1
|
High-pressure crystallography shows noble gas intervention into protein-lipid interaction and suggests a model for anaesthetic action. Commun Biol 2022; 5:360. [PMID: 35422073 PMCID: PMC9010423 DOI: 10.1038/s42003-022-03233-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2021] [Accepted: 02/22/2022] [Indexed: 11/09/2022] Open
Abstract
In this work we examine how small hydrophobic molecules such as inert gases interact with membrane proteins (MPs) at a molecular level. High pressure atmospheres of argon and krypton were used to produce noble gas derivatives of crystals of three well studied MPs (two different proton pumps and a sodium light-driven ion pump). The structures obtained using X-ray crystallography showed that the vast majority of argon and krypton binding sites were located on the outer hydrophobic surface of the MPs – a surface usually accommodating hydrophobic chains of annular lipids (which are known structural and functional determinants for MPs). In conformity with these results, supplementary in silico molecular dynamics (MD) analysis predicted even greater numbers of argon and krypton binding positions on MP surface within the bilayer. These results indicate a potential importance of such interactions, particularly as related to the phenomenon of noble gas-induced anaesthesia. Noble gases are known to interact with proteins and can be good anaesthetics in hyperbaric conditions. This study identifies argon and krypton binding sites on membrane proteins and proposes as a hypothesis that noble gases, by altering protein/lipid contacts, may affect protein function.
Collapse
|
2
|
Comert F, Greenwood A, Maramba J, Acevedo R, Lucas L, Kulasinghe T, Cairns LS, Wen Y, Fu R, Hammer J, Blazyk J, Sukharev S, Cotten ML, Mihailescu M. The host-defense peptide piscidin P1 reorganizes lipid domains in membranes and decreases activation energies in mechanosensitive ion channels. J Biol Chem 2019; 294:18557-18570. [PMID: 31619519 PMCID: PMC6901303 DOI: 10.1074/jbc.ra119.010232] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2019] [Revised: 10/01/2019] [Indexed: 11/06/2022] Open
Abstract
The host-defense peptide (HDP) piscidin 1 (P1), isolated from the mast cells of striped bass, has potent activities against bacteria, viruses, fungi, and cancer cells and can also modulate the activity of membrane receptors. Given its broad pharmacological potential, here we used several approaches to better understand its interactions with multicomponent bilayers representing models of bacterial (phosphatidylethanolamine (PE)/phosphatidylglycerol) and mammalian (phosphatidylcholine/cholesterol (PC/Chol)) membranes. Using solid-state NMR, we solved the structure of P1 bound to PC/Chol and compared it with that of P3, a less potent homolog. The comparison disclosed that although both peptides are interfacially bound and α-helical, they differ in bilayer orientations and depths of insertion, and these differences depend on bilayer composition. Although Chol is thought to make mammalian membranes less susceptible to HDP-mediated destabilization, we found that Chol does not affect the permeabilization effects of P1. X-ray diffraction experiments revealed that both piscidins produce a demixing effect in PC/Chol membranes by increasing the fraction of the Chol-depleted phase. Furthermore, P1 increased the temperature required for the lamellar-to-hexagonal phase transition in PE bilayers, suggesting that it imposes positive membrane curvature. Patch-clamp measurements on the inner Escherichia coli membrane showed that P1 and P3, at concentrations sufficient for antimicrobial activity, substantially decrease the activating tension for bacterial mechanosensitive channels. This indicated that piscidins can cause lipid redistribution and restructuring in the microenvironment near proteins. We conclude that the mechanism of piscidin's antimicrobial activity extends beyond simple membrane destabilization, helping to rationalize its broader spectrum of pharmacological effects.
Collapse
Affiliation(s)
- Fatih Comert
- Institute for Bioscience and Biotechnology Research, Rockville, Maryland 20850
| | - Alexander Greenwood
- Department of Applied Science, William and Mary, Williamsburg, Virginia 23185
| | - Joseph Maramba
- Biology Department, University of Maryland, College Park, Maryland 20742
| | - Roderico Acevedo
- Institute for Bioscience and Biotechnology Research, Rockville, Maryland 20850
| | - Laura Lucas
- Institute for Bioscience and Biotechnology Research, Rockville, Maryland 20850
| | - Thulasi Kulasinghe
- Institute for Bioscience and Biotechnology Research, Rockville, Maryland 20850
| | - Leah S Cairns
- Department of Biochemistry and Molecular Biology, The Johns Hopkins University, Baltimore, Maryland 21205
| | - Yi Wen
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York 14853
| | - Riqiang Fu
- National High Magnetic Field Laboratory, Tallahassee, Florida 32310
| | - Janet Hammer
- Department of Biomedical Sciences, Ohio University, Athens, Ohio 45701
| | - Jack Blazyk
- Department of Biomedical Sciences, Ohio University, Athens, Ohio 45701
| | - Sergei Sukharev
- Biology Department, University of Maryland, College Park, Maryland 20742
| | - Myriam L Cotten
- Department of Applied Science, William and Mary, Williamsburg, Virginia 23185.
| | - Mihaela Mihailescu
- Institute for Bioscience and Biotechnology Research, Rockville, Maryland 20850.
| |
Collapse
|
3
|
Jerusalem A, Al-Rekabi Z, Chen H, Ercole A, Malboubi M, Tamayo-Elizalde M, Verhagen L, Contera S. Electrophysiological-mechanical coupling in the neuronal membrane and its role in ultrasound neuromodulation and general anaesthesia. Acta Biomater 2019; 97:116-140. [PMID: 31357005 DOI: 10.1016/j.actbio.2019.07.041] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2019] [Revised: 07/20/2019] [Accepted: 07/23/2019] [Indexed: 01/23/2023]
Abstract
The current understanding of the role of the cell membrane is in a state of flux. Recent experiments show that conventional models, considering only electrophysiological properties of a passive membrane, are incomplete. The neuronal membrane is an active structure with mechanical properties that modulate electrophysiology. Protein transport, lipid bilayer phase, membrane pressure and stiffness can all influence membrane capacitance and action potential propagation. A mounting body of evidence indicates that neuronal mechanics and electrophysiology are coupled, and together shape the membrane potential in tight coordination with other physical properties. In this review, we summarise recent updates concerning electrophysiological-mechanical coupling in neuronal function. In particular, we aim at making the link with two relevant yet often disconnected fields with strong clinical potential: the use of mechanical vibrations-ultrasound-to alter the electrophysiogical state of neurons, e.g., in neuromodulation, and the theories attempting to explain the action of general anaesthetics. STATEMENT OF SIGNIFICANCE: General anaesthetics revolutionised medical practice; now an apparently unrelated technique, ultrasound neuromodulation-aimed at controlling neuronal activity by means of ultrasound-is poised to achieve a similar level of impact. While both technologies are known to alter the electrophysiology of neurons, the way they achieve it is still largely unknown. In this review, we argue that in order to explain their mechanisms/effects, the neuronal membrane must be considered as a coupled mechano-electrophysiological system that consists of multiple physical processes occurring concurrently and collaboratively, as opposed to sequentially and independently. In this framework the behaviour of the cell membrane is not the result of stereotypical mechanisms in isolation but instead emerges from the integrative behaviour of a complexly coupled multiphysics system.
Collapse
Affiliation(s)
- Antoine Jerusalem
- Department of Engineering Science, University of Oxford, Parks Road, Oxford OX1 3PJ, UK.
| | - Zeinab Al-Rekabi
- Department of Physics, University of Oxford, Parks Road, Oxford OX1 3PU, UK
| | - Haoyu Chen
- Department of Engineering Science, University of Oxford, Parks Road, Oxford OX1 3PJ, UK
| | - Ari Ercole
- Division of Anaesthesia, University of Cambridge, Addenbrooke's Hospital, Hills Road, Cambridge CB2 0QQ, UK
| | - Majid Malboubi
- Department of Engineering Science, University of Oxford, Parks Road, Oxford OX1 3PJ, UK
| | - Miren Tamayo-Elizalde
- Department of Engineering Science, University of Oxford, Parks Road, Oxford OX1 3PJ, UK
| | - Lennart Verhagen
- Wellcome Centre for Integrative Neuroimaging (WIN), Department of Experimental Psychology, University of Oxford, Oxford OX1 3TA, UK; WIN, Centre for Functional MRI of the Brain, Nuffield Department of Clinical Neurosciences, John Radcliffe Hospital, University of Oxford, Oxford OX3 9DU, UK
| | - Sonia Contera
- Department of Physics, University of Oxford, Parks Road, Oxford OX1 3PU, UK.
| |
Collapse
|
4
|
Effects of gabergic phenols on the dynamic and structure of lipid bilayers: A molecular dynamic simulation approach. PLoS One 2019; 14:e0218042. [PMID: 31237897 PMCID: PMC6592534 DOI: 10.1371/journal.pone.0218042] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2019] [Accepted: 05/24/2019] [Indexed: 11/19/2022] Open
Abstract
γ-Aminobutyric acid (GABA) is the major inhibitory neurotransmitter in the vertebrate and invertebrate nervous system. GABAA receptors are activated by GABA and their agonists, and modulated by a wide variety of recognized drugs, including barbiturates, anesthetics, and benzodiazepines. The phenols propofol, thymol, chlorothymol, carvacrol and eugenol act as positive allosteric modulators on GABAA-R receptor. These GABAergic phenols interact with the lipid membrane, therefore, their anesthetic activity could be the combined result of their specific activity (with receptor proteins) as well as nonspecific interactions (with surrounding lipid molecules) modulating the supramolecular organization of the receptor environment. Therefore, we aimed to contribute to a description of the molecular events that occur at the membrane level as part of the mechanism of general anesthesia, using a molecular dynamic simulation approach. Equilibrium molecular dynamics simulations indicate that the presence of GABAergic phenols in a DPPC bilayer orders lipid acyl chains for carbons near the interface and their effect is not significant at the bilayer center. Phenols interacts with the polar interface of phospholipid bilayer, particularly forming hydrogen bonds with the glycerol and phosphate group. Also, potential of mean force calculations using umbrella sampling show that propofol partition is mainly enthalpic driven at the polar region and entropic driven at the hydrocarbon chains. Finally, potential of mean force indicates that propofol partition into a gel DPPC phase is not favorable. Our in silico results were positively contrasted with previous experimental data.
Collapse
|
5
|
Kimchi O, Veatch SL, Machta BB. Ion channels can be allosterically regulated by membrane domains near a de-mixing critical point. J Gen Physiol 2018; 150:1769-1777. [PMID: 30455180 PMCID: PMC6279359 DOI: 10.1085/jgp.201711900] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2017] [Revised: 08/24/2018] [Accepted: 10/25/2018] [Indexed: 12/17/2022] Open
Abstract
Ion channels are embedded in the plasma membrane, a compositionally diverse two-dimensional liquid that has the potential to exert profound influence on their function. Recent experiments suggest that this membrane is poised close to an Ising critical point, below which cell-derived plasma membrane vesicles phase separate into coexisting liquid phases. Related critical points have long been the focus of study in simplified physical systems, but their potential roles in biological function have been underexplored. Here we apply both exact and stochastic techniques to the lattice Ising model to study several ramifications of proximity to criticality for idealized lattice channels, whose function is coupled through boundary interactions to critical fluctuations of membrane composition. Because of diverging susceptibilities of system properties to thermodynamic parameters near a critical point, such a lattice channel's activity becomes strongly influenced by perturbations that affect the critical temperature of the underlying Ising model. In addition, its kinetics acquire a range of time scales from its surrounding membrane, naturally leading to non-Markovian dynamics. Our model may help to unify existing experimental results relating the effects of small-molecule perturbations on membrane properties and ion channel function. We also suggest ways in which the role of this mechanism in regulating real ion channels and other membrane-bound proteins could be tested in the future.
Collapse
Affiliation(s)
- Ofer Kimchi
- Department of Physics, Princeton University, Princeton, NJ.,Harvard Graduate Program in Biophysics, Harvard University, Cambridge, MA
| | - Sarah L Veatch
- Department of Biophysics, University of Michigan, Ann Arbor, MI
| | - Benjamin B Machta
- Department of Physics, Princeton University, Princeton, NJ .,Lewis-Sigler Institute, Princeton University, Princeton, NJ.,Department of Physics, Yale University, New Haven, CT.,Systems Biology Institute, Yale University, West Haven, CT
| |
Collapse
|
6
|
Gerstle Z, Desai R, Veatch SL. Giant Plasma Membrane Vesicles: An Experimental Tool for Probing the Effects of Drugs and Other Conditions on Membrane Domain Stability. Methods Enzymol 2018; 603:129-150. [PMID: 29673522 DOI: 10.1016/bs.mie.2018.02.007] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Giant plasma membrane vesicles (GPMVs) are isolated directly from living cells and provide an alternative to vesicles constructed of synthetic or purified lipids as an experimental model system for use in a wide range of assays. GPMVs capture much of the compositional protein and lipid complexity of intact cell plasma membranes, are filled with cytoplasm, and are free from contamination with membranes from internal organelles. GPMVs often exhibit a miscibility transition below the growth temperature of their parent cells. GPMVs labeled with a fluorescent protein or lipid analog appear uniform on the micron-scale when imaged above the miscibility transition temperature, and separate into coexisting liquid domains with differing membrane compositions and physical properties below this temperature. The presence of this miscibility transition in isolated GPMVs suggests that a similar phase-like heterogeneity occurs in intact plasma membranes under growth conditions, albeit on smaller length scales. In this context, GPMVs provide a simple and controlled experimental system to explore how drugs and other environmental conditions alter the composition and stability of phase-like domains in intact cell membranes. This chapter describes methods to generate and isolate GPMVs from adherent mammalian cells and to interrogate their miscibility transition temperatures using fluorescence microscopy.
Collapse
Affiliation(s)
- Zoe Gerstle
- University of Michigan, Ann Arbor, MI, United States
| | - Rohan Desai
- University of Michigan, Ann Arbor, MI, United States
| | | |
Collapse
|
7
|
Herold KF, Andersen OS, Hemmings HC. Divergent effects of anesthetics on lipid bilayer properties and sodium channel function. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2017; 46:617-626. [PMID: 28695248 DOI: 10.1007/s00249-017-1239-1] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/24/2017] [Revised: 06/27/2017] [Accepted: 07/01/2017] [Indexed: 02/07/2023]
Abstract
General anesthetics revolutionized medicine by allowing surgeons to perform more complex and much longer procedures. This widely used class of drugs is essential to patient care, yet their exact molecular mechanism(s) are incompletely understood. One early hypothesis over a century ago proposed that nonspecific interactions of anesthetics with the lipid bilayer lead to changes in neuronal function via effects on membrane properties. This model was supported by the Meyer-Overton correlation between anesthetic potency and lipid solubility and despite more recent evidence for specific protein targets, in particular ion-channels, lipid bilayer-mediated effects of anesthetics is still under debate. We therefore tested a wide range of chemically diverse general anesthetics on lipid bilayer properties using a sensitive and functional gramicidin-based assay. None of the tested anesthetics altered lipid bilayer properties at clinically relevant concentrations. Some anesthetics did affect the bilayer, though only at high supratherapeutic concentrations, which are unlikely relevant for clinical anesthesia. These results suggest that anesthetics directly interact with membrane proteins without altering lipid bilayer properties at clinically relevant concentrations. Voltage-gated Na+ channels are potential anesthetic targets and various isoforms are inhibited by a wide range of volatile anesthetics. They inhibit channel function by reducing peak Na+ current and shifting steady-state inactivation toward more hyperpolarized potentials. Recent advances in crystallography of prokaryotic Na+ channels, which are sensitive to volatile anesthetics, together with molecular dynamics simulations and electrophysiological studies will help identify potential anesthetic interaction sites within the channel protein itself.
Collapse
Affiliation(s)
- Karl F Herold
- Department of Anesthesiology, Weill Cornell Medicine, New York, NY, 10065, USA
| | - Olaf S Andersen
- Department of Physiology and Biophysics, Weill Cornell Medicine, New York, NY, 10065, USA
| | - Hugh C Hemmings
- Department of Anesthesiology, Weill Cornell Medicine, New York, NY, 10065, USA. .,Department of Pharmacology, Weill Cornell Medicine, New York, NY, 10065, USA.
| |
Collapse
|
8
|
Clinical concentrations of chemically diverse general anesthetics minimally affect lipid bilayer properties. Proc Natl Acad Sci U S A 2017; 114:3109-3114. [PMID: 28265069 DOI: 10.1073/pnas.1611717114] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
General anesthetics have revolutionized medicine by facilitating invasive procedures, and have thus become essential drugs. However, detailed understanding of their molecular mechanisms remains elusive. A mechanism proposed over a century ago involving unspecified interactions with the lipid bilayer known as the unitary lipid-based hypothesis of anesthetic action, has been challenged by evidence for direct anesthetic interactions with a range of proteins, including transmembrane ion channels. Anesthetic concentrations in the membrane are high (10-100 mM), however, and there is no experimental evidence ruling out a role for the lipid bilayer in their ion channel effects. A recent hypothesis proposes that anesthetic-induced changes in ion channel function result from changes in bilayer lateral pressure that arise from partitioning of anesthetics into the bilayer. We examined the effects of a broad range of chemically diverse general anesthetics and related nonanesthetics on lipid bilayer properties using an established fluorescence assay that senses drug-induced changes in lipid bilayer properties. None of the compounds tested altered bilayer properties sufficiently to produce meaningful changes in ion channel function at clinically relevant concentrations. Even supra-anesthetic concentrations caused minimal bilayer effects, although much higher (toxic) concentrations of certain anesthetic agents did alter lipid bilayer properties. We conclude that general anesthetics have minimal effects on bilayer properties at clinically relevant concentrations, indicating that anesthetic effects on ion channel function are not bilayer-mediated but rather involve direct protein interactions.
Collapse
|
9
|
Paxman J, Hunt B, Hallan D, Zarbock SR, Woodbury DJ. Drunken Membranes: Short-Chain Alcohols Alter Fusion of Liposomes to Planar Lipid Bilayers. Biophys J 2017; 112:121-132. [PMID: 28076803 PMCID: PMC5232861 DOI: 10.1016/j.bpj.2016.11.3205] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2016] [Revised: 11/18/2016] [Accepted: 11/30/2016] [Indexed: 12/31/2022] Open
Abstract
Although the effects of ethanol on protein receptors and lipid membranes have been studied extensively, ethanol's effect on vesicles fusing to lipid bilayers is not known. To determine the effect of alcohols on fusion rates, we utilized the nystatin/ergosterol fusion assay to measure fusion of liposomes to a planar lipid bilayer (BLM). The addition of ethanol excited fusion when applied on the cis (vesicle) side, and inhibited fusion on the trans side. Other short-chain alcohols followed a similar pattern. In general, the inhibitory effect of alcohols (trans) occurs at lower doses than the excitatory (cis) effect, with a decrease of 29% in fusion rates at the legal driving limit of 0.08% (w/v) ethanol (IC50 = 0.2% v/v, 34 mM). Similar inhibitory effects were observed with methanol, propanol, and butanol, with ethanol being the most potent. Significant variability was observed with different alcohols when applied to the cis side. Ethanol and propanol enhanced fusion, butanol also enhanced fusion but was less potent, and low doses of methanol mildly inhibited fusion. The inhibition by trans addition of alcohols implies that they alter the planar membrane structure and thereby increase the activation energy required for fusion, likely through an increase in membrane fluidity. The cis data are likely a combination of the above effect and a proportionally greater lowering of the vesicle lysis tension and hydration repulsive pressure that combine to enhance fusion. Alternate hypotheses are also discussed. The inhibitory effect of ethanol on liposome-membrane fusion is large enough to provide a possible biophysical explanation of compromised neuronal behavior.
Collapse
Affiliation(s)
- Jason Paxman
- Department of Physiology and Developmental Biology, Brigham Young University, Provo, Utah
| | - Brady Hunt
- Department of Physiology and Developmental Biology, Brigham Young University, Provo, Utah
| | - David Hallan
- Department of Physiology and Developmental Biology, Brigham Young University, Provo, Utah
| | - Samuel R Zarbock
- Department of Physiology and Developmental Biology, Brigham Young University, Provo, Utah
| | - Dixon J Woodbury
- Department of Physiology and Developmental Biology, Brigham Young University, Provo, Utah.
| |
Collapse
|
10
|
Machta BB, Gray E, Nouri M, McCarthy NLC, Gray EM, Miller AL, Brooks NJ, Veatch SL. Conditions that Stabilize Membrane Domains Also Antagonize n-Alcohol Anesthesia. Biophys J 2016; 111:537-545. [PMID: 27508437 PMCID: PMC4982967 DOI: 10.1016/j.bpj.2016.06.039] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2016] [Revised: 06/24/2016] [Accepted: 06/28/2016] [Indexed: 10/21/2022] Open
Abstract
Diverse molecules induce general anesthesia with potency strongly correlated with both their hydrophobicity and their effects on certain ion channels. We recently observed that several n-alcohol anesthetics inhibit heterogeneity in plasma-membrane-derived vesicles by lowering the critical temperature (Tc) for phase separation. Here, we exploit conditions that stabilize membrane heterogeneity to further test the correlation between the anesthetic potency of n-alcohols and effects on Tc. First, we show that hexadecanol acts oppositely to n-alcohol anesthetics on membrane mixing and antagonizes ethanol-induced anesthesia in a tadpole behavioral assay. Second, we show that two previously described "intoxication reversers" raise Tc and counter ethanol's effects in vesicles, mimicking the findings of previous electrophysiological and behavioral measurements. Third, we find that elevated hydrostatic pressure, long known to reverse anesthesia, also raises Tc in vesicles with a magnitude that counters the effect of butanol at relevant concentrations and pressures. Taken together, these results demonstrate that ΔTc predicts anesthetic potency for n-alcohols better than hydrophobicity in a range of contexts, supporting a mechanistic role for membrane heterogeneity in general anesthesia.
Collapse
Affiliation(s)
| | | | | | - Nicola L C McCarthy
- Department of Chemistry, Imperial College London, South Kensington Campus, London, United Kingdom
| | | | - Ann L Miller
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, Michigan
| | - Nicholas J Brooks
- Department of Chemistry, Imperial College London, South Kensington Campus, London, United Kingdom
| | | |
Collapse
|
11
|
Reigada R, Sagués F. Chloroform alters interleaflet coupling in lipid bilayers: an entropic mechanism. J R Soc Interface 2016; 12:rsif.2015.0197. [PMID: 25833246 DOI: 10.1098/rsif.2015.0197] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
The interaction of the two leaflets of the plasmatic cell membrane is conjectured to play an important role in many cell processes. Experimental and computational studies have investigated the mechanisms that modulate the interaction between the two membrane leaflets. Here, by means of coarse-grained molecular dynamics simulations, we show that the addition of a small and polar compound such as chloroform alters interleaflet coupling by promoting domain registration. This is interpreted in terms of an entropic gain that would favour frequent chloroform commuting between the two leaflets. The implication of this effect is discussed in relation to the general anaesthetic action.
Collapse
Affiliation(s)
- Ramon Reigada
- Departament de Quimica Fisica and Institut de Quimica Teorica i Computacional (IQTCUB), Universitat de Barcelona, c/Martí i Franquès 1, Pta. 4, 08028 Barcelona, Spain
| | - Francesc Sagués
- Departament de Quimica Fisica and Institut de Nanociencia i Nanotecnologia (IN2UB), Universitat de Barcelona, c/Martı́ i Franquès 1, Pta. 4, 08028 Barcelona, Spain
| |
Collapse
|
12
|
Vadakkan KI. A pressure-reversible cellular mechanism of general anesthetics capable of altering a possible mechanism for consciousness. SPRINGERPLUS 2015; 4:485. [PMID: 26380161 PMCID: PMC4561946 DOI: 10.1186/s40064-015-1283-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/22/2015] [Accepted: 08/28/2015] [Indexed: 12/20/2022]
Abstract
Different anesthetics are known to modulate different types of membrane-bound receptors. Their common mechanism of action is expected to alter the mechanism for consciousness. Consciousness is hypothesized as the integral of all the units of internal sensations induced by reactivation of inter-postsynaptic membrane functional LINKs during mechanisms that lead to oscillating potentials. The thermodynamics of the spontaneous lateral curvature of lipid membranes induced by lipophilic anesthetics can lead to the formation of non-specific inter-postsynaptic membrane functional LINKs by different mechanisms. These include direct membrane contact by excluding the inter-membrane hydrophilic region and readily reversible partial membrane hemifusion. The constant reorganization of the lipid membranes at the lateral edges of the postsynaptic terminals (dendritic spines) resulting from AMPA receptor-subunit vesicle exocytosis and endocytosis can favor the effect of anesthetic molecules on lipid membranes at this location. Induction of a large number of non-specific LINKs can alter the conformation of the integral of the units of internal sensations that maintain consciousness. Anesthetic requirement is reduced in the presence of dopamine that causes enlargement of dendritic spines. Externally applied pressure can transduce from the middle ear through the perilymph, cerebrospinal fluid, and the recently discovered glymphatic pathway to the extracellular matrix space, and finally to the paravenular space. The pressure gradient reduce solubility and displace anesthetic molecules from the membranes into the paravenular space, explaining the pressure reversal of anesthesia. Changes in membrane composition and the conversion of membrane hemifusion to fusion due to defects in the checkpoint mechanisms can lead to cytoplasmic content mixing between neurons and cause neurodegenerative changes. The common mechanism of anesthetics presented here can operate along with the known specific actions of different anesthetics.
Collapse
Affiliation(s)
- Kunjumon I Vadakkan
- Division of Neurology, Department of Medicine, University of Toronto, Sunnybrook Health Sciences Centre, 2075 Bayview Avenue, Room A4-08, Toronto, ON M4N 3M5 Canada
| |
Collapse
|
13
|
Herold KF, Sanford RL, Lee W, Schultz MF, Ingólfsson HI, Andersen OS, Hemmings HC. Volatile anesthetics inhibit sodium channels without altering bulk lipid bilayer properties. J Gen Physiol 2014; 144:545-60. [PMID: 25385786 PMCID: PMC4242807 DOI: 10.1085/jgp.201411172] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2014] [Accepted: 10/08/2014] [Indexed: 01/05/2023] Open
Abstract
Although general anesthetics are clinically important and widely used, their molecular mechanisms of action remain poorly understood. Volatile anesthetics such as isoflurane (ISO) are thought to alter neuronal function by depressing excitatory and facilitating inhibitory neurotransmission through direct interactions with specific protein targets, including voltage-gated sodium channels (Na(v)). Many anesthetics alter lipid bilayer properties, suggesting that ion channel function might also be altered indirectly through effects on the lipid bilayer. We compared the effects of ISO and of a series of fluorobenzene (FB) model volatile anesthetics on Na(v) function and lipid bilayer properties. We examined the effects of these agents on Na(v) in neuronal cells using whole-cell electrophysiology, and on lipid bilayer properties using a gramicidin-based fluorescence assay, which is a functional assay for detecting changes in lipid bilayer properties sensed by a bilayer-spanning ion channel. At clinically relevant concentrations (defined by the minimum alveolar concentration), both the FBs and ISO produced prepulse-dependent inhibition of Na(v) and shifted the voltage dependence of inactivation toward more hyperpolarized potentials without affecting lipid bilayer properties, as sensed by gramicidin channels. Only at supra-anesthetic (toxic) concentrations did ISO alter lipid bilayer properties. These results suggest that clinically relevant concentrations of volatile anesthetics alter Na(v) function through direct interactions with the channel protein with little, if any, contribution from changes in bulk lipid bilayer properties. Our findings further suggest that changes in lipid bilayer properties are not involved in clinical anesthesia.
Collapse
Affiliation(s)
- Karl F Herold
- Department of Anesthesiology, Department of Physiology and Biophysics, and Department of Pharmacology, Weill Cornell Medical College, New York, NY 10065
| | - R Lea Sanford
- Department of Anesthesiology, Department of Physiology and Biophysics, and Department of Pharmacology, Weill Cornell Medical College, New York, NY 10065
| | - William Lee
- Department of Anesthesiology, Department of Physiology and Biophysics, and Department of Pharmacology, Weill Cornell Medical College, New York, NY 10065
| | - Margaret F Schultz
- Department of Anesthesiology, Department of Physiology and Biophysics, and Department of Pharmacology, Weill Cornell Medical College, New York, NY 10065
| | - Helgi I Ingólfsson
- Department of Anesthesiology, Department of Physiology and Biophysics, and Department of Pharmacology, Weill Cornell Medical College, New York, NY 10065
| | - Olaf S Andersen
- Department of Anesthesiology, Department of Physiology and Biophysics, and Department of Pharmacology, Weill Cornell Medical College, New York, NY 10065
| | - Hugh C Hemmings
- Department of Anesthesiology, Department of Physiology and Biophysics, and Department of Pharmacology, Weill Cornell Medical College, New York, NY 10065 Department of Anesthesiology, Department of Physiology and Biophysics, and Department of Pharmacology, Weill Cornell Medical College, New York, NY 10065
| |
Collapse
|
14
|
Klacsová M, Karlovská J, Uhríková D, Funari SS, Balgavý P. Phase behavior of the DOPE + DOPC + alkanol system. SOFT MATTER 2014; 10:5842-5848. [PMID: 24980804 DOI: 10.1039/c4sm00530a] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Small- and wide-angle X-ray diffraction was used to study the effect of 1-alkanols, as simple models of general anesthetics, (abbreviation CnOH, n = 8-18 is the even number of carbons in the aliphatic chain) on the lamellar to hexagonal Lα→ H(II) phase transition in the dioleoylphosphatidylethanolamine-dioleoylphosphatidylcholine = 3 : 1 mol/mol (DOPE + DOPC) system. All studied CnOHs were found to decrease the phase transition temperature of the DOPE + DOPC system in a CnOH chain length and concentration dependent manner and thus promote the formation of the HII phase. Anesthetically active C8OH and C10OH were found to decrease the lattice parameter d of the Lα phase, however longer non-anesthetic CnOHs increased the parameter d; this effect being more pronounced with increasing CnOH concentration. The lattice parameter of the HII phase was decreased in the presence of all CnOHs, even at the lowest concentrations studied. In the scope of the indirect mechanism of general anesthesia observed changes in the lattice parameter d (reflecting changes in the bilayer thickness) due to the intercalation of C8OH and C10OH might induce changes in the activity of integral membrane proteins engaged in neuronal pathways.
Collapse
Affiliation(s)
- Mária Klacsová
- Department of Physical Chemistry of Drugs, Faculty of Pharmacy, Comenius University, Odbojárov 10, SK-832 32 Bratislava, Slovakia.
| | | | | | | | | |
Collapse
|
15
|
Ingólfsson HI, Thakur P, Herold KF, Hobart EA, Ramsey NB, Periole X, de Jong DH, Zwama M, Yilmaz D, Hall K, Maretzky T, Hemmings HC, Blobel C, Marrink SJ, Koçer A, Sack JT, Andersen OS. Phytochemicals perturb membranes and promiscuously alter protein function. ACS Chem Biol 2014; 9:1788-98. [PMID: 24901212 PMCID: PMC4136704 DOI: 10.1021/cb500086e] [Citation(s) in RCA: 208] [Impact Index Per Article: 20.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
![]()
A wide
variety of phytochemicals are consumed for their perceived
health benefits. Many of these phytochemicals have been found to alter
numerous cell functions, but the mechanisms underlying their biological
activity tend to be poorly understood. Phenolic phytochemicals are
particularly promiscuous modifiers of membrane protein function, suggesting
that some of their actions may be due to a common, membrane bilayer-mediated
mechanism. To test whether bilayer perturbation may underlie this
diversity of actions, we examined five bioactive phenols reported
to have medicinal value: capsaicin from chili peppers, curcumin from
turmeric, EGCG from green tea, genistein from soybeans, and resveratrol
from grapes. We find that each of these widely consumed phytochemicals
alters lipid bilayer properties and the function of diverse membrane
proteins. Molecular dynamics simulations show that these phytochemicals
modify bilayer properties by localizing to the bilayer/solution interface.
Bilayer-modifying propensity was verified using a gramicidin-based
assay, and indiscriminate modulation of membrane protein function
was demonstrated using four proteins: membrane-anchored metalloproteases,
mechanosensitive ion channels, and voltage-dependent potassium and
sodium channels. Each protein exhibited similar responses to multiple
phytochemicals, consistent with a common, bilayer-mediated mechanism.
Our results suggest that many effects of amphiphilic phytochemicals
are due to cell membrane perturbations, rather than specific protein
binding.
Collapse
Affiliation(s)
| | - Pratima Thakur
- Dept.
Physiology and Membrane Biology, University of California, Davis, California, United States
| | | | | | | | | | | | | | | | - Katherine Hall
- Hospital for Special
Surgery, New York, New York, United States
| | | | | | - Carl Blobel
- Hospital for Special
Surgery, New York, New York, United States
| | | | | | - Jon T. Sack
- Dept.
Physiology and Membrane Biology, University of California, Davis, California, United States
| | | |
Collapse
|
16
|
Gray E, Karslake J, Machta BB, Veatch SL. Liquid general anesthetics lower critical temperatures in plasma membrane vesicles. Biophys J 2014; 105:2751-9. [PMID: 24359747 DOI: 10.1016/j.bpj.2013.11.005] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2013] [Revised: 10/31/2013] [Accepted: 11/04/2013] [Indexed: 12/21/2022] Open
Abstract
A large and diverse array of small hydrophobic molecules induce general anesthesia. Their efficacy as anesthetics has been shown to correlate both with their affinity for a hydrophobic environment and with their potency in inhibiting certain ligand-gated ion channels. In this study we explore the effects that n-alcohols and other liquid anesthetics have on the two-dimensional miscibility critical point observed in cell-derived giant plasma membrane vesicles (GPMVs). We show that anesthetics depress the critical temperature (Tc) of these GPMVs without strongly altering the ratio of the two liquid phases found below Tc. The magnitude of this affect is consistent across n-alcohols when their concentration is rescaled by the median anesthetic concentration (AC50) for tadpole anesthesia, but not when plotted against the overall concentration in solution. At AC50 we see a 4°C downward shift in Tc, much larger than is typically seen in the main chain transition at these anesthetic concentrations. GPMV miscibility critical temperatures are also lowered to a similar extent by propofol, phenylethanol, and isopropanol when added at anesthetic concentrations, but not by tetradecanol or 2,6 diterbutylphenol, two structural analogs of general anesthetics that are hydrophobic but have no anesthetic potency. We propose that liquid general anesthetics provide an experimental tool for lowering critical temperatures in plasma membranes of intact cells, which we predict will reduce lipid-mediated heterogeneity in a way that is complimentary to increasing or decreasing cholesterol. Also, several possible implications of our results are discussed in the context of current models of anesthetic action on ligand-gated ion channels.
Collapse
Affiliation(s)
- Ellyn Gray
- Department of Biophysics, University of Michigan, Ann Arbor MI 48109
| | - Joshua Karslake
- Department of Biophysics, University of Michigan, Ann Arbor MI 48109
| | - Benjamin B Machta
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton NJ 08544.
| | - Sarah L Veatch
- Department of Biophysics, University of Michigan, Ann Arbor MI 48109.
| |
Collapse
|
17
|
Abstract
We show that the general anesthetics xenon, sulfur hexafluoride, nitrous oxide, and chloroform cause rapid increases of different magnitude and time course in the electron spin content of Drosophila. With the exception of CHCl3, these changes are reversible. Anesthetic-resistant mutant strains of Drosophila exhibit a different pattern of spin responses to anesthetic. In two such mutants, the spin response to CHCl3 is absent. We propose that these spin changes are caused by perturbation of the electronic structure of proteins by general anesthetics. Using density functional theory, we show that general anesthetics perturb and extend the highest occupied molecular orbital of a nine-residue α-helix. The calculated perturbations are qualitatively in accord with the Meyer-Overton relationship and some of its exceptions. We conclude that there may be a connection between spin, electron currents in cells, and the functioning of the nervous system.
Collapse
|
18
|
Weinrich M, Worcester DL. Xenon and other volatile anesthetics change domain structure in model lipid raft membranes. J Phys Chem B 2013; 117:16141-7. [PMID: 24299622 DOI: 10.1021/jp411261g] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Inhalation anesthetics have been in clinical use for over 160 years, but the molecular mechanisms of action continue to be investigated. Direct interactions with ion channels received much attention after it was found that anesthetics do not change the structure of homogeneous model membranes. However, it was recently found that halothane, a prototypical anesthetic, changes domain structure of a binary lipid membrane. The noble gas xenon is an excellent anesthetic and provides a pivotal test of the generality of this finding, extended to ternary lipid raft mixtures. We report that xenon and conventional anesthetics change the domain equilibrium in two canonical ternary lipid raft mixtures. These findings demonstrate a membrane-mediated mechanism whereby inhalation anesthetics can affect the lipid environment of transmembrane proteins.
Collapse
Affiliation(s)
- Michael Weinrich
- Eunice Kennedy Shriver National Institute of Child Health and Human Development , Bethesda, Maryland 20892, United States
| | | |
Collapse
|
19
|
Weinrich M, Nanda H, Worcester DL, Majkrzak CF, Maranville BB, Bezrukov SM. Halothane changes the domain structure of a binary lipid membrane. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2012; 28:4723-8. [PMID: 22352350 PMCID: PMC3302933 DOI: 10.1021/la204317k] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
X-ray and neutron diffraction studies of a binary lipid membrane demonstrate that halothane at physiological concentrations produces a pronounced redistribution of lipids between domains of different lipid types identified by different lamellar d-spacings and isotope composition. In contrast, dichlorohexafluorocyclobutane (F6), a halogenated nonanesthetic, does not produce such significant effects. These findings demonstrate a specific effect of inhalational anesthetics on mixing phase equilibria of a lipid mixture.
Collapse
Affiliation(s)
- Michael Weinrich
- National Center for Medical Rehabilitation Research, Eunice Kennedy Shriver Institute of Child Health and Human Development, Bethesda, Maryland, United States.
| | | | | | | | | | | |
Collapse
|
20
|
Pinnick ER, Erramilli S, Wang F. The potential of mean force of nitrous oxide in a 1,2-dimyristoylphosphatidylcholine lipid bilayer. Chem Phys Lett 2010. [DOI: 10.1016/j.cplett.2010.02.047] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
|
21
|
Vemparala S, Domene C, Klein ML. Computational studies on the interactions of inhalational anesthetics with proteins. Acc Chem Res 2010; 43:103-10. [PMID: 19788306 DOI: 10.1021/ar900149j] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Despite the widespread clinical use of anesthetics since the 19th century, a clear understanding of the mechanism of anesthetic action has yet to emerge. On the basis of early experiments by Meyer, Overton, and subsequent researchers, the cell's lipid membrane was generally concluded to be the primary site of action of anesthetics. However, later experiments with lipid-free globular proteins, such as luciferase and apoferritin, shifted the focus of anesthetic action to proteins. Recent experimental studies, such as photoaffinity labeling and mutagenesis on membrane proteins, have suggested specific binding sites for anesthetic molecules, further strengthening the proteocentric view of anesthetic mechanism. With the increased availability of high-resolution crystal structures of ion channels and other integral membrane proteins, as well as the availability of powerful computers, the structure-function relationship of anesthetic-protein interactions can now be investigated in atomic detail. In this Account, we review recent experiments and related computer simulation studies involving interactions of inhalational anesthetics and proteins, with a particular focus on membrane proteins. Globular proteins have long been used as models for understanding the role of protein-anesthetic interactions and are accordingly examined in this Account. Using selected examples of membrane proteins, such as nicotinic acetyl choline receptor (nAChR) and potassium channels, we address the issues of anesthetic binding pockets in proteins, the role of conformation in anesthetic effects, and the modulation of local as well as global dynamics of proteins by inhaled anesthetics. In the case of nicotinic receptors, inhalational anesthetic halothane binds to the hydrophobic cavity close to the M2-M3 loop. This binding modulates the dynamics of the M2-M3 loop, which is implicated in allosterically transmitting the effects to the channel gate, thus altering the function of the protein. In potassium channels, anesthetic molecules preferentially potentiate the open conformation by quenching the motion of the aromatic residues implicated in the gating of the channel. These simulations suggest that low-affinity drugs (such as inhalational anesthetics) modulate the protein function by influencing local as well as global dynamics of proteins. Because of intrinsic experimental limitations, computational approaches represent an important avenue for exploring the mode of action of anesthetics. Molecular dynamics simulations-a computational technique frequently used in the general study of proteins-offer particular insight in the study of the interaction of inhalational anesthetics with membrane proteins.
Collapse
Affiliation(s)
- Satyavani Vemparala
- The Institute of Mathematical Sciences, C.I.T Campus, Taramani, Chennai 600 113, India
| | - Carmen Domene
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, Oxford OX1 3QZ U.K
| | - Michael L. Klein
- Center for Molecular Modeling and Department of Chemistry, University of Pennsylvania, 231 South 34th Street, Philadelphia, Pennsylvania 19104-6323
| |
Collapse
|
22
|
Pan J, Tristram-Nagle S, Nagle JF. Alamethicin aggregation in lipid membranes. J Membr Biol 2009; 231:11-27. [PMID: 19789905 DOI: 10.1007/s00232-009-9199-8] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2009] [Accepted: 09/02/2009] [Indexed: 10/20/2022]
Abstract
X-ray scattering features induced by aggregates of alamethicin (Alm) were obtained in oriented stacks of model membranes of DOPC(diC18:1PC) and diC22:1PC. The first feature obtained near full hydration was Bragg rod in-plane scattering near 0.11 A(-1) in DOPC and near 0.08 A(-1) in diC22:1PC at a 1:10 Alm:lipid ratio. This feature is interpreted as bundles consisting of n Alm monomers in a barrel-stave configuration surrounding a water pore. Fitting the scattering data to previously published molecular dynamics simulations indicates that the number of peptides per bundle is n = 6 in DOPC and n >or= 9 in diC22:1PC. The larger bundle size in diC22:1PC is explained by hydrophobic mismatch of Alm with the thicker bilayer. A second diffuse scattering peak located at q(r) approximately 0.7 A(-1) is obtained for both DOPC and diC22:1PC at several peptide concentrations. Theoretical calculations indicate that this peak cannot be caused by the Alm bundle structure. Instead, we interpret it as being due to two-dimensional hexagonally packed clusters in equilibrium with Alm bundles. As the relative humidity was reduced, interactions between Alm in neighboring bilayers produced more peaks with three-dimensional crystallographic character that do not index with the conventional hexagonal space groups.
Collapse
Affiliation(s)
- Jianjun Pan
- Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213, USA
| | | | | |
Collapse
|
23
|
Weinrich M, Rostovtseva TK, Bezrukov SM. Lipid-dependent effects of halothane on gramicidin channel kinetics: a new role for lipid packing stress. Biochemistry 2009; 48:5501-3. [PMID: 19405539 DOI: 10.1021/bi900494y] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We find that the sensitivity of gramicidin A channels to the anesthetic halothane is highly lipid dependent. Specifically, exposure of membranes made of lamellar DOPC to halothane in concentrations close to clinically relevant reduces channel lifetimes by 1 order of magnitude. At the same time, gramicidin channels in membranes of nonlamellar DOPE are affected little, if at all, by halothane. We attribute this difference in channel behavior to a difference in the stress of lipid packing into a planar lipid bilayer, wherein the higher stress of DOPE packing reduces the degree of halothane partitioning into the hydrophobic interior.
Collapse
Affiliation(s)
- Michael Weinrich
- National Center for Medical Rehabilitation Research, National Institutes of Health,Bethesda, Maryland 20892, USA.
| | | | | |
Collapse
|
24
|
Chieffo LR, Shattuck JT, Pinnick E, Amsden JJ, Hong MK, Wang F, Erramilli S, Ziegler LD. Nitrous Oxide Vibrational Energy Relaxation Is a Probe of Interfacial Water in Lipid Bilayers. J Phys Chem B 2008; 112:12776-82. [DOI: 10.1021/jp8012283] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Logan R. Chieffo
- Department of Chemistry, Department of Physics, Department of Biomedical Engineering and the Photonics Center, Boston University, 590 Commonwealth Avenue, Boston, MA 02215
| | - Jeffrey T. Shattuck
- Department of Chemistry, Department of Physics, Department of Biomedical Engineering and the Photonics Center, Boston University, 590 Commonwealth Avenue, Boston, MA 02215
| | - Eric Pinnick
- Department of Chemistry, Department of Physics, Department of Biomedical Engineering and the Photonics Center, Boston University, 590 Commonwealth Avenue, Boston, MA 02215
| | - Jason J. Amsden
- Department of Chemistry, Department of Physics, Department of Biomedical Engineering and the Photonics Center, Boston University, 590 Commonwealth Avenue, Boston, MA 02215
| | - M. K. Hong
- Department of Chemistry, Department of Physics, Department of Biomedical Engineering and the Photonics Center, Boston University, 590 Commonwealth Avenue, Boston, MA 02215
| | - Feng Wang
- Department of Chemistry, Department of Physics, Department of Biomedical Engineering and the Photonics Center, Boston University, 590 Commonwealth Avenue, Boston, MA 02215
| | - Shyamsunder Erramilli
- Department of Chemistry, Department of Physics, Department of Biomedical Engineering and the Photonics Center, Boston University, 590 Commonwealth Avenue, Boston, MA 02215
| | - Lawrence D. Ziegler
- Department of Chemistry, Department of Physics, Department of Biomedical Engineering and the Photonics Center, Boston University, 590 Commonwealth Avenue, Boston, MA 02215
| |
Collapse
|
25
|
Sonner JM. A hypothesis on the origin and evolution of the response to inhaled anesthetics. Anesth Analg 2008; 107:849-54. [PMID: 18713893 DOI: 10.1213/ane.0b013e31817ee684] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
In this article, I present an evolutionary explanation for why organisms respond to inhaled anesthetics. It is conjectured that organisms today respond to inhaled anesthetics owing to the sensitivity of ion channels to inhaled anesthetics, which in turn has arisen by common descent from ancestral, anesthetic-sensitive ion channels in one-celled organisms (i.e., that the response to anesthetics did not arise as an adaptation of the nervous system, but rather of ion channels that preceded the origin of multicellularity). This sensitivity may have been refined by continuing selection at synapses in multicellular organisms. In particular, it is hypothesized that 1) the beneficial trait that was selected for in one-celled organisms was the coordinated response of ion channels to compounds that were present in the environment, which influenced the conformational equilibrium of ion channels; 2) this coordinated response prevented the deleterious consequences of entry of positive charges into the cell, thereby increasing the fitness of the organism; and 3) these compounds (which may have included organic anions, cations, and zwitterions as well as uncharged compounds) mimicked inhaled anesthetics in that they were interfacially active, and modulated ion channel function by altering bilayer properties coupled to channel function. The proposed hypothesis is consistent with known properties of inhaled anesthetics. In addition, it leads to testable experimental predictions of nonvolatile compounds having anesthetic-like modulatory effects on ion channels and in animals, including endogenous compounds that may modulate ion channel function in health and disease. The latter included metabolites that are increased in some types of end-stage organ failure, and genetic metabolic diseases. Several of these predictions have been tested and proved to be correct.
Collapse
Affiliation(s)
- James M Sonner
- Department of Anesthesia and Perioperative Care, University of California, San Francisco, CA 94143-0464, USA.
| |
Collapse
|
26
|
Yamamoto Y, Taga K, Yoshida T, Kamaya H, Ueda I. Temperature dependence of thermodynamic activity in volatile anesthetics: correlation between anesthetic potency and activity. J Colloid Interface Sci 2006; 301:488-92. [PMID: 16790248 DOI: 10.1016/j.jcis.2006.05.030] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2006] [Revised: 05/12/2006] [Accepted: 05/12/2006] [Indexed: 11/20/2022]
Abstract
Temperature dependence of the saturated concentration and the activity coefficient of anesthetics (1-propanol, diethyl ether, chloroform, and halothane) in water were evaluated using vapor pressure and H NMR measurement. We found that these physical values (quantities) correlate with anesthetic potencies estimated according to the thermodynamic equilibrium model. The anesthetic potency for hydrophilic anesthetic (diethyl ether) decreased with decreasing temperature because of the temperature specificity of this saturated concentration. In contrast, potencies of hydrophobic anesthetics (chloroform and halothane) increased with decreasing temperature because of the temperature specificity of those activity coefficients. By assuming that anesthetics interact with hydrated water of cell membranes, the temperature dependence of anesthetic potencies in vivo is qualitatively explicable.
Collapse
Affiliation(s)
- Yasushi Yamamoto
- Department of Life and Materials Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555, Japan.
| | | | | | | | | |
Collapse
|
27
|
Abstract
The question has arisen in recent literature: how to partition the total area in simulations of membranes consisting of more than one kind of molecule into average areas for each kind of molecule. Several definitions have been proposed, each of which has arbitrary features. When applied to mixtures of cholesterol and DPPC, these definitions give different results. This note recalls that physical chemistry provides a canonical way to define molecular area, in analogy to the definition of partial-specific volume. Results for partial-specific area are obtained from simulations of DPPC/cholesterol bilayers and compared to the results from the other recent definitions. The partial-specific-area formalism dramatically demonstrates the condensing effect of cholesterol and this leads to the introduction of a specific model that accounts for the area of mixtures of cholesterol and lipid over the entire range of cholesterol concentrations.
Collapse
Affiliation(s)
- Olle Edholm
- Theoretical Biological Physics, Royal Institute of Technology, Stockholm, Sweden.
| | | |
Collapse
|
28
|
Høyrup P, Callisen TH, Jensen MØ, Halperin A, Mouritsen OG. Lipid protrusions, membrane softness, and enzymatic activity. Phys Chem Chem Phys 2004. [DOI: 10.1039/b314146b] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
29
|
Krasowski MD. Contradicting a unitary theory of general anesthetic action: a history of three compounds from 1901 to 2001. BULLETIN OF ANESTHESIA HISTORY 2003; 21:1, 4-8, 21 passim. [PMID: 17494361 PMCID: PMC2701367 DOI: 10.1016/s1522-8649(03)50031-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
|
30
|
Eldho NV, Feller SE, Tristram-Nagle S, Polozov IV, Gawrisch K. Polyunsaturated docosahexaenoic vs docosapentaenoic acid-differences in lipid matrix properties from the loss of one double bond. J Am Chem Soc 2003; 125:6409-21. [PMID: 12785780 DOI: 10.1021/ja029029o] [Citation(s) in RCA: 189] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Insufficient supply to the developing brain of docosahexaenoic acid (22:6n3, DHA), or its omega-3 fatty acid precursors, results in replacement of DHA with docosapentaenoic acid (22:5n6, DPA), an omega-6 fatty acid that is lacking a double bond near the chain's methyl end. We investigated membranes of 1-stearoyl(d(35))-2-docosahexaenoyl-sn-glycero-3-phosphocholine and 1-stearoyl(d(35))-2-docosapentaenoyl-sn-glycero-3-phosphocholine by solid-state NMR, X-ray diffraction, and molecular dynamics simulations to determine if the loss of this double bond alters membrane physical properties. The low order parameters of polyunsaturated chains and the NMR relaxation data indicate that both DHA and DPA undergo rapid conformational transitions with correlation times of the order of nanoseconds at carbon atom C(2) and of picoseconds near the terminal methyl group. However, there are important differences between DHA- and DPA-containing lipids: the DHA chain with one additional double bond is more flexible at the methyl end and isomerizes with shorter correlation times. Furthermore, the stearic acid paired with the DHA in mixed-chain lipids has lower order, in particular in the middle of the chain near carbons C(10)(-)(12), indicating differences in the packing of hydrocarbon chains. Such differences are also reflected in the electron density profiles of the bilayers and in the simulation results. The DHA chain has a higher density near the lipid-water interface, whereas the density of the stearic acid chain is higher in the bilayer center. The loss of a single double bond from DHA to DPA results in a more even distribution of chain densities along the bilayer normal. We propose that the function of integral membrane proteins such as rhodopsin is sensitive to such a redistribution.
Collapse
Affiliation(s)
- Nadukkudy V Eldho
- Contribution from the Laboratory of Membrane Biochemistry and Biophysics, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Rockville, Maryland 20852, USA
| | | | | | | | | |
Collapse
|
31
|
Traïkia M, Warschawski DE, Lambert O, Rigaud JL, Devaux PF. Asymmetrical membranes and surface tension. Biophys J 2002; 83:1443-54. [PMID: 12202370 PMCID: PMC1302243 DOI: 10.1016/s0006-3495(02)73915-5] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
The (31)P-nuclear magnetic resonance chemical shift of phosphatidic acid in a membrane is sensitive to the lipid head group packing and can report qualitatively on membrane lateral compression near the aqueous interface. We have used high-resolution (31)P-nuclear magnetic resonance to evaluate the lateral compression on each side of asymmetrical lipid vesicles. When monooleoylphosphatidylcholine was added to the external monolayer of sonicated vesicles containing dioleoylphosphatidylcholine and dioleoylphosphatidic acid, the variation of (31)P chemical shift of phosphatidic acid indicated a lateral compression in the external monolayer. Simultaneously, a slight dilation was observed in the inner monolayer. In large unilamellar vesicles on the other hand the lateral pressure increased in both monolayers after asymmetrical insertion of monooleoylphosphatidylcholine. This can be explained by assuming that when monooleoylphosphatidylcholine is added to large unilamellar vesicles, the membrane bends until the strain is the same in both monolayers. In the case of sonicated vesicles, a change of curvature is not possible, and therefore differential packing in the two layers remains. We infer that a variation of lipid asymmetry by generating a lateral strain in the membrane can be a physiological way of modulating the conformation of membrane proteins.
Collapse
Affiliation(s)
- Mounir Traïkia
- Institut de Biologie Physico-Chimique, Unité Mixte de Recherche Centre National de la Recherche Scientifique 7099, Paris 75005 France
| | | | | | | | | |
Collapse
|
32
|
Petrache HI, Salmon A, Brown MF. Structural properties of docosahexaenoyl phospholipid bilayers investigated by solid-state 2H NMR spectroscopy. J Am Chem Soc 2001; 123:12611-22. [PMID: 11741426 DOI: 10.1021/ja011745n] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Polyunsaturated lipids in cellular membranes are known to play key roles in such diverse biological processes as vision, neuronal signaling, and apoptosis. One hypothesis is that polyunsaturated lipids are involved in second messenger functions in biological signaling. Another current hypothesis affirms that the functional role of polyunsaturated lipids relies on their ability to modulate physical properties of the lipid bilayer. The present research has employed solid-state 2H NMR spectroscopy to acquire knowledge of the molecular organization and material properties of polyunsaturated lipid bilayers. We report measurements for a homologous series of mixed-chain phosphatidylcholines containing a perdeuterated, saturated acyl chain (n:0) at the sn-1 position, adjacent to docosahexaenoic acid (DHA, 22:6omega3) at the sn-2 position. Measurements have been performed on fluid (L(alpha))-state multilamellar dispersions as a function of temperature for saturated acyl chain lengths of n = 12, 14, 16, and 18 carbons. The saturated sn-1 chains are therefore used as an intrinsic probe with site-specific resolution of the polyunsaturated bilayer structure. The 2H NMR order parameters as a function of acyl position (order profiles) have been analyzed using a mean-torque potential model for the chain segments, and the results are discussed in comparison with the homologous series of disaturated lipid bilayers. At a given absolute temperature, as the sn-1 acyl length adjacent to the sn-2 DHA chain is greater, the order of the initial chain segments increases, whereas that of the end segments decreases, in marked contrast with the corresponding disaturated series. For the latter, the order of the end segments is practically constant with acyl length, thus revealing a universal chain packing profile. We find that the DHA-containing series, while more complex, is still characterized by a universal chain packing profile, which is shifted relative to the homologous saturated series. Moreover, we show how introduction of DHA chains translates the order profile along the saturated chains, making more disordered states accessible within the bilayer central region. As a result, the area per lipid headgroup is increased as compared to disaturated bilayers. The systematic analysis of the 2H NMR data provides a basis for studies of lipid interactions with integral membrane proteins, for instance in relation to characteristic biological functions of highly unsaturated lipid membranes.
Collapse
Affiliation(s)
- H I Petrache
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
| | | | | |
Collapse
|
33
|
Tanaka Y, Gamo S. Sensitivity to diethylether anesthesia of fruit flies primarily depends on the genotypes of the sodium channel gene rather than the states of the membranes and the mechanisms might be different from heat-induced paralysis. Colloids Surf B Biointerfaces 2001; 22:39-53. [PMID: 11438239 DOI: 10.1016/s0927-7765(01)00156-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The para locus of Drosophila melanogaster encodes the alpha subunit of a voltage-sensitive sodium channel. Many of the mutants develop paralysis at the high temperature (37 degrees C) and are hypersensitive to diethylether anesthesia. We examined whether the two aspects of the phenotype are mediated by a same mechanism that involves the sodium channel molecule by investigating properties of the three para alleles (para(hd838), para(ts1) and para(ts3)). Larvae of the all para strains showed almost normal sensitivities to diethylether anesthesia while adult flies of them showed hypersensitivities to that in the following manner: para(hd838)<==para(ts1)<para(ts3)<Canton-S. Larvae of the two para strains showed hypersensitivities to heat-induced paralysis in the following manner: para(ts1)=para(ts3)<para(hd838)=Canton-S, while adult flies of the all para strains showed hypersensitivities to that in the following manner: para(ts1)=para(ts3)<para(hd838)<Canton-S. The distinct phenotype of para(hd838) from para(ts1) or para(ts3) observed in the larval and adult heat-induced paralysis, would be the reflection of the difference of the mutation sites between in para(hd838) and para(ts1) or para(ts3). In addition, because the rank of sensitivity in the adult anesthesia and heat-induced paralysis were reversed between para(hd838) and para(ts1) or para(ts3), the mechanisms of diethylether anesthesia and heat-induced paralysis are not the same. There would be the anesthesia-specific mechanisms because the sensitivity to anesthesia became more remarkable in para(hd838) than in para(ts1) or para(ts3). para(hd838) has an insertion of P-element, one of a transposable element, in the second intron of the para sodium channel gene. Excision of the P-element from the para locus of the para(hd838) conferred the flies the wild-typic phenotype and reduction of the para gene in para(hd838) dramatically enhanced the hypersensitivity to anesthesia, suggesting that the phenotype of the strain was caused exclusively by the mutation of the para locus. The susceptibility to anesthesia also depends on the temperature at which the flies were assayed, not at which they were cultured, but the dependence on the assay temperature was smaller than that on the genotype. By these findings we could assure that the sensitivity to diethylether anesthesia of para(hd838) primarily depends on the genotypes of the sodium channel gene rather than other reasons such as the fluidity of the membranes.
Collapse
Affiliation(s)
- Y Tanaka
- Department of Life Sciences, College of Integrated Arts and Sciences, Osaka Prefecture University, 1-1 Gakuen-Cho, Sakai, 599-8531, Osaka, Japan
| | | |
Collapse
|
34
|
Hartman PS, Ishii N, Kayser EB, Morgan PG, Sedensky MM. Mitochondrial mutations differentially affect aging, mutability and anesthetic sensitivity in Caenorhabditis elegans. Mech Ageing Dev 2001; 122:1187-201. [PMID: 11389932 DOI: 10.1016/s0047-6374(01)00259-7] [Citation(s) in RCA: 82] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
In the nematode Caenorhabditis elegans, mutations have been previously isolated that affect the activities of Complex I (gas-1) and Complex II (mev-1), two of the five membrane-bound complexes that control electron flow in mitochondrial respiration. We compared the effects of gas-1 and mev-1 mutations on different traits influenced by mitochondrial function. Mutations in Complex I and II both increased sensitivity to free radicals as measured during development and in aging animals. However, gas-1 and mev-1 mutations differentially affected mutability and anesthetic sensitivity. Specifically, gas-1 was anesthetic hypersensitive but not hypermutable while mev-1 was hypermutable but displayed normal responses to anesthetics. These results indicate that Complexes I and II may differ in their effects on behavior and development, and are consistent with the wide variation in phenotypes that result from mitochondrial changes in other organisms.
Collapse
Affiliation(s)
- P S Hartman
- Department of Biology, Texas Christian University, Fort Worth, TX 76129, USA
| | | | | | | | | |
Collapse
|
35
|
Brennan LK, Froemming GR, Ohlendieck K. Effect of halothane on the oligomerization of the sarcoplasmic reticulum Ca(2+)-ATPase. Biochem Biophys Res Commun 2000; 271:770-6. [PMID: 10814537 DOI: 10.1006/bbrc.2000.2688] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The exact molecular mechanism of inhalational anesthetics remains obscure. Since the enzyme activity of the sarcoplasmic reticulum Ca(2+)-ATPase from skeletal muscle fibres is modified by halothane and because protein-protein interactions play an important role in the regulation of Ca(2+)-regulatory proteins, we investigated the effect of this volatile drug on the oligomerization of the fast-twitch Ca(2+)-ATPase. Using electrophoretic separation following incubation with halothane, increases in relative molecular mass were determined by immunoblotting with a monoclonal antibody to the SERCA1 isoform of the Ca(2+)-ATPase. Distinct drug-induced decreases in electrophoretic mobility indicated oligomerization of the native Ca(2+)-pump by halothane, comparable to crosslinking-mediated formation of homo-tetramers. Determination of the effect of halothane on enzyme activity suggested that halothane-mediated protein aggregation triggers a partial inhibition of Ca(2+)-pump units. Thus, halothane appears to exert its action via specific peptide binding sites and not indirectly by lipid perturbation. These findings support the protein theory of anesthetic action.
Collapse
Affiliation(s)
- L K Brennan
- Department of Pharmacology, Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Belfield, Dublin, 4, Ireland
| | | | | |
Collapse
|
36
|
Mason PC, Gaulin BD, Epand RM, Katsaras J. Critical swelling in single phospholipid bilayers. PHYSICAL REVIEW. E, STATISTICAL PHYSICS, PLASMAS, FLUIDS, AND RELATED INTERDISCIPLINARY TOPICS 2000; 61:5634-9. [PMID: 11031619 DOI: 10.1103/physreve.61.5634] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/1999] [Revised: 11/19/1999] [Indexed: 11/07/2022]
Abstract
We approach the controversial anomalous swelling problem in membrane systems using small angle neutron scattering to measure relative changes in the bilayer thickness of unilamellar vesicles of dimyristoylphosphatidylcholine lipid bilayers in the vicinity of the main transition. These measurements conclusively demonstrate that at least half of the anomalous swelling previously observed in multilamellar vesicles of this system can be accounted for by the critical thickening of the bilayer itself, in contrast to conclusions drawn from several recent studies.
Collapse
Affiliation(s)
- P C Mason
- National Research Council, Steacie Institute for Molecular Sciences, Chalk River Laboratories, Ontario, Canada
| | | | | | | |
Collapse
|
37
|
Chen Y, Schindler M, Simon SM. A mechanism for tamoxifen-mediated inhibition of acidification. J Biol Chem 1999; 274:18364-73. [PMID: 10373441 DOI: 10.1074/jbc.274.26.18364] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Tamoxifen has been reported to inhibit acidification of cytoplasmic organelles in mammalian cells. Here, the mechanism of this inhibition is investigated using in vitro assays on isolated organelles and liposomes. Tamoxifen inhibited ATP-dependent acidification in organelles from a variety of sources, including isolated microsomes from mammalian cells, vacuoles from Saccharomyces cerevisiae, and inverted membrane vesicles from Escherichia coli. Tamoxifen increased the ATPase activity of the vacuolar proton ATPase but decreased the membrane potential (Vm) generated by this proton pump, suggesting that tamoxifen may act by increasing proton permeability. In liposomes, tamoxifen increased the rate of pH dissipation. Studies comparing the effect of tamoxifen on pH gradients using different salt conditions and with other known ionophores suggest that tamoxifen affects transmembrane pH through two independent mechanisms. First, as a lipophilic weak base, it partitions into acidic vesicles, resulting in rapid neutralization. Second, it mediates coupled, electroneutral transport of proton or hydroxide with chloride. An understanding of the biochemical mechanism(s) for the effects of tamoxifen that are independent of the estrogen receptor could contribute to predicting side effects of tamoxifen and in designing screens to select for estrogen-receptor antagonists without these side effects.
Collapse
Affiliation(s)
- Y Chen
- Laboratory of Cellular Biophysics, Rockefeller University, New York, New York 10021, USA
| | | | | |
Collapse
|
38
|
Chapter 10 Lipid Membrane and Ligand-Gated Ion Channels in General Anesthetic Action. CURRENT TOPICS IN MEMBRANES 1999. [DOI: 10.1016/s0070-2161(08)61048-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register]
|
39
|
Abstract
1. A lipid-mediated mechanism of general anesthesia is suggested and investigated using lattice statistical thermodynamics. 2. Anesthetics are predicted to shift the distribution of lateral pressure within a lipid bilayer, and thus alter the mechanical work required to open ion channel proteins, if channel opening is accompanied by a non-uniform change in cross-sectional area of the protein. 3. Calculations based on this mechanical thermodynamic hypothesis yield qualitative agreement with anesthetic potency at clinical anesthetic membrane concentrations, and predict the alkanol cutoff and anomalously low potencies of strongly hydrophobic molecules with little attraction for the aqueous interface, such as perfluorocarbons.
Collapse
Affiliation(s)
- R S Cantor
- Department of Chemistry, Dartmouth College, Hanover, NH 03755, USA.
| |
Collapse
|
40
|
Cafiso DS. Dipole potentials and spontaneous curvature: membrane properties that could mediate anesthesia. Toxicol Lett 1998; 100-101:431-9. [PMID: 10049176 DOI: 10.1016/s0378-4274(98)00217-3] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
General anesthetics alter both the membrane dipole potential and the membrane spontaneous curvature, two membrane properties that are likely to have a significant effect on membrane protein function. The dipole potential is a large hydrocarbon positive potential that appears to arise from the lipid carbonyl groups and/or water at the membrane-solution interface. Anesthetics reduce the magnitude of the membrane dipole potential at clinical levels of anesthetics, while non-anesthetics do not, and these changes in potential could modulate conformational transitions in membrane proteins that are electrically active. When the membrane distribution of anesthetic versus non anesthetic compounds is examined, anesthetics exhibit a preference for the membrane interface, whereas non-anesthetic compounds reside within the membrane hydrocarbon core. The preferential localization of anesthetics within the interface accounts for their effect on the membrane dipole potential, and may also serve to alter the membrane spontaneous curvature or lateral stress through the bilayer.
Collapse
Affiliation(s)
- D S Cafiso
- Department of Chemistry and Biophysics Program, University of Virginia, Charlottesville 22901, USA.
| |
Collapse
|
41
|
Gil T, Ipsen JH, Mouritsen OG, Sabra MC, Sperotto MM, Zuckermann MJ. Theoretical analysis of protein organization in lipid membranes. BIOCHIMICA ET BIOPHYSICA ACTA 1998; 1376:245-66. [PMID: 9804966 DOI: 10.1016/s0304-4157(98)00022-7] [Citation(s) in RCA: 165] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The fundamental physical principles of the lateral organization of trans-membrane proteins and peptides as well as peripheral membrane proteins and enzymes are considered from the point of view of the lipid-bilayer membrane, its structure, dynamics, and cooperative phenomena. Based on a variety of theoretical considerations and model calculations, the nature of lipid-protein interactions is considered both for a single protein and an assembly of proteins that can lead to aggregation and protein crystallization in the plane of the membrane. Phenomena discussed include lipid sorting and selectivity at protein surfaces, protein-lipid phase equilibria, lipid-mediated protein-protein interactions, wetting and capillary condensation as means of protein organization, mechanisms of two-dimensional protein crystallization, as well as non-equilibrium organization of active proteins in membranes. The theoretical findings are compared with a variety of experimental data.
Collapse
Affiliation(s)
- T Gil
- Department of Chemistry, Technical University of Denmark, Building 206, DK-2800 Lyngby, Denmark
| | | | | | | | | | | |
Collapse
|
42
|
Sirois JE, Pancrazio JJ, Lynch C, Bayliss DA. Multiple ionic mechanisms mediate inhibition of rat motoneurones by inhalation anaesthetics. J Physiol 1998; 512 ( Pt 3):851-62. [PMID: 9769427 PMCID: PMC2231236 DOI: 10.1111/j.1469-7793.1998.851bd.x] [Citation(s) in RCA: 95] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
1. We studied the effects of inhalation anaesthetics on the membrane properties of hypoglossal motoneurones in a neonatal rat brainstem slice preparation. 2. In current clamp, halothane caused a membrane hyperpolarization that was invariably associated with decreased input resistance; in voltage clamp, halothane induced an outward current and increased input conductance. Qualitatively similar results were obtained with isoflurane and sevoflurane. 3. The halothane current reversed near the predicted K+ equilibrium potential (EK) and was reduced in elevated extracellular K+ and in the presence of Ba2+ (2 mM). Moreover, the Ba2+-sensitive component of halothane current was linear and reversed near EK. The halothane current was not sensitive to glibenclamide or thyrotropin-releasing hormone (TRH). Therefore, the halothane current was mediated, in part, by activation of a Ba2+-sensitive K+ current distinct from the ATP- and neurotransmitter-sensitive K+ currents in hypoglossal motoneurones. 4. Halothane also inhibited Ih, a hyperpolarization-activated cationic current; this was primarily due to a decrease in the absolute amount of current, although halothane also caused a small, but statistically significant, shift in the voltage dependence of Ih activation. Extracellular Cs+ (3 mM) blocked Ih and a component of halothane-sensitive current with properties reminiscent of Ih. 5. A small component of halothane current, resistant to Ba2+ and Cs+, was observed in TTX-containing solutions at potentials depolarized to approximately -70 mV. Partial Na+ substitution by N-methyl-D-glucamine completely abolished this residual current, indicating that halothane also inhibited a TTX-resistant Na+ current active near rest potentials. 6. Thus, halothane activates a Ba2+-sensitive, relatively voltage-independent K+ current and inhibits both Ih and a TTX-insensitive persistent Na+ current in hypoglossal motoneurones. These effects of halothane decrease motoneuronal excitability and may contribute to the immobilization that accompanies inhalation anaesthesia.
Collapse
Affiliation(s)
- J E Sirois
- Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, USA.
| | | | | | | |
Collapse
|
43
|
Rajaram S, Sedensky MM, Morgan PG. Unc-1: a stomatin homologue controls sensitivity to volatile anesthetics in Caenorhabditis elegans. Proc Natl Acad Sci U S A 1998; 95:8761-6. [PMID: 9671752 PMCID: PMC21150 DOI: 10.1073/pnas.95.15.8761] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
To identify sites of action of volatile anesthetics, we are studying genes in a functional pathway that controls sensitivity to volatile anesthetics in the nematode Caenorhabditis elegans. The unc-1 gene occupies a central position in this pathway. Different alleles of unc-1 have unique effects on sensitivity to the different volatile anesthetics. UNC-1 shows extensive homology to human stomatin, an integral membrane protein thought to regulate an associated ion channel. We postulate that UNC-1 has a direct effect on anesthetic sensitivity in C. elegans and may represent a molecular target for volatile anesthetics.
Collapse
Affiliation(s)
- S Rajaram
- Departments of Anesthesiology and Genetics, University Hospitals, Case Western Reserve University, Cleveland, OH 44106, USA
| | | | | |
Collapse
|
44
|
Rummel G, Hardmeyer A, Widmer C, Chiu ML, Nollert P, Locher KP, Pedruzzi I, Landau EM, Rosenbusch JP. Lipidic Cubic Phases: New Matrices for the Three-Dimensional Crystallization of Membrane Proteins. J Struct Biol 1998; 121:82-91. [PMID: 9618339 DOI: 10.1006/jsbi.1997.3952] [Citation(s) in RCA: 149] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The major constraint in attaining high resolution structures of membrane proteins by X-ray crystallography is the growth of well-ordered three-dimensional crystals. To enable such crystallizations, we have used lipidic cubic phases consisting of monoglycerides and water. Bacteriorhodopsin and lysozyme, as paradigms of membrane and soluble proteins, nucleate and grow to well-ordered crystals that diffract X-rays isotropically in all three dimensions to 2.0 Å. We envisage bacteriorhodopsin to partition into, and diffuse within, the bilayer of a lipidic cubic matrix, while the polar lysozyme resides in the aqueous compartment thereof. The phenomenology of bicontinuous cubic phases, consisting of curved bilayers whose structures follow infinitely periodic minimal surfaces (IPMS), is presented. Detailed prescriptions of the preparation of lipidic cubic phase matrices are given and their potential for the crystallization of other biological macromolecules is discussed. Copyright 1998 Academic Press.
Collapse
Affiliation(s)
- G Rummel
- Biozentrum, University of Basel, Klingelbergstrasse 70, Basel, CH-4056, Switzerland
| | | | | | | | | | | | | | | | | |
Collapse
|
45
|
Hønger T, Jørgensen K, Stokes D, Biltonen RL, Mouritsen OG. Phospholipase A2 activity and physical properties of lipid-bilayer substrates. Methods Enzymol 1997; 286:168-90. [PMID: 9309651 DOI: 10.1016/s0076-6879(97)86011-9] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Affiliation(s)
- T Hønger
- Department of Chemistry, Technical University of Denmark, Lyngby, Denmark
| | | | | | | | | |
Collapse
|
46
|
Hasegawa T, Kawato H, Toudou M, Nishijo J. Thermally Hydrated DPPC Langmuir Film: A Trial Application to the Analysis of Interaction of Sucrose with DPPC Liposome. J Phys Chem B 1997. [DOI: 10.1021/jp970889e] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Takeshi Hasegawa
- Kobe Pharmaceutical University, Motoyama-kita, Higashinada-ku, Kobe 658, Japan
| | - Hiromi Kawato
- Kobe Pharmaceutical University, Motoyama-kita, Higashinada-ku, Kobe 658, Japan
| | - Miwa Toudou
- Kobe Pharmaceutical University, Motoyama-kita, Higashinada-ku, Kobe 658, Japan
| | - Jujiro Nishijo
- Kobe Pharmaceutical University, Motoyama-kita, Higashinada-ku, Kobe 658, Japan
| |
Collapse
|
47
|
North C, Cafiso DS. Contrasting membrane localization and behavior of halogenated cyclobutanes that follow or violate the Meyer-Overton hypothesis of general anesthetic potency. Biophys J 1997; 72:1754-61. [PMID: 9083679 PMCID: PMC1184369 DOI: 10.1016/s0006-3495(97)78821-0] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The membrane localization and properties of two halogenated cyclobutanes were examined using 2H and 19F NMR. The common predictors of potency indicate that these two compounds will have anesthetic activity; however, 1,2-dichlorohexafluorocyclobutane (c(CCIFCCIFCF2CF2)) is not an effective anesthetic, whereas 1-chloro-1,2,2-trifluorocyclobutane (c(CCIFCF2CH2CH2)) is an effective general anesthetic. Using 2H NMR, the effect of these compounds on the acyl chain packing in palmitoyl (d31) oleoylphosphatidylcholine membranes was examined. The addition of the anesthetic c(CCIFCF2CH2CH2) results in small increases in the segmental order near the headgroup, whereas segments deeper in the bilayer show decreases in order. These results are consistent with those obtained previously for halothane, isoflurane, and enflurane. On the addition of the nonanesthetic c(CCIFCCIFCF2CF2), the segmental order in vitually unchanged, except for a slightly changed order near the segents 10-12 of the palmitoyl chains. These results, and the 19F chemical shifts, indicate that the anesthetic c(CCIFCF2CH2CH2) exhibits a preference for the membrane interface, as do the other general anesthetics, whereas the nonanesthetic c(CCIFCIFCF2CF2) resides within the membrane hydrocarbon core. The compound c(CCIFCCIFCF2CF2) and other nonanesthetic halocarbons have lower molecular dipole moments compared to effective anesthetic halocarbons, which may account for their altered distribution within the membrane. These data strongly suggest that preferential localization of a halocarbon within the membrane interface is a predictor of anesthetic potency. Furthermore, the data indicate that the properties and forces in the membrane interface deserve consideration as mediators of anesthetic activity.
Collapse
Affiliation(s)
- C North
- Department of Chemistry, University of Virginia, Charlottesville 22901, USA
| | | |
Collapse
|
48
|
|
49
|
Eger EI, Koblin DD, Harris RA, Kendig JJ, Pohorille A, Halsey MJ, Trudell JR. Hypothesis: inhaled anesthetics produce immobility and amnesia by different mechanisms at different sites. Anesth Analg 1997; 84:915-8. [PMID: 9085981 DOI: 10.1097/00000539-199704000-00039] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Affiliation(s)
- E I Eger
- Department of Anesthesia, University of California, San Francisco 94143-0464, USA
| | | | | | | | | | | | | |
Collapse
|
50
|
Tanelian DL, Markin VS. Biophysical and functional consequences of receptor-mediated nerve fiber transformation. Biophys J 1997; 72:1092-108. [PMID: 9138558 PMCID: PMC1184495 DOI: 10.1016/s0006-3495(97)78759-9] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Stimulation of the nervous system by substance P, a G protein-coupled receptor, and subsequent receptor internalization causes dendrites to change their shape from homogeneous cylinders to a heterogeneous string of swollen varicosities (beads) connected by thin segments. In this paper we have analyzed this phenomenon and propose quantitative mechanisms to explain this type of physical shape transformation. We developed a mathematical solution to describe the relationship between the initial radius of a cylindrical nerve fiber and the average radii of the subsequently created varicosities and connecting segments, as well as the periodicity of the varicosities along the nerve fiber. Theoretical predictions are in good agreement with our own and published experimental data from dorsal root ganglion neurons, spinal cord, and brain. Modeling the electrical properties of these beaded fibers has led to an understanding of the functional biophysical consequences of nerve fiber transformation. Several hypotheses for how this shape transformation can be used to process information within the nervous system have been put forth.
Collapse
Affiliation(s)
- D L Tanelian
- Eugene McDermott Center for Pain Management, Department of Anesthesiology and Pain Management, University of Texas Southwestern Medical Center, Dallas 75235-9068, USA
| | | |
Collapse
|