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Regulation of Insulin Receptor Pathway and Glucose Metabolism by CD36 Signaling.
Samovski D, Dhule P, Pietka T, Jacome-Sosa M, Penrose E, Son NH, Flynn CR, Shoghi KI, Hyrc KL, Goldberg IJ, Gamazon ER, Abumrad NA
(2018) Diabetes 67: 1272-1284
MeSH Terms: Animals, CD36 Antigens, CHO Cells, Carbohydrate Metabolism, Cells, Cultured, Cricetinae, Cricetulus, Diabetes Mellitus, Type 2, Female, Glucose, Humans, Insulin, Insulin Resistance, Male, Mice, Mice, Inbred C57BL, Mice, Knockout, Muscle, Skeletal, Receptor, Insulin, Signal Transduction
Show Abstract · Added May 26, 2018
During reduced energy intake, skeletal muscle maintains homeostasis by rapidly suppressing insulin-stimulated glucose utilization. Loss of this adaptation is observed with deficiency of the fatty acid transporter CD36. A similar loss is also characteristic of the insulin-resistant state where CD36 is dysfunctional. To elucidate what links CD36 to muscle glucose utilization, we examined whether CD36 signaling might influence insulin action. First, we show that CD36 deletion specific to skeletal muscle reduces expression of insulin signaling and glucose metabolism genes. It decreases muscle ceramides but impairs glucose disposal during a meal. Second, depletion of CD36 suppresses insulin signaling in primary-derived human myotubes, and the mechanism is shown to involve functional CD36 interaction with the insulin receptor (IR). CD36 promotes tyrosine phosphorylation of IR by the Fyn kinase and enhances IR recruitment of P85 and downstream signaling. Third, pretreatment for 15 min with saturated fatty acids suppresses CD36-Fyn enhancement of IR phosphorylation, whereas unsaturated fatty acids are neutral or stimulatory. These findings define mechanisms important for muscle glucose metabolism and optimal insulin responsiveness. Potential human relevance is suggested by genome-wide analysis and RNA sequencing data that associate genetically determined low muscle CD36 expression to incidence of type 2 diabetes.
© 2018 by the American Diabetes Association.
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20 MeSH Terms
C Flux Analysis Reveals that Rebalancing Medium Amino Acid Composition can Reduce Ammonia Production while Preserving Central Carbon Metabolism of CHO Cell Cultures.
McAtee Pereira AG, Walther JL, Hollenbach M, Young JD
(2018) Biotechnol J 13: e1700518
MeSH Terms: Amino Acids, Ammonia, Animals, Antibodies, Monoclonal, CHO Cells, Carbon, Cricetulus, Culture Media, Glycosylation, Metabolic Flux Analysis, Recombinant Proteins
Show Abstract · Added March 14, 2018
C metabolic flux analysis (MFA) provides a rigorous approach to quantify intracellular metabolism of industrial cell lines. In this study, C MFA was used to characterize the metabolic response of Chinese hamster ovary (CHO) cells to a novel medium variant designed to reduce ammonia production. Ammonia inhibits growth and viability of CHO cell cultures, alters glycosylation of recombinant proteins, and enhances product degradation. Ammonia production was reduced by manipulating the amino acid composition of the culture medium; specifically, glutamine, glutamate, asparagine, aspartate, and serine levels were adjusted. Parallel C flux analysis experiments determined that, while ammonia production decreased by roughly 40%, CHO cell metabolic phenotype, growth, viability, and monoclonal antibody (mAb) titer were not significantly altered by the changes in media composition. This study illustrates how C flux analysis can be applied to assess the metabolic effects of media manipulations on mammalian cell cultures. The analysis revealed that adjusting the amino acid composition of CHO cell culture media can effectively reduce ammonia production while preserving fluxes throughout central carbon metabolism.
© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
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11 MeSH Terms
Formulation and characterization of poly(propylacrylic acid)/poly(lactic-co-glycolic acid) blend microparticles for pH-dependent membrane disruption and cytosolic delivery.
Fernando LP, Lewis JS, Evans BC, Duvall CL, Keselowsky BG
(2018) J Biomed Mater Res A 106: 1022-1033
MeSH Terms: Acrylic Resins, Animals, CHO Cells, Cell Death, Cell Membrane, Cricetinae, Cricetulus, Cytosol, Dendritic Cells, Endocytosis, Endosomes, Humans, Hydrogen-Ion Concentration, Mice, Inbred C57BL, Microspheres, Particle Size, Polylactic Acid-Polyglycolic Acid Copolymer, Proton Magnetic Resonance Spectroscopy
Show Abstract · Added March 14, 2018
Poly(lactic-co-glycolic acid) (PLGA) is widely used as a vehicle for delivery of pharmaceutically relevant payloads. PLGA is readily fabricated as a nano- or microparticle (MP) matrix to load both hydrophobic and hydrophilic small molecular drugs as well as biomacromolecules such as nucleic acids and proteins. However, targeting such payloads to the cell cytosol is often limited by MP entrapment and degradation within acidic endolysosomes. Poly(propylacrylic acid) (PPAA) is a polyelectrolyte polymer with the membrane disruptive capability triggered at low pH. PPAA has been previously formulated in various carrier configurations to enable cytosolic payload delivery, but requires sophisticated carrier design. Taking advantage of PPAA functionality, we have incorporated PPAA into PLGA MPs as a simple polymer mixture to enhance cytosolic delivery of PLGA-encapsulated payloads. Rhodamine loaded PLGA and PPAA/PLGA blend MPs were prepared by a modified nanoprecipitation method. Incorporation of PPAA into PLGA MPs had little to no effect on the size, shape, or loading efficiency, and evidenced no toxicity in Chinese hamster ovary epithelial cells. Notably, incorporation of PPAA into PLGA MPs enabled pH-dependent membrane disruption in a hemolysis assay, and a three-fold increased endosomal escape and cytosolic delivery in dendritic cells after 2 h of MP uptake. These results demonstrate that a simple PLGA/PPAA polymer blend is readily fabricated into composite MPs, enabling cytosolic delivery of an encapsulated payload. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 1022-1033, 2018.
© 2017 Wiley Periodicals, Inc.
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18 MeSH Terms
Functional defects in TcdB toxin uptake identify CSPG4 receptor-binding determinants.
Gupta P, Zhang Z, Sugiman-Marangos SN, Tam J, Raman S, Julien JP, Kroh HK, Lacy DB, Murgolo N, Bekkari K, Therien AG, Hernandez LD, Melnyk RA
(2017) J Biol Chem 292: 17290-17301
MeSH Terms: Animals, Antibodies, Monoclonal, Antibodies, Neutralizing, Bacterial Proteins, Bacterial Toxins, CHO Cells, Caco-2 Cells, Cercopithecus aethiops, Chondroitin Sulfate Proteoglycans, Clostridium difficile, Cricetinae, Cricetulus, Glucosyltransferases, HEK293 Cells, Humans, Membrane Proteins, Protein Binding, Protein Domains
Show Abstract · Added April 3, 2018
is a major nosocomial pathogen that produces two exotoxins, TcdA and TcdB, with TcdB thought to be the primary determinant in human disease. TcdA and TcdB are large, multidomain proteins, each harboring a cytotoxic glucosyltransferase domain that is delivered into the cytosol from endosomes via a translocation domain after receptor-mediated endocytosis of toxins from the cell surface. Although there are currently no known host cell receptors for TcdA, three cell-surface receptors for TcdB have been identified: CSPG4, NECTIN3, and FZD1/2/7. The sites on TcdB that mediate binding to each receptor are not defined. Furthermore, it is not known whether the combined repetitive oligopeptide (CROP) domain is involved in or required for receptor binding. Here, in a screen designed to identify sites in TcdB that are essential for target cell intoxication, we identified a region at the junction of the translocation and the CROP domains that is implicated in CSPG4 binding. Using a series of C-terminal truncations, we show that the CSPG4-binding site on TcdB extends into the CROP domain, requiring three short repeats for binding and for full toxicity on CSPG4-expressing cells. Consistent with the location of the CSPG4-binding site on TcdB, we show that the anti-TcdB antibody bezlotoxumab, which binds partially within the first three short repeats, prevents CSPG4 binding to TcdB. In addition to establishing the binding region for CSPG4, this work ascribes for the first time a role in TcdB CROPs in receptor binding and further clarifies the relative roles of host receptors in TcdB pathogenesis.
© 2017 by The American Society for Biochemistry and Molecular Biology, Inc.
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MeSH Terms
The glucagon-like peptide-1 receptor in the ventromedial hypothalamus reduces short-term food intake in male mice by regulating nutrient sensor activity.
Burmeister MA, Brown JD, Ayala JE, Stoffers DA, Sandoval DA, Seeley RJ, Ayala JE
(2017) Am J Physiol Endocrinol Metab 313: E651-E662
MeSH Terms: Acetyl-CoA Carboxylase, Adenylate Kinase, Animals, Body Composition, CHO Cells, Cricetulus, Dose-Response Relationship, Drug, Eating, Exenatide, Food, Glucagon-Like Peptide-1 Receptor, Glycolysis, Homeostasis, Male, Mice, Mice, Inbred C57BL, Peptides, Sensation, TOR Serine-Threonine Kinases, Venoms, Ventromedial Hypothalamic Nucleus
Show Abstract · Added October 23, 2017
Pharmacological activation of the glucagon-like peptide-1 receptor (GLP-1R) in the ventromedial hypothalamus (VMH) reduces food intake. Here, we assessed whether suppression of food intake by GLP-1R agonists (GLP-1RA) in this region is dependent on AMP-activated protein kinase (AMPK) and mammalian target of rapamycin (mTOR). We found that pharmacological inhibition of glycolysis, and thus activation of AMPK, in the VMH attenuates the anorectic effect of the GLP-1R agonist exendin-4 (Ex4), indicating that glucose metabolism and inhibition of AMPK are both required for this effect. Furthermore, we found that Ex4-mediated anorexia in the VMH involved mTOR but not acetyl-CoA carboxylase, two downstream targets of AMPK. We support this by showing that Ex4 activates mTOR signaling in the VMH and Chinese hamster ovary (CHO)-K1 cells. In contrast to the clear acute pharmacological impact of the these receptors on food intake, knockdown of the VMH conferred no changes in energy balance in either chow- or high-fat-diet-fed mice, and the acute anorectic and glucose tolerance effects of peripherally dosed GLP-1RA were preserved. These results show that the VMH GLP-1R regulates food intake by engaging key nutrient sensors but is dispensable for the effects of GLP-1RA on nutrient homeostasis.
Copyright © 2017 the American Physiological Society.
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21 MeSH Terms
Azithromycin Causes a Novel Proarrhythmic Syndrome.
Yang Z, Prinsen JK, Bersell KR, Shen W, Yermalitskaya L, Sidorova T, Luis PB, Hall L, Zhang W, Du L, Milne G, Tucker P, George AL, Campbell CM, Pickett RA, Shaffer CM, Chopra N, Yang T, Knollmann BC, Roden DM, Murray KT
(2017) Circ Arrhythm Electrophysiol 10:
MeSH Terms: Action Potentials, Animals, Anti-Bacterial Agents, Arrhythmias, Cardiac, Azithromycin, CHO Cells, Calcium Channel Blockers, Calcium Channels, L-Type, Cricetulus, Dose-Response Relationship, Drug, Electrocardiography, Ambulatory, Female, HEK293 Cells, Heart Rate, Humans, KCNQ1 Potassium Channel, Mice, Inbred C57BL, Myocytes, Cardiac, NAV1.5 Voltage-Gated Sodium Channel, Potassium Channel Blockers, Potassium Channels, Inwardly Rectifying, Potassium Channels, Voltage-Gated, Rabbits, Sodium Channel Blockers, Telemetry, Time Factors, Transfection, Young Adult
Show Abstract · Added July 6, 2017
BACKGROUND - The widely used macrolide antibiotic azithromycin increases risk of cardiovascular and sudden cardiac death, although the underlying mechanisms are unclear. Case reports, including the one we document here, demonstrate that azithromycin can cause rapid, polymorphic ventricular tachycardia in the absence of QT prolongation, indicating a novel proarrhythmic syndrome. We investigated the electrophysiological effects of azithromycin in vivo and in vitro using mice, cardiomyocytes, and human ion channels heterologously expressed in human embryonic kidney (HEK 293) and Chinese hamster ovary (CHO) cells.
METHODS AND RESULTS - In conscious telemetered mice, acute intraperitoneal and oral administration of azithromycin caused effects consistent with multi-ion channel block, with significant sinus slowing and increased PR, QRS, QT, and QTc intervals, as seen with azithromycin overdose. Similarly, in HL-1 cardiomyocytes, the drug slowed sinus automaticity, reduced phase 0 upstroke slope, and prolonged action potential duration. Acute exposure to azithromycin reduced peak SCN5A currents in HEK cells (IC=110±3 μmol/L) and Na current in mouse ventricular myocytes. However, with chronic (24 hour) exposure, azithromycin caused a ≈2-fold increase in both peak and late SCN5A currents, with findings confirmed for I in cardiomyocytes. Mild block occurred for K currents representing I (CHO cells expressing hERG; IC=219±21 μmol/L) and I (CHO cells expressing KCNQ1+KCNE1; IC=184±12 μmol/L), whereas azithromycin suppressed L-type Ca currents (rabbit ventricular myocytes, IC=66.5±4 μmol/L) and I (HEK cells expressing Kir2.1, IC=44±3 μmol/L).
CONCLUSIONS - Chronic exposure to azithromycin increases cardiac Na current to promote intracellular Na loading, providing a potential mechanistic basis for the novel form of proarrhythmia seen with this macrolide antibiotic.
© 2017 American Heart Association, Inc.
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28 MeSH Terms
In vivo histone H1 migration from necrotic to viable tissue.
Luhrs KA, Pink D, Schulte W, Zijlstra A, Lewis JD, Parseghian MH
(2017) Oncotarget 8: 16275-16292
MeSH Terms: Animals, CHO Cells, Cell Line, Tumor, Cell Survival, Cricetinae, Cricetulus, Endocytosis, Histones, Humans, Necrosis, Protein Transport
Show Abstract · Added April 6, 2017
Necrosis is induced by ischemic conditions within the core of many solid tumors. Using fluorescent fusion proteins, we provide in vivo evidence of histone trafficking among cancer cells in implanted tumors. In particular, the most abundant H1 isoform (H1.2) was found to be transported from necrotic tumor cells into surrounding viable cells where histones are selectively taken up by energy-dependent endocytosis. We propose that intercellular histone trafficking could function as a target for drug delivery. This concept was validated using an anti-histone antibody that was co-internalized with histones from dead cells into viable ones surrounding the necrotic regions of a tumor, where some of the most chemoresistant cells reside. These findings demonstrate that cellular translocation of conjugated drugs using anti-histone antibodies is a promising strategy for targeted drug delivery to chemoresistant tumors.
1 Communities
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11 MeSH Terms
Application of C flux analysis to identify high-productivity CHO metabolic phenotypes.
Templeton N, Smith KD, McAtee-Pereira AG, Dorai H, Betenbaugh MJ, Lang SE, Young JD
(2017) Metab Eng 43: 218-225
MeSH Terms: Animals, Antibodies, Monoclonal, CHO Cells, Carbon Isotopes, Citric Acid Cycle, Cricetulus, Gene Expression, Immunoglobulin G, Isotope Labeling, Recombinant Proteins
Show Abstract · Added April 27, 2017
Industrial bioprocesses place high demands on the energy metabolism of host cells to meet biosynthetic requirements for maximal protein expression. Identifying metabolic phenotypes that promote high expression is therefore a major goal of the biotech industry. We conducted a series of C flux analysis studies to examine the metabolic response to IgG expression during early stationary phase of CHO cell cultures grown in 3L fed-batch bioreactors. We examined eight clones expressing four different IgGs and compared with three non-expressing host-cell controls. Some clones were genetically manipulated to be apoptosis-resistant by expressing Bcl-2Δ, which correlated with increased IgG production and elevated glucose metabolism. The metabolic phenotypes of the non-expressing, IgG-expressing, and Bcl-2Δ/IgG-expressing clones were fully segregated by hierarchical clustering analysis. Lactate consumption and citric acid cycle fluxes were most strongly associated with specific IgG productivity. These studies indicate that enhanced oxidative metabolism is a characteristic of high-producing CHO cell lines.
Copyright © 2017 International Metabolic Engineering Society. Published by Elsevier Inc. All rights reserved.
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10 MeSH Terms
Structural Insights into Reovirus σ1 Interactions with Two Neutralizing Antibodies.
Dietrich MH, Ogden KM, Katen SP, Reiss K, Sutherland DM, Carnahan RH, Goff M, Cooper T, Dermody TS, Stehle T
(2017) J Virol 91:
MeSH Terms: Amino Acid Sequence, Animals, Antibodies, Neutralizing, Antibodies, Viral, Binding Sites, CHO Cells, Cell Line, Cricetulus, Hemagglutinin Glycoproteins, Influenza Virus, Immunoglobulin Fab Fragments, Mice, Molecular Docking Simulation, Molecular Dynamics Simulation, Neutralization Tests, Protein Binding, Protein Conformation, Protein Interaction Domains and Motifs, Reoviridae, Structure-Activity Relationship, Viral Proteins, Virus Replication
Show Abstract · Added April 26, 2017
Reovirus attachment protein σ1 engages glycan receptors and junctional adhesion molecule-A (JAM-A) and is thought to undergo a conformational change during the proteolytic disassembly of virions to infectious subvirion particles (ISVPs) that accompanies cell entry. The σ1 protein is also the primary target of neutralizing antibodies. Here, we present a structural and functional characterization of two neutralizing antibodies that target σ1 of serotype 1 (T1) and serotype 3 (T3) reoviruses. The crystal structures revealed that each antibody engages its cognate σ1 protein within the head domain via epitopes distinct from the JAM-A-binding site. Surface plasmon resonance and cell-binding assays indicated that both antibodies likely interfere with JAM-A engagement by steric hindrance. To define the interplay between the carbohydrate receptor and antibody binding, we conducted hemagglutination inhibition assays using virions and ISVPs. The glycan-binding site of T1 σ1 is located in the head domain and is partly occluded by the bound Fab in the crystal structure. The T1-specific antibody inhibited hemagglutination by virions and ISVPs, probably via direct interference with glycan engagement. In contrast to T1 σ1, the carbohydrate-binding site of T3 σ1 is located in the tail domain, distal to the antibody epitope. The T3-specific antibody inhibited hemagglutination by T3 virions but not ISVPs, indicating that the antibody- and glycan-binding sites in σ1 are in closer spatial proximity on virions than on ISVPs. Our results provide direct evidence for a structural rearrangement of σ1 during virion-to-ISVP conversion and contribute new information about the mechanisms of antibody-mediated neutralization of reovirus.
IMPORTANCE - Virus attachment proteins mediate binding to host cell receptors, serve critical functions in cell and tissue tropism, and are often targeted by the neutralizing antibody response. The structural investigation of antibody-antigen complexes can provide valuable information for understanding the molecular basis of virus neutralization. Studies with enveloped viruses, such as HIV and influenza virus, have helped to define sites of vulnerability and guide vaccination strategies. By comparison, less is known about antibody binding to nonenveloped viruses. Here, we structurally investigated two neutralizing antibodies that bind the attachment protein σ1 of reovirus. Furthermore, we characterized the neutralization efficiency, the binding affinity for σ1, and the effect of the antibodies on reovirus receptor engagement. Our analysis defines reovirus interactions with two neutralizing antibodies, allows us to propose a mechanism by which they block virus infection, and provides evidence for a conformational change in the σ1 protein during viral cell entry.
Copyright © 2017 American Society for Microbiology.
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21 MeSH Terms
Ligand-based virtual screen for the discovery of novel M5 inhibitor chemotypes.
Geanes AR, Cho HP, Nance KD, McGowan KM, Conn PJ, Jones CK, Meiler J, Lindsley CW
(2016) Bioorg Med Chem Lett 26: 4487-4491
MeSH Terms: Animals, CHO Cells, Cricetulus, Drug Discovery, Humans, Ligands, Muscarinic Antagonists, Quantitative Structure-Activity Relationship, Receptor, Muscarinic M5
Show Abstract · Added April 6, 2017
This Letter describes a ligand-based virtual screening campaign utilizing SAR data around the M5 NAMs, ML375 and VU6000181. Both QSAR and shape scores were employed to virtually screen a 98,000-member compound library. Neither approach alone proved productive, but a consensus score of the two models identified a novel scaffold which proved to be a modestly selective, but weak inhibitor (VU0549108) of the M5 mAChR (M5 IC50=6.2μM, M1-4 IC50s>10μM) based on an unusual 8-((1,3,5-trimethyl-1H-pyrazol-4-yl)sulfonyl)-1-oxa-4-thia-8-azaspiro[4,5]decane scaffold. [(3)H]-NMS binding studies showed that VU0549108 interacts with the orthosteric site (Ki of 2.7μM), but it is not clear if this is negative cooperativity or orthosteric binding. Interestingly, analogs synthesized around VU0549108 proved weak, and SAR was very steep. However, this campaign validated the approach and warranted further expansion to identify additional novel chemotypes.
Copyright © 2016 Elsevier Ltd. All rights reserved.
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9 MeSH Terms