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Dunlap KR, Laskin GR, Waddell DS, Black AJ, Steiner JL, Vied C, Gordon BS. Aerobic exercise-mediated changes in the expression of glucocorticoid responsive genes in skeletal muscle differ across the day. Mol Cell Endocrinol 2022; 550:111652. [PMID: 35461977 DOI: 10.1016/j.mce.2022.111652] [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] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/02/2022] [Revised: 03/30/2022] [Accepted: 04/18/2022] [Indexed: 10/18/2022]
Abstract
Glucocorticoids are released in response to acute aerobic exercise. The objective was to define changes in the expression of glucocorticoid target genes in skeletal muscle in response to acute aerobic exercise at different times of day. We identified glucocorticoid target genes altered in skeletal muscle by acute exercise by comparing data sets from rodents subjected to acute aerobic exercise in the light or dark cycles to data sets from C2C12 myotubes treated with glucocorticoids. The role of glucocorticoid receptor signaling and REDD1 protein in mediating gene expression was assessed in exercised mice. Changes to expression of glucocorticoid genes were greater when exercise occurred in the dark cycle. REDD1 was required for the induction of genes induced at both times of day. In all, the time of day at which aerobic exercise is conducted dictates changes to the expression of glucocorticoid target genes in skeletal muscle with REDD1 contributing to those changes.
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Affiliation(s)
- Kirsten R Dunlap
- Department of Nutrition and Integrative Physiology, Florida State University, 600 W. Cottage Avenue, Tallahassee, FL, 32306, USA
| | - Grant R Laskin
- Department of Nutrition and Integrative Physiology, Florida State University, 600 W. Cottage Avenue, Tallahassee, FL, 32306, USA
| | - David S Waddell
- Department of Biology, University of North Florida, 1 UNF Drive, Jacksonville, FL, 32224, USA
| | - Adam J Black
- Department of Cell Biology and Physiology, University of North Carolina, 111 Mason Farm Rd, Chapel Hill, NC, 27599, USA
| | - Jennifer L Steiner
- Department of Nutrition and Integrative Physiology, Florida State University, 600 W. Cottage Avenue, Tallahassee, FL, 32306, USA; Institute of Sports Sciences and Medicine, Florida State University, 600 W. Cottage Ave, Tallahassee, FL, 32306, USA
| | - Cynthia Vied
- Translational Sciences Laboratory, Florida State University College of Medicine, 1115 West Call Street, Tallahassee, FL, 32306, USA
| | - Bradley S Gordon
- Department of Nutrition and Integrative Physiology, Florida State University, 600 W. Cottage Avenue, Tallahassee, FL, 32306, USA; Institute of Sports Sciences and Medicine, Florida State University, 600 W. Cottage Ave, Tallahassee, FL, 32306, USA.
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2
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Hughes DC, Baehr LM, Waddell DS, Bodine SC. Overexpression of Multiple E3 Ubiquitin Ligases in Gastrocnemius Muscles from Mice. FASEB J 2022. [DOI: 10.1096/fasebj.2022.36.s1.r2147] [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]
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Hughes DC, Hardee JP, Waddell DS, Goodman CA. CORP: Gene delivery into murine skeletal muscle using in vivo electroporation. J Appl Physiol (1985) 2022; 133:41-59. [PMID: 35511722 DOI: 10.1152/japplphysiol.00088.2022] [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: 11/22/2022] Open
Abstract
The strategy of gene delivery into skeletal muscles has provided exciting avenues in identifying new potential therapeutics towards muscular disorders and addressing basic research questions in muscle physiology through overexpression and knockdown studies. In vivo electroporation methodology offers a simple, rapidly effective technique for the delivery of plasmid DNA into post-mitotic skeletal muscle fibers and the ability to easily explore the molecular mechanisms of skeletal muscle plasticity. The purpose of this review is to describe how to robustly electroporate plasmid DNA into different hindlimb muscles of rodent models. Further, key parameters (e.g., voltage, hyaluronidase, plasmid concentration) which contribute to the successful introduction of plasmid DNA into skeletal muscle fibers will be discussed. In addition, details on processing tissue for immunohistochemistry and fiber cross-sectional area (CSA) analysis will be outlined. The overall goal of this review is to provide the basic and necessary information needed for successful implementation of in vivo electroporation of plasmid DNA and thus open new avenues of discovery research in skeletal muscle physiology.
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Affiliation(s)
- David C Hughes
- Division of Endocrinology and Metabolism, Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, IA, United States
| | - Justin P Hardee
- Centre for Muscle Research (CMR), Department of Anatomy and Physiology, The University of Melbourne, Victoria, Australia
| | - David S Waddell
- Department of Biology, University of North Florida, Jacksonville, FL, United States
| | - Craig A Goodman
- Centre for Muscle Research (CMR), Department of Anatomy and Physiology, The University of Melbourne, Victoria, Australia
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Abstract
Skeletal muscle size is highly plastic and sensitive to a variety of stimuli. Muscle atrophy occurs as the result of changes in multiple signaling pathways that regulate both protein synthesis and degradation. The signaling pathways that are activated or inhibited depend on the specific stimuli that are altered. To view this SnapShot, open of download the PDF.
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Smith AL, Gjoka E, Izhar M, Novo KJ, Mason BC, De Las Casas A, Waddell DS. FGGY carbohydrate kinase domain containing is expressed and alternatively spliced in skeletal muscle and attenuates MAP kinase and Akt signaling. Gene 2021; 800:145836. [PMID: 34280510 DOI: 10.1016/j.gene.2021.145836] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2021] [Revised: 06/09/2021] [Accepted: 07/13/2021] [Indexed: 01/03/2023]
Abstract
Skeletal muscle atrophy can result from a range of physiological conditions, including denervation, immobilization, hindlimb unweighting, and aging. To better characterize the molecular genetic events of atrophy, a microarray analysis revealed that FGGY carbohydrate kinase domain containing (Fggy) is expressed in skeletal muscle and is induced in response to denervation. Bioinformatic analysis of the Fggy gene locus revealed two validated isoforms with alternative transcription initiation sites that we have designated Fggy-L-552 and Fggy-S-387. Additionally, we cloned two novel alternative splice variants, designated Fggy-L-482 and Fggy-S-344, from cultured muscle cells suggesting that at least four Fggy splice variants are expressed in skeletal muscle. Quantitative RT-PCR was performed using RNA isolated from muscle cells and primers designed to distinguish the four alternative Fggy transcripts and found that the Fggy-L transcripts are more highly expressed during myoblast differentiation, while the Fggy-S transcripts show relatively stable expression in proliferating myoblasts and differentiated myotubes. Confocal fluorescent microscopy revealed that the Fggy-L variants appear to localize evenly throughout the cytoplasm, while the Fggy-S variants produce a more punctuate cytoplasmic localization pattern in proliferating muscle cells. Finally, ectopic expression of Fggy-L-552 and Fggy-S-387 resulted in inhibition of muscle cell differentiation and attenuation of the MAP kinase and Akt signaling pathways. The identification and characterization of novel genes such as Fggy helps to improve our understanding of the molecular and cellular events that lead to atrophy and may eventually result in the identification of new therapeutic targets for the treatment of muscle wasting.
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Affiliation(s)
- Anastasia L Smith
- University of North Florida, Department of Biology, 1 UNF Drive, Jacksonville, FL 32224, USA
| | - Erisa Gjoka
- University of North Florida, Department of Biology, 1 UNF Drive, Jacksonville, FL 32224, USA
| | - Mahnoor Izhar
- University of North Florida, Department of Biology, 1 UNF Drive, Jacksonville, FL 32224, USA
| | - Karla J Novo
- University of North Florida, Department of Biology, 1 UNF Drive, Jacksonville, FL 32224, USA
| | - Brittany C Mason
- University of North Florida, Department of Biology, 1 UNF Drive, Jacksonville, FL 32224, USA
| | - Annabella De Las Casas
- University of North Florida, Department of Biology, 1 UNF Drive, Jacksonville, FL 32224, USA
| | - David S Waddell
- University of North Florida, Department of Biology, 1 UNF Drive, Jacksonville, FL 32224, USA.
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Baehr LM, Hughes DC, Lynch SA, Van Haver D, Maia TM, Marshall AG, Radoshevich L, Impens F, Waddell DS, Bodine SC. Identification of the MuRF1 Skeletal Muscle Ubiquitylome Through Quantitative Proteomics. Function (Oxf) 2021; 2:zqab029. [PMID: 34179788 PMCID: PMC8218097 DOI: 10.1093/function/zqab029] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Revised: 05/12/2021] [Accepted: 05/17/2021] [Indexed: 02/07/2023]
Abstract
MuRF1 (TRIM63) is a muscle-specific E3 ubiquitin ligase and component of the ubiquitin proteasome system. MuRF1 is transcriptionally upregulated under conditions that cause muscle loss, in both rodents and humans, and is a recognized marker of muscle atrophy. In this study, we used in vivo electroporation to determine whether MuRF1 overexpression alone can cause muscle atrophy and, in combination with ubiquitin proteomics, identify the endogenous MuRF1 substrates in skeletal muscle. Overexpression of MuRF1 in adult mice increases ubiquitination of myofibrillar and sarcoplasmic proteins, increases expression of genes associated with neuromuscular junction instability, and causes muscle atrophy. A total of 169 ubiquitination sites on 56 proteins were found to be regulated by MuRF1. MuRF1-mediated ubiquitination targeted both thick and thin filament contractile proteins, as well as, glycolytic enzymes, deubiquitinases, p62, and VCP. These data reveal a potential role for MuRF1 in not only the breakdown of the sarcomere but also the regulation of metabolism and other proteolytic pathways in skeletal muscle.
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Affiliation(s)
| | | | - Sarah A Lynch
- Department of Biology, University of North Florida, 1 UNF Drive, Jacksonville, FL 32224, USA
| | - Delphi Van Haver
- Department of Biomolecular Medicine, Ghent University, Ghent, Belgium,VIB Center for Medical Biotechnology, Ghent, Belgium,VIB Proteomics Core, Ghent, Belgium
| | - Teresa Mendes Maia
- Department of Biomolecular Medicine, Ghent University, Ghent, Belgium,VIB Center for Medical Biotechnology, Ghent, Belgium,VIB Proteomics Core, Ghent, Belgium
| | - Andrea G Marshall
- Department of Internal Medicine, Division of Endocrinology and Metabolism, Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA
| | - Lilliana Radoshevich
- Department of Microbiology and Immunology, Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA
| | - Francis Impens
- Department of Biomolecular Medicine, Ghent University, Ghent, Belgium,VIB Center for Medical Biotechnology, Ghent, Belgium,VIB Proteomics Core, Ghent, Belgium
| | - David S Waddell
- Department of Biology, University of North Florida, 1 UNF Drive, Jacksonville, FL 32224, USA
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Hughes DC, Baehr LM, Driscoll JR, Lynch SA, Waddell DS, Bodine SC. Identification and characterization of Fbxl22, a novel skeletal muscle atrophy-promoting E3 ubiquitin ligase. Am J Physiol Cell Physiol 2020; 319:C700-C719. [PMID: 32783651 DOI: 10.1152/ajpcell.00253.2020] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [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: 02/07/2023]
Abstract
Muscle-specific E3 ubiquitin ligases have been identified in muscle atrophy-inducing conditions. The purpose of the current study was to explore the functional role of F-box and leucine-rich protein 22 (Fbxl22), and a newly identified splice variant (Fbxl22-193), in skeletal muscle homeostasis and neurogenic muscle atrophy. In mouse C2C12 muscle cells, promoter fragments of the Fbxl22 gene were cloned and fused with the secreted alkaline phosphatase reporter gene to assess the transcriptional regulation of Fbxl22. The tibialis anterior muscles of male C57/BL6 mice (12-16 wk old) were electroporated with expression plasmids containing the cDNA of two Fbxl22 splice variants and tissues collected after 7, 14, and 28 days. Gastrocnemius muscles of wild-type and muscle-specific RING finger 1 knockout (MuRF1 KO) mice were electroporated with an Fbxl22 RNAi or empty plasmid and denervated 3 days posttransfection, and tissues were collected 7 days postdenervation. The full-length gene and novel splice variant are transcriptionally induced early (after 3 days) during neurogenic muscle atrophy. In vivo overexpression of Fbxl22 isoforms in mouse skeletal muscle leads to evidence of myopathy/atrophy, suggesting that both are involved in the process of neurogenic muscle atrophy. Knockdown of Fbxl22 in the muscles of MuRF1 KO mice resulted in significant additive muscle sparing 7 days after denervation. Targeting two E3 ubiquitin ligases appears to have a strong additive effect on protecting muscle mass loss with denervation, and these findings have important implications in the development of therapeutic strategies to treat muscle atrophy.
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Affiliation(s)
- David C Hughes
- Division of Endocrinology and Metabolism, Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, Iowa
| | - Leslie M Baehr
- Division of Endocrinology and Metabolism, Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, Iowa
| | - Julia R Driscoll
- Department of Biology, University of North Florida, Jacksonville, Florida
| | - Sarah A Lynch
- Department of Biology, University of North Florida, Jacksonville, Florida
| | - David S Waddell
- Department of Biology, University of North Florida, Jacksonville, Florida
| | - Sue C Bodine
- Division of Endocrinology and Metabolism, Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, Iowa
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Cooper LM, West RC, Hayes CS, Waddell DS. Dual-specificity phosphatase 29 is induced during neurogenic skeletal muscle atrophy and attenuates glucocorticoid receptor activity in muscle cell culture. Am J Physiol Cell Physiol 2020; 319:C441-C454. [PMID: 32639872 DOI: 10.1152/ajpcell.00200.2020] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Skeletal muscle atrophy is caused by a decrease in muscle size and strength and results from a range of physiological conditions, including denervation, immobilization, corticosteroid exposure and aging. Newly named dual-specificity phosphatase 29 (Dusp29) has been identified as a novel neurogenic atrophy-induced gene in skeletal muscle. Quantitative PCR analysis revealed that Dusp29 expression is significantly higher in differentiated myotubes compared with proliferating myoblasts. To determine how Dusp29 is transcriptionally regulated in skeletal muscle, fragments of the promoter region of Dusp29 were cloned, fused to a reporter gene, and found to be highly inducible in response to ectopic expression of the myogenic regulatory factors (MRF), MyoD and myogenin. Furthermore, site-directed mutagenesis of conserved E-box elements within the proximal promoter of Dusp29 rendered a Dusp29 reporter gene unresponsive to MRF overexpression. Dusp29, an atypical Dusp also known as Dupd1/Dusp27, was found to attenuate the ERK1/2 branch of the MAP kinase signaling pathway in muscle cells and inhibit muscle cell differentiation when ectopically expressed in proliferating myoblasts. Interestingly, Dusp29 was also found to destabilize AMPK protein while simultaneously enriching the phosphorylated pool of AMPK in muscle cells. Additionally, Dusp29 overexpression resulted in a significant increase in the glucocorticoid receptor (GR) protein and elevation in GR phosphorylation. Finally, Dusp29 was found to significantly impair the ability of the glucocorticoid receptor to function as a transcriptional activator in muscle cells treated with dexamethasone. Identifying and characterizing the function of Dusp29 in muscle provides novel insights into the molecular and cellular mechanisms for skeletal muscle atrophy.
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Affiliation(s)
- Lisa M Cooper
- Department of Biology, University of North Florida, Jacksonville, Florida
| | - Rita C West
- Department of Biology, University of North Florida, Jacksonville, Florida
| | - Caleb S Hayes
- Department of Biology, University of North Florida, Jacksonville, Florida
| | - David S Waddell
- Department of Biology, University of North Florida, Jacksonville, Florida
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9
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Cooper LM, Waddell DS. A tale of two DUSP27s: proposed resolution for the naming of distinct dual-specificity phosphatases. Am J Physiol Cell Physiol 2020; 319:C148-C150. [PMID: 32491926 DOI: 10.1152/ajpcell.00201.2020] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
- Lisa M Cooper
- Department of Biology, University of North Florida, Jacksonville, Florida
| | - David S Waddell
- Department of Biology, University of North Florida, Jacksonville, Florida
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Labuzan SA, Lynch SA, Cooper LM, Waddell DS. Inhibition of protein phosphatase methylesterase 1 dysregulates MAP kinase signaling and attenuates muscle cell differentiation. Gene 2020; 739:144515. [DOI: 10.1016/j.gene.2020.144515] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2020] [Revised: 02/24/2020] [Accepted: 02/25/2020] [Indexed: 02/07/2023]
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Cooper LM, Hanson A, Kavanagh JA, Waddell DS. Fam83d modulates MAP kinase and AKT signaling and is induced during neurogenic skeletal muscle atrophy. Cell Signal 2020; 70:109576. [PMID: 32092437 DOI: 10.1016/j.cellsig.2020.109576] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2019] [Revised: 02/20/2020] [Accepted: 02/20/2020] [Indexed: 01/08/2023]
Abstract
Skeletal muscle atrophy is a serious health condition that can arise due to aging, cancer, corticosteroid exposure, and denervation. Previous work comparing gene expression profiles in control and denervated muscle tissue revealed for the first time that Fam83d is expressed in skeletal muscle and is significantly induced in response to denervation. Quantitative PCR and Western blot analysis found that Fam83d is more highly expressed in proliferating myoblasts compared to differentiated myotubes. Characterization of the transcriptional regulation of Fam83d showed that ectopic expression of myogenic regulatory factors inhibits Fam83d reporter gene activity. To assess where Fam83d is localized in the cell, Fam83d was fused with green fluorescent protein, expressed in C2C12 cells, and found to localize in a punctate manner to the cytoplasm of muscle cells. To assess function, Fam83d was ectopically expressed in cultured muscle cells and markers of muscle cell differentiation, the MAP Kinase signaling pathway, and the AKT signaling pathway were analyzed. Fam83d overexpression resulted in significant repression of myosin heavy chain and myogenin expression, while phosphorylated ERK and AKT were also significantly repressed. Interestingly, inhibition of the 26S proteasome and the MAP kinase signaling pathway both resulted in stabilization of Fam83d during muscle cell differentiation. Finally, Fam83d has a putative phospholipase D-like domain that appears to be necessary for destabilizing casein kinase Iα and inhibiting ERK phosphorylation in cultured myoblasts. The discovery that Fam83d is expressed in skeletal muscle combined with the observation that Fam83d, a potential modulator of MAP kinase and AKT signaling, is induced in response to neurogenic atrophy helps further our understanding of the molecular and cellular events of skeletal muscle wasting.
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Affiliation(s)
- Lisa M Cooper
- University of North Florida, Department of Biology, 1 UNF Drive, Jacksonville, FL 32224, United States of America
| | - Abby Hanson
- University of North Florida, Department of Biology, 1 UNF Drive, Jacksonville, FL 32224, United States of America
| | - Jack A Kavanagh
- University of North Florida, Department of Biology, 1 UNF Drive, Jacksonville, FL 32224, United States of America
| | - David S Waddell
- University of North Florida, Department of Biology, 1 UNF Drive, Jacksonville, FL 32224, United States of America.
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Hayes CS, Labuzan SA, Menke JA, Haddock AN, Waddell DS. Ttc39c is upregulated during skeletal muscle atrophy and modulates ERK1/2 MAP kinase and hedgehog signaling. J Cell Physiol 2019; 234:23807-23824. [DOI: 10.1002/jcp.28950] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2019] [Revised: 05/15/2019] [Accepted: 05/20/2019] [Indexed: 12/19/2022]
Affiliation(s)
- Caleb S. Hayes
- Department of Biology University of North Florida Jacksonville Florida
| | - Sydney A. Labuzan
- Department of Biology University of North Florida Jacksonville Florida
| | - Jacob A. Menke
- Department of Biology University of North Florida Jacksonville Florida
| | - Ashley N. Haddock
- Department of Biology University of North Florida Jacksonville Florida
| | - David S. Waddell
- Department of Biology University of North Florida Jacksonville Florida
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Hughes DC, Baehr LM, Driscoll J, Waddell DS, Bodine SC. Overexpression of a Novel E3 Ligase leads to a Skeletal Muscle Myopathy through Alterations in Cytoskeleton Proteins and Enhanced Protein Degradation. FASEB J 2019. [DOI: 10.1096/fasebj.2019.33.1_supplement.700.2] [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)
- David C. Hughes
- Department of Internal MedicineUniversity of IowaIowa CityIA
| | - Leslie M. Baehr
- Department of Internal MedicineUniversity of IowaIowa CityIA
| | - Julia Driscoll
- Department of BiologyUniversity of North FloridaJacksonvilleFL
| | | | - Sue C Bodine
- Department of Internal MedicineUniversity of IowaIowa CityIA
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Haddock AN, Labuzan SA, Haynes AE, Hayes CS, Kakareka KM, Waddell DS. Dual-specificity phosphatase 4 is upregulated during skeletal muscle atrophy and modulates extracellular signal-regulated kinase activity. Am J Physiol Cell Physiol 2019; 316:C567-C581. [DOI: 10.1152/ajpcell.00234.2018] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Skeletal muscle atrophy results from disparate physiological conditions, including denervation, corticosteroid treatment, and aging. The purpose of this study was to describe and characterize the function of dual-specificity phosphatase 4 (Dusp4) in skeletal muscle after it was found to be induced in response to neurogenic atrophy. Quantitative PCR and Western blot analysis revealed that Dusp4 is expressed during myoblast proliferation but rapidly disappears as muscle cells differentiate. The Dusp4 regulatory region was cloned and found to contain a conserved E-box element that negatively regulates Dusp4 reporter gene activity in response to myogenic regulatory factor expression. In addition, the proximal 3′-untranslated region of Dusp4 acts in an inhibitory manner to repress reporter gene activity as muscle cells progress through the differentiation process. To determine potential function, Dusp4 was fused with green fluorescent protein, expressed in C2C12 cells, and found to localize to the nucleus of proliferating myoblasts. Furthermore, Dusp4 overexpression delayed C2C12 muscle cell differentiation and resulted in repression of a MAP kinase signaling pathway reporter gene. Ectopic expression of a Dusp4 dominant negative mutant blocked muscle cell differentiation and attenuated MAP kinase signaling by preferentially targeting the ERK1/2 branch, but not the p38 branch, of the MAP kinase signaling cascade in skeletal muscle cells. The findings presented in this study provide the first description of Dusp4 in skeletal muscle and suggest that Dusp4 may play an important role in the regulation of muscle cell differentiation by regulating MAP kinase signaling.
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Affiliation(s)
- Ashley N. Haddock
- Department of Biology, University of North Florida, Jacksonville, Florida
| | - Sydney A. Labuzan
- Department of Biology, University of North Florida, Jacksonville, Florida
| | - Amy E. Haynes
- Department of Biology, University of North Florida, Jacksonville, Florida
| | - Caleb S. Hayes
- Department of Biology, University of North Florida, Jacksonville, Florida
| | - Karina M. Kakareka
- Department of Biology, University of North Florida, Jacksonville, Florida
| | - David S. Waddell
- Department of Biology, University of North Florida, Jacksonville, Florida
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Furlow JD, Watson ML, Waddell DS, Neff ES, Baehr LM, Ross AP, Bodine SC. Altered gene expression patterns in muscle ring finger 1 null mice during denervation- and dexamethasone-induced muscle atrophy. Physiol Genomics 2013; 45:1168-85. [PMID: 24130153 DOI: 10.1152/physiolgenomics.00022.2013] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Muscle atrophy can result from inactivity or unloading on one hand or the induction of a catabolic state on the other. Muscle-specific ring finger 1 (MuRF1), a member of the tripartite motif family of E3 ubiquitin ligases, is an essential mediator of multiple conditions inducing muscle atrophy. While most studies have focused on the role of MuRF1 in protein degradation, the protein may have other roles in regulating skeletal muscle mass and metabolism. We therefore systematically evaluated the effect of MuRF1 on gene expression during denervation and dexamethasone-induced atrophy. We find that the lack of MuRF1 leads to few differences in control animals, but there were several significant differences in specific sets of genes upon denervation- and dexamethasone-induced atrophy. For example, during denervation, MuRF1 knockout mice showed delayed repression of metabolic and structural genes and blunted induction of genes associated with the neuromuscular junction. In the latter case, this pattern correlates with blunted HDAC4 and myogenin upregulation. Lack of MuRF1 caused fewer changes in the dexamethasone-induced atrophy program, but certain genes involved in fat metabolism and intracellular signaling were affected. Our results demonstrate a new role for MuRF1 in influencing gene expression in two important models of muscle atrophy.
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Affiliation(s)
- J David Furlow
- Department of Neurobiology, Physiology, and Behavior, University of California, Davis, California; and
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Waddell DS, Baehr LM, van den Brandt J, Johnsen SA, Reichardt HM, Furlow JD, Bodine SC. The glucocorticoid receptor and FOXO1 synergistically activate the skeletal muscle atrophy-associated MuRF1 gene. Am J Physiol Endocrinol Metab 2008; 295:E785-97. [PMID: 18612045 PMCID: PMC2652500 DOI: 10.1152/ajpendo.00646.2007] [Citation(s) in RCA: 253] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The muscle specific ubiquitin E3 ligase MuRF1 has been implicated as a key regulator of muscle atrophy under a variety of conditions, such as during synthetic glucocorticoid treatment. FOXO class transcription factors have been proposed as important regulators of MuRF1 expression, but its regulation by glucocorticoids is not well understood. The MuRF1 promoter contains a near-perfect palindromic glucocorticoid response element (GRE) 200 base pairs upstream of the transcription start site. The GRE is highly conserved in the mouse, rat, and human genes along with a directly adjacent FOXO binding element (FBE). Transient transfection assays in HepG2 cells and C(2)C(12) myotubes demonstrate that the MuRF1 promoter is responsive to both the dexamethasone (DEX)-activated glucocorticoid receptor (GR) and FOXO1, whereas coexpression of GR and FOXO1 leads to a dramatic synergistic increase in reporter gene activity. Mutation of either the GRE or the FBE significantly impairs activation of the MuRF1 promoter. Consistent with these findings, DEX-induced upregulation of MuRF1 is significantly attenuated in mice expressing a homodimerization-deficient GR despite no effect on the degree of muscle loss in these mice vs. their wild-type counterparts. Finally, chromatin immunoprecipitation analysis reveals that both GR and FOXO1 bind to the endogenous MuRF1 promoter in C(2)C(12) myotubes, and IGF-I inhibition of DEX-induced MuRF1 expression correlates with the loss of FOXO1 binding. These findings present new insights into the role of the GR and FOXO family of transcription factors in the transcriptional regulation of the MuRF1 gene, a direct target of the GR in skeletal muscle.
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Affiliation(s)
- David S Waddell
- Department of Neurobiology, Physiology, and Behavior, University of California, Davis, California 95616, USA
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17
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Guo X, Waddell DS, Wang W, Wang Z, Liberati NT, Yong S, Liu X, Wang XF. Ligand-dependent ubiquitination of Smad3 is regulated by casein kinase 1 gamma 2, an inhibitor of TGF-beta signaling. Oncogene 2008; 27:7235-47. [PMID: 18794808 DOI: 10.1038/onc.2008.337] [Citation(s) in RCA: 28] [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] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Transforming growth factor-beta (TGF-beta) elicits a variety of cellular activities primarily through a signaling cascade mediated by two key transcription factors, Smad2 and Smad3. Numerous regulatory mechanisms exist to control the activity of Smad3, thereby modulating the strength and specificity of TGF-beta responses. In search for potential regulators of Smad3 through a yeast two-hybrid screen, we identified casein kinase 1 gamma 2 (CKIgamma2) as a novel Smad3-interacting protein. In mammalian cells, CKIgamma2 selectively and constitutively binds Smad3 but not Smad1, -2 or -4. Functionally, CKIgamma2 inhibits Smad3-mediated TGF-beta responses including induction of target genes and cell growth arrest, and this inhibition is dependent on CKIgamma2 kinase activity. Mechanistically, CKIgamma2 does not affect the basal levels of Smad proteins or activity of the receptors. Rather, CKIgamma2 preferentially promotes the ubiquitination and degradation of activated Smad3 through direct phosphorylation of its MH2 domain at Ser418. Importantly, mutation of Ser418 to alanine or aspartic acid causes an increase or decrease of Smad3 activity, respectively, in the presence of TGF-beta. CKIgamma2 is the first kinase known to mark activated Smad3 for destruction. Given its negative function in TGF-beta signaling and its reported overexpression in human cancers, CKIgamma2 may act as an oncoprotein during tumorigenesis.
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Affiliation(s)
- X Guo
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC, 27710, USA
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18
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Cohen TJ, Waddell DS, Barrientos T, Lu Z, Feng G, Cox GA, Bodine SC, Yao TP. The histone deacetylase HDAC4 connects neural activity to muscle transcriptional reprogramming. J Biol Chem 2007; 282:33752-33759. [PMID: 17873280 DOI: 10.1074/jbc.m706268200] [Citation(s) in RCA: 138] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Neural activity actively regulates muscle gene expression. This regulation is crucial for specifying muscle functionality and synaptic protein expression. How neural activity is relayed into nuclei and connected to the muscle transcriptional machinery, however, is not known. Here we identify the histone deacetylase HDAC4 as the critical linker connecting neural activity to muscle transcription. We found that HDAC4 is normally concentrated at the neuromuscular junction (NMJ), where nerve innervates muscle. Remarkably, reduced neural input by surgical denervation or neuromuscular diseases dissociates HDAC4 from the NMJ and dramatically induces its expression, leading to robust HDAC4 nuclear accumulation. We present evidence that nuclear accumulated HDAC4 is responsible for the coordinated induction of synaptic genes upon denervation. Inactivation of HDAC4 prevents denervation-induced synaptic acetyl-choline receptor (nAChR) and MUSK transcription whereas forced expression of HDAC4 mimics denervation and activates ectopic nAChR transcription throughout myofibers. We determined that HDAC4 executes activity-dependent transcription by regulating the Dach2-myogenin transcriptional cascade where inhibition of the repressor Dach2 by HDAC4 permits the induction of the transcription factor myogenin, which in turn activates synaptic gene expression. Our findings establish HDAC4 as a neural activity-regulated deacetylase and a key signaling component that relays neural activity to the muscle transcriptional machinery.
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Affiliation(s)
- Todd J Cohen
- Department of Pharmacology and Cancer Biology, Duke University, Durham, North Carolina, 27710
| | - David S Waddell
- Section of Neurobiology, Physiology & Behavior, University of California, Davis, California 95616
| | - Tomasa Barrientos
- Department of Pharmacology and Cancer Biology, Duke University, Durham, North Carolina, 27710
| | - Zhonghua Lu
- Department of Neurobiology, Duke University, Durham, North Carolina 27710
| | - Guoping Feng
- Department of Neurobiology, Duke University, Durham, North Carolina 27710
| | | | - Sue C Bodine
- Section of Neurobiology, Physiology & Behavior, University of California, Davis, California 95616
| | - Tso-Pang Yao
- Department of Pharmacology and Cancer Biology, Duke University, Durham, North Carolina, 27710.
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19
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Baehr LM, Waddell DS, Yang HY, Furlow JD, Bodine SC. Upregulation of FOXO1 and FOXO3a Following Denervation and Dexamethasone Treatment. FASEB J 2007. [DOI: 10.1096/fasebj.21.6.a1308-b] [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)
| | - David S Waddell
- NeurobiologyPhysiology, & BehaviorUC Davis, One Shields AveDavisCA95616
| | - Ha Yung Yang
- NeurobiologyPhysiology, & BehaviorUC Davis, One Shields AveDavisCA95616
| | - J David Furlow
- NeurobiologyPhysiology, & BehaviorUC Davis, One Shields AveDavisCA95616
| | - Sue C Bodine
- NeurobiologyPhysiology, & BehaviorUC Davis, One Shields AveDavisCA95616
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20
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Weidner WJ, Waddell DS, Furlow JD. Measurement of the filtration coefficient (Kfc) in the lung of Gallus domesticus and the effects of increased microvascular permeability. J Comp Physiol B 2006; 176:567-74. [PMID: 16538461 DOI: 10.1007/s00360-006-0079-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [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] [Received: 09/22/2005] [Revised: 01/13/2006] [Accepted: 03/01/2006] [Indexed: 10/24/2022]
Abstract
The filtration coefficient (Kfc) is a sensitive measure of microvascular hydraulic conductivity and has been reported for the alveolar lungs of many mammalian species, but not for the parabronchial avian lung. This study reports the Kfc in the isolated lungs of normal chickens and in the lungs of chickens given the edemogenic agents oleic acid (OA) or dimethyl amiloride (DMA). The control Kfc =0.04+/-0.01 ml min(-1) kPa(-1) g(-1). This parameter increased significantly following the administration of both OA (0.12+/-0.02 ml min(-1) kPa(-1) g(-1)) and DMA (0.07+/-0.01 ml min kPa(-1) g(-1)). As endothelial cadherins are thought to play a role in the dynamic response to acute lung injury, we utilized Western blot analysis to assess lung cadherin content and Northern blot analysis to assess pulmonary vascular endothelial (VE) cadherin expression following drug administration. Lung cadherin content decreases markedly following DMA, but not OA administration. VE cadherin expression increases as a result of DMA treatment, but is unchanged following OA. Our results suggest that the permeability characteristics of the avian lung are more closely consistent with those of the mammalian rather than the reptilian lung, and, that cadherins may play a significant role in the response to acute increases in avian pulmonary microvascular permeability.
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Affiliation(s)
- W Jeffrey Weidner
- Section of Neurobiology, Physiology, and Behavior, College of Biological Sciences, University of California, Davis, CA 95616, USA.
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21
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Waddell DS, Furlow JD, Bodine SC. The MuRF1 Promoter is Synergistically Activated by the Glucocorticoid Receptor and the Forkhead Family Member, FoxO1. FASEB J 2006. [DOI: 10.1096/fasebj.20.4.a391-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)
- David S Waddell
- NeurobiologyPhysiology & BehaviorUC Davis, One Shields Ave.DavisCA95616
| | - J. David Furlow
- NeurobiologyPhysiology & BehaviorUC Davis, One Shields Ave.DavisCA95616
| | - Sue C Bodine
- NeurobiologyPhysiology & BehaviorUC Davis, One Shields Ave.DavisCA95616
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22
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Waddell DS, Liberati NT, Guo X, Frederick JP, Wang XF. Casein kinase Iepsilon plays a functional role in the transforming growth factor-beta signaling pathway. J Biol Chem 2004; 279:29236-46. [PMID: 15133026 DOI: 10.1074/jbc.m400880200] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The transforming growth factor-beta (TGF-beta) signaling pathway is known to be involved in a wide range of biological events, including development, cellular differentiation, apoptosis, and oncogenesis. The TGF-beta signal is mediated by ligand binding to the type II receptor, leading to the recruitment and activation of the type I receptor, and subsequent activation of a family of intracellular signal transducing proteins called Smads. Here we report a regulatory role for casein kinase Iepsilon (CKIepsilon) in the TGF-beta signaling cascade. We find that CKIepsilon binds to all Smads and the cytoplasmic domains of the type I and type II receptors both in vitro and in vivo. The interaction of CKIepsilon with the type I and type II receptors is independent of TGF-beta stimulation, whereas the CKIepsilon/Smad interaction is transiently disrupted by ligand treatment. Additionally, CKIepsilon is able to phosphorylate the receptor-activated Smads (Smads 1-3 and 5) and the type II receptor in vitro. Transcriptional reporter assays reveal that transient overexpression of wild type CKIepsilon dramatically reduces basal reporter activity but enhances TGF-beta-stimulated transcription. Furthermore, overexpression of a kinase-dead mutant of CKIepsilon inhibits both basal and ligand-induced transcription, whereas inhibition of endogenous CKI catalytic activity with IC261 blocks only TGF-beta-stimulated reporter activity. Finally, knocking down CKIepsilon protein levels results in a significant increase in basal and TGF-beta-induced transcription. These results suggest that CKIepsilon plays a ligand-dependent, differential, and dual regulatory role within the TGF-beta signaling pathway.
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Affiliation(s)
- David S Waddell
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, North Carolina 27710, USA
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23
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Frederick JP, Liberati NT, Waddell DS, Shi Y, Wang XF. Transforming growth factor beta-mediated transcriptional repression of c-myc is dependent on direct binding of Smad3 to a novel repressive Smad binding element. Mol Cell Biol 2004; 24:2546-59. [PMID: 14993291 PMCID: PMC355825 DOI: 10.1128/mcb.24.6.2546-2559.2004] [Citation(s) in RCA: 177] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2003] [Revised: 05/20/2003] [Accepted: 12/19/2003] [Indexed: 12/15/2022] Open
Abstract
Smad proteins are the most well-characterized intracellular effectors of the transforming growth factor beta (TGF-beta) signal. The ability of the Smads to act as transcriptional activators via TGF-beta-induced recruitment to Smad binding elements (SBE) within the promoters of TGF-beta target genes has been firmly established. However, the elucidation of the molecular mechanisms involved in TGF-beta-mediated transcriptional repression are only recently being uncovered. The proto-oncogene c-myc is repressed by TGF-beta, and this repression is required for the manifestation of the TGF-beta cytostatic program in specific cell types. We have shown that Smad3 is required for both TGF-beta-induced repression of c-myc and subsequent growth arrest in keratinocytes. The transcriptional repression of c-myc is dependent on direct Smad3 binding to a novel Smad binding site, termed a repressive Smad binding element (RSBE), within the TGF-beta inhibitory element (TIE) of the c-myc promoter. The c-myc TIE is a composite element, comprised of an overlapping RSBE and a consensus E2F site, that is capable of binding at least Smad3, Smad4, E2F-4, and p107. The RSBE is distinct from the previously defined SBE and may partially dictate, in conjunction with the promoter context of the overlapping E2F site, whether the Smad3-containing complex actively represses, as opposed to transactivates, the c-myc promoter.
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Affiliation(s)
- Joshua P Frederick
- Department of Pharmacology and Cancer Biology, Duke University, Durham, North Carolina 27710, USA
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24
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Curtis JM, Dennis D, Waddell DS, MacGillivray T, Ewart HS. Determination of angiotensin-converting enzyme inhibitory peptide Leu-Lys-Pro-Asn-Met (LKPNM) in bonito muscle hydrolysates by LC-MS/MS. J Agric Food Chem 2002; 50:3919-3925. [PMID: 12083859 DOI: 10.1021/jf011684c] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Proteolytic digestion of dried bonito muscle with thermolysin produces a hydrolysate with strong angiotensin-converting enzyme (ACE) inhibitory activity and is the basis of a dietary supplement with antihypertensive activity. A major portion of the ACE activity was shown previously to arise from the peptide Leu-Lys-Pro-Asn-Met (LKPNM). A straightforward method to quantify this peptide was developed using one-step C18 solid-phase extraction (SPE) followed by LC-MS/MS quantification. The SPE step resulted in a hydrolysate that was still crude, as illustrated by combined size-exclusion chromatography/multi-angle laser light scattering detection that showed that a major fraction of oligopeptides were in the 2-20 kDa range. This fraction has a weight-average molecular weight (M(w)) of approximately 5.0 kDa. Method validation for specificity, linearity, accuracy, precision, and reproducibility showed that standard additions of synthetic LKPNM to bonito extract with SPE enrichment followed by LC-MS/MS is a suitably robust procedure for the determination of LKPNM content. The method was also successful for encapsulated powders in which the excipients used are insoluble in water and could be removed by centrifugation.
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Affiliation(s)
- Jonathan M Curtis
- Ocean Nutrition Canada Ltd., 1721 Lower Water Street, Halifax, Nova Scotia, Canada, B3J 1S5.
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25
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Taylor KZ, Waddell DS, Reiner EJ, MacPherson KA. Direct Elution of Solid Phase Extraction Disks for the Determination of Polychlorinated Dibenzo-p-dioxins and Polychlorinated Dibenzofurans in Effluent Samples. Anal Chem 2002. [DOI: 10.1021/ac00103a008] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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26
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Seto C, Grossert JS, Waddell DS, Curtis JM, Boyd RK. Effects of ionization mode on charge-site-remote and related fragmentation reactions of long-chain quaternary ammonium ions. J Am Soc Mass Spectrom 2001; 12:571-579. [PMID: 11349955 DOI: 10.1016/s1044-0305(01)00220-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Comparison of collisionally activated fragment spectra of long-chain quaternary ammonium ions, formed by liquid-assisted secondary ion mass spectrometry (LSIMS) and electrospray ionization (ESI), shows the latter are dominated by radical cations while the former yield mainly even-electron charge-site-remote (CSR) fragments, similar to the report for different precursors by Cheng et al., J. Am. Soc. Mass Spectrom. 1998, 9, 840. Here, mixed-site fragmentation products (formal loss of a radical directly bonded to the nitrogen plus a radical derived from the long chain) are of comparable importance for both ionization techniques. These observations are difficult to understand if the CSR ions are formed by a concerted rearrangement-elimination reaction, since precollision internal energies of the ESI ions are much lower than those of the ions from LSIMS. Alternatively, if one discards the concerted mechanism for high-energy CA, and assumes that the even-electron fragments are predominantly formed via homolytic bond cleavage, the colder radical cations from ESI survive to the detector while the more energized counterparts from LSIMS preferentially lose a hydrogen atom to yield the CSR ions, as proposed by Wysocki and Ross (Int. J. Mass Spectrom. Ion Processes 1991, 104, 179). The present work also attempts to reconcile discrepancies involving critical energies and known structures for neutral fragments.
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Affiliation(s)
- C Seto
- Department of Chemistry, Dalhousie University, Halifax, Nova Scotia, Canada
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27
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Abstract
The effect of cadmium chloride on the immunoprecipitation of cadherin and the associated adherens junctional proteins, alpha- and beta-catenin, was examined in isolated bullfrog (Rana catesbeiana) corneas utilizing Western blot and enhanced chemoluminescent techniques. Application of either 1.0 microM or 75.0 microM CdCl2 to the corneal endothelium for 2 h markedly decreased the immunoprecipitation of cadherins as compared to paired control corneas. Immunoprecipitation of alpha-catenin was increased in response to both doses of CdCl2, while the immunoprecipitation of beta-catenin was little changed by either cadmium dose. There is accumulating evidence that cadmium may increase epithelial paracellular permeability by interfering with cadherin complex activity at intercellular junctions. The present study suggests that inorganic cadmium in low micromolar concentrations may decrease the integrity of the corneal endothelium, at least in part through a similar mechanism involving disruption of junctional cadherin complex function.
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Affiliation(s)
- W J Weidner
- Division of Biological Sciences, University of California, Davis 95616, USA.
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28
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Denekamp C, Voinov VG, Claeys M, Seto C, Grossert JS, Waddell DS, Curtis JM, Boyd RK. Charge-remote fragmentation characteristics of functionalized alkanes in high-energy collision-induced dissociation. Rapid Commun Mass Spectrom 2000; 14:1035-1043. [PMID: 10861984 DOI: 10.1002/1097-0231(20000630)14:12<1035::aid-rcm986>3.0.co;2-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
In this study we report on high-energy, collision-induced dissociation processes leading to charge-remote fragmentations, using three alkyl cations, namely n-hexadecylpyridinium, n-hexadecyltriphenylphosphonium and n-hexadecyltriethylammonium, each with and without (2)H(2)-labelling at the C(9) position of the hexadecyl chain. The characteristic patterns corresponding to the formal elimination of alkane elements were observed, and the (2)H(2)-labelling at C(9) clearly affected only one charge-remote fragment ion of the homologous series. However, in addition to the expected fragment ion containing only one deuterium atom, a significant ion retaining two deuterium atoms was observed. MS/MS/MS experiments demonstrated clearly that the latter ion showed partial deuteration around the charge site, the level of deuteration depending on the structure of the original precursor cation. These results can be interpreted in terms of two novel, distinct mechanisms, one of which involves an excited state in an aromatic ring. Mixed-site fragmentation (MSF) ions were also observed from the phosphonium and ammonium ion precursors. We believe that the observation of the MSF process occurring at an sp(2)-hybridized center in the phosphonium series has not been reported previously. It thus becomes apparent that high-energy collisions leading to charge-remote reactions in fact lead to a broad range of pathways. Copyright 2000 John Wiley & Sons, Ltd.
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Affiliation(s)
- C Denekamp
- Department of Pharmaceutical Sciences, University of Antwerp (UIA), Universiteitsplein 1, B-2610 Antwerp, Belgium
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29
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Cefalu CA, Waddell DS. Viscosupplementation: treatment alternative for osteoarthritis of the knee. Geriatrics (Basel) 1999; 54:51-4, 57. [PMID: 10542861] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/14/2023] Open
Affiliation(s)
- C A Cefalu
- Department of Family Medicine, Louisiana State University School of Medicine, Shreveport
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30
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Kim AE, Dintaman JM, Waddell DS, Silverman JA. Saquinavir, an HIV protease inhibitor, is transported by P-glycoprotein. J Pharmacol Exp Ther 1998; 286:1439-45. [PMID: 9732409] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Saquinavir, a peptidomimetic HIV protease inhibitor, has been shown to be effective in reducing patient viral load and reducing mortality. In this report we investigated whether saquinavir is a substrate for the multidrug resistance transporter P-glycoprotein (P-gp), which may reduce the effective intracellular concentration of the drug. G185 cells, which highly express P-gp, are resistant to saquinavir-mediated cytotoxicity, and co-administration of cyclosporine reversed this resistance. Saquinavir and saquinavir mesylate inhibited basolateral to apical transport of the fluorescent dye rhodamine 123 in a polarized epithelial transport assay, a result that suggests competition of these drugs for the P-gp transporter. Finally, we measured specific, directional transport of saquinavir and saquinavir mesylate in an epithelial monolayer model. Transport in the basolateral to apical direction was 3-fold greater than apical to basolateral flux for both saquinavir and saquinavir mesylate and was blocked by co-incubation with the established P-gp reversal agents cyclosporine and verapamil. These data provide evidence that saquinavir is a substrate for the P-gp transporter and suggest that this protein may affect intracellular accumulation of the drug and contribute to its poor oral bioavailability.
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Affiliation(s)
- A E Kim
- Drug Transport Division, AvMax, Inc., Berkeley, California, USA
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31
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Waddell DS, McKinnon HS, Chittim BG, Safe S, Boyd RK. Gas chromatographic/mass spectrometric characteristics of purified synthetic isomers of tetrachlorodibenzofuran. ACTA ACUST UNITED AC 1987. [DOI: 10.1002/bms.1200140813] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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