinsic cues to form synapses onto their correct targets in a stereotyped manner. In the past decades, the nervous system of nematode (Caenorhabditis elegans) has provided the genetic platform to reveal the genetic and molecular mechanisms of synapse formation and specificity. In this review, we will summarize the recent discoveries in synapse formation and specificity in C. elegans.
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Affiliation(s)
- Ardalan Hendi
- Department of Zoology, The University of British Columbia, 2406-2350 Health Sciences Mall, Vancouver, BC, V6T 1Z3, Canada
| | - Mizuki Kurashina
- Department of Zoology, The University of British Columbia, 2406-2350 Health Sciences Mall, Vancouver, BC, V6T 1Z3, Canada
| | - Kota Mizumoto
- Department of Zoology, The University of British Columbia, 2406-2350 Health Sciences Mall, Vancouver, BC, V6T 1Z3, Canada.
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17
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Blazie SM, Jin Y. Pharming for Genes in Neurotransmission: Combining Chemical and Genetic Approaches in Caenorhabditis elegans. ACS Chem Neurosci 2018; 9:1963-1974. [PMID: 29432681 DOI: 10.1021/acschemneuro.7b00509] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Synaptic transmission is central to nervous system function. Chemical and genetic screens are valuable approaches to probe synaptic mechanisms in living animals. The nematode Caenorhabditis elegans is a prime system to apply these methods to discover genes and dissect the cellular pathways underlying neurotransmission. Here, we review key approaches to understand neurotransmission and the action of psychiatric drugs in C. elegans. We start with early studies on cholinergic excitatory signaling at the neuromuscular junction, and move into mechanisms mediated by biogenic amines. Finally, we discuss emerging work toward understanding the mechanisms driving synaptic plasticity with a focus on regulation of protein translation.
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Affiliation(s)
- Stephen M. Blazie
- Neurobiology Section, Division of Biological Sciences, University of California, San Diego, La Jolla, California 92093, United States
| | - Yishi Jin
- Neurobiology Section, Division of Biological Sciences, University of California, San Diego, La Jolla, California 92093, United States
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18
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Philbrook A, Ramachandran S, Lambert CM, Oliver D, Florman J, Alkema MJ, Lemons M, Francis MM. Neurexin directs partner-specific synaptic connectivity in C. elegans. eLife 2018; 7:35692. [PMID: 30039797 PMCID: PMC6057746 DOI: 10.7554/elife.35692] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2018] [Accepted: 06/21/2018] [Indexed: 01/14/2023] Open
Abstract
In neural circuits, individual neurons often make projections onto multiple postsynaptic partners. Here, we investigate molecular mechanisms by which these divergent connections are generated, using dyadic synapses in C. elegans as a model. We report that C. elegans nrx-1/neurexin directs divergent connectivity through differential actions at synapses with partnering neurons and muscles. We show that cholinergic outputs onto neurons are, unexpectedly, located at previously undefined spine-like protrusions from GABAergic dendrites. Both these spine-like features and cholinergic receptor clustering are strikingly disrupted in the absence of nrx-1. Excitatory transmission onto GABAergic neurons, but not neuromuscular transmission, is also disrupted. Our data indicate that NRX-1 located at presynaptic sites specifically directs postsynaptic development in GABAergic neurons. Our findings provide evidence that individual neurons can direct differential patterns of connectivity with their post-synaptic partners through partner-specific utilization of synaptic organizers, offering a novel view into molecular control of divergent connectivity. Nervous systems are complex networks of interconnected cells called neurons. These networks vary in size from a few hundred cells in worms, to tens of billions in the human brain. Within these networks, each individual neuron forms connections – called synapses – with many others. But these partner neurons are not necessarily alike. In fact, they may be different cell types. How neurons form distinct connections with different partner cells remains unclear. Part of the answer may lie in specialized proteins called cell adhesion molecules. These proteins occur on the cell surface and enable neurons to recognize one another. This helps ensure that the cells form appropriate connections via synapses. Cell adhesion molecules are therefore also known as synaptic organizers. Philbrook et al. have now examined the role of synaptic organizers in wiring up the nervous system of the nematode worm and model organism Caenorhabditis elegans. Motor neurons form connections with two types of partner cell: muscle cells and neurons. Philbrook et al. screened C. elegans that have mutations in genes encoding various synaptic organizers. This revealed that a protein called neurexin must be present for motor neurons to form synapses with other neurons. By contrast, neurexin is not required for the same neurons to establish synapses with muscles. Philbrook et al. found that neuron-to-neuron synapses arise at specialized finger-like projections. These resemble the dendritic spines at which synapses form in the brains of mammals, and had not been previously identified in C. elegans. In worms that lack neurexin, these spine-like structures do not form correctly, disrupting the formation of neuron-to-neuron connections. Previous work has implicated neurexin in synapse formation in the mammalian brain. But this is the first study to reveal a role for neurexin in establishing partner-specific synaptic connections. Mutations in synaptic organizers, including neurexin, contribute to disorders of brain development. These include schizophrenia and autism spectrum disorders. Learning more about how neurexin helps establish specific synaptic connections may help us understand how these disorders arise.
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Affiliation(s)
- Alison Philbrook
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, United States
| | - Shankar Ramachandran
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, United States
| | - Christopher M Lambert
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, United States
| | - Devyn Oliver
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, United States
| | - Jeremy Florman
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, United States
| | - Mark J Alkema
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, United States
| | - Michele Lemons
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, United States.,Department of Natural Sciences, Assumption College, Worcester, United States
| | - Michael M Francis
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, United States
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19
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The Claudin-like Protein HPO-30 Is Required to Maintain LAChRs at the C. elegans Neuromuscular Junction. J Neurosci 2018; 38:7072-7087. [PMID: 29950505 PMCID: PMC6083452 DOI: 10.1523/jneurosci.3487-17.2018] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2017] [Revised: 06/07/2018] [Accepted: 06/07/2018] [Indexed: 12/22/2022] Open
Abstract
Communications across chemical synapses are primarily mediated by neurotransmitters and their postsynaptic receptors. There are diverse molecular systems to localize and regulate the receptors at the synapse. Here, we identify HPO-30, a member of the claudin superfamily of membrane proteins, as a positive regulator for synaptic localization of levamisole-dependent AChRs (LAChRs) at the Caenorhabditis elegans neuromuscular junction (NMJ). The HPO-30 protein localizes at the NMJ and shows genetic and physical association with the LAChR subunits LEV-8, UNC-29, and UNC-38. Using genetic and electrophysiological assays in the hermaphrodite C. elegans, we demonstrate that HPO-30 functions through Neuroligin at the NMJ to maintain postsynaptic LAChR levels at the synapse. Together, this work suggests a novel function for a tight junction protein in maintaining normal receptor levels at the NMJ. SIGNIFICANCE STATEMENT Claudins are a large superfamily of membrane proteins. Their role in maintaining the functional integrity of tight junctions has been widely explored. Our experiments suggest a critical role for the claudin-like protein, HPO-30, in maintaining synaptic levamisole-dependent AChR (LAChR) levels. LAChRs contribute to <20% of the acetylcholine-mediated conductance in adult Caenorhabditis elegans; however, they play a significant functional role in worm locomotion. This study provides a new perspective in the study of LAChR physiology.
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20
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Martin AA, Richmond JE. The sarco(endo)plasmic reticulum calcium ATPase SCA-1 regulates the Caenorhabditis elegans nicotinic acetylcholine receptor ACR-16. Cell Calcium 2018; 72:104-115. [PMID: 29748129 DOI: 10.1016/j.ceca.2018.02.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2018] [Revised: 02/22/2018] [Accepted: 02/22/2018] [Indexed: 12/26/2022]
Abstract
Nicotinic acetylcholine receptors (nAChR) are present in many excitable tissues and are found both pre and post-synaptically. Through their non-specific cationic permeability, these nAChRs have excitatory roles in neurotransmission, neuromodulation, synaptic plasticity, and neuroprotection. Thus, nAChR mislocalization or functional deficits are associated with many neurological disease states. Therefore identifying the mechanisms that regulate nAChR expression and function will inform our understanding of normal as well as pathological physiological conditions and offer avenues for potential therapeutic advances. Taking advantage of the genetic tractability of the soil nematode Caenorhabditis elegans, a forward genetic screen was performed to isolate regulators of the vertebrate α7 nAChR homologue ACR-16. From this screen a novel regulator of the ACR-16 receptor was identified, the sarco(endo)plasmic reticulum calcium ATPase sca-1. The sca-1 mutant affects ACR-16 receptor level at the NMJ, receptor functionality, and synaptic transmission. Responses to pressure-ejected nicotine in sca-1 mutants are indistinguishable from wild type, which implies the ACR-16 receptors are mislocalized at the NMJ. Changes in cytosolic baseline calcium levels in sca-1 and other mutants indicates a calcium-driven regulation mechanism of the α7-like NAChR ACR-16.
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Affiliation(s)
- Ashley A Martin
- Department of Biological Sciences, University of Illinois at Chicago, Chicago, IL 60607, United States.
| | - Janet E Richmond
- Department of Biological Sciences, University of Illinois at Chicago, Chicago, IL 60607, United States
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21
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Preventing Illegitimate Extrasynaptic Acetylcholine Receptor Clustering Requires the RSU-1 Protein. J Neurosci 2017; 36:6525-37. [PMID: 27307240 DOI: 10.1523/jneurosci.3733-15.2016] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2015] [Accepted: 05/06/2016] [Indexed: 12/28/2022] Open
Abstract
UNLABELLED Diffuse extrasynaptic neurotransmitter receptors constitute an abundant pool of receptors that can be recruited to modulate synaptic strength. Whether the diffuse distribution of receptors in extrasynaptic membranes is a default state or is actively controlled remains essentially unknown. Here we show that RSU-1 (Ras Suppressor-1) is required for the proper distribution of extrasynaptic acetylcholine receptors (AChRs) in Caenorhabditis elegans muscle cells. RSU-1 is an evolutionary conserved cytoplasmic protein that contains multiple leucine-rich repeats (LRRs) and interacts with integrin-dependent adhesion complexes. In rsu-1 mutants, neuromuscular junctions differentiate as in the wild type, but AChRs assemble into ectopic clusters that progressively enlarge during development. As a consequence, the synaptic content of AChRs is reduced. Our study provides the first evidence that an RSU-1-dependent active mechanism maintains extrasynaptic receptors dispersed and indirectly regulates synapse maturation. SIGNIFICANCE STATEMENT Using Caenorhabditis elegans neuromuscular junction as a model synapse, we uncovered a novel mechanism that regulates the distribution of acetylcholine receptors (AChRs). In an unbiased visual screen for mutants with abnormal AChR distribution, we isolated the ras suppressor 1 (rsu-1) mutant based on the presence of large extrasynaptic clusters. We show that disrupting rsu-1 causes spontaneous clustering of extrasynaptic receptors that are normally dispersed, independently of synaptic cues. These clusters outcompete synaptic domains and cause a decrease of synaptic receptor content. These results indicate that the diffuse state of extrasynaptic receptors is not a default state that is simply explained by the lack of synaptic cues but necessitates additional proteins to prevent spontaneous clustering, a concept that is relevant for developmental and pathological situations.
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22
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Howell K, Hobert O. Morphological Diversity of C. elegans Sensory Cilia Instructed by the Differential Expression of an Immunoglobulin Domain Protein. Curr Biol 2017; 27:1782-1790.e5. [PMID: 28578929 DOI: 10.1016/j.cub.2017.05.006] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2017] [Revised: 04/27/2017] [Accepted: 05/03/2017] [Indexed: 01/08/2023]
Abstract
Cilia on dendritic endings of sensory neurons organize distinct types of sensory machinery [1]. Ciliated endings display neuron-type-specific patterns of membrane elaborations [1-3], but it is not well understood how such neuron-type-specific morphologies are generated and whether they are coupled to the specification of other identity aspects of a terminally differentiated sensory neuron. In the course of a genome-wide analysis of members of a small family of immunoglobulin domain proteins, we found that OIG-8, a previously uncharacterized transmembrane protein with a single immunoglobulin (Ig) domain, instructs the distinct, neuron-type-specific elaboration of ciliated endings of different olfactory neuron types in the nematode C. elegans. OIG-8 protein localizes to ciliated endings of these sensory neurons, and is transcribed at different levels in distinct olfactory neuron types. oig-8 expression levels correlate with the extent of sensory cilia growth and branching patterns. Loss of oig-8 leads to a reduction in the branching patterns of cilia, whereas raising the levels of oig-8 results in an increase in elaborations. Levels of OIG-8 expression are controlled by the specific combination of a terminal selector type of transcription factors that also specify other identity features of distinct olfactory neuron types.
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Affiliation(s)
- Kelly Howell
- Department of Biological Sciences, Howard Hughes Medical Institute, Columbia University, New York, NY 10027, USA.
| | - Oliver Hobert
- Department of Biological Sciences, Howard Hughes Medical Institute, Columbia University, New York, NY 10027, USA.
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23
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Ng FS, Sengupta S, Huang Y, Yu AM, You S, Roberts MA, Iyer LK, Yang Y, Jackson FR. TRAP-seq Profiling and RNAi-Based Genetic Screens Identify Conserved Glial Genes Required for Adult Drosophila Behavior. Front Mol Neurosci 2016; 9:146. [PMID: 28066175 PMCID: PMC5177635 DOI: 10.3389/fnmol.2016.00146] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2016] [Accepted: 11/30/2016] [Indexed: 01/06/2023] Open
Abstract
Although, glial cells have well characterized functions in the developing and mature brain, it is only in the past decade that roles for these cells in behavior and plasticity have been delineated. Glial astrocytes and glia-neuron signaling, for example, are now known to have important modulatory functions in sleep, circadian behavior, memory and plasticity. To better understand mechanisms of glia-neuron signaling in the context of behavior, we have conducted cell-specific, genome-wide expression profiling of adult Drosophila astrocyte-like brain cells and performed RNA interference (RNAi)-based genetic screens to identify glial factors that regulate behavior. Importantly, our studies demonstrate that adult fly astrocyte-like cells and mouse astrocytes have similar molecular signatures; in contrast, fly astrocytes and surface glia-different classes of glial cells-have distinct expression profiles. Glial-specific expression of 653 RNAi constructs targeting 318 genes identified multiple factors associated with altered locomotor activity, circadian rhythmicity and/or responses to mechanical stress (bang sensitivity). Of interest, 1 of the relevant genes encodes a vesicle recycling factor, 4 encode secreted proteins and 3 encode membrane transporters. These results strongly support the idea that glia-neuron communication is vital for adult behavior.
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Affiliation(s)
- Fanny S Ng
- Department of Neuroscience, Sackler Program in Biomedical Sciences, Tufts University School of Medicine Boston, MA, USA
| | - Sukanya Sengupta
- Department of Neuroscience, Sackler Program in Biomedical Sciences, Tufts University School of Medicine Boston, MA, USA
| | - Yanmei Huang
- Department of Neuroscience, Sackler Program in Biomedical Sciences, Tufts University School of Medicine Boston, MA, USA
| | - Amy M Yu
- Department of Neuroscience, Sackler Program in Biomedical Sciences, Tufts University School of Medicine Boston, MA, USA
| | - Samantha You
- Department of Neuroscience, Sackler Program in Biomedical Sciences, Tufts University School of Medicine Boston, MA, USA
| | - Mary A Roberts
- Department of Neuroscience, Sackler Program in Biomedical Sciences, Tufts University School of Medicine Boston, MA, USA
| | - Lakshmanan K Iyer
- Department of Neuroscience, Sackler Program in Biomedical Sciences, Tufts University School of Medicine Boston, MA, USA
| | - Yongjie Yang
- Department of Neuroscience, Sackler Program in Biomedical Sciences, Tufts University School of Medicine Boston, MA, USA
| | - F Rob Jackson
- Department of Neuroscience, Sackler Program in Biomedical Sciences, Tufts University School of Medicine Boston, MA, USA
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24
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Howell K, Hobert O. Small Immunoglobulin Domain Proteins at Synapses and the Maintenance of Neuronal Features. Neuron 2016; 89:239-41. [PMID: 26796686 DOI: 10.1016/j.neuron.2016.01.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The integrity of neural circuits must be maintained throughout the lifetime of an organism. In this issue of Neuron, Cherra and Jin (2016) characterize a small, two-Ig domain protein, ZIG-10, and its role in maintaining synaptic density in a specific set of C. elegans neurons.
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Affiliation(s)
- Kelly Howell
- Department of Biology, Howard Hughes Medical Institute, Columbia University, New York, NY 10032, USA.
| | - Oliver Hobert
- Department of Biology, Howard Hughes Medical Institute, Columbia University, New York, NY 10032, USA.
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25
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The Matrix Proteins Hasp and Hig Exhibit Segregated Distribution within Synaptic Clefts and Play Distinct Roles in Synaptogenesis. J Neurosci 2016; 36:590-606. [PMID: 26758847 DOI: 10.1523/jneurosci.2300-15.2016] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
UNLABELLED The synaptic cleft is the space through which neurotransmitters convey neural information between two synaptic terminals. This space is presumably filled with extracellular matrix molecules involved in synaptic function or differentiation. However, little is known about the identities of the matrix components, and it remains unclear how these molecules organize the matrix in synaptic clefts. In this study, we identified Hasp, a Drosophila secretory protein containing CCP and WAP domains. Molecular genetic analysis revealed that Hasp diffuses extracellularly and is predominantly captured at synaptic clefts of cholinergic synapses. Furthermore, Hasp regulates levels of DLG and the nAChR subunits Dα6 and Dα7 at postsynaptic terminals. Hasp is required for trapping of another matrix protein, Hig, which is also secreted and diffused in the brain, at synaptic clefts of cholinergic synapses; however, Hig is dispensable for localization of Hasp at synaptic clefts. In addition, in the brains of triple mutants for the nAChR subunits Dα5, Dα6, and Dα7, the level of Hig, but not Hasp, was markedly reduced in synaptic regions, indicating that these nAChR subunits are required to anchor Hig to synaptic clefts. High-resolution microscopy revealed that Hasp and Hig exhibit segregated distribution within individual synaptic clefts, reflecting their differing roles in synaptogenesis. These data provide insight into how Hasp and Hig construct the synaptic cleft matrix and regulate the differentiation of cholinergic synapses, and also illuminate a previously unidentified architecture within synaptic clefts. SIGNIFICANCE STATEMENT The synapse has been extensively studied because it is essential for neurotransmission. By contrast, the space between the synaptic terminals, the synaptic cleft, is still an undeveloped research area despite its ubiquity in synapses. In fruit fly brains, we obtained evidence that the matrix protein Hasp and the previously identified Hig, both of which are secreted extracellularly, localize predominantly to synaptic clefts of cholinergic synapses, and modulate the levels of nAChR subunits on postsynaptic membranes. However, Hasp and Hig play differential roles in matrix formation and exhibit segregated distribution within synaptic clefts. These results reveal the molecular mechanisms of synaptic matrix construction and illuminate a molecular architecture within synaptic clefts previously unrevealed in any animal species.
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26
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Tu H, Huhtala P, Lee HM, Adams JC, Pihlajaniemi T. Membrane-associated collagens with interrupted triple-helices (MACITs): evolution from a bilaterian common ancestor and functional conservation in C. elegans. BMC Evol Biol 2015; 15:281. [PMID: 26667623 PMCID: PMC4678570 DOI: 10.1186/s12862-015-0554-3] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2015] [Accepted: 12/02/2015] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND Collagens provide structural support and guidance cues within the extracellular matrix of metazoans. Mammalian collagens XIII, XXIII and XXV form a unique subgroup of type II transmembrane proteins, each comprising a short N-terminal cytosolic domain, a transmembrane domain and a largely collagenous ectodomain. We name these collagens as MACITs (Membrane-Associated Collagens with Interrupted Triple-helices), and here investigate their evolution and conserved properties. To date, these collagens have been studied only in mammals. Knowledge of the representation of MACITs in other extant metazoans is lacking. This question is of interest for understanding structural/functional relationships in the MACIT family and also for insight into the evolution of MACITs in relation to the secreted, fibrillar collagens that are present throughout the metazoa. RESULTS MACITs are restricted to bilaterians and are represented in the Ecdysozoa, Hemichordata, Urochordata and Vertebrata (Gnathostomata). They were not identified in available early-diverging metazoans, Lophotrochozoa, Echinodermata, Cephalochordata or Vertebrata (Cyclostomata). Whereas invertebrates encode a single MACIT, collagens XIII/XXIII/XXV of jawed vertebrates are paralogues that originated from the two rounds of en-bloc genome duplication occurring early in vertebrate evolution. MACITs have conserved domain architecture in which a juxta-membrane furin-cleavage site and the C-terminal 34 residues are especially highly conserved, whereas the cytoplasmic domains are weakly conserved. To study protein expression and function in a metazoan with a single MACIT gene, we focused on Caenorhabditis elegans and its col-99 gene. A col-99 cDNA was cloned and expressed as protein in mammalian CHO cells, two antibodies against COL-99 protein were generated, and a col-99-bearing fosmid gene construct col-99::egfp::flag was used to generate transgenic C. elegans lines. The encoded COL-99 polypeptide is 85 kDa in size and forms a trimeric protein. COL-99 is plasma membrane-associated and undergoes furin-dependent ectodomain cleavage and shedding. COL-99 is detected in mouth, pharynx, body wall and the tail, mostly in motor neurons and muscle systems and is enriched at neuromuscular junctions. CONCLUSIONS Through identification of MACITs in multiple metazoan phyla we developed a model for the evolution of MACITs. The experimental data demonstrate conservation of MACIT molecular and cellular properties and tissue localisations in the invertebrate, C. elegans.
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Affiliation(s)
- Hongmin Tu
- Centre of Excellence in Cell-Extracellular Matrix Research, Faculty of Biochemistry and Molecular Medicine, Biocenter Oulu, University of Oulu, Aapistie 5, Oulu, FIN 90014, Finland.
| | - Pirkko Huhtala
- Centre of Excellence in Cell-Extracellular Matrix Research, Faculty of Biochemistry and Molecular Medicine, Biocenter Oulu, University of Oulu, Aapistie 5, Oulu, FIN 90014, Finland.
| | - Hang-Mao Lee
- Centre of Excellence in Cell-Extracellular Matrix Research, Faculty of Biochemistry and Molecular Medicine, Biocenter Oulu, University of Oulu, Aapistie 5, Oulu, FIN 90014, Finland.
| | - Josephine C Adams
- School of Biochemistry, University of Bristol, Biomedical Sciences Building, University Walk, Bristol, BS8 1TD, UK.
| | - Taina Pihlajaniemi
- Centre of Excellence in Cell-Extracellular Matrix Research, Faculty of Biochemistry and Molecular Medicine, Biocenter Oulu, University of Oulu, Aapistie 5, Oulu, FIN 90014, Finland.
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He S, Philbrook A, McWhirter R, Gabel CV, Taub DG, Carter MH, Hanna IM, Francis MM, Miller DM. Transcriptional Control of Synaptic Remodeling through Regulated Expression of an Immunoglobulin Superfamily Protein. Curr Biol 2015; 25:2541-8. [PMID: 26387713 DOI: 10.1016/j.cub.2015.08.022] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2015] [Revised: 07/04/2015] [Accepted: 08/10/2015] [Indexed: 11/24/2022]
Abstract
Neural circuits are actively remodeled during brain development, but the molecular mechanisms that trigger circuit refinement are poorly understood. Here, we describe a transcriptional program in C. elegans that regulates expression of an Ig domain protein, OIG-1, to control the timing of synaptic remodeling. DD GABAergic neurons reverse polarity during larval development by exchanging the locations of pre- and postsynaptic components. In newly born larvae, DDs receive cholinergic inputs in the dorsal nerve cord. These inputs are switched to the ventral side by the end of the first larval (L1) stage. VD class GABAergic neurons are generated in the late L1 and are postsynaptic to cholinergic neurons in the dorsal nerve cord but do not remodel. We investigated remodeling of the postsynaptic apparatus in DD and VD neurons using targeted expression of the acetylcholine receptor (AChR) subunit, ACR-12::GFP. We determined that OIG-1 antagonizes the relocation of ACR-12 from the dorsal side in L1 DD neurons. During the L1/L2 transition, OIG-1 is downregulated in DD neurons by the transcription factor IRX-1/Iroquois, allowing the repositioning of synaptic inputs to the ventral side. In VD class neurons, which normally do not remodel, the transcription factor UNC-55/COUP-TF turns off IRX-1, thus maintaining high levels of OIG-1 to block the removal of dorsally located ACR-12 receptors. OIG-1 is secreted from GABA neurons, but its anti-plasticity function is cell autonomous and may not require secretion. Our study provides a novel mechanism by which synaptic remodeling is set in motion through regulated expression of an Ig domain protein.
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Affiliation(s)
- Siwei He
- Neuroscience Graduate Program, Vanderbilt International Scholar Program, Vanderbilt University, 465 21(st) Avenue South, Nashville, TN 37240-7935, USA
| | - Alison Philbrook
- Department of Neurobiology, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01605, USA
| | - Rebecca McWhirter
- Department of Cell and Developmental Biology, Vanderbilt University, 465 21(st) Avenue South, Nashville, TN 37240-7935, USA
| | - Christopher V Gabel
- Department of Physiology and Biophysics, Boston University Medical Campus, 700 Albany Street, Boston, MA 02118, USA
| | - Daniel G Taub
- Department of Physiology and Biophysics, Boston University Medical Campus, 700 Albany Street, Boston, MA 02118, USA
| | - Maximilian H Carter
- Department of Cell and Developmental Biology, Vanderbilt University, 465 21(st) Avenue South, Nashville, TN 37240-7935, USA
| | - Isabella M Hanna
- Department of Cell and Developmental Biology, Vanderbilt University, 465 21(st) Avenue South, Nashville, TN 37240-7935, USA
| | - Michael M Francis
- Department of Neurobiology, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01605, USA.
| | - David M Miller
- Neuroscience Graduate Program, Vanderbilt International Scholar Program, Vanderbilt University, 465 21(st) Avenue South, Nashville, TN 37240-7935, USA; Department of Cell and Developmental Biology, Vanderbilt University, 465 21(st) Avenue South, Nashville, TN 37240-7935, USA.
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Howell K, White JG, Hobert O. Spatiotemporal control of a novel synaptic organizer molecule. Nature 2015; 523:83-7. [PMID: 26083757 PMCID: PMC9134992 DOI: 10.1038/nature14545] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2014] [Accepted: 05/12/2015] [Indexed: 12/13/2022]
Abstract
Synapse formation is a process tightly controlled in space and time. How gene regulatory mechanisms specify spatial and temporal aspects of synapse formation is not well understood. In the nematode C.elegans, two subtypes of the D-type inhibitory motor neuron (MN) classes, the dorsal D (DD) and ventral D (VD) neurons, extend axons along both the dorsal and ventral nerve cords 1. The embryonically generated DD MNs initially innervate ventral muscles in the first (L1) larval stage and receive their synaptic input from cholinergic MNs in the dorsal cord. They rewire by the end of the L1 molt to innervate dorsal muscles and to be innervated by newly formed ventral cholinergic MNs 1. VD MNs develop after the L1 molt; they take over the innervation of ventral muscles and receive their synaptic input from dorsal cholinergic MNs. We show here that the spatiotemporal control of synaptic wiring of the D-type neurons is controlled by an intersectional transcriptional strategy in which the UNC-30 Pitx-type homeodomain transcription factor acts together in embryonic and early larval stages with the temporally controlled LIN-14 transcription factor to prevent premature synapse rewiring of the DD MNs and, together with the UNC-55 nuclear hormone receptor, to prevent aberrant VD synaptic wiring in later larval and adult stages. A key effector of this intersectional transcription factor combination is a novel synaptic organizer molecule, the single immunoglobulin domain protein OIG-1. OIG-1 is perisynaptically localized along the synaptic outputs of the D-type MNs in a temporally controlled manner and is required for appropriate selection of both pre- and post-synaptic partners.
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C. elegans Punctin Clusters GABAA Receptors via Neuroligin Binding and UNC-40/DCC Recruitment. Neuron 2015; 86:1407-19. [DOI: 10.1016/j.neuron.2015.05.013] [Citation(s) in RCA: 64] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2014] [Revised: 02/13/2015] [Accepted: 03/27/2015] [Indexed: 12/21/2022]
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Cherra SJ, Jin Y. Advances in synapse formation: forging connections in the worm. WILEY INTERDISCIPLINARY REVIEWS. DEVELOPMENTAL BIOLOGY 2015; 4:85-97. [PMID: 25472860 PMCID: PMC4339659 DOI: 10.1002/wdev.165] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2014] [Revised: 10/09/2014] [Accepted: 10/24/2014] [Indexed: 12/27/2022]
Abstract
UNLABELLED Synapse formation is the quintessential process by which neurons form specific connections with their targets to enable the development of functional circuits. Over the past few decades, intense research efforts have identified thousands of proteins that localize to the pre- and postsynaptic compartments. Genetic dissection has provided important insights into the nexus of the molecular and cellular network, and has greatly advanced our knowledge about how synapses form and function physiologically. Moreover, recent studies have highlighted the complex regulation of synapse formation with the identification of novel mechanisms involving cell interactions from non-neuronal sources. In this review, we cover the conserved pathways required for synaptogenesis and place specific focus on new themes of synapse modulation arising from studies in Caenorhabditis elegans. For further resources related to this article, please visit the WIREs website. CONFLICT OF INTEREST The authors have declared no conflicts of interest for this article.
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Affiliation(s)
- Salvatore J. Cherra
- Section of Neurobiology, Division of Biological Sciences, University of California San Diego
| | - Yishi Jin
- Section of Neurobiology, Division of Biological Sciences, University of California San Diego
- Howard Hughes Medical Institute
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Pinan-Lucarré B, Tu H, Pierron M, Cruceyra PI, Zhan H, Stigloher C, Richmond JE, Bessereau JL. C. elegans Punctin specifies cholinergic versus GABAergic identity of postsynaptic domains. Nature 2014; 511:466-70. [DOI: 10.1038/nature13313] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2013] [Accepted: 04/07/2014] [Indexed: 11/09/2022]
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Briseño-Roa L, Bessereau JL. Proteolytic processing of the extracellular scaffolding protein LEV-9 is required for clustering acetylcholine receptors. J Biol Chem 2014; 289:10967-10974. [PMID: 24619422 DOI: 10.1074/jbc.c113.534677] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Correct positioning of neurotransmitter-gated receptors at postsynapses is essential for synaptic transmission. At Caenorhabditis elegans neuromuscular junctions, clustering of levamisole-sensitive acetylcholine receptors (L-AChRs) requires the muscle-secreted scaffolding protein LEV-9, a multidomain factor containing complement control protein (CCP) modules. Here we show that LEV-9 needs to be cleaved at its C terminus to exert its function. LEV-9 cleavage is not required for trafficking nor secretion but directly controls scaffolding activity. The cleavage site is evolutionarily conserved, and post-translational cleavage ensures the structural and functional decoupling between different isoforms encoded by the lev-9 gene. Data mining indicates that most human CCP-containing factors are likely cleaved C-terminally from CCP tandems, suggesting that not only domain architectures but also cleavage location can be conserved in distant architecturally related proteins.
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Affiliation(s)
- Luis Briseño-Roa
- Institute of Biology of Ecole Normale Supérieure, 75005 Paris,; INSERM, U1024, 75005 Paris,; Institut Jacques Monod UMR CNRS 7592, 75013 Paris, France.
| | - Jean-Louis Bessereau
- Institute of Biology of Ecole Normale Supérieure, 75005 Paris,; INSERM, U1024, 75005 Paris,; University Claude Bernard Lyon 1, Centre de Génétique et de Physiologie Moléculaire et Cellulaire (CGphiMC) UMR CNRS 5534, 69622 Villeurbanne, and.
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Holden-Dye L, Joyner M, O'Connor V, Walker RJ. Nicotinic acetylcholine receptors: a comparison of the nAChRs of Caenorhabditis elegans and parasitic nematodes. Parasitol Int 2013; 62:606-15. [PMID: 23500392 DOI: 10.1016/j.parint.2013.03.004] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2012] [Revised: 02/28/2013] [Accepted: 03/05/2013] [Indexed: 01/15/2023]
Abstract
Nicotinic acetylcholine receptors (nAChRs) play a key role in the normal physiology of nematodes and provide an established target site for anthelmintics. The free-living nematode, Caenorhabditis elegans, has a large number of nAChR subunit genes in its genome and so provides an experimental model for testing novel anthelmintics which act at these sites. However, many parasitic nematodes lack specific genes present in C. elegans, and so care is required in extrapolating from studies using C. elegans to the situation in other nematodes. In this review the properties of C. elegans nAChRs are reviewed and compared to those of parasitic nematodes. This forms the basis for a discussion of the possible subunit composition of nAChRs from different species of parasitic nematodes. Currently our knowledge on this is largely based on studies using heterologous expression and pharmacological analysis of receptor subunits in Xenopus laevis oocytes. It is concluded that more information is required regarding the subunit composition and pharmacology of endogenous nAChRs in parasitic nematodes.
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Affiliation(s)
- Lindy Holden-Dye
- Centre for Biological Sciences, Life Sciences Building 85, University of Southampton, Southampton SO17 1BJ, UK.
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Biosynthesis of ionotropic acetylcholine receptors requires the evolutionarily conserved ER membrane complex. Proc Natl Acad Sci U S A 2013; 110:E1055-63. [PMID: 23431131 DOI: 10.1073/pnas.1216154110] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The number of nicotinic acetylcholine receptors (AChRs) present in the plasma membrane of muscle and neuronal cells is limited by the assembly of individual subunits into mature pentameric receptors. This process is usually inefficient, and a large number of the synthesized subunits are degraded by endoplasmic reticulum (ER)-associated degradation. To identify cellular factors required for the synthesis of AChRs, we performed a genetic screen in the nematode Caenorhabditis elegans for mutants with decreased sensitivity to the cholinergic agonist levamisole. We isolated a partial loss-of-function allele of ER membrane protein complex-6 (emc-6), a previously uncharacterized gene in C. elegans. emc-6 encodes an evolutionarily conserved 111-aa protein with two predicted transmembrane domains. EMC-6 is ubiquitously expressed and localizes to the ER. Partial inhibition of EMC-6 caused decreased expression of heteromeric levamisole-sensitive AChRs by destabilizing unassembled subunits in the ER. Inhibition of emc-6 also reduced the expression of homomeric nicotine-sensitive AChRs and GABAA receptors in C. elegans muscle cells. emc-6 is orthologous to the yeast and human EMC6 genes that code for a component of the recently identified ER membrane complex (EMC). Our data suggest this complex is required for protein folding and is connected to ER-associated degradation. We demonstrated that inactivation of additional EMC members in C. elegans also impaired AChR synthesis and induced the unfolded protein response. These results suggest that the EMC is a component of the ER folding machinery. AChRs might provide a valuable proxy to decipher the function of the EMC further.
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Positive modulation of a Cys-loop acetylcholine receptor by an auxiliary transmembrane subunit. Nat Neurosci 2012; 15:1374-81. [DOI: 10.1038/nn.3197] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2012] [Accepted: 07/30/2012] [Indexed: 02/07/2023]
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Abstract
Wnt proteins are best known for their profound roles in cell patterning, because they are required for the embryonic development of all animal species studied to date. Besides regulating cell fate, Wnt proteins are gaining increasing recognition for their roles in nervous system development and function. New studies indicate that multiple positive and negative Wnt signaling pathways take place simultaneously during the formation of vertebrate and invertebrate neuromuscular junctions. Although some Wnts are essential for the formation of NMJs, others appear to play a more modulatory role as part of multiple signaling pathways. Here we review the most recent findings regarding the function of Wnts at the NMJ from both vertebrate and invertebrate model systems.
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Affiliation(s)
- Kate Koles
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, 01605, USA
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Functional and spatial analysis of C. elegans SYG-1 and SYG-2, orthologs of the Neph/nephrin cell adhesion module directing selective synaptogenesis. PLoS One 2011; 6:e23598. [PMID: 21858180 PMCID: PMC3156230 DOI: 10.1371/journal.pone.0023598] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2011] [Accepted: 07/20/2011] [Indexed: 01/25/2023] Open
Abstract
The assembly of specific synaptic connections represents a prime example of cellular recognition. Members of the Ig superfamily are among the most ancient proteins represented in the genomes of both mammalian and invertebrate organisms, where they constitute a trans-synaptic adhesion system. The correct connectivity patterns of the highly conserved immunoglobulin superfamily proteins nephrin and Neph1 are crucial for the assembly of functional neuronal circuits and the formation of the kidney slit diaphragm, a synapse-like structure forming the filtration barrier. Here, we utilize the nematode C. elegans model for studying the requirements of synaptic specificity mediated by nephrin-Neph proteins. In C. elegans, the nephrin/Neph1 orthologs SYG-2 and SYG-1 form intercellular contacts strictly in trans between epithelial guidepost cells and neurons specifying the localization of synapses. We demonstrate a functional conservation between mammalian nephrin and SYG-2. Expression of nephrin effectively compensated loss of syg-2 function in C. elegans and restored defective synaptic connectivity further establishing the C. elegans system as a valuable model for slit diaphragm proteins. Next, we investigated the effect of SYG-1 and SYG-2 trans homodimerization respectively. Strikingly, synapse assembly could be induced by homophilic SYG-1 but not SYG-2 binding indicating a critical role of SYG-1 intracellular signalling for morphogenetic events and pointing toward the dynamic and stochastic nature of extra- and intracellular nephrin-Neph interactions to generate reproducible patterns of synaptic connectivity.
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