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Johnson SC, Annamdevula NS, Leavesley SJ, Francis CM, Rich TC. Hyperspectral imaging and dynamic region of interest tracking approaches to quantify localized cAMP signals. Biochem Soc Trans 2024; 52:191-203. [PMID: 38334148 PMCID: PMC11115359 DOI: 10.1042/bst20230352] [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: 11/15/2023] [Revised: 01/10/2024] [Accepted: 01/15/2024] [Indexed: 02/10/2024]
Abstract
Cyclic adenosine monophosphate (cAMP) is a ubiquitous second messenger known to orchestrate a myriad of cellular functions over a wide range of timescales. In the last 20 years, a variety of single-cell sensors have been developed to measure second messenger signals including cAMP, Ca2+, and the balance of kinase and phosphatase activities. These sensors utilize changes in fluorescence emission of an individual fluorophore or Förster resonance energy transfer (FRET) to detect changes in second messenger concentration. cAMP and kinase activity reporter probes have provided powerful tools for the study of localized signals. Studies relying on these and related probes have the potential to further revolutionize our understanding of G protein-coupled receptor signaling systems. Unfortunately, investigators have not been able to take full advantage of the potential of these probes due to the limited signal-to-noise ratio of the probes and the limited ability of standard epifluorescence and confocal microscope systems to simultaneously measure the distributions of multiple signals (e.g. cAMP, Ca2+, and changes in kinase activities) in real time. In this review, we focus on recently implemented strategies to overcome these limitations: hyperspectral imaging and adaptive thresholding approaches to track dynamic regions of interest (ROI). This combination of approaches increases signal-to-noise ratio and contrast, and allows identification of localized signals throughout cells. These in turn lead to the identification and quantification of intracellular signals with higher effective resolution. Hyperspectral imaging and dynamic ROI tracking approaches offer investigators additional tools with which to visualize and quantify multiplexed intracellular signaling systems.
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Affiliation(s)
- Santina C Johnson
- Department of Pharmacology, Frederick P. Whiddon College of Medicine, University of South Alabama, Mobile, AL, U.S.A
- Center for Lung Biology, Frederick P. Whiddon College of Medicine, University of South Alabama, Mobile, AL, U.S.A
| | - Naga S Annamdevula
- Department of Pharmacology, Frederick P. Whiddon College of Medicine, University of South Alabama, Mobile, AL, U.S.A
- Department of Physiology and Cell Biology, Frederick P. Whiddon College of Medicine, University of South Alabama, Mobile, AL, U.S.A
- Center for Lung Biology, Frederick P. Whiddon College of Medicine, University of South Alabama, Mobile, AL, U.S.A
| | - Silas J Leavesley
- Department of Pharmacology, Frederick P. Whiddon College of Medicine, University of South Alabama, Mobile, AL, U.S.A
- Center for Lung Biology, Frederick P. Whiddon College of Medicine, University of South Alabama, Mobile, AL, U.S.A
- Chemical and Biomolecular Engineering, University of South Alabama, Mobile, AL, U.S.A
| | - C Michael Francis
- Department of Physiology and Cell Biology, Frederick P. Whiddon College of Medicine, University of South Alabama, Mobile, AL, U.S.A
- Center for Lung Biology, Frederick P. Whiddon College of Medicine, University of South Alabama, Mobile, AL, U.S.A
| | - Thomas C Rich
- Department of Pharmacology, Frederick P. Whiddon College of Medicine, University of South Alabama, Mobile, AL, U.S.A
- Center for Lung Biology, Frederick P. Whiddon College of Medicine, University of South Alabama, Mobile, AL, U.S.A
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2
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Deisl C, Chung JH, Hilgemann DW. Longitudinal diffusion barriers imposed by myofilaments and mitochondria in murine cardiac myocytes. J Gen Physiol 2023; 155:e202213329. [PMID: 37555782 PMCID: PMC10412754 DOI: 10.1085/jgp.202213329] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2023] [Revised: 05/08/2023] [Accepted: 07/14/2023] [Indexed: 08/10/2023] Open
Abstract
Using optical and electrical methods, we document that diffusion in the cytoplasm of BL6 murine cardiomyocytes becomes restricted >20-fold as molecular weight increases from 30 to 2,000, roughly as expected for pores with porin channel dimensions. Bodipy-FL ATP diffuses >40-fold slower than in free water at 25°C. From several fluorophores analyzed, bound fluorophore fractions range from 0.1 for a 2 kD FITC-labeled polyethylene glycol to 0.93 for sulforhodamine. Unbound fluorophores diffuse at 0.5-8 × 10-7 cm2/s (5-80 μm2/s). Analysis of Na/K pump and veratridine-modified Na channel currents suggests that Na diffusion is nearly unrestricted at 35°C (time constant for equilibration with the pipette tip, ∼20 s). Using multiple strategies, we estimate that at 35°C, ATP diffuses four to eight times slower than in free water. To address whether restrictions are caused more by protein or membrane networks, we verified first that a protein gel, 10 g% gelatin, restricts diffusion with strong dependence on molecular weight. Solute diffusion in membrane-extracted cardiac myofilaments, confined laterally by suction into large-diameter pipette tips, is less restricted than in intact myocytes. Notably, myofilaments extracted similarly from skeletal (diaphragm) myocytes are less restrictive. Solute diffusion in myocytes with sarcolemma permeabilized by β-escin (80 µM) is similar to diffusion in intact myocytes. Restrictions are strain-dependent, being twofold greater in BL6 myocytes than in CD1/J6/129svJ myocytes. Furthermore, longitudinal diffusion is 2.5-fold more restricted in CD1/J6/129svJ myocytes lacking the mitochondrial porin, VDAC1, than in WT CD1/J6/129svJ myocytes. Thus, mitochondria networks restrict long-range diffusion while presumably optimizing nucleotide transfer between myofilaments and mitochondria. We project that diffusion restrictions imposed by both myofilaments and the outer mitochondrial membrane are important determinants of total free cytoplasmic AMP and ADP (∼10 μM). However, the capacity of diffusion to deliver ATP to myofilaments remains ∼100-fold greater than ATP consumption.
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Affiliation(s)
- Christine Deisl
- Department of Physiology, Southwestern Medical Center, Dallas, TX, USA
| | - Jay H. Chung
- Laboratory of Obesity and Aging Research, Cardiovascular Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, USA
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3
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Computational investigation of the dynamic control of cAMP signaling by PDE4 isoform types. Biophys J 2022; 121:2693-2711. [PMID: 35717559 DOI: 10.1016/j.bpj.2022.06.019] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2021] [Revised: 05/03/2022] [Accepted: 06/14/2022] [Indexed: 11/24/2022] Open
Abstract
Cyclic adenosine monophosphate (cAMP) is a generic signaling molecule that, through precise control of its signaling dynamics, exerts distinct cellular effects. Consequently, aberrant cAMP signaling can have detrimental effects. Phosphodiesterase 4 (PDE4) enzymes profoundly control cAMP signaling and comprise different isoform types of which the enzymatic activity is modulated by differential feedback mechanisms. Because these feedback dynamics are non-linear and occur coincidentally, their effects are difficult to examine experimentally, but can be well simulated computationally. Through understanding the role of PDE4 isoform types in regulating cAMP signaling, PDE4-targeted therapeutic strategies can be better specified. Here, we established a computational model to study how feedback mechanisms on different PDE4 isoform types lead to dynamic, isoform-specific control of cAMP signaling. Ordinary differential equations describing cAMP dynamics were implemented in the VirtualCell (VCell) environment. Simulations indicated that long PDE4 isoforms exert the most profound control on oscillatory cAMP signaling, as opposed to the PDE4-mediated control of single cAMP input pulses. Moreover, elevating cAMP levels or decreasing PDE4 levels revealed different effects on downstream signaling. Together these results underline that cAMP signaling is distinctly regulated by different PDE4 isoform types and that this isoform-specificity should be considered in both computational and experimental follow-up studies to better define PDE4 enzymes as therapeutic targets in diseases in which cAMP signaling is aberrant.
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Bock A, Annibale P, Konrad C, Hannawacker A, Anton SE, Maiellaro I, Zabel U, Sivaramakrishnan S, Falcke M, Lohse MJ. Optical Mapping of cAMP Signaling at the Nanometer Scale. Cell 2020; 182:1519-1530.e17. [PMID: 32846156 DOI: 10.1016/j.cell.2020.07.035] [Citation(s) in RCA: 100] [Impact Index Per Article: 25.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2019] [Revised: 03/30/2020] [Accepted: 07/23/2020] [Indexed: 10/23/2022]
Abstract
Cells relay a plethora of extracellular signals to specific cellular responses by using only a few second messengers, such as cAMP. To explain signaling specificity, cAMP-degrading phosphodiesterases (PDEs) have been suggested to confine cAMP to distinct cellular compartments. However, measured rates of fast cAMP diffusion and slow PDE activity render cAMP compartmentalization essentially impossible. Using fluorescence spectroscopy, we show that, contrary to earlier data, cAMP at physiological concentrations is predominantly bound to cAMP binding sites and, thus, immobile. Binding and unbinding results in largely reduced cAMP dynamics, which we term "buffered diffusion." With a large fraction of cAMP being buffered, PDEs can create nanometer-size domains of low cAMP concentrations. Using FRET-cAMP nanorulers, we directly map cAMP gradients at the nanoscale around PDE molecules and the areas of resulting downstream activation of cAMP-dependent protein kinase (PKA). Our study reveals that spatiotemporal cAMP signaling is under precise control of nanometer-size domains shaped by PDEs that gate activation of downstream effectors.
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Affiliation(s)
- Andreas Bock
- Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Robert-Rössle-Str. 10, 13125 Berlin, Germany; Institute of Pharmacology and Toxicology, University of Würzburg, Versbacher Str. 9, 97078 Würzburg, Germany.
| | - Paolo Annibale
- Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Robert-Rössle-Str. 10, 13125 Berlin, Germany; Institute of Pharmacology and Toxicology, University of Würzburg, Versbacher Str. 9, 97078 Würzburg, Germany
| | - Charlotte Konrad
- Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Robert-Rössle-Str. 10, 13125 Berlin, Germany; Institute of Pharmacology and Toxicology, University of Würzburg, Versbacher Str. 9, 97078 Würzburg, Germany
| | - Annette Hannawacker
- Institute of Pharmacology and Toxicology, University of Würzburg, Versbacher Str. 9, 97078 Würzburg, Germany
| | - Selma E Anton
- Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Robert-Rössle-Str. 10, 13125 Berlin, Germany; Institute of Pharmacology and Toxicology, University of Würzburg, Versbacher Str. 9, 97078 Würzburg, Germany
| | - Isabella Maiellaro
- Institute of Pharmacology and Toxicology, University of Würzburg, Versbacher Str. 9, 97078 Würzburg, Germany
| | - Ulrike Zabel
- Institute of Pharmacology and Toxicology, University of Würzburg, Versbacher Str. 9, 97078 Würzburg, Germany
| | - Sivaraj Sivaramakrishnan
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, MN 55455, USA
| | - Martin Falcke
- Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Robert-Rössle-Str. 10, 13125 Berlin, Germany; Department of Physics, Humboldt University, Newtonstr. 15, 12489 Berlin, Germany
| | - Martin J Lohse
- Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Robert-Rössle-Str. 10, 13125 Berlin, Germany; Institute of Pharmacology and Toxicology, University of Würzburg, Versbacher Str. 9, 97078 Würzburg, Germany; Institute for Chemistry and Biochemistry, Free University, Takustr. 3, 14195 Berlin, Germany; ISAR Bioscience Institute, 82152 Munich/Planegg, Germany.
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5
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Rich TC, Griswold JR, Deal J, Annamdevula N, McAlister K, Mayes S, Browning C, Parker M, Leavelsey SJ. Hyperspectral imaging microscopy for measurement of localized second messenger signals in single cells. PROCEEDINGS OF SPIE--THE INTERNATIONAL SOCIETY FOR OPTICAL ENGINEERING 2019; 10881:108811F. [PMID: 34045781 PMCID: PMC8151147 DOI: 10.1117/12.2508052] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
Ca2+ and cAMP are ubiquitous second messengers known to differentially regulate a variety of cellular functions over a wide range of timescales. Studies from a variety of groups support the hypothesis that these signals can be localized to discrete locations within cells, and that this subcellular localization is a critical component of signaling specificity. However, to date, it has been difficult to track second messenger signals at multiple locations within a single cell. This difficulty is largely due to the inability to measure multiplexed florescence signals in real time. To overcome this limitation, we have utilized both emission scan- and excitation scan-based hyperspectral imaging approaches to track second messenger signals as well as labeled cellular structures and/or proteins in the same cell. We have previously reported that hyperspectral imaging techniques improve the signal-to-noise ratios of both fluorescence and FRET measurements, and are thus well suited for the measurement of localized second messenger signals. Using these approaches, we have measured near plasma membrane and near nuclear membrane cAMP signals, as well as distributed signals within the cytosol, in several cell types including airway smooth muscle, pulmonary endothelial, and HEK-293 cells. We have also measured cAMP and Ca2+ signals near autofluorescent structures that appear to be golgi. Our data demonstrate that hyperspectral imaging approaches provide unique insight into the spatial and kinetic distributions of cAMP and Ca2+ signals in single cells.
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Affiliation(s)
- Thomas C Rich
- Pharmacology, University of South Alabama, AL 36688
- Center for Lung Biology, University of South Alabama, AL 36688
| | - J R Griswold
- Chemical and Biomolecular Engineering, University of South Alabama, AL 36688
| | - Joshua Deal
- Pharmacology, University of South Alabama, AL 36688
- Center for Lung Biology, University of South Alabama, AL 36688
| | - Naga Annamdevula
- Pharmacology, University of South Alabama, AL 36688
- Center for Lung Biology, University of South Alabama, AL 36688
| | | | - Samuel Mayes
- Chemical and Biomolecular Engineering, University of South Alabama, AL 36688
| | - Craig Browning
- Chemical and Biomolecular Engineering, University of South Alabama, AL 36688
| | - Marina Parker
- Chemical and Biomolecular Engineering, University of South Alabama, AL 36688
| | - Silas J Leavelsey
- Pharmacology, University of South Alabama, AL 36688
- Center for Lung Biology, University of South Alabama, AL 36688
- Chemical and Biomolecular Engineering, University of South Alabama, AL 36688
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Annamdevula NS, Sweat R, Griswold JR, Trinh K, Hoffman C, West S, Deal J, Britain AL, Jalink K, Rich TC, Leavesley SJ. Spectral imaging of FRET-based sensors reveals sustained cAMP gradients in three spatial dimensions. Cytometry A 2018; 93:1029-1038. [PMID: 30176184 DOI: 10.1002/cyto.a.23572] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2016] [Revised: 06/21/2018] [Accepted: 07/09/2018] [Indexed: 11/10/2022]
Abstract
Cyclic AMP is a ubiquitous second messenger that orchestrates a variety of cellular functions over different timescales. The mechanisms underlying specificity within this signaling pathway are still not well understood. Several lines of evidence suggest the existence of spatial cAMP gradients within cells, and that compartmentalization underlies specificity within the cAMP signaling pathway. However, to date, no studies have visualized cAMP gradients in three spatial dimensions (3D: x, y, z).This is in part due to the limitations of FRET-based cAMP sensors, specifically the low signal-to-noise ratio intrinsic to all intracellular FRET probes. Here, we overcome this limitation, at least in part, by implementing spectral imaging approaches to estimate FRET efficiency when multiple fluorescent labels are used and when signals are measured from weakly expressed fluorescent proteins in the presence of background autofluorescence and stray light. Analysis of spectral image stacks in two spatial dimensions (2D) from single confocal slices indicates little or no cAMP gradients formed within pulmonary microvascular endothelial cells (PMVECs) under baseline conditions or following 10 min treatment with the adenylyl cyclase activator forskolin. However, analysis of spectral image stacks in 3D demonstrates marked cAMP gradients from the apical to basolateral face of PMVECs. Results demonstrate that spectral imaging approaches can be used to assess cAMP gradients-and in general gradients in fluorescence and FRET-within intact cells. Results also demonstrate that 2D imaging studies of localized fluorescence signals and, in particular, cAMP signals, whether using epifluorescence or confocal microscopy, may lead to erroneous conclusions about the existence and/or magnitude of gradients in either FRET or the underlying cAMP signals. Thus, with the exception of cellular structures that can be considered in one spatial dimension, such as neuronal processes, 3D measurements are required to assess mechanisms underlying compartmentalization and specificity within intracellular signaling pathways.
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Affiliation(s)
- Naga S Annamdevula
- Department of Chemical & Biomolecular Engineering, University of South Alabama, Mobile, Alabama.,Center for Lung Biology, University of South Alabama, Mobile, Alabama
| | - Rachel Sweat
- Department of Chemical & Biomolecular Engineering, University of South Alabama, Mobile, Alabama
| | - John R Griswold
- Department of Chemical & Biomolecular Engineering, University of South Alabama, Mobile, Alabama
| | - Kenny Trinh
- Department of Chemical & Biomolecular Engineering, University of South Alabama, Mobile, Alabama
| | - Chase Hoffman
- Medical Sciences, University of South Alabama, Mobile, Alabama
| | - Savannah West
- Department of Biomedical Sciences, University of South Alabama, Mobile, Alabama
| | - Joshua Deal
- Department of Chemical & Biomolecular Engineering, University of South Alabama, Mobile, Alabama.,Center for Lung Biology, University of South Alabama, Mobile, Alabama
| | - Andrea L Britain
- Center for Lung Biology, University of South Alabama, Mobile, Alabama.,Department of Pharmacology, University of South Alabama, Mobile, Alabama
| | - Kees Jalink
- The Netherlands Cancer Institute and van Leeuwenhoek Center for Advanced Microscopy, Amsterdam, the Netherlands
| | - Thomas C Rich
- Center for Lung Biology, University of South Alabama, Mobile, Alabama.,Department of Pharmacology, University of South Alabama, Mobile, Alabama.,College of Engineering, University of South Alabama, Mobile, Alabama
| | - Silas J Leavesley
- Department of Chemical & Biomolecular Engineering, University of South Alabama, Mobile, Alabama.,Center for Lung Biology, University of South Alabama, Mobile, Alabama.,Department of Pharmacology, University of South Alabama, Mobile, Alabama
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7
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Agarwal SR, Miyashiro K, Latt H, Ostrom RS, Harvey RD. Compartmentalized cAMP responses to prostaglandin EP 2 receptor activation in human airway smooth muscle cells. Br J Pharmacol 2017; 174:2784-2796. [PMID: 28603838 DOI: 10.1111/bph.13904] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2017] [Revised: 05/25/2017] [Accepted: 06/05/2017] [Indexed: 12/25/2022] Open
Abstract
BACKGROUND AND PURPOSE Previous studies indicate that prostaglandin EP2 receptors selectively couple to AC2 in non-lipid raft domains of airway smooth muscle (ASM) cells, where they regulate specific cAMP-dependent responses. The goal of the present study was to identify the cellular microdomains where EP2 receptors stimulate cAMP production. EXPERIMENTAL APPROACH FRET-based cAMP biosensors were targeted to different subcellular locations of primary human ASM cells. The Epac2-camps biosensor, which expresses throughout the cell, was used to measure bulk cytoplasmic responses. Epac2-MyrPalm and Epac2-CAAX were used to measure responses associated with lipid raft and non-raft regions of the plasma membrane respectively. Epac2-NLS was used to monitor responses at the nucleus. KEY RESULTS Activation of AC with forskolin or β2 -adrenoceptors with isoprenaline increased cAMP in all subcellular locations. Activation of EP2 receptors with butaprost produced cAMP responses that were most readily detected by the non-raft and nuclear sensors, but only weakly detected by the cytosolic sensor and not detected at all by the lipid raft sensor. Exposure to rolipram, a PDE4 inhibitor, unmasked the ability of EP2 receptors to increase cAMP levels associated with lipid raft domains. Overexpression of AC2 selectively increased EP2 receptor-stimulated production of cAMP in non-raft membrane domains. CONCLUSIONS AND IMPLICATIONS EP2 receptor activation of AC2 leads to cAMP production in non-raft and nuclear compartments of human ASMs, while β2 adrenoceptor signalling is broadly detected across microdomains. The activity of PDE4 appears to play a role in maintaining the integrity of compartmentalized EP2 receptor responses in these cells.
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Affiliation(s)
- Shailesh R Agarwal
- Department of Pharmacology, University of Nevada, Reno School of Medicine, Reno, NV, USA
| | - Kathryn Miyashiro
- Department of Pharmacology, University of Nevada, Reno School of Medicine, Reno, NV, USA
| | - Htun Latt
- Department of Pharmacology, University of Nevada, Reno School of Medicine, Reno, NV, USA
| | - Rennolds S Ostrom
- Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Irvine, CA, USA
| | - Robert D Harvey
- Department of Pharmacology, University of Nevada, Reno School of Medicine, Reno, NV, USA
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Rich TC, Annamdevula N, Trinh K, Britain AL, Mayes SA, Griswold JR, Deal J, Hoffman C, West S, Leavesley SJ. 5D imaging approaches reveal the formation of distinct intracellular cAMP spatial gradients. PROCEEDINGS OF SPIE--THE INTERNATIONAL SOCIETY FOR OPTICAL ENGINEERING 2017; 10070:100700R. [PMID: 34054188 PMCID: PMC8157067 DOI: 10.1117/12.2253164] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
Cyclic AMP (cAMP) is a ubiquitous second messenger known to differentially regulate many cellular functions. Several lines of evidence suggest that the distribution of cAMP within cells is not uniform. However, to date, no studies have measured the kinetics of 3D cAMP distributions within cells. This is largely due to the low signal-to-noise ratio of FRET-based probes. We previously reported that hyperspectral imaging improves the signal-to-noise ratio of FRET measurements. Here we utilized hyperspectral imaging approaches to measure FRET signals in five dimensions (5D) - three spatial (x, y, z), wavelength (λ), and time (t) - allowing us to visualize cAMP gradients in pulmonary endothelial cells. cAMP levels were measured using a FRET-based sensor (H188) comprised of a cAMP binding domain sandwiched between FRET donor and acceptor - Turquoise and Venus fluorescent proteins. We observed cAMP gradients in response to 0.1 or 1 μM isoproterenol, 0.1 or 1 μM PGE1, or 50 μM forskolin. Forskolin- and isoproterenol-induced cAMP gradients formed from the apical (high cAMP) to basolateral (low cAMP) face of cells. In contrast, PGE1-induced cAMP gradients originated from both the basolateral and apical faces of cells. Data suggest that 2D (x,y) studies of cAMP compartmentalization may lead to erroneous conclusions about the existence of cAMP gradients, and that 3D (x,y,z) studies are required to assess mechanisms of signaling specificity. Results demonstrate that 5D imaging technologies are powerful tools for measuring biochemical processes in discrete subcellular domains. This work was supported by NIH P01HL066299, R01HL058506, S10RR027535, AHA 16PRE27130004 and the Abraham Mitchell Cancer Research Fund.
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Affiliation(s)
- Thomas C Rich
- Pharmacology, University of South Alabama, AL 36688
- Center for Lung Biology, University of South Alabama, AL 36688
- Basic Medical Sciences Graduate Program, University of South Alabama, AL 36688
| | - Naga Annamdevula
- Center for Lung Biology, University of South Alabama, AL 36688
- Basic Medical Sciences Graduate Program, University of South Alabama, AL 36688
| | - Kenny Trinh
- Chemical and Biomolecular Engineering, University of South Alabama, AL 36688
| | - Andrea L Britain
- Pharmacology, University of South Alabama, AL 36688
- Center for Lung Biology, University of South Alabama, AL 36688
| | - Samuel A Mayes
- Chemical and Biomolecular Engineering, University of South Alabama, AL 36688
| | - John R Griswold
- Chemical and Biomolecular Engineering, University of South Alabama, AL 36688
| | - Joshua Deal
- Center for Lung Biology, University of South Alabama, AL 36688
- Basic Medical Sciences Graduate Program, University of South Alabama, AL 36688
| | | | - Savannah West
- Biomedical Sciences, University of South Alabama, AL 36688
| | - Silas J Leavesley
- Pharmacology, University of South Alabama, AL 36688
- Center for Lung Biology, University of South Alabama, AL 36688
- Basic Medical Sciences Graduate Program, University of South Alabama, AL 36688
- Chemical and Biomolecular Engineering, University of South Alabama, AL 36688
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9
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Rich TC, Annamdevula N, Britain AL, Mayes S, Favreau PF, Leavelsey SJ. Three dimensional measurement of cAMP gradients using hyperspectral confocal microscopy. PROCEEDINGS OF SPIE--THE INTERNATIONAL SOCIETY FOR OPTICAL ENGINEERING 2016; 9713. [PMID: 34045789 DOI: 10.1117/12.2213273] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
Cyclic AMP (cAMP) is a ubiquitous second messenger known to differentially regulate many cellular functions over a wide range of timescales. Several lines of evidence have suggested that the distribution of cAMP within cells is not uniform, and that cAMP compartmentalization is largely responsible for signaling specificity within the cAMP signaling pathway. However, to date, no studies have experimentally measured three dimensional (3D) cAMP distributions within cells. Here we use both 2D and 3D hyperspectral microscopy to visualize cAMP gradients in endothelial cells from the pulmonary microvasculature (PMVECs). cAMP levels were measured using a FRET-based cAMP sensor comprised of a cAMP binding domain from EPAC sandwiched between FRET donors and acceptors - Turquoise and Venus fluorescent proteins. Data were acquired using either a Nikon A1R spectral confocal microscope or custom spectral microscopy system. Analysis of hyperspectral image stacks from a single confocal slice or from summed images of all slices (2D analysis) indicated little or no cAMP gradients were formed within PMVECs under basal conditions or following agonist treatment. However, analysis of hyperspectral image stacks from 3D cellular geometries (z stacks) demonstrate marked cAMP gradients from the apical to basolateral membrane of PMVECs. These results strongly suggest that 2D imaging studies of cAMP compartmentalization - whether epifluorescence or confocal microscopy - may lead to erroneous conclusions about the existence of cAMP gradients, and that 3D studies are required to assess mechanisms of signaling specificity.
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Affiliation(s)
- Thomas C Rich
- Pharmacology, University of South Alabama, AL 36688.,Center for Lung Biology, University of South Alabama, AL 36688
| | | | - Andrea L Britain
- Pharmacology, University of South Alabama, AL 36688.,Center for Lung Biology, University of South Alabama, AL 36688
| | - Samuel Mayes
- Chemical and Biomolecular Engineering, University of South Alabama, AL 36688
| | - Peter F Favreau
- Pharmacology, University of South Alabama, AL 36688.,Center for Lung Biology, University of South Alabama, AL 36688
| | - Silas J Leavelsey
- Pharmacology, University of South Alabama, AL 36688.,Center for Lung Biology, University of South Alabama, AL 36688.,Chemical and Biomolecular Engineering, University of South Alabama, AL 36688
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10
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Agarwal SR, Clancy CE, Harvey RD. Mechanisms Restricting Diffusion of Intracellular cAMP. Sci Rep 2016; 6:19577. [PMID: 26795432 PMCID: PMC4726171 DOI: 10.1038/srep19577] [Citation(s) in RCA: 66] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2015] [Accepted: 12/11/2015] [Indexed: 01/11/2023] Open
Abstract
Although numerous receptors stimulate cAMP production in a wide array of cells, many elicit distinct, highly localized responses, implying that the subcellular distribution of cAMP is not uniform. One often used explanation is that phosphodiesterases, which breakdown cAMP, act as functional barriers limiting diffusion. However, several studies refute the notion that this is sufficient, suggesting that phosphodiesterase-independent movement of cAMP must occur at rates slower than free diffusion. But, until now this has never been demonstrated. Using Raster Image Correlation Spectroscopy (RICS), we measured the diffusion coefficient of a fluorescently-labeled cAMP derivative (φ450-cAMP) as well as other fluorescent molecules in order to investigate the role that molecular size, cell morphology, and buffering by protein kinase A (PKA) play in restricting cAMP mobility in different cell types. Our results demonstrate that cytosolic movement of cAMP is indeed much slower than the rate of free diffusion and that interactions with PKA, especially type II PKA associated with mitochondria, play a significant role. These findings have important implications with respect to cAMP signaling in all cells.
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Affiliation(s)
- Shailesh R Agarwal
- Department of Pharmacology University of Nevada School of Medicine Reno, NV 89557
| | - Colleen E Clancy
- Department of Pharmacology University of California, Davis Davis, CA 95616
| | - Robert D Harvey
- Department of Pharmacology University of Nevada School of Medicine Reno, NV 89557
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