1
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Morito M, Yasuda H, Matsufuji T, Kinoshita M, Matsumori N. Identification of lipid-specific proteins with high-density lipid-immobilized beads. Analyst 2024; 149:3747-3755. [PMID: 38829210 DOI: 10.1039/d4an00579a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/05/2024]
Abstract
In biological membranes, lipids often interact with membrane proteins (MPs), regulating the localization and activity of MPs in cells. Although elucidating lipid-MP interactions is critical to comprehend the physiological roles of lipids, a systematic and comprehensive identification of lipid-binding proteins has not been adequately established. Therefore, we report the development of lipid-immobilized beads where lipid molecules were covalently immobilized. Owing to the detergent tolerance, these beads enable screening of water-soluble proteins and MPs, the latter of which typically necessitate surfactants for solubilization. Herein, two sphingolipid species-ceramide and sphingomyelin-which are major constituents of lipid rafts, were immobilized on the beads. We first showed that the density of immobilized lipid molecules on the beads was as high as that of biological lipid membranes. Subsequently, we confirmed that these beads enabled the selective pulldown of known sphingomyelin- or ceramide-binding proteins (lysenin, p24, and CERT) from protein mixtures, including cell lysates. In contrast, commercial sphingomyelin beads, on which lipid molecules are sparsely immobilized through biotin-streptavidin linkage, failed to capture lysenin, a well-known protein that recognizes clustered sphingomyelin molecules. This clearly demonstrates the applicability of our beads for obtaining proteins that recognize not only a single lipid molecule but also lipid clusters or lipid membranes. Finally, we demonstrated the screening of lipid-binding proteins from Neuro2a cell lysates using these beads. This method is expected to significantly contribute to the understanding of interactions between lipids and proteins and to unravel the complexities of lipid diversity.
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Affiliation(s)
- Masayuki Morito
- Department of Chemistry, Graduate School of Science, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan.
| | - Hiroki Yasuda
- Department of Chemistry, Graduate School of Science, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan.
| | - Takaaki Matsufuji
- Department of Chemistry, Graduate School of Science, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan.
| | - Masanao Kinoshita
- Department of Chemistry, Graduate School of Science, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan.
| | - Nobuaki Matsumori
- Department of Chemistry, Graduate School of Science, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan.
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2
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Oney-Hawthorne SD, Barondeau DP. Fe-S cluster biosynthesis and maturation: Mass spectrometry-based methods advancing the field. BIOCHIMICA ET BIOPHYSICA ACTA. MOLECULAR CELL RESEARCH 2024; 1871:119784. [PMID: 38908802 DOI: 10.1016/j.bbamcr.2024.119784] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/29/2024] [Revised: 04/25/2024] [Accepted: 06/10/2024] [Indexed: 06/24/2024]
Abstract
Iron‑sulfur (FeS) clusters are inorganic protein cofactors that perform essential functions in many physiological processes. Spectroscopic techniques have historically been used to elucidate details of FeS cluster type, their assembly and transfer, and changes in redox and ligand binding properties. Structural probes of protein topology, complex formation, and conformational dynamics are also necessary to fully understand these FeS protein systems. Recent developments in mass spectrometry (MS) instrumentation and methods provide new tools to investigate FeS cluster and structural properties. With the unique advantage of sampling all species in a mixture, MS-based methods can be utilized as a powerful complementary approach to probe native dynamic heterogeneity, interrogate protein folding and unfolding equilibria, and provide extensive insight into protein binding partners within an entire proteome. Here, we highlight key advances in FeS protein studies made possible by MS methodology and contribute an outlook for its role in the field.
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Affiliation(s)
| | - David P Barondeau
- Department of Chemistry, Texas A&M University, College Station, TX 77842, USA.
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3
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Greening DW, Rai A, Simpson RJ. Extracellular vesicles-An omics view. Proteomics 2024; 24:e2400128. [PMID: 38676335 DOI: 10.1002/pmic.202400128] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2024] [Accepted: 04/15/2024] [Indexed: 04/28/2024]
Affiliation(s)
- David W Greening
- Molecular Proteomics, Baker Heart and Diabetes Institute, Melbourne, Australia
- Department of Biochemistry and Chemistry, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Australia
- Department of Cardiovascular Research, Translation and Implementation, La Trobe University, Melbourne, VIC, Australia
- Department of Cardiometabolic Health, University of Melbourne, Melbourne, VIC, Australia
| | - Alin Rai
- Molecular Proteomics, Baker Heart and Diabetes Institute, Melbourne, Australia
- Department of Cardiovascular Research, Translation and Implementation, La Trobe University, Melbourne, VIC, Australia
| | - Richard J Simpson
- Department of Biochemistry and Chemistry, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Australia
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4
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Wu D, Yan R, Song S, Swansiger AK, Li Y, Prell JS, Zhou Q, Robinson CV. The complete assembly of human LAT1-4F2hc complex provides insights into its regulation, function and localisation. Nat Commun 2024; 15:3711. [PMID: 38697966 PMCID: PMC11065870 DOI: 10.1038/s41467-024-47948-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2023] [Accepted: 04/17/2024] [Indexed: 05/05/2024] Open
Abstract
The LAT1-4F2hc complex (SLC7A5-SLC3A2) facilitates uptake of essential amino acids, hormones and drugs. Its dysfunction is associated with many cancers and immune/neurological disorders. Here, we apply native mass spectrometry (MS)-based approaches to provide evidence of super-dimer formation (LAT1-4F2hc)2. When combined with lipidomics, and site-directed mutagenesis, we discover four endogenous phosphatidylethanolamine (PE) molecules at the interface and C-terminus of both LAT1 subunits. We find that interfacial PE binding is regulated by 4F2hc-R183 and is critical for regulation of palmitoylation on neighbouring LAT1-C187. Combining native MS with mass photometry (MP), we reveal that super-dimerization is sensitive to pH, and modulated by complex N-glycans on the 4F2hc subunit. We further validate the dynamic assemblies of LAT1-4F2hc on plasma membrane and in the lysosome. Together our results link PTM and lipid binding with regulation and localisation of the LAT1-4F2hc super-dimer.
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Affiliation(s)
- Di Wu
- Department of Chemistry, University of Oxford, Oxford, OX1 3QZ, UK.
- Kavli Institute for Nanoscience Discovery, University of Oxford, Oxford, OX1 3QU, UK.
| | - Renhong Yan
- Department of Biochemistry, Key University Laboratory of Metabolism and Health of Guangdong, School of Medicine, Southern University of Science and Technology, Shenzhen, 518055, Guangdong Province, China
| | - Siyuan Song
- Department of Chemistry, University of Oxford, Oxford, OX1 3QZ, UK
- Kavli Institute for Nanoscience Discovery, University of Oxford, Oxford, OX1 3QU, UK
| | - Andrew K Swansiger
- Department of Chemistry and Biochemistry, 1253 University of Oregon, Eugene, Oregon, 97403-1253, USA
| | - Yaning Li
- Beijing Advanced Innovation Center for Structural Biology, Tsinghua-Peking Joint Center for Life Sciences, Tsinghua University, Beijing, 100084, China
| | - James S Prell
- Department of Chemistry and Biochemistry, 1253 University of Oregon, Eugene, Oregon, 97403-1253, USA
| | - Qiang Zhou
- Research Center for Industries of the Future, Zhejiang Key Laboratory of Structural Biology, School of Life Sciences, Westlake University; Institute of Biology, Westlake Institute for Advanced Study; Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, 310024, Zhejiang Province, China
| | - Carol V Robinson
- Department of Chemistry, University of Oxford, Oxford, OX1 3QZ, UK.
- Kavli Institute for Nanoscience Discovery, University of Oxford, Oxford, OX1 3QU, UK.
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5
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Upton C, Healey J, Rothnie AJ, Goddard AD. Insights into membrane interactions and their therapeutic potential. Arch Biochem Biophys 2024; 755:109939. [PMID: 38387829 DOI: 10.1016/j.abb.2024.109939] [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: 11/01/2023] [Revised: 01/31/2024] [Accepted: 02/19/2024] [Indexed: 02/24/2024]
Abstract
Recent research into membrane interactions has uncovered a diverse range of therapeutic opportunities through the bioengineering of human and non-human macromolecules. Although the majority of this research is focussed on fundamental developments, emerging studies are showcasing promising new technologies to combat conditions such as cancer, Alzheimer's and inflammatory and immune-based disease, utilising the alteration of bacteriophage, adenovirus, bacterial toxins, type 6 secretion systems, annexins, mitochondrial antiviral signalling proteins and bacterial nano-syringes. To advance the field further, each of these opportunities need to be better understood, and the therapeutic models need to be further optimised. Here, we summarise the knowledge and insights into several membrane interactions and detail their current and potential uses therapeutically.
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Affiliation(s)
- Calum Upton
- School of Biosciences, Health & Life Science, Aston University, Birmingham, B4 7ET, UK
| | - Joseph Healey
- Nanosyrinx, The Venture Centre, University of Warwick Science Park, Coventry, CV4 7EZ, UK
| | - Alice J Rothnie
- School of Biosciences, Health & Life Science, Aston University, Birmingham, B4 7ET, UK
| | - Alan D Goddard
- School of Biosciences, Health & Life Science, Aston University, Birmingham, B4 7ET, UK.
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6
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Jandu RS, Yu H, Zhao Z, Le HT, Kim S, Huan T, Duong van Hoa F. Capture of endogenous lipids in peptidiscs and effect on protein stability and activity. iScience 2024; 27:109382. [PMID: 38577106 PMCID: PMC10993126 DOI: 10.1016/j.isci.2024.109382] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2023] [Revised: 12/17/2023] [Accepted: 02/27/2024] [Indexed: 04/06/2024] Open
Abstract
Compared to protein-protein and protein-nucleic acid interactions, our knowledge of protein-lipid interactions remains limited. This is primarily due to the inherent insolubility of membrane proteins (MPs) in aqueous solution. The traditional use of detergents to overcome the solubility barrier destabilizes MPs and strips away certain lipids that are increasingly recognized as crucial for protein function. Recently, membrane mimetics have been developed to circumvent the limitations. In this study, using the peptidisc, we find that MPs in different lipid states can be isolated based on protein purification and reconstitution methods, leading to observable effects on MP activity and stability. Peptidisc also enables re-incorporating specific lipids to fine-tune the protein microenvironment and assess the impact on downstream protein associations. This study offers a first look at the illusive protein-lipid interaction specificity, laying the path for a systematic evaluation of lipid identity and contributions to membrane protein function.
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Affiliation(s)
- Rupinder Singh Jandu
- Department of Biochemistry and Molecular Biology, Faculty of Medicine, Life Sciences Institute, University of British Columbia, Vancouver, BC V6T 1Z3, Canada
| | - Huaxu Yu
- Department of Chemistry, Faculty of Science, University of British Columbia, Vancouver, BC V6T 1Z3, Canada
| | - Zhiyu Zhao
- Department of Biochemistry and Molecular Biology, Faculty of Medicine, Life Sciences Institute, University of British Columbia, Vancouver, BC V6T 1Z3, Canada
| | - Hai Tuong Le
- Department of Biochemistry and Molecular Biology, Faculty of Medicine, Life Sciences Institute, University of British Columbia, Vancouver, BC V6T 1Z3, Canada
| | - Sehyeon Kim
- Department of Chemistry, Faculty of Science, University of British Columbia, Vancouver, BC V6T 1Z3, Canada
| | - Tao Huan
- Department of Chemistry, Faculty of Science, University of British Columbia, Vancouver, BC V6T 1Z3, Canada
| | - Franck Duong van Hoa
- Department of Biochemistry and Molecular Biology, Faculty of Medicine, Life Sciences Institute, University of British Columbia, Vancouver, BC V6T 1Z3, Canada
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7
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Lawrence SS, Kirschbaum C, Bennett JL, Lutomski CA, El-Baba TJ, Robinson CV. Phospholipids Differentially Regulate Ca 2+ Binding to Synaptotagmin-1. ACS Chem Biol 2024; 19:953-961. [PMID: 38566504 PMCID: PMC11040605 DOI: 10.1021/acschembio.3c00772] [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: 12/14/2023] [Revised: 03/20/2024] [Accepted: 03/21/2024] [Indexed: 04/04/2024]
Abstract
Synaptotagmin-1 (Syt-1) is a calcium sensing protein that is resident in synaptic vesicles. It is well established that Syt-1 is essential for fast and synchronous neurotransmitter release. However, the role of Ca2+ and phospholipid binding in the function of Syt-1, and ultimately in neurotransmitter release, is unclear. Here, we investigate the binding of Ca2+ to Syt-1, first in the absence of lipids, using native mass spectrometry to evaluate individual binding affinities. Syt-1 binds to one Ca2+ with a KD ∼ 45 μM. Each subsequent binding affinity (n ≥ 2) is successively unfavorable. Given that Syt-1 has been reported to bind anionic phospholipids to modulate the Ca2+ binding affinity, we explored the extent that Ca2+ binding was mediated by selected anionic phospholipid binding. We found that phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) and dioleoylphosphatidylserine (DOPS) positively modulated Ca2+ binding. However, the extent of Syt-1 binding to phosphatidylinositol 3,5-bisphosphate (PI(3,5)P2) was reduced with increasing [Ca2+]. Overall, we find that specific lipids differentially modulate Ca2+ binding. Given that these lipids are enriched in different subcellular compartments and therefore may interact with Syt-1 at different stages of the synaptic vesicle cycle, we propose a regulatory mechanism involving Syt-1, Ca2+, and anionic phospholipids that may also control some aspects of vesicular exocytosis.
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Affiliation(s)
- Sophie
A. S. Lawrence
- Department
of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QZ, U.K.
- The
Kavli Institute for Nanoscience Discovery, University of Oxford, South Parks Road, Oxford OX1 3QU, U.K.
| | - Carla Kirschbaum
- Department
of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QZ, U.K.
- The
Kavli Institute for Nanoscience Discovery, University of Oxford, South Parks Road, Oxford OX1 3QU, U.K.
| | - Jack L. Bennett
- Department
of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QZ, U.K.
- The
Kavli Institute for Nanoscience Discovery, University of Oxford, South Parks Road, Oxford OX1 3QU, U.K.
| | - Corinne A. Lutomski
- Department
of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QZ, U.K.
- The
Kavli Institute for Nanoscience Discovery, University of Oxford, South Parks Road, Oxford OX1 3QU, U.K.
| | - Tarick J. El-Baba
- Department
of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QZ, U.K.
- The
Kavli Institute for Nanoscience Discovery, University of Oxford, South Parks Road, Oxford OX1 3QU, U.K.
| | - Carol. V. Robinson
- Department
of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QZ, U.K.
- The
Kavli Institute for Nanoscience Discovery, University of Oxford, South Parks Road, Oxford OX1 3QU, U.K.
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8
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Erazo-Oliveras A, Muñoz-Vega M, Salinas ML, Wang X, Chapkin RS. Dysregulation of cellular membrane homeostasis as a crucial modulator of cancer risk. FEBS J 2024; 291:1299-1352. [PMID: 36282100 PMCID: PMC10126207 DOI: 10.1111/febs.16665] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2022] [Revised: 09/09/2022] [Accepted: 10/24/2022] [Indexed: 11/07/2022]
Abstract
Cellular membranes serve as an epicentre combining extracellular and cytosolic components with membranous effectors, which together support numerous fundamental cellular signalling pathways that mediate biological responses. To execute their functions, membrane proteins, lipids and carbohydrates arrange, in a highly coordinated manner, into well-defined assemblies displaying diverse biological and biophysical characteristics that modulate several signalling events. The loss of membrane homeostasis can trigger oncogenic signalling. More recently, it has been documented that select membrane active dietaries (MADs) can reshape biological membranes and subsequently decrease cancer risk. In this review, we emphasize the significance of membrane domain structure, organization and their signalling functionalities as well as how loss of membrane homeostasis can steer aberrant signalling. Moreover, we describe in detail the complexities associated with the examination of these membrane domains and their association with cancer. Finally, we summarize the current literature on MADs and their effects on cellular membranes, including various mechanisms of dietary chemoprevention/interception and the functional links between nutritional bioactives, membrane homeostasis and cancer biology.
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Affiliation(s)
- Alfredo Erazo-Oliveras
- Program in Integrative Nutrition and Complex Diseases; Texas A&M University; College Station, Texas, 77843; USA
- Department of Nutrition; Texas A&M University; College Station, Texas, 77843; USA
| | - Mónica Muñoz-Vega
- Program in Integrative Nutrition and Complex Diseases; Texas A&M University; College Station, Texas, 77843; USA
- Department of Nutrition; Texas A&M University; College Station, Texas, 77843; USA
| | - Michael L. Salinas
- Program in Integrative Nutrition and Complex Diseases; Texas A&M University; College Station, Texas, 77843; USA
- Department of Nutrition; Texas A&M University; College Station, Texas, 77843; USA
| | - Xiaoli Wang
- Program in Integrative Nutrition and Complex Diseases; Texas A&M University; College Station, Texas, 77843; USA
- Department of Nutrition; Texas A&M University; College Station, Texas, 77843; USA
| | - Robert S. Chapkin
- Program in Integrative Nutrition and Complex Diseases; Texas A&M University; College Station, Texas, 77843; USA
- Department of Nutrition; Texas A&M University; College Station, Texas, 77843; USA
- Center for Environmental Health Research; Texas A&M University; College Station, Texas, 77843; USA
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9
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Cui G, Strickland KM, Vazquez Cegla AJ, McCarty NA. Comparing ATPase activity of ATP-binding cassette subfamily C member 4, lamprey CFTR, and human CFTR using an antimony-phosphomolybdate assay. Front Pharmacol 2024; 15:1363456. [PMID: 38440176 PMCID: PMC10910009 DOI: 10.3389/fphar.2024.1363456] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2023] [Accepted: 02/05/2024] [Indexed: 03/06/2024] Open
Abstract
Introduction: ATP-binding cassette (ABC) transporters use the hydrolysis of ATP to power the active transport of molecules, but paradoxically the cystic fibrosis transmembrane regulator (CFTR, ABCC7) forms an ion channel. We previously showed that ATP-binding cassette subfamily C member 4 (ABCC4) is the closest mammalian paralog to CFTR, compared to other ABC transporters. In addition, Lamprey CFTR (Lp-CFTR) is the oldest known CFTR ortholog and has unique structural and functional features compared to human CFTR (hCFTR). The availability of these evolutionarily distant orthologs gives us the opportunity to study the changes in ATPase activity that may be related to their disparate functions. Methods: We utilized the baculovirus expression system with Sf9 insect cells and made use of the highly sensitive antimony-phosphomolybdate assay for testing the ATPase activity of human ABCC4 (hABCC4), Lp-CFTR, and hCFTR under similar experimental conditions. This assay measures the production of inorganic phosphate (Pi) in the nanomolar range. Results: Crude plasma membranes were purified, and protein concentration, determined semi-quantitatively, of hABCC4, Lp-CFTR, and hCFTR ranged from 0.01 to 0.36 μg/μL. No significant difference in expression level was found although hABCC4 trended toward the highest level. hABCC4 was activated by ATP with the equilibrium constant (Kd) 0.55 ± 0.28 mM (n = 8). Estimated maximum ATPase rate (Vmax) for hABCC4 was about 0.2 nmol/μg/min when the protein was activated with 1 mM ATP at 37°C (n = 7). Estimated maximum ATPase rate for PKA-phosphorylated Lp-CFTR reached about half of hCFTR levels in the same conditions. Vmax for both Lp-CFTR and hCFTR were significantly increased in high PKA conditions compared to low PKA conditions. Maximum intrinsic ATPase rate of hABCC4 in the absence of substrate was twice that of hCFTR when activated in 1 mM ATP. Conclusion: The findings here suggest that while both ABCC4 and hCFTR bear one consensus and one degenerate ATPase site, the hCFTR exhibited a reduced intrinsic ATPase activity. In addition, ATPase activity in the CFTR lineage increased from Lp-CFTR to hCFTR. Finally, the studies pave the way to purify hABCC4, Lp-CFTR, and hCFTR from Sf9 cells for their structural investigation, including by cryo-EM, and for studies of evolution in the ABC transporter superfamily.
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Affiliation(s)
| | | | | | - Nael A. McCarty
- Division of Pulmonology, Asthma, Cystic Fibrosis, and Sleep, Department of Pediatrics, Emory + Children’s Center for Cystic Fibrosis and Airways Disease Research, Emory University School of Medicine and Children’s Healthcare of Atlanta, Atlanta, GA, United States
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10
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Kundlacz T, Schmidt C. Deciphering Solution and Gas-Phase Interactions between Peptides and Lipids by Native Mass Spectrometry. Anal Chem 2023; 95:17292-17299. [PMID: 37956985 PMCID: PMC10688224 DOI: 10.1021/acs.analchem.3c03428] [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: 08/01/2023] [Revised: 10/10/2023] [Accepted: 10/12/2023] [Indexed: 11/21/2023]
Abstract
Many biological processes depend on the interactions between proteins and lipids. Accordingly, the analysis of protein-lipid complexes has become increasingly important. Native mass spectrometry is often used to identify and characterize specific protein-lipid interactions. However, it requires the transfer of the analytes into the gas phase, where electrostatic interactions are enhanced and hydrophobic interactions do not exist. Accordingly, the question remains whether interactions that are observed in the gas phase accurately reflect interactions that are formed in solution. Here, we systematically explore noncovalent interactions between the antimicrobial peptide LL-37 and glycerophospholipids containing different headgroups or varying in fatty acyl chain length. We observe differences in peak intensities for different peptide-lipid complexes, as well as their relative binding strength in the gas phase. Accordingly, we found that ion intensities and gas-phase stability correlate well for complexes formed by electrostatic interactions. Probing hydrophobic interactions by varying the length of fatty acyl chains, we detected differences in ion intensities based on hydrophobic interactions formed in solution. The relative binding strength of these peptide-lipid complexes revealed only minor differences originating from van der Waals interactions and different binding modes of lipid headgroups in solution. In summary, our results demonstrate that hydrophobic interactions are reflected by ion intensities, while electrostatic interactions, including van der Waals interactions, determine the gas-phase stability of complexes.
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Affiliation(s)
- Til Kundlacz
- Interdisciplinary
Research Centre HALOmem, Institute of Biochemistry and Biotechnology,
Charles Tanford Protein Centre, Martin Luther
University Halle-Wittenberg, Kurt-Mothes-Str. 3a, 06120 Halle, Germany
- Institute
of Chemistry, Martin Luther University Halle-Wittenberg, von-Danckelmann-Platz 4, 06120 Halle, Germany
| | - Carla Schmidt
- Interdisciplinary
Research Centre HALOmem, Institute of Biochemistry and Biotechnology,
Charles Tanford Protein Centre, Martin Luther
University Halle-Wittenberg, Kurt-Mothes-Str. 3a, 06120 Halle, Germany
- Department
of Chemistry—Biochemistry, Johannes
Gutenberg University Mainz, Biocenter II, Hanns-Dieter-Hüsch-Weg 17, 55128 Mainz, Germany
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11
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Liu W, Jayasekera HS, Sanders JD, Zhang G, Viner R, Marty MT. Online Buffer Exchange Enables Automated Membrane Protein Analysis by Native Mass Spectrometry. Anal Chem 2023; 95:17212-17219. [PMID: 37963237 PMCID: PMC10696660 DOI: 10.1021/acs.analchem.3c02164] [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] [Indexed: 11/16/2023]
Abstract
Membrane proteins represent the majority of clinical drug targets and are actively involved in a range of cellular processes. However, the complexity of membrane mimetics for membrane protein solubilization poses challenges for native mass spectrometry (MS) analyses. The most common approach for native MS analyses of membrane proteins remains offline buffer exchange into native MS-compatible buffers prior to manual sample loading into static nano-ESI emitters. This laborious process requires relatively high sample consumption and optimization for the individual proteins. Here, we developed online buffer exchange coupled to native mass spectrometry (OBE-nMS) for analyzing membrane proteins in different membrane mimetics, including detergent micelles and nanodiscs. Detergent screening for OBE-nMS reveals that mobile phases containing ammonium acetate with lauryl-dimethylamine oxide are most universal for characterizing both bacterial and mammalian membrane proteins in detergent. Membrane proteins in nanodiscs simply require ammonium acetate as the mobile phase. To preserve the intact nanodiscs, a novel switching electrospray approach was used to capture the high-flow separation on the column with a low-flow injection to MS. Rapid OBE-nMS completes each membrane protein measurement within minutes and thus enables higher-throughput assessment of membrane protein integrity prior to its structural elucidation.
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Affiliation(s)
- Weijing Liu
- Thermo Fisher Scientific, 355 River Oaks Parkway, San Jose, CA 95134
| | - Hiruni S. Jayasekera
- Department of Chemistry and Biochemistry and Bio5 Institute, University of Arizona, Tucson, Arizona 85721
| | - James D. Sanders
- Department of Chemistry and Biochemistry and Bio5 Institute, University of Arizona, Tucson, Arizona 85721
| | - Guozhi Zhang
- Department of Chemistry and Biochemistry and Bio5 Institute, University of Arizona, Tucson, Arizona 85721
| | - Rosa Viner
- Thermo Fisher Scientific, 355 River Oaks Parkway, San Jose, CA 95134
| | - Michael T. Marty
- Department of Chemistry and Biochemistry and Bio5 Institute, University of Arizona, Tucson, Arizona 85721
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12
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Lutomski CA, El‐Baba TJ, Hinkle JD, Liko I, Bennett JL, Kalmankar NV, Dolan A, Kirschbaum C, Greis K, Urner LH, Kapoor P, Yen H, Pagel K, Mullen C, Syka JEP, Robinson CV. Infrared Multiphoton Dissociation Enables Top-Down Characterization of Membrane Protein Complexes and G Protein-Coupled Receptors. Angew Chem Int Ed Engl 2023; 62:e202305694. [PMID: 37329506 PMCID: PMC7615181 DOI: 10.1002/anie.202305694] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2023] [Revised: 05/20/2023] [Accepted: 06/15/2023] [Indexed: 06/19/2023]
Abstract
Membrane proteins are challenging to analyze by native mass spectrometry (MS) as their hydrophobic nature typically requires stabilization in detergent micelles that are removed prior to analysis via collisional activation. There is however a practical limit to the amount of energy which can be applied, which often precludes subsequent characterization by top-down MS. To overcome this barrier, we have applied a modified Orbitrap Eclipse Tribrid mass spectrometer coupled to an infrared laser within a high-pressure linear ion trap. We show how tuning the intensity and time of incident photons enables liberation of membrane proteins from detergent micelles. Specifically, we relate the ease of micelle removal to the infrared absorption of detergents in both condensed and gas phases. Top-down MS via infrared multiphoton dissociation (IRMPD), results in good sequence coverage enabling unambiguous identification of membrane proteins and their complexes. By contrasting and comparing the fragmentation patterns of the ammonia channel with two class A GPCRs, we identify successive cleavage of adjacent amino acids within transmembrane domains. Using gas-phase molecular dynamics simulations, we show that areas prone to fragmentation maintain aspects of protein structure at increasing temperatures. Altogether, we propose a rationale to explain why and where in the protein fragment ions are generated.
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Affiliation(s)
- Corinne A. Lutomski
- Physical and Theoretical Chemistry Laboratory, Department of ChemistryUniversity of OxfordOxfordOX1 3QUUK
- Kavli Institute for Nanoscience Discovery, Dorothy Crowfoot Hodgkin BuildingUniversity of OxfordOxfordOX1 3QUUK
| | - Tarick J. El‐Baba
- Physical and Theoretical Chemistry Laboratory, Department of ChemistryUniversity of OxfordOxfordOX1 3QUUK
- Kavli Institute for Nanoscience Discovery, Dorothy Crowfoot Hodgkin BuildingUniversity of OxfordOxfordOX1 3QUUK
| | | | | | - Jack L. Bennett
- Physical and Theoretical Chemistry Laboratory, Department of ChemistryUniversity of OxfordOxfordOX1 3QUUK
- Kavli Institute for Nanoscience Discovery, Dorothy Crowfoot Hodgkin BuildingUniversity of OxfordOxfordOX1 3QUUK
| | - Neha V. Kalmankar
- Physical and Theoretical Chemistry Laboratory, Department of ChemistryUniversity of OxfordOxfordOX1 3QUUK
- Kavli Institute for Nanoscience Discovery, Dorothy Crowfoot Hodgkin BuildingUniversity of OxfordOxfordOX1 3QUUK
| | - Andrew Dolan
- Physical and Theoretical Chemistry Laboratory, Department of ChemistryUniversity of OxfordOxfordOX1 3QUUK
- Kavli Institute for Nanoscience Discovery, Dorothy Crowfoot Hodgkin BuildingUniversity of OxfordOxfordOX1 3QUUK
| | - Carla Kirschbaum
- Institute of Chemistry and BiochemistryFreie Universität BerlinBerlin14195Germany
- Fritz Haber Institute of the Max Planck SocietyBerlin14195Germany
| | - Kim Greis
- Institute of Chemistry and BiochemistryFreie Universität BerlinBerlin14195Germany
- Fritz Haber Institute of the Max Planck SocietyBerlin14195Germany
| | - Leonhard H. Urner
- Institute of Chemistry and BiochemistryFreie Universität BerlinBerlin14195Germany
- Fritz Haber Institute of the Max Planck SocietyBerlin14195Germany
- Department of Chemistry and Chemical BiologyTU Dortmund UniversityDortmund44227Germany
| | | | - Hsin‐Yung Yen
- OMass TherapeuticsOxfordOX4 2GXUK
- Institute of Biological ChemistryAcademia SinicaTaipei115Taiwan
| | - Kevin Pagel
- Institute of Chemistry and BiochemistryFreie Universität BerlinBerlin14195Germany
- Fritz Haber Institute of the Max Planck SocietyBerlin14195Germany
| | | | | | - Carol V. Robinson
- Physical and Theoretical Chemistry Laboratory, Department of ChemistryUniversity of OxfordOxfordOX1 3QUUK
- Kavli Institute for Nanoscience Discovery, Dorothy Crowfoot Hodgkin BuildingUniversity of OxfordOxfordOX1 3QUUK
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13
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Lutomski CA, El‐Baba TJ, Hinkle JD, Liko I, Bennett JL, Kalmankar NV, Dolan A, Kirschbaum C, Greis K, Urner LH, Kapoor P, Yen H, Pagel K, Mullen C, Syka JEP, Robinson CV. Infrared Multiphoton Dissociation Enables Top-Down Characterization of Membrane Protein Complexes and G Protein-Coupled Receptors. ANGEWANDTE CHEMIE (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2023; 135:e202305694. [PMID: 38516403 PMCID: PMC10953453 DOI: 10.1002/ange.202305694] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/24/2023] [Indexed: 03/23/2024]
Abstract
Membrane proteins are challenging to analyze by native mass spectrometry (MS) as their hydrophobic nature typically requires stabilization in detergent micelles that are removed prior to analysis via collisional activation. There is however a practical limit to the amount of energy which can be applied, which often precludes subsequent characterization by top-down MS. To overcome this barrier, we have applied a modified Orbitrap Eclipse Tribrid mass spectrometer coupled to an infrared laser within a high-pressure linear ion trap. We show how tuning the intensity and time of incident photons enables liberation of membrane proteins from detergent micelles. Specifically, we relate the ease of micelle removal to the infrared absorption of detergents in both condensed and gas phases. Top-down MS via infrared multiphoton dissociation (IRMPD), results in good sequence coverage enabling unambiguous identification of membrane proteins and their complexes. By contrasting and comparing the fragmentation patterns of the ammonia channel with two class A GPCRs, we identify successive cleavage of adjacent amino acids within transmembrane domains. Using gas-phase molecular dynamics simulations, we show that areas prone to fragmentation maintain aspects of protein structure at increasing temperatures. Altogether, we propose a rationale to explain why and where in the protein fragment ions are generated.
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Affiliation(s)
- Corinne A. Lutomski
- Physical and Theoretical Chemistry Laboratory, Department of ChemistryUniversity of OxfordOxfordOX1 3QUUK
- Kavli Institute for Nanoscience Discovery, Dorothy Crowfoot Hodgkin BuildingUniversity of OxfordOxfordOX1 3QUUK
| | - Tarick J. El‐Baba
- Physical and Theoretical Chemistry Laboratory, Department of ChemistryUniversity of OxfordOxfordOX1 3QUUK
- Kavli Institute for Nanoscience Discovery, Dorothy Crowfoot Hodgkin BuildingUniversity of OxfordOxfordOX1 3QUUK
| | | | | | - Jack L. Bennett
- Physical and Theoretical Chemistry Laboratory, Department of ChemistryUniversity of OxfordOxfordOX1 3QUUK
- Kavli Institute for Nanoscience Discovery, Dorothy Crowfoot Hodgkin BuildingUniversity of OxfordOxfordOX1 3QUUK
| | - Neha V. Kalmankar
- Physical and Theoretical Chemistry Laboratory, Department of ChemistryUniversity of OxfordOxfordOX1 3QUUK
- Kavli Institute for Nanoscience Discovery, Dorothy Crowfoot Hodgkin BuildingUniversity of OxfordOxfordOX1 3QUUK
| | - Andrew Dolan
- Physical and Theoretical Chemistry Laboratory, Department of ChemistryUniversity of OxfordOxfordOX1 3QUUK
- Kavli Institute for Nanoscience Discovery, Dorothy Crowfoot Hodgkin BuildingUniversity of OxfordOxfordOX1 3QUUK
| | - Carla Kirschbaum
- Institute of Chemistry and BiochemistryFreie Universität BerlinBerlin14195Germany
- Fritz Haber Institute of the Max Planck SocietyBerlin14195Germany
| | - Kim Greis
- Institute of Chemistry and BiochemistryFreie Universität BerlinBerlin14195Germany
- Fritz Haber Institute of the Max Planck SocietyBerlin14195Germany
| | - Leonhard H. Urner
- Institute of Chemistry and BiochemistryFreie Universität BerlinBerlin14195Germany
- Fritz Haber Institute of the Max Planck SocietyBerlin14195Germany
- Department of Chemistry and Chemical BiologyTU Dortmund UniversityDortmund44227Germany
| | | | - Hsin‐Yung Yen
- OMass TherapeuticsOxfordOX4 2GXUK
- Institute of Biological ChemistryAcademia SinicaTaipei115Taiwan
| | - Kevin Pagel
- Institute of Chemistry and BiochemistryFreie Universität BerlinBerlin14195Germany
- Fritz Haber Institute of the Max Planck SocietyBerlin14195Germany
| | | | | | - Carol V. Robinson
- Physical and Theoretical Chemistry Laboratory, Department of ChemistryUniversity of OxfordOxfordOX1 3QUUK
- Kavli Institute for Nanoscience Discovery, Dorothy Crowfoot Hodgkin BuildingUniversity of OxfordOxfordOX1 3QUUK
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14
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Tzortzini E, Kolocouris A. Molecular Biophysics of Class A G Protein Coupled Receptors-Lipids Interactome at a Glance-Highlights from the A 2A Adenosine Receptor. Biomolecules 2023; 13:957. [PMID: 37371538 DOI: 10.3390/biom13060957] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2023] [Revised: 05/25/2023] [Accepted: 05/28/2023] [Indexed: 06/29/2023] Open
Abstract
G protein-coupled receptors (GPCRs) are embedded in phospholipid membrane bilayers with cholesterol representing 34% of the total lipid content in mammalian plasma membranes. Membrane lipids interact with GPCRs structures and modulate their function and drug-stimulated signaling through conformational selection. It has been shown that anionic phospholipids form strong interactions between positively charged residues in the G protein and the TM5-TM6-TM 7 cytoplasmic interface of class A GPCRs stabilizing the signaling GPCR-G complex. Cholesterol with a high content in plasma membranes can be identified in more specific sites in the transmembrane region of GPCRs, such as the Cholesterol Consensus Motif (CCM) and Cholesterol Recognition Amino Acid Consensus (CRAC) motifs and other receptor dependent and receptor state dependent sites. Experimental biophysical methods, atomistic (AA) MD simulations and coarse-grained (CG) molecular dynamics simulations have been applied to investigate these interactions. We emphasized here the impact of phosphatidyl inositol-4,5-bisphosphate (PtdIns(4,5)P2 or PIP2), a minor phospholipid component and of cholesterol on the function-related conformational equilibria of the human A2A adenosine receptor (A2AR), a representative receptor in class A GPCR. Several GPCRs of class A interacted with PIP2 and cholesterol and in many cases the mechanism of the modulation of their function remains unknown. This review provides a helpful comprehensive overview for biophysics that enter the field of GPCRs-lipid systems.
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Affiliation(s)
- Efpraxia Tzortzini
- Laboratory of Medicinal Chemistry, Section of Pharmaceutical Chemistry, Department of Pharmacy, School of Health Sciences, National and Kapodistrian University of Athens, 15771 Athens, Greece
| | - Antonios Kolocouris
- Laboratory of Medicinal Chemistry, Section of Pharmaceutical Chemistry, Department of Pharmacy, School of Health Sciences, National and Kapodistrian University of Athens, 15771 Athens, Greece
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15
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Kozhinov AN, Johnson A, Nagornov KO, Stadlmeier M, Martin WL, Dayon L, Corthésy J, Wühr M, Tsybin YO. Super-Resolution Mass Spectrometry Enables Rapid, Accurate, and Highly Multiplexed Proteomics at the MS2 Level. Anal Chem 2023; 95:3712-3719. [PMID: 36749928 PMCID: PMC9974827 DOI: 10.1021/acs.analchem.2c04742] [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] [Indexed: 02/09/2023]
Abstract
In tandem mass spectrometry (MS2)-based multiplexed quantitative proteomics, the complement reporter ion approaches (TMTc and TMTproC) were developed to eliminate the ratio-compression problem of conventional MS2-level approaches. Resolving all high m/z complement reporter ions (∼6.32 mDa-spaced) requires mass resolution and scan speeds above the performance levels of OrbitrapTM instruments. Therefore, complement reporter ion quantification with TMT/TMTpro reagents is currently limited to 5 out of 11 (TMT) or 9 out of 18 (TMTpro) channels (∼1 Da spaced). We first demonstrate that a FusionTM LumosTM Orbitrap can resolve 6.32 mDa-spaced complement reporter ions with standard acquisition modes extended with 3 s transients. We then implemented a super-resolution mass spectrometry approach using the least-squares fitting (LSF) method for processing Orbitrap transients to achieve shotgun proteomics-compatible scan rates. The LSF performance resolves the 6.32 mDa doublets for all TMTproC channels in the standard mass range with transients as short as ∼108 ms (Orbitrap resolution setting of 50,000 at m/z 200). However, we observe a slight decrease in measurement precision compared to 1 Da spacing with the 108 ms transients. With 256 ms transients (resolution of 120,000 at m/z 200), coefficients of variation are essentially indistinguishable from 1 Da samples. We thus demonstrate the feasibility of highly multiplexed, accurate, and precise shotgun proteomics at the MS2 level.
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Affiliation(s)
| | - Alex Johnson
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, New Jersey 08544, United States
- Department of Molecular Biology, Princeton University, Princeton, New Jersey 08544, United States
- Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08544, United States
| | | | - Michael Stadlmeier
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, New Jersey 08544, United States
- Department of Molecular Biology, Princeton University, Princeton, New Jersey 08544, United States
| | - Warham Lance Martin
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, New Jersey 08544, United States
- Department of Molecular Biology, Princeton University, Princeton, New Jersey 08544, United States
| | - Loïc Dayon
- Nestlé Institute of Food Safety & Analytical Sciences, Nestlé Research, 1015 Lausanne, Switzerland
| | - John Corthésy
- Nestlé Institute of Food Safety & Analytical Sciences, Nestlé Research, 1015 Lausanne, Switzerland
| | - Martin Wühr
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, New Jersey 08544, United States
- Department of Molecular Biology, Princeton University, Princeton, New Jersey 08544, United States
- Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08544, United States
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16
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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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17
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Emergence of mass spectrometry detergents for membrane proteomics. Anal Bioanal Chem 2023:10.1007/s00216-023-04584-z. [PMID: 36808272 PMCID: PMC10328889 DOI: 10.1007/s00216-023-04584-z] [Citation(s) in RCA: 13] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2022] [Revised: 01/25/2023] [Accepted: 02/02/2023] [Indexed: 02/21/2023]
Abstract
Detergents enable the investigation of membrane proteins by mass spectrometry. Detergent designers aim to improve underlying methodologies and are confronted with the challenge to design detergents with optimal solution and gas-phase properties. Herein, we review literature related to the optimization of detergent chemistry and handling and identify an emerging research direction: the optimization of mass spectrometry detergents for individual applications in mass spectrometry-based membrane proteomics. We provide an overview about qualitative design aspects including their relevance for the optimization of detergents in bottom-up proteomics, top-down proteomics, native mass spectrometry, and Nativeomics. In addition to established design aspects, such as charge, concentration, degradability, detergent removal, and detergent exchange, it becomes apparent that detergent heterogeneity is a promising key driver for innovation. We anticipate that rationalizing the role of detergent structures in membrane proteomics will serve as an enabling step for the analysis of challenging biological systems.
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18
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Regulation of membrane protein structure and function by their lipid nano-environment. Nat Rev Mol Cell Biol 2023; 24:107-122. [PMID: 36056103 PMCID: PMC9892264 DOI: 10.1038/s41580-022-00524-4] [Citation(s) in RCA: 121] [Impact Index Per Article: 121.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/19/2022] [Indexed: 02/04/2023]
Abstract
Transmembrane proteins comprise ~30% of the mammalian proteome, mediating metabolism, signalling, transport and many other functions required for cellular life. The microenvironment of integral membrane proteins (IMPs) is intrinsically different from that of cytoplasmic proteins, with IMPs solvated by a compositionally and biophysically complex lipid matrix. These solvating lipids affect protein structure and function in a variety of ways, from stereospecific, high-affinity protein-lipid interactions to modulation by bulk membrane properties. Specific examples of functional modulation of IMPs by their solvating membranes have been reported for various transporters, channels and signal receptors; however, generalizable mechanistic principles governing IMP regulation by lipid environments are neither widely appreciated nor completely understood. Here, we review recent insights into the inter-relationships between complex lipidomes of mammalian membranes, the membrane physicochemical properties resulting from such lipid collectives, and the regulation of IMPs by either or both. The recent proliferation of high-resolution methods to study such lipid-protein interactions has led to generalizable insights, which we synthesize into a general framework termed the 'functional paralipidome' to understand the mutual regulation between membrane proteins and their surrounding lipid microenvironments.
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19
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Role of the membrane anchor in the regulation of Lck activity. J Biol Chem 2022; 298:102663. [PMID: 36372231 PMCID: PMC9763865 DOI: 10.1016/j.jbc.2022.102663] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2022] [Revised: 10/10/2022] [Accepted: 10/12/2022] [Indexed: 11/13/2022] Open
Abstract
Theoretical work suggests that collective spatiotemporal behavior of integral membrane proteins should be modulated by boundary lipids sheathing their membrane anchors. Here, we show evidence for this prediction while investigating the mechanism for maintaining a steady amount of the active form of integral membrane protein Lck kinase (LckA) by Lck trans-autophosphorylation regulated by the phosphatase CD45. We used super-resolution microscopy, flow cytometry, and pharmacological and genetic perturbation to gain insight into the spatiotemporal context of this process. We found that LckA is generated exclusively at the plasma membrane, where CD45 maintains it in a ceaseless dynamic equilibrium with its unphosphorylated precursor. Steady LckA shows linear dependence, after an initial threshold, over a considerable range of Lck expression levels. This behavior fits a phenomenological model of trans-autophosphorylation that becomes more efficient with increasing LckA. We then challenged steady LckA formation by genetically swapping the Lck membrane anchor with structurally divergent ones, such as that of Src or the transmembrane domains of LAT, CD4, palmitoylation-defective CD4 and CD45 that were expected to drastically modify Lck boundary lipids. We observed small but significant changes in LckA generation, except for the CD45 transmembrane domain that drastically reduced LckA due to its excessive lateral proximity to CD45. Comprehensively, LckA formation and maintenance can be best explained by lipid bilayer critical density fluctuations rather than liquid-ordered phase-separated nanodomains, as previously thought, with "like/unlike" boundary lipids driving dynamical proximity and remoteness of Lck with itself and with CD45.
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20
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Lyu J, Liu C, Zhang T, Schrecke S, Elam NP, Packianathan C, Hochberg GKA, Russell D, Zhao M, Laganowsky A. Structural basis for lipid and copper regulation of the ABC transporter MsbA. Nat Commun 2022; 13:7291. [PMID: 36435815 PMCID: PMC9701195 DOI: 10.1038/s41467-022-34905-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2022] [Accepted: 11/10/2022] [Indexed: 11/28/2022] Open
Abstract
A critical step in lipopolysaccharide (LPS) biogenesis involves flipping lipooligosaccharide, an LPS precursor, from the cytoplasmic to the periplasmic leaflet of the inner membrane, an operation carried out by the ATP-binding cassette transporter MsbA. Although LPS binding to the inner cavity of MsbA is well established, the selectivity of MsbA-lipid interactions at other site(s) remains poorly understood. Here we use native mass spectrometry (MS) to characterize MsbA-lipid interactions and guide structural studies. We show the transporter co-purifies with copper(II) and metal binding modulates protein-lipid interactions. A 2.15 Å resolution structure of an N-terminal region of MsbA in complex with copper(II) is presented, revealing a structure reminiscent of the GHK peptide, a high-affinity copper(II) chelator. Our results demonstrate conformation-dependent lipid binding affinities, particularly for the LPS-precursor, 3-deoxy-D-manno-oct-2-ulosonic acid (Kdo)2-lipid A (KDL). We report a 3.6 Å-resolution structure of MsbA trapped in an open, outward-facing conformation with adenosine 5'-diphosphate and vanadate, revealing a distinct KDL binding site, wherein the lipid forms extensive interactions with the transporter. Additional studies provide evidence that the exterior KDL binding site is conserved and a positive allosteric modulator of ATPase activity, serving as a feedforward activation mechanism to couple transporter activity with LPS biosynthesis.
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Affiliation(s)
- Jixing Lyu
- Department of Chemistry, Texas A&M University, College Station, 77843, TX, USA
| | - Chang Liu
- Department of Biochemistry and Molecular biology, University of Chicago, Chicago, 60637, IL, USA
| | - Tianqi Zhang
- Department of Chemistry, Texas A&M University, College Station, 77843, TX, USA
| | - Samantha Schrecke
- Department of Chemistry, Texas A&M University, College Station, 77843, TX, USA
| | - Nicklaus P Elam
- Department of Chemistry, Texas A&M University, College Station, 77843, TX, USA
| | - Charles Packianathan
- Department of Chemistry, Texas A&M University, College Station, 77843, TX, USA
- Walter Reed Army Institute of Research, Pilot Bioproduction Facility, Silver Spring, 20910, MD, USA
| | - Georg K A Hochberg
- Max Planck Institute for Terrestrial Microbiology and Department of Chemistry, University of Marburg, Marburg, Germany
- Center for Synthetic Microbiology (SYNMIKRO), Department of Chemistry, University of Marburg, Marburg, Germany
| | - David Russell
- Department of Chemistry, Texas A&M University, College Station, 77843, TX, USA
| | - Minglei Zhao
- Department of Biochemistry and Molecular biology, University of Chicago, Chicago, 60637, IL, USA
| | - Arthur Laganowsky
- Department of Chemistry, Texas A&M University, College Station, 77843, TX, USA.
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21
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Schmidpeter PAM, Wu D, Rheinberger J, Riegelhaupt PM, Tang H, Robinson CV, Nimigean CM. Anionic lipids unlock the gates of select ion channels in the pacemaker family. Nat Struct Mol Biol 2022; 29:1092-1100. [PMID: 36352139 PMCID: PMC10022520 DOI: 10.1038/s41594-022-00851-2] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2022] [Accepted: 09/25/2022] [Indexed: 11/11/2022]
Abstract
Lipids play important roles in regulating membrane protein function, but the molecular mechanisms used are elusive. Here we investigated how anionic lipids modulate SthK, a bacterial pacemaker channel homolog, and HCN2, whose activity contributes to pacemaking in the heart and brain. Using SthK allowed the reconstitution of purified channels in controlled lipid compositions for functional and structural assays that are not available for the eukaryotic channels. We identified anionic lipids bound tightly to SthK and their exact binding locations and determined that they potentiate channel activity. Cryo-EM structures in the most potentiating lipids revealed an open state and identified a nonannular lipid bound with its headgroup near an intersubunit salt bridge that clamps the intracellular channel gate shut. Breaking this conserved salt bridge abolished lipid modulation in SthK and eukaryotic HCN2 channels, indicating that anionic membrane lipids facilitate channel opening by destabilizing these interactions. Our findings underline the importance of state-dependent protein-lipid interactions.
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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
| | - Jan Rheinberger
- Department of Anesthesiology, Weill Cornell Medicine, New York, NY, USA
- Department of Structural Biology, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Groningen, the Netherlands
| | | | - Haiping Tang
- 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
| | - Crina M Nimigean
- Department of Anesthesiology, Weill Cornell Medicine, New York, NY, USA.
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22
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Regulation of the Sae Two-Component System by Branched-Chain Fatty Acids in Staphylococcus aureus. mBio 2022; 13:e0147222. [PMID: 36135382 PMCID: PMC9600363 DOI: 10.1128/mbio.01472-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Staphylococcus aureus is a ubiquitous Gram-positive bacterium and an opportunistic human pathogen. S. aureus pathogenesis relies on a complex network of regulatory factors that adjust gene expression. Two important factors in this network are CodY, a repressor protein responsive to nutrient availability, and the SaeRS two-component system (TCS), which responds to neutrophil-produced factors. Our previous work revealed that CodY regulates the secretion of many toxins indirectly via Sae through an unknown mechanism. We report that disruption of codY results in increased levels of phosphorylated SaeR (SaeR~P) and that codY mutant cell membranes contain a higher percentage of branched-chain fatty acids (BCFAs) than do wild-type membranes, prompting us to hypothesize that changes to membrane composition modulate the activity of the SaeS sensor kinase. Disrupting the lpdA gene encoding dihydrolipoyl dehydrogenase, which is critical for BCFA synthesis, significantly reduced the abundance of SaeR, phosphorylated SaeR, and BCFAs in the membrane, resulting in reduced toxin production and attenuated virulence. Lower SaeR levels could be explained in part by reduced stability. Sae activity in the lpdA mutant could be complemented genetically and chemically with exogenous short- or full-length BCFAs. Intriguingly, lack of lpdA also alters the activity of other TCSs, suggesting a specific BCFA requirement managing the basal activity of multiple TCSs. These results reveal a novel method of posttranscriptional virulence regulation via BCFA synthesis, potentially linking CodY activity to multiple virulence regulators in S. aureus.
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23
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Urner LH, Liko I, Pagel K, Haag R, Robinson CV. Non-ionic hybrid detergents for protein delipidation. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2022; 1864:183958. [PMID: 35551920 DOI: 10.1016/j.bbamem.2022.183958] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2022] [Revised: 04/05/2022] [Accepted: 05/02/2022] [Indexed: 01/03/2023]
Abstract
Non-ionic detergents are important tools for the investigation of interactions between membrane proteins and lipid membranes. Recent studies led to the question as to whether the ability to capture protein-lipid interactions depends on the properties of detergents or their concentration in purification buffers. To address this question, we present the synthesis of an asymmetric, hybrid detergent that combines the head groups of detergents with opposing delipidating properties. We discuss detergent properties and protein purification outcomes to reveal whether the properties of detergent micelles or the detergent concentration in purification buffers drive membrane protein delipidation. We anticipate that our findings will enable the development of rationally design detergents for future applications in membrane protein research.
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Affiliation(s)
- Leonhard H Urner
- Freie Universität Berlin, Institute of Chemistry and Biochemistry, Arnimallee 22, 14195 Berlin, Germany; University of Oxford, Physical and Theoretical Chemistry Laboratory, South Parks Road, Oxford OX13QZ, United Kingdom; TU Dortmund University, Department of Chemistry and Chemical Biology, Otto-Hahn-Str. 6, 44227 Dortmund, Germany.
| | - Idlir Liko
- University of Oxford, Physical and Theoretical Chemistry Laboratory, South Parks Road, Oxford OX13QZ, United Kingdom
| | - Kevin Pagel
- Freie Universität Berlin, Institute of Chemistry and Biochemistry, Arnimallee 22, 14195 Berlin, Germany
| | - Rainer Haag
- Freie Universität Berlin, Institute of Chemistry and Biochemistry, Arnimallee 22, 14195 Berlin, Germany
| | - Carol V Robinson
- University of Oxford, Physical and Theoretical Chemistry Laboratory, South Parks Road, Oxford OX13QZ, United Kingdom
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24
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Dafun AS, Marcoux J. Structural mass spectrometry of membrane proteins. BIOCHIMICA ET BIOPHYSICA ACTA. PROTEINS AND PROTEOMICS 2022; 1870:140813. [PMID: 35750312 DOI: 10.1016/j.bbapap.2022.140813] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2021] [Revised: 06/10/2022] [Accepted: 06/17/2022] [Indexed: 06/15/2023]
Abstract
The analysis of proteins and protein complexes by mass spectrometry (MS) has come a long way since the invention of electrospray ionization (ESI) in the mid 80s. Originally used to characterize small soluble polypeptide chains, MS has progressively evolved over the past 3 decades towards the analysis of samples of ever increasing heterogeneity and complexity, while the instruments have become more and more sensitive and resolutive. The proofs of concepts and first examples of most structural MS methods appeared in the early 90s. However, their application to membrane proteins, key targets in the biopharma industry, is more recent. Nowadays, a wealth of information can be gathered from such MS-based methods, on all aspects of membrane protein structure: sequencing (and more precisely proteoform characterization), but also stoichiometry, non-covalent ligand binding (metals, drug, lipids, carbohydrates), conformations, dynamics and distance restraints for modelling. In this review, we present the concept and some historical and more recent applications on membrane proteins, for the major structural MS methods.
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Affiliation(s)
- Angelique Sanchez Dafun
- Institut de Pharmacologie et de Biologie Structurale (IPBS), Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Julien Marcoux
- Institut de Pharmacologie et de Biologie Structurale (IPBS), Université de Toulouse, CNRS, UPS, Toulouse, France.
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25
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Keener JE, Jayasekera HS, Marty MT. Investigating the Lipid Selectivity of Membrane Proteins in Heterogeneous Nanodiscs. Anal Chem 2022; 94:8497-8505. [PMID: 35621361 DOI: 10.1021/acs.analchem.2c01488] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The structure and function of membrane proteins can be significantly impacted by the surrounding lipid environment, but membrane protein-lipid interactions in lipid bilayers are often difficult to study due to their transient and polydisperse nature. Here, we used two native mass spectrometry (MS) approaches to investigate how the Escherichia coli ammonium transporter trimer (AmtB) and aquaporin Z (AqpZ) selectively remodel their local lipid environment in heterogeneous lipoprotein nanodiscs. First, we used gas-phase ejection to isolate the membrane protein with bound lipids from heterogeneous nanodiscs with different combinations of lipids. Second, we used solution-phase detergent extraction as an orthogonal approach to study membrane protein remodeling of lipids in the nanodisc with native MS. Our results showed that Triton X-100 and lauryldimethylamine oxide retain lipid selectivity that agrees with gas-phase ejection, but C8E4 distorts some preferential lipid interactions. Both approaches reveal that AmtB has a few selective binding sites for phosphatidylcholine (PC) lipids, is selective for binding phosphatidylglycerols (PG) overall, and is nonselective for phosphatidylethanolamines (PE). In contrast, AqpZ prefers either PC or PG over PE and prefers PC over PG. Overall, these experiments provide a picture of how membrane proteins bind different lipid head groups in the context of mixed lipid bilayers.
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Affiliation(s)
- James E Keener
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721, United States
| | - Hiruni S Jayasekera
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721, United States
| | - Michael T Marty
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721, United States.,Bio5 Institute, University of Arizona, Tucson, Arizona 85721, United States
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26
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Abstract
Native mass spectrometry (nMS) has emerged as an important tool in studying the structure and function of macromolecules and their complexes in the gas phase. In this review, we cover recent advances in nMS and related techniques including sample preparation, instrumentation, activation methods, and data analysis software. These advances have enabled nMS-based techniques to address a variety of challenging questions in structural biology. The second half of this review highlights recent applications of these technologies and surveys the classes of complexes that can be studied with nMS. Complementarity of nMS to existing structural biology techniques and current challenges in nMS are also addressed.
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Affiliation(s)
- Kelly R Karch
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, Ohio, USA;
- Resource for Native Mass Spectrometry Guided Structural Biology, The Ohio State University, Columbus, Ohio, USA
| | - Dalton T Snyder
- Resource for Native Mass Spectrometry Guided Structural Biology, The Ohio State University, Columbus, Ohio, USA
| | - Sophie R Harvey
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, Ohio, USA;
- Resource for Native Mass Spectrometry Guided Structural Biology, The Ohio State University, Columbus, Ohio, USA
| | - Vicki H Wysocki
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, Ohio, USA;
- Resource for Native Mass Spectrometry Guided Structural Biology, The Ohio State University, Columbus, Ohio, USA
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27
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Kehlenbeck DM, Traore DAK, Josts I, Sander S, Moulin M, Haertlein M, Prevost S, Forsyth VT, Tidow H. Cryo-EM structure of MsbA in saposin-lipid nanoparticles (Salipro) provides insights into nucleotide coordination. FEBS J 2022; 289:2959-2970. [PMID: 34921499 DOI: 10.1111/febs.16327] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2021] [Revised: 12/05/2021] [Accepted: 12/16/2021] [Indexed: 01/28/2023]
Abstract
The ATP-binding cassette transporter MsbA is a lipid flippase, translocating lipid A, glycolipids, and lipopolysaccharides from the inner to the outer leaflet of the inner membrane of Gram-negative bacteria. It has been used as a model system for time-resolved structural studies as several MsbA structures in different states and reconstitution systems (detergent/nanodiscs/peptidiscs) are available. However, due to the limited resolution of the available structures, detailed structural information on the bound nucleotides has remained elusive. Here, we have reconstituted MsbA in saposin A-lipoprotein nanoparticles (Salipro) and determined the structure of ADP-vanadate-bound MsbA by single-particle cryo-electron microscopy to 3.5 Å resolution. This procedure has resulted in significantly improved resolution and enabled us to model all side chains and visualise detailed ADP-vanadate interactions in the nucleotide-binding domains. The approach may be applicable to other dynamic membrane proteins.
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Affiliation(s)
- Dominique-Maurice Kehlenbeck
- The Hamburg Advanced Research Center for Bioorganic Chemistry (HARBOR), Germany.,Department of Chemistry, Institute for Biochemistry and Molecular Biology, University of Hamburg, Germany.,Life Sciences Group, Institut Laue-Langevin, Grenoble, France.,Partnership for Structural Biology (PSB), Grenoble, France
| | - Daouda A K Traore
- Life Sciences Group, Institut Laue-Langevin, Grenoble, France.,Partnership for Structural Biology (PSB), Grenoble, France.,Faculty of Natural Sciences, Keele University, UK.,Faculté des Sciences et Techniques, Université des Sciences, des Techniques et des Technologies de Bamako (USTTB), Bamako, Mali
| | - Inokentijs Josts
- The Hamburg Advanced Research Center for Bioorganic Chemistry (HARBOR), Germany.,Department of Chemistry, Institute for Biochemistry and Molecular Biology, University of Hamburg, Germany
| | - Simon Sander
- The Hamburg Advanced Research Center for Bioorganic Chemistry (HARBOR), Germany.,Department of Chemistry, Institute for Biochemistry and Molecular Biology, University of Hamburg, Germany
| | - Martine Moulin
- Life Sciences Group, Institut Laue-Langevin, Grenoble, France.,Partnership for Structural Biology (PSB), Grenoble, France
| | - Michael Haertlein
- Life Sciences Group, Institut Laue-Langevin, Grenoble, France.,Partnership for Structural Biology (PSB), Grenoble, France
| | - Sylvain Prevost
- Large Scale Structures Group, Institut Laue-Langevin, Grenoble, France
| | - V Trevor Forsyth
- Life Sciences Group, Institut Laue-Langevin, Grenoble, France.,Partnership for Structural Biology (PSB), Grenoble, France.,Faculty of Natural Sciences, Keele University, UK
| | - Henning Tidow
- The Hamburg Advanced Research Center for Bioorganic Chemistry (HARBOR), Germany
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28
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Gavriilidou AFM, Sokratous K, Yen HY, De Colibus L. High-Throughput Native Mass Spectrometry Screening in Drug Discovery. Front Mol Biosci 2022; 9:837901. [PMID: 35495635 PMCID: PMC9047894 DOI: 10.3389/fmolb.2022.837901] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Accepted: 02/15/2022] [Indexed: 12/15/2022] Open
Abstract
The design of new therapeutic molecules can be significantly informed by studying protein-ligand interactions using biophysical approaches directly after purification of the protein-ligand complex. Well-established techniques utilized in drug discovery include isothermal titration calorimetry, surface plasmon resonance, nuclear magnetic resonance spectroscopy, and structure-based drug discovery which mainly rely on protein crystallography and, more recently, cryo-electron microscopy. Protein-ligand complexes are dynamic, heterogeneous, and challenging systems that are best studied with several complementary techniques. Native mass spectrometry (MS) is a versatile method used to study proteins and their non-covalently driven assemblies in a native-like folded state, providing information on binding thermodynamics and stoichiometry as well as insights on ternary and quaternary protein structure. Here, we discuss the basic principles of native mass spectrometry, the field’s recent progress, how native MS is integrated into a drug discovery pipeline, and its future developments in drug discovery.
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29
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Structural basis of tethered agonism of the adhesion GPCRs ADGRD1 and ADGRF1. Nature 2022; 604:779-785. [PMID: 35418679 PMCID: PMC9046087 DOI: 10.1038/s41586-022-04580-w] [Citation(s) in RCA: 51] [Impact Index Per Article: 25.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Accepted: 02/24/2022] [Indexed: 12/14/2022]
Abstract
Adhesion G protein-coupled receptors (aGPCRs) are essential for a variety of physiological processes such as immune responses, organ development, cellular communication, proliferation and homeostasis1–7. An intrinsic manner of activation that involves a tethered agonist in the N-terminal region of the receptor has been proposed for the aGPCRs8,9, but its molecular mechanism remains elusive. Here we report the G protein-bound structures of ADGRD1 and ADGRF1, which exhibit many unique features with regard to the tethered agonism. The stalk region that proceeds the first transmembrane helix acts as the tethered agonist by forming extensive interactions with the transmembrane domain; these interactions are mostly conserved in ADGRD1 and ADGRF1, suggesting that a common stalk–transmembrane domain interaction pattern is shared by members of the aGPCR family. A similar stalk binding mode is observed in the structure of autoproteolysis-deficient ADGRF1, supporting a cleavage-independent manner of receptor activation. The stalk-induced activation is facilitated by a cascade of inter-helix interaction cores that are conserved in positions but show sequence variability in these two aGPCRs. Furthermore, the intracellular region of ADGRF1 contains a specific lipid-binding site, which proves to be functionally important and may serve as the recognition site for the previously discovered endogenous ADGRF1 ligand synaptamide. These findings highlight the diversity and complexity of the signal transduction mechanisms of the aGPCRs. Cryo-electron microscopy structures of the adhesion G protein-coupled receptors ADGRD1 and ADGRF1 provide insight into how these receptors are activated in an intrinsic manner through a ‘stalk’ region that acts as a tethered agonist.
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30
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Swansiger AK, Marty MT, Prell JS. Fourier-Transform Approach for Reconstructing Macromolecular Mass Defect Profiles. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2022; 33:172-180. [PMID: 34913687 DOI: 10.1021/jasms.1c00317] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
State-of-the-art native mass spectrometry (MS) methods have been developed for analysis of highly heterogeneous intact complexes and have provided much insight into the structure and properties of noncovalent assemblies that can be difficult to study using denatured proteins. These native MS methods can often be used to study even highly polydisperse membrane proteins embedded in detergent micelles, nanodiscs, and other membrane mimics. However, characterizing highly polydisperse native complexes which are also heterogeneous presents additional challenges for native MS. Macromolecular mass defect (MMD) analysis aims to characterize heterogeneous ion populations obfuscated by adduct polydispersity and reveal the distribution of "base" masses, and was recently implemented in the Bayesian analysis software UniDec. Here, we illustrate an alternative, orthogonal MMD analysis method implemented in the deconvolution program iFAMS, which takes advantage of Fourier transform (FT) to deconvolve low-resolution data with few user-input parameters and which can provide high quality results even for mass spectra with a signal-to-noise ratio of ∼5:1. Agreement between this method, which is based on frequency-domain data, and the mass-domain algorithm of UniDec provides strong evidence that both methods can accurately characterize highly polydisperse and heterogeneous ion populations. The FT algorithm is expected to be very useful in characterizing many types of analytes ranging from membrane proteins to polymer-conjugated proteins, branched polymers, and other large analytes, as well as for reconstructing isotope profiles for highly complex but still isotope-resolved mass spectra.
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Affiliation(s)
- Andrew K Swansiger
- Department of Chemistry and Biochemistry, University of Oregon, Eugene, Oregon 97403-1253, United States
| | - Michael T Marty
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721, United States
| | - James S Prell
- Department of Chemistry and Biochemistry, University of Oregon, Eugene, Oregon 97403-1253, United States
- Materials Science Institute, University of Oregon, Eugene, Oregon 97403-1252, United States
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31
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Sych T, Levental KR, Sezgin E. Lipid–Protein Interactions in Plasma Membrane Organization and Function. Annu Rev Biophys 2022; 51:135-156. [DOI: 10.1146/annurev-biophys-090721-072718] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Lipid–protein interactions in cells are involved in various biological processes, including metabolism, trafficking, signaling, host–pathogen interactions, and transmembrane transport. At the plasma membrane, lipid–protein interactions play major roles in membrane organization and function. Several membrane proteins have motifs for specific lipid binding, which modulate protein conformation and consequent function. In addition to such specific lipid–protein interactions, protein function can be regulated by the dynamic, collective behavior of lipids in membranes. Emerging analytical, biochemical, and computational technologies allow us to study the influence of specific lipid–protein interactions, as well as the collective behavior of membranes on protein function. In this article, we review the recent literature on lipid–protein interactions with a specific focus on the current state-of-the-art technologies that enable novel insights into these interactions. Expected final online publication date for the Annual Review of Biophysics, Volume 51 is May 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
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Affiliation(s)
- Taras Sych
- Science for Life Laboratory, Department of Women's and Children's Health, Karolinska Institutet, Solna, Sweden;,
| | - Kandice R. Levental
- Department of Molecular Physiology and Biological Physics, Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, Virginia, USA
| | - Erdinc Sezgin
- Science for Life Laboratory, Department of Women's and Children's Health, Karolinska Institutet, Solna, Sweden;,
- MRC Human Immunology Unit, MRC Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, United Kingdom
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32
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Quetschlich D, Esser TK, Newport TD, Fiorentino F, Shutin D, Chen S, Davis R, Lovera S, Liko I, Stansfeld PJ, Robinson CV. NaViA: a program for the visual analysis of complex mass spectra. Bioinformatics 2021; 37:4876-4878. [PMID: 34145888 PMCID: PMC8665753 DOI: 10.1093/bioinformatics/btab436] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Revised: 04/28/2021] [Accepted: 06/17/2021] [Indexed: 01/04/2023] Open
Abstract
MOTIVATION Native mass spectrometry is now a well-established method for the investigation of protein complexes, specifically their subunit stoichiometry and ligand binding properties. Recent advances allowing the analysis of complex mixtures lead to an increasing diversity and complexity in the spectra obtained. These spectra can be time-consuming to tackle through manual assignment and challenging for automated approaches. RESULTS Native Mass Spectrometry Visual Analyser is a web-based tool to augment the manual process of peak assignment. In addition to matching masses to the stoichiometry of its component subunits, it allows raw data processing, assignment and annotation and permits mass spectra to be shared with their respective interpretation. AVAILABILITY AND IMPLEMENTATION NaViA is open-source and can be accessed online under https://navia.ms. The source code and documentation can be accessed at https://github.com/d-que/navia, under the BSD 2-Clause licence. SUPPLEMENTARY INFORMATION Supplementary data are available at Bioinformatics online.
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Affiliation(s)
- Daniel Quetschlich
- Department of Chemistry, University of Oxford, Oxford OX1 3TF, UK
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK
| | - Tim K Esser
- Department of Chemistry, University of Oxford, Oxford OX1 3TF, UK
| | - Thomas D Newport
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK
| | | | - Denis Shutin
- Department of Chemistry, University of Oxford, Oxford OX1 3TF, UK
| | - Siyun Chen
- Department of Chemistry, University of Oxford, Oxford OX1 3TF, UK
| | | | - Silvia Lovera
- UCB Pharma, Chemin du Foriest, 1420 Braine-l’Alleud, Belgium
| | | | - Phillip J Stansfeld
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK
- School of Life Sciences & Department of Chemistry, University of Warwick, Coventry CV4 7AL, UK
| | - Carol V Robinson
- Department of Chemistry, University of Oxford, Oxford OX1 3TF, UK
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33
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Guo D, Singh H, Shimoyama A, Guffick C, Tang Y, Rowe SM, Noel T, Spring DR, Fukase K, van Veen HW. Energetics of lipid transport by the ABC transporter MsbA is lipid dependent. Commun Biol 2021; 4:1379. [PMID: 34887543 PMCID: PMC8660845 DOI: 10.1038/s42003-021-02902-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2021] [Accepted: 11/18/2021] [Indexed: 12/13/2022] Open
Abstract
The ABC multidrug exporter MsbA mediates the translocation of lipopolysaccharides and phospholipids across the plasma membrane in Gram-negative bacteria. Although MsbA is structurally well characterised, the energetic requirements of lipid transport remain unknown. Here, we report that, similar to the transport of small-molecule antibiotics and cytotoxic agents, the flopping of physiologically relevant long-acyl-chain 1,2-dioleoyl (C18)-phosphatidylethanolamine in proteoliposomes requires the simultaneous input of ATP binding and hydrolysis and the chemical proton gradient as sources of metabolic energy. In contrast, the flopping of the large hexa-acylated (C12-C14) Lipid-A anchor of lipopolysaccharides is only ATP dependent. This study demonstrates that the energetics of lipid transport by MsbA is lipid dependent. As our mutational analyses indicate lipid and drug transport via the central binding chamber in MsbA, the lipid availability in the membrane can affect the drug transport activity and vice versa.
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Affiliation(s)
- Dawei Guo
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge, CB2 1PD, UK
| | - Himansha Singh
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge, CB2 1PD, UK
| | - Atsushi Shimoyama
- Department of Chemistry, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka, 560-0043, Japan
| | - Charlotte Guffick
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge, CB2 1PD, UK
| | - Yakun Tang
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge, CB2 1PD, UK
| | - Sam M Rowe
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK
| | - Timothy Noel
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge, CB2 1PD, UK
| | - David R Spring
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK
| | - Koichi Fukase
- Department of Chemistry, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka, 560-0043, Japan
| | - Hendrik W van Veen
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge, CB2 1PD, UK.
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34
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Yoon H, Shaw JL, Haigis MC, Greka A. Lipid metabolism in sickness and in health: Emerging regulators of lipotoxicity. Mol Cell 2021; 81:3708-3730. [PMID: 34547235 PMCID: PMC8620413 DOI: 10.1016/j.molcel.2021.08.027] [Citation(s) in RCA: 117] [Impact Index Per Article: 39.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2021] [Revised: 08/10/2021] [Accepted: 08/19/2021] [Indexed: 12/12/2022]
Abstract
Lipids play crucial roles in signal transduction, contribute to the structural integrity of cellular membranes, and regulate energy metabolism. Questions remain as to which lipid species maintain metabolic homeostasis and which disrupt essential cellular functions, leading to metabolic disorders. Here, we discuss recent advances in understanding lipid metabolism with a focus on catabolism, synthesis, and signaling. Technical advances, including functional genomics, metabolomics, lipidomics, lipid-protein interaction maps, and advances in mass spectrometry, have uncovered new ways to prioritize molecular mechanisms mediating lipid function. By reviewing what is known about the distinct effects of specific lipid species in physiological pathways, we provide a framework for understanding newly identified targets regulating lipid homeostasis with implications for ameliorating metabolic diseases.
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Affiliation(s)
- Haejin Yoon
- Department of Cell Biology, Blavatnik Institute, Harvard Medical School, Boston, MA, USA; Ludwig Center for Cancer Research at Harvard, Boston, MA 02115, USA
| | - Jillian L Shaw
- Kidney Disease Initiative, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Marcia C Haigis
- Department of Cell Biology, Blavatnik Institute, Harvard Medical School, Boston, MA, USA; Ludwig Center for Cancer Research at Harvard, Boston, MA 02115, USA.
| | - Anna Greka
- Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA; Kidney Disease Initiative, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA.
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35
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Pipatpolkai T, Quetschlich D, Stansfeld PJ. From Bench to Biomolecular Simulation: Phospholipid Modulation of Potassium Channels. J Mol Biol 2021; 433:167105. [PMID: 34139216 PMCID: PMC8361781 DOI: 10.1016/j.jmb.2021.167105] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2021] [Revised: 06/09/2021] [Accepted: 06/10/2021] [Indexed: 12/05/2022]
Abstract
Potassium (K+) ion channels are crucial in numerous cellular processes as they hyperpolarise a cell through K+ conductance, returning a cell to its resting potential. K+ channel mutations result in multiple clinical complications such as arrhythmia, neonatal diabetes and migraines. Since 1995, the regulation of K+ channels by phospholipids has been heavily studied using a range of interdisciplinary methods such as cellular electrophysiology, structural biology and computational modelling. As a result, K+ channels are model proteins for the analysis of protein-lipid interactions. In this review, we will focus on the roles of lipids in the regulation of K+ channels, and how atomic-level structures, along with experimental techniques and molecular simulations, have helped guide our understanding of the importance of phospholipid interactions.
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Affiliation(s)
- Tanadet Pipatpolkai
- Department of Biochemistry, South Parks Road, Oxford OX1 3QU, UK; Department of Physiology Anatomy and Genetics, Parks Road, Oxford OX1 3PT, UK; OXION Initiative in Ion Channels and Disease, University of Oxford, Oxford OX1 3PT, UK
| | - Daniel Quetschlich
- Department of Biochemistry, South Parks Road, Oxford OX1 3QU, UK; Department of Chemistry, South Parks Road, Oxford OX1 3QZ, UK
| | - Phillip J Stansfeld
- School of Life Sciences & Department of Chemistry, University of Warwick, Coventry CV4 7AL, UK.
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36
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Abstract
![]()
Native mass spectrometry
(MS) involves the analysis and characterization
of macromolecules, predominantly intact proteins and protein complexes,
whereby as much as possible the native structural features of the
analytes are retained. As such, native MS enables the study of secondary,
tertiary, and even quaternary structure of proteins and other biomolecules.
Native MS represents a relatively recent addition to the analytical
toolbox of mass spectrometry and has over the past decade experienced
immense growth, especially in enhancing sensitivity and resolving
power but also in ease of use. With the advent of dedicated mass analyzers,
sample preparation and separation approaches, targeted fragmentation
techniques, and software solutions, the number of practitioners and
novel applications has risen in both academia and industry. This review
focuses on recent developments, particularly in high-resolution native
MS, describing applications in the structural analysis of protein
assemblies, proteoform profiling of—among others—biopharmaceuticals
and plasma proteins, and quantitative and qualitative analysis of
protein–ligand interactions, with the latter covering lipid,
drug, and carbohydrate molecules, to name a few.
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Affiliation(s)
- Sem Tamara
- Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, University of Utrecht, Padualaan 8, 3584 CH Utrecht, The Netherlands.,Netherlands Proteomics Center, Padualaan 8, 3584 CH Utrecht, The Netherlands
| | - Maurits A den Boer
- Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, University of Utrecht, Padualaan 8, 3584 CH Utrecht, The Netherlands.,Netherlands Proteomics Center, Padualaan 8, 3584 CH Utrecht, The Netherlands
| | - Albert J R Heck
- Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, University of Utrecht, Padualaan 8, 3584 CH Utrecht, The Netherlands.,Netherlands Proteomics Center, Padualaan 8, 3584 CH Utrecht, The Netherlands
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37
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Abstract
The mechanosensitive channel of small conductance (MscS) protects bacteria against hypoosmotic shock. It can sense the tension in the surrounding membrane and releases solutes if the pressure in the cell is getting too high. The membrane contacts MscS at sensor paddles, but lipids also leave the membrane and move along grooves between the paddles to reside as far as 15 Å away from the membrane in hydrophobic pockets. One sensing model suggests that a higher tension pulls lipids from the grooves back to the membrane, which triggers gating. However, it is still unclear to what degree this model accounts for sensing and what contribution the direct interaction of the membrane with the channel has. Here, we show that MscS opens when it is sufficiently delipidated by incubation with the detergent dodecyl-β-maltoside or the branched detergent lauryl maltose neopentyl glycol. After addition of detergent-solubilized lipids, it closes again. These results support the model that lipid extrusion causes gating: Lipids are slowly removed from the grooves and pockets by the incubation with detergent, which triggers opening. Addition of lipids in micelles allows lipids to migrate back into the pockets, which closes the channel even in the absence of a membrane. Based on the distribution of the aliphatic chains in the open and closed conformation, we propose that during gating, lipids leave the complex on the cytosolic leaflet at the height of highest lateral tension, while on the periplasmic side, lipids flow into gaps, which open between transmembrane helices.
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38
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Gaudet RG, Zhu S, Halder A, Kim BH, Bradfield CJ, Huang S, Xu D, Mamiñska A, Nguyen TN, Lazarou M, Karatekin E, Gupta K, MacMicking JD. A human apolipoprotein L with detergent-like activity kills intracellular pathogens. Science 2021; 373:eabf8113. [PMID: 34437126 PMCID: PMC8422858 DOI: 10.1126/science.abf8113] [Citation(s) in RCA: 44] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2020] [Revised: 04/29/2021] [Accepted: 06/03/2021] [Indexed: 12/11/2022]
Abstract
Activation of cell-autonomous defense by the immune cytokine interferon-γ (IFN-γ) is critical to the control of life-threatening infections in humans. IFN-γ induces the expression of hundreds of host proteins in all nucleated cells and tissues, yet many of these proteins remain uncharacterized. We screened 19,050 human genes by CRISPR-Cas9 mutagenesis and identified IFN-γ-induced apolipoprotein L3 (APOL3) as a potent bactericidal agent protecting multiple non-immune barrier cell types against infection. Canonical apolipoproteins typically solubilize mammalian lipids for extracellular transport; APOL3 instead targeted cytosol-invasive bacteria to dissolve their anionic membranes into human-bacterial lipoprotein nanodiscs detected by native mass spectrometry and visualized by single-particle cryo-electron microscopy. Thus, humans have harnessed the detergent-like properties of extracellular apolipoproteins to fashion an intracellular lysin, thereby endowing resident nonimmune cells with a mechanism to achieve sterilizing immunity.
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Affiliation(s)
- Ryan G Gaudet
- Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT 06510, USA
- Yale Systems Biology Institute, West Haven, CT 06477, USA
- Department of Immunobiology, Yale University School of Medicine, New Haven, CT 06510, USA
- Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Shiwei Zhu
- Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT 06510, USA
- Yale Systems Biology Institute, West Haven, CT 06477, USA
- Department of Immunobiology, Yale University School of Medicine, New Haven, CT 06510, USA
- Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Anushka Halder
- Yale Nanobiology Institute, West Haven, CT 06477, USA
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Bae-Hoon Kim
- Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT 06510, USA
- Yale Systems Biology Institute, West Haven, CT 06477, USA
- Department of Immunobiology, Yale University School of Medicine, New Haven, CT 06510, USA
- Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Clinton J Bradfield
- Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT 06510, USA
- Yale Systems Biology Institute, West Haven, CT 06477, USA
- Department of Immunobiology, Yale University School of Medicine, New Haven, CT 06510, USA
- Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Shuai Huang
- Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT 06510, USA
- Yale Systems Biology Institute, West Haven, CT 06477, USA
- Department of Immunobiology, Yale University School of Medicine, New Haven, CT 06510, USA
- Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Dijin Xu
- Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT 06510, USA
- Yale Systems Biology Institute, West Haven, CT 06477, USA
- Department of Immunobiology, Yale University School of Medicine, New Haven, CT 06510, USA
- Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Agnieszka Mamiñska
- Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT 06510, USA
- Yale Systems Biology Institute, West Haven, CT 06477, USA
- Department of Immunobiology, Yale University School of Medicine, New Haven, CT 06510, USA
- Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Thanh Ngoc Nguyen
- Department of Biochemistry and Molecular Biology, Monash Biomedicine Discovery Institute, Monash University, Melbourne 3800, Australia
| | - Michael Lazarou
- Department of Biochemistry and Molecular Biology, Monash Biomedicine Discovery Institute, Monash University, Melbourne 3800, Australia
| | - Erdem Karatekin
- Yale Nanobiology Institute, West Haven, CT 06477, USA
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, CT 06510, USA
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06510, USA
- Saints-Pères Paris Institute for the Neurosciences, Centre National de la Recherche Scientifique (CNRS), Université de Paris, F-75006 Paris, France
| | - Kallol Gupta
- Yale Nanobiology Institute, West Haven, CT 06477, USA
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06510, USA
| | - John D MacMicking
- Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT 06510, USA.
- Yale Systems Biology Institute, West Haven, CT 06477, USA
- Department of Immunobiology, Yale University School of Medicine, New Haven, CT 06510, USA
- Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, CT 06510, USA
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39
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Jodaitis L, van Oene T, Martens C. Assessing the Role of Lipids in the Molecular Mechanism of Membrane Proteins. Int J Mol Sci 2021; 22:7267. [PMID: 34298884 PMCID: PMC8306737 DOI: 10.3390/ijms22147267] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2021] [Revised: 06/30/2021] [Accepted: 07/01/2021] [Indexed: 02/06/2023] Open
Abstract
Membrane proteins have evolved to work optimally within the complex environment of the biological membrane. Consequently, interactions with surrounding lipids are part of their molecular mechanism. Yet, the identification of lipid-protein interactions and the assessment of their molecular role is an experimental challenge. Recently, biophysical approaches have emerged that are compatible with the study of membrane proteins in an environment closer to the biological membrane. These novel approaches revealed specific mechanisms of regulation of membrane protein function. Lipids have been shown to play a role in oligomerization, conformational transitions or allosteric coupling. In this review, we summarize the recent biophysical approaches, or combination thereof, that allow to decipher the role of lipid-protein interactions in the mechanism of membrane proteins.
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Affiliation(s)
| | | | - Chloé Martens
- Center for Structural Biology and Bioinformatics, Université Libre de Bruxelles, 1050 Brussels, Belgium; (L.J.); (T.v.O.)
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40
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Hossain M, Blanchard GJ. Ceramide-mediation of diffusion in supported lipid bilayers. Chem Phys Lipids 2021; 238:105090. [PMID: 33971138 DOI: 10.1016/j.chemphyslip.2021.105090] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2021] [Revised: 04/09/2021] [Accepted: 05/05/2021] [Indexed: 11/30/2022]
Abstract
The fluidity and compositional heterogeneity of the mammalian plasma membrane play deterministic roles in a variety of membrane functions. Designing model bilayer systems allows for compositional control over these properties. Ceramide is a phospholipid capable of extensive headgroup-region hydrogen bonding, and we report here on the role of ceramide in planar model bilayers. We use fluorescence recovery after photobleaching (FRAP) to obtain translational diffusion constants of two chromophores in supported model bilayers composed of cholesterol, 1,2-dioleoyl-sn-phosphatidylcholine (DOPC), sphingomyelin, and ceramide. FRAP data for perylene report on the acyl chain region of the model bilayer and FRAP data for 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine-N-(lissamine rhodamine B sulfonyl) sense diffusional dynamics in the bilayer headgroup region. Dynamics in the headgroup region exhibit anomalous diffusion behavior that is characteristic of spatially heterogeneous media.
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Affiliation(s)
- Masroor Hossain
- Michigan State University, Department of Chemistry, 578 S. Shaw Lane, East Lansing, MI, 48824, USA
| | - G J Blanchard
- Michigan State University, Department of Chemistry, 578 S. Shaw Lane, East Lansing, MI, 48824, USA.
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41
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Agasid MT, Robinson CV. Probing membrane protein-lipid interactions. Curr Opin Struct Biol 2021; 69:78-85. [PMID: 33930613 DOI: 10.1016/j.sbi.2021.03.010] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2020] [Revised: 03/08/2021] [Accepted: 03/21/2021] [Indexed: 12/15/2022]
Abstract
Structure determination of membrane proteins has highlighted the many roles played by lipids in influencing overall protein architecture. It is now widely accepted that lipids surrounding membrane proteins play crucial roles by modulating their conformational, structural, and functional properties. Capturing often transient lipid interactions and defining their chemical identity, however, remains challenging. Recent advances in mass spectrometry have resolved questions concerning lipid interactions by providing the molecular composition of intact complexes in association with lipids. Together with other biophysical tools, a picture is emerging of the dynamic nature of lipid-mediated interactions and their effects on conformation, interactions, and signaling.
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Affiliation(s)
- Mark T Agasid
- Department of Chemistry, University of Oxford, 12 Mansfield Road, Oxford, OX1 3TA, UK
| | - Carol V Robinson
- Department of Chemistry, University of Oxford, 12 Mansfield Road, Oxford, OX1 3TA, UK.
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42
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Ion mobility-mass spectrometry reveals the role of peripheral myelin protein dimers in peripheral neuropathy. Proc Natl Acad Sci U S A 2021; 118:2015331118. [PMID: 33893233 DOI: 10.1073/pnas.2015331118] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Peripheral myelin protein (PMP22) is an integral membrane protein that traffics inefficiently even in wild-type (WT) form, with only 20% of the WT protein reaching its final plasma membrane destination in myelinating Schwann cells. Misfolding of PMP22 has been identified as a key factor in multiple peripheral neuropathies, including Charcot-Marie-Tooth disease and Dejerine-Sottas syndrome. While biophysical analyses of disease-associated PMP22 mutants show altered protein stabilities, leading to reduced surface trafficking and loss of PMP22 function, it remains unclear how destabilization of PMP22 mutations causes mistrafficking. Here, native ion mobility-mass spectrometry (IM-MS) is used to compare the gas phase stabilities and abundances for an array of mutant PM22 complexes. We find key differences in the PMP22 mutant stabilities and propensities to form homodimeric complexes. Of particular note, we observe that severely destabilized forms of PMP22 exhibit a higher propensity to dimerize than WT PMP22. Furthermore, we employ lipid raft-mimicking SCOR bicelles to study PMP22 mutants, and find that the differences in dimer abundances are amplified in this medium when compared to micelle-based data, with disease mutants exhibiting up to 4 times more dimer than WT when liberated from SCOR bicelles. We combine our findings with previous cellular data to propose that the formation of PMP22 dimers from destabilized monomers is a key element of PMP22 mistrafficking.
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43
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Senevirathna JDM, Asakawa S. Multi-Omics Approaches and Radiation on Lipid Metabolism in Toothed Whales. Life (Basel) 2021; 11:364. [PMID: 33923876 PMCID: PMC8074237 DOI: 10.3390/life11040364] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2021] [Revised: 04/09/2021] [Accepted: 04/17/2021] [Indexed: 11/25/2022] Open
Abstract
Lipid synthesis pathways of toothed whales have evolved since their movement from the terrestrial to marine environment. The synthesis and function of these endogenous lipids and affecting factors are still little understood. In this review, we focused on different omics approaches and techniques to investigate lipid metabolism and radiation impacts on lipids in toothed whales. The selected literature was screened, and capacities, possibilities, and future approaches for identifying unusual lipid synthesis pathways by omics were evaluated. Omics approaches were categorized into the four major disciplines: lipidomics, transcriptomics, genomics, and proteomics. Genomics and transcriptomics can together identify genes related to unique lipid synthesis. As lipids interact with proteins in the animal body, lipidomics, and proteomics can correlate by creating lipid-binding proteome maps to elucidate metabolism pathways. In lipidomics studies, recent mass spectroscopic methods can address lipid profiles; however, the determination of structures of lipids are challenging. As an environmental stress, the acoustic radiation has a significant effect on the alteration of lipid profiles. Radiation studies in different omics approaches revealed the necessity of multi-omics applications. This review concluded that a combination of many of the omics areas may elucidate the metabolism of lipids and possible hazards on lipids in toothed whales by radiation.
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Affiliation(s)
- Jayan D. M. Senevirathna
- Laboratory of Aquatic Molecular Biology and Biotechnology, Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo 113-8657, Japan;
- Department of Animal Science, Faculty of Animal Science and Export Agriculture, Uva Wellassa University, Badulla 90000, Sri Lanka
| | - Shuichi Asakawa
- Laboratory of Aquatic Molecular Biology and Biotechnology, Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo 113-8657, Japan;
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44
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Lemel L, Nieścierowicz K, García-Fernández MD, Darré L, Durroux T, Busnelli M, Pezet M, Rébeillé F, Jouhet J, Mouillac B, Domene C, Chini B, Cherezov V, Moreau CJ. The ligand-bound state of a G protein-coupled receptor stabilizes the interaction of functional cholesterol molecules. J Lipid Res 2021; 62:100059. [PMID: 33647276 PMCID: PMC8050779 DOI: 10.1016/j.jlr.2021.100059] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2021] [Accepted: 02/11/2021] [Indexed: 12/30/2022] Open
Abstract
Cholesterol is a major component of mammalian plasma membranes that not only affects the physical properties of the lipid bilayer but also is the function of many membrane proteins including G protein-coupled receptors. The oxytocin receptor (OXTR) is involved in parturition and lactation of mammals and in their emotional and social behaviors. Cholesterol acts on OXTR as an allosteric modulator inducing a high-affinity state for orthosteric ligands through a molecular mechanism that has yet to be determined. Using the ion channel-coupled receptor technology, we developed a functional assay of cholesterol modulation of G protein-coupled receptors that is independent of intracellular signaling pathways and operational in living cells. Using this assay, we discovered a stable binding of cholesterol molecules to the receptor when it adopts an orthosteric ligand-bound state. This stable interaction preserves the cholesterol-dependent activity of the receptor in cholesterol-depleted membranes. This mechanism was confirmed using time-resolved FRET experiments on WT OXTR expressed in CHO cells. Consequently, a positive cross-regulation sequentially occurs in OXTR between cholesterol and orthosteric ligands.
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Affiliation(s)
- Laura Lemel
- Univ. Grenoble Alpes, CNRS, CEA, IBS, Grenoble, France
| | | | | | - Leonardo Darré
- Functional Genomics Laboratory and Biomolecular Simulations Laboratory, Institut Pasteur de Montevideo, Montevideo, Uruguay
| | - Thierry Durroux
- Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS, INSERM, Montpellier, France
| | - Marta Busnelli
- CNR, Institute of Neuroscience, U28 and NeuroMI Center for Neuroscience, University of Milano-Bicocca, Vedano al Lambro (MB), Italy
| | - Mylène Pezet
- Institute for Advanced Biosciences, Inserm U 1209, CNRS UMR 5309, Grenoble Alpes University, Grenoble, France
| | - Fabrice Rébeillé
- Laboratoire de Physiologie Cellulaire Végétale, Univ. Grenoble Alpes, CNRS, CEA, INRAE, Grenoble, France
| | - Juliette Jouhet
- Laboratoire de Physiologie Cellulaire Végétale, Univ. Grenoble Alpes, CNRS, CEA, INRAE, Grenoble, France
| | - Bernard Mouillac
- Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS, INSERM, Montpellier, France
| | - Carmen Domene
- Department of Chemistry, University of Bath, Bath, United Kingdom; Chemistry Research Laboratory, University of Oxford, Oxford, United Kingdom
| | - Bice Chini
- CNR, Institute of Neuroscience, U28 and NeuroMI Center for Neuroscience, University of Milano-Bicocca, Vedano al Lambro (MB), Italy
| | - Vadim Cherezov
- Bridge Institute, Department of Chemistry, University of Southern California, Los Angeles, CA, USA
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45
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Affiliation(s)
- James E. Keener
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721, USA
| | - Guozhi Zhang
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721, USA
| | - Michael T. Marty
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721, USA
- Bio5 Institute, University of Arizona, Tucson, AZ 85721, USA
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46
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Bagheri Y, Ali AA, You M. Current Methods for Detecting Cell Membrane Transient Interactions. Front Chem 2020; 8:603259. [PMID: 33365301 PMCID: PMC7750205 DOI: 10.3389/fchem.2020.603259] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2020] [Accepted: 10/16/2020] [Indexed: 12/28/2022] Open
Abstract
Short-lived cell membrane complexes play a key role in regulating cell signaling and communication. Many of these complexes are formed based on low-affinity and transient interactions among various lipids and proteins. New techniques have emerged to study these previously overlooked membrane transient interactions. Exciting functions of these transient interactions have been discovered in cellular events such as immune signaling, host-pathogen interactions, and diseases such as cancer. In this review, we have summarized current experimental methods that allow us to detect and analyze short-lived cell membrane protein-protein, lipid-protein, and lipid-lipid interactions. These methods can provide useful information about the strengths, kinetics, and/or spatial patterns of membrane transient interactions. However, each method also has its own limitations. We hope this review can be used as a guideline to help the audience to choose proper approaches for studying membrane transient interactions in different membrane trafficking and cell signaling events.
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Affiliation(s)
| | | | - Mingxu You
- Department of Chemistry, University of Massachusetts, Amherst, MA, United States
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47
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Jiao F, Cannon KS, Lin YC, Gladfelter AS, Scheuring S. The hierarchical assembly of septins revealed by high-speed AFM. Nat Commun 2020; 11:5062. [PMID: 33033254 PMCID: PMC7545167 DOI: 10.1038/s41467-020-18778-x] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2020] [Accepted: 09/15/2020] [Indexed: 12/15/2022] Open
Abstract
Septins are GTP-binding proteins involved in diverse cellular processes including division and membrane remodeling. Septins form linear, palindromic heteromeric complexes that can assemble in filaments and higher-order structures. Structural studies revealed various septin architectures, but questions concerning assembly-dynamics and -pathways persist. Here we used high-speed atomic force microscopy (HS-AFM) and kinetic modeling which allowed us to determine that septin filament assembly was a diffusion-driven process, while formation of higher-order structures was complex and involved self-templating. Slightly acidic pH and increased monovalent ion concentrations favor filament-assembly, -alignment and -pairing. Filament-alignment and -pairing further favored diffusion-driven assembly. Pairing is mediated by the septin N-termini face, and may occur symmetrically or staggered, likely important for the formation of higher-order structures of different shapes. Multilayered structures are templated by the morphology of the underlying layers. The septin C-termini face, namely the C-terminal extension of Cdc12, may be involved in membrane binding.
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Affiliation(s)
- Fang Jiao
- Department of Anesthesiology, Weill Cornell Medicine, New York, NY, 10065, USA
- Department of Physiology and Biophysics, Weill Cornell Medicine, New York, NY, 10065, USA
| | - Kevin S Cannon
- Department of Biology, University of North Carolina and Chapel Hill, Chapel Hill, NC, 27599, USA
| | - Yi-Chih Lin
- Department of Anesthesiology, Weill Cornell Medicine, New York, NY, 10065, USA
- Department of Physiology and Biophysics, Weill Cornell Medicine, New York, NY, 10065, USA
| | - Amy S Gladfelter
- Department of Biology, University of North Carolina and Chapel Hill, Chapel Hill, NC, 27599, USA
- Marine Biological Laboratory, Woods Hole, MA, 02543, USA
| | - Simon Scheuring
- Department of Anesthesiology, Weill Cornell Medicine, New York, NY, 10065, USA.
- Department of Physiology and Biophysics, Weill Cornell Medicine, New York, NY, 10065, USA.
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48
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de Vlugt JE, Xiao P, Munro R, Charchoglyan A, Brewer D, Al-Abdul-Wahid MS, Brown LS, Ladizhansky V. Identifying lipids tightly bound to an integral membrane protein. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2020; 1862:183345. [DOI: 10.1016/j.bbamem.2020.183345] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2020] [Revised: 04/11/2020] [Accepted: 05/05/2020] [Indexed: 01/02/2023]
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49
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Park J, Fu Z, Frangaj A, Liu J, Mosyak L, Shen T, Slavkovich VN, Ray KM, Taura J, Cao B, Geng Y, Zuo H, Kou Y, Grassucci R, Chen S, Liu Z, Lin X, Williams JP, Rice WJ, Eng ET, Huang RK, Soni RK, Kloss B, Yu Z, Javitch JA, Hendrickson WA, Slesinger PA, Quick M, Graziano J, Yu H, Fiehn O, Clarke OB, Frank J, Fan QR. Structure of human GABA B receptor in an inactive state. Nature 2020; 584:304-309. [PMID: 32581365 PMCID: PMC7725281 DOI: 10.1038/s41586-020-2452-0] [Citation(s) in RCA: 54] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2019] [Accepted: 05/01/2020] [Indexed: 01/21/2023]
Abstract
The human GABAB receptor-a member of the class C family of G-protein-coupled receptors (GPCRs)-mediates inhibitory neurotransmission and has been implicated in epilepsy, pain and addiction1. A unique GPCR that is known to require heterodimerization for function2-6, the GABAB receptor has two subunits, GABAB1 and GABAB2, that are structurally homologous but perform distinct and complementary functions. GABAB1 recognizes orthosteric ligands7,8, while GABAB2 couples with G proteins9-14. Each subunit is characterized by an extracellular Venus flytrap (VFT) module, a descending peptide linker, a seven-helix transmembrane domain and a cytoplasmic tail15. Although the VFT heterodimer structure has been resolved16, the structure of the full-length receptor and its transmembrane signalling mechanism remain unknown. Here we present a near full-length structure of the GABAB receptor, captured in an inactive state by cryo-electron microscopy. Our structure reveals several ligands that preassociate with the receptor, including two large endogenous phospholipids that are embedded within the transmembrane domains to maintain receptor integrity and modulate receptor function. We also identify a previously unknown heterodimer interface between transmembrane helices 3 and 5 of both subunits, which serves as a signature of the inactive conformation. A unique 'intersubunit latch' within this transmembrane interface maintains the inactive state, and its disruption leads to constitutive receptor activity.
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Affiliation(s)
- Jinseo Park
- Department of Pharmacology, Columbia University, New York, NY, USA
| | - Ziao Fu
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY, USA
| | - Aurel Frangaj
- Department of Pharmacology, Columbia University, New York, NY, USA
| | - Jonathan Liu
- Department of Pharmacology, Columbia University, New York, NY, USA
| | - Lidia Mosyak
- Department of Pharmacology, Columbia University, New York, NY, USA
| | - Tong Shen
- NIH West Coast Metabolomics Center, University of California Davis, Davis, CA, USA
| | - Vesna N Slavkovich
- Department of Environmental Health Sciences, Columbia University, New York, NY, USA
| | - Kimberly M Ray
- Department of Pharmacology, Columbia University, New York, NY, USA
| | - Jaume Taura
- Nash Family Department of Neuroscience, Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Baohua Cao
- Department of Pharmacology, Columbia University, New York, NY, USA
| | - Yong Geng
- Department of Pharmacology, Columbia University, New York, NY, USA
- Key Laboratory of Receptor Research, Center for Structure and Function of Drug Targets, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Hao Zuo
- Department of Pharmacology, Columbia University, New York, NY, USA
| | - Yongjun Kou
- Key Laboratory of Receptor Research, Center for Structure and Function of Drug Targets, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Robert Grassucci
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY, USA
| | - Shaoxia Chen
- MRC Laboratory of Molecular Biology, Cambridge, UK
| | - Zheng Liu
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY, USA
| | - Xin Lin
- Department of Psychiatry, Columbia University, New York, NY, USA
- Division of Molecular Therapeutics, New York State Psychiatric Institute, New York, NY, USA
| | - Justin P Williams
- Department of Physiology and Cellular Biophysics, Columbia University, New York, NY, USA
| | - William J Rice
- National Resource for Automated Molecular Microscopy, Simons Electron Microscopy Center, New York Structural Biology Center, New York, NY, USA
| | - Edward T Eng
- National Resource for Automated Molecular Microscopy, Simons Electron Microscopy Center, New York Structural Biology Center, New York, NY, USA
| | - Rick K Huang
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, USA
| | - Rajesh K Soni
- Proteomics Shared Resource, Herbert Irving Comprehensive Cancer Center, Columbia University, New York, NY, USA
| | - Brian Kloss
- Center on Membrane Protein Production and Analysis, New York Structural Biology Center, New York, NY, USA
| | - Zhiheng Yu
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, USA
| | - Jonathan A Javitch
- Department of Pharmacology, Columbia University, New York, NY, USA
- Department of Psychiatry, Columbia University, New York, NY, USA
- Division of Molecular Therapeutics, New York State Psychiatric Institute, New York, NY, USA
- Department of Physiology and Cellular Biophysics, Columbia University, New York, NY, USA
| | - Wayne A Hendrickson
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY, USA
- Department of Physiology and Cellular Biophysics, Columbia University, New York, NY, USA
- Center on Membrane Protein Production and Analysis, New York Structural Biology Center, New York, NY, USA
| | - Paul A Slesinger
- Nash Family Department of Neuroscience, Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Matthias Quick
- Department of Psychiatry, Columbia University, New York, NY, USA
- Division of Molecular Therapeutics, New York State Psychiatric Institute, New York, NY, USA
| | - Joseph Graziano
- Department of Environmental Health Sciences, Columbia University, New York, NY, USA
| | - Hongtao Yu
- Howard Hughes Medical Institute, Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Oliver Fiehn
- NIH West Coast Metabolomics Center, University of California Davis, Davis, CA, USA
| | - Oliver B Clarke
- Department of Physiology and Cellular Biophysics, Columbia University, New York, NY, USA.
- Department of Anesthesiology and the Irving Institute for Clinical and Translational Research, Columbia University, New York, NY, USA.
| | - Joachim Frank
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY, USA.
- Department of Biological Sciences, Columbia University, New York, NY, USA.
| | - Qing R Fan
- Department of Pharmacology, Columbia University, New York, NY, USA.
- Department of Pathology and Cell Biology, Columbia University, New York, NY, USA.
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50
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Cleary SP, Prell JS. Distinct classes of multi-subunit heterogeneity: analysis using Fourier Transform methods and native mass spectrometry. Analyst 2020; 145:4688-4697. [PMID: 32459233 PMCID: PMC8483610 DOI: 10.1039/d0an00726a] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Native electrospray mass spectrometry is a powerful method for determining the native stoichiometry of many polydisperse multi-subunit biological complexes, including multi-subunit protein complexes and lipid-bound transmembrane proteins. However, when polydispersity results from incorporation of multiple copies of two or more different subunits, it can be difficult to analyze subunit stoichiometry using conventional mass spectrometry analysis methods, especially when m/z distributions for different charge states overlap in the mass spectrum. It was recently demonstrated by Marty and co-workers (K. K. Hoi, et al., Anal. Chem., 2016, 88, 6199-6204) that Fourier Transform (FT)-based methods can determine the bulk average lipid composition of protein-lipid Nanodiscs assembled with two different lipids, but a detailed statistical description of the composition of more general polydisperse two-subunit populations is still difficult to achieve. This results from the vast number of ways in which the two types of subunit can be distributed within the analyte ensemble. Here, we present a theoretical description of three common classes of heterogeneity for mixed-subunit analytes and demonstrate how to differentiate and analyze them using mass spectrometry and FT methods. First, we first describe FT-based analysis of mass spectra corresponding to simple superpositions, convolutions, and multinomial distributions for two or more different subunit types using model data sets. We then apply these principles with real samples, including mixtures of single-lipid Nanodiscs in the same solution (superposition), mixed-lipid Nanodiscs and copolymers (convolutions), and isotope distribution for ubiquitin (multinomial distribution). This classification scheme and the FT method used to study these analyte classes should be broadly useful in mass spectrometry as well as other techniques where overlapping, periodic signals arising from analyte mixtures are common.
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Affiliation(s)
- Sean P Cleary
- Department of Chemistry and Biochemistry, 1253 University of Oregon, Eugene, OR 97403-1253, USA.
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