Publications
35 results found
Vikhorev P, Vikhoreva N, Yeung W, et al., 2022, Titin-truncating mutations associated with dilated cardiomyopathy alter length-dependent activation and its modulation via phosphorylation, Cardiovascular Research, Vol: 118, Pages: 241-253, ISSN: 0008-6363
Aims Dilated cardiomyopathy (DCM) is associated with mutations in many genes encoding sarcomere proteins. Truncating mutations in the titin gene TTN are the most frequent. Proteomic and functional characterizations are required to elucidate the origin of the disease and the pathogenic mechanisms of TTN-truncating variants.Methods and results We isolated myofibrils from DCM hearts carrying truncating TTN mutations and measured the Ca2+ sensitivity of force and its length dependence. Simultaneous measurement of force and adenosine triphosphate (ATP) consumption in skinned cardiomyocytes was also performed. Phosphorylation levels of troponin I (TnI) and myosin binding protein-C (MyBP-C) were manipulated using protein kinase A and λ phosphatase. mRNA sequencing was employed to overview gene expression profiles. We found that Ca2+ sensitivity of myofibrils carrying TTN mutations was significantly higher than in myofibrils from donor hearts. The length dependence of the Ca2+ sensitivity was absent in DCM myofibrils with TTN-truncating variants. No significant difference was found in the expression level of TTN mRNA between the DCM and donor groups. TTN exon usage and splicing were also similar. However, we identified down-regulation of genes encoding Z-disk proteins, while the atrial-specific regulatory myosin light chain gene, MYL7, was up-regulated in DCM patients with TTN-truncating variants.Conclusion Titin-truncating mutations lead to decreased length-dependent activation and increased elasticity of myofibrils. Phosphorylation levels of TnI and MyBP-C seen in the left ventricles are essential for the length-dependent changes in Ca2+ sensitivity in healthy donors, but they are reduced in DCM patients with TTN-truncating variants. A decrease in expression of Z-disk proteins may explain the observed decrease in myofibril passive stiffness and length-dependent activation.
Tucholski T, Cai W, Gregorich ZR, et al., 2020, Distinct hypertrophic cardiomyopathy genotypes result in convergent sarcomeric proteoform profiles revealed by top-down proteomics, Proceedings of the National Academy of Sciences, Vol: 117, Pages: 24691-24700, ISSN: 0027-8424
Hypertrophic cardiomyopathy (HCM) is the most common heritable heart disease. Although the genetic cause of HCM has been linked to mutations in genes encoding sarcomeric proteins, the ability to predict clinical outcomes based on specific mutations in HCM patients is limited. Moreover, how mutations in different sarcomeric proteins can result in highly similar clinical phenotypes remains unknown. Posttranslational modifications (PTMs) and alternative splicing regulate the function of sarcomeric proteins; hence, it is critical to study HCM at the level of proteoforms to gain insights into the mechanisms underlying HCM. Herein, we employed high-resolution mass spectrometry–based top-down proteomics to comprehensively characterize sarcomeric proteoforms in septal myectomy tissues from HCM patients exhibiting severe outflow track obstruction (n = 16) compared to nonfailing donor hearts (n = 16). We observed a complex landscape of sarcomeric proteoforms arising from combinatorial PTMs, alternative splicing, and genetic variation in HCM. A coordinated decrease of phosphorylation in important myofilament and Z-disk proteins with a linear correlation suggests PTM cross-talk in the sarcomere and dysregulation of protein kinase A pathways in HCM. Strikingly, we discovered that the sarcomeric proteoform alterations in the myocardium of HCM patients undergoing septal myectomy were remarkably consistent, regardless of the underlying HCM-causing mutations. This study suggests that the manifestation of severe HCM coalesces at the proteoform level despite distinct genotype, which underscores the importance of molecular characterization of HCM phenotype and presents an opportunity to identify broad-spectrum treatments to mitigate the most severe manifestations of this genetically heterogenous disease.
Vikhorev P, Tucholski T, Cai W, et al., 2019, Differential Regulation of Post-translational Modifications in Human Hypertrophic Cardiomyopathy Revealed by Top-down Proteomics, US HUPO 2020 - 16th Annual conference
Vikhorev P, Yeung W, Li A, et al., 2018, Contractility of myofibrils from patients with dilated cardiomyopathy associated mutations, Alpbach Meeting on Muscle Molecular Motors
Vikhorev PG, Smoktunowicz N, Munster AB, et al., 2018, Author Correction: Abnormal contractility in human heart myofibrils from patients with dilated cardiomyopathy due to mutations in TTN and contractile protein genes, Scientific Reports, Vol: 8, ISSN: 2045-2322
Correction to: Scientific Reportshttps://doi.org/10.1038/s41598-017-13675-8, published online 01 November 2017
Vikhorev P, Yeung W, Li A, et al., 2018, Contractility of ventricular myofibrils from patients with dilated cardiomyopathy associated mutations, 47th European Muscle Conference, Publisher: Springer Science and Business Media LLC, Pages: 65-115, ISSN: 0142-4319
Vikhorev P, Vikhoreva N, 2018, Cardiomyopathies and related changes in contractility of human heart muscle, International Journal of Molecular Sciences, Vol: 19, ISSN: 1422-0067
About half of hypertrophic and dilated cardiomyopathies cases have been recognized as genetic diseases with mutations in sarcomeric proteins. The sarcomeric proteins are involved in cardiomyocyte contractility and its regulation, and play a structural role. Mutations in non-sarcomeric proteins may induce changes in cell signaling pathways that modify contractile response of heart muscle. These facts strongly suggest that contractile dysfunction plays a central role in initiation and progression of cardiomyopathies. In fact, abnormalities in contractile mechanics of myofibrils have been discovered. However, it has not been revealed how these mutations increase risk for cardiomyopathy and cause the disease. Much research has been done and still much is being done to understand how the mechanism works. Here, we review the facts of cardiac myofilament contractility in patients with cardiomyopathy and heart failure.
Vikhorev P, Li A, dos Remedios C, et al., 2018, Effect of truncated mutations in the titin gene on cardiac function, Biophysical Journal, Vol: 114, ISSN: 0006-3495
Vikhorev PG, Li A, Lal S, et al., 2018, Effect of truncated mutations in the Titin gene on cardiac function, 62nd Annual Meeting of the Biophysical-Society, Publisher: Cell Press, Pages: 498A-498A, ISSN: 0006-3495
Vikhorev, Smoktunowicz N, Munster A, et al., 2017, Abnormal contractility in human heart myofibrils from patients with dilated cardiomyopathy due to mutations in TTN and contractile protein genes., Scientific Reports, Vol: 7, ISSN: 2045-2322
Dilated cardiomyopathy (DCM) is an important cause of heart failure. Single gene mutations in at least 50 genes have been proposed to account for 25–50% of DCM cases and up to 25% of inherited DCM has been attributed to truncating mutations in the sarcomeric structural protein titin (TTNtv). Whilst the primary molecular mechanism of some DCM-associated mutations in the contractile apparatus has been studied in vitro and in transgenic mice, the contractile defect in human heart muscle has not been studied. In this study we isolated cardiac myofibrils from 3 TTNtv mutants, and 3 with contractile protein mutations (TNNI3 K36Q, TNNC1 G159D and MYH7 E1426K) and measured their contractility and passive stiffness in comparison with donor heart muscle as a control. We found that the three contractile protein mutations but not the TTNtv mutations had faster relaxation kinetics. Passive stiffness was reduced about 38% in all the DCM mutant samples. However, there was no change in maximum force or the titin N2BA/N2B isoform ratio and there was no titin haploinsufficiency. The decrease in myofibril passive stiffness was a common feature in all hearts with DCM-associated mutations and may be causative of DCM.
Smoktunowicz N, Vikhorev P, Montgiraud C, et al., 2016, Investigation of titin expression in explanted hearts with familial dilated cardiomyopathy and TTN truncating variants, Cardiovascular Research, Vol: 111, Pages: S7-S7, ISSN: 1755-3245
Messer AE, Papadaki M, Vikhorev PG, et al., 2016, Uncoupling of myofilament Ca2+-sensitivity from troponin I phosphorylation by hypertrophic and dilated cardiomyopathy mutations can be reversed by EGCG and related Hsp90 inhibitors, Cardiovascular Research, Vol: 111, Pages: S47-S47, ISSN: 1755-3245
Vikhorev P, Marston S, 2016, THE EFFECT OF DCM-ASSOCIATED MUTATIONS IN TITIN ON HUMAN CARDIAC MYOFIBRIL ELASTICITY AND CONTRACTILITY., 15th Alpbach Motors Workshop. Myosin & Muscles, and other Motors., Pages: 115-115
Vikhorev P, Marston S, Ferenczi M, 2016, Instrumentation to Study Myofibril Mechanics from Static to Artificial Simulations of Cardiac Cycle, MethodsX, Vol: 3, Pages: 156-170, ISSN: 2215-0161
Many causes of heart muscle diseases and skeletal muscle diseases are inherited and caused by mutations in genes of sarcomere proteins which play either a structural or contractile role in the muscle cell. Tissue samples from human hearts with mutations can be obtained but often samples are only a few milligrams and it is necessary to freeze them for storage and transportation. Myofibrils are the fundamental contractile components of the muscle cell and retain all structural elements and contractile proteins performing in contractile event; moreover viable myofibrils can be obtained from frozen tissue.We are describing a versatile technique for measuring the contractility and its Ca2+ regulation in single myofibrils. The control of myofibril length, incubation medium and data acquisition is carried out using a digital acquisition board via computer software. Using computer control it is possible not only to measure contractile and mechanical parameters but also simulate complex protocols such as a cardiac cycle to vary length and medium independently.This single myofibril force assay is well suited for physiological measurements. The system can be adapted to measure tension amplitude, rates of contraction and relaxation, Ca2+ dependence of these parameters in dose-response measurements, length-dependent activation, stretch response, myofibril elasticity and response to simulated cardiac cycle length changes. Our approach provides an all-round quantitative way to measure myofibrils performance and to observe the effect of mutations or posttranslational modifications. The technique has been demonstrated by the study of contraction in heart with hypertrophic or dilated cardiomyopathy mutations in sarcomere proteins.
Messer AE, Papadaki M, Vikhorev PG, et al., 2016, Primary effects of HCM mutations in humans and cats, 60th Annual Meeting of the Biophysical-Society, Publisher: Biophysical Society, Pages: 123A-124A, ISSN: 1542-0086
Papadaki M, Vikhorev PG, Marston SB, et al., 2015, Uncoupling of myofilament Ca2+-sensitivity from troponin I phosphorylation by mutations can be reversed by Epigallocatechin-3-Gallate., Cardiovascular Research, Vol: 108, Pages: 99-110, ISSN: 1755-3245
AIMS: Heart muscle contraction is regulated via the β-adrenergic response that leads to phosphorylation of Troponin I (TnI) at Ser22/23, which changes the Ca(2+)-sensitivity of the cardiac myofilament. Mutations in thin filament proteins that cause Dilated Cardiomyopathy (DCM) and some mutations that cause Hypertrophic Cardiomyopathy (HCM) abolish the relationship between TnI phosphorylation and Ca(2+)-sensitivity (uncoupling). Small molecule Ca(2+)-sensitisers and Ca(2+)-desensitisers that act upon troponin alter the Ca(2+)-sensitivity of the thin filament but their relationship with TnI phosphorylation has never been studied before. METHODS AND RESULTS: Quantitative in vitro motility assay showed that 30 µM EMD57033 and 100 µM Bepridil increase Ca(2+)-sensitivity of phosphorylated cardiac thin filaments by 3.1 and 2.8-fold respectively. Additionally they uncoupled Ca(2+)-sensitivity from TnI phosphorylation, mimicking the effect of HCM mutations. EGCG decreased Ca(2+)-sensitivity of phosphorylated and unphosphorylated wild-type thin filaments equally (by 2.15±0.45 and 2.80±0.48-fold respectively), retaining the coupling. Moreover, EGCG also reduced Ca(2+)-sensitivity of phosphorylated but not unphosphorylated thin filaments containing DCM and HCM-causing mutations, thus the dependence of Ca(2+)-sensitivity upon TnI phosphorylation of uncoupled mutant thin filaments was restored in every case. In single mouse heart myofibrils, EGCG reduced Ca(2+)-sensitivity of force and kACT and also preserved coupling. Myofibrils from the ACTC E361G (DCM) mouse were uncoupled; EGCG reduced Ca(2+)-sensitivity more for phosphorylated than unphosphorylated myofibrils, thus restoring coupling. CONCLUSION: We conclude that it is possible to both mimic and reverse the pathological defects in troponin caused by cardiomyopathy mutations pharmacologically. Re-coupling by EGCG may be of potential therapeutic significance for treating cardiomyopathies.
Vikhorev PG, Song W, Wilkinson R, et al., 2015, DCM Mutation <i>ACTCE361G</i> Causes Uncoupling of Myofibril Sensitivity from TnI Phosphorylation that can be Reversed by Epigallocatechin-3-Gallate, BIOPHYSICAL JOURNAL, Vol: 108, Pages: 292A-292A, ISSN: 0006-3495
Papadaki M, Vikhorev P, Marston S, et al., 2015, Epigallocatechin-3-Gallate Reverses the Defects in Modulation of Ca<SUP>2+</SUP>-Sensitivity by Troponin I Phosphorylation Caused by Hypertrophic and Dilated Cardiomyopathy Mutations in Cardiac Muscle, 59th Annual Meeting of the Biophysical-Society, Publisher: CELL PRESS, Pages: 361A-362A, ISSN: 0006-3495
- Author Web Link
- Cite
- Citations: 1
Vikhorev PG, Song W, Wilkinson R, et al., 2014, The dilated cardiomyopathy-causing mutation ACTC E361G in cardiac muscle myofibrils specifically abolishes modulation of Ca2+ regulation by phosphorylation of Troponin I, Biophysical Journal, Vol: 107, Pages: 2369-2380, ISSN: 1542-0086
Phosphorylation of troponin I by protein kinase A (PKA) reduces Ca2þ sensitivity and increases the rate of Ca2þrelease from troponin C and the rate of relaxation in cardiac muscle. In vitro experiments indicate that mutations that causedilated cardiomyopathy (DCM) uncouple this modulation, but this has not been demonstrated in an intact contractile system.Using a Ca2þ-jump protocol, we measured the effect of the DCM-causing mutation ACTC E361G on the equilibrium and kineticparameters of Ca2þ regulation of contractility in single transgenic mouse heart myofibrils. We used propranolol treatment of miceto reduce the level of troponin I and myosin binding protein C (MyBP-C) phosphorylation in their hearts before isolating the myo-fibrils. In nontransgenic mouse myofibrils, the Ca2þ sensitivity of force was increased, the fast relaxation phase rate constant,kREL, was reduced, and the length of the slow linear phase, tLIN, was increased when the troponin I phosphorylation level wasreduced from 1.02 to 0.3 molPi/TnI (EC50 P/unp ¼ 1.8 5 0.2, p < 0.001). Native myofibrils from ACTC E361G transgenic micehad a 2.4-fold higher Ca2þ sensitivity than nontransgenic mouse myofibrils. Strikingly, the Ca2þ sensitivity and relaxation parametersof ACTC E361G myofibrils did not depend on the troponin I phosphorylation level (EC50 P/unp ¼ 0.88 5 0.17, p ¼ 0.39).Nevertheless, modulation of the Ca2þ sensitivity of ACTC E361G myofibrils by sarcomere length or EMD57033 was indistinguishablefrom that of nontransgenic myofibrils. Overall, EC50 measured in different conditions varied over a 7-fold range.The time course of relaxation, as defined by tLIN and kREL, was correlated with EC50 but varied by just 2.7- and 3.3-fold, respectively.Our results confirm that troponin I phosphorylation specifically alters the Ca2þ sensitivity of isometric tension and the timecourse of relaxation in cardiac muscle myofibrils. Moreove
Messer AE, Papadaki M, Vikhorev P, et al., 2014, The modulation of cardiac muscle Ca2+-sensitivity by PKA phosphorylation can be uncoupled by EMD57033 and re-coupled by EGCG, CARDIOVASCULAR RESEARCH, Vol: 103, ISSN: 0008-6363
Vikhorev PG, Wilkinson R, Song W, et al., 2014, Dcm-Causing Mutation E361G in Actin Uncouples Myofibril Ca<SUP>2+</SUP> Sensitivity from Protein Phosphorylation, 58th Annual Meeting of the Biophysical-Society, Publisher: CELL PRESS, Pages: 774A-775A, ISSN: 0006-3495
Song W, Vikhorev PG, Kashyap MN, et al., 2013, Mechanical and energetic properties of papillary muscle from <i>ACTC</i> E99K transgenic mouse models of hypertrophic cardiomyopathy, AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY, Vol: 304, Pages: H1513-H1524, ISSN: 0363-6135
- Author Web Link
- Cite
- Citations: 20
Wilkinson R, Vikhorev P, Song W, et al., 2013, Evidence that a familial DCM mutation uncouples troponin I phosphorylation from calcium sensitivity, blunts the lusitropic response and generates symptoms of heart failure under stress, EUROPEAN JOURNAL OF HEART FAILURE, Vol: 12, Pages: S50-S50, ISSN: 1388-9842
Vikhorev PG, Wilkinson R, Song W, et al., 2013, DCM-Causing Mutation E361G in Actin Slows Myofibril Relaxation Kinetics and Uncouples Myofibril Ca<SUP>2+</SUP> Sensitivity from Protein Phosphorylation, 57th Annual Meeting of the Biophysical-Society, Publisher: CELL PRESS, Pages: 312A-312A, ISSN: 0006-3495
- Author Web Link
- Cite
- Citations: 2
Song W, Vikhorev P, Marston SB, et al., 2012, Reduced Efficiency of Contraction in the <i>ACTC</i> E99k Mouse Model of Hypertrophic Cardiomyopathy, CIRCULATION, Vol: 126, ISSN: 0009-7322
Vikhorev PG, Vikhoreva NN, Cammarato A, et al., 2010, In vitro motility of native thin filaments from Drosophila indirect flight muscles reveals that the <i>held-up</i> 2 TnI mutation affects calcium activation, JOURNAL OF MUSCLE RESEARCH AND CELL MOTILITY, Vol: 31, Pages: 171-179, ISSN: 0142-4319
- Author Web Link
- Cite
- Citations: 7
Vikhoreva NN, Vikhorev PG, Fedorova MA, et al., 2009, The <i>in vitro</i> motility assay parameters of actin filaments from <i>Mytilus edulis</i> exposed <i>in vivo</i> to copper ions, ARCHIVES OF BIOCHEMISTRY AND BIOPHYSICS, Vol: 491, Pages: 32-38, ISSN: 0003-9861
- Author Web Link
- Cite
- Citations: 9
Vikhorev PG, Vikhoreva NN, Mansson A, 2009, Flexibility of Actin Filaments During Myosin Induced Sliding, Publisher: CELL PRESS, Pages: 496A-496A, ISSN: 0006-3495
Vikhorev PG, Vikhoreva NN, Mansson A, 2008, Bending Flexibility of Actin Filaments during Motor-Induced Sliding, BIOPHYSICAL JOURNAL, Vol: 95, Pages: 5809-5819, ISSN: 0006-3495
- Author Web Link
- Cite
- Citations: 41
Vikhorev PG, Vikhoreva NN, Sundberg M, et al., 2008, Diffusion Dynamics of Motor-Driven Transport: Gradient Production and Self-Organization of Surfaces, LANGMUIR, Vol: 24, Pages: 13509-13517, ISSN: 0743-7463
- Author Web Link
- Cite
- Citations: 24
This data is extracted from the Web of Science and reproduced under a licence from Thomson Reuters. You may not copy or re-distribute this data in whole or in part without the written consent of the Science business of Thomson Reuters.