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Ghahremani S, Kanwal A, Pettinato A, Ladha F, Legere N, Thakar K, Zhu Y, Tjong H, Wilderman A, Stump WT, Greenberg L, Greenberg MJ, Cotney J, Wei CL, Hinson JT. CRISPR Activation Reverses Haploinsufficiency and Functional Deficits Caused by TTN Truncation Variants. Circulation 2024; 149:1285-1297. [PMID: 38235591 PMCID: PMC11031707 DOI: 10.1161/circulationaha.123.063972] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/13/2023] [Accepted: 12/13/2023] [Indexed: 01/19/2024]
Abstract
BACKGROUND TTN truncation variants (TTNtvs) are the most common genetic lesion identified in individuals with dilated cardiomyopathy, a disease with high morbidity and mortality rates. TTNtvs reduce normal TTN (titin) protein levels, produce truncated proteins, and impair sarcomere content and function. Therapeutics targeting TTNtvs have been elusive because of the immense size of TTN, the rarity of specific TTNtvs, and incomplete knowledge of TTNtv pathogenicity. METHODS We adapted CRISPR activation using dCas9-VPR to functionally interrogate TTNtv pathogenicity and develop a therapeutic in human cardiomyocytes and 3-dimensional cardiac microtissues engineered from induced pluripotent stem cell models harboring a dilated cardiomyopathy-associated TTNtv. We performed guide RNA screening with custom TTN reporter assays, agarose gel electrophoresis to quantify TTN protein levels and isoforms, and RNA sequencing to identify molecular consequences of TTN activation. Cardiomyocyte epigenetic assays were also used to nominate DNA regulatory elements to enable cardiomyocyte-specific TTN activation. RESULTS CRISPR activation of TTN using single guide RNAs targeting either the TTN promoter or regulatory elements in spatial proximity to the TTN promoter through 3-dimensional chromatin interactions rescued TTN protein deficits disturbed by TTNtvs. Increasing TTN protein levels normalized sarcomere content and contractile function despite increasing truncated TTN protein. In addition to TTN transcripts, CRISPR activation also increased levels of myofibril assembly-related and sarcomere-related transcripts. CONCLUSIONS TTN CRISPR activation rescued TTNtv-related functional deficits despite increasing truncated TTN levels, which provides evidence to support haploinsufficiency as a relevant genetic mechanism underlying heterozygous TTNtvs. CRISPR activation could be developed as a therapeutic to treat a large proportion of TTNtvs.
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Affiliation(s)
| | - Aditya Kanwal
- The Jackson Laboratory for Genomic Medicine, Farmington, CT 06032, USA
| | - Anthony Pettinato
- Cardiology Center, University of Connecticut Health Center, Farmington, CT 06030, USA
| | - Feria Ladha
- Cardiology Center, University of Connecticut Health Center, Farmington, CT 06030, USA
| | - Nicholas Legere
- The Jackson Laboratory for Genomic Medicine, Farmington, CT 06032, USA
| | - Ketan Thakar
- The Jackson Laboratory for Genomic Medicine, Farmington, CT 06032, USA
| | - Yanfen Zhu
- The Jackson Laboratory for Genomic Medicine, Farmington, CT 06032, USA
| | - Harianto Tjong
- The Jackson Laboratory for Genomic Medicine, Farmington, CT 06032, USA
| | - Andrea Wilderman
- Cardiology Center, University of Connecticut Health Center, Farmington, CT 06030, USA
| | - W. Tom Stump
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Lina Greenberg
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Michael J. Greenberg
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Justin Cotney
- Cardiology Center, University of Connecticut Health Center, Farmington, CT 06030, USA
| | - Chia-Lin Wei
- The Jackson Laboratory for Genomic Medicine, Farmington, CT 06032, USA
| | - J. Travis Hinson
- The Jackson Laboratory for Genomic Medicine, Farmington, CT 06032, USA
- Cardiology Center, University of Connecticut Health Center, Farmington, CT 06030, USA
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Greenberg L, Tom Stump W, Lin Z, Bredemeyer AL, Blackwell T, Han X, Greenberg AE, Garcia BA, Lavine KJ, Greenberg MJ. Harnessing molecular mechanism for precision medicine in dilated cardiomyopathy caused by a mutation in troponin T. bioRxiv 2024:2024.04.05.588306. [PMID: 38645235 PMCID: PMC11030379 DOI: 10.1101/2024.04.05.588306] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/23/2024]
Abstract
Familial dilated cardiomyopathy (DCM) is frequently caused by autosomal dominant point mutations in genes involved in diverse cellular processes, including sarcomeric contraction. While patient studies have defined the genetic landscape of DCM, genetics are not currently used in patient care, and patients receive similar treatments regardless of the underlying mutation. It has been suggested that a precision medicine approach based on the molecular mechanism of the underlying mutation could improve outcomes; however, realizing this approach has been challenging due to difficulties linking genotype and phenotype and then leveraging this information to identify therapeutic approaches. Here, we used multiscale experimental and computational approaches to test whether knowledge of molecular mechanism could be harnessed to connect genotype, phenotype, and drug response for a DCM mutation in troponin T, deletion of K210. Previously, we showed that at the molecular scale, the mutation reduces thin filament activation. Here, we used computational modeling of this molecular defect to predict that the mutant will reduce cellular and tissue contractility, and we validated this prediction in human cardiomyocytes and engineered heart tissues. We then used our knowledge of molecular mechanism to computationally model the effects of a small molecule that can activate the thin filament. We demonstrate experimentally that the modeling correctly predicts that the small molecule can partially rescue systolic dysfunction at the expense of diastolic function. Taken together, our results demonstrate how molecular mechanism can be harnessed to connect genotype and phenotype and inspire strategies to optimize mechanism-based therapeutics for DCM.
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Affiliation(s)
- Lina Greenberg
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - W. Tom Stump
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Zongtao Lin
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Andrea L. Bredemeyer
- Department of Medicine, Cardiovascular Division, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Thomas Blackwell
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Xian Han
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Akiva E. Greenberg
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Benjamin A. Garcia
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Kory J. Lavine
- Department of Medicine, Cardiovascular Division, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Michael J. Greenberg
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO, 63110, USA
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3
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Garg A, Jansen S, Zhang R, Lavine KJ, Greenberg MJ. Dilated cardiomyopathy-associated skeletal muscle actin (ACTA1) mutation R256H disrupts actin structure and function and causes cardiomyocyte hypocontractility. bioRxiv 2024:2024.03.10.583979. [PMID: 38559046 PMCID: PMC10979883 DOI: 10.1101/2024.03.10.583979] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/04/2024]
Abstract
Skeletal muscle actin (ACTA1) mutations are a prevalent cause of skeletal myopathies consistent with ACTA1's high expression in skeletal muscle. Rare de novo mutations in ACTA1 associated with combined cardiac and skeletal myopathies have been reported, but ACTA1 represents only ~20% of the total actin pool in cardiomyocytes, making its role in cardiomyopathy controversial. Here we demonstrate how a mutation in an actin isoform expressed at low levels in cardiomyocytes can cause cardiomyopathy by focusing on a unique ACTA1 mutation, R256H. We previously identified this mutation in multiple family members with dilated cardiomyopathy (DCM), who had reduced systolic function without clinical skeletal myopathy. Using a battery of multiscale biophysical tools, we show that R256H has potent functional effects on ACTA1 function at the molecular scale and in human cardiomyocytes. Importantly, we demonstrate that R256H acts in a dominant manner, where the incorporation of small amounts of mutant protein into thin filaments is sufficient to disrupt molecular contractility, and that this effect is dependent on the presence of troponin and tropomyosin. To understand the structural basis of this change in regulation, we resolved a structure of R256H filaments using Cryo-EM, and we see alterations in actin's structure that have the potential to disrupt interactions with tropomyosin. Finally, we show that ACTA1R256H/+ human induced pluripotent stem cell cardiomyocytes demonstrate reduced contractility and sarcomeric disorganization. Taken together, we demonstrate that R256H has multiple effects on ACTA1 function that are sufficient to cause reduced contractility and establish a likely causative relationship between ACTA1 R256H and clinical cardiomyopathy.
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Affiliation(s)
- Ankit Garg
- Division of Cardiology, Department of Medicine Johns Hopkins University Baltimore MD USA
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri, USA
- Cardiovascular Division, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Silvia Jansen
- Department of Cell Biology and Physiology, Washington University in St. Louis, St. Louis, MO, United States
| | - Rui Zhang
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Kory J. Lavine
- Cardiovascular Division, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, USA
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO
| | - Michael J. Greenberg
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri, USA
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4
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Garg A, Lavine KJ, Greenberg MJ. Assessing Cardiac Contractility From Single Molecules to Whole Hearts. JACC Basic Transl Sci 2024; 9:414-439. [PMID: 38559627 PMCID: PMC10978360 DOI: 10.1016/j.jacbts.2023.07.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/08/2023] [Revised: 07/14/2023] [Accepted: 07/14/2023] [Indexed: 04/04/2024]
Abstract
Fundamentally, the heart needs to generate sufficient force and power output to dynamically meet the needs of the body. Cardiomyocytes contain specialized structures referred to as sarcomeres that power and regulate contraction. Disruption of sarcomeric function or regulation impairs contractility and leads to cardiomyopathies and heart failure. Basic, translational, and clinical studies have adapted numerous methods to assess cardiac contraction in a variety of pathophysiological contexts. These tools measure aspects of cardiac contraction at different scales ranging from single molecules to whole organisms. Moreover, these studies have revealed new pathogenic mechanisms of heart disease leading to the development of novel therapies targeting contractility. In this review, the authors explore the breadth of tools available for studying cardiac contractile function across scales, discuss their strengths and limitations, highlight new insights into cardiac physiology and pathophysiology, and describe how these insights can be harnessed for therapeutic candidate development and translational.
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Affiliation(s)
- Ankit Garg
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri, USA
- Center for Cardiovascular Research, Division of Cardiology, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Kory J. Lavine
- Center for Cardiovascular Research, Division of Cardiology, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Michael J. Greenberg
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri, USA
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5
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Meyer GA, Ferey JLA, Sanford JA, Fitzgerald LS, Greenberg AE, Svensson K, Greenberg MJ, Schenk S. Insights into post-translational regulation of skeletal muscle contractile function by the acetyltransferases, p300 and CBP. bioRxiv 2024:2024.02.27.582179. [PMID: 38463996 PMCID: PMC10925228 DOI: 10.1101/2024.02.27.582179] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/12/2024]
Abstract
Mice with skeletal muscle-specific inducible double knockout of the lysine acetyltransferases, p300 (E1A binding protein p300) and CBP (cAMP-response element-binding protein binding protein), referred to as i-mPCKO, demonstrate a dramatic loss of contractile function in skeletal muscle and ultimately die within 7 days. Given that many proteins involved in ATP generation and cross-bridge cycling are acetylated, we investigated whether these processes are dysregulated in skeletal muscle from i-mPCKO mice and thus could underlie the rapid loss of muscle contractile function. Just 4-5 days after inducing knockout of p300 and CBP in skeletal muscle from adult i-mPCKO mice, there was ∼90% reduction in ex vivo contractile function in the extensor digitorum longus (EDL) and a ∼65% reduction in in vivo ankle dorsiflexion torque, as compared to wildtype (WT; i.e. Cre negative) littermates. Despite the profound loss of contractile force in i-mPCKO mice, there were no genotype-driven differences in fatigability during repeated contractions, nor were there genotype differences in mitochondrial specific pathway enrichment of the proteome, intermyofibrillar mitochondrial volume or mitochondrial respiratory function. As it relates to cross-bridge cycling, remarkably, the overt loss of contractile function in i-mPCKO muscle was reversed in permeabilized fibers supplied with exogenous Ca 2+ and ATP, with active tension being similar between i-mPCKO and WT mice, regardless of Ca 2+ concentration. Actin-myosin motility was also similar in skeletal muscle from i-mPCKO and WT mice. In conclusion, neither mitochondrial abundance/function, nor actomyosin cross-bridge cycling, are the underlying driver of contractile dysfunction in i-mPCKO mice. New & Noteworthy The mechanism underlying dramatic loss of muscle contractile function with inducible deletion of both p300 and CBP in skeletal muscle remains unknown. Here we find that impairments in mitochondrial function or cross-bridge cycling are not the underlying mechanism of action. Future work will investigate other aspects of excitation-contraction coupling, such as Ca 2+ handling and membrane excitability, as contractile function could be rescued by permeabilizing skeletal muscle, which provides exogenous Ca 2+ and bypasses membrane depolarization.
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6
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Scott B, Greenberg MJ. Multiscale biophysical models of cardiomyopathies reveal complexities challenging existing dogmas. Biophys J 2023; 122:4632-4634. [PMID: 38006882 PMCID: PMC10754685 DOI: 10.1016/j.bpj.2023.11.014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2023] [Revised: 11/14/2023] [Accepted: 11/15/2023] [Indexed: 11/27/2023] Open
Abstract
Mutations in sarcomeric proteins, including myosin, cause a variety of cardiomyopathies. A prominent hypothesis has been that myosin mutations causing hypercontractility of the motor lead to hypertrophic cardiomyopathy, while those causing hypocontractility lead to dilated cardiomyopathy; however, recent biophysical studies using multiscale computational and experimental models have revealed complexities not captured by this hypothesis. We summarize recent publications in Biophysical Journal challenging this dogma and highlighting the need for multiscale modeling of these complex diseases.
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Affiliation(s)
- Brent Scott
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri
| | - Michael J Greenberg
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri.
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7
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Lehman SJ, Meller A, Solieva SO, Lotthammer JM, Greenberg L, Langer SJ, Greenberg MJ, Tardiff JC, Bowman GR, Leinwand L. Divergent Molecular Phenotypes in Point Mutations at the Same Residue in Beta-Myosin Heavy Chain Lead to Distinct Cardiomyopathies. bioRxiv 2023:2023.07.03.547580. [PMID: 37461648 PMCID: PMC10349964 DOI: 10.1101/2023.07.03.547580] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 07/25/2023]
Abstract
In genetic cardiomyopathies, a frequently described phenomenon is how similar mutations in one protein can lead to discrete clinical phenotypes. One example is illustrated by two mutations in beta myosin heavy chain (β-MHC) that are linked to hypertrophic cardiomyopathy (HCM) (Ile467Val, I467V) and left ventricular non-compaction (LVNC) (Ile467Thr, I467T). To investigate how these missense mutations lead to independent diseases, we studied the molecular effects of each mutation using recombinant human β-MHC Subfragment 1 (S1) in in vitro assays. Both HCM-I467V and LVNC-I467T S1 mutations exhibited similar mechanochemical function, including unchanged ATPase and enhanced actin velocity but had opposing effects on the super-relaxed (SRX) state of myosin. HCM-I467V S1 showed a small reduction in the SRX state, shifting myosin to a more actin-available state that may lead to the "gain-of-function" phenotype commonly described in HCM. In contrast, LVNC-I467T significantly increased the population of myosin in the ultra-slow SRX state. Interestingly, molecular dynamics simulations reveal that I467T allosterically disrupts interactions between ADP and the nucleotide-binding pocket, which may result in an increased ADP release rate. This predicted change in ADP release rate may define the enhanced actin velocity measured in LVNC-I467T, but also describe the uncoupled mechanochemical function for this mutation where the enhanced ADP release rate may be sufficient to offset the increased SRX population of myosin. These contrasting molecular effects may lead to contractile dysregulation that initiates LVNC-associated signaling pathways that progress the phenotype. Together, analysis of these mutations provides evidence that phenotypic complexity originates at the molecular level and is critical to understanding disease progression and developing therapies.
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Affiliation(s)
- Sarah J Lehman
- University of Colorado, Molecular, Cellular, and Developmental Biology, Boulder, CO, USA
| | - Artur Meller
- Washington University in St. Louis, Department of Biochemistry and Molecular Biophysics, St. Louis, MO, USA
- Medical Scientist Training Program, Washington University in St. Louis, St. Louis, MO, USA
| | - Shahlo O Solieva
- University of Pennsylvania, Department of Biochemistry and Biophysics, Philadelphia, PA, USA
| | - Jeffrey M Lotthammer
- Washington University in St. Louis, Department of Biochemistry and Molecular Biophysics, St. Louis, MO, USA
| | - Lina Greenberg
- Washington University in St. Louis, Department of Biochemistry and Molecular Biophysics, St. Louis, MO, USA
| | - Stephen J Langer
- University of Colorado, Molecular, Cellular, and Developmental Biology, Boulder, CO, USA
| | - Michael J Greenberg
- Washington University in St. Louis, Department of Biochemistry and Molecular Biophysics, St. Louis, MO, USA
| | - Jil C Tardiff
- University of Arizona, Department of Biomedical Engineering, Tucson, AZ, USA
| | - Gregory R Bowman
- University of Pennsylvania, Department of Biochemistry and Biophysics, Philadelphia, PA, USA
| | - Leslie Leinwand
- University of Colorado, Molecular, Cellular, and Developmental Biology, Boulder, CO, USA
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8
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Clippinger Schulte SR, Scott B, Barrick SK, Stump WT, Blackwell T, Greenberg MJ. Single Molecule Mechanics and Kinetics of Cardiac Myosin Interacting with Regulated Thin Filaments. Biophys J 2023:S0006-3495(23)00306-5. [PMID: 37165621 DOI: 10.1016/j.bpj.2023.05.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2023] [Revised: 04/18/2023] [Accepted: 05/05/2023] [Indexed: 05/12/2023] Open
Abstract
The cardiac cycle is a tightly regulated process wherein the heart generates force to pump blood to the body during systole and then relaxes during diastole. Disruption of this finely tuned cycle can lead to a range of diseases including cardiomyopathies and heart failure. Cardiac contraction is driven by the molecular motor myosin, which pulls regulated thin filaments in a calcium-dependent manner. In some muscle and non-muscle myosins, regulatory proteins on actin tune the kinetics, mechanics, and load dependence of the myosin working stroke; however, it is not well understood whether or how thin filament regulatory proteins tune the mechanics of the cardiac myosin motor. To address this critical gap in knowledge, we used single-molecule techniques to measure the kinetics and mechanics of the substeps of the cardiac myosin working stroke in the presence and absence of thin filament regulatory proteins. We found that regulatory proteins gate the calcium-dependent interactions between myosin and the thin filament. At physiologically relevant ATP concentrations, cardiac myosin's mechanics and unloaded kinetics are not affected by thin filament regulatory proteins. We also measured the load-dependent kinetics of cardiac myosin at physiologically relevant ATP concentrations using an isometric optical clamp, and we found that thin filament regulatory proteins do not affect either the identity or magnitude of myosin's primary load-dependent transition. Interestingly, at low ATP concentrations at both saturating and physiologically-relevant sub-saturating calcium concentrations, thin filament regulatory proteins have a small effect on actomyosin dissociation kinetics, suggesting a mechanism beyond simple steric blocking. These results have important implications for the modeling of cardiac physiology and diseases.
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Affiliation(s)
- Sarah R Clippinger Schulte
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Brent Scott
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Samantha K Barrick
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - W Tom Stump
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Thomas Blackwell
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Michael J Greenberg
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO, 63110, USA.
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9
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Lee LA, Barrick SK, Buvoli AE, Walklate J, Stump WT, Geeves M, Greenberg MJ, Leinwand LA. Distinct effects of two hearing loss-associated mutations in the sarcomeric myosin MYH7b. J Biol Chem 2023; 299:104631. [PMID: 36963494 PMCID: PMC10141508 DOI: 10.1016/j.jbc.2023.104631] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2022] [Revised: 03/08/2023] [Accepted: 03/17/2023] [Indexed: 03/26/2023] Open
Abstract
For decades, sarcomeric myosin heavy chain proteins were assumed to be restricted to striated muscle where they function as molecular motors that contract muscle. However, MYH7b, an evolutionarily ancient member of this myosin family, has been detected in mammalian nonmuscle tissues, and mutations in MYH7b are linked to hereditary hearing loss in compound heterozygous patients. These mutations are the first associated with hearing loss rather than a muscle pathology, and because there are no homologous mutations in other myosin isoforms, their functional effects were unknown. We generated recombinant human MYH7b harboring the D515N or R1651Q hearing loss-associated mutation and studied their effects on motor activity and structural and assembly properties, respectively. The D515N mutation had no effect on steady-state actin-activated ATPase rate or load-dependent detachment kinetics but increased actin sliding velocity because of an increased displacement during the myosin working stroke. Furthermore, we found that the D515N mutation caused an increase in the proportion of myosin heads that occupy the disordered-relaxed state, meaning more myosin heads are available to interact with actin. Although we found no impact of the R1651Q mutation on myosin rod secondary structure or solubility, we observed a striking aggregation phenotype when this mutation was introduced into nonmuscle cells. Our results suggest that each mutation independently affects MYH7b function and structure. Together, these results provide the foundation for further study of a role for MYH7b outside the sarcomere.
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Affiliation(s)
- Lindsey A Lee
- Molecular, Cellular, and Developmental Biology Department, Boulder, Colorado, USA; BioFrontiers Institute, Boulder, Colorado, USA
| | - Samantha K Barrick
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St Louis, Missouri, USA
| | - Ada E Buvoli
- Molecular, Cellular, and Developmental Biology Department, Boulder, Colorado, USA; BioFrontiers Institute, Boulder, Colorado, USA
| | - Jonathan Walklate
- School of Biosciences, University of Kent, Canterbury, United Kingdom
| | - W Tom Stump
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St Louis, Missouri, USA
| | - Michael Geeves
- School of Biosciences, University of Kent, Canterbury, United Kingdom
| | - Michael J Greenberg
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St Louis, Missouri, USA
| | - Leslie A Leinwand
- Molecular, Cellular, and Developmental Biology Department, Boulder, Colorado, USA; BioFrontiers Institute, Boulder, Colorado, USA.
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10
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Barrick SK, Garg A, Greenberg L, Zhang S, Lin CY, Stitziel NO, Greenberg MJ. Functional assays reveal the pathogenic mechanism of a de novo tropomyosin variant identified in patient with dilated cardiomyopathy. J Mol Cell Cardiol 2023; 176:58-67. [PMID: 36739943 DOI: 10.1016/j.yjmcc.2023.01.014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/06/2022] [Revised: 01/09/2023] [Accepted: 01/31/2023] [Indexed: 02/05/2023]
Abstract
Dilated cardiomyopathy (DCM) is a leading cause of heart failure and a major indicator for heart transplant. Human genetic studies have identified over a thousand causal mutations for DCM in genes involved in a variety of cellular processes, including sarcomeric contraction. A substantial clinical challenge is determining the pathogenicity of novel variants in disease-associated genes. This challenge of connecting genotype and phenotype has frustrated attempts to develop effective, mechanism-based treatments for patients. Here, we identified a de novo mutation (T237S) in TPM1, the gene that encodes the thin filament protein tropomyosin, in a patient with DCM and conducted in vitro experiments to characterize the pathogenicity of this novel variant. We expressed recombinant mutant protein, reconstituted it into thin filaments, and examined the effects of the mutation on thin filament function. We show that the mutation reduces the calcium sensitivity of thin filament activation, as previously seen for known pathogenic mutations. Mechanistically, this shift is due to mutation-induced changes in tropomyosin positioning along the thin filament. We demonstrate that the thin filament activator omecamtiv mecarbil restores the calcium sensitivity of thin filaments regulated by the mutant tropomyosin, which lays the foundation for additional experiments to explore the therapeutic potential of this drug for patients harboring the T237S mutation. Taken together, our results suggest that the TPM1 T237S mutation is likely pathogenic and demonstrate how functional in vitro characterization of pathogenic protein variants in the lab might guide precision medicine in the clinic.
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Affiliation(s)
- Samantha K Barrick
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Ankit Garg
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110, USA; Center for Cardiovascular Research, Division of Cardiology, Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Lina Greenberg
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Shanshan Zhang
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Chieh-Yu Lin
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Nathan O Stitziel
- Center for Cardiovascular Research, Division of Cardiology, Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA; Department of Genetics, Washington University School of Medicine, St. Louis, MO 63110, USA; McDonnell Genome Institute, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Michael J Greenberg
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110, USA.
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11
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Modak SS, Greenberg L, Stump W, Li W, Huebsch N, Greenberg MJ. Establishment of an in vivo human engineered heart tissue platform to model iron overload cardiomyopathy. Biophys J 2023; 122:453a-454a. [PMID: 36784327 DOI: 10.1016/j.bpj.2022.11.2441] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/12/2023] Open
Affiliation(s)
- Sayli S Modak
- Biomedical Engineering, Washington University in St. Louis, St. Louis, MO, USA
| | - Lina Greenberg
- Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO, USA
| | - William Stump
- Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO, USA
| | - Weikai Li
- Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO, USA
| | - Nathaniel Huebsch
- Biomedical Engineering, Washington University in St. Louis, St. Louis, MO, USA
| | - Michael J Greenberg
- Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO, USA
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12
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Meller A, Lotthammer JM, Smith LG, Novak B, Lee LA, Kuhn CC, Greenberg L, Leinwand LA, Greenberg MJ, Bowman GR. Drug specificity and affinity are encoded in the probability of cryptic pocket opening in myosin motor domains. eLife 2023; 12:83602. [PMID: 36705568 PMCID: PMC9995120 DOI: 10.7554/elife.83602] [Citation(s) in RCA: 12] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2022] [Accepted: 01/23/2023] [Indexed: 01/28/2023] Open
Abstract
The design of compounds that can discriminate between closely related target proteins remains a central challenge in drug discovery. Specific therapeutics targeting the highly conserved myosin motor family are urgently needed as mutations in at least six of its members cause numerous diseases. Allosteric modulators, like the myosin-II inhibitor blebbistatin, are a promising means to achieve specificity. However, it remains unclear why blebbistatin inhibits myosin-II motors with different potencies given that it binds at a highly conserved pocket that is always closed in blebbistatin-free experimental structures. We hypothesized that the probability of pocket opening is an important determinant of the potency of compounds like blebbistatin. To test this hypothesis, we used Markov state models (MSMs) built from over 2 ms of aggregate molecular dynamics simulations with explicit solvent. We find that blebbistatin's binding pocket readily opens in simulations of blebbistatin-sensitive myosin isoforms. Comparing these conformational ensembles reveals that the probability of pocket opening correctly identifies which isoforms are most sensitive to blebbistatin inhibition and that docking against MSMs quantitatively predicts blebbistatin binding affinities (R2=0.82). In a blind prediction for an isoform (Myh7b) whose blebbistatin sensitivity was unknown, we find good agreement between predicted and measured IC50s (0.67 μM vs. 0.36 μM). Therefore, we expect this framework to be useful for the development of novel specific drugs across numerous protein targets.
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Affiliation(s)
- Artur Meller
- Department of Biochemistry and Molecular Biophysics, Washington University in St. LouisSt LouisUnited States
- Medical Scientist Training Program, Washington University in St. LouisPhiladelphiaUnited States
| | - Jeffrey M Lotthammer
- Department of Biochemistry and Molecular Biophysics, Washington University in St. LouisSt LouisUnited States
| | - Louis G Smith
- Department of Biochemistry and Molecular Biophysics, Washington University in St. LouisSt LouisUnited States
- Department of Biochemistry and Biophysics, University of PennsylvaniaPhiladelphiaUnited States
| | - Borna Novak
- Department of Biochemistry and Molecular Biophysics, Washington University in St. LouisSt LouisUnited States
- Medical Scientist Training Program, Washington University in St. LouisPhiladelphiaUnited States
| | - Lindsey A Lee
- Molecular, Cellular, and Developmental Biology Department, University of Colorado BoulderBoulderUnited States
- BioFrontiers InstituteBoulderUnited States
| | - Catherine C Kuhn
- Department of Biochemistry and Molecular Biophysics, Washington University in St. LouisSt LouisUnited States
| | - Lina Greenberg
- Department of Biochemistry and Molecular Biophysics, Washington University in St. LouisSt LouisUnited States
| | - Leslie A Leinwand
- Molecular, Cellular, and Developmental Biology Department, University of Colorado BoulderBoulderUnited States
- BioFrontiers InstituteBoulderUnited States
| | - Michael J Greenberg
- Department of Biochemistry and Molecular Biophysics, Washington University in St. LouisSt LouisUnited States
| | - Gregory R Bowman
- Department of Biochemistry and Molecular Biophysics, Washington University in St. LouisSt LouisUnited States
- Department of Biochemistry and Biophysics, University of PennsylvaniaPhiladelphiaUnited States
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13
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Clippinger Schulte SR, Scott B, Barrick SK, Stump WT, Blackwell T, Greenberg MJ. Single Molecule Mechanics and Kinetics of Cardiac Myosin Interacting with Regulated Thin Filaments. bioRxiv 2023:2023.01.09.522880. [PMID: 36711892 PMCID: PMC9881944 DOI: 10.1101/2023.01.09.522880] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
The cardiac cycle is a tightly regulated process wherein the heart generates force to pump blood to the body during systole and then relaxes during diastole. Disruption of this finely tuned cycle can lead to a range of diseases including cardiomyopathies and heart failure. Cardiac contraction is driven by the molecular motor myosin, which pulls regulated thin filaments in a calcium-dependent manner. In some muscle and non-muscle myosins, regulatory proteins on actin tune the kinetics, mechanics, and load dependence of the myosin working stroke; however, it is not well understood whether or how thin filament regulatory proteins tune the mechanics of the cardiac myosin motor. To address this critical gap in knowledge, we used single-molecule techniques to measure the kinetics and mechanics of the substeps of the cardiac myosin working stroke in the presence and absence of thin filament regulatory proteins. We found that regulatory proteins gate the calcium-dependent interactions between myosin and the thin filament. At physiologically relevant ATP concentrations, cardiac myosin's mechanics and unloaded kinetics are not affected by thin filament regulatory proteins. We also measured the load-dependent kinetics of cardiac myosin at physiologically relevant ATP concentrations using an isometric optical clamp, and we found that thin filament regulatory proteins do not affect either the identity or magnitude of myosin's primary load-dependent transition. Interestingly, at low ATP concentrations, thin filament regulatory proteins have a small effect on actomyosin dissociation kinetics, suggesting a mechanism beyond simple steric blocking. These results have important implications for both disease modeling and computational models of muscle contraction. Significance Statement Human heart contraction is powered by the molecular motor β-cardiac myosin, which pulls on thin filaments consisting of actin and the regulatory proteins troponin and tropomyosin. In some muscle and non-muscle systems, these regulatory proteins tune the kinetics, mechanics, and load dependence of the myosin working stroke. Despite having a central role in health and disease, it is not well understood whether the mechanics or kinetics of β-cardiac myosin are affected by regulatory proteins. We show that regulatory proteins do not affect the mechanics or load-dependent kinetics of the working stroke at physiologically relevant ATP concentrations; however, they can affect the kinetics at low ATP concentrations, suggesting a mechanism beyond simple steric blocking. This has important implications for modeling of cardiac physiology and diseases.
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14
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Lee LA, Barrick SK, Meller A, Walklate J, Lotthammer JM, Tay JW, Stump WT, Bowman G, Geeves MA, Greenberg MJ, Leinwand LA. Functional divergence of the sarcomeric myosin, MYH7b, supports species-specific biological roles. J Biol Chem 2022; 299:102657. [PMID: 36334627 PMCID: PMC9800208 DOI: 10.1016/j.jbc.2022.102657] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2022] [Revised: 10/14/2022] [Accepted: 10/27/2022] [Indexed: 11/11/2022] Open
Abstract
Myosin heavy chain 7b (MYH7b) is an evolutionarily ancient member of the sarcomeric myosin family, which typically supports striated muscle function. However, in mammals, alternative splicing prevents MYH7b protein production in cardiac and most skeletal muscles and limits expression to a subset of specialized muscles and certain nonmuscle environments. In contrast, MYH7b protein is abundant in python cardiac and skeletal muscles. Although the MYH7b expression pattern diverges in mammals versus reptiles, MYH7b shares high sequence identity across species. So, it remains unclear how mammalian MYH7b function may differ from that of other sarcomeric myosins and whether human and python MYH7b motor functions diverge as their expression patterns suggest. Thus, we generated recombinant human and python MYH7b protein and measured their motor properties to investigate any species-specific differences in activity. Our results reveal that despite having similar working strokes, the MYH7b isoforms have slower actin-activated ATPase cycles and actin sliding velocities than human cardiac β-MyHC. Furthermore, python MYH7b is tuned to have slower motor activity than human MYH7b because of slower kinetics of the chemomechanical cycle. We found that the MYH7b isoforms adopt a higher proportion of myosin heads in the ultraslow, super-relaxed state compared with human cardiac β-MyHC. These findings are supported by molecular dynamics simulations that predict MYH7b preferentially occupies myosin active site conformations similar to those observed in the structurally inactive state. Together, these results suggest that MYH7b is specialized for slow and energy-conserving motor activity and that differential tuning of MYH7b orthologs contributes to species-specific biological roles.
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Affiliation(s)
- Lindsey A. Lee
- Molecular, Cellular, and Developmental Biology Department, Boulder, Colorado, USA,BioFrontiers Institute, University of Colorado Boulder, Boulder, Colorado, USA
| | - Samantha K. Barrick
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St Louis, Missouri, USA
| | - Artur Meller
- The Center for Science and Engineering of Living Systems, Washington University in St Louis, St Louis, Missouri, USA
| | - Jonathan Walklate
- School of Biosciences, University of Kent, Canterbury, United Kingdom
| | - Jeffrey M. Lotthammer
- The Center for Science and Engineering of Living Systems, Washington University in St Louis, St Louis, Missouri, USA
| | - Jian Wei Tay
- BioFrontiers Institute, University of Colorado Boulder, Boulder, Colorado, USA
| | - W. Tom Stump
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St Louis, Missouri, USA
| | - Gregory Bowman
- The Center for Science and Engineering of Living Systems, Washington University in St Louis, St Louis, Missouri, USA,Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Michael A. Geeves
- School of Biosciences, University of Kent, Canterbury, United Kingdom
| | - Michael J. Greenberg
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St Louis, Missouri, USA
| | - Leslie A. Leinwand
- Molecular, Cellular, and Developmental Biology Department, Boulder, Colorado, USA,BioFrontiers Institute, University of Colorado Boulder, Boulder, Colorado, USA,For correspondence: Leslie A. Leinwand
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15
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McAdow J, Yang S, Ou T, Huang G, Dobbs MB, Gurnett CA, Greenberg MJ, Johnson AN. A pathogenic mechanism associated with myopathies and structural birth defects involves TPM2-directed myogenesis. JCI Insight 2022; 7:152466. [PMID: 35579956 PMCID: PMC9309062 DOI: 10.1172/jci.insight.152466] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2021] [Accepted: 05/13/2022] [Indexed: 11/18/2022] Open
Abstract
Nemaline myopathy (NM) is the most common congenital myopathy, characterized by extreme weakness of the respiratory, limb, and facial muscles. Pathogenic variants in Tropomyosin 2 (TPM2), which encodes a skeletal muscle-specific actin binding protein essential for sarcomere function, cause a spectrum of musculoskeletal disorders that include NM as well as cap myopathy, congenital fiber type disproportion, and distal arthrogryposis (DA). The in vivo pathomechanisms underlying TPM2-related disorders are unknown, so we expressed a series of dominant, pathogenic TPM2 variants in Drosophila embryos and found 4 variants significantly affected muscle development and muscle function. Transient overexpression of the 4 variants also disrupted the morphogenesis of mouse myotubes in vitro and negatively affected zebrafish muscle development in vivo. We used transient overexpression assays in zebrafish to characterize 2 potentially novel TPM2 variants and 1 recurring variant that we identified in patients with DA (V129A, E139K, A155T, respectively) and found these variants caused musculoskeletal defects similar to those of known pathogenic variants. The consistency of musculoskeletal phenotypes in our assays correlated with the severity of clinical phenotypes observed in our patients with DA, suggesting disrupted myogenesis is a potentially novel pathomechanism of TPM2 disorders and that our myogenic assays can predict the clinical severity of TPM2 variants.
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Affiliation(s)
- Jennifer McAdow
- Department of Developmental Biology, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Shuo Yang
- Department of Developmental Biology, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Tiffany Ou
- Department of Developmental Biology, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Gary Huang
- Department of Developmental Biology, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Matthew B Dobbs
- Paley Orthopedic and Spine Institute, West Palm Beach, Florida, USA
| | - Christina A Gurnett
- Department of Neurology.,Department of Orthopedic Surgery.,Department of Pediatrics, and
| | - Michael J Greenberg
- Department of Biochemistry and Molecular Biophysics, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Aaron N Johnson
- Department of Developmental Biology, Washington University in St. Louis, St. Louis, Missouri, USA
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16
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Lotthammer JM, Meller A, Greenberg MJ, Bowman GR. Exploring the myosin active/auto-inhibited state equilibrium by Markov state modeling. Biophys J 2022. [DOI: 10.1016/j.bpj.2021.11.1442] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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17
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Barrick SK, Greenberg MJ. Structural differences in vinculin and metavinculin actin-binding domains explored by molecular dynamics simulations. Biophys J 2022. [DOI: 10.1016/j.bpj.2021.11.2649] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022] Open
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18
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Greenberg L, Stump W, Bredemeyer AL, Lavine KJ, Greenberg MJ. Harnessing multiscale models of a dilated cardiomyopathy mutation for precision medicine. Biophys J 2022. [DOI: 10.1016/j.bpj.2021.11.780] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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19
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Papadaki M, Kampaengsri T, Barrick SK, Campbell SG, von Lewinski D, Rainer PP, Harris SP, Greenberg MJ, Kirk JA. Myofilament glycation in diabetes reduces contractility by inhibiting tropomyosin movement, is rescued by cMyBPC domains. J Mol Cell Cardiol 2022; 162:1-9. [PMID: 34487755 PMCID: PMC8766917 DOI: 10.1016/j.yjmcc.2021.08.012] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/22/2021] [Revised: 07/21/2021] [Accepted: 08/19/2021] [Indexed: 01/17/2023]
Abstract
Diabetes doubles the risk of developing heart failure (HF). As the prevalence of diabetes grows, so will HF unless the mechanisms connecting these diseases can be identified. Methylglyoxal (MG) is a glycolysis by-product that forms irreversible modifications on lysine and arginine, called glycation. We previously found that myofilament MG glycation causes sarcomere contractile dysfunction and is increased in patients with diabetes and HF. The aim of this study was to discover the molecular mechanisms by which MG glycation of myofilament proteins cause sarcomere dysfunction and to identify therapeutic avenues to compensate. In humans with type 2 diabetes without HF, we found increased glycation of sarcomeric actin compared to non-diabetics and it correlated with decreased calcium sensitivity. Depressed calcium sensitivity is pathogenic for HF, therefore myofilament glycation represents a promising therapeutic target to inhibit the development of HF in diabetics. To identify possible therapeutic targets, we further defined the molecular actions of myofilament glycation. Skinned myocytes exposed to 100 μM MG exhibited decreased calcium sensitivity, maximal calcium-activated force, and crossbridge kinetics. Replicating MG's functional affects using a computer simulation of sarcomere function predicted simultaneous decreases in tropomyosin's blocked-to-closed rate transition and crossbridge duty cycle were consistent with all experimental findings. Stopped-flow experiments and ATPase activity confirmed MG decreased the blocked-to-closed transition rate. Currently, no therapeutics target tropomyosin, so as proof-of-principal, we used a n-terminal peptide of myosin-binding protein C, previously shown to alter tropomyosin's position on actin. C0C2 completely rescued MG-induced calcium desensitization, suggesting a possible treatment for diabetic HF.
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Affiliation(s)
- Maria Papadaki
- Department of Cell and Molecular Physiology, Loyola University of Chicago, Maywood, Illinois, USA
| | - Theerachat Kampaengsri
- Department of Cell and Molecular Physiology, Loyola University of Chicago, Maywood, Illinois, USA
| | - Samantha K. Barrick
- Department of Biochemistry and Molecular Biophysics, Washington University in St Louis, St Louis, Missouri, USA
| | - Stuart G. Campbell
- Department of Bioengineering, Yale University, New Haven, Connecticut, USA
| | | | - Peter P. Rainer
- Division of Cardiology, Medical University of Graz, Graz, Austria
| | - Samantha P. Harris
- Department of Cellular and Molecular Medicine, The University of Arizona, Tucson, Arizona, USA
| | - Michael J. Greenberg
- Department of Biochemistry and Molecular Biophysics, Washington University in St Louis, St Louis, Missouri, USA
| | - Jonathan A. Kirk
- Department of Cell and Molecular Physiology, Loyola University of Chicago, Maywood, Illinois, USA,Corresponding Author: Jonathan A. Kirk, Ph.D., Department of Cell and Molecular Physiology, Loyola University Chicago Stritch School of Medicine, Center for Translational Research and Education, Room 522, 2160 S. First Ave., Maywood, IL 60153, Ph: 708-216-6348,
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20
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Abstract
Cardiac myosin is the molecular motor that powers heart contraction by converting chemical energy from ATP hydrolysis into mechanical force. The power output of the heart is tightly regulated to meet the physiological needs of the body. Recent multiscale studies spanning from molecules to tissues have revealed complex regulatory mechanisms that fine-tune cardiac contraction, in which myosin not only generates power output but also plays an active role in its regulation. Thus, myosin is both shaped by and actively involved in shaping its mechanical environment. Moreover, these studies have shown that cardiac myosin-generated tension affects physiological processes beyond muscle contraction. Here, we review these novel regulatory mechanisms, as well as the roles that myosin-based force generation and mechanotransduction play in development and disease. We describe how key intra- and intermolecular interactions contribute to the regulation of myosin-based contractility and the role of mechanical forces in tuning myosin function. We also discuss the emergence of cardiac myosin as a drug target for diseases including heart failure, leading to the discovery of therapeutics that directly tune myosin contractility. Finally, we highlight some of the outstanding questions that must be addressed to better understand myosin's functions and regulation, and we discuss prospects for translating these discoveries into precision medicine therapeutics targeting contractility and mechanotransduction.
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Affiliation(s)
- Samantha K Barrick
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Michael J Greenberg
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri, USA.
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21
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Greenberg L, Stump WT, Bredemeyer AL, Lavine KJ, Greenberg MJ. Abstract P439: Harnessing Multiscale Models Of A Dilated Cardiomyopathy Mutation For Precision Medicine. Circ Res 2021. [DOI: 10.1161/res.129.suppl_1.p439] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Familial dilated cardiomyopathy (DCM) is a leading cause of both adult and pediatric heart failure. Currently, there is no cure for DCM, and the 5-year transplant free survival rate is <50%. There is therefore an outstanding need to develop new therapeutics. Prior studies have established a strong genetic basis for DCM and identified causative genetic mutations. These observations provide unique opportunities to apply precision medicine approaches that target and circumvent the effects of deleterious mutations. Here, we used a multiscale approach to study the consequences of a human mutation in troponin T that causes DCM, ΔK210. We found that at the molecular scale ΔK210 changes the positioning of tropomyosin along the thin filament, leading to molecular hypocontractility. Using genome edited human stem cell derived cardiomyocytes heterozygous for the mutation, we show reduced cellular contractility at the single cell and tissue levels. Importantly, we demonstrate that mutant tissues show a reduced Frank-Starling response, increased stiffness, and misaligned myocytes. Based on our molecular mechanism, we hypothesized that treatment of ΔK210 with Omecamtiv Mecarbil (OM), a thin filament activator in clinical trials for heart failure, would improve the function of mutant tissues. We found that treatment of ΔK210 molecular complexes and tissues with OM causes a dose-dependent increase in cardiac function, reversing the mutation-induced contractile defect. Taken together, our study demonstrates how mechanistic molecular studies can be harnessed to identify precision medicine therapeutics.
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22
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Barrick SK, Greenberg L, Greenberg MJ. A troponin T variant linked with pediatric dilated cardiomyopathy reduces the coupling of thin filament activation to myosin and calcium binding. Mol Biol Cell 2021; 32:1677-1689. [PMID: 34161147 PMCID: PMC8684737 DOI: 10.1091/mbc.e21-02-0082] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Dilated cardiomyopathy (DCM) is a significant cause of pediatric heart failure. Mutations in proteins that regulate cardiac muscle contraction can cause DCM; however, the mechanisms by which molecular-level mutations contribute to cellular dysfunction are not well understood. Better understanding of these mechanisms might enable the development of targeted therapeutics that benefit patient subpopulations with mutations that cause common biophysical defects. We examined the molecular- and cellular-level impacts of a troponin T variant associated with pediatric-onset DCM, R134G. The R134G variant decreased calcium sensitivity in an in vitro motility assay. Using stopped-flow and steady-state fluorescence measurements, we determined the molecular mechanism of the altered calcium sensitivity: R134G decouples calcium binding by troponin from the closed-to-open transition of the thin filament and decreases the cooperativity of myosin binding to regulated thin filaments. Consistent with the prediction that these effects would cause reduced force per sarcomere, cardiomyocytes carrying the R134G mutation are hypocontractile. They also show hallmarks of DCM that lie downstream of the initial insult, including disorganized sarcomeres and cellular hypertrophy. These results reinforce the importance of multiscale studies to fully understand mechanisms underlying human disease and highlight the value of mechanism-based precision medicine approaches for DCM.
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Affiliation(s)
- Samantha K Barrick
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110
| | - Lina Greenberg
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110
| | - Michael J Greenberg
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110
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23
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Clippinger SR, Cloonan PE, Wang W, Greenberg L, Stump WT, Angsutararux P, Nerbonne JM, Greenberg MJ. Mechanical dysfunction of the sarcomere induced by a pathogenic mutation in troponin T drives cellular adaptation. J Gen Physiol 2021; 153:211992. [PMID: 33856419 PMCID: PMC8054178 DOI: 10.1085/jgp.202012787] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2020] [Accepted: 03/18/2021] [Indexed: 12/15/2022] Open
Abstract
Familial hypertrophic cardiomyopathy (HCM), a leading cause of sudden cardiac death, is primarily caused by mutations in sarcomeric proteins. The pathogenesis of HCM is complex, with functional changes that span scales, from molecules to tissues. This makes it challenging to deconvolve the biophysical molecular defect that drives the disease pathogenesis from downstream changes in cellular function. In this study, we examine an HCM mutation in troponin T, R92Q, for which several models explaining its effects in disease have been put forward. We demonstrate that the primary molecular insult driving disease pathogenesis is mutation-induced alterations in tropomyosin positioning, which causes increased molecular and cellular force generation during calcium-based activation. Computational modeling shows that the increased cellular force is consistent with the molecular mechanism. These changes in cellular contractility cause downstream alterations in gene expression, calcium handling, and electrophysiology. Taken together, our results demonstrate that molecularly driven changes in mechanical tension drive the early disease pathogenesis of familial HCM, leading to activation of adaptive mechanobiological signaling pathways.
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Affiliation(s)
- Sarah R Clippinger
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO
| | - Paige E Cloonan
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO
| | - Wei Wang
- Cardiovascular Division, Department of Medicine, Washington University School of Medicine, St. Louis, MO
| | - Lina Greenberg
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO
| | - W Tom Stump
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO
| | | | - Jeanne M Nerbonne
- Cardiovascular Division, Department of Medicine, Washington University School of Medicine, St. Louis, MO
| | - Michael J Greenberg
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO
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24
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Bailey AL, Dmytrenko O, Greenberg L, Bredemeyer AL, Ma P, Liu J, Penna V, Winkler ES, Sviben S, Brooks E, Nair AP, Heck KA, Rali AS, Simpson L, Saririan M, Hobohm D, Stump WT, Fitzpatrick JA, Xie X, Zhang X, Shi PY, Hinson JT, Gi WT, Schmidt C, Leuschner F, Lin CY, Diamond MS, Greenberg MJ, Lavine KJ. SARS-CoV-2 Infects Human Engineered Heart Tissues and Models COVID-19 Myocarditis. JACC Basic Transl Sci 2021; 6:331-345. [PMID: 33681537 PMCID: PMC7909907 DOI: 10.1016/j.jacbts.2021.01.002] [Citation(s) in RCA: 93] [Impact Index Per Article: 31.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/03/2020] [Revised: 01/05/2021] [Accepted: 01/05/2021] [Indexed: 02/06/2023]
Abstract
There is ongoing debate as to whether cardiac complications of coronavirus disease-2019 (COVID-19) result from myocardial viral infection or are secondary to systemic inflammation and/or thrombosis. We provide evidence that cardiomyocytes are infected in patients with COVID-19 myocarditis and are susceptible to severe acute respiratory syndrome coronavirus 2. We establish an engineered heart tissue model of COVID-19 myocardial pathology, define mechanisms of viral pathogenesis, and demonstrate that cardiomyocyte severe acute respiratory syndrome coronavirus 2 infection results in contractile deficits, cytokine production, sarcomere disassembly, and cell death. These findings implicate direct infection of cardiomyocytes in the pathogenesis of COVID-19 myocardial pathology and provides a model system to study this emerging disease.
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Affiliation(s)
- Adam L Bailey
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Oleksandr Dmytrenko
- Cardiovascular Division, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Lina Greenberg
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Andrea L Bredemeyer
- Cardiovascular Division, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Pan Ma
- Cardiovascular Division, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Jing Liu
- Cardiovascular Division, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Vinay Penna
- Cardiovascular Division, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Emma S Winkler
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Sanja Sviben
- Washington University Center for Cellular Imaging, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Erin Brooks
- Department of Pathology & Laboratory Medicine, University of Wisconsin Hospital and Clinics, Madison, Wisconsin, USA
| | - Ajith P Nair
- Department of Medicine, Baylor College of Medicine, Houston, Texas, USA
| | - Kent A Heck
- Department of Pathology, Baylor College of Medicine, Houston, Texas, USA
| | - Aniket S Rali
- Department of Medicine, Vanderbilt University, Nashville, Tennessee, USA
| | - Leo Simpson
- Department of Medicine, Baylor College of Medicine, Houston, Texas, USA
| | | | - Dan Hobohm
- Valleywise Health/Creighton University, Phoenix, Arizona, USA
| | - W Tom Stump
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri, USA
| | - James A Fitzpatrick
- Washington University Center for Cellular Imaging, Washington University School of Medicine, St. Louis, Missouri, USA.,Departments of Neuroscience, Cell Biology & Physiology, and Biomedical Engineering, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Xuping Xie
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, Texas, USA
| | - Xianwen Zhang
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, Texas, USA
| | - Pei-Yong Shi
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, Texas, USA
| | - J Travis Hinson
- Departments of Cardiology, Genetics and Genome Sciences, UConn Health, Farmington, Connecticut, USA.,The Jackson Laboratory for Genomic Medicine, Farmington, Connecticut, USA
| | - Weng-Tein Gi
- Department of Internal Medicine III, University Hospital Heidelberg, University of Heidelberg, Heidelberg, Germany
| | - Constanze Schmidt
- Department of Internal Medicine III, University Hospital Heidelberg, University of Heidelberg, Heidelberg, Germany
| | - Florian Leuschner
- Department of Internal Medicine III, University Hospital Heidelberg, University of Heidelberg, Heidelberg, Germany
| | - Chieh-Yu Lin
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Michael S Diamond
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, Missouri, USA.,Cardiovascular Division, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, USA.,Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Michael J Greenberg
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Kory J Lavine
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, Missouri, USA.,Cardiovascular Division, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, USA.,Department of Developmental Biology, Washington University School of Medicine, St. Louis, Missouri, USA
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25
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Clippinger SR, Stump W, Blackwell T, Greenberg MJ. Step Size and Kinetics of Cardiac Myosin Crossbridges are not Affected by Troponin and Tropomyosin. Biophys J 2021. [DOI: 10.1016/j.bpj.2020.11.791] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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26
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Greenberg MJ, Tardiff JC. Complexity in genetic cardiomyopathies and new approaches for mechanism-based precision medicine. J Gen Physiol 2021; 153:211741. [PMID: 33512404 PMCID: PMC7852459 DOI: 10.1085/jgp.202012662] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2020] [Accepted: 01/07/2021] [Indexed: 12/11/2022] Open
Abstract
Genetic cardiomyopathies have been studied for decades, and it has become increasingly clear that these progressive diseases are more complex than originally thought. These complexities can be seen both in the molecular etiologies of these disorders and in the clinical phenotypes observed in patients. While these disorders can be caused by mutations in cardiac genes, including ones encoding sarcomeric proteins, the disease presentation varies depending on the patient mutation, where mutations even within the same gene can cause divergent phenotypes. Moreover, it is challenging to connect the mutation-induced molecular insult that drives the disease pathogenesis with the various compensatory and maladaptive pathways that are activated during the course of the subsequent progressive, pathogenic cardiac remodeling. These inherent complexities have frustrated our ability to understand and develop broadly effective treatments for these disorders. It has been proposed that it might be possible to improve patient outcomes by adopting a precision medicine approach. Here, we lay out a practical framework for such an approach, where patient subpopulations are binned based on common underlying biophysical mechanisms that drive the molecular disease pathogenesis, and we propose that this function-based approach will enable the development of targeted therapeutics that ameliorate these effects. We highlight several mutations to illustrate the need for mechanistic molecular experiments that span organizational and temporal scales, and we describe recent advances in the development of novel therapeutics based on functional targets. Finally, we describe many of the outstanding questions for the field and how fundamental mechanistic studies, informed by our more nuanced understanding of the clinical disorders, will play a central role in realizing the potential of precision medicine for genetic cardiomyopathies.
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Affiliation(s)
- Michael J Greenberg
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO
| | - Jil C Tardiff
- Department of Biomedical Engineering, University of Arizona, Tucson, AZ.,Department of Medicine, University of Arizona, Tucson, AZ
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27
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Bailey AL, Dmytrenko O, Greenberg L, Bredemeyer AL, Ma P, Liu J, Penna V, Lai L, Winkler ES, Sviben S, Brooks E, Nair AP, Heck KA, Rali AS, Simpson L, Saririan M, Hobohm D, Stump WT, Fitzpatrick JA, Xie X, Shi PY, Hinson JT, Gi WT, Schmidt C, Leuschner F, Lin CY, Diamond MS, Greenberg MJ, Lavine KJ. SARS-CoV-2 Infects Human Engineered Heart Tissues and Models COVID-19 Myocarditis. bioRxiv 2020. [PMID: 33173875 DOI: 10.1101/2020.11.04.364315] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Epidemiological studies of the COVID-19 pandemic have revealed evidence of cardiac involvement and documented that myocardial injury and myocarditis are predictors of poor outcomes. Nonetheless, little is understood regarding SARS-CoV-2 tropism within the heart and whether cardiac complications result directly from myocardial infection. Here, we develop a human engineered heart tissue model and demonstrate that SARS-CoV-2 selectively infects cardiomyocytes. Viral infection is dependent on expression of angiotensin-I converting enzyme 2 (ACE2) and endosomal cysteine proteases, suggesting an endosomal mechanism of cell entry. After infection with SARS-CoV-2, engineered tissues display typical features of myocarditis, including cardiomyocyte cell death, impaired cardiac contractility, and innate immune cell activation. Consistent with these findings, autopsy tissue obtained from individuals with COVID-19 myocarditis demonstrated cardiomyocyte infection, cell death, and macrophage-predominate immune cell infiltrate. These findings establish human cardiomyocyte tropism for SARS-CoV-2 and provide an experimental platform for interrogating and mitigating cardiac complications of COVID-19.
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28
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Abstract
Dilated cardiomyopathy (DCM) is a major cause of heart failure and cardiovascular mortality. In the past 20 years, there has been an overwhelming focus on developing therapeutics that target common downstream disease pathways thought to be involved in all forms of heart failure independent of the initial etiology. While this strategy is effective at the population level, individual responses vary tremendously and only approximately one third of patients receive benefit from modern heart failure treatments. In this perspective, we propose that DCM should be considered as a collection of diseases with a common phenotype of left ventricular dilation and systolic dysfunction rather than a single disease entity, and that mechanism-based classification of disease subtypes will revolutionize our understanding and clinical approach towards DCM. We discuss how these efforts are central to realizing the potential of precision medicine and how they are empowered by the development of new tools that allow investigators to strategically employ genomic and transcriptomic information. Finally, we outline an investigational strategy to (1) define DCM at the patient level, (2) develop new tools to model and mechanistically dissect subtypes of human heart failure, and (3) harness these insights for the development of precision therapeutics.
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Affiliation(s)
- Kory J Lavine
- Center for Cardiovascular Research, Cardiovascular Division, Department of Medicine, Washington University School of Medicine, 660 S. Euclid Ave., Campus Box 8086, St. Louis, MO, 63110, USA.
| | - Michael J Greenberg
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, 660 S. Euclid Ave., Campus Box 8231, St. Louis, MO, 63110, USA.
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29
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Porter JR, Meller A, Zimmerman MI, Greenberg MJ, Bowman GR. Conformational distributions of isolated myosin motor domains encode their mechanochemical properties. eLife 2020; 9:e55132. [PMID: 32479265 PMCID: PMC7259954 DOI: 10.7554/elife.55132] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2020] [Accepted: 05/04/2020] [Indexed: 01/25/2023] Open
Abstract
Myosin motor domains perform an extraordinary diversity of biological functions despite sharing a common mechanochemical cycle. Motors are adapted to their function, in part, by tuning the thermodynamics and kinetics of steps in this cycle. However, it remains unclear how sequence encodes these differences, since biochemically distinct motors often have nearly indistinguishable crystal structures. We hypothesized that sequences produce distinct biochemical phenotypes by modulating the relative probabilities of an ensemble of conformations primed for different functional roles. To test this hypothesis, we modeled the distribution of conformations for 12 myosin motor domains by building Markov state models (MSMs) from an unprecedented two milliseconds of all-atom, explicit-solvent molecular dynamics simulations. Comparing motors reveals shifts in the balance between nucleotide-favorable and nucleotide-unfavorable P-loop conformations that predict experimentally measured duty ratios and ADP release rates better than sequence or individual structures. This result demonstrates the power of an ensemble perspective for interrogating sequence-function relationships.
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Affiliation(s)
- Justin R Porter
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine in St. LouisSt. LouisUnited States
| | - Artur Meller
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine in St. LouisSt. LouisUnited States
| | - Maxwell I Zimmerman
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine in St. LouisSt. LouisUnited States
| | - Michael J Greenberg
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine in St. LouisSt. LouisUnited States
| | - Gregory R Bowman
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine in St. LouisSt. LouisUnited States
- Center for the Science and Engineering of Living Systems, Washington University in St. LouisSt. LouisUnited States
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30
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Ezekian JE, Clippinger SR, Garcia JM, Yang Q, Denfield S, Jeewa A, Dreyer WJ, Zou W, Fan Y, Allen HD, Kim JJ, Greenberg MJ, Landstrom AP. Variant R94C in TNNT2-Encoded Troponin T Predisposes to Pediatric Restrictive Cardiomyopathy and Sudden Death Through Impaired Thin Filament Relaxation Resulting in Myocardial Diastolic Dysfunction. J Am Heart Assoc 2020; 9:e015111. [PMID: 32098556 PMCID: PMC7335540 DOI: 10.1161/jaha.119.015111] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Background Pediatric‐onset restrictive cardiomyopathy (RCM) is associated with high mortality, but underlying mechanisms of disease are under investigated. RCM‐associated diastolic dysfunction secondary to variants in TNNT2‐encoded cardiac troponin T (TNNT2) is poorly described. Methods and Results Genetic analysis of a proband and kindred with RCM identified TNNT2‐R94C, which cosegregated in a family with 2 generations of RCM, ventricular arrhythmias, and sudden death. TNNT2‐R94C was absent among large, population‐based cohorts Genome Aggregation Database (gnomAD) and predicted to be pathologic by in silico modeling. Biophysical experiments using recombinant human TNNT2‐R94C demonstrated impaired cardiac regulation at the molecular level attributed to reduced calcium‐dependent blocking of myosin's interaction with the thin filament. Computational modeling predicted a shift in the force‐calcium curve for the R94C mutant toward submaximal calcium activation compared within the wild type, suggesting low levels of muscle activation even at resting calcium concentrations and hypercontractility following activation by calcium. Conclusions The pathogenic TNNT2‐R94C variant activates thin‐filament–mediated sarcomeric contraction at submaximal calcium concentrations, likely resulting in increased muscle tension during diastole and hypercontractility during systole. This describes the proximal biophysical mechanism for development of RCM in this family.
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Affiliation(s)
- Jordan E Ezekian
- Division of Paediatric Cardiology Department of Pediatrics Duke University School of Medicine Durham NC
| | - Sarah R Clippinger
- Department of Biochemistry and Molecular Biophysics Washington University in St. Louis St. Louis MO
| | - Jaquelin M Garcia
- Department of Biochemistry and Molecular Biophysics Washington University in St. Louis St. Louis MO
| | - Qixin Yang
- Division of Paediatric Cardiology Department of Pediatrics Duke University School of Medicine Durham NC
| | - Susan Denfield
- Department of Pediatrics The Lillie Frank Abercrombie Section of Pediatric Cardiology Baylor College of Medicine Houston TX
| | - Aamir Jeewa
- Department of Pediatrics The Hospital for Sick Children Toronto Ontario Canada
| | - William J Dreyer
- Department of Pediatrics The Lillie Frank Abercrombie Section of Pediatric Cardiology Baylor College of Medicine Houston TX
| | - Wenxin Zou
- Department of Pediatrics The Lillie Frank Abercrombie Section of Pediatric Cardiology Baylor College of Medicine Houston TX
| | - Yuxin Fan
- Department of Pediatrics The Lillie Frank Abercrombie Section of Pediatric Cardiology Baylor College of Medicine Houston TX
| | - Hugh D Allen
- Department of Pediatrics The Lillie Frank Abercrombie Section of Pediatric Cardiology Baylor College of Medicine Houston TX
| | - Jeffrey J Kim
- Department of Pediatrics The Lillie Frank Abercrombie Section of Pediatric Cardiology Baylor College of Medicine Houston TX
| | - Michael J Greenberg
- Department of Biochemistry and Molecular Biophysics Washington University in St. Louis St. Louis MO
| | - Andrew P Landstrom
- Division of Paediatric Cardiology Department of Pediatrics Duke University School of Medicine Durham NC.,Department of Cell Biology Duke University School of Medicine Durham NC
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31
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Barrick SK, Greenberg L, Greenberg MJ. Distinct Mutation-Specific Effects on Thin Filament Activation Lead to Dilated Cardiomyopathy Phenotype in Cells. Biophys J 2020. [DOI: 10.1016/j.bpj.2019.11.1835] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
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32
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Porter JR, Meller A, Zimmerman MI, Greenberg MJ, Bowman G. Myosin Motors’ Kinetic Diversity is Encoded by the Conformational Dynamics of the Motor Domain. Biophys J 2020. [DOI: 10.1016/j.bpj.2019.11.2436] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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33
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Stump W, Blackwell T, Clippinger SR, Greenberg MJ. Design of An Optical Tweezers System with Fast Digital Feedback for Studying the Mechanochemistry of Cardiac Myosin. Biophys J 2020. [DOI: 10.1016/j.bpj.2019.11.3224] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
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34
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Clippinger SR, Cloonan PE, Greenberg L, Ernst M, Stump WT, Greenberg MJ. Disrupted mechanobiology links the molecular and cellular phenotypes in familial dilated cardiomyopathy. Proc Natl Acad Sci U S A 2019; 116:17831-17840. [PMID: 31427533 PMCID: PMC6731759 DOI: 10.1073/pnas.1910962116] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Familial dilated cardiomyopathy (DCM) is a leading cause of sudden cardiac death and a major indicator for heart transplant. The disease is frequently caused by mutations of sarcomeric proteins; however, it is not well understood how these molecular mutations lead to alterations in cellular organization and contractility. To address this critical gap in our knowledge, we studied the molecular and cellular consequences of a DCM mutation in troponin-T, ΔK210. We determined the molecular mechanism of ΔK210 and used computational modeling to predict that the mutation should reduce the force per sarcomere. In mutant cardiomyocytes, we found that ΔK210 not only reduces contractility but also causes cellular hypertrophy and impairs cardiomyocytes' ability to adapt to changes in substrate stiffness (e.g., heart tissue fibrosis that occurs with aging and disease). These results help link the molecular and cellular phenotypes and implicate alterations in mechanosensing as an important factor in the development of DCM.
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Affiliation(s)
- Sarah R Clippinger
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110
| | - Paige E Cloonan
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110
| | - Lina Greenberg
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110
| | - Melanie Ernst
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110
| | - W Tom Stump
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110
| | - Michael J Greenberg
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110
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35
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Porter JR, Moeder KE, Sibbald CA, Zimmerman MI, Hart KM, Greenberg MJ, Bowman GR. Cooperative changes in solvent exposure identify cryptic pockets, conformational switches and allosteric coupling. Acta Crystallogr A Found Adv 2019. [DOI: 10.1107/s0108767319095795] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/03/2023] Open
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36
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Barrick SK, Clippinger SR, Greenberg L, Greenberg MJ. Computational Tool to Study Perturbations in Muscle Regulation and Its Application to Heart Disease. Biophys J 2019; 116:2246-2252. [PMID: 31126584 PMCID: PMC6588827 DOI: 10.1016/j.bpj.2019.05.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2019] [Revised: 04/29/2019] [Accepted: 05/01/2019] [Indexed: 11/21/2022] Open
Abstract
Striated muscle contraction occurs when myosin thick filaments bind to thin filaments in the sarcomere and generate pulling forces. This process is regulated by calcium, and it can be perturbed by pathological conditions (e.g., myopathies), physiological adaptations (e.g., β-adrenergic stimulation), and pharmacological interventions. Therefore, it is important to have a methodology to robustly determine the impact of these perturbations and statistically evaluate their effects. Here, we present an approach to measure the equilibrium constants that govern muscle activation, estimate uncertainty in these parameters, and statistically test the effects of perturbations. We provide a MATLAB-based computational tool for these analyses, along with easy-to-follow tutorials that make this approach accessible. The hypothesis testing and error estimation approaches described here are broadly applicable, and the provided tools work with other types of data, including cellular measurements. To demonstrate the utility of the approach, we apply it to elucidate the biophysical mechanism of a mutation that causes familial hypertrophic cardiomyopathy. This approach is generally useful for studying muscle diseases and therapeutic interventions that target muscle contraction.
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Affiliation(s)
- Samantha K Barrick
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri
| | - Sarah R Clippinger
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri
| | - Lina Greenberg
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri
| | - Michael J Greenberg
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri.
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37
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Barrick SK, Greenberg MJ. Molecular Mechanism of a Mutation Implicated in Pediatric-Onset Heart Disesase. Biophys J 2019. [DOI: 10.1016/j.bpj.2018.11.648] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
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38
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Porter JR, Moeder KE, Sibbald CA, Zimmerman MI, Hart KM, Greenberg MJ, Bowman GR. Cooperative Changes in Solvent Exposure Identify Cryptic Pockets, Switches, and Allosteric Coupling. Biophys J 2019; 116:818-830. [PMID: 30744991 DOI: 10.1016/j.bpj.2018.11.3144] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2018] [Revised: 11/09/2018] [Accepted: 11/14/2018] [Indexed: 01/19/2023] Open
Abstract
Proteins are dynamic molecules that undergo conformational changes to a broad spectrum of different excited states. Unfortunately, the small populations of these states make it difficult to determine their structures or functional implications. Computer simulations are an increasingly powerful means to identify and characterize functionally relevant excited states. However, this advance has uncovered a further challenge: it can be extremely difficult to identify the most salient features of large simulation data sets. We reasoned that many functionally relevant conformational changes are likely to involve large, cooperative changes to the surfaces that are available to interact with potential binding partners. To examine this hypothesis, we introduce a method that returns a prioritized list of potentially functional conformational changes by segmenting protein structures into clusters of residues that undergo cooperative changes in their solvent exposure, along with the hierarchy of interactions between these groups. We term these groups exposons to distinguish them from other types of clusters that arise in this analysis and others. We demonstrate, using three different model systems, that this method identifies experimentally validated and functionally relevant conformational changes, including conformational switches, allosteric coupling, and cryptic pockets. Our results suggest that key functional sites are hubs in the network of exposons. As a further test of the predictive power of this approach, we apply it to discover cryptic allosteric sites in two different β-lactamase enzymes that are widespread sources of antibiotic resistance. Experimental tests confirm our predictions for both systems. Importantly, we provide the first evidence, to our knowledge, for a cryptic allosteric site in CTX-M-9 β-lactamase. Experimentally testing this prediction did not require any mutations and revealed that this site exerts the most potent allosteric control over activity of any pockets found in β-lactamases to date. Discovery of a similar pocket that was previously overlooked in the well-studied TEM-1 β-lactamase demonstrates the utility of exposons.
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Affiliation(s)
- Justin R Porter
- Department of Biochemistry & Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri
| | - Katelyn E Moeder
- Department of Biochemistry & Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri
| | - Carrie A Sibbald
- Department of Biochemistry & Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri
| | - Maxwell I Zimmerman
- Department of Biochemistry & Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri
| | - Kathryn M Hart
- Department of Chemistry, Williams College, Williamstown, Massachusetts
| | - Michael J Greenberg
- Department of Biochemistry & Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri
| | - Gregory R Bowman
- Department of Biochemistry & Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri; Department of Biomedical Engineering and Center for Biological Systems Engineering, Washington University in St. Louis, St. Louis, Missouri.
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39
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Woody MS, Greenberg MJ, Barua B, Winkelmann DA, Goldman YE, Ostap EM. Positive cardiac inotrope omecamtiv mecarbil activates muscle despite suppressing the myosin working stroke. Nat Commun 2018; 9:3838. [PMID: 30242219 PMCID: PMC6155018 DOI: 10.1038/s41467-018-06193-2] [Citation(s) in RCA: 87] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2018] [Accepted: 08/21/2018] [Indexed: 02/05/2023] Open
Abstract
Omecamtiv mecarbil (OM) is a positive cardiac inotrope in phase-3 clinical trials for treatment of heart failure. Although initially described as a direct myosin activator, subsequent studies are at odds with this description and do not explain OM-mediated increases in cardiac performance. Here we show, via single-molecule, biophysical experiments on cardiac myosin, that OM suppresses myosin's working stroke and prolongs actomyosin attachment 5-fold, which explains inhibitory actions of the drug observed in vitro. OM also causes the actin-detachment rate to become independent of both applied load and ATP concentration. Surprisingly, increased myocardial force output in the presence of OM can be explained by cooperative thin-filament activation by OM-inhibited myosin molecules. Selective suppression of myosin is an unanticipated route to muscle activation that may guide future development of therapeutic drugs.
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Affiliation(s)
- Michael S Woody
- Graduate Group in Biochemistry and Molecular Biophysics, Perelman School of Medicine, University of Pennsylvania, 700A Clinical Research Building, Philadelphia, PA, 19104-6085, USA
| | - Michael J Greenberg
- Pennsylvania Muscle Institute, Perelman School of Medicine, University of Pennsylvania, 700A Clinical Research Building, Philadelphia, PA, 19104-6085, USA.,Department of Biochemistry and Molecular Biophysics, Washington University in Saint Louis, St. Louis, 63110, MO, USA
| | - Bipasha Barua
- Department of Pathology and Laboratory Medicine, Robert Wood Johnson Medical School, Rutgers University, 675 Hoes Lane, Piscataway, NJ, 08854, USA
| | - Donald A Winkelmann
- Department of Pathology and Laboratory Medicine, Robert Wood Johnson Medical School, Rutgers University, 675 Hoes Lane, Piscataway, NJ, 08854, USA
| | - Yale E Goldman
- Pennsylvania Muscle Institute, Perelman School of Medicine, University of Pennsylvania, 700A Clinical Research Building, Philadelphia, PA, 19104-6085, USA.
| | - E Michael Ostap
- Pennsylvania Muscle Institute, Perelman School of Medicine, University of Pennsylvania, 700A Clinical Research Building, Philadelphia, PA, 19104-6085, USA.
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40
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Greenberg MJ, Daily NJ, Wang A, Conway MK, Wakatsuki T. Genetic and Tissue Engineering Approaches to Modeling the Mechanics of Human Heart Failure for Drug Discovery. Front Cardiovasc Med 2018; 5:120. [PMID: 30283789 PMCID: PMC6156537 DOI: 10.3389/fcvm.2018.00120] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2018] [Accepted: 08/13/2018] [Indexed: 12/14/2022] Open
Abstract
Heart failure is the leading cause of death in the western world and as such, there is a great need for new therapies. Heart failure has a variable presentation in patients and a complex etiology; however, it is fundamentally a condition that affects the mechanics of cardiac contraction, preventing the heart from generating sufficient cardiac output under normal operating pressures. One of the major issues hindering the development of new therapies has been difficulties in developing appropriate in vitro model systems of human heart failure that recapitulate the essential changes in cardiac mechanics seen in the disease. Recent advances in stem cell technologies, genetic engineering, and tissue engineering have the potential to revolutionize our ability to model and study heart failure in vitro. Here, we review how these technologies are being applied to develop personalized models of heart failure and discover novel therapeutics.
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Affiliation(s)
- Michael J Greenberg
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO, United States
| | | | - Ann Wang
- InvivoSciences Inc., Madison, WI, United States
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41
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Clippinger S, Cloonan P, Greenberg L, Stump T, Greenberg MJ. Abstract 438: Familial Cardiomyopathy Mutations Affect Mechanosensing at the Molecular and Cellular Levels. Circ Res 2018. [DOI: 10.1161/res.123.suppl_1.438] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Familial cardiomyopathies are the leading cause of sudden cardiac death in young people, affecting more than 1 in 500 people. Two common forms, hypertrophic (HCM) and dilated (DCM) cardiomyopathies, are characterized by remodeling of the heart tissue, frequently accompanied by fibrosis and myocyte disarray. These diseases are primarily caused by mutations in sarcomeric proteins that regulate the contraction of the heart; however, it is not clear how these point mutations at the molecular level lead to the disease phenotype seen in patients. To better understand this process, we have examined the molecular and cellular consequences of two mutations in troponin T, R92Q and ΔK210, that cause HCM and DCM, respectively. Using recombinant proteins and a battery of in vitro biochemical and biophysical techniques, we find that R92Q increases activation of the thin filament by stabilizing myosin force generating states while ΔK210 reduces the ability of myosin to access these states at submaximal calcium levels. To study these mutations at the single cell level, we used CRISPR/Cas9 to generate human stem cell derived cardiomyocytes bearing these mutations. We examined the structural and contractile properties of single cells on engineered hydrogels that mimic either healthy or diseased hearts. Consistent with our molecular studies, we find that R92Q causes increased force production and power output. Interestingly, the ΔK210 mutation does not affect cellular force or power output on substrates that mimic the stiffness of the healthy heart, but it causes disordering of the sarcomeres on stiff substrates. This suggests a mechanism for ΔK210 where fibrosis leads to progressive loss of contractile function via mechanosensitive structural remodeling. Taken together, these results (1) demonstrate that alterations in force production and mechanosensing contribute to the disease pathogenesis in familial cardiomyopathies and (2) illuminate the differential mechanisms that lead to either HCM or DCM.
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Woody MS, Greenberg MJ, Barua B, Winkelmann DA, Goldman YE, Ostap EM. Single Molecule, Optical Trapping Studies of Omecamtiv Mercarbil on Human Cardiac Myosin's Force Production. Biophys J 2018. [DOI: 10.1016/j.bpj.2017.11.1787] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
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Clippinger SR, Greenberg L, Greenberg MJ. Dissecting the Molecular Mechanism for Familial Cardiomyopathies. Biophys J 2018. [DOI: 10.1016/j.bpj.2017.11.787] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
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Woody MS, Lewis JH, Greenberg MJ, Goldman YE, Ostap EM. MEMLET: An Easy-to-Use Tool for Data Fitting and Model Comparison Using Maximum-Likelihood Estimation. Biophys J 2017; 111:273-282. [PMID: 27463130 DOI: 10.1016/j.bpj.2016.06.019] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2016] [Revised: 06/06/2016] [Accepted: 06/10/2016] [Indexed: 11/28/2022] Open
Abstract
We present MEMLET (MATLAB-enabled maximum-likelihood estimation tool), a simple-to-use and powerful program for utilizing maximum-likelihood estimation (MLE) for parameter estimation from data produced by single-molecule and other biophysical experiments. The program is written in MATLAB and includes a graphical user interface, making it simple to integrate into the existing workflows of many users without requiring programming knowledge. We give a comparison of MLE and other fitting techniques (e.g., histograms and cumulative frequency distributions), showing how MLE often outperforms other fitting methods. The program includes a variety of features. 1) MEMLET fits probability density functions (PDFs) for many common distributions (exponential, multiexponential, Gaussian, etc.), as well as user-specified PDFs without the need for binning. 2) It can take into account experimental limits on the size of the shortest or longest detectable event (i.e., instrument "dead time") when fitting to PDFs. The proper modification of the PDFs occurs automatically in the program and greatly increases the accuracy of fitting the rates and relative amplitudes in multicomponent exponential fits. 3) MEMLET offers model testing (i.e., single-exponential versus double-exponential) using the log-likelihood ratio technique, which shows whether additional fitting parameters are statistically justifiable. 4) Global fitting can be used to fit data sets from multiple experiments to a common model. 5) Confidence intervals can be determined via bootstrapping utilizing parallel computation to increase performance. Easy-to-follow tutorials show how these features can be used. This program packages all of these techniques into a simple-to-use and well-documented interface to increase the accessibility of MLE fitting.
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Affiliation(s)
- Michael S Woody
- Pennsylvania Muscle Institute, University of Pennsylvania, Philadelphia, Pennsylvania
| | - John H Lewis
- Department of Physiology, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Michael J Greenberg
- Pennsylvania Muscle Institute, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Yale E Goldman
- Pennsylvania Muscle Institute, University of Pennsylvania, Philadelphia, Pennsylvania.
| | - E Michael Ostap
- Pennsylvania Muscle Institute, University of Pennsylvania, Philadelphia, Pennsylvania.
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McGrath RE, Greenberg MJ, Hall-Simmonds A. Scarecrow, Tin Woodsman, and Cowardly Lion: The three-factor model of virtue. The Journal of Positive Psychology 2017. [DOI: 10.1080/17439760.2017.1326518] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Affiliation(s)
- Robert E. McGrath
- School of Psychology, Fairleigh Dickinson University, Teaneck, NJ, USA
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Abstract
The myosin superfamily of molecular motors utilizes energy from ATP hydrolysis to generate force and motility along actin filaments in a diverse array of cellular processes. These motors are structurally, kinetically, and mechanically tuned to their specific molecular roles in the cell. Optical trapping techniques have played a central role in elucidating the mechanisms by which myosins generate force and in exposing the remarkable diversity of myosin functions. Here, we present thorough methods for measuring and analyzing interactions between actin and non-processive myosins using optical trapping techniques.
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Affiliation(s)
- Michael J Greenberg
- Department of Physiology, The Pennsylvania Muscle Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA. .,Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, 660 S. Euclid Ave., Campus Box 8231, St. Louis, MO, 63110, USA.
| | - Henry Shuman
- Department of Physiology, The Pennsylvania Muscle Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - E Michael Ostap
- Department of Physiology, The Pennsylvania Muscle Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA
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Greenberg MJ, Arpağ G, Tüzel E, Ostap EM. A Perspective on the Role of Myosins as Mechanosensors. Biophys J 2016; 110:2568-2576. [PMID: 27332116 PMCID: PMC4919425 DOI: 10.1016/j.bpj.2016.05.021] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2015] [Revised: 04/13/2016] [Accepted: 05/16/2016] [Indexed: 11/26/2022] Open
Abstract
Cells are dynamic systems that generate and respond to forces over a range of spatial and temporal scales, spanning from single molecules to tissues. Substantial progress has been made in recent years in identifying the molecules and pathways responsible for sensing and transducing mechanical signals to short-term cellular responses and longer-term changes in gene expression, cell identity, and tissue development. In this perspective article, we focus on myosin motors, as they not only function as the primary force generators in well-studied mechanobiological processes, but also act as key mechanosensors in diverse functions including intracellular transport, signaling, cell migration, muscle contraction, and sensory perception. We discuss how the biochemical and mechanical properties of different myosin isoforms are tuned to fulfill these roles in an array of cellular processes, and we highlight the underappreciated diversity of mechanosensing properties within the myosin superfamily. In particular, we use modeling and simulations to make predictions regarding how diversity in force sensing affects the lifetime of the actomyosin bond, the myosin power output, and the ability of myosin to respond to a perturbation in force for several nonprocessive myosin isoforms.
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Affiliation(s)
- Michael J Greenberg
- Biochemistry and Molecular Biophysics, Washington University, St. Louis, Missouri
| | - Göker Arpağ
- Worcester Polytechnic Institute, Worcester, Massachusetts
| | - Erkan Tüzel
- Worcester Polytechnic Institute, Worcester, Massachusetts
| | - E Michael Ostap
- Pennsylvania Muscle Institute and Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania.
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Greenberg MJ, Shuman H, Ostap EM. Inherent force-dependent properties of β-cardiac myosin contribute to the force-velocity relationship of cardiac muscle. Biophys J 2016; 107:L41-L44. [PMID: 25517169 DOI: 10.1016/j.bpj.2014.11.005] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2014] [Revised: 11/05/2014] [Accepted: 11/06/2014] [Indexed: 01/14/2023] Open
Abstract
The heart adjusts its power output to meet specific physiological needs through the coordination of several mechanisms, including force-induced changes in contractility of the molecular motor, the β-cardiac myosin (βCM). Despite its importance in driving and regulating cardiac power output, the effect of force on the contractility of a single βCM has not been measured. Using single molecule optical-trapping techniques, we found that βCM has a two-step working stroke. Forces that resist the power stroke slow the myosin-driven contraction by slowing the rate of ADP release, which is the kinetic step that limits fiber shortening. The kinetic properties of βCM are affected by load, suggesting that the properties of myosin contribute to the force-velocity relationship in intact muscle and play an important role in the regulation of cardiac power output.
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Affiliation(s)
- Michael J Greenberg
- Pennsylvania Muscle Institute and Department of Physiology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania
| | - Henry Shuman
- Pennsylvania Muscle Institute and Department of Physiology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania
| | - E Michael Ostap
- Pennsylvania Muscle Institute and Department of Physiology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania.
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Kee AJ, Yang L, Lucas CA, Greenberg MJ, Martel N, Leong GM, Hughes WE, Cooney GJ, James DE, Ostap EM, Han W, Gunning PW, Hardeman EC. An Actin Filament Population Defined by the Tropomyosin Tpm3.1 Regulates Glucose Uptake. Traffic 2016; 17:80-1. [PMID: 26688443 DOI: 10.1111/tra.12342] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Anthony J Kee
- Cellular and Genetic Medicine Unit, School of Medical Sciences, UNSW Australia, Sydney, NSW 2052, Australia
| | - Lingyan Yang
- Cellular and Genetic Medicine Unit, School of Medical Sciences, UNSW Australia, Sydney, NSW 2052, Australia
| | - Christine A Lucas
- Cellular and Genetic Medicine Unit, School of Medical Sciences, UNSW Australia, Sydney, NSW 2052, Australia
| | - Michael J Greenberg
- The Pennsylvania Muscle Institute and Department of Physiology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104-6085, USA
| | - Nick Martel
- Obesity Research Centre, Institute for Molecular Bioscience, The University of Queensland, St Lucia, QLD 4072, Australia
| | - Gary M Leong
- Obesity Research Centre, Institute for Molecular Bioscience, The University of Queensland, St Lucia, QLD 4072, Australia.,Department of Paediatric Endocrinology and Diabetes, Mater Children's Hospital, South Brisbane, QLD 4010, Australia
| | - William E Hughes
- Diabetes and Obesity Program, Garvan Institute of Medical Research, Sydney, NSW 2010, Australia
| | - Gregory J Cooney
- Diabetes and Obesity Program, Garvan Institute of Medical Research, Sydney, NSW 2010, Australia
| | - David E James
- Charles Perkins Centre, School of Molecular Bioscience, University of Sydney, Sydney, NSW 2006, Australia
| | - E Michael Ostap
- The Pennsylvania Muscle Institute and Department of Physiology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104-6085, USA
| | - Weiping Han
- Singapore Bioimaging Consortium, Agency for Science, Technology and Research (A*STAR), Singapore, 138667, Singapore
| | - Peter W Gunning
- Oncology Research Unit, School of Medical Sciences, UNSW Australia, Sydney, NSW 2052, Australia
| | - Edna C Hardeman
- Cellular and Genetic Medicine Unit, School of Medical Sciences, UNSW Australia, Sydney, NSW 2052, Australia
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Woody MS, Lewis JH, Greenberg MJ, Goldman YE, Ostap EM. Accessible, Feature-Rich Software for Rigorous Model Fitting using Maximum Likelihood Estimation. Biophys J 2016. [DOI: 10.1016/j.bpj.2015.11.1778] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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