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Chen L, Liu J, Rastegarpouyani H, Janssen PML, Pinto JR, Taylor KA. Structure of mavacamten-free human cardiac thick filaments within the sarcomere by cryoelectron tomography. Proc Natl Acad Sci U S A 2024; 121:e2311883121. [PMID: 38386705 PMCID: PMC10907299 DOI: 10.1073/pnas.2311883121] [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: 07/16/2023] [Accepted: 01/18/2024] [Indexed: 02/24/2024] Open
Abstract
Heart muscle has the unique property that it can never rest; all cardiomyocytes contract with each heartbeat which requires a complex control mechanism to regulate cardiac output to physiological requirements. Changes in calcium concentration regulate the thin filament activation. A separate but linked mechanism regulates the thick filament activation, which frees sufficient myosin heads to bind the thin filament, thereby producing the required force. Thick filaments contain additional nonmyosin proteins, myosin-binding protein C and titin, the latter being the protein that transmits applied tension to the thick filament. How these three proteins interact to control thick filament activation is poorly understood. Here, we show using 3-D image reconstruction of frozen-hydrated human cardiac muscle myofibrils lacking exogenous drugs that the thick filament is structured to provide three levels of myosin activation corresponding to the three crowns of myosin heads in each 429Å repeat. In one crown, the myosin heads are almost completely activated and disordered. In another crown, many myosin heads are inactive, ordered into a structure called the interacting heads motif. At the third crown, the myosin heads are ordered into the interacting heads motif, but the stability of that motif is affected by myosin-binding protein C. We think that this hierarchy of control explains many of the effects of length-dependent activation as well as stretch activation in cardiac muscle control.
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Affiliation(s)
- Liang Chen
- Institute of Molecular Biophysics, Florida State University, Tallahassee, FL32306
| | - Jun Liu
- Microbial Sciences Institute, Yale University, West Haven, CT06516
- Department of Microbial Pathogenesis, Yale School of Medicine, New Haven, CT06536
| | - Hosna Rastegarpouyani
- Institute of Molecular Biophysics, Florida State University, Tallahassee, FL32306
- Department of Biological Science, Florida State University, Tallahassee, FL32306
| | - Paul M. L. Janssen
- Department of Physiology and Cell Biology, College of Medicine, The Ohio State University, Columbus, OH43210
| | - Jose R. Pinto
- Department of Biomedical Sciences, Florida State College of Medicine, Florida State University, Tallahassee, FL32306
| | - Kenneth A. Taylor
- Institute of Molecular Biophysics, Florida State University, Tallahassee, FL32306
- Department of Biological Science, Florida State University, Tallahassee, FL32306
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Nag S, Gollapudi SK, Del Rio CL, Spudich JA, McDowell R. Mavacamten, a precision medicine for hypertrophic cardiomyopathy: From a motor protein to patients. SCIENCE ADVANCES 2023; 9:eabo7622. [PMID: 37506209 DOI: 10.1126/sciadv.abo7622] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/23/2022] [Accepted: 06/23/2023] [Indexed: 07/30/2023]
Abstract
Hypertrophic cardiomyopathy (HCM) is a primary myocardial disorder characterized by left ventricular hypertrophy, hyperdynamic contraction, and impaired relaxation of the heart. These functional derangements arise directly from altered sarcomeric function due to either mutations in genes encoding sarcomere proteins, or other defects such as abnormal energetics. Current treatment options do not directly address this causal biology but focus on surgical and extra-sarcomeric (sarcolemmal) pharmacological symptomatic relief. Mavacamten (formerly known as MYK-461), is a small molecule designed to regulate cardiac function at the sarcomere level by selectively but reversibly inhibiting the enzymatic activity of myosin, the fundamental motor of the sarcomere. This review summarizes the mechanism and translational progress of mavacamten from proteins to patients, describing how the mechanism of action and pharmacological characteristics, involving both systolic and diastolic effects, can directly target pathophysiological derangements within the cardiac sarcomere to improve cardiac structure and function in HCM. Mavacamten was approved by the Food and Drug Administration in April 2022 for the treatment of obstructive HCM and now goes by the commercial name of Camzyos. Full information about the risks, limitations, and side effects can be found at www.accessdata.fda.gov/drugsatfda_docs/label/2022/214998s000lbl.pdf.
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Affiliation(s)
- Suman Nag
- MyoKardia Inc., a wholly owned subsidiary of Bristol Myers Squibb, Brisbane, CA 94005, USA
| | - Sampath K Gollapudi
- MyoKardia Inc., a wholly owned subsidiary of Bristol Myers Squibb, Brisbane, CA 94005, USA
| | - Carlos L Del Rio
- MyoKardia Inc., a wholly owned subsidiary of Bristol Myers Squibb, Brisbane, CA 94005, USA
- Cardiac Consulting, 1630 S Delaware St. #56426, San Mateo, CA 94403, USA
| | | | - Robert McDowell
- MyoKardia Inc., a wholly owned subsidiary of Bristol Myers Squibb, Brisbane, CA 94005, USA
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Hitsumoto T, Tsukamoto O, Matsuoka K, Li J, Liu L, Kuramoto Y, Higo S, Ogawa S, Fujino N, Yoshida S, Kioka H, Kato H, Hakui H, Saito Y, Okamoto C, Inoue H, Hyejin J, Ueda K, Segawa T, Nishimura S, Asano Y, Asanuma H, Tani A, Imamura R, Komagawa S, Kanai T, Takamura M, Sakata Y, Kitakaze M, Haruta JI, Takashima S. Restoration of Cardiac Myosin Light Chain Kinase Ameliorates Systolic Dysfunction by Reducing Superrelaxed Myosin. Circulation 2023; 147:1902-1918. [PMID: 37128901 PMCID: PMC10270284 DOI: 10.1161/circulationaha.122.062885] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/16/2022] [Accepted: 04/05/2023] [Indexed: 05/03/2023]
Abstract
BACKGROUND Cardiac-specific myosin light chain kinase (cMLCK), encoded by MYLK3, regulates cardiac contractility through phosphorylation of ventricular myosin regulatory light chain. However, the pathophysiological and therapeutic implications of cMLCK in human heart failure remain unclear. We aimed to investigate whether cMLCK dysregulation causes cardiac dysfunction and whether the restoration of cMLCK could be a novel myotropic therapy for systolic heart failure. METHODS We generated the knock-in mice (Mylk3+/fs and Mylk3fs/fs) with a familial dilated cardiomyopathy-associated MYLK3 frameshift mutation (MYLK3+/fs) that had been identified previously by us (c.1951-1G>T; p.P639Vfs*15) and the human induced pluripotent stem cell-derived cardiomyocytes from the carrier of the mutation. We also developed a new small-molecule activator of cMLCK (LEUO-1154). RESULTS Both mice (Mylk3+/fs and Mylk3fs/fs) showed reduced cMLCK expression due to nonsense-mediated messenger RNA decay, reduced MLC2v (ventricular myosin regulatory light chain) phosphorylation in the myocardium, and systolic dysfunction in a cMLCK dose-dependent manner. Consistent with this result, myocardium from the mutant mice showed an increased ratio of cardiac superrelaxation/disordered relaxation states that may contribute to impaired cardiac contractility. The phenotypes observed in the knock-in mice were rescued by cMLCK replenishment through the AAV9_MYLK3 vector. Human induced pluripotent stem cell-derived cardiomyocytes with MYLK3+/fs mutation reduced cMLCK expression by 50% and contractile dysfunction, accompanied by an increased superrelaxation/disordered relaxation ratio. CRISPR-mediated gene correction, or cMLCK replenishment by AAV9_MYLK3 vector, successfully recovered cMLCK expression, the superrelaxation/disordered relaxation ratio, and contractile dysfunction. LEUO-1154 increased human cMLCK activity ≈2-fold in the Vmax for ventricular myosin regulatory light chain phosphorylation without affecting the Km. LEUO-1154 treatment of human induced pluripotent stem cell-derived cardiomyocytes with MYLK3+/fs mutation restored the ventricular myosin regulatory light chain phosphorylation level and superrelaxation/disordered relaxation ratio and improved cardiac contractility without affecting calcium transients, indicating that the cMLCK activator acts as a myotrope. Finally, human myocardium from advanced heart failure with a wide variety of causes had a significantly lower MYLK3/PPP1R12B messenger RNA expression ratio than control hearts, suggesting an altered balance between myosin regulatory light chain kinase and phosphatase in the failing myocardium, irrespective of the causes. CONCLUSIONS cMLCK dysregulation contributes to the development of cardiac systolic dysfunction in humans. Our strategy to restore cMLCK activity could form the basis of a novel myotropic therapy for advanced systolic heart failure.
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Affiliation(s)
- Tatsuro Hitsumoto
- Department of Medical Biochemistry, Osaka University Graduate School of Medicine/Frontier Biosciences, Suita, Osaka, Japan (T.H., O.T., K.M., H. Kioka, H. Kato, H.H., Y.S., C.O., H.I., J.H., K.U., T.S., S.N., S.T.)
| | - Osamu Tsukamoto
- Department of Medical Biochemistry, Osaka University Graduate School of Medicine/Frontier Biosciences, Suita, Osaka, Japan (T.H., O.T., K.M., H. Kioka, H. Kato, H.H., Y.S., C.O., H.I., J.H., K.U., T.S., S.N., S.T.)
| | - Ken Matsuoka
- Department of Medical Biochemistry, Osaka University Graduate School of Medicine/Frontier Biosciences, Suita, Osaka, Japan (T.H., O.T., K.M., H. Kioka, H. Kato, H.H., Y.S., C.O., H.I., J.H., K.U., T.S., S.N., S.T.)
| | - Junjun Li
- Department of Cardiovascular Surgery (J.L., L.L.), Osaka University Graduate School of Medicine. Suita, Osaka, Japan
| | - Li Liu
- Department of Cardiovascular Surgery (J.L., L.L.), Osaka University Graduate School of Medicine. Suita, Osaka, Japan
| | - Yuki Kuramoto
- Department of Cardiology (Y.K., S.H., S.O., H. Kioka, HY.H., S.N., Y.A., Y.S.), Osaka University Graduate School of Medicine. Suita, Osaka, Japan
| | - Shuichiro Higo
- Department of Cardiology (Y.K., S.H., S.O., H. Kioka, HY.H., S.N., Y.A., Y.S.), Osaka University Graduate School of Medicine. Suita, Osaka, Japan
| | - Shou Ogawa
- Department of Cardiology (Y.K., S.H., S.O., H. Kioka, HY.H., S.N., Y.A., Y.S.), Osaka University Graduate School of Medicine. Suita, Osaka, Japan
| | - Noboru Fujino
- Department of Cardiovascular Medicine, Graduate School of Medical Science, Kanazawa University. Kanazawa, Ishikawa, Japan (N.F., S.Y., M.T.)
| | - Shohei Yoshida
- Department of Cardiovascular Medicine, Graduate School of Medical Science, Kanazawa University. Kanazawa, Ishikawa, Japan (N.F., S.Y., M.T.)
| | - Hidetaka Kioka
- Department of Medical Biochemistry, Osaka University Graduate School of Medicine/Frontier Biosciences, Suita, Osaka, Japan (T.H., O.T., K.M., H. Kioka, H. Kato, H.H., Y.S., C.O., H.I., J.H., K.U., T.S., S.N., S.T.)
- Department of Cardiology (Y.K., S.H., S.O., H. Kioka, HY.H., S.N., Y.A., Y.S.), Osaka University Graduate School of Medicine. Suita, Osaka, Japan
| | - Hisakazu Kato
- Department of Medical Biochemistry, Osaka University Graduate School of Medicine/Frontier Biosciences, Suita, Osaka, Japan (T.H., O.T., K.M., H. Kioka, H. Kato, H.H., Y.S., C.O., H.I., J.H., K.U., T.S., S.N., S.T.)
| | - Hideyuki Hakui
- Department of Medical Biochemistry, Osaka University Graduate School of Medicine/Frontier Biosciences, Suita, Osaka, Japan (T.H., O.T., K.M., H. Kioka, H. Kato, H.H., Y.S., C.O., H.I., J.H., K.U., T.S., S.N., S.T.)
- Department of Cardiology (Y.K., S.H., S.O., H. Kioka, HY.H., S.N., Y.A., Y.S.), Osaka University Graduate School of Medicine. Suita, Osaka, Japan
| | - Yuki Saito
- Department of Medical Biochemistry, Osaka University Graduate School of Medicine/Frontier Biosciences, Suita, Osaka, Japan (T.H., O.T., K.M., H. Kioka, H. Kato, H.H., Y.S., C.O., H.I., J.H., K.U., T.S., S.N., S.T.)
| | - Chisato Okamoto
- Department of Medical Biochemistry, Osaka University Graduate School of Medicine/Frontier Biosciences, Suita, Osaka, Japan (T.H., O.T., K.M., H. Kioka, H. Kato, H.H., Y.S., C.O., H.I., J.H., K.U., T.S., S.N., S.T.)
| | - Hijiri Inoue
- Department of Medical Biochemistry, Osaka University Graduate School of Medicine/Frontier Biosciences, Suita, Osaka, Japan (T.H., O.T., K.M., H. Kioka, H. Kato, H.H., Y.S., C.O., H.I., J.H., K.U., T.S., S.N., S.T.)
| | - Jo Hyejin
- Department of Medical Biochemistry, Osaka University Graduate School of Medicine/Frontier Biosciences, Suita, Osaka, Japan (T.H., O.T., K.M., H. Kioka, H. Kato, H.H., Y.S., C.O., H.I., J.H., K.U., T.S., S.N., S.T.)
| | - Kyoko Ueda
- Department of Medical Biochemistry, Osaka University Graduate School of Medicine/Frontier Biosciences, Suita, Osaka, Japan (T.H., O.T., K.M., H. Kioka, H. Kato, H.H., Y.S., C.O., H.I., J.H., K.U., T.S., S.N., S.T.)
| | - Takatsugu Segawa
- Department of Medical Biochemistry, Osaka University Graduate School of Medicine/Frontier Biosciences, Suita, Osaka, Japan (T.H., O.T., K.M., H. Kioka, H. Kato, H.H., Y.S., C.O., H.I., J.H., K.U., T.S., S.N., S.T.)
| | - Shunsuke Nishimura
- Department of Medical Biochemistry, Osaka University Graduate School of Medicine/Frontier Biosciences, Suita, Osaka, Japan (T.H., O.T., K.M., H. Kioka, H. Kato, H.H., Y.S., C.O., H.I., J.H., K.U., T.S., S.N., S.T.)
- Department of Cardiology (Y.K., S.H., S.O., H. Kioka, HY.H., S.N., Y.A., Y.S.), Osaka University Graduate School of Medicine. Suita, Osaka, Japan
| | - Yoshihiro Asano
- Department of Cardiology (Y.K., S.H., S.O., H. Kioka, HY.H., S.N., Y.A., Y.S.), Osaka University Graduate School of Medicine. Suita, Osaka, Japan
- Department of Genomic Medicine, National Cerebral and Cardiovascular Center, Osaka, Japan (Y.A.)
| | - Hiroshi Asanuma
- Department of Internal Medicine, Meiji University of Integrative Medicine, Nantan, Kyoto, Japan (H.A.)
| | - Akiyoshi Tani
- Compound Library Screening Center (A.T.), Graduate School of Pharmaceutical Sciences, Osaka University, Suita, Osaka, Japan
| | - Riyo Imamura
- Drug Discovery Initiative, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Bunkyo-ku, Tokyo, Japan (R.I.)
| | - Shinsuke Komagawa
- Lead Explorating Units (S.K., T.K., J.-i.H.), Graduate School of Pharmaceutical Sciences, Osaka University, Suita, Osaka, Japan
| | - Toshio Kanai
- Lead Explorating Units (S.K., T.K., J.-i.H.), Graduate School of Pharmaceutical Sciences, Osaka University, Suita, Osaka, Japan
| | - Masayuki Takamura
- Department of Cardiovascular Medicine, Graduate School of Medical Science, Kanazawa University. Kanazawa, Ishikawa, Japan (N.F., S.Y., M.T.)
| | - Yasushi Sakata
- Department of Cardiology (Y.K., S.H., S.O., H. Kioka, HY.H., S.N., Y.A., Y.S.), Osaka University Graduate School of Medicine. Suita, Osaka, Japan
| | | | - Jun-ichi Haruta
- Lead Explorating Units (S.K., T.K., J.-i.H.), Graduate School of Pharmaceutical Sciences, Osaka University, Suita, Osaka, Japan
| | - Seiji Takashima
- Department of Medical Biochemistry, Osaka University Graduate School of Medicine/Frontier Biosciences, Suita, Osaka, Japan (T.H., O.T., K.M., H. Kioka, H. Kato, H.H., Y.S., C.O., H.I., J.H., K.U., T.S., S.N., S.T.)
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Grinzato A, Auguin D, Kikuti C, Nandwani N, Moussaoui D, Pathak D, Kandiah E, Ruppel KM, Spudich JA, Houdusse A, Robert-Paganin J. Cryo-EM structure of the folded-back state of human β-cardiac myosin. Nat Commun 2023; 14:3166. [PMID: 37258552 DOI: 10.1038/s41467-023-38698-w] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2022] [Accepted: 05/11/2023] [Indexed: 06/02/2023] Open
Abstract
To save energy and precisely regulate cardiac contractility, cardiac muscle myosin heads are sequestered in an 'off' state that can be converted to an 'on' state when exertion is increased. The 'off' state is equated with a folded-back structure known as the interacting-heads motif (IHM), which is a regulatory feature of all class-2 muscle and non-muscle myosins. We report here the human β-cardiac myosin IHM structure determined by cryo-electron microscopy to 3.6 Å resolution, providing details of all the interfaces stabilizing the 'off' state. The structure shows that these interfaces are hot spots of hypertrophic cardiomyopathy mutations that are thought to cause hypercontractility by destabilizing the 'off' state. Importantly, the cardiac and smooth muscle myosin IHM structures dramatically differ, providing structural evidence for the divergent physiological regulation of these muscle types. The cardiac IHM structure will facilitate development of clinically useful new molecules that modulate IHM stability.
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Affiliation(s)
- Alessandro Grinzato
- CM01 beamline. European Synchrotron Radiation Facility (ESRF), Grenoble, France
| | - Daniel Auguin
- Structural Motility, Institut Curie, Paris Université Sciences et Lettres, Sorbonne Université, CNRS UMR144, F-75005, Paris, France
- Laboratoire de Biologie des Ligneux et des Grandes Cultures, Université d'Orléans, UPRES EA 1207, INRA-USC1328, F-45067, Orléans, France
| | - Carlos Kikuti
- Structural Motility, Institut Curie, Paris Université Sciences et Lettres, Sorbonne Université, CNRS UMR144, F-75005, Paris, France
| | - Neha Nandwani
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA, 94305, USA
| | - Dihia Moussaoui
- BM29 BIOSAXS beamline, European Synchrotron Radiation Facility (ESRF), Grenoble, France
| | - Divya Pathak
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA, 94305, USA
| | - Eaazhisai Kandiah
- CM01 beamline. European Synchrotron Radiation Facility (ESRF), Grenoble, France
| | - Kathleen M Ruppel
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA, 94305, USA.
- Department of Pediatrics, Stanford University School of Medicine, Stanford, CA, 94305, USA.
| | - James A Spudich
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA, 94305, USA
| | - Anne Houdusse
- Structural Motility, Institut Curie, Paris Université Sciences et Lettres, Sorbonne Université, CNRS UMR144, F-75005, Paris, France.
| | - Julien Robert-Paganin
- Structural Motility, Institut Curie, Paris Université Sciences et Lettres, Sorbonne Université, CNRS UMR144, F-75005, Paris, France.
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5
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Grinzato A, Auguin D, Kikuti C, Nandwani N, Moussaoui D, Pathak D, Kandiah E, Ruppel KM, Spudich JA, Houdusse A, Robert-Paganin J. Cryo-EM structure of the folded-back state of human β-cardiac myosin. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.04.15.536999. [PMID: 37131793 PMCID: PMC10153137 DOI: 10.1101/2023.04.15.536999] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
During normal levels of exertion, many cardiac muscle myosin heads are sequestered in an off-state even during systolic contraction to save energy and for precise regulation. They can be converted to an on-state when exertion is increased. Hypercontractility caused by hypertrophic cardiomyopathy (HCM) myosin mutations is often the result of shifting the equilibrium toward more heads in the on-state. The off-state is equated with a folded-back structure known as the interacting head motif (IHM), which is a regulatory feature of all muscle myosins and class-2 non-muscle myosins. We report here the human β-cardiac myosin IHM structure to 3.6 Å resolution. The structure shows that the interfaces are hot spots of HCM mutations and reveals details of the significant interactions. Importantly, the structures of cardiac and smooth muscle myosin IHMs are dramatically different. This challenges the concept that the IHM structure is conserved in all muscle types and opens new perspectives in the understanding of muscle physiology. The cardiac IHM structure has been the missing puzzle piece to fully understand the development of inherited cardiomyopathies. This work will pave the way for the development of new molecules able to stabilize or destabilize the IHM in a personalized medicine approach. *This manuscript was submitted to Nature Communications in August 2022 and dealt efficiently by the editors. All reviewers received this version of the manuscript before 9 208 August 2022. They also received coordinates and maps of our high resolution structure on the 18 208 August 2022. Due to slowness of at least one reviewer, this contribution was delayed for acceptance by Nature Communications and we are now depositing in bioRxiv the originally submitted version written in July 2022 for everyone to see. Indeed, two bioRxiv contributions at lower resolution but adding similar concepts on thick filament regulation were deposited this week in bioRxiv, one of the contributions having had access to our coordinates. We hope that our data at high resolution will be helpful for all readers that appreciate that high resolution information is required to build accurate atomic models and discuss implications for sarcomere regulation and the effects of cardiomyopathy mutations on heart muscle function.
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6
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Li J, Rahmani H, Abbasi Yeganeh F, Rastegarpouyani H, Taylor DW, Wood NB, Previs MJ, Iwamoto H, Taylor KA. Structure of the Flight Muscle Thick Filament from the Bumble Bee, Bombus ignitus, at 6 Å Resolution. Int J Mol Sci 2022; 24:377. [PMID: 36613818 PMCID: PMC9820631 DOI: 10.3390/ijms24010377] [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] [Subscribe] [Scholar Register] [Received: 09/14/2022] [Revised: 12/12/2022] [Accepted: 12/13/2022] [Indexed: 12/28/2022] Open
Abstract
Four insect orders have flight muscles that are both asynchronous and indirect; they are asynchronous in that the wingbeat frequency is decoupled from the frequency of nervous stimulation and indirect in that the muscles attach to the thoracic exoskeleton instead of directly to the wing. Flight muscle thick filaments from two orders, Hemiptera and Diptera, have been imaged at a subnanometer resolution, both of which revealed a myosin tail arrangement referred to as “curved molecular crystalline layers”. Here, we report a thick filament structure from the indirect flight muscles of a third insect order, Hymenoptera, the Asian bumble bee Bombus ignitus. The myosin tails are in general agreement with previous determinations from Lethocerus indicus and Drosophila melanogaster. The Skip 2 region has the same unusual structure as found in Lethocerus indicus thick filaments, an α-helix discontinuity is also seen at Skip 4, but the orientation of the Skip 1 region on the surface of the backbone is less angled with respect to the filament axis than in the other two species. The heads are disordered as in Drosophila, but we observe no non-myosin proteins on the backbone surface that might prohibit the ordering of myosin heads onto the thick filament backbone. There are strong structural similarities among the three species in their non-myosin proteins within the backbone that suggest how one previously unassigned density in Lethocerus might be assigned. Overall, the structure conforms to the previously observed pattern of high similarity in the myosin tail arrangement, but differences in the non-myosin proteins.
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Affiliation(s)
- Jiawei Li
- Institute of Molecular Biophysics, Florida State University, Tallahassee, FL 32306-4380, USA
| | - Hamidreza Rahmani
- Institute of Molecular Biophysics, Florida State University, Tallahassee, FL 32306-4380, USA
| | - Fatemeh Abbasi Yeganeh
- Institute of Molecular Biophysics, Florida State University, Tallahassee, FL 32306-4380, USA
| | - Hosna Rastegarpouyani
- Institute of Molecular Biophysics, Florida State University, Tallahassee, FL 32306-4380, USA
| | - Dianne W. Taylor
- Institute of Molecular Biophysics, Florida State University, Tallahassee, FL 32306-4380, USA
| | - Neil B. Wood
- Department of Molecular Physiology & Biophysics, University of Vermont, Larner College of Medicine, Burlington, VT 05405, USA
| | - Michael J. Previs
- Department of Molecular Physiology & Biophysics, University of Vermont, Larner College of Medicine, Burlington, VT 05405, USA
| | - Hiroyuki Iwamoto
- Scattering and Imaging Division, Japan Synchrotron Radiation Research Institute, SPring-8, Hyogo 679-5198, Japan
| | - Kenneth A. Taylor
- Institute of Molecular Biophysics, Florida State University, Tallahassee, FL 32306-4380, USA
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7
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Martin AA, Thompson BR, Hahn D, Angulski ABB, Hosny N, Cohen H, Metzger JM. Cardiac Sarcomere Signaling in Health and Disease. Int J Mol Sci 2022; 23:16223. [PMID: 36555864 PMCID: PMC9782806 DOI: 10.3390/ijms232416223] [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] [Subscribe] [Scholar Register] [Received: 11/14/2022] [Revised: 12/12/2022] [Accepted: 12/14/2022] [Indexed: 12/24/2022] Open
Abstract
The cardiac sarcomere is a triumph of biological evolution wherein myriad contractile and regulatory proteins assemble into a quasi-crystalline lattice to serve as the central point upon which cardiac muscle contraction occurs. This review focuses on the many signaling components and mechanisms of regulation that impact cardiac sarcomere function. We highlight the roles of the thick and thin filament, both as necessary structural and regulatory building blocks of the sarcomere as well as targets of functionally impactful modifications. Currently, a new focus emerging in the field is inter-myofilament signaling, and we discuss here the important mediators of this mechanism, including myosin-binding protein C and titin. As the understanding of sarcomere signaling advances, so do the methods with which it is studied. This is reviewed here through discussion of recent live muscle systems in which the sarcomere can be studied under intact, physiologically relevant conditions.
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Affiliation(s)
| | | | | | | | | | | | - Joseph M. Metzger
- Department of Integrative Biology and Physiology, University of Minnesota Medical School, Minneapolis, MN 55455, USA
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8
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Rasicci DV, Tiwari P, Bodt SML, Desetty R, Sadler FR, Sivaramakrishnan S, Craig R, Yengo CM. Dilated cardiomyopathy mutation E525K in human beta-cardiac myosin stabilizes the interacting-heads motif and super-relaxed state of myosin. eLife 2022; 11:77415. [PMID: 36422472 PMCID: PMC9691020 DOI: 10.7554/elife.77415] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2022] [Accepted: 11/08/2022] [Indexed: 11/25/2022] Open
Abstract
The auto-inhibited, super-relaxed (SRX) state of cardiac myosin is thought to be crucial for regulating contraction, relaxation, and energy conservation in the heart. We used single ATP turnover experiments to demonstrate that a dilated cardiomyopathy (DCM) mutation (E525K) in human beta-cardiac myosin increases the fraction of myosin heads in the SRX state (with slow ATP turnover), especially in physiological ionic strength conditions. We also utilized FRET between a C-terminal GFP tag on the myosin tail and Cy3ATP bound to the active site of the motor domain to estimate the fraction of heads in the closed, interacting-heads motif (IHM); we found a strong correlation between the IHM and SRX state. Negative stain electron microscopy and 2D class averaging of the construct demonstrated that the E525K mutation increased the fraction of molecules adopting the IHM. Overall, our results demonstrate that the E525K DCM mutation may reduce muscle force and power by stabilizing the auto-inhibited SRX state. Our studies also provide direct evidence for a correlation between the SRX biochemical state and the IHM structural state in cardiac muscle myosin. Furthermore, the E525 residue may be implicated in crucial electrostatic interactions that modulate this conserved, auto-inhibited conformation of myosin.
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Affiliation(s)
- David V Rasicci
- Department of Cellular and Molecular Physiology, Penn State College of Medicine, Hershey, United States
| | - Prince Tiwari
- Department of Radiology, Division of Cell Biology and Imaging, UMass Chan Medical School, Worcester, United States
| | - Skylar M L Bodt
- Department of Cellular and Molecular Physiology, Penn State College of Medicine, Hershey, United States
| | - Rohini Desetty
- Department of Cellular and Molecular Physiology, Penn State College of Medicine, Hershey, United States
| | - Fredrik R Sadler
- Department of Genetics, Cell Biology, and Development, University of Minnesota Twin Cities, Minneapolis, United States
| | - Sivaraj Sivaramakrishnan
- Department of Genetics, Cell Biology, and Development, University of Minnesota Twin Cities, Minneapolis, United States
| | - Roger Craig
- Department of Radiology, Division of Cell Biology and Imaging, UMass Chan Medical School, Worcester, United States
| | - Christopher M Yengo
- Department of Cellular and Molecular Physiology, Penn State College of Medicine, Hershey, United States
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9
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Abstract
Under relaxing conditions, the two heads of myosin II interact with each other and with the proximal part (S2) of the myosin tail, establishing the interacting-heads motif (IHM), found in myosin molecules and thick filaments of muscle and nonmuscle cells. The IHM is normally thought of as a single, unique structure, but there are several variants. In the simplest ("canonical") IHM, occurring in most relaxed thick filaments and in heavy meromyosin, the interacting heads bend back and interact with S2, and the motif lies parallel to the filament surface. In one variant, occurring in insect indirect flight muscle, there is no S2-head interaction and the motif is perpendicular to the filament. In a second variant, found in smooth and nonmuscle single myosin molecules in their inhibited (10S) conformation, S2 is shifted ∼20 Å from the canonical form and the tail folds twice and wraps around the interacting heads. These molecule and filament IHM variants have important energetic and pathophysiological consequences. (1) The canonical motif, with S2-head interaction, correlates with the super-relaxed (SRX) state of myosin. The absence of S2-head interaction in insects may account for the lower stability of this IHM and apparent absence of SRX in indirect flight muscle, contributing to the quick initiation of flight in insects. (2) The ∼20 Å shift of S2 in 10S myosin molecules means that S2-head interactions are different from those in the canonical IHM. This variant therefore cannot be used to analyze the impact of myosin mutations on S2-head interactions that occur in filaments, as has been proposed. It can be used, instead, to analyze the structural impact of mutations in smooth and nonmuscle myosin.
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Affiliation(s)
- Raúl Padrón
- Division of Cell Biology and Imaging, Department of Radiology, University of Massachusetts Chan Medical School, Worcester, MA,Correspondence to Raul Padron:
| | - Debabrata Dutta
- Division of Cell Biology and Imaging, Department of Radiology, University of Massachusetts Chan Medical School, Worcester, MA
| | - Roger Craig
- Division of Cell Biology and Imaging, Department of Radiology, University of Massachusetts Chan Medical School, Worcester, MA
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10
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Kronert WA, Hsu KH, Madan A, Sarsoza F, Cammarato A, Bernstein SI. Myosin Transducer Inter-Strand Communication Is Critical for Normal ATPase Activity and Myofibril Structure. BIOLOGY 2022; 11:biology11081137. [PMID: 36009764 PMCID: PMC9404822 DOI: 10.3390/biology11081137] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/24/2022] [Revised: 07/21/2022] [Accepted: 07/25/2022] [Indexed: 02/07/2023]
Abstract
The R249Q mutation in human β-cardiac myosin results in hypertrophic cardiomyopathy. We previously showed that inserting this mutation into Drosophila melanogaster indirect flight muscle myosin yields mechanical and locomotory defects. Here, we use transgenic Drosophila mutants to demonstrate that residue R249 serves as a critical communication link within myosin that controls both ATPase activity and myofibril integrity. R249 is located on a β-strand of the central transducer of myosin, and our molecular modeling shows that it interacts via a salt bridge with D262 on the adjacent β-strand. We find that disrupting this interaction via R249Q, R249D or D262R mutations reduces basal and actin-activated ATPase activity, actin in vitro motility and flight muscle function. Further, the R249D mutation dramatically affects myofibril assembly, yielding abnormalities in sarcomere lengths, increased Z-line thickness and split myofibrils. These defects are exacerbated during aging. Re-establishing the β-strand interaction via a R249D/D262R double mutation restores both basal ATPase activity and myofibril assembly, indicating that these properties are dependent upon transducer inter-strand communication. Thus, the transducer plays an important role in myosin function and myofibril architecture.
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Affiliation(s)
- William A. Kronert
- Department of Biology, Molecular Biology Institute, Heart Institute, San Diego State University, San Diego, CA 92182, USA; (W.A.K.); (K.H.H.); (F.S.)
| | - Karen H. Hsu
- Department of Biology, Molecular Biology Institute, Heart Institute, San Diego State University, San Diego, CA 92182, USA; (W.A.K.); (K.H.H.); (F.S.)
| | - Aditi Madan
- Department of Medicine, Division of Cardiology, Johns Hopkins University, Baltimore, MD 21205, USA; (A.M.); (A.C.)
| | - Floyd Sarsoza
- Department of Biology, Molecular Biology Institute, Heart Institute, San Diego State University, San Diego, CA 92182, USA; (W.A.K.); (K.H.H.); (F.S.)
| | - Anthony Cammarato
- Department of Medicine, Division of Cardiology, Johns Hopkins University, Baltimore, MD 21205, USA; (A.M.); (A.C.)
| | - Sanford I. Bernstein
- Department of Biology, Molecular Biology Institute, Heart Institute, San Diego State University, San Diego, CA 92182, USA; (W.A.K.); (K.H.H.); (F.S.)
- Correspondence:
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11
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Angelidis A, Vandenboom R. The effect of muscle length on post-tetanic potentiation of C57BL/6 and skMLCK -/- mouse EDL muscles. J Muscle Res Cell Motil 2022; 43:99-111. [PMID: 35771335 DOI: 10.1007/s10974-022-09620-6] [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: 03/17/2022] [Accepted: 05/12/2022] [Indexed: 11/25/2022]
Abstract
Post-tetanic potentiation of fast-twitch skeletal muscle is dependent on muscle length, with greater potentiation observed at shorter compared to longer lengths. The structural effects of the primary potentiation mechanism, phosphorylation of the regulatory light chain (RLC) of myosin, are thought to explain this relationship. The purpose of these experiments was to determine whether the length-dependence of potentiation would be attenuated in the absence of RLC phosphorylation. To this end, we compared isometric twitch potentiation of mouse extensor digitorum longus (EDL) muscles with (wildtype, WT) and without (skeletal myosin light chain kinase knockout, skMLCK-/-) phosphorylation. Force was measured at five muscle lengths (0.90 Lo, 0.95 Lo, Lo, 1.05 Lo, 1.10 Lo, where Lo refers to optimal length) prior to and following a tetanic train. In accordance with prior findings, potentiation was dependent on muscle length, with greater values observed at short (e.g., 44.3 ± 4.6% for WT, 33.5 ± 6.2% for skMLCK-/-, at 0.90 Lo) compared to long lengths (e.g., 16.9 ± 1.3% for WT, 9.1 ± 1.8% for skMLCK-/-, at 1.10 Lo) in both genotypes. WT muscles displayed greater potentiation compared to their skMLCK-/- counterparts across lengths (e.g., 16.9 ± 1.6% vs 7.3 ± 1.5% at Lo). However, the relationship between potentiation and muscle length was not different between genotypes. Thus, the alternative mechanisms of potentiation, present in the skMLCK-/- EDL, display a length-dependence of post-tetanic potentiation similar to RLC phosphorylation-dominant potentiation. Additional mechanisms may be required to explain the length-dependence of potentiation.
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Affiliation(s)
- Angelos Angelidis
- Department of Kinesiology, Centre for Bone and Muscle Health, Brock University, 1812 Sir Isaac Brock Way, St. Catharines, ON, L2S 3A1, Canada.
| | - Rene Vandenboom
- Department of Kinesiology, Centre for Bone and Muscle Health, Brock University, 1812 Sir Isaac Brock Way, St. Catharines, ON, L2S 3A1, Canada
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12
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Two Classes of Myosin Inhibitors, Para-nitroblebbistatin and Mavacamten, Stabilize β-Cardiac Myosin in Different Structural and Functional States. J Mol Biol 2021; 433:167295. [PMID: 34627791 DOI: 10.1016/j.jmb.2021.167295] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2021] [Revised: 09/28/2021] [Accepted: 10/01/2021] [Indexed: 11/20/2022]
Abstract
In addition to a conventional relaxed state, a fraction of myosins in the cardiac muscle exists in a low-energy consuming super-relaxed (SRX) state, which is kept as a reserve pool that may be engaged under sustained increased cardiac demand. The conventional relaxed and the super-relaxed states are widely assumed to correspond to a structure where myosin heads are in an open configuration, free to interact with actin, and a closed configuration, inhibiting binding to actin, respectively. Disruption of the myosin SRX population is an emerging model in different heart diseases, such as hypertrophic cardiomyopathy, which results in excessive muscle contraction, and stabilizing them using myosin inhibitors is budding as an attractive therapeutic strategy. Here we examined the structure-function relationships of two myosin ATPase inhibitors, mavacamten and para-nitroblebbistatin, and found that binding of mavacamten at a site different than para-nitroblebbistatin populates myosin into the SRX state. Para-nitroblebbistatin, binding to a distal pocket to the myosin lever arm near the nucleotide-binding site, does not affect the usual myosin SRX state but instead appears to render myosin into a new, perhaps much more inhibited, 'ultra-relaxed' state. X-ray scattering-based rigid body modeling shows that both mavacamten and para-nitroblebbistatin induce novel conformations in human β-cardiac heavy meromyosin that diverge significantly from the hypothetical open and closed states, and furthermore, mavacamten treatment causes greater compaction than para-nitroblebbistatin. Taken together, we conclude that mavacamten and para-nitroblebbistatin stabilize myosin in different structural states, and such states may give rise to different functional energy-sparing states.
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13
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Chu S, Muretta JM, Thomas DD. Direct detection of the myosin super-relaxed state and interacting-heads motif in solution. J Biol Chem 2021; 297:101157. [PMID: 34481842 PMCID: PMC8479475 DOI: 10.1016/j.jbc.2021.101157] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Revised: 08/31/2021] [Accepted: 08/31/2021] [Indexed: 11/30/2022] Open
Abstract
The interacting-heads motif (IHM) is a structure of myosin that has been proposed to modulate cardiac output by occluding myosin molecules from undergoing the force-generating cycle. It is hypothesized to be the structural basis for the super-relaxed state (SRX), a low-ATPase kinetic state thought to be cardioprotective. The goal of the present study was to test this hypothesis by determining directly and quantitatively the fractions of myosin in the IHM and SRX under the same conditions in solution. To detect the structural IHM, we used time-resolved fluorescence resonance energy transfer to quantitate two distinct populations. One population was observed at a center distance of 2.0 nm, whereas the other was not detectable by fluorescence resonance energy transfer, implying a distance greater than 4 nm. We confirmed the IHM assignment to the 2.0-nm population by applying the same cross-linking protocol used previously to image the IHM by electron microscopy. Under the same conditions, we also measured the fraction of myosin in the SRX using stopped-flow kinetics. Our results show that the populations of SRX and IHM myosin were similar, unless treated with mavacamten, a drug that recently completed phase III clinical trials to treat hypertrophic cardiomyopathy and is proposed to act by stabilizing both the SRX and IHM. However, we found that mavacamten had a much greater effect on the SRX (55% increase) than on the IHM (4% increase). We conclude that the IHM structure is sufficient but not necessary to produce the SRX kinetic state.
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Affiliation(s)
- Sami Chu
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, Minnesota, USA
| | - Joseph M Muretta
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, Minnesota, USA
| | - David D Thomas
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, Minnesota, USA.
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14
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Psaras Y, Margara F, Cicconet M, Sparrow AJ, Repetti GG, Schmid M, Steeples V, Wilcox JA, Bueno-Orovio A, Redwood CS, Watkins HC, Robinson P, Rodriguez B, Seidman JG, Seidman CE, Toepfer CN. CalTrack: High-Throughput Automated Calcium Transient Analysis in Cardiomyocytes. Circ Res 2021; 129:326-341. [PMID: 34018815 PMCID: PMC8260473 DOI: 10.1161/circresaha.121.318868] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/12/2021] [Revised: 05/06/2021] [Accepted: 05/20/2021] [Indexed: 11/21/2022]
Abstract
[Figure: see text].
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Affiliation(s)
- Yiangos Psaras
- Division of Cardiovascular Medicine, Radcliffe Department of Medicine (Y.P., F.M., A.J.S., M.S., V.S., C.S.R., H.C.W., P.R., C.N.T.), University of Oxford, United Kingdom
| | - Francesca Margara
- Computer Science (F.M., A.B.-O., B.R.), University of Oxford, United Kingdom
| | - Marcelo Cicconet
- Division of Cardiovascular Medicine, Radcliffe Department of Medicine (Y.P., F.M., A.J.S., M.S., V.S., C.S.R., H.C.W., P.R., C.N.T.), University of Oxford, United Kingdom
- Computer Science (F.M., A.B.-O., B.R.), University of Oxford, United Kingdom
- Wellcome Centre for Human Genetics (H.C.W., C.N.T.), University of Oxford, United Kingdom
- Image and Data Analysis Core (M.C.), Harvard Medical School, Boston, MA
- Genetics (G.G.R., J.A.L.W., J.G.S., C.E.S., C.N.T.), Harvard Medical School, Boston, MA
- Cardiovascular Division, Department of Medicine, Brigham and Women’s Hospital, Boston, MA (C.E.S.)
- Howard Hughes Medical Institute, Chevy Chase, MD (C.E.S.)
| | - Alexander J. Sparrow
- Division of Cardiovascular Medicine, Radcliffe Department of Medicine (Y.P., F.M., A.J.S., M.S., V.S., C.S.R., H.C.W., P.R., C.N.T.), University of Oxford, United Kingdom
- Computer Science (F.M., A.B.-O., B.R.), University of Oxford, United Kingdom
- Wellcome Centre for Human Genetics (H.C.W., C.N.T.), University of Oxford, United Kingdom
- Image and Data Analysis Core (M.C.), Harvard Medical School, Boston, MA
- Genetics (G.G.R., J.A.L.W., J.G.S., C.E.S., C.N.T.), Harvard Medical School, Boston, MA
- Cardiovascular Division, Department of Medicine, Brigham and Women’s Hospital, Boston, MA (C.E.S.)
- Howard Hughes Medical Institute, Chevy Chase, MD (C.E.S.)
| | - Giuliana G. Repetti
- Genetics (G.G.R., J.A.L.W., J.G.S., C.E.S., C.N.T.), Harvard Medical School, Boston, MA
| | - Manuel Schmid
- Division of Cardiovascular Medicine, Radcliffe Department of Medicine (Y.P., F.M., A.J.S., M.S., V.S., C.S.R., H.C.W., P.R., C.N.T.), University of Oxford, United Kingdom
- Computer Science (F.M., A.B.-O., B.R.), University of Oxford, United Kingdom
- Wellcome Centre for Human Genetics (H.C.W., C.N.T.), University of Oxford, United Kingdom
- Image and Data Analysis Core (M.C.), Harvard Medical School, Boston, MA
- Genetics (G.G.R., J.A.L.W., J.G.S., C.E.S., C.N.T.), Harvard Medical School, Boston, MA
- Cardiovascular Division, Department of Medicine, Brigham and Women’s Hospital, Boston, MA (C.E.S.)
- Howard Hughes Medical Institute, Chevy Chase, MD (C.E.S.)
| | - Violetta Steeples
- Division of Cardiovascular Medicine, Radcliffe Department of Medicine (Y.P., F.M., A.J.S., M.S., V.S., C.S.R., H.C.W., P.R., C.N.T.), University of Oxford, United Kingdom
- Computer Science (F.M., A.B.-O., B.R.), University of Oxford, United Kingdom
- Wellcome Centre for Human Genetics (H.C.W., C.N.T.), University of Oxford, United Kingdom
- Image and Data Analysis Core (M.C.), Harvard Medical School, Boston, MA
- Genetics (G.G.R., J.A.L.W., J.G.S., C.E.S., C.N.T.), Harvard Medical School, Boston, MA
- Cardiovascular Division, Department of Medicine, Brigham and Women’s Hospital, Boston, MA (C.E.S.)
- Howard Hughes Medical Institute, Chevy Chase, MD (C.E.S.)
| | - Jonathan A.L. Wilcox
- Genetics (G.G.R., J.A.L.W., J.G.S., C.E.S., C.N.T.), Harvard Medical School, Boston, MA
| | | | - Charles S. Redwood
- Division of Cardiovascular Medicine, Radcliffe Department of Medicine (Y.P., F.M., A.J.S., M.S., V.S., C.S.R., H.C.W., P.R., C.N.T.), University of Oxford, United Kingdom
- Computer Science (F.M., A.B.-O., B.R.), University of Oxford, United Kingdom
- Wellcome Centre for Human Genetics (H.C.W., C.N.T.), University of Oxford, United Kingdom
- Image and Data Analysis Core (M.C.), Harvard Medical School, Boston, MA
- Genetics (G.G.R., J.A.L.W., J.G.S., C.E.S., C.N.T.), Harvard Medical School, Boston, MA
- Cardiovascular Division, Department of Medicine, Brigham and Women’s Hospital, Boston, MA (C.E.S.)
- Howard Hughes Medical Institute, Chevy Chase, MD (C.E.S.)
| | - Hugh C. Watkins
- Wellcome Centre for Human Genetics (H.C.W., C.N.T.), University of Oxford, United Kingdom
| | - Paul Robinson
- Division of Cardiovascular Medicine, Radcliffe Department of Medicine (Y.P., F.M., A.J.S., M.S., V.S., C.S.R., H.C.W., P.R., C.N.T.), University of Oxford, United Kingdom
| | - Blanca Rodriguez
- Computer Science (F.M., A.B.-O., B.R.), University of Oxford, United Kingdom
| | - Jonathan G. Seidman
- Genetics (G.G.R., J.A.L.W., J.G.S., C.E.S., C.N.T.), Harvard Medical School, Boston, MA
| | - Christine E. Seidman
- Genetics (G.G.R., J.A.L.W., J.G.S., C.E.S., C.N.T.), Harvard Medical School, Boston, MA
- Cardiovascular Division, Department of Medicine, Brigham and Women’s Hospital, Boston, MA (C.E.S.)
- Howard Hughes Medical Institute, Chevy Chase, MD (C.E.S.)
| | - Christopher N. Toepfer
- Division of Cardiovascular Medicine, Radcliffe Department of Medicine (Y.P., F.M., A.J.S., M.S., V.S., C.S.R., H.C.W., P.R., C.N.T.), University of Oxford, United Kingdom
- Wellcome Centre for Human Genetics (H.C.W., C.N.T.), University of Oxford, United Kingdom
- Genetics (G.G.R., J.A.L.W., J.G.S., C.E.S., C.N.T.), Harvard Medical School, Boston, MA
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15
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Iwamoto H. The 3D structure of fibrous material is fully restorable from its X-ray diffraction pattern. IUCRJ 2021; 8:544-548. [PMID: 34258003 PMCID: PMC8256704 DOI: 10.1107/s2052252521004760] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/21/2020] [Accepted: 05/06/2021] [Indexed: 06/13/2023]
Abstract
X-ray fiber diffraction is potentially a powerful technique to study the structure of fibrous materials, such as DNA and synthetic polymers. However, only rotationally averaged diffraction patterns can be recorded and it is difficult to correctly interpret them without the knowledge of esoteric diffraction theories. Here we demonstrate that, in principle, the non-rotationally averaged 3D structure of a fibrous material can be restored from its fiber diffraction pattern. The method is a simple puzzle-solving process and in ideal cases it does not require any prior knowledge about the structure, such as helical symmetry. We believe that the proposed method has a potential to transform the fiber diffraction to a 3D imaging technique, and will be useful for a wide field of life and materials sciences.
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Affiliation(s)
- Hiroyuki Iwamoto
- SPring-8, Japan Synchrotron Radiation Research Institute, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5198, Japan
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16
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Ma W, Duno-Miranda S, Irving T, Craig R, Padrón R. Relaxed tarantula skeletal muscle has two ATP energy-saving mechanisms. J Gen Physiol 2021; 153:211706. [PMID: 33480967 PMCID: PMC7822627 DOI: 10.1085/jgp.202012780] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Accepted: 12/22/2020] [Indexed: 12/15/2022] Open
Abstract
Myosin molecules in the relaxed thick filaments of striated muscle have a helical arrangement in which the heads of each molecule interact with each other, forming the interacting-heads motif (IHM). In relaxed mammalian skeletal muscle, this helical ordering occurs only at temperatures >20°C and is disrupted when temperature is decreased. Recent x-ray diffraction studies of live tarantula skeletal muscle have suggested that the two myosin heads of the IHM (blocked heads [BHs] and free heads [FHs]) have very different roles and dynamics during contraction. Here, we explore temperature-induced changes in the BHs and FHs in relaxed tarantula skeletal muscle. We find a change with decreasing temperature that is similar to that in mammals, while increasing temperature induces a different behavior in the heads. At 22.5°C, the BHs and FHs containing ADP.Pi are fully helically organized, but they become progressively disordered as temperature is lowered or raised. Our interpretation suggests that at low temperature, while the BHs remain ordered the FHs become disordered due to transition of the heads to a straight conformation containing Mg.ATP. Above 27.5°C, the nucleotide remains as ADP.Pi, but while BHs remain ordered, half of the FHs become progressively disordered, released semipermanently at a midway distance to the thin filaments while the remaining FHs are docked as swaying heads. We propose a thermosensing mechanism for tarantula skeletal muscle to explain these changes. Our results suggest that tarantula skeletal muscle thick filaments, in addition to having a superrelaxation–based ATP energy-saving mechanism in the range of 8.5–40°C, also exhibit energy saving at lower temperatures (<22.5°C), similar to the proposed refractory state in mammals.
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Affiliation(s)
- Weikang Ma
- Biophysics Collaborative Access Team, Department of Biological Sciences, Illinois Institute of Technology, Chicago, IL
| | - Sebastian Duno-Miranda
- Department of Molecular Physiology and Biophysics, Cardiovascular Research Institute, University of Vermont, Burlington, VT
| | - Thomas Irving
- Biophysics Collaborative Access Team, Department of Biological Sciences, Illinois Institute of Technology, Chicago, IL
| | - Roger Craig
- Division of Cell Biology and Imaging, Department of Radiology, University of Massachusetts Medical School, Worcester, MA
| | - Raúl Padrón
- Division of Cell Biology and Imaging, Department of Radiology, University of Massachusetts Medical School, Worcester, MA
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17
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Reconditi M. Convergent evolutionary pathways toward energy saving in muscle? J Gen Physiol 2021; 153:211774. [PMID: 33566083 PMCID: PMC7879489 DOI: 10.1085/jgp.202012818] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Reconditi reviews research into the role temperature plays on motor disorders.
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Affiliation(s)
- Massimo Reconditi
- Dipartimento di Medicina Sperimentale e Clinica-PhysioLab, University of Florence, Florence, Italy
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18
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Schmid M, Toepfer CN. Cardiac myosin super relaxation (SRX): a perspective on fundamental biology, human disease and therapeutics. Biol Open 2021; 10:10/2/bio057646. [PMID: 33589442 PMCID: PMC7904003 DOI: 10.1242/bio.057646] [Citation(s) in RCA: 42] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
The fundamental basis of muscle contraction 'the sliding filament model' (Huxley and Niedergerke, 1954; Huxley and Hanson, 1954) and the 'swinging, tilting crossbridge-sliding filament mechanism' (Huxley, 1969; Huxley and Brown, 1967) nucleated a field of research that has unearthed the complex and fascinating role of myosin structure in the regulation of contraction. A recently discovered energy conserving state of myosin termed the super relaxed state (SRX) has been observed in filamentous myosins and is central to modulating force production and energy use within the sarcomere. Modulation of myosin function through SRX is a rapidly developing theme in therapeutic development for both cardiovascular disease and infectious disease. Some 70 years after the first discoveries concerning muscular function, modulation of myosin SRX may bring the first myosin targeted small molecule to the clinic, for treating hypertrophic cardiomyopathy (Olivotto et al., 2020). An often monogenic disease HCM afflicts 1 in 500 individuals, and can cause heart failure and sudden cardiac death. Even as we near therapeutic translation, there remain many questions about the governance of muscle function in human health and disease. With this review, we provide a broad overview of contemporary understanding of myosin SRX, and explore the complexities of targeting this myosin state in human disease.This article has an associated Future Leaders to Watch interview with the authors of the paper.
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Affiliation(s)
- Manuel Schmid
- Division of Cardiovascular Medicine, Radcliffe Department of Medicine, University of Oxford, Oxford OX3 9DU, UK
| | - Christopher N Toepfer
- Division of Cardiovascular Medicine, Radcliffe Department of Medicine, University of Oxford, Oxford OX3 9DU, UK
- Department of Genetics, Harvard Medical School, Boston, MA 02115, USA
- Wellcome Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, UK
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19
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Abstract
Since the discovery of muscle in the 19th century, myosins as molecular motors have been extensively studied. However, in the last decade, a new functional super-relaxed (SRX) state of myosin has been discovered, which has a 10-fold slower ATP turnover rate than the already-known non-actin-bound, disordered relaxed (DRX) state. These two states are in dynamic equilibrium under resting muscle conditions and are thought to be significant contributors to adaptive thermogenesis in skeletal muscle and can act as a reserve pool that may be recruited when there is a sustained demand for increased cardiac muscle power. This report provides an evolutionary perspective of how striated muscle contraction is regulated by modulating this myosin DRX↔SRX state equilibrium. We further discuss this equilibrium with respect to different physiological and pathophysiological perturbations, including insults causing hypertrophic cardiomyopathy, and small-molecule effectors that modulate muscle contractility in diseased pathology.
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Affiliation(s)
- Suman Nag
- Department of Biology, MyoKardia IncBrisbaneUnited States
| | - Darshan V Trivedi
- Department of Biochemistry, Stanford University School of MedicineStanfordUnited States
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20
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Gollapudi SK, Yu M, Gan QF, Nag S. Synthetic thick filaments: A new avenue for better understanding the myosin super-relaxed state in healthy, diseased, and mavacamten-treated cardiac systems. J Biol Chem 2021; 296:100114. [PMID: 33234590 PMCID: PMC7948491 DOI: 10.1074/jbc.ra120.016506] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2020] [Revised: 11/19/2020] [Accepted: 11/23/2020] [Indexed: 12/20/2022] Open
Abstract
A hallmark feature of myosin-II is that it can spontaneously self-assemble into bipolar synthetic thick filaments (STFs) in low-ionic-strength buffers, thereby serving as a reconstituted in vitro model for muscle thick filaments. Although these STFs have been extensively used for structural characterization, their functional evaluation has been limited. In this report, we show that myosins in STFs mirror the more electrostatic and cooperative interactions that underlie the energy-sparing super-relaxed (SRX) state, which are not seen using shorter myosin subfragments, heavy meromyosin (HMM) and myosin subfragment 1 (S1). Using these STFs, we show several pathophysiological insults in hypertrophic cardiomyopathy, including the R403Q myosin mutation, phosphorylation of myosin light chains, and an increased ADP:ATP ratio, destabilize the SRX population. Furthermore, WT myosin containing STFs, but not S1, HMM, or STFs-containing R403Q myosin, recapitulated the ADP-induced destabilization of the SRX state. Studies involving a clinical-stage small-molecule inhibitor, mavacamten, showed that it is more effective in not only increasing myosin SRX population in STFs than in S1 or HMM but also in increasing myosin SRX population equally well in STFs made of healthy and disease-causing R403Q myosin. Importantly, we also found that pathophysiological perturbations such as elevated ADP concentration weakens mavacamten's ability to increase the myosin SRX population, suggesting that mavacamten-bound myosin heads are not permanently protected in the SRX state but can be recruited into action. These findings collectively emphasize that STFs serve as a valuable tool to provide novel insights into the myosin SRX state in healthy, diseased, and therapeutic conditions.
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Affiliation(s)
| | - Ming Yu
- Department of Biology, MyoKardia, Inc., Brisbane, California, USA
| | - Qing-Fen Gan
- Department of Biology, MyoKardia, Inc., Brisbane, California, USA
| | - Suman Nag
- Department of Biology, MyoKardia, Inc., Brisbane, California, USA.
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21
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Profile of Raúl Padrón. Proc Natl Acad Sci U S A 2020; 117:32830-32832. [DOI: 10.1073/pnas.2015960117] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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22
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Nelson SR, Li A, Beck-Previs S, Kennedy GG, Warshaw DM. Imaging ATP Consumption in Resting Skeletal Muscle: One Molecule at a Time. Biophys J 2020; 119:1050-1055. [PMID: 32857963 DOI: 10.1016/j.bpj.2020.07.036] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2020] [Revised: 07/11/2020] [Accepted: 07/20/2020] [Indexed: 12/19/2022] Open
Abstract
Striated muscle contraction is the result of sarcomeres, the basic contractile unit, shortening because of hydrolysis of adenosine triphosphate (ATP) by myosin molecular motors. In noncontracting, "relaxed" muscle, myosin still hydrolyzes ATP slowly, contributing to the muscle's overall resting metabolic rate. Furthermore, when relaxed, myosin partition into two kinetically distinct subpopulations: a faster-hydrolyzing "relaxed" population, and a slower-hydrolyzing "super relaxed" (SRX) population. How these two myosin subpopulations are spatially arranged in the sarcomere is unclear, although it has been proposed that myosin-binding protein C (MyBP-C) may stabilize the SRX state. Because MyBP-C is found only in a distinct region of the sarcomere, i.e., the C-zone, are SRX myosin similarly colocalized in the C-zone? Here, we imaged the binding lifetime and location (38-nm resolution) of single, fluorescently labeled boron-dipyrromethene-labeled ATP molecules in relaxed skeletal muscle sarcomeres from rat soleus. The lifetime distribution of fluorescent ATP-binding events was well fitted as an admixture of two subpopulations with time constants of 26 ± 2 and 146 ± 16 s, with the longer-lived population being 28 ± 4% of the total. These values agree with reported kinetics from bulk studies of skeletal muscle for the relaxed and SRX subpopulations, respectively. Subsarcomeric localization of these events revealed that SRX-nucleotide-binding events are fivefold more frequent in the C-zone (where MyBP-C exists) than in flanking regions devoid of MyBP-C. Treatment with the small molecule myosin inhibitor, mavacamten, caused no change in SRX event frequency in the C-zone but increased their frequency fivefold outside the C-zone, indicating that all myosin are in a dynamic equilibrium between the relaxed and SRX states. With SRX myosin found predominantly in the C-zone, these data suggest that MyBP-C may stabilize and possibly regulate the SRX state.
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Affiliation(s)
- Shane R Nelson
- Department of Molecular Physiology and Biophysics, Larner College of Medicine, Burlington, Vermont
| | - Amy Li
- Department of Molecular Physiology and Biophysics, Larner College of Medicine, Burlington, Vermont
| | - Samantha Beck-Previs
- Department of Molecular Physiology and Biophysics, Larner College of Medicine, Burlington, Vermont
| | - Guy G Kennedy
- Department of Molecular Physiology and Biophysics, Larner College of Medicine, Burlington, Vermont; Instrumentation and Model Facility, University of Vermont, Burlington, Vermont
| | - David M Warshaw
- Department of Molecular Physiology and Biophysics, Larner College of Medicine, Burlington, Vermont.
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23
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The myosin interacting-heads motif present in live tarantula muscle explains tetanic and posttetanic phosphorylation mechanisms. Proc Natl Acad Sci U S A 2020; 117:11865-11874. [PMID: 32444484 DOI: 10.1073/pnas.1921312117] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Striated muscle contraction involves sliding of actin thin filaments along myosin thick filaments, controlled by calcium through thin filament activation. In relaxed muscle, the two heads of myosin interact with each other on the filament surface to form the interacting-heads motif (IHM). A key question is how both heads are released from the surface to approach actin and produce force. We used time-resolved synchrotron X-ray diffraction to study tarantula muscle before and after tetani. The patterns showed that the IHM is present in live relaxed muscle. Tetanic contraction produced only a very small backbone elongation, implying that mechanosensing-proposed in vertebrate muscle-is not of primary importance in tarantula. Rather, thick filament activation results from increases in myosin phosphorylation that release a fraction of heads to produce force, with the remainder staying in the ordered IHM configuration. After the tetanus, the released heads slowly recover toward the resting, helically ordered state. During this time the released heads remain close to actin and can quickly rebind, enhancing the force produced by posttetanic twitches, structurally explaining posttetanic potentiation. Taken together, these results suggest that, in addition to stretch activation in insects, two other mechanisms for thick filament activation have evolved to disrupt the interactions that establish the relaxed helices of IHMs: one in invertebrates, by either regulatory light-chain phosphorylation (as in arthropods) or Ca2+-binding (in mollusks, lacking phosphorylation), and another in vertebrates, by mechanosensing.
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Sulbarán G, Biasutto A, Méndez F, Pinto A, Alamo L, Padrón R. 18O labeling on Ser45 but not on Ser35 supports the cooperative phosphorylation mechanism on tarantula thick filament activation. Biochem Biophys Res Commun 2020; 524:198-204. [PMID: 31983430 DOI: 10.1016/j.bbrc.2020.01.044] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2019] [Accepted: 01/08/2020] [Indexed: 01/25/2023]
Abstract
Thick filaments from some striated muscles are regulated by phosphorylation of myosin regulatory light chains (RLCs). A tarantula thick filament quasi-atomic model achieved by cryo-electron microscopy has advanced our understanding on how this regulation occurs. In native thick filaments, an asymmetric intramolecular interaction between the actin-binding region of one myosin head ("blocked") and the converter region of the other head ("free") switches both heads off, establishing the myosin interacting-heads motif (IHM). This structural finding, together with motility assays, sequence analysis, and mass spectrometry (MS) observations have suggested a cooperative phosphorylation activation (CPA) mechanism for thick filament activation. In the CPA mechanism, some myosin free heads are phosphorylated constitutively in Ser35 by protein kinase C (PKC) and -under Ca2+ control - others (free or blocked) heads temporally on Ser45 by myosin light chain kinase (MLCK), in a way that explains both force development and post-tetanic potentiation in tarantula striated muscle. We tested this model using MS to verify if Ca2+-activation phosphorylates de novo un-phosphorylated Ser35 heads. For this purpose, we standardized an approach based on 18O isotopic ATP labeling to accurately detect by MS-MS the RLC phosphorylation under Ca2+-activation. MS spectra showed de novo18O incorporation only on Ser45 but not on Ser35. As the constitutive Ser35 phosphorylation cannot be dephosphorylated, this result suggests that the number of RLCs on free heads with constitutively phosphorylated Ser35 does remain constant on Ca2+-activation supporting that the myosin has a basal activation and force modulation or potentiation is controlled by MLCK Ser45 phosphorylation.
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Affiliation(s)
- Guidenn Sulbarán
- Centro de Biología Estructural, Instituto Venezolano de Investigaciones Científicas (IVIC), Apdo. 20632, Caracas, 1020A, Venezuela.
| | - Antonio Biasutto
- Centro de Biología Estructural, Instituto Venezolano de Investigaciones Científicas (IVIC), Apdo. 20632, Caracas, 1020A, Venezuela.
| | - Franklin Méndez
- Centro de Biología Estructural, Instituto Venezolano de Investigaciones Científicas (IVIC), Apdo. 20632, Caracas, 1020A, Venezuela.
| | - Antonio Pinto
- Centro de Biología Estructural, Instituto Venezolano de Investigaciones Científicas (IVIC), Apdo. 20632, Caracas, 1020A, Venezuela.
| | - Lorenzo Alamo
- Centro de Biología Estructural, Instituto Venezolano de Investigaciones Científicas (IVIC), Apdo. 20632, Caracas, 1020A, Venezuela.
| | - Raúl Padrón
- Centro de Biología Estructural, Instituto Venezolano de Investigaciones Científicas (IVIC), Apdo. 20632, Caracas, 1020A, Venezuela.
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25
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Trivedi DV, Nag S, Spudich A, Ruppel KM, Spudich JA. The Myosin Family of Mechanoenzymes: From Mechanisms to Therapeutic Approaches. Annu Rev Biochem 2020; 89:667-693. [PMID: 32169021 DOI: 10.1146/annurev-biochem-011520-105234] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Myosins are among the most fascinating enzymes in biology. As extremely allosteric chemomechanical molecular machines, myosins are involved in myriad pivotal cellular functions and are frequently sites of mutations leading to disease phenotypes. Human β-cardiac myosin has proved to be an excellent target for small-molecule therapeutics for heart muscle diseases, and, as we describe here, other myosin family members are likely to be potentially unique targets for treating other diseases as well. The first part of this review focuses on how myosins convert the chemical energy of ATP hydrolysis into mechanical movement, followed by a description of existing therapeutic approaches to target human β-cardiac myosin. The next section focuses on the possibility of targeting nonmuscle members of the human myosin family for several diseases. We end the review by describing the roles of myosin in parasites and the therapeutic potential of targeting them to block parasitic invasion of their hosts.
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Affiliation(s)
- Darshan V Trivedi
- Department of Biochemistry, Stanford University School of Medicine, Stanford, California 94305, USA; , , .,Stanford Cardiovascular Institute, Stanford University School of Medicine, Stanford, California 94305, USA
| | - Suman Nag
- MyoKardia Inc., Brisbane, California 94005, USA;
| | - Annamma Spudich
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore 560-097, India;
| | - Kathleen M Ruppel
- Department of Biochemistry, Stanford University School of Medicine, Stanford, California 94305, USA; , , .,Stanford Cardiovascular Institute, Stanford University School of Medicine, Stanford, California 94305, USA.,Division of Pediatric Cardiology, Department of Pediatrics, Stanford University School of Medicine, Stanford, California 94305, USA
| | - James A Spudich
- Department of Biochemistry, Stanford University School of Medicine, Stanford, California 94305, USA; , , .,Stanford Cardiovascular Institute, Stanford University School of Medicine, Stanford, California 94305, USA
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26
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Robert-Paganin J, Pylypenko O, Kikuti C, Sweeney HL, Houdusse A. Force Generation by Myosin Motors: A Structural Perspective. Chem Rev 2019; 120:5-35. [PMID: 31689091 DOI: 10.1021/acs.chemrev.9b00264] [Citation(s) in RCA: 68] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Generating force and movement is essential for the functions of cells and organisms. A variety of molecular motors that can move on tracks within cells have evolved to serve this role. How these motors interact with their tracks and how that, in turn, leads to the generation of force and movement is key to understanding the cellular roles that these motor-track systems serve. This review is focused on the best understood of these systems, which is the molecular motor myosin that moves on tracks of filamentous (F-) actin. The review highlights both the progress and the limits of our current understanding of how force generation can be controlled by F-actin-myosin interactions. What has emerged are insights they may serve as a framework for understanding the design principles of a number of types of molecular motors and their interactions with their tracks.
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Affiliation(s)
- Julien Robert-Paganin
- Structural Motility , UMR 144 CNRS/Curie Institute , 26 rue d'ulm , 75258 Paris cedex 05 , France
| | - Olena Pylypenko
- Structural Motility , UMR 144 CNRS/Curie Institute , 26 rue d'ulm , 75258 Paris cedex 05 , France
| | - Carlos Kikuti
- Structural Motility , UMR 144 CNRS/Curie Institute , 26 rue d'ulm , 75258 Paris cedex 05 , France
| | - H Lee Sweeney
- Department of Pharmacology & Therapeutics and the Myology Institute , University of Florida College of Medicine , PO Box 100267, Gainesville , Florida 32610-0267 , United States
| | - Anne Houdusse
- Structural Motility , UMR 144 CNRS/Curie Institute , 26 rue d'ulm , 75258 Paris cedex 05 , France
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27
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Spudich JA. Three perspectives on the molecular basis of hypercontractility caused by hypertrophic cardiomyopathy mutations. Pflugers Arch 2019; 471:701-717. [PMID: 30767072 PMCID: PMC6475635 DOI: 10.1007/s00424-019-02259-2] [Citation(s) in RCA: 91] [Impact Index Per Article: 18.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2018] [Revised: 01/11/2019] [Accepted: 01/20/2019] [Indexed: 01/10/2023]
Abstract
Several lines of evidence suggest that the primary effect of hypertrophic cardiomyopathy mutations in human β-cardiac myosin is hypercontractility of the heart, which leads to subsequent hypertrophy, fibrosis, and myofilament disarray. Here, I describe three perspectives on the molecular basis of this hypercontractility. The first is that hypercontractility results from changes in the fundamental parameters of the actin-activated β-cardiac myosin chemo-mechanical ATPase cycle. The second considers that hypercontractility results from an increase in the number of functionally accessible heads in the sarcomere for interaction with actin. The final and third perspective is that load dependence of contractility is affected by cardiomyopathy mutations and small-molecule effectors in a manner that changes the power output of cardiac contraction. Experimental approaches associated with each perspective are described along with concepts of therapeutic approaches that could prove valuable in treating hypertrophic cardiomyopathy.
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Affiliation(s)
- James A Spudich
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA, 94305, USA.
- Cardiovascular Institute, Stanford University School of Medicine, Stanford, CA, 94305, USA.
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28
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Proposed mechanism for the length dependence of the force developed in maximally activated muscles. Sci Rep 2019; 9:1317. [PMID: 30718530 PMCID: PMC6362285 DOI: 10.1038/s41598-018-36706-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2018] [Accepted: 11/20/2018] [Indexed: 11/08/2022] Open
Abstract
The molecular bases of the Frank-Starling law of the heart and of its cellular counterpart, the length dependent activation (LDA), are largely unknown. However, the recent discovery of the thick filament activation, a second pathway beside the well-known calcium mediated thin filament activation, is promising for elucidating these mechanisms. The thick filament activation is mediated by the tension acting on it through the mechano-sensing (MS) mechanism and can be related to the LDA via the titin passive tension. Here, we propose a mechanism to explain the higher maximum tension at longer sarcomere lengths generated by a maximally activated muscle and test it in-silico with a single fiber and a ventricle model. The active tension distribution along the thick filament generates a reservoir of inactive motors at its free-end that can be activated by passive tension on a beat-to-beat timescale. The proposed mechanism is able to quantitatively account for the observed increment in tension at the fiber level, however, the ventricle model suggests that this component of the LDA is not crucial in physiological conditions.
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29
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Wang Y, Ajtai K, Burghardt TP. Cardiac and skeletal actin substrates uniquely tune cardiac myosin strain-dependent mechanics. Open Biol 2018; 8:180143. [PMID: 30463911 PMCID: PMC6282072 DOI: 10.1098/rsob.180143] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2018] [Accepted: 10/26/2018] [Indexed: 01/24/2023] Open
Abstract
Cardiac ventricular myosin (βmys) translates actin by transducing ATP free energy into mechanical work during muscle contraction. Unitary βmys translation of actin is the step-size. In vitro and in vivo βmys regulates contractile force and velocity autonomously by remixing three different step-sizes with adaptive stepping frequencies. Cardiac and skeletal actin isoforms have a specific 1 : 4 stoichiometry in normal adult human ventriculum. Human adults with inheritable hypertrophic cardiomyopathy (HCM) upregulate skeletal actin in ventriculum probably compensating the diseased muscle's inability to meet demand by adjusting βmys force-velocity characteristics. βmys force-velocity characteristics were compared for skeletal versus cardiac actin substrates using ensemble in vitro motility and single myosin assays. Two competing myosin strain-sensitive mechanisms regulate step-size choices dividing single βmys mechanics into low- and high-force regimes. The actin isoforms alter myosin strain-sensitive regulation such that onset of the high-force regime, where a short step-size is a large or major contributor, is offset to higher loads probably by the unique cardiac essential light chain (ELC) N-terminus/cardiac actin contact at Glu6/Ser358. It modifies βmys force-velocity by stabilizing the ELC N-terminus/cardiac actin association. Uneven onset of the high-force regime for skeletal versus cardiac actin modulates force-velocity characteristics as skeletal/cardiac actin fractional content increases in diseased muscle.
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Affiliation(s)
- Yihua Wang
- Department of Biochemistry and Molecular Biology, Mayo Clinic Rochester, Rochester, MN 55905, USA
| | - Katalin Ajtai
- Department of Biochemistry and Molecular Biology, Mayo Clinic Rochester, Rochester, MN 55905, USA
| | - Thomas P Burghardt
- Department of Biochemistry and Molecular Biology, Mayo Clinic Rochester, Rochester, MN 55905, USA
- Department of Physiology and Biomedical Engineering, Mayo Clinic Rochester, Rochester, MN 55905, USA
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30
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Hypertrophic cardiomyopathy disease results from disparate impairments of cardiac myosin function and auto-inhibition. Nat Commun 2018; 9:4019. [PMID: 30275503 PMCID: PMC6167380 DOI: 10.1038/s41467-018-06191-4] [Citation(s) in RCA: 67] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2018] [Accepted: 08/06/2018] [Indexed: 01/18/2023] Open
Abstract
Hypertrophic cardiomyopathies (HCM) result from distinct single-point mutations in sarcomeric proteins that lead to muscle hypercontractility. While different models account for a pathological increase in the power output, clear understanding of the molecular basis of dysfunction in HCM is the mandatory next step to improve current treatments. Here, we present an optimized quasi-atomic model of the sequestered state of cardiac myosin coupled to X-ray crystallography and in silico analysis of the mechanical compliance of the lever arm, allowing the systematic study of a large set of HCM mutations and the definition of different mutation classes based on their effects on lever arm compliance, sequestered state stability, and motor functions. The present work reconciles previous models and explains how distinct HCM mutations can have disparate effects on the motor mechano-chemical parameters and yet lead to the same disease. The framework presented here can guide future investigations aiming at finding HCM treatments. Hypertrophic cardiomyopathy (HCM) is caused by point mutations in sarcomeric proteins. Here the authors develop an optimized model of the sequestered state of cardiac myosin and define the features affecting the lever arm compliance, allowing them to group mutations in classes and to elucidate the molecular mechanisms leading to cardiac dysfunction in HCM.
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31
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Alamo L, Koubassova N, Pinto A, Gillilan R, Tsaturyan A, Padrón R. Lessons from a tarantula: new insights into muscle thick filament and myosin interacting-heads motif structure and function. Biophys Rev 2017; 9:461-480. [PMID: 28871556 DOI: 10.1007/s12551-017-0295-1] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2017] [Accepted: 07/27/2017] [Indexed: 12/13/2022] Open
Abstract
The tarantula skeletal muscle X-ray diffraction pattern suggested that the myosin heads were helically arranged on the thick filaments. Electron microscopy (EM) of negatively stained relaxed tarantula thick filaments revealed four helices of heads allowing a helical 3D reconstruction. Due to its low resolution (5.0 nm), the unambiguous interpretation of densities of both heads was not possible. A resolution increase up to 2.5 nm, achieved by cryo-EM of frozen-hydrated relaxed thick filaments and an iterative helical real space reconstruction, allowed the resolving of both heads. The two heads, "free" and "blocked", formed an asymmetric structure named the "interacting-heads motif" (IHM) which explained relaxation by self-inhibition of both heads ATPases. This finding made tarantula an exemplar system for thick filament structure and function studies. Heads were shown to be released and disordered by Ca2+-activation through myosin regulatory light chain phosphorylation, leading to EM, small angle X-ray diffraction and scattering, and spectroscopic and biochemical studies of the IHM structure and function. The results from these studies have consequent implications for understanding and explaining myosin super-relaxed state and thick filament activation and regulation. A cooperative phosphorylation mechanism for activation in tarantula skeletal muscle, involving swaying constitutively Ser35 mono-phosphorylated free heads, explains super-relaxation, force potentiation and post-tetanic potentiation through Ser45 mono-phosphorylated blocked heads. Based on this mechanism, we propose a swaying-swinging, tilting crossbridge-sliding filament for tarantula muscle contraction.
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Affiliation(s)
- Lorenzo Alamo
- Centro de Biología Estructural "Humberto Fernández-Morán", Instituto Venezolano de Investigaciones Científicas (IVIC), Apdo. 20632, Caracas, 1020A, Venezuela
| | - Natalia Koubassova
- Institute of Mechanics, Moscow State University, Mitchurinsky prosp. 1, Moscow, 119992, Russia
| | - Antonio Pinto
- Centro de Biología Estructural "Humberto Fernández-Morán", Instituto Venezolano de Investigaciones Científicas (IVIC), Apdo. 20632, Caracas, 1020A, Venezuela
| | - Richard Gillilan
- Macromolecular Diffraction Facility, Cornell High Energy Synchrotron Source, Ithaca, NY, USA
| | - Andrey Tsaturyan
- Institute of Mechanics, Moscow State University, Mitchurinsky prosp. 1, Moscow, 119992, Russia
| | - Raúl Padrón
- Centro de Biología Estructural "Humberto Fernández-Morán", Instituto Venezolano de Investigaciones Científicas (IVIC), Apdo. 20632, Caracas, 1020A, Venezuela.
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