Computational Studies of the Effect of the S23D/S24D Troponin I Mutation on Cardiac Troponin Structural Dynamics

Cheng, Yuanhua; Lindert, Steffen; Kekenes‐Huskey, Peter M.; Rao, Vani; Solaro, R. John; Rosevear, Paul R.; Amaro, Rommie E.; McCulloch, Andrew D.; McCammon, J. Andrew; Regnier, Michael

doi:10.1016/j.bpj.2014.08.008

Cited by 51 publications

(94 citation statements)

References 48 publications

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“…The water forms a hydrogen bond with the coordinating oxygen side chain, allowing the oxygen of the water to become the new coordination atom. In previous computational work (23,24), similar effects were found, and there is a small change in coordinating distance; however, overall, none of these effects can be the cause of the variation in measured dissociation rates. Inspection of the trajectories showed that the N-lobe of the cTnC did have some overall movement, whereas the structure of the Ca 2+ binding pocket remained stable.…”

Section: +supporting

confidence: 71%

“…S1, the coordinating oxygento-Ca 2+ distances did not change significantly upon mutation; therefore, it is reasonable to assume that the effect on the rate of Ca 2+ release is not due to the coordinating oxygens of the cTnC binding pocket and the strength to which they bind Ca 2+ . This result is complementary to similar work comparing the WT with the cTnI S23D/S24D double mutation (23) and the WT with the cTnI R145G mutation (24). However, with the full CTF model, we are able to investigate the effects of mutations that are not within the core region of cTn.…”

Section: +supporting

confidence: 54%

“…WT (A), the R92L (B), and the R92W (C) are shown. S1 heads (23,38) and reported rates that are similar to the rate of cardiac relaxation (∼15 s −1 ). However, each of these systems has notable limitations.…”

Section: +mentioning

confidence: 68%

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Atomic resolution probe for allostery in the regulatory thin filament

Williams

Lehman

Tardiff

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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Calcium binding and dissociation within the cardiac thin filament (CTF) is a fundamental regulator of normal contraction and relaxation. Although the disruption of this complex, allosterically mediated process has long been implicated in human disease, the precise atomiclevel mechanisms remain opaque, greatly hampering the development of novel targeted therapies. To address this question, we used a fully atomistic CTF model to test both Ca 2+ binding strength and the energy required to remove Ca 2+ from the N-lobe binding site in WT and mutant troponin complexes that have been linked to genetic cardiomyopathies. This computational approach is combined with measurements of in vitro Ca 2+ dissociation rates in fully reconstituted WT and cardiac troponin T R92L and R92W thin filaments. These human disease mutations represent known substitutions at the same residue, reside at a significant distance from the calcium binding site in cardiac troponin C, and do not affect either the binding pocket affinity or EF-hand structure of the binding domain. Both have been shown to have significantly different effects on cardiac function in vivo. We now show that these mutations independently alter the interaction between the Ca 2+ ion and cardiac troponin I subunit. This interaction is a previously unidentified mechanism, in which mutations in one protein of a complex indirectly affect a third via structural and dynamic changes in a second to yield a pathogenic change in thin filament function that results in mutation-specific disease states. We can now provide atom-level insight that is potentially highly actionable in drug design.cardiac thin filament | hypertrophic cardiomyopathy | calcium homeostasis | molecular modeling | steered molecular dynamics C ardiac contraction is regulated by the binding of Ca 2+ to cardiac troponin C (cTnC) (1, 2) ( Fig. 1). The Ca 2+ binds in an EF-hand motif, consisting of two α-helices separated by a loop region containing seven coordinating oxygens that interact with the Ca 2+ , as seen in Fig. 2. Once Ca 2+ is bound, interactions between cTnC and the switch peptide domain of cardiac troponin I (cTnI) cause conformational changes that reduce the ability of cTnI to bind to actin (3). When bound to actin, cTnI shifts the equilibrium location of cardiac tropomyosin (cTM) to a position that prevents the interaction of actin with myosin, thereby inhibiting the power stroke that drives contraction of cardiac muscle (4, 5). Thus, Ca 2+ binding can be viewed as the initial step in a process that results in the eventual hydrolysis of ATP, with the sliding of the thin filament over the thick filament and the generation of mechanical work (5, 6). In disease states, changes in the ability of the cardiac muscle to be properly regulated by and to regulate Ca 2+ are often observed and play a central role in pathogenic remodeling and sudden cardiac death (SCD) (7). What is not well understood is the proximal biophysical cause by which mutation affects function at the molecular level.Due to both the size (ove...

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Section: +supporting

confidence: 71%

Section: +supporting

confidence: 54%

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Atomic resolution probe for allostery in the regulatory thin filament

Williams

Lehman

Tardiff

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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“…In general, upon introduction of either R145W or T143E, we observed increased mobility of cTnC within the low affinity Site II Ca 2ϩ binding domain. Of note, previous MD simulations have reported altered intramolecular interactions within cTnI between the N terminus and the IP domain upon introduction of the PKA S23D/S24D phosphomimetic, and this was disrupted by the presence of the HCM-associated cTnI R145G mutation (26,40,41). However, we did not see such intramolecular interactions in preliminary MD simulation runs.…”

Section: Discussioncontrasting

confidence: 58%

Restrictive Cardiomyopathy Troponin I R145W Mutation Does Not Perturb Myofilament Length-dependent Activation in Human Cardiac Sarcomeres

Dvornikov

Smolin

Zhang

et al. 2016

Journal of Biological Chemistry

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The cardiac troponin I (cTnI) R145W mutation is associated with restrictive cardiomyopathy (RCM). Recent evidence suggests that this mutation induces perturbed myofilament lengthdependent activation (LDA) under conditions of maximal protein kinase A (PKA) stimulation. Some cardiac disease-causing mutations, however, have been associated with a blunted response to PKA-mediated phosphorylation; whether this includes LDA is unknown. Endogenous troponin was exchanged in isolated skinned human myocardium for recombinant troponin containing either cTnI R145W, PKA/PKC phosphomimetic charge mutations (S23D/S24D and T143E), or various combinations thereof. Myofilament Ca 2؉ sensitivity of force, tension cost, LDA, and single myofibril activation/relaxation parameters were measured. Our results show that both R145W and T143E uncouple the impact of S23D/S24D phosphomimetic on myofilament function, including LDA. Molecular dynamics simulations revealed a marked reduction in interactions between helix C of cTnC (residues 56, 59, and 63), and cTnI (residue 145) in the presence of either cTnI RCM mutation or cTnI PKC phosphomimetic. These results suggest that the RCM-associated cTnI R145W mutation induces a permanent structural state that is similar to, but more extensive than, that induced by PKC-mediated phosphorylation of cTnI Thr-143. We suggest that this structural conformational change induces an increase in myofilament Ca 2؉ sensitivity and, moreover, uncoupling from the impact of phosphorylation of cTnI mediated by PKA at the Ser-23/Ser-24 target sites. The R145W RCM mutation by itself, however, does not impact LDA. These perturbed biophysical and biochemical myofilament properties are likely to significantly contribute to the diastolic cardiac pump dysfunction that is seen in patients suffering from a restrictive cardiomyopathy that is associated with the cTnI R145W mutation.Cardiomyopathies are diseases of the heart muscle that are either acquired or inherited (1). Several forms of the disease are formally recognized, including dilated cardiomyopathy, hypertrophic cardiomyopathy (HCM), 2 and restrictive cardiomyopathy (RCM) cardiomyopathy. Numerous mutations in sarcomeric proteins have been identified that associate with, and may indeed be causal to, inherited cardiomyopathy, notably the giant elastic protein titin (TTN) in dilated cardiomyopathy (2) and myosin heavy chain (MYH7) and myosin-binding protein C (MYBPC3) in HCM (3). RCM is a rare form of cardiomyopathy characterized by severe diastolic dysfunction secondary to significant increased ventricular diastolic stiffness but without the prominent increase in wall thickness that is commonly seen in HCM (4). RCM is associated with a poor prognosis (1), and the inherited form is believed to be caused by mutations in various sarcomeric proteins, including cardiac troponin I (TNNI3) (5).Troponin-I (TnI) is the inhibitory component of troponin, the trimeric thin filament-associated protein complex that mediates calcium-initiated contraction in striated muscle (see Fig...

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“…This rearrangement could involve new intramolecular interactions between the NЈ and the inhibitory peptide (IP) domain of cTnI (34). This in turn may strengthen the interaction between cardiac troponin C and the switch peptide domain of cTnI, thereby inducing a reduction in myofilament Ca 2ϩ sensitivity and at the same time weaken the interaction between the IP domain and actin.…”

Section: Discussionmentioning

confidence: 99%

Cardiac Myosin-binding Protein C and Troponin-I Phosphorylation Independently Modulate Myofilament Length-dependent Activation

Kumar

Govindan

Zhang

et al. 2015

Journal of Biological Chemistry

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Background: Myofilament length-dependent activation (LDA) is modulated by phosphorylation. Results: Myosin binding protein C (MyBP-C) constitutes the dominant molecular mechanism underlying phosphorylation, with a minor and independent contribution of cardiac troponin-I (cTnI). Conclusion: MyBP-C, and to a lesser extent cTnI, both contribute to enhance LDA. Significance: Novel insights into the molecular basis LDA and its regulation by phosphorylation.

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Computational Studies of the Effect of the S23D/S24D Troponin I Mutation on Cardiac Troponin Structural Dynamics

Cited by 51 publications

References 48 publications

Atomic resolution probe for allostery in the regulatory thin filament

Atomic resolution probe for allostery in the regulatory thin filament

Restrictive Cardiomyopathy Troponin I R145W Mutation Does Not Perturb Myofilament Length-dependent Activation in Human Cardiac Sarcomeres

Cardiac Myosin-binding Protein C and Troponin-I Phosphorylation Independently Modulate Myofilament Length-dependent Activation

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