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Crawford MA, Sinclair AJ, Hall B, Ogundipe E, Wang Y, Bitsanis D, Djahanbakhch OB, Harbige L, Ghebremeskel K, Golfetto I, Moodley T, Hassam A, Sassine A, Johnson MR. The imperative of arachidonic acid in early human development. Prog Lipid Res 2023; 91:101222. [PMID: 36746351 DOI: 10.1016/j.plipres.2023.101222] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2022] [Accepted: 01/26/2023] [Indexed: 02/06/2023]
Abstract
This review is about the role of arachidonic acid (ArA) in foetal and early growth and development. In 1975 and '76, we reported the preferential incorporation of ArA into the developing brain of rat pups, its conservation as a principal component in the brains of 32 mammalian species and the high proportion delivered by the human placenta for foetal nutrition, compared to its parent linoleic acid (LA). ArA is quantitatively the principal acyl component of membrane lipids from foetal red cells, mononuclear cells, astrocytes, endothelium, and placenta. Functionally, we present evidence that ArA, but not DHA, relaxes the foetal mesenteric arteries. The placenta biomagnifies ArA, doubling the proportion of the maternal level in cord blood. The proportions of ArA and its allies (di-homo-gamma-linolenic acid (DGLA), adrenic acid and ω6 docosapentaenoic acid) are similar or higher than the total of ω3 fatty acids in human milk, maintaining the abundant supply to the developing infant. Despite the evidence of the importance of ArA, the European Food Standard Agency, in 2014 rejected the joint FAO and WHO recommendation on the inclusion of ArA in infant formula, although they recommended DHA. The almost universal dominance of ArA in the membrane phosphoglycerides during human organogenesis and prenatal growth suggests that the importance of ArA and its allies in reproductive biology needs to be re-evaluated urgently.
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Affiliation(s)
- Michael A Crawford
- Chelsea and Westminster Hospital Campus of Imperial College, London, UK; The Institute of Brain Chemistry and Human Nutrition, SW10 9NH, UK.
| | - Andrew J Sinclair
- Department of Nutrition, Dietetics and Food, Monash University, Notting Hill, Victoria, Australia; Faculty of Health, Deakin University, Burwood, Victoria, Australia
| | - Barbara Hall
- The Institute of Brain Chemistry and Human Nutrition, SW10 9NH, UK
| | - Enitan Ogundipe
- Chelsea and Westminster Hospital Campus of Imperial College, London, UK
| | - Yiqun Wang
- Chelsea and Westminster Hospital Campus of Imperial College, London, UK; The Institute of Brain Chemistry and Human Nutrition, SW10 9NH, UK
| | - Dimitrios Bitsanis
- The Institute of Brain Chemistry and Human Nutrition, SW10 9NH, UK; EvexiaDiet dietetic practise, Athens, Greece
| | | | - Laurence Harbige
- The Institute of Brain Chemistry and Human Nutrition, SW10 9NH, UK; School of Human Sciences, London Metropolitan University, UK
| | | | - Ivan Golfetto
- The Institute of Brain Chemistry and Human Nutrition, SW10 9NH, UK; Department of General Pathology and Physiopathology, Central University of Venezuela, Venezuela
| | - Therishnee Moodley
- The Institute of Brain Chemistry and Human Nutrition, SW10 9NH, UK; Centre for Reproductive Medicine, St Bartholomew's, Barts Health NHS Trust, London, UK
| | | | - AnnieBelle Sassine
- Chelsea and Westminster Hospital Campus of Imperial College, London, UK; The Institute of Brain Chemistry and Human Nutrition, SW10 9NH, UK
| | - Mark R Johnson
- Chelsea and Westminster Hospital Campus of Imperial College, London, UK
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2
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Zimmerberg J, Soubias O, Pastor RW. Special issue for Klaus Gawrisch. Biophys J 2023; 122:E1-E8. [PMID: 36921597 PMCID: PMC10111273 DOI: 10.1016/j.bpj.2023.02.022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2023] [Revised: 02/15/2023] [Accepted: 02/15/2023] [Indexed: 03/17/2023] Open
Affiliation(s)
- Joshua Zimmerberg
- Section on Integrative Biophysics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA
| | - Olivier Soubias
- Macromolecular NMR Section, Center for Structural Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Frederick, MD, USA
| | - Richard W Pastor
- Laboratory of Computational Biology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA.
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3
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Qin H, Miao Y, Cross TA, Fu R. Beyond Structural Biology to Functional Biology: Solid-State NMR Experiments and Strategies for Understanding the M2 Proton Channel Conductance. J Phys Chem B 2017; 121:4799-4809. [PMID: 28425709 DOI: 10.1021/acs.jpcb.7b02468] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
In terms of structural biology, solid-state NMR experiments and strategies have been well established for resonance assignments, leading to the determination of three-dimensional structures of insoluble membrane proteins in their native-like environment. It is also known that NMR has the unique capabilities to characterize structure-function relationships of membrane-bound biological systems beyond structural biology. Here, we report on solid-state NMR experiments and strategies for extracting functional activities on a sub-millisecond time scale. Specifically, we use the His37-labeled full length M2 (M2FL) protein of the Influenza A virus embedded in synthetic lipid bilayers as an example to characterize the proton conduction mechanism and kinetics. The integral membrane M2 protein assembles as a tetrameric bundle to form a proton-conducting channel that is activated by low pH and is essential for the viral lifecycle. Our results present convincing evidence for the formation of imidazolium-imidazole hydrogen bonds in the His37 tetrad at low pH and that these hydrogen bonds have a low barrier that facilitates the proton conduction mechanism in the M2FL protein. Moreover, it has been possible to measure hydronium ion exchange between water and the protons in the His37 NH bonds based on chemical exchange spectroscopy with minimized spin diffusion. The results identify an exchange rate constant of ∼4000 s-1 for pH 5.8 at -10 °C.
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Affiliation(s)
- Huajun Qin
- Department of Chemistry and Biochemistry, Florida State University , Tallahassee, Florida 32306, United States
| | - Yimin Miao
- Department of Chemistry and Biochemistry, Florida State University , Tallahassee, Florida 32306, United States
| | - Timothy A Cross
- Department of Chemistry and Biochemistry, Florida State University , Tallahassee, Florida 32306, United States.,National High Magnet Field Lab , 1800 East Paul Dirac Drive, Tallahassee, Florida 32310, United States
| | - Riqiang Fu
- National High Magnet Field Lab , 1800 East Paul Dirac Drive, Tallahassee, Florida 32310, United States
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4
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Fu R, Miao Y, Qin H, Cross TA. Probing Hydronium Ion Histidine NH Exchange Rate Constants in the M2 Channel via Indirect Observation of Dipolar-Dephased 15N Signals in Magic-Angle-Spinning NMR. J Am Chem Soc 2016; 138:15801-15804. [PMID: 27960325 PMCID: PMC5368641 DOI: 10.1021/jacs.6b08376] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Water-protein chemical exchange in membrane-bound proteins is an important parameter for understanding how proteins interact with their aqueous environment, but has been difficult to observe in membrane-bound biological systems. Here, we demonstrate the feasibility of probing specific water-protein chemical exchange in membrane-bound proteins in solid-state MAS NMR. By spin-locking the 1H magnetization along the magic angle, the 1H spin diffusion is suppressed such that a water-protein chemical exchange process can be monitored indirectly by dipolar-dephased 15N signals through polarization transfer from 1H. In the example of the Influenza A full length M2 protein, the buildup of dipolar-dephased 15N signals from the tetrad of His37 side chains have been observed as a function of spin-lock time. This confirms that hydronium ions are in exchange with protons in the His37 NH bonds at the heart of the M2 proton conduction mechanism, with an exchange rate constant of ∼1750 s-1 for pH 6.2 at -10 °C.
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Affiliation(s)
- Riqiang Fu
- National High Magnet Field Lab, 1800 East Paul Dirac Drive, Tallahassee, Florida 32310, United States
| | - Yimin Miao
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306, United States
| | - Huajun Qin
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306, United States
| | - Timothy A. Cross
- National High Magnet Field Lab, 1800 East Paul Dirac Drive, Tallahassee, Florida 32310, United States
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306, United States
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5
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Randolph AL, Mokrab Y, Bennett AL, Sansom MS, Ramsey IS. Proton currents constrain structural models of voltage sensor activation. eLife 2016; 5. [PMID: 27572256 PMCID: PMC5065317 DOI: 10.7554/elife.18017] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2016] [Accepted: 08/29/2016] [Indexed: 11/13/2022] Open
Abstract
The Hv1 proton channel is evidently unique among voltage sensor domain proteins in mediating an intrinsic 'aqueous' H+ conductance (GAQ). Mutation of a highly conserved 'gating charge' residue in the S4 helix (R1H) confers a resting-state H+ 'shuttle' conductance (GSH) in VGCs and Ci VSP, and we now report that R1H is sufficient to reconstitute GSH in Hv1 without abrogating GAQ. Second-site mutations in S3 (D185A/H) and S4 (N4R) experimentally separate GSH and GAQ gating, which report thermodynamically distinct initial and final steps, respectively, in the Hv1 activation pathway. The effects of Hv1 mutations on GSH and GAQ are used to constrain the positions of key side chains in resting- and activated-state VS model structures, providing new insights into the structural basis of VS activation and H+ transfer mechanisms in Hv1.
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Affiliation(s)
- Aaron L Randolph
- Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond, United States.,Medical College of Virginia Campus, Virginia Commonwealth University School of Medicine, Richmond, United States
| | - Younes Mokrab
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - Ashley L Bennett
- Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond, United States.,Medical College of Virginia Campus, Virginia Commonwealth University School of Medicine, Richmond, United States
| | - Mark Sp Sansom
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - Ian Scott Ramsey
- Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond, United States.,Medical College of Virginia Campus, Virginia Commonwealth University School of Medicine, Richmond, United States
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6
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Garcia-Fandiño R, Piñeiro Á, Trick JL, Sansom MSP. Lipid Bilayer Membrane Perturbation by Embedded Nanopores: A Simulation Study. ACS NANO 2016; 10:3693-3701. [PMID: 26943498 DOI: 10.1021/acsnano.6b00202] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
A macromolecular nanopore inserted into a membrane may perturb the dynamic organization of the surrounding lipid bilayer. To better understand the nature of such perturbations, we have undertaken a systematic molecular dynamics simulation study of lipid bilayer structure and dynamics around three different classes of nanopore: a carbon nanotube, three related cyclic peptide nanotubes differing in the nature of their external surfaces, and a model of a β-barrel nanopore protein. Periodic spatial distributions of several lipid properties as a function of distance from the nanopore were observed. This was especially clear for the carbon nanotube system, for which the density of lipids, the bilayer thickness, the projection of lipid head-to-tail vectors onto the membrane plane, and lipid lateral diffusion coefficients exhibited undulatory behavior as a function of the distance from the surface of the channel. Overall, the differences in lipid behavior as a function of the nanopore structure reveal local adaptation of the bilayer structure and dynamics to different embedded nanopore structures. Both the local structure and dynamic behavior of lipids around membrane-embedded nanopores are sensitive to the geometry and nature of the outer surface of the macromolecule/molecular assembly forming the pore.
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Affiliation(s)
- Rebeca Garcia-Fandiño
- Center for Research in Biological Chemistry and Molecular Materials (CIQUS), University of Santiago de Compostela , 15782 Santiago de Compostela, Spain
- Department of Biochemistry, University of Oxford , South Parks Road, Oxford OX1 3QU, United Kingdom
| | - Ángel Piñeiro
- Soft Matter & Molecular Biophysics Group, Department of Applied Physics, Faculty of Physics, University of Santiago de Compostela , 15782 Santiago de Compostela, Spain
| | - Jemma L Trick
- Department of Biochemistry, University of Oxford , South Parks Road, Oxford OX1 3QU, United Kingdom
| | - Mark S P Sansom
- Department of Biochemistry, University of Oxford , South Parks Road, Oxford OX1 3QU, United Kingdom
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7
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Kitjaruwankul S, Boonamnaj P, Fuklang S, Supunyabut C, Sompornpisut P. Shaping the Water Crevice To Accommodate the Voltage Sensor in a Down Conformation: A Molecular Dynamics Simulation Study. J Phys Chem B 2015; 119:6516-24. [DOI: 10.1021/acs.jpcb.5b00787] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Sunan Kitjaruwankul
- Graduate
School of Nanoscience and Technology, Chulalongkorn University, Bangkok 10330, Thailand
| | - Panisak Boonamnaj
- Department
of Chemistry, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand
| | - Sunit Fuklang
- Department
of Chemistry, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand
| | - Chirayut Supunyabut
- Department
of Chemistry, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand
| | - Pornthep Sompornpisut
- Department
of Chemistry, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand
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8
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Voltage Sensing in Membranes: From Macroscopic Currents to Molecular Motions. J Membr Biol 2015; 248:419-30. [PMID: 25972106 DOI: 10.1007/s00232-015-9805-x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2015] [Accepted: 04/24/2015] [Indexed: 01/06/2023]
Abstract
Voltage-sensing domains (VSDs) are integral membrane protein units that sense changes in membrane electric potential, and through the resulting conformational changes, regulate a specific function. VSDs confer voltage-sensitivity to a large superfamily of membrane proteins that includes voltage-gated Na[Formula: see text], K[Formula: see text], Ca[Formula: see text] ,and H[Formula: see text] selective channels, hyperpolarization-activated cyclic nucleotide-gated channels, and voltage-sensing phosphatases. VSDs consist of four transmembrane segments (termed S1 through S4). Their most salient structural feature is the highly conserved positions for charged residues in their sequences. S4 exhibits at least three conserved triplet repeats composed of one basic residue (mostly arginine) followed by two hydrophobic residues. These S4 basic side chains participate in a state-dependent internal salt-bridge network with at least four acidic residues in S1-S3. The signature of voltage-dependent activation in electrophysiology experiments is a transient current (termed gating or sensing current) upon a change in applied membrane potential as the basic side chains in S4 move across the membrane electric field. Thus, the unique structural features of the VSD architecture allow for competing requirements: maintaining a series of stable transmembrane conformations, while allowing charge motion, as briefly reviewed here.
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9
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Abstract
K-selective voltage-gated channels (Kv) are multi-conformation bilayer-embedded proteins whose mechanosensitive (MS) Popen(V) implies that at least one conformational transition requires the restructuring of the channel-bilayer interface. Unlike Morris and colleagues, who attributed MS-Kv responses to a cooperative V-dependent closed-closed expansion↔compaction transition near the open state, Mackinnon and colleagues invoke expansion during a V-independent closed↔open transition. With increasing membrane tension, they suggest, the closed↔open equilibrium constant, L, can increase >100-fold, thereby taking steady-state Popen from 0→1; "exquisite sensitivity to small…mechanical perturbations", they state, makes a Kv "as much a mechanosensitive…as…a voltage-dependent channel". Devised to explain successive gK(V) curves in excised patches where tension spontaneously increased until lysis, their L-based model falters in part because of an overlooked IK feature; with recovery from slow inactivation factored in, their g(V) datasets are fully explained by the earlier model (a MS V-dependent closed-closed transition, invariant L≥4). An L-based MS-Kv predicts neither known Kv time courses nor the distinctive MS responses of Kv-ILT. It predicts Kv densities (hence gating charge per V-sensor) several-fold different from established values. If opening depended on elevated tension (L-based model), standard gK(V) operation would be compromised by animal cells' membrane flaccidity. A MS V-dependent transition is, by contrast, unproblematic on all counts. Since these issues bear directly on recent findings that mechanically-modulated Kv channels subtly tune pain-related excitability in peripheral mechanoreceptor neurons we undertook excitability modeling (evoked action potentials). Kvs with MS V-dependent closed-closed transitions produce nuanced mechanically-modulated excitability whereas an L-based MS-Kv yields extreme, possibly excessive (physiologically-speaking) inhibition.
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10
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Structural interactions of a voltage sensor toxin with lipid membranes. Proc Natl Acad Sci U S A 2014; 111:E5463-70. [PMID: 25453087 DOI: 10.1073/pnas.1415324111] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Protein toxins from tarantula venom alter the activity of diverse ion channel proteins, including voltage, stretch, and ligand-activated cation channels. Although tarantula toxins have been shown to partition into membranes, and the membrane is thought to play an important role in their activity, the structural interactions between these toxins and lipid membranes are poorly understood. Here, we use solid-state NMR and neutron diffraction to investigate the interactions between a voltage sensor toxin (VSTx1) and lipid membranes, with the goal of localizing the toxin in the membrane and determining its influence on membrane structure. Our results demonstrate that VSTx1 localizes to the headgroup region of lipid membranes and produces a thinning of the bilayer. The toxin orients such that many basic residues are in the aqueous phase, all three Trp residues adopt interfacial positions, and several hydrophobic residues are within the membrane interior. One remarkable feature of this preferred orientation is that the surface of the toxin that mediates binding to voltage sensors is ideally positioned within the lipid bilayer to favor complex formation between the toxin and the voltage sensor.
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11
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Li Q, Wong YL, Ng HQ, Gayen S, Kang C. Structural insight into the transmembrane segments 3 and 4 of the hERG potassium channel. J Pept Sci 2014; 20:935-44. [PMID: 25331429 DOI: 10.1002/psc.2704] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2014] [Revised: 08/26/2014] [Accepted: 09/11/2014] [Indexed: 12/27/2022]
Abstract
The hERG (human ether-a-go-go related gene) potassium channel is a voltage-gated potassium channel containing an N-terminal domain, a voltage-sensor domain, a pore domain and a C-terminal domain. The transmembrane segment 4 (S4) is important for sensing changes of membrane potentials through positively charge residues. A construct containing partial S2-S3 linker, S3, S4 and the S4-S5 linker of the hERG channel was purified into detergent micelles. This construct exhibits good quality NMR spectrum when it was purified in lyso-myristoyl phosphatidylglycerol (LMPG) micelles. Structural study showed that S3 contains two short helices with a negatively charged surface. The S4 and S4-S5 linker adopt helical structures. The six positively charged residues in S4 localize at different sides, suggesting that they may have different functions in channel gating. Relaxation studies indicated that S3 is more flexible than S4. The boundaries of S3-S4 and S4-S4-S5 linker were identified. Our results provided structural information of the S3 and S4, which will be helpful to understand their roles in channel gating.
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Affiliation(s)
- Qingxin Li
- Institute of Chemical and Engineering Sciences, Agency for Science, Technology and Research (A*STAR), Singapore, Singapore
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12
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Cardiolipin interaction with subunit c of ATP synthase: solid-state NMR characterization. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1848:260-5. [PMID: 25168468 DOI: 10.1016/j.bbamem.2014.08.021] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2014] [Revised: 08/12/2014] [Accepted: 08/16/2014] [Indexed: 01/29/2023]
Abstract
The interaction of lipids with subunit c from F1F0 ATP synthase is studied by biophysical methods. Subunit c from both Escherichia coli and Streptococcus pneumoniae interacts and copurifies with cardiolipin. Solid state NMR data on oligomeric rings of F0 show that the cardiolipin interacts with the c subunit in membrane bilayers. These studies offer strong support for the hypothesis that F0 has specific interactions with cardiolipin.
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13
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Faure É, Thompson C, Blunck R. Do lipids show state-dependent affinity to the voltage-gated potassium channel KvAP? J Biol Chem 2014; 289:16452-61. [PMID: 24742679 DOI: 10.1074/jbc.m113.537134] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
As all integral membrane proteins, voltage-gated ion channels are embedded in a lipid matrix that regulates their channel behavior either by physicochemical properties or by direct binding. Because manipulation of the lipid composition in cells is difficult, we investigated the influence of different lipids on purified KvAP channels reconstituted in planar lipid bilayers of known composition. Lipids developed two distinct and independent effects on the KvAP channels; lipids interacting with the pore lowered the energy barriers for the final transitions, whereas voltage sensor-bound lipids shifted the midpoint of activation dependent on their electrostatic charge. Above all, the midpoint of activation was determined only by those lipids the channels came in contact with first after purification and can seemingly only be exchanged if the channel resides in the open state. The high affinity of the bound lipids to the binding site has implications not only on our understanding of the gating mechanism but also on the general experimental design of any lipid dependence study.
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Affiliation(s)
- Élise Faure
- Groupe d'étude des protéines membranaires (GÉPROM), Université de Montréal, Montréal CH3C 3J7, Canada Physiology
| | - Christine Thompson
- Groupe d'étude des protéines membranaires (GÉPROM), Université de Montréal, Montréal CH3C 3J7, CanadaFrom the Departments of Physics and
| | - Rikard Blunck
- Groupe d'étude des protéines membranaires (GÉPROM), Université de Montréal, Montréal CH3C 3J7, Canada Physiology, From the Departments of Physics and
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14
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Kornilov P, Peretz A, Lee Y, Son K, Lee JH, Refaeli B, Roz N, Rehavi M, Choi S, Attali B. Promiscuous gating modifiers target the voltage sensor of K(v)7.2, TRPV1, and H(v)1 cation channels. FASEB J 2014; 28:2591-602. [PMID: 24599966 DOI: 10.1096/fj.14-250647] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Some of the fascinating features of voltage-sensing domains (VSDs) in voltage-gated cation channels (VGCCs) are their modular nature and adaptability. Here we examined the VSD sensitivity of different VGCCs to 2 structurally related nontoxin gating modifiers, NH17 and NH29, which stabilize K(v)7.2 potassium channels in the closed and open states, respectively. The effects of NH17 and NH29 were examined in Chinese hamster ovary cells transfected with transient receptor potential vanilloid 1 (TRPV1) or K(v)7.2 channels, as well as in dorsal root ganglia neurons, using the whole-cell patch-clamp technique. NH17 and NH29 exert opposite effects on TRPV1 channels, operating, respectively, as an activator and a blocker of TRPV1 currents (EC50 and IC50 values ranging from 4 to 40 μM). Combined mutagenesis, electrophysiology, structural homology modeling, molecular docking, and molecular dynamics simulation indicate that both compounds target the VSDs of TRPV1 channels, which, like vanilloids, are involved in π-π stacking, H-bonding, and hydrophobic interactions. Reflecting their promiscuity, the drugs also affect the lone VSD proton channel mVSOP. Thus, the same gating modifier can promiscuously interact with different VGCCs, and subtle differences at the VSD-ligand interface will dictate whether the gating modifier stabilizes channels in either the closed or the open state.
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Affiliation(s)
- Polina Kornilov
- Department of Physiology and Pharmacology, The Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel; and
| | - Asher Peretz
- Department of Physiology and Pharmacology, The Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel; and
| | - Yoonji Lee
- National Leading Research Laboratory of Molecular Modeling and Drug Design, College of Pharmacy, Graduate School of Pharmaceutical Sciences, and Global Top5 Research Program, Ewha Womans University, Seoul, Korea
| | - Karam Son
- National Leading Research Laboratory of Molecular Modeling and Drug Design, College of Pharmacy, Graduate School of Pharmaceutical Sciences, and Global Top5 Research Program, Ewha Womans University, Seoul, Korea
| | - Jin Hee Lee
- National Leading Research Laboratory of Molecular Modeling and Drug Design, College of Pharmacy, Graduate School of Pharmaceutical Sciences, and Global Top5 Research Program, Ewha Womans University, Seoul, Korea
| | - Bosmat Refaeli
- Department of Physiology and Pharmacology, The Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel; and
| | - Netta Roz
- Department of Physiology and Pharmacology, The Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel; and
| | - Moshe Rehavi
- Department of Physiology and Pharmacology, The Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel; and
| | - Sun Choi
- National Leading Research Laboratory of Molecular Modeling and Drug Design, College of Pharmacy, Graduate School of Pharmaceutical Sciences, and Global Top5 Research Program, Ewha Womans University, Seoul, Korea
| | - Bernard Attali
- Department of Physiology and Pharmacology, The Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel; and
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15
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Li Q, Wanderling S, Sompornpisut P, Perozo E. Structural basis of lipid-driven conformational transitions in the KvAP voltage-sensing domain. Nat Struct Mol Biol 2014; 21:160-6. [PMID: 24413055 PMCID: PMC3946318 DOI: 10.1038/nsmb.2747] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2013] [Accepted: 11/14/2013] [Indexed: 11/30/2022]
Abstract
Voltage-gated ion channels respond to transmembrane electric fields through reorientations of the positively charged S4 helix within the voltage-sensing domain (VSD). Despite a wealth of structural and functional data, the details of this conformational change remain controversial. Recent electrophysiological evidence showed that equilibrium between the resting ('down') and activated ('up') conformations of the KvAP VSD from Aeropyrum pernix can be biased through reconstitution in lipids with or without phosphate groups. We investigated the structural transition between these functional states, using site-directed spin-labeling and EPR spectroscopic methods. Solvent accessibility and interhelical distance determinations suggest that KvAP gates through S4 movements involving an ∼3-Å upward tilt and simultaneous ∼2-Å axial shift. This motion leads to large accessibly changes in the intracellular water-filled crevice and supports a new model of gating that combines structural rearrangements and electric-field remodeling.
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Affiliation(s)
- Qufei Li
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois, USA
| | - Sherry Wanderling
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois, USA
| | - Pornthep Sompornpisut
- Department of Chemistry, Faculty of Science, Chulalongkorn University, Bangkok, Thailand
| | - Eduardo Perozo
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois, USA
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Huster D. Solid-state NMR spectroscopy to study protein-lipid interactions. Biochim Biophys Acta Mol Cell Biol Lipids 2013; 1841:1146-60. [PMID: 24333800 DOI: 10.1016/j.bbalip.2013.12.002] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2013] [Accepted: 12/04/2013] [Indexed: 12/22/2022]
Abstract
The appropriate lipid environment is crucial for the proper function of membrane proteins. There is a tremendous variety of lipid molecules in the membrane and so far it is often unclear which component of the lipid matrix is essential for the function of a respective protein. Lipid molecules and proteins mutually influence each other; parameters such as acyl chain order, membrane thickness, membrane elasticity, permeability, lipid-domain and annulus formation are strongly modulated by proteins. More recent data also indicates that the influence of proteins goes beyond a single annulus of next-neighbor boundary lipids. Therefore, a mesoscopic approach to membrane lipid-protein interactions in terms of elastic membrane deformations has been developed. Solid-state NMR has greatly contributed to the understanding of lipid-protein interactions and the modern view of biological membranes. Methods that detect the influence of proteins on the membrane as well as direct lipid-protein interactions have been developed and are reviewed here. Examples for solid-state NMR studies on the interaction of Ras proteins, the antimicrobial peptide protegrin-1, the G protein-coupled receptor rhodopsin, and the K(+) channel KcsA are discussed. This article is part of a Special Issue entitled Tools to study lipid functions.
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Affiliation(s)
- Daniel Huster
- Institute of Medical Physics and Biophysics, University of Leipzig, Härtelstr. 16-18, D-04107 Leipzig, Germany.
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Combs DJ, Shin HG, Xu Y, Ramu Y, Lu Z. Tuning voltage-gated channel activity and cellular excitability with a sphingomyelinase. ACTA ACUST UNITED AC 2013; 142:367-80. [PMID: 24043861 PMCID: PMC3787777 DOI: 10.1085/jgp.201310986] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Voltage-gated ion channels generate action potentials in excitable cells and help set the resting membrane potential in nonexcitable cells like lymphocytes. It has been difficult to investigate what kinds of phospholipids interact with these membrane proteins in their native environments and what functional impacts such interactions create. This problem might be circumvented if we could modify specific lipid types in situ. Using certain voltage-gated K(+) (KV) channels heterologously expressed in Xenopus laevis oocytes as a model, our group has shown previously that sphingomyelinase (SMase) D may serve this purpose. SMase D is known to remove the choline group from sphingomyelin, a phospholipid primarily present in the outer leaflet of plasma membranes. This SMase D action lowers the energy required for voltage sensors of a KV channel to enter the activated state, causing a hyperpolarizing shift of the Q-V and G-V curves and thus activating them at more hyperpolarized potentials. Here, we find that this SMase D effect vanishes after removing most of the voltage-sensor paddle sequence, a finding supporting the notion that SMase D modification of sphingomyelin molecules alters these lipids' interactions with voltage sensors. Then, using SMase D to probe lipid-channel interactions, we find that SMase D not only similarly stimulates voltage-gated Na(+) (Na(V)) and Ca(2+) channels but also markedly slows Na(V) channel inactivation. However, the latter effect is not observed in tested mammalian cells, an observation highlighting the profound impact of the membrane environment on channel function. Finally, we directly demonstrate that SMase D stimulates both native K(V)1.3 in nonexcitable human T lymphocytes at their typical resting membrane potential and native Na(V) channels in excitable cells, such that it shifts the action potential threshold in the hyperpolarized direction. These proof-of-concept studies illustrate that the voltage-gated channel activity in both excitable and nonexcitable cells can be tuned by enzymatically modifying lipid head groups.
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Affiliation(s)
- David J Combs
- Department of Physiology, Howard Hughes Medical Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104
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Akgun B, Satija S, Nanda H, Pirrone GF, Shi X, Engen JR, Kent MS. Conformational transition of membrane-associated terminally acylated HIV-1 Nef. Structure 2013; 21:1822-33. [PMID: 24035710 DOI: 10.1016/j.str.2013.08.008] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2013] [Revised: 07/08/2013] [Accepted: 08/02/2013] [Indexed: 01/26/2023]
Abstract
Many proteins are posttranslationally modified by acylation targeting them to lipid membranes. While methods such as X-ray crystallography and nuclear magnetic resonance are available to determine the structure of folded proteins in solution, the precise position of folded domains relative to a membrane remains largely unknown. We used neutron and X-ray reflection methods to measure the displacement of the core domain of HIV Nef from lipid membranes upon insertion of the N-terminal myristate group. Nef is one of several HIV-1 accessory proteins and an essential factor in AIDS progression. Upon insertion of the myristate and residues from the N-terminal arm, Nef transitions from a closed-to-open conformation that positions the core domain 70 Å from the lipid headgroups. This work rules out previous speculation that the Nef core remains closely associated with the membrane to optimize interactions with the cytoplasmic domain of MHC-1.
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Affiliation(s)
- Bulent Akgun
- National Institute of Standards and Technology, Gaithersburg, MD 20899, USA; Department of Materials Science and Engineering, University of Maryland, College Park, MD 20742, USA; Department of Chemistry, Boğaziçi University, Bebek 34342, Istanbul, Turkey
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The design principle of paddle motifs in voltage sensors. Nat Struct Mol Biol 2013; 20:534-5. [DOI: 10.1038/nsmb.2578] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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