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Zhao J, Qi L, Yuan S, Irving TC, Ma W. Differences in thick filament activation in fast rodent skeletal muscle and slow porcine cardiac muscle. J Physiol 2024; 602:2751-2762. [PMID: 38695322 PMCID: PMC11178443 DOI: 10.1113/jp286072] [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: 11/30/2023] [Accepted: 04/16/2024] [Indexed: 06/15/2024] Open
Abstract
There is a growing appreciation that regulation of muscle contraction requires both thin filament and thick filament activation in order to fully activate the sarcomere. The prevailing mechano-sensing model for thick filament activation was derived from experiments on fast-twitch muscle. We address the question whether, or to what extent, this mechanism can be extrapolated to the slow muscle in the hearts of large mammals, including humans. We investigated the similarities and differences in structural signatures of thick filament activation in porcine myocardium as compared to fast rat extensor digitorum longus (EDL) skeletal muscle under relaxed conditions and sub-maximal contraction using small angle X-ray diffraction. Thick and thin filaments were found to adopt different structural configurations under relaxing conditions, and myosin heads showed different changes in configuration upon sub-maximal activation, when comparing the two muscle types. Titin was found to have an X-ray diffraction signature distinct from those of the overall thick filament backbone, and its spacing change appeared to be positively correlated to the force exerted on the thick filament. Structural changes in fast EDL muscle were found to be consistent with the mechano-sensing model. In porcine myocardium, however, the structural basis of mechano-sensing is blunted suggesting the need for additional activation mechanism(s) in slow cardiac muscle. These differences in thick filament regulation can be related to their different physiological roles where fast muscle is optimized for rapid, burst-like, contractions, and the slow cardiac muscle in large mammalian hearts adopts a more finely tuned, graded response to allow for their substantial functional reserve. KEY POINTS: Both thin filament and thick filament activation are required to fully activate the sarcomere. Thick and thin filaments adopt different structural configurations under relaxing conditions, and myosin heads show different changes in configuration upon sub-maximal activation in fast extensor digitorum longus muscle and slow porcine cardiac muscle. Titin has an X-ray diffraction signature distinct from those of the overall thick filament backbone and this titin reflection spacing change appeared to be directly proportional to the force exerted on the thick filament. Mechano-sensing is blunted in porcine myocardium suggesting the need for additional activation mechanism(s) in slow cardiac muscle. Fast skeletal muscle is optimized for rapid, burst-like contractions, and the slow cardiac muscle in large mammalian hearts adopts a more finely tuned graded response to allow for their substantial functional reserve.
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Affiliation(s)
- Jing Zhao
- College of Basic Medical Sciences, Dalian Medical University, Dalian, Liaoning, China
| | - Lin Qi
- Department of Biology, Illinois Institute of Technology, Chicago, IL, USA
| | - Shengyao Yuan
- BioCAT, Department of Biology, Illinois Institute of Technology, Chicago, IL, USA
| | - Thomas C Irving
- BioCAT, Department of Biology, Illinois Institute of Technology, Chicago, IL, USA
- Center for Synchrotron Radiation Research and Instrumentation, Illinois Institute of Technology, Chicago, IL, USA
| | - Weikang Ma
- BioCAT, Department of Biology, Illinois Institute of Technology, Chicago, IL, USA
- Center for Synchrotron Radiation Research and Instrumentation, Illinois Institute of Technology, Chicago, IL, USA
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Hessel AL, Kuehn MN, Han SW, Ma W, Irving TC, Momb BA, Song T, Sadayappan S, Linke WA, Palmer BM. Fast myosin binding protein C knockout in skeletal muscle alters length-dependent activation and myofilament structure. Commun Biol 2024; 7:648. [PMID: 38802450 PMCID: PMC11130249 DOI: 10.1038/s42003-024-06265-8] [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: 11/17/2023] [Accepted: 04/29/2024] [Indexed: 05/29/2024] Open
Abstract
In striated muscle, the sarcomeric protein myosin-binding protein-C (MyBP-C) is bound to the myosin thick filament and is predicted to stabilize myosin heads in a docked position against the thick filament, which limits crossbridge formation. Here, we use the homozygous Mybpc2 knockout (C2-/-) mouse line to remove the fast-isoform MyBP-C from fast skeletal muscle and then conduct mechanical functional studies in parallel with small-angle X-ray diffraction to evaluate the myofilament structure. We report that C2-/- fibers present deficits in force production and calcium sensitivity. Structurally, passive C2-/- fibers present altered sarcomere length-independent and -dependent regulation of myosin head conformations, with a shift of myosin heads towards actin. At shorter sarcomere lengths, the thin filament is axially extended in C2-/-, which we hypothesize is due to increased numbers of low-level crossbridges. These findings provide testable mechanisms to explain the etiology of debilitating diseases associated with MyBP-C.
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Affiliation(s)
- Anthony L Hessel
- Institute of Physiology II, University of Muenster, Muenster, Germany.
| | - Michel N Kuehn
- Institute of Physiology II, University of Muenster, Muenster, Germany
| | - Seong-Won Han
- Institute of Physiology II, University of Muenster, Muenster, Germany
| | - Weikang Ma
- BioCAT, Department of Biology, Illinois Institute of Technology, Chicago, USA
| | - Thomas C Irving
- BioCAT, Department of Biology, Illinois Institute of Technology, Chicago, USA
| | - Brent A Momb
- Department of Kinesiology, University of Massachusetts-Amherst, Amherst, MA, USA
| | - Taejeong Song
- Center for Cardiovascular Research, Division of Cardiovascular Health and Disease, Department of Internal Medicine, University of Cincinnati, Cincinnati, OH, USA
| | - Sakthivel Sadayappan
- Center for Cardiovascular Research, Division of Cardiovascular Health and Disease, Department of Internal Medicine, University of Cincinnati, Cincinnati, OH, USA
| | - Wolfgang A Linke
- Institute of Physiology II, University of Muenster, Muenster, Germany
| | - Bradley M Palmer
- Department of Molecular Physiology and Biophysics, University of Vermont, Burlington, VT, USA.
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Hessel AL, Kuehn M, Han SW, Ma W, Irving TC, Momb BA, Song T, Sadayappan S, Linke WA, Palmer BM. Fast myosin binding protein C knockout in skeletal muscle alters length-dependent activation and myofilament structure. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.10.19.563160. [PMID: 37961718 PMCID: PMC10634671 DOI: 10.1101/2023.10.19.563160] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2023]
Abstract
In striated muscle, some sarcomere proteins regulate crossbridge cycling by varying the propensity of myosin heads to interact with actin. Myosin-binding protein C (MyBP-C) is bound to the myosin thick filament and is predicted to interact and stabilize myosin heads in a docked position against the thick filament and limit crossbridge formation, the so-called OFF state. Via an unknown mechanism, MyBP-C is thought to release heads into the so-called ON state, where they are more likely to form crossbridges. To study this proposed mechanism, we used the C2-/- mouse line to knock down fast-isoform MyBP-C completely and total MyBP-C by ~24%, and conducted mechanical functional studies in parallel with small-angle X-ray diffraction to evaluate the myofilament structure. We report that C2-/- fibers presented deficits in force production and reduced calcium sensitivity. Structurally, passive C2-/- fibers presented altered SL-independent and SL-dependent regulation of myosin head ON/OFF states, with a shift of myosin heads towards the ON state. Unexpectedly, at shorter sarcomere lengths, the thin filament was axially extended in C2-/- vs. non-transgenic controls, which we postulate is due to increased low-level crossbridge formation arising from relatively more ON myosins in the passive muscle that elongates the thin filament. The downstream effect of increasing crossbridge formation in a passive muscle on contraction performance is not known. Such widespread structural changes to sarcomere proteins provide testable mechanisms to explain the etiology of debilitating MyBP-C-associated diseases.
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Affiliation(s)
- Anthony L. Hessel
- Institute of Physiology II, University of Muenster; Muenster, Germany
| | - Michel Kuehn
- Institute of Physiology II, University of Muenster; Muenster, Germany
| | - Seong-Won Han
- Institute of Physiology II, University of Muenster; Muenster, Germany
| | - Weikang Ma
- BioCAT, Department of Biology, Illinois Institute of Technology; Chicago, USA
| | - Thomas C. Irving
- BioCAT, Department of Biology, Illinois Institute of Technology; Chicago, USA
| | - Brent A. Momb
- Department of Kinesiology, University of Massachusetts – Amherst; Amherst, MA, USA
| | - Taejeong Song
- Center for Cardiovascular Research, Division of Cardiovascular Health and Disease, Department of Internal Medicine, University of Cincinnati, Cincinnati, OH, USA
| | - Sakthivel Sadayappan
- Center for Cardiovascular Research, Division of Cardiovascular Health and Disease, Department of Internal Medicine, University of Cincinnati, Cincinnati, OH, USA
| | - Wolfgang A. Linke
- Institute of Physiology II, University of Muenster; Muenster, Germany
| | - Bradley M. Palmer
- Department of Molecular Physiology and Biophysics, University of Vermont; Burlington, VT, USA
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Hessel AL, Engels NM, Kuehn M, Nissen D, Sadler RL, Ma W, Irving TC, Linke WA, Harris SP. Myosin-binding protein C forms C-links and stabilizes OFF states of myosin. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.09.10.556972. [PMID: 37745361 PMCID: PMC10515747 DOI: 10.1101/2023.09.10.556972] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/26/2023]
Abstract
Contraction force in muscle is produced by the interaction of myosin motors in the thick filaments and actin in the thin filaments and is fine-tuned by other proteins such as myosin-binding protein C (MyBP-C). One form of control is through the regulation of myosin heads between an ON and OFF state in passive sarcomeres, which leads to their ability or inability to interact with the thin filaments during contraction, respectively. MyBP-C is a flexible and long protein that is tightly bound to the thick filament at its C-terminal end but may be loosely bound at its middle- and N-terminal end (MyBP-CC1C7). Under considerable debate is whether the MyBP-CC1C7 domains directly regulate myosin head ON/OFF states, and/or link thin filaments ("C-links"). Here, we used a combination of mechanics and small-angle X-ray diffraction to study the immediate and selective removal of the MyBP-CC1C7 domains of fast MyBP-C in permeabilized skeletal muscle. After cleavage, the thin filaments were significantly shorter, a result consistent with direct interactions of MyBP-C with thin filaments thus confirming C-links. Ca2+ sensitivity was reduced at shorter sarcomere lengths, and crossbridge kinetics were increased across sarcomere lengths at submaximal activation levels, demonstrating a role in crossbridge kinetics. Structural signatures of the thick filaments suggest that cleavage also shifted myosin heads towards the ON state - a marker that typically indicates increased Ca2+ sensitivity but that may account for increased crossbridge kinetics at submaximal Ca2+ and/or a change in the force transmission pathway. Taken together, we conclude that MyBP-CC1C7 domains play an important role in contractile performance which helps explain why mutations in these domains often lead to debilitating diseases.
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Affiliation(s)
- Anthony L Hessel
- Institute of Physiology II, University of Muenster; Muenster, Germany
| | - Nichlas M Engels
- Department of Cellular and Molecular Medicine, University of Arizona; Tucson, AZ, USA
| | - Michel Kuehn
- Institute of Physiology II, University of Muenster; Muenster, Germany
| | - Devin Nissen
- BioCAT, Department of Biology, Illinois Institute of Technology; Chicago, IL, USA
| | - Rachel L Sadler
- Department of Physiology, University of Arizona, Tucson, AZ, USA
| | - Weikang Ma
- BioCAT, Department of Biology, Illinois Institute of Technology; Chicago, IL, USA
| | - Thomas C Irving
- BioCAT, Department of Biology, Illinois Institute of Technology; Chicago, IL, USA
| | - Wolfgang A Linke
- Institute of Physiology II, University of Muenster; Muenster, Germany
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Hessel AL, Kuehn M, Palmer BM, Nissen D, Mishra D, Joumaa V, Freundt J, Ma W, Nishikawa KC, Irving T, Linke WA. The distinctive mechanical and structural signatures of residual force enhancement in myofibers. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.02.19.529125. [PMID: 36865266 PMCID: PMC9980001 DOI: 10.1101/2023.02.19.529125] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/23/2023]
Abstract
In muscle, titin proteins connect myofilaments together and are thought to be critical for contraction, especially during residual force enhancement (RFE) when force is elevated after an active stretch. We investigated titin's function during contraction using small-angle X-ray diffraction to track structural changes before and after 50% titin cleavage and in the RFE-deficient, mdm titin mutant. We report that the RFE state is structurally distinct from pure isometric contractions, with increased thick filament strain and decreased lattice spacing, most likely caused by elevated titin-based forces. Furthermore, no RFE structural state was detected in mdm muscle. We posit that decreased lattice spacing, increased thick filament stiffness, and increased non-crossbridge forces are the major contributors to RFE. We conclude that titin directly contributes to RFE.
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Affiliation(s)
- Anthony L. Hessel
- Institute of Physiology II, University of Muenster; Muenster, Germany
| | - Michel Kuehn
- Institute of Physiology II, University of Muenster; Muenster, Germany
| | - Bradley M. Palmer
- Department of Molecular Physiology and Biophysics, University of Vermont; Burlington, VT, 05405-1705, USA
| | - Devin Nissen
- BioCAT, Department of Biology, Illinois Institute of Technology; Chicago, IL, USA
| | - Dhruv Mishra
- Department of Biological Sciences, University of Northern Arizona; Flagstaff AZ, USA
| | - Venus Joumaa
- Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, AB T2N1N4, Canada
| | - Johanna Freundt
- Institute of Physiology II, University of Muenster; Muenster, Germany
| | - Weikang Ma
- BioCAT, Department of Biology, Illinois Institute of Technology; Chicago, IL, USA
| | - Kiisa C. Nishikawa
- Department of Biological Sciences, University of Northern Arizona; Flagstaff AZ, USA
| | - Thomas Irving
- BioCAT, Department of Biology, Illinois Institute of Technology; Chicago, IL, USA
| | - Wolfgang A. Linke
- Institute of Physiology II, University of Muenster; Muenster, Germany
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Hinks A, Jacob K, Mashouri P, Medak KD, Franchi MV, Wright DC, Brown SHM, Power GA. Influence of weighted downhill running training on serial sarcomere number and work loop performance in the rat soleus. Biol Open 2022; 11:276077. [PMID: 35876382 PMCID: PMC9346294 DOI: 10.1242/bio.059491] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2022] [Accepted: 06/23/2022] [Indexed: 12/16/2022] Open
Abstract
Increased serial sarcomere number (SSN) has been observed in rats following downhill running training due to the emphasis on active lengthening contractions; however, little is known about the influence on dynamic contractile function. Therefore, we employed 4 weeks of weighted downhill running training in rats, then assessed soleus SSN and work loop performance. We hypothesised trained rats would produce greater net work output during work loops due to a greater SSN. Thirty-one Sprague-Dawley rats were assigned to a training or sedentary control group. Weight was added during downhill running via a custom-made vest, progressing from 5–15% body mass. Following sacrifice, the soleus was dissected, and a force-length relationship was constructed. Work loops (cyclic muscle length changes) were then performed about optimal muscle length (LO) at 1.5–3-Hz cycle frequencies and 1–7-mm length changes. Muscles were then fixed in formalin at LO. Fascicle lengths and sarcomere lengths were measured to calculate SSN. Intramuscular collagen content and crosslinking were quantified via a hydroxyproline content and pepsin-solubility assay. Trained rats had longer fascicle lengths (+13%), greater SSN (+8%), and a less steep passive force-length curve than controls (P<0.05). There were no differences in collagen parameters (P>0.05). Net work output was greater (+78–209%) in trained than control rats for the 1.5-Hz work loops at 1 and 3-mm length changes (P<0.05), however, net work output was more related to maximum specific force (R2=0.17-0.48, P<0.05) than SSN (R2=0.03-0.07, P=0.17-0.86). Therefore, contrary to our hypothesis, training-induced sarcomerogenesis likely contributed little to the improvements in work loop performance. This article has an associated First Person interview with the first author of the paper. Summary: An investigation of adaptations in mechanical function induced by a novel method of weighted downhill running training in rats, and the connections to adaptations in muscle architecture.
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Affiliation(s)
- Avery Hinks
- Department of Human Health and Nutritional Sciences, College of Biological Sciences, University of Guelph, 50 Stone Road East, Guelph, ON N1G 2W1, Canada
| | - Kaitlyn Jacob
- Department of Human Health and Nutritional Sciences, College of Biological Sciences, University of Guelph, 50 Stone Road East, Guelph, ON N1G 2W1, Canada
| | - Parastoo Mashouri
- Department of Human Health and Nutritional Sciences, College of Biological Sciences, University of Guelph, 50 Stone Road East, Guelph, ON N1G 2W1, Canada
| | - Kyle D Medak
- Department of Human Health and Nutritional Sciences, College of Biological Sciences, University of Guelph, 50 Stone Road East, Guelph, ON N1G 2W1, Canada
| | - Martino V Franchi
- Department of Biomedical Sciences, Neuromuscular Physiology Laboratory, University of Padua, Padua 35122, Italy
| | - David C Wright
- Department of Human Health and Nutritional Sciences, College of Biological Sciences, University of Guelph, 50 Stone Road East, Guelph, ON N1G 2W1, Canada.,School of Kinesiology, Faculty of Land and Food Systems, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - Stephen H M Brown
- Department of Human Health and Nutritional Sciences, College of Biological Sciences, University of Guelph, 50 Stone Road East, Guelph, ON N1G 2W1, Canada
| | - Geoffrey A Power
- Department of Human Health and Nutritional Sciences, College of Biological Sciences, University of Guelph, 50 Stone Road East, Guelph, ON N1G 2W1, Canada
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Herzog W. What Can We Learn from Single Sarcomere and Myofibril Preparations? Front Physiol 2022; 13:837611. [PMID: 35574477 PMCID: PMC9092595 DOI: 10.3389/fphys.2022.837611] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Accepted: 04/06/2022] [Indexed: 11/13/2022] Open
Abstract
Sarcomeres are the smallest functional contractile unit of muscle, and myofibrils are striated muscle organelles that are comprised of sarcomeres that are strictly aligned in series. Furthermore, passive forces in sarcomeres and myofibrils are almost exclusively produced by the structural protein titin, and all contractile, regulatory, and structural proteins are in their natural configuration. For these mechanical and structural reasons single sarcomere and myofibril preparations are arguably the most powerful to answer questions on the mechanisms of striated muscle contraction. We developed and optimized single myofibril research over the past 20 years and were the first to mechanically isolate and test single sarcomeres. The results from this research led to the uncovering of the crucial role of titin in muscle contraction, first molecular explanations for the origins of the passive and the residual force enhancement properties of skeletal and cardiac muscles, the discovery of sarcomere length stability on the descending limb of the force-length relationship, and culminating in the formulation of the three-filament theory of muscle contraction that, aside from actin and myosin, proposes a crucial role of titin in active force production. Aside from all the advantages and possibilities that single sarcomere and myofibril preparations offer, there are also disadvantages. These include the fragility of the preparation, the time-consuming training to master these preparations, the limited spatial resolution for length and force measurements, and the unavailability of commercial systems for single sarcomere/myofibril research. Ignoring the mechanics that govern serially linked systems, not considering the spatial resolution and associated accuracies of myofibril systems, and neglecting the fragility of myofibril preparations, has led to erroneous interpretations of results and misleading conclusions. Here, we will attempt to describe the methods and possible applications of single sarcomere/myofibril research and discuss the advantages and disadvantages by focusing on specific applications. It is hoped that this discussion may contribute to identifying the enormous potential of single sarcomere/myofibril research in discovering the secrets of muscle contraction.
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Affiliation(s)
- Walter Herzog
- Faculty of Kinesiology, The University of Calgary, Calgary, AB, Canada
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Ma W, Irving TC. Small Angle X-ray Diffraction as a Tool for Structural Characterization of Muscle Disease. Int J Mol Sci 2022; 23:3052. [PMID: 35328477 PMCID: PMC8949570 DOI: 10.3390/ijms23063052] [Citation(s) in RCA: 32] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2022] [Revised: 03/01/2022] [Accepted: 03/02/2022] [Indexed: 02/01/2023] Open
Abstract
Small angle X-ray fiber diffraction is the method of choice for obtaining molecular level structural information from striated muscle fibers under hydrated physiological conditions. For many decades this technique had been used primarily for investigating basic biophysical questions regarding muscle contraction and regulation and its use confined to a relatively small group of expert practitioners. Over the last 20 years, however, X-ray diffraction has emerged as an important tool for investigating the structural consequences of cardiac and skeletal myopathies. In this review we show how simple and straightforward measurements, accessible to non-experts, can be used to extract biophysical parameters that can help explain and characterize the physiology and pathology of a given experimental system. We provide a comprehensive guide to the range of the kinds of measurements that can be made and illustrate how they have been used to provide insights into the structural basis of pathology in a comprehensive review of the literature. We also show how these kinds of measurements can inform current controversies and indicate some future directions.
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Affiliation(s)
- Weikang Ma
- The Biophysics Collaborative Access Team (BioCAT), Center for Synchrotron Radiation Research and Instrumentation (CSSRI), Illinois Institute of Technology, Chicago, IL 60616, USA;
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Thomas C. Irving
- The Biophysics Collaborative Access Team (BioCAT), Center for Synchrotron Radiation Research and Instrumentation (CSSRI), Illinois Institute of Technology, Chicago, IL 60616, USA;
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA
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Ma W, Childers M, Murray J, Moussavi-Harami F, Gong H, Weiss R, Daggett V, Irving T, Regnier M. Myosin dynamics during relaxation in mouse soleus muscle and modulation by 2'-deoxy-ATP. J Physiol 2020; 598:5165-5182. [PMID: 32818298 PMCID: PMC7719615 DOI: 10.1113/jp280402] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2020] [Accepted: 08/13/2020] [Indexed: 01/29/2023] Open
Abstract
KEY POINTS Skeletal muscle relaxation has been primarily studied by assessing the kinetics of force decay. Little is known about the resultant dynamics of structural changes in myosin heads during relaxation. The naturally occurring nucleotide 2-deoxy-ATP (dATP) is a myosin activator that enhances cross-bridge binding and kinetics. X-ray diffraction data indicate that with elevated dATP, myosin heads were extended closer to actin in relaxed muscle and myosin heads return to an ordered, resting state after contraction more quickly. Molecular dynamics simulations of post-powerstroke myosin suggest that dATP induces structural changes in myosin heads that increase the surface area of the actin-binding regions promoting myosin interaction with actin, which could explain the observed delays in the onset of relaxation. This study of the dATP-induced changes in myosin may be instructive for determining the structural changes desired for other potential myosin-targeted molecular compounds to treat muscle diseases. ABSTRACT Here we used time-resolved small-angle X-ray diffraction coupled with force measurements to study the structural changes in FVB mouse skeletal muscle sarcomeres during relaxation after tetanus contraction. To estimate the rate of myosin deactivation, we followed the rate of the intensity recovery of the first-order myosin layer line (MLL1) and restoration of the resting spacing of the third and sixth order of meridional reflection (SM3 and SM6 ) following tetanic contraction. A transgenic mouse model with elevated skeletal muscle 2-deoxy-ATP (dATP) was used to study how myosin activators may affect soleus muscle relaxation. X-ray diffraction evidence indicates that with elevated dATP, myosin heads were extended closer to actin in resting muscle. Following contraction, there is a slight but significant delay in the decay of force relative to WT muscle while the return of myosin heads to an ordered resting state was initially slower, then became more rapid than in WT muscle. Molecular dynamics simulations of post-powerstroke myosin suggest that dATP induces structural changes in myosin that increase the surface area of the actin-binding regions, promoting myosin interaction with actin. With dATP, myosin heads may remain in an activated state near the thin filaments following relaxation, accounting for the delay in force decay and the initial delay in recovery of resting head configuration, and this could facilitate subsequent contractions.
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Affiliation(s)
- Weikang Ma
- BioCAT, Department of Biological Sciences, Illinois Institute of Technology, Chicago IL
| | - Matthew Childers
- Department of Bioengineering, University of Washington, Seattle WA
| | - Jason Murray
- Department of Bioengineering, University of Washington, Seattle WA
| | | | - Henry Gong
- BioCAT, Department of Biological Sciences, Illinois Institute of Technology, Chicago IL
| | - Robert Weiss
- Department of Biomedical Sciences, Cornell University, Ithaca NY
| | - Valerie Daggett
- Department of Bioengineering, University of Washington, Seattle WA
| | - Thomas Irving
- BioCAT, Department of Biological Sciences, Illinois Institute of Technology, Chicago IL
| | - Michael Regnier
- Department of Bioengineering, University of Washington, Seattle WA
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10
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Chen J, Mashouri P, Fontyn S, Valvano M, Elliott-Mohamed S, Noonan AM, Brown SHM, Power GA. The influence of training-induced sarcomerogenesis on the history dependence of force. J Exp Biol 2020; 223:jeb218776. [PMID: 32561632 DOI: 10.1242/jeb.218776] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2019] [Accepted: 06/09/2020] [Indexed: 12/21/2022]
Abstract
The increase or decrease in isometric force following active muscle lengthening or shortening, relative to a reference isometric contraction at the same muscle length and level of activation, are referred to as residual force enhancement (rFE) and residual force depression (rFD), respectively. The purpose of these experiments was to investigate the trainability of rFE and rFD on the basis of serial sarcomere number (SSN) alterations to history-dependent force properties. Maximal rFE/rFD measures from the soleus and extensor digitorum longus (EDL) of rats were compared after 4 weeks of uphill or downhill running with a no-running control. SSN adapted to the training: soleus SSN was greater with downhill compared with uphill running, while EDL demonstrated a trend towards more SSN for downhill compared with no running. In contrast, rFE and rFD did not differ across training groups for either muscle. As such, it appears that training-induced SSN adaptations do not modify rFE or rFD at the whole-muscle level.
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Affiliation(s)
- Jackey Chen
- Department of Human Health and Nutritional Sciences, College of Biological Sciences, University of Guelph, Guelph, ON N1G 2W1, Canada
| | - Parastoo Mashouri
- Department of Human Health and Nutritional Sciences, College of Biological Sciences, University of Guelph, Guelph, ON N1G 2W1, Canada
| | - Stephanie Fontyn
- Department of Human Health and Nutritional Sciences, College of Biological Sciences, University of Guelph, Guelph, ON N1G 2W1, Canada
| | - Mikella Valvano
- Department of Human Health and Nutritional Sciences, College of Biological Sciences, University of Guelph, Guelph, ON N1G 2W1, Canada
| | - Shakeap Elliott-Mohamed
- Department of Human Health and Nutritional Sciences, College of Biological Sciences, University of Guelph, Guelph, ON N1G 2W1, Canada
| | - Alex M Noonan
- Department of Human Health and Nutritional Sciences, College of Biological Sciences, University of Guelph, Guelph, ON N1G 2W1, Canada
| | - Stephen H M Brown
- Department of Human Health and Nutritional Sciences, College of Biological Sciences, University of Guelph, Guelph, ON N1G 2W1, Canada
| | - Geoffrey A Power
- Department of Human Health and Nutritional Sciences, College of Biological Sciences, University of Guelph, Guelph, ON N1G 2W1, Canada
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Fukutani A, Herzog W. Current Understanding of Residual Force Enhancement: Cross-Bridge Component and Non-Cross-Bridge Component. Int J Mol Sci 2019; 20:ijms20215479. [PMID: 31689920 PMCID: PMC6862632 DOI: 10.3390/ijms20215479] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2019] [Revised: 10/31/2019] [Accepted: 11/01/2019] [Indexed: 02/06/2023] Open
Abstract
Muscle contraction is initiated by the interaction between actin and myosin filaments. The sliding of actin filaments relative to myosin filaments is produced by cross-bridge cycling, which is governed by the theoretical framework of the cross-bridge theory. The cross-bridge theory explains well a number of mechanical responses, such as isometric and concentric contractions. However, some experimental observations cannot be explained with the cross-bridge theory; for example, the increased isometric force after eccentric contractions. The steady-state, isometric force after an eccentric contraction is greater than that attained in a purely isometric contraction at the same muscle length and same activation level. This well-acknowledged and universally observed property is referred to as residual force enhancement (rFE). Since rFE cannot be explained by the cross-bridge theory, alternative mechanisms for explaining this force response have been proposed. In this review, we introduce the basic concepts of sarcomere length non-uniformity and titin elasticity, which are the primary candidates that have been used for explaining rFE, and discuss unresolved problems regarding these mechanisms, and how to proceed with future experiments in this exciting area of research.
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Affiliation(s)
- Atsuki Fukutani
- Faculty of Sport and Health Science, Ritsumeikan University, 1-1-1 Noji-higashi, Kusatsu, Shiga 525-8577, Japan.
| | - Walter Herzog
- Faculty of Kinesiology, The University of Calgary, 2500 University Drive, NW, Calgary, AB T2N 1N4, Canada.
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