1
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Combe CW, Graham M, Kolbowski L, Fischer L, Rappsilber J. xiVIEW: Visualisation of Crosslinking Mass Spectrometry Data. J Mol Biol 2024; 436:168656. [PMID: 39237202 DOI: 10.1016/j.jmb.2024.168656] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2024] [Revised: 05/17/2024] [Accepted: 06/07/2024] [Indexed: 09/07/2024]
Abstract
Crosslinking mass spectrometry (MS) has emerged as an important technique for elucidating the in-solution structures of protein complexes and the topology of protein-protein interaction networks. However, the expanding user community lacked an integrated visualisation tool that helped them make use of the crosslinking data for investigating biological mechanisms. We addressed this need by developing xiVIEW, a web-based application designed to streamline crosslinking MS data analysis, which we present here. xiVIEW provides a user-friendly interface for accessing coordinated views of mass spectrometric data, network visualisation, annotations extracted from trusted repositories like UniProtKB, and available 3D structures. In accordance with recent recommendations from the crosslinking MS community, xiVIEW (i) provides a standards compliant parser to improve data integration and (ii) offers accessible visualisation tools. By promoting the adoption of standard file formats and providing a comprehensive visualisation platform, xiVIEW empowers both experimentalists and modellers alike to pursue their respective research interests. We anticipate that xiVIEW will advance crosslinking MS-inspired research, and facilitate broader and more effective investigations into complex biological systems.
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Affiliation(s)
- Colin W Combe
- University of Edinburgh, School of Biological Sciences, Edinburgh EH9 3JR, UK.
| | - Martin Graham
- University of Edinburgh, School of Biological Sciences, Edinburgh EH9 3JR, UK
| | - Lars Kolbowski
- University of Edinburgh, School of Biological Sciences, Edinburgh EH9 3JR, UK; Technische Universität Berlin, 10623 Berlin, Germany
| | - Lutz Fischer
- Technische Universität Berlin, 10623 Berlin, Germany.
| | - Juri Rappsilber
- University of Edinburgh, School of Biological Sciences, Edinburgh EH9 3JR, UK; Technische Universität Berlin, 10623 Berlin, Germany.
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2
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Bakhtina AA, Campbell MD, Sibley BD, Sanchez-Contreras M, Sweetwyne MT, Bruce JE. Intra-organ cell specific mitochondrial quantitative interactomics. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.06.10.598354. [PMID: 38915719 PMCID: PMC11195139 DOI: 10.1101/2024.06.10.598354] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/26/2024]
Abstract
Almost every organ consists of many cell types, each with its unique functions. Proteomes of these cell types are thus unique too. But it is reasonable to assume that interactome (inter and intra molecular interactions of proteins) are also distinct since protein interactions are what ultimately carry out the function. Podocytes and tubules are two cell types within kidney with vastly different functions: podocytes envelop the blood vessels in the glomerulus and act as filters while tubules are located downstream of the glomerulus and are responsible for reabsorption of important nutrients. It has been long known that for tubules mitochondria plays an important role as they require a lot of energy to carry out their functions. In podocytes, however, it has been assumed that mitochondria might not matter as much in both normal physiology and pathology1. Here we have applied quantitative cross-linking mass spectrometry to compare mitochondrial interactomes of tubules and podocytes using a transgenic mitochondrial tagging strategy to immunoprecipitate cell-specific mitochondria directly from whole kidney. We have uncovered that mitochondrial proteomes of these cell types are quite similar, although still showing unique features that correspond to known functions, such as high energy production through TCA cycle in tubules and requirements for detoxification in podocytes which are on the frontline of filtration where they encounter toxic compounds and therefore, as a non-renewing cell type they must have ways to protect themselves from cellular toxicity. But we gained much deeper insight with the interactomics data. We were able to find pathways differentially regulated in podocytes and tubules based on changing cross-link levels and not just protein levels. Among these pathways are betaine metabolism, lysine degradation, and many others. We have also demonstrated how quantitative interactomics could be used to detect different activity levels of an enzyme even when protein abundances of it are the same between cell types. We have validated this finding with an orthogonal activity assay. Overall, this work presents a new view of mitochondrial biology for two important, but functionally distinct, cell types within the mouse kidney showing both similarities and unique features. This data can continue to be explored to find new aspects of mitochondrial biology, especially in podocytes, where mitochondria has been understudied. In the future this methodology can also be applied to other organs to uncover differences in the function of cell types.
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Affiliation(s)
- A A Bakhtina
- University of Washington, Department of Genome Sciences
| | - M D Campbell
- University of Washington, Department of Anesthesiology
| | - B D Sibley
- University of Washington, Department of Laboratory Medicine and Pathology
| | | | - M T Sweetwyne
- University of Washington, Department of Laboratory Medicine and Pathology
| | - J E Bruce
- University of Washington, Department of Genome Sciences
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3
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Keller A, Tang X, Bruce JE. Integrated Analysis of Cross-Links and Dead-End Peptides for Enhanced Interpretation of Quantitative XL-MS. J Proteome Res 2023; 22:2900-2908. [PMID: 37552582 PMCID: PMC10866149 DOI: 10.1021/acs.jproteome.3c00191] [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] [Indexed: 08/10/2023]
Abstract
Chemical cross-linking with mass spectrometry provides low-resolution structural information on proteins in cells and tissues. Combined with quantitation, it can identify changes in the interactome between samples, for example, control and drug-treated cells or young and old mice. A difference can originate from protein conformational changes that alter the solvent-accessible distance separating the cross-linked residues. Alternatively, a difference can result from conformational changes localized to the cross-linked residues, for example, altering the solvent exposure or reactivity of those residues or post-translational modifications of the cross-linked peptides. In this manner, cross-linking is sensitive to a variety of protein conformational features. Dead-end peptides are cross-links attached only at one end to a protein with the other terminus being hydrolyzed. As a result, changes in their abundance reflect only conformational changes localized to the attached residue. For this reason, analyzing both quantified cross-links and their corresponding dead-end peptides can help elucidate the likely conformational changes giving rise to observed differences in cross-link abundance. We describe analysis of dead-end peptides in the XLinkDB public cross-link database and, with quantified mitochondrial data isolated from failing heart versus healthy mice, show how a comparison of abundance ratios between cross-links and their corresponding dead-end peptides can be leveraged to reveal possible conformational explanations.
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Affiliation(s)
- Andrew Keller
- Department of Genome Sciences, University of Washington, Seattle, Washington 98105 ,United States
| | - Xiaoting Tang
- Department of Genome Sciences, University of Washington, Seattle, Washington 98105 ,United States
| | - James E Bruce
- Department of Genome Sciences, University of Washington, Seattle, Washington 98105 ,United States
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4
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Mathay M, Keller A, Bruce JE. Studying Protein-Ligand Interactions by Protein Denaturation and Quantitative Cross-Linking Mass Spectrometry. Anal Chem 2023; 95:9432-9436. [PMID: 37307416 PMCID: PMC10848897 DOI: 10.1021/acs.analchem.2c04501] [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: 06/14/2023]
Abstract
Recently, several mass spectrometry methods have utilized protein structural stability for the quantitative study of protein-ligand engagement. These protein-denaturation approaches, which include thermal proteome profiling (TPP) and stability of proteins from rates of oxidation (SPROX), evaluate ligand-induced denaturation susceptibility changes with a MS-based readout. The different techniques of bottom-up protein-denaturation methods each have their own advantages and challenges. Here, we report the combination of protein-denaturation principles with quantitative cross-linking mass spectrometry using isobaric quantitative protein interaction reporter technologies. This method enables the evaluation of ligand-induced protein engagement through analysis of cross-link relative ratios across chemical denaturation. As a proof of concept, we found ligand-stabilized cross-linked lysine pairs in well-studied bovine serum albumin and ligand bilirubin. These links map to the known binding sites Sudlow Site I and subdomain IB. We propose that protein denaturation and qXL-MS can be combined with similar peptide-level quantification approaches, like SPROX, to increase the coverage information profiled for facilitating protein-ligand engagement efforts.
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Affiliation(s)
- Martin Mathay
- Department of Genome Sciences, University of Washington, Seattle, Washington 98109, United States
| | - Andrew Keller
- Department of Genome Sciences, University of Washington, Seattle, Washington 98109, United States
| | - James E Bruce
- Department of Genome Sciences, University of Washington, Seattle, Washington 98109, United States
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5
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Keller A, Tang X, Bruce JE. Integrated Analysis of Cross-Links and Dead-End Peptides for Enhanced Interpretation of Quantitative XL-MS. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.05.26.542474. [PMID: 37398466 PMCID: PMC10312474 DOI: 10.1101/2023.05.26.542474] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/04/2023]
Abstract
XL-MS provides low-resolution structural information of proteins in cells and tissues. Combined with quantitation, it can identify changes in the interactome between samples, for example, control and drug-treated cells, or young and old mice. A difference can originate from protein conformational changes altering the solvent-accessible distance separating the cross-linked residues. Alternatively, a difference can result from conformational changes localized to the cross-linked residues, for example, altering the solvent exposure or reactivity of those residues or post-translational modifications on the cross-linked peptides. In this manner, cross-linking is sensitive to a variety of protein conformational features. Dead-end peptides are cross-links attached only at one end to a protein, the other terminus being hydrolyzed. As a result, changes in their abundance reflect only conformational changes localized to the attached residue. For this reason, analyzing both quantified cross-links and their corresponding dead-end peptides can help elucidate the likely conformational changes giving rise to observed differences of cross-link abundance. We describe analysis of dead-end peptides in the XLinkDB public cross-link database and, with quantified mitochondrial data isolated from failing heart versus healthy mice, show how a comparison of abundance ratios between cross-links and their corresponding dead-end peptides can be leveraged to reveal possible conformational explanations.
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6
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Bakhtina AA, Pharaoh GA, Campbell MD, Keller A, Stuppard RS, Marcinek DJ, Bruce JE. Skeletal muscle mitochondrial interactome remodeling is linked to functional decline in aged female mice. NATURE AGING 2023; 3:313-326. [PMID: 37118428 PMCID: PMC10154043 DOI: 10.1038/s43587-023-00366-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/21/2022] [Accepted: 01/10/2023] [Indexed: 04/30/2023]
Abstract
Genomic, transcriptomic and proteomic approaches have been used to gain insight into molecular underpinnings of aging in laboratory animals and in humans. However, protein function in biological systems is under complex regulation and includes factors besides abundance levels, such as modifications, localization, conformation and protein-protein interactions. By making use of quantitative chemical cross-linking technologies, we show that changes in the muscle mitochondrial interactome contribute to mitochondrial functional decline in aging in female mice. Specifically, we identify age-related changes in protein cross-links relating to assembly of electron transport system complexes I and IV, activity of glutamate dehydrogenase, and coenzyme-A binding in fatty acid β-oxidation and tricarboxylic acid cycle enzymes. These changes show a remarkable correlation with complex I respiration differences within the same young-old animal pairs. Each observed cross-link can serve as a protein conformational or protein-protein interaction probe in future studies, which will provide further molecular insights into commonly observed age-related phenotypic differences. Therefore, this data set could become a valuable resource for additional in-depth molecular studies that are needed to better understand complex age-related molecular changes.
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Affiliation(s)
- Anna A Bakhtina
- Department of Genome Sciences, University of Washington, Seattle, WA, USA
| | - Gavin A Pharaoh
- Department of Radiology, University of Washington, Seattle, WA, USA
| | | | - Andrew Keller
- Department of Genome Sciences, University of Washington, Seattle, WA, USA
| | | | - David J Marcinek
- Department of Radiology, University of Washington, Seattle, WA, USA.
| | - James E Bruce
- Department of Genome Sciences, University of Washington, Seattle, WA, USA.
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7
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Keller A, Bakhtina AA, Chavez JD, Bruce JE. Improved Interpretation of Protein Conformational Differences and Ligand Occupancy in Large-Scale Cross-Link Data. J Proteome Res 2022; 21:1475-1484. [PMID: 35594376 DOI: 10.1021/acs.jproteome.2c00109] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Chemical cross-linking of proteins in complex samples, cells, or even tissues is emerging to provide unique structural information on proteins and complexes that exist within native or nativelike environments. The public database XLinkDB automatically maps cross-links to available structures based on sequence homology. Structures most likely to reflect protein conformations in the cross-linked sample are routinely identified by having cross-linked residues separated by Euclidean distances within the maximum span of the applied cross-linker. Solvent accessible surface distance (SASD), which considers the accessibility of the cross-linked residues and the path connecting them, is a better predictor of consistency than the Euclidean distance. However, SASDs of structures are not publicly available, and their calculation is computationally intensive. Here, we describe in XLinkDB version 4.0 the automatic calculation of SASDs using Jwalk for all cross-links mapped to structures, both with and without regard to ligands, and derive empirical maximum SASD spans for BDP-NHP and DSSO cross-linkers of 51 and 43 Å, respectively. We document ligands proximal to cross-links in structures and demonstrate how SASDs can be used to help infer sample protein conformations and ligand occupancy, highlighting cross-links sensitive to ADP binding in mitochondria isolated from HEK293 cells.
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Affiliation(s)
- Andrew Keller
- Department of Genome Sciences, University of Washington, Seattle, Washington 98105, United States
| | - Anna A Bakhtina
- Department of Genome Sciences, University of Washington, Seattle, Washington 98105, United States
| | - Juan D Chavez
- Department of Genome Sciences, University of Washington, Seattle, Washington 98105, United States
| | - James E Bruce
- Department of Genome Sciences, University of Washington, Seattle, Washington 98105, United States
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8
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Zhou B, Caudal A, Tang X, Chavez JD, McMillen TS, Keller A, Villet O, Zhao M, Liu Y, Ritterhoff J, Wang P, Kolwicz SC, Wang W, Bruce JE, Tian R. Upregulation of mitochondrial ATPase inhibitory factor 1 (ATPIF1) mediates increased glycolysis in mouse hearts. J Clin Invest 2022; 132:e155333. [PMID: 35575090 PMCID: PMC9106352 DOI: 10.1172/jci155333] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Accepted: 04/01/2022] [Indexed: 12/20/2022] Open
Abstract
In hypertrophied and failing hearts, fuel metabolism is reprogrammed to increase glucose metabolism, especially glycolysis. This metabolic shift favors biosynthetic function at the expense of ATP production. Mechanisms responsible for the switch are poorly understood. We found that inhibitory factor 1 of the mitochondrial FoF1-ATP synthase (ATPIF1), a protein known to inhibit ATP hydrolysis by the reverse function of ATP synthase during ischemia, was significantly upregulated in pathological cardiac hypertrophy induced by pressure overload, myocardial infarction, or α-adrenergic stimulation. Chemical cross-linking mass spectrometry analysis of hearts hypertrophied by pressure overload suggested that increased expression of ATPIF1 promoted the formation of FoF1-ATP synthase nonproductive tetramer. Using ATPIF1 gain- and loss-of-function cell models, we demonstrated that stalled electron flow due to impaired ATP synthase activity triggered mitochondrial ROS generation, which stabilized HIF1α, leading to transcriptional activation of glycolysis. Cardiac-specific deletion of ATPIF1 in mice prevented the metabolic switch and protected against the pathological remodeling during chronic stress. These results uncover a function of ATPIF1 in nonischemic hearts, which gives FoF1-ATP synthase a critical role in metabolic rewiring during the pathological remodeling of the heart.
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Affiliation(s)
- Bo Zhou
- Mitochondria and Metabolism Center, Department of Anesthesiology & Pain Medicine, and
| | - Arianne Caudal
- Mitochondria and Metabolism Center, Department of Anesthesiology & Pain Medicine, and
| | - Xiaoting Tang
- Department of Genome Sciences, University of Washington, Seattle, Washington, USA
| | - Juan D. Chavez
- Department of Genome Sciences, University of Washington, Seattle, Washington, USA
| | - Timothy S. McMillen
- Mitochondria and Metabolism Center, Department of Anesthesiology & Pain Medicine, and
| | - Andrew Keller
- Department of Genome Sciences, University of Washington, Seattle, Washington, USA
| | - Outi Villet
- Mitochondria and Metabolism Center, Department of Anesthesiology & Pain Medicine, and
| | - Mingyue Zhao
- Mitochondria and Metabolism Center, Department of Anesthesiology & Pain Medicine, and
| | - Yaxin Liu
- Mitochondria and Metabolism Center, Department of Anesthesiology & Pain Medicine, and
| | - Julia Ritterhoff
- Mitochondria and Metabolism Center, Department of Anesthesiology & Pain Medicine, and
| | - Pei Wang
- Mitochondria and Metabolism Center, Department of Anesthesiology & Pain Medicine, and
| | - Stephen C. Kolwicz
- Mitochondria and Metabolism Center, Department of Anesthesiology & Pain Medicine, and
| | - Wang Wang
- Mitochondria and Metabolism Center, Department of Anesthesiology & Pain Medicine, and
| | - James E. Bruce
- Department of Genome Sciences, University of Washington, Seattle, Washington, USA
| | - Rong Tian
- Mitochondria and Metabolism Center, Department of Anesthesiology & Pain Medicine, and
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9
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Chavez JD, Park SG, Mohr JP, Bruce JE. Applications and advancements of FT-ICR-MS for interactome studies. MASS SPECTROMETRY REVIEWS 2022; 41:248-261. [PMID: 33289940 PMCID: PMC8184889 DOI: 10.1002/mas.21675] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/12/2020] [Revised: 10/16/2020] [Accepted: 10/16/2020] [Indexed: 05/05/2023]
Abstract
The set of all intra- and intermolecular interactions, collectively known as the interactome, is currently an unmet challenge for any analytical method, but if measured, could provide unparalleled insight on molecular function in living systems. Developments and applications of chemical cross-linking and high-performance mass spectrometry technologies are beginning to reveal details on how proteins interact in cells and how protein conformations and interactions inside cells change with phenotype or during drug treatment or other perturbations. A major contributor to these advances is Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) technology and its implementation with accurate mass measurements on cross-linked peptide-pair precursor and fragment ions to enable improved identification methods. However, these applications place increased demands on mass spectrometer performance in terms of high-resolution spectral acquisition rates for on-line MSn experiments. Moreover, FT-ICR-MS also offers unique opportunities to develop and implement parallel ICR cells for multiplexed signal acquisition and the potential to greatly advance accurate mass acquisition rates for interactome studies. This review highlights our efforts to exploit accurate mass FT-ICR-MS technologies with chemical cross-linking and developments being pursued to realize parallel MS array capabilities that will further advance visualization of the interactome.
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Affiliation(s)
- Juan D. Chavez
- Department of Genome Sciences, University of Washington, Seattle, WA 98109
| | - Sung-Gun Park
- Department of Genome Sciences, University of Washington, Seattle, WA 98109
| | - Jared P. Mohr
- Department of Genome Sciences, University of Washington, Seattle, WA 98109
| | - James E. Bruce
- Department of Genome Sciences, University of Washington, Seattle, WA 98109
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10
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Wippel HH, Chavez JD, Tang X, Bruce JE. Quantitative interactome analysis with chemical cross-linking and mass spectrometry. Curr Opin Chem Biol 2022; 66:102076. [PMID: 34393043 PMCID: PMC8837725 DOI: 10.1016/j.cbpa.2021.06.011] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2021] [Revised: 06/17/2021] [Accepted: 06/23/2021] [Indexed: 01/03/2023]
Abstract
Structural plasticity and dynamic protein-protein interactions are critical determinants of protein function within living systems. Quantitative chemical cross-linking with mass spectrometry (qXL-MS) is an emerging technology able to provide information on changes in protein conformations and interactions. Importantly, qXL-MS is applicable to complex biological systems, including living cells and tissues, thereby providing insights into proteins within their native environments. Here, we present an overview of recent technological developments and applications involving qXL-MS, including design and synthesis of isotope-labeled cross-linkers, development of new liquid chromatography-MS methodologies, and computational developments enabling interpretation of the data.
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Affiliation(s)
- Helisa H Wippel
- Department of Genome Sciences, University of Washington, Seattle, WA, USA
| | - Juan D Chavez
- Department of Genome Sciences, University of Washington, Seattle, WA, USA
| | - Xiaoting Tang
- Department of Genome Sciences, University of Washington, Seattle, WA, USA
| | - James E Bruce
- Department of Genome Sciences, University of Washington, Seattle, WA, USA.
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11
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Chavez JD, Keller A, Wippel HH, Mohr JP, Bruce JE. Multiplexed Cross-Linking with Isobaric Quantitative Protein Interaction Reporter Technology. Anal Chem 2021; 93:16759-16768. [PMID: 34882395 PMCID: PMC9014865 DOI: 10.1021/acs.analchem.1c02209] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Chemical cross-linking with mass spectrometry (XL-MS) has emerged as a useful technique for interrogating protein structures and interactions. When combined with quantitative proteomics strategies, protein conformational and interaction dynamics can be probed. Quantitative XL-MS has been demonstrated with the use of stable isotopes incorporated metabolically or into the cross-linker molecules. Isotope-labeled cross-linkers have primarily utilized deuterium and rely on MS1-based quantitation of precursor ion extracted ion chromatograms. Recently the development and application of isobaric quantitative protein interaction reporter (iqPIR) cross-linkers were reported, which utilize 13C and 15N isotope labels. Quantitation is accomplished using relative fragment ion isotope abundances in tandem mass spectra. Here we describe the synthesis and initial evaluation of a multiplexed set of iqPIR molecules, allowing for up to six cross-linked samples to be quantified simultaneously. To analyze data for such cross-linkers, the two-channel mode of iqPIR quantitative analysis was adapted to accommodate any number of channels with defined ion isotope peak mass offsets. The summed ion peak intensities in the overlapping channel isotope envelopes are apportioned among the channels to minimize the difference with respect to the predicted ion isotope envelopes. The result is accurate and reproducible relative quantitation enabling direct comparison among six differentially labeled cross-linked samples. The approach described here is generally extensible for the iqPIR strategy, accommodating future iqPIR reagent design, and enables large-scale in vivo quantitative XL-MS investigation of the interactome.
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Affiliation(s)
| | | | - Helisa H. Wippel
- Department of Genome Sciences, University of Washington, Seattle, WA
| | - Jared P. Mohr
- Department of Genome Sciences, University of Washington, Seattle, WA
| | - James E. Bruce
- Department of Genome Sciences, University of Washington, Seattle, WA
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12
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Wippel HH, Fioramonte M, Chavez JD, Bruce JE. Deciphering the architecture and interactome of hnRNP proteins and enigmRBPs. Mol Omics 2021; 17:503-516. [PMID: 34017973 PMCID: PMC8355073 DOI: 10.1039/d1mo00024a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
RNA-binding proteins (RBPs) have conserved domains and consensus sequences that interact with RNAs and other proteins forming ribonucleoprotein (RNP) complexes. RNPs are involved in the regulation of several cellular processes, including transcription, pre-mRNA splicing, mRNA transport, localization, degradation and storage, and ultimately control of translation. Heterogeneous nuclear ribonucleoproteins (hnRNPs) comprise a family of RBPs that mediate transcription control and nuclear processing of transcripts. Some hnRNPs are part of the spliceosome complex, a dynamic machinery formed by RNPs that regulate alternative splicing of pre-mRNAs. Here, chemical crosslinking of proteins was applied to identify specific interacting regions and protein structural features of hnRNPs: hnRNPA1, hnRNPA2/B1, hnRNPC, and RALY. The results reveal interaction of these proteins within RNA-binding domains and conserved motifs, providing evidence of a coordinated action of known regulatory sequences of RBPs. Moreover, these crosslinking data enable structural model generation for RBPs, illustrating how crosslinking mass spectrometry can complement other structural methods.
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Affiliation(s)
- Helisa H Wippel
- Department of Genome Sciences, University of Washington, Seattle, WA, USA.
| | - Mariana Fioramonte
- Department of Genome Sciences, University of Washington, Seattle, WA, USA. and University of Campinas, Campinas, SP, Brazil
| | - Juan D Chavez
- Department of Genome Sciences, University of Washington, Seattle, WA, USA.
| | - James E Bruce
- Department of Genome Sciences, University of Washington, Seattle, WA, USA.
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13
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Chavez JD, Wippel HH, Tang X, Keller A, Bruce JE. In-Cell Labeling and Mass Spectrometry for Systems-Level Structural Biology. Chem Rev 2021; 122:7647-7689. [PMID: 34232610 PMCID: PMC8966414 DOI: 10.1021/acs.chemrev.1c00223] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Biological systems have evolved to utilize proteins to accomplish nearly all functional roles needed to sustain life. A majority of biological functions occur within the crowded environment inside cells and subcellular compartments where proteins exist in a densely packed complex network of protein-protein interactions. The structural biology field has experienced a renaissance with recent advances in crystallography, NMR, and CryoEM that now produce stunning models of large and complex structures previously unimaginable. Nevertheless, measurements of such structural detail within cellular environments remain elusive. This review will highlight how advances in mass spectrometry, chemical labeling, and informatics capabilities are merging to provide structural insights on proteins, complexes, and networks that exist inside cells. Because of the molecular detection specificity provided by mass spectrometry and proteomics, these approaches provide systems-level information that not only benefits from conventional structural analysis, but also is highly complementary. Although far from comprehensive in their current form, these approaches are currently providing systems structural biology information that can uniquely reveal how conformations and interactions involving many proteins change inside cells with perturbations such as disease, drug treatment, or phenotypic differences. With continued advancements and more widespread adaptation, systems structural biology based on in-cell labeling and mass spectrometry will provide an even greater wealth of structural knowledge.
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Affiliation(s)
- Juan D Chavez
- Department of Genome Sciences, University of Washington, Seattle, Washington 98109, United States
| | - Helisa H Wippel
- Department of Genome Sciences, University of Washington, Seattle, Washington 98109, United States
| | - Xiaoting Tang
- Department of Genome Sciences, University of Washington, Seattle, Washington 98109, United States
| | - Andrew Keller
- Department of Genome Sciences, University of Washington, Seattle, Washington 98109, United States
| | - James E Bruce
- Department of Genome Sciences, University of Washington, Seattle, Washington 98109, United States
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14
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Mitochondria and Peroxisome Remodeling across Cytomegalovirus Infection Time Viewed through the Lens of Inter-ViSTA. Cell Rep 2021; 32:107943. [PMID: 32726614 DOI: 10.1016/j.celrep.2020.107943] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2020] [Revised: 05/20/2020] [Accepted: 06/30/2020] [Indexed: 12/31/2022] Open
Abstract
Nearly all biological processes rely on the finely tuned coordination of protein interactions across cellular space and time. Accordingly, generating protein interactomes has become routine in biological studies, yet interpreting these datasets remains computationally challenging. Here, we introduce Inter-ViSTA (Interaction Visualization in Space and Time Analysis), a web-based platform that quickly builds animated protein interaction networks and automatically synthesizes information on protein abundances, functions, complexes, and subcellular localizations. Using Inter-ViSTA with proteomics and molecular virology, we define virus-host interactions for the human cytomegalovirus (HCMV) anti-apoptotic protein, pUL37x1. We find that spatiotemporal controlled interactions underlie pUL37x1 functions, facilitating the pro-viral remodeling of mitochondria and peroxisomes during infection. Reciprocal isolations, microscopy, and genetic manipulations further characterize these associations, revealing the interplay between pUL37x1 and the MIB complex, which is critical for mitochondrial integrity. At the peroxisome, we show that pUL37x1 activates PEX11β to regulate fission, a key aspect of virus assembly and spread.
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15
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Keller A, Chavez JD, Tang X, Bruce JE. Leveraging the Entirety of the Protein Data Bank to Enable Improved Structure Prediction Based on Cross-Link Data. J Proteome Res 2020; 20:1087-1095. [PMID: 33263396 DOI: 10.1021/acs.jproteome.0c00495] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
XLinkDB is a fast-expanding public database now storing more than 100 000 distinct identified cross-linked protein residue pairs acquired by chemical cross-linking with mass spectrometry from samples of 12 species (J. Proteome Res. 2019, 18 (2), 753-758). Mapping identified cross-links to protein structures, when available, provides valuable guidance on protein conformations detected in the cross-linked samples. As more and more structures become available in the Protein Data Bank (Nucleic Acids Res. 2000, 28 (1), 235-242), we sought to leverage their utility for cross-link studies by automatically mapping identified cross-links to structures based on sequence homology of the cross-linked proteins with those within structures. This enables use of structures derived from organisms different from those of samples, including large multiprotein complexes and complexes in alternative states. We demonstrate utility of mapping to orthologous structures, highlighting a cross-link between two subunits of mouse mitochondrial Complex I that was mapped to 15 structures derived from five mammals, its distances there of 16.2 ± 0.4 Å indicating strong conservation of the protein interaction. We also show how multimeric structures enable reassessment of cross-links presumed to be intraprotein as potentially homodimeric interprotein in origin.
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Affiliation(s)
- Andrew Keller
- Department of Genome Sciences, University of Washington, Seattle, Washington 98105, United States
| | - Juan D Chavez
- Department of Genome Sciences, University of Washington, Seattle, Washington 98105, United States
| | - Xiaoting Tang
- Department of Genome Sciences, University of Washington, Seattle, Washington 98105, United States
| | - James E Bruce
- Department of Genome Sciences, University of Washington, Seattle, Washington 98105, United States
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Howard TR, Cristea IM. Interrogating Host Antiviral Environments Driven by Nuclear DNA Sensing: A Multiomic Perspective. Biomolecules 2020; 10:biom10121591. [PMID: 33255247 PMCID: PMC7761228 DOI: 10.3390/biom10121591] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2020] [Revised: 11/23/2020] [Accepted: 11/23/2020] [Indexed: 12/11/2022] Open
Abstract
Nuclear DNA sensors are critical components of the mammalian innate immune system, recognizing the presence of pathogens and initiating immune signaling. These proteins act in the nuclei of infected cells by binding to foreign DNA, such as the viral genomes of nuclear-replicating DNA viruses herpes simplex virus type 1 (HSV-1) and human cytomegalovirus (HCMV). Upon binding to pathogenic DNA, the nuclear DNA sensors were shown to initiate antiviral cytokines, as well as to suppress viral gene expression. These host defense responses involve complex signaling processes that, through protein–protein interactions (PPIs) and post-translational modifications (PTMs), drive extensive remodeling of the cellular transcriptome, proteome, and secretome to generate an antiviral environment. As such, a holistic understanding of these changes is required to understand the mechanisms through which nuclear DNA sensors act. The advent of omics techniques has revolutionized the speed and scale at which biological research is conducted and has been used to make great strides in uncovering the molecular underpinnings of DNA sensing. Here, we review the contribution of proteomics approaches to characterizing nuclear DNA sensors via the discovery of functional PPIs and PTMs, as well as proteome and secretome changes that define a host antiviral environment. We also highlight the value of and future need for integrative multiomic efforts to gain a systems-level understanding of DNA sensors and their influence on epigenetic and transcriptomic alterations during infection.
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17
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Toward Increased Reliability, Transparency, and Accessibility in Cross-linking Mass Spectrometry. Structure 2020; 28:1259-1268. [PMID: 33065067 DOI: 10.1016/j.str.2020.09.011] [Citation(s) in RCA: 37] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Revised: 09/02/2020] [Accepted: 09/24/2020] [Indexed: 01/09/2023]
Abstract
Cross-linking mass spectrometry (MS) has substantially matured as a method over the past 2 decades through parallel development in multiple labs, demonstrating its applicability to protein structure determination, conformation analysis, and mapping protein interactions in complex mixtures. Cross-linking MS has become a much-appreciated and routinely applied tool, especially in structural biology. Therefore, it is timely that the community commits to the development of methodological and reporting standards. This white paper builds on an open process comprising a number of events at community conferences since 2015 and identifies aspects of Cross-linking MS for which guidelines should be developed as part of a Cross-linking MS standards initiative.
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18
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Chavez JD, Tang X, Campbell MD, Reyes G, Kramer PA, Stuppard R, Keller A, Zhang H, Rabinovitch PS, Marcinek DJ, Bruce JE. Mitochondrial protein interaction landscape of SS-31. Proc Natl Acad Sci U S A 2020; 117:15363-15373. [PMID: 32554501 PMCID: PMC7334473 DOI: 10.1073/pnas.2002250117] [Citation(s) in RCA: 93] [Impact Index Per Article: 23.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Mitochondrial dysfunction underlies the etiology of a broad spectrum of diseases including heart disease, cancer, neurodegenerative diseases, and the general aging process. Therapeutics that restore healthy mitochondrial function hold promise for treatment of these conditions. The synthetic tetrapeptide, elamipretide (SS-31), improves mitochondrial function, but mechanistic details of its pharmacological effects are unknown. Reportedly, SS-31 primarily interacts with the phospholipid cardiolipin in the inner mitochondrial membrane. Here we utilize chemical cross-linking with mass spectrometry to identify protein interactors of SS-31 in mitochondria. The SS-31-interacting proteins, all known cardiolipin binders, fall into two groups, those involved in ATP production through the oxidative phosphorylation pathway and those involved in 2-oxoglutarate metabolic processes. Residues cross-linked with SS-31 reveal binding regions that in many cases, are proximal to cardiolipin-protein interacting regions. These results offer a glimpse of the protein interaction landscape of SS-31 and provide mechanistic insight relevant to SS-31 mitochondrial therapy.
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Affiliation(s)
- Juan D Chavez
- Department of Genome Sciences, University of Washington, Seattle, WA 98105
| | - Xiaoting Tang
- Department of Genome Sciences, University of Washington, Seattle, WA 98105
| | | | - Gustavo Reyes
- Department of Radiology, University of Washington, Seattle, WA 98105
| | - Philip A Kramer
- Department of Radiology, University of Washington, Seattle, WA 98105
| | - Rudy Stuppard
- Department of Radiology, University of Washington, Seattle, WA 98105
| | - Andrew Keller
- Department of Genome Sciences, University of Washington, Seattle, WA 98105
| | - Huiliang Zhang
- Department of Pathology, University of Washington, Seattle, WA 98195
| | | | - David J Marcinek
- Department of Radiology, University of Washington, Seattle, WA 98105
| | - James E Bruce
- Department of Genome Sciences, University of Washington, Seattle, WA 98105;
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19
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Yugandhar K, Wang TY, Leung AKY, Lanz MC, Motorykin I, Liang J, Shayhidin EE, Smolka MB, Zhang S, Yu H. MaXLinker: Proteome-wide Cross-link Identifications with High Specificity and Sensitivity. Mol Cell Proteomics 2020; 19:554-568. [PMID: 31839598 PMCID: PMC7050104 DOI: 10.1074/mcp.tir119.001847] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Indexed: 11/06/2022] Open
Abstract
Protein-protein interactions play a vital role in nearly all cellular functions. Hence, understanding their interaction patterns and three-dimensional structural conformations can provide crucial insights about various biological processes and underlying molecular mechanisms for many disease phenotypes. Cross-linking mass spectrometry (XL-MS) has the unique capability to detect protein-protein interactions at a large scale along with spatial constraints between interaction partners. The inception of MS-cleavable cross-linkers enabled the MS2-MS3 XL-MS acquisition strategy that provides cross-link information from both MS2 and MS3 level. However, the current cross-link search algorithm available for MS2-MS3 strategy follows a "MS2-centric" approach and suffers from a high rate of mis-identified cross-links. We demonstrate the problem using two new quality assessment metrics ["fraction of mis-identifications" (FMI) and "fraction of interprotein cross-links from known interactions" (FKI)]. We then address this problem, by designing a novel "MS3-centric" approach for cross-link identification and implementing it as a search engine named MaXLinker. MaXLinker outperforms the currently popular search engine with a lower mis-identification rate, and higher sensitivity and specificity. Moreover, we performed human proteome-wide cross-linking mass spectrometry using K562 cells. Employing MaXLinker, we identified a comprehensive set of 9319 unique cross-links at 1% false discovery rate, comprising 8051 intraprotein and 1268 interprotein cross-links. Finally, we experimentally validated the quality of a large number of novel interactions identified in our study, providing a conclusive evidence for MaXLinker's robust performance.
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Affiliation(s)
- Kumar Yugandhar
- Department of Computational Biology, Cornell University, Ithaca, New York,14853; Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, New York, 14853
| | - Ting-Yi Wang
- Department of Computational Biology, Cornell University, Ithaca, New York,14853; Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, New York, 14853
| | - Alden King-Yung Leung
- Department of Computational Biology, Cornell University, Ithaca, New York,14853; Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, New York, 14853
| | - Michael Charles Lanz
- Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, New York, 14853; Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York 14853
| | - Ievgen Motorykin
- Mass Spectrometry and Proteomics Facility, Institute of Biotechnology, Cornell University, Ithaca, New York,14853
| | - Jin Liang
- Department of Computational Biology, Cornell University, Ithaca, New York,14853; Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, New York, 14853
| | - Elnur Elyar Shayhidin
- Department of Computational Biology, Cornell University, Ithaca, New York,14853; Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, New York, 14853
| | - Marcus Bustamante Smolka
- Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, New York, 14853; Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York 14853
| | - Sheng Zhang
- Mass Spectrometry and Proteomics Facility, Institute of Biotechnology, Cornell University, Ithaca, New York,14853
| | - Haiyuan Yu
- Department of Computational Biology, Cornell University, Ithaca, New York,14853; Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, New York, 14853.
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20
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Bartolec TK, Smith DL, Pang CNI, Xu YD, Hamey JJ, Wilkins MR. Cross-linking Mass Spectrometry Analysis of the Yeast Nucleus Reveals Extensive Protein-Protein Interactions Not Detected by Systematic Two-Hybrid or Affinity Purification-Mass Spectrometry. Anal Chem 2020; 92:1874-1882. [PMID: 31851481 DOI: 10.1021/acs.analchem.9b03975] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Saccharomyces cerevisiae has the most comprehensively characterized protein-protein interaction network, or interactome, of any eukaryote. This has predominantly been generated through multiple, systematic studies of protein-protein interactions by two-hybrid techniques and of affinity-purified protein complexes. A pressing question is to understand how large-scale cross-linking mass spectrometry (XL-MS) can confirm and extend this interactome. Here, intact yeast nuclei were subject to cross-linking with disuccinimidyl sulfoxide (DSSO) and analyzed using hybrid MS2-MS3 methods. XlinkX identified a total of 2,052 unique residue pair cross-links at 1% FDR. Intraprotein cross-links were found to provide extensive structural constraint data, with almost all intralinks that mapped to known structures and slightly fewer of those mapping to homology models being within 30 Å. Intralinks provided structural information for a further 366 proteins. A method for optimizing interprotein cross-link score cut-offs was developed, through use of extensive known yeast interactions. Its application led to a high confidence, yeast nuclear interactome. Strikingly, almost half of the interactions were not previously detected by two-hybrid or AP-MS techniques. Multiple lines of evidence existed for many such interactions, whether through literature or ortholog interaction data, through multiple unique interlinks between proteins, and/or through replicates. We conclude that XL-MS is a powerful means to measure interactions, that complements two-hybrid and affinity-purification techniques.
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Affiliation(s)
- Tara K Bartolec
- Systems Biology Initiative, School of Biotechnology and Biomolecular Sciences , University of New South Wales , Sydney , New South Wales 2052 , Australia
| | - Daniela-Lee Smith
- Systems Biology Initiative, School of Biotechnology and Biomolecular Sciences , University of New South Wales , Sydney , New South Wales 2052 , Australia
| | - Chi Nam Ignatius Pang
- Systems Biology Initiative, School of Biotechnology and Biomolecular Sciences , University of New South Wales , Sydney , New South Wales 2052 , Australia
| | - You Dan Xu
- Centre for Advanced Macromolecular Design, School of Chemistry , University of New South Wales , Sydney , New South Wales 2052 , Australia
| | - Joshua J Hamey
- Systems Biology Initiative, School of Biotechnology and Biomolecular Sciences , University of New South Wales , Sydney , New South Wales 2052 , Australia
| | - Marc R Wilkins
- Systems Biology Initiative, School of Biotechnology and Biomolecular Sciences , University of New South Wales , Sydney , New South Wales 2052 , Australia
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21
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Chavez JD, Keller A, Zhou B, Tian R, Bruce JE. Cellular Interactome Dynamics during Paclitaxel Treatment. Cell Rep 2019; 29:2371-2383.e5. [PMID: 31747606 PMCID: PMC6910234 DOI: 10.1016/j.celrep.2019.10.063] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2019] [Revised: 09/23/2019] [Accepted: 10/15/2019] [Indexed: 12/12/2022] Open
Abstract
Cell-cycle inhibitors, including paclitaxel, are among the most widely used and effective cancer therapies. However, several challenges limit the success of paclitaxel, including drug resistance and toxic side effects. Paclitaxel is thought to act primarily by stabilizing microtubules, locking cells in a mitotic state. However, the resulting cytotoxicity and tumor shrinkage rates observed cannot be fully explained by this mechanism alone. Here we apply quantitative chemical cross-linking with mass spectrometry analysis to paclitaxel-treated cells. Our results provide large-scale measurements of relative protein levels and, perhaps more importantly, changes to protein conformations and interactions that occur upon paclitaxel treatment. Drug concentration-dependent changes are revealed in known drug targets including tubulins, as well as many other proteins and protein complexes involved in apoptotic signaling and cellular homeostasis. As such, this study provides insight into systems-level changes to protein structures and interactions that occur with paclitaxel treatment.
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Affiliation(s)
- Juan D Chavez
- Department of Genome Sciences, University of Washington, Seattle, WA 98105, USA
| | - Andrew Keller
- Department of Genome Sciences, University of Washington, Seattle, WA 98105, USA
| | - Bo Zhou
- Department of Bioengineering, University of Washington, Seattle, WA 98105, USA; Department of Anesthesiology and Pain Medicine, University of Washington, Seattle, WA 98105, USA; Mitochondria and Metabolism Center, University of Washington, Seattle, WA 98105, USA
| | - Rong Tian
- Department of Bioengineering, University of Washington, Seattle, WA 98105, USA; Department of Anesthesiology and Pain Medicine, University of Washington, Seattle, WA 98105, USA; Mitochondria and Metabolism Center, University of Washington, Seattle, WA 98105, USA
| | - James E Bruce
- Department of Genome Sciences, University of Washington, Seattle, WA 98105, USA.
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Chavez JD, Mohr JP, Mathay M, Zhong X, Keller A, Bruce JE. Systems structural biology measurements by in vivo cross-linking with mass spectrometry. Nat Protoc 2019; 14:2318-2343. [PMID: 31270507 DOI: 10.1038/s41596-019-0181-3] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2018] [Accepted: 04/18/2019] [Indexed: 12/23/2022]
Abstract
This protocol describes a workflow for utilizing large-scale cross-linking with mass spectrometry (XL-MS) to make systems-level structural biology measurements in complex biological samples, including cells, isolated organelles, and tissue samples. XL-MS is a structural biology technique that provides information on the molecular structure of proteins and protein complexes using chemical probes that report the proximity of probe-reactive amino acids within proteins, typically lysine residues. Information gained through XL-MS studies is often complementary to more traditional methods, such as X-ray crystallography, nuclear magnetic resonance, and cryo-electron microscopy. The use of MS-cleavable cross-linkers, including protein interaction reporter (PIR) technologies, enables XL-MS studies on protein structures and interactions in extremely complex biological samples, including intact living cells. PIR cross-linkers are designed to contain chemical bonds at specific locations within the cross-linker molecule that can be selectively cleaved by collision-induced dissociation or UV light. When broken, these bonds release the intact peptides that were cross-linked, as well as a reporter ion. Conservation of mass dictates that the sum of the two released peptide masses and the reporter mass equals the measured precursor mass. This relationship is used to identify cross-linked peptide pairs. Release of the individual peptides permits accurate measurement of their masses and independent amino acid sequence determination by tandem MS, allowing the use of standard proteomics search engines such as Comet for peptide sequence assignment, greatly simplifying data analysis of cross-linked peptide pairs. Search results are processed with XLinkProphet for validation and can be uploaded into XlinkDB for interaction network and structural analysis.
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Affiliation(s)
- Juan D Chavez
- Department of Genome Sciences, University of Washington, Seattle, WA, USA
| | - Jared P Mohr
- Department of Genome Sciences, University of Washington, Seattle, WA, USA
| | - Martin Mathay
- Department of Genome Sciences, University of Washington, Seattle, WA, USA
| | - Xuefei Zhong
- Department of Genome Sciences, University of Washington, Seattle, WA, USA
| | - Andrew Keller
- Department of Genome Sciences, University of Washington, Seattle, WA, USA
| | - James E Bruce
- Department of Genome Sciences, University of Washington, Seattle, WA, USA.
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