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Gur D, Bain EJ, Johnson KR, Aman AJ, Pasoili HA, Flynn JD, Allen MC, Deheyn DD, Lee JC, Lippincott-Schwartz J, Parichy DM. In situ differentiation of iridophore crystallotypes underlies zebrafish stripe patterning. Nat Commun 2020; 11:6391. [PMID: 33319779 PMCID: PMC7738553 DOI: 10.1038/s41467-020-20088-1] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2020] [Accepted: 11/06/2020] [Indexed: 02/06/2023] Open
Abstract
Skin color patterns are ubiquitous in nature, impact social behavior, predator avoidance, and protection from ultraviolet irradiation. A leading model system for vertebrate skin patterning is the zebrafish; its alternating blue stripes and yellow interstripes depend on light-reflecting cells called iridophores. It was suggested that the zebrafish’s color pattern arises from a single type of iridophore migrating differentially to stripes and interstripes. However, here we find that iridophores do not migrate between stripes and interstripes but instead differentiate and proliferate in-place, based on their micro-environment. RNA-sequencing analysis further reveals that stripe and interstripe iridophores have different transcriptomic states, while cryogenic-scanning-electron-microscopy and micro-X-ray diffraction identify different crystal-arrays architectures, indicating that stripe and interstripe iridophores are different cell types. Based on these results, we present an alternative model of skin patterning in zebrafish in which distinct iridophore crystallotypes containing specialized, physiologically responsive, organelles arise in stripe and interstripe by in-situ differentiation. The skin of zebrafish is patterned by alternating blue stripes and yellow interstripes which arises from guanine crystal-containing cells called iridophores that reflect light. Here the authors track iridophores and see that they do not migrate between stripes and interstripes, but instead differentiate and proliferate in place based on their micro-environment.
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Lippincott-Schwartz J. The evolution of a cell biologist. Mol Biol Cell 2020; 31:2763-2767. [PMID: 33253077 PMCID: PMC7851866 DOI: 10.1091/mbc.e20-09-0603] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
I am honored and humbled to receive the E. B. Wilson Medal and happy to share some reflections on my journey as a cell biologist. It took me a while to realize that my interest in biology would center on how cells are spatially and dynamically organized. From an initial fascination with cellular structures I came to appreciate that cells exhibit dynamism across all scales-from their molecules, to molecular complexes, to organelles. Uncovering the principles of this dynamism, including new ways to observe and quantify it, has been the guiding star of my work.
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Omari S, Makareeva E, Gorrell L, Jarnik M, Lippincott-Schwartz J, Leikin S. Mechanisms of procollagen and HSP47 sorting during ER-to-Golgi trafficking. Matrix Biol 2020; 93:79-94. [DOI: 10.1016/j.matbio.2020.06.002] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2020] [Revised: 06/08/2020] [Accepted: 06/09/2020] [Indexed: 12/27/2022]
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Zheng Q, Ayala AX, Chung I, Weigel AV, Ranjan A, Falco N, Grimm JB, Tkachuk AN, Wu C, Lippincott-Schwartz J, Singer RH, Lavis LD. Correction to Rational Design of Fluorogenic and Spontaneously Blinking Labels for Super-Resolution Imaging. ACS CENTRAL SCIENCE 2020; 6:1844. [PMID: 33145421 PMCID: PMC7596852 DOI: 10.1021/acscentsci.0c01119] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/20/2020] [Indexed: 06/11/2023]
Abstract
[This corrects the article DOI: 10.1021/acscentsci.9b00676.].
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Sengupta P, Lippincott-Schwartz J. Revisiting Membrane Microdomains and Phase Separation: A Viral Perspective. Viruses 2020; 12:v12070745. [PMID: 32664429 PMCID: PMC7412473 DOI: 10.3390/v12070745] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2020] [Revised: 06/29/2020] [Accepted: 07/07/2020] [Indexed: 12/11/2022] Open
Abstract
Retroviruses selectively incorporate a specific subset of host cell proteins and lipids into their outer membrane when they bud out from the host plasma membrane. This specialized viral membrane composition is critical for both viral survivability and infectivity. Here, we review recent findings from live cell imaging of single virus assembly demonstrating that proteins and lipids sort into the HIV retroviral membrane by a mechanism of lipid-based phase partitioning. The findings showed that multimerizing HIV Gag at the assembly site creates a liquid-ordered lipid phase enriched in cholesterol and sphingolipids. Proteins with affinity for this specialized lipid environment partition into it, resulting in the selective incorporation of proteins into the nascent viral membrane. Building on this and other work in the field, we propose a model describing how HIV Gag induces phase separation of the viral assembly site through a mechanism involving transbilayer coupling of lipid acyl chains and membrane curvature changes. Similar phase-partitioning pathways in response to multimerizing structural proteins likely help sort proteins into the membranes of other budding structures within cells.
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Ioannou MS, Liu Z, Lippincott-Schwartz J. A Neuron-Glia Co-culture System for Studying Intercellular Lipid Transport. ACTA ACUST UNITED AC 2020; 84:e95. [PMID: 31483110 PMCID: PMC9285924 DOI: 10.1002/cpcb.95] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Neurons and glia operate in a highly coordinated fashion in the brain. Although glial cells have long been known to supply lipids to neurons via lipoprotein particles, new evidence reveals that lipid transport between neurons and glia is bidirectional. Here, we describe a co‐culture system to study transfer of lipids and lipid‐associated proteins from neurons to glia. The assay entails culturing neurons and glia on separate coverslips, pulsing the neurons with fluorescently labeled fatty acids, and then incubating the coverslips together. As astrocytes internalize and store neuron‐derived fatty acids in lipid droplets, analyzing the number, size, and fluorescence intensity of lipid droplets containing the fluorescent fatty acids provides an easy and quantifiable measure of fatty acid transport. © 2019 The Authors.
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Hoffman DP, Shtengel G, Xu CS, Campbell KR, Freeman M, Wang L, Milkie DE, Pasolli HA, Iyer N, Bogovic JA, Stabley DR, Shirinifard A, Pang S, Peale D, Schaefer K, Pomp W, Chang CL, Lippincott-Schwartz J, Kirchhausen T, Solecki DJ, Betzig E, Hess HF. Correlative three-dimensional super-resolution and block-face electron microscopy of whole vitreously frozen cells. Science 2020; 367:eaaz5357. [PMID: 31949053 PMCID: PMC7339343 DOI: 10.1126/science.aaz5357] [Citation(s) in RCA: 197] [Impact Index Per Article: 49.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2019] [Accepted: 11/20/2019] [Indexed: 12/27/2022]
Abstract
Within cells, the spatial compartmentalization of thousands of distinct proteins serves a multitude of diverse biochemical needs. Correlative super-resolution (SR) fluorescence and electron microscopy (EM) can elucidate protein spatial relationships to global ultrastructure, but has suffered from tradeoffs of structure preservation, fluorescence retention, resolution, and field of view. We developed a platform for three-dimensional cryogenic SR and focused ion beam-milled block-face EM across entire vitreously frozen cells. The approach preserves ultrastructure while enabling independent SR and EM workflow optimization. We discovered unexpected protein-ultrastructure relationships in mammalian cells including intranuclear vesicles containing endoplasmic reticulum-associated proteins, web-like adhesions between cultured neurons, and chromatin domains subclassified on the basis of transcriptional activity. Our findings illustrate the value of a comprehensive multimodal view of ultrastructural variability across whole cells.
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Boyken SE, Benhaim MA, Busch F, Jia M, Bick MJ, Choi H, Klima JC, Chen Z, Walkey C, Mileant A, Sahasrabuddhe A, Wei KY, Hodge EA, Byron S, Quijano-Rubio A, Sankaran B, King NP, Lippincott-Schwartz J, Wysocki VH, Lee KK, Baker D. De novo design of tunable, pH-driven conformational changes. Science 2019; 364:658-664. [PMID: 31097662 DOI: 10.1126/science.aav7897] [Citation(s) in RCA: 85] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2018] [Accepted: 04/24/2019] [Indexed: 01/03/2023]
Abstract
The ability of naturally occurring proteins to change conformation in response to environmental changes is critical to biological function. Although there have been advances in the de novo design of stable proteins with a single, deep free-energy minimum, the design of conformational switches remains challenging. We present a general strategy to design pH-responsive protein conformational changes by precisely preorganizing histidine residues in buried hydrogen-bond networks. We design homotrimers and heterodimers that are stable above pH 6.5 but undergo cooperative, large-scale conformational changes when the pH is lowered and electrostatic and steric repulsion builds up as the network histidine residues become protonated. The transition pH and cooperativity can be controlled through the number of histidine-containing networks and the strength of the surrounding hydrophobic interactions. Upon disassembly, the designed proteins disrupt lipid membranes both in vitro and after being endocytosed in mammalian cells. Our results demonstrate that environmentally triggered conformational changes can now be programmed by de novo protein design.
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Cai D, Feliciano D, Dong P, Flores E, Gruebele M, Porat-Shliom N, Sukenik S, Liu Z, Lippincott-Schwartz J. Phase separation of YAP reorganizes genome topology for long-term YAP target gene expression. Nat Cell Biol 2019; 21:1578-1589. [PMID: 31792379 PMCID: PMC8259329 DOI: 10.1038/s41556-019-0433-z] [Citation(s) in RCA: 206] [Impact Index Per Article: 41.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2018] [Accepted: 10/30/2019] [Indexed: 12/21/2022]
Abstract
Yes-associated Protein (YAP) is a transcriptional co-activator that regulates cell proliferation and survival by binding to a select set of enhancers for target gene activation. How YAP coordinates these transcriptional responses is unknown. Here, we demonstrate that YAP forms liquid-like condensates in the nucleus. Formed within seconds of hyperosmotic stress, YAP condensates compartmentalized YAP’s transcription factor TEAD1 and other YAP-related co-activators, including TAZ, and subsequently induced transcription of YAP-specific proliferation genes. Super-resolution imaging using Assay for Transposase Accessible Chromatin with photoactivated localization microscopy (ATAC-PALM) revealed that YAP nuclear condensates were areas enriched in accessible chromatin domains organized as super-enhancers. Initially devoid of RNA Polymerase II (RNAPII), the accessible chromatin domains later acquired RNAPII, transcribing RNA. Removal of YAP’s intrinsically-disordered transcription activation domain (TAD) prevented YAP condensate formation and diminished downstream YAP signaling. Thus, dynamic changes in genome organization and gene activation during YAP reprogramming is mediated by liquid-liquid phase separation.
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Zheng Q, Ayala AX, Chung I, Weigel AV, Ranjan A, Falco N, Grimm JB, Tkachuk AN, Wu C, Lippincott-Schwartz J, Singer RH, Lavis LD. Rational Design of Fluorogenic and Spontaneously Blinking Labels for Super-Resolution Imaging. ACS CENTRAL SCIENCE 2019; 5:1602-1613. [PMID: 31572787 PMCID: PMC6764213 DOI: 10.1021/acscentsci.9b00676] [Citation(s) in RCA: 122] [Impact Index Per Article: 24.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/09/2019] [Indexed: 05/24/2023]
Abstract
Rhodamine dyes exist in equilibrium between a fluorescent zwitterion and a nonfluorescent lactone. Tuning this equilibrium toward the nonfluorescent lactone form can improve cell-permeability and allow creation of "fluorogenic" compounds-ligands that shift to the fluorescent zwitterion upon binding a biomolecular target. An archetype fluorogenic dye is the far-red tetramethyl-Si-rhodamine (SiR), which has been used to create exceptionally useful labels for advanced microscopy. Here, we develop a quantitative framework for the development of new fluorogenic dyes, determining that the lactone-zwitterion equilibrium constant (K L-Z) is sufficient to predict fluorogenicity. This rubric emerged from our analysis of known fluorophores and yielded new fluorescent and fluorogenic labels with improved performance in cellular imaging experiments. We then designed a novel fluorophore-Janelia Fluor 526 (JF526)-with SiR-like properties but shorter fluorescence excitation and emission wavelengths. JF526 is a versatile scaffold for fluorogenic probes including ligands for self-labeling tags, stains for endogenous structures, and spontaneously blinking labels for super-resolution immunofluorescence. JF526 constitutes a new label for advanced microscopy experiments, and our quantitative framework will enable the rational design of other fluorogenic probes for bioimaging.
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Liao YC, Fernandopulle MS, Wang G, Choi H, Hao L, Drerup CM, Patel R, Qamar S, Nixon-Abell J, Shen Y, Meadows W, Vendruscolo M, Knowles TPJ, Nelson M, Czekalska MA, Musteikyte G, Gachechiladze MA, Stephens CA, Pasolli HA, Forrest LR, St George-Hyslop P, Lippincott-Schwartz J, Ward ME. RNA Granules Hitchhike on Lysosomes for Long-Distance Transport, Using Annexin A11 as a Molecular Tether. Cell 2019; 179:147-164.e20. [PMID: 31539493 PMCID: PMC6890474 DOI: 10.1016/j.cell.2019.08.050] [Citation(s) in RCA: 276] [Impact Index Per Article: 55.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2019] [Revised: 05/21/2019] [Accepted: 08/26/2019] [Indexed: 02/06/2023]
Abstract
Long-distance RNA transport enables local protein synthesis at metabolically-active sites distant from the nucleus. This process ensures an appropriate spatial organization of proteins, vital to polarized cells such as neurons. Here, we present a mechanism for RNA transport in which RNA granules "hitchhike" on moving lysosomes. In vitro biophysical modeling, live-cell microscopy, and unbiased proximity labeling proteomics reveal that annexin A11 (ANXA11), an RNA granule-associated phosphoinositide-binding protein, acts as a molecular tether between RNA granules and lysosomes. ANXA11 possesses an N-terminal low complexity domain, facilitating its phase separation into membraneless RNA granules, and a C-terminal membrane binding domain, enabling interactions with lysosomes. RNA granule transport requires ANXA11, and amyotrophic lateral sclerosis (ALS)-associated mutations in ANXA11 impair RNA granule transport by disrupting their interactions with lysosomes. Thus, ANXA11 mediates neuronal RNA transport by tethering RNA granules to actively-transported lysosomes, performing a critical cellular function that is disrupted in ALS.
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Chang CL, Weigel AV, Ioannou MS, Pasolli HA, Xu CS, Peale DR, Shtengel G, Freeman M, Hess HF, Blackstone C, Lippincott-Schwartz J. Spastin tethers lipid droplets to peroxisomes and directs fatty acid trafficking through ESCRT-III. J Cell Biol 2019; 218:2583-2599. [PMID: 31227594 PMCID: PMC6683741 DOI: 10.1083/jcb.201902061] [Citation(s) in RCA: 114] [Impact Index Per Article: 22.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2019] [Revised: 04/29/2019] [Accepted: 05/28/2019] [Indexed: 12/22/2022] Open
Abstract
Lipid droplets (LDs) are neutral lipid storage organelles that transfer lipids to various organelles including peroxisomes. Here, we show that the hereditary spastic paraplegia protein M1 Spastin, a membrane-bound AAA ATPase found on LDs, coordinates fatty acid (FA) trafficking from LDs to peroxisomes through two interrelated mechanisms. First, M1 Spastin forms a tethering complex with peroxisomal ABCD1 to promote LD-peroxisome contact formation. Second, M1 Spastin recruits the membrane-shaping ESCRT-III proteins IST1 and CHMP1B to LDs via its MIT domain to facilitate LD-to-peroxisome FA trafficking, possibly through IST1- and CHMP1B-dependent modifications in LD membrane morphology. Furthermore, LD-to-peroxisome FA trafficking mediated by M1 Spastin is required to relieve LDs of lipid peroxidation. M1 Spastin's dual roles in tethering LDs to peroxisomes and in recruiting ESCRT-III components to LD-peroxisome contact sites for FA trafficking may underlie the pathogenesis of diseases associated with defective FA metabolism in LDs and peroxisomes.
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Lewis VM, Saunders LM, Larson TA, Bain EJ, Sturiale SL, Gur D, Chowdhury S, Flynn JD, Allen MC, Deheyn DD, Lee JC, Simon JA, Lippincott-Schwartz J, Raible DW, Parichy DM. Fate plasticity and reprogramming in genetically distinct populations of Danio leucophores. Proc Natl Acad Sci U S A 2019; 116:11806-11811. [PMID: 31138706 PMCID: PMC6575160 DOI: 10.1073/pnas.1901021116] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Understanding genetic and cellular bases of adult form remains a fundamental goal at the intersection of developmental and evolutionary biology. The skin pigment cells of vertebrates, derived from embryonic neural crest, are a useful system for elucidating mechanisms of fate specification, pattern formation, and how particular phenotypes impact organismal behavior and ecology. In a survey of Danio fishes, including the zebrafish Danio rerio, we identified two populations of white pigment cells-leucophores-one of which arises by transdifferentiation of adult melanophores and another of which develops from a yellow-orange xanthophore or xanthophore-like progenitor. Single-cell transcriptomic, mutational, chemical, and ultrastructural analyses of zebrafish leucophores revealed cell-type-specific chemical compositions, organelle configurations, and genetic requirements. At the organismal level, we identified distinct physiological responses of leucophores during environmental background matching, and we showed that leucophore complement influences behavior. Together, our studies reveal independently arisen pigment cell types and mechanisms of fate acquisition in zebrafish and illustrate how concerted analyses across hierarchical levels can provide insights into phenotypes and their evolution.
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Ioannou MS, Jackson J, Sheu SH, Chang CL, Weigel AV, Liu H, Pasolli HA, Xu CS, Pang S, Matthies D, Hess HF, Lippincott-Schwartz J, Liu Z. Neuron-Astrocyte Metabolic Coupling Protects against Activity-Induced Fatty Acid Toxicity. Cell 2019; 177:1522-1535.e14. [PMID: 31130380 DOI: 10.1016/j.cell.2019.04.001] [Citation(s) in RCA: 325] [Impact Index Per Article: 65.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2018] [Revised: 02/20/2019] [Accepted: 03/28/2019] [Indexed: 01/08/2023]
Abstract
Metabolic coordination between neurons and astrocytes is critical for the health of the brain. However, neuron-astrocyte coupling of lipid metabolism, particularly in response to neural activity, remains largely uncharacterized. Here, we demonstrate that toxic fatty acids (FAs) produced in hyperactive neurons are transferred to astrocytic lipid droplets by ApoE-positive lipid particles. Astrocytes consume the FAs stored in lipid droplets via mitochondrial β-oxidation in response to neuronal activity and turn on a detoxification gene expression program. Our findings reveal that FA metabolism is coupled in neurons and astrocytes to protect neurons from FA toxicity during periods of enhanced activity. This coordinated mechanism for metabolizing FAs could underlie both homeostasis and a variety of disease states of the brain.
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Sengupta P, Seo AY, Pasolli HA, Song YE, Johnson MC, Lippincott-Schwartz J. Author Correction: A lipid-based partitioning mechanism for selective incorporation of proteins into membranes of HIV particles. Nat Cell Biol 2019; 21:662. [PMID: 30971772 DOI: 10.1038/s41556-019-0327-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
In the version of this article originally published, the name of co-author Marc C. Johnson was missing the middle initial. The middle initial 'C.' has been added in the author list as well as in the 'author contributions' section (as M.C.J.). The error has been corrected in the PDF and HTML versions of the paper.
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Arnspang EC, Sengupta P, Mortensen KI, Jensen HH, Hahn U, Jensen EBV, Lippincott-Schwartz J, Nejsum LN. Regulation of Plasma Membrane Nanodomains of the Water Channel Aquaporin-3 Revealed by Fixed and Live Photoactivated Localization Microscopy. NANO LETTERS 2019; 19:699-707. [PMID: 30584808 DOI: 10.1021/acs.nanolett.8b03721] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Several aquaporin (AQP) water channels are short-term regulated by the messenger cyclic adenosine monophosphate (cAMP), including AQP3. Bulk measurements show that cAMP can change diffusive properties of AQP3; however, it remains unknown how elevated cAMP affects AQP3 organization at the nanoscale. Here we analyzed AQP3 nano-organization following cAMP stimulation using photoactivated localization microscopy (PALM) of fixed cells combined with pair correlation analysis. Moreover, in live cells, we combined PALM acquisitions of single fluorophores with single-particle tracking (spt-PALM). These analyses revealed that AQP3 tends to cluster and that the diffusive mobility is confined to nanodomains with radii of ∼150 nm. This domain size increases by ∼30% upon elevation of cAMP, which, however, is not accompanied by a significant increase in the confined diffusion coefficient. This regulation of AQP3 organization at the nanoscale may be important for understanding the mechanisms of water AQP3-mediated water transport across plasma membranes.
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Gao R, Asano SM, Upadhyayula S, Pisarev I, Milkie DE, Liu TL, Singh V, Graves A, Huynh GH, Zhao Y, Bogovic J, Colonell J, Ott CM, Zugates C, Tappan S, Rodriguez A, Mosaliganti KR, Sheu SH, Pasolli HA, Pang S, Xu CS, Megason SG, Hess H, Lippincott-Schwartz J, Hantman A, Rubin GM, Kirchhausen T, Saalfeld S, Aso Y, Boyden ES, Betzig E. Cortical column and whole-brain imaging with molecular contrast and nanoscale resolution. Science 2019; 363:eaau8302. [PMID: 30655415 PMCID: PMC6481610 DOI: 10.1126/science.aau8302] [Citation(s) in RCA: 196] [Impact Index Per Article: 39.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2018] [Accepted: 11/30/2018] [Indexed: 12/20/2022]
Abstract
Optical and electron microscopy have made tremendous inroads toward understanding the complexity of the brain. However, optical microscopy offers insufficient resolution to reveal subcellular details, and electron microscopy lacks the throughput and molecular contrast to visualize specific molecular constituents over millimeter-scale or larger dimensions. We combined expansion microscopy and lattice light-sheet microscopy to image the nanoscale spatial relationships between proteins across the thickness of the mouse cortex or the entire Drosophila brain. These included synaptic proteins at dendritic spines, myelination along axons, and presynaptic densities at dopaminergic neurons in every fly brain region. The technology should enable statistically rich, large-scale studies of neural development, sexual dimorphism, degree of stereotypy, and structural correlations to behavior or neural activity, all with molecular contrast.
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Guo Y, Li D, Zhang S, Yang Y, Liu JJ, Wang X, Liu C, Milkie DE, Moore RP, Tulu US, Kiehart DP, Hu J, Lippincott-Schwartz J, Betzig E, Li D. Visualizing Intracellular Organelle and Cytoskeletal Interactions at Nanoscale Resolution on Millisecond Timescales. Cell 2018; 175:1430-1442.e17. [DOI: 10.1016/j.cell.2018.09.057] [Citation(s) in RCA: 290] [Impact Index Per Article: 48.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2018] [Revised: 07/21/2018] [Accepted: 09/26/2018] [Indexed: 11/26/2022]
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Napolitano G, Esposito A, Choi H, Matarese M, Benedetti V, Di Malta C, Monfregola J, Medina DL, Lippincott-Schwartz J, Ballabio A. mTOR-dependent phosphorylation controls TFEB nuclear export. Nat Commun 2018; 9:3312. [PMID: 30120233 PMCID: PMC6098152 DOI: 10.1038/s41467-018-05862-6] [Citation(s) in RCA: 235] [Impact Index Per Article: 39.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2018] [Accepted: 07/25/2018] [Indexed: 01/17/2023] Open
Abstract
During starvation the transcriptional activation of catabolic processes is induced by the nuclear translocation and consequent activation of transcription factor EB (TFEB), a master modulator of autophagy and lysosomal biogenesis. However, how TFEB is inactivated upon nutrient refeeding is currently unknown. Here we show that TFEB subcellular localization is dynamically controlled by its continuous shuttling between the cytosol and the nucleus, with the nuclear export representing a limiting step. TFEB nuclear export is mediated by CRM1 and is modulated by nutrient availability via mTOR-dependent hierarchical multisite phosphorylation of serines S142 and S138, which are localized in proximity of a nuclear export signal (NES). Our data on TFEB nucleo-cytoplasmic shuttling suggest an unpredicted role of mTOR in nuclear export.
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Lippincott-Schwartz J, Snapp EL, Phair RD. The Development and Enhancement of FRAP as a Key Tool for Investigating Protein Dynamics. Biophys J 2018; 115:1146-1155. [PMID: 30219286 DOI: 10.1016/j.bpj.2018.08.007] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2018] [Revised: 07/27/2018] [Accepted: 08/06/2018] [Indexed: 01/18/2023] Open
Abstract
The saga of fluorescence recovery after photobleaching (FRAP) illustrates how disparate technical developments impact science. Starting with the classic 1976 Axelrod et al. work in Biophysical Journal, FRAP (originally fluorescence photobleaching recovery) opened the door to extraction of quantitative information from photobleaching experiments, laying the experimental and theoretical groundwork for quantifying both the mobility and the mobile fraction of a labeled population of proteins. Over the ensuing years, FRAP's reach dramatically expanded, with new developments in GFP technology and turn-key confocal microscopy, which enabled measurement of protein diffusion and binding/dissociation rates in virtually every compartment within the cell. The FRAP technique and data catalyzed an exchange of ideas between biophysicists studying membrane dynamics, cell biologists focused on intracellular dynamics, and systems biologists modeling the dynamics of cell activity. The outcome transformed the field of cellular biology, leading to a fundamental rethinking of long-held theories of cellular dynamism. Here, we review the pivotal FRAP studies that made these developments and conceptual changes possible, which gave rise to current models of complex cell dynamics.
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Feliciano D, Nixon-Abell J, Lippincott-Schwartz J. Triggered Cell-Cell Fusion Assay for Cytoplasmic and Organelle Intermixing Studies. ACTA ACUST UNITED AC 2018; 81:e61. [PMID: 30102462 DOI: 10.1002/cpcb.61] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Different multicellular organisms undergo cell-cell fusion to form functional syncytia that support specialized functions necessary for proper development and survival. For years, monitoring the structural consequences of this process using live-cell imaging has been challenging due to the unpredictable timing of cell fusion events in tissue systems. Here we present a triggered vesicular stomatitis virus G-protein (VSV-G)-mediated cell-cell fusion assay that can be used to synchronize fusion between cells. This allows the study of cellular changes that occur during cell fusion. The process is induced using a fast wash of low pH isotonic buffer, promoting the fusion of plasma membranes of two or more adjacent cells within seconds. This approach is suitable for studying mixing of small cytoplasmic molecules between fusing cells as well as changes in organelle distribution and dynamics. © 2018 by John Wiley & Sons, Inc.
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Cohen S, Valm AM, Lippincott-Schwartz J. Interacting organelles. Curr Opin Cell Biol 2018; 53:84-91. [PMID: 30006038 DOI: 10.1016/j.ceb.2018.06.003] [Citation(s) in RCA: 144] [Impact Index Per Article: 24.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2018] [Revised: 06/06/2018] [Accepted: 06/12/2018] [Indexed: 12/11/2022]
Abstract
Eukaryotic cells are organized into membrane-bound organelles. These organelles communicate with one another through vesicular trafficking pathways and membrane contact sites (MCSs). MCSs are sites of close apposition between two or more organelles that play diverse roles in the exchange of metabolites, lipids and proteins. Organelle interactions at MCSs also are important for organelle division and biogenesis. For example, the division of several organelles, including mitochondria and endosomes, seem to be regulated by contacts with the endoplasmic reticulum (ER). Moreover, the biogenesis of autophagosomes and peroxisomes involves contributions from the ER and multiple other cellular compartments. Thus, organelle-organelle interactions allow cells to alter the shape and activities of their membrane-bound compartments, allowing them to cope with different developmental and environmental conditions.
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Fu D, Lippincott-Schwartz J. Monitoring the Effects of Pharmacological Reagents on Mitochondrial Morphology. ACTA ACUST UNITED AC 2018; 79:e45. [PMID: 29924486 DOI: 10.1002/cpcb.45] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
This protocol describes how to apply appropriate pharmacological controls to induce mitochondrial fusion or fission in studies of mitochondria morphology for four different mammalian cell types, HepG2 human liver hepatocellular carcinoma cells, MCF7 human breast adenocarcinoma cells, HEK293 human embryonic kidney cells, and collagen sandwich culture of primary rat hepatocytes. The protocol provides methods of treating cells with these pharmacological controls, staining mitochondria with commercially available MitoTracker Green and TMRE dyes, and imaging the mitochondrial morphology in live cells using a confocal fluorescent microscope. It also describes the cell culture methods needed for this protocol. © 2018 by John Wiley & Sons, Inc.
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Abstract
Fluorescent proteins and vital dyes are invaluable tools for studying dynamic processes within living cells. However, the ability to distinguish more than a few different fluorescent reporters in a single sample is limited by the spectral overlap of available fluorophores. Here, we present a protocol for imaging live cells labeled with six fluorophores simultaneously. A confocal microscope with a spectral detector is used to acquire images, and linear unmixing algorithms are applied to identify the fluorophores present in each pixel of the image. We describe the application of this method to visualize the dynamics of six different organelles, and to quantify the contacts between organelles. However, this method can be used to image any molecule amenable to tagging with a fluorescent probe. Thus, multispectral live-cell imaging is a powerful tool for systems-level analysis of cellular organization and dynamics. © 2018 by John Wiley & Sons, Inc.
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Cohen S, Rambold AS, Lippincott-Schwartz J. Mitochondrial and Lipid Droplet Dynamics Regulate Intra- and Intercellular Fatty Acid Trafficking. Mol Cell Oncol 2018; 5:e1043038. [PMID: 30263932 PMCID: PMC6154839 DOI: 10.1080/23723556.2015.1043038] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2015] [Revised: 04/10/2015] [Accepted: 04/14/2015] [Indexed: 06/08/2023]
Abstract
Imaging of fatty acid (FA) trafficking revealed that FAs stored in lipid droplets were delivered to mitochondria when the cells were starved. This delivery required cytoplasmic lipases and mitochondrial fusion activity, whereas lipid droplets were replenished with FAs supplied by autophagy. These findings have important implications for cancer.
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