1
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Ono S. Segregated localization of two calponin-related proteins within sarcomeric thin filaments in Caenorhabditis elegans striated muscle. Cytoskeleton (Hoboken) 2024; 81:127-140. [PMID: 37792405 DOI: 10.1002/cm.21794] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2023] [Revised: 09/14/2023] [Accepted: 09/15/2023] [Indexed: 10/05/2023]
Abstract
The calponin family proteins are expressed in both muscle and non-muscle cells and involved in the regulation of cytoskeletal dynamics and cell contractility. In the nematode Caenorhabditis elegans, UNC-87 and CLIK-1 are calponin-related proteins with 42% identical amino acid sequences containing seven calponin-like motifs. Genetic studies demonstrated that UNC-87 and CLIK-1 have partially redundant function in regulating actin cytoskeletal organization in striated and non-striated muscle cells. However, biochemical studies showed that UNC-87 and CLIK-1 are different in their ability to bundle actin filaments. In this study, I extended comparison between UNC-87 and CLIK-1 and found additional differences in vitro and in vivo. Although UNC-87 and CLIK-1 bound to actin filaments similarly, UNC-87, but not CLIK-1, bound to myosin and inhibited actomyosin ATPase in vitro. In striated muscle, UNC-87 and CLIK-1 were segregated into different subregions within sarcomeric actin filaments. CLIK-1 was concentrated near the actin pointed ends, whereas UNC-87 was enriched toward the actin barbed ends. Restricted localization of UNC-87 was not altered in a clik-1-null mutant, suggesting that their segregated localization is not due to competition between the two related proteins. These results suggest that the two calponin-related proteins have both common and distinct roles in regulating actin filaments.
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Affiliation(s)
- Shoichiro Ono
- Departments of Pathology and Cell Biology, Emory University School of Medicine, Atlanta, Georgia, USA
- Winship Cancer Institute, Emory University School of Medicine, Atlanta, Georgia, USA
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2
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Endo T. Postnatal skeletal muscle myogenesis governed by signal transduction networks: MAPKs and PI3K-Akt control multiple steps. Biochem Biophys Res Commun 2023; 682:223-243. [PMID: 37826946 DOI: 10.1016/j.bbrc.2023.09.048] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2023] [Revised: 09/06/2023] [Accepted: 09/18/2023] [Indexed: 10/14/2023]
Abstract
Skeletal muscle myogenesis represents one of the most intensively and extensively examined systems of cell differentiation, tissue formation, and regeneration. Muscle regeneration provides an in vivo model system of postnatal myogenesis. It comprises multiple steps including muscle stem cell (or satellite cell) quiescence, activation, migration, myogenic determination, myoblast proliferation, myocyte differentiation, myofiber maturation, and hypertrophy. A variety of extracellular signaling and subsequent intracellular signal transduction pathways or networks govern the individual steps of postnatal myogenesis. Among them, MAPK pathways (the ERK, JNK, p38 MAPK, and ERK5 pathways) and PI3K-Akt signaling regulate multiple steps of myogenesis. Ca2+, cytokine, and Wnt signaling also participate in several myogenesis steps. These signaling pathways often control cell cycle regulatory proteins or the muscle-specific MyoD family and the MEF2 family of transcription factors. This article comprehensively reviews molecular mechanisms of the individual steps of postnatal skeletal muscle myogenesis by focusing on signal transduction pathways or networks. Nevertheless, no or only a partial signaling molecules or pathways have been identified in some responses during myogenesis. The elucidation of these unidentified signaling molecules and pathways leads to an extensive understanding of the molecular mechanisms of myogenesis.
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Affiliation(s)
- Takeshi Endo
- Department of Biology, Graduate School of Science, Chiba University, Yayoicho, Inageku, Chiba, Chiba 263-8522, Japan.
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3
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Zapater I Morales C, Carman PJ, Soffar DB, Windner SE, Dominguez R, Baylies MK. Drosophila Tropomodulin is required for multiple actin-dependent processes within developing myofibers. Development 2023; 150:dev201194. [PMID: 36806912 PMCID: PMC10112908 DOI: 10.1242/dev.201194] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2022] [Accepted: 02/09/2023] [Indexed: 02/22/2023]
Abstract
Proper muscle contraction requires the assembly and maintenance of sarcomeres and myofibrils. Although the protein components of myofibrils are generally known, less is known about the mechanisms by which they individually function and together synergize for myofibril assembly and maintenance. For example, it is unclear how the disruption of actin filament (F-actin) regulatory proteins leads to the muscle weakness observed in myopathies. Here, we show that knockdown of Drosophila Tropomodulin (Tmod), results in several myopathy-related phenotypes, including reduction of muscle cell (myofiber) size, increased sarcomere length, disorganization and misorientation of myofibrils, ectopic F-actin accumulation, loss of tension-mediating proteins at the myotendinous junction, and misshaped and internalized nuclei. Our findings support and extend the tension-driven self-organizing myofibrillogenesis model. We show that, like its mammalian counterpart, Drosophila Tmod caps F-actin pointed-ends, and we propose that this activity is crucial for cellular processes in different locations within the myofiber that directly and indirectly contribute to the maintenance of muscle function. Our findings provide significant insights to the role of Tmod in muscle development, maintenance and disease.
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Affiliation(s)
- Carolina Zapater I Morales
- Biochemistry, Cell & Developmental Biology, and Molecular Biology (BCMB) program, Weill Cornell Graduate School of Medical Sciences, New York, NY 10065, USA
- Developmental Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering, Cancer Center, New York, NY 10065, USA
| | - Peter J Carman
- Biochemistry and Molecular Biophysics Graduate Group, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - David B Soffar
- Developmental Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering, Cancer Center, New York, NY 10065, USA
| | - Stefanie E Windner
- Developmental Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering, Cancer Center, New York, NY 10065, USA
| | - Roberto Dominguez
- Biochemistry and Molecular Biophysics Graduate Group, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Mary K Baylies
- Biochemistry, Cell & Developmental Biology, and Molecular Biology (BCMB) program, Weill Cornell Graduate School of Medical Sciences, New York, NY 10065, USA
- Developmental Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering, Cancer Center, New York, NY 10065, USA
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4
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Brooks D, Bawa S, Bontrager A, Stetsiv M, Guo Y, Geisbrecht ER. Independent pathways control muscle tissue size and sarcomere remodeling. Dev Biol 2022; 490:1-12. [PMID: 35760368 PMCID: PMC9648737 DOI: 10.1016/j.ydbio.2022.06.014] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2022] [Revised: 06/03/2022] [Accepted: 06/21/2022] [Indexed: 01/09/2023]
Abstract
Cell growth and proliferation must be balanced during development to attain a final adult size with the appropriate proportions of internal organs to maximize fitness and reproduction. While multiple signaling pathways coordinate Drosophila development, it is unclear how multi-organ communication within and between tissues converge to regulate systemic growth. One such growth pathway, mediated by insulin-like peptides that bind to and activate the insulin receptor in multiple target tissues, is a primary mediator of organismal size. Here we uncover a signaling role for the NUAK serine/threonine kinase in muscle tissue that impinges upon insulin pathway activity to limit overall body size, including a reduction in the growth of individual organs. In skeletal muscle tissue, manipulation of NUAK or insulin pathway components influences sarcomere number concomitant with modulation of thin and thick filament lengths, possibly by modulating the localization of Lasp, a nebulin repeat protein known to set thin filament length. This mode of sarcomere remodeling does not occur in other mutants that also exhibit smaller muscles, suggesting that a sensing mechanism exists in muscle tissue to regulate sarcomere growth that is independent of tissue size control.
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Affiliation(s)
- David Brooks
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, KS, 66506, USA
| | - Simranjot Bawa
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, KS, 66506, USA
| | - Alexandria Bontrager
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, KS, 66506, USA
| | - Marta Stetsiv
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, KS, 66506, USA
| | - Yungui Guo
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, KS, 66506, USA
| | - Erika R Geisbrecht
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, KS, 66506, USA.
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5
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The Mechanisms of Thin Filament Assembly and Length Regulation in Muscles. Int J Mol Sci 2022; 23:ijms23105306. [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] [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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6
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Ono S, Lewis M, Ono K. Mutual dependence between tropomodulin and tropomyosin in the regulation of sarcomeric actin assembly in Caenorhabditis elegans striated muscle. Eur J Cell Biol 2022; 101:151215. [PMID: 35306452 PMCID: PMC9081161 DOI: 10.1016/j.ejcb.2022.151215] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2021] [Revised: 02/24/2022] [Accepted: 03/14/2022] [Indexed: 11/25/2022] Open
Abstract
Tropomodulin and tropomyosin are important components of sarcomeric thin filaments in striated muscles. Tropomyosin decorates the side of actin filaments and enhances tropomodulin capping at the pointed ends of the filaments. Their functional relationship has been extensively characterized in vitro, but in vivo and cellular studies in mammals are often complicated by the presence of functionally redundant isoforms. Here, we used the nematode Caenorhabditis elegans, which has a relatively simple composition of tropomodulin and tropomyosin genes, and demonstrated that tropomodulin (unc-94) and tropomyosin (lev-11) are mutually dependent on each other in their sarcomere localization and regulation of sarcomeric actin assembly. Mutation of tropomodulin caused sarcomere disorganization with formation of actin aggregates. However, the actin aggregation was suppressed when tropomyosin was depleted in the tropomodulin mutant. Tropomyosin was mislocalized to the actin aggregates in the tropomodulin mutants, while sarcomere localization of tropomodulin was lost when tropomyosin was depleted. These results indicate that tropomodulin and tropomyosin are interdependent in the regulation of organized sarcomeric assembly of actin filaments in vivo.
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Affiliation(s)
- Shoichiro Ono
- Departments of Pathology and Cell Biology, Emory University School of Medicine, Atlanta, GA, USA; Winship Cancer Institute, Emory University School of Medicine, Atlanta, GA, USA.
| | - Mario Lewis
- Departments of Pathology and Cell Biology, Emory University School of Medicine, Atlanta, GA, USA; Winship Cancer Institute, Emory University School of Medicine, Atlanta, GA, USA
| | - Kanako Ono
- Departments of Pathology and Cell Biology, Emory University School of Medicine, Atlanta, GA, USA; Winship Cancer Institute, Emory University School of Medicine, Atlanta, GA, USA
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7
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Mechanobiology of muscle and myofibril morphogenesis. Cells Dev 2021; 168:203760. [PMID: 34863916 DOI: 10.1016/j.cdev.2021.203760] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2021] [Revised: 11/22/2021] [Accepted: 11/22/2021] [Indexed: 01/05/2023]
Abstract
Muscles generate forces for animal locomotion. The contractile apparatus of muscles is the sarcomere, a highly regular array of large actin and myosin filaments linked by gigantic titin springs. During muscle development many sarcomeres assemble in series into long periodic myofibrils that mechanically connect the attached skeleton elements. Thus, ATP-driven myosin forces can power movement of the skeleton. Here we review muscle and myofibril morphogenesis, with a particular focus on their mechanobiology. We describe recent progress on the molecular structure of sarcomeres and their mechanical connections to the skeleton. We discuss current models predicting how tension coordinates the assembly of key sarcomeric components to periodic myofibrils that then further mature during development. This requires transcriptional feedback mechanisms that may help to coordinate myofibril assembly and maturation states with the transcriptional program. To fuel the varying energy demands of muscles we also discuss the close mechanical interactions of myofibrils with mitochondria and nuclei to optimally support powerful or enduring muscle fibers.
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8
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Noonan AM, Brown SHM. Paraspinal muscle pathophysiology associated with low back pain and spine degenerative disorders. JOR Spine 2021; 4:e1171. [PMID: 34611593 PMCID: PMC8479522 DOI: 10.1002/jsp2.1171] [Citation(s) in RCA: 35] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/10/2021] [Revised: 06/17/2021] [Accepted: 08/21/2021] [Indexed: 12/18/2022] Open
Abstract
Low back pain disorders affect more than 80% of adults in their lifetime and are the leading cause of global disability. The muscles attaching to the spine (ie, paraspinal muscles) are critical for proper spine health and play a crucial role in the functioning of the spine and whole body; however, reports of muscle dysfunction and insufficiency in chronic LBP (CLBP) patients are common. This article presents a review of the current understanding of the relationship between paraspinal muscle pathophysiology and spine-related disorders. Human literature demonstrates a clear association between altered muscle structure/function, most notably fatty infiltration and fibrosis, and low back pain disorders; other associations, including muscle cell atrophy and fiber type changes, are less clear. Animal literature then provides some mechanistic insight into the complex relationships, including initiating factors and time courses, between the spine and spine muscles under pathological conditions. It is apparent that spine pathology can directly lead to changes in the paraspinal muscle structure, function, and biology. It also appears that changes to the muscle structure and function can directly lead to changes in the spine (eg, deformity); however, this relationship is less well studied. Future work must focus on providing insight into possible mechanisms that regulate spine and paraspinal muscle health, as well as probing how muscle degeneration/dysfunction might be an initiating factor in the progression of spine pathology.
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Affiliation(s)
- Alex M. Noonan
- Department of Human Health and Nutritional SciencesUniversity of GuelphGuelphOntarioCanada
| | - Stephen H. M. Brown
- Department of Human Health and Nutritional SciencesUniversity of GuelphGuelphOntarioCanada
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9
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Chiang MY, Lo YC, Lai YH, Yong YYA, Chang SJ, Chen WL, Chen SY. Protein-based soft actuator with high photo-response and easy modulation for anisotropic cell alignment and proliferation in a liquid environment. J Mater Chem B 2021; 9:6634-6645. [PMID: 34365493 DOI: 10.1039/d1tb01198g] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Cell alignment and elongation, which are critical factors correlated with differentiation and maturation in cell biology and tissue engineering, have been widely studied in organisms. Several strategies such as external mechanical strain, geometric topography, micropatterning approaches, and microfabricated substrates have been developed to guide cell alignment, but these methodologies cannot be used for easily denatured natural proteins to modulate the cell behaviour. Herein, for the first time, a novel biocompatible light-controlled protein-based bilayer soft actuator composed of elastin-like polypeptides (ELPs), silk fibroin (SF), graphene oxide (GO), and reduced graphene oxide (rGO), named ESGRG, is developed for efficiently driving cellular orientation and elongation with anisotropic features on soft actuator via remote NIR laser exposure. The actuation of ESGRG could be manipulated by modulating the intensity of NIR and the relative ratio of GO to rGO for promoting myoblasts alignment and nucleus elongation to generate different motions. The results indicate that the YAP and MHC protein expression of C2C12 skeletal muscle cells on ESGRG can be rapidly induced and enhanced by controlling the relative ratio of rGO/GO = 1/4 at a multiple-cycle stimulation with a very low power intensity of 1.2 W cm-2 in friendly liquid environments. This study demonstrates that the ESGRG hydrogel actuator system can modulate the cell-level behaviors via light-driven cyclic bending-motions and can be utilized in applications of soft robotic and tissue engineering such as artificial muscle and maturation of cardiomyocytes.
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Affiliation(s)
- Min-Yu Chiang
- Department of Materials Science and Engineering, National Yang Ming Chiao Tung University, No. 1001 Ta-Hsueh Rd, Hsinchu, Taiwan 300, Republic of China.
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10
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Wang C, Xu Y, Xia J, Zhou Z, Fang Y, Zhang L, Sun W. Multi-scale hierarchical scaffolds with aligned micro-fibers for promoting cell alignment. Biomed Mater 2021; 16. [PMID: 34116518 DOI: 10.1088/1748-605x/ac0a90] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2021] [Accepted: 06/11/2021] [Indexed: 01/29/2023]
Abstract
Cell alignment plays an essential role in cytoskeleton reorganization, extracellular matrix remodeling, and biomechanical properties regulation of tissues such as vascular tissues, cardiac muscles, and tendons. Based on the natural-oriented features of cells in native tissues, various biomimetic scaffolds have been reported with the introduction of well-arranged ultrafine fibers to induce cell alignment. However, it is still a challenge to fabricate scaffolds with suitable mechanical properties, biomimetic microenvironment, and ability to promote cell alignment. In this paper, we propose an integrated 3D printing system to fabricate multi-scale hierarchical scaffolds combined with meso-, micro-, and nano-fibrous filaments, in which the meso-, micro-, and nano-fibers fabricated via fused deposition modeling, melt electrospining writing, and solution electrospining can provide structural support, promote cell alignment, and create a biomimetic microenvironment to facilitate cell function, respectively. The plasma surface modification was performed improve the surface wettability of the scaffolds by measuring the contact angle. The obtainedin vitrobiological results validate the ability of multi-scale hierarchical scaffolds to enhance cell adhesion and proliferation, and promote cell alignment with the guidance of the aligned microfibers produced via melt electrospining writing in hierarchical scaffolds.
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Affiliation(s)
- Chengjin Wang
- Biomanufacturing Center, Department of Mechanical Engineering, Tsinghua University, Beijing 100084, People's Republic of China.,Biomanufacturing and Rapid Forming Technology Key Laboratory of Beijing, Beijing 100084, People's Republic of China.,'Biomanufacturing and Engineering Living Systems' Innovation International Talents Base (111 Base), Beijing 100084, People's Republic of China
| | - Yuanyuan Xu
- Biomanufacturing Center, Department of Mechanical Engineering, Tsinghua University, Beijing 100084, People's Republic of China.,Biomanufacturing and Rapid Forming Technology Key Laboratory of Beijing, Beijing 100084, People's Republic of China.,'Biomanufacturing and Engineering Living Systems' Innovation International Talents Base (111 Base), Beijing 100084, People's Republic of China
| | - Jingjing Xia
- Biomanufacturing Center, Department of Mechanical Engineering, Tsinghua University, Beijing 100084, People's Republic of China.,Biomanufacturing and Rapid Forming Technology Key Laboratory of Beijing, Beijing 100084, People's Republic of China.,'Biomanufacturing and Engineering Living Systems' Innovation International Talents Base (111 Base), Beijing 100084, People's Republic of China
| | - Zhenzhen Zhou
- Biomanufacturing Center, Department of Mechanical Engineering, Tsinghua University, Beijing 100084, People's Republic of China.,Biomanufacturing and Rapid Forming Technology Key Laboratory of Beijing, Beijing 100084, People's Republic of China.,'Biomanufacturing and Engineering Living Systems' Innovation International Talents Base (111 Base), Beijing 100084, People's Republic of China
| | - Yongcong Fang
- Biomanufacturing Center, Department of Mechanical Engineering, Tsinghua University, Beijing 100084, People's Republic of China.,Biomanufacturing and Rapid Forming Technology Key Laboratory of Beijing, Beijing 100084, People's Republic of China.,'Biomanufacturing and Engineering Living Systems' Innovation International Talents Base (111 Base), Beijing 100084, People's Republic of China
| | - Lei Zhang
- Biomanufacturing Center, Department of Mechanical Engineering, Tsinghua University, Beijing 100084, People's Republic of China.,Biomanufacturing and Rapid Forming Technology Key Laboratory of Beijing, Beijing 100084, People's Republic of China.,'Biomanufacturing and Engineering Living Systems' Innovation International Talents Base (111 Base), Beijing 100084, People's Republic of China
| | - Wei Sun
- Biomanufacturing Center, Department of Mechanical Engineering, Tsinghua University, Beijing 100084, People's Republic of China.,Biomanufacturing and Rapid Forming Technology Key Laboratory of Beijing, Beijing 100084, People's Republic of China.,'Biomanufacturing and Engineering Living Systems' Innovation International Talents Base (111 Base), Beijing 100084, People's Republic of China.,Department of Mechanical Engineering, Drexel University, Philadelphia, PA 19104, United States of America
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11
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Liu R, Wu GY, Li KY, Ge QF, Wu MG, Yu H, Wu SL, Bao WB. Comparative Study on Pale, Soft and Exudative (PSE) and Red, Firm and Non-Exudative (RFN) Pork: Protein Changes during Aging and the Differential Protein Expression of the Myofibrillar Fraction at 1 h Postmortem. Foods 2021; 10:foods10040733. [PMID: 33808327 PMCID: PMC8066169 DOI: 10.3390/foods10040733] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2021] [Revised: 03/23/2021] [Accepted: 03/25/2021] [Indexed: 01/06/2023] Open
Abstract
In this paper, the protein changes during aging and the differences in the myofibrillar protein fraction at 1 h postmortem of pale, soft and exudative (PSE), and red, firm and non-exudative (RFN) pork longissimus thoracis (LT) were comparatively studied. The PSE and RFN groups were screened out based on the differences in their pH and lightness (L*) at 1 h, and their purge loss at 24 h postmortem. Based on the measured MFI, desmin degradation, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis, PSE meat presented more significant changes in the myofibrillar protein fraction compared to RFN meat during postmortem aging. Through liquid chromatograph-mass spectrometer/mass spectrometer (LC-MS/MS) analysis, a total of 172 differential proteins were identified, among which 151 were up-regulated and 21 were down-regulated in the PSE group. The differential proteins were muscle contraction, motor proteins, microfilaments, microtubules, glycolysis, glycogen metabolism, energy metabolism, molecular chaperones, transport, and enzyme proteins. The AMP activated protein kinase (AMPK) signaling pathway, HIF-1 signaling pathway, calcium signaling pathway, and PI3K-Akt signaling pathway were identified as the significant pathways related to meat quality. This study suggested that the different changes of the myofibrillar protein fraction were involved in the biochemical metabolism in postmortem muscle, which may contribute to the molecular understanding of PSE meat formation.
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Affiliation(s)
- Rui Liu
- Industrial Engineering Center for Huaiyang Cuisine of Jiangsu Province, College of Food Science and Engineering, Yangzhou University, Yangzhou 225127, China; (R.L.); (G.-Y.W.); (K.-Y.L.); (M.-G.W.); (H.Y.)
- Jiangsu Key Laboratory of Animal Genetic Breeding and Molecular Design, College of Animal Science and Technology, Yangzhou University, Yangzhou 225009, China;
| | - Guo-Yue Wu
- Industrial Engineering Center for Huaiyang Cuisine of Jiangsu Province, College of Food Science and Engineering, Yangzhou University, Yangzhou 225127, China; (R.L.); (G.-Y.W.); (K.-Y.L.); (M.-G.W.); (H.Y.)
| | - Ke-Yue Li
- Industrial Engineering Center for Huaiyang Cuisine of Jiangsu Province, College of Food Science and Engineering, Yangzhou University, Yangzhou 225127, China; (R.L.); (G.-Y.W.); (K.-Y.L.); (M.-G.W.); (H.Y.)
| | - Qing-Feng Ge
- Industrial Engineering Center for Huaiyang Cuisine of Jiangsu Province, College of Food Science and Engineering, Yangzhou University, Yangzhou 225127, China; (R.L.); (G.-Y.W.); (K.-Y.L.); (M.-G.W.); (H.Y.)
- Correspondence: (Q.-F.G.); (W.-B.B.); Tel.: +86-0514-89786171 (Q.-F.G.)
| | - Man-Gang Wu
- Industrial Engineering Center for Huaiyang Cuisine of Jiangsu Province, College of Food Science and Engineering, Yangzhou University, Yangzhou 225127, China; (R.L.); (G.-Y.W.); (K.-Y.L.); (M.-G.W.); (H.Y.)
| | - Hai Yu
- Industrial Engineering Center for Huaiyang Cuisine of Jiangsu Province, College of Food Science and Engineering, Yangzhou University, Yangzhou 225127, China; (R.L.); (G.-Y.W.); (K.-Y.L.); (M.-G.W.); (H.Y.)
| | - Sheng-Long Wu
- Jiangsu Key Laboratory of Animal Genetic Breeding and Molecular Design, College of Animal Science and Technology, Yangzhou University, Yangzhou 225009, China;
| | - Wen-Bin Bao
- Jiangsu Key Laboratory of Animal Genetic Breeding and Molecular Design, College of Animal Science and Technology, Yangzhou University, Yangzhou 225009, China;
- Correspondence: (Q.-F.G.); (W.-B.B.); Tel.: +86-0514-89786171 (Q.-F.G.)
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12
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The actin polymerization factor Diaphanous and the actin severing protein Flightless I collaborate to regulate sarcomere size. Dev Biol 2021; 469:12-25. [PMID: 32980309 DOI: 10.1016/j.ydbio.2020.09.014] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2018] [Revised: 09/15/2020] [Accepted: 09/19/2020] [Indexed: 12/22/2022]
Abstract
The sarcomere is the basic contractile unit of muscle, composed of repeated sets of actin thin filaments and myosin thick filaments. During muscle development, sarcomeres grow in size to accommodate the growth and function of muscle fibers. Failure in regulating sarcomere size results in muscle dysfunction; yet, it is unclear how the size and uniformity of sarcomeres are controlled. Here we show that the formin Diaphanous is critical for the growth and maintenance of sarcomere size: Dia sets sarcomere length and width through regulation of the number and length of the actin thin filaments in the Drosophila flight muscle. To regulate thin filament length and sarcomere size, Dia interacts with the Gelsolin superfamily member Flightless I (FliI). We suggest that these actin regulators, by controlling actin dynamics and turnover, generate uniformly sized sarcomeres tuned for the muscle contractions required for flight.
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13
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Gohlke J, Tonino P, Lindqvist J, Smith JE, Granzier H. The number of Z-repeats and super-repeats in nebulin greatly varies across vertebrates and scales with animal size. J Gen Physiol 2020; 153:211611. [PMID: 33337482 PMCID: PMC7754682 DOI: 10.1085/jgp.202012783] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Accepted: 11/20/2020] [Indexed: 12/18/2022] Open
Abstract
Nebulin is a skeletal muscle protein that associates with the sarcomeric thin filaments and has functions in regulating the length of the thin filament and the structure of the Z-disk. Here we investigated the nebulin gene in 53 species of birds, fish, amphibians, reptiles, and mammals. In all species, nebulin has a similar domain composition that mostly consists of ∼30-residue modules (or simple repeats), each containing an actin-binding site. All species have a large region where simple repeats are organized into seven-module super-repeats, each containing a tropomyosin binding site. The number of super-repeats shows high interspecies variation, ranging from 21 (zebrafish, hummingbird) to 31 (camel, chimpanzee), and, importantly, scales with body size. The higher number of super-repeats in large animals was shown to increase thin filament length, which is expected to increase the sarcomere length for optimal force production, increase the energy efficiency of isometric force production, and lower the shortening velocity of muscle. It has been known since the work of A.V. Hill in 1950 that as species increase in size, the shortening velocity of their muscle is reduced, and the present work shows that nebulin contributes to the mechanistic basis. Finally, we analyzed the differentially spliced simple repeats in nebulin's C terminus, whose inclusion correlates with the width of the Z-disk. The number of Z-repeats greatly varies (from 5 to 18) and correlates with the number of super-repeats. We propose that the resulting increase in the width of the Z-disk in large animals increases the number of contacts between nebulin and structural Z-disk proteins when the Z-disk is stressed for long durations.
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Affiliation(s)
- Jochen Gohlke
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ
| | - Paola Tonino
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ
| | - Johan Lindqvist
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ
| | - John E Smith
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ
| | - Henk Granzier
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ
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14
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Kiss B, Gohlke J, Tonino P, Hourani Z, Kolb J, Strom J, Alekhina O, Smith JE, Ottenheijm C, Gregorio C, Granzier H. Nebulin and Lmod2 are critical for specifying thin-filament length in skeletal muscle. SCIENCE ADVANCES 2020; 6:6/46/eabc1992. [PMID: 33177085 PMCID: PMC7673738 DOI: 10.1126/sciadv.abc1992] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/11/2020] [Accepted: 09/23/2020] [Indexed: 06/07/2023]
Abstract
Regulating the thin-filament length in muscle is crucial for controlling the number of myosin motors that generate power. The giant protein nebulin forms a long slender filament that associates along the length of the thin filament in skeletal muscle with functions that remain largely obscure. Here nebulin's role in thin-filament length regulation was investigated by targeting entire super-repeats in the Neb gene; nebulin was either shortened or lengthened by 115 nm. Its effect on thin-filament length was studied using high-resolution structural and functional techniques. Results revealed that thin-filament length is strictly regulated by the length of nebulin in fast muscles. Nebulin's control is less tight in slow muscle types where a distal nebulin-free thin-filament segment exists, the length of which was found to be regulated by leiomodin-2 (Lmod2). We propose that strict length control by nebulin promotes high-speed shortening and that dual-regulation by nebulin/Lmod2 enhances contraction efficiency.
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Affiliation(s)
- Balázs Kiss
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ 85721, USA
| | - Jochen Gohlke
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ 85721, USA
| | - Paola Tonino
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ 85721, USA
| | - Zaynab Hourani
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ 85721, USA
| | - Justin Kolb
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ 85721, USA
| | - Joshua Strom
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ 85721, USA
| | - Olga Alekhina
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ 85721, USA
| | - John E Smith
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ 85721, USA
| | - Coen Ottenheijm
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ 85721, USA
| | - Carol Gregorio
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ 85721, USA
| | - Henk Granzier
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ 85721, USA.
- Allan and Alfie Endowed Chair for Heart Disease in Women Research, Sarver Molecular Cardiovascular Research Program, University of Arizona, Tucson, AZ 85721, USA
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15
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Li F, Barton ER, Granzier H. Deleting nebulin's C-terminus reveals its importance to sarcomeric structure and function and is sufficient to invoke nemaline myopathy. Hum Mol Genet 2020; 28:1709-1725. [PMID: 30689900 DOI: 10.1093/hmg/ddz016] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2018] [Revised: 12/17/2018] [Accepted: 01/10/2019] [Indexed: 01/10/2023] Open
Abstract
Nebulin is a large skeletal muscle protein wound around the thin filaments, with its C-terminus embedded within the Z-disk and its N-terminus extending out toward the thin filament pointed end. While nebulin's C-terminus has been implicated in both sarcomeric structure and function as well as the development of nemaline myopathy, the contributions of this region remain largely unknown. Additionally, the C-terminus is reported to contribute to muscle hypertrophy via the IGF-1 growth pathway. To study the functions of nebulin's C-terminus, we generated a mouse model deleting the final two unique C-terminal domains, the serine-rich region (SRR) and the SH3 domain (NebΔ163-165). Homozygous NebΔ163-165 mice that survive past the neonatal stage exhibit a mild weight deficit. Characterization of these mice revealed that the truncation caused a moderate myopathy phenotype reminiscent of nemaline myopathy despite the majority of nebulin being localized properly in the thin filaments. This phenotype included muscle weight loss, changes in sarcomere structure, as well as a decrease in force production. Glutathione S-transferase (GST) pull-down experiments found novel binding partners with the SRR, several of which are associated with myopathies. While the C-terminus does not appear to be a limiting step in muscle growth, the IGF-1 growth pathway remained functional despite the deleted domains being proposed to be essential for IGF-1 mediated hypertrophy. The NebΔ163-165 mouse model emphasizes that nebulin's C-terminus is necessary for proper sarcomeric development and shows that its loss is sufficient to induce myopathy.
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Affiliation(s)
- Frank Li
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, Arizona, USA
| | - Elisabeth R Barton
- Department of Applied Physiology and Kinesiology, University of Florida, Gainesville, Florida, USA
| | - Henk Granzier
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, Arizona, USA
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16
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Li F, Kolb J, Crudele J, Tonino P, Hourani Z, Smith JE, Chamberlain JS, Granzier H. Expressing a Z-disk nebulin fragment in nebulin-deficient mouse muscle: effects on muscle structure and function. Skelet Muscle 2020; 10:2. [PMID: 31992366 PMCID: PMC6986074 DOI: 10.1186/s13395-019-0219-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2019] [Accepted: 12/17/2019] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND Nebulin is a critical thin filament-binding protein that spans from the Z-disk of the skeletal muscle sarcomere to near the pointed end of the thin filament. Its massive size and actin-binding property allows it to provide the thin filaments with structural and regulatory support. When this protein is lost, nemaline myopathy occurs. Nemaline myopathy causes severe muscle weakness as well as structural defects on a sarcomeric level. There is no known cure for this disease. METHODS We studied whether sarcomeric structure and function can be improved by introducing nebulin's Z-disk region into a nebulin-deficient mouse model (Neb cKO) through adeno-associated viral (AAV) vector therapy. Following this treatment, the structural and functional characteristics of both vehicle-treated and AAV-treated Neb cKO and control muscles were studied. RESULTS Intramuscular injection of this AAV construct resulted in a successful expression of the Z-disk fragment within the target muscles. This expression was significantly higher in Neb cKO mice than control mice. Analysis of protein expression revealed that the nebulin fragment was localized exclusively to the Z-disks and that Neb cKO expressed the nebulin fragment at levels comparable to the level of full-length nebulin in control mice. Additionally, the Z-disk fragment displaced full-length nebulin in control mice, resulting in nemaline rod body formation and a worsening of muscle function. Neb cKO mice experienced a slight functional benefit from the AAV treatment, with a small increase in force and fatigue resistance. Disease progression was also slowed as indicated by improved muscle structure and myosin isoform expression. CONCLUSIONS This study reveals that nebulin fragments are well-received by nebulin-deficient mouse muscles and that limited functional benefits are achievable.
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Affiliation(s)
- Frank Li
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ, 85721, USA
| | - Justin Kolb
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ, 85721, USA
| | - Julie Crudele
- Department of Neurology, University of Washington, Seattle, WA, 98109-8055, USA
| | - Paola Tonino
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ, 85721, USA
| | - Zaynab Hourani
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ, 85721, USA
| | - John E Smith
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ, 85721, USA
| | | | - Henk Granzier
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ, 85721, USA.
- Medical Research Building, RM 325, 1656 E Mabel St, Tucson, AZ, 85721, USA.
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17
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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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18
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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: 15] [Impact Index Per Article: 3.8] [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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19
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González-Morales N, Xiao YS, Schilling MA, Marescal O, Liao KA, Schöck F. Myofibril diameter is set by a finely tuned mechanism of protein oligomerization in Drosophila. eLife 2019; 8:50496. [PMID: 31746737 PMCID: PMC6910826 DOI: 10.7554/elife.50496] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2019] [Accepted: 11/18/2019] [Indexed: 11/13/2022] Open
Abstract
Myofibrils are huge cytoskeletal assemblies embedded in the cytosol of muscle cells. They consist of arrays of sarcomeres, the smallest contractile unit of muscles. Within a muscle type, myofibril diameter is highly invariant and contributes to its physiological properties, yet little is known about the underlying mechanisms setting myofibril diameter. Here we show that the PDZ and LIM domain protein Zasp, a structural component of Z-discs, mediates Z-disc and thereby myofibril growth through protein oligomerization. Oligomerization is induced by an interaction of its ZM domain with LIM domains. Oligomerization is terminated upon upregulation of shorter Zasp isoforms which lack LIM domains at later developmental stages. The balance between these two isoforms, which we call growing and blocking isoforms sets the stereotyped diameter of myofibrils. If blocking isoforms dominate, myofibrils become smaller. If growing isoforms dominate, myofibrils and Z-discs enlarge, eventually resulting in large pathological aggregates that disrupt muscle function.
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Affiliation(s)
| | - Yu Shu Xiao
- Department of Biology, McGill University, Montreal, Canada
| | | | | | - Kuo An Liao
- Department of Biology, McGill University, Montreal, Canada
| | - Frieder Schöck
- Department of Biology, McGill University, Montreal, Canada
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20
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Holt NC. Beyond bouncy gaits: The role of multiscale compliance in skeletal muscle performance. JOURNAL OF EXPERIMENTAL ZOOLOGY PART 2019; 333:50-59. [DOI: 10.1002/jez.2261] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2018] [Revised: 01/15/2019] [Accepted: 03/05/2019] [Indexed: 01/21/2023]
Affiliation(s)
- Natalie C. Holt
- Department of Biological Sciences; Northern Arizona University; Flagstaff Arizona
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21
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Dasbiswas K, Hu S, Schnorrer F, Safran SA, Bershadsky AD. Ordering of myosin II filaments driven by mechanical forces: experiments and theory. Philos Trans R Soc Lond B Biol Sci 2019; 373:rstb.2017.0114. [PMID: 29632266 DOI: 10.1098/rstb.2017.0114] [Citation(s) in RCA: 44] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/30/2017] [Indexed: 12/27/2022] Open
Abstract
Myosin II filaments form ordered superstructures in both cross-striated muscle and non-muscle cells. In cross-striated muscle, myosin II (thick) filaments, actin (thin) filaments and elastic titin filaments comprise the stereotypical contractile units of muscles called sarcomeres. Linear chains of sarcomeres, called myofibrils, are aligned laterally in registry to form cross-striated muscle cells. The experimentally observed dependence of the registered organization of myofibrils on extracellular matrix elasticity has been proposed to arise from the interactions of sarcomeric contractile elements (considered as force dipoles) through the matrix. Non-muscle cells form small bipolar filaments built of less than 30 myosin II molecules. These filaments are associated in registry forming superstructures ('stacks') orthogonal to actin filament bundles. Formation of myosin II filament stacks requires the myosin II ATPase activity and function of the actin filament crosslinking, polymerizing and depolymerizing proteins. We propose that the myosin II filaments embedded into elastic, intervening actin network (IVN) function as force dipoles that interact attractively through the IVN. This is in analogy with the theoretical picture developed for myofibrils where the elastic medium is now the actin cytoskeleton itself. Myosin stack formation in non-muscle cells provides a novel mechanism for the self-organization of the actin cytoskeleton at the level of the entire cell.This article is part of the theme issue 'Self-organization in cell biology'.
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Affiliation(s)
- Kinjal Dasbiswas
- James Franck Institute, University of Chicago, Chicago, IL 60637, USA
| | - Shiqiong Hu
- Mechanobiology Institute, National University of Singapore, Singapore 117411, Republic of Singapore.,Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Frank Schnorrer
- Aix Marseille University, CNRS, IBDM, 13288 Marseille, France
| | - Samuel A Safran
- Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Alexander D Bershadsky
- Mechanobiology Institute, National University of Singapore, Singapore 117411, Republic of Singapore .,Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot 76100, Israel
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22
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Parreno J, Fowler VM. Multifunctional roles of tropomodulin-3 in regulating actin dynamics. Biophys Rev 2018; 10:1605-1615. [PMID: 30430457 DOI: 10.1007/s12551-018-0481-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2018] [Accepted: 11/08/2018] [Indexed: 12/12/2022] Open
Abstract
Tropomodulins (Tmods) are proteins that cap the slow-growing (pointed) ends of actin filaments (F-actin). The basis for our current understanding of Tmod function comes from studies in cells with relatively stable and highly organized F-actin networks, leading to the view that Tmod capping functions principally to preserve F-actin stability. However, not only is Tmod capping dynamic, but it also can play major roles in regulating diverse cellular processes involving F-actin remodeling. Here, we highlight the multifunctional roles of Tmod with a focus on Tmod3. Like other Tmods, Tmod3 binds tropomyosin (Tpm) and actin, capping pure F-actin at submicromolar and Tpm-coated F-actin at nanomolar concentrations. Unlike other Tmods, Tmod3 can also bind actin monomers and its ability to bind actin is inhibited by phosphorylation of Tmod3 by Akt2. Tmod3 is ubiquitously expressed and is present in a diverse array of cytoskeletal structures, including contractile structures such as sarcomere-like units of actomyosin stress fibers and in the F-actin network encompassing adherens junctions. Tmod3 participates in F-actin network remodeling in lamellipodia during cell migration and in the assembly of specialized F-actin networks during exocytosis. Furthermore, Tmod3 is required for development, regulating F-actin mesh formation during meiosis I of mouse oocytes, erythroblast enucleation in definitive erythropoiesis, and megakaryocyte morphogenesis in the mouse fetal liver. Thus, Tmod3 plays vital roles in dynamic and stable F-actin networks in cell physiology and development, with further research required to delineate the mechanistic details of Tmod3 regulation in the aforementioned processes, or in other yet to be discovered processes.
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Affiliation(s)
- Justin Parreno
- Department of Molecular Medicine, The Scripps Research Institute, 10550 N. Torrey Pines Road, La Jolla, CA, 92037, USA
| | - Velia M Fowler
- Department of Molecular Medicine, The Scripps Research Institute, 10550 N. Torrey Pines Road, La Jolla, CA, 92037, USA.
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23
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Spletter ML, Barz C, Yeroslaviz A, Zhang X, Lemke SB, Bonnard A, Brunner E, Cardone G, Basler K, Habermann BH, Schnorrer F. A transcriptomics resource reveals a transcriptional transition during ordered sarcomere morphogenesis in flight muscle. eLife 2018; 7:34058. [PMID: 29846170 PMCID: PMC6005683 DOI: 10.7554/elife.34058] [Citation(s) in RCA: 53] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2017] [Accepted: 05/26/2018] [Indexed: 01/07/2023] Open
Abstract
Muscles organise pseudo-crystalline arrays of actin, myosin and titin filaments to build force-producing sarcomeres. To study sarcomerogenesis, we have generated a transcriptomics resource of developing Drosophila flight muscles and identified 40 distinct expression profile clusters. Strikingly, most sarcomeric components group in two clusters, which are strongly induced after all myofibrils have been assembled, indicating a transcriptional transition during myofibrillogenesis. Following myofibril assembly, many short sarcomeres are added to each myofibril. Subsequently, all sarcomeres mature, reaching 1.5 µm diameter and 3.2 µm length and acquiring stretch-sensitivity. The efficient induction of the transcriptional transition during myofibrillogenesis, including the transcriptional boost of sarcomeric components, requires in part the transcriptional regulator Spalt major. As a consequence of Spalt knock-down, sarcomere maturation is defective and fibers fail to gain stretch-sensitivity. Together, this defines an ordered sarcomere morphogenesis process under precise transcriptional control - a concept that may also apply to vertebrate muscle or heart development.
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Affiliation(s)
- Maria L Spletter
- Muscle Dynamics GroupMax Planck Institute of BiochemistryMartinsriedGermany
- Biomedical Center, Physiological ChemistryLudwig-Maximilians-Universität MünchenMartinsriedGermany
| | - Christiane Barz
- Muscle Dynamics GroupMax Planck Institute of BiochemistryMartinsriedGermany
| | - Assa Yeroslaviz
- Computational Biology GroupMax Planck Institute of BiochemistryMartinsriedGermany
| | - Xu Zhang
- Muscle Dynamics GroupMax Planck Institute of BiochemistryMartinsriedGermany
- Aix Marseille Univ, CNRS, IBDMMarseilleFrance
- School of Life Science and EngineeringFoshan UniversityGuangdongChina
| | - Sandra B Lemke
- Muscle Dynamics GroupMax Planck Institute of BiochemistryMartinsriedGermany
| | - Adrien Bonnard
- Aix Marseille Univ, CNRS, IBDMMarseilleFrance
- Aix Marseille Univ, INSERM, TAGCMarseilleFrance
| | - Erich Brunner
- Institute of Molecular Life SciencesUniversity of ZurichZurichSwitzerland
| | - Giovanni Cardone
- Imaging FacilityMax Planck Institute of BiochemistryMartinsriedGermany
| | - Konrad Basler
- Institute of Molecular Life SciencesUniversity of ZurichZurichSwitzerland
| | - Bianca H Habermann
- Computational Biology GroupMax Planck Institute of BiochemistryMartinsriedGermany
- Aix Marseille Univ, CNRS, IBDMMarseilleFrance
- Aix Marseille Univ, INSERM, TAGCMarseilleFrance
| | - Frank Schnorrer
- Muscle Dynamics GroupMax Planck Institute of BiochemistryMartinsriedGermany
- Aix Marseille Univ, CNRS, IBDMMarseilleFrance
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24
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HSPB7 is indispensable for heart development by modulating actin filament assembly. Proc Natl Acad Sci U S A 2017; 114:11956-11961. [PMID: 29078393 DOI: 10.1073/pnas.1713763114] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Small heat shock protein HSPB7 is highly expressed in the heart. Several mutations within HSPB7 are associated with dilated cardiomyopathy and heart failure in human patients. However, the precise role of HSPB7 in the heart is still unclear. In this study, we generated global as well as cardiac-specific HSPB7 KO mouse models and found that loss of HSPB7 globally or specifically in cardiomyocytes resulted in embryonic lethality before embryonic day 12.5. Using biochemical and cell culture assays, we identified HSPB7 as an actin filament length regulator that repressed actin polymerization by binding to monomeric actin. Consistent with HSPB7's inhibitory effects on actin polymerization, HSPB7 KO mice had longer actin/thin filaments and developed abnormal actin filament bundles within sarcomeres that interconnected Z lines and were cross-linked by α-actinin. In addition, loss of HSPB7 resulted in up-regulation of Lmod2 expression and mislocalization of Tmod1. Furthermore, crossing HSPB7 null mice into an Lmod2 null background rescued the elongated thin filament phenotype of HSPB7 KOs, but double KO mice still exhibited formation of abnormal actin bundles and early embryonic lethality. These in vivo findings indicated that abnormal actin bundles, not elongated thin filament length, were the cause of embryonic lethality in HSPB7 KOs. Our findings showed an unsuspected and critical role for a specific small heat shock protein in directly modulating actin thin filament length in cardiac muscle by binding monomeric actin and limiting its availability for polymerization.
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25
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Fowler VM, Dominguez R. Tropomodulins and Leiomodins: Actin Pointed End Caps and Nucleators in Muscles. Biophys J 2017; 112:1742-1760. [PMID: 28494946 DOI: 10.1016/j.bpj.2017.03.034] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2017] [Revised: 03/27/2017] [Accepted: 03/30/2017] [Indexed: 12/29/2022] Open
Abstract
Cytoskeletal structures characterized by actin filaments with uniform lengths, including the thin filaments of striated muscles and the spectrin-based membrane skeleton, use barbed and pointed-end capping proteins to control subunit addition/dissociation at filament ends. While several proteins cap the barbed end, tropomodulins (Tmods), a family of four closely related isoforms in vertebrates, are the only proteins known to specifically cap the pointed end. Tmods are ∼350 amino acids in length, and comprise alternating tropomyosin- and actin-binding sites (TMBS1, ABS1, TMBS2, and ABS2). Leiomodins (Lmods) are related in sequence to Tmods, but display important differences, including most notably the lack of TMBS2 and the presence of a C-terminal extension featuring a proline-rich domain and an actin-binding WASP-Homology 2 domain. The Lmod subfamily comprises three somewhat divergent isoforms expressed predominantly in muscle cells. Biochemically, Lmods differ from Tmods, acting as powerful nucleators of actin polymerization, not capping proteins. Structurally, Lmods and Tmods display crucial differences that correlate well with their different biochemical activities. Physiologically, loss of Lmods in striated muscle results in cardiomyopathy or nemaline myopathy, whereas complete loss of Tmods leads to failure of myofibril assembly and developmental defects. Yet, interpretation of some of the in vivo data has led to the idea that Tmods and Lmods are interchangeable or, at best, different variants of two subfamilies of pointed-end capping proteins. Here, we review and contrast the existing literature on Tmods and Lmods, and propose a model of Lmod function that attempts to reconcile the in vitro and in vivo data, whereby Lmods nucleate actin filaments that are subsequently capped by Tmods during sarcomere assembly, turnover, and repair.
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Affiliation(s)
- Velia M Fowler
- Department of Molecular Medicine, The Scripps Research Institute, La Jolla, California.
| | - Roberto Dominguez
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania.
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26
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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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27
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Resistance to radial expansion limits muscle strain and work. Biomech Model Mechanobiol 2017; 16:1633-1643. [PMID: 28432448 DOI: 10.1007/s10237-017-0909-3] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2016] [Accepted: 04/07/2017] [Indexed: 10/19/2022]
Abstract
The collagenous extracellular matrix (ECM) of skeletal muscle functions to transmit force, protect sensitive structures, and generate passive tension to resist stretch. The mechanical properties of the ECM change with age, atrophy, and neuromuscular pathologies, resulting in an increase in the relative amount of collagen and an increase in stiffness. Although numerous studies have focused on the effect of muscle fibrosis on passive muscle stiffness, few have examined how these structural changes may compromise contractile performance. Here we combine a mathematical model and experimental manipulations to examine how changes in the mechanical properties of the ECM constrain the ability of muscle fibers and fascicles to radially expand and how such a constraint may limit active muscle shortening. We model the mechanical interaction between a contracting muscle and the ECM using a constant volume, pressurized, fiber-wound cylinder. Our model shows that as the proportion of a muscle cross section made up of ECM increases, the muscle's ability to expand radially is compromised, which in turn restricts muscle shortening. In our experiments, we use a physical constraint placed around the muscle to restrict radial expansion during a contraction. Our experimental results are consistent with model predictions and show that muscles restricted from radial expansion undergo less shortening and generate less mechanical work under identical loads and stimulation conditions. This work highlights the intimate mechanical interaction between contractile and connective tissue structures within skeletal muscle and shows how a deviation from a healthy, well-tuned relationship can compromise performance.
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28
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Mechanical forces during muscle development. Mech Dev 2017; 144:92-101. [DOI: 10.1016/j.mod.2016.11.003] [Citation(s) in RCA: 80] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2016] [Revised: 11/20/2016] [Accepted: 11/21/2016] [Indexed: 01/09/2023]
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Weitkunat M, Brasse M, Bausch AR, Schnorrer F. Mechanical tension and spontaneous muscle twitching precede the formation of cross-striated muscle in vivo. Development 2017; 144:1261-1272. [PMID: 28174246 PMCID: PMC5399620 DOI: 10.1242/dev.140723] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2016] [Accepted: 01/28/2017] [Indexed: 02/05/2023]
Abstract
Muscle forces are produced by repeated stereotypical actomyosin units called sarcomeres. Sarcomeres are chained into linear myofibrils spanning the entire muscle fiber. In mammalian body muscles, myofibrils are aligned laterally, resulting in their typical cross-striated morphology. Despite this detailed textbook knowledge about the adult muscle structure, it is still unclear how cross-striated myofibrils are built in vivo. Here, we investigate the morphogenesis of Drosophila abdominal muscles and establish them as an in vivo model for cross-striated muscle development. By performing live imaging, we find that long immature myofibrils lacking a periodic actomyosin pattern are built simultaneously in the entire muscle fiber and then align laterally to give mature cross-striated myofibrils. Interestingly, laser micro-lesion experiments demonstrate that mechanical tension precedes the formation of the immature myofibrils. Moreover, these immature myofibrils do generate spontaneous Ca2+-dependent contractions in vivo, which, when chemically blocked, result in cross-striation defects. Taken together, these results suggest a myofibrillogenesis model in which mechanical tension and spontaneous muscle twitching synchronize the simultaneous self-organization of different sarcomeric protein complexes to build highly regular cross-striated myofibrils spanning the length of large muscle fibers. Summary: In Drosophila, immature myofibrils are built simultaneously across an entire muscle fiber, and then self-organize in a manner dependent on spontaneous contractions and mechanical tension.
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Affiliation(s)
- Manuela Weitkunat
- Muscle Dynamics Group, Max Planck Institute of Biochemistry, Am Klopferspitz 18, Martinsried 82152, Germany
| | - Martina Brasse
- Lehrstuhl für Biophysik E27, Technische Universität München, James-Franck-Straße 1, Garching 85748, Germany
| | - Andreas R Bausch
- Lehrstuhl für Biophysik E27, Technische Universität München, James-Franck-Straße 1, Garching 85748, Germany
| | - Frank Schnorrer
- Muscle Dynamics Group, Max Planck Institute of Biochemistry, Am Klopferspitz 18, Martinsried 82152, Germany .,Developmental Biology Institute of Marseille (IBDM), CNRS, UMR 7288, Aix-Marseille Université, Case 907, Parc Scientifique de Luminy, Marseille 13288, France
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30
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Gautel M, Djinović-Carugo K. The sarcomeric cytoskeleton: from molecules to motion. ACTA ACUST UNITED AC 2016; 219:135-45. [PMID: 26792323 DOI: 10.1242/jeb.124941] [Citation(s) in RCA: 143] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Highly ordered organisation of striated muscle is the prerequisite for the fast and unidirectional development of force and motion during heart and skeletal muscle contraction. A group of proteins, summarised as the sarcomeric cytoskeleton, is essential for the ordered assembly of actin and myosin filaments into sarcomeres, by combining architectural, mechanical and signalling functions. This review discusses recent cell biological, biophysical and structural insight into the regulated assembly of sarcomeric cytoskeleton proteins and their roles in dissipating mechanical forces in order to maintain sarcomere integrity during passive extension and active contraction. α-Actinin crosslinks in the Z-disk show a pivot-and-rod structure that anchors both titin and actin filaments. In contrast, the myosin crosslinks formed by myomesin in the M-band are of a ball-and-spring type and may be crucial in providing stable yet elastic connections during active contractions, especially eccentric exercise.
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Affiliation(s)
- Mathias Gautel
- King's College London BHF Centre of Research Excellence, Randall Division for Cell and Molecular Biophysics, and Cardiovascular Division, New Hunt's House, London SE1 1UL, UK
| | - Kristina Djinović-Carugo
- Department of Structural and Computational Biology, Max F. Perutz Laboratories, University of Vienna, Campus Vienna Biocenter 5, Vienna A-1030, Austria Department of Biochemistry, Faculty of Chemistry and Chemical Technology, University of Ljubljana, Aškerčeva 5, Ljubljana 1000, Slovenia
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31
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Tiffany H, Sonkar K, Gage MJ. The insertion sequence of the N2A region of titin exists in an extended structure with helical characteristics. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2016; 1865:1-10. [PMID: 27742555 DOI: 10.1016/j.bbapap.2016.10.003] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2016] [Revised: 10/05/2016] [Accepted: 10/07/2016] [Indexed: 12/15/2022]
Abstract
The giant sarcomere protein titin is the third filament in muscle and is integral to maintaining sarcomere integrity as well as contributing to both active and passive tension. Titin is a multi-domain protein that contains regions of repeated structural elements. The N2A region sits at the boundary between the proximal Ig region of titin that is extended under low force and the PEVK region that is extended under high force. Multiple binding interactions have been associated with the N2A region and it has been proposed that this region acts as a mechanical stretch sensor. The focus of this work is a 117 amino acid portion of the N2A region (N2A-IS), which resides between the proximal Ig domains and the PEVK region. Our work has shown that the N2A-IS region is predicted to contain helical structure in the center while both termini are predicted to be disordered. Recombinantly expressed N2A-IS protein contains 13% α-helical structure, as measured via circular dichroism. Additional α-helical structure can be induced with 2,2,2-trifluoroethanol, suggesting that there is transient helical structure that might be stabilized in the context of the entire N2A region. The N2A-IS region does not exhibit any cooperativity in either thermal or chemical denaturation studies while size exclusion chromatography and Fluorescence Resonance Energy Transfer demonstrates that the N2A-IS region has an extended structure. Combined, these results lead to a model of the N2A-IS region having a helical core with extended N- and C-termini.
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Affiliation(s)
- Holly Tiffany
- Department of Biology, Northern Arizona University, Flagstaff, AZ, United States
| | - Kanchan Sonkar
- Department of Chemistry and Biochemistry, Northern Arizona University, Flagstaff, AZ, United States
| | - Matthew J Gage
- Department of Chemistry and Biochemistry, Northern Arizona University, Flagstaff, AZ, United States; Center for Bioengineering Innovation, Northern Arizona University, Flagstaff, AZ, United States; Department of Chemistry, University of Massachusetts Lowell, Lowell, MA, United States.
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Gokhin DS, Fowler VM. Software-based measurement of thin filament lengths: an open-source GUI for Distributed Deconvolution analysis of fluorescence images. J Microsc 2016; 265:11-20. [PMID: 27644080 DOI: 10.1111/jmi.12456] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2016] [Revised: 06/09/2016] [Accepted: 07/19/2016] [Indexed: 12/25/2022]
Abstract
The periodically arranged thin filaments within the striated myofibrils of skeletal and cardiac muscle have precisely regulated lengths, which can change in response to developmental adaptations, pathophysiological states, and genetic perturbations. We have developed a user-friendly, open-source ImageJ plugin that provides a graphical user interface (GUI) for super-resolution measurement of thin filament lengths by applying Distributed Deconvolution (DDecon) analysis to periodic line scans collected from fluorescence images. In the workflow presented here, we demonstrate thin filament length measurement using a phalloidin-stained cryosection of mouse skeletal muscle. The DDecon plugin is also capable of measuring distances of any periodically localized fluorescent signal from the Z- or M-line, as well as distances between successive Z- or M-lines, providing a broadly applicable tool for quantitative analysis of muscle cytoarchitecture. These functionalities can also be used to analyse periodic fluorescence signals in nonmuscle cells.
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Affiliation(s)
- David S Gokhin
- Department of Cell and Molecular Biology, The Scripps Research Institute, La Jolla, California, U.S.A
| | - Velia M Fowler
- Department of Cell and Molecular Biology, The Scripps Research Institute, La Jolla, California, U.S.A
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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: 23] [Impact Index Per Article: 2.9] [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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Mazelet L, Parker MO, Li M, Arner A, Ashworth R. Role of Active Contraction and Tropomodulins in Regulating Actin Filament Length and Sarcomere Structure in Developing Zebrafish Skeletal Muscle. Front Physiol 2016; 7:91. [PMID: 27065876 PMCID: PMC4814503 DOI: 10.3389/fphys.2016.00091] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2015] [Accepted: 02/26/2016] [Indexed: 01/13/2023] Open
Abstract
Whilst it is recognized that contraction plays an important part in maintaining the structure and function of mature skeletal muscle, its role during development remains undefined. In this study the role of movement in skeletal muscle maturation was investigated in intact zebrafish embryos using a combination of genetic and pharmacological approaches. An immotile mutant line (cacnb1 (ts25) ) which lacks functional voltage-gated calcium channels (dihydropyridine receptors) in the muscle and pharmacological immobilization of embryos with a reversible anesthetic (Tricaine), allowed the study of paralysis (in mutants and anesthetized fish) and recovery of movement (reversal of anesthetic treatment). The effect of paralysis in early embryos (aged between 17 and 24 hours post-fertilization, hpf) on skeletal muscle structure at both myofibrillar and myofilament level was determined using both immunostaining with confocal microscopy and small angle X-ray diffraction. The consequences of paralysis and subsequent recovery on the localization of the actin capping proteins Tropomodulin 1 & 4 (Tmod) in fish aged from 17 hpf until 42 hpf was also assessed. The functional consequences of early paralysis were investigated by examining the mechanical properties of the larval muscle. The length-force relationship, active and passive tension, was measured in immotile, recovered and control skeletal muscle at 5 and 7 day post-fertilization (dpf). Recovery of muscle function was also assessed by examining swimming patterns in recovered and control fish. Inhibition of the initial embryonic movements (up to 24 hpf) resulted in an increase in myofibril length and a decrease in width followed by almost complete recovery in both moving and paralyzed fish by 42 hpf. In conclusion, myofibril organization is regulated by a dual mechanism involving movement-dependent and movement-independent processes. The initial contractile event itself drives the localization of Tmod1 to its sarcomeric position, capping the actin pointed ends and ultimately regulating actin length. This study demonstrates that both contraction and contractile-independent mechanisms are important for the regulation of myofibril organization, which in turn is necessary for establishing proper skeletal muscle structure and function during development in vivo in zebrafish.
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Affiliation(s)
- Lise Mazelet
- School of Biological and Chemical Sciences, Queen Mary, University of London London, UK
| | - Matthew O Parker
- School of Health Sciences and Social Work, University of Portsmouth Portsmouth, UK
| | - Mei Li
- Department of Physiology and Pharmacology, Karolinska Institutet Stockholm, Sweden
| | - Anders Arner
- Department of Physiology and Pharmacology, Karolinska Institutet Stockholm, Sweden
| | - Rachel Ashworth
- The Blizard Institute/Institute of Health Sciences Education, Barts and The London School of Medicine and Dentistry London, UK
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35
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Kooij V, Viswanathan MC, Lee DI, Rainer PP, Schmidt W, Kronert WA, Harding SE, Kass DA, Bernstein SI, Van Eyk JE, Cammarato A. Profilin modulates sarcomeric organization and mediates cardiomyocyte hypertrophy. Cardiovasc Res 2016; 110:238-48. [PMID: 26956799 PMCID: PMC4836629 DOI: 10.1093/cvr/cvw050] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/24/2015] [Accepted: 02/28/2016] [Indexed: 11/17/2022] Open
Abstract
Aims Heart failure is often preceded by cardiac hypertrophy, which is characterized by increased cell size, altered protein abundance, and actin cytoskeletal reorganization. Profilin is a well-conserved, ubiquitously expressed, multifunctional actin-binding protein, and its role in cardiomyocytes is largely unknown. Given its involvement in vascular hypertrophy, we aimed to test the hypothesis that profilin-1 is a key mediator of cardiomyocyte-specific hypertrophic remodelling. Methods and results Profilin-1 was elevated in multiple mouse models of hypertrophy, and a cardiomyocyte-specific increase of profilin in Drosophila resulted in significantly larger heart tube dimensions. Moreover, adenovirus-mediated overexpression of profilin-1 in neonatal rat ventricular myocytes (NRVMs) induced a hypertrophic response, measured by increased myocyte size and gene expression. Profilin-1 silencing suppressed the response in NRVMs stimulated with phenylephrine or endothelin-1. Mechanistically, we found that profilin-1 regulates hypertrophy, in part, through activation of the ERK1/2 signalling cascade. Confocal microscopy showed that profilin localized to the Z-line of Drosophila myofibrils under normal conditions and accumulated near the M-line when overexpressed. Elevated profilin levels resulted in elongated sarcomeres, myofibrillar disorganization, and sarcomeric disarray, which correlated with impaired muscle function. Conclusion Our results identify novel roles for profilin as an important mediator of cardiomyocyte hypertrophy. We show that overexpression of profilin is sufficient to induce cardiomyocyte hypertrophy and sarcomeric remodelling, and silencing of profilin attenuates the hypertrophic response.
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Affiliation(s)
- Viola Kooij
- Department of Medicine, Division of Cardiology, The Johns Hopkins University, Baltimore, MD, USA National Heart and Lung Institute, Imperial College London, 4th floor, ICTEM, Hammersmith Campus, Du Cane Road, London W12 0NN, UK
| | - Meera C Viswanathan
- Department of Medicine, Division of Cardiology, The Johns Hopkins University, Baltimore, MD, USA
| | - Dong I Lee
- Department of Medicine, Division of Cardiology, The Johns Hopkins University, Baltimore, MD, USA
| | - Peter P Rainer
- Department of Medicine, Division of Cardiology, The Johns Hopkins University, Baltimore, MD, USA Division of Cardiology, Medical University of Graz, Graz, Austria
| | - William Schmidt
- Department of Medicine, Division of Cardiology, The Johns Hopkins University, Baltimore, MD, USA
| | - William A Kronert
- Department of Biology, San Diego State University, San Diego, CA, USA
| | - Sian E Harding
- National Heart and Lung Institute, Imperial College London, 4th floor, ICTEM, Hammersmith Campus, Du Cane Road, London W12 0NN, UK
| | - David A Kass
- Department of Medicine, Division of Cardiology, The Johns Hopkins University, Baltimore, MD, USA
| | | | - Jennifer E Van Eyk
- Department of Medicine, Division of Cardiology, The Johns Hopkins University, Baltimore, MD, USA Advanced Clinical Biosystems Research Institute, Heart Institute and Department of Medicine, Cedars-Sinai Medical Center, Los Angeles, CA, USA
| | - Anthony Cammarato
- Department of Medicine, Division of Cardiology, The Johns Hopkins University, Baltimore, MD, USA
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Abstract
Efficient muscle contraction in skeletal muscle is predicated on the regulation of actin filament lengths. In one long-standing model that was prominent for decades, the giant protein nebulin was proposed to function as a 'molecular ruler' to specify the lengths of the thin filaments. This theory was questioned by many observations, including experiments in which the length of nebulin was manipulated in skeletal myocytes; this approach revealed that nebulin functions to stabilize filamentous actin, allowing thin filaments to reach mature lengths. In addition, more recent data, mostly from in vivo models and identification of new interacting partners, have provided evidence that nebulin is not merely a structural protein. Nebulin plays a role in numerous cellular processes including regulation of muscle contraction, Z-disc formation, and myofibril organization and assembly.
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Affiliation(s)
- Miensheng Chu
- Department of Cellular and Molecular Medicine and the Sarver Molecular Cardiovascular Research Program, The University of Arizona, 1656 East Mabel, MRB315, Tucson, AZ 85724, USA
| | - Carol C Gregorio
- Department of Cellular and Molecular Medicine and the Sarver Molecular Cardiovascular Research Program, The University of Arizona, 1656 East Mabel, MRB315, Tucson, AZ 85724, USA
| | - Christopher T Pappas
- Department of Cellular and Molecular Medicine and the Sarver Molecular Cardiovascular Research Program, The University of Arizona, 1656 East Mabel, MRB315, Tucson, AZ 85724, USA
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37
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Gokhin DS, Ochala J, Domenighetti AA, Fowler VM. Tropomodulin 1 directly controls thin filament length in both wild-type and tropomodulin 4-deficient skeletal muscle. Development 2015; 142:4351-62. [PMID: 26586224 DOI: 10.1242/dev.129171] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2015] [Accepted: 11/05/2015] [Indexed: 01/10/2023]
Abstract
The sarcomeric tropomodulin (Tmod) isoforms Tmod1 and Tmod4 cap thin filament pointed ends and functionally interact with the leiomodin (Lmod) isoforms Lmod2 and Lmod3 to control myofibril organization, thin filament lengths, and actomyosin crossbridge formation in skeletal muscle fibers. Here, we show that Tmod4 is more abundant than Tmod1 at both the transcript and protein level in a variety of muscle types, but the relative abundances of sarcomeric Tmods are muscle specific. We then generate Tmod4(-/-) mice, which exhibit normal thin filament lengths, myofibril organization, and skeletal muscle contractile function owing to compensatory upregulation of Tmod1, together with an Lmod isoform switch wherein Lmod3 is downregulated and Lmod2 is upregulated. However, RNAi depletion of Tmod1 from either wild-type or Tmod4(-/-) muscle fibers leads to thin filament elongation by ∼15%. Thus, Tmod1 per se, rather than total sarcomeric Tmod levels, controls thin filament lengths in mouse skeletal muscle, whereas Tmod4 appears to be dispensable for thin filament length regulation. These findings identify Tmod1 as the key direct regulator of thin filament length in skeletal muscle, in both adult muscle homeostasis and in developmentally compensated contexts.
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Affiliation(s)
- David S Gokhin
- Department of Cell and Molecular Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Julien Ochala
- Centre of Human and Aerospace Physiological Sciences, King's College London, London SE1 1UL, UK
| | - Andrea A Domenighetti
- Department of Physical Medicine and Rehabilitation, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA Rehabilitation Institute of Chicago, Chicago, IL 60611, USA
| | - Velia M Fowler
- Department of Cell and Molecular Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
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Feng S, Lu L, Zan X, Wu Y, Lin Y, Wang Q. Genetically Engineered Plant Viral Nanoparticles Direct Neural Cells Differentiation and Orientation. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:9402-9409. [PMID: 26247572 DOI: 10.1021/acs.langmuir.5b02226] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
An important aim of tissue engineering is to design biomimetic materials with specific cell binding motifs and precisely controlled structural organization, thereby providing biochemical and physical cues for desired cellular behaviors. Previously, our group generated genetically modified tobacco mosaic virus (TMV) displaying integrin binding motifs, RGD1, RGD7, PSHRN3, P15, and DGEA. The resulting rod-like virus particles displaying integrin binding motifs were biocompatible with Neuro 2A (N2a), a mouse neural crest-derived cell line, and could promote the neurite outgrowth of N2a. The genetically modified viruses could be assembled with aligned orientation in the capillary by applying a shear force. The resulting aligned substrates were able to dictate directional neurite outgrowth of N2a cells. Therefore, this method could be potentially applied for neural tissue engineering, as a neural conduit for repairing peripheral nerve injuries.
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Affiliation(s)
- Sheng Feng
- Department of Chemistry and Biochemistry, University of South Carolina , Columbia, South Carolina 29208, United States
| | - Lin Lu
- Department of Chemistry and Biochemistry, University of South Carolina , Columbia, South Carolina 29208, United States
| | - Xingjie Zan
- Department of Chemistry and Biochemistry, University of South Carolina , Columbia, South Carolina 29208, United States
| | - Yehong Wu
- State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences , Changchun 130022, P. R. China
| | - Yuan Lin
- State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences , Changchun 130022, P. R. China
| | - Qian Wang
- Department of Chemistry and Biochemistry, University of South Carolina , Columbia, South Carolina 29208, United States
- State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences , Changchun 130022, P. R. China
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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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40
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Wang L, Li Y, Chen B, Liu S, Li M, Zheng L, Wang P, Lu TJ, Xu F. Patterning Cellular Alignment through Stretching Hydrogels with Programmable Strain Gradients. ACS APPLIED MATERIALS & INTERFACES 2015; 7:15088-15097. [PMID: 26079936 DOI: 10.1021/acsami.5b04450] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The graded mechanical properties (e.g., stiffness and stress/strain) of excellular matrix play an important role in guiding cellular alignment, as vital in tissue reconstruction with proper functions. Though various methods have been developed to engineer a graded mechanical environment to study its effect on cellular behaviors, most of them failed to distinguish stiffness effect from stress/strain effect during mechanical loading. Here, we construct a mechanical environment with programmable strain gradients by using a hydrogel of a linear elastic property. When seeding cells on such hydrogels, we demonstrate that the pattern of cellular alignment can be rather precisely tailored by substrate strains. The experiment is in consistency with a theoritical prediction when assuming that focal adhesions (FAs) would drive a cell to reorient to the directions where they are most stable. A fundamental theory has also been developed and is excellent in agreement with the complete temporal alignment of cells. This work not only provides important insights into the cellular response to the local mechanical microenvironment but can also be utilized to engineer patterned cellular alignment that can be critical in tissue remodeling and regenerative medicine applications.
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Affiliation(s)
| | | | - Bin Chen
- ∥Department of Engineering Mechanics, Zhejiang University, Hangzhou 310027, People's Republic of China
| | | | | | | | - Pengfei Wang
- §Qian Xuesen Laboratory of Space Technology, China Academy of Space Technology, Beijing 100094, People's Republic of China
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Li F, Buck D, De Winter J, Kolb J, Meng H, Birch C, Slater R, Escobar YN, Smith JE, Yang L, Konhilas J, Lawlor MW, Ottenheijm C, Granzier HL. Nebulin deficiency in adult muscle causes sarcomere defects and muscle-type-dependent changes in trophicity: novel insights in nemaline myopathy. Hum Mol Genet 2015; 24:5219-33. [PMID: 26123491 DOI: 10.1093/hmg/ddv243] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2015] [Accepted: 06/22/2015] [Indexed: 01/07/2023] Open
Abstract
Nebulin is a giant filamentous protein that is coextensive with the actin filaments of the skeletal muscle sarcomere. Nebulin mutations are the main cause of nemaline myopathy (NEM), with typical adult patients having low expression of nebulin, yet the roles of nebulin in adult muscle remain poorly understood. To establish nebulin's functional roles in adult muscle, we studied a novel conditional nebulin KO (Neb cKO) mouse model in which nebulin deletion was driven by the muscle creatine kinase (MCK) promotor. Neb cKO mice are born with high nebulin levels in their skeletal muscles, but within weeks after birth nebulin expression rapidly falls to barely detectable levels Surprisingly, a large fraction of the mice survive to adulthood with low nebulin levels (<5% of control), contain nemaline rods and undergo fiber-type switching toward oxidative types. Nebulin deficiency causes a large deficit in specific force, and mechanistic studies provide evidence that a reduced fraction of force-generating cross-bridges and shortened thin filaments contribute to the force deficit. Muscles rich in glycolytic fibers upregulate proteolysis pathways (MuRF-1, Fbxo30/MUSA1, Gadd45a) and undergo hypotrophy with smaller cross-sectional areas (CSAs), worsening their force deficit. Muscles rich in oxidative fibers do not have smaller weights and can even have hypertrophy, offsetting their specific-force deficit. These studies reveal nebulin as critically important for force development and trophicity in adult muscle. The Neb cKO phenocopies important aspects of NEM (muscle weakness, oxidative fiber-type predominance, variable trophicity effects, nemaline rods) and will be highly useful to test therapeutic approaches to ameliorate muscle weakness.
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Affiliation(s)
- Frank Li
- Department of Cellular and Molecular Medicine
| | | | - Josine De Winter
- Department of Physiology, VU University Medical Center, Amsterdam, The Netherlands
| | - Justin Kolb
- Department of Cellular and Molecular Medicine
| | - Hui Meng
- Department of Pathology and Laboratory Medicine, Medical College of Wisconsin, Milwaukee, WI, USA and
| | - Camille Birch
- Department of Physiology, University of Arizona, Tucson, AZ, USA
| | | | | | | | - Lin Yang
- Department of Biomedical Engineering, University of Florida, Gainesville, FL, USA
| | - John Konhilas
- Department of Physiology, University of Arizona, Tucson, AZ, USA
| | - Michael W Lawlor
- Department of Pathology and Laboratory Medicine, Medical College of Wisconsin, Milwaukee, WI, USA and
| | - Coen Ottenheijm
- Department of Cellular and Molecular Medicine, Department of Physiology, VU University Medical Center, Amsterdam, The Netherlands
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42
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Ono S. Regulation of structure and function of sarcomeric actin filaments in striated muscle of the nematode Caenorhabditis elegans. Anat Rec (Hoboken) 2015; 297:1548-59. [PMID: 25125169 DOI: 10.1002/ar.22965] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2014] [Revised: 02/26/2014] [Accepted: 02/26/2014] [Indexed: 02/01/2023]
Abstract
The nematode Caenorhabditis elegans has been used as a valuable system to study structure and function of striated muscle. The body wall muscle of C. elegans is obliquely striated muscle with highly organized sarcomeric assembly of actin, myosin, and other accessory proteins. Genetic and molecular biological studies in C. elegans have identified a number of genes encoding structural and regulatory components for the muscle contractile apparatuses, and many of them have counterparts in mammalian cardiac and skeletal muscles or striated muscles in other invertebrates. Applicability of genetics, cell biology, and biochemistry has made C. elegans an excellent system to study mechanisms of muscle contractility and assembly and maintenance of myofibrils. This review focuses on the regulatory mechanisms of structure and function of actin filaments in the C. elegans body wall muscle. Sarcomeric actin filaments in C. elegans muscle are associated with the troponin-tropomyosin system that regulates the actin-myosin interaction. Proteins that bind to the side and ends of actin filaments support ordered assembly of thin filaments. Furthermore, regulators of actin dynamics play important roles in initial assembly, growth, and maintenance of sarcomeres. The knowledge acquired in C. elegans can serve as bases to understand the basic mechanisms of muscle structure and function.
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Affiliation(s)
- Shoichiro Ono
- Department of Pathology, Emory University, Atlanta, Georgia; Department of Cell Biology, Emory University, Atlanta, Georgia
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43
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Kremneva E, Makkonen MH, Skwarek-Maruszewska A, Gateva G, Michelot A, Dominguez R, Lappalainen P. Cofilin-2 controls actin filament length in muscle sarcomeres. Dev Cell 2015; 31:215-26. [PMID: 25373779 DOI: 10.1016/j.devcel.2014.09.002] [Citation(s) in RCA: 58] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2014] [Revised: 07/03/2014] [Accepted: 09/03/2014] [Indexed: 01/26/2023]
Abstract
ADF/cofilins drive cytoskeletal dynamics by promoting the disassembly of "aged" ADP-actin filaments. Mammals express several ADF/cofilin isoforms, but their specific biochemical activities and cellular functions have not been studied in detail. Here, we demonstrate that the muscle-specific isoform cofilin-2 promotes actin filament disassembly in sarcomeres to control the precise length of thin filaments in the contractile apparatus. In contrast to other isoforms, cofilin-2 efficiently binds and disassembles both ADP- and ATP/ADP-Pi-actin filaments. We mapped surface-exposed cofilin-2-specific residues required for ATP-actin binding and propose that these residues function as an "actin nucleotide-state sensor" among ADF/cofilins. The results suggest that cofilin-2 evolved specific biochemical and cellular properties that allow it to control actin dynamics in sarcomeres, where filament pointed ends may contain a mixture of ADP- and ATP/ADP-Pi-actin subunits. Our findings also offer a rationale for why cofilin-2 mutations in humans lead to myopathies.
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Affiliation(s)
- Elena Kremneva
- Institute of Biotechnology, University of Helsinki, P.O. Box 56, 00014 Helsinki, Finland
| | - Maarit H Makkonen
- Institute of Biotechnology, University of Helsinki, P.O. Box 56, 00014 Helsinki, Finland
| | | | - Gergana Gateva
- Institute of Biotechnology, University of Helsinki, P.O. Box 56, 00014 Helsinki, Finland
| | - Alphee Michelot
- Laboratoire de Physiologie Cellulaire et Végétale, Institut de Recherches en Technologies et Sciences pour le Vivant, iRTSV, CNRS/CEA/INRA/UJF, 38054 Grenoble, France
| | - Roberto Dominguez
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Pekka Lappalainen
- Institute of Biotechnology, University of Helsinki, P.O. Box 56, 00014 Helsinki, Finland.
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44
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Berger J, Tarakci H, Berger S, Li M, Hall TE, Arner A, Currie PD. Loss of Tropomodulin4 in the zebrafish mutant träge causes cytoplasmic rod formation and muscle weakness reminiscent of nemaline myopathy. Dis Model Mech 2014; 7:1407-15. [PMID: 25288681 PMCID: PMC4257009 DOI: 10.1242/dmm.017376] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Nemaline myopathy is an inherited muscle disease that is mainly diagnosed by the presence of nemaline rods in muscle biopsies. Of the nine genes associated with the disease, five encode components of striated muscle sarcomeres. In a genetic zebrafish screen, the mutant träge (trg) was isolated based on its reduction in muscle birefringence, indicating muscle damage. Myofibres in trg appeared disorganised and showed inhomogeneous cytoplasmic eosin staining alongside malformed nuclei. Linkage analysis of trg combined with sequencing identified a nonsense mutation in tropomodulin4 (tmod4), a regulator of thin filament length and stability. Accordingly, although actin monomers polymerize to form thin filaments in the skeletal muscle of tmod4trg mutants, thin filaments often appeared to be dispersed throughout myofibres. Organised myofibrils with the typical striation rarely assemble, leading to severe muscle weakness, impaired locomotion and early death. Myofibrils of tmod4trg mutants often featured thin filaments of various lengths, widened Z-disks, undefined H-zones and electron-dense aggregations of various shapes and sizes. Importantly, Gomori trichrome staining and the lattice pattern of the detected cytoplasmic rods, together with the reactivity of rods with phalloidin and an antibody against actinin, is reminiscent of nemaline rods found in nemaline myopathy, suggesting that misregulation of thin filament length causes cytoplasmic rod formation in tmod4trg mutants. Although Tropomodulin4 has not been associated with myopathy, the results presented here implicateTMOD4 as a novel candidate for unresolved nemaline myopathies and suggest that the tmod4trg mutant will be a valuable tool to study human muscle disorders.
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Affiliation(s)
- Joachim Berger
- Australian Regenerative Medicine Institute, Monash University, Clayton, VIC 3800, Australia
| | - Hakan Tarakci
- Australian Regenerative Medicine Institute, Monash University, Clayton, VIC 3800, Australia
| | - Silke Berger
- Australian Regenerative Medicine Institute, Monash University, Clayton, VIC 3800, Australia
| | - Mei Li
- Department of Physiology and Pharmacology, Karolinska Institute, Stockholm, SE 17177, Sweden
| | - Thomas E Hall
- Institute for Molecular Bioscience, University of Queensland, St Lucia, QLD 4072, Australia
| | - Anders Arner
- Department of Physiology and Pharmacology, Karolinska Institute, Stockholm, SE 17177, Sweden
| | - Peter D Currie
- Australian Regenerative Medicine Institute, Monash University, Clayton, VIC 3800, Australia
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45
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Gokhin DS, Dubuc EA, Lian KQ, Peters LL, Fowler VM. Alterations in thin filament length during postnatal skeletal muscle development and aging in mice. Front Physiol 2014; 5:375. [PMID: 25324783 PMCID: PMC4178374 DOI: 10.3389/fphys.2014.00375] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2014] [Accepted: 09/10/2014] [Indexed: 11/13/2022] Open
Abstract
The lengths of the sarcomeric thin filaments vary in a skeletal muscle-specific manner and help specify the physiological properties of skeletal muscle. Since the extent of overlap between the thin and thick filaments determines the amount of contractile force that a sarcomere can actively produce, thin filament lengths are accurate predictors of muscle-specific sarcomere length-tension relationships and sarcomere operating length ranges. However, the striking uniformity of thin filament lengths within sarcomeres, specified during myofibril assembly, has led to the widely held assumption that thin filament lengths remain constant throughout an organism's lifespan. Here, we rigorously tested this assumption by using computational super-resolution image analysis of confocal fluorescence images to explore the effects of postnatal development and aging on thin filament length in mice. We found that thin filaments shorten in postnatal tibialis anterior (TA) and gastrocnemius muscles between postnatal days 7 and 21, consistent with the developmental program of myosin heavy chain (MHC) gene expression in this interval. By contrast, thin filament lengths in TA and extensor digitorum longus (EDL) muscles remained constant between 2 mo and 2 yr of age, while thin filament lengths in soleus muscle became shorter, suggestive of a slow-muscle-specific mechanism of thin filament destabilization associated with aging. Collectively, these data are the first to show that thin filament lengths change as part of normal skeletal muscle development and aging, motivating future investigations into the cellular and molecular mechanisms underlying thin filament adaptation across the lifespan.
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Affiliation(s)
- David S Gokhin
- Department of Cell and Molecular Biology, The Scripps Research Institute La Jolla, CA, USA
| | - Emily A Dubuc
- Department of Cell and Molecular Biology, The Scripps Research Institute La Jolla, CA, USA
| | - Kendra Q Lian
- Department of Cell and Molecular Biology, The Scripps Research Institute La Jolla, CA, USA
| | | | - Velia M Fowler
- Department of Cell and Molecular Biology, The Scripps Research Institute La Jolla, CA, USA
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46
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Fernandes I, Schöck F. The nebulin repeat protein Lasp regulates I-band architecture and filament spacing in myofibrils. ACTA ACUST UNITED AC 2014; 206:559-72. [PMID: 25113030 PMCID: PMC4137052 DOI: 10.1083/jcb.201401094] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
With just two nebulin repeats, the Drosophila protein Lasp controls muscle thin filament length and filament spacing. Mutations in nebulin, a giant muscle protein with 185 actin-binding nebulin repeats, are the major cause of nemaline myopathy in humans. Nebulin sets actin thin filament length in sarcomeres, potentially by stabilizing thin filaments in the I-band, where nebulin and thin filaments coalign. However, the precise role of nebulin in setting thin filament length and its other functions in regulating power output are unknown. Here, we show that Lasp, the only member of the nebulin family in Drosophila melanogaster, acts at two distinct sites in the sarcomere and controls thin filament length with just two nebulin repeats. We found that Lasp localizes to the Z-disc edges to control I-band architecture and also localizes at the A-band, where it interacts with both actin and myosin to set proper filament spacing. Furthermore, introducing a single amino acid change into the two nebulin repeats of Lasp demonstrated different roles for each domain and established Lasp as a suitable system for studying nebulin repeat function.
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Affiliation(s)
- Isabelle Fernandes
- Department of Biology, McGill University, Montreal, Quebec, Canada H3A 1B1
| | - Frieder Schöck
- Department of Biology, McGill University, Montreal, Quebec, Canada H3A 1B1
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47
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Li Y, Huang G, Zhang X, Wang L, Du Y, Lu TJ, Xu F. Engineering cell alignment in vitro. Biotechnol Adv 2014; 32:347-65. [DOI: 10.1016/j.biotechadv.2013.11.007] [Citation(s) in RCA: 171] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2013] [Revised: 11/16/2013] [Accepted: 11/17/2013] [Indexed: 01/03/2023]
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48
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Gokhin DS, Tierney MT, Sui Z, Sacco A, Fowler VM. Calpain-mediated proteolysis of tropomodulin isoforms leads to thin filament elongation in dystrophic skeletal muscle. Mol Biol Cell 2014; 25:852-65. [PMID: 24430868 PMCID: PMC3952854 DOI: 10.1091/mbc.e13-10-0608] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Calpain-mediated proteolysis of the thin filament pointed-end–capping protein tropomodulin results in actin subunit association onto pointed ends and increased thin filament lengths in two different murine models of Duchenne muscular dystrophy. This mechanism affects different skeletal muscles in a use- and disease severity–dependent manner. Duchenne muscular dystrophy (DMD) induces sarcolemmal mechanical instability and rupture, hyperactivity of intracellular calpains, and proteolytic breakdown of muscle structural proteins. Here we identify the two sarcomeric tropomodulin (Tmod) isoforms, Tmod1 and Tmod4, as novel proteolytic targets of m-calpain, with Tmod1 exhibiting ∼10-fold greater sensitivity to calpain-mediated cleavage than Tmod4 in situ. In mdx mice, increased m-calpain levels in dystrophic soleus muscle are associated with loss of Tmod1 from the thin filament pointed ends, resulting in ∼11% increase in thin filament lengths. In mdx/mTR mice, a more severe model of DMD, Tmod1 disappears from the thin filament pointed ends in both tibialis anterior (TA) and soleus muscles, whereas Tmod4 additionally disappears from soleus muscle, resulting in thin filament length increases of ∼10 and ∼12% in TA and soleus muscles, respectively. In both mdx and mdx/mTR mice, both TA and soleus muscles exhibit normal localization of α-actinin, the nebulin M1M2M3 domain, Tmod3, and cytoplasmic γ-actin, indicating that m-calpain does not cause wholesale proteolysis of other sarcomeric and actin cytoskeletal proteins in dystrophic skeletal muscle. These results implicate Tmod proteolysis and resultant thin filament length misspecification as novel mechanisms that may contribute to DMD pathology, affecting muscles in a use- and disease severity–dependent manner.
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Affiliation(s)
- David S Gokhin
- Department of Cell and Molecular Biology, The Scripps Research Institute, La Jolla, CA 92037 Sanford Children's Health Research Center, Sanford-Burnham Medical Research Institute, La Jolla, CA 92037
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49
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Ochala J, Gokhin DS, Iwamoto H, Fowler VM. Pointed-end capping by tropomodulin modulates actomyosin crossbridge formation in skeletal muscle fibers. FASEB J 2013; 28:408-15. [PMID: 24072783 DOI: 10.1096/fj.13-239640] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
In skeletal muscle, thick and thin filaments are arranged in a myofibrillar lattice. Tropomodulin 1 (Tmod1) is a pointed-end capping and tropomyosin-binding protein that controls thin-filament assembly, stability, and lengths. It remains unknown whether Tmods have other functional roles, such as regulating muscle contractility. To investigate this, we recorded and analyzed the mechanical properties and X-ray diffraction patterns of single membrane-permeabilized skeletal muscle fibers from mice lacking Tmod1. Results show that absence of Tmod1 and its replacement by Tmod3 and Tmod4 may impair initial tropomyosin movement over actin subunits during thin-filament activation, thus reducing both the fraction of actomyosin crossbridges in the strongly bound state (-29%) and fiber force-generating capacity (-31%). Therefore, Tmods are novel regulators of actomyosin crossbridge formation and muscle contractility, and future investigations and models of skeletal muscle force production must incorporate Tmods.
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Affiliation(s)
- Julien Ochala
- 1Centre of Human and Aerospace Physiological Sciences, School of Biomedical Sciences, King's College London, Rm. 3.3, Shepherd's House, Guy's Campus, London SE1 1UL, UK.
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50
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Yamamoto DL, Vitiello C, Zhang J, Gokhin DS, Castaldi A, Coulis G, Piaser F, Filomena MC, Eggenhuizen PJ, Kunderfranco P, Camerini S, Takano K, Endo T, Crescenzi M, Luther PKL, Lieber RL, Chen J, Bang ML. The nebulin SH3 domain is dispensable for normal skeletal muscle structure but is required for effective active load bearing in mouse. J Cell Sci 2013; 126:5477-89. [PMID: 24046450 DOI: 10.1242/jcs.137026] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Nemaline myopathy (NM) is a congenital myopathy with an estimated incidence of 150,000 live births. It is caused by mutations in thin filament components, including nebulin, which accounts for about 50% of the cases. The identification of NM cases with nonsense mutations resulting in loss of the extreme C-terminal SH3 domain of nebulin suggests an important role of the nebulin SH3 domain, which is further supported by the recent demonstration of its role in IGF-1-induced sarcomeric actin filament formation through targeting of N-WASP to the Z-line. To provide further insights into the functional significance of the nebulin SH3 domain in the Z-disk and to understand the mechanisms by which truncations of nebulin lead to NM, we took two approaches: (1) an affinity-based proteomic screening to identify novel interaction partners of the nebulin SH3 domain; and (2) generation and characterization of a novel knockin mouse model with a premature stop codon in the nebulin gene, eliminating its C-terminal SH3 domain (NebΔSH3 mouse). Surprisingly, detailed analyses of NebΔSH3 mice revealed no structural or histological skeletal muscle abnormalities and no changes in gene expression or localization of interaction partners of the nebulin SH3 domain, including myopalladin, palladin, zyxin and N-WASP. Also, no significant effect on peak isometric stress production, passive tensile stress or Young's modulus was found. However, NebΔSH3 muscle displayed a slightly altered force-frequency relationship and was significantly more susceptible to eccentric contraction-induced injury, suggesting that the nebulin SH3 domain protects against eccentric contraction-induced injury and possibly plays a role in fine-tuning the excitation-contraction coupling mechanism.
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Affiliation(s)
- Daniel L Yamamoto
- Institute of Biomedical Technologies, National Research Council, 20090 Milan, Italy
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