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Hagen LH, Brooke CG, Shaw CA, Norbeck AD, Piao H, Arntzen MØ, Olson HM, Copeland A, Isern N, Shukla A, Roux S, Lombard V, Henrissat B, O'Malley MA, Grigoriev IV, Tringe SG, Mackie RI, Pasa-Tolic L, Pope PB, Hess M. Proteome specialization of anaerobic fungi during ruminal degradation of recalcitrant plant fiber. ISME J 2020; 15:421-434. [PMID: 32929206 PMCID: PMC8026616 DOI: 10.1038/s41396-020-00769-x] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/20/2020] [Revised: 08/21/2020] [Accepted: 09/02/2020] [Indexed: 12/17/2022]
Abstract
The rumen harbors a complex microbial mixture of archaea, bacteria, protozoa, and fungi that efficiently breakdown plant biomass and its complex dietary carbohydrates into soluble sugars that can be fermented and subsequently converted into metabolites and nutrients utilized by the host animal. While rumen bacterial populations have been well documented, only a fraction of the rumen eukarya are taxonomically and functionally characterized, despite the recognition that they contribute to the cellulolytic phenotype of the rumen microbiota. To investigate how anaerobic fungi actively engage in digestion of recalcitrant fiber that is resistant to degradation, we resolved genome-centric metaproteome and metatranscriptome datasets generated from switchgrass samples incubated for 48 h in nylon bags within the rumen of cannulated dairy cows. Across a gene catalog covering anaerobic rumen bacteria, fungi and viruses, a significant portion of the detected proteins originated from fungal populations. Intriguingly, the carbohydrate-active enzyme (CAZyme) profile suggested a domain-specific functional specialization, with bacterial populations primarily engaged in the degradation of hemicelluloses, whereas fungi were inferred to target recalcitrant cellulose structures via the detection of a number of endo- and exo-acting enzymes belonging to the glycoside hydrolase (GH) family 5, 6, 8, and 48. Notably, members of the GH48 family were amongst the highest abundant CAZymes and detected representatives from this family also included dockerin domains that are associated with fungal cellulosomes. A eukaryote-selected metatranscriptome further reinforced the contribution of uncultured fungi in the ruminal degradation of recalcitrant fibers. These findings elucidate the intricate networks of in situ recalcitrant fiber deconstruction, and importantly, suggest that the anaerobic rumen fungi contribute a specific set of CAZymes that complement the enzyme repertoire provided by the specialized plant cell wall degrading rumen bacteria.
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Affiliation(s)
- Live H Hagen
- Faculty of Biotechnology, Chemistry and Food Science, Norwegian University of Life Sciences, Aas, Norway.
| | | | | | | | - Hailan Piao
- Washington State University, Richland, WA, USA
| | - Magnus Ø Arntzen
- Faculty of Biotechnology, Chemistry and Food Science, Norwegian University of Life Sciences, Aas, Norway
| | - Heather M Olson
- Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, CA, USA
| | - Alex Copeland
- U.S. Department of Energy Joint Genome Institute, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Nancy Isern
- Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, CA, USA
| | - Anil Shukla
- Pacific Northwest National Laboratory, Richland, WA, USA
| | - Simon Roux
- U.S. Department of Energy Joint Genome Institute, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Vincent Lombard
- CNRS, UMR 7257, Université Aix-Marseille, 13288, Marseille, France.,Institut National de la Recherche Agronomique, USC 1408 Architecture et Fonction des Macromolécules Biologiques, 13288, Marseille, France
| | - Bernard Henrissat
- CNRS, UMR 7257, Université Aix-Marseille, 13288, Marseille, France.,Institut National de la Recherche Agronomique, USC 1408 Architecture et Fonction des Macromolécules Biologiques, 13288, Marseille, France.,Department of Biological Sciences, King Abdulaziz University, Jeddah, 21589, Saudi Arabia
| | - Michelle A O'Malley
- Department of Chemical Engineering, University of California, Santa Barbara, CA, USA
| | - Igor V Grigoriev
- U.S. Department of Energy Joint Genome Institute, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.,Department of Plant and Microbial Biology, University of California, Berkeley, CA, USA
| | - Susannah G Tringe
- U.S. Department of Energy Joint Genome Institute, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Roderick I Mackie
- Department of Animal Science, University of Illinois, Urbana-Champaign, IL, USA
| | - Ljiljana Pasa-Tolic
- Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, CA, USA
| | - Phillip B Pope
- Faculty of Biotechnology, Chemistry and Food Science, Norwegian University of Life Sciences, Aas, Norway.,Faculty of Biosciences, Norwegian University of Life Sciences, Aas, Norway
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Abstract
We propose a new reaction-diffusion model with an eclipse time to study the spread of viruses on bacterial populations. This new model is both biologically and physically sound, unlike previous ones. We determine important parameter values from experimental data, such as the one-step growth. We verify the proposed model by comparing theoretical and experimental data of the front propagation speed for several T7 virus strains.
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Affiliation(s)
- V L de Rioja
- Complex Systems Laboratory, Departament de Física, Universitat de Girona, 17071 Girona, Catalonia, Spain.
| | - J Fort
- Complex Systems Laboratory, Departament de Física, Universitat de Girona, 17071 Girona, Catalonia, Spain
| | - N Isern
- Complex Systems Laboratory, Departament de Física, Universitat de Girona, 17071 Girona, Catalonia, Spain
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Ledee D, Smith L, Bruce M, Kajimoto M, Isern N, Portman MA, Olson AK. c-Myc Alters Substrate Utilization and O-GlcNAc Protein Posttranslational Modifications without Altering Cardiac Function during Early Aortic Constriction. PLoS One 2015; 10:e0135262. [PMID: 26266538 PMCID: PMC4534195 DOI: 10.1371/journal.pone.0135262] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2015] [Accepted: 07/20/2015] [Indexed: 11/19/2022] Open
Abstract
Hypertrophic stimuli cause transcription of the proto-oncogene c-Myc (Myc). Prior work showed that myocardial knockout of c-Myc (Myc) attenuated hypertrophy and decreased expression of metabolic genes after aortic constriction. Accordingly, we assessed the interplay between Myc, substrate oxidation and cardiac function during early pressure overload hypertrophy. Mice with cardiac specific, inducible Myc knockout (MycKO-TAC) and non-transgenic littermates (Cont-TAC) were subjected to transverse aortic constriction (TAC; n = 7/group). Additional groups underwent sham surgery (Cont-Sham and MycKO-Sham, n = 5 per group). After two weeks, function was measured in isolated working hearts along with substrate fractional contributions to the citric acid cycle by using perfusate with 13C labeled mixed fatty acids, lactate, ketone bodies and unlabeled glucose and insulin. Cardiac function was similar between groups after TAC although +dP/dT and -dP/dT trended towards improvement in MycKO-TAC versus Cont-TAC. In sham hearts, Myc knockout did not affect cardiac function or substrate preferences for the citric acid cycle. However, Myc knockout altered fractional contributions during TAC. The unlabeled fractional contribution increased in MycKO-TAC versus Cont-TAC, whereas ketone and free fatty acid fractional contributions decreased. Additionally, protein posttranslational modifications by O-GlcNAc were significantly greater in Cont-TAC versus both Cont-Sham and MycKO-TAC. In conclusion, Myc alters substrate preferences for the citric acid cycle during early pressure overload hypertrophy without negatively affecting cardiac function. Myc also affects protein posttranslational modifications by O-GlcNAc during hypertrophy, which may regulate Myc-induced metabolic changes.
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Affiliation(s)
- Dolena Ledee
- Seattle Children’s Research Institute, Seattle, WA, United States of America
| | - Lincoln Smith
- Department of Pediatrics, Division of Critical Care Medicine, University of Washington, Seattle, Washington, United States of America
| | - Margaret Bruce
- Seattle Children’s Research Institute, Seattle, WA, United States of America
| | - Masaki Kajimoto
- Seattle Children’s Research Institute, Seattle, WA, United States of America
| | - Nancy Isern
- Environmental Molecular Sciences Laboratory (EMSL), Pacific Northwest National Laboratory, Richland, WA, United States of America
| | - Michael A. Portman
- Seattle Children’s Research Institute, Seattle, WA, United States of America
- Department of Pediatrics, Division of Cardiology, University of Washington, Seattle, Washington, United States of America
| | - Aaron K. Olson
- Seattle Children’s Research Institute, Seattle, WA, United States of America
- Department of Pediatrics, Division of Cardiology, University of Washington, Seattle, Washington, United States of America
- * E-mail:
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Ledee DR, Kajimoto M, O'Kelly Priddy CM, Olson AK, Isern N, Robillard-Frayne I, Des Rosiers C, Portman MA. Pyruvate modifies metabolic flux and nutrient sensing during extracorporeal membrane oxygenation in an immature swine model. Am J Physiol Heart Circ Physiol 2015; 309:H137-46. [PMID: 25910802 DOI: 10.1152/ajpheart.00011.2015] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/07/2015] [Accepted: 04/20/2015] [Indexed: 11/22/2022]
Abstract
Extracorporeal membrane oxygenation (ECMO) provides mechanical circulatory support for infants and children with postoperative cardiopulmonary failure. Nutritional support is mandatory during ECMO although specific actions for substrates on the heart have not been delineated. Prior work shows that enhancing pyruvate oxidation promotes successful weaning from ECMO. Accordingly, we tested the hypothesis that prolonged systemic pyruvate supplementation activates pyruvate oxidation in an immature swine model in vivo. Twelve male mixed-breed Yorkshire piglets (age 30-49 days) received systemic infusion of either normal saline (group C) or pyruvate (group P) during the final 6 h of 8 h of ECMO. Over the final hour, piglets received [2-(13)C] pyruvate, as a reference substrate for oxidation, and [(13)C6]-l-leucine, as an indicator for amino acid oxidation and protein synthesis. A significant increase in lactate and pyruvate concentrations occurred, along with an increase in the absolute concentration of the citric acid cycle intermediates. An increase in anaplerotic flux through pyruvate carboxylation in group P occurred compared with no change in pyruvate oxidation. Additionally, pyruvate promoted an increase in the phosphorylation state of several nutrient-sensitive enzymes, like AMP-activated protein kinase and acetyl CoA carboxylase, suggesting activation for fatty acid oxidation. Pyruvate also promoted O-GlcNAcylation through the hexosamine biosynthetic pathway. In conclusion, although prolonged pyruvate supplementation did not alter pyruvate oxidation, it did elicit changes in nutrient- and energy-sensitive pathways. Therefore, the observed results support the further study of pyruvate and its downstream effect on cardiac function.
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Affiliation(s)
- Dolena R Ledee
- Center for Developmental Therapeutics, Seattle Children's Research Institute, Seattle, Washington
| | - Masaki Kajimoto
- Center for Developmental Therapeutics, Seattle Children's Research Institute, Seattle, Washington
| | | | - Aaron K Olson
- Center for Developmental Therapeutics, Seattle Children's Research Institute, Seattle, Washington; Division of Cardiology, Department of Pediatrics, University of Washington, Seattle, Washington
| | - Nancy Isern
- Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington
| | - Isabelle Robillard-Frayne
- Department of Nutrition, Université de Montréal and Montréal Heart Institute, Montréal, Quebec, Canada
| | - Christine Des Rosiers
- Department of Nutrition, Université de Montréal and Montréal Heart Institute, Montréal, Quebec, Canada
| | - Michael A Portman
- Center for Developmental Therapeutics, Seattle Children's Research Institute, Seattle, Washington; Division of Cardiology, Department of Pediatrics, University of Washington, Seattle, Washington
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Files MD, Kajimoto M, O'Kelly Priddy CM, Ledee DR, Xu C, Des Rosiers C, Isern N, Portman MA. Triiodothyronine facilitates weaning from extracorporeal membrane oxygenation by improved mitochondrial substrate utilization. J Am Heart Assoc 2014; 3:e000680. [PMID: 24650924 PMCID: PMC4187495 DOI: 10.1161/jaha.113.000680] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
BACKGROUND Extracorporeal membrane oxygenation (ECMO) provides a bridge to recovery after myocardial injury in infants and children, yet morbidity and mortality remain high. Weaning from the circuit requires adequate cardiac contractile function, which can be impaired by metabolic disturbances induced either by ischemia-reperfusion and/or by ECMO. We tested the hypothesis that although ECMO partially ameliorates metabolic abnormalities induced by ischemia-reperfusion, these abnormalities persist or recur with weaning. We also determined if thyroid hormone supplementation (triiodothyronine) during ECMO improves oxidative metabolism and cardiac function. METHODS AND RESULTS Neonatal piglets underwent transient coronary ischemia to induce cardiac injury then were separated into 4 groups based on loading status. Piglets without coronary ischemia served as controls. We infused into the left coronary artery [2-(13)C]pyruvate and [(13)C6, (15)N]l-leucine to evaluate oxidative metabolism by gas chromatography-mass spectroscopy and nuclear magnetic resonance methods. ECMO improved survival, increased oxidative substrate contribution through pyruvate dehydrogenase, reduced succinate and fumarate accumulation, and ameliorated ATP depletion induced by ischemia. The functional and metabolic benefit of ECMO was lost with weaning, yet triiodothyronine supplementation during ECMO restored function, increased relative pyruvate dehydrogenase flux, reduced succinate and fumarate, and preserved ATP stores. CONCLUSIONS Although ECMO provides metabolic rest by decreasing energy demand, metabolic impairments persist, and are exacerbated with weaning. Treating ECMO-induced thyroid depression with triiodothyronine improves substrate flux, myocardial oxidative capacity and cardiac contractile function. This translational model suggests that metabolic targeting can improve weaning.
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Affiliation(s)
- Matthew D Files
- Department of Cardiology, Seattle Children's Hospital, Seattle, WA
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Kajimoto M, Priddy CMO, Ledee DR, Xu C, Isern N, Olson AK, Portman MA. Effects of continuous triiodothyronine infusion on the tricarboxylic acid cycle in the normal immature swine heart under extracorporeal membrane oxygenation in vivo. Am J Physiol Heart Circ Physiol 2014; 306:H1164-70. [PMID: 24531815 DOI: 10.1152/ajpheart.00964.2013] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Extracorporeal membrane oxygenation (ECMO) is frequently used in infants with postoperative cardiopulmonary failure. ECMO also suppresses circulating triiodothyronine (T3) levels and modifies myocardial metabolism. We assessed the hypothesis that T3 supplementation reverses ECMO-induced metabolic abnormalities in the immature heart. Twenty-two male Yorkshire pigs (age: 25-38 days) with ECMO received [2-(13)C]lactate, [2,4,6,8-(13)C4]octanoate (medium-chain fatty acid), and [U-(13)C]long-chain fatty acids as metabolic tracers either systemically (totally physiological intracoronary concentration) or directly into the coronary artery (high substrate concentration) for the last 60 min of each protocol. NMR analysis of left ventricular tissue determined the fractional contribution of these substrates to the tricarboxylic acid cycle. Fifty percent of the pigs in each group received intravenous T3 supplement (bolus at 0.6 μg/kg and then continuous infusion at 0.2 μg·kg(-1)·h(-1)) during ECMO. Under both substrate loading conditions, T3 significantly increased the fractional contribution of lactate with a marginal increase in the fractional contribution of octanoate. Both T3 and high substrate provision increased the myocardial energy status, as indexed by phosphocreatine concentration/ATP concentration. In conclusion, T3 supplementation promoted lactate metabolism to the tricarboxylic acid cycle during ECMO, suggesting that T3 releases the inhibition of pyruvate dehydrogenase. Manipulation of substrate utilization by T3 may be used therapeutically during ECMO to improve the resting energy state and facilitate weaning.
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Affiliation(s)
- Masaki Kajimoto
- Center for Developmental Therapeutics, Seattle Children's Research Institute, Seattle, Washington
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Kuo NW, Gao YG, Schill MS, Isern N, Dupureur CM, LiWang PJ. Structural insights into the interaction between a potent anti-inflammatory protein, viral CC chemokine inhibitor (vCCI), and the human CC chemokine, Eotaxin-1. J Biol Chem 2014; 289:6592-6603. [PMID: 24482230 DOI: 10.1074/jbc.m113.538991] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Chemokines play important roles in the immune system, not only recruiting leukocytes to the site of infection and inflammation but also guiding cell homing and cell development. The soluble poxvirus-encoded protein viral CC chemokine inhibitor (vCCI), a CC chemokine inhibitor, can bind to human CC chemokines tightly to impair the host immune defense. This protein has no known homologs in eukaryotes and may represent a potent method to stop inflammation. Previously, our structure of the vCCI·MIP-1β (macrophage inflammatory protein-1β) complex indicated that vCCI uses negatively charged residues in β-sheet II to interact with positively charged residues in the MIP-1β N terminus, 20s region and 40s loop. However, the interactions between vCCI and other CC chemokines have not yet been fully explored. Here, we used NMR and fluorescence anisotropy to study the interaction between vCCI and eotaxin-1 (CCL11), a CC chemokine that is an important factor in the asthma response. NMR results reveal that the binding pattern is very similar to the vCCI·MIP-1β complex and suggest that electrostatic interactions provide a major contribution to binding. Fluorescence anisotropy results on variants of eotaxin-1 further confirm the critical roles of the charged residues in eotaxin-1. In addition, the binding affinity between vCCI and other wild type CC chemokines, MCP-1 (monocyte chemoattractant protein-1), MIP-1β, and RANTES (regulated on activation normal T cell expressed and secreted), were determined as 1.1, 1.2, and 0.22 nm, respectively. To our knowledge, this is the first work quantitatively measuring the binding affinity between vCCI and multiple CC chemokines.
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Affiliation(s)
- Nai-Wei Kuo
- Molecular Cell Biology, University of California, Merced, California 95343
| | - Yong-Guang Gao
- Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China
| | - Megan S Schill
- Molecular Cell Biology, University of California, Merced, California 95343
| | - Nancy Isern
- High Field NMR Facility, William R. Wiley Environmental Molecular Sciences Laboratory, Richland, Washington 99352
| | - Cynthia M Dupureur
- Department of Chemistry and Biochemistry, University of Missouri, St. Louis, Missouri 63121
| | - Patricia J LiWang
- Molecular Cell Biology, University of California, Merced, California 95343.
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Kajimoto M, O'Kelly Priddy CM, Ledee DR, Xu C, Isern N, Olson AK, Des Rosiers C, Portman MA. Myocardial reloading after extracorporeal membrane oxygenation alters substrate metabolism while promoting protein synthesis. J Am Heart Assoc 2013; 2:e000106. [PMID: 23959443 PMCID: PMC3828804 DOI: 10.1161/jaha.113.000106] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Background Extracorporeal membrane oxygenation (ECMO) unloads the heart, providing a bridge to recovery in children after myocardial stunning. ECMO also induces stress which can adversely affect the ability to reload or wean the heart from the circuit. Metabolic impairments induced by altered loading and/or stress conditions may impact weaning. However, cardiac substrate and amino acid requirements upon weaning are unknown. We assessed the hypothesis that ventricular reloading with ECMO modulates both substrate entry into the citric acid cycle (CAC) and myocardial protein synthesis. Methods and Results Sixteen immature piglets (7.8 to 15.6 kg) were separated into 2 groups based on ventricular loading status: 8‐hour ECMO (UNLOAD) and postwean from ECMO (RELOAD). We infused into the coronary artery [2‐13C]‐pyruvate as an oxidative substrate and [13C6]‐L‐leucine as an indicator for amino acid oxidation and protein synthesis. Upon RELOAD, each functional parameter, which were decreased substantially by ECMO, recovered to near‐baseline level with the exclusion of minimum dP/dt. Accordingly, myocardial oxygen consumption was also increased, indicating that overall mitochondrial metabolism was reestablished. At the metabolic level, when compared to UNLOAD, RELOAD altered the contribution of various substrates/pathways to tissue pyruvate formation, favoring exogenous pyruvate versus glycolysis, and acetyl‐CoA formation, shifting away from pyruvate decarboxylation to endogenous substrate, presumably fatty acids. Furthermore, there was also a significant increase of tissue concentrations for all CAC intermediates (≈80%), suggesting enhanced anaplerosis, and of fractional protein synthesis rates (>70%). Conclusions RELOAD alters both cytosolic and mitochondrial energy substrate metabolism, while favoring leucine incorporation into protein synthesis rather than oxidation in the CAC. Improved understanding of factors governing these metabolic perturbations may serve as a basis for interventions and thereby improve success rate from weaning from ECMO.
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Affiliation(s)
- Masaki Kajimoto
- Center for Developmental Therapeutics, Seattle Children's Research Institute, Seattle, WA
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Ledee D, Portman MA, Kajimoto M, Isern N, Olson AK. Thyroid hormone reverses aging-induced myocardial fatty acid oxidation defects and improves the response to acutely increased afterload. PLoS One 2013; 8:e65532. [PMID: 23762386 PMCID: PMC3676337 DOI: 10.1371/journal.pone.0065532] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2013] [Accepted: 04/27/2013] [Indexed: 01/15/2023] Open
Abstract
Background Subclinical hypothyroidism occurs during aging in humans and mice and may contribute to the development of heart failure. Aging also impairs myocardial fatty acid oxidation, causing increased reliance on flux through pyruvate dehydrogenase (PDH) to maintain function. We hypothesize that the metabolic changes in aged hearts make them less tolerant to acutely increased work and that thyroid hormone supplementation reverses these defects. Methods Studies were performed on young (Young, 4–6 months) and aged (Old, 22–24 months) C57/BL6 mice at standard (50 mmHg) and high afterload (80 mmHg). Another aged group received thyroid hormone for 3 weeks (Old-TH, high afterload only). Function was measured in isolated working hearts along with substrate fractional contributions (Fc) to the citric acid cycle (CAC) using perfusate with 13C labeled lactate, pyruvate, glucose and unlabeled palmitate and insulin. Results Old mice maintained cardiac function under standard workload conditions, despite a marked decrease in unlabeled (presumably palmitate) Fc and relatively similar individual carbohydrate contributions. However, old mice exhibited reduced palmitate oxidation with diastolic dysfunction exemplified by lower -dP/dT. Thyroid hormone abrogated the functional and substrate flux abnormalities in aged mice. Conclusion The aged heart shows diminished ability to increase cardiac work due to substrate limitations, primarily impaired fatty acid oxidation. The heart accommodates slightly by increasing efficiency through oxidation of carbohydrate substrates. Thyroid hormone supplementation in aged mice significantly improves cardiac function potentially through restoration of fatty acid oxidation.
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Affiliation(s)
- Dolena Ledee
- Seattle Children's Research Institute, Seattle, Washington, United States of America
| | - Michael A. Portman
- Seattle Children's Research Institute, Seattle, Washington, United States of America
- Division of Cardiology, Department of Pediatrics, University of Washington, Seattle, Washington, United States of America
| | - Masaki Kajimoto
- Seattle Children's Research Institute, Seattle, Washington, United States of America
| | - Nancy Isern
- Environmental Molecular Sciences Laboratory (EMSL), Pacific Northwest National Laboratory, Richland, Washington, United States of America
| | - Aaron K. Olson
- Seattle Children's Research Institute, Seattle, Washington, United States of America
- Division of Cardiology, Department of Pediatrics, University of Washington, Seattle, Washington, United States of America
- * E-mail:
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Kajimoto M, O'Kelly Priddy CM, Ledee DR, Xu C, Isern N, Olson AK, Portman MA. Extracorporeal membrane oxygenation promotes long chain fatty acid oxidation in the immature swine heart in vivo. J Mol Cell Cardiol 2013; 62:144-52. [PMID: 23727393 DOI: 10.1016/j.yjmcc.2013.05.014] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/25/2013] [Revised: 05/18/2013] [Accepted: 05/21/2013] [Indexed: 12/29/2022]
Abstract
Extracorporeal membrane oxygenation (ECMO) supports infants and children with severe cardiopulmonary compromise. Nutritional support for these children includes provision of medium- and long-chain fatty acids (FAs). However, ECMO induces a stress response, which could limit the capacity for FA oxidation. Metabolic impairment could induce new or exacerbate existing myocardial dysfunction. Using a clinically relevant piglet model, we tested the hypothesis that ECMO maintains the myocardial capacity for FA oxidation and preserves myocardial energy state. Provision of 13-Carbon labeled medium-chain FA (octanoate), long-chain free FAs (LCFAs), and lactate into systemic circulation showed that ECMO promoted relative increases in myocardial LCFA oxidation while inhibiting lactate oxidation. Loading of these labeled substrates at high dose into the left coronary artery demonstrated metabolic flexibility as the heart preferentially oxidized octanoate. ECMO preserved this octanoate metabolic response, but also promoted LCFA oxidation and inhibited lactate utilization. Rapid upregulation of pyruvate dehydrogenase kinase-4 (PDK4) protein appeared to participate in this metabolic shift during ECMO. ECMO also increased relative flux from lactate to alanine further supporting the role for pyruvate dehydrogenase inhibition by PDK4. High dose substrate loading during ECMO also elevated the myocardial energy state indexed by phosphocreatine to ATP ratio. ECMO promotes LCFA oxidation in immature hearts, while maintaining myocardial energy state. These data support the appropriateness of FA provision during ECMO support for the immature heart.
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Affiliation(s)
- Masaki Kajimoto
- Center for Developmental Therapeutics, Seattle Children's Research Institute, Seattle, WA, USA
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Priddy CMO, Kajimoto M, Ledee DR, Bouchard B, Isern N, Olson AK, Des Rosiers C, Portman MA. Myocardial oxidative metabolism and protein synthesis during mechanical circulatory support by extracorporeal membrane oxygenation. Am J Physiol Heart Circ Physiol 2012. [PMID: 23203964 DOI: 10.1152/ajpheart.00672.2012] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Extracorporeal membrane oxygenation (ECMO) provides essential mechanical circulatory support necessary for survival in infants and children with acute cardiac decompensation. However, ECMO also causes metabolic disturbances, which contribute to total body wasting and protein loss. Cardiac stunning can also occur, which prevents ECMO weaning, and contributes to high mortality. The heart may specifically undergo metabolic impairments, which influence functional recovery. We tested the hypothesis that ECMO alters oxidative metabolism and protein synthesis. We focused on the amino acid leucine and integration with myocardial protein synthesis. We used a translational immature swine model in which we assessed in heart 1) the fractional contribution of leucine (FcLeucine) and pyruvate to mitochondrial acetyl-CoA formation by nuclear magnetic resonance and 2) global protein fractional synthesis (FSR) by gas chromatography-mass spectrometry. Immature mixed breed Yorkshire male piglets (n = 22) were divided into four groups based on loading status (8 h of normal circulation or ECMO) and intracoronary infusion [(13)C(6),(15)N]-L-leucine (3.7 mM) alone or with [2-(13)C]-pyruvate (7.4 mM). ECMO decreased pulse pressure and correspondingly lowered myocardial oxygen consumption (∼40%, n = 5), indicating decreased overall mitochondrial oxidative metabolism. However, FcLeucine was maintained and myocardial protein FSR was marginally increased. Pyruvate addition decreased tissue leucine enrichment, FcLeucine, and Fc for endogenous substrates as well as protein FSR. The heart under ECMO shows reduced oxidative metabolism of substrates, including amino acids, while maintaining 1) metabolic flexibility indicated by ability to respond to pyruvate and 2) a normal or increased capacity for global protein synthesis.
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12
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Olson AK, Ledee D, Iwamoto K, Kajimoto M, O'Kelly Priddy C, Isern N, Portman MA. C-Myc induced compensated cardiac hypertrophy increases free fatty acid utilization for the citric acid cycle. J Mol Cell Cardiol 2012; 55:156-64. [PMID: 22828478 DOI: 10.1016/j.yjmcc.2012.07.005] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/08/2012] [Revised: 07/12/2012] [Accepted: 07/13/2012] [Indexed: 10/28/2022]
Abstract
The protooncogene C-Myc (Myc) regulates cardiac hypertrophy. Myc promotes compensated cardiac function, suggesting that the operative mechanisms differ from those leading to heart failure. Myc regulation of substrate metabolism is a reasonable target, as Myc alters metabolism in other tissues. We hypothesize that Myc induced shifts in substrate utilization signal and promote compensated hypertrophy. We used cardiac specific Myc-inducible C57/BL6 male mice between 4-6 months old that develop hypertrophy with tamoxifen (tam) injections. Isolated working hearts and (13)Carbon ((13)C)-NMR were used to measure function and fractional contributions (Fc) to the citric acid cycle by using perfusate containing (13)C-labeled free fatty acids, acetoacetate, lactate, unlabeled glucose and insulin. Studies were performed at pre-hypertrophy (3-days tam, 3dMyc), established hypertrophy (7-days tam, 7dMyc) or vehicle control (Cont). Non-transgenic siblings (NTG) received 7-days tam or vehicle to assess drug effect. Hypertrophy was assessed by echocardiograms and heart weights. Western blots were performed on key metabolic enzymes. Hypertrophy occurred in 7dMyc only. Cardiac function did not differ between groups. Tam alone did not affect substrate contributions in NTG. Substrate utilization was not significantly altered in 3dMyc versus Cont. The free fatty acid FC was significantly greater in 7dMyc versus Cont with decreased unlabeled Fc, which is predominately exogenous glucose. Free fatty acid flux to the citric acid cycle increased while lactate flux was diminished in 7dMyc compared to Cont. Total protein levels of a panel of key metabolic enzymes were unchanged; however total protein O-GlcNAcylation was increased in 7dMyc. Substrate utilization changes for the citric acid cycle did not precede hypertrophy; therefore they are not the primary signal for cardiac growth in this model. Free fatty acid utilization and oxidation increase at established hypertrophy. Understanding the mechanisms whereby this change maintained compensated function could provide useful information for developing metabolic therapies to treat heart failure. The molecular signaling for this metabolic change may occur through O-GlcNAcylation. This article is part of a Special Issue entitled "Focus on Cardiac Metabolism".
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Affiliation(s)
- Aaron K Olson
- Division of Cardiology, Department of Pediatrics, University of Washington, Seattle Children's Hospital, 4800 Sand Point Way NE, Seattle, WA 98105, USA.
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Kajimoto M, O'Kelly Priddy CM, Ledee DR, Bouchard B, Isern N, Olson AK, Des Rosiers C, Portman MA. Mechanical Circulatory Unloading Promotes Proteins Synthesis and Maintains Leucine Oxidation. FASEB J 2012. [DOI: 10.1096/fasebj.26.1_supplement.1127.1] [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)
- Masaki Kajimoto
- PediatricsUniversity of Washington and Seattle Children'sSeattleWA
| | | | - Dolena R. Ledee
- PediatricsUniversity of Washington and Seattle Children'sSeattleWA
| | - Bertrand Bouchard
- Department of NutritionUniversité de Montréal and Montreal Heart InstituteMontrealQCCanada
| | - Nancy Isern
- Environmental Molecular Sciences LaboratoryPacific Northwest National LaboratoriesRichlandWA
| | - Aaron K. Olson
- PediatricsUniversity of Washington and Seattle Children'sSeattleWA
| | - Christine Des Rosiers
- Department of NutritionUniversité de Montréal and Montreal Heart InstituteMontrealQCCanada
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Olson AK, Bouchard B, Ning XH, Isern N, Rosiers CD, Portman MA. Triiodothyronine increases myocardial function and pyruvate entry into the citric acid cycle after reperfusion in a model of infant cardiopulmonary bypass. Am J Physiol Heart Circ Physiol 2011; 302:H1086-93. [PMID: 22180654 DOI: 10.1152/ajpheart.00959.2011] [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] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Triiodothyronine (T3) supplementation improves clinical outcomes in infants after cardiac surgery using cardiopulmonary bypass by unknown mechanisms. We utilized a translational model of infant cardiopulmonary bypass to test the hypothesis that T3 modulates pyruvate entry into the citric acid cycle (CAC), thereby providing the energy support for improved cardiac function after ischemia-reperfusion (I/R). Neonatal piglets received intracoronary [2-(13)Carbon((13)C)]pyruvate for 40 min (8 mM) during control aerobic conditions (control) or immediately after reperfusion (I/R) from global hypothermic ischemia. A third group (I/R-Tr) received T3 (1.2 μg/kg) during reperfusion. We assessed absolute CAC intermediate levels and flux parameters into the CAC through oxidative pyruvate decarboxylation (PDC) and anaplerotic carboxylation (PC) using [2-(13)C]pyruvate and isotopomer analysis by gas and liquid chromatography-mass spectrometry and (13)C-nuclear magnetic resonance spectroscopy. When compared with I/R, T3 (group I/R-Tr) increased cardiac power and oxygen consumption after I/R while elevating flux of both PDC and PC (∼4-fold). Although neither I/R nor I/R-Tr modified absolute CAC levels, T3 inhibited I/R-induced reductions in their molar percent enrichment. Furthermore, (13)C-labeling of CAC intermediates suggests that T3 may decrease entry of unlabeled carbons at the level of oxaloacetate through anaplerosis or exchange reaction with asparate. T3 markedly enhances PC and PDC fluxes, thereby providing potential substrate for elevated cardiac function after reperfusion. This T3-induced increase in pyruvate fluxes occurs with preservation of the CAC intermediate pool. Our labeling data raise the possibility that T3 reduces reliance on amino acids for anaplerosis after reperfusion.
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Affiliation(s)
- Aaron K Olson
- Division of Cardiology, Department of Pediatrics, University of Washington, WA, USA
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Morrish F, Isern N, Sadilek M, Jeffrey M, Hockenbery DM. c-Myc activates multiple metabolic networks to generate substrates for cell-cycle entry. Oncogene 2009; 28:2485-91. [PMID: 19448666 DOI: 10.1038/onc.2009.112] [Citation(s) in RCA: 126] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Cell proliferation requires the coordinated activity of cytosolic and mitochondrial metabolic pathways to provide ATP and building blocks for DNA, RNA and protein synthesis. Many metabolic pathway genes are targets of the c-myc oncogene and cell-cycle regulator. However, the contribution of c-Myc to the activation of cytosolic and mitochondrial metabolic networks during cell-cycle entry is unknown. Here, we report the metabolic fates of [U-(13)C] glucose in serum-stimulated myc(-/-) and myc(+/+) fibroblasts by (13)C isotopomer NMR analysis. We demonstrate that endogenous c-myc increased (13)C labeling of ribose sugars, purines and amino acids, indicating partitioning of glucose carbons into C1/folate and pentose phosphate pathways, and increased tricarboxylic acid cycle turnover at the expense of anaplerotic flux. Myc expression also increased global O-linked N-acetylglucosamine protein modification, and inhibition of hexosamine biosynthesis selectively reduced growth of Myc-expressing cells, suggesting its importance in Myc-induced proliferation. These data reveal a central organizing function for the Myc oncogene in the metabolism of cycling cells. The pervasive deregulation of this oncogene in human cancers may be explained by its function in directing metabolic networks required for cell proliferation.
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Affiliation(s)
- F Morrish
- Clinical Research Division, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA
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16
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Olson AK, Hyyti OM, Cohen GA, Ning XH, Sadilek M, Isern N, Portman MA. Superior cardiac function via anaplerotic pyruvate in the immature swine heart after cardiopulmonary bypass and reperfusion. Am J Physiol Heart Circ Physiol 2008; 295:H2315-20. [PMID: 18849332 DOI: 10.1152/ajpheart.00739.2008] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Pyruvate produces inotropic responses in the adult reperfused heart. Pyruvate oxidation and anaplerotic entry into the tricarboxylic acid (TCA) cycle via carboxylation are linked to the stimulation of contractile function. The goals of this study were to determine if these metabolic pathways operate and are maintained in the developing myocardium after reperfusion. Immature male swine (age: 10-18 days) were subjected to cardiopulmonary bypass (CPB). Intracoronary infusion of [2-(13)C]pyruvate (to achieve an estimated final concentration of 8 mM) was given for 35 min, starting either during weaning (group I) and after its discontinuation (group II) or without (control) CPB. Hemodynamic data were collected. 13C NMR spectroscopy was used to determine the fraction of pyruvate entering the TCA cycle via pyruvate carboxylation (PC) to total TCA cycle entry (PC plus decarboxlyation via pyruvate dehydrogenase). Liquid chromatography-mass spectrometry was used to determine total glutamate enrichment. Pyruvate infusion starting during the weaning of mechanical circulatory support improved maximum dP/dt (P<0.05) but waiting to start the infusion until after the discontinuation of CPB did not. Glutamate fractional enrichment was confirmed by liquid chromatography-mass spectroscopy as adequate (>5%) to provide signal to noise in the NMR experiment in all groups. The ratio of pyruvate carboxylase to total pyruvate entry into the TCA cycle did not differ between groups (group I: 20+/-4%, group II: 23+/-7%, and control: 27+/-7%). These data show that robust PC operates in the neonatal pig heart and is maintained during reperfusion under conditions that emulate CPB and reperfusion in human infants.
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Affiliation(s)
- Aaron K Olson
- Department of Pediatrics, University of Washington, Children's Hospital and Regional Medical Center, MSW 4841, 4800 Sand Point Way NE, Seattle, WA 98105, USA
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Randall WJ, Droege MW, Mizuno N, Nomiya K, Weakley TJR, Finke RG, Isern N, Salta J, Zubieta J. Metal Complexes of the Lacunary Heteropolytungstates [B-α-PW9O34]9-and [α-P2W15O56]12-. ACTA ACUST UNITED AC 2007. [DOI: 10.1002/9780470132623.ch28] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/11/2023]
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18
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Zhang L, DeRider M, McCornack MA, Jao SC, Isern N, Ness T, Moyer R, LiWang PJ. Solution structure of the complex between poxvirus-encoded CC chemokine inhibitor vCCI and human MIP-1beta. Proc Natl Acad Sci U S A 2006; 103:13985-90. [PMID: 16963564 PMCID: PMC1599900 DOI: 10.1073/pnas.0602142103] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.7] [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: 03/15/2006] [Indexed: 11/18/2022] Open
Abstract
Chemokines (chemotactic cytokines) comprise a large family of proteins that recruit and activate leukocytes, giving chemokines a major role in both immune response and inflammation-related diseases. The poxvirus-encoded viral CC chemokine inhibitor (vCCI) binds to many CC chemokines with high affinity, acting as a potent inhibitor of chemokine action. We have used heteronuclear multidimensional NMR to determine the structure of an orthopoxvirus vCCI in complex with a human CC chemokine, MIP-1beta (macrophage inflammatory protein 1beta). vCCI binds to the chemokine with 1:1 stoichiometry, forming a complex of 311 aa. vCCI uses residues from its beta-sheet II to interact with a surface of MIP-1beta that includes residues adjacent to its N terminus, as well as residues in the 20's region and the 40's loop. This structure reveals the strategy used by vCCI to tightly bind numerous chemokines while retaining selectivity for the CC chemokine subfamily.
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Affiliation(s)
- Li Zhang
- *Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX 77843-2128
| | - Michele DeRider
- *Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX 77843-2128
| | - Melissa A. McCornack
- *Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX 77843-2128
| | - Shu-chuan Jao
- *Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX 77843-2128
| | - Nancy Isern
- High Field NMR Facility, William R. Wiley Environmental Molecular Sciences Laboratory, Richland, WA 99352; and
| | - Traci Ness
- Department of Molecular Genetics and Microbiology, University of Florida, Gainesville, FL 32610
| | - Richard Moyer
- Department of Molecular Genetics and Microbiology, University of Florida, Gainesville, FL 32610
| | - Patricia J. LiWang
- *Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX 77843-2128
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Kim S, Zhang Z, Upchurch S, Isern N, Chen Y. Structure and DNA-binding Sites of the SWI1 AT-rich Interaction Domain (ARID) Suggest Determinants for Sequence-specific DNA Recognition. J Biol Chem 2004; 279:16670-6. [PMID: 14722072 DOI: 10.1074/jbc.m312115200] [Citation(s) in RCA: 36] [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] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
ARID (AT-rich interaction domain) is a homologous family of DNA-binding domains that occur in DNA-binding proteins from a wide variety of species, ranging from yeast to nematodes, insects, mammals, and plants. SWI1, a member of the SWI/SNF protein complex that is involved in chromatin remodeling during transcription, contains the ARID motif. The ARID domain of human SWI1 (also known as p270) does not select for a specific DNA sequence from a random sequence pool. The lack of sequence specificity shown by the SWI1 ARID domain stands in contrast to the other characterized ARID domains, which recognize specific AT-rich sequences. We have solved the three-dimensional structure of human SWI1 ARID using solution NMR methods. In addition, we have characterized nonspecific DNA binding by the SWI1 ARID domain. Results from this study indicate that a flexible, long, internal loop in the ARID motif is likely to be important for sequence-specific DNA recognition. The structure of the human SWI1 ARID domain also represents a distinct structural subfamily. Studies of ARID indicate that the boundary of DNA binding structural and functional domains can extend beyond the sequence homologous region in a homologous family of proteins. Structural studies of homologous domains such as the ARID family of DNA-binding domains should provide information to better predict the boundary of structural and functional domains in structural genomic studies.
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Affiliation(s)
- Suhkmann Kim
- Division of Immunology, Beckman Research Institute of the City of Hope, Duarte, California 91010, USA
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20
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Yang J, Silks L, Wu R, Isern N, Unkefer C, Kennedy MA. Improvements for measuring 1H-1H coupling constants in DNA via new stripe-COSY and superstripe-COSY pulse sequences combined with a novel strategy of selective deuteration. J Magn Reson 1997; 129:212-218. [PMID: 9441887 DOI: 10.1006/jmre.1997.1261] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Three bond proton-proton vicinal coupling constants are of potential value for analyzing sugar conformations in DNA. However, self-cancellation in antiphase cross peaks and modulation of peak splittings by transverse cross relaxation can alter the apparent coupling constants such that they do not accurately reflect the sugar conformations. Transverse cross relaxation is most effective between strongly coupled geminal proton pairs. Here we report the use of stereospecific deuteration at the H2" position in the A5 and A6 residues in the 12 base pair DNA sequence [d(CGCGAATTCGCG)2] as a means of investigating the effect of transverse cross relaxation on P.E.COSY type cross peaks. Deuteration of the H2" proton is expected to reduce the transverse cross relaxation rate by the square of ratio of the proton to deuteron gyromagnetic ratios, i.e., by a factor of 42. Additionally, a striking eight- to ninefold increase in the signal intensity was observed for cross peaks involving the remaining H2' proton resulting from diminished dipolar relaxation. Further improvements in signal-to-noise ratio were realized by collecting P.E.COSY spectra in strips, using an experiment referred to as stripe-COSY, employing selective excitation pulses which reduced the number of required t1 increments by a factor of four. A final improvement was achieved by employing selective time-shared homonuclear decoupling during the acquisition period, in an experiment referred to as superstripe-COSY, to collapse splittings due to passive couplings. Collectively, these approaches provide P.E. COSY-type spectra with two to three orders of magnitude increased sensitivity per unit time and that are relatively free from artifacts.
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Affiliation(s)
- J Yang
- Environmental Molecular Science Laboratory, Pacific Northwest National Laboratory, P7-55, Richland, Washington 99352, USA
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21
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Abstract
Microtubule assembly is known to be regulated by the phosphorylation of microtubule-associated proteins (MAPs), and is thus sensitive to phosphatase inhibitors. We have investigated the direct interaction between phosphatase inhibitors (vanadate, sodium fluoride, and okadaic acid) and microtubule proteins. Vanadate self-assembles into oligomers, primarily dimer, tetramer, and decamer in 0.1 M Pipes, pH 6.9. Oligomer concentrations and their direct binding to tubulin and MAPs were determined by 51V NMR. The assembly of microtubule protein (MTP) is strongly inhibited by decavanadate binding to MAPs and only weakly inhibited by tetravanadate binding to MAPs. Decavanadate will inhibit both MAP2 and tau-induced assembly. Decavanadate binds to MAP2 at 26 sites [Ka > or = (1.0-1.3) x 10(5) M-1]. The mechanism appears to involve competitive binding to MAPs, presumably at or near the microtubule binding domains, and reduced affinity for microtubules. The assembly of MAP-free, phosphocellulose-purified tubulin (PC-tubulin) is only weakly inhibited by decavanadate, although decavanadate binds to tubulin at four independent sites (Ka > or = 1.0 x 10(5) M-1). Monomeric vanadate, a strong phosphatase inhibitor, does not interact with tubulin or MAPs, and thus does not bind to the exchangeable nucleotide binding site on tubulin. Sodium fluoride stimulates both PC-tubulin and MTP assembly by a nonspecific effect, probably involving water structure formation. Wyman analysis suggests an absence of direct or specific binding to tubulin (d ln K/d ln [NaF] = 0.214). NaCl is nearly as effective in promoting assembly of PC-tubulin, but inhibits MTP assembly.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- S Lobert
- School of Nursing, University of Mississippi Medical Center, Jackson 39216
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22
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Abstract
Vanadate is known to cleave proteins in a near-uv-dependent manner. We have found that vanadate will cleave alpha- and beta-tubulin upon photoirradiation (419 nm emission maxima) under conditions when tetravanadate, pentavanadate, and decavanadate are in solution. The reaction is independent of GTPMg or GDPMg, and cleavage occurs at two or more sites per chain. Cleavage was studied at pH 6.0 (2(N-morpholino)ethanesulfonic acid (Mes) and phosphate), pH 6.9 (piperazine-N,N'-bis(2-ethanesulfonic acid) (Pipes)), pH 7.0 (phosphate), and pH 8.0 (N-(2-hydroxyethyl)piperazine-N'-bis(2-ethanesulfonic acid) (Hepes) and phosphate). The concentration of vanadate oligomer species, as determined by 51V NMR, was correlated with the extent of cutting. In organic buffers, low pH and high vanadate concentration favored oligomer formation, especially tetra and decavanadate. In phosphate buffer at pH 7 and 8, decamer is more prevalent, and at pH 6, phosphate buffer appears to favor a different oligomer form, V', appearing at -582 ppm. Cleavage is best correlated with the presence of cyclic tetravanadate at pH 6.9 in Pipes buffer and the V' species at pH 6.0 in phosphate buffer. Cleavage efficiency is also affected by interactions of photoactivated vanadate species with organic buffer components. In phosphate buffer no photochemical degradation of vanadate species occurs. Analysis using sodium dodecyl sulfate (SDS) gel electrophoresis and western blotting showed that vanadate produced cleavage patterns and nonenzymatic cleavage patterns resulting from boiling tubulin in SDS sample buffer (J. J. Correia, L. D. Lipscomb, and S. Lobert, 1993, Arch. Biochem. Biophys. 300, 105-114) are not the same. Attempts to identify the locations of the vanadate cleavage sites on the protein through N-terminal sequencing was unsuccessful, apparently due to the presence of blocked amino groups. We conclude that tetravandate cleaves tubulin upon photoirradiation, that organic buffers can interact with vanadate oligomers upon photoirradiation, and that in phosphate buffer photocleavage is enhanced by an absence of photochemical degradation and a preference for forming photoactive vanadate oligomers. These results have general application to photoirradiation studies of any protein in the presence of vanadate.
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Affiliation(s)
- J J Correia
- Department of Biochemistry, University of Mississippi Medical Center, Jackson 39216
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