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Heuser JE. The Structural Basis of Long-Term Potentiation in Hippocampal Synapses, Revealed by Electron Microscopy Imaging of Lanthanum-Induced Synaptic Vesicle Recycling. Front Cell Neurosci 2022; 16:920360. [PMID: 35978856 PMCID: PMC9376242 DOI: 10.3389/fncel.2022.920360] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2022] [Accepted: 05/05/2022] [Indexed: 11/29/2022] Open
Abstract
Hippocampal neurons in dissociated cell cultures were exposed to the trivalent cation lanthanum for short periods (15–30 min) and prepared for electron microscopy (EM), to evaluate the stimulatory effects of this cation on synaptic ultrastructure. Not only were characteristic ultrastructural changes of exaggerated synaptic vesicle turnover seen within the presynapses of these cultures—including synaptic vesicle depletion and proliferation of vesicle-recycling structures—but the overall architecture of a large proportion of the synapses in the cultures was dramatically altered, due to large postsynaptic “bulges” or herniations into the presynapses. Moreover, in most cases, these postsynaptic herniations or protrusions produced by lanthanum were seen by EM to distort or break or “perforate” the so-called postsynaptic densities (PSDs) that harbor receptors and recognition molecules essential for synaptic function. These dramatic EM observations lead us to postulate that such PSD breakages or “perforations” could very possibly create essential substrates or “tags” for synaptic growth, simply by creating fragmented free edges around the PSDs, into which new receptors and recognition molecules could be recruited more easily, and thus, they could represent the physical substrate for the important synaptic growth process known as “long-term potentiation” (LTP). All of this was created simply in hippocampal dissociated cell cultures, and simply by pushing synaptic vesicle recycling way beyond its normal limits with the trivalent cation lanthanum, but we argued in this report that such fundamental changes in synaptic architecture—given that they can occur at all—could also occur at the extremes of normal neuronal activity, which are presumed to lead to learning and memory.
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Garten M, Beck J, Roth R, Heuser JE, Tenkova-Heuser T, Bleck CK, Goldberg DE, Zimmerberg J. Characterization of Membrane Contact Sites for the Facilitation of Lipid Exchange at the Malaria Parasite - Red Blood Cell Interface. Biophys J 2020. [DOI: 10.1016/j.bpj.2019.11.3119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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3
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Glushakova SE, Beck J, Garten M, Busse B, Nasamu AS, Tenkova-Heuser T, Heuser JE, Goldberg DE, Zimmerberg J. Malaria Parasites Break and Degrade Two Membranes to Egress from Human Erythrocyte. Biophys J 2019. [DOI: 10.1016/j.bpj.2018.11.1201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
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4
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Friend JE, Sayyad WA, Arasada R, McCormick CD, Heuser JE, Pollard TD. Fission yeast Myo2: Molecular organization and diffusion in the cytoplasm. Cytoskeleton (Hoboken) 2017; 75:164-173. [PMID: 29205883 DOI: 10.1002/cm.21425] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2017] [Revised: 11/22/2017] [Accepted: 11/27/2017] [Indexed: 12/20/2022]
Abstract
Myosin-II is required for the assembly and constriction of cytokinetic contractile rings in fungi and animals. We used electron microscopy, fluorescence recovery after photobleaching (FRAP), and fluorescence correlation spectroscopy (FCS) to characterize the physical properties of Myo2 from fission yeast Schizosaccharomyces pombe. By electron microscopy, Myo2 has two heads and a coiled-coiled tail like myosin-II from other species. The first 65 nm of the tail is a stiff rod, followed by a flexible, less-ordered region up to 30 nm long. Myo2 sediments as a 7 S molecule in high salt, but aggregates rather than forming minifilaments at lower salt concentrations; this is unaffected by heavy chain phosphorylation. We used FRAP and FCS to observe the dynamics of Myo2 in live S. pombe cells and in cell extracts at different salt concentrations; both show that Myo2 with an N-terminal mEGFP tag has a diffusion coefficient of ∼ 3 µm2 s-1 in the cytoplasm of live cells during interphase and mitosis. Photon counting histogram analysis of the FCS data confirmed that Myo2 diffuses as doubled-headed molecules in the cytoplasm. FCS measurements on diluted cell extracts showed that mEGFP-Myo2 has a diffusion coefficient of ∼ 30 µm2 s-1 in 50 to 400 mM KCl concentrations.
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Affiliation(s)
- Janice E Friend
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, Connecticut 06520-8103
| | - Wasim A Sayyad
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, Connecticut 06520-8103
| | - Rajesh Arasada
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, Connecticut 06520-8103
| | - Chad D McCormick
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06520-8103.,Section on Integrative Biophysics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, NIH, Bethesda, Maryland 20892-1855
| | - John E Heuser
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06520-8103
| | - Thomas D Pollard
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, Connecticut 06520-8103.,Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06520-8103.,Department of Cell Biology, Yale University, New Haven, Connecticut 06520-8103
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5
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Suleiman HY, Roth R, Jain S, Heuser JE, Shaw AS, Miner JH. Injury-induced actin cytoskeleton reorganization in podocytes revealed by super-resolution microscopy. JCI Insight 2017; 2:94137. [PMID: 28814668 DOI: 10.1172/jci.insight.94137] [Citation(s) in RCA: 50] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2017] [Accepted: 07/07/2017] [Indexed: 02/06/2023] Open
Abstract
The architectural integrity of tissues requires complex interactions, both between cells and between cells and the extracellular matrix. Fundamental to cell and tissue homeostasis are the specific mechanical forces conveyed by the actomyosin cytoskeleton. Here we used super-resolution imaging methods to visualize the actin cytoskeleton in the kidney glomerulus, an organized collection of capillaries that filters the blood to make the primary urine. Our analysis of both mouse and human glomeruli reveals a network of myosin IIA-containing contractile actin cables within podocyte cell bodies and major processes at the outer aspects of the glomerular tuft. These likely exert force on an underlying network of myosin IIA-negative, noncontractile actin fibers present within podocyte foot processes that function to both anchor the cells to the glomerular basement membrane and stabilize the slit diaphragm against the pressure of fluid flow. After injuries that disrupt the kidney filtration barrier and cause foot process effacement, the podocyte's contractile actomyosin network relocates to the basolateral surface of the cell, manifesting as sarcomere-like structures juxtaposed to the basement membrane. Our findings suggest a new model of the podocyte actin cytoskeleton in health and disease and suggest the existence of novel mechanisms that regulate podocyte architecture.
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Affiliation(s)
- Hani Y Suleiman
- Division of Nephrology, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Robyn Roth
- Washington University Center for Cellular Imaging, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Sanjay Jain
- Division of Nephrology, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, USA
| | - John E Heuser
- Institute for Integrated Cell-Material Sciences (iCeMS), Kyoto University, Kyoto, Japan
| | | | - Jeffrey H Miner
- Division of Nephrology, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, USA
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6
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Sone M, Morone N, Nakamura T, Tanaka A, Okita K, Woltjen K, Nakagawa M, Heuser JE, Yamada Y, Yamanaka S, Yamamoto T. Hybrid Cellular Metabolism Coordinated by Zic3 and Esrrb Synergistically Enhances Induction of Naive Pluripotency. Cell Metab 2017; 25:1103-1117.e6. [PMID: 28467928 DOI: 10.1016/j.cmet.2017.04.017] [Citation(s) in RCA: 58] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/10/2016] [Revised: 03/06/2017] [Accepted: 04/15/2017] [Indexed: 01/05/2023]
Abstract
Naive pluripotent stem cells (PSCs) utilize both glycolysis and oxidative phosphorylation (OXPHOS) to satisfy their metabolic demands. However, it is unclear how somatic cells acquire this hybrid energy metabolism during reprogramming toward naive pluripotency. Here, we show that when transduced with Oct4, Sox2, and Klf4 (OSK) into murine fibroblasts, Zic3 and Esrrb synergistically enhance the reprogramming efficiency by regulating cellular metabolic pathways. These two transcription factors (TFs) cooperatively activate glycolytic metabolism independently of hypoxia inducible factors (HIFs). In contrast, the regulatory modes of the TFs on OXPHOS are antagonistic: Zic3 represses OXPHOS, whereas Esrrb activates it. Therefore, when introduced with Zic3, Esrrb restores OXPHOS activity, which is essential for efficient reprogramming. In addition, Esrrb-mediated OXPHOS activation is critical for the conversion of primed PSCs into the naive state. Our study suggests that the combinatorial function of TFs achieves an appropriate balance of metabolic pathways to induce naive PSCs.
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Affiliation(s)
- Masamitsu Sone
- Department of Life Science Frontiers, Center for iPS Cell Research and Application (CiRA), Kyoto University, Sakyo-ku, Kyoto 606-8507, Japan; Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Sakyo-ku, Kyoto 606-8507, Japan
| | - Nobuhiro Morone
- Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Sakyo-ku, Kyoto 606-8507, Japan; MRC Toxicology Unit, University of Leicester, Leicester, LE1 9HN, UK
| | - Tomonori Nakamura
- Department of Life Science Frontiers, Center for iPS Cell Research and Application (CiRA), Kyoto University, Sakyo-ku, Kyoto 606-8507, Japan
| | - Akito Tanaka
- Department of Life Science Frontiers, Center for iPS Cell Research and Application (CiRA), Kyoto University, Sakyo-ku, Kyoto 606-8507, Japan
| | - Keisuke Okita
- Department of Life Science Frontiers, Center for iPS Cell Research and Application (CiRA), Kyoto University, Sakyo-ku, Kyoto 606-8507, Japan
| | - Knut Woltjen
- Department of Life Science Frontiers, Center for iPS Cell Research and Application (CiRA), Kyoto University, Sakyo-ku, Kyoto 606-8507, Japan; Hakubi Center for Advanced Research, Kyoto University, Kyoto 606-8501, Japan
| | - Masato Nakagawa
- Department of Life Science Frontiers, Center for iPS Cell Research and Application (CiRA), Kyoto University, Sakyo-ku, Kyoto 606-8507, Japan
| | - John E Heuser
- Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Sakyo-ku, Kyoto 606-8507, Japan
| | - Yasuhiro Yamada
- Department of Life Science Frontiers, Center for iPS Cell Research and Application (CiRA), Kyoto University, Sakyo-ku, Kyoto 606-8507, Japan; Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Sakyo-ku, Kyoto 606-8507, Japan
| | - Shinya Yamanaka
- Department of Life Science Frontiers, Center for iPS Cell Research and Application (CiRA), Kyoto University, Sakyo-ku, Kyoto 606-8507, Japan; Gladstone Institute of Cardiovascular Disease, San Francisco, CA 94158, USA
| | - Takuya Yamamoto
- Department of Life Science Frontiers, Center for iPS Cell Research and Application (CiRA), Kyoto University, Sakyo-ku, Kyoto 606-8507, Japan; Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Sakyo-ku, Kyoto 606-8507, Japan; AMED-CREST, AMED 1-7-1 Otemach, Chiyodaku, Tokyo, 100-0004, Japan.
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7
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Kim H, Okamoto H, Felber AE, Polomska A, Morone N, Heuser JE, Leroux JC, Murakami T. Polymer-coated pH-responsive high-density lipoproteins. J Control Release 2016; 228:132-140. [PMID: 26959846 DOI: 10.1016/j.jconrel.2016.03.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2015] [Revised: 02/22/2016] [Accepted: 03/03/2016] [Indexed: 02/01/2023]
Abstract
Intracellular drug delivery by nanoparticles is often hampered by their endosomal entrapment followed by their degradation in the lysosomal compartment and/or exocytosis. Here, we show that internalization and endosomal escape of cargoes in a cationized natural nanocarrier, high-density lipoprotein (HDL), can be controlled in a pH-dependent manner through stable complexation with a membranolytic anionic block polymer. A genetically and chemically cationized form of HDL (catHDL) is prepared for the first time by both genetic fusion with YGRKKRRQRRR peptide and incorporation of 1,2-dioleoyloxy-3-(trimethylammonium)propane. Upon addition of poly(ethylene glycol)-block-poly(propyl methacrylate-co-methacrylic acid) (PA), catHDL yields inhibition of internalization at neutral pH and its subsequent recovery at mildly acidic pH. catHDL forms a stable discoidal-shape complex with PA (catHDL/PA) (ca. 50 nm in diameter), even in the presence of serum. Significant enhancement of endosomal escape of a catHDL component is observed after a 1-h treatment of human cancer cells with catHDL/PA. Doxorubicin and curcumin, fluorescent anti-cancer drugs, encapsulated into catHDL/PA are also translocated outside of endosomes, compared with that into catHDL, and their cytotoxicities are enhanced inside the cells. These data suggest that catHDL/PA may have a potential benefit to improve the cellular delivery and endosomal escape of therapeutics under mildly acidic conditions such as in tumor tissues.
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Affiliation(s)
- Hyungjin Kim
- Institute for Integrated Cell-Material Science (WPI-iCeMS), Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
| | - Haruki Okamoto
- Institute for Integrated Cell-Material Science (WPI-iCeMS), Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
| | - Arnaud E Felber
- Department of Chemistry and Applied Biosciences, Institute of Pharmaceutical Sciences, ETH Zürich, Vladimir-Prelog-Weg 1-5/10, 8093 Zurich, Switzerland
| | - Anna Polomska
- Department of Chemistry and Applied Biosciences, Institute of Pharmaceutical Sciences, ETH Zürich, Vladimir-Prelog-Weg 1-5/10, 8093 Zurich, Switzerland
| | - Nobuhiro Morone
- Institute for Integrated Cell-Material Science (WPI-iCeMS), Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
| | - John E Heuser
- Institute for Integrated Cell-Material Science (WPI-iCeMS), Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
| | - Jean-Christophe Leroux
- Department of Chemistry and Applied Biosciences, Institute of Pharmaceutical Sciences, ETH Zürich, Vladimir-Prelog-Weg 1-5/10, 8093 Zurich, Switzerland
| | - Tatsuya Murakami
- Institute for Integrated Cell-Material Science (WPI-iCeMS), Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan.
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8
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Honda M, Minami I, Tooi N, Morone N, Nishioka H, Uemura K, Kinoshita A, Heuser JE, Nakatsuji N, Aiba K. The modeling of Alzheimer's disease by the overexpression of mutant Presenilin 1 in human embryonic stem cells. Biochem Biophys Res Commun 2015; 469:587-92. [PMID: 26687948 DOI: 10.1016/j.bbrc.2015.12.025] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2015] [Accepted: 12/04/2015] [Indexed: 11/28/2022]
Abstract
Cellular disease models are useful tools for Alzheimer's disease (AD) research. Pluripotent stem cells, including human embryonic stem cells (hESCs) and induced pluripotent stem cells (iPSCs), are promising materials for creating cellular models of such diseases. In the present study, we established cellular models of AD in hESCs that overexpressed the mutant Presenilin 1 (PS1) gene with the use of a site-specific gene integration system. The overexpression of PS1 did not affect the undifferentiated status or the neural differentiation ability of the hESCs. We found increases in the ratios of amyloid-β 42 (Aβ42)/Aβ40 and Aβ43/Aβ40. Furthermore, synaptic dysfunction was observed in a cellular model of AD that overexpressed mutant PS1. These results suggest that the AD phenotypes, in particular, the electrophysiological abnormality of the synapses in our AD models might be useful for AD research and drug discovery.
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Affiliation(s)
- Makoto Honda
- Stem Cell and Drug Discovery Institute, Kyoto 600-8813, Japan
| | - Itsunari Minami
- Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Kyoto 606-8501, Japan
| | - Norie Tooi
- Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Kyoto 606-8501, Japan
| | - Nobuhiro Morone
- Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Kyoto 606-8501, Japan
| | - Hisae Nishioka
- Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Kyoto 606-8501, Japan
| | - Kengo Uemura
- Department of Neurology, Kyoto University Graduate School of Medicine, Kyoto 606-8507, Japan
| | - Ayae Kinoshita
- School of Human Health Sciences, Kyoto University Graduate School of Medicine, Kyoto 606-8507, Japan
| | - John E Heuser
- Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Kyoto 606-8501, Japan; Department of Cell Biology, Washington University, St. Louis, MO 63110, USA
| | - Norio Nakatsuji
- Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Kyoto 606-8501, Japan; Institute for Frontier Medical Sciences, Kyoto University, Kyoto 606-8507, Japan
| | - Kazuhiro Aiba
- Stem Cell and Drug Discovery Institute, Kyoto 600-8813, Japan; Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Kyoto 606-8501, Japan.
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Abstract
This brief essay talks up the advantages of metal replicas for electron microscopy and explains why they are still the best way to image frozen cells in the electron microscope. Then it explains our approach to freezing, namely the Van Harreveld trick of "slamming" living cells onto a supercold block of metal sprayed with liquid helium at -269ºC, and further talks up this slamming over the alternative of high-pressure freezing, which is much trickier but enjoys greater favor at the moment. This leads me to bemoan the fact that there are not more young investigators today who want to get their hands on electron microscopes and use our approach to get the most "true to life" views of cells out of them with a minimum of hassle. Finally, it ends with a few perspectives on my own career and concludes that, personally, I'm permanently stuck with the view of the "founding fathers" that cell ultrastructure will ultimately display and explain all of cell function, or as Palade said in his Nobel lecture,electron micrographs are "irresistible and half transparent … their meaning buried under only a few years of work," and "reasonable working hypotheses are already suggested by the ultrastructural organization itself."
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Affiliation(s)
- John E Heuser
- WPI Institute, Kyoto University, Kyoto 606-8501, Japan; Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110
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10
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Muia J, Zhu J, Gupta G, Haberichter SL, Friedman KD, Feys HB, Deforche L, Vanhoorelbeke K, Westfield LA, Roth R, Tolia NH, Heuser JE, Sadler JE. Allosteric activation of ADAMTS13 by von Willebrand factor. Proc Natl Acad Sci U S A 2014; 111:18584-9. [PMID: 25512528 PMCID: PMC4284596 DOI: 10.1073/pnas.1413282112] [Citation(s) in RCA: 89] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The metalloprotease ADAMTS13 cleaves von Willebrand factor (VWF) within endovascular platelet aggregates, and ADAMTS13 deficiency causes fatal microvascular thrombosis. The proximal metalloprotease (M), disintegrin-like (D), thrombospondin-1 (T), Cys-rich (C), and spacer (S) domains of ADAMTS13 recognize a cryptic site in VWF that is exposed by tensile force. Another seven T and two complement C1r/C1s, sea urchin epidermal growth factor, and bone morphogenetic protein (CUB) domains of uncertain function are C-terminal to the MDTCS domains. We find that the distal T8-CUB2 domains markedly inhibit substrate cleavage, and binding of VWF or monoclonal antibodies to distal ADAMTS13 domains relieves this autoinhibition. Small angle X-ray scattering data indicate that distal T-CUB domains interact with proximal MDTCS domains. Thus, ADAMTS13 is regulated by substrate-induced allosteric activation, which may optimize VWF cleavage under fluid shear stress in vivo. Distal domains of other ADAMTS proteases may have similar allosteric properties.
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Affiliation(s)
| | | | | | | | | | - Hendrik B Feys
- Transfusion Research Center, Belgian Red Cross-Flanders, Ghent, Belgium; and
| | - Louis Deforche
- Laboratory for Thrombosis Research, KU Leuven Kulak, 8500 Kortrijk, Belgium
| | | | | | | | - Niraj Harish Tolia
- Biochemistry and Molecular Biophysics, and Molecular Microbiology and Microbial Pathogenesis, Washington University School of Medicine, St. Louis, MO 63110
| | | | - J Evan Sadler
- Departments of Medicine, Biochemistry and Molecular Biophysics, and
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Hirai K, Reboul J, Morone N, Heuser JE, Furukawa S, Kitagawa S. Diffusion-Coupled Molecular Assembly: Structuring of Coordination Polymers Across Multiple Length Scales. J Am Chem Soc 2014; 136:14966-73. [DOI: 10.1021/ja507971r] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Affiliation(s)
- Kenji Hirai
- Department
of Synthetic Chemistry and Biological Chemistry, Graduate School of
Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510, Japan
| | - Julien Reboul
- Institute
for Integrated Cell-Material Science (WPI-iCeMS), Kyoto University, Yoshida, Sakyo-ku,
Kyoto 606-8501, Japan
| | - Nobuhiro Morone
- Institute
for Integrated Cell-Material Science (WPI-iCeMS), Kyoto University, Yoshida, Sakyo-ku,
Kyoto 606-8501, Japan
| | - John E. Heuser
- Institute
for Integrated Cell-Material Science (WPI-iCeMS), Kyoto University, Yoshida, Sakyo-ku,
Kyoto 606-8501, Japan
| | - Shuhei Furukawa
- Institute
for Integrated Cell-Material Science (WPI-iCeMS), Kyoto University, Yoshida, Sakyo-ku,
Kyoto 606-8501, Japan
| | - Susumu Kitagawa
- Department
of Synthetic Chemistry and Biological Chemistry, Graduate School of
Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510, Japan
- Institute
for Integrated Cell-Material Science (WPI-iCeMS), Kyoto University, Yoshida, Sakyo-ku,
Kyoto 606-8501, Japan
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12
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Murakami T, Nakatsuji H, Morone N, Heuser JE, Ishidate F, Hashida M, Imahori H. Mesoscopic metal nanoparticles doubly functionalized with natural and engineered lipidic dispersants for therapeutics. ACS Nano 2014; 8:7370-7376. [PMID: 24945782 DOI: 10.1021/nn5024818] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Surface engineering of mesoscopic metal nanoparticles to increase biocompatibility and cell interaction is important for improvement of their therapeutic properties. Here, we describe a strategy to stabilize mesoscopic metal nanoparticles and to enhance their cell interaction by stepwise addition of (Z)-9-octadecenoate (oleate) and a cell-penetrating peptide-fused high-density lipoprotein (cpHDL). Oleate replaces a cytotoxic dispersant on the surface of gold nanorods (AuNRs), which enables subsequent cpHDL binding without causing aggregation. Notably, these two lipidic dispersants are probably intercalated on the surface. This procedure was also used to stabilize 20 nm spherical gold nanoparticles and 40 nm aggregates of 10 nm magnetite nanoparticles. cpHDL-bound AuNRs were internalized greater than 80 times more efficiently than poly(ethylene glycol)-conjugated AuNRs and were able to elicit cancer cell photoablation.
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Affiliation(s)
- Tatsuya Murakami
- Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University , Sakyo-ku, Kyoto 606-8501, Japan
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13
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Vitre B, Gudimchuk N, Borda R, Kim Y, Heuser JE, Cleveland DW, Grishchuk EL. Kinetochore-microtubule attachment throughout mitosis potentiated by the elongated stalk of the kinetochore kinesin CENP-E. Mol Biol Cell 2014; 25:2272-81. [PMID: 24920822 PMCID: PMC4116301 DOI: 10.1091/mbc.e14-01-0698] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Centromere protein E (CENP-E) is a highly elongated kinesin that transports pole-proximal chromosomes during congression in prometaphase. During metaphase, it facilitates kinetochore-microtubule end-on attachment required to achieve and maintain chromosome alignment. In vitro CENP-E can walk processively along microtubule tracks and follow both growing and shrinking microtubule plus ends. Neither the CENP-E-dependent transport along microtubules nor its tip-tracking activity requires the unusually long coiled-coil stalk of CENP-E. The biological role for the CENP-E stalk has now been identified through creation of "Bonsai" CENP-E with significantly shortened stalk but wild-type motor and tail domains. We demonstrate that Bonsai CENP-E fails to bind microtubules in vitro unless a cargo is contemporaneously bound via its C-terminal tail. In contrast, both full-length and truncated CENP-E that has no stalk and tail exhibit robust motility with and without cargo binding, highlighting the importance of CENP-E stalk for its activity. Correspondingly, kinetochore attachment to microtubule ends is shown to be disrupted in cells whose CENP-E has a shortened stalk, thereby producing chromosome misalignment in metaphase and lagging chromosomes during anaphase. Together these findings establish an unexpected role of CENP-E elongated stalk in ensuring stability of kinetochore-microtubule attachments during chromosome congression and segregation.
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Affiliation(s)
- Benjamin Vitre
- Ludwig Institute for Cancer Research and Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA 92093
| | - Nikita Gudimchuk
- Physiology Department, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104
| | - Ranier Borda
- Ludwig Institute for Cancer Research and Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA 92093
| | - Yumi Kim
- Ludwig Institute for Cancer Research and Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA 92093
| | - John E Heuser
- Department of Cell Biology, Washington University in Saint Louis, St Louis, MO 63110WPI Institute for Cell and Material Sciences, Kyoto University, Kyoto 606-8501, Japan
| | - Don W Cleveland
- Ludwig Institute for Cancer Research and Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA 92093
| | - Ekaterina L Grishchuk
- Physiology Department, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104
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Cashikar AG, Shim S, Roth R, Maldazys MR, Heuser JE, Hanson PI. Structure of cellular ESCRT-III spirals and their relationship to HIV budding. eLife 2014; 3. [PMID: 24878737 PMCID: PMC4073282 DOI: 10.7554/elife.02184] [Citation(s) in RCA: 90] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2013] [Accepted: 05/27/2014] [Indexed: 12/23/2022] Open
Abstract
The ESCRT machinery along with the AAA+ ATPase Vps4 drive membrane scission for trafficking into multivesicular bodies in the endocytic pathway and for the topologically related processes of viral budding and cytokinesis, but how they accomplish this remains unclear. Using deep-etch electron microscopy, we find that endogenous ESCRT-III filaments stabilized by depleting cells of Vps4 create uniform membrane-deforming conical spirals which are assemblies of specific ESCRT-III heteropolymers. To explore functional roles for ESCRT-III filaments, we examine HIV-1 Gag-mediated budding of virus-like particles and find that depleting Vps4 traps ESCRT-III filaments around nascent Gag assemblies. Interpolating between the observed structures suggests a new role for Vps4 in separating ESCRT-III from Gag or other cargo to allow centripetal growth of a neck constricting ESCRT-III spiral. DOI:http://dx.doi.org/10.7554/eLife.02184.001 Cells contain compartments called organelles that are enclosed within membranes similar to the plasma membrane that surrounds the cell itself. Cells police the proteins on their membranes and move old or damaged proteins into a type of organelle called an endosome. This involves the membrane folding in on itself to form a multivesicular body. The multivesicular bodies deliver their contents to organelles called lysosomes where the old proteins are destroyed. Although it is known that over 30 proteins are involved in the formation of multivesicular bodies, many aspects of how they operate are not well understood. Moreover, disruptions to this process contribute to a large number of diseases including forms of cancer and neurodegeneration. Importantly, the same proteins are hijacked by viruses such as HIV to help them escape from the cells they have infected. Most of the proteins involved in forming multivesicular bodies are part of the ESCRT (Endosomal Sorting Complex Required for Transport) system of proteins. A special set of these proteins—ESCRT-III—is thought to cut the membrane to release vesicles and viruses, as well as helping the membrane to deform. Previously, researchers have been unsure how the ESCRT-III complex works because it has a short lifespan and is too small to see on cellular membranes using standard techniques. Now Cashikar, Shim et al. have used a technique called deep-etch electron microscopy in combination with gene knockdown strategies to reveal the structure of the ESCRT-III complex inside cells. A protein called Vps4 is known to recycle ESCRT-III complexes, so Cashikar, Shim et al. studied cells in which the levels of Vps4 had been depleted in order to increase the lifespan of ESCRT-III complexes. In these cells filaments made of ESCRT-III complexes tended to form conical spirals that matched the size and shape of the vesicles and viruses ESCRT-III is thought to produce. ESCRT-III filaments also accumulated as rings around the molecules destined for incorporation into a vesicle or virus. This indicated a new role for Vps4: it separates ESCRT-III from the contents of the vesicle, leaving it free to form a spiral that drives release of the vesicle or virus from the cell. The next challenge will be to test the predictions of this model using techniques that can capture individual vesicle formation events in real time. Understanding the function of ESCRT-III in greater detail may suggest ways to manipulate this pathway to limit the replication of viruses or the degradation of membrane proteins. DOI:http://dx.doi.org/10.7554/eLife.02184.002
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Affiliation(s)
- Anil G Cashikar
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, United States
| | - Soomin Shim
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, United States
| | - Robyn Roth
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, United States
| | - Michael R Maldazys
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, United States
| | - John E Heuser
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, United States
| | - Phyllis I Hanson
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, United States
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15
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Endo M, Yamamoto S, Emura T, Hidaka K, Morone N, Heuser JE, Sugiyama H. Helical DNA Origami Tubular Structures with Various Sizes and Arrangements. Angew Chem Int Ed Engl 2014. [DOI: 10.1002/ange.201402973] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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16
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Endo M, Yamamoto S, Emura T, Hidaka K, Morone N, Heuser JE, Sugiyama H. Helical DNA origami tubular structures with various sizes and arrangements. Angew Chem Int Ed Engl 2014; 53:7484-90. [PMID: 24888699 DOI: 10.1002/anie.201402973] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2014] [Revised: 04/28/2014] [Indexed: 11/11/2022]
Abstract
We developed a novel method to design various helical tubular structures using the DNA origami method. The size-controlled tubular structures which have 192, 256, and 320 base pairs for one turn of the tube were designed and prepared. We observed the formation of the expected short tubes and unexpected long ones. Detailed analyses of the surface patterns of the tubes showed that the short tubes had mainly a left-handed helical structure. The long tubes mainly formed a right-handed helical structure and extended to the directions of the double helical axes as structural isomers of the short tubes. The folding pathways of the tubes were estimated by analyzing the proportions of short and long tubes obtained at different annealing conditions. Depending on the number of base pairs involved in one turn of the tube, the population of left-/right-handed and short/long tubes changed. The bending stress caused by the stiffness of the bundled double helices and the non-natural helical pitch determine the structural variety of the tubes.
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Affiliation(s)
- Masayuki Endo
- Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Yoshida-ushinomiyacho, Sakyo-ku, Kyoto 606-8501 (Japan).
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17
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Otsuji TG, Bin J, Yoshimura A, Tomura M, Tateyama D, Minami I, Yoshikawa Y, Aiba K, Heuser JE, Nishino T, Hasegawa K, Nakatsuji N. A 3D Sphere Culture System Containing Functional Polymers for Large-Scale Human Pluripotent Stem Cell Production. Stem Cell Reports 2014; 2:746. [PMID: 28081436 PMCID: PMC4050484 DOI: 10.1016/j.stemcr.2014.04.013] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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18
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Vassilopoulos S, Gentil C, Lainé J, Buclez PO, Franck A, Ferry A, Précigout G, Roth R, Heuser JE, Brodsky FM, Garcia L, Bonne G, Voit T, Piétri-Rouxel F, Bitoun M. Actin scaffolding by clathrin heavy chain is required for skeletal muscle sarcomere organization. ACTA ACUST UNITED AC 2014; 205:377-93. [PMID: 24798732 PMCID: PMC4018784 DOI: 10.1083/jcb.201309096] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Clathrin heavy chain contributes to the formation and maintenance of the contractile apparatus in skeletal muscle through interactions with costameric proteins. The ubiquitous clathrin heavy chain (CHC), the main component of clathrin-coated vesicles, is well characterized for its role in intracellular membrane traffic and endocytosis from the plasma membrane (PM). Here, we demonstrate that in skeletal muscle CHC regulates the formation and maintenance of PM–sarcomere attachment sites also known as costameres. We show that clathrin forms large coated lattices associated with actin filaments and the muscle-specific isoform of α-actinin at the PM of differentiated myotubes. Depletion of CHC in myotubes induced a loss of actin and α-actinin sarcomeric organization, whereas CHC depletion in vivo induced a loss of contractile force due to the detachment of sarcomeres from the PM. Our results suggest that CHC contributes to the formation and maintenance of the contractile apparatus through interactions with costameric proteins and highlight an unconventional role for CHC in skeletal muscle that may be relevant to pathophysiology of neuromuscular disorders.
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Affiliation(s)
- Stéphane Vassilopoulos
- Institut National de la Santé et de la Recherche Médicale (INSERM) U974, 2 Centre National de la Recherche Scientifique (CNRS) UMR 7215, and 3 Université Pierre et Marie Curie-Paris 6, UM 76, Paris F-75013, France
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19
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Otsuji TG, Bin J, Yoshimura A, Tomura M, Tateyama D, Minami I, Yoshikawa Y, Aiba K, Heuser JE, Nishino T, Hasegawa K, Nakatsuji N. A 3D sphere culture system containing functional polymers for large-scale human pluripotent stem cell production. Stem Cell Reports 2014; 2:734-45. [PMID: 24936458 PMCID: PMC4050473 DOI: 10.1016/j.stemcr.2014.03.012] [Citation(s) in RCA: 96] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2013] [Revised: 03/27/2014] [Accepted: 03/27/2014] [Indexed: 01/01/2023] Open
Abstract
Utilizing human pluripotent stem cells (hPSCs) in cell-based therapy and drug discovery requires large-scale cell production. However, scaling up conventional adherent cultures presents challenges of maintaining a uniform high quality at low cost. In this regard, suspension cultures are a viable alternative, because they are scalable and do not require adhesion surfaces. 3D culture systems such as bioreactors can be exploited for large-scale production. However, the limitations of current suspension culture methods include spontaneous fusion between cell aggregates and suboptimal passaging methods by dissociation and reaggregation. 3D culture systems that dynamically stir carrier beads or cell aggregates should be refined to reduce shearing forces that damage hPSCs. Here, we report a simple 3D sphere culture system that incorporates mechanical passaging and functional polymers. This setup resolves major problems associated with suspension culture methods and dynamic stirring systems and may be optimal for applications involving large-scale hPSC production. Suspended sphere culture of hPSCs with expansion rates similar to adherent culture Uniform hPSC spheres made by mechanical passaging and adding methylcellulose 3D hPSC sphere culture suspended with gellan gum polymer without dynamic agitation Proof of principle 3D hPSC culture using 200 ml culture bag for large-scale trial
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Affiliation(s)
- Tomomi G Otsuji
- Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Ushinomiya-cho, Yoshida, Sakyo-ku, Kyoto 606-8501, Japan
| | - Jiang Bin
- Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Ushinomiya-cho, Yoshida, Sakyo-ku, Kyoto 606-8501, Japan
| | - Azumi Yoshimura
- Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Ushinomiya-cho, Yoshida, Sakyo-ku, Kyoto 606-8501, Japan
| | - Misayo Tomura
- Nissan Chemical Industries, Ltd., 3-7-1 Kanda Nishiki-cho, Chiyoda-ku, Tokyo 101-1154, Japan
| | - Daiki Tateyama
- Nipro Corporation, 3023 Noji-cho, Kusatsu, Shiga 525-0055, Japan
| | - Itsunari Minami
- Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Ushinomiya-cho, Yoshida, Sakyo-ku, Kyoto 606-8501, Japan
| | | | - Kazuhiro Aiba
- Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Ushinomiya-cho, Yoshida, Sakyo-ku, Kyoto 606-8501, Japan
| | - John E Heuser
- Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Ushinomiya-cho, Yoshida, Sakyo-ku, Kyoto 606-8501, Japan
| | - Taito Nishino
- Nissan Chemical Industries, Ltd., 3-7-1 Kanda Nishiki-cho, Chiyoda-ku, Tokyo 101-1154, Japan
| | - Kouichi Hasegawa
- Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Ushinomiya-cho, Yoshida, Sakyo-ku, Kyoto 606-8501, Japan ; Institute for Stem Cell Biology and Regenerative Medicine, National Centre for Biological Sciences, GKVK, Bellary Road, Bangalore 560065, India
| | - Norio Nakatsuji
- Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Ushinomiya-cho, Yoshida, Sakyo-ku, Kyoto 606-8501, Japan ; Institute for Frontier Medical Sciences, Kyoto University, 53 Kawahara-cho, Sakyo-ku, Kyoto 606-8507, Japan
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20
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Mathew S, Murakami T, Nakatsuji H, Okamoto H, Morone N, Heuser JE, Hashida M, Imahori H. Exclusive photothermal heat generation by a gadolinium bis(naphthalocyanine) complex and inclusion into modified high-density lipoprotein nanocarriers for therapeutic applications. ACS Nano 2013; 7:8908-8916. [PMID: 24053139 DOI: 10.1021/nn403384k] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
A hydrophobic gadolinium bis(naphthalocyanine) sandwich complex (GdSand) possessing several absorbances across visible and infrared wavelengths (up to 2500 nm) was solubilized in aqueous solution by uptake into a nascent mutant high-density lipoprotein (HDL) nanocarrier. The HDL nanocarrier was additionally functionalized with a trans-activator of transcription peptide sequence to promote efficient cell penetration of the drug delivery system (cpHDL). The dye-loaded nanocarrier (GdSand@cpHDL) exhibited photothermal heat generation properties upon irradiation with near-infrared (NIR) laser light, with controllable heat generation abilities as a function of the incident laser light power. Comparison of the photothermal behavior of the dyes GdSand and the well-explored molecular photothermal agent indocyanine green (ICG) in the cpHDL nanocarrier (i.e., ICG@cpHDL) revealed two significant advantages of GdSand@cpHDL: (1) the ability to maintain elevated temperatures upon light absorption for extended periods of time, with a reduced degree of self-destruction of the dye, and (2) exclusive photothermal heat generation with no detectable singlet oxygen production leading to improved integrity of the cpHDL nanocarrier after irradiation. Finally, GdSand@cpHDL was successfully subjected to an in vitro study against NCI-H460 human lung cancer cells, demonstrating the proof-of-principle utility of lanthanide sandwich complexes in photothermal therapeutic applications.
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Affiliation(s)
- Simon Mathew
- Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University , Sakyo-ku, Kyoto 606-8501, Japan
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21
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Suleiman H, Zhang L, Roth R, Heuser JE, Miner JH, Shaw AS, Dani A. Nanoscale protein architecture of the kidney glomerular basement membrane. eLife 2013; 2:e01149. [PMID: 24137544 PMCID: PMC3790497 DOI: 10.7554/elife.01149] [Citation(s) in RCA: 119] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2013] [Accepted: 09/02/2013] [Indexed: 12/12/2022] Open
Abstract
In multicellular organisms, proteins of the extracellular matrix (ECM) play structural and functional roles in essentially all organs, so understanding ECM protein organization in health and disease remains an important goal. Here, we used sub-diffraction resolution stochastic optical reconstruction microscopy (STORM) to resolve the in situ molecular organization of proteins within the kidney glomerular basement membrane (GBM), an essential mediator of glomerular ultrafiltration. Using multichannel STORM and STORM-electron microscopy correlation, we constructed a molecular reference frame that revealed a laminar organization of ECM proteins within the GBM. Separate analyses of domains near the N- and C-termini of agrin, laminin, and collagen IV in mouse and human GBM revealed a highly oriented macromolecular organization. Our analysis also revealed disruptions in this GBM architecture in a mouse model of Alport syndrome. These results provide the first nanoscopic glimpse into the organization of a complex ECM. DOI:http://dx.doi.org/10.7554/eLife.01149.001.
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Affiliation(s)
- Hani Suleiman
- Department of Pathology and Immunology , Washington University School of Medicine , St. Louis , United States
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22
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Keyel PA, Roth R, Yokoyama WM, Heuser JE, Salter RD. Reduction of streptolysin O (SLO) pore-forming activity enhances inflammasome activation. Toxins (Basel) 2013; 5:1105-18. [PMID: 23744055 PMCID: PMC3717772 DOI: 10.3390/toxins5061105] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2013] [Revised: 05/29/2013] [Accepted: 06/03/2013] [Indexed: 12/21/2022] Open
Abstract
Pore-forming toxins are utilized by bacterial and mammalian cells to exert pathogenic effects and induce cell lysis. In addition to rapid plasma membrane repair, macrophages respond to pore-forming toxins through activation of the NLRP3 inflammasome, leading to IL-1β secretion and pyroptosis. The structural determinants of pore-forming toxins required for NLRP3 activation remain unknown. Here, we demonstrate using streptolysin O (SLO) that pore-formation controls IL-1β secretion and direct toxicity. An SLO mutant incapable of pore-formation did not promote direct killing, pyroptosis or IL-1β production. This indicated that pore formation is necessary for inflammasome activation. However, a partially active mutant (SLO N402C) that was less toxic to macrophages than wild-type SLO, even at concentrations that directly lysed an equivalent number of red blood cells, enhanced IL-1β production but did not alter pyroptosis. This suggests that direct lysis may attenuate immune responses by preventing macrophages from successfully repairing their plasma membrane and elaborating more robust cytokine production. We suggest that mutagenesis of pore-forming toxins represents a strategy to enhance adjuvant activity.
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Affiliation(s)
- Peter A. Keyel
- Department of Immunology, University of Pittsburgh, Pittsburgh, PA 15260, USA; E-Mail:
| | - Robyn Roth
- Department of Cell Biology and Physiology, Washington University, St. Louis, MO 63110, USA; E-Mails: (R.R.); (J.E.H.)
| | - Wayne M. Yokoyama
- Howard Hughes Medical Institute and Rheumatology Division, Department of Medicine, Washington University, St. Louis, MO 63110, USA; E-Mail:
| | - John E. Heuser
- Department of Cell Biology and Physiology, Washington University, St. Louis, MO 63110, USA; E-Mails: (R.R.); (J.E.H.)
| | - Russell D. Salter
- Department of Immunology, University of Pittsburgh, Pittsburgh, PA 15260, USA; E-Mail:
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +1-412-648-9471; Fax: +1-412-383-8096
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23
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Abstract
Exosomes are extracellular membrane vesicles whose biogenesis by exocytosis of multivesicular endosomes was discovered in 1983. Since their discovery 30 years ago, it has become clear that exosomes contribute to many aspects of physiology and disease, including intercellular communication. We discuss the initial experiments that led to the discovery of exosomes and highlight some of the exciting current directions in the field.
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Affiliation(s)
- Clifford V Harding
- Department of Pathology, Case Western Reserve University and University Hospitals Case Medical Center, Cleveland, OH 44106, USA
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24
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25
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Abstract
AIMS Development of a human cell-derived reentrant arrhythmia model is needed for studying the mechanisms of disease and accurate drug response. METHODS AND RESULTS We differentiated human pluripotent stem cells (hPSCs) into cardiomyocytes, and then re-plated them into cell sheets that proved capable of forming electrically coupled assemblies. We monitored the function of these re-plated sheets optically with the Ca(2+) sensitive dye Fluo-4, and found that they generated characteristic waves of activity whose velocity and patterns of propagation depended upon the concentration of sodium channel blockers; lidocaine and tetrodotoxin, and also the time after re-plating, as well as the applied stimulation frequency. Importantly, reentrant spiral-wave propagation could be generated in these sheets by applying high-frequency stimulation, particularly when cell-density in the sheets was relatively low. This was because cardiac troponin T-positive cells were more non-homogeneously distributed at low cell densities. Especially in such sheets, we could terminate spiral waves by administering the anti-arrhythmic drugs; nifekalant, E-4031, sotalol, and quinidine. We also found that in these sheets, nifekalant showed a clear dose-dependent increase in the size of the unexcitable 'cores' of these induced spiral waves, an important parallel with the treatment for ventricular tachycardia in the clinical situation, which was not shown properly in cardiac-cell sheets derived from dissociated rodent hearts. CONCLUSIONS We have succeeded in creating from hPSCs a valuable type of cardiomyocyte sheet that is capable of generating reentrant arrhythmias, and thus is demonstrably useful for screening and testing all sorts of drugs with anti-arrhythmic potential.
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Affiliation(s)
- Shin Kadota
- Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, iCeMS Research Building, Yoshida Honmachi, Kyoto 606-8501, Japan
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26
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Minami I, Yamada K, Otsuji TG, Yamamoto T, Shen Y, Otsuka S, Kadota S, Morone N, Barve M, Asai Y, Tenkova-Heuser T, Heuser JE, Uesugi M, Aiba K, Nakatsuji N. A small molecule that promotes cardiac differentiation of human pluripotent stem cells under defined, cytokine- and xeno-free conditions. Cell Rep 2012; 2:1448-60. [PMID: 23103164 DOI: 10.1016/j.celrep.2012.09.015] [Citation(s) in RCA: 185] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2012] [Revised: 05/18/2012] [Accepted: 09/12/2012] [Indexed: 12/15/2022] Open
Abstract
Human pluripotent stem cells (hPSCs), including embryonic stem cells and induced pluripotent stem cells, are potentially useful in regenerative therapies for heart disease. For medical applications, clinical-grade cardiac cells must be produced from hPSCs in a defined, cost-effective manner. Cell-based screening led to the discovery of KY02111, a small molecule that promotes differentiation of hPSCs to cardiomyocytes. Although the direct target of KY02111 remains unknown, results of the present study suggest that KY02111 promotes differentiation by inhibiting WNT signaling in hPSCs but in a manner that is distinct from that of previously studied WNT inhibitors. Combined use of KY02111 and WNT signaling modulators produced robust cardiac differentiation of hPSCs in a xeno-free, defined medium, devoid of serum and any kind of recombinant cytokines and hormones, such as BMP4, Activin A, or insulin. The methodology has potential as a means for the practical production of human cardiomyocytes for regeneration therapies.
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Affiliation(s)
- Itsunari Minami
- Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Kyoto 606-8501, Japan
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27
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Filbert EL, Le Borgne M, Lin J, Heuser JE, Shaw AS. Stathmin regulates microtubule dynamics and microtubule organizing center polarization in activated T cells. J Immunol 2012; 188:5421-7. [PMID: 22529300 DOI: 10.4049/jimmunol.1200242] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Polarization of T cells involves reorientation of the microtubule organizing center (MTOC). Because activated ERK is localized at the immunological synapse, we investigated its role by showing that ERK activation is important for MTOC polarization. Suspecting that ERK phosphorylates a regulator of microtubules, we next focused on stathmin, a known ERK substrate. Our work indicates that during T cell activation, ERK is recruited to the synapse, allowing it to phosphorylate stathmin molecules near the immunological synapse. Supporting an important role of stathmin phosphorylation in T cell activation, we showed that T cell activation results in increased microtubule growth rate dependent on the presence of stathmin. The significance of this finding was demonstrated by results showing that CTLs from stathmin(-/-) mice displayed defective MTOC polarization and defective target cell cytolysis. These data implicate stathmin as a regulator of the microtubule network during T cell activation.
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Affiliation(s)
- Erin L Filbert
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO 63110, USA
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28
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Numata T, Murakami T, Kawashima F, Morone N, Heuser JE, Takano Y, Ohkubo K, Fukuzumi S, Mori Y, Imahori H. Utilization of Photoinduced Charge-Separated State of Donor–Acceptor-Linked Molecules for Regulation of Cell Membrane Potential and Ion Transport. J Am Chem Soc 2012; 134:6092-5. [DOI: 10.1021/ja3007275] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Tomohiro Numata
- Department
of Synthetic Chemistry
and Biological Chemistry, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510, Japan
| | - Tatsuya Murakami
- Institute for Integrated Cell-Material
Sciences (WPI-iCeMS), Kyoto University,
Sakyo-ku, Kyoto 606-8501, Japan
| | - Fumiaki Kawashima
- Department of Molecular Engineering,
Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510, Japan
| | - Nobuhiro Morone
- Institute for Integrated Cell-Material
Sciences (WPI-iCeMS), Kyoto University,
Sakyo-ku, Kyoto 606-8501, Japan
| | - John E. Heuser
- Institute for Integrated Cell-Material
Sciences (WPI-iCeMS), Kyoto University,
Sakyo-ku, Kyoto 606-8501, Japan
| | - Yuta Takano
- Institute for Integrated Cell-Material
Sciences (WPI-iCeMS), Kyoto University,
Sakyo-ku, Kyoto 606-8501, Japan
| | - Kei Ohkubo
- Department of Material and Life
Science, Graduate School of Engineering, Osaka University, and ALCA, Japan Science and Technology Agency (JST), Suita, Osaka
565-0871, Japan
| | - Shunichi Fukuzumi
- Department of Material and Life
Science, Graduate School of Engineering, Osaka University, and ALCA, Japan Science and Technology Agency (JST), Suita, Osaka
565-0871, Japan
- Department
of Bioinspired Science, Ewha Womans University, Seoul 120-750, Korea
| | - Yasuo Mori
- Department
of Synthetic Chemistry
and Biological Chemistry, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510, Japan
| | - Hiroshi Imahori
- Institute for Integrated Cell-Material
Sciences (WPI-iCeMS), Kyoto University,
Sakyo-ku, Kyoto 606-8501, Japan
- Department of Molecular Engineering,
Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510, Japan
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Yuan S, Yu X, Asara JM, Heuser JE, Ludtke SJ, Akey CW. The holo-apoptosome: activation of procaspase-9 and interactions with caspase-3. Structure 2011; 19:1084-96. [PMID: 21827945 DOI: 10.1016/j.str.2011.07.001] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2011] [Revised: 06/12/2011] [Accepted: 06/23/2011] [Indexed: 10/17/2022]
Abstract
Activation of procaspase-9 on the apoptosome is a pivotal step in the intrinsic cell death pathway. We now provide further evidence that caspase recruitment domains of pc-9 and Apaf-1 form a CARD-CARD disk that is flexibly tethered to the apoptosome. In addition, a 3D reconstruction of the pc-9 apoptosome was calculated without symmetry restraints. In this structure, p20 and p10 catalytic domains of a single pc-9 interact with nucleotide binding domains of adjacent Apaf-1 subunits. Together, disk assembly and pc-9 binding create an asymmetric proteolysis machine. We also show that CARD-p20 and p20-p10 linkers play important roles in pc-9 activation. Based on the data, we propose a proximity-induced association model for pc-9 activation on the apoptosome. We also show that pc-9 and caspase-3 have overlapping binding sites on the central hub. These binding sites may play a role in pc-3 activation and could allow the formation of hybrid apoptosomes with pc-9 and caspase-3 proteolytic activities.
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Affiliation(s)
- Shujun Yuan
- Department of Physiology and Biophysics, Boston University School of Medicine, 700 Albany Street, Boston, MA 02118-2526, USA
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Keyel PA, Loultcheva L, Roth R, Salter RD, Watkins SC, Yokoyama WM, Heuser JE. Streptolysin O clearance through sequestration into blebs that bud passively from the plasma membrane. J Cell Sci 2011; 124:2414-23. [PMID: 21693578 DOI: 10.1242/jcs.076182] [Citation(s) in RCA: 111] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Cells survive exposure to bacterial pore-forming toxins, such as streptolysin O (SLO), through mechanisms that remain unclear. Previous studies have suggested that these toxins are cleared by endocytosis. However, the experiments reported here failed to reveal any evidence for endocytosis of SLO, nor did they reveal any signs of damage to endosomal membranes predicted from such endocytosis. Instead, we illustrate that SLO induces a characteristic form of plasma membrane blebbing that allows cells to shed SLO by the process known as ectocytosis. Specifically, 'deep-etch' electron microscopy of cells exposed to SLO illustrates that the toxin is rapidly sequestered into domains in the plasmalemma greatly enriched in SLO pores, and these domains bleb outwards and bud from the cell surface into the medium. Such ectocytosis is even observed in cells that have been chemically fixed before exposure to SLO, suggesting that it is caused by a direct physical action of the toxin on the cell membrane, rather than by an active cellular reaction. We conclude, therefore, that ectocytosis is an important means for SLO clearance and hypothesize that this is a primary method by which cells defend themselves generally against pore-forming toxins.
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Affiliation(s)
- Peter A Keyel
- Howard Hughes Medical Institute, St Louis, MO 63110, USA
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Abstract
The introduction of the Balzers freeze-fracture machine by Moor in 1961 had a much greater impact on the advancement of electron microscopy than he could have imagined. Devised originally to circumvent the dangers of classical thin-section techniques, as well as to provide unique en face views of cell membranes, freeze-fracturing proved to be crucial for developing modern concepts of how biological membranes are organized and proved that membranes are bilayers of lipids within which proteins float and self-assemble. Later, when freeze-fracturing was combined with methods for freezing cells that avoided the fixation and cryoprotection steps that Moor still had to use to prepare the samples for his original invention, it became a means for capturing membrane dynamics on the millisecond time-scale, thus allowing a deeper understanding of the functions of biological membranes in living cells as well as their static ultrastructure. Finally, the realization that unfixed, non-cryoprotected samples could be deeply vacuum-etched or even freeze-dried after freeze-fracturing opened up a whole new way to image all the other molecular components of cells besides their membranes and also provided a powerful means to image the interactions of all the cytoplasmic components with the various membranes of the cell. The purpose of this review is to outline the history of these technical developments, to describe how they are being used in electron microscopy today and to suggest how they can be improved in order to further their utility for biological electron microscopy in the future.
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Affiliation(s)
- John E Heuser
- Department of Cell Biology, Washington University School of Medicine, St. Louis, MO, USA.
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Brady RJ, Damer CK, Heuser JE, O'Halloran TJ. Regulation of Hip1r by epsin controls the temporal and spatial coupling of actin filaments to clathrin-coated pits. J Cell Sci 2010; 123:3652-61. [PMID: 20923836 DOI: 10.1242/jcs.066852] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Recently, it has become clear that the actin cytoskeleton is involved in clathrin-mediated endocytosis. During clathrin-mediated endocytosis, clathrin triskelions and adaptor proteins assemble into lattices, forming clathrin-coated pits. These coated pits invaginate and detach from the membrane, a process that requires dynamic actin polymerization. We found an unexpected role for the clathrin adaptor epsin in regulating actin dynamics during this late stage of coated vesicle formation. In Dictyostelium cells, epsin is required for both the membrane recruitment and phosphorylation of the actin- and clathrin-binding protein Hip1r. Epsin-null and Hip1r-null cells exhibit deficiencies in the timing and organization of actin filaments at clathrin-coated pits. Consequently, clathrin structures persist on the membranes of epsin and Hip1r mutants and the internalization of clathrin structures is delayed. We conclude that epsin works with Hip1r to regulate actin dynamics by controlling the spatial and temporal coupling of actin filaments to clathrin-coated pits. Specific residues in the ENTH domain of epsin that are required for the membrane recruitment and phosphorylation of Hip1r are also required for normal actin and clathrin dynamics at the plasma membrane. We propose that epsin promotes the membrane recruitment and phosphorylation of Hip1r, which in turn regulates actin polymerization at clathrin-coated pits.
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Affiliation(s)
- Rebecca J Brady
- Department of Molecular Cell and Developmental Biology, University of Texas at Austin, Austin, TX 78712, USA
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33
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Wu M, Huang B, Graham M, Raimondi A, Heuser JE, Zhuang X, De Camilli P. Coupling between clathrin-dependent endocytic budding and F-BAR-dependent tubulation in a cell-free system. Nat Cell Biol 2010; 12:902-8. [PMID: 20729836 PMCID: PMC3338250 DOI: 10.1038/ncb2094] [Citation(s) in RCA: 121] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2009] [Accepted: 07/29/2010] [Indexed: 12/30/2022]
Abstract
Cell-free reconstitution of membrane traffic reactions and the morphological characterization of membrane intermediates that accumulate under these conditions have helped elucidate the physical and molecular mechanisms involved in membrane transport1–3. Towards an improved understanding of endocytosis we have reconstituted vesicle budding and fission from isolated plasma membrane sheets and imaged these events. Electron and fluorescence microscopy, including sub-diffraction-limit imaging by stochastic optical reconstruction microscopy (STORM) 4–6, revealed F-BAR (FBP17) domain coated tubules nucleated by clathrin-coated buds when fission was blocked (presence of GTPγS). Triggering fission by replacement of GTPγS with GTP led not only to separation of clathrin-coated buds, but also to vesicle formation by fragmentation of the tubules. These results suggest a functional link between FBP17 dependent membrane tubulation and clathrin-dependent budding. They also show that clathrin spatially directs plasma membrane invaginations that lead to the generation of endocytic vesicles larger than those enclosed by the coat.
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Affiliation(s)
- Min Wu
- Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT 06520, USA
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34
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Abstract
The mt(+) sexual agglutinin from Chlamydomonas reinhardi is shown to contain approximately 12% hydroxyproline, and two inhibitors of hydroxyproline formation, alpha,alpha'-dipyridyl and 3,4-dehydroproline, are shown to block the production of agglutinin activity in an in vivo bioassay system. These results indicate that the agglutinin glycoprotein may be related to a class of hydroxyproline-rich glycoproteins found in the extracellular matrix of higher plants, several of which have been shown to have lectin activity.
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Affiliation(s)
- J B Cooper
- Department of Biology, Washington University, Washington University School of Medicine, St. Louis, Missouri 63130
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35
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Soman NR, Baldwin SL, Hu G, Marsh JN, Lanza GM, Heuser JE, Arbeit JM, Wickline SA, Schlesinger PH. Molecularly targeted nanocarriers deliver the cytolytic peptide melittin specifically to tumor cells in mice, reducing tumor growth. J Clin Invest 2009; 119:2830-42. [PMID: 19726870 DOI: 10.1172/jci38842] [Citation(s) in RCA: 214] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2009] [Accepted: 06/03/2009] [Indexed: 12/21/2022] Open
Abstract
The in vivo application of cytolytic peptides for cancer therapeutics is hampered by toxicity, nonspecificity, and degradation. We previously developed a specific strategy to synthesize a nanoscale delivery vehicle for cytolytic peptides by incorporating the nonspecific amphipathic cytolytic peptide melittin into the outer lipid monolayer of a perfluorocarbon nanoparticle. Here, we have demonstrated that the favorable pharmacokinetics of this nanocarrier allows accumulation of melittin in murine tumors in vivo and a dramatic reduction in tumor growth without any apparent signs of toxicity. Furthermore, direct assays demonstrated that molecularly targeted nanocarriers selectively delivered melittin to multiple tumor targets, including endothelial and cancer cells, through a hemifusion mechanism. In cells, this hemifusion and transfer process did not disrupt the surface membrane but did trigger apoptosis and in animals caused regression of precancerous dysplastic lesions. Collectively, these data suggest that the ability to restrain the wide-spectrum lytic potential of a potent cytolytic peptide in a nanovehicle, combined with the flexibility of passive or active molecular targeting, represents an innovative molecular design for chemotherapy with broad-spectrum cytolytic peptides for the treatment of cancer at multiple stages.
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Affiliation(s)
- Neelesh R Soman
- Department of Biomedical Engineering, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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36
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Martens EC, Roth R, Heuser JE, Gordon JI. Coordinate regulation of glycan degradation and polysaccharide capsule biosynthesis by a prominent human gut symbiont. J Biol Chem 2009; 284:18445-57. [PMID: 19403529 PMCID: PMC2709373 DOI: 10.1074/jbc.m109.008094] [Citation(s) in RCA: 133] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Bacteria in the distal human gut have evolved diverse abilities to metabolize complex glycans, including the capacity to degrade these compounds as nutrients and to assemble their component sugars into new polymers such as extracellular capsules. The human gut bacterium Bacteroides thetaiotaomicron is well endowed with the ability to metabolize both host- and diet-derived glycans. Its genome contains 88 different polysaccharide utilization loci (PULs) for complex glycan catabolism and eight different gene clusters for capsular polysaccharide biosynthesis. Here, we investigate one of the prominent mechanisms by which this gut symbiont regulates many PULs involved in host mucin O-glycan degradation; namely, transcriptional regulation via the concerted interactions of cell-envelope-localized TonB-dependent transporters, extra-cytoplasmic function sigma factors and anti-sigma factors, which participate together in a regulatory pathway termed trans-envelope signaling. Unexpectedly, we found that several different trans-envelope signaling switches involved in PUL-mediated O-glycan degradation also modulate capsular polysaccharide synthesis. A novel regulatory pathway, which is dependent on expression of O-glycan-targeting outer membrane proteins, governs this coordinated regulation of glycan catabolism and capsule synthesis. This latter finding provides a new link in the dynamic interplay between complex glycan metabolism, microbial physiology, and host responses that occurs during colonization of the gut.
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Affiliation(s)
- Eric C Martens
- Center for Genome Sciences, Washington University School of Medicine, St. Louis, Missouri 63108, USA
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37
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Keyel PA, Thieman JR, Roth R, Erkan E, Everett ET, Watkins SC, Heuser JE, Traub LM. The AP-2 adaptor beta2 appendage scaffolds alternate cargo endocytosis. Mol Biol Cell 2008; 19:5309-26. [PMID: 18843039 DOI: 10.1091/mbc.e08-07-0712] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The independently folded appendages of the large alpha and beta2 subunits of the endocytic adaptor protein (AP)-2 complex coordinate proper assembly and operation of endocytic components during clathrin-mediated endocytosis. The beta2 subunit appendage contains a common binding site for beta-arrestin or the autosomal recessive hypercholesterolemia (ARH) protein. To determine the importance of this interaction surface in living cells, we used small interfering RNA-based gene silencing. The effect of extinguishing beta2 subunit expression on the internalization of transferrin is considerably weaker than an AP-2 alpha subunit knockdown. We show the mild sorting defect is due to fortuitous substitution of the beta2 chain with the closely related endogenous beta1 subunit of the AP-1 adaptor complex. Simultaneous silencing of both beta1 and beta2 subunit transcripts recapitulates the strong alpha subunit RNA interference (RNAi) phenotype and results in loss of ARH from endocytic clathrin coats. An RNAi-insensitive beta2-yellow fluorescent protein (YFP) expressed in the beta1 + beta2-silenced background restores cellular AP-2 levels, robust transferrin internalization, and ARH colocalization with cell surface clathrin. The importance of the beta appendage platform subdomain over clathrin for precise deposition of ARH at clathrin assembly zones is revealed by a beta2-YFP with a disrupted ARH binding interface, which does not restore ARH colocalization with clathrin. We also show a beta-arrestin 1 mutant, which engages coated structures in the absence of any G protein-coupled receptor stimulation, colocalizes with beta2-YFP and clathrin even in the absence of an operational clathrin binding sequence. These findings argue against ARH and beta-arrestin binding to a site upon the beta2 appendage platform that is later obstructed by polymerized clathrin. We conclude that ARH and beta-arrestin depend on a privileged beta2 appendage site for proper cargo recruitment to clathrin bud sites.
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Affiliation(s)
- Peter A Keyel
- Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
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38
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Sheridan SD, Yu X, Roth R, Heuser JE, Sehorn MG, Sung P, Egelman EH, Bishop DK. A comparative analysis of Dmc1 and Rad51 nucleoprotein filaments. Nucleic Acids Res 2008; 36:4057-66. [PMID: 18535008 PMCID: PMC2475612 DOI: 10.1093/nar/gkn352] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
The eukaryotic RecA homologs Rad51 and Dmc1 are essential for strand exchange between homologous chromosomes during meiosis. All members of the RecA family of recombinases polymerize on DNA to form helical nucleoprotein filaments, which is the active form of the protein. Here we compare the filament structures of the Rad51 and Dmc1 proteins from both human and budding yeast. Previous studies of Dmc1 filaments suggested that they might be structurally distinct from filaments of other members of the RecA family, including Rad51. The data presented here indicate that Rad51 and Dmc1 filaments are essentially identical with respect to several structural parameters, including persistence length, helical pitch, filament diameter, DNA base pairs per helical turn and helical handedness. These data, together with previous studies demonstrating similar in vitro recombinase activity for Dmc1 and Rad51, support the view that differences in the meiotic function of Rad51 and Dmc1 are more likely to result from the influence of distinct sets of accessory proteins than from intrinsic differences in filament structure.
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Affiliation(s)
- Sean D Sheridan
- Committee on Genetics, University of Chicago, Chicago, IL 60637, USA
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39
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Kim Y, Heuser JE, Waterman CM, Cleveland DW. CENP-E combines a slow, processive motor and a flexible coiled coil to produce an essential motile kinetochore tether. ACTA ACUST UNITED AC 2008; 181:411-9. [PMID: 18443223 PMCID: PMC2364708 DOI: 10.1083/jcb.200802189] [Citation(s) in RCA: 111] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
The mitotic kinesin centromere protein E (CENP-E) is an essential kinetochore component that directly contributes to the capture and stabilization of spindle microtubules by kinetochores. Although reduction in CENP-E leads to high rates of whole chromosome missegregation, neither its properties as a microtubule-dependent motor nor how it contributes to the dynamic linkage between kinetochores and microtubules is known. Using single-molecule assays, we demonstrate that CENP-E is a very slow, highly processive motor that maintains microtubule attachment for long periods. Direct visualization of full-length Xenopus laevis CENP-E reveals a highly flexible 230-nm coiled coil separating its kinetochore-binding and motor domains. We also show that full-length CENP-E is a slow plus end–directed motor whose activity is essential for metaphase chromosome alignment. We propose that the highly processive microtubule-dependent motor activity of CENP-E serves to power chromosome congression and provides a flexible, motile tether linking kinetochores to dynamic spindle microtubules.
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Affiliation(s)
- Yumi Kim
- Ludwig Institute for Cancer Research, University of California, San Diego, La Jolla, CA 92093, USA
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40
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Abstract
Endosomal sorting complex required for transport III (ESCRT-III) proteins function in multivesicular body biogenesis and viral budding. They are recruited from the cytoplasm to the membrane, where they assemble into large complexes. We used “deep-etch” electron microscopy to examine polymers formed by the ESCRT-III proteins hSnf7-1 (CHMP4A) and hSnf7-2 (CHMP4B). When overexpressed, these proteins target to endosomes and the plasma membrane. Both hSnf7 proteins assemble into regular approximately 5-nm filaments that curve and self-associate to create circular arrays. Binding to a coexpressed adenosine triphosphate hydrolysis–deficient mutant of VPS4B draws these filaments together into tight circular scaffolds that bend the membrane away from the cytoplasm to form buds and tubules protruding from the cell surface. Similar buds develop in the absence of mutant VPS4B when hSnf7-1 is expressed without its regulatory C-terminal domain. We demonstrate that hSnf7 proteins form novel membrane-attached filaments that can promote or stabilize negative curvature and outward budding. We suggest that ESCRT-III polymers delineate and help generate the luminal vesicles of multivesicular bodies.
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Affiliation(s)
- Phyllis I Hanson
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110, USA.
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41
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Huang RH, Wang Y, Roth R, Yu X, Purvis AR, Heuser JE, Egelman EH, Sadler JE. Assembly of Weibel-Palade body-like tubules from N-terminal domains of von Willebrand factor. Proc Natl Acad Sci U S A 2008; 105:482-7. [PMID: 18182488 PMCID: PMC2206562 DOI: 10.1073/pnas.0710079105] [Citation(s) in RCA: 124] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2007] [Indexed: 11/18/2022] Open
Abstract
Endothelial cells assemble von Willebrand factor (VWF) multimers into ordered tubules within storage organelles called Weibel-Palade bodies, and tubular packing is necessary for the secretion of VWF filaments that can bind connective tissue and recruit platelets to sites of vascular injury. We now have recreated VWF tubule assembly in vitro, starting with only pure VWF propeptide (domains D1D2) and disulfide-linked dimers of adjacent N-terminal D'D3 domains. Assembly requires low pH and calcium ions and is reversed at neutral pH. Quick-freeze deep-etch electron microscopy and three-dimensional reconstruction of negatively stained images show that tubules contain a repeating unit of one D'D3 dimer and two propeptides arranged in a right-handed helix with 4.2 units per turn. The symmetry and location of interdomain contacts suggest that decreasing pH along the secretory pathway coordinates the disulfide-linked assembly of VWF multimers with their tubular packaging.
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Affiliation(s)
| | - Ying Wang
- Department of Biochemistry and Molecular Genetics, University of Virginia, Charlottesville, VA 22908
| | | | - Xiong Yu
- Department of Biochemistry and Molecular Genetics, University of Virginia, Charlottesville, VA 22908
| | - Angie R. Purvis
- Medicine, Washington University School of Medicine, St. Louis, MO 63110; and
| | | | - Edward H. Egelman
- Department of Biochemistry and Molecular Genetics, University of Virginia, Charlottesville, VA 22908
| | - J. Evan Sadler
- *Howard Hughes Medical Institute and
- Medicine, Washington University School of Medicine, St. Louis, MO 63110; and
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42
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Cardone G, Winkler DC, Trus BL, Cheng N, Heuser JE, Newcomb WW, Brown JC, Steven AC. Visualization of the herpes simplex virus portal in situ by cryo-electron tomography. Virology 2006; 361:426-34. [PMID: 17188319 PMCID: PMC1930166 DOI: 10.1016/j.virol.2006.10.047] [Citation(s) in RCA: 98] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2006] [Revised: 10/17/2006] [Accepted: 10/27/2006] [Indexed: 11/18/2022]
Abstract
Herpes simplex virus type 1 (HSV-1), the prototypical herpesvirus, has an icosahedral nucleocapsid surrounded by a proteinaceous tegument and a lipoprotein envelope. As in tailed bacteriophages, the icosahedral symmetry of the capsid is broken at one of the 12 vertices, which is occupied by a dodecameric ring of portal protein, UL6, instead of a pentamer of the capsid protein, UL19. The portal ring serves as a conduit for DNA entering and exiting the capsid. From a cryo-EM reconstruction of capsids immuno-gold-labeled with anti-UL6 antibodies, we confirmed that UL6 resides at a vertex. To visualize the portal in the context of the assembled capsid, we used cryo-electron tomography to determine the three-dimensional structures of individual A-capsids (empty, mature capsids). The similarity in size and overall shape of the portal and a UL19 pentamer--both are cylinders of approximately 800 kDa--combined with residual noise in the tomograms, prevented us from identifying the portal vertices directly; however, this was accomplished by a computational classification procedure. Averaging the portal-containing subtomograms produced a structure that tallies with the isolated portal, as previously reconstructed by cryo-EM. The portal is mounted on the outer surface of the capsid floor layer, with its narrow end pointing outwards. This disposition differs from that of known phage portals in that the bulk of its mass lies outside, not inside, the floor. This distinction may be indicative of divergence at the level of portal-related functions other than its role as a DNA channel.
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Affiliation(s)
- Giovanni Cardone
- Laboratory of Structural Biology Research, National Institute of Arthritis and Musculoskeletal and Skin Diseases, Bethesda, MD 20892
| | - Dennis C. Winkler
- Laboratory of Structural Biology Research, National Institute of Arthritis and Musculoskeletal and Skin Diseases, Bethesda, MD 20892
| | - Benes L. Trus
- Laboratory of Structural Biology Research, National Institute of Arthritis and Musculoskeletal and Skin Diseases, Bethesda, MD 20892
- Imaging Sciences Laboratory, Division of Computational Bioscience, Center for Information Technology; National Institutes of Health, Bethesda, MD 20892
| | - Naiqian Cheng
- Laboratory of Structural Biology Research, National Institute of Arthritis and Musculoskeletal and Skin Diseases, Bethesda, MD 20892
| | - John E. Heuser
- Department of Cell Biology, Washington University School of Medicine, St. Louis, MO 63110
| | - William W. Newcomb
- Department of Microbiology and Cancer Center, University of Virginia Health System, Charlottesville, VA 22908
| | - Jay C. Brown
- Department of Microbiology and Cancer Center, University of Virginia Health System, Charlottesville, VA 22908
| | - Alasdair C. Steven
- Laboratory of Structural Biology Research, National Institute of Arthritis and Musculoskeletal and Skin Diseases, Bethesda, MD 20892
- * Correspondence : Building 50, Rm 1517, MSC 8025, 50 South Drive, National Institutes of Health, Bethesda MD 20892-8025, tel: 301 496 0132; fax 301 443 7651;
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43
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Keyel PA, Mishra SK, Roth R, Heuser JE, Watkins SC, Traub LM. A single common portal for clathrin-mediated endocytosis of distinct cargo governed by cargo-selective adaptors. Mol Biol Cell 2006; 17:4300-17. [PMID: 16870701 PMCID: PMC1635374 DOI: 10.1091/mbc.e06-05-0421] [Citation(s) in RCA: 103] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Sorting of transmembrane cargo into clathrin-coated vesicles requires endocytic adaptors, yet RNA interference (RNAi)-mediated gene silencing of the AP-2 adaptor complex only disrupts internalization of a subset of clathrin-dependent cargo. This suggests alternate clathrin-associated sorting proteins participate in cargo capture at the cell surface, and a provocative recent proposal is that discrete endocytic cargo are sorted into compositionally and functionally distinct clathrin coats. We show here that the FXNPXY-type internalization signal within cytosolic domain of the LDL receptor is recognized redundantly by two phosphotyrosine-binding domain proteins, Dab2 and ARH; diminishing both proteins by RNAi leads to conspicuous LDL receptor accumulation at the cell surface. AP-2-dependent uptake of transferrin ensues relatively normally in the absence of Dab2 and ARH, clearly revealing delegation of sorting operations at the bud site. AP-2, Dab2, ARH, transferrin, and LDL receptors are all present within the vast majority of clathrin structures at the surface, challenging the general existence of specialized clathrin coats for segregated internalization of constitutively internalized cargo. However, Dab2 expression is exceptionally low in hepatocytes, likely accounting for the pathological hypercholesterolemia that accompanies ARH loss.
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Affiliation(s)
- Peter A. Keyel
- *Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261; and
| | - Sanjay K. Mishra
- *Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261; and
| | - Robyn Roth
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110
| | - John E. Heuser
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110
| | - Simon C. Watkins
- *Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261; and
| | - Linton M. Traub
- *Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261; and
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Abstract
Epsin 1 engages several core components of the endocytic clathrin coat, yet the precise mode of operation of the protein remains controversial. The occurrence of tandem ubiquitin-interacting motifs (UIMs) suggests that epsin could recognize a ubiquitin internalization tag, but the association of epsin with clathrin-coat components or monoubiquitin is reported to be mutually exclusive. Here, we show that endogenous epsin 1 is clearly an integral component of clathrin coats forming at the cell surface and is essentially absent from caveolin-1-containing structures under normal conditions. The UIM region of epsin 1 associates directly with polyubiquitin chains but has extremely poor affinity for monoubiquitin. Polyubiquitin binding is retained when epsin synchronously associates with phosphoinositides, the AP-2 adaptor complex and clathrin. The enrichment of epsin within clathrin-coated vesicles purified from different tissue sources varies and correlates with sorting of multiubiquitinated cargo, and in cultured cells, polyubiquitin, rather than non-conjugable monoubiquitin, promotes rapid internalization. As epsin interacts with eps15, which also contains a UIM region that binds to polyubiquitin, epsin and eps15 appear to be central components of the vertebrate poly/multiubiquitin-sorting endocytic clathrin machinery.
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Affiliation(s)
- Matthew J Hawryluk
- Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
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Lapaque N, Forquet F, de Chastellier C, Mishal Z, Jolly G, Moreno E, Moriyon I, Heuser JE, He HT, Gorvel JP. Characterization of Brucella abortus lipopolysaccharide macrodomains as mega rafts. Cell Microbiol 2006; 8:197-206. [PMID: 16441431 DOI: 10.1111/j.1462-5822.2005.00609.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The lipopolysaccharides (LPS) of intracellular Proteobacteria such as Brucella, Chlamydia, Legionella and Rickettsia, have properties distinct from enterobacterial LPSs. These properties include deficient LPS induction of host cell activation, low endotoxicity and resistance to macrophage degradation. Together these constitute key virulence mechanisms for intracellular survival and replication. We previously demonstrated that B. abortus LPS captured by macrophages was recycled back to the plasma membrane where it was found associated with macrodomains. Furthermore, this LPS interferes with the MHC class II (MHC-II) presentation of peptides to specific T cell hybridomas. Here, we characterized the Brucella LPS macrodomains by microscopy and biochemistry approaches. We show for the first time that LPS macrodomains act as detergent resistant membranes (DRMs), segregating several lipid-raft components, LPS-binding proteins and MHC-II molecules. Brucella LPS macrodomains remain intact for several months in macrophages and are resistant to the disruptive effects of methyl beta-cyclodextrin. Fluorescent anisotropy measurements show that B. abortus LPS is responsible for the formation of rigid surface membrane complexes. In addition, relocalization of MHC-II molecules is observed in these structures. The effects of B. abortus LPS on membrane properties could be responsible for pathogenic effects such as the inhibition of MHC-II-dependent antigen presentation.
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Affiliation(s)
- Nicolas Lapaque
- Centre d'Immunologie INSERM-CNRS-Université Méditerranée, case 906, 13288 Marseille Cedex 9, France
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Edeling MA, Mishra SK, Keyel PA, Steinhauser AL, Collins BM, Roth R, Heuser JE, Owen DJ, Traub LM. Molecular Switches Involving the AP-2 β2 Appendage Regulate Endocytic Cargo Selection and Clathrin Coat Assembly. Dev Cell 2006; 10:329-42. [PMID: 16516836 DOI: 10.1016/j.devcel.2006.01.016] [Citation(s) in RCA: 131] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2005] [Revised: 12/30/2005] [Accepted: 01/12/2006] [Indexed: 10/24/2022]
Abstract
Clathrin-associated sorting proteins (CLASPs) expand the repertoire of endocytic cargo sorted into clathrin-coated vesicles beyond the transmembrane proteins that bind physically to the AP-2 adaptor. LDL and GPCRs are internalized by ARH and beta-arrestin, respectively. We show that these two CLASPs bind selectively to the AP-2 beta2 appendage platform via an alpha-helical [DE](n)X(1-2)FXX[FL]XXXR motif, and that this motif also occurs and is functional in the epsins. In beta-arrestin, this motif maintains the endocytosis-incompetent state by binding back on the folded core of the protein in a beta strand conformation. Triggered via a beta-arrestin/GPCR interaction, the motif must be displaced and must undergo a strand to helix transition to enable the beta2 appendage binding that drives GPCR-beta-arrestin complexes into clathrin coats. Another interaction surface on the beta2 appendage sandwich is identified for proteins such as eps15 and clathrin, suggesting a mechanism by which clathrin displaces eps15 to lattice edges during assembly.
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Affiliation(s)
- Melissa A Edeling
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge CB2 2XY, United Kingdom
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Abstract
Following attachment of Neisseria gonorrhoeae to human epithelial cell lines, the cellular pilus receptor CD46 is shed from the cell and accumulates in the media. In this report, we assess Neisseria-induced alterations in CD46 surface distribution and characterize this complement regulatory protein following its release from the infected cell. Within 3 h of attachment of gonococci to human epithelial cell lines, CD46 is enriched beneath sites of microcolony adhesion. By 6 h post infection, differential ultracentrifugation of culture media from ME-180 monolayers resulted in sedimentation of structurally and functionally intact CD46. Electron microscopy of these 100,000 g pellets revealed 30-200 nm vesicles. These vesicles likely originated from the host cell as they contained additional host cell surface proteins including CD55 and the epidermal growth factor receptor. Further, these vesicles were visualized by quick-freeze, deep-etch electron microscopy in association with the surface of infected ME-180 cells and with pili of adherent gonococci. Like CD46 shedding, CD46 redistribution and vesicle release were insensitive to colchicine and cytochalasin-D but dependent on expression of the pilus retraction protein PilT. This vesiculation may represent a host cell defence response in which surface proteins that are commonly exploited by pathogens, such as CD46, are removed from the cell.
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Affiliation(s)
- Darcy B Gill
- Department of Medicine, Washington University School of Medicine, St Louis, MO 63112, USA
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Abstract
The actin cytoskeleton is essential for many cellular functions including shape determination, intracellular transport and locomotion. Previous work has identified two factors--the Arp2/3 complex and the formin family of proteins--that nucleate new actin filaments via different mechanisms. Here we show that the Drosophila protein Spire represents a third class of actin nucleation factor. In vitro, Spire nucleates new filaments at a rate that is similar to that of the formin family of proteins but slower than in the activated Arp2/3 complex, and it remains associated with the slow-growing pointed end of the new filament. Spire contains a cluster of four WASP homology 2 (WH2) domains, each of which binds an actin monomer. Maximal nucleation activity requires all four WH2 domains along with an additional actin-binding motif, conserved among Spire proteins. Spire itself is conserved among metazoans and, together with the formin Cappuccino, is required for axis specification in oocytes and embryos, suggesting that multiple actin nucleation factors collaborate to construct essential cytoskeletal structures.
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Affiliation(s)
- Margot E Quinlan
- Department of Cellular and Molecular Pharmacology, UCSF Medical School, San Francisco, California 94107, USA
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Mishra SK, Hawryluk MJ, Brett TJ, Keyel PA, Dupin AL, Jha A, Heuser JE, Fremont DH, Traub LM. Dual Engagement Regulation of Protein Interactions with the AP-2 Adaptor α Appendage. J Biol Chem 2004; 279:46191-203. [PMID: 15292237 DOI: 10.1074/jbc.m408095200] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Clathrin-mediated endocytosis depends upon the coordinated assembly of a large number of discrete clathrin coat components to couple cargo selection with rapid internalization from the cell surface. Accordingly, the heterotetrameric AP-2 adaptor complex binds not only to clathrin and select cargo molecules, but also to an extensive family of endocytic accessory factors and alternate sorting adaptors. Physical associations between accessory proteins and AP-2 occur primarily through DP(F/W) or FXDXF motifs, which engage an interaction surface positioned on the C-terminal platform subdomain of the independently folded alpha subunit appendage. Here, we find that the WXX(F/W)X(D/E) interaction motif found in several endocytic proteins, including synaptojanin 1, stonin 2, AAK1, GAK, and NECAP1, binds a second interaction site on the bilobal alpha appendage, located on the N-terminal beta sandwich subdomain. Both alpha appendage binding sites can be engaged synchronously, and our data reveal that varied assemblies of interaction motifs with different affinities for two sites upon the alpha appendage can provide a mechanism for temporal ordering of endocytic accessory proteins during clathrin-mediated endocytosis.
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Affiliation(s)
- Sanjay K Mishra
- Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, USA
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Abstract
Early-onset torsion dystonia, a CNS-based movement disorder, is usually associated with a single amino acid deletion (Delta E302/303) in the protein torsinA. TorsinA is an AAA+ ATPase in the endoplasmic reticulum, but what it does is unknown. Here, we use torsinA mutants with defects in ATP hydrolysis (E171Q, ATP-bound) and ATP binding (K108A, ATP-free) to probe torsinA's normal cellular function. Surprisingly, ATP-bound torsinA is recruited to the nuclear envelope (NE) of transfected cells, where it alters connections between inner and outer nuclear membranes. In contrast, ATP-free torsinA is diffusely distributed throughout the endoplasmic reticulum and has no effect on the NE. Among AAA+ ATPases, affinity for substrates is high in the ATP-bound and low in the ATP-free state, leading us to propose that component(s) of the NE may be substrates for torsinA. We also find that the disease-promoting Delta E302/303 mutant is in the NE, and that this relocalization, as well as the mutant's previously described ability to induce membranous inclusions, is eliminated by the K108A ATP-binding mutation. These results suggest that changes in interactions involving torsinA in the NE could be important for the pathogenesis of dystonia and point to torsinA and related proteins as a class of ATPases that may operate in the NE.
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Affiliation(s)
- Teresa V Naismith
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110, USA
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