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Pierce SA, Jacobelli J, Given KS, Macklin WB, Gopinath JT, Siemens ME, Restrepo D, Gibson EA. OpenSTED: open-source dynamic intensity minimum system for stimulated emission depletion microscopy. NEUROPHOTONICS 2024; 11:034311. [PMID: 38867758 PMCID: PMC11167952 DOI: 10.1117/1.nph.11.3.034311] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/28/2023] [Revised: 05/14/2024] [Accepted: 05/20/2024] [Indexed: 06/14/2024]
Abstract
Significance Stimulated emission depletion (STED) is a powerful super-resolution microscopy technique that can be used for imaging live cells. However, the high STED laser powers can cause significant photobleaching and sample damage in sensitive biological samples. The dynamic intensity minimum (DyMIN) technique turns on the STED laser only in regions of the sample where there is fluorescence signal, thus saving significant sample photobleaching. The reduction in photobleaching allows higher resolution images to be obtained and longer time-lapse imaging of live samples. A stand-alone module to perform DyMIN is not available commercially. Aim In this work, we developed an open-source design to implement three-step DyMIN on a STED microscope and demonstrated reduced photobleaching for timelapse imaging of beads, cells, and tissue. Approach The DyMIN system uses a fast multiplexer circuit and inexpensive field-programmable gate array controlled by Labview software that operates as a stand-alone module for a STED microscope. All software and circuit diagrams are freely available. Results We compared time-lapse images of bead samples using our custom DyMIN system to conventional STED and recorded a ∼ 46 % higher signal when using DyMIN after a 50-image sequence. We further demonstrated the DyMIN system for time-lapse STED imaging of live cells and brain tissue slices. Conclusions Our open-source DyMIN system is an inexpensive add-on to a conventional STED microscope that can reduce photobleaching. The system can significantly improve signal to noise for dynamic time-lapse STED imaging of live samples.
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Affiliation(s)
- Stephanie A. Pierce
- University of Colorado Anschutz Medical Campus, Department of Bioengineering, Aurora, Colorado, United States
| | - Jordan Jacobelli
- University of Colorado Anschutz Medical Campus, Department of Immunology and Microbiology, Aurora, Colorado, United States
- University of Colorado Anschutz Medical Campus, Barbara Davis Research Center, Aurora, Colorado, United States
| | - Katherine S. Given
- University of Colorado Anschutz Medical Campus, Department of Cell and Developmental Biology, Aurora, Colorado, United States
| | - Wendy B. Macklin
- University of Colorado Anschutz Medical Campus, Department of Cell and Developmental Biology, Aurora, Colorado, United States
| | - Juliet T. Gopinath
- University of Colorado Boulder, Department of Electrical, Computer, and Energy Engineering, Boulder, Colorado, United States
- University of Colorado Boulder, Department of Physics, Boulder, Colorado, United States
| | - Mark E. Siemens
- University of Denver, Department of Physics and Astronomy, Denver, Colorado, United States
| | - Diego Restrepo
- University of Colorado Anschutz Medical Campus, Department of Cell and Developmental Biology, Aurora, Colorado, United States
| | - Emily A. Gibson
- University of Colorado Anschutz Medical Campus, Department of Bioengineering, Aurora, Colorado, United States
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2
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Weiss LE, Love JF, Yoon J, Comerci CJ, Milenkovic L, Kanie T, Jackson PK, Stearns T, Gustavsson AK. Single-molecule imaging in the primary cilium. Methods Cell Biol 2023; 176:59-83. [PMID: 37164543 PMCID: PMC10509820 DOI: 10.1016/bs.mcb.2023.01.003] [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: 02/26/2023]
Abstract
The primary cilium is an important signaling organelle critical for normal development and tissue homeostasis. Its small dimensions and complexity necessitate advanced imaging approaches to uncover the molecular mechanisms behind its function. Here, we outline how single-molecule fluorescence microscopy can be used for tracking molecular dynamics and interactions and for super-resolution imaging of nanoscale structures in the primary cilium. Specifically, we describe in detail how to capture and quantify the 2D dynamics of individual transmembrane proteins PTCH1 and SMO and how to map the 3D nanoscale distributions of the inversin compartment proteins INVS, ANKS6, and NPHP3. This protocol can, with minor modifications, be adapted for studies of other proteins and cell lines to further elucidate the structure and function of the primary cilium at the molecular level.
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Affiliation(s)
- Lucien E Weiss
- Department of Engineering Physics, Polytechnique Montréal, Montreal, QC, Canada.
| | - Julia F Love
- Department of Chemistry, Rice University, Houston, TX, United States
| | | | - Colin J Comerci
- Division of Biological Sciences, University of California San Diego, La Jolla, CA, United States
| | | | - Tomoharu Kanie
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma, OK, United States
| | - Peter K Jackson
- Baxter Laboratory, Department of Microbiology & Immunology, Stanford University School of Medicine, Stanford, CA, United States; Department of Pathology, Stanford University School of Medicine, Stanford, CA, United States
| | - Tim Stearns
- Department of Biology, Stanford University, Stanford, CA, United States; Rockefeller University, New York City, NY, United States
| | - Anna-Karin Gustavsson
- Department of Chemistry, Rice University, Houston, TX, United States; Department of BioSciences, Rice University, Houston, TX, United States; Institute of Biosciences and Bioengineering, Rice University, Houston, TX, United States; Smalley-Curl Institute, Rice University, Houston, TX, United States.
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3
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de Moliner F, Konieczna Z, Mendive-Tapia L, Saleeb RS, Morris K, Gonzalez-Vera JA, Kaizuka T, Grant SGN, Horrocks MH, Vendrell M. Small Fluorogenic Amino Acids for Peptide-Guided Background-Free Imaging. Angew Chem Int Ed Engl 2023; 62:e202216231. [PMID: 36412996 PMCID: PMC10108274 DOI: 10.1002/anie.202216231] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2022] [Revised: 11/21/2022] [Accepted: 11/22/2022] [Indexed: 11/23/2022]
Abstract
The multiple applications of super-resolution microscopy have prompted the need for minimally invasive labeling strategies for peptide-guided fluorescence imaging. Many fluorescent reporters display limitations (e.g., large and charged scaffolds, non-specific binding) as building blocks for the construction of fluorogenic peptides. Herein we have built a library of benzodiazole amino acids and systematically examined them as reporters for background-free fluorescence microscopy. We have identified amine-derivatized benzoselenadiazoles as scalable and photostable amino acids for the straightforward solid-phase synthesis of fluorescent peptides. Benzodiazole amino acids retain the binding capabilities of bioactive peptides and display excellent signal-to-background ratios. Furthermore, we have demonstrated their application in peptide-PAINT imaging of postsynaptic density protein-95 nanoclusters in the synaptosomes from mouse brain tissues.
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Affiliation(s)
- Fabio de Moliner
- Centre for Inflammation Research, The University of Edinburgh, UK
| | | | | | | | - Katie Morris
- EaStCHEM School of Chemistry, The University of Edinburgh, UK
| | | | - Takeshi Kaizuka
- Centre for Clinical Brain Sciences, The University of Edinburgh, UK
| | - Seth G N Grant
- Centre for Clinical Brain Sciences, The University of Edinburgh, UK
| | | | - Marc Vendrell
- Centre for Inflammation Research, The University of Edinburgh, UK
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4
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de Moliner F, Konieczna Z, Mendive‐Tapia L, Saleeb RS, Morris K, Gonzalez‐Vera JA, Kaizuka T, Grant SGN, Horrocks MH, Vendrell M. Small Fluorogenic Amino Acids for Peptide-Guided Background-Free Imaging. ANGEWANDTE CHEMIE (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2023; 135:e202216231. [PMID: 38515539 PMCID: PMC10952862 DOI: 10.1002/ange.202216231] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/03/2022] [Indexed: 11/23/2022]
Abstract
The multiple applications of super-resolution microscopy have prompted the need for minimally invasive labeling strategies for peptide-guided fluorescence imaging. Many fluorescent reporters display limitations (e.g., large and charged scaffolds, non-specific binding) as building blocks for the construction of fluorogenic peptides. Herein we have built a library of benzodiazole amino acids and systematically examined them as reporters for background-free fluorescence microscopy. We have identified amine-derivatized benzoselenadiazoles as scalable and photostable amino acids for the straightforward solid-phase synthesis of fluorescent peptides. Benzodiazole amino acids retain the binding capabilities of bioactive peptides and display excellent signal-to-background ratios. Furthermore, we have demonstrated their application in peptide-PAINT imaging of postsynaptic density protein-95 nanoclusters in the synaptosomes from mouse brain tissues.
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Affiliation(s)
| | | | | | | | - Katie Morris
- EaStCHEM School of ChemistryThe University of EdinburghUK
| | | | - Takeshi Kaizuka
- Centre for Clinical Brain SciencesThe University of EdinburghUK
| | | | | | - Marc Vendrell
- Centre for Inflammation ResearchThe University of EdinburghUK
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5
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Soubeyre V, Merle L, Jarriault D, Grégoire S, Bretillon L, Acar N, Grosmaitre X, Le Bon AM. Dietary n-3 polyunsaturated fatty acid deficiency alters olfactory mucosa sensitivity in young mice but has no impact on olfactory behavior. Nutr Neurosci 2022:1-14. [PMID: 35694841 DOI: 10.1080/1028415x.2022.2082642] [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: 10/18/2022]
Abstract
BACKGROUND AND OBJECTIVE We recently showed that perinatal exposure to diets with unbalanced n-6:n-3 polyunsaturated fatty acid (PUFA) ratios affects the olfactory mucosa (OM) fatty acid composition. To assess the repercussions of these modifications, we investigated the impact of diets unbalanced in n-3 PUFAs on the molecular composition and functionality of the OM in young mice. METHODS After mating, female mice were fed diets either deficient in α-linolenic acid (LOW diet) or supplemented with n-3 long-chain PUFAs (HIGH diet) during the perinatal period. Weaned male offspring were then fed ad libitum with the same experimental diets for 5 weeks. At 8 weeks of age, olfactory behavior tests were performed in young mice. The fatty acid composition of OM and olfactory cilia, as well as the expression of genes involved in different cellular pathways, were analyzed. The electroolfactograms induced by odorant stimuli were recorded to assess the impact of diets on OM functionality. RESULTS AND CONCLUSION Both diets significantly modified the fatty acid profiles of OM and olfactory cilia in young mice. They also induced changes in the expression of genes involved in olfactory signaling and in olfactory neuron maturation. The electroolfactogram amplitudes were reduced in mice fed the LOW diet. Nevertheless, the LOW diet and the HIGH diet did not affect mouse olfactory behavior. Our study demonstrated that consumption of diets deficient in or supplemented with n-3 PUFAs during the perinatal and postweaning periods caused significant changes in young mouse OM. However, these modifications did not impair their olfactory capacities.
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Affiliation(s)
- Vanessa Soubeyre
- Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS UMR-5203, INSERM U1091, Montpellier, France
| | - Laetitia Merle
- Centre des Sciences du Goût et de l'Alimentation, AgroSup Dijon, CNRS, INRAE, Université Bourgogne Franche-Comté, Dijon, France
| | - David Jarriault
- NutriNeuro, UMR 1286 INRAE, Bordeaux INP, Université de Bordeaux, Bordeaux, France
| | - Stéphane Grégoire
- Centre des Sciences du Goût et de l'Alimentation, AgroSup Dijon, CNRS, INRAE, Université Bourgogne Franche-Comté, Dijon, France
| | - Lionel Bretillon
- Centre des Sciences du Goût et de l'Alimentation, AgroSup Dijon, CNRS, INRAE, Université Bourgogne Franche-Comté, Dijon, France
| | - Niyazi Acar
- Centre des Sciences du Goût et de l'Alimentation, AgroSup Dijon, CNRS, INRAE, Université Bourgogne Franche-Comté, Dijon, France
| | - Xavier Grosmaitre
- Centre des Sciences du Goût et de l'Alimentation, AgroSup Dijon, CNRS, INRAE, Université Bourgogne Franche-Comté, Dijon, France
| | - Anne Marie Le Bon
- Centre des Sciences du Goût et de l'Alimentation, AgroSup Dijon, CNRS, INRAE, Université Bourgogne Franche-Comté, Dijon, France
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6
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Kinetics of Odorant Recognition with a Graphene-Based Olfactory Receptor Mimicry. CHEMOSENSORS 2022. [DOI: 10.3390/chemosensors10060203] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Malaria vector mosquito species rely on a handful of specific pheromones for mating; one of them, sulcatone (6-methyl-5-hepten-2-one), is also found in human exudation. Therefore, a complete understanding of the insect’s olfaction, and rapid real-time methods for odorant detection, are required. Here, we mimic the odorant recognition of the nerve cells of an insect’s antenna with a synthetic graphene-based bio-electro-interfacial odorant receptor. By this means, we obtain the kinetics of the genuine odorant recognition reaction and compare them to electro-antennogram data that represent the more complex scenario of a living insect. The odorant-binding proteins OBP 9A and 9B only associate with their ligands weakly, showing KDs of between 2.1 mM and 3 mM, while the binding kinetics of OBP proteins depend on the structural feature of a cystine knot and are modulated by the local milieu within a protein-aided enhancement zone.
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7
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Crosby KC, Gookin SE, Garcia JD, Hahm KM, Dell'Acqua ML, Smith KR. Nanoscale Subsynaptic Domains Underlie the Organization of the Inhibitory Synapse. Cell Rep 2020; 26:3284-3297.e3. [PMID: 30893601 DOI: 10.1016/j.celrep.2019.02.070] [Citation(s) in RCA: 69] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2018] [Revised: 01/03/2019] [Accepted: 02/19/2019] [Indexed: 12/15/2022] Open
Abstract
Inhibitory synapses mediate the majority of synaptic inhibition in the brain, thereby controlling neuronal excitability, firing, and plasticity. Although essential for neuronal function, the central question of how these synapses are organized at the subsynaptic level remains unanswered. Here, we use three-dimensional (3D) super-resolution microscopy to image key components of the inhibitory postsynaptic domain and presynaptic terminal, revealing that inhibitory synapses are organized into nanoscale subsynaptic domains (SSDs) of the gephyrin scaffold, GABAARs and the active-zone protein Rab3-interacting molecule (RIM). Gephyrin SSDs cluster GABAAR SSDs, demonstrating nanoscale architectural interdependence between scaffold and receptor. GABAAR SSDs strongly associate with active-zone RIM SSDs, indicating an important role for GABAAR nanoscale organization near sites of GABA release. Finally, we find that in response to elevated activity, synapse growth is mediated by an increase in the number of postsynaptic SSDs, suggesting a modular mechanism for increasing inhibitory synaptic strength.
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Affiliation(s)
- Kevin C Crosby
- Department of Pharmacology, University of Colorado School of Medicine, Aurora, CO 80045, USA
| | - Sara E Gookin
- Department of Pharmacology, University of Colorado School of Medicine, Aurora, CO 80045, USA
| | - Joshua D Garcia
- Department of Pharmacology, University of Colorado School of Medicine, Aurora, CO 80045, USA
| | - Katlin M Hahm
- Department of Pharmacology, University of Colorado School of Medicine, Aurora, CO 80045, USA
| | - Mark L Dell'Acqua
- Department of Pharmacology, University of Colorado School of Medicine, Aurora, CO 80045, USA
| | - Katharine R Smith
- Department of Pharmacology, University of Colorado School of Medicine, Aurora, CO 80045, USA.
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8
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Cramer K, Bolender AL, Stockmar I, Jungmann R, Kasper R, Shin JY. Visualization of Bacterial Protein Complexes Labeled with Fluorescent Proteins and Nanobody Binders for STED Microscopy. Int J Mol Sci 2019; 20:ijms20143376. [PMID: 31295803 PMCID: PMC6678925 DOI: 10.3390/ijms20143376] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2019] [Revised: 07/05/2019] [Accepted: 07/08/2019] [Indexed: 12/18/2022] Open
Abstract
In situ visualization of molecular assemblies near their macromolecular scale is a powerful tool to investigate fundamental cellular processes. Super-resolution light microscopies (SRM) overcome the diffraction limit and allow researchers to investigate molecular arrangements at the nanoscale. However, in bacterial cells, visualization of these assemblies can be challenging because of their small size and the presence of the cell wall. Thus, although conceptually promising, successful application of SRM techniques requires careful optimization in labeling biochemistry, fluorescent dye choice, bacterial biology and microscopy to gain biological insights. Here, we apply Stimulated Emission Depletion (STED) microscopy to visualize cell division proteins in bacterial cells, specifically E. coli and B. subtilis. We applied nanobodies that specifically recognize fluorescent proteins, such as GFP, mCherry2 and PAmCherry, fused to targets for STED imaging and evaluated the effect of various organic fluorescent dyes on the performance of STED in bacterial cells. We expect this research to guide scientists for in situ macromolecular visualization using STED in bacterial systems.
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Affiliation(s)
- Kimberly Cramer
- Max Plank Institute of Biochemistry, 82152 Martinsried, 82152 Munich, Germany
- Faculty of Physics and Center for Nanoscience, Ludwig Maximilian University, 80539 Munich, Germany
| | - Anna-Lena Bolender
- Max Plank Institute of Neurobiology, 82152 Martinsried, 82152 Munich, Germany
| | - Iris Stockmar
- Max Plank Institute of Biochemistry, 82152 Martinsried, 82152 Munich, Germany
- Faculty of Physics and Center for Nanoscience, Ludwig Maximilian University, 80539 Munich, Germany
| | - Ralf Jungmann
- Max Plank Institute of Biochemistry, 82152 Martinsried, 82152 Munich, Germany
- Faculty of Physics and Center for Nanoscience, Ludwig Maximilian University, 80539 Munich, Germany
| | - Robert Kasper
- Max Plank Institute of Neurobiology, 82152 Martinsried, 82152 Munich, Germany.
| | - Jae Yen Shin
- Max Plank Institute of Biochemistry, 82152 Martinsried, 82152 Munich, Germany.
- Faculty of Physics and Center for Nanoscience, Ludwig Maximilian University, 80539 Munich, Germany.
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9
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Zhang C. Calcium Imaging of Individual Olfactory Sensory Neurons from Intact Olfactory Turbinates. Methods Mol Biol 2019; 1820:57-68. [PMID: 29884937 DOI: 10.1007/978-1-4939-8609-5_5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/07/2023]
Abstract
The olfactory epithelium is an extremely functionally diversified organ. Scattered distribution of over 1000 different types of olfactory sensory neurons (OSNs) and concha structures of mouse olfactory turbinates have greatly increased technical difficulties in research and limited applicability of certain methods. We have developed a method to monitor intracellular calcium transients of individual OSNs from intact olfactory turbinates. With this method, it becomes feasible to locate OSNs of the same specificity from preparation to preparation based on anatomical landmarks of olfactory turbinates, zonal distribution patterns of OSNs, and neuronal response characteristics. This preparation is steady under perfusion, which largely minimizes artifacts. Since this method does not involve enzymatic digestions or mechanic tearing and chopping, the preparation gives OSNs an environment close to in vivo physiological conditions. This approach has provided a platform for studying interaction between OSNs or modulations of OSN activity by other epithelial cells.
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10
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Purkey AM, Woolfrey KM, Crosby KC, Stich DG, Chick WS, Aoto J, Dell'Acqua ML. AKAP150 Palmitoylation Regulates Synaptic Incorporation of Ca 2+-Permeable AMPA Receptors to Control LTP. Cell Rep 2018; 25:974-987.e4. [PMID: 30355502 PMCID: PMC6263960 DOI: 10.1016/j.celrep.2018.09.085] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2018] [Revised: 09/06/2018] [Accepted: 09/25/2018] [Indexed: 11/22/2022] Open
Abstract
Ca2+-permeable AMPA-type glutamate receptors (CP-AMPARs) containing GluA1 but lacking GluA2 subunits contribute to multiple forms of synaptic plasticity, including long-term potentiation (LTP), but mechanisms regulating CP-AMPARs are poorly understood. A-kinase anchoring protein (AKAP) 150 scaffolds kinases and phosphatases to regulate GluA1 phosphorylation and trafficking, and trafficking of AKAP150 itself is modulated by palmitoylation on two Cys residues. Here, we developed a palmitoylation-deficient knockin mouse to show that AKAP150 palmitoylation regulates CP-AMPAR incorporation at hippocampal synapses. Using biochemical, super-resolution imaging, and electrophysiological approaches, we found that palmitoylation promotes AKAP150 localization to recycling endosomes and the postsynaptic density (PSD) to limit CP-AMPAR basal synaptic incorporation. In addition, we found that AKAP150 palmitoylation is required for LTP induced by weaker stimulation that recruits CP-AMPARs to synapses but not stronger stimulation that recruits GluA2-containing AMPARs. Thus, AKAP150 palmitoylation controls its subcellular localization to maintain proper basal and activity-dependent regulation of synaptic AMPAR subunit composition.
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Affiliation(s)
- Alicia M Purkey
- Department of Pharmacology, University of Colorado School of Medicine, Aurora, CO 80045, USA
| | - Kevin M Woolfrey
- Department of Pharmacology, University of Colorado School of Medicine, Aurora, CO 80045, USA
| | - Kevin C Crosby
- Department of Pharmacology, University of Colorado School of Medicine, Aurora, CO 80045, USA
| | - Dominik G Stich
- Advanced Light Microscopy Core, University of Colorado School of Medicine, Aurora, CO 80045, USA
| | - Wallace S Chick
- Department of Cell and Developmental Biology, University of Colorado School of Medicine, Aurora, CO 80045, USA
| | - Jason Aoto
- Department of Pharmacology, University of Colorado School of Medicine, Aurora, CO 80045, USA
| | - Mark L Dell'Acqua
- Department of Pharmacology, University of Colorado School of Medicine, Aurora, CO 80045, USA; Advanced Light Microscopy Core, University of Colorado School of Medicine, Aurora, CO 80045, USA.
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11
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Tai JSB, Smalyukh II. Super-resolution stimulated emission depletion microscopy of director structures in liquid crystals. OPTICS LETTERS 2018; 43:5158-5161. [PMID: 30320844 DOI: 10.1364/ol.43.005158] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/24/2018] [Accepted: 09/24/2018] [Indexed: 06/08/2023]
Abstract
Extending the optical imaging of director structures in liquid crystals (LCs) beyond the diffraction limit is poised to provide insights into previously elusive LC physics at the nanoscale. Here, we develop and characterize super-resolution stimulated emission depletion microscopy with molecular orientation sensitivity and apply it to reveal spatially localized director structures in chiral nematic and smectic LCs. As examples, we demonstrate director imaging and reconstruction of nanoscale LC configurations, including solitonic Bloch walls and two-dimensional skyrmions, both observed in sub-micrometer-thick strongly confined LC films, and focal conic domains in smectic LCs. The ≲100 nm resolution of our orientation-resolved STED imaging is three times better than that of fluorescence confocal polarizing microscopy and polarized nonlinear imaging techniques, but can be potentially improved even further.
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12
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Bowen AB, Bourke AM, Hiester BG, Hanus C, Kennedy MJ. Golgi-independent secretory trafficking through recycling endosomes in neuronal dendrites and spines. eLife 2017; 6:27362. [PMID: 28875935 PMCID: PMC5624785 DOI: 10.7554/elife.27362] [Citation(s) in RCA: 76] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2017] [Accepted: 08/30/2017] [Indexed: 12/13/2022] Open
Abstract
Neurons face the challenge of regulating the abundance, distribution and repertoire of integral membrane proteins within their immense, architecturally complex dendritic arbors. While the endoplasmic reticulum (ER) supports dendritic translation, most dendrites lack the Golgi apparatus (GA), an essential organelle for conventional secretory trafficking. Thus, whether secretory cargo is locally trafficked in dendrites through a non-canonical pathway remains a fundamental question. Here we define the dendritic trafficking itinerary for key synaptic molecules in rat cortical neurons. Following ER exit, the AMPA-type glutamate receptor GluA1 and neuroligin 1 undergo spatially restricted entry into the dendritic secretory pathway and accumulate in recycling endosomes (REs) located in dendrites and spines before reaching the plasma membrane. Surprisingly, GluA1 surface delivery occurred even when GA function was disrupted. Thus, in addition to their canonical role in protein recycling, REs also mediate forward secretory trafficking in neuronal dendrites and spines through a specialized GA-independent trafficking network. All cells must produce, sort and deliver molecular building blocks to the right places at the right time and in appropriate amounts. This is particularly important for neurons, which are the largest and most structurally complex cells in the body. A typical neuron consists of a cell body covered in branches called dendrites, plus a single cable-like structure known as an axon. Dendrites receive inputs from other neurons and relay the information to the cell body in the form of electrical signals. The cell body processes these electrical signals and the resulting signals then travel along the axon to terminals at the far-end. The axon terminals in turn pass the signals on to the dendrites of other neurons via junctions called synapses. For synapses to work correctly, the membranes surrounding the dendrites need to contain receptor proteins that can detect incoming signals. These proteins must be continually replenished, raising the question of how newly made receptor molecules are shuttled to the appropriate locations within the dendrites. A series of compartments called the Golgi complex play an important role in processing newly-made proteins in many different types of cells. As proteins pass through the Golgi, enzymes within the tunnel walls modify the proteins by adding or removing molecular groups. Therefore, it has been suggested that the route that the synapse receptor proteins take through the neuron to reach the dendrites always includes a visit to the Golgi. However, the Golgi complex in neurons is mostly confined to the cell body, raising the question of whether proteins that are locally produced within dendrites can make the journey to nearby synapses without visiting the Golgi complex. Bowen et al. used a microscope to follow the movements of synapse receptor proteins through neurons grown in a dish. The experiments show that proteins destined for the dendrites make a number of stops after leaving the cell body. However, some synaptic proteins reach the dendrites without passing through the Golgi at all, suggesting neurons are much less dependent on the Golgi to process newly-made proteins than other types of cells. Genetic mutations that prevent proteins from finding their way to their required destinations, or that disrupt the work of enzymes inside trafficking stations like the Golgi, cause numerous human diseases. Understanding how proteins travel to specific destinations inside healthy cells should also help reveal what happens when this process fails.
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Affiliation(s)
- Aaron B Bowen
- Department of Pharmacology, University of Colorado School of Medicine, Aurora, United States
| | - Ashley M Bourke
- Department of Pharmacology, University of Colorado School of Medicine, Aurora, United States
| | - Brian G Hiester
- Department of Pharmacology, University of Colorado School of Medicine, Aurora, United States
| | - Cyril Hanus
- Center for Psychiatry and Neurosciences, University Paris-Descartes, Paris, France
| | - Matthew J Kennedy
- Department of Pharmacology, University of Colorado School of Medicine, Aurora, United States
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13
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Soltys JN, Meyer SA, Schumann H, Gibson EA, Restrepo D, Bennett JL. Determining the Spatial Relationship of Membrane-Bound Aquaporin-4 Autoantibodies by STED Nanoscopy. Biophys J 2017; 112:1692-1702. [PMID: 28445760 DOI: 10.1016/j.bpj.2017.03.012] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2016] [Revised: 03/07/2017] [Accepted: 03/15/2017] [Indexed: 02/05/2023] Open
Abstract
Determining the spatial relationship of individual proteins in dense assemblies remains a challenge for superresolution nanoscopy. The organization of aquaporin-4 (AQP4) into large plasma membrane assemblies provides an opportunity to image membrane-bound AQP4 antibodies (AQP4-IgG) and evaluate changes in their spatial distribution due to alterations in AQP4 isoform expression and AQP4-IgG epitope specificity. Using stimulated emission depletion nanoscopy, we imaged secondary antibody labeling of monoclonal AQP4-IgGs with differing epitope specificity bound to isolated tetramers (M1-AQP4) and large orthogonal arrays of AQP4 (M23-AQP4). Imaging secondary antibodies bound to M1-AQP4 allowed us to infer the size of individual AQP4-IgG binding events. This information was used to model the assembly of larger AQP4-IgG complexes on M23-AQP4 arrays. A scoring algorithm was generated from these models to characterize the spatial arrangement of bound AQP4-IgG antibodies, yielding multiple epitope-specific patterns of bound antibodies on M23-AQP4 arrays. Our results delineate an approach to infer spatial relationships within protein arrays using stimulated emission depletion nanoscopy, offering insight into how information on single antibody fluorescence events can be used to extract information from dense protein assemblies under a biologic context.
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Affiliation(s)
- John N Soltys
- Medical Scientist Training and Neuroscience Graduate Training Programs, University of Colorado Anschutz Medical Campus, Aurora, Colorado
| | - Stephanie A Meyer
- Department of Bioengineering, University of Colorado Anschutz Medical Campus, Aurora, Colorado
| | - Hannah Schumann
- Department of Neurology, University of Colorado Anschutz Medical Campus, Aurora, Colorado
| | - Emily A Gibson
- Department of Bioengineering, University of Colorado Anschutz Medical Campus, Aurora, Colorado
| | - Diego Restrepo
- Department of Cell and Developmental Biology, University of Colorado Anschutz Medical Campus, Aurora, Colorado
| | - Jeffrey L Bennett
- Department of Neurology, University of Colorado Anschutz Medical Campus, Aurora, Colorado; Department of Ophthalmology, University of Colorado Anschutz Medical Campus, Aurora, Colorado.
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