1
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CaMKII regulates neuromuscular activity and survival of the human blood fluke Schistosoma mansoni. Sci Rep 2022; 12:19831. [PMID: 36400915 PMCID: PMC9674609 DOI: 10.1038/s41598-022-23962-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Accepted: 11/08/2022] [Indexed: 11/19/2022] Open
Abstract
Calcium/calmodulin dependant protein kinase II (CaMKII), an important transducer of Ca2+ signals, orchestrates multiple cellular functions in animals. Here we investigated the importance of CaMKII to Schistosoma mansoni, a blood parasite that causes human schistosomiasis. We demonstrate that phosphorylated (activated) CaMKII is present in cercariae, schistosomula and adult worms, and show that striking activation occurs in the nervous tissue of these parasite life-stages; CaMKII was also activated in the tegument and muscles of adult worms and the vitellaria of females. Exposure of worms to the anti-schistosomal drug praziquantel (PZQ) induced significant CaMKII activation and depletion of CaMKII protein/activation in adult worms resulted in hypokinesia, reduced vitality and death. At medium confidence (global score ≥ 0.40), S. mansoni CaMKII was predicted to interact with 51 proteins, with many containing CaMKII phosphorylation sites and nine mapped to phosphoproteome data including sites within a ryanodine receptor. The CaMKII network was functionally enriched with mitogen-activated protein kinase, Wnt, and notch pathways, and ion-transport and voltage-dependent channel protein domains. Collectively, these data highlight the intricacies of CaMKII signalling in S. mansoni, show CaMKII to be an active player in the PZQ-mediated response of schistosomes and highlight CaMKII as a possible target for the development of novel anti-schistosome therapeutics.
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2
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Further Extension of Lifespan by Unc-43/CaMKII and Egl-8/PLCβ Mutations in Germline-Deficient Caenorhabditis elegans. Cells 2022; 11:cells11223527. [PMID: 36428956 PMCID: PMC9688844 DOI: 10.3390/cells11223527] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2022] [Revised: 10/30/2022] [Accepted: 11/05/2022] [Indexed: 11/09/2022] Open
Abstract
Reduction of insulin/insulin-like growth factor 1 (IGF1) signaling (IIS) promotes longevity across species. In the nematode Caenorhabditis elegans, ablation of germline stem cells (GSCs) and activity changes of the conserved signaling mediators unc-43/CaMKII (calcium/calmodulin-dependent kinase type II) and egl-8/PLCβ (phospholipase Cβ) also increase lifespan. Like IIS, these pathways depend on the conserved transcription factor daf-16/FOXO for lifespan extension, but how they functionally interact is unknown. Here, we show that altered unc-43/egl-8 activity further increases the lifespan of long-lived GSC-deficient worms, but not of worms that are long-lived due to a strong reduction-of-function mutation in the insulin/IGF1-like receptor daf-2. Additionally, we provide evidence for unc-43 and, to a lesser extent, egl-8 modulating the expression of certain collagen genes, which were reported to be dispensable for longevity of these particular daf-2 mutant worms, but not for other forms of longevity. Together, these results provide new insights into the conditions and potential mechanisms by which CaMKII- and PLCβ-signals modulate C. elegans lifespan.
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3
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Mechanisms of Regulation in Intraflagellar Transport. Cells 2022; 11:cells11172737. [PMID: 36078145 PMCID: PMC9454703 DOI: 10.3390/cells11172737] [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: 08/16/2022] [Revised: 08/30/2022] [Accepted: 08/31/2022] [Indexed: 11/30/2022] Open
Abstract
Cilia are eukaryotic organelles essential for movement, signaling or sensing. Primary cilia act as antennae to sense a cell’s environment and are involved in a wide range of signaling pathways essential for development. Motile cilia drive cell locomotion or liquid flow around the cell. Proper functioning of both types of cilia requires a highly orchestrated bi-directional transport system, intraflagellar transport (IFT), which is driven by motor proteins, kinesin-2 and IFT dynein. In this review, we explore how IFT is regulated in cilia, focusing from three different perspectives on the issue. First, we reflect on how the motor track, the microtubule-based axoneme, affects IFT. Second, we focus on the motor proteins, considering the role motor action, cooperation and motor-train interaction plays in the regulation of IFT. Third, we discuss the role of kinases in the regulation of the motor proteins. Our goal is to provide mechanistic insights in IFT regulation in cilia and to suggest directions of future research.
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4
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Harrington S, Knox JJ, Burns AR, Choo KL, Au A, Kitner M, Haeberli C, Pyche J, D'Amata C, Kim YH, Volpatti JR, Guiliani M, Snider J, Wong V, Palmeira BM, Redman EM, Vaidya AS, Gilleard JS, Stagljar I, Cutler SR, Kulke D, Dowling JJ, Yip CM, Keiser J, Zasada I, Lautens M, Roy PJ. Egg-laying and locomotory screens with C. elegans yield a nematode-selective small molecule stimulator of neurotransmitter release. Commun Biol 2022; 5:865. [PMID: 36002479 PMCID: PMC9402605 DOI: 10.1038/s42003-022-03819-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2022] [Accepted: 08/08/2022] [Indexed: 12/05/2022] Open
Abstract
Nematode parasites of humans, livestock and crops dramatically impact human health and welfare. Alarmingly, parasitic nematodes of animals have rapidly evolved resistance to anthelmintic drugs, and traditional nematicides that protect crops are facing increasing restrictions because of poor phylogenetic selectivity. Here, we exploit multiple motor outputs of the model nematode C. elegans towards nematicide discovery. This work yielded multiple compounds that selectively kill and/or immobilize diverse nematode parasites. We focus on one compound that induces violent convulsions and paralysis that we call nementin. We find that nementin stimulates neuronal dense core vesicle release, which in turn enhances cholinergic signaling. Consequently, nementin synergistically enhances the potency of widely-used non-selective acetylcholinesterase (AChE) inhibitors, but in a nematode-selective manner. Nementin therefore has the potential to reduce the environmental impact of toxic AChE inhibitors that are used to control nematode infections and infestations. A C. elegans-based screening approach identifies nementin as a nematode-selective nematicide that can be used synergistically with acetylcholinesterase inhibitors
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Affiliation(s)
- Sean Harrington
- Department of Pharmacology and Toxicology, University of Toronto, Toronto, Canada.,The Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Toronto, Canada
| | - Jessica J Knox
- The Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Toronto, Canada.,Department of Molecular Genetics, University of Toronto, Toronto, Canada
| | - Andrew R Burns
- The Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Toronto, Canada.,Department of Molecular Genetics, University of Toronto, Toronto, Canada
| | - Ken-Loon Choo
- The Department of Chemistry, University of Toronto, Toronto, Canada
| | - Aaron Au
- The Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Toronto, Canada.,Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Canada
| | - Megan Kitner
- USDA-ARS Horticultural Crops Research Laboratory, Corvallis, OR, USA
| | - Cecile Haeberli
- Department of Medical Parasitology and Infection Biology, Swiss-Tropical and Public Health Institute, (Swiss TPH), Basel, Switzerland.,Faculty of Science, University of Basel, Basel, Switzerland
| | - Jacob Pyche
- Department of Pharmacology and Toxicology, University of Toronto, Toronto, Canada.,The Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Toronto, Canada
| | - Cassandra D'Amata
- The Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Toronto, Canada
| | - Yong-Hyun Kim
- The Department of Chemistry, University of Toronto, Toronto, Canada
| | - Jonathan R Volpatti
- Program in Developmental and Stem Cell Biology, The Hospital for Sick Children, Toronto, Canada.,Program in Genetics and Genome Biology, The Hospital for Sick Children, Toronto, Canada
| | - Maximillano Guiliani
- The Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Toronto, Canada.,Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Canada
| | - Jamie Snider
- The Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Toronto, Canada
| | - Victoria Wong
- The Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Toronto, Canada
| | - Bruna M Palmeira
- Department of Comparative Biology and Experimental Medicine, Host-Parasite Interactions (HPI) Program, Faculty of Veterinary Medicine, University of Calgary, Calgary, Canada
| | - Elizabeth M Redman
- Department of Comparative Biology and Experimental Medicine, Host-Parasite Interactions (HPI) Program, Faculty of Veterinary Medicine, University of Calgary, Calgary, Canada
| | - Aditya S Vaidya
- Institute for Integrative Genome Biology, University of California, Riverside, CA, USA.,Department of Botany and Plant Sciences, University of California, Riverside, CA, USA
| | - John S Gilleard
- Department of Comparative Biology and Experimental Medicine, Host-Parasite Interactions (HPI) Program, Faculty of Veterinary Medicine, University of Calgary, Calgary, Canada
| | - Igor Stagljar
- The Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Toronto, Canada.,Department of Molecular Genetics, University of Toronto, Toronto, Canada.,Department of Biochemistry, University of Toronto, Toronto, Canada.,Mediterranean Institute for Life Sciences, Split, Croatia.,School of Medicine, University of Split, Split, Croatia
| | - Sean R Cutler
- Institute for Integrative Genome Biology, University of California, Riverside, CA, USA.,Department of Botany and Plant Sciences, University of California, Riverside, CA, USA
| | - Daniel Kulke
- Research Parasiticides, Bayer Animal Health GmbH, Monheim, Germany.,Department of Biomedical Sciences, Iowa State University, Ames, IA, USA.,Global Innovation, Boehringer Ingelheim Vetmedica GmbH, Ingelheim am Rhein, Germany
| | - James J Dowling
- Program in Developmental and Stem Cell Biology, The Hospital for Sick Children, Toronto, Canada.,Program in Genetics and Genome Biology, The Hospital for Sick Children, Toronto, Canada
| | - Christopher M Yip
- The Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Toronto, Canada.,Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Canada
| | - Jennifer Keiser
- Department of Medical Parasitology and Infection Biology, Swiss-Tropical and Public Health Institute, (Swiss TPH), Basel, Switzerland.,Faculty of Science, University of Basel, Basel, Switzerland
| | - Inga Zasada
- USDA-ARS Horticultural Crops Research Laboratory, Corvallis, OR, USA
| | - Mark Lautens
- The Department of Chemistry, University of Toronto, Toronto, Canada
| | - Peter J Roy
- Department of Pharmacology and Toxicology, University of Toronto, Toronto, Canada. .,The Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Toronto, Canada. .,Department of Molecular Genetics, University of Toronto, Toronto, Canada.
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5
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Dhakal P, Chaudhry SI, Signorelli R, Collins KM. Serotonin signals through postsynaptic Gαq, Trio RhoGEF, and diacylglycerol to promote Caenorhabditis elegans egg-laying circuit activity and behavior. Genetics 2022; 221:iyac084. [PMID: 35579369 PMCID: PMC9252285 DOI: 10.1093/genetics/iyac084] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2022] [Accepted: 04/26/2022] [Indexed: 11/12/2022] Open
Abstract
Activated Gαq signals through phospholipase-Cβ and Trio, a Rho GTPase exchange factor (RhoGEF), but how these distinct effector pathways promote cellular responses to neurotransmitters like serotonin remains poorly understood. We used the egg-laying behavior circuit of Caenorhabditis elegans to determine whether phospholipase-Cβ and Trio mediate serotonin and Gαq signaling through independent or related biochemical pathways. Our genetic rescue experiments suggest that phospholipase-Cβ functions in neurons while Trio Rho GTPase exchange factor functions in both neurons and the postsynaptic vulval muscles. While Gαq, phospholipase-Cβ, and Trio Rho GTPase exchange factor mutants fail to lay eggs in response to serotonin, optogenetic stimulation of the serotonin-releasing HSN neurons restores egg laying only in phospholipase-Cβ mutants. Phospholipase-Cβ mutants showed vulval muscle Ca2+ transients while strong Gαq and Trio Rho GTPase exchange factor mutants had little or no vulval muscle Ca2+ activity. Treatment with phorbol 12-myristate 13-acetate that mimics 1,2-diacylglycerol, a product of PIP2 hydrolysis, rescued egg-laying circuit activity and behavior defects of Gαq signaling mutants, suggesting both phospholipase-C and Rho signaling promote synaptic transmission and egg laying via modulation of 1,2-diacylglycerol levels. 1,2-Diacylglycerol activates effectors including UNC-13; however, we find that phorbol esters, but not serotonin, stimulate egg laying in unc-13 and phospholipase-Cβ mutants. These results support a model where serotonin signaling through Gαq, phospholipase-Cβ, and UNC-13 promotes neurotransmitter release, and that serotonin also signals through Gαq, Trio Rho GTPase exchange factor, and an unidentified, phorbol 12-myristate 13-acetate-responsive effector to promote postsynaptic muscle excitability. Thus, the same neuromodulator serotonin can signal in distinct cells and effector pathways to coordinate activation of a motor behavior circuit.
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Affiliation(s)
- Pravat Dhakal
- Department of Biology, University of Miami, Coral Gables, FL 33146, USA
| | - Sana I Chaudhry
- Department of Biology, University of Miami, Coral Gables, FL 33146, USA
| | | | - Kevin M Collins
- Department of Biology, University of Miami, Coral Gables, FL 33146, USA
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6
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Hoerndli FJ, Brockie PJ, Wang R, Mellem JE, Kallarackal A, Doser RL, Pierce DM, Madsen DM, Maricq AV. MAPK signaling and a mobile scaffold complex regulate AMPA receptor transport to modulate synaptic strength. Cell Rep 2022; 38:110577. [PMID: 35354038 PMCID: PMC9965202 DOI: 10.1016/j.celrep.2022.110577] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2021] [Revised: 01/31/2022] [Accepted: 03/04/2022] [Indexed: 12/27/2022] Open
Abstract
Synaptic plasticity depends on rapid experience-dependent changes in the number of neurotransmitter receptors. Previously, we demonstrated that motor-mediated transport of AMPA receptors (AMPARs) to and from synapses is a critical determinant of synaptic strength. Here, we describe two convergent signaling pathways that coordinate the loading of synaptic AMPARs onto scaffolds, and scaffolds onto motors, thus providing a mechanism for experience-dependent changes in synaptic strength. We find that an evolutionarily conserved JIP-protein scaffold complex and two classes of mitogen-activated protein kinase (MAPK) proteins mediate AMPAR transport by kinesin-1 motors. Genetic analysis combined with in vivo, real-time imaging in Caenorhabditis elegans revealed that CaMKII is required for loading AMPARs onto the scaffold, and MAPK signaling is required for loading the scaffold complex onto motors. Our data support a model where CaMKII signaling and a MAPK-signaling pathway cooperate to facilitate the rapid exchange of AMPARs required for early stages of synaptic plasticity.
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Affiliation(s)
- Frédéric J. Hoerndli
- Department of Biomedical Sciences, Colorado State University, Fort Collins, CO 80523, USA,Correspondence: (F.J.H.), (A.V.M.)
| | - Penelope J. Brockie
- Department of Neurobiology, University of Utah, Salt Lake City, UT 84112-9458, USA
| | - Rui Wang
- Pathology Department, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
| | - Jerry E. Mellem
- Department of Neurobiology, University of Utah, Salt Lake City, UT 84112-9458, USA
| | - Angy Kallarackal
- Department of Psychology, Mount Saint Mary’s University, Emmitsburg, MD 21727, USA
| | - Rachel L. Doser
- Department of Biomedical Sciences, Colorado State University, Fort Collins, CO 80523, USA
| | - Dayton M. Pierce
- Department of Biomedical Sciences, Colorado State University, Fort Collins, CO 80523, USA
| | - David M. Madsen
- Department of Neurobiology, University of Utah, Salt Lake City, UT 84112-9458, USA
| | - Andres V. Maricq
- Department of Neurobiology, University of Utah, Salt Lake City, UT 84112-9458, USA,Lead contact,Correspondence: (F.J.H.), (A.V.M.)
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7
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Ding C, Wu Y, Dabas H, Hammarlund M. Activation of the CaMKII-Sarm1-ASK1-p38 MAP kinase pathway protects against axon degeneration caused by loss of mitochondria. eLife 2022; 11:73557. [PMID: 35285800 PMCID: PMC8920508 DOI: 10.7554/elife.73557] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2021] [Accepted: 01/25/2022] [Indexed: 12/22/2022] Open
Abstract
Mitochondrial defects are tightly linked to axon degeneration, yet the underlying cellular mechanisms remain poorly understood. In Caenorhabditis elegans, PVQ axons that lack mitochondria degenerate spontaneously with age. Using an unbiased genetic screen, we found that cell-specific activation of CaMKII/UNC-43 suppresses axon degeneration due to loss of mitochondria. Unexpectedly, CaMKII/UNC-43 activates the conserved Sarm1/TIR-1-ASK1/NSY-1-p38 MAPK pathway and eventually the transcription factor CEBP-1 to protect against degeneration. In addition, we show that disrupting a trafficking complex composed of calsyntenin/CASY-1, Mint/LIN-10, and kinesin suppresses axon degeneration. Further analysis indicates that disruption of this trafficking complex activates the CaMKII-Sarm1-MAPK pathway through L-type voltage-gated calcium channels. Our findings identify CaMKII as a pivot point between mitochondrial defects and axon degeneration, describe how it is regulated, and uncover a surprising neuroprotective role for the Sarm1-p38 MAPK pathway in this context.
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Affiliation(s)
- Chen Ding
- Department of Neuroscience, Yale University School of MedicineNew HavenUnited States
| | - Youjun Wu
- Department of Genetics, Yale University School of MedicineNew HavenUnited States
| | - Hadas Dabas
- Department of Genetics, Yale University School of MedicineNew HavenUnited States
| | - Marc Hammarlund
- Department of Neuroscience, Yale University School of MedicineNew HavenUnited States,Department of Genetics, Yale University School of MedicineNew HavenUnited States
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8
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Parallel Rap1>RalGEF>Ral and Ras signals sculpt the C. elegans nervous system. Dev Biol 2021; 477:37-48. [PMID: 33991533 DOI: 10.1016/j.ydbio.2021.05.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2021] [Revised: 05/04/2021] [Accepted: 05/07/2021] [Indexed: 11/23/2022]
Abstract
Ras is the most commonly mutated oncogene in humans and uses three oncogenic effectors: Raf, PI3K, and RalGEF activation of Ral. Understanding the importance of RalGEF>Ral signaling in cancer is hampered by the paucity of knowledge about their function in animal development, particularly in cell movements. We found that mutations that disrupt function of RalGEF or Ral enhance migration phenotypes of mutants for genes with established roles in cell migration. We used as a model the migration of the canal associated neurons (CANs), and validated our results in HSN cell migration, neurite guidance, and general animal locomotion. These functions of RalGEF and Ral are specific to their control of Ral signaling output rather than other published functions of these proteins. In this capacity Ral functions cell autonomously as a permissive developmental signal. In contrast, we observed Ras, the canonical activator of RalGEF>Ral signaling in cancer, to function as an instructive signal. Furthermore, we unexpectedly identified a function for the close Ras relative, Rap1, consistent with activation of RalGEF>Ral. These studies define functions of RalGEF>Ral, Rap1 and Ras signaling in morphogenetic processes that fashion the nervous system. We have also defined a model for studying how small GTPases partner with downstream effectors. Taken together, this analysis defines novel molecules and relationships in signaling networks that control cell movements during development of the nervous system.
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9
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Proietti Onori M, van Woerden GM. Role of calcium/calmodulin-dependent kinase 2 in neurodevelopmental disorders. Brain Res Bull 2021; 171:209-220. [PMID: 33774142 DOI: 10.1016/j.brainresbull.2021.03.014] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2020] [Revised: 03/17/2021] [Accepted: 03/18/2021] [Indexed: 01/28/2023]
Abstract
Neurodevelopmental disorders are a complex and heterogeneous group of neurological disorders characterized by their early-onset and estimated to affect more than 3% of children worldwide. The rapid advancement of sequencing technologies in the past years allowed the identification of hundreds of variants in several different genes causing neurodevelopmental disorders. Between those, new variants in the Calcium/calmodulin dependent protein kinase II (CAMK2) genes were recently linked to intellectual disability. Despite many years of research on CAMK2, this proves for the first time that this well-known and highly conserved molecule plays an important role in the human brain. In this review, we give an overview of the identified CAMK2 variants, and we speculate on potential mechanisms through which dysfunctions in CAMK2 result in neurodevelopmental disorders. Additionally, we discuss how the identification of CAMK2 variants might result in new exciting discoveries regarding the function of CAMK2 in the human brain.
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Affiliation(s)
- Martina Proietti Onori
- Department of Neuroscience, Erasmus MC, Rotterdam, 3015 GD, the Netherlands; The ENCORE Expertise Center for Neurodevelopmental Disorders, Erasmus MC, Rotterdam, 3015 GD, the Netherlands
| | - Geeske M van Woerden
- Department of Neuroscience, Erasmus MC, Rotterdam, 3015 GD, the Netherlands; The ENCORE Expertise Center for Neurodevelopmental Disorders, Erasmus MC, Rotterdam, 3015 GD, the Netherlands.
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10
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Araki S, Osuka K, Takata T, Tsuchiya Y, Watanabe Y. Coordination between Calcium/Calmodulin-Dependent Protein Kinase II and Neuronal Nitric Oxide Synthase in Neurons. Int J Mol Sci 2020; 21:ijms21217997. [PMID: 33121174 PMCID: PMC7662388 DOI: 10.3390/ijms21217997] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2020] [Revised: 10/21/2020] [Accepted: 10/22/2020] [Indexed: 12/15/2022] Open
Abstract
Ca2+/calmodulin (CaM)-dependent protein kinase II (CaMKII) is highly abundant in the brain and exhibits broad substrate specificity, thereby it is thought to participate in the regulation of neuronal death and survival. Nitric oxide (NO), produced by neuronal NO synthase (nNOS), is an important neurotransmitter and plays a role in neuronal activity including learning and memory processes. However, high levels of NO can contribute to excitotoxicity following a stroke and neurodegenerative disease. Aside from NO, nNOS also generates superoxide which is involved in both cell injury and signaling. CaMKII is known to activate and translocate from the cytoplasm to the post-synaptic density in response to neuronal activation where nNOS is predominantly located. Phosphorylation of nNOS at Ser847 by CaMKII decreases NO generation and increases superoxide generation. Conversely, NO-induced S-nitrosylation of CaMKII at Cys6 is a prominent determinant of the CaMKII inhibition in ATP competitive fashion. Thus, the "cross-talk" between CaMKII and NO/superoxide may represent important signal transduction pathways in brain. In this review, we introduce the molecular mechanism of and pathophysiological role of mutual regulation between CaMKII and nNOS in neurons.
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Affiliation(s)
- Shoma Araki
- Department of Pharmacology, Showa Pharmaceutical University, Machida, Tokyo 194-8543, Japan; (S.A.); (T.T.); (Y.T.)
| | - Koji Osuka
- Department of Neurological Surgery, Aichi Medical University, Aichi 480-1195, Japan;
| | - Tsuyoshi Takata
- Department of Pharmacology, Showa Pharmaceutical University, Machida, Tokyo 194-8543, Japan; (S.A.); (T.T.); (Y.T.)
- Department of Environmental Health Sciences and Molecular Toxicology, Graduate School of Medicine, Tohoku University, Miyagi 980-8575, Japan
| | - Yukihiro Tsuchiya
- Department of Pharmacology, Showa Pharmaceutical University, Machida, Tokyo 194-8543, Japan; (S.A.); (T.T.); (Y.T.)
| | - Yasuo Watanabe
- Department of Pharmacology, Showa Pharmaceutical University, Machida, Tokyo 194-8543, Japan; (S.A.); (T.T.); (Y.T.)
- Correspondence:
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11
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Doser RL, Amberg GC, Hoerndli FJ. Reactive Oxygen Species Modulate Activity-Dependent AMPA Receptor Transport in C. elegans. J Neurosci 2020; 40:7405-7420. [PMID: 32847966 PMCID: PMC7511182 DOI: 10.1523/jneurosci.0902-20.2020] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2020] [Revised: 07/26/2020] [Accepted: 08/16/2020] [Indexed: 12/22/2022] Open
Abstract
The AMPA subtype of synaptic glutamate receptors (AMPARs) plays an essential role in cognition. Their function, numbers, and change at synapses during synaptic plasticity are tightly regulated by neuronal activity. Although we know that long-distance transport of AMPARs is essential for this regulation, we do not understand the associated regulatory mechanisms of it. Neuronal transmission is a metabolically demanding process in which ATP consumption and production are tightly coupled and regulated. Aerobic ATP synthesis unavoidably produces reactive oxygen species (ROS), such as hydrogen peroxide, which are known modulators of calcium signaling. Although a role for calcium signaling in AMPAR transport has been described, there is little understanding of the mechanisms involved and no known link to physiological ROS signaling. Here, using real-time in vivo imaging of AMPAR transport in the intact C. elegans nervous system, we demonstrate that long-distance synaptic AMPAR transport is bidirectionally regulated by calcium influx and activation of calcium/calmodulin-dependent protein kinase II. Quantification of in vivo calcium dynamics revealed that modest, physiological increases in ROS decrease calcium transients in C. elegans glutamatergic neurons. By combining genetic and pharmacological manipulation of ROS levels and calcium influx, we reveal a mechanism in which physiological increases in ROS cause a decrease in synaptic AMPAR transport and delivery by modulating activity-dependent calcium signaling. Together, our results identify a novel role for oxidant signaling in the regulation of synaptic AMPAR transport and delivery, which in turn could be critical for coupling the metabolic demands of neuronal activity with excitatory neurotransmission.SIGNIFICANCE STATEMENT Synaptic AMPARs are critical for excitatory synaptic transmission. The disruption of their synaptic localization and numbers is associated with numerous psychiatric, neurologic, and neurodegenerative conditions. However, very little is known about the regulatory mechanisms controlling transport and delivery of AMPAR to synapses. Here, we describe a novel physiological signaling mechanism in which ROS, such as hydrogen peroxide, modulate AMPAR transport by modifying activity-dependent calcium signaling. Our findings provide the first evidence in support of a mechanistic link between physiological ROS signaling, AMPAR transport, localization, and excitatory transmission. This is of fundamental and clinical significance since dysregulation of intracellular calcium and ROS signaling is implicated in aging and the pathogenesis of several neurodegenerative disorders, including Alzheimer's and Parkinson's disease.
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Affiliation(s)
- Rachel L Doser
- Department of Biomedical Science, Colorado State University, Fort Collins, Colorado 80523
| | - Gregory C Amberg
- Department of Biomedical Science, Colorado State University, Fort Collins, Colorado 80523
| | - Frederic J Hoerndli
- Department of Biomedical Science, Colorado State University, Fort Collins, Colorado 80523
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12
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Choi MK, Liu H, Wu T, Yang W, Zhang Y. NMDAR-mediated modulation of gap junction circuit regulates olfactory learning in C. elegans. Nat Commun 2020; 11:3467. [PMID: 32651378 PMCID: PMC7351742 DOI: 10.1038/s41467-020-17218-0] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2019] [Accepted: 06/19/2020] [Indexed: 02/07/2023] Open
Abstract
Modulation of gap junction-mediated electrical synapses is a common form of neural plasticity. However, the behavioral consequence of the modulation and the underlying molecular cellular mechanisms are not understood. Here, using a C. elegans circuit of interneurons that are connected by gap junctions, we show that modulation of the gap junctions facilitates olfactory learning. Learning experience weakens the gap junctions and induces a repulsive sensory response to the training odorants, which together decouple the responses of the interneurons to the training odorants to generate learned olfactory behavior. The weakening of the gap junctions results from downregulation of the abundance of a gap junction molecule, which is regulated by cell-autonomous function of the worm homologs of a NMDAR subunit and CaMKII. Thus, our findings identify the function of a gap junction modulation in an in vivo model of learning and a conserved regulatory pathway underlying the modulation.
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Affiliation(s)
- Myung-Kyu Choi
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, 02138, USA.,Center for Brain Science, Harvard University, Cambridge, MA, 02138, USA
| | - He Liu
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, 02138, USA.,Center for Brain Science, Harvard University, Cambridge, MA, 02138, USA
| | - Taihong Wu
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, 02138, USA.,Center for Brain Science, Harvard University, Cambridge, MA, 02138, USA
| | - Wenxing Yang
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, 02138, USA.,Center for Brain Science, Harvard University, Cambridge, MA, 02138, USA
| | - Yun Zhang
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, 02138, USA. .,Center for Brain Science, Harvard University, Cambridge, MA, 02138, USA.
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13
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Thornquist SC, Langer K, Zhang SX, Rogulja D, Crickmore MA. CaMKII Measures the Passage of Time to Coordinate Behavior and Motivational State. Neuron 2020; 105:334-345.e9. [PMID: 31786014 PMCID: PMC7374950 DOI: 10.1016/j.neuron.2019.10.018] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2019] [Revised: 08/30/2019] [Accepted: 10/09/2019] [Indexed: 12/18/2022]
Abstract
Electrical events in neurons occur on the order of milliseconds, but the brain can process and reproduce intervals millions of times longer. We present what we believe to be the first neuronal mechanism for timing intervals longer than a few seconds. The activation and gradual relaxation of calcium-independent CaMKII measure a 6-min time window to coordinate two male-specific events during Drosophila mating: sperm transfer and a simultaneous decrease in motivation. We localize these functions to four neurons whose electrical activity is necessary only to report the conclusion of the decline in CaMKII's activity, not for the measurement of the interval. The computation of elapsed time is therefore largely invisible to standard methods of monitoring neuronal activity. Its broad conservation, ubiquitous expression, and tunable duration of activity suggest that CaMKII may time a wide variety of behavioral and cognitive processes.
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Affiliation(s)
- Stephen C Thornquist
- FM Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Kirill Langer
- FM Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Stephen X Zhang
- Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA
| | - Dragana Rogulja
- Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA
| | - Michael A Crickmore
- FM Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA.
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14
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Forward Genetic Screen for Caenorhabditis elegans Mutants with a Shortened Locomotor Healthspan. G3-GENES GENOMES GENETICS 2019; 9:2415-2423. [PMID: 31213517 PMCID: PMC6686916 DOI: 10.1534/g3.119.400241] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Two people with the same lifespan do not necessarily have the same healthspan. One person may retain locomotor and cognitive abilities until the end of life, while another person may lose them during adulthood. Unbiased searches for genes that are required to maintain locomotor ability during adulthood may uncover key regulators of locomotor healthspan. Here, we take advantage of the relatively short lifespan of the nematode Caenorhabditis elegans and develop a novel screening procedure to collect mutants with locomotor deficits that become apparent in adulthood. After ethyl methanesulfonate mutagenesis, we isolated five C. elegans mutant strains that progressively lose adult locomotor ability. In one of the mutant strains, a nonsense mutation in elpc-2, which encodes Elongator Complex Protein Component 2, causes a progressive decline in locomotor ability during adulthood. Mutants and mutations identified in the present screen may provide insights into mechanisms of age-related locomotor impairment and the maintenance of locomotor healthspan.
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15
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Wong SQ, Jones A, Dodd S, Grimes D, Barclay JW, Marson AG, Cunliffe VT, Burgoyne RD, Sills GJ, Morgan A. A Caenorhabditis elegans assay of seizure-like activity optimised for identifying antiepileptic drugs and their mechanisms of action. J Neurosci Methods 2018; 309:132-142. [PMID: 30189284 PMCID: PMC6200019 DOI: 10.1016/j.jneumeth.2018.09.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2018] [Revised: 08/14/2018] [Accepted: 09/02/2018] [Indexed: 11/28/2022]
Abstract
Worms with mutant GABAA receptors exhibit convulsions upon exposure to pentylenetetrazol. Convulsions are prevented by the approved anti-epileptic drug, ethosuximide. C. elegans model is a higher throughput, ethical alternative to rodent seizure models.
Background Epilepsy affects around 1% of people, but existing antiepileptic drugs (AEDs) only offer symptomatic relief and are ineffective in approximately 30% of patients. Hence, new AEDs are sorely needed. However, a major bottleneck is the low-throughput nature of early-stage AED screens in conventional rodent models. This process could potentially be expedited by using simpler invertebrate systems, such as the nematode Caenorhabditis elegans. New method Head-bobbing convulsions were previously reported to be inducible by pentylenetetrazol (PTZ) in C. elegans with loss-of-function mutations in unc-49, which encodes a GABAA receptor. Given that epilepsy-linked mutations in human GABAA receptors are well documented, this could represent a clinically-relevant system for early-stage AED screens. However, the original agar plate-based assay is unsuited to large-scale screening and has not been validated for identifying AEDs. Therefore, we established an alternative streamlined, higher-throughput approach whereby mutants were treated with PTZ and AEDs via liquid-based incubation. Results Convulsions induced within minutes of PTZ exposure in unc-49 mutants were strongly inhibited by the established AED ethosuximide. This protective activity was independent of ethosuximide’s suggested target, the T-type calcium channel, as a null mutation in the worm cca-1 ortholog did not affect ethosuximide’s anticonvulsant action. Comparison with existing method Our streamlined assay is AED-validated, feasible for higher throughput compound screens, and can facilitate insights into AED mechanisms of action. Conclusions Based on an epilepsy-associated genetic background, this C. elegans unc-49 model of seizure-like activity presents an ethical, higher throughput alternative to conventional rodent seizure models for initial AED screens.
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Affiliation(s)
- Shi Quan Wong
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Liverpool, UK.
| | - Alistair Jones
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Liverpool, UK.
| | - Steven Dodd
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Liverpool, UK.
| | - Douglas Grimes
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Liverpool, UK.
| | - Jeff W Barclay
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Liverpool, UK.
| | - Anthony G Marson
- Department of Molecular and Clinical Pharmacology, Institute of Translational Medicine, University of Liverpool, Liverpool, UK.
| | - Vincent T Cunliffe
- Department of Biomedical Science, University of Sheffield, Sheffield, UK.
| | - Robert D Burgoyne
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Liverpool, UK.
| | - Graeme J Sills
- Department of Molecular and Clinical Pharmacology, Institute of Translational Medicine, University of Liverpool, Liverpool, UK.
| | - Alan Morgan
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Liverpool, UK.
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16
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Chia PH, Zhong FL, Niwa S, Bonnard C, Utami KH, Zeng R, Lee H, Eskin A, Nelson SF, Xie WH, Al-Tawalbeh S, El-Khateeb M, Shboul M, Pouladi MA, Al-Raqad M, Reversade B. A homozygous loss-of-function CAMK2A mutation causes growth delay, frequent seizures and severe intellectual disability. eLife 2018; 7:e32451. [PMID: 29784083 PMCID: PMC5963920 DOI: 10.7554/elife.32451] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2017] [Accepted: 03/30/2018] [Indexed: 12/02/2022] Open
Abstract
Calcium/calmodulin-dependent protein kinase II (CAMK2) plays fundamental roles in synaptic plasticity that underlies learning and memory. Here, we describe a new recessive neurodevelopmental syndrome with global developmental delay, seizures and intellectual disability. Using linkage analysis and exome sequencing, we found that this disease maps to chromosome 5q31.1-q34 and is caused by a biallelic germline mutation in CAMK2A. The missense mutation, p.His477Tyr is located in the CAMK2A association domain that is critical for its function and localization. Biochemically, the p.His477Tyr mutant is defective in self-oligomerization and unable to assemble into the multimeric holoenzyme.In vivo, CAMK2AH477Y failed to rescue neuronal defects in C. elegans lacking unc-43, the ortholog of human CAMK2A. In vitro, neurons derived from patient iPSCs displayed profound synaptic defects. Together, our data demonstrate that a recessive germline mutation in CAMK2A leads to neurodevelopmental defects in humans and suggest that dysfunctional CAMK2 paralogs may contribute to other neurological disorders.
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Affiliation(s)
| | - Franklin Lei Zhong
- Institute of Medical BiologyImmunosSingapore
- Institute of Molecular and Cell BiologyProteosSingapore
| | - Shinsuke Niwa
- Frontier Research Institute for Interdisciplinary SciencesTohoku UniversitySendaiJapan
- Graduate School of Life SciencesTohoku UniversitySendaiJapan
| | | | - Kagistia Hana Utami
- Translational Laboratory in Genetic MedicineAgency for Science, Technology and ResearchSingaporeSingapore
| | - Ruizhu Zeng
- Translational Laboratory in Genetic MedicineAgency for Science, Technology and ResearchSingaporeSingapore
| | - Hane Lee
- Department of Pathology and Laboratory MedicineDavid Geffen School of Medicine, University of California, Los AngelesLos AngelesUnited States
- Department of Human GeneticsDavid Geffen School of Medicine University of California, Los AngelesLos AngelesUnited States
| | - Ascia Eskin
- Department of Pathology and Laboratory MedicineDavid Geffen School of Medicine, University of California, Los AngelesLos AngelesUnited States
- Department of Human GeneticsDavid Geffen School of Medicine University of California, Los AngelesLos AngelesUnited States
| | - Stanley F Nelson
- Department of Pathology and Laboratory MedicineDavid Geffen School of Medicine, University of California, Los AngelesLos AngelesUnited States
- Department of Human GeneticsDavid Geffen School of Medicine University of California, Los AngelesLos AngelesUnited States
| | | | - Samah Al-Tawalbeh
- Queen Rania Paediatric HospitalKing Hussein Medical Centre, Royal Medical ServicesAmmanJordan
| | | | | | - Mahmoud A Pouladi
- Translational Laboratory in Genetic MedicineAgency for Science, Technology and ResearchSingaporeSingapore
- Department of Medicine, Yong Loo Lin School of MedicineNational University of SingaporeSingaporeSingapore
| | - Mohammed Al-Raqad
- Queen Rania Paediatric HospitalKing Hussein Medical Centre, Royal Medical ServicesAmmanJordan
| | - Bruno Reversade
- Institute of Medical BiologyImmunosSingapore
- Institute of Molecular and Cell BiologyProteosSingapore
- Department of PaediatricsNational University of SingaporeSingaporeSingapore
- Medical Genetics DepartmentKoç University School of MedicineIstanbulTurkey
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17
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An atlas of Caenorhabditis elegans chemoreceptor expression. PLoS Biol 2018; 16:e2004218. [PMID: 29293491 PMCID: PMC5749674 DOI: 10.1371/journal.pbio.2004218] [Citation(s) in RCA: 55] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2017] [Accepted: 11/22/2017] [Indexed: 12/20/2022] Open
Abstract
One goal of modern day neuroscience is the establishment of molecular maps that assign unique features to individual neuron types. Such maps provide important starting points for neuron classification, for functional analysis, and for developmental studies aimed at defining the molecular mechanisms of neuron identity acquisition and neuron identity diversification. In this resource paper, we describe a nervous system-wide map of the potential expression sites of 244 members of the largest gene family in the C. elegans genome, rhodopsin-like (class A) G-protein-coupled receptor (GPCR) chemoreceptors, using classic gfp reporter gene technology. We cover representatives of all sequence families of chemoreceptor GPCRs, some of which were previously entirely uncharacterized. Most reporters are expressed in a very restricted number of cells, often just in single cells. We assign GPCR reporter expression to all but two of the 37 sensory neuron classes of the sex-shared, core nervous system. Some sensory neurons express a very small number of receptors, while others, particularly nociceptive neurons, coexpress several dozen GPCR reporter genes. GPCR reporters are also expressed in a wide range of inter- and motorneurons, as well as non-neuronal cells, suggesting that GPCRs may constitute receptors not just for environmental signals, but also for internal cues. We observe only one notable, frequent association of coexpression patterns, namely in one nociceptive amphid (ASH) and two nociceptive phasmid sensory neurons (PHA, PHB). We identified GPCRs with sexually dimorphic expression and several GPCR reporters that are expressed in a left/right asymmetric manner. We identified a substantial degree of GPCR expression plasticity; particularly in the context of the environmentally-induced dauer diapause stage when one third of all tested GPCRs alter the cellular specificity of their expression within and outside the nervous system. Intriguingly, in a number of cases, the dauer-specific alterations of GPCR reporter expression in specific neuron classes are maintained during postdauer life and in some case new patterns are induced post-dauer, demonstrating that GPCR gene expression may serve as traits of life history. Taken together, our resource provides an entry point for functional studies and also offers a host of molecular markers for studying molecular patterning and plasticity of the nervous system. Maps of gene expression patterns in nervous systems provide an important resource for neuron classification, for functional analysis, and for developmental studies that ask how different neurons acquire their unique identities. By analyzing transgenic GFP reporter strains, we describe here the expression pattern of 244 putative chemosensory receptor-encoding genes, which constitute the largest gene family in Caenorhabditis elegans. As expected, chemoreceptor expression is enriched in chemosensory neurons. Putative chemoreceptors are also expressed in a wide range of interneurons and motor neurons, as well as non-neuronal cells, suggesting that these receptors may sense internal cues in addition to environmental signals. Each chemoreceptor is expressed sparsely, often in just one neuron type, but each neuron type can express many chemoreceptors. Chemoreceptor expression is remarkably plastic, particularly in the context of the environmentally induced dauer diapause stage. Taken together, this molecular atlas of chemosensory receptors provides an entry point for functional studies and offers a host of markers for studying neuronal patterning and plasticity.
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18
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Chaudhuri J, Bose N, Gong J, Hall D, Rifkind A, Bhaumik D, Peiris TH, Chamoli M, Le CH, Liu J, Lithgow GJ, Ramanathan A, Xu XZS, Kapahi P. A Caenorhabditis elegans Model Elucidates a Conserved Role for TRPA1-Nrf Signaling in Reactive α-Dicarbonyl Detoxification. Curr Biol 2016; 26:3014-3025. [PMID: 27773573 DOI: 10.1016/j.cub.2016.09.024] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2016] [Revised: 08/17/2016] [Accepted: 09/13/2016] [Indexed: 01/13/2023]
Abstract
Reactive α-dicarbonyls (α-DCs), like methylglyoxal (MGO), accumulate with age and have been implicated in aging and various age-associated pathologies, such as diabetic complications and neurodegenerative disorders like Alzheimer's and Parkinson's diseases. Evolutionarily conserved glyoxalases are responsible for α-DC detoxification; however, their core biochemical regulation has remained unclear. We have established a Caenorhabditis elegans model, based on an impaired glyoxalase (glod-4/GLO1), to broadly study α-DC-related stress. We show that, in comparison to wild-type (N2, Bristol), glod-4 animals rapidly exhibit several pathogenic phenotypes, including hyperesthesia, neuronal damage, reduced motility, and early mortality. We further demonstrate TRPA-1/TRPA1 as a sensor for α-DCs, conserved between worms and mammals. Moreover, TRPA-1 activates SKN-1/Nrf via calcium-modulated kinase signaling, ultimately regulating the glutathione-dependent (GLO1) and co-factor-independent (DJ1) glyoxalases to detoxify α-DCs. Interestingly, this pathway is in stark contrast to the TRPA-1 activation and the ensuing calcium flux implicated in cold sensation in C. elegans, whereby DAF-16/FOXO gets activated via complementary kinase signaling. Finally, a phenotypic drug screen using C. elegans identified podocarpic acid as a novel activator of TRPA1 that rescues α-DC-induced pathologies in C. elegans and mammalian cells. Our work thus identifies TRPA1 as a bona fide drug target for the amelioration of α-DC stress, which represents a viable option to address aging-related pathologies in diabetes and neurodegenerative diseases.
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Affiliation(s)
- Jyotiska Chaudhuri
- The Buck Institute for Research on Aging, 8001 Redwood Boulevard, Novato, CA 94945, USA
| | - Neelanjan Bose
- The Buck Institute for Research on Aging, 8001 Redwood Boulevard, Novato, CA 94945, USA; Department of Urology, University of California, 400 Parnassus Avenue, San Francisco, CA 94143, USA
| | - Jianke Gong
- College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China; Life Sciences Institute and Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI 48109, USA
| | - David Hall
- The Buck Institute for Research on Aging, 8001 Redwood Boulevard, Novato, CA 94945, USA
| | - Alexander Rifkind
- The Buck Institute for Research on Aging, 8001 Redwood Boulevard, Novato, CA 94945, USA
| | - Dipa Bhaumik
- The Buck Institute for Research on Aging, 8001 Redwood Boulevard, Novato, CA 94945, USA
| | - T Harshani Peiris
- The Buck Institute for Research on Aging, 8001 Redwood Boulevard, Novato, CA 94945, USA
| | - Manish Chamoli
- The Buck Institute for Research on Aging, 8001 Redwood Boulevard, Novato, CA 94945, USA
| | - Catherine H Le
- The Buck Institute for Research on Aging, 8001 Redwood Boulevard, Novato, CA 94945, USA
| | - Jianfeng Liu
- College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China
| | - Gordon J Lithgow
- The Buck Institute for Research on Aging, 8001 Redwood Boulevard, Novato, CA 94945, USA
| | - Arvind Ramanathan
- The Buck Institute for Research on Aging, 8001 Redwood Boulevard, Novato, CA 94945, USA
| | - X Z Shawn Xu
- Life Sciences Institute and Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Pankaj Kapahi
- The Buck Institute for Research on Aging, 8001 Redwood Boulevard, Novato, CA 94945, USA; Department of Urology, University of California, 400 Parnassus Avenue, San Francisco, CA 94143, USA.
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19
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Starnes DL, Lichtenberg SS, Unrine JM, Starnes CP, Oostveen EK, Lowry GV, Bertsch PM, Tsyusko OV. Distinct transcriptomic responses of Caenorhabditis elegans to pristine and sulfidized silver nanoparticles. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2016; 213:314-321. [PMID: 26925754 DOI: 10.1016/j.envpol.2016.01.020] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/2015] [Revised: 12/23/2015] [Accepted: 01/07/2016] [Indexed: 06/05/2023]
Abstract
Manufactured nanoparticles (MNP) rapidly undergo aging processes once released from products. Silver sulfide (Ag2S) is the major transformation product formed during the wastewater treatment process for Ag-MNP. We examined toxicogenomic responses of pristine Ag-MNP, sulfidized Ag-MNP (sAg-MNP), and AgNO3 to a model soil organism, Caenorhabditis elegans. Transcriptomic profiling of nematodes which were exposed at the EC30 for reproduction for AgNO3, Ag-MNP, and sAg-MNP resulted in 571 differentially expressed genes. We independently verified expression of 4 genes (numr-1, rol-8, col-158, and grl-20) using qRT-PCR. Only 11% of differentially expressed genes were common among the three treatments. Gene ontology enrichment analysis also revealed that Ag-MNP and sAg-MNP had distinct toxicity mechanisms and did not share any of the biological processes. The processes most affected by Ag-MNP relate to metabolism, while those processes most affected by sAg-MNP relate to molting and the cuticle, and the most impacted processes for AgNO3 exposed nematodes was stress related. Additionally, as observed from qRT-PCR and mutant experiments, the responses to sAg-MNP were distinct from AgNO3 while some of the effects of pristine MNP were similar to AgNO3, suggesting that effects from Ag-MNP is partially due to dissolved silver ions.
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Affiliation(s)
- Daniel L Starnes
- Department of Plant and Soil Sciences, University of Kentucky, 1100 South Limestone Street, Lexington, KY 40546, United States
| | - Stuart S Lichtenberg
- Department of Plant and Soil Sciences, University of Kentucky, 1100 South Limestone Street, Lexington, KY 40546, United States; Center for Environmental Implications of NanoTechnology (CEINT), P.O. Box 90287, Duke University, Durham, NC 27708-0287, United States
| | - Jason M Unrine
- Department of Plant and Soil Sciences, University of Kentucky, 1100 South Limestone Street, Lexington, KY 40546, United States; Center for Environmental Implications of NanoTechnology (CEINT), P.O. Box 90287, Duke University, Durham, NC 27708-0287, United States
| | - Catherine P Starnes
- Department of Statistics, University of Kentucky, 725 Rose Street, MDS Building 305, Lexington, KY 40536, United States
| | - Emily K Oostveen
- Department of Plant and Soil Sciences, University of Kentucky, 1100 South Limestone Street, Lexington, KY 40546, United States
| | - Gregory V Lowry
- Center for Environmental Implications of NanoTechnology (CEINT), P.O. Box 90287, Duke University, Durham, NC 27708-0287, United States; Department of Civil & Environmental Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, United States
| | - Paul M Bertsch
- Department of Plant and Soil Sciences, University of Kentucky, 1100 South Limestone Street, Lexington, KY 40546, United States; Center for Environmental Implications of NanoTechnology (CEINT), P.O. Box 90287, Duke University, Durham, NC 27708-0287, United States; Division of Land and Water, CSIRO, Ecosciences Precinct, Brisbane, QLD, Australia
| | - Olga V Tsyusko
- Department of Plant and Soil Sciences, University of Kentucky, 1100 South Limestone Street, Lexington, KY 40546, United States; Center for Environmental Implications of NanoTechnology (CEINT), P.O. Box 90287, Duke University, Durham, NC 27708-0287, United States.
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20
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Kobayashi K, Nakano S, Amano M, Tsuboi D, Nishioka T, Ikeda S, Yokoyama G, Kaibuchi K, Mori I. Single-Cell Memory Regulates a Neural Circuit for Sensory Behavior. Cell Rep 2015; 14:11-21. [PMID: 26725111 DOI: 10.1016/j.celrep.2015.11.064] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2014] [Revised: 09/06/2015] [Accepted: 11/22/2015] [Indexed: 01/12/2023] Open
Abstract
Unveiling the molecular and cellular mechanisms underlying memory has been a challenge for the past few decades. Although synaptic plasticity is proven to be essential for memory formation, the significance of "single-cell memory" still remains elusive. Here, we exploited a primary culture system for the analysis of C. elegans neurons and show that a single thermosensory neuron has an ability to form, retain, and reset a temperature memory. Genetic and proteomic analyses found that the expression of the single-cell memory exhibits inter-individual variability, which is controlled by the evolutionarily conserved CaMKI/IV and Raf pathway. The variable responses of a sensory neuron influenced the neural activity of downstream interneurons, suggesting that modulation of the sensory neurons ultimately determines the behavioral output in C. elegans. Our results provide proof of single-cell memory and suggest that the individual differences in neural responses at the single-cell level can confer individuality.
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Affiliation(s)
- Kyogo Kobayashi
- Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya 464-8602, Japan
| | - Shunji Nakano
- Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya 464-8602, Japan
| | - Mutsuki Amano
- Department of Cell Pharmacology, Graduate School of Medicine, Nagoya University, Nagoya 466-8550, Japan
| | - Daisuke Tsuboi
- Department of Cell Pharmacology, Graduate School of Medicine, Nagoya University, Nagoya 466-8550, Japan
| | - Tomoki Nishioka
- Department of Cell Pharmacology, Graduate School of Medicine, Nagoya University, Nagoya 466-8550, Japan
| | - Shingo Ikeda
- Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya 464-8602, Japan
| | - Genta Yokoyama
- Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya 464-8602, Japan
| | - Kozo Kaibuchi
- Department of Cell Pharmacology, Graduate School of Medicine, Nagoya University, Nagoya 466-8550, Japan
| | - Ikue Mori
- Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya 464-8602, Japan; CREST, JST, 4-1-8 Honcho, Kawaguchi, Saitama, 332-0012, Japan.
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21
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Nagy S, Huang YC, Alkema MJ, Biron D. Caenorhabditis elegans exhibit a coupling between the defecation motor program and directed locomotion. Sci Rep 2015; 5:17174. [PMID: 26597056 PMCID: PMC4657007 DOI: 10.1038/srep17174] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2015] [Accepted: 10/26/2015] [Indexed: 12/27/2022] Open
Abstract
Distinct motor programs can be coupled to refine the repertoire of behavior dynamics. However, mechanisms underlying such coupling are poorly understood. The defecation motor program (DMP) of C. elegans is composed of a succession of body contraction and expulsion steps, performed repeatedly with a period of 50-60 sec. We show that recurring patterns of directed locomotion are executed in tandem with, co-reset, and co-terminate with the DMP cycle. Calcium waves in the intestine and proton signaling were shown to regulate the DMP. We found that genetic manipulations affecting these calcium dynamics regulated the corresponding patterns of directed locomotion. Moreover, we observed the initiation of a recurring locomotion pattern 10 seconds prior to the posterior body contraction, suggesting that the synchronized motor program may initiate prior to the DMP. This study links two multi-step motor programs executed by C. elegans in synchrony, utilizing non-neuronal tissue to drive directed locomotion.
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Affiliation(s)
- Stanislav Nagy
- The Institute for Biophysical Dynamics, The University of Chicago, Chicago, IL
| | - Yung-Chi Huang
- Department of Neurobiology, University of Ma ssachusetts Medical School, Worcester, MA
| | - Mark J Alkema
- Department of Neurobiology, University of Ma ssachusetts Medical School, Worcester, MA
| | - David Biron
- The Institute for Biophysical Dynamics, The University of Chicago, Chicago, IL
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22
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Neural activity and CaMKII protect mitochondria from fragmentation in aging Caenorhabditis elegans neurons. Proc Natl Acad Sci U S A 2015; 112:8768-73. [PMID: 26124107 DOI: 10.1073/pnas.1501831112] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Decline in mitochondrial morphology and function is a hallmark of neuronal aging. Here we report that progressive mitochondrial fragmentation is a common manifestation of aging Caenorhabditis elegans neurons and body wall muscles. We show that sensory-evoked activity was essential for maintaining neuronal mitochondrial morphology, and this activity-dependent mechanism required the Degenerin/ENaC sodium channel MEC-4, the L-type voltage-gated calcium channel EGL-19, and the Ca/calmodulin-dependent kinase II (CaMKII) UNC-43. Importantly, UNC-43 phosphorylated and inhibited the dynamin-related protein (DRP)-1, which was responsible for excessive mitochondrial fragmentation in neurons that lacked sensory-evoked activity. Moreover, enhanced activity in the aged neurons ameliorated mitochondrial fragmentation. These findings provide a detailed description of mitochondrial behavior in aging neurons and identify activity-dependent DRP-1 phosphorylation by CaMKII as a key mechanism in neuronal mitochondrial maintenance.
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23
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Hoerndli FJ, Wang R, Mellem JE, Kallarackal A, Brockie PJ, Thacker C, Madsen DM, Maricq AV. Neuronal Activity and CaMKII Regulate Kinesin-Mediated Transport of Synaptic AMPARs. Neuron 2015; 86:457-74. [PMID: 25843407 DOI: 10.1016/j.neuron.2015.03.011] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2014] [Revised: 01/20/2015] [Accepted: 02/25/2015] [Indexed: 11/29/2022]
Abstract
Excitatory glutamatergic synaptic transmission is critically dependent on maintaining an optimal number of postsynaptic AMPA receptors (AMPARs) at each synapse of a given neuron. Here, we show that presynaptic activity, postsynaptic potential, voltage-gated calcium channels (VGCCs) and UNC-43, the C. elegans homolog of CaMKII, control synaptic strength by regulating motor-driven AMPAR transport. Genetic mutations in unc-43, or spatially and temporally restricted inactivation of UNC-43/CaMKII, revealed its essential roles in the transport of AMPARs from the cell body and in the insertion and removal of synaptic AMPARs. We found that an essential target of UNC-43/CaMKII is kinesin light chain and that mouse CaMKII rescued unc-43 mutants, suggesting conservation of function. Transient expression of UNC-43/CaMKII in adults rescued the transport defects, while optogenetic stimulation of select synapses revealed CaMKII's role in activity-dependent plasticity. Our results demonstrate unanticipated, fundamentally important roles for UNC-43/CaMKII in the regulation of synaptic strength.
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Affiliation(s)
- Frédéric J Hoerndli
- Department of Biology and Center for Cell and Genome Science, University of Utah, Salt Lake City, UT 84112-0840, USA
| | - Rui Wang
- Department of Biology and Center for Cell and Genome Science, University of Utah, Salt Lake City, UT 84112-0840, USA
| | - Jerry E Mellem
- Department of Biology and Center for Cell and Genome Science, University of Utah, Salt Lake City, UT 84112-0840, USA
| | - Angy Kallarackal
- Department of Biology and Center for Cell and Genome Science, University of Utah, Salt Lake City, UT 84112-0840, USA
| | - Penelope J Brockie
- Department of Biology and Center for Cell and Genome Science, University of Utah, Salt Lake City, UT 84112-0840, USA
| | - Colin Thacker
- Department of Biology and Center for Cell and Genome Science, University of Utah, Salt Lake City, UT 84112-0840, USA
| | - David M Madsen
- Department of Biology and Center for Cell and Genome Science, University of Utah, Salt Lake City, UT 84112-0840, USA
| | - Andres V Maricq
- Department of Biology and Center for Cell and Genome Science, University of Utah, Salt Lake City, UT 84112-0840, USA.
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Abstract
Ca(2+)/calmodulin-dependent Kinase II (CaMKII) is a calcium-regulated serine threonine kinase whose functions include regulation of synaptic activity (Coultrap and Bayer 2012). A postsynaptic role for CaMKII in triggering long-lasting changes in synaptic activity at some synapses has been established, although the relevant downstream targets remain to be defined (Nicoll and Roche 2013). A presynaptic role for CaMKII in regulating synaptic activity is less clear with evidence for CaMKII either increasing or decreasing release of neurotransmitter from synaptic vesicles (SVs) (Wang 2008). In this issue Hoover et al. (2014) further expand upon the role of CaMKII in presynaptic cells by demonstrating a role in regulating another form of neuronal signaling, that of dense core vesicles (DCVs), whose contents can include neuropeptides and insulin-related peptides, as well as other neuromodulators such as serotonin and dopamine (Michael et al. 2006). Intriguingly, Hoover et al. (2014) demonstrate that active CaMKII is required cell autonomously to prevent premature release of DCVs after they bud from the Golgi in the soma and before they are trafficked to their release sites in the axon. This role of CaMKII requires it to have kinase activity as well as an activating calcium signal released from internal ER stores via the ryanodine receptor. Not only does this represent a novel function for CaMKII but also it offers new insights into how DCVs are regulated. Compared to SVs we know much less about how DCVs are trafficked, docked, and primed for release. This is despite the fact that neuropeptides are major regulators of human brain function, including mood, anxiety, and social interactions (Garrison et al. 2012; Kormos and Gaszner 2013; Walker and Mcglone 2013). This is supported by studies showing mutations in genes for DCV regulators or cargoes are associated with human mental disorders (Sadakata and Furuichi 2009; Alldredge 2010; Quinn 2013; Quinn et al. 2013). We lack even a basic understanding of DCV function, such as, are there defined DCV docking sites and, if so, how are DCVs delivered to these release sites? These results from Hoover et al. (2014) promise to be a starting point in answering some of these questions.
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25
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Steinkellner T, Mus L, Eisenrauch B, Constantinescu A, Leo D, Konrad L, Rickhag M, Sørensen G, Efimova EV, Kong E, Willeit M, Sotnikova TD, Kudlacek O, Gether U, Freissmuth M, Pollak DD, Gainetdinov RR, Sitte HH. In vivo amphetamine action is contingent on αCaMKII. Neuropsychopharmacology 2014; 39:2681-93. [PMID: 24871545 PMCID: PMC4207348 DOI: 10.1038/npp.2014.124] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/09/2014] [Revised: 05/01/2014] [Accepted: 05/05/2014] [Indexed: 11/09/2022]
Abstract
Addiction to psychostimulants (ie, amphetamines and cocaine) imposes a major socioeconomic burden. Prevention and treatment represent unmet medical needs, which may be addressed, if the mechanisms underlying psychostimulant action are understood. Cocaine acts as a blocker at the transporters for dopamine (DAT), serotonin (SERT), and norepinephrine (NET), but amphetamines are substrates that do not only block the uptake of monoamines but also induce substrate efflux by promoting reverse transport. Reverse transport has been a focus of research for decades but its mechanistic basis still remains enigmatic. Recently, transporter-interacting proteins were found to regulate amphetamine-triggered reverse transport: calmodulin kinase IIα (αCaMKII) is a prominent example, because it binds the carboxyl terminus of DAT, phosphorylates its amino terminus, and supports amphetamine-induced substrate efflux in vitro. Here, we investigated whether, in vivo, the action of amphetamine was contingent on the presence of αCaMKII by recording the behavioral and neurochemical effects of amphetamine. Measurement of dopamine efflux in the dorsal striatum by microdialysis revealed that amphetamine induced less dopamine efflux in mice lacking αCaMKII. Consistent with this observation, the acute locomotor responses to amphetamine were also significantly blunted in αCaMKII-deficient mice. In addition, while the rewarding properties of amphetamine were preserved in αCaMKII-deficient mice, their behavioral sensitization to amphetamine was markedly reduced. Our findings demonstrate that amphetamine requires the presence of αCaMKII to elicit a full-fledged effect on DAT in vivo: αCaMKII does not only support acute amphetamine-induced dopamine efflux but is also important in shaping the chronic response to amphetamine.
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Affiliation(s)
- Thomas Steinkellner
- Institute of Pharmacology, Center for
Physiology and Pharmacology, Medical University Vienna, Waehringer Strasse,
Vienna, Austria
| | - Liudmilla Mus
- Department of Neuroscience and Brain
Technologies, Istituto Italiano di Tecnologia (IIT), Via Morego,
Genova, Italy,Department of Psychopharmacology,
Institute of Pharmacology, Pavlov Medical University, St
Petersburg, Russia
| | - Birgit Eisenrauch
- Institute of Pharmacology, Center for
Physiology and Pharmacology, Medical University Vienna, Waehringer Strasse,
Vienna, Austria
| | - Andreea Constantinescu
- Institute of Pharmacology, Center for
Physiology and Pharmacology, Medical University Vienna, Waehringer Strasse,
Vienna, Austria
| | - Damiana Leo
- Department of Neuroscience and Brain
Technologies, Istituto Italiano di Tecnologia (IIT), Via Morego,
Genova, Italy
| | - Lisa Konrad
- Institute of Pharmacology, Center for
Physiology and Pharmacology, Medical University Vienna, Waehringer Strasse,
Vienna, Austria
| | - Mattias Rickhag
- Molecular Neuropharmacology and Genetics
Laboratory, Department of Neuroscience and Pharmacology, Faculty of Health and
Medical Sciences, The Panum Institute, University of Copenhagen,
Copenhagen, Denmark
| | - Gunnar Sørensen
- Molecular Neuropharmacology and Genetics
Laboratory, Department of Neuroscience and Pharmacology, Faculty of Health and
Medical Sciences, The Panum Institute, University of Copenhagen,
Copenhagen, Denmark
| | - Evgenia V Efimova
- Skolkovo Institute of Science and
Technology (Skoltech), Skolkovo, Moscow,
Russia
| | - Eryan Kong
- Department of Neurophysiology and
Neuropharmacology, Center for Physiology and Pharmacology, Medical University
Vienna, Waehringer Strasse, Vienna, Austria
| | - Matthäus Willeit
- Department of Psychiatry and
Psychotherapy, Medical University of Vienna, Waehringer Guertel,
Vienna, Austria
| | - Tatyana D Sotnikova
- Department of Neuroscience and Brain
Technologies, Istituto Italiano di Tecnologia (IIT), Via Morego,
Genova, Italy
| | - Oliver Kudlacek
- Institute of Pharmacology, Center for
Physiology and Pharmacology, Medical University Vienna, Waehringer Strasse,
Vienna, Austria
| | - Ulrik Gether
- Molecular Neuropharmacology and Genetics
Laboratory, Department of Neuroscience and Pharmacology, Faculty of Health and
Medical Sciences, The Panum Institute, University of Copenhagen,
Copenhagen, Denmark
| | - Michael Freissmuth
- Institute of Pharmacology, Center for
Physiology and Pharmacology, Medical University Vienna, Waehringer Strasse,
Vienna, Austria
| | - Daniela D Pollak
- Department of Neurophysiology and
Neuropharmacology, Center for Physiology and Pharmacology, Medical University
Vienna, Waehringer Strasse, Vienna, Austria
| | - Raul R Gainetdinov
- Department of Neuroscience and Brain
Technologies, Istituto Italiano di Tecnologia (IIT), Via Morego,
Genova, Italy,Skolkovo Institute of Science and
Technology (Skoltech), Skolkovo, Moscow,
Russia,Faculty of Biology and Soil Science, St
Petersburg State University, St Petersburg,
Russia
| | - Harald H Sitte
- Institute of Pharmacology, Center for
Physiology and Pharmacology, Medical University Vienna, Waehringer Strasse,
Vienna, Austria,Institute of Pharmacology, Center for Physiology and
Pharmacology, Medical University Vienna, Waehringer Strasse 13A,
Vienna
1090, Austria, Tel: +43 1 40160 31323, Fax: +43 1
40160 931300, E-mail:
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Functional evolution of Erg potassium channel gating reveals an ancient origin for IKr. Proc Natl Acad Sci U S A 2014; 111:5712-7. [PMID: 24706772 DOI: 10.1073/pnas.1321716111] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Mammalian Ether-a-go-go related gene (Erg) family voltage-gated K(+) channels possess an unusual gating phenotype that specializes them for a role in delayed repolarization. Mammalian Erg currents rectify during depolarization due to rapid, voltage-dependent inactivation, but rebound during repolarization due to a combination of rapid recovery from inactivation and slow deactivation. This is exemplified by the mammalian Erg1 channel, which is responsible for IKr, a current that repolarizes cardiac action potential plateaus. The Drosophila Erg channel does not inactivate and closes rapidly upon repolarization. The dramatically different properties observed in mammalian and Drosophila Erg homologs bring into question the evolutionary origins of distinct Erg K(+) channel functions. Erg channels are highly conserved in eumetazoans and first evolved in a common ancestor of the placozoans, cnidarians, and bilaterians. To address the ancestral function of Erg channels, we identified and characterized Erg channel paralogs in the sea anemone Nematostella vectensis. N. vectensis Erg1 (NvErg1) is highly conserved with respect to bilaterian homologs and shares the IKr-like gating phenotype with mammalian Erg channels. Thus, the IKr phenotype predates the divergence of cnidarians and bilaterians. NvErg4 and Caenorhabditis elegans Erg (unc-103) share the divergent Drosophila Erg gating phenotype. Phylogenetic and sequence analysis surprisingly indicates that this alternate gating phenotype arose independently in protosomes and cnidarians. Conversion from an ancestral IKr-like gating phenotype to a Drosophila Erg-like phenotype correlates with loss of the cytoplasmic Ether-a-go-go domain. This domain is required for slow deactivation in mammalian Erg1 channels, and thus its loss may partially explain the change in gating phenotype.
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27
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Hoover CM, Edwards SL, Yu SC, Kittelmann M, Richmond JE, Eimer S, Yorks RM, Miller KG. A novel CaM kinase II pathway controls the location of neuropeptide release from Caenorhabditis elegans motor neurons. Genetics 2014; 196:745-65. [PMID: 24653209 PMCID: PMC3948804 DOI: 10.1534/genetics.113.158568] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2013] [Accepted: 11/17/2013] [Indexed: 12/29/2022] Open
Abstract
Neurons release neuropeptides via the regulated exocytosis of dense core vesicles (DCVs) to evoke or modulate behaviors. We found that Caenorhabditis elegans motor neurons send most of their DCVs to axons, leaving very few in the cell somas. How neurons maintain this skewed distribution and the extent to which it can be altered to control DCV numbers in axons or to drive release from somas for different behavioral impacts is unknown. Using a forward genetic screen, we identified loss-of-function mutations in UNC-43 (CaM kinase II) that reduce axonal DCV levels by ∼90% and cell soma/dendrite DCV levels by ∼80%, leaving small synaptic vesicles largely unaffected. Blocking regulated secretion in unc-43 mutants restored near wild-type axonal levels of DCVs. Time-lapse video microscopy showed no role for CaM kinase II in the transport of DCVs from cell somas to axons. In vivo secretion assays revealed that much of the missing neuropeptide in unc-43 mutants is secreted via a regulated secretory pathway requiring UNC-31 (CAPS) and UNC-18 (nSec1). DCV cargo levels in unc-43 mutants are similarly low in cell somas and the axon initial segment, indicating that the secretion occurs prior to axonal transport. Genetic pathway analysis suggests that abnormal neuropeptide function contributes to the sluggish basal locomotion rate of unc-43 mutants. These results reveal a novel pathway controlling the location of DCV exocytosis and describe a major new function for CaM kinase II.
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Affiliation(s)
- Christopher M. Hoover
- Genetic Models of Disease Program, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma 73104
| | - Stacey L. Edwards
- Genetic Models of Disease Program, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma 73104
| | - Szi-chieh Yu
- Department of Biological Sciences, University of Illinois, Chicago, Illinois 60607
| | - Maike Kittelmann
- European Neuroscience Institute, Center for Molecular Physiology of the Brain, Georg-August University, Goettingen, Germany 37073
| | - Janet E. Richmond
- Department of Biological Sciences, University of Illinois, Chicago, Illinois 60607
| | - Stefan Eimer
- European Neuroscience Institute, Center for Molecular Physiology of the Brain, Georg-August University, Goettingen, Germany 37073
- BIOSS Center for Biological Signaling Studies, Albert-Ludwigs-University, Freiburg, Germany 79085
| | - Rosalina M. Yorks
- Genetic Models of Disease Program, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma 73104
| | - Kenneth G. Miller
- Genetic Models of Disease Program, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma 73104
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28
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Steinlein OK. Animal models for autosomal dominant frontal lobe epilepsy: on the origin of seizures. Expert Rev Neurother 2014; 10:1859-67. [DOI: 10.1586/ern.10.130] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
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29
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Pandey P, Mersha MD, Dhillon HS. A synergistic approach towards understanding the functional significance of dopamine receptor interactions. J Mol Signal 2013; 8:13. [PMID: 24308343 PMCID: PMC3878971 DOI: 10.1186/1750-2187-8-13] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2012] [Accepted: 11/18/2013] [Indexed: 11/10/2022] Open
Abstract
The importance of the neurotransmitter dopamine (DA) in the nervous system is underscored by its role in a wide variety of physiological and neural functions in both vertebrates and invertebrates. Binding of dopamine to its membrane receptors initiates precise signaling cascades that result in specific cellular responses. Dopamine receptors belong to a super-family of G-protein coupled receptors (GPCRs) that are characterized by seven trans-membrane domains. In mammals, five dopamine receptors have been identified which are grouped into two different categories D1- and D2-like receptors. The interactions of DA receptors with other proteins including specific Gα subunits are critical in deciding the fate of downstream molecular events carried out by effector proteins. In this mini-review we provide a synopsis of known protein-protein interactions of DA receptors and a perspective on the potential synergistic utility of Caenorhabditis elegans as a model eukaryote with a comparatively simpler nervous system to gain insight on the neuronal and behavioral consequences of the receptor interactions.
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Affiliation(s)
| | | | - Harbinder S Dhillon
- Department of Biological Sciences, Center for Neuroscience Research, Delaware State University, Dover, DE 19901, USA.
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30
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Tao L, Xie Q, Ding YH, Li ST, Peng S, Zhang YP, Tan D, Yuan Z, Dong MQ. CAMKII and calcineurin regulate the lifespan of Caenorhabditis elegans through the FOXO transcription factor DAF-16. eLife 2013; 2:e00518. [PMID: 23805378 PMCID: PMC3691573 DOI: 10.7554/elife.00518] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2013] [Accepted: 05/24/2013] [Indexed: 01/03/2023] Open
Abstract
The insulin-like signaling pathway maintains a relatively short wild-type lifespan in Caenorhabditis elegans by phosphorylating and inactivating DAF-16, the ortholog of the FOXO transcription factors of mammalian cells. DAF-16 is phosphorylated by the AKT kinases, preventing its nuclear translocation. Calcineurin (PP2B phosphatase) also limits the lifespan of C. elegans, but the mechanism through which it does so is unknown. Herein, we show that TAX-6•CNB-1 and UNC-43, the C. elegans Calcineurin and Ca(2+)/calmodulin-dependent kinase type II (CAMKII) orthologs, respectively, also regulate lifespan through DAF-16. Moreover, UNC-43 regulates DAF-16 in response to various stress conditions, including starvation, heat or oxidative stress, and cooperatively contributes to lifespan regulation by insulin signaling. However, unlike insulin signaling, UNC-43 phosphorylates and activates DAF-16, thus promoting its nuclear localization. The phosphorylation of DAF-16 at S286 by UNC-43 is removed by TAX-6•CNB-1, leading to DAF-16 inactivation. Mammalian FOXO3 is also regulated by CAMKIIA and Calcineurin. DOI:http://dx.doi.org/10.7554/eLife.00518.001.
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Affiliation(s)
- Li Tao
- Graduate Program in Chinese Academy of Medical Sciences and Peking Union Medical College , Beijing , China ; National Institute of Biological Sciences, Beijing , Beijing , China
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31
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Zhang Y, Zhao H, Wang J, Ge J, Li Y, Gu J, Li P, Feng Y, Yang M. Structural insight into Caenorhabditis elegans sex-determining protein FEM-2. J Biol Chem 2013; 288:22058-66. [PMID: 23760267 DOI: 10.1074/jbc.m113.464339] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
In the nematode Caenorhabditis elegans, fem-1, fem-2, and fem-3 play crucial roles in male sexual development. Among these three genes, fem-2 encodes a PP2C (serine/threonine phosphatase type 2C)-like protein, whose activity promotes the development of masculinity. Different from the canonical PP2Cs, FEM-2 consists of an additional N-terminal domain (NTD) apart from its C-terminal catalytic domain. Interestingly, genetic studies have indicated indispensable roles for both of these two domains of FEM-2 in promoting male development, but the underlying mechanism remains unknown. In the present study, we solved the crystal structure of full-length FEM-2, which revealed a novel structural fold formed by its NTD. Structural and functional analyses demonstrated that the NTD did not directly regulate the in vitro dephosphorylation activity of FEM-2, but instead functioned as a scaffold domain in the assembly of the FEM-1/2/3 complex, the executioner in the final step of the sex determination pathway. Biochemical studies further identified the regions in the NTD involved in FEM-1 and FEM-3 interactions. Our results not only identified a novel fold formed by the extra domain of a noncanonical PP2C enzyme, but also provided important insights into the molecular mechanism of how the NTD works in mediating the sex-determining role of FEM-1/2/3 complex.
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Affiliation(s)
- Yi Zhang
- Ministry of Education (MOE) Key Laboratory of Protein Sciences, Tsinghua-Peking Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China
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32
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Smith MA, Zhang Y, Polli JR, Wu H, Zhang B, Xiao P, Farwell MA, Pan X. Impacts of chronic low-level nicotine exposure on Caenorhabditis elegans reproduction: identification of novel gene targets. Reprod Toxicol 2013; 40:69-75. [PMID: 23735997 DOI: 10.1016/j.reprotox.2013.05.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2013] [Revised: 04/25/2013] [Accepted: 05/24/2013] [Indexed: 12/17/2022]
Abstract
Effects and mechanisms of chronic exposure to low levels of nicotine is an area fundamentally important however less investigated. We employed the model organism Caenorhabditis elegans to investigate potential impacts of chronic (24h) and low nicotine exposure (6.17-194.5 μM) on stimulus-response, reproduction, and gene expressions. Nicotine significantly affects the organism's response to touch stimulus (p=0.031), which follows a dose-dependent pattern. Chronic nicotine exposure promotes early egg-laying events and slightly increased egg productions during the first 72 h of adulthood. The expressions of 10 (egl-10, egl-44, hlh-14, ric-3, unc-103, unc-50, unc-68, sod-1, oxi-1, and old-1) out of 18 selected genes were affected significantly. Other tested genes were cat-4, egl-19, egl-47, egl-5, lin-39, unc-43, pink-1, and age-1. Changes in gene expression were more evident at low dosages than at relatively high levels. Genes implicated in reproduction, cholinergic signaling, and stress response were regulated by nicotine, suggesting widespread physiological impacts of nicotine.
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Affiliation(s)
- Michael A Smith
- Department of Biology, East Carolina University, Greenville, NC 27858, USA
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33
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Caylor RC, Jin Y, Ackley BD. The Caenorhabditis elegans voltage-gated calcium channel subunits UNC-2 and UNC-36 and the calcium-dependent kinase UNC-43/CaMKII regulate neuromuscular junction morphology. Neural Dev 2013; 8:10. [PMID: 23663262 PMCID: PMC3661369 DOI: 10.1186/1749-8104-8-10] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2013] [Accepted: 04/25/2013] [Indexed: 11/30/2022] Open
Abstract
Background The conserved Caenorhabditis elegans proteins NID-1/nidogen and PTP-3A/LAR-RPTP function to efficiently localize the presynaptic scaffold protein SYD-2/α-liprin at active zones. Loss of function in these molecules results in defects in the size, morphology and spacing of neuromuscular junctions. Results Here we show that the Cav2-like voltage-gated calcium channel (VGCC) proteins, UNC-2 and UNC-36, and the calmodulin kinase II (CaMKII), UNC-43, function to regulate the size and morphology of presynaptic domains in C. elegans. Loss of function in unc-2, unc-36 or unc-43 resulted in slightly larger GABAergic neuromuscular junctions (NMJs), but could suppress the synaptic morphology defects found in nid-1/nidogen or ptp-3/LAR mutants. A gain-of-function mutation in unc-43 caused defects similar to those found in nid-1 mutants. Mutations in egl-19, Cav1-like, or cca-1, Cav3-like, α1 subunits, or the second α2/δ subunit, tag-180, did not suppress nid-1, suggesting a specific interaction between unc-2 and the synaptic extracellular matrix (ECM) component nidogen. Using a synaptic vesicle marker in time-lapse microscopy studies, we observed GABAergic motor neurons adding NMJ-like structures during late larval development. The synaptic bouton addition appeared to form in at least two ways: (1) de novo formation, where a cluster of vesicles appeared to coalesce, or (2) when a single punctum became enlarged and then divided to form two discrete fluorescent puncta. In comparison to wild type animals, we found unc-2 mutants exhibited reduced NMJ dynamics, with fewer observed divisions during a similar stage of development. Conclusions We identified UNC-2/UNC-36 VGCCs and UNC-43/CaMKII as regulators of C. elegans synaptogenesis. UNC-2 has a modest role in synapse formation, but a broader role in regulating dynamic changes in the size and morphology of synapses that occur during organismal development. During the late 4th larval stage (L4), wild type animals exhibit synaptic morphologies that are similar to those found in animals lacking NID-1/PTP-3 adhesion, as well as those with constitutive activation of UNC-43. Genetic evidence indicates that the VGCCs and the NID-1/PTP-3 adhesion complex provide opposing functions in synaptic development, suggesting that modulation of synaptic adhesion may underlie synapse development in C. elegans.
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Affiliation(s)
- Raymond C Caylor
- Department of Molecular Biosciences, University of Kansas, 5004 Haworth Hall, 1200 Sunnyside Ave, Lawrence, KS 66045, USA
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34
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A genetic program promotes C. elegans longevity at cold temperatures via a thermosensitive TRP channel. Cell 2013; 152:806-17. [PMID: 23415228 DOI: 10.1016/j.cell.2013.01.020] [Citation(s) in RCA: 176] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2012] [Revised: 10/23/2012] [Accepted: 01/11/2013] [Indexed: 12/26/2022]
Abstract
Both poikilotherms and homeotherms live longer at lower body temperatures, highlighting a general role of temperature reduction in lifespan extension. However, the underlying mechanisms remain unclear. One prominent model is that cold temperatures reduce the rate of chemical reactions, thereby slowing the rate of aging. This view suggests that cold-dependent lifespan extension is simply a passive thermodynamic process. Here, we challenge this view in C. elegans by showing that genetic programs actively promote longevity at cold temperatures. We find that TRPA-1, a cold-sensitive TRP channel, detects temperature drop in the environment to extend lifespan. This effect requires cold-induced, TRPA-1-mediated calcium influx and a calcium-sensitive PKC that signals to the transcription factor DAF-16/FOXO. Human TRPA1 can functionally substitute for worm TRPA-1 in promoting longevity. Our results reveal a previously unrecognized function for TRP channels, link calcium signaling to longevity, and, importantly, demonstrate that genetic programs contribute to lifespan extension at cold temperatures.
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35
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A neuronal signaling pathway of CaMKII and Gqα regulates experience-dependent transcription of tph-1. J Neurosci 2013; 33:925-35. [PMID: 23325232 DOI: 10.1523/jneurosci.2355-12.2013] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Dynamic serotonin biosynthesis is important for serotonin function; however, the mechanisms that underlie experience-dependent transcriptional regulation of the rate-limiting serotonin biosynthetic enzyme tryptophan hydroxylase (TPH) are poorly understood. Here, we characterize the molecular and cellular mechanisms that regulate increased transcription of Caenorhabditis elegans tph-1 in a pair of serotonergic neurons ADF during an aversive experience with pathogenic bacteria, a common environmental peril for worms. Training with pathogenic bacteria induces a learned aversion to the smell of the pathogen, a behavioral plasticity that depends on the serotonin signal from ADF neurons. We demonstrate that pathogen training increases ADF neuronal activity. While activating ADF increases tph-1 transcription, inhibiting ADF activity abolishes the training effect on tph-1, demonstrating the dependence of tph-1 transcriptional regulation on ADF neural activity. At the molecular level, the C. elegans homolog of CaMKII, UNC-43, functions cell-autonomously in ADF neurons to generate training-dependent enhancement in neuronal activity and tph-1 transcription, and this cell-autonomous function of UNC-43 is required for learning. Furthermore, selective expression of an activated form of UNC-43 in ADF neurons is sufficient to increase ADF activity and tph-1 transcription, mimicking the training effect. Upstream of ADF, the Gqα protein EGL-30 facilitates training-dependent induction of tph-1 by functional regulation of olfactory sensory neurons, which underscores the importance of sensory experience. Together, our work elucidates the molecular and cellular mechanisms whereby experience modulates tph-1 transcription.
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Zhang Y, Chen D, Ennis AC, Polli JR, Xiao P, Zhang B, Stellwag EJ, Overton A, Pan X. Chemical dispersant potentiates crude oil impacts on growth, reproduction, and gene expression in Caenorhabditis elegans. Arch Toxicol 2012; 87:371-82. [PMID: 22990136 DOI: 10.1007/s00204-012-0936-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2012] [Accepted: 08/28/2012] [Indexed: 01/09/2023]
Abstract
The economic, environmental, and human health impacts of the deepwater horizon (DWH) oil spill have been of significant concern in the general public and among scientists. This study employs parallel experiments to test the effects of crude oil from the DWH oil well, chemical dispersant Corexit 9500A, and dispersant-oil mixture on growth and reproduction in the model organism Caenorhabditis elegans. Both the crude oil and the dispersant significantly inhibited the reproduction of C. elegans. Dose-dependent inhibitions of hatched larvae production were observed in worms exposed to both crude oil and dispersant. Importantly, the chemical dispersant Corexit 9500A potentiated crude oil effects; dispersant-oil mixture induced more significant effects than oil or dispersant-alone exposures. While oil-alone exposure and dispersant-alone exposure have none to moderate inhibitory effects on hatched larvae production, respectively, the mixture of dispersant and oil induced much more significant inhibition of offspring production. The production of hatched larvae was almost completely inhibited by several high concentrations of the dispersant-oil mixture. This suggests a sensitive bioassay for future investigation of oil/dispersant impacts on organisms. We also investigated the effects of crude oil/dispersant exposure at the molecular level by measuring the expressions of 31 functional genes. Results showed that the dispersant and the dispersant-oil mixture induced aberrant expressions of 12 protein-coding genes (cat-4, trxr-2, sdhb-1, lev-8, lin-39, unc-115, prdx-3, sod-1, acr-16, ric-3, unc-68, and acr-8). These 12 genes are associated with a variety of biological processes, including egg-laying, oxidative stress, muscle contraction, and neurological functions. In summary, the toxicity potentiating effect of chemical dispersant must be taken into consideration in future crude oil cleanup applications.
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Affiliation(s)
- Yanqiong Zhang
- Department of Biology, East Carolina University, N108 Howell Science Complex, Greenville, NC 27858, USA
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Pasch E, Muenz TS, Rössler W. CaMKII is differentially localized in synaptic regions of Kenyon cells within the mushroom bodies of the honeybee brain. J Comp Neurol 2012; 519:3700-12. [PMID: 21674485 DOI: 10.1002/cne.22683] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Calcium/calmodulin-dependent protein kinase II (CaMKII) has been linked to neuronal plasticity associated with long-term potentiation as well as structural synaptic plasticity. Previous work in adult honeybees has shown that a single CaMKII gene is strongly expressed in the mushroom bodies (MBs), brain centers associated with sensory integration, and learning and memory formation. To study a potential role of CaMKII in synaptic plasticity, the cellular and subcellular distribution of activated (phosphorylated) pCaMKII protein was investigated at various life stages of the honeybee using immunocytochemistry, confocal microscopy, and western blot analyses. Whereas at pupal stages 3-4 most parts of the brain showed high levels of pCaMKII immunoreactivity, the protein was predominantly concentrated in the MBs in the adult brain. The results show that pCaMKII is present in a specific subpopulation of Kenyon cells, the noncompact cells. Within the olfactory (lip) and visual (collar) subregion of the MB calyx neuropil pCaMKII was colocalized with f-actin in postsynaptic compartments of microglomeruli, indicating that it is enriched in Kenyon cell dendritic spines. This suggests a potential role of CaMKII in Kenyon cell dendritic plasticity. Interestingly, pCaMKII protein was absent in two other types of Kenyon cells, the inner compact cells associated with the multimodal basal ring and the outer compact cells. During adult behavioral maturation from nurse bees to foragers, pCaMKII distribution remained essentially similar at the qualitative level, suggesting a potential role in dendritic plasticity of Kenyon cells throughout the entire life span of a worker bee.
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Affiliation(s)
- Elisabeth Pasch
- Department of Behavioral Physiology and Sociobiology, Biozentrum, University of Würzburg, Würzburg, 97074, Germany
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Cell excitability necessary for male mating behavior in Caenorhabditis elegans is coordinated by interactions between big current and ether-a-go-go family K(+) channels. Genetics 2011; 190:1025-41. [PMID: 22174070 DOI: 10.1534/genetics.111.137455] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Variations in K(+) channel composition allow for differences in cell excitability and, at an organismal level, provide flexibility to behavioral regulation. When the function of a K(+) channel is disrupted, the remaining K(+) channels might incompletely compensate, manifesting as abnormal organismal behavior. In this study, we explored how different K(+) channels interact to regulate the neuromuscular circuitry used by Caenorhabditis elegans males to protract their copulatory spicules from their tail and insert them into the hermaphrodite's vulva during mating. We determined that the big current K(+) channel (BK)/SLO-1 genetically interacts with ether-a-go-go (EAG)/EGL-2 and EAG-related gene/UNC-103 K(+) channels to control spicule protraction. Through rescue experiments, we show that specific slo-1 isoforms affect spicule protraction. Gene expression studies show that slo-1 and egl-2 expression can be upregulated in a calcium/calmodulin-dependent protein kinase II-dependent manner to compensate for the loss of unc-103 and conversely, unc-103 can partially compensate for the loss of SLO-1 function. In conclusion, an interaction between BK and EAG family K(+) channels produces the muscle excitability levels that regulate the timing of spicule protraction and the success of male mating behavior.
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Pietsch K, Saul N, Chakrabarti S, Stürzenbaum SR, Menzel R, Steinberg CEW. Hormetins, antioxidants and prooxidants: defining quercetin-, caffeic acid- and rosmarinic acid-mediated life extension in C. elegans. Biogerontology 2011; 12:329-47. [PMID: 21503726 DOI: 10.1007/s10522-011-9334-7] [Citation(s) in RCA: 139] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2010] [Accepted: 04/04/2011] [Indexed: 12/26/2022]
Abstract
Quercetin, Caffeic- and Rosmarinic acid exposure extend lifespan in Caenorhabditis elegans. This comparative study uncovers basic common and contrasting underlying mechanisms: For all three compounds, life extension was characterized by hormetic dose response curves, but hsp-level expression was variable. Quercetin and Rosmarinic acid both suppressed bacterial growth; however, antibacterial properties were not the dominant reason for life extension. Exposure to Quercetin, Caffeic- and Rosmarinic acid resulted in reduced body size, altered lipid-metabolism and a tendency towards a delay in reproductive timing; however the total number of offspring was not affected. An indirect dietary restriction effect, provoked by either chemo-repulsion or diminished pharyngeal pumping was rejected. Quercetin and Caffeic acid were shown to increase the antioxidative capacity in vivo and, by means of a lipofuscin assay, reduce the oxidative damage in the nematodes. Finally, it was possible to demonstrate that the life and thermotolerance enhancing properties of Caffeic- and Rosmarinic acid both rely on osr-1, sek-1, sir-2.1 and unc-43 plus daf-16 in the case of Caffeic acid. Taken together, hormesis, in vivo antioxidative/prooxidative properties, modulation of genetic players, as well as the re-allocation of energy all contribute (to some extent and dependent on the polyphenol) to life extension.
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Affiliation(s)
- Kerstin Pietsch
- Humboldt-Universität zu Berlin, Department of Biology, Laboratory of Freshwater & Stress Ecology, Späthstr. 80/81, 12437, Berlin, Germany.
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LeBoeuf B, Guo X, García LR. The effects of transient starvation persist through direct interactions between CaMKII and ether-a-go-go K+ channels in C. elegans males. Neuroscience 2011; 175:1-17. [PMID: 21145946 PMCID: PMC3059131 DOI: 10.1016/j.neuroscience.2010.12.002] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2010] [Revised: 11/30/2010] [Accepted: 12/01/2010] [Indexed: 12/29/2022]
Abstract
Prolonged nutrient limitation has been extensively studied due to its positive effects on life span. However, less is understood of how brief periods of starvation can have lasting consequences. In this study, we used genetics, biochemistry, pharmacology and behavioral analysis to show that after a limited period of starvation, the synthesis of egl-2-encoded ether-a-go-go (EAG) K+ channels and its C-terminal modifications by unc-43-encoded CaMKII have a perduring effect on C. elegans male sexual behavior. EGL-2 and UNC-43 interactions, induced after food deprivation, maintain reduced excitability in muscles involved in sex. In young adult males, spastic contractions occur in cholinergic-activated sex muscles that lack functional unc-103-encoded ERG-like K+ channels. Promoting EGL-2 and UNC-43 interactions in unc-103 mutant adult males by starving them for a few hours reduce spastic muscle contractions over multiple days. Although transient starvation during early adulthood has a hormetic effect of suppressing mutation-induced muscle contractions, the treatment reduces the ability of young wild-type (WT) males to compete with well-fed cohorts in siring progeny.
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Affiliation(s)
- Brigitte LeBoeuf
- Howard Hughes Medical Institute, Texas A&M University, 3258 TAMU, College Station, TX 77843-3258
- Department of Biology, Texas A&M University, 3258 TAMU, College Station, TX 77843-3258
| | - Xiaoyan Guo
- Department of Biology, Texas A&M University, 3258 TAMU, College Station, TX 77843-3258
| | - L. René García
- Howard Hughes Medical Institute, Texas A&M University, 3258 TAMU, College Station, TX 77843-3258
- Department of Biology, Texas A&M University, 3258 TAMU, College Station, TX 77843-3258
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Kullyev A, Dempsey CM, Miller S, Kuan CJ, Hapiak VM, Komuniecki RW, Griffin CT, Sze JY. A genetic survey of fluoxetine action on synaptic transmission in Caenorhabditis elegans. Genetics 2010; 186:929-41. [PMID: 20739712 PMCID: PMC2975281 DOI: 10.1534/genetics.110.118877] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2010] [Accepted: 08/13/2010] [Indexed: 11/18/2022] Open
Abstract
Fluoxetine is one of the most commonly prescribed medications for many behavioral and neurological disorders. Fluoxetine acts primarily as an inhibitor of the serotonin reuptake transporter (SERT) to block the removal of serotonin from the synaptic cleft, thereby enhancing serotonin signals. While the effects of fluoxetine on behavior are firmly established, debate is ongoing whether inhibition of serotonin reuptake is a sufficient explanation for its therapeutic action. Here, we provide evidence of two additional aspects of fluoxetine action through genetic analyses in Caenorhabditis elegans. We show that fluoxetine treatment and null mutation in the sole SERT gene mod-5 eliminate serotonin in specific neurons. These neurons do not synthesize serotonin but import extracellular serotonin via MOD-5/SERT. Furthermore, we show that fluoxetine acts independently of MOD-5/SERT to regulate discrete properties of acetylcholine (Ach), gamma-aminobutyric acid (GABA), and glutamate neurotransmission in the locomotory circuit. We identified that two G-protein-coupled 5-HT receptors, SER-7 and SER-5, antagonistically regulate the effects of fluoxetine and that fluoxetine binds to SER-7. Epistatic analyses suggest that SER-7 and SER-5 act upstream of AMPA receptor GLR-1 signaling. Our work provides genetic evidence that fluoxetine may influence neuronal functions and behavior by directly targeting serotonin receptors.
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Affiliation(s)
- Andrey Kullyev
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York 10461 Department of Biology, National University of Ireland, Maynooth, County Kilare, Ireland Department of Biological Sciences, University of Toledo, Toledo, Ohio 43606
| | - Catherine M. Dempsey
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York 10461 Department of Biology, National University of Ireland, Maynooth, County Kilare, Ireland Department of Biological Sciences, University of Toledo, Toledo, Ohio 43606
| | - Sarah Miller
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York 10461 Department of Biology, National University of Ireland, Maynooth, County Kilare, Ireland Department of Biological Sciences, University of Toledo, Toledo, Ohio 43606
| | - Chih-Jen Kuan
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York 10461 Department of Biology, National University of Ireland, Maynooth, County Kilare, Ireland Department of Biological Sciences, University of Toledo, Toledo, Ohio 43606
| | - Vera M. Hapiak
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York 10461 Department of Biology, National University of Ireland, Maynooth, County Kilare, Ireland Department of Biological Sciences, University of Toledo, Toledo, Ohio 43606
| | - Richard W. Komuniecki
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York 10461 Department of Biology, National University of Ireland, Maynooth, County Kilare, Ireland Department of Biological Sciences, University of Toledo, Toledo, Ohio 43606
| | - Christine T. Griffin
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York 10461 Department of Biology, National University of Ireland, Maynooth, County Kilare, Ireland Department of Biological Sciences, University of Toledo, Toledo, Ohio 43606
| | - Ji Ying Sze
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York 10461 Department of Biology, National University of Ireland, Maynooth, County Kilare, Ireland Department of Biological Sciences, University of Toledo, Toledo, Ohio 43606
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Van Epps H, Dai Y, Qi Y, Goncharov A, Jin Y. Nuclear pre-mRNA 3'-end processing regulates synapse and axon development in C. elegans. Development 2010; 137:2237-50. [PMID: 20530551 DOI: 10.1242/dev.049692] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Nuclear pre-mRNA 3'-end processing is vital for the production of mature mRNA and the generation of the 3' untranslated region (UTR). However, the roles and regulation of this event in cellular development remain poorly understood. Here, we report the function of a nuclear pre-mRNA 3'-end processing pathway in synapse and axon formation in C. elegans. In a genetic enhancer screen for synaptogenesis mutants, we identified a novel polyproline-rich protein, Synaptic defective enhancer-1 (SYDN-1). Loss of function of sydn-1 causes abnormal synapse and axon development, and displays striking synergistic interactions with several genes that regulate specific aspects of synapses. SYDN-1 is required in neurons and localizes to distinct regions of the nucleus. Through a genetic suppressor screen, we found that the neuronal defects of sydn-1 mutants are suppressed by loss of function in Polyadenylation factor subunit-2 (PFS-2), a conserved WD40-repeat protein that interacts with multiple subcomplexes of the pre-mRNA 3'-end processing machinery. PFS-2 partially colocalizes with SYDN-1, and SYDN-1 influences the nuclear abundance of PFS-2. Inactivation of several members of the nuclear 3'-end processing complex suppresses sydn-1 mutants. Furthermore, lack of sydn-1 can increase the activity of 3'-end processing. Our studies provide in vivo evidence for pre-mRNA 3'-end processing in synapse and axon development and identify SYDN-1 as a negative regulator of this cellular event in neurons.
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Affiliation(s)
- Heather Van Epps
- Division of Biological Sciences, Section of Neurobiology, University of California, San Diego, CA 92093, USA
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Yang Y, Han SM, Miller MA. MSP hormonal control of the oocyte MAP kinase cascade and reactive oxygen species signaling. Dev Biol 2010; 342:96-107. [PMID: 20380830 DOI: 10.1016/j.ydbio.2010.03.026] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2009] [Revised: 03/12/2010] [Accepted: 03/31/2010] [Indexed: 11/28/2022]
Abstract
The MSP domain is a conserved immunoglobulin-like structure that is important for C. elegans reproduction and human motor neuron survival. C. elegans MSPs are the most abundant proteins in sperm, where they function as intracellular cytoskeletal proteins and secreted hormones. Secreted MSPs bind to multiple receptors on oocyte and ovarian sheath cell surfaces to induce oocyte maturation and sheath contraction. MSP binding stimulates oocyte MPK-1 ERK MAP Kinase (MAPK) phosphorylation, but the function and mechanism are not well understood. Here we show that the Shp class protein-tyrosine phosphatase PTP-2 acts in oocytes downstream of sheath/oocyte gap junctions to promote MSP-induced MPK-1 phosphorylation. PTP-2 functions in the oocyte cytoplasm, not at the cell surface to inhibit multiple RasGAPs, resulting in sustained Ras activation. We also provide evidence that MSP promotes production of reactive oxygen species (ROS), which act as second messengers to augment MPK-1 phosphorylation. The Cu/Zn superoxide dismutase SOD-1, an enzyme that catalyzes ROS breakdown in the cytoplasm, inhibits MPK-1 phosphorylation downstream of or in parallel to ptp-2. Our results support the model that MSP triggers PTP-2/Ras activation and ROS production to stimulate MPK-1 activity essential for oocyte maturation. We propose that secreted MSP domains and Cu/Zn superoxide dismutases function antagonistically to control ROS and MAPK signaling.
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Affiliation(s)
- Youfeng Yang
- Department of Cell Biology, University of Alabama at Birmingham, Birmingham, AL 35294, USA
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Perez-Mansilla B, Nurrish S. A network of G-protein signaling pathways control neuronal activity in C. elegans. ADVANCES IN GENETICS 2009; 65:145-192. [PMID: 19615533 DOI: 10.1016/s0065-2660(09)65004-5] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The Caenorhabditis elegans neuromuscular junction (NMJ) is one of the best studied synapses in any organism. A variety of genetic screens have identified genes required both for the essential steps of neurotransmitter release from motorneurons as well as the signaling pathways that regulate rates of neurotransmitter release. A number of these regulatory genes encode proteins that converge to regulate neurotransmitter release. In other cases genes are known to regulate signaling at the NMJ but how they act remains unknown. Many of the proteins that regulate activity at the NMJ participate in a network of heterotrimeric G-protein signaling pathways controlling the release of synaptic vesicles and/or dense-core vesicles (DCVs). At least four heterotrimeric G-proteins (Galphaq, Galpha12, Galphao, and Galphas) act within the motorneurons to control the activity of the NMJ. The Galphaq, Galpha12, and Galphao pathways converge to control production and destruction of the lipid-bound second messenger diacylglycerol (DAG) at sites of neurotransmitter release. DAG acts via at least two effectors, MUNC13 and PKC, to control the release of both neurotransmitters and neuropeptides from motorneurons. The Galphas pathway converges with the other three heterotrimeric G-protein pathways downstream of DAG to regulate neuropeptide release. Released neurotransmitters and neuropeptides then act to control contraction of the body-wall muscles to control locomotion. The lipids and proteins involved in these networks are conserved between C. elegans and mammals. Thus, the C. elegans NMJ acts as a model synapse to understand how neuronal activity in the human brain is regulated.
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Affiliation(s)
- Borja Perez-Mansilla
- MRC Cell Biology Unit, MRC Laboratory for Molecular Cell Biology and Department of Neurobiology, Physiology and Pharmacology, University College London, London, United Kingdom
| | - Stephen Nurrish
- MRC Cell Biology Unit, MRC Laboratory for Molecular Cell Biology and Department of Neurobiology, Physiology and Pharmacology, University College London, London, United Kingdom
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Pietsch K, Saul N, Menzel R, Stürzenbaum SR, Steinberg CEW. Quercetin mediated lifespan extension in Caenorhabditis elegans is modulated by age-1, daf-2, sek-1 and unc-43. Biogerontology 2008; 10:565-78. [PMID: 19043800 DOI: 10.1007/s10522-008-9199-6] [Citation(s) in RCA: 107] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2008] [Accepted: 11/11/2008] [Indexed: 01/05/2023]
Abstract
The nematode Caenorhabditis elegans responds to flavonoid-rich diets with improved health and longevity. The precise mechanism(s) responsible for this remains to be identified, but is believed to be linked to the highly antioxidative properties of flavonoids. This study provides a dissection of lifespan modulation by the flavonoid quercetin. In detail, quercetin was shown not to act as a simple antimicrobial agent or exclusively via radical scavenging capacities. Likewise, lifespan extension had no effect on reproduction and body length. Furthermore, neither a caloric restriction mimetic nor a sirtuin (sir-2.1) dependence was identified as a likely mode of action. However, four genes were pinpointed to be required for the quercetin derived lifespan extension, namely age-1, daf-2, unc-43 and sek-1. The latter two have, to date, not been linked to quercetin-mediated lifespan extension.
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Affiliation(s)
- Kerstin Pietsch
- Department of Biology, Humboldt-Universität zu Berlin, Germany.
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Mukhopadhyay S, Lu Y, Shaham S, Sengupta P. Sensory signaling-dependent remodeling of olfactory cilia architecture in C. elegans. Dev Cell 2008; 14:762-74. [PMID: 18477458 DOI: 10.1016/j.devcel.2008.03.002] [Citation(s) in RCA: 104] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2007] [Revised: 01/21/2008] [Accepted: 03/03/2008] [Indexed: 10/22/2022]
Abstract
Nonmotile primary cilia are sensory organelles composed of a microtubular axoneme and a surrounding membrane sheath that houses signaling molecules. Optimal cellular function requires the precise regulation of axoneme assembly, membrane biogenesis, and signaling protein targeting and localization via as yet poorly understood mechanisms. Here, we show that sensory signaling is required to maintain the architecture of the specialized AWB olfactory neuron cilia in C. elegans. Decreased sensory signaling results in alteration of axoneme length and expansion of a membraneous structure, thereby altering the topological distribution of a subset of ciliary transmembrane signaling molecules. Signaling-regulated alteration of ciliary structures can be bypassed by modulation of intracellular cGMP or calcium levels and requires kinesin-II-driven intraflagellar transport (IFT), as well as BBS- and RAB8-related proteins. Our results suggest that compensatory mechanisms in response to altered levels of sensory activity modulate AWB cilia architecture, revealing remarkable plasticity in the regulation of cilia structure.
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Affiliation(s)
- Saikat Mukhopadhyay
- Department of Biology and National Center for Behavioral Genomics, Brandeis University, Waltham, MA 02454, USA
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Nitric oxide-mediated modulation of calcium/calmodulin-dependent protein kinase II. Biochem J 2008; 412:223-31. [DOI: 10.1042/bj20071195] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The mechanisms of NO inhibition of CaMK [Ca2+/CaM (calmodulin)-dependent protein kinase] II activity were studied. In rat pituitary tumour GH3 cells, TRH [thyrotrophin (TSH)-releasing hormone]-stimulated phosphorylation of nNOS [neuronal NOS (NO synthase)] at Ser847 was sensitive to an inhibitor of CaMKs, KN-93, and was enhanced by inhibition of nNOS with 7NI (7-nitroindazole). Enzyme activity of CaMKII following in situ treatment with 7NI was also increased. The in vitro activity of CaMKII was inhibited by co-incubation either with nNOS and L-arginine or with NO donors SNAP (S-nitroso-N-acetyl-DL-penicillamine) and DEA-NONOate [diethylamine-NONOate (diazeniumdiolate)]. Once inhibited by these treatments, CaMKII was observed to undergo full reactivation on the addition of a reducing reagent, DTT (dithiothreitol). In transfected cells expressing CaMKII and nNOS, treatment with the calcium ionophore A23187 further revealed nNOS phosphorylation at Ser847, which was enhanced by 7NI and CaMKII S-nitrosylation. Mutated CaMKII (C6A), in which Cys6 was substituted with an alanine residue, was refractory to 7NI-induced enhancement of nNOS phosphorylation or to CaMKII S-nitrosylation. Furthermore, we could identify Cys6 as a direct target for S-nitrosylation of CaMKII using MS. In addition, treatment with glutamate caused an increase in CaMKII S-nitrosylation in rat hippocampal slices. This glutamate-induced S-nitrosylation was blocked by 7NI. These results suggest that inactivation of CaMKII mediated by S-nitrosylation at Cys6 may contribute to NO-induced neurotoxicity in the brain.
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Vashlishan AB, Madison JM, Dybbs M, Bai J, Sieburth D, Ch'ng Q, Tavazoie M, Kaplan JM. An RNAi Screen Identifies Genes that Regulate GABA Synapses. Neuron 2008; 58:346-61. [DOI: 10.1016/j.neuron.2008.02.019] [Citation(s) in RCA: 100] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2007] [Revised: 02/12/2008] [Accepted: 02/19/2008] [Indexed: 01/29/2023]
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Liu Q, Chen B, Ge Q, Wang ZW. Presynaptic Ca2+/calmodulin-dependent protein kinase II modulates neurotransmitter release by activating BK channels at Caenorhabditis elegans neuromuscular junction. J Neurosci 2007; 27:10404-13. [PMID: 17898212 PMCID: PMC6673169 DOI: 10.1523/jneurosci.5634-06.2007] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Although Ca2+/calmodulin-dependent protein kinase II (CaMKII) is enriched at the presynaptic nerve terminal, its role in neurotransmitter release is poorly defined. We assessed the function of presynaptic CaMKII in neurotransmitter release and tested the hypothesis that BK channel is a mediator of presynaptic CaMKII function by analyzing miniature and evoked postsynaptic currents at the Caenorhabditis elegans neuromuscular junction. Both loss-of-function (lf) and gain-of-function (gf) of unc-43, the gene encoding CaMKII, inhibited neurotransmitter release. The inhibitory effect of unc-43(gf) was reversed by mutation or blockade of the BK channel SLO-1. SLO-1 expressed in Xenopus oocytes could be activated by recombinant rat alpha-CaMKII, and this effect of CaMKII was abolished by mutating a threonine residue (T425) at a consensus CaMKII phosphorylation site in the first RCK (regulator of conductance for K+) domain of the channel. Expression of slo-1(T425A) in neurons antagonized the inhibitory effect of unc-43(gf) on neurotransmitter release as slo-1(lf) did. The inhibitory effect of unc-43(gf) was not reversed by unc-103(lf), dgk-1(lf), or eat-16(lf), which reportedly suppress behavioral phenotypes of unc-43(gf). These observations suggest that presynaptic CaMKII is a bidirectional modulator of neurotransmitter release, presumably by phosphorylating different molecular targets, and that its negative modulatory effect on the release is mainly mediated by SLO-1 activation.
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Affiliation(s)
- Qiang Liu
- Department of Neuroscience, University of Connecticut Health Center, Farmington, Connecticut 06030
| | - Bojun Chen
- Department of Neuroscience, University of Connecticut Health Center, Farmington, Connecticut 06030
| | - Qian Ge
- Department of Neuroscience, University of Connecticut Health Center, Farmington, Connecticut 06030
| | - Zhao-Wen Wang
- Department of Neuroscience, University of Connecticut Health Center, Farmington, Connecticut 06030
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Nehrke K, Denton J, Mowrey W. Intestinal Ca2+ wave dynamics in freely moving C. elegans coordinate execution of a rhythmic motor program. Am J Physiol Cell Physiol 2007; 294:C333-44. [PMID: 17942636 DOI: 10.1152/ajpcell.00303.2007] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Defecation in the nematode worm Caenorhabditis elegans is a highly rhythmic behavior that is regulated by a Ca(2+) wave generated in the 20 epithelial cells of the intestine, in part through activation of the inositol 1,4,5-trisphosphate receptor. Execution of the defecation motor program (DMP) can be modified by external cues such as nutrient availability or mechanical stimulation. To address the likelihood that environmental regulation of the DMP requires integrating distinct cellular and organismal processes, we have developed a method for studying coordinate Ca(2+) oscillations and defecation behavior in intact, freely behaving animals. We tested this technique by examining how mutations in genes known to alter Ca(2+) handling [including egl-8/phospholipase C (PLC)-beta, kqt-3/KCNQ1, sca-1/sarco(endo)plasmic reticulum Ca(2+) ATPase, and unc-43/Ca(2+)-CaMKII] contribute to shaping the Ca(2+) wave and asked how Ca(2+) wave dynamics in the mutant backgrounds altered execution of the DMP. Notably, we find that Ca(2+) waves in the absence of PLCbeta initiate ectopically, often traveling in reverse, and fail to trigger a complete DMP. These results suggest that the normal supremacy of the posterior intestinal cells is not obligatory for Ca(2+) wave occurrence but instead helps to coordinate the DMP. Furthermore, we present evidence suggesting that an underlying pacemaker appears to oscillate at a faster frequency than the defecation cycle and that arrhythmia may result from uncoupling the pacemaker from the DMP rather than from disrupting the pacemaker itself. We also show that chronic elevations in Ca(2+) have limited influence on the defecation period but instead alter the interval between successive steps of the DMP. Finally, our results demonstrate that it is possible to assess Ca(2+) dynamics and muscular contractions in a completely unrestrained model organism.
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Affiliation(s)
- K Nehrke
- Dept. of Medicine, Nephrology Division, Medical Center Box 675, 601 Elmwood Ave., Rochester NY 14642, USA.
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