1
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Matharu SS, Nordmann CS, Ottman KR, Akkem R, Palumbo D, Cruz DRD, Campbell K, Sievert G, Sturgill J, Porterfield JZ, Joshi S, Alfar HR, Peng C, Pokrovskaya ID, Kamykowski JA, Wood JP, Garvy B, Aronova MA, Whiteheart SW, Leapman RD, Storrie B. Deep learning, 3D ultrastructural analysis reveals quantitative differences in platelet and organelle packing in COVID-19/SARSCoV2 patient-derived platelets. Platelets 2023; 34:2264978. [PMID: 37933490 PMCID: PMC10809228 DOI: 10.1080/09537104.2023.2264978] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [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: 07/06/2023] [Accepted: 09/20/2023] [Indexed: 11/08/2023]
Abstract
Platelets contribute to COVID-19 clinical manifestations, of which microclotting in the pulmonary vasculature has been a prominent symptom. To investigate the potential diagnostic contributions of overall platelet morphology and their α-granules and mitochondria to the understanding of platelet hyperactivation and micro-clotting, we undertook a 3D ultrastructural approach. Because differences might be small, we used the high-contrast, high-resolution technique of focused ion beam scanning EM (FIB-SEM) and employed deep learning computational methods to evaluate nearly 600 individual platelets and 30 000 included organelles within three healthy controls and three severely ill COVID-19 patients. Statistical analysis reveals that the α-granule/mitochondrion-to-plateletvolume ratio is significantly greater in COVID-19 patient platelets indicating a denser packing of organelles, and a more compact platelet. The COVID-19 patient platelets were significantly smaller -by 35% in volume - with most of the difference in organelle packing density being due to decreased platelet size. There was little to no 3D ultrastructural evidence for differential activation of the platelets from COVID-19 patients. Though limited by sample size, our studies suggest that factors outside of the platelets themselves are likely responsible for COVID-19 complications. Our studies show how deep learning 3D methodology can become the gold standard for 3D ultrastructural studies of platelets.
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Affiliation(s)
- Sagar S Matharu
- Laboratory of Cellular Imaging and Macromolecular Biophysics, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD, USA
| | - Cassidy S Nordmann
- Laboratory of Cellular Imaging and Macromolecular Biophysics, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD, USA
| | - Kurtis R Ottman
- Laboratory of Cellular Imaging and Macromolecular Biophysics, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD, USA
| | - Rahul Akkem
- Laboratory of Cellular Imaging and Macromolecular Biophysics, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD, USA
| | - Douglas Palumbo
- Laboratory of Cellular Imaging and Macromolecular Biophysics, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD, USA
| | - Denzel R D Cruz
- Laboratory of Cellular Imaging and Macromolecular Biophysics, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD, USA
| | - Kenneth Campbell
- Department of Internal Medicine, University of Kentucky College of Medicine, Lexington, KY, USA
| | - Gail Sievert
- Center for Clinical Translational Science, University of Kentucky College of Medicine, Lexington, KY, USA
| | - Jamie Sturgill
- Department of Internal Medicine, University of Kentucky College of Medicine, Lexington, KY, USA
| | - James Z Porterfield
- Department of Microbiology, Immunology and Molecular Genetics, University of Kentucky College of Medicine, Lexington, KY, USA
| | - Smita Joshi
- Department of Molecular and Cellular Biochemistry, University of Kentucky College of Medicine, Lexington, KY, USA
| | - Hammodah R Alfar
- Department of Molecular and Cellular Biochemistry, University of Kentucky College of Medicine, Lexington, KY, USA
| | - Chi Peng
- Department of Molecular and Cellular Biochemistry, University of Kentucky College of Medicine, Lexington, KY, USA
| | - Irina D Pokrovskaya
- Department of Physiology and Cell Biology, University of Arkansas for Medical Sciences, Little Rock, AR, USA
| | - Jeffrey A Kamykowski
- Department of Physiology and Cell Biology, University of Arkansas for Medical Sciences, Little Rock, AR, USA
| | - Jeremy P Wood
- Department of Internal Medicine, University of Kentucky College of Medicine, Lexington, KY, USA
| | - Beth Garvy
- Department of Microbiology, Immunology and Molecular Genetics, University of Kentucky College of Medicine, Lexington, KY, USA
| | - Maria A Aronova
- Laboratory of Cellular Imaging and Macromolecular Biophysics, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD, USA
| | - Sidney W Whiteheart
- Department of Molecular and Cellular Biochemistry, University of Kentucky College of Medicine, Lexington, KY, USA
| | - Richard D Leapman
- Laboratory of Cellular Imaging and Macromolecular Biophysics, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD, USA
| | - Brian Storrie
- Department of Physiology and Cell Biology, University of Arkansas for Medical Sciences, Little Rock, AR, USA
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2
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Marsilia C, Batra M, Pokrovskaya ID, Wang C, Chaput D, Naumova DA, Lupashin VV, Suvorova ES. Essential role of the conserved oligomeric Golgi complex in Toxoplasma gondii. mBio 2023; 14:e0251323. [PMID: 37966241 PMCID: PMC10746232 DOI: 10.1128/mbio.02513-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2023] [Accepted: 10/05/2023] [Indexed: 11/16/2023] Open
Abstract
IMPORTANCE The Golgi is an essential eukaryotic organelle and a major place for protein sorting and glycosylation. Among apicomplexan parasites, Toxoplasma gondii retains the most developed Golgi structure and produces many glycosylated factors necessary for parasite survival. Despite its importance, Golgi function received little attention in the past. In the current study, we identified and characterized the conserved oligomeric Golgi complex and its novel partners critical for protein transport in T. gondii tachyzoites. Our results suggest that T. gondii broadened the role of the conserved elements and reinvented the missing components of the trafficking machinery to accommodate the specific needs of the opportunistic parasite T. gondii.
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Affiliation(s)
- Clem Marsilia
- Division of Infectious Diseases, Department of Internal Medicine, Morsani College of Medicine, University of South Florida, Tampa, Florida, USA
| | - Mrinalini Batra
- Division of Infectious Diseases, Department of Internal Medicine, Morsani College of Medicine, University of South Florida, Tampa, Florida, USA
| | - Irina D. Pokrovskaya
- Department of Physiology and Cell Biology, College of Medicine, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA
| | - Changqi Wang
- College of Public Health, University of South Florida, Tampa, Florida, USA
| | - Dale Chaput
- Proteomics Core, College of Arts and Sciences, University of South Florida, Tampa, Florida, USA
| | - Daria A. Naumova
- Division of Infectious Diseases, Department of Internal Medicine, Morsani College of Medicine, University of South Florida, Tampa, Florida, USA
| | - Vladimir V. Lupashin
- Department of Physiology and Cell Biology, College of Medicine, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA
| | - Elena S. Suvorova
- Division of Infectious Diseases, Department of Internal Medicine, Morsani College of Medicine, University of South Florida, Tampa, Florida, USA
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3
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Dimori M, Pokrovskaya ID, Liu S, Sherrill JT, Gomez-Acevedo H, Fu Q, Storrie B, Lupashin VV, Morello R. A Rab33b missense mouse model for Smith-McCort dysplasia shows bone resorption defects and altered protein glycosylation. Front Genet 2023; 14:1204296. [PMID: 37359363 PMCID: PMC10285484 DOI: 10.3389/fgene.2023.1204296] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2023] [Accepted: 05/25/2023] [Indexed: 06/28/2023] Open
Abstract
Smith McCort (SMC) dysplasia is a rare, autosomal recessive, osteochondrodysplasia that can be caused by pathogenic variants in either RAB33B or DYM genes. These genes codes for proteins that are located at the Golgi apparatus and have a role in intracellular vesicle trafficking. We generated mice that carry a Rab33b disease-causing variant, c.136A>C (p.Lys46Gln), which is identical to that of members from a consanguineous family diagnosed with SMC. In male mice at 4 months of age, the Rab33b variant caused a mild increase in trabecular bone thickness in the spine and femur and in femoral mid-shaft cortical thickness with a concomitant reduction of the femoral medullary area, suggesting a bone resorption defect. In spite of the increase in trabecular and cortical thickness, bone histomorphometry showed a 4-fold increase in osteoclast parameters in homozygous Rab33b mice suggesting a putative impairment in osteoclast function, while dynamic parameters of bone formation were similar in mutant versus control mice. Femur biomechanical tests showed an increased in yield load and a progressive elevation, from WT to heterozygote to homozygous mutants, of bone intrinsic properties. These findings suggest an overall impact on bone material properties which may be caused by disturbed protein glycosylation in cells contributing to skeletal formation, supported by the altered and variable pattern of lectin staining in murine and human tissue cultured cells and in liver and bone murine tissues. The mouse model only reproduced some of the features of the human disease and was sex-specific, manifesting in male but not female mice. Our data reveal a potential novel role of RAB33B in osteoclast function and protein glycosylation and their dysregulation in SMC and lay the foundation for future studies.
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Affiliation(s)
- Milena Dimori
- Department of Physiology and Cell Biology, University of Arkansas for Medical Sciences, Little Rock, AR, United States
| | - Irina D Pokrovskaya
- Department of Physiology and Cell Biology, University of Arkansas for Medical Sciences, Little Rock, AR, United States
| | - Shijie Liu
- Department of Physiology and Cell Biology, University of Arkansas for Medical Sciences, Little Rock, AR, United States
| | - John T Sherrill
- Department of Orthopaedic Surgery, University of Arkansas for Medical Sciences, Little Rock, AR, United States
| | - Horacio Gomez-Acevedo
- Department of Biomedical Informatics, University of Arkansas for Medical Sciences, Little Rock, AR, United States
| | - Qiang Fu
- Department of Internal Medicine, Division of Endocrinology, University of Arkansas for Medical Sciences, Little Rock, AR, United States
| | - Brian Storrie
- Department of Physiology and Cell Biology, University of Arkansas for Medical Sciences, Little Rock, AR, United States
| | - Vladimir V Lupashin
- Department of Physiology and Cell Biology, University of Arkansas for Medical Sciences, Little Rock, AR, United States
| | - Roy Morello
- Department of Physiology and Cell Biology, University of Arkansas for Medical Sciences, Little Rock, AR, United States
- Department of Orthopaedic Surgery, University of Arkansas for Medical Sciences, Little Rock, AR, United States
- Division of Genetics, University of Arkansas for Medical Sciences, Little Rock, AR, United States
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4
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Sumya FT, Pokrovskaya ID, D'Souza Z, Lupashin VV. Acute COG complex inactivation unveiled its immediate impact on Golgi and illuminated the nature of intra-Golgi recycling vesicles. Traffic 2023; 24:52-75. [PMID: 36468177 PMCID: PMC9969905 DOI: 10.1111/tra.12876] [Citation(s) in RCA: 0] [Impact Index Per Article: 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: 10/05/2022] [Revised: 11/12/2022] [Accepted: 11/29/2022] [Indexed: 12/07/2022]
Abstract
Conserved Oligomeric Golgi (COG) complex controls Golgi trafficking and glycosylation, but the precise COG mechanism is unknown. The auxin-inducible acute degradation system was employed to investigate initial defects resulting from COG dysfunction. We found that acute COG inactivation caused a massive accumulation of COG-dependent (CCD) vesicles that carry the bulk of Golgi enzymes and resident proteins. v-SNAREs (GS15, GS28) and v-tethers (giantin, golgin84, and TMF1) were relocalized into CCD vesicles, while t-SNAREs (STX5, YKT6), t-tethers (GM130, p115), and most of Rab proteins remained Golgi-associated. Airyscan microscopy and velocity gradient analysis revealed that different Golgi residents are segregated into different populations of CCD vesicles. Acute COG depletion significantly affected three Golgi-based vesicular coats-COPI, AP1, and GGA, suggesting that COG uniquely orchestrates tethering of multiple types of intra-Golgi CCD vesicles produced by different coat machineries. This study provided the first detailed view of primary cellular defects associated with COG dysfunction in human cells.
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Affiliation(s)
- Farhana Taher Sumya
- Department of Physiology and Cell Biology University of Arkansas for Medical Sciences Little Rock Arkansas USA
| | - Irina D. Pokrovskaya
- Department of Physiology and Cell Biology University of Arkansas for Medical Sciences Little Rock Arkansas USA
| | - Zinia D'Souza
- Department of Physiology and Cell Biology University of Arkansas for Medical Sciences Little Rock Arkansas USA
| | - Vladimir V. Lupashin
- Department of Physiology and Cell Biology University of Arkansas for Medical Sciences Little Rock Arkansas USA
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5
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Pokrovskaya ID, Rhee SW, Ball KK, Kamykowski JA, Zhao OS, Cruz DRD, Cohen J, Aronova MA, Leapman RD, Storrie B. Tethered platelet capture provides a mechanism for restricting circulating platelet activation to the wound site. Res Pract Thromb Haemost 2023; 7:100058. [PMID: 36865905 PMCID: PMC9971284 DOI: 10.1016/j.rpth.2023.100058] [Citation(s) in RCA: 0] [Impact Index Per Article: 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: 11/27/2022] [Revised: 12/20/2022] [Accepted: 12/30/2022] [Indexed: 01/24/2023] Open
Abstract
Background Puncture wounding is a longstanding challenge to human health for which understanding is limited, in part, by a lack of detailed morphological data on how the circulating platelet capture to the vessel matrix leads to sustained, self-limiting platelet accumulation. Objectives The objective of this study was to produce a paradigm for self-limiting thrombus growth in a mouse jugular vein model. Methods Data mining of advanced electron microscopy images was performed from authors' laboratories. Results Wide-area transmission electron mcrographs revealed initial platelet capture to the exposed adventitia resulted in localized patches of degranulated, procoagulant-like platelets. Platelet activation to a procoagulant state was sensitive to dabigatran, a direct-acting PAR receptor inhibitor, but not to cangrelor, a P2Y12 receptor inhibitor. Subsequent thrombus growth was sensitive to both cangrelor and dabigatran and sustained by the capture of discoid platelet strings first to collagen-anchored platelets and later to loosely adherent peripheral platelets. Spatial examination indicated that staged platelet activation resulted in a discoid platelet tethering zone that was pushed progressively outward as platelets converted from one activation state to another. As thrombus growth slowed, discoid platelet recruitment became rare and loosely adherent intravascular platelets failed to convert to tightly adherent platelets. Conclusions In summary, the data support a model that we term Capture and Activate, in which the initial high platelet activation is directly linked to the exposed adventitia, all subsequent tethering of discoid platelets is to loosely adherent platelets that convert to tightly adherent platelets, and self-limiting, intravascular platelet activation over time is the result of decreased signaling intensity.
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Affiliation(s)
- Irina D Pokrovskaya
- Department of Physiology and Cell Biology, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA
| | - Sung W Rhee
- Department of Pharmacology and Toxicology, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA
| | - Kelly K Ball
- Department of Physiology and Cell Biology, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA.,Department of Pharmacology and Toxicology, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA
| | - Jeffrey A Kamykowski
- Department of Physiology and Cell Biology, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA
| | - Oliver S Zhao
- Laboratory of Cellular Imaging and Macromolecular Biophysics, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, Maryland, USA
| | - Denzel R D Cruz
- Laboratory of Cellular Imaging and Macromolecular Biophysics, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, Maryland, USA
| | - Joshua Cohen
- Laboratory of Cellular Imaging and Macromolecular Biophysics, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, Maryland, USA
| | - Maria A Aronova
- Laboratory of Cellular Imaging and Macromolecular Biophysics, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, Maryland, USA
| | - Richard D Leapman
- Laboratory of Cellular Imaging and Macromolecular Biophysics, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, Maryland, USA
| | - Brian Storrie
- Department of Physiology and Cell Biology, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA
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6
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Liu S, Pokrovskaya ID, Storrie B. High-Pressure Freezing Followed by Freeze Substitution: An Optimal Electron Microscope Technique to Study Golgi Apparatus Organization and Membrane Trafficking. Methods Mol Biol 2023; 2557:211-223. [PMID: 36512217 DOI: 10.1007/978-1-0716-2639-9_13] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
A major goal of structural biologists is to preserve samples as close to their living state as possible. High-pressure freezing (HPF) is a state-of-art technique that freezes the samples at high pressure (~2100 bar) and low temperature (-196 °C) within milliseconds. This ultrarapid fixation enables simultaneous immobilization of all cellular components and preserves the samples in a near-native state. This facilitates the study of dynamic processes in Golgi apparatus organization and membrane trafficking. The work in our laboratory shows that high-pressure freezing followed by freeze substitution (FS), the introduction of organic solvents at low temperature prior to plastic embedding, can better preserve the structure of Golgi apparatus and Golgi-associated vesicles. Here, we present a protocol for freezing monolayer cell cultures on sapphire disks followed by freeze substitution. We were able to use this protocol to successfully study Golgi organization and membrane trafficking in HeLa cells. The protocol gives decidedly better preservation of Golgi apparatus and associated vesicles than conventional chemically fixed preparation and as a plastic embedded preparation can be readily extended to 3D electron microscopy imaging through sequential block face-scanning electron microscopy. The 3D imaging of a multi-micron thick organelle such as the Golgi apparatus located near the cell nucleus is greatly facilitated relative to hydrated sample imaging techniques such as cryo-electron microscopy.
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Affiliation(s)
- Shijie Liu
- Department of Physiology and Cell Biology, University of Arkansas for Medical Sciences, Little Rock, AR, USA
| | - Irina D Pokrovskaya
- Department of Physiology and Cell Biology, University of Arkansas for Medical Sciences, Little Rock, AR, USA
| | - Brian Storrie
- Department of Physiology and Cell Biology, University of Arkansas for Medical Sciences, Little Rock, AR, USA.
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7
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Sumya FT, Pokrovskaya ID, Lupashin VV. Rapid COG Depletion in Mammalian Cell by Auxin-Inducible Degradation System. Methods Mol Biol 2023; 2557:365-390. [PMID: 36512227 PMCID: PMC10019459 DOI: 10.1007/978-1-0716-2639-9_23] [Citation(s) in RCA: 0] [Impact Index Per Article: 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] [Indexed: 12/15/2022]
Abstract
Conserved oligomeric Golgi (COG) complex orchestrates intra-Golgi retrograde trafficking and glycosylation of macromolecules, but the detailed mechanism of COG action is unknown. Previous studies employed prolonged protein knockout and knockdown approaches which may potentially generate off-target and indirect mutant phenotypes. To achieve a fast depletion of COG subunits in human cells, the auxin-inducible degradation system was employed. This method of protein regulation allows a very fast and efficient depletion of COG subunits, which provides the ability to accumulate COG complex dependent (CCD) vesicles and investigate initial cellular defects associated with the acute depletion of COG complex subunits. This protocol is applicable to other vesicle tethering complexes and can be utilized to investigate anterograde and retrograde intracellular membrane trafficking pathways.
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Affiliation(s)
- Farhana Taher Sumya
- Department of Physiology and Cell Biology, University of Arkansas for Medical Sciences, Little Rock, AR, USA
| | - Irina D Pokrovskaya
- Department of Physiology and Cell Biology, University of Arkansas for Medical Sciences, Little Rock, AR, USA
| | - Vladimir V Lupashin
- Department of Physiology and Cell Biology, University of Arkansas for Medical Sciences, Little Rock, AR, USA.
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8
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Aronova MA, Cruz DR, Palumbo DJ, Akkem RR, Emam ZA, Guay MD, Rhee SW, Pokrovskaya ID, Storrie B, Leapman RD. Combined use of serial block face SEM and focused ion beam SEM elucidates the 3D ultrastructure of blood platelets and thrombi. Biophys J 2022. [DOI: 10.1016/j.bpj.2021.11.1984] [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: 11/15/2022] Open
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9
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Sumya FT, Pokrovskaya ID, Lupashin V. Development and Initial Characterization of Cellular Models for COG Complex-Related CDG-II Diseases. Front Genet 2021; 12:733048. [PMID: 34603392 PMCID: PMC8484713 DOI: 10.3389/fgene.2021.733048] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Accepted: 09/06/2021] [Indexed: 12/12/2022] Open
Abstract
Conserved Oligomeric Golgi (COG) is an octameric protein complex that orchestrates intra-Golgi trafficking of glycosylation enzymes. Over a hundred individuals with 31 different COG mutations have been identified until now. The cellular phenotypes and clinical presentations of COG-CDGs are heterogeneous, and patients primarily represent neurological, skeletal, and hepatic abnormalities. The establishment of a cellular COG disease model will benefit the molecular study of the disease, explaining the detailed sequence of the interplay between the COG complex and the trafficking machinery. Moreover, patient fibroblasts are not a good representative of all the organ systems and cell types that are affected by COG mutations. We developed and characterized cellular models for human COG4 mutations, specifically in RPE1 and HEK293T cell lines. Using a combination of CRISPR/Cas9 and lentiviral transduction technologies, both myc-tagged wild-type and mutant (G516R and R729W) COG4 proteins were expressed under the endogenous COG4 promoter. Constructed isogenic cell lines were comprehensively characterized using biochemical, microscopy (superresolution and electron), and proteomics approaches. The analysis revealed similar stability and localization of COG complex subunits, wild-type cell growth, and normal Golgi morphology in all three cell lines. Importantly, COG4-G516R cells demonstrated increased HPA-647 binding to the plasma membrane glycoconjugates, while COG4-R729W cells revealed high GNL-647 binding, indicating specific defects in O- and N-glycosylation. Both mutant cell lines express an elevated level of heparin sulfate proteoglycans. Moreover, a quantitative mass-spectrometry analysis of proteins secreted by COG-deficient cell lines revealed abnormal secretion of SIL1 and ERGIC-53 proteins by COG4-G516R cells. Interestingly, the clinical phenotype of patients with congenital mutations in the SIL1 gene (Marinesco-Sjogren syndrome) overlaps with the phenotype of COG4-G516R patients (Saul-Wilson syndrome). Our work is the first compressive study involving the creation of different COG mutations in different cell lines other than the patient's fibroblast. It may help to address the underlying cause of the phenotypic defects leading to the discovery of a proper treatment guideline for COG-CDGs.
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Affiliation(s)
| | | | - Vladimir Lupashin
- Department of Physiology and Cell Biology, University of Arkansas for Medical Sciences, Little Rock, AR, United States
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10
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Guay MD, Emam ZAS, Anderson AB, Aronova MA, Pokrovskaya ID, Storrie B, Leapman RD. Dense cellular segmentation for EM using 2D-3D neural network ensembles. Sci Rep 2021; 11:2561. [PMID: 33510185 PMCID: PMC7844272 DOI: 10.1038/s41598-021-81590-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [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: 05/28/2020] [Accepted: 01/05/2021] [Indexed: 12/23/2022] Open
Abstract
Biologists who use electron microscopy (EM) images to build nanoscale 3D models of whole cells and their organelles have historically been limited to small numbers of cells and cellular features due to constraints in imaging and analysis. This has been a major factor limiting insight into the complex variability of cellular environments. Modern EM can produce gigavoxel image volumes containing large numbers of cells, but accurate manual segmentation of image features is slow and limits the creation of cell models. Segmentation algorithms based on convolutional neural networks can process large volumes quickly, but achieving EM task accuracy goals often challenges current techniques. Here, we define dense cellular segmentation as a multiclass semantic segmentation task for modeling cells and large numbers of their organelles, and give an example in human blood platelets. We present an algorithm using novel hybrid 2D–3D segmentation networks to produce dense cellular segmentations with accuracy levels that outperform baseline methods and approach those of human annotators. To our knowledge, this work represents the first published approach to automating the creation of cell models with this level of structural detail.
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Affiliation(s)
- Matthew D Guay
- National Institute of Biomedical Imaging and Bioengineering, NIH, Bethesda, 20892, USA.
| | - Zeyad A S Emam
- National Institute of Biomedical Imaging and Bioengineering, NIH, Bethesda, 20892, USA.,University of Maryland, College Park, 20740, USA
| | - Adam B Anderson
- National Institute of Biomedical Imaging and Bioengineering, NIH, Bethesda, 20892, USA.,University of Maryland, College Park, 20740, USA
| | - Maria A Aronova
- National Institute of Biomedical Imaging and Bioengineering, NIH, Bethesda, 20892, USA
| | | | - Brian Storrie
- University of Arkansas for Medical Sciences, Little Rock, 72205, USA
| | - Richard D Leapman
- National Institute of Biomedical Imaging and Bioengineering, NIH, Bethesda, 20892, USA
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11
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Pokrovskaya ID, Tobin M, Desai R, Joshi S, Kamykowski JA, Zhang G, Aronova MA, Whiteheart SW, Leapman RD, Storrie B. Canalicular system reorganization during mouse platelet activation as revealed by 3D ultrastructural analysis. Platelets 2020; 32:97-104. [PMID: 32000578 DOI: 10.1080/09537104.2020.1719993] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
The canalicular system (CS) has been defined as: 1) an inward, invaginated membrane connector that supports entry into and exit from the platelet; 2) a static structure stable during platelet isolation; and 3) the major source of plasma membrane (PM) for surface area expansion during activation. Recent analysis from STEM tomography and serial block face electron microscopy has challenged the relative importance of CS as the route for granule secretion. Here, We used 3D ultrastructural imaging to reexamine the CS in mouse platelets by generating high-resolution 3D reconstructions to test assumptions 2 and 3. Qualitative and quantitative analysis of whole platelet reconstructions, obtained from immediately fixed or washed platelets fixed post-washing, indicated that CS, even in the presence of activation inhibitors, reorganized during platelet isolation to generate a more interconnected network. Further, CS redistribution into the PM at different times, post-activation, appeared to account for only about half the PM expansion seen in thrombin-activated platelets, in vitro, suggesting that CS reorganization is not sufficient to serve as a dominant membrane reservoir for activated platelets. In sum, our analysis highlights the need to revisit past assumptions about the platelet CS to better understand how this membrane system contributes to platelet function.
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Affiliation(s)
- Irina D Pokrovskaya
- Department of Physiology and Biophysics, University of Arkansas for Medical Sciences , Little Rock, AR, USA
| | - Michael Tobin
- Laboratory of Cellular Imaging and Macromolecular Biophysics, NIBIB, NIH , Bethesda, MD, USA
| | - Rohan Desai
- Laboratory of Cellular Imaging and Macromolecular Biophysics, NIBIB, NIH , Bethesda, MD, USA
| | - Smita Joshi
- Department of Molecular and Cellular Biochemistry, University of Kentucky , Lexington, Kentucky, USA
| | - Jeffrey A Kamykowski
- Department of Physiology and Biophysics, University of Arkansas for Medical Sciences , Little Rock, AR, USA
| | - Guofeng Zhang
- Laboratory of Cellular Imaging and Macromolecular Biophysics, NIBIB, NIH , Bethesda, MD, USA
| | - Maria A Aronova
- Laboratory of Cellular Imaging and Macromolecular Biophysics, NIBIB, NIH , Bethesda, MD, USA
| | - Sidney W Whiteheart
- Department of Molecular and Cellular Biochemistry, University of Kentucky , Lexington, Kentucky, USA
| | - Richard D Leapman
- Laboratory of Cellular Imaging and Macromolecular Biophysics, NIBIB, NIH , Bethesda, MD, USA
| | - Brian Storrie
- Department of Physiology and Biophysics, University of Arkansas for Medical Sciences , Little Rock, AR, USA
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Pokrovskaya ID, Yadav S, Rao A, McBride E, Kamykowski JA, Zhang G, Aronova MA, Leapman RD, Storrie B. 3D ultrastructural analysis of α-granule, dense granule, mitochondria, and canalicular system arrangement in resting human platelets. Res Pract Thromb Haemost 2020; 4:72-85. [PMID: 31989087 PMCID: PMC6971324 DOI: 10.1002/rth2.12260] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2019] [Revised: 08/29/2019] [Accepted: 09/04/2019] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND State-of-the-art 3-dimensional (3D) electron microscopy approaches provide a new standard for the visualization of human platelet ultrastructure. Application of these approaches to platelets rapidly fixed prior to purification to minimize activation should provide new insights into resting platelet ultrastructure. OBJECTIVES Our goal was to determine the 3D organization of α-granules, dense granules, mitochondria, and canalicular system in resting human platelets and map their spatial relationships. METHODS We used serial block face-scanning electron microscopy images to render the 3D ultrastructure of α-granules, dense granules, mitochondria, canalicular system, and plasma membrane for 30 human platelets, 10 each from 3 donors. α-Granule compositional data were assessed by sequential, serial section cryo-immunogold electron microscopy and by immunofluorescence (structured illumination microscopy). RESULTS AND CONCLUSIONS α-Granule number correlated linearly with platelet size, while dense granule and mitochondria number had little correlation with platelet size. For all subcellular compartments, individual organelle parameters varied considerably and organelle volume fraction had little correlation with platelet size. Three-dimensional data from 30 platelets indicated only limited spatial intermixing of the different organelle classes. Interestingly, almost 70% of α-granules came within ≤35 nm of each other, a distance associated in other cell systems with protein-mediated contact sites. Size and shape analysis of the 1488 α-granules analyzed revealed no more variation than that expected for a Gaussian distribution. Protein distribution data indicated that all α-granules likely contained the same major set of proteins, albeit at varying amounts and varying distribution within the granule matrix.
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Affiliation(s)
- Irina D. Pokrovskaya
- Department of Physiology and BiophysicsUniversity of Arkansas for Medical SciencesLittle RockARUSA
| | - Shilpi Yadav
- Department of Physiology and BiophysicsUniversity of Arkansas for Medical SciencesLittle RockARUSA
| | - Amith Rao
- Laboratory of Cellular Imaging and Macromolecular BiophysicsNIBIBNIHBethesdaMDUSA
| | - Emma McBride
- Laboratory of Cellular Imaging and Macromolecular BiophysicsNIBIBNIHBethesdaMDUSA
| | - Jeffrey A. Kamykowski
- Department of Physiology and BiophysicsUniversity of Arkansas for Medical SciencesLittle RockARUSA
| | - Guofeng Zhang
- Laboratory of Cellular Imaging and Macromolecular BiophysicsNIBIBNIHBethesdaMDUSA
| | - Maria A. Aronova
- Laboratory of Cellular Imaging and Macromolecular BiophysicsNIBIBNIHBethesdaMDUSA
| | - Richard D. Leapman
- Laboratory of Cellular Imaging and Macromolecular BiophysicsNIBIBNIHBethesdaMDUSA
| | - Brian Storrie
- Department of Physiology and BiophysicsUniversity of Arkansas for Medical SciencesLittle RockARUSA
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D'Souza Z, Blackburn JB, Kudlyk T, Pokrovskaya ID, Lupashin VV. Defects in COG-Mediated Golgi Trafficking Alter Endo-Lysosomal System in Human Cells. Front Cell Dev Biol 2019; 7:118. [PMID: 31334232 PMCID: PMC6616090 DOI: 10.3389/fcell.2019.00118] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [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: 04/09/2019] [Accepted: 06/11/2019] [Indexed: 12/27/2022] Open
Abstract
The conserved oligomeric complex (COG) is a multi-subunit vesicle tethering complex that functions in retrograde trafficking at the Golgi. We have previously demonstrated that the formation of enlarged endo-lysosomal structures (EELSs) is one of the major glycosylation-independent phenotypes of cells depleted for individual COG complex subunits. Here, we characterize the EELSs in HEK293T cells using microscopy and biochemical approaches. Our analysis revealed that the EELSs are highly acidic and that vATPase-dependent acidification is essential for the maintenance of this enlarged compartment. The EELSs are accessible to both trans-Golgi enzymes and endocytic cargo. Moreover, the EELSs specifically accumulate endolysosomal proteins Lamp2, CD63, Rab7, Rab9, Rab39, Vamp7, and STX8 on their surface. The EELSs are distinct from lysosomes and do not accumulate active Cathepsin B. Retention using selective hooks (RUSH) experiments revealed that biosynthetic cargo mCherry-Lamp1 reaches the EELSs much faster as compared to both receptor-mediated and soluble endocytic cargo, indicating TGN origin of the EELSs. In support to this hypothesis, EELSs are enriched with TGN specific lipid PI4P. Additionally, analysis of COG4/VPS54 double KO cells revealed that the activity of the GARP tethering complex is necessary for EELSs’ accumulation, indicating that protein mistargeting and the imbalance of Golgi-endosome membrane flow leads to the formation of EELSs in COG-deficient cells. The EELSs are likely to serve as a degradative storage hybrid organelle for mistargeted Golgi enzymes and underglycosylated glycoconjugates. To our knowledge this is the first report of the formation of an enlarged hybrid endosomal compartment in a response to malfunction of the intra-Golgi trafficking machinery.
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Affiliation(s)
- Zinia D'Souza
- Department of Physiology, University of Arkansas for Medical Sciences, Little Rock, AR, United States
| | - Jessica Bailey Blackburn
- Department of Physiology, University of Arkansas for Medical Sciences, Little Rock, AR, United States
| | - Tetyana Kudlyk
- Department of Physiology, University of Arkansas for Medical Sciences, Little Rock, AR, United States
| | - Irina D Pokrovskaya
- Department of Physiology, University of Arkansas for Medical Sciences, Little Rock, AR, United States
| | - Vladimir V Lupashin
- Department of Physiology, University of Arkansas for Medical Sciences, Little Rock, AR, United States
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Ling K, Vedanaparti Y, Tobin MP, Desai RP, Zhang G, Pokrovskaya ID, Storrie B, Aronova MA, Leapman RD. Structural Analysis of Mouse Platelets using Serial Block-Face Scanning Electron Microscopy. Biophys J 2019. [DOI: 10.1016/j.bpj.2018.11.3082] [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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Abstract
COG is a multisubunit vesicle tethering complex in the Golgi. We demonstrate that both COG subcomplexes can be permanently attached to Golgi membranes and that major COG functions do not require cycling between the membrane and cytosol. The conserved oligomeric Golgi (COG) complex is a vesicle tether of the “complexes associated with tethering containing helical rods” family, which functions on the cytoplasmic side of Golgi. It is currently unknown whether COG function, or function of any multisubunit vesicular tether, depends on cycling between the membrane and cytosol. Therefore, we permanently anchored key subunits of COG subcomplexes (COG4, COG7, and COG8) to Golgi membranes using transmembrane protein TMEM115 (TMEM-COG). All TMEM-COG subunits tested were Golgi localized, integrated into the COG complex, and stabilized membrane association of endogenous subunits. Interestingly, TMEM-COG4 and TMEM-COG7 equally rescued COG function in organization of Golgi markers, glycosylation, and abundance of COG-sensitive proteins. In contrast, TMEM-COG8 was not as effective, indicating that N-terminal attachment of COG8 interfered with overall COG structure and function, and none of the TMEM-COG subunits rescued the abnormal Golgi architecture caused by COG knockout. Collectively, these data indicate that both subcomplexes of the COG complex can perform most of COG function when permanently attached to membranes and that the cytosolic pool of COG is not completely essential to COG function.
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Affiliation(s)
- Leslie K Climer
- College of Medicine, Physiology and Biophysics, University of Arkansas for Medical Sciences, Little Rock, AR 72205
| | - Irina D Pokrovskaya
- College of Medicine, Physiology and Biophysics, University of Arkansas for Medical Sciences, Little Rock, AR 72205
| | - Jessica B Blackburn
- College of Medicine, Physiology and Biophysics, University of Arkansas for Medical Sciences, Little Rock, AR 72205
| | - Vladimir V Lupashin
- College of Medicine, Physiology and Biophysics, University of Arkansas for Medical Sciences, Little Rock, AR 72205
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Yadav S, Williamson JK, Aronova MA, Prince AA, Pokrovskaya ID, Leapman RD, Storrie B. Golgi proteins in circulating human platelets are distributed across non-stacked, scattered structures. Platelets 2016; 28:400-408. [PMID: 27753523 DOI: 10.1080/09537104.2016.1235685] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
Platelets are small, anucleate cell fragments that are central to hemostasis, thrombosis, and inflammation. They are derived from megakaryocytes from which they inherit their organelles. As platelets can synthesize proteins and contain many of the enzymes of the secretory pathway, one might expect all mature human platelets to contain a stacked Golgi apparatus, the central organelle of the secretory pathway. By thin section electron microscopy, stacked membranes resembling the stacked Golgi compartment in megakaryocytes and other nucleated cells can be detected in both proplatelets and platelets. However, the incidence of such structures is low and whether each and every platelet contains such a structure remains an open question. By single-label, immunofluorescence staining, Golgi glycosyltransferases are found within each platelet and map to scattered structures. Whether these structures are positive for marker proteins from multiple Golgi subcompartments remains unknown. Here, we have applied state-of-the-art techniques to probe the organization state of the Golgi apparatus in resting human platelets. By the whole cell volume technique of serial-block-face scanning electron microscopy (SBF-SEM), we failed to observe stacked, Golgi-like structures in any of the 65 platelets scored. When antibodies directed against Golgi proteins were tested against HeLa cells, labeling was restricted to an elongated juxtanuclear ribbon characteristic of a stacked Golgi apparatus. By multi-label immunofluorescence microscopy, we found that each and every resting human platelet was positive for cis, trans, and trans Golgi network (TGN) proteins. However, in each case, the proteins were found in small puncta scattered about the platelet. At the resolution of deconvolved, widefield fluorescence microscopy, these proteins had limited tendency to map adjacent to one another. When the results of 3D structured illumination microscopy (3D SIM), a super resolution technique, were scored quantitatively, the Golgi marker proteins failed to map together indicating at the protein level considerable degeneration of the platelet Golgi apparatus relative to the layered stack as seen in the megakaryocyte. In conclusion, we suggest that these results have important implications for organelle structure/function relationships in the mature platelet and the extent to which Golgi apparatus organization is maintained in platelets. Our results suggest that Golgi proteins in circulating platelets are present within a series of scattered, separated structures. As separate elements, selective sets of Golgi enzymes or sugar nucleotides could be secreted during platelet activation. The establishment of the functional importance, if any, of these scattered structures in sequential protein modification in circulating platelets will require further research.
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Affiliation(s)
- Shilpi Yadav
- a Department of Physiology and Biophysics , University of Arkansas for Medical Sciences , Little Rock , AR , USA
| | - Jonathan K Williamson
- a Department of Physiology and Biophysics , University of Arkansas for Medical Sciences , Little Rock , AR , USA
| | - Maria A Aronova
- b National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health , Bethesda , MD , USA
| | - Andrew A Prince
- a Department of Physiology and Biophysics , University of Arkansas for Medical Sciences , Little Rock , AR , USA
| | - Irina D Pokrovskaya
- a Department of Physiology and Biophysics , University of Arkansas for Medical Sciences , Little Rock , AR , USA
| | - Richard D Leapman
- b National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health , Bethesda , MD , USA
| | - Brian Storrie
- a Department of Physiology and Biophysics , University of Arkansas for Medical Sciences , Little Rock , AR , USA
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Pokrovskaya ID, Aronova MA, Kamykowski JA, Prince AA, Hoyne JD, Calco GN, Kuo BC, He Q, Leapman RD, Storrie B. STEM tomography reveals that the canalicular system and α-granules remain separate compartments during early secretion stages in blood platelets. J Thromb Haemost 2016; 14:572-84. [PMID: 26663480 PMCID: PMC4829117 DOI: 10.1111/jth.13225] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [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] [Received: 06/30/2015] [Accepted: 11/30/2015] [Indexed: 12/21/2022]
Abstract
UNLABELLED ESSENTIALS: How platelets organize their α-granule cargo and use their canalicular system remains controversial. Past structural studies were limited due to small sampling volumes or decreased resolution. Our analyses revealed homogeneous granules and a closed canalicular system that opened on activation. Understanding how platelets alter their membranes during activation and secretion elucidates hemostasis. SUMMARY BACKGROUND Platelets survey the vasculature for damage and, in response, activate and release a wide range of proteins from their α-granules. Alpha-granules may be biochemically and structurally heterogeneous; however, other studies suggest that they may be more homogeneous with the observed variation reflecting granule dynamics rather than fundamental differences. OBJECTIVES Our aim was to address how the structural organization of α-granules supports their dynamics. METHODS To preserve the native state, we prepared platelets by high-pressure freezing and freeze-substitution; and to image nearly entire cells, we recorded tomographic data in the scanning transmission electron microscope (STEM). RESULTS AND CONCLUSIONS In resting platelets, we observed a morphologically homogeneous α-granule population that displayed little variation in overall matrix electron density in freeze-substituted preparations (i.e., macro-homogeneity). In resting platelets, the incidence of tubular granule extensions was low, ~4%, but this increased by > 10-fold during early steps in platelet secretion. Using STEM, we observed that the initially decondensing α-granules and the canalicular system remained as separate membrane domains. Decondensing α-granules were found to fuse heterotypically with the plasma membrane via long, tubular connections or homotypically with each other. The frequency of canalicular system fusion with the plasma membrane also increased by about three-fold. Our results validate the utility of freeze-substitution and STEM tomography for characterizing platelet granule secretion and suggest a model in which fusion of platelet α-granules with the plasma membrane occurs via long tubular connections that may provide a spatially limited access route for the timed release of α-granule proteins.
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Affiliation(s)
| | - Maria A. Aronova
- National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD 20892
| | | | - Andrew A. Prince
- University of Arkansas for Medical Sciences, Little Rock, AR 72205
| | - Jake D. Hoyne
- National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD 20892
| | - Gina N. Calco
- National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD 20892
| | - Bryan C. Kuo
- National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD 20892
| | - Qianping He
- National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD 20892
| | - Richard D. Leapman
- National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD 20892
| | - Brian Storrie
- University of Arkansas for Medical Sciences, Little Rock, AR 72205
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Willett RA, Pokrovskaya ID, Lupashin VV. Fluorescent microscopy as a tool to elucidate dysfunction and mislocalization of Golgi glycosyltransferases in COG complex depleted mammalian cells. Methods Mol Biol 2013; 1022:61-72. [PMID: 23765654 DOI: 10.1007/978-1-62703-465-4_6] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Staining of molecules such as proteins and glycoconjugates allows for an analysis of their localization within the cell and provides insight into their functional status. Glycosyltransferases, a class of enzymes which are responsible for glycosylating host proteins, are mostly localized to the Golgi apparatus, and their localization is maintained in part by a protein vesicular tethering complex, the conserved oligomeric Golgi (COG) complex. Here we detail a combination of fluorescent lectin and immuno-staining in cells depleted of COG complex subunits to examine the status of Golgi glycosyltransferases. The combination of these techniques allows for a detailed characterization of the changes in function and localization of Golgi glycosyltransferases with respect to transient COG subunit depletion.
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Affiliation(s)
- Rose A Willett
- Department of Physiology and Biophysics, University of Arkansas for Medical Sciences, Little Rock, AR, USA
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Kudlyk T, Willett R, Pokrovskaya ID, Lupashin V. COG6 interacts with a subset of the Golgi SNAREs and is important for the Golgi complex integrity. Traffic 2012; 14:194-204. [PMID: 23057818 DOI: 10.1111/tra.12020] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2012] [Revised: 10/09/2012] [Accepted: 10/11/2012] [Indexed: 12/18/2022]
Abstract
Vesicular tethers and SNAREs are two key protein components that govern docking and fusion of intracellular membrane carriers in eukaryotic cells. The conserved oligomeric Golgi (COG) complex has been specifically implicated in the tethering of retrograde intra-Golgi vesicles. Using yeast two-hybrid and co-immunoprecipitation approaches, we show that the COG6 subunit of the COG complex is capable of interacting with a subset of Golgi SNAREs, namely STX5, STX6, GS27 and SNAP29. Interaction with SNAREs is accomplished via the universal SNARE-binding motif of COG6. Overexpression of COG6, or its depletion from cells, disrupts the integrity of the Golgi complex. Importantly, COG6 protein lacking the SNARE-binding domain is deficient in Golgi binding, and is not capable of inducing Golgi complex fragmentation when overexpressed. These results indicate that COG6-SNARE interactions are important for both COG6 localization and Golgi integrity.
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Affiliation(s)
- Tetyana Kudlyk
- Department of Physiology and Biophysics, University of Arkansas for Medical Sciences, Little Rock, AR, USA
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Pokrovskaya ID, Szwedo JW, Goodwin A, Lupashina TV, Nagarajan UM, Lupashin VV. Chlamydia trachomatis hijacks intra-Golgi COG complex-dependent vesicle trafficking pathway. Cell Microbiol 2012; 14:656-68. [PMID: 22233276 DOI: 10.1111/j.1462-5822.2012.01747.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Chlamydia spp. are obligate intracellular bacteria that replicate inside the host cell in a bacterial modified unique compartment called the inclusion. As other intracellular pathogens, chlamydiae exploit host membrane trafficking pathways to prevent lysosomal fusion and to acquire energy and nutrients essential for their survival and replication. The Conserved Oligomeric Golgi (COG) complex is a ubiquitously expressed membrane-associated protein complex that functions in a retrograde intra-Golgi trafficking through associations with coiled-coil tethers, SNAREs, Rabs and COPI proteins. Several COG complex-interacting proteins, including Rab1, Rab6, Rab14 and Syntaxin 6 are implicated in chlamydial development. In this study, we analysed the recruitment of the COG complex and GS15-positive COG complex-dependent vesicles to Chlamydia trachomatis inclusion and their participation in chlamydial growth. Immunofluorescent analysis revealed that both GFP-tagged and endogenous COG complex subunits associated with inclusions in a serovar-independent manner by 8 h post infection and were maintained throughout the entire developmental cycle. Golgi v-SNARE GS15 was associated with inclusions 24 h post infection, but was absent on the mid-cycle (8 h) inclusions, indicating that this Golgi SNARE is directed to inclusions after COG complex recruitment. Silencing of COG8 and GS15 by siRNA significantly decreased infectious yield of chlamydiae. Further, membranous structures likely derived from lysed bacteria were observed inside inclusions by electron microscopy in cells depleted of COG8 or GS15. Our results showed that C. trachomatis hijacks the COG complex to redirect the population of Golgi-derived retrograde vesicles to inclusions. These vesicles likely deliver nutrients that are required for bacterial development and replication.
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Affiliation(s)
- I D Pokrovskaya
- Department of Physiology and Biophysics, UAMS, Arkansas Childrens Hospital Research Institute, Little Rock, AR, USA
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Ranganathan G, Unal R, Pokrovskaya ID, Tripathi P, Rotter JI, Goodarzi MO, Kern PA. The lipoprotein lipase (LPL) S447X gain of function variant involves increased mRNA translation. Atherosclerosis 2011; 221:143-7. [PMID: 22244040 DOI: 10.1016/j.atherosclerosis.2011.12.028] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/07/2011] [Revised: 12/16/2011] [Accepted: 12/19/2011] [Indexed: 11/18/2022]
Abstract
OBJECTIVE A common gain-of-function LPL variant, LPLS447X, has favorable clinical features and involves a C→G base change at nucleotide 1595 of the LPL cDNA, along with a haplotype, which includes other non-coding SNPs. The mechanism for the LPL gain-in-function is not clear. LPL translation is regulated by epinephrine by an RNA-protein complex, consisting of PKA subunits and an A kinase anchoring protein (AKAP), which targets the 3'UTR. METHODS To examine LPL translation of the LPLS447X variant, in vitro translation of LPL mRNA constructs was studied in the presence of cytoplasmic extracts from 3T3-F442A adipocytes treated with/without epinephrine. RESULTS When the C→G base change at nucleotide 1595 was introduced, LPL mRNA was less susceptible to inhibition by the adipocyte extract. Similarly, a lessened susceptibility to translation inhibition occurred when the complete haplotype was constructed in the full-length 3.6 kb LPL mRNA, when an irrelevant coding sequence was introduced into the LPL mRNA construct, and in response to the use of components of the RNA binding complex (PKA C and R subunits, and KH region of AKAP149). CONCLUSION These studies suggest that the LPLS447X gain of function may be due to the base change in the LPL mRNA resulting in a decreased susceptibility to translational inhibition.
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Affiliation(s)
- Gouri Ranganathan
- The Central Arkansas Veterans Healthcare System and the Department of Medicine, Division of Endocrinology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, United States
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Pokrovskaya ID, Willett R, Smith RD, Morelle W, Kudlyk T, Lupashin VV. Conserved oligomeric Golgi complex specifically regulates the maintenance of Golgi glycosylation machinery. Glycobiology 2011; 21:1554-69. [PMID: 21421995 DOI: 10.1093/glycob/cwr028] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Cell surface lectin staining, examination of Golgi glycosyltransferases stability and localization, and matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) analysis were employed to investigate conserved oligomeric Golgi (COG)-dependent glycosylation defects in HeLa cells. Both Griffonia simplicifolia lectin-II and Galanthus nivalus lectins were specifically bound to the plasma membrane glycoconjugates of COG-depleted cells, indicating defects in activity of medial- and trans-Golgi-localized enzymes. In response to siRNA-induced depletion of COG complex subunits, several key components of Golgi glycosylation machinery, including MAN2A1, MGAT1, B4GALT1 and ST6GAL1, were severely mislocalized. MALDI-TOF analysis of total N-linked glycoconjugates indicated a decrease in the relative amount of sialylated glycans in both COG3 KD and COG4 KD cells. In agreement to a proposed role of the COG complex in retrograde membrane trafficking, all types of COG-depleted HeLa cells were deficient in the Brefeldin A- and Sar1 DN-induced redistribution of Golgi resident glycosyltransferases to the endoplasmic reticulum. The retrograde trafficking of medial- and trans-Golgi-localized glycosylation enzymes was affected to a larger extent, strongly indicating that the COG complex regulates the intra-Golgi protein movement. COG complex-deficient cells were not defective in Golgi re-assembly after the Brefeldin A washout, confirming specificity in the retrograde trafficking block. The lobe B COG subcomplex subunits COG6 and COG8 were localized on trafficking intermediates that carry Golgi glycosyltransferases, indicating that the COG complex is directly involved in trafficking and maintenance of Golgi glycosylation machinery.
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Affiliation(s)
- Irina D Pokrovskaya
- Department of Physiology and Biophysics, University of Arkansas for Medical Sciences, 4301 W. Markham, Slot 505, Little Rock, AR 72205, USA
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Unal R, Pokrovskaya ID, Tripathi P, Kern PA, Ranganathan G. Inhibition of LPL by PKCα depletion in adipocytes involves PKA activation. FASEB J 2007. [DOI: 10.1096/fasebj.21.5.a238-c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Resat Unal
- EndocrinologyUniversity of Arkansas medical science4300 West 7th streetLittle RockAR72205
| | - Irina D Pokrovskaya
- EndocrinologyUniversity of Arkansas medical science4300 West 7th streetLittle RockAR72205
| | - Preeti Tripathi
- EndocrinologyUniversity of Arkansas medical science4300 West 7th streetLittle RockAR72205
| | - Philip A Kern
- EndocrinologyUniversity of Arkansas medical science4300 West 7th streetLittle RockAR72205
- Central Arkansas Veterans Healthcare system4300 West 7th streetLittle RockAR72205
| | - Gouri Ranganathan
- EndocrinologyUniversity of Arkansas medical science4300 West 7th streetLittle RockAR72205
- Central Arkansas Veterans Healthcare system4300 West 7th streetLittle RockAR72205
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Ranganathan G, Phan D, Pokrovskaya ID, McEwen JE, Li C, Kern PA. The translational regulation of lipoprotein lipase by epinephrine involves an RNA binding complex including the catalytic subunit of protein kinase A. J Biol Chem 2002; 277:43281-7. [PMID: 12218046 DOI: 10.1074/jbc.m202560200] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.5] [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
The balance of lipid flux in adipocytes is controlled by the opposing actions of lipolysis and lipogenesis, which are controlled primarily by hormone-sensitive lipase and lipoprotein lipase (LPL), respectively. Catecholamines stimulate adipocyte lipolysis through reversible phosphorylation of hormone-sensitive lipase, and simultaneously inhibit LPL activity. However, LPL regulation is complex and previous studies have described translational regulation of LPL in response to catecholamines because of an RNA-binding protein that interacts with the 3'-untranslated region of LPL mRNA. In this study, we identified several protein components of an LPL RNA binding complex. Using an LPL RNA affinity column, we identified two of the RNA-binding proteins as the catalytic (C) subunit of cAMP-dependent protein kinase (PKA), and A kinase anchoring protein (AKAP) 121/149, one of the PKA anchoring proteins, which has known RNA binding activity. To determine whether the C subunit was involved in LPL translation inhibition, the C subunit was depleted from the cytoplasmic extract of epinephrine-stimulated adipocytes by immunoprecipitation. This resulted in the loss of LPL translation inhibition activity of the extract, along with decreased RNA binding activity in a gel shift assay. To demonstrate the importance of the AKAPs, inhibition of PKA-AKAP binding with a peptide competitor (HT31) prevented epinephrine-mediated inhibition of LPL translation. C subunit kinase activity was necessary for LPL RNA binding and translation inhibition, suggesting that the phosphorylation of AKAP121/149 or other proteins was an important part of RNA binding complex formation. The hormonal activation of PKA results in the reversible phosphorylation of hormone-sensitive lipase, which is the primary mediator of adipocyte lipolysis. These studies demonstrate a dual role for PKA to simultaneously inhibit LPL-mediated lipogenesis through inhibition of LPL translation.
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Affiliation(s)
- Gouri Ranganathan
- Central Arkansas Veterans HealthCare System, and Department of Medicine, Division of Endocrinology, and the Department of Geriatrics, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205, USA
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Radominska-Pandya A, Pokrovskaya ID, Xu J, Little JM, Jude AR, Kurten RC, Czernik PJ. Nuclear UDP-glucuronosyltransferases: identification of UGT2B7 and UGT1A6 in human liver nuclear membranes. Arch Biochem Biophys 2002; 399:37-48. [PMID: 11883901 DOI: 10.1006/abbi.2001.2743] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [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: 11/22/2022]
Abstract
We have demonstrated the subcellular localization of the human UDP-glucuronosyltransferases (UGTs), UGT2B7 and UGT1A6, in endoplasmic reticulum (ER) and nuclear membrane from human hepatocytes and cell lines, by in situ immunostaining and Western blot. Double immunostaining for UGT2B7 and calnexin, an ER resident protein, showed that UGT2B7 was equally present in ER and nuclear membrane whereas calnexin was present almost exclusively in ER. Immunogold labeling of HK293 cells expressing UGT2B7 established the presence of UGT2B7 in both nuclear membranes. Enzymatic assays with UGT2B7 substrates confirmed the presence of functional UGT2B7 protein in ER, whole nuclei, and both outer and inner nuclear membranes. This study has identified, for the first time, the presence of UGT2B7 and UGT1A6 in the nucleus and of UGT2B7 in the inner and outer nuclear membranes. This localization may play an important functional role within nuclei: protection from toxic compounds and/or control of steady-state concentrations of nuclear receptor ligands.
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Affiliation(s)
- Anna Radominska-Pandya
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, Arkansas, 77205, USA.
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Landweber LF, Pokrovskaya ID. Emergence of a dual-catalytic RNA with metal-specific cleavage and ligase activities: the spandrels of RNA evolution. Proc Natl Acad Sci U S A 1999; 96:173-8. [PMID: 9874791 PMCID: PMC15112 DOI: 10.1073/pnas.96.1.173] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/1998] [Accepted: 10/26/1998] [Indexed: 11/18/2022] Open
Abstract
In vitro selection, or directed molecular evolution, allows the isolation and amplification of rare sequences that satisfy a functional-selection criterion. This technique can be used to isolate novel ribozymes (RNA enzymes) from large pools of random sequences. We used in vitro evolution to select a ribozyme that catalyzes a novel template-directed RNA ligation that requires surprisingly few nucleotides for catalytic activity. With the exception of two nucleotides, most of the ribozyme contributes to a template, suggesting that it is a general prebiotic ligase. More surprisingly, the catalytic core built from randomized sequences actually contains a 7-nt manganese-dependent self-cleavage motif originally discovered in the Tetrahymena group I intron. Further experiments revealed that we have selected a dual-catalytic RNA from random sequences: the RNA promotes both cleavage at one site and ligation at another site, suggesting two conformations surrounding at least one divalent metal ion-binding site. Together, these results imply that similar catalytic RNA motifs can arise under fairly simple conditions and that multiple catalytic structures, including bifunctional ligases, can evolve from very small preexisting parts. By breaking apart and joining different RNA strands, such ribozymes could have led to the production of longer and more complex RNA polymers in prebiotic evolution.
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Affiliation(s)
- L F Landweber
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ 08544, USA.
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Abstract
The protein trafficking machinery of eukaryotic cells is employed for protein secretion and for the localization of resident proteins of the exocytic and endocytic pathways. Protein transit between organelles is mediated by transport vesicles that bear integral membrane proteins (v-SNAREs) which selectively interact with similar proteins on the target membrane (t-SNAREs), resulting in a docked vesicle. A novel Saccharomyces cerevisiae SNARE protein, which has been termed Vti1p, was identified by its sequence similarity to known SNAREs. Vti1p is a predominantly Golgi-localized 25-kDa type II integral membrane protein that is essential for yeast viability. Vti1p can bind Sec17p (yeast SNAP) and enter into a Sec18p (NSF)-sensitive complex with the cis-Golgi t-SNARE Sed5p. This Sed5p/Vti1p complex is distinct from the previously described Sed5p/Sec22p anterograde vesicle docking complex. Depletion of Vti1p in vivo causes a defect in the transport of the vacuolar protein carboxypeptidase Y through the Golgi. Temperature-sensitive mutants of Vti1p show a similar carboxypeptidase Y trafficking defect, but the secretion of invertase and gp400/hsp150 is not significantly affected. The temperature-sensitive vti1 growth defect can be rescued by the overexpression of the v-SNARE, Ykt6p, which physically interacts with Vti1p. We propose that Vti1p, along with Ykt6p and perhaps Sft1p, acts as a retrograde v-SNARE capable of interacting with the cis-Golgi t-SNARE Sed5p.
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Affiliation(s)
- V V Lupashin
- Department of Molecular Biology, Princeton University, Princeton, New Jersey 08544, USA
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Abstract
A new method of in vitro transcription with the use of SP6, T7, and T3 RNA polymerases is described. The method makes it possible to obtain, using only 1.6-2.6 micrograms of DNA template in as little as 50 microliters of transcription reaction in just 2 h, more than 200 micrograms of pure mRNA (with high translatability). Optimal conditions for the synthesis by all three RNA polymerases of transcripts 1500-1700 nt long and also for very long transcripts were determined. Reaction conditions that minimize DNA template or RNA polymerase requirements are also described, and these provide synthesis of either 1200-2100 RNA copies per DNA molecule or more than 5-15 micrograms of RNA per unit of RNA polymerase. Reactions can be easily scaled up to volumes of several milliliters, yielding up to 5.2 mg/ml of 1500- to 1700-nt-long RNA or up to 7.1 mg/ml of very long RNA.
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Affiliation(s)
- I D Pokrovskaya
- Branch of Shemyakin Institute of Bioorganic Chemistry, Pushchino, Moscow Region, Russia
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Abstract
A method for preparative in vitro mRNA synthesis is presented. The method makes it possible to generate several hundred RNA copies per molecule of linearized DNA template. The protocol is applicable to the synthesis of RNAs of differing lengths (from 200 to 3000 bases), and both SP6 and T7 RNA polymerases can be used. The transcription can be scaled up to at least 6-12 ml, yielding 4.5-18 mg of homogeneous biologically active mRNA.
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Affiliation(s)
- V V Gurevich
- Branch of M. M. Shemyakin Institute of Bioorganic Chemistry, Academy of Sciences of the USSR, Pushchino, Moscow Region
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