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Brunet MA, Kraft ML. Toward Understanding the Subcellular Distributions of Cholesterol and Sphingolipids Using High-Resolution NanoSIMS Imaging. Acc Chem Res 2023; 56:752-762. [PMID: 36913670 DOI: 10.1021/acs.accounts.2c00760] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/15/2023]
Abstract
ConspectusCharacterizing the subcellular distributions of biomolecules of interest is a basic inquiry that helps inform on the potential roles of these molecules in biological functions. Presently, the functions of specific lipid species and cholesterol are not well understood, partially because cholesterol and lipid species of interest are difficult to image with high spatial resolution but without perturbing them. Because cholesterol and lipids are relatively small and their distributions are influenced by noncovalent interactions with other biomolecules, functionalizing them with relatively large labels that permit their detection may alter their distributions in membranes and between organelles. This challenge has been surmounted by exploiting rare stable isotopes as labels that may be metabolically incorporated into cholesterol and lipids without altering their chemical compositions, and the Cameca NanoSIMS 50 instrument's ability to image rare stable isotope labels with high spatial resolution. This Account covers the use of secondary ion mass spectrometry (SIMS) performed with a Cameca NanoSIMS 50 instrument for imaging cholesterol and sphingolipids in the membranes of mammalian cells. The NanoSIMS 50 detects monatomic and diatomic secondary ions ejected from the sample to map the elemental and isotopic composition at the surface of the sample with better than 50 nm lateral resolution and 5 nm depth resolution. Much effort has focused on using NanoSIMS imaging of rare isotope-labeled cholesterol and sphingolipids for testing the long-standing hypothesis that cholesterol and sphingolipids colocalize within distinct domains in the plasma membrane. By using a NanoSIMS 50 to image rare isotope-labeled cholesterol and sphingolipids in parallel with affinity-labeled proteins of interest, a hypothesis regarding the colocalization of specific membrane proteins with cholesterol and sphingolipids in distinct plasma membrane domains has been tested. NanoSIMS performed in a depth profiling mode has enabled imaging the intracellular distributions of cholesterol and sphingolipids. Important progress has also been made in developing a computational depth correction strategy for constructing more accurate three-dimensional (3D) NanoSIMS depth profiling images of intracellular component distribution without requiring additional measurements with complementary techniques or signal collection. This Account provides an overview of this exciting progress, focusing on the studies from our laboratory that shifted understanding of plasma membrane organization, and the development of enabling tools for visualizing intracellular lipids.
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Brunet MA, Gorman BL, Kraft ML. Depth Correction of 3D NanoSIMS Images Shows Intracellular Lipid and Cholesterol Distributions while Capturing the Effects of Differential Sputter Rate. ACS NANO 2022; 16:16221-16233. [PMID: 36218061 DOI: 10.1021/acsnano.2c05148] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Knowledge of the distributions of drugs, metabolites, and drug carriers within cells is a prerequisite for the development of effective disease treatments. Intracellular component distribution may be imaged with high sensitivity and spatial resolution by using a NanoSIMS in the depth profiling mode. Depth correction strategies that capture the effects of differential sputtering without requiring additional measurements could enable producing accurate 3D NanoSIMS depth profiling images of intracellular component distributions. Here we describe an approach for depth correcting 3D NanoSIMS depth profiling images of cells that accounts for differential sputter rates. Our approach uses the secondary ion and secondary electron depth profiling images to reconstruct the cell's morphology at every raster plane. These cell morphology reconstructions are used to adjust the z-positions and heights of the voxels in the component-specific 3D NanoSIMS images. We validated this strategy using AFM topography data and reconstructions created from depth profiling images acquired with focused ion beam-secondary electron microscopy. Good agreement was found for the shapes and relative heights of the reconstructed morphologies. Application of this depth correction strategy to 3D NanoSIMS depth profiling images of a metabolically labeled cell better resolved the transport vesicles, organelles, and organellar membranes containing 18O-cholesterol and 15N-sphingolipids. Accurate 3D NanoSIMS images of intracellular component distributions may now be produced without requiring correlated analyses with separate instruments or the assumption of a constant sputter rate. This will allow visualization of the subcellular distributions of lipids, metabolites, drugs, and nanoparticles in 3D, information pivotal to understanding and treating disease.
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Gorman BL, Brunet MA, Pham SN, Kraft ML. Measurement of Absolute Concentration at the Subcellular Scale. ACS NANO 2020; 14:6414-6419. [PMID: 32510923 DOI: 10.1021/acsnano.0c04285] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The concentration of a pharmaceutical drug or bioactive metabolite within the target organelle influences the effects elicited by the drug or metabolite. Although the relative concentrations of many compounds of interest within subcellular compartments have been measured, measurements of absolute concentrations in the organelle remain elusive. In this Perspective, we discuss a significant advance in using nano secondary ion mass spectrometry (nanoSIMS) to measure the absolute concentration of a 13C-labeled metabolite within secretory vesicles, as reported by Thomen et al. in the April issue of ACS Nano.
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Stopka SA, Samarah LZ, Shaw JB, Liyu AV, Veličković D, Agtuca BJ, Kukolj C, Koppenaal DW, Stacey G, Paša-Tolić L, Anderton CR, Vertes A. Ambient Metabolic Profiling and Imaging of Biological Samples with Ultrahigh Molecular Resolution Using Laser Ablation Electrospray Ionization 21 Tesla FTICR Mass Spectrometry. Anal Chem 2019; 91:5028-5035. [PMID: 30821434 DOI: 10.1021/acs.analchem.8b05084] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Mass spectrometry (MS) is an indispensable analytical tool to capture the array of metabolites within complex biological systems. However, conventional MS-based metabolomic workflows require extensive sample processing and separation resulting in limited throughput and potential alteration of the native molecular states in these systems. Ambient ionization methods, capable of sampling directly from tissues, circumvent some of these issues but require high-performance MS to resolve the molecular complexity within these samples. Here, we demonstrate a unique combination of laser ablation electrospray ionization (LAESI) coupled with a 21 tesla Fourier transform ion cyclotron resonance (21T-FTICR) for direct MS analysis and imaging applications. This analytical platform provides isotopic fine structure information directly from biological tissues, enabling the rapid assignment of molecular formulas and delivering a higher degree of confidence for molecular identification.
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Affiliation(s)
- Sylwia A Stopka
- Department of Chemistry , The George Washington University , Washington , D.C. 20052 , United States
| | - Laith Z Samarah
- Department of Chemistry , The George Washington University , Washington , D.C. 20052 , United States
| | - Jared B Shaw
- Environmental Molecular Sciences Laboratory and Biological Sciences Division , Pacific Northwest National Laboratory , Richland , Washington 99354 , United States
| | - Andrey V Liyu
- Environmental Molecular Sciences Laboratory and Biological Sciences Division , Pacific Northwest National Laboratory , Richland , Washington 99354 , United States
| | - Dušan Veličković
- Environmental Molecular Sciences Laboratory and Biological Sciences Division , Pacific Northwest National Laboratory , Richland , Washington 99354 , United States
| | - Beverly J Agtuca
- Divisions of Plant Sciences and Biochemistry, C. S. Bond Life Sciences Center , University of Missouri , Columbia , Missouri 65211 , United States
| | - Caroline Kukolj
- Divisions of Plant Sciences and Biochemistry, C. S. Bond Life Sciences Center , University of Missouri , Columbia , Missouri 65211 , United States
| | - David W Koppenaal
- Environmental Molecular Sciences Laboratory and Biological Sciences Division , Pacific Northwest National Laboratory , Richland , Washington 99354 , United States
| | - Gary Stacey
- Divisions of Plant Sciences and Biochemistry, C. S. Bond Life Sciences Center , University of Missouri , Columbia , Missouri 65211 , United States
| | - Ljiljana Paša-Tolić
- Environmental Molecular Sciences Laboratory and Biological Sciences Division , Pacific Northwest National Laboratory , Richland , Washington 99354 , United States
| | - Christopher R Anderton
- Environmental Molecular Sciences Laboratory and Biological Sciences Division , Pacific Northwest National Laboratory , Richland , Washington 99354 , United States
| | - Akos Vertes
- Department of Chemistry , The George Washington University , Washington , D.C. 20052 , United States
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5
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Mass Spectrometry Imaging of Cholesterol. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1115:155-166. [DOI: 10.1007/978-3-030-04278-3_7] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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Cholesterol-Dependent Gating Effects on Ion Channels. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1115:167-190. [PMID: 30649760 DOI: 10.1007/978-3-030-04278-3_8] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Biomembranes separate a live cell from its environment and keep it in an off-equilibrium, steady state. They contain both phospholipids and nonphospholipids, depending on whether there are phosphate groups in the headgroup regions. Cholesterol (CHOL) is one type of nonphospholipids, and one of the most abundant lipid molecules in humans. Its content in plasma membranes and intracellular membranes varies and is tightly regulated. Voltage-gated ion channels are universally present in every cell and are fairly diversified in the eukaryotic domain of life. Our lipid-dependent gating hypothesis postulates that the controlled switch of the voltage-sensor domains (VSDs) in a voltage-gated potassium (Kv) channel between the "down" and the "up" state (gating) is sensitive to the ratio of phospholipids:nonphospholipids in the annular layer around the channel. High CHOL content is found to exert strong inhibitory effects on Kv channels. Such effects have been observed in in vitro membranes, cultured cells, and animal models for cholesterol metabolic defects. Thermodynamic analysis of the CHOL-dependent gating suggests that the inhibitory effects of CHOL result from collective interactions between annular CHOL molecules and the channel, which appear to be a more generic principle behind the CHOL effects on other ion channels and transporters. We will review the recent progress in the CHOL-dependent gating of voltage-gated ion channels, discuss the current technical limitations, and then expand briefly the learned principles to other ion channels that are known to be sensitive to the CHOL-channel interactions.
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Observation of endoplasmic reticulum tubules via TOF-SIMS tandem mass spectrometry imaging of transfected cells. Biointerphases 2018; 13:03B409. [PMID: 29482330 DOI: 10.1116/1.5019736] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Advances in three-dimensional secondary ion mass spectrometry (SIMS) imaging have enabled visualizing the subcellular distributions of various lipid species within individual cells. However, the difficulty of locating organelles using SIMS limits efforts to study their lipid compositions. Here, the authors have assessed whether endoplasmic reticulum (ER)-Tracker Blue White DPX®, which is a commercially available stain for visualizing the endoplasmic reticulum using fluorescence microscopy, produces distinctive ions that can be used to locate the endoplasmic reticulum using SIMS. Time-of-flight-SIMS tandem mass spectrometry (MS2) imaging was used to identify positively and negatively charged ions produced by the ER-Tracker stain. Then, these ions were used to localize the stain and thus the endoplasmic reticulum, within individual human embryonic kidney cells that contained higher numbers of endoplasmic reticulum-plasma membrane junctions on their surfaces. By performing MS2 imaging of selected ions in parallel with the precursor ion (MS1) imaging, the authors detected a chemical interference native to the cell at the same nominal mass as the pentafluorophenyl fragment from the ER-Tracker stain. Nonetheless, the fluorine secondary ions produced by the ER-Tracker stain provided a distinctive signal that enabled locating the endoplasmic reticulum using SIMS. This simple strategy for visualizing the endoplasmic reticulum in individual cells using SIMS could be combined with existing SIMS methodologies for imaging intracellular lipid distribution and to study the lipid composition within the endoplasmic reticulum.
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Sans M, Feider CL, Eberlin LS. Advances in mass spectrometry imaging coupled to ion mobility spectrometry for enhanced imaging of biological tissues. Curr Opin Chem Biol 2018; 42:138-146. [PMID: 29275246 PMCID: PMC5828985 DOI: 10.1016/j.cbpa.2017.12.005] [Citation(s) in RCA: 75] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2017] [Revised: 12/04/2017] [Accepted: 12/11/2017] [Indexed: 11/20/2022]
Abstract
Tissues present complex biochemical and morphological composition associated with their various cell types and physiological functions. Mass spectrometry (MS) imaging technologies are powerful tools to investigate the molecular information from biological tissue samples and visualize their complex spatial distributions. Coupling of gas-phase ion mobility spectrometry (IMS) technologies to MS imaging has been increasingly explored to improve performance for biological tissue imaging. This approach allows improved detection of low abundance ions and separation of isobaric molecular species, thus resulting in more accurate determination of the spatial distribution of molecular ions. In this review, we highlight recent advances in the field focusing on promising applications of these technologies for metabolite, lipid and protein tissue imaging.
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Affiliation(s)
- Marta Sans
- Department of Chemistry, The University of Texas at Austin, Austin, TX 78712, United States
| | - Clara L Feider
- Department of Chemistry, The University of Texas at Austin, Austin, TX 78712, United States
| | - Livia S Eberlin
- Department of Chemistry, The University of Texas at Austin, Austin, TX 78712, United States.
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Kraft ML. Sphingolipid Organization in the Plasma Membrane and the Mechanisms That Influence It. Front Cell Dev Biol 2017; 4:154. [PMID: 28119913 PMCID: PMC5222807 DOI: 10.3389/fcell.2016.00154] [Citation(s) in RCA: 63] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2016] [Accepted: 12/27/2016] [Indexed: 11/13/2022] Open
Abstract
Sphingolipids are structural components in the plasma membranes of eukaryotic cells. Their metabolism produces bioactive signaling molecules that modulate fundamental cellular processes. The segregation of sphingolipids into distinct membrane domains is likely essential for cellular function. This review presents the early studies of sphingolipid distribution in the plasma membranes of mammalian cells that shaped the most popular current model of plasma membrane organization. The results of traditional imaging studies of sphingolipid distribution in stimulated and resting cells are described. These data are compared with recent results obtained with advanced imaging techniques, including super-resolution fluorescence detection and high-resolution secondary ion mass spectrometry (SIMS). Emphasis is placed on the new insight into the sphingolipid organization within the plasma membrane that has resulted from the direct imaging of stable isotope-labeled lipids in actual cell membranes with high-resolution SIMS. Super-resolution fluorescence techniques have recently revealed the biophysical behaviors of sphingolipids and the unhindered diffusion of cholesterol analogs in the membranes of living cells are ultimately in contrast to the prevailing hypothetical model of plasma membrane organization. High-resolution SIMS studies also conflicted with the prevailing hypothesis, showing sphingolipids are concentrated in micrometer-scale membrane domains, but cholesterol is evenly distributed within the plasma membrane. Reductions in cellular cholesterol decreased the number of sphingolipid domains in the plasma membrane, whereas disruption of the cytoskeleton eliminated them. In addition, hemagglutinin, a transmembrane protein that is thought to be a putative raft marker, did not cluster within sphingolipid-enriched regions in the plasma membrane. Thus, sphingolipid distribution in the plasma membrane is dependent on the cytoskeleton, but not on favorable interactions with cholesterol or hemagglutinin. The alternate views of plasma membrane organization suggested by these findings are discussed.
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Affiliation(s)
- Mary L Kraft
- Department of Chemical and Biomolecular Engineering, University of Illinois Urbana, IL, USA
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Three-dimensional imaging of cholesterol and sphingolipids within a Madin-Darby canine kidney cell. Biointerphases 2016; 11:02A309. [PMID: 26746168 DOI: 10.1116/1.4939681] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Metabolic stable isotope incorporation and secondary ion mass spectrometry (SIMS) depth profiling performed on a Cameca NanoSIMS 50 were used to image the (18)O-cholesterol and (15)N-sphingolipid distributions within a portion of a Madin-Darby canine kidney (MDCK) cell. Three-dimensional representations of the component-specific isotope distributions show clearly defined regions of (18)O-cholesterol and (15)N-sphingolipid enrichment that seem to be separate subcellular compartments. The low levels of nitrogen-containing secondary ions detected at the (18)O-enriched regions suggest that these (18)O-cholesterol-rich structures may be lipid droplets, which have a core consisting of cholesterol esters and triacylglycerides.
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Wilson RL, Frisz JF, Klitzing HA, Zimmerberg J, Weber PK, Kraft ML. Hemagglutinin clusters in the plasma membrane are not enriched with cholesterol and sphingolipids. Biophys J 2016; 108:1652-1659. [PMID: 25863057 DOI: 10.1016/j.bpj.2015.02.026] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2014] [Revised: 02/11/2015] [Accepted: 02/18/2015] [Indexed: 01/28/2023] Open
Abstract
The clusters of the influenza envelope protein, hemagglutinin, within the plasma membrane are hypothesized to be enriched with cholesterol and sphingolipids. Here, we directly tested this hypothesis by using high-resolution secondary ion mass spectrometry to image the distributions of antibody-labeled hemagglutinin and isotope-labeled cholesterol and sphingolipids in the plasma membranes of fibroblast cells that stably express hemagglutinin. We found that the hemagglutinin clusters were neither enriched with cholesterol nor colocalized with sphingolipid domains. Thus, hemagglutinin clustering and localization in the plasma membrane is not controlled by cohesive interactions between hemagglutinin and liquid-ordered domains enriched with cholesterol and sphingolipids, or from specific binding interactions between hemagglutinin, cholesterol, and/or the majority of sphingolipid species in the plasma membrane.
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Affiliation(s)
- Robert L Wilson
- Department of Chemistry, University of Illinois, Urbana, Illinois
| | - Jessica F Frisz
- Department of Chemistry, University of Illinois, Urbana, Illinois
| | - Haley A Klitzing
- Department of Chemistry, University of Illinois, Urbana, Illinois
| | - Joshua Zimmerberg
- Section on Cellular and Membrane Biophysics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland
| | - Peter K Weber
- Glenn T. Seaborg Institute, Lawrence Livermore National Laboratory, Livermore, California
| | - Mary L Kraft
- Department of Chemistry, University of Illinois, Urbana, Illinois; Department of Chemical and Biomolecular Engineering, University of Illinois, Urbana, Illnois.
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Ifa DR, Eberlin LS. Ambient Ionization Mass Spectrometry for Cancer Diagnosis and Surgical Margin Evaluation. Clin Chem 2015; 62:111-23. [PMID: 26555455 DOI: 10.1373/clinchem.2014.237172] [Citation(s) in RCA: 124] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2015] [Accepted: 09/28/2015] [Indexed: 01/12/2023]
Abstract
BACKGROUND There is a clinical need for new technologies that would enable rapid disease diagnosis based on diagnostic molecular signatures. Ambient ionization mass spectrometry has revolutionized the means by which molecular information can be obtained from tissue samples in real time and with minimal sample pretreatment. New developments in ambient ionization techniques applied to clinical research suggest that ambient ionization mass spectrometry will soon become a routine medical tool for tissue diagnosis. CONTENT This review summarizes the main developments in ambient ionization techniques applied to tissue analysis, with focus on desorption electrospray ionization mass spectrometry, probe electrospray ionization, touch spray, and rapid evaporative ionization mass spectrometry. We describe their applications to human cancer research and surgical margin evaluation, highlighting integrated approaches tested for ex vivo and in vivo human cancer tissue analysis. We also discuss the challenges for clinical implementation of these tools and offer perspectives on the future of the field. SUMMARY A variety of studies have showcased the value of ambient ionization mass spectrometry for rapid and accurate cancer diagnosis. Small molecules have been identified as potential diagnostic biomarkers, including metabolites, fatty acids, and glycerophospholipids. Statistical analysis allows tissue discrimination with high accuracy rates (>95%) being common. This young field has challenges to overcome before it is ready to be broadly accepted as a medical tool for cancer diagnosis. Growing research in new, integrated ambient ionization mass spectrometry technologies and the ongoing improvements in the existing tools make this field very promising for future translation into the clinic.
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Affiliation(s)
- Demian R Ifa
- Department of Chemistry, York University, Toronto, ON, Canada
| | - Livia S Eberlin
- Department of Chemistry, The University of Texas at Austin, Austin, TX.
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Muro E, Atilla-Gokcumen GE, Eggert US. Lipids in cell biology: how can we understand them better? Mol Biol Cell 2015; 25:1819-23. [PMID: 24925915 PMCID: PMC4055261 DOI: 10.1091/mbc.e13-09-0516] [Citation(s) in RCA: 129] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Lipids are a major class of biological molecules and play many key roles in different processes. The diversity of lipids is on the same order of magnitude as that of proteins: cells express tens of thousands of different lipids and hundreds of proteins to regulate their metabolism and transport. Despite their clear importance and essential functions, lipids have not been as well studied as proteins. We discuss here some of the reasons why it has been challenging to study lipids and outline technological developments that are allowing us to begin lifting lipids out of their “Cinderella” status. We focus on recent advances in lipid identification, visualization, and investigation of their biophysics and perturbations and suggest that the field has sufficiently advanced to encourage broader investigation into these intriguing molecules.
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Affiliation(s)
- Eleonora Muro
- Department of Chemistry and Randall Division of Cell and Molecular Biophysics, King's College London, London SE1 1UL, United Kingdom
| | - G Ekin Atilla-Gokcumen
- Department of Chemistry, University at Buffalo, State University of New York, Buffalo, NY 14260
| | - Ulrike S Eggert
- Department of Chemistry and Randall Division of Cell and Molecular Biophysics, King's College London, London SE1 1UL, United Kingdom
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Romanova EV, Aerts JT, Croushore CA, Sweedler JV. Small-volume analysis of cell-cell signaling molecules in the brain. Neuropsychopharmacology 2014; 39:50-64. [PMID: 23748227 PMCID: PMC3857641 DOI: 10.1038/npp.2013.145] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/26/2013] [Revised: 04/26/2013] [Accepted: 05/06/2013] [Indexed: 12/19/2022]
Abstract
Modern science is characterized by integration and synergy between research fields. Accordingly, as technological advances allow new and more ambitious quests in scientific inquiry, numerous analytical and engineering techniques have become useful tools in biological research. The focus of this review is on cutting edge technologies that aid direct measurement of bioactive compounds in the nervous system to facilitate fundamental research, diagnostics, and drug discovery. We discuss challenges associated with measurement of cell-to-cell signaling molecules in the nervous system, and advocate for a decrease of sample volumes to the nanoliter volume regimen for improved analysis outcomes. We highlight effective approaches for the collection, separation, and detection of such small-volume samples, present strategies for targeted and discovery-oriented research, and describe the required technology advances that will empower future translational science.
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Affiliation(s)
- Elena V Romanova
- Beckman Institute for Advanced Science and Technology and the Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Jordan T Aerts
- Beckman Institute for Advanced Science and Technology and the Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL, USA
- Neuroscience Program, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Callie A Croushore
- Beckman Institute for Advanced Science and Technology and the Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Jonathan V Sweedler
- Beckman Institute for Advanced Science and Technology and the Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL, USA
- Neuroscience Program, University of Illinois at Urbana-Champaign, Urbana, IL, USA
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Frisz JF, Klitzing HA, Lou K, Hutcheon ID, Weber PK, Zimmerberg J, Kraft ML. Sphingolipid domains in the plasma membranes of fibroblasts are not enriched with cholesterol. J Biol Chem 2013; 288:16855-16861. [PMID: 23609440 PMCID: PMC3675618 DOI: 10.1074/jbc.m113.473207] [Citation(s) in RCA: 121] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The plasma membranes of mammalian cells are widely expected to contain domains that are enriched with cholesterol and sphingolipids. In this work, we have used high-resolution secondary ion mass spectrometry to directly map the distributions of isotope-labeled cholesterol and sphingolipids in the plasma membranes of intact fibroblast cells. Although acute cholesterol depletion reduced sphingolipid domain abundance, cholesterol was evenly distributed throughout the plasma membrane and was not enriched within the sphingolipid domains. Thus, we rule out favorable cholesterol-sphingolipid interactions as dictating plasma membrane organization in fibroblast cells. Because the sphingolipid domains are disrupted by drugs that depolymerize the cells actin cytoskeleton, cholesterol must instead affect the sphingolipid organization via an indirect mechanism that involves the cytoskeleton.
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Affiliation(s)
| | | | - Kaiyan Lou
- Chemical and Biomolecular Engineering, University of Illinois, Urbana, Illinois 61801
| | - Ian D Hutcheon
- Glenn T. Seaborg Institute, Lawrence Livermore National Laboratory, Livermore, California 94551
| | - Peter K Weber
- Glenn T. Seaborg Institute, Lawrence Livermore National Laboratory, Livermore, California 94551
| | - Joshua Zimmerberg
- Program in Physical Biology, Eunice Kennedy Shriver NICHD, National Institutes of Health, Bethesda, Maryland 20892
| | - Mary L Kraft
- Departments of Chemistry, Urbana, Illinois 61801; Chemical and Biomolecular Engineering, University of Illinois, Urbana, Illinois 61801.
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Direct chemical evidence for sphingolipid domains in the plasma membranes of fibroblasts. Proc Natl Acad Sci U S A 2013; 110:E613-22. [PMID: 23359681 DOI: 10.1073/pnas.1216585110] [Citation(s) in RCA: 159] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Sphingolipids play important roles in plasma membrane structure and cell signaling. However, their lateral distribution in the plasma membrane is poorly understood. Here we quantitatively analyzed the sphingolipid organization on the entire dorsal surface of intact cells by mapping the distribution of (15)N-enriched ions from metabolically labeled (15)N-sphingolipids in the plasma membrane, using high-resolution imaging mass spectrometry. Many types of control experiments (internal, positive, negative, and fixation temperature), along with parallel experiments involving the imaging of fluorescent sphingolipids--both in living cells and during fixation of living cells--exclude potential artifacts. Micrometer-scale sphingolipid patches consisting of numerous (15)N-sphingolipid microdomains with mean diameters of ∼200 nm are always present in the plasma membrane. Depletion of 30% of the cellular cholesterol did not eliminate the sphingolipid domains, but did reduce their abundance and long-range organization in the plasma membrane. In contrast, disruption of the cytoskeleton eliminated the sphingolipid domains. These results indicate that these sphingolipid assemblages are not lipid rafts and are instead a distinctly different type of sphingolipid-enriched plasma membrane domain that depends upon cortical actin.
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