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Guo J, Jiang H, Schuftan D, Moreno JD, Ramahdita G, Aryan L, Bhagavan D, Silva J, Huebsch N. Substrate mechanics unveil early structural and functional pathology in iPSC micro-tissue models of hypertrophic cardiomyopathy. iScience 2024; 27:109954. [PMID: 38827401 PMCID: PMC11141149 DOI: 10.1016/j.isci.2024.109954] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2023] [Revised: 03/22/2024] [Accepted: 05/08/2024] [Indexed: 06/04/2024] Open
Abstract
Hypertension is a major cause of morbidity and mortality in patients with hypertrophic cardiomyopathy (HCM), suggesting a potential role for mechanics in HCM pathogenesis. Here, we developed an in vitro physiological model to investigate how mechanics acts together with HCM-linked myosin binding protein C (MYBPC3) mutations to trigger disease. Micro-heart muscles (μHM) were engineered from induced pluripotent stem cell (iPSC)-derived cardiomyocytes bearing MYBPC3+/- mutations and challenged to contract against substrates of different elasticity. μHMs that worked against substrates with stiffness at or exceeding the stiffness of healthy adult heart muscle exhibited several hallmarks of HCM, including cellular hypertrophy, impaired contractile energetics, and maladaptive calcium handling. Remarkably, we discovered changes in troponin C and T localization in MYBPC3+/- μHM that were entirely absent in 2D culture. Pharmacologic studies suggested that excessive Ca2+ intake through membrane-embedded channels underlie the observed electrophysiological abnormalities. These results illustrate the power of physiologically relevant engineered tissue models to study inherited disease with iPSC technology.
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Affiliation(s)
- Jingxuan Guo
- Department of Mechanical Engineering and Material Science, Washington University in Saint Louis, Saint Louis, MO 63130, USA
| | - Huanzhu Jiang
- Department of Biomedical Engineering, Washington University in Saint Louis, Saint Louis, MO 63130, USA
| | - David Schuftan
- Department of Biomedical Engineering, Washington University in Saint Louis, Saint Louis, MO 63130, USA
| | - Jonathan D. Moreno
- Division of Cardiology, Department of Medicine, Washington University in Saint Louis, Saint Louis, MO 63130, USA
| | - Ghiska Ramahdita
- Department of Mechanical Engineering and Material Science, Washington University in Saint Louis, Saint Louis, MO 63130, USA
- NSF Science and Technology Center for Engineering Mechanobiology, Washington University in Saint Louis, Saint Louis, MO 63130, USA
| | - Lavanya Aryan
- Department of Biomedical Engineering, Washington University in Saint Louis, Saint Louis, MO 63130, USA
| | - Druv Bhagavan
- Department of Biomedical Engineering, Washington University in Saint Louis, Saint Louis, MO 63130, USA
| | - Jonathan Silva
- Department of Biomedical Engineering, Washington University in Saint Louis, Saint Louis, MO 63130, USA
| | - Nathaniel Huebsch
- Department of Biomedical Engineering, Washington University in Saint Louis, Saint Louis, MO 63130, USA
- NSF Science and Technology Center for Engineering Mechanobiology, Washington University in Saint Louis, Saint Louis, MO 63130, USA
- Center for Cardiovascular Research, Center for Regenerative Medicine, Center for Investigation of Membrane Excitability Diseases, Washington University in Saint Louis, Saint Louis, MO 63130, USA
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2
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Ma W, del Rio CL, Qi L, Prodanovic M, Mijailovich S, Zambataro C, Gong H, Shimkunas R, Gollapudi S, Nag S, Irving TC. Myosin in autoinhibited off state(s), stabilized by mavacamten, can be recruited in response to inotropic interventions. Proc Natl Acad Sci U S A 2024; 121:e2314914121. [PMID: 38346202 PMCID: PMC10895252 DOI: 10.1073/pnas.2314914121] [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: 08/28/2023] [Accepted: 01/08/2024] [Indexed: 02/15/2024] Open
Abstract
Mavacamten is a FDA-approved small-molecule therapeutic designed to regulate cardiac function at the sarcomere level by selectively but reversibly inhibiting the enzymatic activity of myosin. It shifts myosin toward ordered off states close to the thick filament backbone. It remains elusive whether these myosin heads in the off state(s) can be recruited in response to physiological stimuli when required to boost cardiac output. We show that cardiac myosins stabilized in these off state(s) by mavacamten are recruitable by 1) Ca2+, 2) increased chronotropy [heart rate (HR)], 3) stretch, and 4) β-adrenergic (β-AR) stimulation, all known physiological inotropic interventions. At the molecular level, we show that Ca2+ increases myosin ATPase activity by shifting mavacamten-stabilized myosin heads from the inactive super-relaxed state to the active disordered relaxed state. At the myofilament level, both Ca2+ and passive lengthening can shift mavacamten-ordered off myosin heads from positions close to the thick filament backbone to disordered on states closer to the thin filaments. In isolated rat cardiomyocytes, increased stimulation rates enhanced shortening fraction in mavacamten-treated cells. This observation was confirmed in vivo in telemetered rats, where left-ventricular dP/dtmax, an index of inotropy, increased with HR in mavacamten-treated animals. Finally, we show that β-AR stimulation in vivo increases left-ventricular function and stroke volume in the setting of mavacamten. Our data demonstrate that the mavacamten-promoted off states of myosin in the thick filament are at least partially activable, thus preserving cardiac reserve mechanisms.
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Affiliation(s)
- Weikang Ma
- Biophysics Collaborative Access Team, Department of Biology, Illinois Institute of Technology, Chicago, IL60616
- Center for Synchrotron Radiation Research and Instrumentation, Illinois Institute of Technology, Chicago, IL60616
| | - Carlos L. del Rio
- Cardiovascular Drug Discovery, Bristol Myers Squibb, Brisbane, CA94005
- Cardiac Consulting, San Mateo, CA94010
| | - Lin Qi
- Department of Biology, Illinois Institute of Technology, Chicago, IL60616
| | - Momcilo Prodanovic
- Institute for Information Technologies, University of Kragujevac, Kragujevac34000, Serbia
- FilamenTech, Inc., Newtown, MA02458
| | | | | | - Henry Gong
- Department of Biology, Illinois Institute of Technology, Chicago, IL60616
| | - Rafael Shimkunas
- Cardiovascular Drug Discovery, Bristol Myers Squibb, Brisbane, CA94005
| | - Sampath Gollapudi
- Cardiovascular Drug Discovery, Bristol Myers Squibb, Brisbane, CA94005
| | - Suman Nag
- Cardiovascular Drug Discovery, Bristol Myers Squibb, Brisbane, CA94005
| | - Thomas C. Irving
- Biophysics Collaborative Access Team, Department of Biology, Illinois Institute of Technology, Chicago, IL60616
- Center for Synchrotron Radiation Research and Instrumentation, Illinois Institute of Technology, Chicago, IL60616
- Department of Biology, Illinois Institute of Technology, Chicago, IL60616
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3
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Jani VP, Song T, Gao C, Gong H, Sadayappan S, Kass DA, Irving TC, Ma W. The structural OFF and ON states of myosin can be decoupled from the biochemical super- and disordered-relaxed states. PNAS NEXUS 2024; 3:pgae039. [PMID: 38328779 PMCID: PMC10849796 DOI: 10.1093/pnasnexus/pgae039] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/14/2023] [Accepted: 01/19/2024] [Indexed: 02/09/2024]
Abstract
There is a growing awareness that both thick-filament and classical thin-filament regulations play central roles in modulating muscle contraction. Myosin ATPase assays have demonstrated that under relaxed conditions, myosin may reside either in a high-energy-consuming disordered-relaxed (DRX) state available for binding actin to generate force or in an energy-sparing super-relaxed (SRX) state unavailable for actin binding. X-ray diffraction studies have shown that the majority of myosin heads are in a quasi-helically ordered OFF state in a resting muscle and that this helical ordering is lost when myosin heads are turned ON for contraction. It has been assumed that myosin heads in SRX and DRX states are equivalent to the OFF and ON states, respectively, and the terms have been used interchangeably. In this study, we use X-ray diffraction and ATP turnover assays to track the structural and biochemical transitions of myosin heads, respectively, induced with either omecamtiv mecarbil (OM) or piperine in relaxed porcine myocardium. We find that while OM and piperine induce dramatic shifts of myosin heads from the OFF to the ON state, there are no appreciable changes in the population of myosin heads in the SRX and DRX states in both unloaded and loaded preparations. Our results show that biochemically defined SRX and DRX can be decoupled from structurally defined OFF and ON states. In summary, while SRX/DRX and OFF/ON transitions can be correlated in some cases, these two phenomena are measured using different approaches, reflect different properties of the thick filament, and should be investigated and interpreted separately.
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Affiliation(s)
- Vivek P Jani
- Department of Biomedical Engineering, The Johns Hopkins School of Medicine, Baltimore, MD 21205, USA
- Division of Cardiology, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Taejeong Song
- Division of Cardiovascular Health and Disease, Department of Internal Medicine, University of Cincinnati, Cincinnati, OH 45229, USA
| | - Chengqian Gao
- College of Basic Medical Sciences, Dalian Medical University, Dalian, Liaoning 116044, China
| | - Henry Gong
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Sakthivel Sadayappan
- Division of Cardiovascular Health and Disease, Department of Internal Medicine, University of Cincinnati, Cincinnati, OH 45229, USA
| | - David A Kass
- Department of Biomedical Engineering, The Johns Hopkins School of Medicine, Baltimore, MD 21205, USA
- Division of Cardiology, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Thomas C Irving
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA
- Center for Synchrotron Radiation Research and Instrumentation, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Weikang Ma
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA
- Center for Synchrotron Radiation Research and Instrumentation, Illinois Institute of Technology, Chicago, IL 60616, USA
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Hessel AL, Kuehn MN, Engels NM, Nissen DL, Freundt JK, Ma W, Irving TC, Linke WA. Titin-based force regulates cardiac myofilament structures mediating length-dependent activation. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.11.09.566413. [PMID: 38014235 PMCID: PMC10680614 DOI: 10.1101/2023.11.09.566413] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2023]
Abstract
The Frank-Starling law states that the heart's stroke volume increases with greater preload due to increased venous return, allowing the heart to adapt to varying circulatory demands. Molecularly, increasing preload increases sarcomere length (SL), which alters sarcomere structures that are correlated to increased calcium sensitivity upon activation. The titin protein, spanning the half-sarcomere, acts as a spring in the I-band, applying a SL-dependent force suggested to pull against and alter myofilaments in a way that supports the Frank-Starling effect. To evaluate this, we employed the titin cleavage (TC) model, where a tobacco-etch virus protease recognition site is inserted into distal I-band titin and allows for rapid, specific cleavage of titin in an otherwise-healthy sarcomere. Here, we evaluated the atomic-level structures of amyopathic cardiac myofilaments following 50% titin cleavage under passive stretch conditions using small-angle X-ray diffraction, which measures these structures under near-physiological (functional) conditions. We report that titin-based forces in permeabilized papillary muscle regulate both thick and thin myofilament structures clearly supporting titin's role in the Frank-Starling mechanism.
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5
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Ma W, Jani VP, Song T, Gao C, Gong H, Sadayappan S, Kass DA, Irving TC. The structural OFF and ON states of myosin can be decoupled from the biochemical super-relaxed and disordered-relaxed states. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.10.18.562891. [PMID: 37904972 PMCID: PMC10614925 DOI: 10.1101/2023.10.18.562891] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/01/2023]
Abstract
There is a growing awareness that both thick filament and classical thin filament regulation play central roles in modulating muscle contraction. Myosin ATPase assays have demonstrated that under relaxed conditions, myosin may reside in either a high energy-consuming disordered-relaxed (DRX) state available for binding actin to generate force, or in an energy-sparing super-relaxed (SRX) state unavailable for actin binding. X-ray diffraction studies have shown the majority of myosin heads are in a quasi-helically ordered OFF state in a resting muscle and that this helical ordering is lost when myosin heads are turned ON for contraction. It has been assumed that myosin heads in SRX and DRX states are equivalent to the OFF and ON state respectively and the terms have been used interchangeably. Here, we use X-ray diffraction and ATP turnover assays to track the structural and biochemical transitions of myosin heads respectively induced with either omecamtiv mecarbil (OM) or piperine in relaxed porcine myocardium. We find that while OM and piperine induce dramatic shifts of myosin heads from the OFF to ON states, there are no appreciable changes in the population of myosin heads in the SRX and DRX states in both unloaded and loaded preparations. Our results show that biochemically defined SRX and DRX can be decoupled from structurally-defined OFF and ON states. In summary, while SRX/DRX and OFF/ON transitions can be correlated in some cases, these two phenomena are measured using different approaches, do not necessarily reflect the same properties of the thick filament and should be investigated and interpreted separately.
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Affiliation(s)
- Weikang Ma
- Department of Biology, Illinois Institute of Technology, Chicago, IL, USA
| | - Vivek P. Jani
- Department of Biomedical Engineering, The Johns Hopkins School of Medicine, Baltimore, MD
- Division of Cardiology, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD
| | - Taejeong Song
- Division of Cardiovascular Health and Disease, Department of Internal Medicine, University of Cincinnati, OH, USA
| | - Chengqian Gao
- College of Basic Medical Sciences, Dalian Medical University, Dalian, Liaoning, China
| | - Henry Gong
- Department of Biology, Illinois Institute of Technology, Chicago, IL, USA
| | - Sakthivel Sadayappan
- Division of Cardiovascular Health and Disease, Department of Internal Medicine, University of Cincinnati, OH, USA
| | - David A. Kass
- Department of Biomedical Engineering, The Johns Hopkins School of Medicine, Baltimore, MD
- Division of Cardiology, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD
| | - Thomas C. Irving
- Department of Biology, Illinois Institute of Technology, Chicago, IL, USA
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Rodriguez Garcia M, Schmeckpeper J, Landim-Vieira M, Coscarella IL, Fang X, Ma W, Spran PA, Yuan S, Qi L, Kahmini AR, Shoemaker MB, Atkinson JB, Kekenes-Huskey PM, Irving TC, Chase PB, Knollmann BC, Pinto JR. Disruption of Z-Disc Function Promotes Mechanical Dysfunction in Human Myocardium: Evidence for a Dual Myofilament Modulatory Role by Alpha-Actinin 2. Int J Mol Sci 2023; 24:14572. [PMID: 37834023 PMCID: PMC10572656 DOI: 10.3390/ijms241914572] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2023] [Revised: 09/19/2023] [Accepted: 09/20/2023] [Indexed: 10/15/2023] Open
Abstract
The ACTN2 gene encodes α-actinin 2, located in the Z-disc of the sarcomeres in striated muscle. In this study, we sought to investigate the effects of an ACTN2 missense variant of unknown significance (p.A868T) on cardiac muscle structure and function. Left ventricular free wall samples were obtained at the time of cardiac transplantation from a heart failure patient with the ACTN2 A868T heterozygous variant. This variant is in the EF 3-4 domain known to interact with titin and α-actinin. At the ultrastructural level, ACTN2 A868T cardiac samples presented small structural changes in cardiomyocytes when compared to healthy donor samples. However, contractile mechanics of permeabilized ACTN2 A868T variant cardiac tissue displayed higher myofilament Ca2+ sensitivity of isometric force, reduced sinusoidal stiffness, and faster rates of tension redevelopment at all Ca2+ levels. Small-angle X-ray diffraction indicated increased separation between thick and thin filaments, possibly contributing to changes in muscle kinetics. Molecular dynamics simulations indicated that while the mutation does not significantly impact the structure of α-actinin on its own, it likely alters the conformation associated with titin binding. Our results can be explained by two Z-disc mediated communication pathways: one pathway that involves α-actinin's interaction with actin, affecting thin filament regulation, and the other pathway that involves α-actinin's interaction with titin, affecting thick filament activation. This work establishes the role of α-actinin 2 in modulating cross-bridge kinetics and force development in the human myocardium as well as how it can be involved in the development of cardiac disease.
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Affiliation(s)
| | - Jeffrey Schmeckpeper
- Department of Medicine, Division of Cardiovascular Medicine, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | | | | | - Xuan Fang
- Department of Cell & Molecular Physiology, Loyola University, Chicago, IL 60660, USA
| | - Weikang Ma
- BioCAT, Department of Biological Sciences, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Payton A. Spran
- Department of Biological Science, Florida State University, Tallahassee, FL 32306, USA
| | - Shengyao Yuan
- BioCAT, Department of Biological Sciences, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Lin Qi
- BioCAT, Department of Biological Sciences, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Aida Rahimi Kahmini
- Department of Nutrition and Integrative Physiology, Florida State University, Tallahassee, FL 32306, USA;
| | - M. Benjamin Shoemaker
- Department of Medicine, Division of Cardiovascular Medicine, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - James B. Atkinson
- Department of Pathology, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | | | - Thomas C. Irving
- BioCAT, Department of Biological Sciences, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Prescott Bryant Chase
- Department of Biological Science, Florida State University, Tallahassee, FL 32306, USA
| | - Björn C. Knollmann
- Department of Medicine, Division of Cardiovascular Medicine, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Jose Renato Pinto
- Biomedical Sciences, Florida State University, Tallahassee, FL 32306, USA
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Ma W, Lee KH, Delligatti CE, Davis MT, Zheng Y, Gong H, Kirk JA, Craig R, Irving T. The structural and functional integrities of porcine myocardium are mostly preserved by cryopreservation. J Gen Physiol 2023; 155:e202313345. [PMID: 37398997 PMCID: PMC10318404 DOI: 10.1085/jgp.202313345] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2023] [Revised: 05/05/2023] [Accepted: 06/21/2023] [Indexed: 07/04/2023] Open
Abstract
Structural and functional studies of heart muscle are important to gain insights into the physiological bases of cardiac muscle contraction and the pathological bases of heart disease. While fresh muscle tissue works best for these kinds of studies, this is not always practical to obtain, especially for heart tissue from large animal models and humans. Conversely, tissue banks of frozen human hearts are available and could be a tremendous resource for translational research. It is not well understood, however, how liquid nitrogen freezing and cryostorage may impact the structural integrity of myocardium from large mammals. In this study, we directly compared the structural and functional integrity of never-frozen to previously frozen porcine myocardium to investigate the consequences of freezing and cryostorage. X-ray diffraction measurements from hydrated tissue under near-physiological conditions and electron microscope images from chemically fixed porcine myocardium showed that prior freezing has only minor effects on structural integrity of the muscle. Furthermore, mechanical studies similarly showed no significant differences in contractile capabilities of porcine myocardium with and without freezing and cryostorage. These results demonstrate that liquid nitrogen preservation is a practical approach for structural and functional studies of myocardium.
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Affiliation(s)
- Weikang Ma
- BioCAT, Department of Biology, Illinois Institute of Technology, Chicago, IL, USA
| | - Kyoung Hwan Lee
- Electron Microscopy Facility, UMass Chan Medical School, Worcester, MA, USA
| | | | - M. Therese Davis
- Department of Cell and Molecular Physiology, Loyola University Chicago, Chicago, IL, USA
| | - Yahan Zheng
- College of Basic Medical Sciences, Dalian Medical University, Dalian, China
| | - Henry Gong
- BioCAT, Department of Biology, Illinois Institute of Technology, Chicago, IL, USA
| | - Jonathan A. Kirk
- Department of Cell and Molecular Physiology, Loyola University Chicago, Chicago, IL, USA
| | - Roger Craig
- Division of Cell Biology and Imaging, Department of Radiology, University of Massachusetts Medical School, Worcester, MA, USA
| | - Thomas Irving
- BioCAT, Department of Biology, Illinois Institute of Technology, Chicago, IL, USA
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Ma W, del Rio CL, Qi L, Prodanovic M, Mijailovich S, Zambataro C, Gong H, Shimkunas R, Gollapudi S, Nag S, Irving TC. Myosin in autoinhibited off state(s), stabilized by mavacamten, can be recruited via inotropic effectors. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.04.10.536292. [PMID: 37090664 PMCID: PMC10120679 DOI: 10.1101/2023.04.10.536292] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/25/2023]
Abstract
Mavacamten is a novel, FDA-approved, small molecule therapeutic designed to regulate cardiac function by selectively but reversibly inhibiting the enzymatic activity of myosin. It shifts myosin towards ordered off states close to the thick filament backbone. It remains unresolved whether mavacamten permanently sequesters these myosin heads in the off state(s) or whether these heads can be recruited in response to physiological stimuli when required to boost cardiac output. We show that cardiac myosins stabilized in these off state(s) by mavacamten are recruitable by Ca2+, increased heart rate, stretch, and β-adrenergic (β-AR) stimulation, all known physiological inotropic effectors. At the molecular level, we show that, in presence of mavacamten, Ca2+ increases myosin ATPase activity by shifting myosin heads from the reserve super-relaxed (SRX) state to the active disordered relaxed (DRX) state. At the myofilament level, both Ca2+ and passive lengthening can shift ordered off myosin heads from positions close to the thick filament backbone to disordered on states closer to the thin filaments in the presence of mavacamten. In isolated rat cardiomyocytes, increased stimulation rates enhanced shortening fraction in mavacamten-treated cells. This observation was confirmed in vivo in telemetered rats, where left-ventricular dP/dtmax, an index of inotropy, increased with heart rate in mavacamten treated animals. Finally, we show that β-AR stimulation in vivo increases left-ventricular function and stroke volume in the setting of mavacamten. Our data demonstrate that the mavacamten-promoted off states of myosin in the thick filament are activable, at least partially, thus leading to preservation of cardiac reserve mechanisms.
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Affiliation(s)
- Weikang Ma
- BioCAT, Department of Biology, Illinois Institute of Technology, Chicago, IL, USA
| | - Carlos L. del Rio
- Cardiovascular Drug Discovery, Bristol Myers Squibb, Brisbane, CA 94005
| | - Lin Qi
- Department of Biology, Illinois Institute of Technology, Chicago, IL, USA
| | - Momcilo Prodanovic
- Institute for Information Technologies, University of Kragujevac, Kragujevac, Serbia
- FilamenTech, Inc., Newtown, MA 02458, USA
| | | | | | - Henry Gong
- Department of Biology, Illinois Institute of Technology, Chicago, IL, USA
| | - Rafael Shimkunas
- Cardiovascular Drug Discovery, Bristol Myers Squibb, Brisbane, CA 94005
| | - Sampath Gollapudi
- Cardiovascular Drug Discovery, Bristol Myers Squibb, Brisbane, CA 94005
| | - Suman Nag
- Cardiovascular Drug Discovery, Bristol Myers Squibb, Brisbane, CA 94005
| | - Thomas C. Irving
- BioCAT, Department of Biology, Illinois Institute of Technology, Chicago, IL, USA
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9
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Landim-Vieira M, Ma W, Song T, Rastegarpouyani H, Gong H, Coscarella IL, Bogaards SJP, Conijn SP, Ottenheijm CAC, Hwang HS, Papadaki M, Knollmann BC, Sadayappan S, Irving TC, Galkin VE, Chase PB, Pinto JR. Cardiac troponin T N-domain variant destabilizes the actin interface resulting in disturbed myofilament function. Proc Natl Acad Sci U S A 2023; 120:e2221244120. [PMID: 37252999 PMCID: PMC10265946 DOI: 10.1073/pnas.2221244120] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2022] [Accepted: 05/04/2023] [Indexed: 06/01/2023] Open
Abstract
Missense variant Ile79Asn in human cardiac troponin T (cTnT-I79N) has been associated with hypertrophic cardiomyopathy and sudden cardiac arrest in juveniles. cTnT-I79N is located in the cTnT N-terminal (TnT1) loop region and is known for its pathological and prognostic relevance. A recent structural study revealed that I79 is part of a hydrophobic interface between the TnT1 loop and actin, which stabilizes the relaxed (OFF) state of the cardiac thin filament. Given the importance of understanding the role of TnT1 loop region in Ca2+ regulation of the cardiac thin filament along with the underlying mechanisms of cTnT-I79N-linked pathogenesis, we investigated the effects of cTnT-I79N on cardiac myofilament function. Transgenic I79N (Tg-I79N) muscle bundles displayed increased myofilament Ca2+ sensitivity, smaller myofilament lattice spacing, and slower crossbridge kinetics. These findings can be attributed to destabilization of the cardiac thin filament's relaxed state resulting in an increased number of crossbridges during Ca2+ activation. Additionally, in the low Ca2+-relaxed state (pCa8), we showed that more myosin heads are in the disordered-relaxed state (DRX) that are more likely to interact with actin in cTnT-I79N muscle bundles. Dysregulation of the myosin super-relaxed state (SRX) and the SRX/DRX equilibrium in cTnT-I79N muscle bundles likely result in increased mobility of myosin heads at pCa8, enhanced actomyosin interactions as evidenced by increased active force at low Ca2+, and increased sinusoidal stiffness. These findings point to a mechanism whereby cTnT-I79N weakens the interaction of the TnT1 loop with the actin filament, which in turn destabilizes the relaxed state of the cardiac thin filament.
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Affiliation(s)
- Maicon Landim-Vieira
- Department of Biomedical Sciences, Florida State University College of Medicine, Tallahassee, FL32306
| | - Weikang Ma
- Department of Biology, Illinois Institute of Technology, Chicago, IL60616
| | - Taejeong Song
- Division of Cardiovascular Health and Disease, Department of Internal Medicine, University of Cincinnati College of Medicine, Cincinnati, OH45267
| | - Hosna Rastegarpouyani
- Department of Biological Science, Florida State University, Tallahassee, FL32306
- Institude of Molecular Biophysics, Florida State University, Tallahassee, FL32306
| | - Henry Gong
- Department of Biology, Illinois Institute of Technology, Chicago, IL60616
| | - Isabella Leite Coscarella
- Department of Biomedical Sciences, Florida State University College of Medicine, Tallahassee, FL32306
| | - Sylvia J. P. Bogaards
- Department of Physiology, Amsterdam University Medical Center, Amsterdam, De Boelelaan 1108, 1081 HZ Amsterdam, The Netherlands
| | - Stefan P. Conijn
- Department of Physiology, Amsterdam University Medical Center, Amsterdam, De Boelelaan 1108, 1081 HZ Amsterdam, The Netherlands
| | - Coen A. C. Ottenheijm
- Department of Physiology, Amsterdam University Medical Center, Amsterdam, De Boelelaan 1108, 1081 HZ Amsterdam, The Netherlands
| | - Hyun S. Hwang
- Department of Nutrition and Integrative Physiology, Florida State University, Tallahassee, FL32306
| | - Maria Papadaki
- Department of Cell and Molecular Physiology, Loyola University Chicago Stritch School of Medicine, Chicago, IL60153
| | - Bjorn C. Knollmann
- Department of Medicine, Vanderbilt University Medical Center, Nashville, TN37232
| | - Sakthivel Sadayappan
- Division of Cardiovascular Health and Disease, Department of Internal Medicine, University of Cincinnati College of Medicine, Cincinnati, OH45267
| | - Thomas C. Irving
- Department of Biology, Illinois Institute of Technology, Chicago, IL60616
| | - Vitold E. Galkin
- Department of Physiological Sciences, Eastern Virginia Medical School, Norfolk, VA23507
| | - P. Bryant Chase
- Department of Biological Science, Florida State University, Tallahassee, FL32306
| | - Jose Renato Pinto
- Department of Biomedical Sciences, Florida State University College of Medicine, Tallahassee, FL32306
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10
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Prodanovic M, Wang Y, Mijailovich SM, Irving T. Using Multiscale Simulations as a Tool to Interpret Equatorial X-ray Fiber Diffraction Patterns from Skeletal Muscle. Int J Mol Sci 2023; 24:8474. [PMID: 37239821 PMCID: PMC10218096 DOI: 10.3390/ijms24108474] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2023] [Revised: 05/04/2023] [Accepted: 05/05/2023] [Indexed: 05/28/2023] Open
Abstract
Synchrotron small-angle X-ray diffraction is the method of choice for nm-scale structural studies of striated muscle under physiological conditions and on millisecond time scales. The lack of generally applicable computational tools for modeling X-ray diffraction patterns from intact muscles has been a significant barrier to exploiting the full potential of this technique. Here, we report a novel "forward problem" approach using the spatially explicit computational simulation platform MUSICO to predict equatorial small-angle X-ray diffraction patterns and the force output simultaneously from resting and isometrically contracting rat skeletal muscle that can be compared to experimental data. The simulation generates families of thick-thin filament repeating units, each with their individually predicted occupancies of different populations of active and inactive myosin heads that can be used to generate 2D-projected electron density models based on known Protein Data Bank structures. We show how, by adjusting only a few selected parameters, we can achieve a good correspondence between experimental and predicted X-ray intensities. The developments presented here demonstrate the feasibility of combining X-ray diffraction and spatially explicit modeling to form a powerful hypothesis-generating tool that can be used to motivate experiments that can reveal emergent properties of muscle.
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Affiliation(s)
- Momcilo Prodanovic
- Institute for Information Technologies, University of Kragujevac, 34000 Kragujevac, Serbia;
- FilamenTech, Inc., Newton, MA 02458, USA;
| | - Yiwei Wang
- Department of Applied Mathematics, Illinois Institute of Technology, Chicago, IL 60616, USA;
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA
- Department of Mathematics, University of California, Riverside, CA 92521, USA
| | | | - Thomas Irving
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA
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11
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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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12
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Ma W, Nag S, Gong H, Qi L, Irving TC. Cardiac myosin filaments are directly regulated by calcium. J Gen Physiol 2022; 154:e202213213. [PMID: 36327149 PMCID: PMC9629851 DOI: 10.1085/jgp.202213213] [Citation(s) in RCA: 24] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2022] [Revised: 07/25/2022] [Accepted: 10/03/2022] [Indexed: 11/06/2022] Open
Abstract
Classically, striated muscle contraction is initiated by calcium (Ca2+)-dependent structural changes in regulatory proteins on actin-containing thin filaments, which allow the binding of myosin motors to generate force. Additionally, dynamic switching between resting off and active on myosin states has been shown to regulate muscle contractility, a recently validated mechanism by novel myosin-targeted therapeutics. The molecular nature of this switching, however, is not understood. Here, using a combination of small-angle x-ray fiber diffraction and biochemical assays with reconstituted systems, we show that cardiac thick filaments are directly Ca2+-regulated. We find that Ca2+ induces a structural transition of myosin heads from ordered off states close to the thick filament to disordered on states closer to the thin filaments. Biochemical assays show a Ca2+-induced transition from an inactive super-relaxed (SRX) state(s) to an active disordered-relaxed (DRX) state(s) in synthetic thick filaments. We show that these transitions are an intrinsic property of cardiac myosin only when assembled into thick filaments and provide a fresh perspective on nature's two orthogonal mechanisms to regulate muscle contraction through the thin and the thick filaments.
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Affiliation(s)
- Weikang Ma
- BioCAT, Department of Biology, Illinois Institute of Technology, Chicago, IL
| | - Suman Nag
- Department of Biochemistry, Bristol Myers Squibb, Brisbane, CA
| | - Henry Gong
- BioCAT, Department of Biology, Illinois Institute of Technology, Chicago, IL
| | - Lin Qi
- BioCAT, Department of Biology, Illinois Institute of Technology, Chicago, IL
| | - Thomas C. Irving
- BioCAT, Department of Biology, Illinois Institute of Technology, Chicago, IL
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13
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Basu A, Paul MK, Weiss S. The actin cytoskeleton: Morphological changes in pre- and fully developed lung cancer. BIOPHYSICS REVIEWS 2022; 3:041304. [PMID: 38505516 PMCID: PMC10903407 DOI: 10.1063/5.0096188] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2022] [Accepted: 12/09/2022] [Indexed: 03/21/2024]
Abstract
Actin, a primary component of the cell cytoskeleton can have multiple isoforms, each of which can have specific properties uniquely suited for their purpose. These monomers are then bound together to form polymeric filaments utilizing adenosine triphosphate hydrolysis as a source of energy. Proteins, such as Arp2/3, VASP, formin, profilin, and cofilin, serve important roles in the polymerization process. These filaments can further be linked to form stress fibers by proteins called actin-binding proteins, such as α-actinin, myosin, fascin, filamin, zyxin, and epsin. These stress fibers are responsible for mechanotransduction, maintaining cell shape, cell motility, and intracellular cargo transport. Cancer metastasis, specifically epithelial mesenchymal transition (EMT), which is one of the key steps of the process, is accompanied by the formation of thick stress fibers through the Rho-associated protein kinase, MAPK/ERK, and Wnt pathways. Recently, with the advent of "field cancerization," pre-malignant cells have also been demonstrated to possess stress fibers and related cytoskeletal features. Analytical methods ranging from western blot and RNA-sequencing to cryo-EM and fluorescent imaging have been employed to understand the structure and dynamics of actin and related proteins including polymerization/depolymerization. More recent methods involve quantifying properties of the actin cytoskeleton from fluorescent images and utilizing them to study biological processes, such as EMT. These image analysis approaches exploit the fact that filaments have a unique structure (curvilinear) compared to the noise or other artifacts to separate them. Line segments are extracted from these filament images that have assigned lengths and orientations. Coupling such methods with statistical analysis has resulted in development of a new reporter for EMT in lung cancer cells as well as their drug responses.
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Affiliation(s)
| | | | - Shimon Weiss
- Author to whom correspondence should be addressed:
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14
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Hessel AL, Ma W, Mazara N, Rice PE, Nissen D, Gong H, Kuehn M, Irving T, Linke WA. Titin force in muscle cells alters lattice order, thick and thin filament protein formation. Proc Natl Acad Sci U S A 2022; 119:e2209441119. [PMID: 36409887 PMCID: PMC9860331 DOI: 10.1073/pnas.2209441119] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2022] [Accepted: 10/25/2022] [Indexed: 11/22/2022] Open
Abstract
Skeletal muscle force production is increased at longer compared to shorter muscle lengths because of length-dependent priming of thick filament proteins in the contractile unit before contraction. Using small-angle X-ray diffraction in combination with a mouse model that specifically cleaves the stretch-sensitive titin protein, we found that titin cleavage diminished the length-dependent priming of the thick filament. Strikingly, a titin-sensitive, length-dependent priming was also present in thin filaments, which seems only possible via bridge proteins between thick and thin filaments in resting muscle, potentially myosin-binding protein C. We further show that these bridges can be forcibly ruptured via high-speed stretches. Our results advance a paradigm shift to the fundamental regulation of length-dependent priming, with titin as the key driver.
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Affiliation(s)
- Anthony L. Hessel
- Institute of Physiology II, University of Muenster, Muenster, 48149Germany
| | - Weikang Ma
- BioCAT, Department of Biology, Illinois Institute of Technology, Chicago, IL 60616
| | - Nicole Mazara
- School of Kinesiology, University of British Columbia, Vancouver, CanadaV6T 1Z1
| | - Paige E. Rice
- Department of Biological Sciences, Northern Arizona University, FlagstaffAZ 86011
| | - Devin Nissen
- BioCAT, Department of Biology, Illinois Institute of Technology, Chicago, IL 60616
| | - Henry Gong
- BioCAT, Department of Biology, Illinois Institute of Technology, Chicago, IL 60616
| | - Michel Kuehn
- Institute of Physiology II, University of Muenster, Muenster, 48149Germany
| | - Thomas Irving
- BioCAT, Department of Biology, Illinois Institute of Technology, Chicago, IL 60616
| | - Wolfgang A. Linke
- Institute of Physiology II, University of Muenster, Muenster, 48149Germany
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15
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Jani V, Qian W, Yuan S, Irving T, Ma W. EMD-57033 Augments the Contractility in Porcine Myocardium by Promoting the Activation of Myosin in Thick Filaments. Int J Mol Sci 2022; 23:14517. [PMID: 36498844 PMCID: PMC9737153 DOI: 10.3390/ijms232314517] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2022] [Revised: 11/20/2022] [Accepted: 11/21/2022] [Indexed: 11/23/2022] Open
Abstract
Sufficient cardiac contractility is necessary to ensure the sufficient cardiac output to provide an adequate end-organ perfusion. Inadequate cardiac output and the diminished perfusion of vital organs from depressed myocardium contractility is a hallmark end-stage of heart failure. There are no available therapeutics that directly target contractile proteins to improve the myocardium contractility and reduce mortality. The purpose of this study is to present a proof of concept to aid in the development of muscle activators (myotropes) for augmenting the contractility in clinical heart failure. Here we use a combination of cardiomyocyte mechanics, the biochemical quantification of the ATP turnover, and small angle X-ray diffraction on a permeabilized porcine myocardium to study the mechanisms of EMD-57033 (EMD) for activating myosin. We show that EMD increases the contractility in a porcine myocardium at submaximal and systolic calcium concentrations. Biochemical assays show that EMD decreases the proportion of myosin heads in the energy sparing super-relaxed (SRX) state under relaxing conditions, which are less likely to interact with actin during contraction. Structural assays show that EMD moves the myosin heads in relaxed muscles from a structurally ordered state close to the thick filament backbone, to a disordered state closer to the actin filament, while simultaneously inducing structural changes in the troponin complex on the actin filament. The dual effects of EMD on activating myosin heads and the troponin complex provides a proof of concept for the use of small molecule muscle activators for augmenting the contractility in heart failure.
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Affiliation(s)
- Vivek Jani
- Department of Biomedical Engineering, The Johns Hopkins School of Medicine, The Johns Hopkins University, Baltimore, MD 20205, USA
- Division of Cardiology, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Wenjing Qian
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Shengyao Yuan
- BioCAT, Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Thomas Irving
- BioCAT, Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Weikang Ma
- BioCAT, Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA
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16
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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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