1
|
Reddien PW. The purpose and ubiquity of turnover. Cell 2024; 187:2657-2681. [PMID: 38788689 DOI: 10.1016/j.cell.2024.04.034] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2024] [Revised: 03/19/2024] [Accepted: 04/24/2024] [Indexed: 05/26/2024]
Abstract
Turnover-constant component production and destruction-is ubiquitous in biology. Turnover occurs across organisms and scales, including for RNAs, proteins, membranes, macromolecular structures, organelles, cells, hair, feathers, nails, antlers, and teeth. For many systems, turnover might seem wasteful when degraded components are often fully functional. Some components turn over with shockingly high rates and others do not turn over at all, further making this process enigmatic. However, turnover can address fundamental problems by yielding powerful properties, including regeneration, rapid repair onset, clearance of unpredictable damage and errors, maintenance of low constitutive levels of disrepair, prevention of stable hazards, and transitions. I argue that trade-offs between turnover benefits and metabolic costs, combined with constraints on turnover, determine its presence and rates across distinct contexts. I suggest that the limits of turnover help explain aging and that turnover properties and the basis for its levels underlie this fundamental component of life.
Collapse
Affiliation(s)
- Peter W Reddien
- Whitehead Institute for Biomedical Research, Cambridge, MA 02142, USA; Department of Biology, MIT, Cambridge, MA 02139, USA; Howard Hughes Medical Institute, MIT, Cambridge, MA 02139, USA.
| |
Collapse
|
2
|
Poukalov KK, Valero MC, Muscato DR, Adams LM, Chun H, Lee YI, Andrade NS, Zeier Z, Sweeney HL, Wang ET. Myospreader improves gene editing in skeletal muscle by myonuclear propagation. Proc Natl Acad Sci U S A 2024; 121:e2321438121. [PMID: 38687782 PMCID: PMC11087771 DOI: 10.1073/pnas.2321438121] [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: 12/05/2023] [Accepted: 03/12/2024] [Indexed: 05/02/2024] Open
Abstract
Successful CRISPR/Cas9-based gene editing in skeletal muscle is dependent on efficient propagation of Cas9 to all myonuclei in the myofiber. However, nuclear-targeted gene therapy cargos are strongly restricted to their myonuclear domain of origin. By screening nuclear localization signals and nuclear export signals, we identify "Myospreader," a combination of short peptide sequences that promotes myonuclear propagation. Appending Myospreader to Cas9 enhances protein stability and myonuclear propagation in myoblasts and myofibers. AAV-delivered Myospreader dCas9 better inhibits transcription of toxic RNA in a myotonic dystrophy mouse model. Furthermore, Myospreader Cas9 achieves higher rates of gene editing in CRISPR reporter and Duchenne muscular dystrophy mouse models. Myospreader reveals design principles relevant to all nuclear-targeted gene therapies and highlights the importance of the spatial dimension in therapeutic development.
Collapse
Affiliation(s)
- Kiril K. Poukalov
- Department of Molecular Genetics and Microbiology, University of Florida, Gainesville, FL32610
- Center for NeuroGenetics, University of Florida, Gainesville, FL32610
- Genetics Institute, University of Florida, Gainesville, FL32610
| | - M. Carmen Valero
- Department of Molecular Genetics and Microbiology, University of Florida, Gainesville, FL32610
- Center for NeuroGenetics, University of Florida, Gainesville, FL32610
- Genetics Institute, University of Florida, Gainesville, FL32610
| | - Derek R. Muscato
- Department of Molecular Genetics and Microbiology, University of Florida, Gainesville, FL32610
- Center for NeuroGenetics, University of Florida, Gainesville, FL32610
- Genetics Institute, University of Florida, Gainesville, FL32610
| | - Leanne M. Adams
- Department of Molecular Genetics and Microbiology, University of Florida, Gainesville, FL32610
- Center for NeuroGenetics, University of Florida, Gainesville, FL32610
- Genetics Institute, University of Florida, Gainesville, FL32610
| | - Heejae Chun
- Department of Pharmacology, University of Florida, Gainesville, FL32610
- Myology Institute, University of Florida, Gainesville, FL32610
| | - Young il Lee
- Department of Pharmacology, University of Florida, Gainesville, FL32610
- Myology Institute, University of Florida, Gainesville, FL32610
| | - Nadja S. Andrade
- Department of Psychiatry and Behavioral Sciences, University of Miami, Miami, FL33136
| | - Zane Zeier
- Department of Psychiatry and Behavioral Sciences, University of Miami, Miami, FL33136
| | - H. Lee Sweeney
- Department of Pharmacology, University of Florida, Gainesville, FL32610
- Myology Institute, University of Florida, Gainesville, FL32610
| | - Eric T. Wang
- Department of Molecular Genetics and Microbiology, University of Florida, Gainesville, FL32610
- Center for NeuroGenetics, University of Florida, Gainesville, FL32610
- Genetics Institute, University of Florida, Gainesville, FL32610
- Myology Institute, University of Florida, Gainesville, FL32610
| |
Collapse
|
3
|
Vasileva F, Font-Lladó R, Carreras-Badosa G, Roman-Viñas B, Cadellans-Arróniz A, López-Bermejo A, Prats-Puig A. Salivary cardiac-enriched FHL2-interacting protein is associated with higher diastolic-to-systolic-blood pressure ratio, sedentary time and center of pressure displacement in healthy 7-9 years old school-children. Front Endocrinol (Lausanne) 2024; 15:1292653. [PMID: 38304464 PMCID: PMC10830845 DOI: 10.3389/fendo.2024.1292653] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/13/2023] [Accepted: 01/04/2024] [Indexed: 02/03/2024] Open
Abstract
Introduction Cardiac-enriched FHL2-interacting protein (CEFIP) is a recently identified protein, first found in the z-disc of striated muscles, and related to cardiovascular diseases. Our objectives are: 1) to quantify CEFIP in saliva in healthy 7-9 years old school-children; and 2) to assess the associations of salivary CEFIP concentration and blood pressure, physical (in)activity and physical fitness in these children. Methods A total of 72 children (7.6 ± 0.3 years) were included in the study, recruited in primary schools in Girona (Spain). A sandwich enzyme-linked immunosorbent assay was used (abx506878; Abbexa, United Kingdom) to quantify CEFIP in saliva. Anthropometric evaluation was performed [body mass, height and body mass index (BMI)]. Systolic and diastolic blood pressure were measured by means of an electronic oscillometer and the diastolic-to-systolic blood pressure ratio (D/S BP ratio) was calculated. Physical (in)activity [sedentary time and time spent in physical activity (PA)] were assessed by means of a triaxial Actigraph GT3X accelerometer (Actigraph, Pensacola, FL, USA) that children were instructed to wear for 24h during 7 conssecutive days. Finally, physical fitness (speed and agility, explosive power of legs, handgrip strength, flexibility and balance) were assessed through validated and standardized testing batteries. Results CEFIP was easily detected and measured in all saliva samples (mean concentration: 0.6 ± 0.2 pg/ml). Salivary CEFIP was positively associated with D/S BP ratio (r=0.305, p=0.010) and sedentary time (r=0.317, p=0.012), but negatively associated with PA in 7-9 years old school-children (r=-0.350, p=0.002). Furthermore, salivary CEFIP was related to lower level of balance i.e., higher center of pressure (CoP) displacement in these children (r=0.411, p<0.001). The associations of salivary CEFIP with D/S BP ratio (Beta=0.349, p=0.004), sedentary time (Beta=0.354, p=0.009) and CoP displacement (Beta=0.401, p=0.001), were maintained significant after adjustment for potential confounding variables such as age, gender and BMI in linear regression analyses. Conclusion CEFIP can be easily assessed in saliva as a promising biomarker associated with cardiovascular health in 7-9 years old school-children. Interestingly, higher salivary CEFIP concentration was related to higher D/S BP ratio, more sedentary time and higher CoP displacement i.e., lower level of balance in these children.
Collapse
Affiliation(s)
- Fidanka Vasileva
- Pediatric Endocrinology Research Group, Girona Institute for Biomedical Research, Girona, Spain
- University School of Health and Sport, University of Girona, Girona, Spain
| | - Raquel Font-Lladó
- University School of Health and Sport, University of Girona, Girona, Spain
- Research Group of Culture and Education, Institute of Educational Research, University of Girona, Girona, Spain
| | - Gemma Carreras-Badosa
- Pediatric Endocrinology Research Group, Girona Institute for Biomedical Research, Girona, Spain
| | - Blanca Roman-Viñas
- University School of Health and Sport, University of Girona, Girona, Spain
- Department of Physical Activity and Sport Sciences, Blanquerna-Universitat Ramon Llull, Barcelona, Spain
| | - Aïda Cadellans-Arróniz
- Department of Physiotherapy, Faculty of Medicine and Health Sciences, International University of Catalonia, Barcelona, Spain
| | - Abel López-Bermejo
- Pediatric Endocrinology Research Group, Girona Institute for Biomedical Research, Girona, Spain
- Department of Medical Sciences, University of Girona, Girona, Spain
- Pediatric Endocrinology, Dr. Josep Trueta Hospital, Girona, Spain
| | - Anna Prats-Puig
- University School of Health and Sport, University of Girona, Girona, Spain
- Research Group of Clinical Anatomy, Embryology and Neuroscience, Department of Medical Sciences, University of Girona, Girona, Spain
| |
Collapse
|
4
|
Kelly CM, Martin JL, Coseno M, Previs MJ. Visualization of cardiac thick filament dynamics in ex vivo heart preparations. J Mol Cell Cardiol 2023; 185:88-98. [PMID: 37923195 PMCID: PMC10959293 DOI: 10.1016/j.yjmcc.2023.10.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/11/2023] [Revised: 10/27/2023] [Accepted: 10/30/2023] [Indexed: 11/07/2023]
Abstract
RATIONALE Cardiac muscle cells are terminally differentiated after birth and must beat continually throughout one's lifetime. This mechanical process is driven by the sliding of actin-based thin filaments along myosin-based thick filaments, organized within sarcomeres. Despite costly energetic demand, the half-life of the proteins that comprise the cardiac thick filaments is ∼10 days, with individual molecules being replaced stochastically, by unknown mechanisms. OBJECTIVES To allow for the stochastic replacement of molecules, we hypothesized that the structure of thick filaments must be highly dynamic in vivo. METHODS AND RESULTS To test this hypothesis in adult mouse hearts, we replaced a fraction of the endogenous myosin regulatory light chain (RLC), a component of thick filaments, with GFP-labeled RLC by adeno-associated viral (AAV) transduction. The RLC-GFP was properly localized to the heads of the myosin molecules within thick filaments in ex vivo heart preparations and had no effect on heart size or actin filament siding in vitro. However, the localization of the RLC-GFP molecules was highly mobile, changing its position within the sarcomere on the minute timescale, when quantified by fluorescence recovery after photobleaching (FRAP) using multiphoton microscopy. Interestingly, RLC-GFP mobility was restricted to within the boundaries of single sarcomeres. When cardiomyocytes were lysed, the RLC-GFP remained strongly bound to myosin heavy chain, and the intact myosin molecules adopted a folded, compact configuration, when disassociated from the filaments at physiological ionic conditions. CONCLUSIONS These data demonstrate that the structure of the thick filament is highly dynamic in the intact heart, with a rate of molecular exchange into and out of thick filaments that is ∼1500 times faster than that required for the replacement of molecules through protein synthesis or degradation.
Collapse
Affiliation(s)
- Colleen M Kelly
- Molecular Physiology and Biophysics Department, University of Vermont, Larner College of Medicine, Burlington, VT 05405, United States of America
| | - Jody L Martin
- Department of Pharmacology, University of California, Davis, Davis, CA 90095, United States of America
| | - Molly Coseno
- Fluidic Analytics, The Paddocks Business Centre, Cambridge CB1 8DH, United Kingdom
| | - Michael J Previs
- Molecular Physiology and Biophysics Department, University of Vermont, Larner College of Medicine, Burlington, VT 05405, United States of America.
| |
Collapse
|
5
|
Poukalov KK, Valero MC, Muscato DR, Adams LM, Chun H, Lee YI, Andrade NS, Zeier Z, Sweeney HL, Wang ET. Myospreader improves gene editing in skeletal muscle by myonuclear propagation. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.11.06.565807. [PMID: 37986992 PMCID: PMC10659306 DOI: 10.1101/2023.11.06.565807] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2023]
Abstract
Successful CRISPR/Cas9-based gene editing in skeletal muscle is dependent on efficient propagation of Cas9 to all myonuclei in the myofiber. However, nuclear-targeted gene therapy cargos are strongly restricted to their myonuclear domain of origin. By screening nuclear localization signals and nuclear export signals, we identify "Myospreader", a combination of short peptide sequences that promotes myonuclear propagation. Appending Myospreader to Cas9 enhances protein stability and myonuclear propagation in myoblasts and myofibers. AAV-delivered Myospreader dCas9 better inhibits transcription of toxic RNA in a myotonic dystrophy mouse model. Furthermore, Myospreader Cas9 achieves higher rates of gene editing in CRISPR reporter and Duchenne muscular dystrophy mouse models. Myospreader reveals design principles relevant to all nuclear-targeted gene therapies and highlights the importance of the spatial dimension in therapeutic development.
Collapse
Affiliation(s)
- Kiril K. Poukalov
- Department of Molecular Genetics & Microbiology, University of Florida
- Center for NeuroGenetics, University of Florida
- Genetics Institute, University of Florida
| | - M. Carmen Valero
- Department of Molecular Genetics & Microbiology, University of Florida
- Center for NeuroGenetics, University of Florida
- Genetics Institute, University of Florida
| | - Derek R. Muscato
- Department of Molecular Genetics & Microbiology, University of Florida
- Center for NeuroGenetics, University of Florida
- Genetics Institute, University of Florida
| | - Leanne M. Adams
- Department of Molecular Genetics & Microbiology, University of Florida
- Center for NeuroGenetics, University of Florida
- Genetics Institute, University of Florida
| | - Heejae Chun
- Department of Pharmacology, University of Florida
- Myology Institute, University of Florida
| | - Young il Lee
- Department of Pharmacology, University of Florida
- Myology Institute, University of Florida
| | - Nadja S. Andrade
- Department of Psychiatry & Behavioral Sciences, University of Miami
| | - Zane Zeier
- Department of Psychiatry & Behavioral Sciences, University of Miami
| | - H. Lee Sweeney
- Department of Pharmacology, University of Florida
- Myology Institute, University of Florida
| | - Eric T. Wang
- Department of Molecular Genetics & Microbiology, University of Florida
- Center for NeuroGenetics, University of Florida
- Genetics Institute, University of Florida
- Myology Institute, University of Florida
| |
Collapse
|
6
|
Kenworthy AK. What's past is prologue: FRAP keeps delivering 50 years later. Biophys J 2023; 122:3577-3586. [PMID: 37218127 PMCID: PMC10541474 DOI: 10.1016/j.bpj.2023.05.016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2023] [Revised: 03/03/2023] [Accepted: 05/11/2023] [Indexed: 05/24/2023] Open
Abstract
Fluorescence recovery after photobleaching (FRAP) has emerged as one of the most widely utilized techniques to quantify binding and diffusion kinetics of biomolecules in biophysics. Since its inception in the mid-1970s, FRAP has been used to address an enormous array of questions including the characteristic features of lipid rafts, how cells regulate the viscosity of their cytoplasm, and the dynamics of biomolecules inside condensates formed by liquid-liquid phase separation. In this perspective, I briefly summarize the history of the field and discuss why FRAP has proven to be so incredibly versatile and popular. Next, I provide an overview of the extensive body of knowledge that has emerged on best practices for quantitative FRAP data analysis, followed by some recent examples of biological lessons learned using this powerful approach. Finally, I touch on new directions and opportunities for biophysicists to contribute to the continued development of this still-relevant research tool.
Collapse
Affiliation(s)
- Anne K Kenworthy
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, Virginia; Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Charlottesville, Virginia.
| |
Collapse
|
7
|
Gu C, Fan X, Yu W. Functional Diversity of Mammalian Small Heat Shock Proteins: A Review. Cells 2023; 12:1947. [PMID: 37566026 PMCID: PMC10417760 DOI: 10.3390/cells12151947] [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: 06/27/2023] [Revised: 07/22/2023] [Accepted: 07/24/2023] [Indexed: 08/12/2023] Open
Abstract
The small heat shock proteins (sHSPs), whose molecular weight ranges from 12∼43 kDa, are members of the heat shock protein (HSP) family that are widely found in all organisms. As intracellular stress resistance molecules, sHSPs play an important role in maintaining the homeostasis of the intracellular environment under various stressful conditions. A total of 10 sHSPs have been identified in mammals, sharing conserved α-crystal domains combined with variable N-terminal and C-terminal regions. Unlike large-molecular-weight HSP, sHSPs prevent substrate protein aggregation through an ATP-independent mechanism. In addition to chaperone activity, sHSPs were also shown to suppress apoptosis, ferroptosis, and senescence, promote autophagy, regulate cytoskeletal dynamics, maintain membrane stability, control the direction of cellular differentiation, modulate angiogenesis, and spermatogenesis, as well as attenuate the inflammatory response and reduce oxidative damage. Phosphorylation is the most significant post-translational modification of sHSPs and is usually an indicator of their activation. Furthermore, abnormalities in sHSPs often lead to aggregation of substrate proteins and dysfunction of client proteins, resulting in disease. This paper reviews the various biological functions of sHSPs in mammals, emphasizing the roles of different sHSPs in specific cellular activities. In addition, we discuss the effect of phosphorylation on the function of sHSPs and the association between sHSPs and disease.
Collapse
Affiliation(s)
- Chaoguang Gu
- Institute of Biochemistry, College of Life Sciences and Medicine, Zhejiang Sci-Tech University, Xiasha High-Tech Zone No.2 Road, Hangzhou 310018, China
| | - Xinyi Fan
- Faculty of Arts and Science, University of Toronto, Toronto, ON M5S1A1, Canada
| | - Wei Yu
- Institute of Biochemistry, College of Life Sciences and Medicine, Zhejiang Sci-Tech University, Xiasha High-Tech Zone No.2 Road, Hangzhou 310018, China
| |
Collapse
|
8
|
Banga S, Cardoso R, Castellani C, Srivastava S, Watkins J, Lima J. Cardiac MRI as an Imaging Tool in Titin Variant-Related Dilated Cardiomyopathy. CARDIOVASCULAR REVASCULARIZATION MEDICINE 2023; 52:86-93. [PMID: 36934006 DOI: 10.1016/j.carrev.2023.03.001] [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: 11/07/2022] [Revised: 02/05/2023] [Accepted: 03/01/2023] [Indexed: 03/08/2023]
Abstract
Dilated Cardiomyopathy is a common myocardial disease characterized by dilation and loss of function of one or both ventricles. A variety of etiologies have been implicated including genetic variation. Advancement in genetic sequencing, and diagnostic imaging allows for detection of genetic mutations in sarcomere protein titin (TTN) and high resolution assessment of cardiac function. This review article discusses the role of cardiac MRI in diagnosing dilated cardiomyopathy in patients with TTN variant related cardiomyopathy.
Collapse
Affiliation(s)
- Sandeep Banga
- Division of Cardiology, Michigan State University, Sparrow Hospital, Lansing, MI, USA.
| | | | - Carson Castellani
- Division of Internal Medicine, Medical College of Wisconsin, Milwaukee, WI, USA
| | - Shaurya Srivastava
- Division of Internal Medicine, Michigan State University, Lansing, MI, USA
| | - Jennifer Watkins
- Division of Cardiology, Michigan State University, Sparrow Hospital, Lansing, MI, USA
| | - Joao Lima
- Division of Cardiology, Johns Hopkins University, Baltimore, MD, USA
| |
Collapse
|
9
|
Hansson KA, Eftestøl E. Scaling of nuclear numbers and their spatial arrangement in skeletal muscle cell size regulation. Mol Biol Cell 2023; 34:pe3. [PMID: 37339435 PMCID: PMC10398882 DOI: 10.1091/mbc.e22-09-0424] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2022] [Revised: 03/29/2023] [Accepted: 04/28/2023] [Indexed: 06/22/2023] Open
Abstract
Many cells display considerable functional plasticity and depend on the regulation of numerous organelles and macromolecules for their maintenance. In large cells, organelles also need to be carefully distributed to supply the cell with essential resources and regulate intracellular activities. Having multiple copies of the largest eukaryotic organelle, the nucleus, epitomizes the importance of scaling gene products to large cytoplasmic volumes in skeletal muscle fibers. Scaling of intracellular constituents within mammalian muscle fibers is, however, poorly understood, but according to the myonuclear domain hypothesis, a single nucleus supports a finite amount of cytoplasm and is thus postulated to act autonomously, causing the nuclear number to be commensurate with fiber volume. In addition, the orderly peripheral distribution of myonuclei is a hallmark of normal cell physiology, as nuclear mispositioning is associated with impaired muscle function. Because underlying structures of complex cell behaviors are commonly formalized by scaling laws and thus emphasize emerging principles of size regulation, the work presented herein offers more of a unified conceptual platform based on principles from physics, chemistry, geometry, and biology to explore cell size-dependent correlations of the largest mammalian cell by means of scaling.
Collapse
Affiliation(s)
- Kenth-Arne Hansson
- Section for Health and Exercise Physiology, Inland Norway University of Applied Sciences, 2624 Lillehammer, Norway
| | - Einar Eftestøl
- Department of Biosciences, University of Oslo, 0371 Oslo, Norway
| |
Collapse
|
10
|
Zhang Z, Zhang W, Blakes R, Sundby LJ, Shi Z, Rockey DC, Ervasti JM, Nam YJ. Fibroblast fate determination during cardiac reprogramming by remodeling of actin filaments. Stem Cell Reports 2022; 17:1604-1619. [PMID: 35688153 PMCID: PMC9287671 DOI: 10.1016/j.stemcr.2022.05.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2022] [Revised: 05/12/2022] [Accepted: 05/13/2022] [Indexed: 11/23/2022] Open
Abstract
Fibroblasts can be reprogrammed into induced cardiomyocyte-like cells (iCMs) by forced expression of cardiogenic transcription factors. However, it remains unknown how fibroblasts adopt a cardiomyocyte (CM) fate during their spontaneous ongoing transdifferentiation toward myofibroblasts (MFs). By tracing fibroblast lineages following cardiac reprogramming in vitro, we found that most mature iCMs are derived directly from fibroblasts without transition through the MF state. This direct conversion is attributable to mutually exclusive induction of cardiac sarcomeres and MF cytoskeletal structures in the cytoplasm of fibroblasts during reprogramming. For direct fate switch from fibroblasts to iCMs, significant remodeling of actin isoforms occurs in fibroblasts, including induction of α-cardiac actin and decrease of the actin isoforms predominant in MFs. Accordingly, genetic or pharmacological ablation of MF-enriched actin isoforms significantly enhances cardiac reprogramming. Our results demonstrate that remodeling of actin isoforms is required for fibroblast to CM fate conversion by cardiac reprogramming.
Collapse
Affiliation(s)
- Zhentao Zhang
- Department of Medicine, Division of Cardiovascular Medicine, Vanderbilt University Medical Center, Nashville, TN, USA; Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN, USA; Vanderbilt Center for Stem Cell Biology, Vanderbilt University, Nashville, TN, USA
| | - Wenhui Zhang
- Department of Medicine, Division of Cardiovascular Medicine, Vanderbilt University Medical Center, Nashville, TN, USA; Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN, USA; Vanderbilt Center for Stem Cell Biology, Vanderbilt University, Nashville, TN, USA
| | - Robert Blakes
- Department of Medicine, Division of Cardiovascular Medicine, Vanderbilt University Medical Center, Nashville, TN, USA; Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN, USA; Vanderbilt Center for Stem Cell Biology, Vanderbilt University, Nashville, TN, USA
| | - Lauren J Sundby
- Program in Molecular, Cellular, Developmental Biology, and Genetics, University of Minnesota, Minneapolis, MN, USA
| | - Zengdun Shi
- Department of Internal Medicine, Medical University of South Carolina, Charleston, SC, USA
| | - Don C Rockey
- Department of Internal Medicine, Medical University of South Carolina, Charleston, SC, USA
| | - James M Ervasti
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN, USA; Program in Molecular, Cellular, Developmental Biology, and Genetics, University of Minnesota, Minneapolis, MN, USA
| | - Young-Jae Nam
- Department of Medicine, Division of Cardiovascular Medicine, Vanderbilt University Medical Center, Nashville, TN, USA; Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN, USA; Vanderbilt Center for Stem Cell Biology, Vanderbilt University, Nashville, TN, USA.
| |
Collapse
|
11
|
Kötter S, Krüger M. Protein Quality Control at the Sarcomere: Titin Protection and Turnover and Implications for Disease Development. Front Physiol 2022; 13:914296. [PMID: 35846001 PMCID: PMC9281568 DOI: 10.3389/fphys.2022.914296] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2022] [Accepted: 06/10/2022] [Indexed: 11/26/2022] Open
Abstract
Sarcomeres are mainly composed of filament and signaling proteins and are the smallest molecular units of muscle contraction and relaxation. The sarcomere protein titin serves as a molecular spring whose stiffness mediates myofilament extensibility in skeletal and cardiac muscle. Due to the enormous size of titin and its tight integration into the sarcomere, the incorporation and degradation of the titin filament is a highly complex task. The details of the molecular processes involved in titin turnover are not fully understood, but the involvement of different intracellular degradation mechanisms has recently been described. This review summarizes the current state of research with particular emphasis on the relationship between titin and protein quality control. We highlight the involvement of the proteasome, autophagy, heat shock proteins, and proteases in the protection and degradation of titin in heart and skeletal muscle. Because the fine-tuned balance of degradation and protein expression can be disrupted under pathological conditions, the review also provides an overview of previously known perturbations in protein quality control and discusses how these affect sarcomeric proteins, and titin in particular, in various disease states.
Collapse
|
12
|
Ojima K, Kigaki M, Ichimura E, Suzuki T, Kobayashi K, Muroya S, Nishimura T. Endogenous slow and fast myosin dynamics in myofibers isolated from mice expressing GFP-Myh7 and Kusabira Orange-Myh1. Am J Physiol Cell Physiol 2022; 323:C520-C535. [PMID: 35759444 DOI: 10.1152/ajpcell.00415.2021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Skeletal muscle consists of slow and fast myofibers in which different myosin isoforms are expressed. Approximately 300 myosins form a single thick filament in the myofibrils, where myosin is continuously exchanged. However, endogenous slow and fast myosin dynamics have not been fully understood. To elucidate those dynamics, here we generated mice expressing green fluorescence protein-tagged slow myosin heavy chain (GFP-Myh7) and Kusabira Orange fluorescence protein-tagged fast myosin heavy chain (KuO-Myh1). First, these mice enabled us to distinguish between GFP- and KuO-myofibers under fluorescence microscopy: GFP-Myh7 and KuO-Myh1 were exclusively expressed in slow myofibers and fast myofibers, respectively. Next, to monitor endogenous myosin dynamics, fluorescence recovery after photobleaching (FRAP) was conducted. The mobile fraction (Mf) of GFP-Myh7 and that of KuO-Myh1 were almost constant values independent of the regions of the myofibers and the muscle portions where the myofibers were isolated. Intriguingly, proteasome inhibitor treatment significantly decreased the Mf in GFP-Myh7 but not in KuO-Myh1 myofibers, indicating that the response to a disturbance in protein turnover depended on muscle fiber type. Taken together, the present results indicated that the mice we generated are promising tools not only for distinguishing between GFP- and KuO-myofibers but also for studying the dynamics of endogenous myosin isoforms by live-cell fluorescence imaging.
Collapse
Affiliation(s)
- Koichi Ojima
- Muscle Biology Research Unit, Division of Animal Products Research, Institute of Livestock and Grassland Science, NARO, Tsukuba, Ibaraki, Japan
| | - Masahiro Kigaki
- Research Faculty of Agriculture, Graduate School of Agriculture, Hokkaido University, Sapporo, Hokkaido, Japan
| | - Emi Ichimura
- Research Faculty of Agriculture, Graduate School of Agriculture, Hokkaido University, Sapporo, Hokkaido, Japan
| | - Takahiro Suzuki
- Laboratory of Muscle and Meat Science, Department of Animal and Marine Bioresource Sciences, Faculty of Agriculture, Graduate School of Agriculture, Kyushu University, Fukuoka, Japan
| | - Ken Kobayashi
- Research Faculty of Agriculture, Graduate School of Agriculture, Hokkaido University, Sapporo, Hokkaido, Japan
| | - Susumu Muroya
- Muscle Biology Research Unit, Division of Animal Products Research, Institute of Livestock and Grassland Science, NARO, Tsukuba, Ibaraki, Japan
| | - Takanori Nishimura
- Research Faculty of Agriculture, Graduate School of Agriculture, Hokkaido University, Sapporo, Hokkaido, Japan
| |
Collapse
|
13
|
Riley LA, Zhang X, Douglas CM, Mijares JM, Hammers DW, Wolff CA, Wood NB, Olafson HR, Du P, Labeit S, Previs MJ, Wang ET, Esser KA. The skeletal muscle circadian clock regulates titin splicing through RBM20. eLife 2022; 11:76478. [PMID: 36047761 PMCID: PMC9473687 DOI: 10.7554/elife.76478] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Accepted: 08/31/2022] [Indexed: 02/01/2023] Open
Abstract
Circadian rhythms are maintained by a cell-autonomous, transcriptional-translational feedback loop known as the molecular clock. While previous research suggests a role of the molecular clock in regulating skeletal muscle structure and function, no mechanisms have connected the molecular clock to sarcomere filaments. Utilizing inducible, skeletal muscle specific, Bmal1 knockout (iMSBmal1-/-) mice, we showed that knocking out skeletal muscle clock function alters titin isoform expression using RNAseq, liquid chromatography-mass spectrometry, and sodium dodecyl sulfate-vertical agarose gel electrophoresis. This alteration in titin's spring length resulted in sarcomere length heterogeneity. We demonstrate the direct link between altered titin splicing and sarcomere length in vitro using U7 snRNPs that truncate the region of titin altered in iMSBmal1-/- muscle. We identified a mechanism whereby the skeletal muscle clock regulates titin isoform expression through transcriptional regulation of Rbm20, a potent splicing regulator of titin. Lastly, we used an environmental model of circadian rhythm disruption and identified significant downregulation of Rbm20 expression. Our findings demonstrate the importance of the skeletal muscle circadian clock in maintaining titin isoform through regulation of RBM20 expression. Because circadian rhythm disruption is a feature of many chronic diseases, our results highlight a novel pathway that could be targeted to maintain skeletal muscle structure and function in a range of pathologies.
Collapse
Affiliation(s)
- Lance A Riley
- Department of Physiology and Functional Genomics, University of FloridaGainesvilleUnited States,Myology Institute, University of FloridaGainesvilleUnited States
| | - Xiping Zhang
- Department of Physiology and Functional Genomics, University of FloridaGainesvilleUnited States,Myology Institute, University of FloridaGainesvilleUnited States
| | - Collin M Douglas
- Department of Physiology and Functional Genomics, University of FloridaGainesvilleUnited States,Myology Institute, University of FloridaGainesvilleUnited States
| | - Joseph M Mijares
- Department of Physiology and Functional Genomics, University of FloridaGainesvilleUnited States,Myology Institute, University of FloridaGainesvilleUnited States
| | - David W Hammers
- Myology Institute, University of FloridaGainesvilleUnited States,Department of Pharmacology and Therapeutics, University of FloridaGainesvilleUnited States
| | - Christopher A Wolff
- Department of Physiology and Functional Genomics, University of FloridaGainesvilleUnited States,Myology Institute, University of FloridaGainesvilleUnited States
| | - Neil B Wood
- Department of Molecular Physiology and Biophysics, University of VermontBurlingtonUnited States
| | - Hailey R Olafson
- Department of Molecular Genetics of Microbiology, Center for Neurogenetics, University of FloridaGainesvilleUnited States
| | - Ping Du
- Department of Physiology and Functional Genomics, University of FloridaGainesvilleUnited States
| | - Siegfried Labeit
- Medical Faculty Mannheim, University of HeidelbergMannheimGermany
| | - Michael J Previs
- Department of Molecular Physiology and Biophysics, University of VermontBurlingtonUnited States
| | - Eric T Wang
- Myology Institute, University of FloridaGainesvilleUnited States,Department of Molecular Genetics of Microbiology, Center for Neurogenetics, University of FloridaGainesvilleUnited States
| | - Karyn A Esser
- Department of Physiology and Functional Genomics, University of FloridaGainesvilleUnited States,Myology Institute, University of FloridaGainesvilleUnited States
| |
Collapse
|
14
|
Dube DK, Wang J, Fan Y, Dube S, Abbott L, Sanger JM, Channaveerappa D, Darie CC, Poiesz BJ, Sanger JW. Effect of MG-132 on myofibrillogenesis and the ubiquitination of GAPDH in quail myotubes. Cytoskeleton (Hoboken) 2021; 78:375-390. [PMID: 34698442 DOI: 10.1002/cm.21690] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2021] [Revised: 10/07/2021] [Accepted: 10/15/2021] [Indexed: 11/10/2022]
Abstract
In the three-step myofibrillogenesis model, mature myofibrils are formed through two intermediate structures: premyofibrils and nascent myofibrils. We have recently reported that several inhibitors of the Ubiquitin Proteosome System, for example, MG-132, and DBeQ, reversibly block progression of nascent myofibrils to mature myofibrils. In this investigation, we studied the effects of MG132 and DBeQ on the expression of various myofibrillar proteins including actin, myosin light and heavy chains, tropomyosin, myomesin, and myosin binding protein-C in cultured embryonic quail myotubes by western blotting using two loading controls-α-tubulin and glyceraldehyde 3-phosphate dehydrogenase (GAPDH). Surprisingly, we found that MG-132 affected the level of expression of GAPDH but DBeQ did not. Reverse transcription polymerase chain reaction (RT-PCR) and quantitative reverse transcription-PCR (qRT-PCR) showed no significant effect of MG-132 on GAPDH transcription. Two-dimensional (2D) western blot analyses with extracts of control and MG-132-treated cells using anti-ubiquitin antibody indicated that MG132-treated myotubes show a stronger emitter-coupled logic signal. However, Spot% and Spot volume calculations for all spots from both western blot film signals and matched Coomassie-stained 2D polyacrylamide gel electrophoresis showed that the intensity of staining in a spot of ~39 kDa protein is 3.5-fold lower in the gel of MG-132-treated extracts. Mass spectrometry analyses identified the ~39 kDa protein as quail GAPDH. Immunohistochemical analysis of fixed MG-132-treated myotubes with anti-GAPDH antibody showed extensive clump formation, which may be analogous to granule formation by stress response factors in MG132-treated cells. This is the first report on in vivo ubiquitination of GAPDH. This may be essential for the moonlighting (Jeffery, 1999) activity of GAPDH for tailoring stress in myotubes.
Collapse
Affiliation(s)
- Dipak K Dube
- Department of Medicine, SUNY Upstate Medical University, Syracuse, New York, USA
| | - Jushuo Wang
- Department of Cell and Developmental Biology, SUNY Upstate Medical University, Syracuse, New York, USA
| | - Yingli Fan
- Department of Cell and Developmental Biology, SUNY Upstate Medical University, Syracuse, New York, USA
| | - Syamalima Dube
- Department of Medicine, SUNY Upstate Medical University, Syracuse, New York, USA
| | - Lynn Abbott
- Department of Medicine, SUNY Upstate Medical University, Syracuse, New York, USA
| | - Jean M Sanger
- Department of Cell and Developmental Biology, SUNY Upstate Medical University, Syracuse, New York, USA
| | - Devika Channaveerappa
- Biochemistry and Proteomics Group, Department of Chemistry and Biomolecular Science, Clarkson University, Potsdam, New York, USA
| | - Costel C Darie
- Biochemistry and Proteomics Group, Department of Chemistry and Biomolecular Science, Clarkson University, Potsdam, New York, USA
| | - Bernard J Poiesz
- Department of Medicine, SUNY Upstate Medical University, Syracuse, New York, USA
| | - Joseph W Sanger
- Department of Cell and Developmental Biology, SUNY Upstate Medical University, Syracuse, New York, USA
| |
Collapse
|
15
|
Crocini C, Gotthardt M. Cardiac sarcomere mechanics in health and disease. Biophys Rev 2021; 13:637-652. [PMID: 34745372 PMCID: PMC8553709 DOI: 10.1007/s12551-021-00840-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2021] [Accepted: 08/27/2021] [Indexed: 12/23/2022] Open
Abstract
The sarcomere is the fundamental structural and functional unit of striated muscle and is directly responsible for most of its mechanical properties. The sarcomere generates active or contractile forces and determines the passive or elastic properties of striated muscle. In the heart, mutations in sarcomeric proteins are responsible for the majority of genetically inherited cardiomyopathies. Here, we review the major determinants of cardiac sarcomere mechanics including the key structural components that contribute to active and passive tension. We dissect the molecular and structural basis of active force generation, including sarcomere composition, structure, activation, and relaxation. We then explore the giant sarcomere-resident protein titin, the major contributor to cardiac passive tension. We discuss sarcomere dynamics exemplified by the regulation of titin-based stiffness and the titin life cycle. Finally, we provide an overview of therapeutic strategies that target the sarcomere to improve cardiac contraction and filling.
Collapse
Affiliation(s)
- Claudia Crocini
- Max Delbrück Center for Molecular Medicine in the Helmholtz Association (MDC), Neuromuscular and Cardiovascular Cell Biology, Berlin, Germany
- German Center for Cardiovascular Research (DZHK) Partner Site Berlin, Berlin, Germany
- BioFrontiers Institute & Department of Molecular and Cellular Development, University of Colorado Boulder, Boulder, USA
| | - Michael Gotthardt
- Max Delbrück Center for Molecular Medicine in the Helmholtz Association (MDC), Neuromuscular and Cardiovascular Cell Biology, Berlin, Germany
- German Center for Cardiovascular Research (DZHK) Partner Site Berlin, Berlin, Germany
- Charité-Universitätsmedizin Berlin, 10117 Berlin, Germany
| |
Collapse
|
16
|
Zhang Y, Wang F, Wu F, Wang Y, Wang X, Gui Y, Li Q. Tnni1b-ECR183-d2, an 87 bp cardiac enhancer of zebrafish. PeerJ 2020; 8:e10289. [PMID: 33194440 PMCID: PMC7648457 DOI: 10.7717/peerj.10289] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2019] [Accepted: 10/12/2020] [Indexed: 12/12/2022] Open
Abstract
Background Several heart malformations are associated with mutations in the regulatory regions of cardiac genes. Troponin I type 1b (tnni1b) is important for the formation of the atrioventricular canal in zebrafish hearts; however, the regulation of tnni1b is poorly understand. We aimed to identify a small but functional enhancer that is distal to tnni1b. Methods Evolutionary Conserved Region (ECR) Browser was used to analyze the 219 kb zebrafish and human genomes covering the tnni1b gene as well as the 100 kb regions upstream and downstream of tnni1b. Putative transcription factor binding sites (TFBSs) were analyzed using JASPAR and PROMO, and the enhancer activity was identified using zebrafish embryos and the luciferase reporter assay. A correlation analysis between the enhancer and transcription factors (TFs) was performed via TF overexpression and TFBS mutation experiments and the electrophoretic mobility shift assay (EMSA). To analyze the conservation between zebrafish and human enhancers, human DNA fragments were functionally verified. Images were captured and analyzed by fluorescence microscopy or confocal microscopy. Results Combined with comparative analysis and functional validation, we identified a 183 bp ECR (termed tnni1b-ECR183) that was located approximately 84 kb upstream of tnni1b that had the heart-specific enhancer activity in zebrafish. TFBS analysis and the enhancer activity detection assay data showed that the 87 bp core region (termed tnni1b-ECR183-d2) was capable of driving specific GFP expression near the atrioventricular junction and increased luciferase expression in HEK293 and HL1 cell lines. The GFP pattern in zebrafish embryos was similar to the expression profiles of tnni1b. A correlation analysis showed that the enhancer activity of tnni1b-ECR183-d2 was increased when NKX2.5 (p = 0.0006) or JUN (p < 0.0001) was overexpressed and was decreased when the TFBSs of NKX2.5 (p < 0.0001) or JUN (p = 0.0018) were mutated. In addition, DNA-protein interactions were not observed between these TFs and tnni1b-ECR183-d2 in the EMSA experiment. The conservation analysis showed that tnni1b-ECR183-h179 (aligned from tnni1b-ECR183) drove GFP expression in the heart and skeletal muscles and increased the luciferase expression after NKX2.5 (p < 0.0001), JUN (p < 0.0001) or ETS1 (p < 0.0001) was overexpressed. Interestingly, the truncated fragment tnni1b-ECR183-h84 mainly drove GFP expression in the skeletal muscles of zebrafish and the enhancer activity decreased when NKX2.5 (p = 0.0028), ETS1 (p = 0.0001) or GATA4 (p < 0.0001) was overexpressed. Conclusions An 87 bp cardiac-specific enhancer located 84 kb upstream of tnni1b in zebrafish was positively correlated with NKX2.5 or JUN. The zebrafish and human enhancers in this study target different tissues. The GFP expression mediated by tnni1b-ECR183-d2 is a valuable tool for marking the domain around the atrioventricular junction.
Collapse
Affiliation(s)
- Yawen Zhang
- Translational Medical Center for Development and Disease, Shanghai Key Laboratory of Birth Defect, Institute of Pediatrics, Children's Hospital of Fudan University, Shanghai, China.,Department of Cardiology, Children's Hospital of Fudan University, Shanghai, China
| | - Feng Wang
- Translational Medical Center for Development and Disease, Shanghai Key Laboratory of Birth Defect, Institute of Pediatrics, Children's Hospital of Fudan University, Shanghai, China.,Department of Cardiology, Children's Hospital of Fudan University, Shanghai, China
| | - Fang Wu
- Translational Medical Center for Development and Disease, Shanghai Key Laboratory of Birth Defect, Institute of Pediatrics, Children's Hospital of Fudan University, Shanghai, China.,Department of Cardiology, Children's Hospital of Fudan University, Shanghai, China
| | - Youhua Wang
- Department of Cardiology, Longhua Hospital, Shanghai University of Traditional Chinese Medicine, Shanghai, China
| | - Xu Wang
- Cancer Institute, Fudan University Shanghai Cancer Center, Shanghai, China
| | - Yonghao Gui
- Department of Cardiology, Children's Hospital of Fudan University, Shanghai, China
| | - Qiang Li
- Translational Medical Center for Development and Disease, Shanghai Key Laboratory of Birth Defect, Institute of Pediatrics, Children's Hospital of Fudan University, Shanghai, China
| |
Collapse
|
17
|
Zhang Z, Nam YJ. Assessing Cardiac Reprogramming using High Content Imaging Analysis. J Vis Exp 2020. [PMID: 33165328 DOI: 10.3791/61859] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
The goal of this protocol is to describe a method for quantifying induced cardiomyocyte-like cells (iCMs), which are directly reprogrammed in vitro by a reprogramming technique. Cardiac reprogramming provides a strategy to generate new cardiomyocytes. By introducing core cardiogenic transcription factors into fibroblasts; fibroblasts can be converted to iCMs without transition through the pluripotent stem cell state. However, the conversion rate of fibroblasts to iCMs still remains low. Accordingly, there have been numerous additional approaches to enhance cardiac reprogramming efficiency. Most of these studies assessed cardiac reprogramming efficiency using flow cytometry, while at the same time performed immunocytochemistry to visualize iCMs. Thus, at least two separate sets of reprogramming experiments are required to demonstrate the success of iCM reprogramming. In contrast, automated high content imaging analysis will provide both quantification and qualification of iCM reprogramming with a relatively small number of cells. With this method, it is possible to directly assess the quantity and quality of iCMs with a single reprogramming experiment. This approach will be able to facilitate future cardiac reprogramming studies that require large-scale reprogramming experiments such as screening genetic or pharmacological factors for enhancing reprogramming efficiency. In addition, the application of high content imaging analysis protocol is not limited to cardiac reprogramming. It can be applied to reprogramming of other cell lineages as well as any immunostaining experiments which need both quantification and visualization of immunostained cells.
Collapse
Affiliation(s)
- Zhentao Zhang
- Department of Medicine, Division of Cardiovascular Medicine, Vanderbilt University Medical Center; Department of Cell and Developmental Biology, Vanderbilt University; Vanderbilt Center for Stem Cell Biology, Vanderbilt University
| | - Young-Jae Nam
- Department of Medicine, Division of Cardiovascular Medicine, Vanderbilt University Medical Center; Department of Cell and Developmental Biology, Vanderbilt University; Vanderbilt Center for Stem Cell Biology, Vanderbilt University;
| |
Collapse
|
18
|
Deconstructing sarcomeric structure-function relations in titin-BioID knock-in mice. Nat Commun 2020; 11:3133. [PMID: 32561764 PMCID: PMC7305127 DOI: 10.1038/s41467-020-16929-8] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2020] [Accepted: 05/27/2020] [Indexed: 12/04/2022] Open
Abstract
Proximity proteomics has greatly advanced the analysis of native protein complexes and subcellular structures in culture, but has not been amenable to study development and disease in vivo. Here, we have generated a knock-in mouse with the biotin ligase (BioID) inserted at titin’s Z-disc region to identify protein networks that connect the sarcomere to signal transduction and metabolism. Our census of the sarcomeric proteome from neonatal to adult heart and quadriceps reveals how perinatal signaling, protein homeostasis and the shift to adult energy metabolism shape the properties of striated muscle cells. Mapping biotinylation sites to sarcomere structures refines our understanding of myofilament dynamics and supports the hypothesis that myosin filaments penetrate Z-discs to dampen contraction. Extending this proof of concept study to BioID fusion proteins generated with Crispr/CAS9 in animal models recapitulating human pathology will facilitate the future analysis of molecular machines and signaling hubs in physiological, pharmacological, and disease context. Titin determines the elasticity of the sarcomere and integrates into both the Z-disc and the M-band. Here, the authors generate a BioID mouse to study the titin interactome at the Z-disc region in neonatal and adult heart and skeletal muscle.
Collapse
|
19
|
Islam M, Diwan A, Mani K. Come Together: Protein Assemblies, Aggregates and the Sarcostat at the Heart of Cardiac Myocyte Homeostasis. Front Physiol 2020; 11:586. [PMID: 32581848 PMCID: PMC7287178 DOI: 10.3389/fphys.2020.00586] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2020] [Accepted: 05/11/2020] [Indexed: 12/13/2022] Open
Abstract
Homeostasis in vertebrate systems is contingent on normal cardiac function. This, in turn, depends on intricate protein-based cellular machinery, both for contractile function, as well as, durability of cardiac myocytes. The cardiac small heat shock protein (csHsp) chaperone system, highlighted by αB-crystallin (CRYAB), a small heat shock protein (sHsp) that forms ∼3–5% of total cardiac mass, plays critical roles in maintaining proteostatic function via formation of self-assembled multimeric chaperones. In this work, we review these ancient proteins, from the evolutionarily preserved role of homologs in protists, fungi and invertebrate systems, as well as, the role of sHsps and chaperones in maintaining cardiac myocyte structure and function. We propose the concept of the “sarcostat” as a protein quality control mechanism in the sarcomere. The roles of the proteasomal and lysosomal proteostatic network, as well as, the roles of the aggresome, self-assembling protein complexes and protein aggregation are discussed in the context of cardiac myocyte homeostasis. Finally, we will review the potential for targeting the csHsp system as a novel therapeutic approach to prevent and treat cardiomyopathy and heart failure.
Collapse
Affiliation(s)
- Moydul Islam
- Division of Cardiology, Washington University School of Medicine, St. Louis, MO, United States.,Center for Cardiovascular Research, Washington University School of Medicine, St. Louis, MO, United States.,Department of Chemistry, Washington University in St. Louis, St. Louis, MO, United States
| | - Abhinav Diwan
- Division of Cardiology, Washington University School of Medicine, St. Louis, MO, United States.,Center for Cardiovascular Research, Washington University School of Medicine, St. Louis, MO, United States.,John Cochran Veterans Affairs Medical Center, St. Louis, MO, United States
| | - Kartik Mani
- Division of Cardiology, Washington University School of Medicine, St. Louis, MO, United States.,Center for Cardiovascular Research, Washington University School of Medicine, St. Louis, MO, United States.,John Cochran Veterans Affairs Medical Center, St. Louis, MO, United States
| |
Collapse
|
20
|
Rivas-Pardo JA, Li Y, Mártonfalvi Z, Tapia-Rojo R, Unger A, Fernández-Trasancos Á, Herrero-Galán E, Velázquez-Carreras D, Fernández JM, Linke WA, Alegre-Cebollada J. A HaloTag-TEV genetic cassette for mechanical phenotyping of proteins from tissues. Nat Commun 2020; 11:2060. [PMID: 32345978 PMCID: PMC7189229 DOI: 10.1038/s41467-020-15465-9] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2019] [Accepted: 03/09/2020] [Indexed: 11/09/2022] Open
Abstract
Single-molecule methods using recombinant proteins have generated transformative hypotheses on how mechanical forces are generated and sensed in biological tissues. However, testing these mechanical hypotheses on proteins in their natural environment remains inaccesible to conventional tools. To address this limitation, here we demonstrate a mouse model carrying a HaloTag-TEV insertion in the protein titin, the main determinant of myocyte stiffness. Using our system, we specifically sever titin by digestion with TEV protease, and find that the response of muscle fibers to length changes requires mechanical transduction through titin's intact polypeptide chain. In addition, HaloTag-based covalent tethering enables examination of titin dynamics under force using magnetic tweezers. At pulling forces < 10 pN, titin domains are recruited to the unfolded state, and produce 41.5 zJ mechanical work during refolding. Insertion of the HaloTag-TEV cassette in mechanical proteins opens opportunities to explore the molecular basis of cellular force generation, mechanosensing and mechanotransduction.
Collapse
Affiliation(s)
- Jaime Andrés Rivas-Pardo
- Department of Biological Sciences, Columbia University, New York, NY, 10027, USA
- Center for Genomics and Bioinformatics, Facultad de Ciencias, Universidad Mayor, Santiago, Chile
| | - Yong Li
- Institute of Physiology II, University of Muenster, Muenster, Germany
| | - Zsolt Mártonfalvi
- Department of Biophysics and Radiation Biology, Semmelweis University, Budapest, Hungary
| | - Rafael Tapia-Rojo
- Department of Biological Sciences, Columbia University, New York, NY, 10027, USA
| | - Andreas Unger
- Institute of Physiology II, University of Muenster, Muenster, Germany
| | | | | | | | - Julio M Fernández
- Department of Biological Sciences, Columbia University, New York, NY, 10027, USA
| | - Wolfgang A Linke
- Institute of Physiology II, University of Muenster, Muenster, Germany.
| | | |
Collapse
|
21
|
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.
Collapse
|
22
|
Cadar AG, Feaster TK, Bersell KR, Wang L, Hong T, Balsamo JA, Zhang Z, Chun YW, Nam YJ, Gotthardt M, Knollmann BC, Roden DM, Lim CC, Hong CC. Real-time visualization of titin dynamics reveals extensive reversible photobleaching in human induced pluripotent stem cell-derived cardiomyocytes. Am J Physiol Cell Physiol 2020; 318:C163-C173. [PMID: 31747312 PMCID: PMC6985833 DOI: 10.1152/ajpcell.00107.2019] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2019] [Revised: 11/08/2019] [Accepted: 11/08/2019] [Indexed: 12/17/2022]
Abstract
Fluorescence recovery after photobleaching (FRAP) has been useful in delineating cardiac myofilament biology, and innovations in fluorophore chemistry have expanded the array of microscopic assays used. However, one assumption in FRAP is the irreversible photobleaching of fluorescent proteins after laser excitation. Here we demonstrate reversible photobleaching regarding the photoconvertible fluorescent protein mEos3.2. We used CRISPR/Cas9 genome editing in human induced pluripotent stem cells (hiPSCs) to knock-in mEos3.2 into the COOH terminus of titin to visualize sarcomeric titin incorporation and turnover. Upon cardiac induction, the titin-mEos3.2 fusion protein is expressed and integrated in the sarcomeres of hiPSC-derived cardiomyocytes (CMs). STORM imaging shows M-band clustered regions of bound titin-mEos3.2 with few soluble titin-mEos3.2 molecules. FRAP revealed a baseline titin-mEos3.2 fluorescence recovery of 68% and half-life of ~1.2 h, suggesting a rapid exchange of sarcomeric titin with soluble titin. However, paraformaldehyde-fixed and permeabilized titin-mEos3.2 hiPSC-CMs surprisingly revealed a 55% fluorescence recovery. Whole cell FRAP analysis in paraformaldehyde-fixed, cycloheximide-treated, and untreated titin-mEos3.2 hiPSC-CMs displayed no significant differences in fluorescence recovery. FRAP in fixed HEK 293T expressing cytosolic mEos3.2 demonstrates a 58% fluorescence recovery. These data suggest that titin-mEos3.2 is subject to reversible photobleaching following FRAP. Using a mouse titin-eGFP model, we demonstrate that no reversible photobleaching occurs. Our results reveal that reversible photobleaching accounts for the majority of titin recovery in the titin-mEos3.2 hiPSC-CM model and should warrant as a caution in the extrapolation of reliable FRAP data from specific fluorescent proteins in long-term cell imaging.
Collapse
Affiliation(s)
- Adrian G Cadar
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee
- Department of Medicine, Division of Cardiovascular Medicine, Vanderbilt University School of Medicine, Tennessee
| | - Tromondae K Feaster
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Kevin R Bersell
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Lili Wang
- Department of Medicine, Division of Clinical Pharmacology, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - TingTing Hong
- Smidt Heart Institute and Department of Medicine, Cedars-Sinai Medical Center, Los Angeles, California
| | - Joseph A Balsamo
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Zhentao Zhang
- Department of Medicine, Division of Cardiovascular Medicine, Vanderbilt University School of Medicine, Tennessee
| | - Young Wook Chun
- Department of Medicine, Division of Cardiovascular Medicine, University of Maryland School of Medicine, Baltimore, Maryland
| | - Young-Jae Nam
- Department of Medicine, Division of Cardiovascular Medicine, Vanderbilt University School of Medicine, Tennessee
| | - Michael Gotthardt
- Neuromuscular and Cardiovascular Cell Biology, Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany
| | - Björn C Knollmann
- Department of Medicine, Division of Clinical Pharmacology, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Dan M Roden
- Department of Medicine, Division of Clinical Pharmacology, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Chee C Lim
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee
- Department of Medicine, Division of Cardiovascular Medicine, Vanderbilt University School of Medicine, Tennessee
| | - Charles C Hong
- Department of Medicine, Division of Cardiovascular Medicine, University of Maryland School of Medicine, Baltimore, Maryland
| |
Collapse
|
23
|
Resolving titin's lifecycle and the spatial organization of protein turnover in mouse cardiomyocytes. Proc Natl Acad Sci U S A 2019; 116:25126-25136. [PMID: 31757849 DOI: 10.1073/pnas.1904385116] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Cardiac protein homeostasis, sarcomere assembly, and integration of titin as the sarcomeric backbone are tightly regulated to facilitate adaptation and repair. Very little is known on how the >3-MDa titin protein is synthesized, moved, inserted into sarcomeres, detached, and degraded. Here, we generated a bifluorescently labeled knockin mouse to simultaneously visualize both ends of the molecule and follow titin's life cycle in vivo. We find titin mRNA, protein synthesis and degradation compartmentalized toward the Z-disk in adult, but not embryonic cardiomyocytes. Originating at the Z-disk, titin contributes to a soluble protein pool (>15% of total titin) before it is integrated into the sarcomere lattice. Titin integration, disintegration, and reintegration are stochastic and do not proceed sequentially from Z-disk to M-band, as suggested previously. Exchange between soluble and integrated titin depends on titin protein composition and differs between individual cardiomyocytes. Thus, titin dynamics facilitate embryonic vs. adult sarcomere remodeling with implications for cardiac development and disease.
Collapse
|
24
|
Higashikuse Y, Mittal N, Arimura T, Yoon SH, Oda M, Enomoto H, Kaneda R, Hattori F, Suzuki T, Kawakami A, Gasch A, Furukawa T, Labeit S, Fukuda K, Kimura A, Makino S. Perturbation of the titin/MURF1 signaling complex is associated with hypertrophic cardiomyopathy in a fish model and in human patients. Dis Model Mech 2019; 12:dmm.041103. [PMID: 31628103 PMCID: PMC6899042 DOI: 10.1242/dmm.041103] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2019] [Accepted: 09/25/2019] [Indexed: 11/24/2022] Open
Abstract
Hypertrophic cardiomyopathy (HCM) is a hereditary disease characterized by cardiac hypertrophy with diastolic dysfunction. Gene mutations causing HCM have been found in about half of HCM patients, while the genetic etiology and pathogenesis remain unknown for many cases of HCM. To identify novel mechanisms underlying HCM pathogenesis, we generated a cardiovascular-mutant medaka fish, non-spring heart (nsh), which showed diastolic dysfunction and hypertrophic myocardium. The nsh homozygotes had fewer myofibrils, disrupted sarcomeres and expressed pathologically stiffer titin isoforms. In addition, the nsh heterozygotes showed M-line disassembly that is similar to the pathological changes found in HCM. Positional cloning revealed a missense mutation in an immunoglobulin (Ig) domain located in the M-line–A-band transition zone of titin. Screening of mutations in 96 unrelated patients with familial HCM, who had no previously implicated mutations in known sarcomeric gene candidates, identified two mutations in Ig domains close to the M-line region of titin. In vitro studies revealed that the mutations found both in medaka fish and in familial HCM increased binding of titin to muscle-specific ring finger protein 1 (MURF1) and enhanced titin degradation by ubiquitination. These findings implicate an impaired interaction between titin and MURF1 as a novel mechanism underlying the pathogenesis of HCM. Summary: The authors identified and characterized a medaka mutation in titin that leads to a phenotype similar to hypertrophic cardiomyopathy. Similar mutations were also observed in human patients.
Collapse
Affiliation(s)
- Yuta Higashikuse
- Department of Cardiology, Keio University School of Medicine, 35-Shinanomachi Shinjuku-ku, Tokyo 160-8582, Japan.,Division of Basic Biological Sciences, Faculty of Pharmacy, Keio University, Tokyo 105-8512, Japan
| | - Nishant Mittal
- Department of Cardiology, Keio University School of Medicine, 35-Shinanomachi Shinjuku-ku, Tokyo 160-8582, Japan
| | - Takuro Arimura
- Laboratory of Genome Diversity, Graduate School of Biomedical Science, Tokyo Medical and Dental University, Tokyo 113-8510, Japan
| | - Sung Han Yoon
- Department of Interventional Cardiology, Cedars-Sinai Medical Center, 8700 Beverly Boulevard, AHSP A9229, Los Angeles, CA 90048, USA
| | - Mayumi Oda
- Department of Cardiology, Keio University School of Medicine, 35-Shinanomachi Shinjuku-ku, Tokyo 160-8582, Japan
| | - Hirokazu Enomoto
- Department of Cardiology, Keio University School of Medicine, 35-Shinanomachi Shinjuku-ku, Tokyo 160-8582, Japan
| | - Ruri Kaneda
- Department of Cardiology, Keio University School of Medicine, 35-Shinanomachi Shinjuku-ku, Tokyo 160-8582, Japan
| | - Fumiyuki Hattori
- Department of Cardiology, Keio University School of Medicine, 35-Shinanomachi Shinjuku-ku, Tokyo 160-8582, Japan
| | - Takeshi Suzuki
- Division of Basic Biological Sciences, Faculty of Pharmacy, Keio University, Tokyo 105-8512, Japan
| | - Atsushi Kawakami
- Department of Biological Information, Tokyo Institute of Technology, Yokohama 226-8501, Japan
| | - Alexander Gasch
- Department of Integrative Pathophysiology, Medical Faculty Mannheim, Mannheim 68167, Germany
| | - Tetsushi Furukawa
- Department of Bio-informational Pharmacology, Medical Research Institute, Tokyo Medical and Dental University, Tokyo 113-8510, Japan
| | - Siegfried Labeit
- Department of Integrative Pathophysiology, Medical Faculty Mannheim, Mannheim 68167, Germany
| | - Keiichi Fukuda
- Department of Cardiology, Keio University School of Medicine, 35-Shinanomachi Shinjuku-ku, Tokyo 160-8582, Japan
| | - Akinori Kimura
- Laboratory of Genome Diversity, Graduate School of Biomedical Science, Tokyo Medical and Dental University, Tokyo 113-8510, Japan
| | - Shinji Makino
- Department of Cardiology, Keio University School of Medicine, 35-Shinanomachi Shinjuku-ku, Tokyo 160-8582, Japan .,Keio University Health Centre, 35-Shinanomachi Shinjuku-ku, Tokyo 160-8582, Japan
| |
Collapse
|
25
|
Zhang Z, Zhang W, Nam YJ. Stoichiometric optimization of Gata4, Hand2, Mef2c, and Tbx5 expression for contractile cardiomyocyte reprogramming. Sci Rep 2019; 9:14970. [PMID: 31628386 PMCID: PMC6800441 DOI: 10.1038/s41598-019-51536-8] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2019] [Accepted: 10/03/2019] [Indexed: 01/10/2023] Open
Abstract
Reprogramming of fibroblasts to induced cardiomyocyte-like cells (iCMs) offers potential strategies for new cardiomyocyte generation. However, a major challenge of this approach remains its low efficiency for contractile iCMs. Here, we showed that controlled stoichiometric expression of Gata4 (G), Hand2 (H), Mef2c (M), and Tbx5 (T) significantly enhanced contractile cardiomyocyte reprogramming over previously defined stoichiometric expression of GMT or uncontrolled expression of GHMT. We generated quad-cistronic vectors expressing distinct relative protein levels of GHMT within the context of a previously defined splicing order of M-G-T with high Mef2c level. Transduction of the quad-cistronic vector with a splicing order of M-G-T-H (referred to as M-G-T-H) inducing relatively low Hand2 and high Mef2c protein levels not only increased sarcomeric protein induction, but also markedly promoted the development of contractile structures and functions in fibroblasts. The expressed Gata4 and Tbx5 protein levels by M-G-T-H transduction were relatively higher than those by transductions of other quad-cistronic vectors, but lower than those by previously defined M-G-T tri-cistronic vector transduction. Taken together, our results demonstrate the stoichiometric requirement of GHMT expression for structural and functional progresses of cardiomyocyte reprogramming and provide a new basic tool-set for future studies.
Collapse
Affiliation(s)
- Zhentao Zhang
- Department of Medicine, Division of Cardiovascular Medicine, Vanderbilt University Medical Center, Nashville, TN, USA.,Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN, USA.,Vanderbilt Center for Stem Cell Biology, Vanderbilt University, Nashville, TN, USA
| | - Wenhui Zhang
- Department of Medicine, Division of Cardiovascular Medicine, Vanderbilt University Medical Center, Nashville, TN, USA.,Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN, USA.,Vanderbilt Center for Stem Cell Biology, Vanderbilt University, Nashville, TN, USA
| | - Young-Jae Nam
- Department of Medicine, Division of Cardiovascular Medicine, Vanderbilt University Medical Center, Nashville, TN, USA. .,Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN, USA. .,Vanderbilt Center for Stem Cell Biology, Vanderbilt University, Nashville, TN, USA.
| |
Collapse
|
26
|
Salcan S, Bongardt S, Monteiro Barbosa D, Efimov IR, Rassaf T, Krüger M, Kötter S. Elastic titin properties and protein quality control in the aging heart. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2019; 1867:118532. [PMID: 31421188 DOI: 10.1016/j.bbamcr.2019.118532] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2018] [Revised: 07/12/2019] [Accepted: 08/12/2019] [Indexed: 01/09/2023]
Abstract
Cardiac aging affects the heart on the functional, structural, and molecular level and shares characteristic hallmarks with the development of chronic heart failure. Apart from age-dependent left ventricular hypertrophy and fibrosis that impairs diastolic function, diminished activity of cardiac protein-quality-control systems increases the risk of cytotoxic accumulation of defective proteins. Here, we studied the impact of cardiac aging on the sarcomeric protein titin by analyzing titin-based cardiomyocyte passive tension, titin modification and proteasomal titin turnover. We analyzed left ventricular samples from young (6 months) and old (20 months) wild-type mice and healthy human donor patients grouped according to age in young (17-50 years) and aged hearts (51-73 years). We found no age-dependent differences in titin isoform composition of mouse or human hearts. In aged hearts from mice and human we determined altered titin phosphorylation at serine residues S4010 and S4099 in the elastic N2B domain, but no significant changes in phosphorylation of S11878 and S12022 in the elastic PEVK region. Importantly, overall titin-based cardiomyocyte passive tension remained unchanged. In aged hearts, the calcium-activated protease calpain-1, which provides accessibility to ubiquitination by releasing titin from the sarcomere, showed decreased proteolytic activity. In addition, we observed a reduction in the proteasomal activities. Taken together, our data indicate that cardiac aging does not affect titin-based passive properties of the cardiomyocytes, but impairs protein-quality control, including titin, which may result in a diminished adaptive capacity of the aged myocardium.
Collapse
Affiliation(s)
- Senem Salcan
- Department of Cardiovascular Physiology, Medical Faculty, Heinrich Heine-University Düsseldorf, D-40225 Düsseldorf, Germany
| | - Sabine Bongardt
- Department of Cardiovascular Physiology, Medical Faculty, Heinrich Heine-University Düsseldorf, D-40225 Düsseldorf, Germany
| | - David Monteiro Barbosa
- Department of Cardiovascular Physiology, Medical Faculty, Heinrich Heine-University Düsseldorf, D-40225 Düsseldorf, Germany
| | - Igor R Efimov
- George Washington University, Department of Biomedical Engineering, Science and Engineering Hall, Washington DC-20052, USA
| | - Tienush Rassaf
- University Hospital Essen, Department of Cardiology and Vascular Medicine, West German Heart and Vascular Center, 45147 Essen, Germany
| | - Martina Krüger
- Department of Cardiovascular Physiology, Medical Faculty, Heinrich Heine-University Düsseldorf, D-40225 Düsseldorf, Germany.
| | - Sebastian Kötter
- Department of Cardiovascular Physiology, Medical Faculty, Heinrich Heine-University Düsseldorf, D-40225 Düsseldorf, Germany.
| |
Collapse
|
27
|
Ojima K. Myosin: Formation and maintenance of thick filaments. Anim Sci J 2019; 90:801-807. [PMID: 31134719 PMCID: PMC6618170 DOI: 10.1111/asj.13226] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2019] [Revised: 03/27/2019] [Accepted: 04/18/2019] [Indexed: 12/17/2022]
Abstract
Skeletal muscle consists of bundles of myofibers containing millions of myofibrils, each of which is formed of longitudinally aligned sarcomere structures. Sarcomeres are the minimum contractile unit, which mainly consists of four components: Z‐bands, thin filaments, thick filaments, and connectin/titin. The size and shape of the sarcomere component is strictly controlled. Surprisingly, skeletal muscle cells not only synthesize a series of myofibrillar proteins but also regulate the assembly of those proteins into the sarcomere structures. However, authentic sarcomere structures cannot be reconstituted by combining purified myofibrillar proteins in vitro, therefore there must be an elaborate mechanism ensuring the correct formation of myofibril structure in skeletal muscle cells. This review discusses the role of myosin, a main component of the thick filament, in thick filament formation and the dynamics of myosin in skeletal muscle cells. Changes in the number of myofibrils in myofibers can cause muscle hypertrophy or atrophy. Therefore, it is important to understand the fundamental mechanisms by which myofibers control myofibril formation at the molecular level to develop approaches that effectively enhance muscle growth in animals.
Collapse
Affiliation(s)
- Koichi Ojima
- Muscle Biology Research Unit, Division of Animal Products Research, National Institute of Livestock and Grassland Science, NARO, Tsukuba, Japan
| |
Collapse
|
28
|
Ensuring expression of four core cardiogenic transcription factors enhances cardiac reprogramming. Sci Rep 2019; 9:6362. [PMID: 31019236 PMCID: PMC6482135 DOI: 10.1038/s41598-019-42945-w] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2019] [Accepted: 04/12/2019] [Indexed: 01/12/2023] Open
Abstract
Previous studies have shown that forced expression of core cardiogenic transcription factors can directly reprogram fibroblasts to induced cardiomyocyte-like cells (iCMs). This cardiac reprogramming approach suggests a potential strategy for cardiomyocyte regeneration. However, a major challenge of this approach remains the low conversion rate. Here, we showed that ensuring expression of four cardiogenic transcription factors (i.e. Gata4 (G), Hand2 (H), Mef2c (M), and Tbx5 (T)) in individual fibroblasts is an initial bottleneck for cardiac reprogramming. Following co-transduction of three or four retroviral vectors encoding individual cardiogenic transcription factors, only a minor subpopulation of cells indeed expressed all three (GMT) or four (GHMT) factors. By selectively analyzing subpopulations of cells expressing various combinations of reprogramming factors, we found that co-expression of GMT in individual fibroblasts is sufficient to induce sarcomeric proteins. However, only a small fraction of those cells expressing GMT were able to develop organized sarcomeric structures and contractility. In contrast, ensuring expression of GHMT markedly enhanced the development of contractile cardiac structures and functions in fibroblasts, although its incremental effect on sarcomeric protein induction was relatively small. Our findings provide new insights into the mechanistic basis of inefficient cardiac reprogramming and can help to devise efficient reprogramming strategies.
Collapse
|
29
|
Dierck F, Kuhn C, Rohr C, Hille S, Braune J, Sossalla S, Molt S, van der Ven PFM, Fürst DO, Frey N. The novel cardiac z-disc protein CEFIP regulates cardiomyocyte hypertrophy by modulating calcineurin signaling. J Biol Chem 2017; 292:15180-15191. [PMID: 28717008 DOI: 10.1074/jbc.m117.786764] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2017] [Revised: 07/04/2017] [Indexed: 11/06/2022] Open
Abstract
The z-disc is a structural component at the lateral borders of the sarcomere and is important for mechanical stability and contractility of both cardiac and skeletal muscles. Of note, the sarcomeric z-disc also represents a nodal point in cardiomyocyte function and signaling. Mutations of numerous z-disc proteins are associated with cardiomyopathies and muscle diseases. To identify additional z-disc proteins that might contribute to cardiac disease, we employed an in silico screen for cardiac-enriched cDNAs. This screen yielded a previously uncharacterized protein named cardiac-enriched FHL2-interacting protein (CEFIP), which exhibited a heart- and skeletal muscle-specific expression profile. Importantly, CEFIP was located at the z-disc and was up-regulated in several models of cardiomyopathy. We also found that CEFIP overexpression induced the fetal gene program and cardiomyocyte hypertrophy. Yeast two-hybrid screens revealed that CEFIP interacts with the calcineurin-binding protein four and a half LIM domains 2 (FHL2). Because FHL2 binds calcineurin, a phosphatase controlling hypertrophic signaling, we examined the effects of CEFIP on the calcineurin/nuclear factor of activated T-cell (NFAT) pathway. These experiments revealed that CEFIP overexpression further enhances calcineurin-dependent hypertrophic signal transduction, and its knockdown repressed hypertrophy and calcineurin/NFAT activity. In summary, we report on a previously uncharacterized protein CEFIP that modulates calcineurin/NFAT signaling in cardiomyocytes, a finding with possible implications for the pathogenesis of cardiomyopathy.
Collapse
Affiliation(s)
- Franziska Dierck
- From the Department of Internal Medicine III, University Medical Center of Schleswig-Holstein, 24105 Kiel.,the DZHK (German Centre for Cardiovascular Research), partner site Hamburg/Kiel/Lübeck, 24105 Kiel
| | - Christian Kuhn
- From the Department of Internal Medicine III, University Medical Center of Schleswig-Holstein, 24105 Kiel.,the DZHK (German Centre for Cardiovascular Research), partner site Hamburg/Kiel/Lübeck, 24105 Kiel
| | - Claudia Rohr
- the Department of Internal Medicine III, University of Heidelberg, 69120 Heidelberg, and
| | - Susanne Hille
- From the Department of Internal Medicine III, University Medical Center of Schleswig-Holstein, 24105 Kiel.,the DZHK (German Centre for Cardiovascular Research), partner site Hamburg/Kiel/Lübeck, 24105 Kiel
| | - Julia Braune
- the Department of Molecular Cell Biology, Institute for Cell Biology, University of Bonn, 53121 Bonn, Germany
| | - Samuel Sossalla
- From the Department of Internal Medicine III, University Medical Center of Schleswig-Holstein, 24105 Kiel.,the DZHK (German Centre for Cardiovascular Research), partner site Hamburg/Kiel/Lübeck, 24105 Kiel
| | - Sibylle Molt
- the Department of Molecular Cell Biology, Institute for Cell Biology, University of Bonn, 53121 Bonn, Germany
| | - Peter F M van der Ven
- the Department of Molecular Cell Biology, Institute for Cell Biology, University of Bonn, 53121 Bonn, Germany
| | - Dieter O Fürst
- the Department of Molecular Cell Biology, Institute for Cell Biology, University of Bonn, 53121 Bonn, Germany
| | - Norbert Frey
- From the Department of Internal Medicine III, University Medical Center of Schleswig-Holstein, 24105 Kiel, .,the DZHK (German Centre for Cardiovascular Research), partner site Hamburg/Kiel/Lübeck, 24105 Kiel
| |
Collapse
|
30
|
Robertson AS, Majchrzak MJ, Smith CM, Gagnon RC, Devidze N, Banks GB, Little SC, Nabbie F, Bounous DI, DiPiero J, Jacobsen LK, Bristow LJ, Ahlijanian MK, Stimpson SA. Dramatic elevation in urinary amino terminal titin fragment excretion quantified by immunoassay in Duchenne muscular dystrophy patients and in dystrophin deficient rodents. Neuromuscul Disord 2017; 27:635-645. [PMID: 28554556 DOI: 10.1016/j.nmd.2017.05.009] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2017] [Revised: 04/29/2017] [Accepted: 05/09/2017] [Indexed: 11/27/2022]
Abstract
Enzyme-linked and electrochemiluminescence immunoassays were developed for quantification of amino (N-) terminal fragments of the skeletal muscle protein titin (N-ter titin) and qualified for use in detection of urinary N-ter titin excretion. Urine from normal subjects contained a small but measurable level of N-ter titin (1.0 ± 0.4 ng/ml). A 365-fold increase (365.4 ± 65.0, P = 0.0001) in urinary N-ter titin excretion was seen in Duchene muscular dystrophy (DMD) patients. Urinary N-ter titin was also evaluated in dystrophin deficient rodent models. Mdx mice exhibited low urinary N-ter titin levels at 2 weeks of age followed by a robust and sustained elevation starting at 3 weeks of age, coincident with the development of systemic skeletal muscle damage in this model; fold elevation could not be determined because urinary N-ter titin was not detected in age-matched wild type mice. Levels of serum creatine kinase and serum skeletal muscle troponin I (TnI) were also low at 2 weeks, elevated at later time points and were significantly correlated with urinary N-ter titin excretion in mdx mice. Corticosteroid treatment of mdx mice resulted in improved exercise performance and lowering of both urinary N-ter titin and serum skeletal muscle TnI concentrations. Low urinary N-ter titin levels were detected in wild type rats (3.0 ± 0.6 ng/ml), while Dmdmdx rats exhibited a 556-fold increase (1652.5 ± 405.7 ng/ml, P = 0.002) (both at 5 months of age). These results suggest that urinary N-ter titin is present at low basal concentrations in normal urine and increases dramatically coincident with muscle damage produced by dystrophin deficiency. Urinary N-ter titin has potential as a facile, non-invasive and translational biomarker for DMD.
Collapse
Affiliation(s)
- Alan S Robertson
- Genetically Defined Diseases, Bristol-Myers Squibb, Wallingford, CT, USA
| | - Mark J Majchrzak
- Genetically Defined Diseases, Bristol-Myers Squibb, Wallingford, CT, USA
| | | | - Robert C Gagnon
- Non-Clinical Biostatistics, Bristol-Myers Squibb, Lawrenceville, NJ, USA
| | - Nino Devidze
- Genetically Defined Diseases, Bristol-Myers Squibb, Wallingford, CT, USA
| | - Glen B Banks
- Genetically Defined Diseases, Bristol-Myers Squibb, Wallingford, CT, USA
| | - Sean C Little
- Genetically Defined Diseases, Bristol-Myers Squibb, Wallingford, CT, USA
| | - Fizal Nabbie
- Genetically Defined Diseases, Bristol-Myers Squibb, Wallingford, CT, USA
| | - Denise I Bounous
- Discovery Toxicology Clinical Pathology Laboratory, Bristol-Myers Squibb, Lawrenceville, NJ, USA
| | - Janet DiPiero
- Discovery Toxicology Clinical Pathology Laboratory, Bristol-Myers Squibb, Lawrenceville, NJ, USA
| | - Leslie K Jacobsen
- Genetically Defined Diseases, Bristol-Myers Squibb, Wallingford, CT, USA
| | - Linda J Bristow
- Genetically Defined Diseases, Bristol-Myers Squibb, Wallingford, CT, USA
| | | | - Stephen A Stimpson
- Genetically Defined Diseases, Bristol-Myers Squibb, Wallingford, CT, USA
| |
Collapse
|
31
|
Genetic epidemiology of titin-truncating variants in the etiology of dilated cardiomyopathy. Biophys Rev 2017; 9:207-223. [PMID: 28510119 PMCID: PMC5498329 DOI: 10.1007/s12551-017-0265-7] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2017] [Accepted: 04/10/2017] [Indexed: 02/07/2023] Open
Abstract
Heart failure (HF) is a complex clinical syndrome defined by the inability of the heart to pump enough blood to meet the body's metabolic demands. Major causes of HF are cardiomyopathies (diseases of the myocardium associated with mechanical and/or electrical dysfunction), among which the most common form is dilated cardiomyopathy (DCM). DCM is defined by ventricular chamber enlargement and systolic dysfunction with normal left ventricular wall thickness, which leads to progressive HF. Over 60 genes are linked to the etiology of DCM. Titin (TTN) is the largest known protein in biology, spanning half the cardiac sarcomere and, as such, is a basic structural and functional unit of striated muscles. It is essential for heart development as well as mechanical and regulatory functions of the sarcomere. Next-generation sequencing (NGS) in clinical DCM cohorts implicated truncating variants in titin (TTNtv) as major disease alleles, accounting for more than 25% of familial DCM cases, but these variants have also been identified in 2-3% of the general population, where these TTNtv blur diagnostic and clinical utility. Taking into account the published TTNtv and their association to DCM, it becomes clear that TTNtv harm the heart with position-dependent occurrence, being more harmful when present in the A-band TTN, presumably with dominant negative/gain-of-function mechanisms. However, these insights are challenged by the depiction of position-independent toxicity of TTNtv acting via haploinsufficient alleles, which are sufficient to induce cardiac pathology upon stress. In the current review, we provide an overview of TTN and discuss studies investigating various TTN mutations. We also present an overview of different mechanisms postulated or experimentally validated in the pathogenicity of TTNtv. DCM-causing genes are also discussed with respect to non-truncating mutations in the etiology of DCM. One way of understanding pathogenic variants is probably to understand the context in which they may or may not affect protein-protein interactions, changes in cell signaling, and substrate specificity. In this regard, we also provide a brief overview of TTN interactions in situ. Quantitative models in the risk assessment of TTNtv are also discussed. In summary, we highlight the importance of gene-environment interactions in the etiology of DCM and further mechanistic studies used to delineate the pathways which could be targeted in the management of DCM.
Collapse
|
32
|
α-Actinin/titin interaction: A dynamic and mechanically stable cluster of bonds in the muscle Z-disk. Proc Natl Acad Sci U S A 2017; 114:1015-1020. [PMID: 28096424 DOI: 10.1073/pnas.1612681114] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Stable anchoring of titin within the muscle Z-disk is essential for preserving muscle integrity during passive stretching. One of the main candidates for anchoring titin in the Z-disk is the actin cross-linker α-actinin. The calmodulin-like domain of α-actinin binds to the Z-repeats of titin. However, the mechanical and kinetic properties of this important interaction are still unknown. Here, we use a dual-beam optical tweezers assay to study the mechanics of this interaction at the single-molecule level. A single interaction of α-actinin and titin turns out to be surprisingly weak if force is applied. Depending on the direction of force application, the unbinding forces can more than triple. Our results suggest a model where multiple α-actinin/Z-repeat interactions cooperate to ensure long-term stable titin anchoring while allowing the individual components to exchange dynamically.
Collapse
|
33
|
Brandenburg S, Kohl T, Williams GSB, Gusev K, Wagner E, Rog-Zielinska EA, Hebisch E, Dura M, Didié M, Gotthardt M, Nikolaev VO, Hasenfuss G, Kohl P, Ward CW, Lederer WJ, Lehnart SE. Axial tubule junctions control rapid calcium signaling in atria. J Clin Invest 2016; 126:3999-4015. [PMID: 27643434 DOI: 10.1172/jci88241] [Citation(s) in RCA: 95] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2016] [Accepted: 08/09/2016] [Indexed: 11/17/2022] Open
Abstract
The canonical atrial myocyte (AM) is characterized by sparse transverse tubule (TT) invaginations and slow intracellular Ca2+ propagation but exhibits rapid contractile activation that is susceptible to loss of function during hypertrophic remodeling. Here, we have identified a membrane structure and Ca2+-signaling complex that may enhance the speed of atrial contraction independently of phospholamban regulation. This axial couplon was observed in human and mouse atria and is composed of voluminous axial tubules (ATs) with extensive junctions to the sarcoplasmic reticulum (SR) that include ryanodine receptor 2 (RyR2) clusters. In mouse AM, AT structures triggered Ca2+ release from the SR approximately 2 times faster at the AM center than at the surface. Rapid Ca2+ release correlated with colocalization of highly phosphorylated RyR2 clusters at AT-SR junctions and earlier, more rapid shortening of central sarcomeres. In contrast, mice expressing phosphorylation-incompetent RyR2 displayed depressed AM sarcomere shortening and reduced in vivo atrial contractile function. Moreover, left atrial hypertrophy led to AT proliferation, with a marked increase in the highly phosphorylated RyR2-pS2808 cluster fraction, thereby maintaining cytosolic Ca2+ signaling despite decreases in RyR2 cluster density and RyR2 protein expression. AT couplon "super-hubs" thus underlie faster excitation-contraction coupling in health as well as hypertrophic compensatory adaptation and represent a structural and metabolic mechanism that may contribute to contractile dysfunction and arrhythmias.
Collapse
|
34
|
Ojima K, Ichimura E, Yasukawa Y, Wakamatsu JI, Nishimura T. Dynamics of myosin replacement in skeletal muscle cells. Am J Physiol Cell Physiol 2015; 309:C669-79. [PMID: 26377314 DOI: 10.1152/ajpcell.00170.2015] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2015] [Accepted: 09/06/2015] [Indexed: 01/04/2023]
Abstract
Highly organized thick filaments in skeletal muscle cells are formed from ~300 myosin molecules. Each thick-filament-associated myosin molecule is thought to be constantly exchanged. However, the mechanism of myosin replacement remains unclear, as does the source of myosin for substitution. Here, we investigated the dynamics of myosin exchange in the myofibrils of cultured myotubes by fluorescent recovery after photobleaching and found that myofibrillar myosin is actively replaced with an exchange half-life of ~3 h. Myosin replacement was not disrupted by the absence of the microtubule system or by actomyosin interactions, suggesting that known cytoskeletal systems are dispensable for myosin substitution. Intriguingly, myosin replacement was independent of myosin binding protein C, which links myosin molecules together to form thick filaments. This implies that an individual myosin molecule rather than a thick filament functions as an exchange unit. Furthermore, the myosin substitution rate was decreased by the inhibition of protein synthesis, suggesting that newly synthesized myosin, as well as preexisting cytosolic myosin, contributes to myosin replacement in myofibrils. Notably, incorporation and release of myosin occurred simultaneously in myofibrils, but rapid myosin release from myofibrils was observed without protein synthesis. Collectively, our results indicate that myosin shuttles between myofibrils and the nonmyofibrillar cytosol to maintain a dynamic equilibrium in skeletal muscle cells.
Collapse
Affiliation(s)
- Koichi Ojima
- Animal Products Research Division, NARO Institute of Livestock and Grassland Science, Ibaraki, Japan; and
| | - Emi Ichimura
- Research Faculty of Agriculture, Graduate School of Agriculture, Hokkaido University, Hokkaido, Japan
| | - Yuya Yasukawa
- Research Faculty of Agriculture, Graduate School of Agriculture, Hokkaido University, Hokkaido, Japan
| | - Jun-Ichi Wakamatsu
- Research Faculty of Agriculture, Graduate School of Agriculture, Hokkaido University, Hokkaido, Japan
| | - Takanori Nishimura
- Research Faculty of Agriculture, Graduate School of Agriculture, Hokkaido University, Hokkaido, Japan
| |
Collapse
|
35
|
Elhamine F, Radke MH, Pfitzer G, Granzier H, Gotthardt M, Stehle R. Deletion of the titin N2B region accelerates myofibrillar force development but does not alter relaxation kinetics. J Cell Sci 2014; 127:3666-74. [PMID: 24982444 DOI: 10.1242/jcs.141796] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Cardiac titin is the main determinant of sarcomere stiffness during diastolic relaxation. To explore whether titin stiffness affects the kinetics of cardiac myofibrillar contraction and relaxation, we used subcellular myofibrils from the left ventricles of homozygous and heterozygous N2B-knockout mice which express truncated cardiac titins lacking the unique elastic N2B region. Compared with myofibrils from wild-type mice, myofibrils from knockout and heterozygous mice exhibit increased passive myofibrillar stiffness. To determine the kinetics of Ca(2+)-induced force development (rate constant kACT), myofibrils from knockout, heterozygous and wild-type mice were stretched to the same sarcomere length (2.3 µm) and rapidly activated with Ca(2+). Additionally, mechanically induced force-redevelopment kinetics (rate constant kTR) were determined by slackening and re-stretching myofibrils during Ca(2+)-mediated activation. Myofibrils from knockout mice exhibited significantly higher kACT, kTR and maximum Ca(2+)-activated tension than myofibrils from wild-type mice. By contrast, the kinetic parameters of biphasic force relaxation induced by rapidly reducing [Ca(2+)] were not significantly different among the three genotypes. These results indicate that increased titin stiffness promotes myocardial contraction by accelerating the formation of force-generating cross-bridges without decelerating relaxation.
Collapse
Affiliation(s)
- Fatiha Elhamine
- Institute of Vegetative Physiology, University of Cologne, Robert Koch Str. 39, D-50931 Köln, Germany
| | - Michael H Radke
- Neuromuscular and Cardiovascular Cell Biology, Max-Delbrück-Center for Molecular Medicine, Robert-Rössle-Str. 10, D-13125 Berlin, Germany
| | - Gabriele Pfitzer
- Institute of Vegetative Physiology, University of Cologne, Robert Koch Str. 39, D-50931 Köln, Germany
| | - Henk Granzier
- Sarver Molecular Cardiovascular Research and Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ 85724, USA
| | - Michael Gotthardt
- Neuromuscular and Cardiovascular Cell Biology, Max-Delbrück-Center for Molecular Medicine, Robert-Rössle-Str. 10, D-13125 Berlin, Germany
| | - Robert Stehle
- Institute of Vegetative Physiology, University of Cologne, Robert Koch Str. 39, D-50931 Köln, Germany
| |
Collapse
|
36
|
Molt S, Bührdel JB, Yakovlev S, Schein P, Orfanos Z, Kirfel G, Winter L, Wiche G, van der Ven PFM, Rottbauer W, Just S, Belkin AM, Fürst DO. Aciculin interacts with filamin C and Xin and is essential for myofibril assembly, remodeling and maintenance. J Cell Sci 2014; 127:3578-92. [PMID: 24963132 DOI: 10.1242/jcs.152157] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Filamin C (FLNc) and Xin actin-binding repeat-containing proteins (XIRPs) are multi-adaptor proteins that are mainly expressed in cardiac and skeletal muscles and which play important roles in the assembly and repair of myofibrils and their attachment to the membrane. We identified the dystrophin-binding protein aciculin (also known as phosphoglucomutase-like protein 5, PGM5) as a new interaction partner of FLNc and Xin. All three proteins colocalized at intercalated discs of cardiac muscle and myotendinous junctions of skeletal muscle, whereas FLNc and aciculin also colocalized in mature Z-discs. Bimolecular fluorescence complementation experiments in developing cultured mammalian skeletal muscle cells demonstrated that Xin and aciculin also interact in FLNc-containing immature myofibrils and areas of myofibrillar remodeling and repair induced by electrical pulse stimulation (EPS). Fluorescence recovery after photobleaching (FRAP) experiments showed that aciculin is a highly dynamic and mobile protein. Aciculin knockdown in myotubes led to failure in myofibril assembly, alignment and membrane attachment, and a massive reduction in myofibril number. A highly similar phenotype was found upon depletion of aciculin in zebrafish embryos. Our results point to a thus far unappreciated, but essential, function of aciculin in myofibril formation, maintenance and remodeling.
Collapse
Affiliation(s)
- Sibylle Molt
- Institute for Cell Biology, University of Bonn, 53121 Bonn, Germany
| | - John B Bührdel
- Department of Internal Medicine II, University of Ulm, 89081 Ulm, Germany
| | - Sergiy Yakovlev
- University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Peter Schein
- Institute for Cell Biology, University of Bonn, 53121 Bonn, Germany
| | | | - Gregor Kirfel
- Institute for Cell Biology, University of Bonn, 53121 Bonn, Germany
| | - Lilli Winter
- Department of Biochemistry and Molecular Cell Biology, Max F. Perutz Laboratories, University of Vienna, 1030 Vienna, Austria
| | - Gerhard Wiche
- Department of Biochemistry and Molecular Cell Biology, Max F. Perutz Laboratories, University of Vienna, 1030 Vienna, Austria
| | | | - Wolfgang Rottbauer
- Department of Internal Medicine II, University of Ulm, 89081 Ulm, Germany
| | - Steffen Just
- Department of Internal Medicine II, University of Ulm, 89081 Ulm, Germany
| | - Alexey M Belkin
- University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Dieter O Fürst
- Institute for Cell Biology, University of Bonn, 53121 Bonn, Germany
| |
Collapse
|
37
|
Perkins AD, Tanentzapf G. An ongoing role for structural sarcomeric components in maintaining Drosophila melanogaster muscle function and structure. PLoS One 2014; 9:e99362. [PMID: 24915196 PMCID: PMC4051695 DOI: 10.1371/journal.pone.0099362] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2014] [Accepted: 05/14/2014] [Indexed: 11/29/2022] Open
Abstract
Animal muscles must maintain their function while bearing substantial mechanical loads. How muscles withstand persistent mechanical strain is presently not well understood. The basic unit of muscle is the sarcomere, which is primarily composed of cytoskeletal proteins. We hypothesized that cytoskeletal protein turnover is required to maintain muscle function. Using the flight muscles of Drosophila melanogaster, we confirmed that the sarcomeric cytoskeleton undergoes turnover throughout adult life. To uncover which cytoskeletal components are required to maintain adult muscle function, we performed an RNAi-mediated knockdown screen targeting the entire fly cytoskeleton and associated proteins. Gene knockdown was restricted to adult flies and muscle function was analyzed with behavioural assays. Here we analyze the results of that screen and characterize the specific muscle maintenance role for several hits. The screen identified 46 genes required for muscle maintenance: 40 of which had no previously known role in this process. Bioinformatic analysis highlighted the structural sarcomeric proteins as a candidate group for further analysis. Detailed confocal and electron microscopic analysis showed that while muscle architecture was maintained after candidate gene knockdown, sarcomere length was disrupted. Specifically, we found that ongoing synthesis and turnover of the key sarcomere structural components Projectin, Myosin and Actin are required to maintain correct sarcomere length and thin filament length. Our results provide in vivo evidence of adult muscle protein turnover and uncover specific functional defects associated with reduced expression of a subset of cytoskeletal proteins in the adult animal.
Collapse
Affiliation(s)
- Alexander D. Perkins
- Department of Cellular and Physiological Sciences, University of British Columbia, Life Sciences Institute, Vancouver, British Columbia, Canada
| | - Guy Tanentzapf
- Department of Cellular and Physiological Sciences, University of British Columbia, Life Sciences Institute, Vancouver, British Columbia, Canada
| |
Collapse
|
38
|
Macaluso F, Isaacs AW, Di Felice V, Myburgh KH. Acute change of titin at mid-sarcomere remains despite 8 wk of plyometric training. J Appl Physiol (1985) 2014; 116:1512-9. [DOI: 10.1152/japplphysiol.00420.2013] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The purpose of this study was to investigate skeletal muscle changes induced by an acute bout of plyometric exercise (PlyEx) both before and after PlyEx training, to understand if titin is affected differently after PlyEx training. Healthy untrained individuals ( N = 11) completed the 1stPlyEx (10 × 10 squat-jumps, 1-min rest). Thereafter, six subjects completed 8 wk of PlyEx, while five controls abstained from any jumping activity. Seven days after the last training session, all subjects completed the 2ndPlyEx. Blood samples were collected before and 6 h and 1, 2, 3, and 4 days after each acute bout of PlyEx, and muscle biopsies 4 days before and 3 days after each acute bout of PlyEx. The 1stPlyEx induced an increase in circulating myoglobin concentration. Muscle sample analysis revealed Z-disk streaming, a stretch or a fragmentation of titin (immunogold), and increased calpain-3 autolysis. After training, 2ndPlyEx did not induce Z-disk streaming or calpain-3 activation. The previously observed post-1stPlyEx positional change of the titin COOH terminus was still present pre-2ndPlyEx, in all trained and all control subjects. Only two controls presented with Z-disk streaming after 2ndPlyEx, while calpain-3 activation was absent in all controls. Eccentric explosive exercise induced a stretch or fragmentation of titin, which presented as a positional change of the COOH terminus. Calpain-3 activation does not occur when titin is already stretched before explosive jumping. Enzymatic digestion results in titin fragmentation, but since an increase in calpain-3 autolysis was visible only after the 1stPlyEx acute bout, fragmentation cannot explain the prolonged positional change.
Collapse
Affiliation(s)
- F. Macaluso
- Department of Physiological Sciences, Stellenbosch University, Stellenbosch, South Africa; and
- Dipartimento di Biomedicina Sperimentale e Neuroscienze Cliniche, Università di Palermo, Palermo, Italy
| | - A. W. Isaacs
- Department of Physiological Sciences, Stellenbosch University, Stellenbosch, South Africa; and
| | - V. Di Felice
- Dipartimento di Biomedicina Sperimentale e Neuroscienze Cliniche, Università di Palermo, Palermo, Italy
| | - K. H. Myburgh
- Department of Physiological Sciences, Stellenbosch University, Stellenbosch, South Africa; and
| |
Collapse
|
39
|
Interspecies differences in virus uptake versus cardiac function of the coxsackievirus and adenovirus receptor. J Virol 2014; 88:7345-56. [PMID: 24741103 DOI: 10.1128/jvi.00104-14] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
UNLABELLED The coxsackievirus and adenovirus receptor (CAR) is a cell contact protein with an important role in virus uptake. Its extracellular immunoglobulin domains mediate the binding to coxsackievirus and adenovirus as well as homophilic and heterophilic interactions between cells. The cytoplasmic tail links CAR to the cytoskeleton and intracellular signaling cascades. In the heart, CAR is crucial for embryonic development, electrophysiology, and coxsackievirus B infection. Noncardiac functions are less well understood, in part due to the lack of suitable animal models. Here, we generated a transgenic mouse that rescued the otherwise embryonic-lethal CAR knockout (KO) phenotype by expressing chicken CAR exclusively in the heart. Using this rescue model, we addressed interspecies differences in coxsackievirus uptake and noncardiac functions of CAR. Survival of the noncardiac CAR KO (ncKO) mouse indicates an essential role for CAR in the developing heart but not in other tissues. In adult animals, cardiac activity was normal, suggesting that chicken CAR can replace the physiological functions of mouse CAR in the cardiomyocyte. However, chicken CAR did not mediate virus entry in vivo, so that hearts expressing chicken instead of mouse CAR were protected from infection and myocarditis. Comparison of sequence homology and modeling of the D1 domain indicate differences between mammalian and chicken CAR that relate to the sites important for virus binding but not those involved in homodimerization. Thus, CAR-directed anticoxsackievirus therapy with only minor adverse effects in noncardiac tissue could be further improved by selectively targeting the virus-host interaction while maintaining cardiac function. IMPORTANCE Coxsackievirus B3 (CVB3) is one of the most common human pathogens causing myocarditis. Its receptor, the coxsackievirus and adenovirus receptor (CAR), not only mediates virus uptake but also relates to cytoskeletal organization and intracellular signaling. Animals without CAR die prenatally with major cardiac malformations. In the adult heart, CAR is important for virus entry and electrical conduction, but its nonmuscle functions are largely unknown. Here, we show that chicken CAR expression exclusively in the heart can rescue the otherwise embryonic-lethal CAR knockout phenotype but does not support CVB3 infection of adult cardiomyocytes. Our findings have implications for the evolution of virus-host versus physiological interactions involving CAR and could help to improve future coxsackievirus-directed therapies inhibiting virus replication while maintaining CAR's cellular functions.
Collapse
|
40
|
Kötter S, Unger A, Hamdani N, Lang P, Vorgerd M, Nagel-Steger L, Linke WA. Human myocytes are protected from titin aggregation-induced stiffening by small heat shock proteins. ACTA ACUST UNITED AC 2014; 204:187-202. [PMID: 24421331 PMCID: PMC3897184 DOI: 10.1083/jcb.201306077] [Citation(s) in RCA: 81] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Small heat shock proteins translocate to unfolded titin Ig domains under stress conditions to prevent titin aggregation and myocyte stiffening. In myocytes, small heat shock proteins (sHSPs) are preferentially translocated under stress to the sarcomeres. The functional implications of this translocation are poorly understood. We show here that HSP27 and αB-crystallin associated with immunoglobulin-like (Ig) domain-containing regions, but not the disordered PEVK domain (titin region rich in proline, glutamate, valine, and lysine), of the titin springs. In sarcomeres, sHSP binding to titin was actin filament independent and promoted by factors that increased titin Ig unfolding, including sarcomere stretch and the expression of stiff titin isoforms. Titin spring elements behaved predominantly as monomers in vitro. However, unfolded Ig segments aggregated, preferentially under acidic conditions, and αB-crystallin prevented this aggregation. Disordered regions did not aggregate. Promoting titin Ig unfolding in cardiomyocytes caused elevated stiffness under acidic stress, but HSP27 or αB-crystallin suppressed this stiffening. In diseased human muscle and heart, both sHSPs associated with the titin springs, in contrast to the cytosolic/Z-disk localization seen in healthy muscle/heart. We conclude that aggregation of unfolded titin Ig domains stiffens myocytes and that sHSPs translocate to these domains to prevent this aggregation.
Collapse
Affiliation(s)
- Sebastian Kötter
- Department of Cardiovascular Physiology and 2 Neurological University Clinic Bergmannsheil, Ruhr University Bochum, 44780 Bochum, Germany
| | | | | | | | | | | | | |
Collapse
|
41
|
Yaniv Y, Juhaszova M, Wang S, Fishbein KW, Zorov DB, Sollott SJ. Analysis of mitochondrial 3D-deformation in cardiomyocytes during active contraction reveals passive structural anisotropy of orthogonal short axes. PLoS One 2011; 6:e21985. [PMID: 21779362 PMCID: PMC3136939 DOI: 10.1371/journal.pone.0021985] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2011] [Accepted: 06/13/2011] [Indexed: 11/19/2022] Open
Abstract
The cardiomyocyte cytoskeleton, composed of rigid and elastic elements, maintains the isolated cell in an elongated cylindrical shape with an elliptical cross-section, even during contraction-relaxation cycles. Cardiomyocyte mitochondria are micron-sized, fluid-filled passive spheres distributed throughout the cell in a crystal-like lattice, arranged in pairs sandwiched between the sarcomere contractile machinery, both longitudinally and radially. Their shape represents the extant 3-dimensional (3D) force-balance. We developed a novel method to examine mitochondrial 3D-deformation in response to contraction and relaxation to understand how dynamic forces are balanced inside cardiomyocytes. The variation in transmitted light intensity induced by the periodic lattice of myofilaments alternating with mitochondrial rows can be analyzed by Fourier transformation along a given cardiomyocyte axis to measure mitochondrial deformation along that axis. This technique enables precise detection of changes in dimension of ∼1% in ∼1 µm (long-axis) structures with 8 ms time-resolution. During active contraction (1 Hz stimulation), mitochondria deform along the length- and width-axes of the cell with similar deformation kinetics in both sarcomere and mitochondrial structures. However, significant deformation anisotropy (without hysteresis) was observed between the orthogonal short-axes (i.e., width and depth) of mitochondria during electrical stimulation. The same degree of deformation anisotropy was also found between the myocyte orthogonal short-axes during electrical stimulation. Therefore, the deformation of the mitochondria reflects the overall deformation of the cell, and the apparent stiffness and stress/strain characteristics of the cytoskeleton differ appreciably between the two cardiomyocyte orthogonal short-axes. This method may be applied to obtaining a better understanding of the dynamic force-balance inside cardiomyocytes and of changes in the spatial stiffness characteristics of the cytoskeleton that may accompany aging or pathological conditions.
Collapse
Affiliation(s)
- Yael Yaniv
- Laboratory of Cardiovascular Science, Gerontology Research Center, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Magdalena Juhaszova
- Laboratory of Cardiovascular Science, Gerontology Research Center, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Su Wang
- Laboratory of Cardiovascular Science, Gerontology Research Center, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Kenneth W. Fishbein
- Laboratory of Clinical Investigation, Gerontology Research Center, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Dmitry B. Zorov
- Laboratory of Cardiovascular Science, Gerontology Research Center, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Steven J. Sollott
- Laboratory of Cardiovascular Science, Gerontology Research Center, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America
- * E-mail:
| |
Collapse
|
42
|
da Silva Lopes K, Pietas A, Radke MH, Gotthardt M. Titin visualization in real time reveals an unexpected level of mobility within and between sarcomeres. J Gen Physiol 2011. [DOI: 10.1085/jgp1376oia4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
|
43
|
Abstract
Photobleaching reveals that the backbone of muscle myofibrils is surprisingly mobile.
Collapse
|