1
|
Alcohol. Alcohol 2021. [DOI: 10.1016/b978-0-12-816793-9.00001-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
|
2
|
Cui C, Koob GF. Titrating Tipsy Targets: The Neurobiology of Low-Dose Alcohol. Trends Pharmacol Sci 2017; 38:556-568. [PMID: 28372826 DOI: 10.1016/j.tips.2017.03.002] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2017] [Revised: 03/04/2017] [Accepted: 03/06/2017] [Indexed: 11/30/2022]
Abstract
Limited attention has been given to our understanding of how the brain responds to low-dose alcohol (ethanol) and what molecular and cellular targets mediate these effects. Even at concentrations lower than 10mM (0.046 g% blood alcohol concentration, BAC), below the legal driving limit in the USA (BAC 0.08 g%), alcohol impacts brain function and behavior. Understanding what molecular and cellular targets mediate the initial effects of alcohol and subsequent neuroplasticity could provide a better understanding of vulnerability or resilience to developing alcohol use disorders. We review here what is known about the neurobiology of low-dose alcohol, provide insights into potential molecular targets, and discuss future directions and challenges in further defining targets of low-dose alcohol at the molecular, cellular, and circuitry levels.
Collapse
Affiliation(s)
- Changhai Cui
- National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, MD 20892, USA
| | - George F Koob
- National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, MD 20892, USA.
| |
Collapse
|
3
|
Burgos CF, Muñoz B, Guzman L, Aguayo LG. Ethanol effects on glycinergic transmission: From molecular pharmacology to behavior responses. Pharmacol Res 2015; 101:18-29. [PMID: 26158502 DOI: 10.1016/j.phrs.2015.07.002] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/16/2015] [Revised: 07/01/2015] [Accepted: 07/01/2015] [Indexed: 10/23/2022]
Abstract
It is well accepted that ethanol is able to produce major health and economic problems associated to its abuse. Because of its intoxicating and addictive properties, it is necessary to analyze its effect in the central nervous system. However, we are only now learning about the mechanisms controlling the modification of important membrane proteins such as ligand-activated ion channels by ethanol. Furthermore, only recently are these effects being correlated to behavioral changes. Current studies show that the glycine receptor (GlyR) is a susceptible target for low concentrations of ethanol (5-40mM). GlyRs are relevant for the effects of ethanol because they are found in the spinal cord and brain stem where they primarily express the α1 subunit. More recently, the presence of GlyRs was described in higher regions, such as the hippocampus and nucleus accumbens, with a prevalence of α2/α3 subunits. Here, we review data on the following aspects of ethanol effects on GlyRs: (1) direct interaction of ethanol with amino acids in the extracellular or transmembrane domains, and indirect mechanisms through the activation of signal transduction pathways; (2) analysis of α2 and α3 subunits having different sensitivities to ethanol which allows the identification of structural requirements for ethanol modulation present in the intracellular domain and C-terminal region; (3) Genetically modified knock-in mice for α1 GlyRs that have an impaired interaction with G protein and demonstrate reduced ethanol sensitivity without changes in glycinergic transmission; and (4) GlyRs as potential therapeutic targets.
Collapse
Affiliation(s)
- Carlos F Burgos
- Laboratory of Neurophysiology, Department of Physiology, University of Concepción, Chile
| | - Braulio Muñoz
- Laboratory of Neurophysiology, Department of Physiology, University of Concepción, Chile
| | - Leonardo Guzman
- Laboratory of Molecular Neurobiology, Department of Physiology, University of Concepción, Chile
| | - Luis G Aguayo
- Laboratory of Neurophysiology, Department of Physiology, University of Concepción, Chile.
| |
Collapse
|
4
|
Mariqueo TA, Agurto A, Muñoz B, San Martin L, Coronado C, Fernández-Pérez EJ, Murath P, Sánchez A, Homanics GE, Aguayo LG. Effects of ethanol on glycinergic synaptic currents in mouse spinal cord neurons. J Neurophysiol 2014; 111:1940-8. [PMID: 24572089 DOI: 10.1152/jn.00789.2013] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Ethanol increased the frequency of miniature glycinergic currents [miniature inhibitory postsynaptic currents (mIPSCs)] in cultured spinal neurons. This effect was dependent on intracellular calcium augmentation, since preincubation with BAPTA (an intracellular calcium chelator) or thapsigargin [a sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA) pump inhibitor] significantly attenuated this effect. Similarly, U73122 (a phospholipase C inhibitor) or 2-aminoethoxydiphenyl borate [2-APB, an inositol 1,4,5-trisphosphate (IP₃) receptor (IP3R) inhibitor] reduced this effect. Block of ethanol action was also achieved after preincubation with Rp-cAMPS, inhibitor of the adenylate cyclase (AC)/PKA signaling pathway. These data suggest that there is a convergence at the level of IP₃R that accounts for presynaptic ethanol effects. At the postsynaptic level, ethanol increased the decay time constant of mIPSCs in a group of neurons (30 ± 10% above control, n = 13/26 cells). On the other hand, the currents activated by exogenously applied glycine were consistently potentiated (55 ± 10% above control, n = 11/12 cells), which suggests that ethanol modulates synaptic and nonsynaptic glycine receptors (GlyRs) in a different fashion. Supporting the role of G protein modulation on ethanol responses, we found that a nonhydrolyzable GTP analog [guanosine 5'-O-(3-thiotriphosphate) (GTPγS)] increased the decay time constant in ∼50% of the neurons (28 ± 12%, n = 11/19 cells) but potentiated the glycine-activated Cl(-) current in most of the neurons examined (83 ± 29%, n = 7/9 cells). In addition, confocal microscopy showed that α1-containing GlyRs colocalized with Gβ and Piccolo (a presynaptic cytomatrix protein) in ∼40% of synaptic receptor clusters, suggesting that colocalization of Gβγ and GlyRs might account for the difference in ethanol sensitivity at the postsynaptic level.
Collapse
Affiliation(s)
- Trinidad A Mariqueo
- Department of Physiology-Laboratory of Neurophysiology, University of Concepción, Concepción, Chile; PhD Program in Pharmacology, University of Chile, Santiago, Chile; and
| | - Adolfo Agurto
- Department of Physiology-Laboratory of Neurophysiology, University of Concepción, Concepción, Chile
| | - Braulio Muñoz
- Department of Physiology-Laboratory of Neurophysiology, University of Concepción, Concepción, Chile
| | - Loreto San Martin
- Department of Physiology-Laboratory of Neurophysiology, University of Concepción, Concepción, Chile
| | - Cesar Coronado
- Department of Physiology-Laboratory of Neurophysiology, University of Concepción, Concepción, Chile
| | | | - Pablo Murath
- Department of Physiology-Laboratory of Neurophysiology, University of Concepción, Concepción, Chile
| | - Andrea Sánchez
- Department of Physiology-Laboratory of Neurophysiology, University of Concepción, Concepción, Chile
| | - Gregg E Homanics
- Department of Anesthesiology and Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Luis G Aguayo
- Department of Physiology-Laboratory of Neurophysiology, University of Concepción, Concepción, Chile;
| |
Collapse
|
5
|
Pamenter ME, Powell FL. Signalling mechanisms of long term facilitation of breathing with intermittent hypoxia. F1000PRIME REPORTS 2013; 5:23. [PMID: 23864930 PMCID: PMC3702218 DOI: 10.12703/p5-23] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Intermittent hypoxia causes long-term facilitation (LTF) of respiratory motor nerve activity and ventilation, which manifests as a persistent increase over the normoxic baseline for an hour or more after the acute hypoxic ventilatory response. LTF is likely involved in sleep apnea, but its exact role is uncertain. Previously, LTF was defined as a serotonergic mechanism, but new evidence shows that multiple signaling pathways can elicit LTF. This raises new questions about the interactions between signaling pathways in different time domains of the hypoxic ventilatory response, which can no longer be defined simply in terms of neurochemical mechanisms.
Collapse
Affiliation(s)
- Matthew E Pamenter
- Physiology Division, Department of Medicine, University of California San DiegoLa Jolla, CA 92092-0623USA
- Department of Zoology, University of British ColumbiaVancouver, BC V6T 1Z4Canada
| | - Frank L Powell
- Physiology Division, Department of Medicine, University of California San DiegoLa Jolla, CA 92092-0623USA
| |
Collapse
|
6
|
Tobar-Rubin R, Sultan D, Janevska D, Turcic K, Carroll J, Ooms L, Pals-Rylaarsdam R. Intragenic suppression of a constitutively active allele of Gsα associated with McCune-Albright syndrome. J Mol Endocrinol 2013; 50:193-201. [PMID: 23288949 PMCID: PMC3836019 DOI: 10.1530/jme-12-0087] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
McCune-Albright syndrome (MAS) is a human genetic disorder caused by a mutation that constitutively activates the G(s)α subunit by abolishing GTP hydrolysis. MAS patients suffer from a range of endocrinopathies as well as polyostotic fibrous dysplasia of bone. We previously identified an intragenic suppressor of the MAS mutation in a yeast system, which substituted two residues in the GTP-binding site of Gpa1: L318P and D319V to suppress the constitutive activity of an R297H mutation, corresponding to the human F222P, D223V, and R201H mutations respectively. To extend these studies, the human GNAS gene was subjected to site-directed mutagenesis. Constructs expressing the MAS mutation (R201H), the MAS mutation plus the mutations homologous to the yeast suppressors (R201H, F222P/D223V), or the yeast suppressor mutation alone (F222P/D223V) were transfected into HEK293 cells, and basal and receptor-stimulated cAMP levels were measured. Expression of R201H increased the basal cAMP levels and decreased the EC(50) for hormone-stimulated cAMP production. These effects were dependent on the amount of R201H protein expressed. R201H, F222P/D223V abolished the constitutive activity of the MAS mutation and caused responses to hormone that were not different from those measured in cells expressing WT G(s)α. Interestingly, F222P/D223V behaved similar to R201H in causing increases in basal cAMP production, thus demonstrating constitutive activity. Substitution of another acidic (E) or polar (N, T, and G) amino acid at position 223 caused no suppression of R201H activity, while substitution of a second nonpolar amino acid (A) at this position partially suppressed, and the larger polar I residue completely suppressed the effects of R201H.
Collapse
Affiliation(s)
- Raquel Tobar-Rubin
- Department of Biological Science, Benedictine University, Lisle, Illinois 60532, USA
| | | | | | | | | | | | | |
Collapse
|
7
|
McCracken LM, Blednov YA, Trudell JR, Benavidez JM, Betz H, Harris RA. Mutation of a zinc-binding residue in the glycine receptor α1 subunit changes ethanol sensitivity in vitro and alcohol consumption in vivo. J Pharmacol Exp Ther 2012; 344:489-500. [PMID: 23230213 DOI: 10.1124/jpet.112.197707] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Ethanol is a widely used drug, yet an understanding of its sites and mechanisms of action remains incomplete. Among the protein targets of ethanol are glycine receptors (GlyRs), which are potentiated by millimolar concentrations of ethanol. In addition, zinc ions also modulate GlyR function, and recent evidence suggests that physiologic concentrations of zinc enhance ethanol potentiation of GlyRs. Here, we first built a homology model of a zinc-bound GlyR using the D80 position as a coordination site for a zinc ion. Next, we investigated in vitro the effects of zinc on ethanol action at recombinant wild-type (WT) and mutant α1 GlyRs containing the D80A substitution, which eliminates zinc potentiation. At D80A GlyRs, the effects of 50 and 200 mM ethanol were reduced as compared with WT receptors. Also, in contrast to what was seen with WT GlyRs, neither adding nor chelating zinc changed the magnitude of ethanol enhancement of mutant D80A receptors. Next, we evaluated the in vivo effects of the D80A substitution by using heterozygous Glra1(D80A) knock-in (KI) mice. The KI mice showed decreased ethanol consumption and preference, and they displayed increased startle responses compared with their WT littermates. Other behavioral tests, including ethanol-induced motor incoordination and strychnine-induced convulsions, revealed no differences between the KI and WT mice. Together, our findings indicate that zinc is critical in determining the effects of ethanol at GlyRs and suggest that zinc binding at the D80 position may be important for mediating some of the behavioral effects of ethanol action at GlyRs.
Collapse
Affiliation(s)
- Lindsay M McCracken
- Waggoner Center for Alcohol and Addiction Research, The University of Texas at Austin, Austin, Texas, USA
| | | | | | | | | | | |
Collapse
|
8
|
Murail S, Howard RJ, Broemstrup T, Bertaccini EJ, Harris RA, Trudell JR, Lindahl E. Molecular mechanism for the dual alcohol modulation of Cys-loop receptors. PLoS Comput Biol 2012; 8:e1002710. [PMID: 23055913 PMCID: PMC3464191 DOI: 10.1371/journal.pcbi.1002710] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2012] [Accepted: 08/15/2012] [Indexed: 11/29/2022] Open
Abstract
Cys-loop receptors constitute a superfamily of pentameric ligand-gated ion channels (pLGICs), including receptors for acetylcholine, serotonin, glycine and γ-aminobutyric acid. Several bacterial homologues have been identified that are excellent models for understanding allosteric binding of alcohols and anesthetics in human Cys-loop receptors. Recently, we showed that a single point mutation on a prokaryotic homologue (GLIC) could transform it from a channel weakly potentiated by ethanol into a highly ethanol-sensitive channel. Here, we have employed molecular simulations to study ethanol binding to GLIC, and to elucidate the role of the ethanol-enhancing mutation in GLIC modulation. By performing 1-µs simulations with and without ethanol on wild-type and mutated GLIC, we observed spontaneous binding in both intra-subunit and inter-subunit transmembrane cavities. In contrast to the glycine receptor GlyR, in which we previously observed ethanol binding primarily in an inter-subunit cavity, ethanol primarily occupied an intra-subunit cavity in wild-type GLIC. However, the highly ethanol-sensitive GLIC mutation significantly enhanced ethanol binding in the inter-subunit cavity. These results demonstrate dramatic effects of the F(14′)A mutation on the distribution of ligands, and are consistent with a two-site model of pLGIC inhibition and potentiation. Communication from one nerve cell to the next is an essential process for brain and muscle function. Nerve impulses result in release of transmitter molecules from one cell that bind to receptors on the next cell. Transmitter binding opens a pore in each receptor and ions flow across the membrane, leading to either enhancement or inhibition of new nerve impulses. These receptors are modulated by numerous drugs, including alcohols and anesthetics; identifying the precise location of modulator binding is critical for drug development. We have used computer simulation methods to model alcohol diffusion and binding to a receptor. By modifying a single residue in the receptor, we were able to move the location of the binding site and dramatically alter alcohol modulation, which supports a model with two separate binding sites for enhancement and inhibition in this family of receptors.
Collapse
Affiliation(s)
- Samuel Murail
- Science for Life Laboratory, KTH Royal Institute of Technology & Stockholm University, Stockholm, Sweden
- Center for Biomembrane Research, Department of Biochemistry & Biophysics, Stockholm University, Stockholm, Sweden
| | - Rebecca J. Howard
- Waggoner Center for Alcohol and Addiction Research, The University of Texas at Austin, Austin, Texas, United States of America
| | - Torben Broemstrup
- Science for Life Laboratory, KTH Royal Institute of Technology & Stockholm University, Stockholm, Sweden
- Center for Biomembrane Research, Department of Biochemistry & Biophysics, Stockholm University, Stockholm, Sweden
| | - Edward J. Bertaccini
- Department of Anesthesia, Palo Alto Veterans Affairs Health Care System, Palo Alto, California, United States of America
- Department of Anesthesia and Beckman Program for Molecular and Genetic Medicine, Stanford University School of Medicine, Stanford, United States of America
| | - R. Adron Harris
- Waggoner Center for Alcohol and Addiction Research, The University of Texas at Austin, Austin, Texas, United States of America
| | - James R. Trudell
- Department of Anesthesia and Beckman Program for Molecular and Genetic Medicine, Stanford University School of Medicine, Stanford, United States of America
| | - Erik Lindahl
- Science for Life Laboratory, KTH Royal Institute of Technology & Stockholm University, Stockholm, Sweden
- Center for Biomembrane Research, Department of Biochemistry & Biophysics, Stockholm University, Stockholm, Sweden
- * E-mail:
| |
Collapse
|