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Wu D, Tang H, Qiu X, Song S, Chen S, Robinson CV. Native MS-guided lipidomics to define endogenous lipid microenvironments of eukaryotic receptors and transporters. Nat Protoc 2024:10.1038/s41596-024-01037-4. [PMID: 39174660 DOI: 10.1038/s41596-024-01037-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2024] [Accepted: 06/06/2024] [Indexed: 08/24/2024]
Abstract
The mammalian membrane is composed of various eukaryotic lipids interacting with extensively post-translationally modified proteins. Probing interactions between these mammalian membrane proteins and their diverse and heterogeneous lipid cohort remains challenging. Recently, native mass spectrometry (MS) combined with bottom-up 'omics' approaches has provided valuable information to relate structural and functional lipids to membrane protein assemblies in eukaryotic membranes. Here we provide a step-by-step protocol to identify and provide relative quantification for endogenous lipids bound to mammalian membrane proteins and their complexes. Using native MS to guide our lipidomics strategies, we describe the necessary sample preparation steps, followed by native MS data acquisition, tailored lipidomics and data interpretation. We also highlight considerations for the integration of different levels of information from native MS and lipidomics and how to deal with the various challenges that arise during the experiments. This protocol begins with the preparation of membrane proteins from mammalian cells and tissues for native MS. The results enable not only direct assessment of copurified endogenous lipids but also determination of the apparent affinities of specific lipids. Detailed sample preparation for lipidomics analysis is also covered, along with comprehensive settings for liquid chromatography-MS analysis. This protocol is suitable for the identification and quantification of endogenous lipids, including fatty acids, sterols, glycerolipids, phospholipids and glycolipids and can be used to interrogate proteins from recombinant sources to native membranes.
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Affiliation(s)
- Di Wu
- Department of Chemistry, University of Oxford, Oxford, UK
- Kavli Institute for Nanoscience Discovery, University of Oxford, Oxford, UK
| | - Haiping Tang
- Department of Chemistry, University of Oxford, Oxford, UK
- Kavli Institute for Nanoscience Discovery, University of Oxford, Oxford, UK
| | - Xingyu Qiu
- Department of Chemistry, University of Oxford, Oxford, UK
- Kavli Institute for Nanoscience Discovery, University of Oxford, Oxford, UK
| | - Siyuan Song
- Department of Chemistry, University of Oxford, Oxford, UK
- Kavli Institute for Nanoscience Discovery, University of Oxford, Oxford, UK
| | - Siyun Chen
- Department of Chemistry, University of Oxford, Oxford, UK
- Kavli Institute for Nanoscience Discovery, University of Oxford, Oxford, UK
| | - Carol V Robinson
- Department of Chemistry, University of Oxford, Oxford, UK.
- Kavli Institute for Nanoscience Discovery, University of Oxford, Oxford, UK.
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2
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Liu J, Li B, Lu G, Wang G, Zheng J, Huang L, Feng Y, Xu S, Jiang Y, Liu N. Toward Selective Transport of Monovalent Metal Ions with High Permeability Based on Crown Ether-Encapsulated Metal-Organic Framework Sub-Nanochannels. ACS APPLIED MATERIALS & INTERFACES 2024; 16:26634-26642. [PMID: 38722947 DOI: 10.1021/acsami.4c05672] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2024]
Abstract
Achieving selective transport of monovalent metal ions with high precision and permeability analogues to biological protein ion channels has long been explored for fundamental research and various applications, such as ion sieving, mineral extraction, and energy harvesting and conversion. However, it still remains a significant challenge to construct artificial nanofluidic devices to realize the trade-off effects between selective ion transportation and high ion permeability. In this work, we report a bioinspired functional micropipet with in situ growth of crown ether-encapsulated metal-organic frameworks (MOFs) inside the tip and realize selective transport of monovalent metal ions. The functional ion-selective micropipet with sub-nanochannels was constructed by the interfacial growth method with the formation of composite MOFs consisting of ZIF-8 and 15-crown-5. The resulting micropipet device exhibited obvious monovalent ion selectivity and high flux of Li+ due to the synergistic effects of size sieving in subnanoconfined space and specific coordination of 15-crown-5 toward Na+. The selectivity of Li+/Na+, Li+/K+, Li+/Ca2+, and Li+/Mg2+ with 15-crown-5@ZIF-8-functionalized micropipet reached 3.9, 5.2, 105.8, and 122.4, respectively, which had an obvious enhancement compared to that with ZIF-8. Notably, the ion flux of Li+ can reach up to 93.8 ± 3.6 mol h-1·m-2 that is much higher than previously reported values. Furthermore, the functional micropipet with 15-crown-5@ZIF-8 sub-nanochannels exhibited stable Li+ selectivity under various conditions, such as different ion concentrations, pH values, and mixed ion solutions. This work not only provides new opportunities for the development of MOF-based nanofluidic devices for selective ion transport but also facilitates the promising practical applications in lithium extraction from salt-like brines, sewage treatment, and other related aspects.
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Affiliation(s)
- Jiahao Liu
- College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou 325000, China
- College of Chemistry, Beijing Normal University, Beijing 100875, China
- Key Laboratory of Carbon Materials of Zhejiang Province, College of Chemistry & Materials Engineering, Wenzhou University, Wenzhou 325027, China
| | - Baijun Li
- College of Chemistry, Beijing Normal University, Beijing 100875, China
| | - Guangwen Lu
- College of Chemistry, Beijing Normal University, Beijing 100875, China
| | - Guofeng Wang
- College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou 325000, China
- Key Laboratory of Carbon Materials of Zhejiang Province, College of Chemistry & Materials Engineering, Wenzhou University, Wenzhou 325027, China
| | - Juanjuan Zheng
- College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou 325000, China
- Key Laboratory of Carbon Materials of Zhejiang Province, College of Chemistry & Materials Engineering, Wenzhou University, Wenzhou 325027, China
| | - Liying Huang
- College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou 325000, China
- Key Laboratory of Carbon Materials of Zhejiang Province, College of Chemistry & Materials Engineering, Wenzhou University, Wenzhou 325027, China
| | - Yueyue Feng
- College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou 325000, China
- Key Laboratory of Carbon Materials of Zhejiang Province, College of Chemistry & Materials Engineering, Wenzhou University, Wenzhou 325027, China
| | - Shiwei Xu
- College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou 325000, China
- Key Laboratory of Carbon Materials of Zhejiang Province, College of Chemistry & Materials Engineering, Wenzhou University, Wenzhou 325027, China
| | - Yanan Jiang
- College of Chemistry, Beijing Normal University, Beijing 100875, China
| | - Nannan Liu
- College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou 325000, China
- Key Laboratory of Carbon Materials of Zhejiang Province, College of Chemistry & Materials Engineering, Wenzhou University, Wenzhou 325027, China
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3
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Pavlyuk E, Yungerman I, Bliznyuk A, Moskovitz Y. Studying the Effects of Dissolved Noble Gases and High Hydrostatic Pressure on the Spherical DOPC Bilayer Using Molecular Dynamic Simulations. MEMBRANES 2024; 14:89. [PMID: 38668117 PMCID: PMC11052037 DOI: 10.3390/membranes14040089] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2024] [Revised: 04/04/2024] [Accepted: 04/10/2024] [Indexed: 04/28/2024]
Abstract
Fine-grained molecular dynamics simulations have been conducted to depict lipid objects enclosed in water and interacting with a series of noble gases dissolved in the medium. The simple point-charge (SPC) water system, featuring a boundary composed of 1,2-Dioleoyl-sn-glycero-3-phosphocholine (DOPC) molecules, maintained stability throughout the simulation under standard conditions. This allowed for the accurate modeling of the effects of hydrostatic pressure at an ambient pressure of 25 bar. The chosen pressure references the 240 m depth of seawater: the horizon frequently used by commercial divers, who comprise the primary patient population of the neurological complication of inert gas narcosis and the consequences of high-pressure neurological syndrome. To quantify and validate the neurological effects of noble gases and discriminate them from high hydrostatic pressure, we reduced the dissolved gas molar concentration to 1.5%, three times smaller than what we previously tested for the planar bilayer (3.5%). The nucleation and growth of xenon, argon and neon nanobubbles proved consistent with the data from the planar bilayer simulations. On the other hand, hyperbaric helium induces only a residual distorting effect on the liposome, with no significant condensed gas fraction observed within the hydrophobic core. The bubbles were distributed over a large volume-both in the bulk solvent and in the lipid phase-thereby causing substantial membrane distortion. This finding serves as evidence of the validity of the multisite distortion hypothesis for the neurological effect of inert gases at high pressure.
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Affiliation(s)
- Eugeny Pavlyuk
- Laboratory of Multi-Scale Mathematical Modeling, Ural Federal University, Ekaterinburg 620002, Russia
| | - Irena Yungerman
- Department of Chemical Engineering, Technion—Israel Technological Institute, Technion City, Haifa 3200003, Israel
| | - Alice Bliznyuk
- Ilse Katz Institute for Nanoscale Science and Technology (IKI), Ben Gurion University of the Negev, Beer Sheva 8410501, Israel
| | - Yevgeny Moskovitz
- Laboratory of Multi-Scale Mathematical Modeling, Ural Federal University, Ekaterinburg 620002, Russia
- Department of Chemical Engineering, Technion—Israel Technological Institute, Technion City, Haifa 3200003, Israel
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4
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Yekefallah M, van Aalst EJ, van Beekveld RAM, Eason IR, Breukink E, Weingarth M, Wylie BJ. Cooperative Gating of a K + Channel by Unmodified Biological Anionic Lipids Viewed by Solid-State NMR Spectroscopy. J Am Chem Soc 2024; 146:4421-4432. [PMID: 38334076 PMCID: PMC10885140 DOI: 10.1021/jacs.3c09266] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2023] [Revised: 01/23/2024] [Accepted: 01/24/2024] [Indexed: 02/10/2024]
Abstract
Lipids adhere to membrane proteins to stimulate or suppress molecular and ionic transport and signal transduction. Yet, the molecular details of lipid-protein interaction and their functional impact are poorly characterized. Here we combine NMR, coarse-grained molecular dynamics (CGMD), and functional assays to reveal classic cooperativity in the binding and subsequent activation of a bacterial inward rectifier potassium (Kir) channel by phosphatidylglycerol (PG), a common component of many membranes. Past studies of lipid activation of Kir channels focused primarily on phosphatidylinositol bisphosphate, a relatively rare signaling lipid that is tightly regulated in space and time. We use solid-state NMR to quantify the binding of unmodified 13C-PG to the K+ channel KirBac1.1 in liposomes. This specific lipid-protein interaction has a dissociation constant (Kd) of ∼7 mol percentage PG (ΧPG) with positive cooperativity (n = 3.8) and approaches saturation near 20% ΧPG. Liposomal flux assays show that K+ flux also increases with PG in a cooperative manner with an EC50 of ∼20% ΧPG, within the physiological range. Further quantitative fitting of these data reveals that PG acts as a partial (80%) agonist with fivefold K+ flux amplification. Comparisons of NMR chemical shift perturbation and CGMD simulations at different ΧPG confirm the direct interaction of PG with key residues, several of which would not be accessible to lipid headgroups in the closed state of the channel. Allosteric regulation by a common lipid is directly relevant to the activation mechanisms of several human ion channels. This study highlights the role of concentration-dependent lipid-protein interactions and tightly controlled protein allostery in the activation and regulation of ion channels.
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Affiliation(s)
- Maryam Yekefallah
- Department
of Chemistry and Biochemistry, Texas Tech
University, Lubbock, Texas 79409, United States
| | - Evan J. van Aalst
- Department
of Chemistry and Biochemistry, Texas Tech
University, Lubbock, Texas 79409, United States
| | - Roy A. M. van Beekveld
- Department
of Chemistry, Faculty of Science, Utrecht
University, Padualaan 8, Utrecht3584
CH, The Netherlands
| | - Isaac R. Eason
- Department
of Chemistry and Biochemistry, Texas Tech
University, Lubbock, Texas 79409, United States
| | - Eefjan Breukink
- Membrane
Biochemistry and Biophysics, Department of Chemistry, Utrecht University, Padualaan 8, Utrecht 3584
CH, The Netherlands
| | - Markus Weingarth
- Department
of Chemistry, Faculty of Science, Utrecht
University, Padualaan 8, Utrecht3584
CH, The Netherlands
| | - Benjamin J. Wylie
- Department
of Chemistry and Biochemistry, Texas Tech
University, Lubbock, Texas 79409, United States
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5
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Baron J, Groschner K, Tiapko O. Calcium transport and sensing in TRPC channels - New insights into a complex feedback regulation. Cell Calcium 2023; 116:102816. [PMID: 37897981 DOI: 10.1016/j.ceca.2023.102816] [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: 09/07/2023] [Revised: 10/16/2023] [Accepted: 10/17/2023] [Indexed: 10/30/2023]
Abstract
Canonical TRP (TRPC) channels are a still enigmatic family of signaling molecules with multimodal sensing features. These channels enable Ca2+ influx through the plasma membrane to control a diverse range of cellular functions. Based on both regulatory- and recently uncovered structural features, TRPC channels are considered to coordinate Ca2+ and other divalent cations not only within the permeation path but also at additional sensory sites. Analysis of TRPC structures by cryo-EM identified multiple regulatory ion binding pockets. With this review, we aim at an overview and a critical discussion of the current concepts of divalent sensing by TRPC channels.
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Affiliation(s)
- Jasmin Baron
- Gottfried-Schatz-Research-Center Medical Physics and Biophysics, Medical University of Graz, Neue Stiftingtalstrasse 6/H03, 8010 Graz, Austria
| | - Klaus Groschner
- Gottfried-Schatz-Research-Center Medical Physics and Biophysics, Medical University of Graz, Neue Stiftingtalstrasse 6/H03, 8010 Graz, Austria
| | - Oleksandra Tiapko
- Gottfried-Schatz-Research-Center Medical Physics and Biophysics, Medical University of Graz, Neue Stiftingtalstrasse 6/H03, 8010 Graz, Austria.
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6
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Gu RX, de Groot BL. Central cavity dehydration as a gating mechanism of potassium channels. Nat Commun 2023; 14:2178. [PMID: 37069187 PMCID: PMC10110622 DOI: 10.1038/s41467-023-37531-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2022] [Accepted: 03/21/2023] [Indexed: 04/19/2023] Open
Abstract
The hydrophobic gating model, in which ion permeation is inhibited by the hydrophobicity, rather than a physical occlusion of the nanopore, functions in various ion channels including potassium channels. Available research focused on the energy barriers for ion/water conduction due to the hydrophobicity, whereas how hydrophobic gating affects the function and structure of channels remains unclear. Here, we use potassium channels as examples and conduct molecular dynamics simulations to investigate this problem. Our simulations find channel activities (ion currents) highly correlated with cavity hydration level, implying insufficient hydration as a barrier for ion permeation. Enforced cavity dehydration successfully induces conformational transitions between known channel states, further implying cavity dewetting as a key step in the gating procedure of potassium channels utilizing different activation mechanisms. Our work reveals how the cavity dewetting is coupled to structural changes of potassium channels and how it affects channel activity. The conclusion may also apply to other ion channels.
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Affiliation(s)
- Ruo-Xu Gu
- School of Life Sciences and Biotechnology, Shanghai Jia Tong University, 800 Dongchuan Road, 200240, Shanghai, China
- Department of Theoretical and Computational Biophysics, Max-Planck Institute for Multidisciplinary Sciences, Am Fassberg 11, 37077, Göttingen, Germany
| | - Bert L de Groot
- Department of Theoretical and Computational Biophysics, Max-Planck Institute for Multidisciplinary Sciences, Am Fassberg 11, 37077, Göttingen, Germany.
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7
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Krajewska M, Szewczyk A, Kulawiak B, Koprowski P. Pharmacological Characterization of a Recombinant Mitochondrial ROMK2 Potassium Channel Expressed in Bacteria and Reconstituted in Planar Lipid Bilayers. MEMBRANES 2023; 13:360. [PMID: 36984747 PMCID: PMC10052516 DOI: 10.3390/membranes13030360] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/31/2023] [Revised: 03/10/2023] [Accepted: 03/16/2023] [Indexed: 06/18/2023]
Abstract
In the inner mitochondrial membrane, several potassium channels that play a role in cell life and death have been identified. One of these channels is the ATP-regulated potassium channel (mitoKATP). The ROMK2 potassium channel is a potential molecular component of the mitoKATP channel. The current study aimed to investigate the pharmacological modulation of the activity of the ROMK2 potassium channel expressed in Escherichia coli bacteria. ROMK2 was solubilized in polymer nanodiscs and incorporated in planar lipid bilayers. The impact of known mitoKATP channel modulators on the activity of the ROMK2 was characterized. We found that the ROMK2 channel was activated by the mitoKATP channel opener diazoxide and blocked by mitoKATP inhibitors such as ATP/Mg2+, 5-hydroxydecanoic acid, and antidiabetic sulfonylurea glibenclamide. These results indicate that the ROMK2 potassium protein may be a pore-forming subunit of mitoKATP and that the impact of channel modulators is not related to the presence of accessory proteins.
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Affiliation(s)
- Milena Krajewska
- Laboratory of Intracellular Ion Channels, Nencki Institute of Experimental Biology PAS, 02-093 Warsaw, Poland
- Interdisciplinary Laboratory of Molecular Biology and Biophysics, Centre of New Technologies, University of Warsaw, 02-097 Warsaw, Poland
| | - Adam Szewczyk
- Laboratory of Intracellular Ion Channels, Nencki Institute of Experimental Biology PAS, 02-093 Warsaw, Poland
| | - Bogusz Kulawiak
- Laboratory of Intracellular Ion Channels, Nencki Institute of Experimental Biology PAS, 02-093 Warsaw, Poland
| | - Piotr Koprowski
- Laboratory of Intracellular Ion Channels, Nencki Institute of Experimental Biology PAS, 02-093 Warsaw, Poland
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8
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Mass spectrometry of intact membrane proteins: shifting towards a more native-like context. Essays Biochem 2023; 67:201-213. [PMID: 36807530 PMCID: PMC10070488 DOI: 10.1042/ebc20220169] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2022] [Revised: 01/20/2023] [Accepted: 01/23/2023] [Indexed: 02/23/2023]
Abstract
Integral membrane proteins are involved in a plethora of biological processes including cellular signalling, molecular transport, and catalysis. Many of these functions are mediated by non-covalent interactions with other proteins, substrates, metabolites, and surrounding lipids. Uncovering such interactions and deciphering their effect on protein activity is essential for understanding the regulatory mechanisms underlying integral membrane protein function. However, the detection of such dynamic complexes has proven to be challenging using traditional approaches in structural biology. Native mass spectrometry has emerged as a powerful technique for the structural characterisation of membrane proteins and their complexes, enabling the detection and identification of protein-binding partners. In this review, we discuss recent native mass spectrometry-based studies that have characterised non-covalent interactions of membrane proteins in the presence of detergents or membrane mimetics. We additionally highlight recent progress towards the study of membrane proteins within native membranes and provide our perspective on how these could be combined with recent developments in instrumentation to investigate increasingly complex biomolecular systems.
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9
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Seiferth D, Biggin PC, Tucker SJ. When is a hydrophobic gate not a hydrophobic gate? J Gen Physiol 2022; 154:213612. [PMID: 36287215 PMCID: PMC9614698 DOI: 10.1085/jgp.202213210] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The flux of ions through a channel is most commonly regulated by changes that result in steric occlusion of its pore. However, ion permeation can also be prevented by formation of a desolvation barrier created by hydrophobic residues that line the pore. As a result of relatively minor structural changes, confined hydrophobic regions in channels may undergo transitions between wet and dry states to gate the pore closed without physical constriction of the permeation pathway. This concept is referred to as hydrophobic gating, and many examples of this process have been demonstrated. However, the term is also now being used in a much broader context that often deviates from its original meaning. In this Viewpoint, we explore the formal definition of a hydrophobic gate, discuss examples of this process compared with other gating mechanisms that simply exploit hydrophobic residues and/or lipids in steric closure of the pore, and describe the best practice for identification of a hydrophobic gate.
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Affiliation(s)
- David Seiferth
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford, UK.,Department of Biochemistry, University of Oxford, Oxford, UK
| | - Philip C Biggin
- Department of Biochemistry, University of Oxford, Oxford, UK
| | - Stephen J Tucker
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford, UK.,Kavli Institute for Nanoscience Discovery, University of Oxford, Oxford, UK
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10
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Beverley KM, Shahi PK, Kabra M, Zhao Q, Heyrman J, Steffen J, Pattnaik BR. Kir7.1 disease mutant T153I within the inner pore affects K+ conduction. Am J Physiol Cell Physiol 2022; 323:C56-C68. [PMID: 35584325 DOI: 10.1152/ajpcell.00093.2022] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Inward-rectifier potassium channel 7.1 (Kir7.1) is present in polarized epithelium, including the RPE. A single amino acid change at position 153 in the KCNJ13 gene, a substitution of threonine to isoleucine in Kir7.1 protein, causes blindness. We hypothesized that the disease caused by this single amino acid substitution within the transmembrane protein domain could alter the translation, localization, or ion transport properties. We assessed the effects of amino acid side-chain length, arrangement, and polarity on channel structure and function. We showed that the T153I mutation yielded a full-length protein localized to the cell membrane. Whole-cell patch-clamp recordings and chord conductance analyses revealed that the T153I mutant channel had negligible K+ conductance and failed to hyperpolarize the membrane potential. However, the mutant channel exhibited enhanced inward current when Rb+ was used as a charge carrier, suggesting that an inner pore had formed, and the channel was dysfunctional. Substituting with a polar, non-polar, or short side-chain amino acid did not affect the localization of the protein. Still, it had an altered channel function due to differences in pore radius. Polar side chains (cysteine and serine) with inner pore radii comparable to wildtype exhibited normal inward K+ conductance. Short side-chains (glycine and alanine) produced a channel with wider than expected inner pore size and lacked the biophysical characteristics of the wildtype channel. Leucine substitution produced results similar to the T153I mutant channel. This study provides direct electrophysiological evidence for the structure and function of the Kir7.1 channel's narrow inner pore in regulating conductance.
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Affiliation(s)
- Katie M Beverley
- Endocrinology and Reproductive Physiology Graduate Program, University of Wisconsin School of Medicine and Public Health, Madison, WI, United States.,Department of Pediatrics, University of Wisconsin School of Medicine and Public Health, Madison, WI, United States.,McPherson Eye Research Institute, University of Wisconsin, Madison, WI, United States
| | - Pawan K Shahi
- Department of Pediatrics, University of Wisconsin School of Medicine and Public Health, Madison, WI, United States.,McPherson Eye Research Institute, University of Wisconsin, Madison, WI, United States
| | - Meha Kabra
- Department of Pediatrics, University of Wisconsin School of Medicine and Public Health, Madison, WI, United States.,McPherson Eye Research Institute, University of Wisconsin, Madison, WI, United States
| | - Qianqian Zhao
- Department of Biostatistics and Medical Informatics, University of Wisconsin School of Medicine and Public Health, Madison, WI, United States
| | - Joseph Heyrman
- Department of Pediatrics, University of Wisconsin School of Medicine and Public Health, Madison, WI, United States
| | - Jack Steffen
- Department of Pediatrics, University of Wisconsin School of Medicine and Public Health, Madison, WI, United States
| | - Bikash R Pattnaik
- Endocrinology and Reproductive Physiology Graduate Program, University of Wisconsin School of Medicine and Public Health, Madison, WI, United States.,Department of Pediatrics, University of Wisconsin School of Medicine and Public Health, Madison, WI, United States.,McPherson Eye Research Institute, University of Wisconsin, Madison, WI, United States.,Department of Ophthalmology and Visual Sciences, University of Wisconsin School of Medicine and Public Health, Madison, WI, United States
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11
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Barrantes FJ. Fluorescence Studies of Nicotinic Acetylcholine Receptor and Its Associated Lipid Milieu: The Influence of Erwin London's Methodological Approaches. J Membr Biol 2022; 255:563-574. [PMID: 35534578 DOI: 10.1007/s00232-022-00239-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2022] [Accepted: 04/11/2022] [Indexed: 11/29/2022]
Abstract
Erwin London dedicated considerable effort to understanding lipid interactions with membrane-resident proteins and how these interactions shaped the formation and maintenance of lipid phases and domains. In this endeavor, he developed ad hoc techniques that greatly contributed to advancements in the field. We have employed and/or modified/extended some of his methodological approaches and applied them to investigate lipid interaction with the nicotinic acetylcholine receptor (nAChR) protein, the paradigm member of the superfamily of rapid pentameric ligand-gated ion channels (pLGIC). Our experimental systems ranged from purified receptor protein reconstituted into synthetic lipid membranes having known effects on receptor function, to cellular systems subjected to modification of their lipid content, e.g., varying cholesterol levels. We have often employed fluorescence techniques, including fluorescence quenching of diphenylhexatriene (DPH) extrinsic fluorescence and of nAChR intrinsic fluorescence by nitroxide spin-labeled phospholipids, DPH anisotropy, excimer formation of pyrene-phosphatidylcholine, and Förster resonance energy transfer (FRET) from the protein moiety to the extrinsic probes Laurdan, DPH, or pyrene-phospholipid to characterize various biophysical properties of lipid-receptor interactions. Some of these strategies are revisited in this review. Special attention is devoted to the anionic phospholipid phosphatidic acid (PA), which stabilizes the functional resting form of the nAChR. The receptor protein was shown to organize its PA-containing immediate microenvironment into microdomains with high lateral packing density and rigidity. PA and cholesterol appear to compete for the same binding sites on the nAChR protein.
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Affiliation(s)
- Francisco J Barrantes
- Laboratory of Molecular Neurobiology, Institute of Biomedical Research (BIOMED), UCA-CONICET, Av. Alicia Moreau de Justo 1600, C1107AFF, Buenos Aires, Argentina.
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