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Monteil A, Guérineau NC, Gil-Nagel A, Parra-Diaz P, Lory P, Senatore A. New insights into the physiology and pathophysiology of the atypical sodium leak channel NALCN. Physiol Rev 2024; 104:399-472. [PMID: 37615954 DOI: 10.1152/physrev.00014.2022] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2022] [Revised: 07/13/2023] [Accepted: 08/15/2023] [Indexed: 08/25/2023] Open
Abstract
Cell excitability and its modulation by hormones and neurotransmitters involve the concerted action of a large repertoire of membrane proteins, especially ion channels. Unique complements of coexpressed ion channels are exquisitely balanced against each other in different excitable cell types, establishing distinct electrical properties that are tailored for diverse physiological contributions, and dysfunction of any component may induce a disease state. A crucial parameter controlling cell excitability is the resting membrane potential (RMP) set by extra- and intracellular concentrations of ions, mainly Na+, K+, and Cl-, and their passive permeation across the cell membrane through leak ion channels. Indeed, dysregulation of RMP causes significant effects on cellular excitability. This review describes the molecular and physiological properties of the Na+ leak channel NALCN, which associates with its accessory subunits UNC-79, UNC-80, and NLF-1/FAM155 to conduct depolarizing background Na+ currents in various excitable cell types, especially neurons. Studies of animal models clearly demonstrate that NALCN contributes to fundamental physiological processes in the nervous system including the control of respiratory rhythm, circadian rhythm, sleep, and locomotor behavior. Furthermore, dysfunction of NALCN and its subunits is associated with severe pathological states in humans. The critical involvement of NALCN in physiology is now well established, but its study has been hampered by the lack of specific drugs that can block or agonize NALCN currents in vitro and in vivo. Molecular tools and animal models are now available to accelerate our understanding of how NALCN contributes to key physiological functions and the development of novel therapies for NALCN channelopathies.
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Affiliation(s)
- Arnaud Monteil
- Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS, INSERM, Montpellier, France
- LabEx "Ion Channel Science and Therapeutics," Montpellier, France
- Department of Physiology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand
| | - Nathalie C Guérineau
- Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS, INSERM, Montpellier, France
- LabEx "Ion Channel Science and Therapeutics," Montpellier, France
| | - Antonio Gil-Nagel
- Department of Neurology, Epilepsy Program, Hospital Ruber Internacional, Madrid, Spain
| | - Paloma Parra-Diaz
- Department of Neurology, Epilepsy Program, Hospital Ruber Internacional, Madrid, Spain
| | - Philippe Lory
- Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS, INSERM, Montpellier, France
- LabEx "Ion Channel Science and Therapeutics," Montpellier, France
| | - Adriano Senatore
- Department of Biology, University of Toronto Mississauga, Mississauga, Ontario, Canada
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Perouansky M, Johnson-Schlitz D, Sedensky MM, Morgan PG. A primordial target: Mitochondria mediate both primary and collateral anesthetic effects of volatile anesthetics. Exp Biol Med (Maywood) 2023; 248:545-552. [PMID: 37208922 PMCID: PMC10350799 DOI: 10.1177/15353702231165025] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/21/2023] Open
Abstract
One of the unsolved mysteries of medicine is how do volatile anesthetics (VAs) cause a patient to reversibly lose consciousness. In addition, identifying mechanisms for the collateral effects of VAs, including anesthetic-induced neurotoxicity (AiN) and anesthetic preconditioning (AP), has proven challenging. Multiple classes of molecules (lipids, proteins, and water) have been considered as potential VA targets, but recently proteins have received the most attention. Studies targeting neuronal receptors or ion channels had limited success in identifying the critical targets of VAs mediating either the phenotype of "anesthesia" or their collateral effects. Recent studies in both nematodes and fruit flies may provide a paradigm shift by suggesting that mitochondria may harbor the upstream molecular switch activating both primary and collateral effects. The disruption of a specific step of electron transfer within the mitochondrion causes hypersensitivity to VAs, from nematodes to Drosophila and to humans, while also modulating the sensitivity to collateral effects. The downstream effects from mitochondrial inhibition are potentially legion, but inhibition of presynaptic neurotransmitter cycling appears to be specifically sensitive to the mitochondrial effects. These findings are perhaps of even broader interest since two recent reports indicate that mitochondrial damage may well underlie neurotoxic and neuroprotective effects of VAs in the central nervous system (CNS). It is, therefore, important to understand how anesthetics interact with mitochondria to affect CNS function, not just for the desired facets of general anesthesia but also for significant collateral effects, both harmful and beneficial. A tantalizing possibility exists that both the primary (anesthesia) and secondary (AiN, AP) mechanisms may at least partially overlap in the mitochondrial electron transport chain (ETC).
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Affiliation(s)
- Misha Perouansky
- Department of Anesthesiology, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI 53792, USA
- Laboratory of Genetics, School of Medicine and Public Health and College of Agricultural and Life Sciences, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Dena Johnson-Schlitz
- Department of Anesthesiology, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI 53792, USA
| | - Margaret M Sedensky
- Department of Anesthesiology and Pain Medicine, University of Washington School of Medicine, Seattle, WA 98101, USA
| | - Philip G Morgan
- Department of Anesthesiology and Pain Medicine, University of Washington School of Medicine, Seattle, WA 98101, USA
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Jung S, Kayser EB, Johnson SC, Li L, Worstman HM, Sun GX, Sedensky MM, Morgan PG. Tetraethylammonium chloride reduces anaesthetic-induced neurotoxicity in Caenorhabditis elegans and mice. Br J Anaesth 2022; 128:77-88. [PMID: 34857359 PMCID: PMC8787783 DOI: 10.1016/j.bja.2021.09.036] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Revised: 08/30/2021] [Accepted: 09/15/2021] [Indexed: 01/03/2023] Open
Abstract
BACKGROUND If anaesthetics cause permanent cognitive deficits in some children, the implications are enormous, but the molecular causes of anaesthetic-induced neurotoxicity, and consequently possible therapies, are still debated. Anaesthetic exposure early in development can be neurotoxic in the invertebrate Caenorhabditis elegans causing endoplasmic reticulum (ER) stress and defects in chemotaxis during adulthood. We screened this model organism for compounds that alleviated neurotoxicity, and then tested these candidates for efficacy in mice. METHODS We screened compounds for alleviation of ER stress induction by isoflurane in C. elegans assayed by induction of a green fluorescent protein (GFP) reporter. Drugs that inhibited ER stress were screened for reduction of the anaesthetic-induced chemotaxis defect. Compounds that alleviated both aspects of neurotoxicity were then blindly tested for the ability to inhibit induction of caspase-3 by isoflurane in P7 mice. RESULTS Isoflurane increased ER stress indicated by increased GFP reporter fluorescence (240% increase, P<0.001). Nine compounds reduced induction of ER stress by isoflurane by 90-95% (P<0.001 in all cases). Of these compounds, tetraethylammonium chloride and trehalose also alleviated the isoflurane-induced defect in chemotaxis (trehalose by 44%, P=0.001; tetraethylammonium chloride by 23%, P<0.001). In mouse brain, tetraethylammonium chloride reduced isoflurane-induced caspase staining in the anterior cortical (-54%, P=0.007) and hippocampal regions (-46%, P=0.002). DISCUSSION Tetraethylammonium chloride alleviated isoflurane-induced neurotoxicity in two widely divergent species, raising the likelihood that it may have therapeutic value. In C. elegans, ER stress predicts isoflurane-induced neurotoxicity, but is not its cause.
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Affiliation(s)
- Sangwook Jung
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, WA, USA
| | - Ernst-Bernhard Kayser
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, WA, USA
| | - Simon C Johnson
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, WA, USA; Department of Anesthesiology and Pain Medicine, Seattle, WA, USA; Department of Neurology, University of Washington, Seattle, WA, USA
| | - Li Li
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, WA, USA; Department of Anesthesiology and Pain Medicine, Seattle, WA, USA
| | - Hailey M Worstman
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, WA, USA
| | - Grace X Sun
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, WA, USA
| | - Margaret M Sedensky
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, WA, USA; Department of Anesthesiology and Pain Medicine, Seattle, WA, USA
| | - Philip G Morgan
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, WA, USA; Department of Anesthesiology and Pain Medicine, Seattle, WA, USA.
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Isoflurane impairs oogenesis through germ cell apoptosis in C. elegans. Sci Rep 2021; 11:14481. [PMID: 34262087 PMCID: PMC8280124 DOI: 10.1038/s41598-021-93737-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2021] [Accepted: 06/23/2021] [Indexed: 02/08/2023] Open
Abstract
Anesthetic isoflurane has been reported to induce toxicity. However, the effects of isoflurane on fecundity remain largely unknown. We established a system in C. elegans to investigate the effects of isoflurane on oogenesis. Synchronized L4 stage C. elegans were treated with 7% isoflurane for 4 h. Dead cells, ROS, embryos, and unfertilized eggs laid by hermaphrodites were measured by fluorescence imaging and counting. The C. elegans with losses of ced-3, cep-1, abl-1, male C. elegans, and oxidative stress inhibitor N-acetyl-cysteine were used in the interaction studies. We found that isoflurane decreased the numbers of embryos and unfertilized eggs and increased the levels of dead cells and ROS in C. elegans. The isoflurane-induced impairment of oogenesis was associated with abl-1, ced-3, but not cep-1. N-acetyl-cysteine attenuated the isoflurane-induced impairment of oogenesis in C. elegans. Mating with male C. elegans did not attenuate the isoflurane-induced changes in oogenesis. These findings suggest that isoflurane may impair oogenesis through abl-1- and ced-3-associated, but not cep-1-associated, germ cell apoptosis and oxidative stress, pending further investigation. These studies will promote more research to determine the potential effects of anesthesia on fecundity.
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Na + leak-current channel (NALCN) at the junction of motor and neuropsychiatric symptoms in Parkinson's disease. J Neural Transm (Vienna) 2021; 128:749-762. [PMID: 33961117 DOI: 10.1007/s00702-021-02348-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2021] [Accepted: 04/30/2021] [Indexed: 12/27/2022]
Abstract
Parkinson's disease (PD) is a debilitating movement disorder often accompanied by neuropsychiatric symptoms that stem from the loss of dopaminergic function in the basal ganglia and altered neurotransmission more generally. Akinesia, postural instability, tremors and frozen gait constitute the major motor disturbances, whereas neuropsychiatric symptoms include altered circadian rhythms, disordered sleep, depression, psychosis and cognitive impairment. Evidence is emerging that the motor and neuropsychiatric symptoms may share etiologic factors. Calcium/ion channels (CACNA1C, NALCN), synaptic proteins (SYNJ1) and neuronal RNA-binding proteins (RBFOX1) are among the risk genes that are common to PD and various psychiatric disorders. The Na+ leak-current channel (NALCN) is the focus of this review because it has been implicated in dystonia, regulation of movement, cognitive impairment, sleep and circadian rhythms. It regulates the resting membrane potential in neurons, mediates pace-making activity, participates in synaptic vesicle recycling and is functionally co-localized to the endoplasmic reticulum (ER)-several of the major processes adversely affected in PD. Here, we summarize the literature on mechanisms and pathways that connect the motor and neuropsychiatric symptoms of PD with a focus on recurring relationships to the NALCN. It is hoped that the various connections outlined here will stimulate further discussion, suggest additional areas for exploration and ultimately inspire novel treatment strategies.
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Jin EJ, Park S, Lyu X, Jin Y. Gap junctions: historical discoveries and new findings in the Caenorhabditiselegans nervous system. Biol Open 2020; 9:bio053983. [PMID: 32883654 PMCID: PMC7489761 DOI: 10.1242/bio.053983] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Gap junctions are evolutionarily conserved structures at close membrane contacts between two cells. In the nervous system, they mediate rapid, often bi-directional, transmission of signals through channels called innexins in invertebrates and connexins in vertebrates. Connectomic studies from Caenorhabditis elegans have uncovered a vast number of gap junctions present in the nervous system and non-neuronal tissues. The genome also has 25 innexin genes that are expressed in spatial and temporal dynamic pattern. Recent findings have begun to reveal novel roles of innexins in the regulation of multiple processes during formation and function of neural circuits both in normal conditions and under stress. Here, we highlight the diverse roles of gap junctions and innexins in the C. elegans nervous system. These findings contribute to fundamental understanding of gap junctions in all animals.
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Affiliation(s)
- Eugene Jennifer Jin
- Neurobiology Section, Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA
| | - Seungmee Park
- Neurobiology Section, Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA
| | - Xiaohui Lyu
- Neurobiology Section, Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA
| | - Yishi Jin
- Neurobiology Section, Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA
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Perouansky M, Hemmings HC. Bioblasts, anaesthesia, and power failure: rein in the excitement. Br J Anaesth 2018; 120:891-895. [PMID: 29661404 DOI: 10.1016/j.bja.2018.02.018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2018] [Accepted: 02/19/2018] [Indexed: 11/30/2022] Open
Affiliation(s)
- M Perouansky
- Department of Anesthesiology, School of Medicine and Public Health, University of Wisconsin, Madison, WI, USA.
| | - H C Hemmings
- Department of Anesthesiology, Weill Cornell Medicine, New York, NY, USA
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Abstract
It is difficult to study the genetics and molecular mechanisms of anesthesia in humans. Fortunately, the genetic approaches in model organisms can, and have, led to profound insights as to the targets of anesthetics. In turn, the organization of these putative targets into meaningful pathways has begun to elucidate the mechanisms of action of these agents. However, it is important to first appreciate the strengths, and limitations, of genetic approaches to understand the anesthetic action. Here we compare the commonly used genetic model organisms, various anesthetic endpoints, and different modes of genetic screens. Coupled with the more specific data presented in subsequent chapters, this chapter places those results in a framework with which to analyze the discoveries across organisms and eventually extend the resulting models to humans.
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Turin L, Skoulakis EM. Electron Spin Resonance (EPR) in Drosophila and General Anesthesia. Methods Enzymol 2018; 603:115-128. [DOI: 10.1016/bs.mie.2018.01.020] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
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10
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van der Bliek AM, Sedensky MM, Morgan PG. Cell Biology of the Mitochondrion. Genetics 2017; 207:843-871. [PMID: 29097398 PMCID: PMC5676242 DOI: 10.1534/genetics.117.300262] [Citation(s) in RCA: 227] [Impact Index Per Article: 32.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2017] [Accepted: 09/05/2017] [Indexed: 01/19/2023] Open
Abstract
Mitochondria are best known for harboring pathways involved in ATP synthesis through the tricarboxylic acid cycle and oxidative phosphorylation. Major advances in understanding these roles were made with Caenorhabditiselegans mutants affecting key components of the metabolic pathways. These mutants have not only helped elucidate some of the intricacies of metabolism pathways, but they have also served as jumping off points for pharmacology, toxicology, and aging studies. The field of mitochondria research has also undergone a renaissance, with the increased appreciation of the role of mitochondria in cell processes other than energy production. Here, we focus on discoveries that were made using C. elegans, with a few excursions into areas that were studied more thoroughly in other organisms, like mitochondrial protein import in yeast. Advances in mitochondrial biogenesis and membrane dynamics were made through the discoveries of novel functions in mitochondrial fission and fusion proteins. Some of these functions were only apparent through the use of diverse model systems, such as C. elegans Studies of stress responses, exemplified by mitophagy and the mitochondrial unfolded protein response, have also benefitted greatly from the use of model organisms. Recent developments include the discoveries in C. elegans of cell autonomous and nonautonomous pathways controlling the mitochondrial unfolded protein response, as well as mechanisms for degradation of paternal mitochondria after fertilization. The evolutionary conservation of many, if not all, of these pathways ensures that results obtained with C. elegans are equally applicable to studies of human mitochondria in health and disease.
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Affiliation(s)
- Alexander M van der Bliek
- Department of Biological Chemistry, Jonsson Comprehensive Cancer Center and Molecular Biology Institute, David Geffen School of Medicine at UCLA, Los Angeles, California 90024
| | - Margaret M Sedensky
- Department of Anesthesiology and Pain Medicine, University of Washington and Center for Developmental Therapeutics, Seattle Children's Research Institute, Washington 98101
| | - Phil G Morgan
- Department of Anesthesiology and Pain Medicine, University of Washington and Center for Developmental Therapeutics, Seattle Children's Research Institute, Washington 98101
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The genetics of isoflurane-induced developmental neurotoxicity. Neurotoxicol Teratol 2016; 60:40-49. [PMID: 27989695 DOI: 10.1016/j.ntt.2016.10.012] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2016] [Revised: 10/07/2016] [Accepted: 10/27/2016] [Indexed: 01/06/2023]
Abstract
INTRODUCTION Neurotoxicity induced by early developmental exposure to volatile anesthetics is a characteristic of organisms across a wide range of species, extending from the nematode C. elegans to mammals. Prevention of anesthetic-induced neurotoxicity (AIN) will rely upon an understanding of its underlying mechanisms. However, no forward genetic screens have been undertaken to identify the critical pathways affected in AIN. By characterizing such pathways, we may identify mechanisms to eliminate isoflurane induced AIN in mammals. METHODS Chemotaxis in adult C. elegans after larval exposure to isoflurane was used to measure AIN. We initially compared changes in chemotaxis indices between classical mutants known to affect nervous system development adding mutants in response to data. Activation of specific genes was visualized using fluorescent markers. Animals were then treated with rapamycin or preconditioned with isoflurane to test effects on AIN. RESULTS Forty-four mutations, as well as pharmacologic manipulations, identified two pathways, highly conserved from invertebrates to humans, that regulate AIN in C. elegans. Activation of one stress-protective pathway (DAF-2 dependent) eliminates AIN, while activation of a second stress-responsive pathway (endoplasmic reticulum (ER) associated stress) causes AIN. Pharmacologic inhibition of the mechanistic Target of Rapamycin (mTOR) blocks ER-stress and AIN. Preconditioning with isoflurane prior to larval exposure also inhibited AIN. DISCUSSION Our data are best explained by a model in which isoflurane acutely inhibits mitochondrial function causing activation of responses that ultimately lead to ER-stress. The neurotoxic effect of isoflurane can be completely prevented by manipulations at multiple points in the pathways that control this response. Endogenous signaling pathways can be recruited to protect organisms from the neurotoxic effects of isoflurane.
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Abstract
Electrophysiological recordings have enabled identification of physiologically distinct yet behaviorally similar states of mammalian sleep. In contrast, sleep in nonmammals has generally been identified behaviorally and therefore regarded as a physiologically uniform state characterized by quiescence of feeding and locomotion, reduced responsiveness, and rapid reversibility. The nematode Caenorhabditis elegans displays sleep-like quiescent behavior under two conditions: developmentally timed quiescence (DTQ) occurs during larval transitions, and stress-induced quiescence (SIQ) occurs in response to exposure to cellular stressors. Behaviorally, DTQ and SIQ appear identical. Here, we use optogenetic manipulations of neuronal and muscular activity, pharmacology, and genetic perturbations to uncover circuit and molecular mechanisms of DTQ and SIQ. We find that locomotion quiescence induced by DTQ- and SIQ-associated neuropeptides occurs via their action on the nervous system, although their neuronal target(s) and/or molecular mechanisms likely differ. Feeding quiescence during DTQ results from a loss of pharyngeal muscle excitability, whereas feeding quiescence during SIQ results from a loss of excitability in the nervous system. Together these results indicate that, as in mammals, quiescence is subserved by different mechanisms during distinct sleep-like states in C. elegans.
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Wang H, Xu Z, Wu A, Dong Y, Zhang Y, Yue Y, Xie Z. 2-deoxy-D-glucose enhances anesthetic effects in mice. Anesth Analg 2015; 120:312-9. [PMID: 25390277 DOI: 10.1213/ane.0000000000000520] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
BACKGROUND The mechanisms of general anesthesia by volatile drugs remain largely unknown. Mitochondrial dysfunction and reduction in energy levels have been suggested to be associated with general anesthesia status. 2-Deoxy-D-glucose (2-DG), an analog of glucose, inhibits hexokinase and reduces cellular levels of adenosine triphosphate (ATP). 3-Nitropropionic acid is another compound which can deplete ATP levels. In contrast, idebenone and L-carnitine could rescue deficits of energy. We therefore sought to determine whether 2-DG and/or 3-nitropropionic acid can enhance the anesthetic effects of isoflurane, and whether idebenone and L-carnitine can reverse the actions of 2-DG. METHODS C57BL/6J mice (8 months old) received different concentrations of isoflurane with and without the treatments of 2-DG, 3-nitropropionic acid, idebenone, and L-carnitine. Isoflurane-induced loss of righting reflex (LORR) was determined in the mice. ATP levels in H4 human neuroglioma cells were assessed after these treatments. Finally, 31P-magnetic resonance spectroscopy was used to determine the effects of isoflurane on brain ATP levels in the mice. RESULTS 2-DG enhanced isoflurane-induced LORR (P = 0.002, N = 15). 3-Nitropropionic acid also enhanced the anesthetic effects of isoflurane (P = 0.005, N = 15). Idebenone (idebenone + saline versus idebenone + 2-DG: P = 0.165, N = 15), but not L-carnitine (L-carnitine + saline versus L-carnitine + 2-DG: P < 0.0001, N = 15), inhibited the effects of 2-DG on enhancing isoflurane-induced LORR in the mice, as evidenced by 2-DG not enhancing isoflurane-induced LORR in the mice pretreated with idebenone. Idebenone (idebenone + saline versus idebenone + 2-DG: P = 0.177, N = 6), but not L-carnitine (L-carnitine + saline versus L-carnitine + 2-DG: P = 0.029, N = 6), also mitigated the effects of 2-DG on reducing ATP levels in cells, as evidenced by 2-DG not decreasing ATP levels in the cells pretreated with idebenone. Finally, isoflurane decreased ATP levels in both cultured cells and mouse brains (β-ATP: P = 0.003, N = 10; β-ATP/phosphocreatine: P = 0.006, N = 10; β-ATP/inorganic phosphate: P = 0.001, N = 10). CONCLUSIONS These results from our pilot studies have established a system and generated a hypothesis that 2-DG enhances anesthetic effects via reducing energy levels. These findings should promote further studies to investigate anesthesia mechanisms.
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Affiliation(s)
- Hui Wang
- From the *Department of Anesthesia, Beijing Chaoyang Hospital, Capital Medical University, Beijing, China; †Geriatric Anesthesia Research Unit, Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital and Harvard Medical School, Charlestown, Massachusetts; and ‡Anesthesia and Operation Center, Chinese PLA General Hospital, Beijing, China
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14
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Morgan PG, Higdon R, Kolker N, Bauman AT, Ilkayeva O, Newgard CB, Kolker E, Steele LM, Sedensky MM. Comparison of proteomic and metabolomic profiles of mutants of the mitochondrial respiratory chain in Caenorhabditis elegans. Mitochondrion 2014; 20:95-102. [PMID: 25530493 DOI: 10.1016/j.mito.2014.12.004] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2014] [Revised: 09/10/2014] [Accepted: 12/10/2014] [Indexed: 01/06/2023]
Abstract
Single-gene mutations that disrupt mitochondrial respiratory chain function in Caenorhabditis elegans change patterns of protein expression and metabolites. Our goal was to develop useful molecular fingerprints employing adaptable techniques to recognize mitochondrial defects in the electron transport chain. We analyzed mutations affecting complex I, complex II, or ubiquinone synthesis and discovered overarching patterns in the response of C. elegans to mitochondrial dysfunction across all of the mutations studied. These patterns are in KEGG pathways conserved from C. elegans to mammals, verifying that the nematode can serve as a model for mammalian disease. In addition, specific differences exist between mutants that may be useful in diagnosing specific mitochondrial diseases in patients.
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Affiliation(s)
- P G Morgan
- Department of Anesthesiology and Pain Medicine, University of Washington, USA; Center for Developmental Therapeutics, Seattle Children's Research Institute, USA.
| | - R Higdon
- Bioinformatics and High-throughput Analysis Laboratory, USA; High-throughput Analysis Core, Seattle Children's Research Institute, USA; Data-Enabled Life Sciences Alliance (DELSA Global), USA
| | - N Kolker
- High-throughput Analysis Core, Seattle Children's Research Institute, USA; Data-Enabled Life Sciences Alliance (DELSA Global), USA
| | - A T Bauman
- Bioinformatics and High-throughput Analysis Laboratory, USA
| | - O Ilkayeva
- Sarah W. Stedman Nutrition and Metabolism Center & Duke Molecular Physiology Institute, Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC, USA; Sarah W. Stedman Nutrition and Metabolism Center & Duke Molecular Physiology Institute, Department of Medicine, Duke University Medical Center, Durham, NC, USA
| | - C B Newgard
- Sarah W. Stedman Nutrition and Metabolism Center & Duke Molecular Physiology Institute, Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC, USA; Sarah W. Stedman Nutrition and Metabolism Center & Duke Molecular Physiology Institute, Department of Medicine, Duke University Medical Center, Durham, NC, USA
| | - E Kolker
- Bioinformatics and High-throughput Analysis Laboratory, USA; High-throughput Analysis Core, Seattle Children's Research Institute, USA; Data-Enabled Life Sciences Alliance (DELSA Global), USA; Department of Biomedical Informatics & Medical Education, University of Washington, Seattle, WA, USA; Department of Pediatrics, University of Washington, Seattle, WA, USA; Department of Chemistry and Chemical Biology, College of Science, Northeastern University, Boston, MA 02115, USA
| | - L M Steele
- Center for Developmental Therapeutics, Seattle Children's Research Institute, USA
| | - M M Sedensky
- Department of Anesthesiology and Pain Medicine, University of Washington, USA; Center for Developmental Therapeutics, Seattle Children's Research Institute, USA
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Dwyer DS, Aamodt E, Cohen B, Buttner EA. Drug elucidation: invertebrate genetics sheds new light on the molecular targets of CNS drugs. Front Pharmacol 2014; 5:177. [PMID: 25120487 PMCID: PMC4112795 DOI: 10.3389/fphar.2014.00177] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2014] [Accepted: 07/09/2014] [Indexed: 02/02/2023] Open
Abstract
Many important drugs approved to treat common human diseases were discovered by serendipity, without a firm understanding of their modes of action. As a result, the side effects and interactions of these medications are often unpredictable, and there is limited guidance for improving the design of next-generation drugs. Here, we review the innovative use of simple model organisms, especially Caenorhabditis elegans, to gain fresh insights into the complex biological effects of approved CNS medications. Whereas drug discovery involves the identification of new drug targets and lead compounds/biologics, and drug development spans preclinical testing to FDA approval, drug elucidation refers to the process of understanding the mechanisms of action of marketed drugs by studying their novel effects in model organisms. Drug elucidation studies have revealed new pathways affected by antipsychotic drugs, e.g., the insulin signaling pathway, a trace amine receptor and a nicotinic acetylcholine receptor. Similarly, novel targets of antidepressant drugs and lithium have been identified in C. elegans, including lipid-binding/transport proteins and the SGK-1 signaling pathway, respectively. Elucidation of the mode of action of anesthetic agents has shown that anesthesia can involve mitochondrial targets, leak currents, and gap junctions. The general approach reviewed in this article has advanced our knowledge about important drugs for CNS disorders and can guide future drug discovery efforts.
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Affiliation(s)
- Donard S. Dwyer
- Department of Psychiatry–Department of Pharmacology, Toxicology and Neuroscience, Louisiana State University Health Sciences Center-ShreveportShreveport, LA, USA
| | - Eric Aamodt
- Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center-ShreveportShreveport, LA, USA
| | - Bruce Cohen
- Department of Psychiatry, Harvard Medical SchoolBoston, MA, USA
- Mailman Research Center, McLean HospitalBelmont, MA, USA
| | - Edgar A. Buttner
- Mailman Research Center, McLean HospitalBelmont, MA, USA
- Department of Neurology–Department of Psychiatry, McLean Hospital, Harvard Medical SchoolBelmont, MA, USA
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16
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Cochet-Bissuel M, Lory P, Monteil A. The sodium leak channel, NALCN, in health and disease. Front Cell Neurosci 2014; 8:132. [PMID: 24904279 PMCID: PMC4033012 DOI: 10.3389/fncel.2014.00132] [Citation(s) in RCA: 100] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2014] [Accepted: 04/28/2014] [Indexed: 12/12/2022] Open
Abstract
Ion channels are crucial components of cellular excitability and are involved in many neurological diseases. This review focuses on the sodium leak, G protein-coupled receptors (GPCRs)-activated NALCN channel that is predominantly expressed in neurons where it regulates the resting membrane potential and neuronal excitability. NALCN is part of a complex that includes not only GPCRs, but also UNC-79, UNC-80, NLF-1 and src family of Tyrosine kinases (SFKs). There is growing evidence that the NALCN channelosome critically regulates its ion conduction. Both in mammals and invertebrates, animal models revealed an involvement in many processes such as locomotor behaviors, sensitivity to volatile anesthetics, and respiratory rhythms. There is also evidence that alteration in this NALCN channelosome can cause a wide variety of diseases. Indeed, mutations in the NALCN gene were identified in Infantile Neuroaxonal Dystrophy (INAD) patients, as well as in patients with an Autosomal Recessive Syndrome with severe hypotonia, speech impairment, and cognitive delay. Deletions in NALCN gene were also reported in diseases such as 13q syndrome. In addition, genes encoding NALCN, NLF- 1, UNC-79, and UNC-80 proteins may be susceptibility loci for several diseases including bipolar disorder, schizophrenia, Alzheimer's disease, autism, epilepsy, alcoholism, cardiac diseases and cancer. Although the physiological role of the NALCN channelosome is poorly understood, its involvement in human diseases should foster interest for drug development in the near future. Toward this goal, we review here the current knowledge on the NALCN channelosome in physiology and diseases.
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Affiliation(s)
- Maud Cochet-Bissuel
- Institut de Génomique Fonctionnelle, CNRS UMR 5203, Universités Montpellier 1&2 Montpellier, France ; INSERM, U 661 Montpellier, France ; LabEx 'Ion Channel Science and Therapeutics' Montpellier, France
| | - Philippe Lory
- Institut de Génomique Fonctionnelle, CNRS UMR 5203, Universités Montpellier 1&2 Montpellier, France ; INSERM, U 661 Montpellier, France ; LabEx 'Ion Channel Science and Therapeutics' Montpellier, France
| | - Arnaud Monteil
- Institut de Génomique Fonctionnelle, CNRS UMR 5203, Universités Montpellier 1&2 Montpellier, France ; INSERM, U 661 Montpellier, France ; LabEx 'Ion Channel Science and Therapeutics' Montpellier, France
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17
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Chung SH, Schmalz A, Ruiz RCH, Gabel CV, Mazur E. Femtosecond laser ablation reveals antagonistic sensory and neuroendocrine signaling that underlie C. elegans behavior and development. Cell Rep 2013; 4:316-326. [PMID: 23871668 PMCID: PMC4780052 DOI: 10.1016/j.celrep.2013.06.027] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2012] [Revised: 02/27/2013] [Accepted: 06/22/2013] [Indexed: 11/27/2022] Open
Abstract
The specific roles of neuronal subcellular components in behavior and development remain largely unknown, even though advances in molecular biology and conventional whole-cell laser ablation have greatly accelerated the identification of contributors at the molecular and cellular levels. We systematically applied femtosecond laser ablation, which has submicrometer resolution in vivo, to dissect the cell bodies, dendrites, or axons of a sensory neuron (ASJ) in Caenorhabditis elegans to determine their roles in modulating locomotion and the developmental decisions for dauer, a facultative, stress-resistant life stage. Our results indicate that the cell body sends out axonally mediated and hormonal signals in order to mediate these functions. Furthermore, our results suggest that antagonistic sensory dendritic signals primarily drive and switch polarity between the decisions to enter and exit dauer. Thus, the improved resolution of femtosecond laser ablation reveals a rich complexity of neuronal signaling at the subcellular level, including multiple neurite and hormonally mediated pathways dependent on life stage.
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Affiliation(s)
- Samuel H Chung
- School of Engineering and Applied Sciences, Harvard University, 9 Oxford Street, Cambridge, MA 02138, USA.,Department of Physiology and Biophysics, Boston University School of Medicine, 72 E. Concord Street, Boston, MA 02118, USA.,Boston University Photonics Center, 8 Saint Mary's Street, Boston, MA 02215, USA
| | - Anja Schmalz
- School of Engineering and Applied Sciences, Harvard University, 9 Oxford Street, Cambridge, MA 02138, USA
| | - Roanna C H Ruiz
- School of Engineering and Applied Sciences, Harvard University, 9 Oxford Street, Cambridge, MA 02138, USA.,Department of Biomedical Engineering, Cornell University, 101 Weill Hall, Ithaca, NY 14853, USA
| | - Christopher V Gabel
- Department of Physiology and Biophysics, Boston University School of Medicine, 72 E. Concord Street, Boston, MA 02118, USA.,Boston University Photonics Center, 8 Saint Mary's Street, Boston, MA 02215, USA
| | - Eric Mazur
- School of Engineering and Applied Sciences, Harvard University, 9 Oxford Street, Cambridge, MA 02138, USA.,Department of Physics, Harvard University, 9 Oxford Street, Cambridge, MA 02138, USA
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18
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Insulin/IGF-1 signaling, including class II/III PI3Ks, β-arrestin and SGK-1, is required in C. elegans to maintain pharyngeal muscle performance during starvation. PLoS One 2013; 8:e63851. [PMID: 23700438 PMCID: PMC3659082 DOI: 10.1371/journal.pone.0063851] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2013] [Accepted: 04/06/2013] [Indexed: 01/07/2023] Open
Abstract
In C. elegans, pharyngeal pumping is regulated by the presence of bacteria. In response to food deprivation, the pumping rate rapidly declines by about 50–60%, but then recovers gradually to baseline levels on food after 24 hr. We used this system to study the role of insulin/IGF-1 signaling (IIS) in the recovery of pharyngeal pumping during starvation. Mutant strains with reduced function in the insulin/IGF-1 receptor, DAF-2, various insulins (INS-1 and INS-18), and molecules that regulate insulin release (UNC-64 and NCA-1; NCA-2) failed to recover normal pumping rates after food deprivation. Similarly, reduction or loss of function in downstream signaling molecules (e.g., ARR-1, AKT-1, and SGK-1) and effectors (e.g., CCA-1 and UNC-68) impaired pumping recovery. Pharmacological studies with kinase and metabolic inhibitors implicated class II/III phosphatidylinositol 3-kinases (PI3Ks) and glucose metabolism in the recovery response. Interestingly, both over- and under-activity in IIS was associated with poorer recovery kinetics. Taken together, the data suggest that optimum levels of IIS are required to maintain high levels of pharyngeal pumping during starvation. This work may ultimately provide insights into the connections between IIS, nutritional status and sarcopenia, a hallmark feature of aging in muscle.
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NLF-1 delivers a sodium leak channel to regulate neuronal excitability and modulate rhythmic locomotion. Neuron 2013; 77:1069-82. [PMID: 23522043 DOI: 10.1016/j.neuron.2013.01.018] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/15/2013] [Indexed: 11/22/2022]
Abstract
A cation channel NCA/UNC-79/UNC-80 affects neuronal activity. We report here the identification of a conserved endoplasmic reticulum protein NLF-1 (NCA localization factor-1) that regulates neuronal excitability and locomotion through the NCA channel. In C. elegans, the loss of either NLF-1 or NCA leads to a reduced sodium leak current, and a hyperpolarized resting membrane potential in premotor interneurons. This results in a decreased premotor interneuron activity that reduces the initiation and sustainability of rhythmic locomotion. NLF-1 promotes axonal localization of all NCA reporters. Its mouse homolog mNLF-1 functionally substitutes for NLF-1 in C. elegans, interacts with the mammalian sodium leak channel NALCN in vitro, and potentiates sodium leak currents in primary cortical neuron cultures. Taken together, an ER protein NLF-1 delivers a sodium leak channel to maintain neuronal excitability and potentiates a premotor interneuron network critical for C. elegans rhythmic locomotion.
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Gentry KR, Steele LM, Sedensky MM, Morgan PG. Early developmental exposure to volatile anesthetics causes behavioral defects in Caenorhabditis elegans. Anesth Analg 2013; 116:185-9. [PMID: 23223110 PMCID: PMC3607665 DOI: 10.1213/ane.0b013e31826d37c5] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
BACKGROUND Mounting evidence from animal studies shows that anesthetic exposure in early life leads to apoptosis in the developing nervous system. This loss of neurons has functional consequences in adulthood. Clinical retrospective reviews have suggested that multiple anesthetic exposures in early childhood are associated with learning disabilities later in life as well. Despite much concern about this phenomenon, little is known about the mechanism by which anesthetics initiate neuronal cell death. Caenorhabditis elegans, a powerful genetic animal model, with precisely characterized neural development and cell death pathways, affords an excellent opportunity to study anesthetic-induced neurotoxicity. We hypothesized that exposing the nematode to volatile anesthetics early in life would induce neuron cell death, producing a behavioral defect that would be manifested in adulthood. METHODS After synchronization and hatching, larval worms were exposed to volatile anesthetics at their 95% effective concentration for 4 hours. On day 4 of life, exposed and control worms were tested for their ability to sense and move to an attractant (i.e., to chemotax). We determined the rate of successful chemotaxis using a standardized chemotaxis index. RESULTS Wild-type nematodes demonstrated striking deficits in chemotaxis indices after exposure to isoflurane (ISO) or sevoflurane (SEVO) in the first larval stage (chemotaxis index: untreated, 85 ± 2; ISO, 52 ± 2; SEVO, 47 ± 2; P < 0.05 for both exposures). The mitochondrial mutant gas-1 had a heightened effect from the anesthetic exposure (chemotaxis index: untreated, 71 ± 2; ISO, 29 ± 12; SEVO, 24 ± 13; P < 0.05 for both exposures). In contrast, animals unable to undergo apoptosis because of a mutation in the pathway that mediates programmed cell death (ced-3) retained their ability to sense and move toward an attractant (chemotaxis index: untreated, 76 ± 10; ISO, 73 ± 9; SEVO, 76 ± 10). Furthermore, we discovered that the window of greatest susceptibility to anesthetic neurotoxicity in nematodes occurs in the first larval stage after hatching (L1). This coincides with a period of neurogenesis in this model. All values are means ± SD. CONCLUSION These data indicate that anesthetics affect neurobehavior in nematodes, extending the range of phyla in which early exposure to volatile anesthetics has been shown to cause functional neurological deficits. This implies that anesthetic-induced neurotoxicity occurs via an ancient underlying mechanism. C elegans is a tractable model organism with which to survey an entire genome for molecules that mediate the toxic effects of volatile anesthetics on the developing nervous system.
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Affiliation(s)
- Katherine R Gentry
- Department of Anesthesiology and Pain Medicine, Seattle Children's Hospital, M/S W 9824, PO Box 5371, Seattle, WA 98105, USA.
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Abstract
PURPOSE OF REVIEW Although general anesthetics have been provided effectively for many years, their exact molecular underpinnings remain relatively unknown. In this article, we discuss the recent findings associated with resistance to anesthetic effects as a way of shedding light on these mechanisms. RECENT FINDINGS The original theories of anesthetic action based upon their effects on cellular membranes have given way to specific theories concerning direct effects on ion channel proteins. These molecular targets are intimately involved in the conduct of neuronal signaling within the central nervous system and are thought to be essential in the modulation of conscious states. It is the lack of a thorough understanding of unperturbed consciousness that fosters great difficulty in understanding how anesthetics alter this conscious state. However, one very fruitful line of analysis in the quest for such answers lies in the examination of both in-vitro and in-vivo ion channel systems that seem to maintain variable levels of resistance to anesthetics. SUMMARY Information about the possible targets and molecular nature of anesthetic action is being derived from studies of anesthetic resistance in γ aminobutyric acid receptors, tandem pore potassium channels, and an apparently wide variety of protein systems within the nematode, Caenorhabditis elegans.
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22
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Quintana A, Morgan PG, Kruse SE, Palmiter RD, Sedensky MM. Altered anesthetic sensitivity of mice lacking Ndufs4, a subunit of mitochondrial complex I. PLoS One 2012; 7:e42904. [PMID: 22912761 PMCID: PMC3422219 DOI: 10.1371/journal.pone.0042904] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2012] [Accepted: 07/12/2012] [Indexed: 02/07/2023] Open
Abstract
Anesthetics are in routine use, yet the mechanisms underlying their function are incompletely understood. Studies in vitro demonstrate that both GABA(A) and NMDA receptors are modulated by anesthetics, but whole animal models have not supported the role of these receptors as sole effectors of general anesthesia. Findings in C. elegans and in children reveal that defects in mitochondrial complex I can cause hypersensitivity to volatile anesthetics. Here, we tested a knockout (KO) mouse with reduced complex I function due to inactivation of the Ndufs4 gene, which encodes one of the subunits of complex I. We tested these KO mice with two volatile and two non-volatile anesthetics. KO and wild-type (WT) mice were anesthetized with isoflurane, halothane, propofol or ketamine at post-natal (PN) days 23 to 27, and tested for loss of response to tail clamp (isoflurane and halothane) or loss of righting reflex (propofol and ketamine). KO mice were 2.5 - to 3-fold more sensitive to isoflurane and halothane than WT mice. KO mice were 2-fold more sensitive to propofol but resistant to ketamine. These changes in anesthetic sensitivity are the largest recorded in a mammal.
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Affiliation(s)
- Albert Quintana
- Howard Hughes Medical Institute and Department of Biochemistry, University of Washington, Seattle, Washington, United States of America
| | - Philip G. Morgan
- Department of Anesthesiology and Pain Medicine, University of Washington and Center for Developmental Therapeutics, Seattle Children's Research Institute, Seattle, Washington, United States of America
- * E-mail:
| | - Shane E. Kruse
- Howard Hughes Medical Institute and Department of Biochemistry, University of Washington, Seattle, Washington, United States of America
| | - Richard D. Palmiter
- Howard Hughes Medical Institute and Department of Biochemistry, University of Washington, Seattle, Washington, United States of America
| | - Margaret M. Sedensky
- Department of Anesthesiology and Pain Medicine, University of Washington and Center for Developmental Therapeutics, Seattle Children's Research Institute, Seattle, Washington, United States of America
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Stomatin inhibits pannexin-1-mediated whole-cell currents by interacting with its carboxyl terminal. PLoS One 2012; 7:e39489. [PMID: 22768083 PMCID: PMC3387187 DOI: 10.1371/journal.pone.0039489] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2011] [Accepted: 05/21/2012] [Indexed: 12/20/2022] Open
Abstract
The pannexin-1 (Panx1) channel (often referred to as the Panx1 hemichannel) is a large-conductance channel in the plasma membrane of many mammalian cells. While opening of the channel is potentially detrimental to the cell, little is known about how it is regulated under physiological conditions. Here we show that stomatin inhibited Panx1 channel activity. In transfected HEK-293 cells, stomatin reduced Panx1-mediated whole-cell currents without altering either the total or membrane surface Panx1 protein expression. Stomatin coimmunoprecipitated with full-length Panx1 as well as a Panx1 fragment containing the fourth membrane-spanning domain and the cytosolic carboxyl terminal. The inhibitory effect of stomatin on Panx1-mediated whole-cell currents was abolished by truncating Panx1 at a site in the cytosolic carboxyl terminal. In primary culture of mouse astrocytes, inhibition of endogenous stomatin expression by small interfering RNA enhanced Panx1-mediated outward whole-cell currents. These observations suggest that stomatin may play important roles in astrocytes and other cells by interacting with Panx1 carboxyl terminal to limit channel opening.
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24
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Anesthetic action of volatile anesthetics by using Paramecium as a model. ACTA ACUST UNITED AC 2012; 32:410-414. [PMID: 22684567 DOI: 10.1007/s11596-012-0071-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2011] [Indexed: 11/27/2022]
Abstract
Although empirically well understood in their clinical administration, volatile anesthetics are not yet well comprehended in their mechanism studies. A major conundrum emerging from these studies is that there is no validated model to assess the presumed candidate sites of the anesthetics. We undertook this study to test the hypothesis that the single-celled Paramecium could be anesthetized and served as a model organism in the study of anesthetics. We assessed the motion of Paramecium cells with Expert Vision system and the chemoresponse of Paramecium cells with T-maze assays in the presence of four different volatile anesthetics, including isoflurane, sevoflurane, enflurane and ether. Each of those volatiles was dissolved in buffers to give drug concentrations equal to 0.8, 1.0, and 1.2 EC50, respectively, in clinical practice. We could see that after application of volatile anesthetics, the swimming of the Paramecium cells was accelerated and then suppressed, or even stopped eventually, and the index of the chemoresponse of the Paramecium cells (denoted as I ( che )) was decreased. All of the above impacts were found in a concentration-dependent fashion. The biphasic effects of the clinical concentrations of volatile anesthetics on Paramecium simulated the situation of high species in anesthesia, and the inhibition of the chemoresponse also indicated anesthetized. In conclusion, the findings in our studies suggested that the single-celled Paramecium could be anesthetized with clinical concentrations of volatile anesthetics and therefore be utilized as a model organism to study the mechanisms of volatile anesthetics.
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Abstract
In the nematode C. elegans, immobility induced by the anesthetic halothane is coupled to its ability to modulate neuronal resting membrane potential, perhaps through effects on leak channels; a similar anesthetic, isoflurane, appears to work a different way.
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Affiliation(s)
- Roderic G Eckenhoff
- Department of Anesthesiology and Critical Care, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.
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26
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Davies AG, Friedberg RI, Gupta H, Chan CL, Shelton KL, Bettinger JC. Different genes influence toluene- and ethanol-induced locomotor impairment in C. elegans. Drug Alcohol Depend 2012; 122:47-54. [PMID: 21945072 PMCID: PMC3260412 DOI: 10.1016/j.drugalcdep.2011.08.030] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/19/2011] [Revised: 08/12/2011] [Accepted: 08/31/2011] [Indexed: 01/25/2023]
Abstract
BACKGROUND The abused volatile solvent toluene shares many behavioral effects with classic central nervous system depressants such as ethanol. Similarities between toluene and ethanol have also been demonstrated using in vitro electrophysiology. Together, these studies suggest that toluene and ethanol may be acting, at least in part, via common mechanisms. METHODS We used the genetic model, Caenorhabditis elegans, to examine the behavioral effects of toluene in a simple system, and used mutant strains known to have altered responses to other CNS depressants to examine the involvement of those genes in the motor effects induced by toluene. RESULTS Toluene vapor brings about an altered pattern of locomotion in wild-type worms that is visibly distinct from that generated by ethanol. Mutants of the slo-1, rab-3 and unc-64 genes that are resistant to ethanol or the volatile anesthetic halothane show no resistance to toluene. A mutation in the unc-79 gene results in hypersensitivity to ethanol, halothane and toluene indicating a possible convergence of mechanisms of the three compounds. We screened for, and isolated, two mutations that generate resistance to the locomotor depressing effects of toluene and do not alter sensitivity to ethanol. CONCLUSIONS In C. elegans, ethanol and toluene have distinct behavioral effects and minimal overlap in terms of the genes responsible for these effects. These findings demonstrate that the C. elegans model system provides a unique and sensitive means of delineating both the commonalities as well as the differences in the neurochemical effects of classical CNS depressants and abused volatile inhalants.
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Affiliation(s)
- Andrew G. Davies
- Department of Pharmacology and Toxicology, Virginia Commonwealth University Richmond, VA 23298-0613 USA,Department of Psychiatry, Virginia Commonwealth University Richmond, VA 23298-0613 USA,Institute for Drug and Alcohol Studies, Virginia Commonwealth University Richmond, VA 23298-0613 USA,Virginia Commonwealth University – Alcohol Research Center Virginia Commonwealth University Richmond, VA 23298-0613 USA,Corresponding author Andrew G. Davies, Ph.D. Department of Pharmacology and Toxicology Virginia Commonwealth University P.O. Box 980613 Richmond VA, 23298-0613 (804) 828-2068 (w) (804) 828-4794 (fax)
| | - Ryan I. Friedberg
- Department of Pharmacology and Toxicology, Virginia Commonwealth University Richmond, VA 23298-0613 USA
| | - Hersh Gupta
- Department of Pharmacology and Toxicology, Virginia Commonwealth University Richmond, VA 23298-0613 USA
| | - Chung-Lung Chan
- Department of Pharmacology and Toxicology, Virginia Commonwealth University Richmond, VA 23298-0613 USA
| | - Keith L. Shelton
- Department of Pharmacology and Toxicology, Virginia Commonwealth University Richmond, VA 23298-0613 USA,Institute for Drug and Alcohol Studies, Virginia Commonwealth University Richmond, VA 23298-0613 USA
| | - Jill C. Bettinger
- Department of Pharmacology and Toxicology, Virginia Commonwealth University Richmond, VA 23298-0613 USA,Department of Psychiatry, Virginia Commonwealth University Richmond, VA 23298-0613 USA,Institute for Drug and Alcohol Studies, Virginia Commonwealth University Richmond, VA 23298-0613 USA,Virginia Commonwealth University – Alcohol Research Center Virginia Commonwealth University Richmond, VA 23298-0613 USA
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Bouhours M, Po MD, Gao S, Hung W, Li H, Georgiou J, Roder JC, Zhen M. A co-operative regulation of neuronal excitability by UNC-7 innexin and NCA/NALCN leak channel. Mol Brain 2011; 4:16. [PMID: 21489288 PMCID: PMC3102621 DOI: 10.1186/1756-6606-4-16] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2011] [Accepted: 04/13/2011] [Indexed: 11/10/2022] Open
Abstract
Gap junctions mediate the electrical coupling and intercellular communication between neighboring cells. Some gap junction proteins, namely connexins and pannexins in vertebrates, and innexins in invertebrates, may also function as hemichannels. A conserved NCA/Dmα1U/NALCN family cation leak channel regulates the excitability and activity of vertebrate and invertebrate neurons. In the present study, we describe a genetic and functional interaction between the innexin UNC-7 and the cation leak channel NCA in Caenorhabditis elegans neurons. While the loss of the neuronal NCA channel function leads to a reduced evoked postsynaptic current at neuromuscular junctions, a simultaneous loss of the UNC-7 function restores the evoked response. The expression of UNC-7 in neurons reverts the effect of the unc-7 mutation; moreover, the expression of UNC-7 mutant proteins that are predicted to be unable to form gap junctions also reverts this effect, suggesting that UNC-7 innexin regulates neuronal activity, in part, through gap junction-independent functions. We propose that, in addition to gap junction-mediated functions, UNC-7 innexin may also form hemichannels to regulate C. elegans' neuronal activity cooperatively with the NCA family leak channels.
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Affiliation(s)
- Magali Bouhours
- Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, Canada M5G 1X5
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Mairhofer M, Steiner M, Salzer U, Prohaska R. Stomatin-like protein-1 interacts with stomatin and is targeted to late endosomes. J Biol Chem 2009; 284:29218-29. [PMID: 19696025 DOI: 10.1074/jbc.m109.014993] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The human stomatin-like protein-1 (SLP-1) is a membrane protein with a characteristic bipartite structure containing a stomatin domain and a sterol carrier protein-2 (SCP-2) domain. This structure suggests a role for SLP-1 in sterol/lipid transfer and transport. Because SLP-1 has not been investigated, we first studied the molecular and cell biological characteristics of the expressed protein. We show here that SLP-1 localizes to the late endosomal compartment, like stomatin. Unlike stomatin, SLP-1 does not localize to the plasma membrane. Overexpression of SLP-1 leads to the redistribution of stomatin from the plasma membrane to late endosomes suggesting a complex formation between these proteins. We found that the targeting of SLP-1 to late endosomes is caused by a GYXXPhi (Phi being a bulky, hydrophobic amino acid) sorting signal at the N terminus. Mutation of this signal results in plasma membrane localization. SLP-1 and stomatin co-localize in the late endosomal compartment, they co-immunoprecipitate, thus showing a direct interaction, and they associate with detergent-resistant membranes. In accordance with the proposed lipid transfer function, we show that, under conditions of blocked cholesterol efflux from late endosomes, SLP-1 induces the formation of enlarged, cholesterol-filled, weakly LAMP-2-positive, acidic vesicles in the perinuclear region. This massive cholesterol accumulation clearly depends on the SCP-2 domain of SLP-1, suggesting a role for this domain in cholesterol transfer to late endosomes.
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Affiliation(s)
- Mario Mairhofer
- Max F. Perutz Laboratories, Department of Medical Biochemistry, Medical University of Vienna, Vienna A-1030, Austria
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Identification of Quantitative Trait Loci and candidate genes influencing ethanol sensitivity in honey bees. Behav Genet 2008; 38:531-53. [PMID: 18661223 DOI: 10.1007/s10519-008-9218-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2007] [Accepted: 07/14/2008] [Indexed: 01/08/2023]
Abstract
Invertebrate models have greatly furthered our understanding of ethanol sensitivity and alcohol addiction. The honey bee (Apis mellifera), a widely used behavioral model, is valuable for comparative studies. A quantitative trait locus (QTL) mapping experiment was designed to identify QTL and genes influencing ethanol vapor sensitivity. A backcross mating between ethanol-sensitive and resistant lines resulted in worker offspring that were tested for sensitivity to the sedative effects of alcohol. A linkage map was constructed with over 500 amplified fragment length polymorphism (AFLP) and sequence-tagged site (STS) markers. Four QTL were identified from three linkage groups with log of odds ratio (LOD) scores of 2.28, 2.26, 2.23, and 2.02. DNA from markers within and near QTL were cloned and sequenced, and this data was utilized to integrate our map with the physical honey bee genome. Many candidate genes were identified that influence synaptic transmission, neuronal growth, and detoxification. Others affect lipid synthesis, apoptosis, alcohol metabolism, cAMP signaling, and electron transport. These results are relevant because they present the first search for QTL that affect resistance to acute ethanol exposure in an invertebrate, could be useful for comparative genomic purposes, and lend credence to the use of honey bees as biomedical models of alcohol metabolism and sensitivity.
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Jospin M, Watanabe S, Joshi D, Young S, Hamming K, Thacker C, Snutch TP, Jorgensen EM, Schuske K. UNC-80 and the NCA ion channels contribute to endocytosis defects in synaptojanin mutants. Curr Biol 2007; 17:1595-600. [PMID: 17825559 DOI: 10.1016/j.cub.2007.08.036] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2007] [Revised: 08/02/2007] [Accepted: 08/07/2007] [Indexed: 11/20/2022]
Abstract
Synaptojanin is a lipid phosphatase required to degrade phosphatidylinositol 4,5 bisphosphate (PIP(2)) at cell membranes during synaptic vesicle recycling. Synaptojanin mutants in C. elegans are severely uncoordinated and are depleted of synaptic vesicles, possibly because of accumulation of PIP(2). To identify proteins that act downstream of PIP(2) during endocytosis, we screened for suppressors of synaptojanin mutants in the nematode C. elegans. A class of uncoordinated mutants called "fainters" partially suppress the locomotory, vesicle depletion, and electrophysiological defects in synaptojanin mutants. These suppressor loci include the genes for the NCA ion channels, which are homologs of the vertebrate cation leak channel NALCN, and a novel gene called unc-80. We demonstrate that unc-80 encodes a novel, but highly conserved, neuronal protein required for the proper localization of the NCA-1 and NCA-2 ion channel subunits. These data suggest that activation of the NCA ion channel in synaptojanin mutants leads to defects in recycling of synaptic vesicles.
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Affiliation(s)
- Maelle Jospin
- Department of Biology, University of Utah, 257 South 1400 East, Salt Lake City, UT 84112-0840, USA
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Chen B, Liu Q, Ge Q, Xie J, Wang ZW. UNC-1 regulates gap junctions important to locomotion in C. elegans. Curr Biol 2007; 17:1334-9. [PMID: 17658257 PMCID: PMC1976340 DOI: 10.1016/j.cub.2007.06.060] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2007] [Revised: 06/24/2007] [Accepted: 06/25/2007] [Indexed: 11/17/2022]
Abstract
In C. elegans, loss-of-function (lf) mutations of the stomatin-like protein (SLP) UNC-1 and the innexin UNC-9 inhibit locomotion [1, 2] and modulate sensitivity to volatile anesthetics [3, 4]. It was unknown why unc-1(lf) and unc-9(lf) mutants have similar phenotypes. We tested the hypothesis that UNC-1 is a regulator of gap junctions formed by UNC-9. Analyses of junctional currents between body-wall muscle cells showed that electrical coupling was inhibited to a similar degree in unc-1(lf), unc-9(lf), and unc-1(lf);unc-9(lf) double mutants, suggesting that UNC-1 and UNC-9 function together. Expression of Punc-1::DsRED2 and Punc-9::GFP transcriptional fusions suggests that unc-1 and unc-9 are coexpressed in neurons and body-wall muscle cells. Immunohistochemistry showed that UNC-1 and UNC-9 colocalized at intercellular junctions and that unc-1(lf) did not alter UNC-9 expression or subcellular localization. Bimolecular fluorescence complementation (BiFC) assays suggest that UNC-1 and UNC-9 are physically very close at intercellular junctions. Targeted rescue experiments suggest that UNC-9 and UNC-1 function predominantly in neurons to control locomotion. Thus, in addition to the recently reported function of regulating mechanosensitive ion channels [5, 6], SLPs might have a novel function of regulating gap junctions.
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Affiliation(s)
- Bojun Chen
- Department of Neuroscience, University of Connecticut Health Center, 263 Farmington Avenue, Farmington, Connecticut 06030
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Humphrey JA, Hamming KS, Thacker CM, Scott RL, Sedensky MM, Snutch TP, Morgan PG, Nash HA. A putative cation channel and its novel regulator: cross-species conservation of effects on general anesthesia. Curr Biol 2007; 17:624-9. [PMID: 17350263 DOI: 10.1016/j.cub.2007.02.037] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2006] [Revised: 01/31/2007] [Accepted: 02/02/2007] [Indexed: 11/18/2022]
Abstract
Volatile anesthetics like halothane and enflurane are of interest to clinicians and neuroscientists because of their ability to preferentially disrupt higher functions that make up the conscious state. All volatiles were once thought to act identically; if so, they should be affected equally by genetic variants. However, mutations in two distinct genes, one in Caenorhabditis and one in Drosophila, have been reported to produce much larger effects on the response to halothane than enflurane [1, 2]. To see whether this anesthesia signature is adventitious or fundamental, we have identified orthologs of each gene and determined the mutant phenotype within each species. The fly gene, narrow abdomen (na), encodes a putative ion channel whose sequence places it in a unique family; the nematode gene, unc-79, is identified here as encoding a large cytosolic protein that lacks obvious motifs. In Caenorhabditis, mutations that inactivate both of the na orthologs produce an Unc-79 phenotype; in Drosophila, mutations that inactivate the unc-79 ortholog produce an na phenotype. In each organism, studies of double mutants place the genes in the same pathway, and biochemical studies show that proteins of the UNC-79 family control NA protein levels by a posttranscriptional mechanism. Thus, the anesthetic signature reflects an evolutionarily conserved role for the na orthologs, implying its intimate involvement in drug action.
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Affiliation(s)
- John A Humphrey
- Department of Genetics, Case Medical Center, Cleveland, OH 44106, USA
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Falk MJ, Kayser EB, Morgan PG, Sedensky MM. Mitochondrial complex I function modulates volatile anesthetic sensitivity in C. elegans. Curr Biol 2006; 16:1641-5. [PMID: 16920626 PMCID: PMC3641903 DOI: 10.1016/j.cub.2006.06.072] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2005] [Revised: 06/22/2006] [Accepted: 06/22/2006] [Indexed: 11/22/2022]
Abstract
Despite the widespread clinical use of volatile anesthetics, their mechanisms of action remain unknown [1-6]. An unbiased genetic screen in the nematode C. elegans for animals with altered volatile anesthetic sensitivity identified a mutant in a nuclear-encoded subunit of mitochondrial complex I [7,8]. This raised the question of whether mitochondrial dysfunction might be the primary mechanism by which volatile anesthetics act, rather than an untoward secondary effect [9,10]. We report here analysis of additional C. elegans mutations in orthologs of human genes that contribute to the formation of complex I, complex II, complex III, and coenzyme Q [11-14]. To further characterize the specific contribution of complex I, we generated four hypomorphic C. elegans mutants encoding different complex I subunits [15]. Our main finding is the identification of a clear correlation between complex I-dependent oxidative phosphorylation capacity and volatile anesthetic sensitivity. These extended data link a physiologic determinant of anesthetic action in a tractable animal model to similar clinical observations in children with mitochondrial myopathies [16]. This work is the first to specifically implicate complex I-dependent oxidative phosphorylation function as a primary mediator of volatile anesthetic effect.
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Affiliation(s)
- Marni J. Falk
- Department of Pediatrics, University Hospitals of Cleveland, CASE School of Medicine, Cleveland, Ohio 44106
- Department of Genetics, University Hospitals of Cleveland, CASE School of Medicine, Cleveland, Ohio 44106
| | - Ernst-Bernhard Kayser
- Department of Anesthesiology, University Hospitals of Cleveland, CASE School of Medicine, Cleveland, Ohio 44106
| | - Philip G. Morgan
- Department of Genetics, University Hospitals of Cleveland, CASE School of Medicine, Cleveland, Ohio 44106
- Department of Anesthesiology, University Hospitals of Cleveland, CASE School of Medicine, Cleveland, Ohio 44106
- Department of Pharmacology, University Hospitals of Cleveland, CASE School of Medicine, Cleveland, Ohio 44106
| | - Margaret M. Sedensky
- Department of Genetics, University Hospitals of Cleveland, CASE School of Medicine, Cleveland, Ohio 44106
- Department of Anesthesiology, University Hospitals of Cleveland, CASE School of Medicine, Cleveland, Ohio 44106
- Correspondence:
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Abstract
General anesthetics abolish behavioral responsiveness in all animals, and in humans this is accompanied by loss of consciousness. Whether similar target mechanisms and behavioral endpoints exist across species remains controversial, although model organisms have been successfully used to study mechanisms of anesthesia. In Drosophila, a number of key mutants have been characterized as hypersensitive or resistant to general anesthetics by behavioral assays. In order to investigate general anesthesia in the Drosophila brain, local field potential (LFP) recordings were made during incremental exposures to isoflurane in wild-type and mutant flies. As in higher animals, general anesthesia in flies was found to involve a succession of distinct endpoints. At low doses, isoflurane uncoupled brain activity from ongoing movement, followed by a sudden attenuation in neural correlates of perception. Average LFP activity in the brain was more gradually attenuated with higher doses, followed by loss of movement behavior. Among mutants, a strong correspondence was found between behavioral and LFP sensitivities, thereby suggesting that LFP phenotypes are proximal to the anesthetic's mechanism of action. Finally, genetic and pharmacological analysis revealed that anesthetic sensitivities in the fly brain are, like other arousal states, influenced by dopaminergic activity. These results suggest that volatile anesthetics such as isoflurane may target the same processes that sustain wakefulness and attention in the brain. LFP correlates of general anesthesia in Drosophila provide a powerful new approach to uncovering the nature of these processes.
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Carroll BT, Dubyak GR, Sedensky MM, Morgan PG. Sulfated signal from ASJ sensory neurons modulates stomatin-dependent coordination in Caenorhabditis elegans. J Biol Chem 2006; 281:35989-96. [PMID: 16973616 DOI: 10.1074/jbc.m606086200] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The neuronal stomatin-like proteins UNC-1 and UNC-24 play important roles in the nervous system of Caenorhabditis elegans. These neuronal stomatin-like proteins are putative chaperone proteins that can modify volatile anesthetic sensitivity and disrupt coordinated locomotion. A suppressor of unc-1 and unc-24, named ssu-1(fc73) (for suppressor of stomatin uncoordination), suppresses three phenotypes of neuronal stomatin-like protein deficiency as follows: volatile anesthetic sensitivity, uncoordinated locomotion, and a constitutive alternative developmental phenotype known as dauer. Here we provide the first phenotypic characterization of ssu-1, predicted to be the only C. elegans cytosolic alcohol sulfotransferase, a family of enzymes that catalyze a sulfate linkage with the alcohol group of small molecules for the purposes of detoxification or modification of signaling. In vitro enzyme analysis of bacterially expressed SSU-1 demonstrates sulfotransferase activity and thus confirms the function predicted by protein sequence similarities. Whereas unc-1 is expressed in the majority of neurons of C. elegans, expression of SSU-1 protein in only the two ASJ amphid interneurons is sufficient to restore the wild type phenotype. This work demonstrates that SSU-1 is a functional sulfotransferase that likely modifies endocrine signaling in C. elegans. The expression of SSU-1 in the ASJ neurons refines the understanding of the function of these cells and supports their classification as endocrine tissue. The relationship of unc-1, unc-24, and ssu-1 is the first association of neuronal stomatin-like proteins sharing regulatory roles with a sulfotransferase enzyme.
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Affiliation(s)
- Bryan T Carroll
- Department of Genetics, Case School of Medicine, Cleveland, Ohio 44106, USA
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36
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Abstract
While our understanding of lipid microdomains has advanced in recent years, many aspects of their formation and dynamics are still unclear. In particular, the molecular determinants that facilitate the partitioning of integral membrane proteins into lipid raft domains are yet to be clarified. This review focuses on a family of raft-associated integral membrane proteins, termed flotillins, which belongs to a larger class of integral membrane proteins that carry an evolutionarily conserved domain called the prohibitin homology (PHB) domain. A number of studies now suggest that eucaryotic proteins carrying this domain have affinity for lipid raft domains. The PHB domain is carried by a diverse array of proteins including stomatin, podocin, the archetypal PHB protein, prohibitin, lower eucaryotic proteins such as the Dictyostelium discoideum proteins vacuolin A and vacuolin B and the Caenorhabditis elegans proteins unc-1, unc-24 and mec-2. The presence of this domain in some procaryotic proteins suggests that the PHB domain may constitute a primordial lipid recognition motif. Recent work has provided new insights into the trafficking and targeting of flotillin and other PHB domain proteins. While the function of this large family of proteins remains unclear, studies of the C. elegans PHB proteins suggest possible links to a class of volatile anaesthetics raising the possibility that these lipophilic agents could influence lipid raft domains. This review will discuss recent insights into the cell biology of flotillins and the large family of evolutionarily conserved PHB domain proteins.
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Affiliation(s)
- Isabel C Morrow
- Institute for Molecular Bioscience, Centre for Microscopy and Microanalysis, University of Queensland, Brisbane, Queensland 4072, Australia
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Hawasli AH, Saifee O, Liu C, Nonet ML, Crowder CM. Resistance to volatile anesthetics by mutations enhancing excitatory neurotransmitter release in Caenorhabditis elegans. Genetics 2005; 168:831-43. [PMID: 15514057 PMCID: PMC1448830 DOI: 10.1534/genetics.104.030502] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
The molecular mechanisms whereby volatile general anesthetics (VAs) disrupt behavior remain undefined. In Caenorhabditis elegans mutations in the gene unc-64, which encodes the presynaptic protein syntaxin 1A, produce large allele-specific differences in VA sensitivity. UNC-64 syntaxin normally functions to mediate fusion of neurotransmitter vesicles with the presynaptic membrane. The precise role of syntaxin in the VA mechanism is as yet unclear, but a variety of results suggests that a protein interacting with syntaxin to regulate neurotransmitter release is essential for VA action in C. elegans. To identify additional proteins that function with syntaxin to control neurotransmitter release and VA action, we screened for suppressors of the phenotypes produced by unc-64 reduction of function. Loss-of-function mutations in slo-1, which encodes a Ca(2+)-activated K+ channel, and in unc-43, which encodes CaM-kinase II, and a gain-of-function mutation in egl-30, which encodes Gqalpha, were isolated as syntaxin suppressors. The slo-1 and egl-30 mutations conferred resistance to VAs, but unc-43 mutations did not. The effects of slo-1 and egl-30 on VA sensitivity can be explained by their actions upstream or parallel to syntaxin to increase the level of excitatory neurotransmitter release. These results strengthen the link between transmitter release and VA action.
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Affiliation(s)
- Ammar H Hawasli
- Department of Anesthesiology, Division of Biology and Biomedical Sciences, Washington University School of Medicine, Saint Louis, Missouri 63110, USA
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Nagele P, Metz LB, Crowder CM. Nitrous oxide (N(2)O) requires the N-methyl-D-aspartate receptor for its action in Caenorhabditis elegans. Proc Natl Acad Sci U S A 2004; 101:8791-6. [PMID: 15159532 PMCID: PMC423274 DOI: 10.1073/pnas.0402825101] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Nitrous oxide (N(2)O, also known as laughing gas) and volatile anesthetics (VAs), the original and still most widely used general anesthetics, produce anesthesia by ill-defined mechanisms. Electrophysiological experiments in vertebrate neurons have suggested that N(2)O and VAs may act by distinct mechanisms; N(2)O antagonizes the N-methyl-d-aspartate (NMDA) subtype of glutamate receptors, whereas VAs alter the function of a variety of other synaptic proteins. However, no genetic or pharmacological experiments have demonstrated that any of these in vitro actions are responsible for the behavioral effects of either class of anesthetics. By using genetic tools in Caenorhabditis elegans, we tested whether the action of N(2)O requires the NMDA receptor in vivo and whether its mechanism is shared by VAs. Distinct from the action of VAs, N(2)O produced behavioral defects highly specific and characteristic of that produced by loss-of-function mutations in both NMDA and non-NMDA glutamate receptors. A null mutant of nmr-1, which encodes a C. elegans NMDA receptor, was completely resistant to the behavioral effects of N(2)O, whereas a non-NMDA receptor-null mutant was normally sensitive. The N(2)O-resistant nmr-1(null) mutant was not resistant to VAs. Likewise, VA-resistant mutants had wild-type sensitivity to N(2)O. Thus, the behavioral effects of N(2)O require the NMDA receptor NMR-1, consistent with the hypothesis formed from vertebrate electrophysiological data that a major target of N(2)O is the NMDA receptor.
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Affiliation(s)
- P Nagele
- Department of Anesthesiology, Division of Biology and Biomedical Sciences, Washington University School of Medicine, St. Louis, MO 63110, USA
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39
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Sedensky MM, Siefker JM, Koh JY, Miller DM, Morgan PG. A stomatin and a degenerin interact in lipid rafts of the nervous system of Caenorhabditis elegans. Am J Physiol Cell Physiol 2004; 287:C468-74. [PMID: 15102610 DOI: 10.1152/ajpcell.00182.2003] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In Caenorhabditis elegans, the gene unc-1 controls anesthetic sensitivity and normal locomotion. The protein UNC-1 is a close homolog of the mammalian protein stomatin and is expressed primarily in the nervous system. Genetic studies in C. elegans have shown that the UNC-1 protein interacts with a sodium channel subunit, UNC-8. In humans, absence of stomatin is associated with abnormal sodium and potassium levels in red blood cells. Stomatin also has been postulated to participate in the formation of lipid rafts, which are membrane microdomains associated with protein complexes, cholesterol, and sphingolipids. In this study, we isolated a low-density, detergent-resistant fraction from cell membranes of C. elegans. This fraction contains cholesterol, sphingolipids, and protein consistent with their identification as lipid rafts. We then probed Western blots of protein from the rafts and found that the UNC-1 protein is almost totally restricted to this fraction. The UNC-8 protein is also found in rafts and coimmunoprecipitates UNC-1. A second stomatin-like protein, UNC-24, also affects anesthetic sensitivity, is found in lipid rafts, and regulates UNC-1 distribution. Mutations in the unc-24 gene alter the distribution of UNC-1 in lipid rafts. Each of these mutations alters anesthetic sensitivity in C. elegans. Because lipid rafts contain many of the putative targets of volatile anesthetics, they may represent a novel class of targets for volatile anesthetics.
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Affiliation(s)
- M M Sedensky
- Departments of Anesthesiology and Genetics, University Hospitals and Case Western Reserve University, 11100 Euclid Avenue, Cleveland, OH 44106, USA
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Killian DJ, Hubbard EJA. C. elegans pro-1 activity is required for soma/germline interactions that influence proliferation and differentiation in the germ line. Development 2004; 131:1267-78. [PMID: 14973273 DOI: 10.1242/dev.01002] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Strict spatial and temporal regulation of proliferation and differentiation is essential for proper germline development and often involves soma/germline interactions. In C. elegans, a particularly striking outcome of defective regulation of the proliferation/differentiation pattern is the Pro phenotype in which an ectopic mass of proliferating germ cells occupies the proximal adult germ line, a region normally occupied by gametes. We describe a reduction-of-function mutation in the gene pro-1 that causes a highly penetrant Pro phenotype. The pro-1 mutant Pro phenotype stems from defects in the time and position of the first meiotic entry during early germline development. pro-1(RNAi) produces a loss of somatic gonad structures and concomitant reduction in germline proliferation and gametogenesis. pro-1 encodes a member of a highly conserved subfamily of WD-repeat proteins. pro-1(+) is required in the sheath/spermatheca lineage of the somatic gonad in its role in the proper establishment of the proliferation/differentiation pattern in the germline. Our results provide a handle for further analysis of this soma-to-germline interaction.
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41
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Kayser EB, Hoppel CL, Morgan PG, Sedensky MM. A Mutation in Mitochondrial Complex I Increases Ethanol Sensitivity in Caenorhabditis elegans. Alcohol Clin Exp Res 2003. [DOI: 10.1111/j.1530-0277.2003.tb04394.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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42
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Kayser EB, Hoppel CL, Morgan PG, Sedensky MM. A mutation in mitochondrial complex I increases ethanol sensitivity in Caenorhabditis elegans. Alcohol Clin Exp Res 2003; 27:584-92. [PMID: 12711920 DOI: 10.1097/01.alc.0000060524.62805.d2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
BACKGROUND The gene gas-1 encodes the 49-kDa subunit of complex I of the mitochondrial electron transport chain in Caenorhabditis elegans. A mutation in gas-1 profoundly increases sensitivity to ethanol and decreases complex I-dependent metabolism in mitochondria. METHODS Mitochondria were isolated from wild-type and gas-1 strains of C. elegans. The effects of ethanol on complex I-, II-, and III-dependent oxidative phosphorylation were measured for mitochondria from each strain. Reversibility of the effects of ethanol was determined by measuring oxidative phosphorylation after removal of mitochondria from 1.5 M ethanol. The effects of ethanol on mitochondrial structure were visualized with electron microscopy. RESULTS We found that ethanol inhibited complex I-, II-, and III-dependent oxidative phosphorylation in isolated wild-type mitochondria at concentrations that immobilize intact worms. It is important to note that the inhibitory effects of ethanol on mitochondria from either C. elegans or rat skeletal muscle were reversible even at molar concentrations. Complex I activity was lower in mitochondria from gas-1 animals than in mitochondria from wild-type animals at equal ethanol concentrations. Complex II activity was higher in gas-1 than in wild-type mitochondria at all concentrations of ethanol. No difference was seen between the strains in the sensitivity of complex III to ethanol. CONCLUSIONS The difference in ethanol sensitivities between gas-1 and wild-type nematodes results solely from altered complex I function. At the respective concentrations of ethanol that immobilize whole animals, mitochondria from each strain of worms displayed identical rates of complex I-dependent state 3 respiration. We conclude that a threshold value of complex I activity controls the transition from mobility to immobility of C. elegans.
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43
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Affiliation(s)
- H A Nash
- Laboratory of Molecular Biology, National Institute of Mental Health, Building 36/Room 1B08, 9000 Rockville Pike, Bethesda, MD 20892-4034, USA
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44
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Campbell JL, Nash HA. Volatile general anesthetics reveal a neurobiological role for the white and brown genes of Drosophila melanogaster. JOURNAL OF NEUROBIOLOGY 2001; 49:339-49. [PMID: 11745669 DOI: 10.1002/neu.10009] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Molecular and cellular evidence argues that a heterodimer between two ABC transporters, the White protein and the Brown protein, is responsible for pumping guanine into pigment-synthesizing cells of the fruit fly, Drosophila melanogaster. Previous studies have not detected White or Brown outside pigment-synthesizing cells nor have behavioral effects of null mutants been reported, other than those that are visually dependent. Nevertheless, we show here that exposure to the volatile general anesthetic (VGA) enflurane reveals a difference in neuromuscular performance between wild-type flies and those that carry a null allele in either the white or brown gene. Specifically, in a test of climbing ability, w1118 or bw1 flies are much less affected by enflurane than are congenic controls. Altered anesthetic sensitivity is still observed when visual cues are reduced or eliminated, arguing that white and brown contribute to neural function outside the eye. This hypothesis is supported by the detection of white message in heads of flies that are genetically altered so as to lack pigment-producing cells. The w1118 or bw1 mutations also alter the response to a second VGA, halothane, albeit somewhat differently. Under some conditions, the combination of w1118 with another mutation that affects anesthesia leads to a drastically altered phenotype. We consider several ways by which diminished transport of guanine could influence neural function and anesthetic sensitivity.
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Affiliation(s)
- J L Campbell
- Laboratory of Molecular Biology, National Institute of Mental Health, Bethesda, Maryland 20892-4034, USA
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45
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Kayser EB, Morgan PG, Hoppel CL, Sedensky MM. Mitochondrial expression and function of GAS-1 in Caenorhabditis elegans. J Biol Chem 2001; 276:20551-8. [PMID: 11278828 DOI: 10.1074/jbc.m011066200] [Citation(s) in RCA: 125] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A mutation in the gene gas-1 alters sensitivity to volatile anesthetics, fecundity, and life span in the nematode Caenorhabditis elegans. gas-1 encodes a close homologue of the 49-kDa iron protein subunit of Complex I of the mitochondrial electron transport chain from bovine heart. gas-1 is widely expressed in the nematode neuromuscular system and in a subcellular pattern consistent with that of a mitochondrial protein. Pharmacological studies indicate that gas-1 functions partially via presynaptic effects. In addition, a mutation in the gas-1 gene profoundly decreases Complex I-dependent metabolism in mitochondria as measured by rates of both oxidative phosphorylation and electron transport. An increase in Complex II-dependent metabolism also is seen in mitochondria from gas-1 animals. There is no apparent alteration in physical structure in mitochondria from gas-1 nematodes compared with those from wild type. These data indicate that gas-1 is the major 49-kDa protein of complex I and that the GAS-1 protein is critical to mitochondrial function in C. elegans. They also reveal the importance of mitochondrial function in determining not only aging and life span, but also anesthetic sensitivity, in this model organism.
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Affiliation(s)
- E B Kayser
- Department of Anesthesiology, University Hospitals, Case Western Reserve University, Cleveland, Ohio 44106, USA
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46
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Abstract
Connexins were first identified in the 1970s as the molecular components of vertebrate gap junctions. Since then a large literature has accumulated on the cell and molecular biology of this multi-gene family culminating recently in the findings that connexin mutations are implicated in a variety of human diseases. Over two decades, the terms "connexin" and "gap junction" had become almost synonymous. In the last few years a second family of gap-junction genes, the innexins, has emerged. These have been shown to form intercellular channels in genetically tractable invertebrate organisms such as Drosophila melanogaster and Caenorhabditis elegans. The completed genomic sequences for the fly and worm allow identification of the full complement of innexin genes in these two organisms and provide valuable resources for genetic analyses of gap junction function.
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Affiliation(s)
- P Phelan
- Department of Biosciences, University of Kent, Canterbury CT2 7NJ, UK.
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47
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Sedensky MM, Siefker JM, Morgan PG. Model organisms: new insights into ion channel and transporter function. Stomatin homologues interact in Caenorhabditis elegans. Am J Physiol Cell Physiol 2001; 280:C1340-8. [PMID: 11287347 DOI: 10.1152/ajpcell.2001.280.5.c1340] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In C. elegans the protein UNC-1 is a major determinant of anesthetic sensitivity and is a close homologue of the mammalian protein stomatin. In humans stomatin is missing from erythrocyte membranes in the hemolytic disease overhydrated hereditary stomatocytosis, despite an apparently normal stomatin gene. Overhydrated hereditary stomatocytosis is characterized by alteration of the normal transmembrane gradients of sodium and potassium. Stomatin has been shown to interact genetically with sodium channels. It is also postulated that stomatin is important in the organization of lipid rafts. We demonstrate here that antibodies against UNC-1 stain the major nerve tracts of Caenorhabditis elegans, with very intense staining of the nerve ring. We also found that a gene encoding a stomatin-like protein, UNC-24, affects anesthetic sensitivity and is genetically epistatic to unc-1. In the absence of UNC-24, the staining of the nerve ring by anti-UNC-1 is abolished, despite normal transcriptional levels of the unc-1 mRNA. Western blots indicate that UNC-24 probably affects the stability of the UNC-1 protein. UNC-24 may therefore be necessary for the correct placement of UNC-1 in the cell membrane and organization of lipid rafts.
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Affiliation(s)
- M M Sedensky
- Department of Anesthesiology, University Hospitals and Case Western Reserve University, Cleveland, Ohio 44106, USA
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48
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Madhavan MC, Kumar RA, Krishnan KS. Genetics of anesthetic response: autosomal mutations that render Drosophila resistant to halothane. Pharmacol Biochem Behav 2000; 67:749-57. [PMID: 11166065 DOI: 10.1016/s0091-3057(00)00420-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Molecular mechanisms of anesthetic action are poorly understood. Genetic approaches to investigate mechanisms of anesthesia, although sparse and rather new, are turning out to be informative and add a new perspective. Before beginning a systematic investigation of anesthesia by this approach, it is necessary to have at hand a large collection of mutations in different loci that alter anesthetic response. We report here the isolation and characterization of six mutant autosomal lines that show a decreased sensitivity to the inhalation of anesthetic halothane. Two of these mutations, Omar(82) and Qajjem(211) are shown to map to separate loci on the third chromosome.
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Affiliation(s)
- M C Madhavan
- Department of Biological Sciences, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400 005, India
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49
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Abstract
The neuronal calcium sensor (NCS) proteins belong to a subfamily of the EF-hand calcium binding proteins. These proteins are primarily expressed in the nervous system and currently include more than 20 members across species [Nakayama et al., J Mol Evol 34:416-448, 1992]. Two homologues of the ncs genes, Ce-ncs-1 and Ce-ncs-2, have recently been identified in the nematode C. elegans. Here we report the cDNA sequence of a third C. elegans ncs homologue, Ce-ncs-3. We demonstrate that a null mutation in this gene caused by a large deletion in the locus does not confer a visible phenotype in C. elegans. This, in addition to the strong homology between Ce-NCS-3 and the other C. elegans NCS proteins, may indicate functional redundancy between the three genes.
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Rajaram S, Spangler TL, Sedensky MM, Morgan PG. A stomatin and a degenerin interact to control anesthetic sensitivity in Caenorhabditis elegans. Genetics 1999; 153:1673-82. [PMID: 10581275 PMCID: PMC1460880 DOI: 10.1093/genetics/153.4.1673] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The mechanism of action of volatile anesthetics is unknown. In Caenorhabditis elegans, mutations in the gene unc-1 alter anesthetic sensitivity. The protein UNC-1 is a close homologue of the mammalian protein stomatin. Mammalian stomatin is thought to interact with an as-yet-unknown ion channel to control sodium flux. Using both reporter constructs and translational fusion constructs for UNC-1 and green fluorescent protein (GFP), we have shown that UNC-1 is expressed primarily within the nervous system. The expression pattern of UNC-1 is similar to that of UNC-8, a sodium channel homologue. We examined the interaction of multiple alleles of unc-1 and unc-8 with each other and with other genes affecting anesthetic sensitivity. The data indicate that the protein products of these genes interact, and that an UNC-1/UNC-8 complex is a possible anesthetic target. We propose that membrane-associated protein complexes may represent a general target for volatile anesthetics.
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Affiliation(s)
- S Rajaram
- Departments of Genetics and Anesthesiology, Case Western Reserve University, School of Medicine and University Hospitals of Cleveland, Cleveland, Ohio 44106, USA
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