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Tian J, Ji M, Liu J, Xia Y, Zhang K, Li H, Gong W, Li Z, Xie W, Wang G, Xie J, Yu E. N-glycosylomic analysis provides new insight into the molecular mechanism of firmness of fish fillet. Food Chem 2023; 424:136417. [PMID: 37244189 DOI: 10.1016/j.foodchem.2023.136417] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2023] [Revised: 05/10/2023] [Accepted: 05/17/2023] [Indexed: 05/29/2023]
Abstract
Post-translational protein modification affects muscle physiochemistry. To understand the roles of N-glycosylation in this process, the muscle N-glycoproteomes of crisp grass carp (CGC) and ordinary grass carp (GC) were analyzed and compared. We identified 325 N-glycosylated sites with the NxT motif, classified 177 proteins, and identified 10 upregulated and 19 downregulated differentially glycosylated proteins (DGPs). Gene Ontology and Kyoto Encyclopedia of Genes and Genomes annotations revealed that these DGPs participate in myogenesis, extracellular matrix content formation, and muscle function. The DGPs partially accounted for the molecular mechanisms associated with the relatively smaller fiber diameter and higher collagen content observed in CGC. Though the DGPs diverged from the identified differentially phosphorylated proteins and differentially expressed proteins detected in previous study, they all shared similar metabolic and signaling pathways. Thus, they might independently alter fish muscle texture. Overall, the present study provides novel insights into the mechanisms underlying fillet quality.
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Affiliation(s)
- Jingjing Tian
- Key Laboratory of Aquatic Animal Immune Technology of Guangdong Province, Key Laboratory of Tropical & Subtropical Fishery Resource Application & Cultivation, Pearl River Fisheries Research Institute, Chinese Academy of Fishery Sciences, Guangzhou 510380, China
| | - Mengmeng Ji
- Key Laboratory of Aquatic Animal Immune Technology of Guangdong Province, Key Laboratory of Tropical & Subtropical Fishery Resource Application & Cultivation, Pearl River Fisheries Research Institute, Chinese Academy of Fishery Sciences, Guangzhou 510380, China
| | - Jie Liu
- BGI Genomics, BGI-Shenzhen, Shenzhen, China
| | - Yun Xia
- Key Laboratory of Aquatic Animal Immune Technology of Guangdong Province, Key Laboratory of Tropical & Subtropical Fishery Resource Application & Cultivation, Pearl River Fisheries Research Institute, Chinese Academy of Fishery Sciences, Guangzhou 510380, China
| | - Kai Zhang
- Key Laboratory of Aquatic Animal Immune Technology of Guangdong Province, Key Laboratory of Tropical & Subtropical Fishery Resource Application & Cultivation, Pearl River Fisheries Research Institute, Chinese Academy of Fishery Sciences, Guangzhou 510380, China
| | - Hongyan Li
- Key Laboratory of Aquatic Animal Immune Technology of Guangdong Province, Key Laboratory of Tropical & Subtropical Fishery Resource Application & Cultivation, Pearl River Fisheries Research Institute, Chinese Academy of Fishery Sciences, Guangzhou 510380, China
| | - Wangbao Gong
- Key Laboratory of Aquatic Animal Immune Technology of Guangdong Province, Key Laboratory of Tropical & Subtropical Fishery Resource Application & Cultivation, Pearl River Fisheries Research Institute, Chinese Academy of Fishery Sciences, Guangzhou 510380, China
| | - Zhifei Li
- Key Laboratory of Aquatic Animal Immune Technology of Guangdong Province, Key Laboratory of Tropical & Subtropical Fishery Resource Application & Cultivation, Pearl River Fisheries Research Institute, Chinese Academy of Fishery Sciences, Guangzhou 510380, China
| | - Wenping Xie
- Key Laboratory of Aquatic Animal Immune Technology of Guangdong Province, Key Laboratory of Tropical & Subtropical Fishery Resource Application & Cultivation, Pearl River Fisheries Research Institute, Chinese Academy of Fishery Sciences, Guangzhou 510380, China
| | - Guangjun Wang
- Key Laboratory of Aquatic Animal Immune Technology of Guangdong Province, Key Laboratory of Tropical & Subtropical Fishery Resource Application & Cultivation, Pearl River Fisheries Research Institute, Chinese Academy of Fishery Sciences, Guangzhou 510380, China
| | - Jun Xie
- Key Laboratory of Aquatic Animal Immune Technology of Guangdong Province, Key Laboratory of Tropical & Subtropical Fishery Resource Application & Cultivation, Pearl River Fisheries Research Institute, Chinese Academy of Fishery Sciences, Guangzhou 510380, China.
| | - Ermeng Yu
- Key Laboratory of Aquatic Animal Immune Technology of Guangdong Province, Key Laboratory of Tropical & Subtropical Fishery Resource Application & Cultivation, Pearl River Fisheries Research Institute, Chinese Academy of Fishery Sciences, Guangzhou 510380, China.
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2
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Noureddine M, Gehmlich K. Structural and signaling proteins in the Z-disk and their role in cardiomyopathies. Front Physiol 2023; 14:1143858. [PMID: 36935760 PMCID: PMC10017460 DOI: 10.3389/fphys.2023.1143858] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2023] [Accepted: 02/21/2023] [Indexed: 03/06/2023] Open
Abstract
The sarcomere is the smallest functional unit of muscle contraction. It is delineated by a protein-rich structure known as the Z-disk, alternating with M-bands. The Z-disk anchors the actin-rich thin filaments and plays a crucial role in maintaining the mechanical stability of the cardiac muscle. A multitude of proteins interact with each other at the Z-disk and they regulate the mechanical properties of the thin filaments. Over the past 2 decades, the role of the Z-disk in cardiac muscle contraction has been assessed widely, however, the impact of genetic variants in Z-disk proteins has still not been fully elucidated. This review discusses the various Z-disk proteins (alpha-actinin, filamin C, titin, muscle LIM protein, telethonin, myopalladin, nebulette, and nexilin) and Z-disk-associated proteins (desmin, and obscurin) and their role in cardiac structural stability and intracellular signaling. This review further explores how genetic variants of Z-disk proteins are linked to inherited cardiac conditions termed cardiomyopathies.
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Affiliation(s)
- Maya Noureddine
- Institute of Cardiovascular Sciences, College of Medical and Dental Sciences, University of Birmingham, Birmingham, United Kingdom
| | - Katja Gehmlich
- Institute of Cardiovascular Sciences, College of Medical and Dental Sciences, University of Birmingham, Birmingham, United Kingdom
- Cardiovascular Medicine, Radcliffe Department of Medicine and British Heart Foundation Centre of Research Excellence Oxford, University of Oxford, Oxford, United Kingdom
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3
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Szikora S, Görög P, Mihály J. The Mechanisms of Thin Filament Assembly and Length Regulation in Muscles. Int J Mol Sci 2022; 23:5306. [PMID: 35628117 PMCID: PMC9140763 DOI: 10.3390/ijms23105306] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2022] [Revised: 05/05/2022] [Accepted: 05/06/2022] [Indexed: 02/01/2023] Open
Abstract
The actin containing tropomyosin and troponin decorated thin filaments form one of the crucial components of the contractile apparatus in muscles. The thin filaments are organized into densely packed lattices interdigitated with myosin-based thick filaments. The crossbridge interactions between these myofilaments drive muscle contraction, and the degree of myofilament overlap is a key factor of contractile force determination. As such, the optimal length of the thin filaments is critical for efficient activity, therefore, this parameter is precisely controlled according to the workload of a given muscle. Thin filament length is thought to be regulated by two major, but only partially understood mechanisms: it is set by (i) factors that mediate the assembly of filaments from monomers and catalyze their elongation, and (ii) by factors that specify their length and uniformity. Mutations affecting these factors can alter the length of thin filaments, and in human cases, many of them are linked to debilitating diseases such as nemaline myopathy and dilated cardiomyopathy.
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Affiliation(s)
- Szilárd Szikora
- Institute of Genetics, Biological Research Centre, H-6726 Szeged, Hungary;
| | - Péter Görög
- Institute of Genetics, Biological Research Centre, H-6726 Szeged, Hungary;
- Doctoral School of Multidisciplinary Medical Science, Faculty of Medicine, University of Szeged, H-6725 Szeged, Hungary
| | - József Mihály
- Institute of Genetics, Biological Research Centre, H-6726 Szeged, Hungary;
- Department of Genetics, University of Szeged, H-6726 Szeged, Hungary
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4
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Fujita Y, Chokki T, Nishioka T, Morimoto K, Nakayama A, Nakae H, Ogasawara M, Terasaki AG. The emergence of nebulin repeats and evolution of lasp family proteins. Cytoskeleton (Hoboken) 2022; 78:419-435. [PMID: 35224880 DOI: 10.1002/cm.21693] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Revised: 02/23/2022] [Accepted: 02/25/2022] [Indexed: 11/10/2022]
Abstract
The LIM and SH3 domain protein (lasp) family, the smallest proteins in the nebulin superfamily, consists of vertebrate lasp-1 expressed in various non-muscle tissues, vertebrate lasp-2 expressed in the brain and cardiac muscle, and invertebrate lasp whose functions have been analyzed in Ascidiacea and Insecta. Gene evolution of the lasp family proteins was investigated by multiple alignments, comparison of gene structure, and synteny analyses in eukaryotes in which mRNA expression was confirmed. All invertebrates analyzed in this study belonging to the clade Filasterea, with the exception of Placozoa, have at least one lasp gene. The minimal actin-binding region (LIM domain and first nebulin repeat) and SH3 domain detected in vertebrate lasp-2 were found to be conserved among the lasp family proteins, and we showed that nematode lasp has actin-binding activity. The linker sequences vary among invertebrate lasp proteins, implying that the lasp family proteins have universal and diverse functions. Gene structures and syntenic analyses suggest that a gene fragment encoding two nebulin repeats and a linker emerged in Filasterea or Holozoa, and the first lasp gene was generated following combination of three gene fragments encoding the LIM domain, two nebulin repeats with a linker, and the SH3 domain. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Yuki Fujita
- Department of Biology, Graduate School of Science, Chiba University, Yayoi-cho, Inage-ku, Chiba, Japan
| | - Tamami Chokki
- Department of Biology, Graduate School of Science, Chiba University, Yayoi-cho, Inage-ku, Chiba, Japan
| | - Tatsuji Nishioka
- Department of Biology, Graduate School of Science, Chiba University, Yayoi-cho, Inage-ku, Chiba, Japan
| | - Kouta Morimoto
- Department of Biology, Graduate School of Science, Chiba University, Yayoi-cho, Inage-ku, Chiba, Japan
| | - Ayako Nakayama
- Department of Biology, Graduate School of Science, Chiba University, Yayoi-cho, Inage-ku, Chiba, Japan
| | - Hiroki Nakae
- BIO-Business Solutions, Hisamoto, Takatsu-ku, Kawasaki, Japan
| | - Michio Ogasawara
- Department of Biology, Graduate School of Science, Chiba University, Yayoi-cho, Inage-ku, Chiba, Japan
| | - Asako G Terasaki
- Department of Biology, Graduate School of Science, Chiba University, Yayoi-cho, Inage-ku, Chiba, Japan
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5
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Wang Z, Grange M, Pospich S, Wagner T, Kho AL, Gautel M, Raunser S. Structures from intact myofibrils reveal mechanism of thin filament regulation through nebulin. Science 2022; 375:eabn1934. [PMID: 35175800 DOI: 10.1126/science.abn1934] [Citation(s) in RCA: 62] [Impact Index Per Article: 31.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
In skeletal muscle, nebulin stabilizes and regulates the length of thin filaments, but the underlying mechanism remains nebulous. In this work, we used cryo-electron tomography and subtomogram averaging to reveal structures of native nebulin bound to thin filaments within intact sarcomeres. This in situ reconstruction provided high-resolution details of the interaction between nebulin and actin, demonstrating the stabilizing role of nebulin. Myosin bound to the thin filaments exhibited different conformations of the neck domain, highlighting its inherent structural variability in muscle. Unexpectedly, nebulin did not interact with myosin or tropomyosin, but it did interact with a troponin T linker through two potential binding motifs on nebulin, explaining its regulatory role. Our structures support the role of nebulin as a thin filament "molecular ruler" and provide a molecular basis for studying nemaline myopathies.
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Affiliation(s)
- Zhexin Wang
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, 44227 Dortmund, Germany
| | - Michael Grange
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, 44227 Dortmund, Germany
| | - Sabrina Pospich
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, 44227 Dortmund, Germany
| | - Thorsten Wagner
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, 44227 Dortmund, Germany
| | - Ay Lin Kho
- Randall Centre for Cell and Molecular Biophysics, School of Basic and Medical Biosciences, Kings College London BHF Centre of Research Excellence, Guy's Campus, London SE1 1UL, UK
| | - Mathias Gautel
- Randall Centre for Cell and Molecular Biophysics, School of Basic and Medical Biosciences, Kings College London BHF Centre of Research Excellence, Guy's Campus, London SE1 1UL, UK
| | - Stefan Raunser
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, 44227 Dortmund, Germany
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6
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Vejandla RM, Orgil BO, Alberson NR, Li N, Munkhsaikhan U, Khuchua Z, Martherus R, Azeloglu EU, Xu F, Lu L, Towbin JA, Purevjav E. Deficiency in nebulin repeats of sarcomeric nebulette is detrimental for cardiomyocyte tolerance to exercise and biomechanical stress. Am J Physiol Heart Circ Physiol 2021; 320:H2130-H2146. [PMID: 33861145 DOI: 10.1152/ajpheart.00732.2020] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The actin-binding sarcomeric nebulette (NEBL) protein provides efficient contractile flexibility via interaction with desmin intermediate filaments. NEBL gene mutations affecting the nebulin repeat (NR) domain are known to induce cardiomyopathy. The study aimed to explore the roles of NEBL in exercise and biomechanical stress response. We ablated exon3 encoding the first NR of Nebl and created global Neblex3-/ex3- knockout mice. Cardiac function, structure, and transcriptome were assessed before and after a 4-wk treadmill regimen. A Nebl-based exercise signaling network was constructed using systems genetics methods. H9C2 and neonatal rat cardiomyocytes (NRCs) expressing wild-type or mutant NEBL underwent cyclic mechanical strain. Neblex3-/ex3- mice demonstrated diastolic dysfunction with preserved systolic function at 6 mo of age. After treadmill running, 4-mo-old Neblex3-/ex3- mice developed concentric cardiac hypertrophy and left ventricular dilation compared with running Nebl+/+ and sedentary Neblex3-/ex3- mice. Disturbance of sarcomeric Z-disks and thin filaments architecture and disruption of intercalated disks and mitochondria were found in exercised Neblex3-/ex3- mice. A Nebl-based exercise signaling network included Csrp3, Des, Fbox32, Jup, Myh6, and Myh7. Disturbed expression of TM1, DES, JUP, β-catenin, MLP, α-actinin2, and vinculin proteins was demonstrated. In H9C2 cells, NEBL was recruited into focal adhesions at 24-h poststrain and redistributed along with F-actin at 72-h poststrain, suggesting time-dependent redistribution of NEBL in response to strain. NEBL mutations cause desmin disorganization in NRCs upon stretch. We conclude that Nebl's NR ablation causes disturbed sarcomere, Z-disks, and desmin organization, and prevents NEBL redistribution to focal adhesions in cardiomyocytes, weakening cardiac tolerance to biomechanical stress.NEW & NOTEWORTHY We demonstrate that ablation of first nebulin-repeats of sarcomeric nebulette (Nebl) causes diastolic dysfunction in Neblex3-/ex3- mice. Exercise-induced development of diastolic dysfunction, cardiac hypertrophy and ventricular dilation in knockouts. This was associated with sarcomere disturbance, intercalated disks disruption, and mitochondrial distortion upon stress and altered expression of genes involved in Nebl-based stress network. We demonstrate that G202R and A592 mutations alter actin and desmin expression causing disorganization of desmin filaments upon cyclic strain.
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Affiliation(s)
- Ramona M Vejandla
- The Heart Institute, Department of Pediatrics, University of Tennessee Health Science Center, Memphis, Tennessee.,Children's Foundation Research Institute, Le Bonheur Children's Hospital, Memphis, Tennessee
| | - Buyan-Ochir Orgil
- The Heart Institute, Department of Pediatrics, University of Tennessee Health Science Center, Memphis, Tennessee.,Children's Foundation Research Institute, Le Bonheur Children's Hospital, Memphis, Tennessee
| | - Neely R Alberson
- The Heart Institute, Department of Pediatrics, University of Tennessee Health Science Center, Memphis, Tennessee.,Children's Foundation Research Institute, Le Bonheur Children's Hospital, Memphis, Tennessee
| | - Ning Li
- The Heart Institute, Department of Pediatrics, University of Tennessee Health Science Center, Memphis, Tennessee.,Children's Foundation Research Institute, Le Bonheur Children's Hospital, Memphis, Tennessee.,Department of Cardiology, Second Affiliated Hospital, Harbin Medical University, Harbin, China
| | - Undral Munkhsaikhan
- The Heart Institute, Department of Pediatrics, University of Tennessee Health Science Center, Memphis, Tennessee.,Children's Foundation Research Institute, Le Bonheur Children's Hospital, Memphis, Tennessee
| | - Zaza Khuchua
- Department of Pediatrics, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio.,Department of Biochemistry, Sechenov University, Moscow, Russia.,Department of Biology and Biotechnology, Higher School of Economics, Moscow, Russia
| | - Ruben Martherus
- Department of Pediatrics, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio
| | - Evren U Azeloglu
- Department of Medicine, Nephrology, Icahn School of Medicine at Mount Sinai, New York, New York
| | - Fuyi Xu
- Department of Genetics, Genomics, and Informatics, University of Tennessee Health Science Center, Memphis, Tennessee
| | - Lu Lu
- Department of Genetics, Genomics, and Informatics, University of Tennessee Health Science Center, Memphis, Tennessee
| | - Jeffrey A Towbin
- The Heart Institute, Department of Pediatrics, University of Tennessee Health Science Center, Memphis, Tennessee.,Children's Foundation Research Institute, Le Bonheur Children's Hospital, Memphis, Tennessee.,Pediatric Cardiology, St. Jude Children's Research Hospital, Memphis, Tennessee
| | - Enkhsaikhan Purevjav
- The Heart Institute, Department of Pediatrics, University of Tennessee Health Science Center, Memphis, Tennessee.,Children's Foundation Research Institute, Le Bonheur Children's Hospital, Memphis, Tennessee
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7
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Benkafadar N, Janesick A, Scheibinger M, Ling AH, Jan TA, Heller S. Transcriptomic characterization of dying hair cells in the avian cochlea. Cell Rep 2021; 34:108902. [PMID: 33761357 DOI: 10.1016/j.celrep.2021.108902] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2020] [Revised: 01/11/2021] [Accepted: 03/03/2021] [Indexed: 12/28/2022] Open
Abstract
Sensory hair cells are prone to apoptosis caused by various drugs including aminoglycoside antibiotics. In mammals, this vulnerability results in permanent hearing loss because lost hair cells are not regenerated. Conversely, hair cells regenerate in birds, making the avian inner ear an exquisite model for studying ototoxicity and regeneration. Here, we use single-cell RNA sequencing and trajectory analysis on control and dying hair cells after aminoglycoside treatment. Interestingly, the two major subtypes of avian cochlear hair cells, tall and short hair cells, respond differently. Dying short hair cells show a noticeable transient upregulation of many more genes than tall hair cells. The most prominent gene group identified is associated with potassium ion conductances, suggesting distinct physiological differences. Moreover, the dynamic characterization of >15,000 genes expressed in tall and short avian hair cells during their apoptotic demise comprises a resource for further investigations toward mammalian hair cell protection and hair cell regeneration.
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Affiliation(s)
- Nesrine Benkafadar
- Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Stanford, CA 94305, USA; Institute for Stem Cell Biology and Regenerative Medicine, Stanford University School of Medicine, Stanford, CA 94305, USA.
| | - Amanda Janesick
- Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Stanford, CA 94305, USA; Institute for Stem Cell Biology and Regenerative Medicine, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Mirko Scheibinger
- Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Stanford, CA 94305, USA; Institute for Stem Cell Biology and Regenerative Medicine, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Angela H Ling
- Department of Otolaryngology-Head and Neck Surgery, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Taha A Jan
- Department of Otolaryngology-Head and Neck Surgery, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Stefan Heller
- Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Stanford, CA 94305, USA; Institute for Stem Cell Biology and Regenerative Medicine, Stanford University School of Medicine, Stanford, CA 94305, USA.
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8
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Ge X, Zhang T, Yu X, Muwonge AN, Anandakrishnan N, Wong NJ, Haydak JC, Reid JM, Fu J, Wong JS, Bhattacharya S, Cuttitta CM, Zhong F, Gordon RE, Salem F, Janssen W, Hone JC, Zhang A, Li H, He JC, Gusella GL, Campbell KN, Azeloglu EU. LIM-Nebulette Reinforces Podocyte Structural Integrity by Linking Actin and Vimentin Filaments. J Am Soc Nephrol 2020; 31:2372-2391. [PMID: 32737144 DOI: 10.1681/asn.2019121261] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2019] [Accepted: 06/06/2020] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND Maintenance of the intricate interdigitating morphology of podocytes is crucial for glomerular filtration. One of the key aspects of specialized podocyte morphology is the segregation and organization of distinct cytoskeletal filaments into different subcellular components, for which the exact mechanisms remain poorly understood. METHODS Cells from rats, mice, and humans were used to describe the cytoskeletal configuration underlying podocyte structure. Screening the time-dependent proteomic changes in the rat puromycin aminonucleoside-induced nephropathy model correlated the actin-binding protein LIM-nebulette strongly with glomerular function. Single-cell RNA sequencing and immunogold labeling were used to determine Nebl expression specificity in podocytes. Automated high-content imaging, super-resolution microscopy, atomic force microscopy (AFM), live-cell imaging of calcium, and measurement of motility and adhesion dynamics characterized the physiologic role of LIM-nebulette in podocytes. RESULTS Nebl knockout mice have increased susceptibility to adriamycin-induced nephropathy and display morphologic, cytoskeletal, and focal adhesion abnormalities with altered calcium dynamics, motility, and Rho GTPase activity. LIM-nebulette expression is decreased in diabetic nephropathy and FSGS patients at both the transcript and protein level. In mice, rats, and humans, LIM-nebulette expression is localized to primary, secondary, and tertiary processes of podocytes, where it colocalizes with focal adhesions as well as with vimentin fibers. LIM-nebulette shRNA knockdown in immortalized human podocytes leads to dysregulation of vimentin filament organization and reduced cellular elasticity as measured by AFM indentation. CONCLUSIONS LIM-nebulette is a multifunctional cytoskeletal protein that is critical in the maintenance of podocyte structural integrity through active reorganization of focal adhesions, the actin cytoskeleton, and intermediate filaments.
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Affiliation(s)
- Xuhua Ge
- Division of Nephrology, Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, New York
| | - Tao Zhang
- Division of Nephrology, Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, New York
| | - Xiaoxia Yu
- Division of Nephrology, Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, New York
| | - Alecia N Muwonge
- Division of Nephrology, Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, New York
| | - Nanditha Anandakrishnan
- Division of Nephrology, Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, New York
| | - Nicholas J Wong
- Division of Nephrology, Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, New York
| | - Jonathan C Haydak
- Division of Nephrology, Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, New York
| | - Jordan M Reid
- Division of Nephrology, Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, New York
| | - Jia Fu
- Division of Nephrology, Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, New York
| | - Jenny S Wong
- Division of Nephrology, Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, New York
| | - Smiti Bhattacharya
- Division of Nephrology, Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, New York.,Department of Mechanical Engineering, Columbia University, New York, New York
| | - Christina M Cuttitta
- Division of Nephrology, Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, New York
| | - Fang Zhong
- Division of Nephrology, Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, New York
| | - Ronald E Gordon
- Department of Pathology, Icahn School of Medicine at Mount Sinai, New York, New York
| | - Fadi Salem
- Department of Pathology, Icahn School of Medicine at Mount Sinai, New York, New York
| | - William Janssen
- Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, New York
| | - James C Hone
- Department of Mechanical Engineering, Columbia University, New York, New York
| | - Aihua Zhang
- Department of Nephrology, Children's Hospital of Nanjing Medical University, Nanjing, China
| | - Hong Li
- Department of Microbiology, Biochemistry and Molecular Genetics, Rutgers University-New Jersey Medical School, Newark, New Jersey
| | - John C He
- Division of Nephrology, Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, New York.,Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, New York
| | - G Luca Gusella
- Division of Nephrology, Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, New York
| | - Kirk N Campbell
- Division of Nephrology, Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, New York
| | - Evren U Azeloglu
- Division of Nephrology, Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, New York .,Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, New York
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9
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Li J, Hu S, Zhang Z, Qian L, Xue Q, Qu X. LASP2 is downregulated in human liver cancer and contributes to hepatoblastoma cell malignant phenotypes through MAPK/ERK pathway. Biomed Pharmacother 2020; 127:110154. [PMID: 32325347 DOI: 10.1016/j.biopha.2020.110154] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Revised: 03/31/2020] [Accepted: 04/04/2020] [Indexed: 01/02/2023] Open
Abstract
LASP2 was recently demonstrated to serve as multifaceted roles in several types of cancers. However, its underlying mechanism in the progression of human liver cancer has not been explored. The aims of the current study were to detect LASP2 expression in a liver tissue microarray, and to determine whether LASP2 contributes to malignant phenotypes of HepG2 human hepatoblastoma cells. Our results revealed that LASP2 expression was downregulated in liver cancer tissues relative to normal non-cancerous tissues, and its downregulated expression was closely correlated with malignant process of liver cancer. In vitro, upregulation of LASP2 expression by transfection with LASP2 vector significantly suppressed HepG2 cells viability, colony formation and migration activities. Conversely, the viability, colony formation and migration abilities of HepG2 cells were increased when downregulating LASP2 expression by transfection with small interfering RNA targeting LASP2. Interaction study showed that silencing of LASP2 in HepG2 cells triggered high expression of Cyclin D1, ERK and p-ERK, and low expression of Bax, respectively. In addition, LASP2 silencing-induced malignant phenotypes were further attenuated after HepG2 cells treatment with ERK1/2 blocker PD98059. Collectively, our data suggest a link between LASP2 and MAPK/ERK axis in the development of hepatoblastoma and LASP2 may be a potential marker for assessment of liver cancer prognosis and staging.
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Affiliation(s)
- Jing Li
- The Basic Medical College, Jiamusi University, Jiamusi, 154007, Heilongjiang, China
| | - Shaojun Hu
- The First Affiliated Hospital, Jiamusi University, Jiamusi, 154002, Heilongjiang, China
| | - Zhiyong Zhang
- The First Affiliated Hospital, Jiamusi University, Jiamusi, 154002, Heilongjiang, China
| | - Lei Qian
- The University Hospital, Jiamusi University, Jiamusi, 154007, Heilongjiang, China
| | - Qing Xue
- The First Affiliated Hospital, Jiamusi University, Jiamusi, 154002, Heilongjiang, China
| | - Xiusheng Qu
- The First Affiliated Hospital, Jiamusi University, Jiamusi, 154002, Heilongjiang, China.
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10
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Abstract
Nebulin, encoded by NEB, is a giant skeletal muscle protein of about 6669 amino acids which forms an integral part of the sarcomeric thin filament. In recent years, the nebula around this protein has been largely lifted resulting in the discovery that nebulin is critical for a number of tasks in skeletal muscle. In this review, we firstly discussed nebulin’s role as a structural component of the thin filament and the Z-disk, regulating the length and the mechanical properties of the thin filament as well as providing stability to myofibrils by interacting with structural proteins within the Z-disk. Secondly, we reviewed nebulin’s involvement in the regulation of muscle contraction, cross-bridge cycling kinetics, Ca2+-homeostasis and excitation contraction (EC) coupling. While its role in Ca2+-homeostasis and EC coupling is still poorly understood, a large number of studies have helped to improve our knowledge on how nebulin affects skeletal muscle contractile mechanics. These studies suggest that nebulin affects the number of force generating actin-myosin cross-bridges and may also affect the force that each cross-bridge produces. It may exert this effect by interacting directly with actin and myosin and/or indirectly by potentially changing the localisation and function of the regulatory complex (troponin and tropomyosin). Besides unravelling the biology of nebulin, these studies are particularly helpful in understanding the patho-mechanism of myopathies caused by NEB mutations, providing knowledge which constitutes the critical first step towards the development of therapeutic interventions. Currently, effective treatments are not available, although a number of therapeutic strategies are being investigated.
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11
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Prill K, Dawson JF. Assembly and Maintenance of Sarcomere Thin Filaments and Associated Diseases. Int J Mol Sci 2020; 21:E542. [PMID: 31952119 PMCID: PMC7013991 DOI: 10.3390/ijms21020542] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2019] [Revised: 01/06/2020] [Accepted: 01/12/2020] [Indexed: 12/22/2022] Open
Abstract
Sarcomere assembly and maintenance are essential physiological processes required for cardiac and skeletal muscle function and organism mobility. Over decades of research, components of the sarcomere and factors involved in the formation and maintenance of this contractile unit have been identified. Although we have a general understanding of sarcomere assembly and maintenance, much less is known about the development of the thin filaments and associated factors within the sarcomere. In the last decade, advancements in medical intervention and genome sequencing have uncovered patients with novel mutations in sarcomere thin filaments. Pairing this sequencing with reverse genetics and the ability to generate patient avatars in model organisms has begun to deepen our understanding of sarcomere thin filament development. In this review, we provide a summary of recent findings regarding sarcomere assembly, maintenance, and disease with respect to thin filaments, building on the previous knowledge in the field. We highlight debated and unknown areas within these processes to clearly define open research questions.
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Affiliation(s)
| | - John F. Dawson
- Centre for Cardiovascular Investigations, Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON N1G 2W1, Canada;
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12
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Nishikawa A, Hanashima A, Nakayama S, Ogasawara M, Kimura S. Transcripts of the nebulin gene from Ciona heart and their implications for the evolution of nebulin family genes. Gene X 2019; 716:144036. [DOI: 10.1016/j.gene.2019.144036] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2019] [Revised: 07/27/2019] [Accepted: 07/31/2019] [Indexed: 10/26/2022] Open
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13
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Chase PB. Elastic domains of giant proteins in striated muscle: Modeling compliance with rulers. J Gen Physiol 2019; 151:619-622. [PMID: 30975697 PMCID: PMC6504283 DOI: 10.1085/jgp.201912345] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Chase examines a study using the MUSICO model of striated muscle to evaluate the function of giant elastic proteins titin and nebulin.
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Affiliation(s)
- P. Bryant Chase
- Department of Biological Science, Florida State University, Tallahassee, FL
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14
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Zhang Y, Li JH, Yuan QG, Cao G, Yang WB. Upregulation of LASP2 inhibits pancreatic cancer cell migration and invasion through suppressing TGF-β-induced EMT. J Cell Biochem 2019; 120:13651-13657. [PMID: 30945341 DOI: 10.1002/jcb.28638] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2018] [Revised: 12/22/2018] [Accepted: 01/07/2019] [Indexed: 12/18/2022]
Abstract
LASP2 (LIM and SH3 protein 2), a member of the LIM-protein subfamily of the nebulin group, was first identified as a splice variant of the nebulin gene. In the past, investigators mainly focused on the impact of LASP2 on cardiac diseases because of its identification in the myocardium. Recently, several studies have reported that LASP2 is associated with the progression of various cancers. However, there have been no investigations on the expression and function of LASP2 in pancreatic cancer (PC). In this study, we performed the quantitative real-time polymerase chain reaction and Western blot analysis to detect the expression of LASP2 in PC tissues and cell lines. PC cells were transfected with LASP2 overexpression plasmid or the negative control in the presence or absence of tumor growth factor-β (TGF-β). The transwell assays were used to measure the effects of LASP2 on PC cell migration and invasion. The protein expression of epithelial-mesenchymal transition (EMT) markers was detected using Western blot assay. Our results demonstrated that LASP2 was downregulated in PC tissues and cell lines. In addition, upregulation of LASP2 inhibited the PC cell migration and invasion. We also found that LASP2 upregulation reversed TGF-β-induced EMT in PC cells. Taken together, we provided novel evidence supporting the tumor-suppressor role of LASP2 in PC and suggested it as a potential therapeutic target in PC treatment.
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Affiliation(s)
- Yan Zhang
- Department of General Surgery, the Second Affiliated Hospital of Medical School, Xi'an Jiaotong University, Xi'an, China
| | - Jun-Hui Li
- Department of General Surgery, the Second Affiliated Hospital of Medical School, Xi'an Jiaotong University, Xi'an, China
| | - Qing-Gong Yuan
- Department of General Surgery, the Second Affiliated Hospital of Medical School, Xi'an Jiaotong University, Xi'an, China
| | - Gang Cao
- Department of General Surgery, the Second Affiliated Hospital of Medical School, Xi'an Jiaotong University, Xi'an, China
| | - Wen-Bin Yang
- Department of General Surgery, the Second Affiliated Hospital of Medical School, Xi'an Jiaotong University, Xi'an, China
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15
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Li Y, Merkel CD, Zeng X, Heier JA, Cantrell PS, Sun M, Stolz DB, Watkins SC, Yates NA, Kwiatkowski AV. The N-cadherin interactome in primary cardiomyocytes as defined using quantitative proximity proteomics. J Cell Sci 2019; 132:jcs.221606. [PMID: 30630894 PMCID: PMC6382013 DOI: 10.1242/jcs.221606] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2018] [Accepted: 12/24/2018] [Indexed: 12/11/2022] Open
Abstract
The junctional complexes that couple cardiomyocytes must transmit the mechanical forces of contraction while maintaining adhesive homeostasis. The adherens junction (AJ) connects the actomyosin networks of neighboring cardiomyocytes and is required for proper heart function. Yet little is known about the molecular composition of the cardiomyocyte AJ or how it is organized to function under mechanical load. Here, we define the architecture, dynamics and proteome of the cardiomyocyte AJ. Mouse neonatal cardiomyocytes assemble stable AJs along intercellular contacts with organizational and structural hallmarks similar to mature contacts. We combine quantitative mass spectrometry with proximity labeling to identify the N-cadherin (CDH2) interactome. We define over 350 proteins in this interactome, nearly 200 of which are unique to CDH2 and not part of the E-cadherin (CDH1) interactome. CDH2-specific interactors comprise primarily adaptor and adhesion proteins that promote junction specialization. Our results provide novel insight into the cardiomyocyte AJ and offer a proteomic atlas for defining the molecular complexes that regulate cardiomyocyte intercellular adhesion. This article has an associated First Person interview with the first authors of the paper.
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Affiliation(s)
- Yang Li
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Chelsea D Merkel
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Xuemei Zeng
- Biomedical Mass Spectrometry Center, University of Pittsburgh Schools of the Health Sciences, Pittsburgh, PA 15261, USA
| | - Jonathon A Heier
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Pamela S Cantrell
- Biomedical Mass Spectrometry Center, University of Pittsburgh Schools of the Health Sciences, Pittsburgh, PA 15261, USA
| | - Mai Sun
- Biomedical Mass Spectrometry Center, University of Pittsburgh Schools of the Health Sciences, Pittsburgh, PA 15261, USA
| | - Donna B Stolz
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Simon C Watkins
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Nathan A Yates
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA.,Biomedical Mass Spectrometry Center, University of Pittsburgh Schools of the Health Sciences, Pittsburgh, PA 15261, USA.,University of Pittsburgh Cancer Institute, Hillman Cancer Center, Pittsburgh, PA 15232, USA
| | - Adam V Kwiatkowski
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
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16
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Zerkalenkova E, Lebedeva S, Kazakova A, Tsaur G, Starichkova Y, Timofeeva N, Soldatkina O, Aprelova E, Popov A, Ponomareva N, Baidun L, Meyer C, Novichkova G, Maschan M, Maschan A, Marschalek R, Olshanskaya Y. Acute myeloid leukemia with t(10;11)(p11-12;q23.3): Results of Russian Pediatric AML registration study. Int J Lab Hematol 2019; 41:287-292. [PMID: 30624859 DOI: 10.1111/ijlh.12969] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2018] [Revised: 11/29/2018] [Accepted: 12/04/2018] [Indexed: 01/04/2023]
Abstract
INTRODUCTION Translocations involving the KMT2A gene (also known as MLL) are frequently diagnosed in pediatric acute leukemia cases with either lymphoblastic or myeloid origin. KMT2A is translocated to multiple partner genes, including MLLT10/AF10 localizing at chromosomal band 10p12. KMT2A-MLLT10 is one of the common chimeric genes diagnosed in acute leukemia with KMT2A rearrangement (8%), especially in acute myeloid leukemia (AML; 18%). MLLT10 is localized in very close proximity to two other KMT2A partner genes at 10p11-12-NEBL and ABI1, so they could not be distinguished by conventional cytogenetics. METHODS In this work, we present a cohort of 28 patients enrolled into Russian Pediatric AML registration study carrying rearrangements between chromosomal regions 11q23.3 and 10p11-12. G-banding, FISH, reverse transcription PCR, and long-distance inverse PCR were used to characterize the KMT2A gene rearrangements in these patients. RESULTS We demonstrate that 25 patients harbor the KMT2A-MLLT10 rearrangement, while three patients show the rare KMT2A rearrangements (2× KMT2A-NEBL; 1× KMT2A-ABI1). CONCLUSIONS Therefore, the combination of cytogenetic and molecular genetic methods is of high importance in diagnosing cases with t(10;11)(p11-12;q23.3).
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Affiliation(s)
- Elena Zerkalenkova
- Dmitry Rogachev National Medical and Research Center of Pediatric Hematology, Oncology and Immunology, Moscow, Russia
| | - Svetlana Lebedeva
- Dmitry Rogachev National Medical and Research Center of Pediatric Hematology, Oncology and Immunology, Moscow, Russia.,Department of Fundamental Medicine, Moscow State University named after M.V. Lomonosov, Moscow, Russia
| | - Anna Kazakova
- Dmitry Rogachev National Medical and Research Center of Pediatric Hematology, Oncology and Immunology, Moscow, Russia
| | - Grigory Tsaur
- Regional Children's Hospital No. 1, Yekaterinburg, Russia.,Research Institute of Medical Cell Technologies, Yekaterinburg, Russia
| | - Yulia Starichkova
- Dmitry Rogachev National Medical and Research Center of Pediatric Hematology, Oncology and Immunology, Moscow, Russia
| | - Natalia Timofeeva
- Dmitry Rogachev National Medical and Research Center of Pediatric Hematology, Oncology and Immunology, Moscow, Russia
| | - Olga Soldatkina
- Dmitry Rogachev National Medical and Research Center of Pediatric Hematology, Oncology and Immunology, Moscow, Russia
| | - Evgenia Aprelova
- Dmitry Rogachev National Medical and Research Center of Pediatric Hematology, Oncology and Immunology, Moscow, Russia
| | - Aleksandr Popov
- Dmitry Rogachev National Medical and Research Center of Pediatric Hematology, Oncology and Immunology, Moscow, Russia
| | | | | | - Claus Meyer
- Institute of Pharmaceutical Biology, Diagnostic Centre of Acute Leukemia (DCAL), Goethe-University of Frankfurt, Frankfurt/Main, Germany
| | - Galina Novichkova
- Dmitry Rogachev National Medical and Research Center of Pediatric Hematology, Oncology and Immunology, Moscow, Russia
| | - Michael Maschan
- Dmitry Rogachev National Medical and Research Center of Pediatric Hematology, Oncology and Immunology, Moscow, Russia
| | - Aleksey Maschan
- Dmitry Rogachev National Medical and Research Center of Pediatric Hematology, Oncology and Immunology, Moscow, Russia
| | - Rolf Marschalek
- Institute of Pharmaceutical Biology, Diagnostic Centre of Acute Leukemia (DCAL), Goethe-University of Frankfurt, Frankfurt/Main, Germany
| | - Yulia Olshanskaya
- Dmitry Rogachev National Medical and Research Center of Pediatric Hematology, Oncology and Immunology, Moscow, Russia
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17
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Kawai M, Karam TS, Kolb J, Wang L, Granzier HL. Nebulin increases thin filament stiffness and force per cross-bridge in slow-twitch soleus muscle fibers. J Gen Physiol 2018; 150:1510-1522. [PMID: 30301869 PMCID: PMC6219688 DOI: 10.1085/jgp.201812104] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2018] [Accepted: 09/19/2018] [Indexed: 01/15/2023] Open
Abstract
Nebulin stabilizes the thin filament and regulates force generation in skeletal muscle, but its precise role is not understood. Using conditional knockout mice, Kawai et al. demonstrate that nebulin functions to increase the force per cross-bridge in skinned slow-twitch soleus muscle fibers. Nebulin (Neb) is associated with the thin filament in skeletal muscle cells, but its functions are not well understood. For this goal, we study skinned slow-twitch soleus muscle fibers from wild-type (Neb+) and conditional Neb knockout (Neb−) mice. We characterize cross-bridge (CB) kinetics and the elementary steps of the CB cycle by sinusoidal analysis during full Ca2+ activation and observe that Neb increases active tension 1.9-fold, active stiffness 2.7-fold, and rigor stiffness 3.0-fold. The ratio of stiffness during activation and rigor states is 62% in Neb+ fibers and 68% in Neb− fibers. These are approximately proportionate to the number of strongly attached CBs during activation. Because the thin filament length is 15% shorter in Neb− fibers than in Neb+ fibers, the increase in force per CB in the presence of Neb is ∼1.5 fold. The equilibrium constant of the CB detachment step (K2), its rate (k2), and the rate of the reverse force generation step (k−4) are larger in Neb+ fibers than in Neb− fibers. The rates of the force generation step (k4) and the reversal detachment step (k−2) change in the opposite direction. These effects can be explained by Le Chatelier’s principle: Increased CB strain promotes less force-generating state(s) and/or detached state(s). Further, when CB distributions among the six states are calculated, there is no significant difference in the number of strongly attached CBs between fibers with and without Neb. These results demonstrate that Neb increases force per CB. We also confirm that force is generated by isomerization of actomyosin (AM) from the AM.ADP.Pi state (ADP, adenosine diphophate; Pi, phosphate) to the AM*ADP.Pi state, where the same force is maintained after Pi release to result in the AM*ADP state. We propose that Neb changes the actin (and myosin) conformation for better ionic and hydrophobic/stereospecific AM interaction, and that the effect of Neb is similar to that of tropomyosin.
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Affiliation(s)
- Masataka Kawai
- Departments of Anatomy and Cell Biology, and Internal Medicine, College of Medicine, University of Iowa, Iowa City, IA
| | - Tarek S Karam
- Departments of Anatomy and Cell Biology, and Internal Medicine, College of Medicine, University of Iowa, Iowa City, IA
| | - Justin Kolb
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ
| | - Li Wang
- Departments of Anatomy and Cell Biology, and Internal Medicine, College of Medicine, University of Iowa, Iowa City, IA.,School of Nursing, Soochow University, Suzhou, China
| | - Henk L Granzier
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ
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18
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Osterberg JS, Cammen KM, Schultz TF, Clark BW, Di Giulio RT. Genome-wide scan reveals signatures of selection related to pollution adaptation in non-model estuarine Atlantic killifish (Fundulus heteroclitus). AQUATIC TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2018; 200:73-82. [PMID: 29727773 PMCID: PMC6957077 DOI: 10.1016/j.aquatox.2018.04.017] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/12/2018] [Revised: 04/21/2018] [Accepted: 04/24/2018] [Indexed: 05/09/2023]
Abstract
In many human-altered ecosystems, organisms are increasingly faced with more diverse and complex environmental stressors and pollutant mixtures, to which the adaptations necessary to survive exposure are likely to be numerous and varied. Improving our understanding of the molecular mechanisms that underlie complex polygenic adaptations in natural settings requires significant toxicological, biochemical, physiological, and genomic data rarely available for non-model organisms. Here, we build upon two decades of study of adaptation to anthropogenic pollutants in a population of Atlantic killifish (Fundulus heteroclitus) that inhabits the creosote-contaminated Atlantic Wood Industries Superfund (AW) site on the Elizabeth River, Virginia in the United States. To better understand the genotypes that underlie previously characterized resistance to PCBs and PAHs, we performed Restriction site-Associated DNA sequencing (RADseq) on killifish from AW and two relatively clean reference sites (King's Creek-KC, and Mains Creek-MC). Across the genome, we analyzed over 83,000 loci and 12,000 single nucleotide polymorphisms (SNPs). Shared across both comparisons of killifish from polluted (AW) and relatively unpolluted (KC and MC) sites, we found eight genomic regions with smoothed FST values significantly (p < 0.001) elevated above background. Using the recently published F. heteroclitus reference genome, we identified candidate genes in these significant regions involved in the AHR pathway (e.g. AIP, ARNT1c), as well as genes relating to cardiac structure and function. These genes represent both previously characterized and potentially novel molecular adaptations involved with various aspects of resistance to these environmental toxins.
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Affiliation(s)
- J S Osterberg
- Duke University, Nicholas School of the Environment, Duke Superfund Research Center, Durham, NC, 27708, USA; Duke University, Nicholas School of the Environment, Duke Marine Lab, Beaufort, NC, 28516, USA.
| | - K M Cammen
- Duke University, Nicholas School of the Environment, Duke Marine Lab, Beaufort, NC, 28516, USA
| | - T F Schultz
- Duke University, Nicholas School of the Environment, Duke Marine Lab, Beaufort, NC, 28516, USA
| | - B W Clark
- Duke University, Nicholas School of the Environment, Duke Superfund Research Center, Durham, NC, 27708, USA
| | - R T Di Giulio
- Duke University, Nicholas School of the Environment, Duke Superfund Research Center, Durham, NC, 27708, USA
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19
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Distinct Mesenchymal Lineages and Niches Promote Epithelial Self-Renewal and Myofibrogenesis in the Lung. Cell 2017; 170:1134-1148.e10. [PMID: 28886382 DOI: 10.1016/j.cell.2017.07.034] [Citation(s) in RCA: 363] [Impact Index Per Article: 51.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Revised: 06/09/2017] [Accepted: 07/21/2017] [Indexed: 02/07/2023]
Abstract
The lung is an architecturally complex organ comprising a heterogeneous mixture of various epithelial and mesenchymal lineages. We use single-cell RNA sequencing and signaling lineage reporters to generate a spatial and transcriptional map of the lung mesenchyme. We find that each mesenchymal lineage has a distinct spatial address and transcriptional profile leading to unique niche regulatory functions. The mesenchymal alveolar niche cell is Wnt responsive, expresses Pdgfrα, and is critical for alveolar epithelial cell growth and self-renewal. In contrast, the Axin2+ myofibrogenic progenitor cell preferentially generates pathologically deleterious myofibroblasts after injury. Analysis of the secretome and receptome of the alveolar niche reveals functional pathways that mediate growth and self-renewal of alveolar type 2 progenitor cells, including IL-6/Stat3, Bmp, and Fgf signaling. These studies define the cellular and molecular framework of lung mesenchymal niches and reveal the functional importance of developmental pathways in promoting self-renewal versus a pathological response to tissue injury.
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20
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Abstract
Cardiac and skeletal striated muscles are intricately designed machines responsible for muscle contraction. Coordination of the basic contractile unit, the sarcomere, and the complex cytoskeletal networks are critical for contractile activity. The sarcomere is comprised of precisely organized individual filament systems that include thin (actin), thick (myosin), titin, and nebulin. Connecting the sarcomere to other organelles (e.g., mitochondria and nucleus) and serving as the scaffold to maintain cellular integrity are the intermediate filaments. The costamere, on the other hand, tethers the sarcomere to the cell membrane. Unique structures like the intercalated disc in cardiac muscle and the myotendinous junction in skeletal muscle help synchronize and transmit force. Intense investigation has been done on many of the proteins that make up these cytoskeletal assemblies. Yet the details of their function and how they interconnect have just started to be elucidated. A vast number of human myopathies are contributed to mutations in muscle proteins; thus understanding their basic function provides a mechanistic understanding of muscle disorders. In this review, we highlight the components of striated muscle with respect to their interactions, signaling pathways, functions, and connections to disease. © 2017 American Physiological Society. Compr Physiol 7:891-944, 2017.
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Affiliation(s)
- Christine A Henderson
- Department of Cellular and Molecular Medicine, The University of Arizona, Tucson, Arizona, USA.,Sarver Molecular Cardiovascular Research Program, The University of Arizona, Tucson, Arizona, USA
| | - Christopher G Gomez
- Department of Cellular and Molecular Medicine, The University of Arizona, Tucson, Arizona, USA.,Sarver Molecular Cardiovascular Research Program, The University of Arizona, Tucson, Arizona, USA
| | - Stefanie M Novak
- Department of Cellular and Molecular Medicine, The University of Arizona, Tucson, Arizona, USA.,Sarver Molecular Cardiovascular Research Program, The University of Arizona, Tucson, Arizona, USA
| | - Lei Mi-Mi
- Department of Cellular and Molecular Medicine, The University of Arizona, Tucson, Arizona, USA.,Sarver Molecular Cardiovascular Research Program, The University of Arizona, Tucson, Arizona, USA
| | - Carol C Gregorio
- Department of Cellular and Molecular Medicine, The University of Arizona, Tucson, Arizona, USA.,Sarver Molecular Cardiovascular Research Program, The University of Arizona, Tucson, Arizona, USA
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21
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Wang B, Zhang L, Zhao L, Zhou R, Ding Y, Li G, Zhao L. LASP2 suppresses colorectal cancer progression through JNK/p38 MAPK pathway meditated epithelial-mesenchymal transition. Cell Commun Signal 2017; 15:21. [PMID: 28606091 PMCID: PMC5469134 DOI: 10.1186/s12964-017-0179-9] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2017] [Accepted: 06/07/2017] [Indexed: 12/31/2022] Open
Abstract
BACKGROUND LASP2 (LIM and SH3 Protein 2) is a small focal adhesion protein belongs to nebulin protein family. As the newest member of nebulette family, the function of LASP2 remains to be identified. METHODS The relationship between LASP2 expression and clinical characteristics of CRC was analyzed in 89 paraffin-embedded archived CRC specimens by immunohistochemistry (IHC). The effects of LASP2 on cell growth and migration were examined in vitro, using CCK-8 and transwell assays. Western blotting was performed to examine the impact of LASP2 on the SAPK/JNK and MAPK signaling pathways. RESULTS In the present study, we observed a decreased LASP2 expression in clinical colorectal cancer samples compared with paired normal tissues. A negative correlation was also found between LASP2 and poor prognosis of CRC patients. Gain- and loss-of-function approaches revealed that LASP2 plays inhibitory effects on the growth and migration of human CRC cells in vitro. Western-blot results showed that LASP2 could attenuate epithelial-mesenchymal transition (EMT) to accomplish its suppression on CRC aggression. In LASP2 knocked down CRC cells, EMT was inhibited along with the inactivation of JNK/p38 MAPK pathway. Consistently, treatment of JNK inhibitor (JNK inhibitor II) together with p38 inhibitor (SB203580) could resume the process of EMT. Interestingly, we found a negative relationship between LASP2 and LASP1 expression in both CRC cell lines and tumors tissues, which suggests their converse function in CRC progression. CONCLUSIONS All the findings indicated that LASP2 may play a significant role in suppressing CRC progression and provided a novel biomarker for CRC therapy.
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Affiliation(s)
- Bin Wang
- Department of Pathology, Nanfang Hospital, Southern Medical University, Guangzhou, China.,Department of General Surgery, Nanfang Hospital, Southern Medical University, Guangdong provincial Engineering Technology Research Center of Minimally Invasive Surgery, Guangzhou, China
| | - Lanzhi Zhang
- Department of Pathology, Nanfang Hospital, Southern Medical University, Guangzhou, China.,Department of Pathology, School of Basic Medical Sciences, Southern Medical University, Guangzhou, China
| | - Liying Zhao
- Department of General Surgery, Nanfang Hospital, Southern Medical University, Guangdong provincial Engineering Technology Research Center of Minimally Invasive Surgery, Guangzhou, China
| | - Rui Zhou
- Department of Pathology, School of Basic Medical Sciences, Southern Medical University, Guangzhou, China
| | - Yanqing Ding
- Department of Pathology, School of Basic Medical Sciences, Southern Medical University, Guangzhou, China
| | - Guoxin Li
- Department of General Surgery, Nanfang Hospital, Southern Medical University, Guangdong provincial Engineering Technology Research Center of Minimally Invasive Surgery, Guangzhou, China.
| | - Liang Zhao
- Department of Pathology, Nanfang Hospital, Southern Medical University, Guangzhou, China. .,Department of Pathology, School of Basic Medical Sciences, Southern Medical University, Guangzhou, China.
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22
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Abstract
Striated cardiac and skeletal muscles play very different roles in the body, but they are similar at the molecular level. In particular, contraction, regardless of the type of muscle, is a precise and complex process involving the integral protein myofilaments and their associated regulatory components. The smallest functional unit of muscle contraction is the sarcomere. Within the sarcomere can be found a sophisticated ensemble of proteins associated with the thick filaments (myosin, myosin binding protein-C, titin, and obscurin) and thin myofilaments (actin, troponin, tropomyosin, nebulin, and nebulette). These parallel thick and thin filaments slide across one another, pulling the two ends of the sarcomere together to regulate contraction. More specifically, the regulation of both timing and force of contraction is accomplished through an intricate network of intra- and interfilament interactions belonging to each myofilament. This review introduces the sarcomere proteins involved in striated muscle contraction and places greater emphasis on the more recently identified and less well-characterized myofilaments: cardiac myosin binding protein-C, titin, nebulin, and obscurin. © 2017 American Physiological Society. Compr Physiol 7:675-692, 2017.
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Affiliation(s)
- Brian Leei Lin
- Department of Cell and Molecular Physiology, Health Sciences Division, Loyola University Chicago, Maywood, Illinois, USA
| | - Taejeong Song
- Department of Cell and Molecular Physiology, Health Sciences Division, Loyola University Chicago, Maywood, Illinois, USA.,Department of Internal Medicine, Heart, Lung and Vascular Institute, Division of Cardiovascular Health and Sciences, University of Cincinnati College of Medicine, Cincinnati, Ohio, USA
| | - Sakthivel Sadayappan
- Department of Cell and Molecular Physiology, Health Sciences Division, Loyola University Chicago, Maywood, Illinois, USA.,Department of Internal Medicine, Heart, Lung and Vascular Institute, Division of Cardiovascular Health and Sciences, University of Cincinnati College of Medicine, Cincinnati, Ohio, USA
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23
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Abstract
In this review we discuss the history and the current state of ideas related to the mechanism of size regulation of the thick (myosin) and thin (actin) filaments in vertebrate striated muscles. Various hypotheses have been considered during of more than half century of research, recently mostly involving titin and nebulin acting as templates or 'molecular rulers', terminating exact assembly. These two giant, single-polypeptide, filamentous proteins are bound in situ along the thick and thin filaments, respectively, with an almost perfect match in the respective lengths and structural periodicities. However, evidence still questions the possibility that the proteins function as templates, or scaffolds, on which the thin and thick filaments could be assembled. In addition, the progress in muscle research during the last decades highlighted a number of other factors that could potentially be involved in the mechanism of length regulation: molecular chaperones that may guide folding and assembly of actin and myosin; capping proteins that can influence the rates of assembly-disassembly of the myofilaments; Ca2+ transients that can activate or deactivate protein interactions, etc. The entire mechanism of sarcomere assembly appears complex and highly dynamic. This mechanism is also capable of producing filaments of about the correct size without titin and nebulin. What then is the role of these proteins? Evidence points to titin and nebulin stabilizing structures of the respective filaments. This stabilizing effect, based on linear proteins of a fixed size, implies that titin and nebulin are indeed molecular rulers of the filaments. Although the proteins may not function as templates in the assembly of the filaments, they measure and stabilize exactly the same size of the functionally important for the muscles segments in each of the respective filaments.
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Reimann L, Wiese H, Leber Y, Schwäble AN, Fricke AL, Rohland A, Knapp B, Peikert CD, Drepper F, van der Ven PFM, Radziwill G, Fürst DO, Warscheid B. Myofibrillar Z-discs Are a Protein Phosphorylation Hot Spot with Protein Kinase C (PKCα) Modulating Protein Dynamics. Mol Cell Proteomics 2016; 16:346-367. [PMID: 28028127 DOI: 10.1074/mcp.m116.065425] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2016] [Indexed: 11/06/2022] Open
Abstract
The Z-disc is a protein-rich structure critically important for the development and integrity of myofibrils, which are the contractile organelles of cross-striated muscle cells. We here used mouse C2C12 myoblast, which were differentiated into myotubes, followed by electrical pulse stimulation (EPS) to generate contracting myotubes comprising mature Z-discs. Using a quantitative proteomics approach, we found significant changes in the relative abundance of 387 proteins in myoblasts versus differentiated myotubes, reflecting the drastic phenotypic conversion of these cells during myogenesis. Interestingly, EPS of differentiated myotubes to induce Z-disc assembly and maturation resulted in increased levels of proteins involved in ATP synthesis, presumably to fulfill the higher energy demand of contracting myotubes. Because an important role of the Z-disc for signal integration and transduction was recently suggested, its precise phosphorylation landscape further warranted in-depth analysis. We therefore established, by global phosphoproteomics of EPS-treated contracting myotubes, a comprehensive site-resolved protein phosphorylation map of the Z-disc and found that it is a phosphorylation hotspot in skeletal myocytes, underscoring its functions in signaling and disease-related processes. In an illustrative fashion, we analyzed the actin-binding multiadaptor protein filamin C (FLNc), which is essential for Z-disc assembly and maintenance, and found that PKCα phosphorylation at distinct serine residues in its hinge 2 region prevents its cleavage at an adjacent tyrosine residue by calpain 1. Fluorescence recovery after photobleaching experiments indicated that this phosphorylation modulates FLNc dynamics. Moreover, FLNc lacking the cleaved Ig-like domain 24 exhibited remarkably fast kinetics and exceedingly high mobility. Our data set provides research community resource for further identification of kinase-mediated changes in myofibrillar protein interactions, kinetics, and mobility that will greatly advance our understanding of Z-disc dynamics and signaling.
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Affiliation(s)
- Lena Reimann
- From the ‡Department of Biochemistry and Functional Proteomics, Institute of Biology II, Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany
| | - Heike Wiese
- From the ‡Department of Biochemistry and Functional Proteomics, Institute of Biology II, Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany
| | - Yvonne Leber
- ¶Department of Molecular Cell Biology, Institute for Cell Biology, University of Bonn, 53121 Bonn, Germany
| | - Anja N Schwäble
- From the ‡Department of Biochemistry and Functional Proteomics, Institute of Biology II, Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany
| | - Anna L Fricke
- From the ‡Department of Biochemistry and Functional Proteomics, Institute of Biology II, Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany
| | - Anne Rohland
- ¶Department of Molecular Cell Biology, Institute for Cell Biology, University of Bonn, 53121 Bonn, Germany
| | - Bettina Knapp
- From the ‡Department of Biochemistry and Functional Proteomics, Institute of Biology II, Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany
| | - Christian D Peikert
- From the ‡Department of Biochemistry and Functional Proteomics, Institute of Biology II, Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany
| | - Friedel Drepper
- From the ‡Department of Biochemistry and Functional Proteomics, Institute of Biology II, Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany
| | - Peter F M van der Ven
- ¶Department of Molecular Cell Biology, Institute for Cell Biology, University of Bonn, 53121 Bonn, Germany
| | - Gerald Radziwill
- From the ‡Department of Biochemistry and Functional Proteomics, Institute of Biology II, Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany.,§BIOSS Centre for Biological Signalling Studies, University of Freiburg
| | - Dieter O Fürst
- ¶Department of Molecular Cell Biology, Institute for Cell Biology, University of Bonn, 53121 Bonn, Germany
| | - Bettina Warscheid
- From the ‡Department of Biochemistry and Functional Proteomics, Institute of Biology II, Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany; .,§BIOSS Centre for Biological Signalling Studies, University of Freiburg
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Hernandez DA, Bennett CM, Dunina-Barkovskaya L, Wedig T, Capetanaki Y, Herrmann H, Conover GM. Nebulette is a powerful cytolinker organizing desmin and actin in mouse hearts. Mol Biol Cell 2016; 27:3869-3882. [PMID: 27733623 PMCID: PMC5170609 DOI: 10.1091/mbc.e16-04-0237] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2016] [Revised: 08/31/2016] [Accepted: 10/05/2016] [Indexed: 12/11/2022] Open
Abstract
Nebulette physically links desmin to sarcomeric actin in hearts. An intact desmin network is required for nebulette to function as major actin-binding protein in sarcomeres. This study provides biochemical evidence that the desmin–nebulette complex is involved in filament-forming desminopathy. In the hearts of patients bearing nebulette mutations, a severe general disorganization in cardiomyocytes of the extrasarcomeric desmin intermediate filament system is frequently observed. However, the molecular and functional relationship between the desmin cytoskeleton and nebulette-containing sarcomeres is still unclear. Here we report a high-affinity in vitro interaction between nebulette and desmin filaments. A major interaction site has been mapped to the desmin α-helical rod domain, indicating that the filament core is directly involved in the binding of nebulette. The disease-mutant desmin variants E245D and T453I exhibited increased binding affinity for nebulette, delayed filament assembly kinetics, and caused significant weakening of networks. In isolated chick cardiomyocytes and sections from canine heart, we revealed by ground-state depletion and confocal microscopies that module 5 of nebulette extends outward from Z-disk–associated desmin filaments toward the center of the sarcomere. Accordingly, in the myocardium of Des−/− mice, elevated levels of cardiac actin correlated with alterations in the distribution of nebulette. Our data suggest that a well-organized desmin network is required to accommodate an optimal conformation of nebulette on sarcomeres to bind and recruit cardiac α-actin. Hence we propose that nebulette acts in synergy with nebulin to reinforce and temporally fine-tune striated muscle relaxation–contraction cycles.
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Affiliation(s)
- Daniel A Hernandez
- Department of Biochemistry & Biophysics, Texas A&M University, College Station, TX 77843-3474
| | - Christina M Bennett
- Department of Biochemistry & Biophysics, Texas A&M University, College Station, TX 77843-3474
| | | | - Tatjana Wedig
- Division of Molecular Genetics, German Cancer Research Center (DKFZ), D-69120 Heidelberg, Germany
| | - Yassemi Capetanaki
- Center of Basic Research, Biomedical Research Foundation Academy of Athens, Athens 11527, Greece
| | - Harald Herrmann
- Division of Molecular Genetics, German Cancer Research Center (DKFZ), D-69120 Heidelberg, Germany.,Institute of Neuropathology, University Hospital Erlangen, D-91054 Erlangen, Germany
| | - Gloria M Conover
- Department of Biochemistry & Biophysics, Texas A&M University, College Station, TX 77843-3474
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Thin filament length in the cardiac sarcomere varies with sarcomere length but is independent of titin and nebulin. J Mol Cell Cardiol 2016; 97:286-94. [PMID: 27139341 DOI: 10.1016/j.yjmcc.2016.04.013] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/24/2015] [Revised: 04/11/2016] [Accepted: 04/22/2016] [Indexed: 01/08/2023]
Abstract
Thin filament length (TFL) is an important determinant of the force-sarcomere length (SL) relation of cardiac muscle. However, the various mechanisms that control TFL are not well understood. Here we tested the previously proposed hypothesis that the actin-binding protein nebulin contributes to TFL regulation in the heart by using a cardiac-specific nebulin cKO mouse model (αMHC Cre Neb cKO). Atrial myocytes were studied because nebulin expression has been reported to be most prominent in this cell type. TFL was measured in right and left atrial myocytes using deconvolution optical microscopy and staining for filamentous actin with phalloidin and for the thin filament pointed-end with an antibody to the capping protein Tropomodulin-1 (Tmod1). Results showed that TFLs in Neb cKO and littermate control mice were not different. Thus, deletion of nebulin in the heart does not alter TFL. However, TFL was found to be ~0.05μm longer in the right than in the left atrium and Tmod1 expression was increased in the right atrium. We also tested the hypothesis that the length of titin's spring region is a factor controlling TFL by studying the Rbm20(ΔRRM) mouse which expresses titins that are ~500kDa (heterozygous mice) and ~1000kDa (homozygous mice) longer than in control mice. Results revealed that TFL was not different in Rbm20(ΔRRM) mice. An unexpected finding in all genotypes studied was that TFL increased as sarcomeres were stretched (~0.1μm per 0.35μm of SL increase). This apparent increase in TFL reached a maximum at a SL of ~3.0μm where TFL was ~1.05μm. The SL dependence of TFL was independent of chemical fixation or the presence of cardiac myosin-binding protein C (cMyBP-C). In summary, we found that in cardiac myocytes TFL varies with SL in a manner that is independent of the size of titin or the presence of nebulin.
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Perrot A, Tomasov P, Villard E, Faludi R, Melacini P, Lossie J, Lohmann N, Richard P, De Bortoli M, Angelini A, Varga-Szemes A, Sperling SR, Simor T, Veselka J, Özcelik C, Charron P. Mutations in NEBL encoding the cardiac Z-disk protein nebulette are associated with various cardiomyopathies. Arch Med Sci 2016; 12:263-78. [PMID: 27186169 PMCID: PMC4848357 DOI: 10.5114/aoms.2016.59250] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/04/2015] [Accepted: 04/29/2015] [Indexed: 11/17/2022] Open
Abstract
INTRODUCTION Transgenic mice overexpressing mutated NEBL, encoding the cardiac-specific Z-disk protein nebulette, develop severe cardiac phenotypes. Since cardiomyopathies are commonly familial and because mutations in a single gene may result in variable phenotypes, we tested the hypothesis that NEBL mutations are associated with cardiomyopathy. MATERIAL AND METHODS We analyzed 389 patients, including cohorts of patients with dilated cardiomyopathy (DCM), hypertrophic cardiomyopathy (HCM), and left ventricular non-compaction cardiomyopathy (LVNC). The 28 coding exons of the NEBL gene were sequenced. Further bioinformatic analysis was used to distinguish variants. RESULTS In total, we identified six very rare heterozygous missense mutations in NEBL in 7 different patients (frequency 1.8%) in highly conserved codons. The mutations were not detectable in 320 Caucasian sex-matched unrelated individuals without cardiomyopathy and 192 Caucasian sex-matched blood donors without heart disease. Known cardiomyopathy genes were excluded in these patients. The mutations p.H171R and p.I652L were found in 2 HCM patients. Further, p.Q581R and p.S747L were detected in 2 DCM patients, while the mutation p.A175T was identified independently in two unrelated patients with DCM. One LVNC patient carried the mutation p.P916L. All HCM and DCM related mutations were located in the nebulin-like repeats, domains responsible for actin binding. Interestingly, the mutation associated with LVNC was located in the C-terminal serine-rich linker region. CONCLUSIONS Our data suggest that NEBL mutations may cause various cardiomyopathies. We herein describe the first NEBL mutations in HCM and LVNC. Our findings underline the notion that the cardiomyopathies are true allelic diseases.
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Affiliation(s)
- Andreas Perrot
- Charité-Universitätsmedizin Berlin, Cardiovascular Genetics, Experimental and Clinical Research Center, Berlin, Germany
| | - Pavol Tomasov
- Department of Cardiology, 2 Medical School, Charles University, University Hospital Motol, Prague, Czech Republic
| | - Eric Villard
- AP-HP, Département de Génétique et Département de Cardiologie et Inserm UMR 1166, Hopital Pitié-Salpêtrière, Paris, France
| | - Reka Faludi
- Heart Institute, Faculty of Medicine, University of Pécs, Pécs, Hungary
| | - Paola Melacini
- Department of Cardiac, Thoracic and Vascular Sciences, University of Padova, Padova, Italy
| | - Janine Lossie
- Charité-Universitätsmedizin Berlin, Cardiovascular Genetics, Experimental and Clinical Research Center, Berlin, Germany
| | - Nadine Lohmann
- Charité-Universitätsmedizin Berlin, Cardiovascular Genetics, Experimental and Clinical Research Center, Berlin, Germany
| | - Pascale Richard
- Assistance Publique-Hôpitaux de Paris, Groupe Hospitalier Pitié-Salpêtrière, UF Cardiogénétique et Myogénétique, Service de Biochimie Métabolique, Paris, France
| | - Marzia De Bortoli
- Department of Cardiac, Thoracic and Vascular Sciences, University of Padova, Padova, Italy
| | - Annalisa Angelini
- Department of Cardiac, Thoracic and Vascular Sciences, University of Padova, Padova, Italy
| | - Akos Varga-Szemes
- Heart Institute, Faculty of Medicine, University of Pécs, Pécs, Hungary
| | - Silke R. Sperling
- Charité-Universitätsmedizin Berlin, Cardiovascular Genetics, Experimental and Clinical Research Center, Berlin, Germany
| | - Tamás Simor
- Heart Institute, Faculty of Medicine, University of Pécs, Pécs, Hungary
| | - Josef Veselka
- Department of Cardiology, 2 Medical School, Charles University, University Hospital Motol, Prague, Czech Republic
| | - Cemil Özcelik
- Charité-Universitätsmedizin Berlin, Cardiovascular Genetics, Experimental and Clinical Research Center, Berlin, Germany
- Knappschaftskrankenhaus Recklinghausen, Medizinischen Klinik I Kardiologie, Gastroenterologie und Diabetologie, Recklinghausen, Germany
| | - Philippe Charron
- AP-HP, Département de Génétique et Département de Cardiologie et Inserm UMR 1166, Hopital Pitié-Salpêtrière, Paris, France
- Université de Versailles Saint Quentin en Yvelines, Versailles, France
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28
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Long PA, Larsen BT, Evans JM, Olson TM. Exome Sequencing Identifies Pathogenic and Modifier Mutations in a Child With Sporadic Dilated Cardiomyopathy. J Am Heart Assoc 2015; 4:JAHA.115.002443. [PMID: 26656454 PMCID: PMC4845292 DOI: 10.1161/jaha.115.002443] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Background Idiopathic dilated cardiomyopathy (DCM) is typically diagnosed in adulthood, yet familial cases exhibit variable age‐dependent penetrance and a subset of patients develop sporadic DCM in childhood. We sought to discover the molecular basis of sporadic DCM in an 11‐year‐old female with severe heart failure necessitating cardiac transplantation. Methods and Results Parental echocardiograms excluded asymptomatic DCM. Whole exome sequencing was performed on the family trio and filtered for rare, deleterious, recessive, and de novo variants. Of the 8 candidate genes identified, only 2 had a role in cardiac physiology. A de novo missense mutation in TNNT2 was identified, previously reported and functionally validated in familial DCM with markedly variable penetrance. Additionally, recessive compound heterozygous truncating mutations were identified in XIRP2, a member of the ancient Xin gene family, which governs intercalated disc (ICD) maturation. Histomorphological analysis of explanted heart tissue revealed misregistration, mislocalization, and shortening of ICDs, findings similar to Xirp2−/− mice. Conclusions The synergistic effects of TNNT2 and XIRP2 mutations, resulting in perturbed sarcomeric force generation and transmission, respectively, would account for an early‐onset heart failure phenotype. Whereas the importance of Xin proteins in cardiac development has been well established in animal models, this study implicates XIRP2 as a novel modifier gene in the pathogenesis of DCM.
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Affiliation(s)
- Pamela A Long
- Mayo Graduate School, Molecular Pharmacology and Experimental Therapeutics Track, Mayo Clinic, Rochester, MN (P.A.L.) Cardiovascular Genetics Research Laboratory, Mayo Clinic, Rochester, MN (P.A.L., T.M.O.)
| | - Brandon T Larsen
- Department of Pathology, University of Arizona Medical Center, Tucson, AZ (B.T.L.)
| | - Jared M Evans
- Division of Biomedical Statistics and Informatics, Department of Health Sciences Research, Mayo Clinic, Rochester, MN (J.M.E.)
| | - Timothy M Olson
- Cardiovascular Genetics Research Laboratory, Mayo Clinic, Rochester, MN (P.A.L., T.M.O.) Division of Pediatric Cardiology, Department of Pediatric and Adolescent Medicine, Mayo Clinic, Rochester, MN (T.M.O.) Division of Cardiovascular Diseases, Department of Internal Medicine, Mayo Clinic, Rochester, MN (T.M.O.)
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Abstract
The members of the nebulin protein family, including nebulin, nebulette, LASP-1, LASP-2, and N-RAP, contain various numbers of nebulin repeats and bind to actin, but are otherwise heterogeneous with regard to size, expression pattern, and function. This review focuses on the roles of nebulin family members in the heart. Nebulin is the largest member predominantly expressed in skeletal muscle, where it stretches along the thin filament. In heart, nebulin is detectable only at low levels and its absence has no apparent effects. Nebulette is similar in structure to the nebulin C-terminal Z-line region and specifically expressed in heart. Nebulette gene mutations have been identified in dilated cardiomyopathy patients and transgenic mice overexpressing nebulette mutants partially recapitulate the human pathology. In contrast, nebulette knockout mice show no functional phenotype, but exhibit Z-line widening. LASP-2 is an isoform of nebulette expressed in multiple tissues, including the heart. It is present in the Z-line and intercalated disc and able to bind and cross-link filamentous actin. LASP-1 is similar in structure to LASP-2, but expressed only in non-muscle tissue. N-RAP is present in myofibril precursors during myofibrillogenesis and thought to be involved in myofibril assembly, while it is localized at the intercalated disc in adult heart. Additional in vivo models are required to provide further insights into the functions of nebulin family members in the heart.
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Affiliation(s)
- Marie-Louise Bang
- Institute of Genetic and Biomedical Research, UOS Milan, National Research Council
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30
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Mlih M, Host L, Martin S, Niederhoffer N, Monassier L, Terrand J, Messaddeq N, Radke M, Gotthardt M, Bruban V, Kober F, Bernard M, Canet-Soulas E, Abt-Jijon F, Boucher P, Matz RL. The Src homology and collagen A (ShcA) adaptor protein is required for the spatial organization of the costamere/Z-disk network during heart development. J Biol Chem 2014; 290:2419-30. [PMID: 25488665 DOI: 10.1074/jbc.m114.597377] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Src homology and collagen A (ShcA) is an adaptor protein that binds to tyrosine kinase receptors. Its germ line deletion is embryonic lethal with abnormal cardiovascular system formation, and its role in cardiovascular development is unknown. To investigate its functional role in cardiovascular development in mice, ShcA was deleted in cardiomyocytes and vascular smooth muscle cells by crossing ShcA flox mice with SM22a-Cre transgenic mice. Conditional mutant mice developed signs of severe dilated cardiomyopathy, myocardial infarctions, and premature death. No evidence of a vascular contribution to the phenotype was observed. Histological analysis of the heart revealed aberrant sarcomeric Z-disk and M-band structures, and misalignments of T-tubules with Z-disks. We find that not only the ErbB3/Neuregulin signaling pathway but also the baroreceptor reflex response, which have been functionally associated, are altered in the mutant mice. We further demonstrate that ShcA interacts with Caveolin-1 and the costameric protein plasma membrane Ca(2+)/calmodulin-dependent ATPase (PMCA), and that its deletion leads to abnormal dystrophin signaling. Collectively, these results demonstrate that ShcA interacts with crucial proteins and pathways that link Z-disk and costamere.
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Affiliation(s)
- Mohamed Mlih
- From the CNRS, UMR 7213, University of Strasbourg, 67401 Illkirch, France
| | - Lionel Host
- From the CNRS, UMR 7213, University of Strasbourg, 67401 Illkirch, France
| | - Sophie Martin
- From the CNRS, UMR 7213, University of Strasbourg, 67401 Illkirch, France
| | - Nathalie Niederhoffer
- the Laboratory of Neurobiology and Cardiovascular Pharmacology Department, EA 7296, Federation of Translational Medicine, University of Strasbourg, 67000 Strasbourg, France
| | - Laurent Monassier
- the Laboratory of Neurobiology and Cardiovascular Pharmacology Department, EA 7296, Federation of Translational Medicine, University of Strasbourg, 67000 Strasbourg, France
| | - Jérôme Terrand
- From the CNRS, UMR 7213, University of Strasbourg, 67401 Illkirch, France
| | - Nadia Messaddeq
- the IGBMC, INSERM U964 CNRS UMR 7104, University of Strasbourg, 67401 Illkirch, France
| | - Michael Radke
- the Neuromuscular and Cardiovascular Cell Biology, Max-Delbrück-Center for Molecular Medicine, 13125 Berlin, Germany, the DZHK, German Centre for Cardiovascular Research, partner site, 13347 Berlin, Germany
| | - Michael Gotthardt
- the Neuromuscular and Cardiovascular Cell Biology, Max-Delbrück-Center for Molecular Medicine, 13125 Berlin, Germany, the DZHK, German Centre for Cardiovascular Research, partner site, 13347 Berlin, Germany
| | - Véronique Bruban
- From the CNRS, UMR 7213, University of Strasbourg, 67401 Illkirch, France
| | - Frank Kober
- the CRMBM, CNRS, UMR 7339, University of Aix-Marseille, 13385 Marseille, France, and
| | - Monique Bernard
- the CRMBM, CNRS, UMR 7339, University of Aix-Marseille, 13385 Marseille, France, and
| | - Emmanuelle Canet-Soulas
- the CREATIS-LRMN, CNRS, UMR 5220, U630 INSERM, 69621 Villeurbanne, Lyon-1 University, Lyon, France
| | | | - Philippe Boucher
- From the CNRS, UMR 7213, University of Strasbourg, 67401 Illkirch, France,
| | - Rachel L Matz
- From the CNRS, UMR 7213, University of Strasbourg, 67401 Illkirch, France,
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Aino M, Nishida E, Fujieda Y, Orimoto A, Mitani A, Noguchi T, Makino H, Murakami S, Umezawa A, Yoneda T, Saito M. Isolation and characterization of the human immature osteoblast culture system from the alveolar bones of aged donors for bone regeneration therapy. Expert Opin Biol Ther 2014; 14:1731-44. [PMID: 25241883 DOI: 10.1517/14712598.2014.960387] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
BACKGROUND Establishment of human osteoblast cultures that retain bone-forming capacity is one of the prerequisites for successful bone regeneration therapy. Because osteoblasts harvested from adults exhibit limited growth, the use of immature osteoblasts that can expand ex vivo should greatly facilitate bone regeneration therapy. In this study, we developed immature human osteoblasts isolated from aged alveolar bone (HAOBs). METHODS HAOBs obtained after the collagenase digestion of alveolar bones from elderly donors. Then, we assessed osteogenic ability of HAOB after treatment with recombinant human bone morphogenic protein-2 or transplantation into immunodeficient mice. In addition, we performed global gene expression analysis to identify functional marker for HAOB. RESULTS HAOBs, which can differentiate into osteoblasts and have a robust bone-forming ability, were successfully extracted from donors who were > 60 years of age. We found that the HAOBs exhibited a higher osteogenic ability compared with those of human mesenchymal stem cells and highly expressed NEBULETTE (NEBL) with osteogenic abilities. CONCLUSIONS HAOBs have properties similar to those of human immature osteoblasts and appear to be a novel material for cell-based bone regeneration therapy. Additionally, the expression level of NEBL may serve as a marker for the osteogenic ability of these cells.
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Affiliation(s)
- Makoto Aino
- Aichi-gakuin University, School of Dentistry, Department of Periodontology , Nagoya, Aichi , Japan
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Moylan JS, Smith JD, Wolf Horrell EM, McLean JB, Deevska GM, Bonnell MR, Nikolova-Karakashian MN, Reid MB. Neutral sphingomyelinase-3 mediates TNF-stimulated oxidant activity in skeletal muscle. Redox Biol 2014; 2:910-20. [PMID: 25180167 PMCID: PMC4143815 DOI: 10.1016/j.redox.2014.07.006] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2014] [Accepted: 07/22/2014] [Indexed: 11/26/2022] Open
Abstract
Aims Sphingolipid and oxidant signaling affect glucose uptake, atrophy, and force production of skeletal muscle similarly and both are stimulated by tumor necrosis factor (TNF), suggesting a connection between systems. Sphingolipid signaling is initiated by neutral sphingomyelinase (nSMase), a family of agonist-activated effector enzymes. Northern blot analyses suggest that nSMase3 may be a striated muscle-specific nSMase. The present study tested the hypothesis that nSMase3 protein is expressed in skeletal muscle and functions to regulate TNF-stimulated oxidant production. Results We demonstrate constitutive nSMase activity in skeletal muscles of healthy mice and humans and in differentiated C2C12 myotubes. nSMase3 (Smpd4 gene) mRNA is highly expressed in muscle. An nSMase3 protein doublet (88 and 85 kD) is derived from alternative mRNA splicing of exon 11. The proteins partition differently. The full-length 88 kD isoform (nSMase3a) fractionates with membrane proteins that are resistant to detergent extraction; the 85 kD isoform lacking exon 11 (nSMase3b) is more readily extracted and fractionates with detergent soluble membrane proteins; neither variant is detected in the cytosol. By immunofluorescence microscopy, nSMase3 resides in both internal and sarcolemmal membranes. Finally, myotube nSMase activity and cytosolic oxidant activity are stimulated by TNF. Both if these responses are inhibited by nSMase3 knockdown. Innovation These findings identify nSMase3 as an intermediate that links TNF receptor activation, sphingolipid signaling, and skeletal muscle oxidant production. Conclusion Our data show that nSMase3 acts as a signaling nSMase in skeletal muscle that is essential for TNF-stimulated oxidant activity. First measures of endogenous nSMase3 protein in muscle. Detection of nSMase3 splice variant proteins. Identification of a functional role for nSMase3 in redox signaling. Identification of an intermediate in TNF/redox signaling.
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Affiliation(s)
- Jennifer S Moylan
- Department of Physiology, University of Kentucky, Lexington, KY, USA ; Center for Muscle Biology, University of Kentucky, Lexington, KY, USA
| | - Jeffrey D Smith
- Department of Physiology, University of Kentucky, Lexington, KY, USA ; Center for Muscle Biology, University of Kentucky, Lexington, KY, USA
| | - Erin M Wolf Horrell
- Department of Physiology, University of Kentucky, Lexington, KY, USA ; Center for Muscle Biology, University of Kentucky, Lexington, KY, USA ; Markey Cancer Center, University of Kentucky, Lexington, KY, USA
| | - Julie B McLean
- Department of Physiology, University of Kentucky, Lexington, KY, USA ; Center for Muscle Biology, University of Kentucky, Lexington, KY, USA
| | - Gergana M Deevska
- Department of Physiology, University of Kentucky, Lexington, KY, USA
| | - Mark R Bonnell
- Department of Surgery, University of Kentucky, Lexington, KY, USA
| | | | - Michael B Reid
- Department of Physiology, University of Kentucky, Lexington, KY, USA ; Center for Muscle Biology, University of Kentucky, Lexington, KY, USA
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Sequeira V, Nijenkamp LLAM, Regan JA, van der Velden J. The physiological role of cardiac cytoskeleton and its alterations in heart failure. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1838:700-22. [PMID: 23860255 DOI: 10.1016/j.bbamem.2013.07.011] [Citation(s) in RCA: 120] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2013] [Revised: 07/01/2013] [Accepted: 07/08/2013] [Indexed: 12/11/2022]
Abstract
Cardiac muscle cells are equipped with specialized biochemical machineries for the rapid generation of force and movement central to the work generated by the heart. During each heart beat cardiac muscle cells perceive and experience changes in length and load, which reflect one of the fundamental principles of physiology known as the Frank-Starling law of the heart. Cardiac muscle cells are unique mechanical stretch sensors that allow the heart to increase cardiac output, and adjust it to new physiological and pathological situations. In the present review we discuss the mechano-sensory role of the cytoskeletal proteins with respect to their tight interaction with the sarcolemma and extracellular matrix. The role of contractile thick and thin filament proteins, the elastic protein titin, and their anchorage at the Z-disc and M-band, with associated proteins are reviewed in physiologic and pathologic conditions leading to heart failure. This article is part of a Special Issue entitled: Reciprocal influences between cell cytoskeleton and membrane channels, receptors and transporters. Guest Editor: Jean Claude Hervé
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Affiliation(s)
- Vasco Sequeira
- Laboratory for Physiology, Institute for Cardiovascular Research, VU University Medical Center, van der Boechorststraat 7, 1081 BT Amsterdam, The Netherlands
| | - Louise L A M Nijenkamp
- Laboratory for Physiology, Institute for Cardiovascular Research, VU University Medical Center, van der Boechorststraat 7, 1081 BT Amsterdam, The Netherlands
| | - Jessica A Regan
- Laboratory for Physiology, Institute for Cardiovascular Research, VU University Medical Center, van der Boechorststraat 7, 1081 BT Amsterdam, The Netherlands; Department of Physiology, Molecular Cardiovascular Research Program, Sarver Heart Center, University of Arizona, Tucson, AZ 85724, USA
| | - Jolanda van der Velden
- Laboratory for Physiology, Institute for Cardiovascular Research, VU University Medical Center, van der Boechorststraat 7, 1081 BT Amsterdam, The Netherlands; ICIN-Netherlands Heart Institute, The Netherlands.
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Bliss KT, Chu M, Jones-Weinert CM, Gregorio CC. Investigating lasp-2 in cell adhesion: new binding partners and roles in motility. Mol Biol Cell 2013; 24:995-1006. [PMID: 23389630 PMCID: PMC3608507 DOI: 10.1091/mbc.e12-10-0723] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Focal adhesions are intricate protein complexes that facilitate cell attachment, migration, and cellular communication. Lasp-2 (LIM-nebulette), a member of the nebulin family of actin-binding proteins, is a newly identified component of these complexes. To gain further insights into the functional role of lasp-2, we identified two additional binding partners of lasp-2: the integral focal adhesion proteins vinculin and paxillin. Of interest, the interaction of lasp-2 with its binding partners vinculin and paxillin is significantly reduced in the presence of lasp-1, another nebulin family member. The presence of lasp-2 appears to enhance the interaction of vinculin and paxillin with each other; however, as with the interaction of lasp-2 with vinculin or paxillin, this effect is greatly diminished in the presence of excess lasp-1. This suggests that the interplay between lasp-2 and lasp-1 could be an adhesion regulatory mechanism. Lasp-2's potential role in metastasis is revealed, as overexpression of lasp-2 in either SW620 or PC-3B1 cells-metastatic cancer cell lines-increases cell migration but impedes cell invasion, suggesting that the enhanced interaction of vinculin and paxillin may functionally destabilize focal adhesion composition. Taken together, these data suggest that lasp-2 has an important role in coordinating and regulating the composition and dynamics of focal adhesions.
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Affiliation(s)
- Katherine T Bliss
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ 85724, USA
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Gokhin DS, Fowler VM. A two-segment model for thin filament architecture in skeletal muscle. Nat Rev Mol Cell Biol 2013; 14:113-9. [PMID: 23299957 DOI: 10.1038/nrm3510] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Correct specification of myofilament length is essential for efficient skeletal muscle contraction. The length of thin actin filaments can be explained by a novel 'two-segment' model, wherein the thin filaments consist of two concatenated segments, which are of either constant or variable length. This is in contrast to the classic 'nebulin ruler' model, which postulates that thin filaments are uniform structures, the lengths of which are dictated by nebulin. The two-segment model implicates position-specific microregulation of actin dynamics as a general principle underlying actin filament length and stability.
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Affiliation(s)
- David S Gokhin
- Department of Cell Biology, The Scripps Research Institute, La Jolla, California 92037, USA
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Ottenheijm CAC, Granzier H, Labeit S. The sarcomeric protein nebulin: another multifunctional giant in charge of muscle strength optimization. Front Physiol 2012; 3:37. [PMID: 22375125 PMCID: PMC3286824 DOI: 10.3389/fphys.2012.00037] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2012] [Accepted: 02/09/2012] [Indexed: 12/01/2022] Open
Abstract
The sliding filament model of the sarcomere was developed more than half a century ago. This model, consisting only of thin and thick filaments, has been successful in explaining many, but not all, features of skeletal muscle. Work during the 1980s revealed the existence of two additional filaments: the giant filamentous proteins titin and nebulin. Whereas the role of titin rapidly progressed, nebulin’s role in muscle structure and function remained long nebulous. An important feature of muscle structure and function that has remained relatively obscure concerns the mechanisms that are involved in regulating thin filament length. Filament length is an important aspect of muscle function as force production is proportional to the amount of overlap between thick and thin filaments. Recent advances, due in part to the generation of nebulin KO models, reveal that nebulin plays an important role in the regulation of thin filament length, most likely by stabilizing F-actin assemblies. Another structural feature of skeletal muscle that has been incompletely understood concerns the mechanisms involved in maintaining Z-disk structure and the regular lateral alignment of adjacent sarcomeres during contraction. Recent studies indicate that nebulin is part of a protein complex that mechanically links adjacent myofibrils. In addition to these structural roles in support of myofibrillar force generation, nebulin has been also shown to regulate directly muscle contraction at the level of individual crossbridges: cycling kinetics and the calcium sensitivity of force producing crossbridges is enhanced in the presence of nebulin. Thus, these recent data all point to nebulin being important for muscle force optimization. Consequently, muscle weakness as the lead symptom develops in the case of patients with nemaline myopathy that have mutations in the nebulin gene. Here, we discuss these important novel insights into the role of nebulin in skeletal muscle function.
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Affiliation(s)
- Coen A C Ottenheijm
- Department of Physiology, Institute for Cardiovascular Research, VU University Medical Center Amsterdam, Netherlands
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Li A, Ponten F, dos Remedios CG. The interactome of LIM domain proteins: The contributions of LIM domain proteins to heart failure and heart development. Proteomics 2012; 12:203-25. [DOI: 10.1002/pmic.201100492] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2011] [Revised: 11/07/2011] [Accepted: 11/08/2011] [Indexed: 12/22/2022]
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Dwyer J, Iskratsch T, Ehler E. Actin in striated muscle: recent insights into assembly and maintenance. Biophys Rev 2011; 4:17-25. [PMID: 28510000 DOI: 10.1007/s12551-011-0062-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2011] [Accepted: 11/17/2011] [Indexed: 01/28/2023] Open
Abstract
Striated muscle cells are characterised by a para-crystalline arrangement of their contractile proteins actin and myosin in sarcomeres, the basic unit of the myofibrils. A multitude of proteins is required to build and maintain the structure of this regular arrangement as well as to ensure regulation of contraction and to respond to alterations in demand. This review focuses on the actin filaments (also called thin filaments) of the sarcomere and will discuss how they are assembled during myofibrillogenesis and in hypertrophy and how their integrity is maintained in the working myocardium.
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Affiliation(s)
- Joseph Dwyer
- The Randall Division of Cell and Molecular Biophysics and The Cardiovascular Division, King's College London, British Heart Foundation Centre of Research Excellence, New Hunt's House, Guy's Campus, London, SE1 1UL, UK
| | - Thomas Iskratsch
- The Randall Division of Cell and Molecular Biophysics and The Cardiovascular Division, King's College London, British Heart Foundation Centre of Research Excellence, New Hunt's House, Guy's Campus, London, SE1 1UL, UK.,Biological Sciences, Columbia University, 713 Fairchild Center, New York, NY, 10027, USA
| | - Elisabeth Ehler
- The Randall Division of Cell and Molecular Biophysics and The Cardiovascular Division, King's College London, British Heart Foundation Centre of Research Excellence, New Hunt's House, Guy's Campus, London, SE1 1UL, UK.
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Lempiäinen H, Müller A, Brasa S, Teo SS, Roloff TC, Morawiec L, Zamurovic N, Vicart A, Funhoff E, Couttet P, Schübeler D, Grenet O, Marlowe J, Moggs J, Terranova R. Phenobarbital mediates an epigenetic switch at the constitutive androstane receptor (CAR) target gene Cyp2b10 in the liver of B6C3F1 mice. PLoS One 2011; 6:e18216. [PMID: 21455306 PMCID: PMC3063791 DOI: 10.1371/journal.pone.0018216] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2010] [Accepted: 02/28/2011] [Indexed: 11/19/2022] Open
Abstract
Evidence suggests that epigenetic perturbations are involved in the adverse effects associated with some drugs and toxicants, including certain classes of non-genotoxic carcinogens. Such epigenetic changes (altered DNA methylation and covalent histone modifications) may take place at the earliest stages of carcinogenesis and their identification holds great promise for biomedical research. Here, we evaluate the sensitivity and specificity of genome-wide epigenomic and transcriptomic profiling in phenobarbital (PB)-treated B6C3F1 mice, a well-characterized rodent model of non-genotoxic liver carcinogenesis. Methylated DNA Immunoprecipitation (MeDIP)-coupled microarray profiling of 17,967 promoter regions and 4,566 intergenic CpG islands was combined with genome-wide mRNA expression profiling to identify liver tissue-specific PB-mediated DNA methylation and transcriptional alterations. Only a limited number of significant anti-correlations were observed between PB-induced transcriptional and promoter-based DNA methylation perturbations. However, the constitutive androstane receptor (CAR) target gene Cyp2b10 was found to be concomitantly hypomethylated and transcriptionally activated in a liver tissue-specific manner following PB treatment. Furthermore, analysis of active and repressive histone modifications using chromatin immunoprecipitation revealed a strong PB-mediated epigenetic switch at the Cyp2b10 promoter. Our data reveal that PB-induced transcriptional perturbations are not generally associated with broad changes in the DNA methylation status at proximal promoters and suggest that the drug-inducible CAR pathway regulates an epigenetic switch from repressive to active chromatin at the target gene Cyp2b10. This study demonstrates the utility of integrated epigenomic and transcriptomic profiling for elucidating early mechanisms and biomarkers of non-genotoxic carcinogenesis.
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Affiliation(s)
- Harri Lempiäinen
- Investigative Toxicology, Preclinical Safety, Translational Sciences, Novartis Institutes for Biomedical Research, Basel, Switzerland
| | - Arne Müller
- Investigative Toxicology, Preclinical Safety, Translational Sciences, Novartis Institutes for Biomedical Research, Basel, Switzerland
| | - Sarah Brasa
- Investigative Toxicology, Preclinical Safety, Translational Sciences, Novartis Institutes for Biomedical Research, Basel, Switzerland
| | - Soon-Siong Teo
- Investigative Toxicology, Preclinical Safety, Translational Sciences, Novartis Institutes for Biomedical Research, Basel, Switzerland
| | | | - Laurent Morawiec
- Investigative Toxicology, Preclinical Safety, Translational Sciences, Novartis Institutes for Biomedical Research, Basel, Switzerland
| | - Natasa Zamurovic
- Investigative Toxicology, Preclinical Safety, Translational Sciences, Novartis Institutes for Biomedical Research, Basel, Switzerland
| | - Axel Vicart
- Investigative Toxicology, Preclinical Safety, Translational Sciences, Novartis Institutes for Biomedical Research, Basel, Switzerland
| | - Enrico Funhoff
- Investigative Toxicology, Preclinical Safety, Translational Sciences, Novartis Institutes for Biomedical Research, Basel, Switzerland
| | - Philippe Couttet
- Investigative Toxicology, Preclinical Safety, Translational Sciences, Novartis Institutes for Biomedical Research, Basel, Switzerland
| | - Dirk Schübeler
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland
| | - Olivier Grenet
- Investigative Toxicology, Preclinical Safety, Translational Sciences, Novartis Institutes for Biomedical Research, Basel, Switzerland
| | - Jennifer Marlowe
- Investigative Toxicology, Preclinical Safety, Translational Sciences, Novartis Institutes for Biomedical Research, Basel, Switzerland
| | - Jonathan Moggs
- Investigative Toxicology, Preclinical Safety, Translational Sciences, Novartis Institutes for Biomedical Research, Basel, Switzerland
| | - Rémi Terranova
- Investigative Toxicology, Preclinical Safety, Translational Sciences, Novartis Institutes for Biomedical Research, Basel, Switzerland
- * E-mail:
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Labeit S, Ottenheijm CAC, Granzier H. Nebulin, a major player in muscle health and disease. FASEB J 2010; 25:822-9. [PMID: 21115852 DOI: 10.1096/fj.10-157412] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Nebulin is a giant 600- to 900-kDa filamentous protein that is an integral component of the skeletal muscle thin filament. Its functions have remained largely nebulous because of its large size and the difficulty in extracting nebulin in a native state from muscle. Recent improvements in the field, especially the development of knockout mouse models deficient in nebulin (NEB-KO mice), indicate now that nebulin performs a surprisingly wide range of functions. In addition to a major role in thin-filament length specification, nebulin also functions in the regulation of muscle contraction, as indicated by the findings that muscle fibers deficient in nebulin have a higher tension cost, and develop less force due to reduced myofilament calcium sensitivity and altered crossbridge cycling kinetics. In addition, the function of nebulin extends to a role in calcium homeostasis. These novel functions indicate that nebulin might have evolved in vertebrate skeletal muscles to develop high levels of muscle force efficiently. Finally, the NEB-KO mouse models also highlight the role of nebulin in the assembly and alignment of the Z disks. Notably, rapid progress in understanding the roles of nebulin in vivo provides clinically important insights into how nebulin deficiency in patients with nemaline myopathy contributes to debilitating muscle weakness.
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Affiliation(s)
- Siegfried Labeit
- Department of Integrative Pathophysiology, Universitätsmedizin Mannheim, University of Heidelberg, Mannheim, Germany.
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Gilliam LAA, Moylan JS, Ferreira LF, Reid MB. TNF/TNFR1 signaling mediates doxorubicin-induced diaphragm weakness. Am J Physiol Lung Cell Mol Physiol 2010; 300:L225-31. [PMID: 21097524 DOI: 10.1152/ajplung.00264.2010] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Doxorubicin, a common chemotherapeutic agent, causes respiratory muscle weakness in both patients and rodents. Tumor necrosis factor-α (TNF), a proinflammatory cytokine that depresses diaphragm force, is elevated following doxorubicin chemotherapy. TNF-induced diaphragm weakness is mediated through TNF type 1 receptor (TNFR1). These findings lead us to hypothesize that TNF/TNFR1 signaling mediates doxorubicin-induced diaphragm muscle weakness. We tested this hypothesis by treating C57BL/6 mice with a clinical dose of doxorubicin (20 mg/kg) via intravenous injection. Three days later, we measured contractile properties of muscle fiber bundles isolated from the diaphragm. We tested the involvement of TNF/TNFR1 signaling using pharmaceutical and genetic interventions. Etanercept, a soluble TNF receptor, and TNFR1 deficiency protected against the depression in diaphragm-specific force caused by doxorubicin. Doxorubicin stimulated an increase in TNFR1 mRNA and protein (P < 0.05) in the diaphragm, along with colocalization of TNFR1 to the plasma membrane. These results suggest that doxorubicin increases diaphragm sensitivity to TNF by upregulating TNFR1, thereby causing respiratory muscle weakness.
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Affiliation(s)
- Laura A A Gilliam
- Department of Physiology, Center for Muscle Biology, University of Kentucky, Lexington, 40536-0298, USA
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43
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Ram R, Blaxall BC. Nebulette mutations in cardiac remodeling: big effects from a small mechanosensor. J Am Coll Cardiol 2010; 56:1503-5. [PMID: 20951327 DOI: 10.1016/j.jacc.2010.06.031] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/24/2010] [Accepted: 06/01/2010] [Indexed: 01/13/2023]
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Purevjav E, Varela J, Morgado M, Kearney DL, Li H, Taylor MD, Arimura T, Moncman CL, McKenna W, Murphy RT, Labeit S, Vatta M, Bowles NE, Kimura A, Boriek AM, Towbin JA. Nebulette mutations are associated with dilated cardiomyopathy and endocardial fibroelastosis. J Am Coll Cardiol 2010; 56:1493-502. [PMID: 20951326 DOI: 10.1016/j.jacc.2010.05.045] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/10/2009] [Revised: 04/21/2010] [Accepted: 05/18/2010] [Indexed: 10/18/2022]
Abstract
OBJECTIVES Four variants (K60N, Q128R, G202R, and A592E) in the nebulette gene were identified in patients with dilated cardiomyopathy (DCM) and endocardial fibroelastosis. We sought to determine if these mutations are cardiomyopathy causing. BACKGROUND Nebulette aligns thin filaments and connects them with the myocardial Z-disk, playing a role in mechanosensation. METHODS We generated transgenic mice with cardiac-restricted overexpression of human wild-type or mutant nebulette. Chimera and transgenic mice were examined at 4, 6, and 12 months of age by echocardiography and cardiac magnetic resonance imaging. The hearts from embryos and adult mice were assessed by histopathologic, immunohistochemical, ultrastructural, and protein analyses. Rat H9C2 cardiomyoblasts with transient expression of nebulette underwent cyclic mechanical strain. RESULTS We identified lethal cardiac structural abnormalities in mutant embryonic hearts (K60N and Q128R). Founders of the mutant mouse lines developed DCM with severe heart failure. An irregular localization pattern for nebulette and impaired desmin expression were noted in the proband and chimeric Q128R mice. Mutant G202R and A592E mice exhibited left ventricular dilation and impaired function with specific changes in I-band and Z-disk proteins by 6 months of age. The mutations modulated distribution of nebulette in the sarcomere and Z-disk during stretch of H9C2 cells. CONCLUSIONS Nebulette is a new susceptibility gene for endocardial fibroelastosis and DCM. Different mutations in nebulette trigger specific mechanisms, converging to a common pathological cascade leading to endocardial fibroelastosis and DCM.
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Affiliation(s)
- Enkhsaikhan Purevjav
- The Heart Institute, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio 45229, USA
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Ono S. Dynamic regulation of sarcomeric actin filaments in striated muscle. Cytoskeleton (Hoboken) 2010; 67:677-92. [PMID: 20737540 PMCID: PMC2963174 DOI: 10.1002/cm.20476] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2010] [Revised: 07/21/2010] [Accepted: 07/29/2010] [Indexed: 01/08/2023]
Abstract
In striated muscle, the actin cytoskeleton is differentiated into myofibrils. Actin and myosin filaments are organized in sarcomeres and specialized for producing contractile forces. Regular arrangement of actin filaments with uniform length and polarity is critical for the contractile function. However, the mechanisms of assembly and maintenance of sarcomeric actin filaments in striated muscle are not completely understood. Live imaging of actin in striated muscle has revealed that actin subunits within sarcomeric actin filaments are dynamically exchanged without altering overall sarcomeric structures. A number of regulators for actin dynamics have been identified, and malfunction of these regulators often result in disorganization of myofibril structures or muscle diseases. Therefore, proper regulation of actin dynamics in striated muscle is critical for assembly and maintenance of functional myofibrils. Recent studies have suggested that both enhancers of actin dynamics and stabilizers of actin filaments are important for sarcomeric actin organization. Further investigation of the regulatory mechanism of actin dynamics in striated muscle should be a key to understanding how myofibrils develop and operate.
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Affiliation(s)
- Shoichiro Ono
- Department of Pathology and Department of Cell Biology, Emory University, Atlanta, Georgia 30322, USA.
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46
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Pappas CT, Bliss KT, Zieseniss A, Gregorio CC. The Nebulin family: an actin support group. Trends Cell Biol 2010; 21:29-37. [PMID: 20951588 DOI: 10.1016/j.tcb.2010.09.005] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2010] [Revised: 09/08/2010] [Accepted: 09/09/2010] [Indexed: 11/25/2022]
Abstract
Nebulin, a giant, actin-binding protein, is the largest member of a family of proteins (including N-RAP, nebulette, lasp-1 and lasp-2) that are assembled in a variety of cytoskeletal structures, and expressed in different tissues. For decades, nebulin has been thought to act as a molecular ruler, specifying the precise length of actin filaments in skeletal muscle. However, emerging evidence suggests that nebulin should not be viewed as a ruler but as an actin filament stabilizer required for length maintenance. Nebulin has also been implicated recently in an array of regulatory functions independent of its role in actin filament length regulation. In this review, we discuss the current evolutionary, biochemical, and functional data for the nebulin family of proteins - a family whose members, both large and small, function as cytoskeletal scaffolds and stabilizers.
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Affiliation(s)
- Christopher T Pappas
- Department of Cell Biology, and Molecular Cardiovascular Research Program, The University of Arizona, Tucson, AZ, USA
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Ottenheijm CAC, Granzier H. Lifting the Nebula: Novel Insights into Skeletal Muscle Contractility. Physiology (Bethesda) 2010; 25:304-10. [DOI: 10.1152/physiol.00016.2010] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Nebulin is a giant protein and a constituent of the skeletal muscle sarcomere. The name of this protein refers to its unknown (i.e., nebulous) function. However, recent rapid advances reveal that nebulin plays important roles in the regulation of muscle contraction. When these functions of nebulin are compromised, muscle weakness ensues, as is the case in patients with nemaline myoptahy.
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Affiliation(s)
- Coen A. C. Ottenheijm
- Department of Physiology, University of Arizona, Tucson, Arizona; and
- Laboratory for Physiology, Institute for Cardiovascular Research, VU University Medical Center, Amsterdam, The Netherlands
| | - Henk Granzier
- Department of Physiology, University of Arizona, Tucson, Arizona; and
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Gokhin DS, Lewis RA, McKeown CR, Nowak RB, Kim NE, Littlefield RS, Lieber RL, Fowler VM. Tropomodulin isoforms regulate thin filament pointed-end capping and skeletal muscle physiology. ACTA ACUST UNITED AC 2010; 189:95-109. [PMID: 20368620 PMCID: PMC2854367 DOI: 10.1083/jcb.201001125] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
In skeletal muscle fibers, tropomodulin 1 (Tmod1) can be compensated for, structurally but not functionally, by Tmod3 and -4. During myofibril assembly, thin filament lengths are precisely specified to optimize skeletal muscle function. Tropomodulins (Tmods) are capping proteins that specify thin filament lengths by controlling actin dynamics at pointed ends. In this study, we use a genetic targeting approach to explore the effects of deleting Tmod1 from skeletal muscle. Myofibril assembly, skeletal muscle structure, and thin filament lengths are normal in the absence of Tmod1. Tmod4 localizes to thin filament pointed ends in Tmod1-null embryonic muscle, whereas both Tmod3 and -4 localize to pointed ends in Tmod1-null adult muscle. Substitution by Tmod3 and -4 occurs despite their weaker interactions with striated muscle tropomyosins. However, the absence of Tmod1 results in depressed isometric stress production during muscle contraction, systemic locomotor deficits, and a shift to a faster fiber type distribution. Thus, Tmod3 and -4 compensate for the absence of Tmod1 structurally but not functionally. We conclude that Tmod1 is a novel regulator of skeletal muscle physiology.
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Affiliation(s)
- David S Gokhin
- Department of Cell Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
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Moncman CL, Andrade FH. Nonmuscle myosin IIB, a sarcomeric component in the extraocular muscles. Exp Cell Res 2010; 316:1958-65. [PMID: 20350540 DOI: 10.1016/j.yexcr.2010.03.018] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2010] [Revised: 03/19/2010] [Accepted: 03/22/2010] [Indexed: 12/26/2022]
Abstract
Extraocular muscles (EOMs) are categorized as skeletal muscles; however, emerging evidence indicates that their gene expression profile, metabolic characteristics and functional properties are significantly different from the prototypical members of this muscle class. Gene expression profiling of developing and adult EOM suggest that many myofilament and cytoskeletal proteins have unique expression patterns in EOMs, including the maintained expression of embryonic and fetal isoforms of myosin heavy chains (MyHC), the presence of a unique EOM specific MyHC and mixtures of both cardiac and skeletal muscle isoforms of thick and thin filament accessory proteins. We demonstrate that nonmuscle myosin IIB (nmMyH IIB) is a sarcomeric component in approximately 20% of the global layer fibers in adult rat EOMs. Comparisons of the myofibrillar distribution of nmMyHC IIB with sarcomeric MyHCs indicate that nmMyH IIB co-exists with slow MyHC isoforms. In longitudinal sections of adult rat EOM, nmMyHC IIB appears to be restricted to the A-bands. Although nmMyHC IIB has been previously identified as a component of skeletal and cardiac sarcomeres at the level of the Z-line, the novel distribution of this protein within the A band in EOMs is further evidence of both the EOMs complexity and unconventional phenotype.
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Affiliation(s)
- Carole L Moncman
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, KY 40536, USA.
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Luther PK. The vertebrate muscle Z-disc: sarcomere anchor for structure and signalling. J Muscle Res Cell Motil 2009; 30:171-85. [PMID: 19830582 PMCID: PMC2799012 DOI: 10.1007/s10974-009-9189-6] [Citation(s) in RCA: 160] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2009] [Accepted: 09/23/2009] [Indexed: 02/04/2023]
Abstract
The Z-disc, appearing as a fine dense line forming sarcomere boundaries in striated muscles, when studied in detail reveals crosslinked filament arrays that transmit tension and house myriads of proteins with diverse functions. At the Z-disc the barbed ends of the antiparallel actin filaments from adjoining sarcomeres interdigitate and are crosslinked primarily by layers of α-actinin. The Z-disc is therefore the site of polarity reversal of the actin filaments, as needed to interact with the bipolar myosin filaments in successive sarcomeres. The layers of α-actinin determine the Z-disc width: fast fibres have narrow (~30–50 nm) Z-discs and slow and cardiac fibres have wide (~100 nm) Z-discs. Comprehensive reviews on the roles of the numerous proteins located at the Z-disc in signalling and disease have been published; the aim here is different, namely to review the advances in structural aspects of the Z-disc.
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Affiliation(s)
- Pradeep K Luther
- Molecular Medicine Section, National Heart and Lung Institute, Imperial College London, London, UK.
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