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Cheng Y, Lindert S, Oxenford L, Tu AY, McCulloch AD, Regnier M. Effects of Cardiac Troponin I Mutation P83S on Contractile Properties and the Modulation by PKA-Mediated Phosphorylation. J Phys Chem B 2016; 120:8238-53. [PMID: 27150586 PMCID: PMC5001945 DOI: 10.1021/acs.jpcb.6b01859] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
cTnI(P82S) (cTnI(P83S) in rodents) resides at the I-T arm of cardiac troponin I (cTnI) and was initially identified as a disease-causing mutation of hypertrophic cardiomyopathy (HCM). However, later studies suggested this may not be true. We recently reported that introduction of an HCM-associated mutation in either inhibitory-peptide (cTnI(R146G)) or cardiac-specific N-terminus (cTnI(R21C)) of cTnI blunts the PKA-mediated modulation on myofibril activation/relaxation kinetics by prohibiting formation of intrasubunit contacts between these regions. Here, we tested whether this also occurs for cTnI(P83S). cTnI(P83S) increased both Ca(2+) binding affinity to cTn (KCa) and affinity of cTnC for cTnI (KC-I), and eliminated the reduction of KCa and KC-I observed for phosphorylated-cTnI(WT). In isolated myofibrils, cTnI(P83S) maintained maximal tension (TMAX) and Ca(2+) sensitivity of tension (pCa50). For cTnI(WT) myofibrils, PKA-mediated phosphorylation decreased pCa50 and sped up the slow-phase relaxation (especially for those Ca(2+) conditions that heart performs in vivo). Those effects were blunted for cTnI(P83S) myofibrils. Molecular-dynamics simulations suggested cTnI(P83S) moderately inhibited an intrasubunit interaction formation between inhibitory-peptide and N-terminus, but this "blunting" effect was weaker than that with cTnI(R146G) or cTnI(R21C). In summary, cTnI(P83S) has similar effects as other HCM-associated cTnI mutations on troponin and myofibril function even though it is in the I-T arm of cTnI.
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Affiliation(s)
- Yuanhua Cheng
- Department of Bioengineering, University of Washington, Seattle, Washington 98105, United States
- National Biomedical Computation Resource, University of California San Diego, La Jolla, California 92093, United States
| | - Steffen Lindert
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, Ohio 43210, United States
| | - Lucas Oxenford
- Department of Bioengineering, University of Washington, Seattle, Washington 98105, United States
| | - An-yue Tu
- Department of Bioengineering, University of Washington, Seattle, Washington 98105, United States
| | - Andrew D. McCulloch
- National Biomedical Computation Resource, University of California San Diego, La Jolla, California 92093, United States
- Department of Bioengineering, University of California San Diego, La Jolla, California 92093, United States
| | - Michael Regnier
- Department of Bioengineering, University of Washington, Seattle, Washington 98105, United States
- Center for Cardiovascular Biology, University of Washington, Seattle, Washington 98195, United States
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Designing proteins to combat disease: Cardiac troponin C as an example. Arch Biochem Biophys 2016; 601:4-10. [PMID: 26901433 DOI: 10.1016/j.abb.2016.02.007] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2016] [Accepted: 02/04/2016] [Indexed: 01/18/2023]
Abstract
Throughout history, muscle research has led to numerous scientific breakthroughs that have brought insight to a more general understanding of all biological processes. Potentially one of the most influential discoveries was the role of the second messenger calcium and its myriad of handling and sensing systems that mechanistically control muscle contraction. In this review we will briefly discuss the significance of calcium as a universal second messenger along with some of the most common calcium binding motifs in proteins, focusing on the EF-hand. We will also describe some of our approaches to rationally design calcium binding proteins to palliate, or potentially even cure cardiovascular disease. Considering not all failing hearts have the same etiology, genetic background and co-morbidities, personalized therapies will need to be developed. We predict designer proteins will open doors for unprecedented personalized, and potentially, even generalized medicines as gene therapy or protein delivery techniques come to fruition.
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Cheng Y, Hogarth KA, O'Sullivan ML, Regnier M, Pyle WG. 2-Deoxyadenosine triphosphate restores the contractile function of cardiac myofibril from adult dogs with naturally occurring dilated cardiomyopathy. Am J Physiol Heart Circ Physiol 2016; 310:H80-91. [PMID: 26497964 PMCID: PMC4796460 DOI: 10.1152/ajpheart.00530.2015] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/07/2015] [Accepted: 10/08/2015] [Indexed: 11/22/2022]
Abstract
Dilated cardiomyopathy (DCM) is a major type of heart failure resulting from loss of systolic function. Naturally occurring canine DCM is a widely accepted experimental paradigm for studying human DCM. 2-Deoxyadenosine triphosphate (dATP) can be used by myosin and is a superior energy substrate over ATP for cross-bridge formation and increased systolic function. The objective of this study was to evaluate the beneficial effect of dATP on contractile function of cardiac myofibrils from dogs with naturally occurring DCM. We measured actomyosin NTPase activity and contraction/relaxation properties of isolated myofibrils from nonfailing (NF) and DCM canine hearts. NTPase assays indicated replacement of ATP with dATP significantly increased myofilament activity in both NF and DCM samples. dATP significantly improved maximal tension of DCM myofibrils to the NF sample level. dATP also restored Ca(2+) sensitivity of tension that was reduced in DCM samples. Similarly, dATP increased the kinetics of contractile activation (kACT), with no impact on the rate of cross-bridge tension redevelopment (kTR). Thus, the activation kinetics (kACT/kTR) that were reduced in DCM samples were restored for dATP to NF sample levels. dATP had little effect on relaxation. The rate of early slow-phase relaxation was slightly reduced with dATP, but its duration was not, nor was the fast-phase relaxation or times to 50 and 90% relaxation. Our findings suggest that myosin utilization of dATP improves cardiac myofibril contractile properties of naturally occurring DCM canine samples, restoring them to NF levels, without compromising relaxation. This suggests elevation of cardiac dATP is a promising approach for the treatment of DCM.
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Affiliation(s)
- Yuanhua Cheng
- Department of Bioengineering, University of Washington, Seattle, Washington
| | - Kaley A Hogarth
- Centre for Cardiovascular Investigations, Department of Biomedical Sciences, University of Guelph, Guelph, Ontario, Canada; and
| | - M Lynne O'Sullivan
- Department of Clinical Studies, University of Guelph, Guelph, Ontario, Canada
| | - Michael Regnier
- Department of Bioengineering, University of Washington, Seattle, Washington
| | - W Glen Pyle
- Centre for Cardiovascular Investigations, Department of Biomedical Sciences, University of Guelph, Guelph, Ontario, Canada; and
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Cheng Y, Rao V, Tu AY, Lindert S, Wang D, Oxenford L, McCulloch AD, McCammon JA, Regnier M. Troponin I Mutations R146G and R21C Alter Cardiac Troponin Function, Contractile Properties, and Modulation by Protein Kinase A (PKA)-mediated Phosphorylation. J Biol Chem 2015; 290:27749-66. [PMID: 26391394 DOI: 10.1074/jbc.m115.683045] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2015] [Indexed: 11/06/2022] Open
Abstract
Two hypertrophic cardiomyopathy-associated cardiac troponin I (cTnI) mutations, R146G and R21C, are located in different regions of cTnI, the inhibitory peptide and the cardiac-specific N terminus. We recently reported that these regions may interact when Ser-23/Ser-24 are phosphorylated, weakening the interaction of cTnI with cardiac TnC. Little is known about how these mutations influence the affinity of cardiac TnC for cTnI (KC-I) or contractile kinetics during β-adrenergic stimulation. Here, we tested how cTnI(R146G) or cTnI(R21C) influences contractile activation and relaxation and their response to protein kinase A (PKA). Both mutations significantly increased Ca(2+) binding affinity to cTn (KCa) and KC-I. PKA phosphorylation resulted in a similar reduction of KCa for all complexes, but KC-I was reduced only with cTnI(WT). cTnI(WT), cTnI(R146G), and cTnI(R21C) were complexed into cardiac troponin and exchanged into rat ventricular myofibrils, and contraction/relaxation kinetics were measured ± PKA phosphorylation. Maximal tension (Tmax) was maintained for cTnI(R146G)- and cTnI(R21C)-exchanged myofibrils, and Ca(2+) sensitivity of tension (pCa50) was increased. PKA phosphorylation decreased pCa50 for cTnI(WT)-exchanged myofibrils but not for either mutation. PKA phosphorylation accelerated the early slow phase relaxation for cTnI(WT) myofibrils, especially at Ca(2+) levels that the heart operates in vivo. Importantly, this effect was blunted for cTnI(R146G)- and cTnI(R21C)-exchanged myofibrils. Molecular dynamics simulations suggest both mutations inhibit formation of intra-subunit contacts between the N terminus and the inhibitory peptide of cTnI that is normally seen with WT-cTn upon PKA phosphorylation. Together, our results suggest that cTnI(R146G) and cTnI(R21C) blunt PKA modulation of activation and relaxation kinetics by prohibiting cardiac-specific N-terminal interaction with the cTnI inhibitory peptide.
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Affiliation(s)
- Yuanhua Cheng
- From the Department of Bioengineering, University of Washington, Seattle, Washington 98105, the National Biomedical Computational Resource and
| | - Vijay Rao
- From the Department of Bioengineering, University of Washington, Seattle, Washington 98105
| | - An-Yue Tu
- From the Department of Bioengineering, University of Washington, Seattle, Washington 98105
| | - Steffen Lindert
- Pharmacology, University of California at San Diego, La Jolla, California 92093, and
| | - Dan Wang
- From the Department of Bioengineering, University of Washington, Seattle, Washington 98105
| | - Lucas Oxenford
- From the Department of Bioengineering, University of Washington, Seattle, Washington 98105
| | - Andrew D McCulloch
- the National Biomedical Computational Resource and Departments of Bioengineering and
| | - J Andrew McCammon
- the National Biomedical Computational Resource and Pharmacology, University of California at San Diego, La Jolla, California 92093, and
| | - Michael Regnier
- From the Department of Bioengineering, University of Washington, Seattle, Washington 98105, the Center for Cardiovascular Biology, University of Washington, Seattle, Washington 98105
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Rao V, Cheng Y, Lindert S, Wang D, Oxenford L, McCulloch AD, McCammon JA, Regnier M. PKA phosphorylation of cardiac troponin I modulates activation and relaxation kinetics of ventricular myofibrils. Biophys J 2015; 107:1196-1204. [PMID: 25185555 DOI: 10.1016/j.bpj.2014.07.027] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2014] [Revised: 07/10/2014] [Accepted: 07/15/2014] [Indexed: 10/24/2022] Open
Abstract
Protein kinase A (PKA) phosphorylation of myofibril proteins constitutes an important pathway for β-adrenergic modulation of cardiac contractility and relaxation. PKA targets the N-terminus (Ser-23/24) of cardiac troponin I (cTnI), cardiac myosin-binding protein C (cMyBP-C) and titin. The effect of PKA-mediated phosphorylation on the magnitude of contraction has been studied in some detail, but little is known about how it modulates the kinetics of thin filament activation and myofibril relaxation as Ca(2+) levels vary. Troponin C (cTnC) interaction with cTnI (C-I interaction) is a critical step in contractile activation that can be modulated by cTnI phosphorylation. We tested the hypothesis that altering C-I interactions by PKA, or by cTnI phosphomimetic mutations (S23D/S24D-cTnI), directly affects thin filament activation and myofilament relaxation kinetics. Rat ventricular myofibrils were isolated and endogenous cTn was exchanged with either wild-type cTnI, or S23D/S24D-cTnI recombinant cTn. Contractile mechanics were monitored at maximum and submaximal Ca(2+) concentrations. PKA treatment of wild-type cTn or exchange of cTn containing S23D/S24D-cTnI resulted in an increase in the rate of early, slow phase of relaxation (kREL,slow) and a decrease in its duration (tREL,slow). These effects were greater for submaximal Ca(2+) activated contractions. PKA treatment also reduced the rate of contractile activation (kACT) at maximal, but not submaximal Ca(2+), and reduced the Ca(2+) sensitivity of contraction. Using a fluorescent probe coupled to cTnC (C35S-IANBD), the Ca(2+)-cTn binding affinity and C-I interaction were monitored. Ca(2+) binding to cTn (pCa50) was significantly decreased when cTnI was phosphorylated by PKA (ΔpCa50 = 0.31). PKA phosphorylation of cTnI also weakened C-I interaction in the presence of Ca(2+). These data suggest that weakened C-I interaction, via PKA phosphorylation of cTnI, may slow thin filament activation and result in increased myofilament relaxation kinetics, the latter of which could enhance early phase diastolic relaxation during β-adrenergic stimulation.
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Affiliation(s)
- Vijay Rao
- University of Washington, Department of Bioengineering, Seattle, Washington
| | - Yuanhua Cheng
- University of Washington, Department of Bioengineering, Seattle, Washington; National Biomedical Computational Resource, La Jolla, California
| | - Steffen Lindert
- University of California San Diego, Department of Pharmacology, La Jolla, California
| | - Dan Wang
- University of Washington, Department of Bioengineering, Seattle, Washington
| | - Lucas Oxenford
- University of Washington, Department of Bioengineering, Seattle, Washington
| | - Andrew D McCulloch
- University of California San Diego, Department of Bioengineering, La Jolla, California; National Biomedical Computational Resource, La Jolla, California
| | - J Andrew McCammon
- University of California San Diego, Department of Pharmacology, La Jolla, California; National Biomedical Computational Resource, La Jolla, California
| | - Michael Regnier
- University of Washington, Department of Bioengineering, Seattle, Washington.
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Schaeffer PJ, Lindstedt SL. How animals move: comparative lessons on animal locomotion. Compr Physiol 2013; 3:289-314. [PMID: 23720288 DOI: 10.1002/cphy.c110059] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Comparative physiology often provides unique insights in animal structure and function. It is specifically through this lens that we discuss the fundamental properties of skeletal muscle and animal locomotion, incorporating variation in body size and evolved difference among species. For example, muscle frequencies in vivo are highly constrained by body size, which apparently tunes muscle use to maximize recovery of elastic recoil potential energy. Secondary to this constraint, there is an expected linking of skeletal muscle structural and functional properties. Muscle is relatively simple structurally, but by changing proportions of the few muscle components, a diverse range of functional outputs is possible. Thus, there is a consistent and predictable relation between muscle function and myocyte composition that illuminates animal locomotion. When animals move, the mechanical properties of muscle diverge from the static textbook force-velocity relations described by A. V. Hill, as recovery of elastic potential energy together with force and power enhancement with activation during stretch combine to modulate performance. These relations are best understood through the tool of work loops. Also, when animals move, locomotion is often conveniently categorized energetically. Burst locomotion is typified by high-power outputs and short durations while sustained, cyclic, locomotion engages a smaller fraction of the muscle tissue, yielding lower force and power. However, closer examination reveals that rather than a dichotomy, energetics of locomotion is a continuum. There is a remarkably predictable relationship between duration of activity and peak sustainable performance.
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Upregulation of cardiomyocyte ribonucleotide reductase increases intracellular 2 deoxy-ATP, contractility, and relaxation. J Mol Cell Cardiol 2011; 51:894-901. [PMID: 21925507 PMCID: PMC3208740 DOI: 10.1016/j.yjmcc.2011.08.026] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/28/2011] [Revised: 08/22/2011] [Accepted: 08/25/2011] [Indexed: 11/22/2022]
Abstract
We have previously demonstrated that substitution of ATP with 2 deoxy-ATP
(dATP) increased the magnitude and rate of force production at all levels of
Ca2+-mediated activation in demembranated cardiac muscle.
In the current study we hypothesized that cellular [dATP] could
be increased by viral-mediated over expression of the ribonucleotide reductase
(Rrm1 and Rrm2) complex, which would increase contractility of adult rat
cardiomyocytes. Cell length and ratiometric (fura2) Ca2+
fluorescence were monitored by video microscopy. At 0.5 Hz stimulation, the
extent of shortening was increased ~40% and maximal rate of shortening
was increased ~80% in cardiomyocytes overexpressing Rrm1+Rrm2 as
compared to non-transduced cardiomyocytes. The maximal rate of relaxation was
also increased ~150% with Rrm1+Rrm2 over expression, resulting
in decreased time to 50% relaxation over non-transduced cardiomyocytes.
These differences were even more dramatic when compared to cardiomyocytes
expressing GFP-only. Interestingly, Rrm1+Rrm2 over expression had no
effect on minimal or maximal intracellular
[Ca2+] (Fura2 fluorescence), indicating
increased contractility is primarily due to increased myofilament activity
without altering Ca2+ release from the sarcoplasmic
reticulum. Additionally, functional potentiation was maintained with
Rrm1+Rrm2 over expression as stimulation frequency was increased (1 Hz
and 2 Hz). HPLC analysis indicated cellular [dATP] was increased
by approximately 10-fold following transduction, becoming ~1.5% of the
adenine nucleotide pool. Furthermore, 2% dATP was sufficient to
significantly increase crossbridge binding and contractile force during
sub-maximal Ca2+ activation in demembranated cardiac muscle.
These experiments demonstrate the feasibility of directly targeting the
actin-myosin chemomechanical crossbridge cycle to enhance cardiac contractility
and relaxation without affecting minimal or maximal Ca2+.
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Kreutziger KL, Piroddi N, McMichael JT, Tesi C, Poggesi C, Regnier M. Calcium binding kinetics of troponin C strongly modulate cooperative activation and tension kinetics in cardiac muscle. J Mol Cell Cardiol 2010; 50:165-74. [PMID: 21035455 DOI: 10.1016/j.yjmcc.2010.10.025] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/09/2010] [Revised: 10/15/2010] [Accepted: 10/18/2010] [Indexed: 11/18/2022]
Abstract
Tension development and relaxation in cardiac muscle are regulated at the thin filament via Ca(2+) binding to cardiac troponin C (cTnC) and strong cross-bridge binding. However, the influence of cTnC Ca(2+)-binding properties on these processes in the organized structure of cardiac sarcomeres is not well-understood and likely differs from skeletal muscle. To study this we generated single amino acid variants of cTnC with altered Ca(2+) dissociation rates (k(off)), as measured in whole troponin (cTn) complex by stopped-flow spectroscopy (I61Q cTn>WT cTn>L48Q cTn), and exchanged them into cardiac myofibrils and demembranated trabeculae. In myofibrils at saturating Ca(2+), L48Q cTnC did not affect maximum tension (T(max)), thin filament activation (k(ACT)) and tension development (k(TR)) rates, or the rates of relaxation, but increased duration of slow phase relaxation. In contrast, I61Q cTnC reduced T(max), k(ACT) and k(TR) by 40-65% with little change in relaxation. Interestingly, k(ACT) was less than k(TR) with I61Q cTnC, and this difference increased with addition of inorganic phosphate, suggesting that reduced cTnC Ca(2+)-affinity can limit thin filament activation kinetics. Trabeculae exchanged with I61Q cTn had reduced T(max), Ca(2+) sensitivity of tension (pCa(50)), and slope (n(H)) of tension-pCa, while L48Q cTn increased pCa(50) and reduced n(H). Increased cross-bridge cycling with 2-deoxy-ATP increased pCa(50) with WT or L48Q cTn, but not I61Q cTn. We discuss the implications of these results for understanding the role of cTn Ca(2+)-binding properties on the magnitude and rate of tension development and relaxation in cardiac muscle.
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Affiliation(s)
- Kareen L Kreutziger
- Department of Bioengineering, University of Washington, Box 355061, 3720 15th Avenue NE, Seattle, WA 98195, USA.
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Sanford JL, Mays TA, Varian KD, Wilson JB, Janssen PM, Rafael-Fortney JA. Truncated CASK does not alter skeletal muscle or protein interactors. Muscle Nerve 2008; 38:1116-27. [DOI: 10.1002/mus.20993] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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