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Tobacman LS. Troponin Revealed: Uncovering the Structure of the Thin Filament On-Off Switch in Striated Muscle. Biophys J 2021; 120:1-9. [PMID: 33221250 PMCID: PMC7820733 DOI: 10.1016/j.bpj.2020.11.014] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2020] [Revised: 11/06/2020] [Accepted: 11/11/2020] [Indexed: 12/25/2022] Open
Abstract
Recently, our understanding of the structural basis of troponin-tropomyosin's Ca2+-triggered regulation of striated muscle contraction has advanced greatly, particularly via cryo-electron microscopy data. Compelling atomic models of troponin-tropomyosin-actin were published for both apo- and Ca2+-saturated states of the cardiac thin filament. Subsequent electron microscopy and computational analyses have supported and further elaborated the findings. Per cryo-electron microscopy, each troponin is highly extended and contacts both tropomyosin strands, which lie on opposite sides of the actin filament. In the apo-state characteristic of relaxed muscle, troponin and tropomyosin hinder strong myosin-actin binding in several different ways, apparently barricading the actin more substantially than does tropomyosin alone. The troponin core domain, the C-terminal third of TnI, and tropomyosin under the influence of a 64-residue helix of TnT located at the overlap of adjacent tropomyosins are all in positions that would hinder strong myosin binding to actin. In the Ca2+-saturated state, the TnI C-terminus dissociates from actin and binds in part to TnC; the core domain pivots significantly; the N-lobe of TnC binds specifically to actin and tropomyosin; and tropomyosin rotates partially away from myosin's binding site on actin. At the overlap domain, Ca2+ causes much less tropomyosin movement, so a more inhibitory orientation persists. In the myosin-saturated state of the thin filament, there is a large additional shift in tropomyosin, with molecular interactions now identified between tropomyosin and both actin and myosin. A new era has arrived for investigation of the thin filament and for functional understandings that increasingly accommodate the recent structural results.
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Affiliation(s)
- Larry S Tobacman
- Departments of Medicine and of Physiology and Biophysics, University of Illinois at Chicago, Chicago, Illinois.
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2
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Kobayashi M, Ramirez BE, Warren CM. Interplay of actin, ADP and Mg 2+ interactions with striated muscle myosin: Implications of their roles in ATPase. Arch Biochem Biophys 2018; 662:101-110. [PMID: 30529103 DOI: 10.1016/j.abb.2018.12.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2018] [Revised: 11/25/2018] [Accepted: 12/03/2018] [Indexed: 12/15/2022]
Abstract
The effects of Mg2+ on the interaction between ADP, a product of the ATPase reaction, and striated muscle myosin-subfragment 1 (S1) were investigated with both functional and spectroscopic methods. Mg2+ inhibited striated muscle myosin ATPase in the presence of F-actin. Significant effects of Mg2+ were observed in both rate constants of NOE build-up and maximal intensities in WaterLOGSY NMR experiments as F-actin concentration increased. In the absence of F-actin, myosin S1 with Mg2+ bound to a fluorescent ADP analog about five-times tighter than without Mg2+. In the presence of F-actin, the affinity of myosin S1 toward the ADP analog significantly decreased both with and without Mg2+. The equilibrium titration of myosin-S1 into F-actin revealed that in the presence of ADP the apparent dissociation constant (Kd) without Mg2+ was more than five-fold smaller than with Mg2+. Further, we examined effects of F-actin, ADP and Mg2+ binding to myosin on the tertiary structure of myosin-S1 using near UV circular dichroism (CD) spectroscopy. Both in the presence and absence of ADP, there was a Mg2+-dependent difference in the near UV CD spectra of actomyosin. Our results show that Mg2+ affects myosin-ADP and actin-myosin interactions which may be reflected in myosin ATPase activity.
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Affiliation(s)
- Minae Kobayashi
- Department of Physiology and Biophysics, University of Illinois at Chicago, Chicago, IL, USA; Center for Cardiovascular Research, University of Illinois at Chicago, Chicago, IL, USA.
| | - Benjamin E Ramirez
- Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, IL, USA
| | - Chad M Warren
- Department of Physiology and Biophysics, University of Illinois at Chicago, Chicago, IL, USA; Center for Cardiovascular Research, University of Illinois at Chicago, Chicago, IL, USA
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3
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Johnson D, Mathur MC, Kobayashi T, Chalovich JM. The Cardiomyopathy Mutation, R146G Troponin I, Stabilizes the Intermediate “C” State of Regulated Actin under High- and Low-Free Ca2+ Conditions. Biochemistry 2016; 55:4533-40. [DOI: 10.1021/acs.biochem.5b01359] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Dylan Johnson
- Department
of Biochemistry and Molecular Biology, Brody School of Medicine, East Carolina University, Greenville, North Carolina 27834, United States
- Department
of Chemistry, East Carolina University, Greenville, North Carolina 27858-4353, United States
| | - Mohit C. Mathur
- Department
of Biochemistry and Molecular Biology, Brody School of Medicine, East Carolina University, Greenville, North Carolina 27834, United States
| | - Tomoyoshi Kobayashi
- Department
of Physiology and Biophysics and Center for Cardiovascular Research,
College of Medicine, University of Illinois, Chicago, Illinois 60612-7342, United States
| | - Joseph M. Chalovich
- Department
of Biochemistry and Molecular Biology, Brody School of Medicine, East Carolina University, Greenville, North Carolina 27834, United States
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4
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Order-Disorder Transitions in the Cardiac Troponin Complex. J Mol Biol 2016; 428:2965-77. [PMID: 27395017 DOI: 10.1016/j.jmb.2016.06.022] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2016] [Revised: 06/21/2016] [Accepted: 06/29/2016] [Indexed: 12/26/2022]
Abstract
The troponin complex is a molecular switch that ties shifting intracellular calcium concentration to association and dissociation of actin and myosin, effectively allowing excitation-contraction coupling in striated muscle. Although there is a long history of muscle biophysics and structural biology, many of the mechanistic details that enable troponin's function remain incompletely understood. This review summarizes the current structural understanding of the troponin complex on the muscle thin filament, focusing on conformational changes in flexible regions of the troponin I subunit. In particular, we focus on order-disorder transitions in the C-terminal domain of troponin I, which have important implications in cardiac disease and could also have potential as a model system for the study of coupled binding and folding.
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5
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Swindle N, Albury ANJ, Baroud B, Burney M, Tikunova SB. Molecular and functional consequences of mutations in the central helix of cardiac troponin C. Arch Biochem Biophys 2014; 548:46-53. [PMID: 24650606 DOI: 10.1016/j.abb.2014.03.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2014] [Revised: 03/04/2014] [Accepted: 03/05/2014] [Indexed: 01/28/2023]
Abstract
The objective of this work was to investigate the role of acidic residues within the exposed middle segment of the central helix of cTnC in (1) cTnC-cTnI interactions, (2) Ca(2+) binding and exchange with the regulatory N-domain of cTnC in increasingly complex biochemical systems, and (3) ability of the cTn complex to regulate actomyosin ATPase. In order to achieve this objective, we introduced the D87A/D88A and E94A/E95A/E96A mutations into the central helix of cTnC. The D87A/D88A and E94A/E95A/E96A mutations decreased affinity of cTnC for the regulatory region of cTnI. The Ca(2+) sensitivity of the regulatory N-domain of isolated cTnC was decreased by the D87A/D88A, but not E94A/E95A/E96A mutation. However, both the D87A/D88A and E94A/E95A/E96A mutations desensitized the cTn complex and reconstituted thin filaments to Ca(2+). Decreases in the Ca(2+) sensitivity of the cTn complex and reconstituted thin filaments were, at least in part, due to faster rates of Ca(2+) dissociation. In addition, the D87A/D88A and E94A/E95A/E96A mutations desensitized actomyosin ATPase to Ca(2+), and decreased maximal actomyosin ATPase activity. Thus, our results indicate that conserved acidic residues within the exposed middle segment of the central helix of cTnC are important for the proper regulatory function of the cTn complex.
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Affiliation(s)
- Nicholas Swindle
- Department of Pharmacological and Pharmaceutical Sciences, University of Houston, Houston, TX 77004, United States
| | - Acchia N J Albury
- Department of Biology, Wingate University, Wingate, NC 28174, United States
| | - Belal Baroud
- Department of Pharmacological and Pharmaceutical Sciences, University of Houston, Houston, TX 77004, United States
| | - Maryam Burney
- Department of Pharmacological and Pharmaceutical Sciences, University of Houston, Houston, TX 77004, United States
| | - Svetlana B Tikunova
- Department of Pharmacological and Pharmaceutical Sciences, University of Houston, Houston, TX 77004, United States.
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6
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Katrukha IA. Human cardiac troponin complex. Structure and functions. BIOCHEMISTRY (MOSCOW) 2014; 78:1447-65. [DOI: 10.1134/s0006297913130063] [Citation(s) in RCA: 104] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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7
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Kobayashi M, Debold EP, Turner MA, Kobayashi T. Cardiac muscle activation blunted by a mutation to the regulatory component, troponin T. J Biol Chem 2013; 288:26335-26349. [PMID: 23897817 DOI: 10.1074/jbc.m113.494096] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
The striated muscle thin filament comprises actin, tropomyosin, and troponin. The Tn complex consists of three subunits, troponin C (TnC), troponin I (TnI), and troponin T (TnT). TnT may serve as a bridge between the Ca(2+) sensor (TnC) and the actin filament. In the short helix preceding the IT-arm region, H1(T2), there are known dilated cardiomyopathy-linked mutations (among them R205L). Thus we hypothesized that there is an element in this short helix that plays an important role in regulating the muscle contraction, especially in Ca(2+) activation. We mutated Arg-205 and several other amino acid residues within and near the H1(T2) helix. Utilizing an alanine replacement method to compare the effects of the mutations, the biochemical and mechanical impact on the actomyosin interaction was assessed by solution ATPase activity assay, an in vitro motility assay, and Ca(2+) binding measurements. Ca(2+) activation was markedly impaired by a point mutation of the highly conserved basic residue R205A, residing in the short helix H1(T2) of cTnT, whereas the mutations to nearby residues exhibited little effect on function. Interestingly, rigor activation was unchanged between the wild type and R205A TnT. In addition to the reduction in Ca(2+) sensitivity observed in Ca(2+) binding to the thin filament, myosin S1-ADP binding to the thin filament was significantly affected by the same mutation, which was also supported by a series of S1 concentration-dependent ATPase assays. These suggest that the R205A mutation alters function through reduction in the nature of cooperative binding of S1.
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Affiliation(s)
- Minae Kobayashi
- From the Department of Physiology and Biophysics, Center for Cardiovascular Research, University of Illinois at Chicago, Chicago, Illinois 60612 and.
| | - Edward P Debold
- the Department of Kinesiology, University of Massachusetts, Amherst, Massachusetts 01003
| | - Matthew A Turner
- the Department of Kinesiology, University of Massachusetts, Amherst, Massachusetts 01003
| | - Tomoyoshi Kobayashi
- From the Department of Physiology and Biophysics, Center for Cardiovascular Research, University of Illinois at Chicago, Chicago, Illinois 60612 and
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8
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Yar S, Chowdhury SAK, Davis RT, Kobayashi M, Monasky MM, Rajan S, Wolska BM, Gaponenko V, Kobayashi T, Wieczorek DF, Solaro RJ. Conserved Asp-137 is important for both structure and regulatory functions of cardiac α-tropomyosin (α-TM) in a novel transgenic mouse model expressing α-TM-D137L. J Biol Chem 2013; 288:16235-16246. [PMID: 23609439 DOI: 10.1074/jbc.m113.458695] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
α-Tropomyosin (α-TM) has a conserved, charged Asp-137 residue located in the hydrophobic core of its coiled-coil structure, which is unusual in that the residue is found at a position typically occupied by a hydrophobic residue. Asp-137 is thought to destabilize the coiled-coil and so impart structural flexibility to the molecule, which is believed to be crucial for its function in the heart. A previous in vitro study indicated that the conversion of Asp-137 to a more typical canonical Leu alters flexibility of TM and affects its in vitro regulatory functions. However, the physiological importance of the residue Asp-137 and altered TM flexibility is unknown. In this study, we further analyzed structural properties of the α-TM-D137L variant and addressed the physiological importance of TM flexibility in cardiac function in studies with a novel transgenic mouse model expressing α-TM-D137L in the heart. Our NMR spectroscopy data indicated that the presence of D137L introduced long range rearrangements in TM structure. Differential scanning calorimetry measurements demonstrated that α-TM-D137L has higher thermal stability compared with α-TM, which correlated with decreased flexibility. Hearts of transgenic mice expressing α-TM-D137L showed systolic and diastolic dysfunction with decreased myofilament Ca(2+) sensitivity and cardiomyocyte contractility without changes in intracellular Ca(2+) transients or post-translational modifications of major myofilament proteins. We conclude that conversion of the highly conserved Asp-137 to Leu results in loss of flexibility of TM that is important for its regulatory functions in mouse hearts. Thus, our results provide insight into the link between flexibility of TM and its function in ejecting hearts.
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Affiliation(s)
- Sumeyye Yar
- Departments of Biochemistry and Molecular Genetics, Chicago, Illinois 60612; Physiology and Biophysics, Chicago, Illinois 60612
| | | | | | | | | | - Sudarsan Rajan
- Department of Molecular Genetics, Biochemistry, and Microbiology, University of Cincinnati College of Medicine, Cincinnati, Ohio 45267
| | - Beata M Wolska
- Physiology and Biophysics, Chicago, Illinois 60612; Medicine, Chicago, Illinois 60612; Center for Cardiovascular Research, University of Illinois, Chicago, Illinois 60612
| | - Vadim Gaponenko
- Departments of Biochemistry and Molecular Genetics, Chicago, Illinois 60612
| | - Tomoyoshi Kobayashi
- Physiology and Biophysics, Chicago, Illinois 60612; Center for Cardiovascular Research, University of Illinois, Chicago, Illinois 60612
| | - David F Wieczorek
- Department of Molecular Genetics, Biochemistry, and Microbiology, University of Cincinnati College of Medicine, Cincinnati, Ohio 45267
| | - R John Solaro
- Physiology and Biophysics, Chicago, Illinois 60612; Center for Cardiovascular Research, University of Illinois, Chicago, Illinois 60612.
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9
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Henze M, Patrick SE, Hinken A, Scruggs SB, Goldspink P, de Tombe PP, Kobayashi M, Ping P, Kobayashi T, Solaro RJ. New insights into the functional significance of the acidic region of the unique N-terminal extension of cardiac troponin I. BIOCHIMICA ET BIOPHYSICA ACTA 2013; 1833:823-32. [PMID: 22940544 PMCID: PMC3548050 DOI: 10.1016/j.bbamcr.2012.08.012] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2012] [Revised: 08/10/2012] [Accepted: 08/18/2012] [Indexed: 11/29/2022]
Abstract
Previous structural studies indicated a special functional role for an acidic region composed of residues 1-10 in the unique N-terminal peptide of cardiac troponin I (cTnI). Employing LC-MS/MS, we determined the presence of phosphorylation sites at S5/S6 in cTnI from wild type mouse hearts as well as in hearts of mice chronically expressing active protein kinase C-ε (PKCε) and exhibiting severe dilated cardiomyopathy (DCM). To determine the functional significance of these phosphorylations, we cloned and expressed wild-type cTnI, (Wt), and cTnI variants expressing pseudo-phosphorylation cTnI-(S5D), cTnI(S6D), as well as cTnI(S5A) and cTnI(S6A). We exchanged native Tn of detergent-extracted (skinned) fiber bundles with Tn reconstituted with the variant cTnIs and measured tension and cross-bridge dynamics. Compared to controls, myofilaments controlled by cTnI with pseudo-phosphorylation (S6D) or Ala substitution (S6A) demonstrated a significant depression in maximum tension, ATPase rate, and ktr, but no change in half-maximally activating Ca(2+). In contrast, pseudo-phosphorylation at position 5 (S5D) had no effects, although S5A induced an increase in Ca(2+)-sensitivity with no change in maximum tension or ktr. We further tested the impact of acidic domain modifications on myofilament function in studies examining the effects of cTnI(A2V), a mutation linked to DCM. This mutation significantly altered the inhibitory activity of cTnI as well as cooperativity of activation of myofilament tension, but not when S23/S24 were pseudo-phosphorylated. Our data indicate a new functional and pathological role of amino acid modifications in the N-terminal acidic domain of cTnI that is modified by phosphorylations at cTnI(S23/S24). This article is part of a Special Issue entitled: Cardiomyocyte Biology: Cardiac Pathways of Differentiation, Metabolism and Contraction.
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Affiliation(s)
- Marcus Henze
- Department of Physiology and Biophysics, Center for Cardiovascular Research, College of Medicine, University of Illinois at Chicago, Chicago, IL 60612
| | - Stacey E. Patrick
- Department of Physiology and Biophysics, Center for Cardiovascular Research, College of Medicine, University of Illinois at Chicago, Chicago, IL 60612
| | - Aaron Hinken
- Department of Physiology and Biophysics, Center for Cardiovascular Research, College of Medicine, University of Illinois at Chicago, Chicago, IL 60612
| | - Sarah B. Scruggs
- Departments of Physiology and Medicine, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095
| | - Paul Goldspink
- Department of Physiology Medical College of Wisconsin, Milwaukee, WI, 53226
| | - Pieter P. de Tombe
- Department of Cellular and Molecular Physiology, Loyola University, Maywood, IL 60153
| | - Minae Kobayashi
- Department of Physiology and Biophysics, Center for Cardiovascular Research, College of Medicine, University of Illinois at Chicago, Chicago, IL 60612
| | - Peipei Ping
- Departments of Physiology and Medicine, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095
| | - Tomoyoshi Kobayashi
- Department of Physiology and Biophysics, Center for Cardiovascular Research, College of Medicine, University of Illinois at Chicago, Chicago, IL 60612
| | - R. John Solaro
- Department of Physiology and Biophysics, Center for Cardiovascular Research, College of Medicine, University of Illinois at Chicago, Chicago, IL 60612
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10
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Sequeira V, Wijnker PJM, Nijenkamp LLAM, Kuster DWD, Najafi A, Witjas-Paalberends ER, Regan JA, Boontje N, Ten Cate FJ, Germans T, Carrier L, Sadayappan S, van Slegtenhorst MA, Zaremba R, Foster DB, Murphy AM, Poggesi C, Dos Remedios C, Stienen GJM, Ho CY, Michels M, van der Velden J. Perturbed length-dependent activation in human hypertrophic cardiomyopathy with missense sarcomeric gene mutations. Circ Res 2013; 112:1491-505. [PMID: 23508784 DOI: 10.1161/circresaha.111.300436] [Citation(s) in RCA: 164] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
RATIONALE High-myofilament Ca(2+) sensitivity has been proposed as a trigger of disease pathogenesis in familial hypertrophic cardiomyopathy (HCM) on the basis of in vitro and transgenic mice studies. However, myofilament Ca(2+) sensitivity depends on protein phosphorylation and muscle length, and at present, data in humans are scarce. OBJECTIVE To investigate whether high myofilament Ca(2+) sensitivity and perturbed length-dependent activation are characteristics for human HCM with mutations in thick and thin filament proteins. METHODS AND RESULTS Cardiac samples from patients with HCM harboring mutations in genes encoding thick (MYH7, MYBPC3) and thin (TNNT2, TNNI3, TPM1) filament proteins were compared with sarcomere mutation-negative HCM and nonfailing donors. Cardiomyocyte force measurements showed higher myofilament Ca(2+) sensitivity in all HCM samples and low phosphorylation of protein kinase A (PKA) targets compared with donors. After exogenous PKA treatment, myofilament Ca(2+) sensitivity was similar (MYBPC3mut, TPM1mut, sarcomere mutation-negative HCM), higher (MYH7mut, TNNT2mut), or even significantly lower (TNNI3mut) compared with donors. Length-dependent activation was significantly smaller in all HCM than in donor samples. PKA treatment increased phosphorylation of PKA-targets in HCM myocardium and normalized length-dependent activation to donor values in sarcomere mutation-negative HCM and HCM with truncating MYBPC3 mutations but not in HCM with missense mutations. Replacement of mutant by wild-type troponin in TNNT2mut and TNNI3mut corrected length-dependent activation to donor values. CONCLUSIONS High-myofilament Ca(2+) sensitivity is a common characteristic of human HCM and partly reflects hypophosphorylation of PKA targets compared with donors. Length-dependent sarcomere activation is perturbed by missense mutations, possibly via posttranslational modifications other than PKA hypophosphorylation or altered protein-protein interactions, and represents a common pathomechanism in HCM.
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Affiliation(s)
- Vasco Sequeira
- Laboratory for Physiology, Institute for Cardiovascular Research, VU University Medical Center, Amsterdam, the Netherlands.
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11
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Abstract
We focus here on the modulation of thin filament activity by cardiac troponin I phosphorylation as an integral and adaptive mechanism in cardiac homeostasis and as a mechanism vulnerable to maladaptive response to stress. We discuss a current concept of cardiac troponin I function in the A-band region of the sarcomere and potential signaling to cardiac troponin I in a network involving the ends of the thin filaments at the Z-disk and the M-band regions. The cardiac sarcomere represents a remarkable set of interacting proteins that functions not only as a molecular machine generating the heartbeat but also as a hub of signaling. We review how phosphorylation signaling to cardiac troponin I is integrated, with parallel signals controlling excitation-contraction coupling, hypertrophy, and metabolism.
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Affiliation(s)
- R John Solaro
- Department of Physiology and Biophysics and Center for Cardiovascular Research, University of Illinois at Chicago, College of Medicine, Chicago, IL 60612, USA.
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12
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Genomic DNA methylation changes in NYGGF4-overexpression 3T3-L1 adipocytes. Int J Mol Sci 2012; 13:15575-87. [PMID: 23443082 PMCID: PMC3546650 DOI: 10.3390/ijms131215575] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2012] [Revised: 11/06/2012] [Accepted: 11/16/2012] [Indexed: 12/21/2022] Open
Abstract
NYGGF4, an obesity-related gene, is proposed to be involved in the development of insulin resistance; however, the underlying molecular mechanisms remain unclear. In the present analysis, NimbleGen tiling arrays were used to determine the patterns of genomic DNA methylation at CpG islands and promoters in NYGGF4-overexpression adipocytes. A total of 2352 CpG dinucleotides in 2018 genes and 3490 CpG dinucleotides in 3064 genes were found to be hypermethylated or hypomethylated, respectively, in NYGGF4-overexpression adipocytes. Furthermore, gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes(KEGG) pathway analysis revealed enrichment of biological processes associated with energy metabolism and signal transduction events, including the peroxisome proliferator-activated receptor gamma (PPARγ) signaling pathway, and mitogen-activated protein kinases(MAPK) and Ras homolog gene family, member A (RhoA) signaling. These data demonstrate that differentially methylated genes are significantly overrepresented in NYGGF4-overexpression adipocytes, providing valuable clues for further exploration of the role of NYGGF4 in insulin sensitivity regulation.
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13
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Kooij V, Stienen GJM, van der Velden J. The role of protein kinase C-mediated phosphorylation of sarcomeric proteins in the heart-detrimental or beneficial? Biophys Rev 2011; 3:107. [PMID: 28510060 DOI: 10.1007/s12551-011-0050-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2011] [Accepted: 06/08/2011] [Indexed: 10/18/2022] Open
Abstract
Protein kinase C (PKC) is a family of serine/threonine protein kinases, and alterations have been found in PKC isoform expression and localization in the failing heart. These alterations in PKC activation levels influence the PKC-mediated phosphorylation status of cellular target proteins involved in Ca2+-handling and sarcomeric contraction. The differences observed in the effects due to PKC-mediated phosphorylation may underlie part of the contractile dysfunction observed in the failing heart. It is therefore important to establish the beneficial and detrimental effects of this kinase in the healthy and failing heart. The function of PKC has been studied intensively; however, the complexity of the regulation of this kinase makes the interpretation of the different effects difficult. The main focus of this review is the (patho)physiological impact of phosphorylation of sarcomeric proteins, myosin light chain-2, troponin I and T, desmin, myosin binding protein-C, and titin by PKC.
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Affiliation(s)
- Viola Kooij
- Division of Cardiology, Johns Hopkins Bayview Proteomics Center, Johns Hopkins University, 5200 Eastern Avenue, MFL Bldg, Center Tower, Rm 601, Baltimore, MD, 21224, USA.
| | - Ger J M Stienen
- Laboratory for Physiology, Institute for Cardiovascular Research, VU University Medical Center, Amsterdam, The Netherlands
| | - Jolanda van der Velden
- Laboratory for Physiology, Institute for Cardiovascular Research, VU University Medical Center, Amsterdam, The Netherlands
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14
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Sung WS, Lee J, Cho J, Lee DG. The functional role of the tachykinin consensus region of urechistachykinin peptide family for its antimicrobial activity. Biol Pharm Bull 2011; 34:921-4. [PMID: 21628896 DOI: 10.1248/bpb.34.921] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In our previous study, we reported that urechistachykinin I (U I) and II (U II) exerted antimicrobial effects. To find out how the tachykinin consensus sequence of the urechistachykinin peptide family affects its antimicrobial activity, analogues substituting the amino acid residues phenylalanine (Phe-6; Anal 1), glycine (Gly-8; Anal 2), and arginine (Arg-10; Anal 3) of U II to alanine (Ala) were designed. Subsequently, the antimicrobial activity was shown on the order of Anal 3>U II=Anal 2>Anal 1, and this activity pattern was correlated with membrane studies such as propidium iodide (PI) influx and fluorescein isothiocyanate dextran (FD) leakage assay. These results suggest that the antimicrobial activity is related to the hydrophobicity values of the peptides. In regards to the activity of U II, it is determined that the hydrophobic Phe-6 plays a more critical role than Gly-8 or Arg-10.
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Affiliation(s)
- Woo Sang Sung
- School of Life Sciences and Biotechnology, College of Natural Sciences, Kyungpook National University, Daegu, Republic of Korea
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15
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Solaro RJ, Kobayashi T. Protein phosphorylation and signal transduction in cardiac thin filaments. J Biol Chem 2011; 286:9935-40. [PMID: 21257760 DOI: 10.1074/jbc.r110.197731] [Citation(s) in RCA: 83] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Affiliation(s)
- R John Solaro
- Department of Physiology and Biophysics and Center for Cardiovascular Research, University of Illinois at Chicago, Chicago, Illinois 60612, USA.
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16
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Kozaili JM, Leek D, Tobacman LS. Dual regulatory functions of the thin filament revealed by replacement of the troponin I inhibitory peptide with a linker. J Biol Chem 2010; 285:38034-41. [PMID: 20889978 DOI: 10.1074/jbc.m110.165753] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Striated muscles are relaxed under low Ca(2+) concentration conditions due to actions of the thin filament protein troponin. To investigate this regulatory mechanism, an 11-residue segment of cardiac troponin I previously termed the inhibitory peptide region was studied by mutagenesis. Several mutant troponin complexes were characterized in which specific effects of the inhibitory peptide region were abrogated by replacements of 4-10 residues with Gly-Ala linkers. The mutations greatly impaired two of troponin's actions under low Ca(2+) concentration conditions: inhibition of myosin subfragment 1 (S1)-thin filament MgATPase activity and cooperative suppression of myosin S1-ADP binding to thin filaments with low myosin saturation. Inhibitory peptide replacement diminished but did not abolish the Ca(2+) dependence of the ATPase rate; ATPase rates were at least 2-fold greater when Ca(2+) rather than EGTA was present. This residual regulation was highly cooperative as a function of Ca(2+) concentration, similar to the degree of cooperativity observed with WT troponin present. Other effects of the mutations included 2-fold or less increases in the apparent affinity of the thin filament regulatory Ca(2+) sites, similar decreases in the affinity of troponin for actin-tropomyosin regardless of Ca(2+), and increases in myosin S1-thin filament ATPase rates in the presence of saturating Ca(2+). The overall results indicate that cooperative myosin binding to Ca(2+)-free thin filaments depends upon the inhibitory peptide region but that a cooperatively activating effect of Ca(2+) binding does not. The findings suggest that these two processes are separable and involve different conformational changes in the thin filament.
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Lu QW, Hinken AC, Patrick SE, Solaro RJ, Kobayashi T. Phosphorylation of cardiac troponin I at protein kinase C site threonine 144 depresses cooperative activation of thin filaments. J Biol Chem 2010; 285:11810-7. [PMID: 20164197 DOI: 10.1074/jbc.m109.055657] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
There is evidence for PKC-dependent multisite phosphorylation of cardiac troponin I (cTnI) at Ser-23 and Ser-24 (also PKA sites) in the cardiac-specific N-terminal extension and at Thr-144, a unique residue in the inhibitory region. The functional effect of these phosphorylations in combination is of interest in view of data indicating intramolecular interaction between the N-terminal extension and the inhibitory region of cTnI. To determine the role of PKC-dependent phosphorylation of cTnI on sarcomeric function, we measured contractile regulation at multiple levels of complexity. Ca(2+) binding to thin filaments reconstituted with either cTnI(wild-type) or pseudo-phosphorylated cTnI(S23D/S24D), cTnI(T144E), and cTnI(S23D/S24D/T144E) was determined. Compared with controls regulated by cTnI(wild-type), thin filaments with cTnI(S23D/S24D) and cTnI(S23D/S24D/T144E) exhibited decreased Ca(2+) sensitivity. In contrast, there was no significant difference between Ca(2+) binding to thin filaments with cTnI(wild-type) and with cTnI(T144E). Studies of the pCa-force relations in skinned papillary fibers regulated by these forms of cTnI yielded similar results. However, in both the Ca(2+) binding measurements and the skinned fiber tension measurements, the presence of cTnI(S23D/S24D/T144E) induced a much lower Hill coefficient than either wild type, S23D/S24D, or T144E. These data highlight the importance of thin filament-based cooperative mechanisms in cardiac regulation, with implications for mechanisms of control of function in normal and pathological hearts.
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Affiliation(s)
- Qun-Wei Lu
- Department of Physiology and Biophysics, College of Medicine, University of Illinois at Chicago, Chicago, Illinois 60612, USA
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